Guillaume Schmidt

Gwenaëlle Trouvé
email: gwenaelle.trouve@uha.fr

Gontrand Leyssens

Cornelius Schönnenbeck

Paul Genevray

Fabrice Cazier

Dorothée Dewaele

Coralie Vandenbilcke

Elodie Faivre

Yann Denance

Céline Le Dreff-Lorimier

Wood washing: Influence on gaseous and particulate emissions during wood combustion in a domestic pellet stove

Keywords: Wood washing, Combustion, Pellet stove, Gaseous emissions, Particulate matter

Nowadays, the use of biomass increasingly replaces the fossil fuels for the domestic heating production. In order to reduce pollutant emissions from biomass combustion, wood was washed at room temperature in order to represent natural rain leaching before burning in a recent pellet stove (2010s) of nominal output of 6.3 kW. Raw and washed woods were combusted for three different types of wood (oak, beech and fir) and the study focused on their particulate and gaseous emissions (Total Suspended Particles (TSP), Particulate Matter with diameter below 2.5 μm (PM2.5), carbon monoxide (CO), nitrogen oxides (NOx) and Total Volatile Organic Compounds (TVOC)). Polycyclic Aromatic Hydrocarbons (PAH), aldehydes and wood tracers as phenols compounds were also measured. In addition, considering the toxic equivalent factor, the human health impact of adsorbed and gaseous PAH is considerably reduced (96%) in the case of washed fir combustion. Emission factors of CO and TSP for washed wood combustion also show a decrease up to 50% depending on the type of wood used. Furthermore, phenolic compounds, Benzene, Toluene, Ethylbenzene, Xylenes and Trimethylbenzene (BTEXT) emissions can also be reduced by the washing of biomass. Washed oak combustion leads to a clear decrease by 60% of the total of BTEXT. In the case of phenols emissions, phenol shows a significant decrease by 91% during the combustion of washed fir wood.

Introduction

Wood pellets have become an important fuel in domestic heat generation, since the costs of fossil fuels are rising and the emissions are nearly CO2 neutral. All households are incited to turn to the use of biomass as energy source for domestic heating. In contrast to other wood based fuels, the utilization of pellets is easy and automatic feeding to stoves and boiler is possible. Furthermore, the pelletization densifies the wood and produces a fuel with high energetic density [START_REF] Whittaker | Factors affecting wood, energy grass and straw pellet durability -a review[END_REF]. On the one hand, wood pellets are a convenient choice for domestic fuel because of its simplicity of implementation and its low cost [START_REF] Orecchio | II Wood pellets for home heating can be considered environmentally friendly fuels? Heavy metals determination by inductively coupled plasma-optical emission spectrometry (ICP-OES) in their ashes and the health risk assessment for the operators[END_REF]. But on the other hand, wood pellets combustion, and more generally wood combustion, is a source of fine particles (PM2.5) and gaseous compounds as carbon monoxide (CO) or other incomplete combustion gas as nitrogen oxides (NOx) or Non-Methane Volatile Organic Compounds (NMVOC) [ [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF], [START_REF] Ineris | Evaluation de l'impact des appareils de chauffage domestique à bois sur la qualité de l'air intérieur et extérieur[END_REF], [START_REF] Tissari | A novel field measurement method for determining fine particle and gas emissions from residential wood combustion[END_REF], [START_REF] Pettersson | Stove performance and emission characteristics in residential wood log and pellet combustion, part 2: wood stove[END_REF], [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF], [START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF]]. But most emissions from pellets combustion are lower than wood log combustion [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF][START_REF] Fachinger | How the user can influence particulate emissions from residential wood and pellet stoves: emission factors for different fuels and burning conditions[END_REF] because in the case of wood logs, parameters as wood species, humidity could disfavor the combustion process and generate big amounts of incomplete combustion products. As example, pollutant emissions from wood log combustion in domestic devices (open and closed fireplaces, traditional and advanced stoves) range from 20 and 120 g•kg -1 for CO, are close to 1 g•kg -1 for NOx, range from 2 to 20 g•kg -1 for NMVOC and range from 0.2 to 2 g•kg -1 for PM emissions [ [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF], [START_REF] Ineris | Evaluation de l'impact des appareils de chauffage domestique à bois sur la qualité de l'air intérieur et extérieur[END_REF], [START_REF] Tissari | A novel field measurement method for determining fine particle and gas emissions from residential wood combustion[END_REF], [START_REF] Pettersson | Stove performance and emission characteristics in residential wood log and pellet combustion, part 2: wood stove[END_REF]]. The high magnitude of emissions from small domestic devices well depends on several parameters as fuel quality and operating conditions (wall material of the combustion chamber, natural draft, primary and/or secondary air, operational practices, etc.). Whereas values from pellets combustion range from 1 to 5 g•kg -1 for CO, are close to 1 g•kg -1 for NOx, range from 60 to 100 mg•kg -1 for NMVOC and range from 0.2 to 0.5 g•kg -1 for PM emissions [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF][START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF][START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF]. More generally, combustion of wood pellets, due to a better complete combustion, is clearly less emissive in comparison with wood logs combustion. The automatic feed of the fuel and the possible presence of a lambda probe are advanced technologies that contribute to complete combustion [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF][START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF].

In the last decade, numerous studies were devoted to the evaluation of emission factors for gaseous compounds or particulate matter from residential wood combustion appliances [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF][START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF][START_REF] Vicente | Emission of carbon monoxide, total hydrocarbons and particulate matter during wood combustion in a stove operating under distinct conditions[END_REF]. The main gaseous pollutants usually followed from wood combustion are carbon monoxide, Volatile Organic Compounds (VOCs) [START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF]. Trace pollutants as Polycyclic Aromatic Hydrocarbons, benzene, toluene, ethylbenzene, xylenes, trimethylbenzene (BTEXT), phenols, aldehydes and ketones are often analyzed too [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF][START_REF] Vicente | Emission of carbon monoxide, total hydrocarbons and particulate matter during wood combustion in a stove operating under distinct conditions[END_REF]. Phenol and methoxy-phenols as syringol and guaiacol are also used as tracers of wood combustions [START_REF] Pissot | Estimation de l'impact du chauffage au bois sur la qualité de l'air intérieur et extérieur: analyse de traceurs organiques spécifiques de la combustion de la biomasse au sein de l'aérosol atmosphérique[END_REF]. Regarding particulate emissions, Total Suspended Particles (TSP) and PM2.5 are constantly measured because it is well known that wood burning is one of the most emitting sources of fine particles [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF][START_REF] Fachinger | How the user can influence particulate emissions from residential wood and pellet stoves: emission factors for different fuels and burning conditions[END_REF][START_REF] Kinsey | Evaluation of methods for the physical characterization of the fine particle emissions from two residential wood combustion appliances[END_REF].

Nowadays, several techniques are developed in order to reduce pollutants from wood combustion. Primary and secondary technologies must be distinguished: on the one hand, primary solutions focus on fuel quality and the conception of stoves and boilers, on the other hand, secondary solutions focus on the post-treatment of fumes [ [START_REF] Ozil | The "zero-CO" domestic fireplace: a catalytic solution to reduce pollutants[END_REF], [START_REF] Omara | Performance evaluation of a model electrostatic precipitator for an advanced wood combustion system[END_REF], [START_REF] Ghafghazi | Particulate matter emissions from combustion of wood in district heating applications[END_REF]]. Secondary technologies largely dominate using technologies as electrostatic filter, catalytic filter, or cyclones [START_REF]Evaluation de solutions de réduction des émissions polluantes (gazeuses et particulaires) d'appareils de chauffages résidentiels alimentés à la biomasse -Etude bibliographique[END_REF][START_REF]Evaluation de solutions de réduction des émissions polluantes (gazeuses et particulaires) d'appareils de chauffages résidentiels alimentés à la biomasse -Résultats de l'étude des performances de systèmes commercialisés[END_REF]. Secondary technologies aim principally at reducing particles emissions, but some techniques as catalytic filter allow to reduce gaseous emissions as carbon monoxide and VOCs [START_REF]Evaluation de solutions de réduction des émissions polluantes (gazeuses et particulaires) d'appareils de chauffages résidentiels alimentés à la biomasse -Résultats de l'étude des performances de systèmes commercialisés[END_REF]. Concerning primary techniques, important efforts from the 2000s were done in order to complain with different National and European standards [ [START_REF] Afnor | NF EN 12809/A1 -Residential Independent Boilers Fired by Solid Fuel -Nominal Heat Output up to 50 kW -Requirements and Test Methods[END_REF], [START_REF] Afnor | NF EN 13240/A2 -Poêles à combustibles solides -Exigences et méthodes d'essai[END_REF], [START_REF] Afnor | NF EN 14785 -Appareils de chauffage domestique à convection à granulés de bois -Exigences et méthodes d'essai -Appareils de chauffage domestique à convection granulés de bois[END_REF], [START_REF] Verte | Le label Flamme Verte : un chauffage au bois écologique, performant, économique et contemporain ![END_REF]] in terms of conception of stoves and boilers [START_REF]Etude de la sensibilité des paramètres de fonctionnement des appareils de chauffage domestique au bois sur la composition et l'émission des particules fines -Etude bibliographique[END_REF], choice of wood species and optimization of the air/fuel ratio [START_REF] Ozgen | Analysis of the chemical composition of ultrafine particles from two domestic solid biomass fired room heaters under simulated real-world use[END_REF]. One of the primary solutions to reduce pollutant emissions from biomass combustion could be a washing pre-treatment of wood. Indeed, by washing wood, some compounds as minerals or extractives from wood could be removed. Deng et al. [START_REF] Deng | Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass[END_REF] have studied demineralization of some biomasses by a washing process with deionized water at temperatures ranging from 30 °C to 90 °C and results show that minerals as potassium or calcium could be extracted. For example from rice straw, extraction efficiency reaches respectively 87 and 19% at 30 °C for both elements. Jiang et al. [START_REF] Jiang | Influence of different demineralization treatments on physicochemical structure and thermal degradation of biomass[END_REF] have also studied rice straw demineralization by several solvents as deionized water, chloride acid or phosphoric acid for example. Results show that, depending on the solvent, demineralization efficiency varies: calcium can be removed by 17% using deionized water versus 98% using chloride acid. Some extractives as phenols or carboxylic acids are also removed by wood washing [ [START_REF] Jiang | Influence of different demineralization treatments on physicochemical structure and thermal degradation of biomass[END_REF], [START_REF] Mourant | Mallee wood fast pyrolysis: effects of alkali and alkaline earth metallic species on the yield and composition of bio-oil[END_REF], [START_REF] Pettersen | The chemical composition of wood[END_REF]].

Most of the studies have attempted to compare pollutant emissions as a function of the nature of the wood or the technology of the domestic heating appliances [START_REF]Etude de la sensibilité des paramètres de fonctionnement des appareils de chauffage domestique au bois sur la composition et l'émission des particules fines -Etude bibliographique[END_REF][START_REF] Ozgen | Analysis of the chemical composition of ultrafine particles from two domestic solid biomass fired room heaters under simulated real-world use[END_REF]. Main literature data focused on the influence of demineralization process on devolatilization phases of lignocellulosic polymers during thermogravimetric analysis [START_REF] Deng | Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass[END_REF][START_REF] Jiang | Influence of different demineralization treatments on physicochemical structure and thermal degradation of biomass[END_REF][START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF]. Investigations on the influence of the wood preparation, particularly the washing process on gaseous and particulate pollutants emitted in the exhaust are scarce at real domestic scale [START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF]. This study aims at studying the leaching at room temperature of woods and their combustion (raw and washed biomasses) in a pellet stove to observe variations of gaseous and particulate emissions thanks to demineralization of wood. This work is a preliminary study of a French project supported by the National Agency of Energy and Environment (ADEME). The ultimate goal of this project is to study the influence of the natural leaching by rain of wood logs stored outside in forest for several months to a few years on gaseous and particulate pollutants during combustion in domestic devices as inserts and stoves. In order to get free of the variability due to the wood log fuel, it was decided to study the influence of leaching at laboratory scale using a pellet stove. Wood chips were then washed using demineralized water before preparing wood pellets. The stabilized conditions of a pellet burning system allow the detection of even small differences between different fuel types. This preliminary study on pellets washing aims to really understand and clearly explain the role of leaching on wood combustion with respect to gaseous and particulate emissions. Combustion of natural leached wood logs in a domestic stove will follow in a near future in order to compare these results.

Experimentals

Washing and pelletization protocols

Washing and pelletization protocols of biomasses are schematized in Fig. 1. Pre-treatment of beech, oak and fir chips was carried out at laboratory in a pilot according to the standard leaching protocol EN 12457/2 of May 2002 [START_REF] Afnor | NF EN 12457-2, Caractérisation des déchets -Essai de conformité pour lixiviation des déchets fragmentés et des boues -Partie 2: essai en bâchée unique avec un rapport liquide-solide de 10L/kg et une granulométrie inférieure à 4mm (sans ou avec réduction de la granularité[END_REF]. A quantity of 20 kg of dried wood chips was introduced into the pilot filled with 200 l of deionized water and mechanically shaken for 6 h. This operation was repeated three times but without drying wood samples between each cycle. For each cycle, the washing water is analyzed by ICP/OES (Thermo Scientific model ICAP 6300 DUO) for the quantification of minerals. The Total Organic Carbon (TOC) of residual leached solutions for 24 h was determined by catalytic oxidation of the organic carbon into dioxide carbon using a SHIMADZU TOC-VCSN apparatus. The moisture content of all raw and washed biomasses was brought to about 12 wt% (wet basis). Biomass chips were then ground and pelletized by a pellet press KAHL 14/175 equipped with a die having channels of 6 mm diameter and 22 or 26 mm length. Natural wood pellets with diameter close to 6 mm (purchased from SOFAG company, Arc sous Cicon, France) according to the DIN CERTCO standard were used as a reference during combustion tests [START_REF] Certco | Certification Scheme -Room Heaters for Solid Fuels with Lowpollution Combustion[END_REF].

Characterization of wood pellet samples

According to Table 1, the weight fractions of the different elements are in the same order of magnitude than those found for raw biomasses and lignocellulosic materials in literature [START_REF] Verma | Agro-pellets for domestic heating boilers: standard laboratory and real life performance[END_REF]. The leaching process does not really affect elemental values CHONS. Both raw and washed woods show values having the same order of magnitude. O/C and H/C atomic ratio values are close to 0.7 and 1.5 respectively, according to Van Krevelen diagram defining biomasses [ [START_REF] Van Krevelen | Properties of Polymers: Their Correlation with Chemical Structure; their Numerical Estimation and Prediction from Additive Group Contributions[END_REF], [START_REF] Loo | The Handbook of Biomass Combustion and Co-firing[END_REF], [START_REF] Senneca | Kinetics of pyrolysis, combustion and gasification of three biomass fuels[END_REF]]. A slightly decrease of the O/C ratios is observed for washed fir and oak, due to the dissolution of labile oxygen organic molecules as extractives (phenols, carboxylic acids, simple sugars, glycosides, fats, etc.) during the washing procedure [START_REF] Jiang | Influence of different demineralization treatments on physicochemical structure and thermal degradation of biomass[END_REF][START_REF] Pettersen | The chemical composition of wood[END_REF]. This loss of organic molecules impacts the LHV as seen in Table 1. The leaching process also extracts low amounts of TOC as shown in Table 1. Oak is well-known to be a hard wood specie that contains higher amounts of tannins [START_REF] Shure | Rainfall effects on plant-herbivore processes in an upland oak Forest[END_REF]. Biochemical composition of wood pellets was determined according the Van Soest's protocol [START_REF] Van Soest | Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition[END_REF] and results are given in Table 1 and are discussed in the following text (part 3). Washing or leaching proceeds to demineralization of the wood with very high removal efficiencies of some minerals as potassium, sodium, calcium, sulfur and phosphor [START_REF] Deng | Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass[END_REF][START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF]. Raw and washed biomasses have been analyzed by ICP/OES (Thermo Scientific model ICAP 6300 DUO). Table 2 shows values of 10 main minerals contained in the raw biomasses and the percentage of extraction thereof from the washing process. Excepted for calcium removal efficiencies, values of the percentage of extraction are according to the literature [START_REF] Deng | Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass[END_REF][START_REF] Jiang | Influence of different demineralization treatments on physicochemical structure and thermal degradation of biomass[END_REF][START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF][START_REF] Yu | Influence of leaching pretreatment on fuel properties of biomass[END_REF], main soluble elements being K, Na and P with extraction balances ranging from 50 to 100% and depending of several factors as temperature, duration time and mass/volume ratios. Ratios of extraction for calcium drastically depend of its chemical speciation in the wood related to nature and the solubility of each salt (NO3 -, Cl -, SO4 2-, HCO3 -, CO3 2-, PO4 3-, etc.) [START_REF] Haynes | CRC Handbook of Chemistry and Physics[END_REF]. [START_REF] Afnor | NF EN 14785 -Appareils de chauffage domestique à convection à granulés de bois -Exigences et méthodes d'essai -Appareils de chauffage domestique à convection granulés de bois[END_REF]. The power can be adjusted by an Intelligent Regulation System (SRI) from 1.3 kW to 6.3 kW. The steel inner wall of the combustion chamber is covered by vermiculite plates in order to concentrate the heat. The pellet is fed to the burn pot by an auger system that consists of an endless screw from the refillable pellets hopper. A fan is used to force air circulation through the burn pot. The ashes migrate to the base of burner pot and are collected. Each combustion test was realized for a power of 100% and a modulation of air of 50% for all wood pellet samples. Air modulation value corresponds to the rotation frequency of the pellet stove fan and so indirectly to the oxygen rate in the fumes (a linear correlation between air modulation value and oxygen rate in the fumes was observed during the tests). The air modulation value allows the adaption of the stove to the chimney and the draught during installation. Air modulation value was then determined by burning DIN+ pellets in order to obtain burning conditions and emission values according to the pellet stove manufacturer specifications. The air modulation value has been then set for all biomasses combusted in order to compare only the influence of the wood but not that of the combustion device. Ignition was accomplished using an electrical resistance. Pellets feeding rate was automatically regulated by the SRI of the stove load and the pellets consumption rate was measured during experiments thanks to a balance under the combustion platform. Emission measurements started 1 h after the stabilization of the combustion. This delay ensured steady state conditions and a total consumption of the initial dry combustible injected for the stove heating-up. The combustion efficiency was calculated using the NF EN 13240 standard related to stoves and boilers with a heating power lower than 50 kW [START_REF] Afnor | NF EN 13240/A2 -Poêles à combustibles solides -Exigences et méthodes d'essai[END_REF]. The environmental impact of the combustion of these different biomasses was estimated using the German BImSchV level 2 regulation related to the emission control of pollutants from domestic appliances with a heating power lower than 50 kW and corresponding to the French label Flamme Verte 7 stars [START_REF] Afnor | NF EN 12809/A1 -Residential Independent Boilers Fired by Solid Fuel -Nominal Heat Output up to 50 kW -Requirements and Test Methods[END_REF].

Table 3 gives the average values of combustion parameters of the pellet stove. In comparison with wood logs combustion, fume temperatures during experiments were not very high with values ranging from 162 °C to 190 °C, in contrast to 230 °C to 350 °C for wood log combustion. These measured temperatures correspond to manufacturer specifications. These low values are related to high oxygen concentrations close to 16-17% that consequently allows significant dilution and cooling of the fumes.

Values of air ratios λ ranging from 4.8 to 6.2 highlight this observation. Moreover, a slight decrease of fume temperatures for washed woods is observed, except for washed oak, with standard deviations of fume temperatures being equal to only few degrees (maximum 4 °C). In our experimental conditions, some parameters were affected by the washing process. Mass wood consumption rates decreased with washed pellets whatever the wood species. Consequently, combustion efficiency and heat output power were also lower for washed wood pellets than raw pellets. LHV of washed pellets decreased and it may explain that the heat released during combustion tests is lower compared to raw pellets. In the stove, pellets are introduced on the combustion grid by a screw working at constant volumetric flow rate. Consequently, the mass flow rate of pellets measured by the balance during the experiments, efficiency and output are significantly affected by the washing process with a decrease observed for all washed samples. Heat output power.

Chemical characterization of gaseous and particulate pollutants

Emissions were measured in the chimney during experiments at laboratory scale on the pellet stove.

According to NF EN 14785 standard [START_REF] Afnor | NF EN 14785 -Appareils de chauffage domestique à convection à granulés de bois -Exigences et méthodes d'essai -Appareils de chauffage domestique à convection granulés de bois[END_REF], concentrations expressed in mg•Nm -3 were referred to 13% of O2 in the exhaust to insure comparison for all experiments. Gaseous compounds as O2, CO, CO2, SOx and NOx were analyzed by specific analyzers Hartmann & Braun-Magnos 6G and URAS 10P and TVOC were recorded by a flame ionization detector Cosma Graphite 655. Their concentrations were recorded for 4 h and their values were calculated as the mean for this time duration. TVOC were expressed in equivalent CH4.

An Electrical Low Pressure Impactor (ELPI Outdoor, version 1.2) manufactured by DEKATI Ltd. (Tampere, Finland) was used to collect particles from 7 nm to 10 μm into 12 size fractions. The ELPI is equipped by a filtration stage with a cut-diameter of 7 nm and eleven impaction stages from 30 nm to 10 μm. ELPI device is well described in Marjamäki et al. [START_REF] Marjamäki | Performance evaluation of the electrical lowpressure impactor (ELPI)[END_REF]. Particle number and concentrations calculated accounts for 1 g•cm -3 of density value. In a dense medium in drops, it was shown by multidimensional numerical calculations that the collection of the aerosols of the inertial field could be modified. The presence of several drops modifies the flow inducing a reduction in the effectiveness of collection and the presence of a layer of incondensable gases around a drop generates an increase in the deposit of the aerosols on these drops on the higher plates of the impactor ranged from 3 to 10 μm by diffusiophoresis and thermophoresis [ [START_REF] Gauchet | Modelling of the aerosol collection efficiency by drops-influence of the distance between the drops[END_REF], [START_REF] Tsai | Correlation for thermophoretic deposition of aerosol particles onto cold plates[END_REF], [START_REF] Zhu | PM2.5 removal-advances in wet collection technologies and a novel approach through temperature swing multi-phase flow[END_REF]]. For these reasons, if particle matter was collected on the twelve plates of the ELPI from 7 nm to 10 μm, number size distributions were only calculated for PM2.5 in this study and do not take into account impaction stages 10 to 12. Only stages 1 to 9 were considered and represent PM2.5. A Fine Particle Sampler (FPS-4000 model) manufactured by DEKATI was used to dilute wood fume before ELPI analyzes. Sampling between the chimney and the FPS was realized by the use of a heated line maintained at 120 °C. The total mass fraction of Total Suspended Particles has been measured by gravimetry according to DIN Certco certification rules [START_REF] Certco | Certification Scheme -Room Heaters for Solid Fuels with Lowpollution Combustion[END_REF]. Three experiments were done for each type of wood pellets and the mean was calculated and given in the section 3 below. Particles emitted during the tests were also collected with a sampling device (CATECO model) provided by CleanAir EUROPE allowing sampling in isokinetic conditions. The system consists of a heated sampling probe connected to a heated filter holder in which glass fiber filter is placed to collect particles. This system was maintained at a temperature of 120 °C. A refrigerated collecting system follows the filter to condense water vapor and collect gaseous volatile organic compounds on a resin trap. As previously shown by Schmidl et al., nature of the pellets (conventional soft wood pellets, triticale, Miscanthus) could highly influence the emissions of pollutants for a same combustion phase (as started-up phase, partial or load phases) [START_REF] Schmidl | Particulate and gaseous emissions from manually and automatically fired small scale combustion systems[END_REF]. Products of incomplete combustion (PIC) as CO and PAH also strongly depend on air staging facilities (primary or/and secondary) with large impacts on air ratios. In our pellet stove as in most domestic pellets stoves and boilers, combustion proceeds with high air ratios between 4 and 7 [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF].

Air ratios for raw fir, beech and oak pellets are similar to this for DIN+ being in the same order of magnitude. This stove is especially designed to produce heat at low output power according to new standard building data [START_REF] Hoben | Poêle à granulé à air ventilé et régulation intelligente[END_REF] using as fuel reference DIN+ pellets. Air ratio was optimized for combustion of DIN+ pellets. For raw pellets, the increase of CO concentrations could not be attributed to a modification of the air ratio. The behavior of these non-conventional pellets, especially for hard woods as beech and oak, could be different during combustion leading to higher concentrations of PIC.

Even if the CO concentrations measured are quite high by comparison with referred DIN+ pellets, the washing process leads to a decrease of this pollutant in the exhaust ranging between 31 and 51% for all type of pellets (i.e. Table 4). This result is similar to that of Ravichandran and Corscadden who burnt in a domestic wood stove unleached and leached agricultural biomass briquettes [START_REF] Ravichandran | Comparison of gaseous and particle emissions produced from leached and un-leached agricultural biomass briquettes[END_REF]. They also observed CO emissions reduced by 50%. As shown in the Table 3, the air ratios increase for washed samples compared to raw pellets except for washed oak. This increase of the air ratio could not explain the reduction of PIC as CO and PAH (see below in part 3.2.4). Leaching of wood species eliminate soluble organic and mineral forms of carbon (mainly wood extractives as shown in Table 1). The reduction of PIC could be related to a loss of the total carbon initially contained in the raw wood species. Another hypothesis to explain the decrease of CO emissions could be pointed out with regards to Nishimura et al. results. Nishimura et al. have investigated the role of the potassium carbonate on the cellulose pyrolysis mechanism [START_REF] Nishimura | The role of potassium carbonate on cellulose pyrolysis[END_REF]. The presence of potassium largely favors the gasification of cellulose with an increase of gaseous species as H2, CO and CO2. The ring-opening of C O C bonds of cellulose were accelerated by the addition of K2CO3 with the emission of light hydrocarbon molecules. The reduction of potassium from biomass samples by the leaching process could disfavor the pyrolysis mechanism of saccharide polymers during the starting phases of the thermal treatment leading to lower CO concentrations in the exhaust.

Regarding to the standard deviation, emission factors for NOx are in the same order of magnitude for DIN+ and fir pellets than this obtained by Ozgen during the combustion of DIN+ pellets in a stove of 8 kW representing the recent Italian market with an average value of 60 mg•MJ -1 at nominal output for 1 h. Pellets manufactured from hard woods (beech and oak) present emission factors two times higher than for soft wood pellets [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF]. The main origin of NOx in solid biomass combustion is generally attributed to the amount of elemental nitrogen in the fuel and then fuel NO. The standard resolution of nitrogen determination during elemental analysis (Table 1) is not sufficiently precise to show differences for fuels with low nitrogen content. As shown in Table 4 and regarding to standard deviations, the washing procedure does not affect the emissions of NOx in the exhaust.

In Table 4, emission values for TSP ranging from 14 to 57 mg•MJ -1 are quite low compare to those given in the literature [START_REF] Nussbaumer | Overview on Technologies for Biomass Combustion and Emission Levels of Particulate Matter[END_REF]. Comparisons need to be careful because values strongly depend on the sampling methodology (sampling temperature, nature of the filter, trapping in impingers, nature of the solvents, etc.) as it was well explained by Nussbaumer [START_REF] Nussbaumer | Overview on Technologies for Biomass Combustion and Emission Levels of Particulate Matter[END_REF]. Our values are in the same order of magnitude than those reported by Nussbaumer for combustion experiments in domestic pellet stoves representing the European market using woods with low bark fraction to manufacture pellets with low ash content [START_REF] Nussbaumer | Overview on Technologies for Biomass Combustion and Emission Levels of Particulate Matter[END_REF].

Ozgen obtained an average value of 109 mg•MJ -1 at nominal output during the combustion of DIN+ pellets in a stove of 8 kW. According to the Norwegian standard, the gas temperature at the quartz filter holder was between 32 and 35 °C [START_REF] Norge | Norwegian Standard "Enclosed Wood Heaters[END_REF]. This low temperature allows the condensation of semivolatile compounds present in the gas phase and could overestimate emission factors compared to the DIN Certco regulation rules [START_REF] Certco | Certification Scheme -Room Heaters for Solid Fuels with Lowpollution Combustion[END_REF]. Applying this regulation, the filter holder in our experiments was maintained at a temperature ranging from 80 °C to 110 °C in order to minimize the condensation of organic and mineral semi-volatile compounds. This difference of temperature explains the higher value obtained by Ozgen in comparison with values measured in this study because semi-volatile compounds are not condensed in our case, the temperature of the sampling probe being much more higher than this used by Ozgen [START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF].

The effect of the washing procedure is also pointed out for the values of TSP emission factors with a main decrease for beech and oak pellets, regarding to the relative standard deviations in the range of 5-13% depending of the samples. Generally, biomasses pretreatment leads to two times less TSP emissions during combustion as shown in Table 4. Ravichandran and Corscadden also observed a more significant effect of the leaching of agricultural biomass briquettes during their combustion in a domestic stove. Indeed, the emissions of TSP decreased close to 40%-50%, depending of the agricultural specie (Switch, Wheat, Reed and Barley) [START_REF] Ravichandran | Comparison of gaseous and particle emissions produced from leached and un-leached agricultural biomass briquettes[END_REF]. While the observed trend is quite similar with this study, their emission values for TSP are higher than these of this study for both unleached and leached samples. This difference could be explained by the difference of the combustion devices. The quasi steady state combustion of pellet stoves is known to reduce TSP emissions in comparison to other wood burning devices.

Effect of washing pre-treatment on chemical speciation of organic compounds

The speciation of organic molecules in gaseous, liquid and solid phases was performed only one time and the following results are trends.

Repartition of VOC and case of BTEXT

As given in Table 4, total VOC were detected only for raw fir pellets. NMVOC largely dominate in the flue gas compared to Methanic Volatile Organic Compounds (MVOC) with proportion values ranging from 90 to 100% of the TVOC. Regarding to the standard deviation, the mean emission factor is very close to this obtained by Ozgen for and pellet stove of 8 kW with an average value of 9 mg•MJ -1 . Boman also got TVOC ranging from 1.1 to 42 mg•MJ -1 for two domestic pellet stoves (a modern Scandinavian stove with air staged combustion applied and a classic North American). Boman got the lowest values at full loads for the modern one and the highest ones for both stoves working at low load. The mixing of air and combustible gases due to lower velocities could explain the highest values [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF][START_REF] Pettersson | Design changes in a fixed-bed pellet combustion device: effects of temperature and residence time on emission performance[END_REF]. For all of cases, concentrations of MVOC were under the limit of quantification. The influence of the pretreatment on total concentrations could not be analyzed for this reason.

BTEXT molecules were analyzed in the gas phase as shown in the Fig. 5. The major compounds are, in increasing order, toluene, benzene and trimethylbenzene which represent 88 to 96% of the six molecules detected for all three. Trimethylbenzene is the major molecule measured with a proportion between 42 and 69%. Concerning benzene and toluene, their concentrations ranged respectively between 15 and 37% for the first, and between 5 and 14% for the second.

About the effect of washing biomass, the observations are not significant for all biomasses as shown in the Fig. 4. Indeed, a decrease of 59% is observed in the case of washed oak combustion but an increase of 250% is recorded for washed fir. Combustion of washed beech wood seems to be equivalent to raw beech in terms of BTEXT emissions. Variations observed on total BTEXT emissions are mainly due to trimethylbenzene evolution. Thereby, for raw biomasses combustion, values for fir, oak and beech wood are respectively 692, 1506 and 1952 μg•kg -1 dw. These factors are lower than the one determined by Boman et al. [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF] for softwood combustion which are close to 5400 μg•kg -1 dw, even if trimethylbenzene was not quantified in this study. This can probably be explained by the difference of generation, i.e. the difference of performance of the stoves used. Environmental performances of wood pretreatment on BTEXT emissions are strongly influenced by the variety of wood studied [START_REF] Pettersson | Stove performance and emission characteristics in residential wood log and pellet combustion, part 2: wood stove[END_REF][START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF].

Case of phenols

In the case of biomass combustion, phenolic compounds come from the thermal degradation of lignin [START_REF] Peng | Pyrolysis of lignin for phenols with alkaline additive[END_REF]. In this study, three phenols have been analyzed in gaseous, liquid and solid phases: phenol, guaiacol and syringol. Syringol was not detected in none of all samples. Guaiacol only represents a maximum of 3% of the total of the three phenols, the main compound detected being the phenol with 97 to 100% of total phenolic emissions mainly found in the liquid phase with emission factors values of 200, 330 and 900 μg•kg -1 dw for raw oak, beech and fir respectively. Phenol distribution in the three phases for all biomasses is represented in Fig. 5. These phenols emissions values are consistent with the study of Tschamber et al. [START_REF] Tschamber | Domestic wood heating appliances with environmental high performance: chemical composition of emission and correlations between emission factors and operating conditions[END_REF] concerning emissions of charm logs in a wood log stove. Indeed, only phenol molecule was detected with values ranged between 250 and 750 μg•kg -1 dw. Thus, the following comments on the effect of washing only focus on phenol values.

Fig. 5. Repartition of phenol molecule in the gas, particulate and condensed phase.

Washing of biomass shows a benefic impact on phenol emissions in comparison with raw biomass burning. In fact, total phenol emissions which are the sum of liquid, gas and solid phase emissions, can be reduced respectively by 91%, 76% and 34% for washed fir, oak and beech. After the washing process, the molecule of phenol is also mainly found in the liquid phase for oak and beech with values of 44 and 158 μg•kg -1 dw. In the case of fir pellets this molecule is mainly found in the gas phase with a value of 87 μg•kg -1 dw. Total phenol emission is twice higher for washed fir than for DIN + pellets combustion, the two biomasses show a similar repartition with approximately 90% of phenol in gas phase and 10% in liquid phase.

These combustion results are in agreement with the pyrolysis-GC/MS study on demineralization of lignocellulosic biomass led by Eom et al. [START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF]. According to Eom et al. [START_REF] Eom | Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents[END_REF], the decrease in phenol emission after biomass demineralization could be explained by the catalytic role of inorganics on the cleavage of carbon-carbon linkage during the pyrolysis of lignin polymer. In a more recent article, Eom et al. demonstrated that an increase in potassium content of poplar wood enhanced the formation of phenol compounds by acting as catalyst in the demethoxylation of guaiacyl units during the pyrolysis of lignin polymer [START_REF] Eom | Effect of essential inorganic metals on primary thermal degradation of lignocellulosic biomass[END_REF]. The molecules of phenol, guaiacol and syringol were the most impacted.

Furthermore, fir and oak bark are rich in phenolic matter [52]. This could also explain that a higher decrease of phenol emissions is observed for the combustion of these two washed species. Indeed, thanks to the solubility of phenolic compounds in water, they could have been extracted during the washing process. This hypothesis is strength by results of the biochemical composition shown in Table 1. Wood extractives cover various compounds in wood other than the major wood constituents such as cellulose, hemicellulose and lignin, which include fatty acids, lipids, terpenoids, phenolic compounds and glycosides mostly soluble in water [START_REF] Fengel | Wood: Chemistry, Ultrastructure, Reactions[END_REF]. The leaching process mainly affects the reduction of extractives ratio for fir and oak, respectively. As it is shown in Table 1, extractives from oak are particularly affected by the leaching process with a decrease close to 60%. This result could be explained by the high level of tannins contained in hard wood specie as oak [START_REF] Müller | Diversity of culturable phyllosphere bacteria on beech and oak: the effects of lepidopterous larvae[END_REF]. Similar trends are found for both TOC and extractives values during the leaching process even if the TOC in residual solutions were very low. 24 h of leaching seems to be not sufficient to extract the total TOC part contained in woods. During the pyrolysis decomposition phase of the biomass, less of these molecules are devolatilized leading to lower emission factors.

Case of aldehydes and ketones

Ten aldehydes from carbon number C1 (Formaldehyde) to C8 (p-tolualdehyde) and two ketones (acetone and butanone) were analyzed in the gas phase as shown in the Table 5. Main aldehydes detected are acetaldehyde and propionaldehyde which both represent 28 to 63% of the total of the 12 compounds quantified for all biomasses (raw and washed). Valeraldehyde accounts for a quarter of raw beech aldehydes emissions. In terms of total aldehydes emissions, combustion of washed woods shows an increase by 33% and 60% for fir and oak respectively, contrary to washed beech emissions which decrease by 9%. It is important to notice that DIN+ pellets emissions are significantly lower than all biomasses burnt by a factor 2.5 to 8.6. Indeed, concerning raw biomasses, emission factors of total aldehydes and ketones for DIN+, fir, oak and beech pellets are respectively 1382, 4524, 3412 and 11,862 μg•kg -1 dw. For washed biomasses, emission factors values for fir, oak and beech pellets combustion are respectively 6029, 5448 and 10,818 μg•kg -1 dw.

Case of PAH

According to the US-EPA, 16 PAH were measured. Fig. 6a shows the PAH profiles determined during the combustion tests of the seven studied biomasses. Detailed emission factors are given in the Table 6. Every wood species present more or less similar PAH profiles except for raw fir mainly due to high concentrations of naphthalene and acenaphthylene. Moreover, raw fir emissions are not in the same range than other wood varieties. DIN+ pellets are mainly constituted of softwood as fir and their own PAH emissions values are higher than hardwood as beech and oak. Excepted for the 3 lighter PAH, DIN+ and raw fir pellets show similar profiles of PAH emissions and the same range of concentrations.

DIN+ emissions are about 870 μg•kg -1 dw and other biomasses emissions are close to 400-600 μg•kg -1 dw, raw fir emissions are much higher with 1570 μg•kg -1 dw. Softwood combustion is well-known for a long time and numerous literature data are available to explain that it largely contributes to give tars and to soot contrary to hardwood. CO and PAH are PIC and PAH are defined as soot precursors [START_REF] Eberle | A sectional PAH model with reversible PAH chemistry for CFD soot simulations[END_REF]. It explains the fact that DIN+ pellets and raw fir pellets show the highest values. The PAH concentrations measured in this study are in accordance with the study of Boman et al. [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF] with values ranging between 135 and 4040 μg•kg -1 dw. One point advanced by Boman to explain the high range of magnitude is related to the age of the combustion device. PAH emissions recorded on a recent pellet stove are largely lower than an old wood stove. As example, Mac Donald et al. has studied hardwood combustion in an old wood stove that exhibited emission factors close to 75 mg•kg -1 dw while in our study, they are close to 0.5 mg•kg -1 dw [START_REF] Mcdonald | Fine particle and gaseous emission rates from residential wood combustion[END_REF]. This significant difference between the two studies shows the progress realized in terms of optimization of the performance of wood heating device. Emissions were corrected by the toxic equivalent factor for individual PAH [START_REF] Zhu | PM2.5 removal-advances in wet collection technologies and a novel approach through temperature swing multi-phase flow[END_REF].

Fig. 7 shows the repartition of total PAH in the different phases. These molecules are mainly present in the gas and liquid phases. But proportions in the gas phase dominate with values ranging from 82 to 94% for raw and washed pellets. Soft wood pellets slightly differ with a small part of total PAH (15 to 25%) in the solid phase related to a sooting behavior. Light PAH (2 to 3 aromatic rings) were mainly found in the gas phase while heavy PAH (a minimum of 5 aromatic rings) were present in solid phase and 4 aromatic rings PAH were mostly in liquid phase. The washing process does not significantly influence the repartition of total PAH in the different phases excepted for fir pellets where the part of solid PAH is strongly reduced (from 12 to 1%). In order to estimate the toxicity of PAH emissions, the French agency INERIS has published factors (toxic equivalent factor) for each of the 16 PAH to convert emission values into toxics emissions values [START_REF] Doornaert | Évaluation de la relation dose-réponse pour des effets cancérigènes: Approche substance par substance (facteurs d'équivalence toxique -FET) et approche par mélanges Évaluation de la relation dose-réponse pour des effets non cancérigènes: Valeurs Toxicologiques de Référence (VTR)[END_REF]. These factors are expressed in equivalent Benzo[a]Pyrene which is the more toxic of the 16 PAH because of its carcinogenic properties for human. Emission factors have been converted using TEF and results are presented in Table 6. DIN+ pellets show higher values than other biomasses with respectively 49.2 μg (Eq. BaP)•kg -1 dw. Washing pre-treatment on beech and oak emissions has not significant effect with values ranging from 0.5 to 3.3 μg (Eq. BaP)•kg -1 dw. Concerning fir emissions, toxicity is reduced by 96% using washed fir. Indeed, washing of fir decreases significantly PAH emissions switching from 35.7 to 1.4 μg (Eq. BaP)•kg -1 dw. Wood pre-treatment does not significantly affect beech and oak emissions contrary to fir PAH emissions which can be reduced by 64%. In general, washing biomass does not influence PAH repartition between the three phases and main PAH detected are the same for raw and washed wood combustion. Only the concentration of some compounds can be influenced by the washing process.

In terms of the number of cycle distribution for PAH calculated from total emission factors, Fig. 6b shows that whatever the species and regardless if the wood is washed or not, the repartition is substantially the same. Only raw softwoods slightly differ with a higher proportion of PAH containing 5 to 7 aromatic rings. Fig. 6c represents the number of cycle distribution for PAH expressed into international toxic equivalent. Considering low values for oak and beech, washing pretreatment does not modify repartition. DIN+ and raw fir repartition are quite similar. In the case of fir washing, the number of cycle distributions from toxic equivalent factor emissions is really influenced: distribution of 5 cycles PAH is reduced by a factor 2 to the benefit of 2 to 4 cycles PAH which are less toxic as shown in Fig. 6c.

As shown in Table 1, the extractive part of the wood is affected by the leaching process. A lot of ethylenic and aromatic molecules present in the composition of the extractives in wood as terpenoids and phenolic compounds [START_REF] Ishida | Direct analysis of phenolic extractives in wood by thermochemolysis-gas chromatography in the presence of tetrabutylammonium hydroxide[END_REF] are reduced by dissolution in water. The reduction of these molecules acting as precursors of PAH could favor the decrease of PAH emission factors, accordingly. Another explanation could be pointed out according to Nishimura et al. results [START_REF] Nishimura | The role of potassium carbonate on cellulose pyrolysis[END_REF]. Nishimura et al. demonstrated the role of the potassium in the gasification of the cellulose with the increase of yields of gases (H2, CO, light VOC) and low molecular weight PAHs, such as naphthalene and anthracene in the range of temperatures studied (up to 1000 °C). Moreover they demonstrated that the yields of other PAHs like Benzo[a]Pyrene increased for temperatures up to 600 °C. As for CO (see Section 3.1), the reduction of potassium from biomass samples by the leaching process could disfavor the pyrolysis mechanism of saccharide polymers during the starting phases of the thermal treatment leading to less PIC as CO and PAHs.

3.3. Effect of washing pre-treatment on size distributions of PM2.5

Mean total number concentrations and emission factors in PM2.5 are given in Table 7. The values are expressed in different units in order to get sufficient comparisons with literature data. Results are equivalent (same orders of magnitude) to previous data obtained thanks to ELPI measurements for similar small output pellet stoves and boilers [ [START_REF] Johansson | Particle emissions from biomass combustion in small combustors[END_REF], [START_REF] Johansson | Emission characteristics of modern and old-type residential boilers fired with wood logs and wood pellets[END_REF], [START_REF] Tissari | Fine particle emissions from residential wood combustion[END_REF], [START_REF] Lamberg | Physicochemical characterization of fine particles from small-scale wood combustion[END_REF], [START_REF] Sippula | Effect of wood fuel on the emissions from a top-feed pellet stove[END_REF]]. In the Fig. 8 are also given the number size distributions related to three size fractions in the PM2.5. PM2.5 are mainly constituted of PM1 for all raw and washed samples, representing 99.9% of the total number of particles. There is a significant difference between the two fractions PM0.1 and PM0.1-1. A similar distribution was previously observed by Sippula et al. during combustion of pellets from different woods and agricultural residues in a commercial top-feed Wodtke GmBH stove working at nominal output of 8 kW [START_REF] Sippula | Effect of wood fuel on the emissions from a top-feed pellet stove[END_REF]. In Sippula's results, PM1 largely dominated in number with emission factors close to 5.1 to 5.9 10 13 1•MJ -1 for birch, fir and spruce stems. The presence of bark during the manufacturing of pellets allows an increase of fine particles in the exhaust ranging from 1.4 10 13 1•MJ -1 to 7.1 10 13 1•MJ -1 for willow barks and fir, respectively [START_REF] Sippula | Effect of wood fuel on the emissions from a top-feed pellet stove[END_REF]. Regarding to standard deviations, raw fir, beech and oak pellets emitted much more PM2.5 than the DIN+ pellets in the exhaust. Because raw beech, raw fir and raw oak pellets contain higher ash contents than DIN+, this increase in PM2.5 concentrations and emissions factors could be attributed to a part of fine fly ash particles emitted during the combustion. As shown in the Table 1, the washing process affects the ash content. The decreases by the dissolution of mineral matter contained in the wood species strength this result. Mass losses observed after the washing process were close to 38%, 32% and 25% for oak, beech and fir, respectively, oak specie being the most impacted by the washing procedure. The mass losses of minerals by dissolution during the process shown in Table 2 are in the same order of magnitude than ash losses for the three wood species with values equal to 17%, 22% and 34% for oak, fir and beech, respectively. Because ash contents are reduced, fly ashes should be less devolatilized in the exhaust. The washing process positively reduces by the same order of magnitude both ash content and emission factors of fine particles only for oak specie with a decrease of PM2.5 emission factors by a factor 1/3. The link between the loss of both ash content and particle emissions for beech and fir pellets is not significant, regarding to standard deviations.

Table 7. Influence of the washing pre-treatment on PM2.5. The influence of the washing procedure on the particle size distribution is shown in Fig. 8a to c. In the following, size number distributions of PM2.5 are presented using the mean diameter (Stokes diameter) defined as the square root of the product of two continuous aerodynamic Dae at 50% of efficiency (Dmean = √Dae1 × √Dae2). Raw and washed samples present unimodal number size distributions with particle diameters centered in the range 100-200 nm. In PM2.5, nanoparticles as PM0.1 and PM0.1-1 largely dominate. These distribution profiles are similar to a lot of literature data and characterize biomass combustion whatever the type of fuel (logs, pellets) and the combustion device (insert, stove, boiler) [START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF][START_REF] Johansson | Particle emissions from biomass combustion in small combustors[END_REF][START_REF] Johansson | Emission characteristics of modern and old-type residential boilers fired with wood logs and wood pellets[END_REF]. The impact of washing wood seems to be positive regarding the total emission of particulate matter (PM2.5). It slightly modifies the size distribution in the PM1 fractions favoring the emission of ultrafine particles (PM0.1) in the exhaust (Table 7).

Np

Conclusions

This work aimed to study the impact of wood washing on combustion emissions of a recent wood pellet stove. Three wood varieties, as fir, oak and beech were burned in their raw and washed form. Natural wood pellets according to the DIN CERTCO standard were also combusted as a reference during combustion tests. Particulate and gaseous emissions like CO, THC, PAH, biomass tracers as phenols or sugars, and some organic compounds as BTEXT and aldehydes were measured in the fumes.

Concerning CO, experiments show that wood washing decreases CO emissions, particularly in the case of oak combustion with a reduction close to 50% in comparison with raw oak. About THC emission factors all values are very low excepted for raw fir combustion, so only a decrease on fir washed wood can be observed. Regarding total PAH emissions factors, washing process decreases PAH emissions and particularly in the case of fir with a diminution up to 60%. Emissions of PAH are mainly composed of light molecules with two and three aromatic rings in the gas phase whether it was washed or not.

Expressed in toxic equivalent factor, toxicity of the total PAH emissions from washed fir combustion can be reduced by 96% due to a change of aromatic rings distribution: the most toxic molecules with five aromatic rings are reduced to the benefit of 2 to 4 ring PAH which are less toxic. Furthermore, phenols and BTEXT emissions can also be reduced by the washing of biomass. Indeed, in the case of phenols emissions, phenol molecule shows a significant decrease of 91% by washing fir wood. Concerning BTEXT emissions, washed oak combustion leads to a decrease of 59% of the total of the five compounds measured. Only aldehydes and ketones emissions are significantly increased by the washing process in the case of fir and oak with an increase of respectively 33 and 60% even if a decrease of 9% is observed for beech combustion. The leaching process affects the biochemical composition of the wood, particularly the ratio of extractives that contain light molecules hardly soluble in water. The loss of extractives consequently could decrease the emissions of organic compounds during the thermal decomposition of biomass, especially during the pyrolysis phase. Due to wood demineralization, particulate emissions are reduced. Indeed, TSP values decreased for all washed biomasses and particularly for washed oak combustion with a decrease up to 50%. Number particle concentrations of PM2.5 can also be reduced with a better effect on washed oak too. But even if PM2.5 are reduced, proportion of PM0.1 increased systematically for washed wood.

Finally, the washing of biomass allows the decrease in its environmental impact during its combustion in a pellet stove although the wood species plays an important role. The slight acidity of demineralized water or of the natural rain probably acts on sugars (hemicellulose and cellulose) and lignin polymers inside the wood during the treatment with modification of chemical bonding and could influence the devolatilization process during thermal treatment. Further investigations are necessary to assess this point.

Fig. 1 .

 1 Fig. 1. Wood fuel preparation for combustion tests.

Fig. 2 .

 2 Fig. 2. Experimental combustion setup.

Fig. 3 .

 3 Fig. 3. Influence of the washing pre-treatment on gaseous and particulate pollutant concentrations and their comparison with French and European standards.

Fig. 4 .

 4 Fig. 4. Evolution of the BTEXT emission factors with the pre-treatment.

  Fig. 6. (a) Evolution of the individual PAH emission factors with the pre-treatment (total emission factors of the three

Fig. 7 .

 7 Fig. 7. Relative distribution of total PAH in the different phases.

PM2. 5 ( 1 • 13 a

 5113 MJ -1 ) 3.64 ± 0.06 × 10 13 4.7 ± 0.6 × 10 13 5.2 ± 0.08 × 10 13 5.2 ± 0.1 × 10 13 5.4 ± 0.1 × 10 13 5.7 ± 0.1 × 10 13 4.2 ± 0.08 × 10Volumes are expressed in STP and referred to 13% O2 in the fume.

Fig. 8 .

 8 Fig. 8. Number size distribution of (a) DIN+ and both raw and washed fir (b) both raw and washed oak (c) both raw and washed beech.

Table 1 .

 1 Physical and chemical properties of the raw and washed wood species.

Properties/woods DIN Certco Fir Beech Oak Raw Washed Raw Washed Raw Washed Humidity a (%)

		9	12	14	9	11	11	9
	Ash content b, c (%) 0.30	0.40	0.30	1.05	0.71	0.87	0.54
	C b (%)	47.1	46.4	48.6	46.3	47.8	46.3	47.6
	H b (%)	6.1	5.7	6.0	6.0	6.0	5.7	6.1
	N b (%)	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1
	O b (%)	46.6	41.0	41.3	43.1	43.7	40.9	39.8
	S b (%)	<0.03	<0.03	<0.03	<0.03	<0.03	<0.03	<0.03

HHV b, d (MJ•kg -1 )

	18.8	20.0	17.3	18.6	17.4	18.2	17.8

LHV b, e (MJ•kg -1 )

		17.2	18.8	15.7	17.5	15.9	17.1	16.3
	H/C f	1.55	1.47	1.48	1.55	1.50	1.47	1.53
	O/C f	0.74	0.66	0.63	0.69	0.68	0.66	0.62

Extractives (%) b, g

	10	8	4	12	10	19	7

Hemicellulose (%) b, g 19 21 17 27 25 21 25 Cellulose (%) b, g

		44	43	50	40	50	45	54
	Lignin (%) b, g	27	28	29	21	15	14	14

TOC (g•kg -1 ) b, h

		n.d i	0.62	0.65	1.41
	a	On raw basis.
	b	On dried basis.
	c	Measured at 550 °C.
	d	HHV for High Heating Value.
	e	LHV for Low Heating Value.
	f	H/C and O/C are atomic ratios according to Van Krevelen [32].

g Biochemical composition was performed according the Van Soest protocol

[START_REF] Van Soest | Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition[END_REF]

. h COT were measured in residual leached solution after a leaching process for 24 h at room temperature. i n.d: non determined.

Table 2 .

 2 Minerals contents and efficiencies of the washing process.

	Raw fir
	(mg/

kg) Fir washing efficiency Raw beech (mg/kg) Beech washing efficiency Raw oak (mg/kg) Oak washing efficiency Al

		3	-10%	7	-5%	27	-1%
	Ca	893	-10%	2264	-4%	3247	-1%
	Fe	6	-5%	8	-5%	25	-3%
	K	279	±100%	1223	-90%	991	-70%
	Mg	68	-20%	386	-13%	136	-5%
	Na	<5	-80%	<5	-60%	6	±100%
	P	18	-59%	47	±100%	68	-36%
	S	50	-58%	115	-58%	158	-7%
	Si	683	-1%	194	-36%	47	-28%
	Zn	5	-14%	2	-4%	2	-3%
	Global extraction	/	-22%	/	-34%	/	-17%
	2.3. Combustion tests
	2.3.1. Experimental set-up platform
	The experimental combustion setup is schematized in the Fig. 2. Combustions tests were performed
	in a pellet stove supplied by Hoben (Model H5 Signature Color Steel), complying with the European
	standard NF EN 14785

Table 3 .

 3 Average values of combustion parameters.

			DIN+	Fir	Washed fir	Beech	Washed beech	Oak	Washed oak
	m a	(kg•h -1 ) 1.66 ± 0.05 1.45 ± 0.05 1.35 ± 0.05	1.42 ± 0.05 1.21 ± 0.05	1.93 ± 0.05 1.53 ± 0.05
	Tfume	(°C)	189	177	165	177	163	165	182
	O2	(%)	15.7 ± 0.1 16.8 ± 0.1 17.4 ± 0.1	16.8 ± 0.1 17.5 ± 0.1	17.2 ± 0.1 16.3 ± 0.1
	Air ratio	λ	4.8	5.0	5.9	5.0	6.2	5.6	4.5
	Ec b	(%)	78.2	77.2	69.7	75.5	69.5	74.6	75.3
	Poutput c (kW) 6.2	5.9	4.1	5.2	3.7	6.8	5.2

a Mass wood consumption rate. b Combustion efficiency.

c

  The whole system is connected to the sampling pump and the flow control device. A half of each filter and the XAD-2 resin (Restek -Ultraclean Resin) collected were submitted to a soxhlet extraction by dichloromethane/acetone (50/50) during 24 h. Condensates were treated by liquid/liquid extraction with dichloromethane only. These extracts were dedicated to the solid, gaseous and condensable (liquid as tars) PAH and phenolic compounds analysis. The other half of the filter was used to quantify the organic biomass combustion tracers (e.g. levoglucosan, mannosan, galactosan). It was sonicated in ethyl acetate during 1 h and then derivatized. The extracts obtained were concentrated under nitrogen flux and analyzed by GC/MS (VARIAN 3800/1200 TQ). Concentrations of CO measured during the combustion of non-standardized wood as leafy species (oak and beech) are higher throughout the process than those of coniferous mixture (DIN+) and/or raw fir pellets. The Table4details the influence of the washing process on emission factors of both gaseous and particulate pollutants. Mean values of CO for DIN+ and fir pellets are 193 and 330 mg•MJ -1 corresponding to high loads. Compared to mean values (95-150 mg•MJ -1 ) obtained by Boman et al. with a standard American pellets stove registered for high load of 5-6 kW with fir and spruce pellets, our emission factor values are in the range but remain quite high[START_REF] Boman | Stove performance and emission characteristics in residential wood log and pellet combustion, part 1: pellet stoves[END_REF]. Ozgen and al. obtained very low emission factor of 88 mg•MJ -1 after 1 h at nominal output with an automatic 8 kW pellet stove representing the Italian market[START_REF] Ozgen | Emission factors from small scale appliances burning wood and pellets[END_REF].

COV as BTEXT are trapped on TENAX cartridge, and aldehydes/ketones on DNPH cartridge connected to a sampling pump equipped with flow control device. TENAX cartridges are then thermally desorbed with a thermodesorber (Perkin Elmer TurboMatrix TD) equipped with a cold trap before being analyzed by GC/MS (PerkinElmer Clarus 680). DNPH cartridges are eluted with acetonitrile and then analyzed by HPLC coupled with a Photo Diode Array detector (Waters Alliance 2695/PDA 996).

3. Results and discussion

3.1. Effect of washing pre-treatment on standardized pollutants Fig.

3

presents the influence of the washing pre-treatment on CO concentrations and its comparison with French and European standards. Concentrations of CO are relatively high for raw biomasses except for DIN+ Certco pellets which are standard solid fuel used for standardized combustion tests on small domestic pellet stoves. The tests carried out with pellets of raw fir, beech and oak wood lead to concentration of CO Two to three times higher than DIN+ pellets results. Comparison of the real time concentrations of CO for both soft (DIN+) and hard (oak) wood pellets is given in the Supplementary Material.

Table 4 .

 4 Emission factors of gaseous and particulate pollutants.

(mg•MJ

-1 ) DIN+ Fir Washed fir Beech Washed beech Oak Washed oak CO

		193 ± 12	330 ± 15	225 ± 22	520 ± 16	396 ± 22	461 ± 18	239 ± 17
	NOx	80 ± 20	73 ± 25	70 ± 34	130 ± 26	120 ± 35	147 ± 30	136 ± 28
	TSP a	23 ± 3	17 ± 2	14 ± 2	57 ± 8	34 ± 3	49 ± 1	23 ± 1
	NMVOC (eq. CH4)	<LOQ b	13 ± 7	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ
	VOC (eq. CH4)	<LOQ	14 ± 7	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ

a Three TSP measurements. b LOQ was determined and is equal to 8 mg•MJ -1 .

Table 5 .

 5 Influence of the washing pre-treatment on emission factors of aldehydes and ketones.

	Compounds/woods	DIN	Fir		Beech		Oak
	(μg•kg -1 dw)	Certco	Raw Washed Raw Washed Raw Washed
	Formaldehyde	295	273 536	1312	1829	729 1140
	Acetaldehyde	271	1868 2341	3767	3116	1475 1317
	Acroleine+acetone	157	695 501	616	0	398 535
	Propionaldehyde	119	722 1000	1830	848	660 636
	Crotonaldehyde	0	0	0	630	3306	0	317
	Methacroleine + butanone 36	299 154	0	0	73	65
	Benzaldehyde	147	190 457	413	618	77	192
	Valeraldehyde	56	477 482	3080	80	0	0
	p-Tolualdehyde	233	0	395	132	849	0	1013
	Hexaldehyde	70	0	162	83	172	0	233
	Total	1384	4524 6028	11,863 10,818	3412 5448

Table 6 .

 6 Influence of the washing pre-treatment on total emission factors of PAH.

	Emission factors of PAH DIN+	Fir Raw Washed Raw Washed Beech	Oak Raw Washed
	Total (μg•kgdw -1 )	870	1570 560	630 590	440 380
	Evolution (%)	-	-64	-6		-14
	Total
	(eq. BaP) a	49.2	35.7 1.4	3.3	2.4	0.5	1.3
	(μg•kgdw -1 )
	Evolution (%)	-	-96	-27		+163
	a

Acknowledgments

The authors thank Mrs F. Proharam from the Agence De l'Environnement et de la Maitrise de l'Energie (ADEME) for the financial support of the PREPABOIS project (no 1501C0039), Sirs S. Labbé and F. Balay from LORFLAM industry and Mr N. Adam from AGRIVALOR industry. Appendix A. Supplementary data Download : Download Word document (224KB)


Pascale Coquard

Mady Guillemot

Arnaud Lelevé

Didier Noterman

Hcene Benmohamed

REMOTE LABORATORIES IN AUTOMATION: AIP-PRIMECA RAO ARI PLATFORM Remote Laboratories in Automation: AIP-Primeca RAO ARI Platform

Keywords: Education, Laboratories, Manufacturing automation, Remote handling

I.INTRODUCTION

For a few years, numerous educational institutions have incorporated tools based on Information and Communication Sciences and Technologies into their educative systems. These new tools contribute to a continuous improvement of educational practices. So, elearning solutions, which were at first essentially based on "abstract" education (online courses, virtual classrooms, e-projects, role-playing, ...), gradually spread to real hands-on activities through Electronic Laboratories (ELABs) [START_REF] Gravier | Distance Learning: Closing the Gap between Remote Labs and Learning Management Systems[END_REF]. ELABs are laboratory activities performed with the help of computers: to catch every variant of ELABs, Ref. [START_REF] Baccigalupi | Overview on Development of Remote Teaching Laboratories: from LabVIEW to Web Services[END_REF] offers an inventory of situations where ELABs occur, from local to distant learning, with or without tutor, with a real or a virtual appliance. This recent trend answers to a recognized need for such activities and enables real experimentation, more particularly in engineering, scientific and technical disciplines.

In this context, AIP-Primeca-RAO has been a pool of resources and competencies since 1987. It continually has made industrial equipment available to many high schools in french Rhône-Alpes Region and it has been playing the role of support for thorough trainings in industrial We thank our sponsors : Schneider Electric which provided the automation components, INSA Lyon and Rhône Alpes Region for their financial help.

engineering. The eight partner universities are also its main users, in Lyon ( [START_REF] Szafnicki | Remote Control of Manufacturing Systems-A Collaborative Course between Engineering Schools[END_REF][START_REF] Guillemot | Towards Remote laboratory platforms with dynamic scenarios[END_REF]. Since 2006, a growing need for laboratories about automation technologies (Programmable Logic Controller (PLC), Human Machine Interface (HMI) programming, Field Network (FN) setting, motion control, ... ) from different institutions and from Schneider Electric has led to build an offer of ELABs (ARI1 project) to its partners. The reasons and the main concepts of this project are described in section III.A To sum up, it consists of providing both local and distant access to sets of appliances (PLC+HMI+FN+Motion control). The means to teleoperate these appliances are currently available on-line from the AIP portal. The corresponding architecture is detailed in following sections of III. First use returns are commented out in section III.E.

In a near future, this platform will be completed with elearning software developed by LIESP e-learning team (former ICTT), to provide fully functional local and remote laboratories. This evolution is given in IV.

II.ELECTRONIC LABORATORIES

Electronic Laboratories can be divided in two main categories: Remote Laboratories (RLABs) and Virtual Laboratories (VLABs):  RLABs (sometimes called "web-based control"), offer remote access to real laboratory equipment and instruments in real time [START_REF] Bellmunt | A distance PLC programming course employing a remote laboratory based on a flexible manufacturing cell[END_REF][START_REF] Kikuchi | DVTS-based remote laboratory across the Pacific over the gigabit network[END_REF]. We include in this category situations where laboratories are local but enhanced with e-learning software. In this last case, laboratories are not remote any longer but reuse RLAB technology to provide a controlled access (mainly in terms of security) to local appliances. Main advantages of RLABs are the realness of systems learners work on. Their main drawbacks are based on a loss of observability (no direct system view : only through a webcam) and commandability (keyboard, mouse or joystick tools to drive remote system).



VLABs are based on simulations of real systems or phenomena such as for Ref. [START_REF] Goudos | Web based laboratory in electromagnetic compatibility using a Java applet[END_REF] and [START_REF] Kuester | A virtualized laboratory for earthquake engineering education[END_REF]. These simulations can be run directly on client host (learner computer) such as with Easy Java Simulation [START_REF] Grau | Virtual Laboratory for Modeling Systems: A Sustainable Approach[END_REF] but we could envisage server-side simulations when specific software or calculus power are required and not easily available on client side. Their main advantages are their scalability (no direct limitation of concurrent users) and their main drawback is that it is not a real system : it is a relatively realistic model of a real system. Notice that some RLABs may include Virtual Reality techniques such as in [START_REF] Lelevé | Towards Remote laboratory platforms with dynamic scenarios[END_REF]. One could suggest a third ELAB category: Hybrid Laboratories (HLABS), which combines advantages of both previous categories. In this sample, virtual system representation is offered to compensate for low quality video feedback : user can zoom and move around the virtual system which is synchronized with the real system in real time. Another aspect of HLABs is depicted in [START_REF] Saygin | A Web-based programmable logic controller laboratory for manufacturing engineering education[END_REF] where the evolution of the virtual system is compared to the one of the real system in order to focus on limitations of modeling.

More precise differences, advantages and drawbacks of RLABs versus VLABs have already been discussed in literature and more precisely in [START_REF] Corter | Remote versus hands-on labs: a comparative study[END_REF].

Applications of RLABs deal with electronics [START_REF] Rapuano | A Learning Management System Including Laboratory Experiments on Measurement Instrumentation[END_REF], automatic control [START_REF] Bauchspiess | Remote experimentation on a three coupled water reservoirs[END_REF], robotics [START_REF] Guimaraes | REAL: a virtual laboratory for mobile robot experiments[END_REF], ... but fewer with automation systems : [START_REF] Buhler | The Virtual Automation Lab-Web based teaching of automation engineering concepts[END_REF] (CAN fieldbus), [START_REF] Lelevé | Towards Remote laboratory platforms with dynamic scenarios[END_REF] (vertical store), [START_REF] Saygin | A Web-based programmable logic controller laboratory for manufacturing engineering education[END_REF] (conveyor) and [START_REF] Bellmunt | A distance PLC programming course employing a remote laboratory based on a flexible manufacturing cell[END_REF] (flexible manufacturing cell) who covered solutions for these kinds of systems.

Concerning engineering process of ELABs, we distinguish two software approaches for ELAB Human Machine Interfaces :

 reusing commercial software such as LabView ® [START_REF] Baccigalupi | Overview on Development of Remote Teaching Laboratories: from LabVIEW to Web Services[END_REF] or Matlab+Simulink ® [START_REF] De Magistris | A MATLAB-based virtual laboratory for teaching introductory quasi-stationary electromagnetics[END_REF]. These softwares now enable teleoperation of laboratory systems but this was not the case in the first times of ELABs;

 specifically designing one's own software such as for Ref. [START_REF] Andria | Remote Didactic Laboratory -G. Savastano : the Italian Experience for the E-learning at the Technical Universities in the Field of the Electrical and Electronic Measurements, Overview on Didactic Experiments[END_REF]. Current generation of research about ELABs is no more based uniquely on teleoperation of devices but it also takes care of actors (authors, tutors and learners) educational goals, from scenario authoring to experimental result reporting and evaluation, as for Ref. [START_REF] Gillet | Collaborative web-based experimentation in flexible engineering education[END_REF] and [START_REF] Rapuano | A Learning Management System Including Laboratory Experiments on Measurement Instrumentation[END_REF]. In this context, works on linking traditional Learning Management Systems (LMS) with ELAB Management Systems (ELaMS) are on way at LIESP and DIOM laboratories [START_REF] Gravier | Distance Learning: Closing the Gap between Remote Labs and Learning Management Systems[END_REF]. Another need for efficient RLABs has been explored in Ref. [START_REF] Callaghan | Paradigms in Remote Experimentation[END_REF]: collaborative group working and tutor driven experiences on a single remote system as for traditional on-campus based laboratories.

III.ARI PROJECT

B. Concept

This platform enables control of automation devices such as motors, motion drives, pneumatic actuators, ... by Programmable Logic Controllers through standard Field Networks. It has been designed into a modular architecture. Every module illustrates a common set-up including a PLC, a motion drive and remote I/O distributed on a standard field network (Modbus/RTU, Modbus/TCP, CanOpen, Profibus, Ethernet TCP/IP and ASi).

Every module (depicted on Fig. 1) is made up of : Nowadays, eight modules are locally available at AIP:

 two prototype modules (Modbus and Profibus (see Fig. 2).

 six modules of second generation:  1 Modbus (see Fig. 3) featuring also a motor starter and a gateway between Modbus/TCP and Modbus/RTU;  1 Profibus, with a touch panel;  1 Ethernet, with a touch panel;  1 Asi with Asi Safe equipment for "safety at work" management;

 2 CanOpen with a motor starter and an HMI. Thanks to Ethernet adapters, all the modules can be connected and synchronized together through the campus LAN, in order to create more complex architectures.

This platform is now partially available on line but, at term, every module will be available on line. Distant users gain access through AIP web portal 5 . Specific web services have been developed to manage and schedule access to these modules.

Global architecture is detailed in next section.

C. In Situ accessibility

A main room has been equipped with six new generation modules (see Fig. 4). Eight desktop PC are available to users. Every necessary software is freely available (Unity, Citect Scada, Vijeo Designer, Open Office, ...). A projector is available to tutors to display information on a collapsing projection wall screen.

D. Web functionalities

Access to the ARI platform is provided through AIP web portal (see Fig. 5) according to the user profile (visitor, student, tutor, administrator). Users such as tutors and administrators must be registered in AIP LDAP repository, while visitors and students must not. The portal is based on TomCat application server technology. Visitors must type in their name and email in order to have access to a set of demonstration resources (whenever they are not previously booked). More precisely, they gain access to a limited amount of time (60 minutes max) to a limited number of functionalities of the platform. After authentication into the intranet, tutors have access to functionalities as :

Once connected into the intranet, tutors can book some modules for their laboratories. They are provided:  booking forms to fill for one or more modules, out of the available ones and according to a time period;

 a personal schedule summing up their own bookings;

 the necessary documentation to help them in using available software and material Tutors can choose to set the mandatory password which will be used by their students to log into the laboratory intranet or use the automatically generated one. They may also add online documentation for their students (demonstration programs, complementary documentation, to-do lists, ...).

Students have to provide the password given by their tutor to gain access to a specifically booked module at a Once the user is connected to a resource, whatever profile he might have, he is led to a single screen shared between tree main frames :  a webcam view;  a help view (including documents, links, ...) and  a main applicative view. Inside a unique browser window, these frames can easily be minimized and resumed, in order to work with a unique maximized view, as soon as the need is being felt. Obviously, the main view automatically includes all the necessary laboratory software and remote widgets permitting to remotely test programs (see Fig. 6).

The documents (programs, reports, ...) produced during the session are either stored on the web server or downloaded on the local desktop.

PLC programming is performed with the help of Schneider Electric PL7-Pro (for prototypes and surface treatment modules) and Unity Pro (for other ones) programming software. This latter is compliant with IEC 61131-3 standard and it enables component based engineering. This software is installed on a Terminal Server Edition (TSE) on a Windows 2003 Server host, which permits distant users to use it remotely without having to install it on their own PC. This software also features a PLC simulator. The whole module can be simulated when Unity PLC simulator is run with a program which simulates operative parts. It then can be used to preventively test one's program before uploading it on the real PLC, through Ethernet LAN.

Once a program is uploaded, real time handling of each module is performed through a local touch panel HMI and also through a web version of the same HMI for distant users. These HMI are designed with the help of supervision software Vijeo Designer or Citect Scada.

A motorized web cam is set up on the ceiling of the main room. It enables a global view of modules or a single user to zoom on its own module.

The whole web architecture is based on J2EE technology. Web services enable a modular architecture able to be extended without having to redesign the whole web site from scratch. Active X components are used to gain web remote access to the Terminal Server in order to offer distant use of different softwares. This constrains every user to use Microsoft Internet Explorer.

E. Distant usage returns

2006-2007 academic year enabled to begin the deployment of prototypes for local and distant use with ASi, Modbus and Profibus field networks. 36 students (of Licence level) from Electric Engineering Department at University Lyon 1 (on the same campus) remotely used this platform. This first experimentation enabled us to validate first laboratory scenarios and led to make adjustments about distant means. For example, for laboratories open out of business hours, it is necessary to drive the surrounding lighting to be able to use efficiently the web cam... Tests at greater distances, from Nantes (650km) and Seville in Spain 1630km) showed us that such distances do not constrain the ergonomy in nomadic usages.

IV.EVOLUTION

A. Appliances

Some new modules will be developed to complete this set so that an entire class of students will be able to simultaneously perform their laboratory work. Moreover, modules are currently available only as single devices but the platform will provide the mean to book and use several linked modules.

B. Distant access

From technical point of view, we remarked that Active X components could be a constraint on student and tutor accessibility. A new version based on Web 2.0 technologies is under development to enhance accessibility.

C. E-Learning environment

At now, means to teleoperate modules are available but minimal learning support is provided to users (as tutors as learners).

We are going to implement works on generic ELAB scenarios from Ref. [START_REF] Benmohamed | Generic framework for remote laboratory integration[END_REF] to provide an ELAB Learning Management System (LMS).

1)Objectives

The aim of this evolution is to provide a way for authors and tutors, in one hand, to edit ELAB scenarios without requiring to be computer science specialists, and, in the other hand to avoid rewriting scenarios written for similar appliances (for instance, two optical benches with different control hardware but with same functionalities). AIP experience where many tutors from different universities use the same appliances but do not efficiently reuse previous common works, clearly demonstrates the need for a mean to reuse scenarios used with the same pool of appliances for different audiences.

2)Working

To do so, they will be provided an environment to edit scenarios for ELABs with the particularity that these scenarios will not be dependent of a particular appliance, but of a same class of similar appliances. These "generic" scenarios will then have to be automatically adapted into appliance specific scenarios to be used with a specific real appliance.

This automated adaptation will be performed by a middleware: an ELAB Management System (ELaMS) which is also used to route different users with their scenarios towards compatible appliances. This working is similar to the one of a printing service one can find in modern operating systems, delivering efficient printing through printer drivers.

Users will gain access to the platform through a standard LMS which will run scenarios. In this way, learners will be more finely guided during their lab work and tutors will be able to follow at distance how far learners have made headway. LMS can be also used to help in assessment. Fig. 7, 8 and 9 illustrate the life cycle of an ELAB scenario. It consists of four main steps, illustrated here with robotic appliances:

1. installation (see Fig. 7), by the ELAB manager, of a new appliance on the ELaMS platform; this new one belongs to an appliance class represented here by a robotic arm template. 2. Creation (see Fig. 8) by authors of generic training scenarios on an authoring tool; each scenario is linked to an appliance class. In actual fact, scenarios include an URL which link them towards the corresponding template and every appliance related actions (here : initialization, linear move, pick and place, ...) and data (status, position, ...) are targeted towards generic items of this template. 3. Adaptation (see Fig. 8), asked by a tutor and performed by ELaMS middleware, of a generic training scenario to a specific set of same appliances : from now on, every action and data are targeted towards real web services which will later deal requests to the right appliance in this set.

3)Technology

Concerning software technologies, scenario edition and running will make use of open source IMS-LD compliant software. Reload6 (A, B and C level compliant) will be used for scenario editing in a first approach but we are thinking of a web-based authoring tool such as the one of LAMS 7 (which is currently not IMS-LD compliant). Selection of available data and actions for a given template is now manually made but should be included in the scenario editor for efficiency reasons in the long term. Scenario player is Coppercore8 engine (A, B and C level compliant).

The middleware initially written in Java for template management and PHP for its Human Machine Interface will be provided as web services to form a global homogeneous application. Templates are coded in OWL 9Web Ontology language. Protégé10 software is used to edit templates.

Fig. 10 sums up the integration of ELaMS model in ARI platform : the LMS and ELaMS layers come on top of existing teleoperation one to bring didactic functions as for any distant learning environment.

V.CONCLUSION

This paper outlines ARI project at AIP-Primeca RAO where a platform including modular appliances featuring PLC and field networks is being built. These appliances are to be used in situ and at distance. The global architecture from client to PLC was depicted and evolutions to come were exposed. This architecture which now covers teleoperation layer will lead to a complete elearning platform enabling hands-on distant learning.



  a power supply area (circuit breaker, AC/DC converter and a safety monitor for Asi-Safe module);  a control area containing a PLC fitted with, in one hand, an Ethernet coupler featuring a web server to gain access from the web and, in the other hand, a field network adapter to communicate with distributed sensors and actuators. The whole is completed with a touch panel HMI;  a field part containing distributed I/O with preactuators, sensors, position encoders, ... , a motor starter, a motion drive and future equipments. Each module features at least an Altivar for motion control, an AC motor and distributed I/O. Modules are fitted with Schneider Electric Premium or M340 PLCs.

Figure 1 .Figure 2 .

 12 Figure 1. Module generic architecture

Figure 3 .

 3 Figure 3. Modbus module

Figure 4 .

 4 Figure 4. Main room with 6 modules

Figure 5 .

 5 Figure 5. Platform architecture  the list of existing resources and their status;  a prioritized access to a module, provided the resource is neither in use nor booked;

Figure 6 .

 6 Figure 6. Screenshot of current student interface to program a module

Figure 7 .Figure 8 .

 78 Figure 7. First step : appliance installation

Figure 9 .

 9 Figure 9. Step #4 : use of a scenario by several users

Figure 10 .

 10 Figure 10. Final platform architecture

  INSA, Ecole Centrale, Université Claude Bernard Lyon 1, ECAM, IUT Lumière of University Lyon 2) and in Saint-Etienne (ENI, Ecole des Mines, Université Jean Monnet Saint-Etienne). The resources at users' disposal are mainly composed of :

	 industrial equipment (such as CNC machine-tool, conveyors, assembly automation systems, robots, ...);

 computer systems featuring industrial software (Computer Aided Design (CAD), Computer Aided Manufacturing (CAM), Manufacturing Execution System (MES), process simulation, shop control, ...);  communication and cooperation systems (LAN, WAN access, video-communication, Computer Supported Cooperative Work (CSCW), ...). AIP has been studying solutions to promote laboratories to ELABs since 2000

  A. Initial need AIP has already studied collaborative means to help people to work together and at distance, more particularly on production systems. In this context, AIP launched in 2006 the ARI project in collaboration with 3 departments of INSA (Electrical Engineering, Industrial Engineering and Mechanical Engineering and Design), long life education center INSACAST and Schneider Electric. This project consists in building a technological platform featuring modern controllers and industrial networks with the aim to illustrate the concept of the "Transparent Factory": Internet-based technologies that provide seamless communication between plant-floor and business systems and improve collaborative management.This shared and centralized platform has been designed to be accessible at distance by every member educative institution and other socio-economic actors (partners and clients) in the frame of initial and long-life learning. This design is set up on the experience acquired during previous projects, more particularly with nomadic students working with CNED 2 institute.Needs from different partners are summed up here:

	 supply (to students alternatively in their enterprise and at school) of access to software and hardware resources, outside office schedules (night and week-end);
	 training cost optimization:
	 decrease of time when employees are away from their enterprise;
	 validation of prerequisites and check of appropriateness between trainee competences and training program before training periods;
	 access to the appliance after training periods to increase trainee acquisition of knowledge or to enable a preparation for an exam or a certification;
	 for partners:
	 supply of distant access to shared equipment;
	 development of a competent team federating the actors of education in the different institutes;
	 providing of a technological showcase to train experts and industrial managers about concepts of the "digital enterprise";
	 common needs:
	 decreasing of time spent in transports for far users;

 for initial learning (INSA, ECAM, ...):  development of student autonomy for self education;  experience of industrial software engineering (functional analysis, design, programming, control);  for long-life learning (alternate or continuous education: CNAM 3 , ITII 4 ):  raising of appliance busy rate.

ARI is a french acronym for Automation and Field Networks

Distance Learning Institute; see http://www.cned.fr/en/

Lifelong Learning Inst.: http://www.cnam.fr/42394825/0/fiche___pagelibre/

Lifelong Learning Inst.: http://www.uimm.fr/fr/reseau/contenu_ITII.html

See http://aipportail.insa-lyon.fr:8085/aiprao

See http://www.reload.ac.uk/ldeditor.html

See http://www.lamsinternational.com/

See http://coppercore.sourceforge.net/

See http://www.w3.org/TR/owl-features/

See http://protege.stanford.edu/

AUTHORS

P.

Coquard is engineer at AIP Primeca, Villeurbanne, France, in charge of communication towards users, information system management and administration (email: coquard@aiprao.insa-lyon.fr).

M.