Arias Barreto

Ivonne Rodriguez Donis

Vincent Gerbaud
email: vincent.gerbaud@ensiacet.fr

Xavier Joulia

Optimisation of heterogeneous batch extractive distillation Alien

Keywords: batch extractive distillation, heterogeneous entrainer, genetic algorithm

This paper considers the optimisation of batch extractive distillation, using heterogeneous entrainers for the first time. The objective function includes the maximum of overall profit and the optimisation variables are the entrainer flowrate and the reflux ratio that is an optimal combination of both decanted phases. Simulation and optimization is performed within MATLAB, by using a genetic algorithm coupled to a short-cut model of the distillation column. The performance of the optimisation scheme is illustrated through the separation of chloroform -methanol mixture with water considering either a constant or a piecewise constant policy for both optimization variables.

Introduction

Batch distillation becomes irreplaceable when it is necessary to treat small quantities of materials with a great diversity in composition. Azeotropic and extractive distillation processes are the most used processes for separating azeotropic or close boiling mixture, always involving the addition of an auxiliary entrainer. Although heterogeneous entrainer has been widely used in batch azeotropic distillation, it has only been recently considered for batch heterogeneous extractive distillation (BHED) of the chloroformmethanol mixture with water [1]. Continuous feeding of the heterogeneous entrainer allows the residue curve map saddle binary heteroazeotrope to be drawn at the top of the column. Besides, unlike to the homogeneous entrainer, the heterogeneous entrainer can be fed at the column top and the process takes place with an extractive section only. The following operating steps for BHED were considered in this work: (T1) start-up of the column at infinite reflux, (T2) filling the top decanter along with continuous feeding of the entrainer F E (T3) total reflux operation keeping the continuous feeding of the entrainer (F E ) until the unstable node is replaced by the saddle binary heterogeneous azeotropic mixture (T4) operation at a given R' together with F E until the still is depleted of the immiscible key component (T5) separation between the remain homogeneous component and the entrainer at R" without F E . The top decanter is considered as a total condenser with a significant liquid hold-up. Both decanted phases can be refluxed and also supplement the entrainer feeding at the column top.

A stochastic optimisation method, genetic algorithm real-coded in MATLAB, is used along with the simulation of the BHED considering the short-cut modelling with the typical assumptions: theoretical plates, negligible pressure drop and liquid hold-up on the trays and constant molar overflow. The global optimization problem is decomposed into a series of independent single optimizations, each one related to an operating task and considering the same objective function. Preliminary parametric studies have demonstrated that the reflux ratio (R') and the entrainer flowrate (F E ) are the variables having a key incidence over the overall profit of the BHED. Mujtaba pointed that the optimal overall profit in homogeneous BED is mainly determined by assuring optimal values for F E and R' in the task (T4) [2]. If unlimited capacity in the boiler is taken into account, optimization of task (T3) is not necessary because the operating time for setting the binary heterogeneous mixture chloroform -water at the top of the column logically decreases when F E increases. Hence, this work is devoted to optimization of task (T4) related to the withdrawal of the heterogeneous key component to improve an overall profit function. A constant value and, also, a piecewise constant policy considering two intervals of time for F E and R' will be considered. We solve the optimisation problem considering all combinations for F E and R'.

Optimization problem formulation

Case of study: Separation of chloroform -methanol azeotropic mixture

Optimisation problem formulation concerns to the separation of azeotropic mixture chloroform -methanol which is widely used for separating bioactives substances from biological sources. Water was shown to be an effective heterogeneous entrainer [1]. Thermodynamic and topological features of the resulting ternary system are shown in Figure 1 including the univolatility curve chloroform -methanol ( 12 ). Thermodynamic calculations were done by using Simulis®Thermodynamics, a thermodynamic property server available in Microsoft Excel [3]. NRTL was chosen as thermodynamic model with literature binary coefficients [1]. As explained [1], because the univolatility line  12 =1 ends at the chloroform -water edge, the saddle binary hetero-azeotrope chloroform -water can be drawn as a vapour overhead at the column if water is fed continuously at the column top generating two liquidliquid phases into the decanter after condensation. The heavy chloroform-rich phase (x II = x D ) can be drawn as distillate product whereas the water -rich phase (x I ) or a mixture composed by both decanted liquid phases can be refluxed toward the column top.

56.3°C [S1]

12

Unstable Separatrix

Feasible Top Region

Figure 1. Chloroform -methanol -water residue curve map 2.2 Modelling of heterogeneous BHED by short-cut model

Dynamic behaviour of BHED is described by the following differential and algebraic equations:

-Boiler mass balances:

D F dt dB E   ( 1
)

) x x ( B D ) x x ( B F dt dx II B B FE E B     where V ) )( ( D      1 1 (2)
-Extractive liquid profile inside the extractive column section (differential mode proposed by Lelkes et al. [4]; column with significant height)

*) y y ( L V dh dx i i i   (3)
* i y is determined applying the modified Rachford-Rice procedure for a three-phase mixture as the vapour phase selected as a reference phase. 0 1 1

1 3 1 3 1         c Phases ij j ij i ) K ( ) K ( z  (4)
 i is the molar amount of each phase, z i is the molar phase composition and K ij is the equilibrium coefficient. The operating vapour composition y i can be expressed in terms of R' and F E /V as:

FE E II i E i x V F x ' R x ) V F ' R ' R ( y       1 1 1 (5)
Usually, BHED involves a reflux combination of the whole water-rich entrainer phase L I along with a portion "" of the chloroform rich-phase L II . The proportion of L I and L II inside the decanter is determined by the liquid -liquid splitting ratio . Therefore, the total reflux liquid L R =L I +L II . The reflux ratio can be determines as:

) )( ( ) ( ' R           1 1 1 (6)

Objective function and constraints

Optimization problem will deal with the maximization of the overall profit of the process and it can be formulated as following:

  ) T ( " R ), T ( ), T , T , T ( F ) t ( * C S * C D * C D * C OP min E total f S 5 4 4 3 2 2 2 1 1       (7) St. 99 0 4 . ) T ( x chloroform D  99 0 5 . ) T ( x methanol D  Re i > 0.90
Where Re i is the recovery yield for component i. If one phenotype of the population doesn't fulfil any constraint, the associated OP takes the mandatory value of 10 6 . C 1 (3.012 $/mol), C 2 (0.5085 $/mol) and C S (0.001 $/mol) are the prices of the products chloroform; methanol and the make-up of water, respectively. C f (0.0027 $/min) is the total operating cost of a real bench column. Optimisation using some market product prices revealed a non sensitive effect for a given C f . It was also assumed that the possible off-cut product (ternary heteroazeotrope) is not a commercial product and it can be recycled to the next batch. The optimization variables are the ratio (F E /V) for tasks T2 T3 and T4 and the reflux policies R' for task T4 and R" for task T5. The aim of the optimization is searching an optimal value of (F E /V) along with a comparison between a constant reflux ratio and a piecewise constant reflux policy considering two time intervals. If off-cut operation is required, reflux ratio is set at unity in order to reduce the chloroform molar content into the boiler lower than 0.01. Genetic algorithm real-coded in MATLAB is used as optimization method. The initial population was set at 50, the selection rate is 0.8 and the mutation rate is 0.01. The optimization is stopped if no improvement of the objective function is achieved after 10 generations. Bounds for the optimization variables are: 1.4(F E /V)2 and 0.40.9 for chloroform recovery and 1R"10 for the separation of methanol -water. Those bounds for (F E /V),  and R" were taken from previous study according to the purity product constraints [1]. Optimisation by genetic algorithm comprises a large evaluation of the objective function including the solution of the dynamic model. Use of short-cut model allows a good approximation of the optimal operation conditions with less computational effort and time. The optimal results obtained by simplified method is validated by rigorous simulation using ProSim Batch for all optimal cases.

Results and discussion

Optimization of the BHED was performed considering several cases: -Case I: (F E /V),  and R" constant; -Case II: constant (F E /V) and piecewise constant  for two time intervals -Case III: piecewise constant (F E /V) and  for two time intervals. Operating conditions for simulation of the separation of chloroform (1) -methanol (2) with water (3) are: initial charge (20 mol), composition charge (x 1 =0.2704/ x 2 =0.6714/ x 3 =0.0582), decanter holdup (1 mol), vapour flow (0.016 kmol/hr) and column pressure (1.013 bar). Real mixture to be separated contains a little amount of water. Table 1 displays the optimal values for (F E /V),  and the respective R' for cases I, II and III along with the objective function for simplified model OP SM and rigorous simulation OP RS and the total operating time. Profitability for cases II and III are similar and they are about 24 % higher compared to case I. Case III, implementation of piecewise constant policy for F E together with  during the withdrawal of chloroform, is the best option because chloroform can be drawn with high purity without increasing the time compared to case II and maintaining the recovery yield. But case II will be preferred for a simpler control of the BHED. Simulation results using the short-cut model are presented in table 2, setting the constraint purities as ending criteria for the concerned task. The optimized variables provided the specified purity and recovery requirements, in particular enabling to achieve significant recovery of the products while maintaining their purity, thus demonstrating the interest of the BHED process. They were in agreement with the experimental validation done in ref. [1]. For all three cases, better than 0.99 molar fraction of chloroform is achieved in the heavy liquid phase into the decanter at the end of task T2 by filling the decanter while feeding the entrainer. Therefore, typical operation at total reflux and F E >0 (task T3) was not necessary. On the other hand, the off-cut operation task is almost negligible for case I. In our study, the cost of the raw material has not been included. It would lower the OP and improve the case I performance and lower the cases II and III. Table 2 also presents the rigorous simulation using BatchColumn® [3] with column features taken from literature [1]: assumptions of negligible liquid hold-up and pressure drop inside the column were considered. Distillation column was considered having 45 theoretical plates with the entrainer fed at the column top. Figure 2 displays the trajectory of the composition into the still for all studied cases involving steps T2, T3 and T4. The break point for changing  and F E /V is pointed for cases II and III as well.

Start-up of the batch column is done at total reflux without F E (task T1). The filling-up of decanter (task T2) shows identical still path for all reflux policies. The filling of the decanter (cross line in Figure 2) was performed until the boiler compositions were similar to those computed by the short-cut method taking about 0.13 hr for all cases.

Then the chloroform-rich phase was drawn as distillate until its average purity was 0.99 (task T4). The operating total time for task (T4) agree well to those determined by shortcut method. In all three cases, the recovery yield of chloroform was higher 99.5% and no off-cut step was necessary. Due to this significant chloroform recovery yield, less difference of OP (approximately 15%) was obtained by rigorous simulation between case I and the other cases than for the short-cut model optimization (Table 1). Figure 2 displays the trajectory of the still during the withdrawal of chloroform-rich phase (task T4). Good agreement was obtained between short-cut model results (continuous lines) and rigorous simulation results (symbols). Rigorous simulation of the separation of methanol -water (task T5) led to similar results of R", time, methanol purity and methanol recovery for all three cases (Table 2). Finally, the entrainer water recovery yield was higher than 98%, with a molar purity around 0.988 retained into the still at the end of the process. These results indicating that optimal operation of BHED is mostly determined by operating variables associated to the separation of chloroform, F E /V and the portion of chloroform rich phase (α) in the top reflux ratio R'.

Conclusions

Optimal operating values for reflux ratio and entrainer flowrate have been determined using the genetic algorithm implemented in MATLAB and connected to a short-cut model for simulation of batch heterogeneous extractive distillation. Three operating alternatives have been considered, combining either a constant or a piecewise variation with two time intervals for both optimization variables; the entrainer flowrate F E /V and the amount () of the chloroform-rich phase returned to the column top from decanter along with the entrainer phase reflux.

The best profitability were achieved with piecewise constant F E /V and , with a 25% better OP than for constant F E /V and . Constraints of purity and recovery for both distillate products were met for all operating alternatives. Good agreement of rigorous simulation results taking the optimal conditions demonstrated the convenience of using the short-cut model along with genetic algorithm in order to accelerate the preliminary optimization analysis. Perspectives concern the incorporation of the energy balance to study the effect of the entrainer and decanter temperature.

Figure 2 .

 2 Figure 2. Comparison of still path computed by short-cut model and rigorous simulation.

Table 1 .

 1 Summary

			of the optimization results
	case	F E /V		R" time (h)	OP SM	OP RS
	I	1.74	0.823	8.2	9.15	20.74	19.1
	II	1.78	0.5751, 0.8468	7.8	8.16	25.23	21.9
	III	1.67, 1.85	0.6159, 0.8866	7.7	8.3	25.86	22.04

Table 2 .

 2 Simulation Results of each operating tasks (short-cut model)

		case	Rigorous	case	Rigorous	case	Rigorous
		I	simulation	II	simulation	III	simulation
	time decanter filling (h)	0.13		0.13		0.13
	x D1 in decanter (task T2)	0.9945		0.9967		0.9981
	time of task T3 (h)	0		0		0
	switch time in task T4 (h)	-	-	0.55	0.55	0.685	0.685
	time of task T4 (h)	2.02	1.93	1.3	1.33	1.57	1.52
	x D1 in chloroform tank I	0.9911	0.99	0.9931	0.99	0.9981	0.99
	chloroform recovery (%)	91.5	99.6	93.7	99.8	93.0	99.81
	off-cut time (h)	0.02	0	0.25	0	0.18	0
	time of task T5 (h)	7.0	7.06	6.7	6.88	6.6	6.3
	x D2 in methanol tank II	0.9901	0.99	0.9901	0.99	0.99	0.9901
	methanol recovery (%)	94.0	95.1	96.8	96.0	96.3	96.6


Kristina Markulin
email: kristina.markulin@iqs.url.edu

Britta Eyrich Jessen

Ignasi Florensa

Britta Eyrich Jessen²

Cross disciplinary characteristics of study and research paths: statistics for business administration

Keywords: cross-disciplinarity, statistics for business, study and research path, teaching and learning of mathematics in other fields, novel approaches to teaching

INTRODUCTION

Traditionally, statistics has been taught in a lot of different university degrees and has recently gained more prominence in numerous professional areas. The importance of information technologies is growing [START_REF] Nolan | Computing in the Statistics Curricula[END_REF], and so are the proposals for training students to gain computational and statistical competencies. As a consequence of the technological development in the past decades, a large number of statistics educators have embraced pedagogical novelties in their teaching. Projectbased learning (PBL) [START_REF] Batanero | El sentido estadístico y su desarrollo[END_REF] in particular has been promoted as a design tool for nurturing reasoning in a statistical context [START_REF] Wild | Statistical thinking in empirical enquiry[END_REF]. PBL is widely present in the literature on statistics teaching (Markulin et al., 2021a), and is commonly described from the perspective of the area of statistics and more general pedagogy.

The numerous implementations of project-based proposals present different characteristics depending on the way statistical knowledge and professional activity are conceived in each institution. Several designs of so-called study and research paths (SRPs), framed within the Anthropological Theory of the Didactic (ATD), have been implemented in statistics, in other disciplines, and in cross-disciplinary contexts at the university level (e.g., [START_REF] Barquero | Study and research paths in the frontier between paradigms[END_REF]. The main aim of SRPs is to support the development of student knowledge in an area of study by posing meaningful and challenging generating questions to students [START_REF] Jessen | How can study and research paths contribute to the teaching of mathematics in an interdisciplinary setting?[END_REF]. According to [START_REF] Barquero | Using research and study courses for teaching mathematical modelling at university level[END_REF], it is important for the generating question to be "of real interest to the students ("alive")" (op. cit., p. 2052).

Considering the recent developments both in business and in statistics, a subsequent question is: What and how to teach Business Administration students? In other words, the organisational goal of PBL and SRPs needs to be adapted to the topic and complexity of the degree in which those tools are implemented to be in line with its specificities. In the following sections, we present the ATD as the framework to analyse the modelling aspects of the proposals. We describe the implementation of SRPs in a statistics course for a degree in Business Administration and explore some issues regarding cross-disciplinary collaboration when designing and implementing an SRP, and how it is perceived by the students.

THEORETICAL FRAMEWORK

Within the field of mathematical modelling, a dominant approach to its teaching and learning is modelling when addressing a real-world problem, transposing it to the realm of mathematics, and addressing the mathematical problem before moving it back to the real world validating the result found in the process [START_REF] Niss | The learning and teaching of mathematical modelling[END_REF]. However, this approach might not capture important aspects of the real modelling activity, as it takes place in the workplace [START_REF] Frejd | Mathematical modelling as a professional task[END_REF]. Some of these aspects were analysed in a study by [START_REF] Serrano | Fitting models to data. The mathematising step in the modelling process[END_REF]. The authors argued that the SRP implemented on the sales forecast of a fashion brand shows the intertwinement of the extra-mathematical and mathematical (or statistics) domains when fitting real data and real-world problems in one-variable functions.

Initially, SRPs were proposed by [START_REF] Chevallard | Vers une didactique de la codisciplinarité[END_REF] as a way to design the crossdisciplinary projects introduced into French secondary schools [START_REF] Winsløw | Study and research courses as an epistemological model for didactics[END_REF]). An SRP is initiated by posing a generating question Q 0 to students, who consider it real [START_REF] Barquero | Using research and study courses for teaching mathematical modelling at university level[END_REF], and worth pursuing, though they cannot answer the question immediately [START_REF] Jessen | How to generate autonomous questioning in secondary mathematics teaching?[END_REF]). To answer the question, they need to engage in the processes of study and research. The study process is characterised as the study of new knowledge, which the students decompose. This means they need to understand what it is made of, how it can be used, etc. During the research process, the students reconstruct the new knowledge (in combination with existing knowledge) into partial answers to the generating question [START_REF] Jessen | How to generate autonomous questioning in secondary mathematics teaching?[END_REF][START_REF] Winsløw | Study and research courses as an epistemological model for didactics[END_REF]. Furthermore, we can see this as a process where students pose derived questions Q' to the generating question, which they construct answers to through study and research processes. Thus, the generating power of Q 0 can be considered as the degree to which it invites students to pose such derived questions. [START_REF] Winsløw | Study and research courses as an epistemological model for didactics[END_REF] depict this dynamic through a question-answer map presented in Figure 1.

When working with SRPs, the intertwinement of the domains involved in a modelling activity is reflected in going back and forth between questions and answers, between study and research. Moreover, we see this interconnection in cross-disciplinary SRPs, when an answer in one knowledge domain leads to a question in others. This can be seen in the SRPs analysed by [START_REF] Jessen | How can study and research paths contribute to the teaching of mathematics in an interdisciplinary setting?[END_REF] on mathematics and biology, where answers in biology turned into questions regarding differential equations in mathematics.

Figure 1: An example of a question-answer map (Winsløw et al., 2013, p. 271).

CONTEXT OF THE STUDY

We analyse the organisation of three SRP implementations in a statistics course in the second year of a bachelor's degree in Business Administration. Each of the implementations, during academic years 2019/20, 2020/21 and 2021/22 had its peculiarities concerning the topic of the project, the scope of the data to be gathered and analysed by the students, and the logistics of the implementation modality due to the COVID19 restrictions. However, the characteristics common to all the implementations were the collaboration with researchers in marketing, the existence of a "client" that was the facilitator of the project topic, and students organised in teams of 4-5 members acting as consultants for the client. More about the topics and the SRP implementations can be found in [START_REF] Markulin | Un recorrido de estudio e investigación para la enseñanza universitaria de la estadística[END_REF]Markulin et al. ( , 2022a[START_REF] Markulin | The evolution of a study and research path in Statistics[END_REF].

RESEARCH QUESTION AND METHODOLOGY

Our work contributes to broadening the scope of SRPs in the domain of statistics in a Business Administration school by analysing constraints and conditions seen from the perspective of students on cross-disciplinary projects. The SRPs presented are implemented in a statistics course, although they could be implemented in other disciplines, encouraging different perspectives from which a certain project can be conceived. In this respect, we formulate our research question (RQ): RQ: How can cross-disciplinary collaboration foster the management of a project in a statistics course in a Business Administration degree?

We will consider the issue from the macro-didactic perspective by analysing the collaboration of statistics lecturers and students, researchers in marketing, and external clients that are not usually involved in the education system. The approach we take is a qualitative analysis based on post-project interviews with the students. We comment on the experience of the project implementation, and finally, contrast it with the statistics students' reflections on the cross-disciplinary characteristics of the SRPs.

The post-project communication with the students is organised as semi-structured interviews, designed by a statistics teacher that also assumes a position as a researcher in didactics, together with five or six students. The students who participate in the interviews represent the students' working teams that participated moderately or actively in the project (according to the teacher's perspective and the students' final grades in the statistics course). The interviews are approximately 30-40 minutes long and structured according to the hypotheses on the SRP development put forward by the teacher-researcher in didactics. As shown below, the interviews are structured in such a way that broader problematic issues than simply the research question of the SRP addressed in this paper are analysed. The hypotheses (H) behind the interview script consider the: H1. Generating question and project aim. The project comes from an external client who also presents the topic to the students. The generating question is a problem to be solved by student teams and is presented to an assessment jury at the end of the project to add realism to the project. An issue to discuss is the pertinence of the generating question, its driving force throughout the inquiry, and the extent to which the final answer presented by the students provides valuable information to the client.

H2. Project survey and data collection. The design of the project survey that students use for data gathering, the understanding of its components and its use to provide meaningful data to be analysed takes place in the interaction between statistics, marketing and the client's needs and possibilities. The interest in discussing its components is threefold: describing the students' involvement in the design part of the survey; the adoption of its raison d'être that fosters the arborescence of the derived questions to be statistically analysed; the insight into the challenges that students encounter when collecting data and the solutions they propose or implement to overcome the obstacles in such a "rudimentary" activity of collecting raw data and cleansing it before the statistical analysis. This is not usually part of a project students would expect in a statistics course but is essential for the profession of statistics.

H3. Integration of the SRP in the statistics course. The SRP is part of the statistics course, but the course is organised for the SRP to be its central activity. The classes preceding the project are organised in bi-weekly (14 days long) case studies or topicrelated exercises that prepare the ground for the SRP to be implemented. The main issue of this section is the students' perspective on the integration of the SRP into the structure of the course. The connection between the bi-weekly studies and the project can be appreciated by recognising the importance of the provided software tools and knowledge for the project work, inquiry strategies developed before or during the project, cleansing the data, raising questions and synthesising results. A more detailed description of the interview design and the hypotheses supporting the script are described in [START_REF] Markulin | Un recorrido de estudio e investigación para la enseñanza universitaria de la estadística[END_REF]Markulin et al. ( , 2022a)).

Even though the different SRPs were implemented in the classroom under the guidance of the statistics teachers only, they were prepared thanks to the cross-disciplinary collaboration mentioned earlier. After analysing the students' interviews and identifying indications related to cross-disciplinary issues, especially concerning the first two hypotheses mentioned above, we present three moments in which collaboration is key: 1) agreement with the client, 2) design of the survey for data analysis, 3) understanding and exploiting the survey.

SRP EXPERIENCE AND DISCUSSION

The first moment: agreement with the client Once a client willing to collaborate on the project is found, chronologically, the first step is to explore the potential of the problem's generating question. Figure 2 is an example of a statistics teacher's a priori test of a potential topic for the third SRP implementation. It can either be developed visually in a question-answer map (we tend to include only the questions in this kind of map, while the answers remain implied), or elaborated as a list of topics that can be derived from the initial generating question. The generating question is Q 0 : "What are the consumer habits and preferences of young people in Spain about sustainability, digitalisation, and leisure time?" The derived questions focus on sustainability issues (Q 1 ), experiences with digital services (Q 2 ), and leisure-time habits (Q 3 ). We will not go into detail about the map components in Figure 2, since it is not the focus of this paper, but the full text of the questions can be found at https://rb.gy/uzez4y. We will consider the moments based on collaboration. The first one is the final agreement with the client. It is worthy of note that, even at this early stage, the statistics teacher tends to leave the boundaries of the discipline to embrace the context of the potential data (something the students will eventually do as well once they start inquiring about the matter). The planning of the project development and its main focuses take place at the same time as the agreement with the client. Then, some of the SRPs trajectories proposed by the teacher are discarded, while new ones gain importance. This teacher-client communication is a pre-test of the communication that the client will later have with the different student teams. This interaction leads to improvements in the a priori analysis and adjustments are made to the teaching design, hence changing the focus of the data analysis at a later stage of the project. Moreover, this makes the situation more akin to genuine business practices.

The topic of the first SRP was vegetarian and vegan diets. Students found it interesting but were not very familiar with it. An illustrative example of this distance from the topic is the statement of one of the students:

Student A: The topic is actually really good and interesting and the things we could see were really interesting, but it affects just a small group of people.

The second implementation concerned an SRP on a less restricted population, but it was locally oriented and about an initiative, the students did not know well -a cooperative supermarket looking for its optimal first location in Barcelona. The statement of one of the students reveals this fact:

Student B: I think it was an interesting topic, different from what is normally dealt with in some projects by better-known brands or companies… I think it's a way that helped us to do a bit of market research, which, in the short term, will be something that we will have to do.

The third implementation was a collaboration with the marketing department of an international company about the attitude of young people in Spain towards sustainability. Thanks to the experiences from previous years, the interaction between the client and the students were given more importance in this implementation. Apart from the client presenting the project topic and ideas, an additional online meeting session with the client was scheduled. During that session, each student team met with the client. The students abandoned their role of "students" and adopted a more professional attitude. This was observed especially in those student teams that abandoned some of their initial problem proposals and redirected their inquiry adjusting it to the client's needs.

Student C: At the meeting with the client, we presented our team's ideas on which to focus our analyses during the project. However, she told us to pursue certain ideas we presented, but also to discard some of them. We realised that not everything we proposed was interesting to her. We continued the analysis based on what the client suggested.

In the implementations where such interaction between students and the client during the project development was not possible to organise, the students sometimes tended to support what they considered to be the teacher's proposal at the expense of what was relevant to the client.

The second moment: design of the survey for data analysis

The second stage that requires collaboration outside the area of statistics is the design of a survey that will be used to gather the data for the project. It is a delicate moment since its production will directly affect the students' work and potentially create extreme actions, as we will show in the discussion on the impact of the collaboration of the third moment. Here, the statistics teacher teams up with researchers in marketing at the same business school. This collaboration is beneficial to both sides: the statistics teacher ensures the data to be gathered using the survey will suffice for the project's goal; the researchers in marketing get involved in a study in their area of interest and possibly enlarge their contribution to marketing research literature based on the ideas and results obtained from the Statistics project.

In the SRP implementations presented in this paper, most of the survey design responsibility was assumed by the researchers in marketing. They engaged in the survey design in teams. The teams differ slightly every year but mostly consist of one experienced researcher and two young researchers (PhD candidates at the business school where the Statistics course and SRPs took place). In the first SRP implementation, the survey was completely done by the marketing experts, since they were the initial "client". In the second implementation, the survey was designed in collaboration with researchers in marketing, the client, and the statistics teachers. In the third implementation, the survey was the final product of the collaboration between everyone involved in the project: researchers in marketing, the client, statistics teachers, and the students.

However, in the second implementation, when there was a chance to engage more with the client who posed the generating problem, the students hesitated to take part in the survey design. The following statement of one of the students shows that designing the survey might cause a feeling of uncertainty.

Student D: If you had asked me to do it [design the survey] at the beginning or in the middle of the course, maybe I would have posed questions that at the end would be of little use for my analysis.

It seems the students lack knowledge, or confidence, to master the task of developing a survey to be statistically exploited. It is a challenge to statistically model a problem from the marketing domain. Collaboration with the researchers in marketing is, therefore, necessary and supportive for both students and statistics teachers.

The third moment: understanding and exploiting the survey Students are the ultimate "miners" of the project survey. They are supposed to collect the data, clean them, and analyse them. Those actions are very common in contemporary business environments, in data science laboratories, and even in numerous professions remotely relying on statistics. However, most of the PBL literature focuses on competencies in data analysis and does not question the origin of the data and the cleansing process (Markulin, 2021a). In the SRPs here presented, the data origin appears to have stimulated even some lower achieving students to engage in the project, as student E states:

Student E: …for the first time I think we have been able to work and contribute to a project that has not only been an ordinary task, but a real case…we realised that our work could provide something to the client.

According to the students' comments from the first two SRP implementations, the external origin of the survey caused certain detachment, even for high achieving students, such as Student F. Some radically stated that it would have been more useful if they could have used their own surveys (Student G), which might also be a sign of difficulties in recognising the relevance of the data coming from an external survey.

Student F: I think the survey was super long. That's why I suppose we couldn't analyse everything.

Student G: If we could start from the beginning and ask the questions that we want to answer from our data, it would have been clearer and more realistic.

Nonetheless, the process of cleansing and analysing the data eventually allowed the students to become familiar with the survey blocks and to start appreciating the design they were asked to follow. Student A describes this progressive process as follows: Student A: For example, when we got the answers and we started analysing the data, we saw that the survey was even clearer than we thought because there were correlations [between the answers to different questions in the survey].

It appears that the inclusion of external clients and survey facilitators represents both a productive condition and a challenging constraint for the students. In any case, this kind of organisation is the closest to a business environment that the teachers could have organised in a university setting under given conditions.

CONCLUSIONS

As shown in the previous section, the three phases involving the design and implementation of the SRP (agreement with the client, survey design and survey exploitation) lead to different levels of cross-disciplinary collaboration. Firstly, the existence of an external client generates two significant interactions, one between statistics teachers and the client in the first steps of the SRP, but also between the client and statistics students. As stressed earlier, the existence of a real client fostered the engagement of the teams. This phenomenon is already described in terms of adidacticity of the SRP by [START_REF] Barquero | Study and research paths in the frontier between paradigms[END_REF]. It concerns observations on how the existence of an external client can favour the conditions under which the development of a final answer becomes the central activity during an SRP [START_REF] Bosch | Real or Fake Inquiries? Study and Research Paths in Statistics and Engineering Education[END_REF]. Consequently, there is a shift of the main purpose of the activity from the academic aspects such as course evaluation towards the production of reports for the clients.

Secondly, the interaction between marketing researchers and statistics teachers helps overcome the so-called thematic confinement [START_REF] Barbé | Didactic restrictions on the teacher's practice: The case of limits of functions in Spanish high schools[END_REF], that often exists in school institutions. However, this cross-disciplinary collaboration is still limited: marketing researchers that are also teachers in the same institution do not incorporate the survey design in their teaching activity. This reveals a clear restriction at the pedagogical level: the SRP is only implemented in one course. We think that an open issue of this research is related to the analysis of the restrictions hindering these cross-course collaborations to explore the ecological viability of crossdisciplinary SRPs.

Finally, the existence of different actors involved in the SRP design and implementation is an important challenge. The interactions between students, researchers, clients, and teachers need to be organised during the a priori and in vivo analysis of the SRP. This is often a new activity for lecturers that might find institutional tools to enable collaboration.

H4.

  SRP organisation and management. The SRP implementation during the statistics course, its development in student teams, the submission of the students' intermediate analyses reports, and the students' presentation of the final results as a poster or a slide show in front of the entire class are the organisational characteristics that are the most closely connected to pedagogical and school interventions.

Figure 2 :

 2 Figure 2: A priori question-answer map for the third SRP implementation

Acknowledgments

Funded by the Spanish R&D Projects: RTI2018-101153-B-C21 and PID2021-126717NB-C31 (MCIU/AEI/FEDER, UE).


PONTALIER Evon Philippe
email: philippe.evon@ensiacet.fr

Rigal Luc

BIOREFINERY OF SUNFLOWER WHOLE PLANT BY THERMO-MECHANO-CHEMICAL FRACTIONATION IN TWIN-SCREW EXTRUDER: REPRESENTATION OF LIQUID/SOLID TRANSPORT INSIDE THE BARREL

Biorefinery of sunflower whole plant can be conducted with water by thermo-mechanochemical fractionation in a Clextral BC 45 (France) co-penetrating and co-rotating twin-screw extruder. An extract and a raffinate are produced separately and in a single continuous step. The arrangement of screw profile makes possible to define three successive zones along the barrel, in which the three unit operations of the aqueous extraction process are taking place. (I) The grinding zone consists of a succession of 10 monolobes paddles, and 5 bilobe paddles. It ensures the conditioning and the grinding of solid matter. (II) The extracting zone begins with water injection. It is composed of a second series of 5 bilobe paddles to mix liquid and solid. (III) The pressing zone is the place where liquid/solid separation is realized. Screw configuration is then arranged with reversed pitch screws used to place pressure on the liquid/solid mixture, and positioned immediately downstream from a filter section. Representation of liquid/solid transport inside the barrel is performed thanks to (i) the measuring of the filling of each screw element after visual observation, (ii) the characteristics of the corresponding solid, and (iii) the modelling of the contribution of each screw element to the residence time distribution of solid and liquid phases. Consequently, twin-screw extruder can be represented as the association of a grinder, a liquid/solid extractor, and a liquid/solid separator, in which material exchanges are intensified. Thus, it is possible to predict the evolution of mean residence times of liquid and solid in the three zones of twin-screw extruder with the main operating variables: screw rotation speed, and inlet flow rates of whole plant and water. The decrease of both screw rotation speed and inlet flow rate of whole plant, simultaneously with the increase of inlet flow rate of water, causes the increase of liquid to solid ratio in the extracting zone, and the increase of residence time of solid in the pressing zone. These operating conditions (60 rpm for screw rotation speed, 5.0 kg/h and 20.3 kg/h for inlet flow rates of whole plant and water, respectively) are favourable to an efficient contact between liquid and solid (8.2 for liquid to solid ratio), and to the liquid/solid separation (156 sec for residence time of solid inside the separator). Oil yield is then around 55%, and residual oil content of the cake meal is only 13% of dry weight. The oil is extracted in the form of oil-in-water emulsions. The emulsion stability is ensured at interface by surface-active agents: phospholipids, proteins, and pectins. Extracts are also made up of a hydrophilic phase. This major fraction contains water-soluble components: proteins, and pectins. Raffinates are rich in fibres, and they have also a significant content of proteins with thermoplastic properties. They can be manufactured into biodegradable agromaterials by compression moulding.

Oleic sunflower whole plant (15 mm homogenate) (La Toulousaine de Céréales, France): 6.0% of moisture content. -6.4% of mineral content; 25.4% of oil content; 10.8% of protein content; 41.1% of fibers content (cell., hemicelluloses and lignins).

Twin-screw extruder:

The biorefinery of sunflower whole plant can be conducted with water by thermo-mechanical fractionation in a Clextral BC 45 (France) co-penetrating and co-rotating twin-screw extruder [1].

Aqueous extraction is an environmentally cleaner alternative technology to the solvent oil extraction process from oilseeds [2][3]. It enables the simultaneous production from whole plant of two different oil-in-water emulsions (hydrophobic phases) and a protein isolate (hydrophilic phase) in the same process [1].

The co-rotating twin-screw extruder behaves like a thermo-mechanical reactor. Its implementation allows the aqueous extraction of sunflower oil [1,[4][5].

It is equipped with a filtration module to obtain separately an extract (filtrate) and a raffinate (cake meal), and wringing out the mixing from whole plant is efficient because of the natural abundance of fibers in the sunflower stalk (until 80%).

This only apparatus is used to carry out three essential unit operations in a single step and in a continuous mode: (i) conditioning and grinding of sunflower whole plant, (ii) liquid/solid extraction, and (iii) liquid/solid separation.

The process can be considered as an original and powerful solution for fractionation and value-adding to sunflower since the obtained fractions may have applications as bases for industrial products [1].

The representation of the liquid/solid transport inside the barrel of the twin-screw extruder is investigated in this study. The biorefinery of sunflower whole plant is possible with water using a co-rotating twin-screw extruder. The representation of the liquid/solid transport inside the barrel makes possible to predict the best operating conditions to obtain the highest oil extraction yield (until 53%).

Oil is extracted in the form of two different oil-in-water emulsions: (i) the higher hydrophobic phase, and (ii) the lower hydrophobic phase. Their stability is ensured at interface by surface-active agents co-extracted: (i) phospholipids, and (ii) proteins. Pectins and non pectic sugars complete the dry matter of the lower hydrophobic phase.

The extract is also made up of a hydrophilic phase. This major fraction contains water-soluble constituents from whole plant: (i) proteins from kernel, (ii) pectins from pith and head, and (iii) hemicelluloses from stalk.

The raffinate (cake meal) is rich in fibers. It has also a significant content of proteins with thermoplastic properties. It can be manufactured into biodegradable agromaterials by compression moulding. Panels can be used as inter-layer sheets for pallets or for the manufacturing of containers by assembly of panels. (iii) The pressing zone is the place where the liquid/solid separation is realized. The screw configuration is then arranged with reversed screws (CF1C) that are used to place pressure on the liquid/solid mixture. These screws are positioned immediately downstream from the filter section. liquid/solid extractor, and (iii) a liquid/solid separator, with intensified material exchanges.

Thus, it is possible to predict the evolution of residence times of liquid and solid in the three zones of the twin-screw extruder with the main operating variables: (i) the screw rotation speed, (ii) the inlet flow rate of whole plant, and (iii) the inlet flow rate of water. S S is the screw rotation speed. Q S and Q W are the inlet flow rates of sunflower whole plant and water, respectively. -Q F and Q C are the flow rates of the filtrate and the cake meal, respectively. L C and P C are the lipid content and the protein content of the cake meal, respectively. -R L is the oil yield based on the residual oil content of the cake meal. R P is the protein yield based on the residual protein content of the cake meal. -I is the The representation of the liquid/solid transport inside the barrel is performed thanks to: (i) the measuring of the filling of each screw element after visual observation.

(ii) the characteristics of the corresponding solid (dry solid mass and moisture content). (iii) the modeling of the contribution of each screw element to the residence time distribution of solid and liquid phases [6].

So, the twin-screw extruder can be represented as the association of (i) a grinder, (ii) a

The decreases of the screw rotation speed and the inlet flow rate of whole plant, with the increase of the inlet flow rate of water, cause the increase of the liquid to solid ratio in the extracting zone, and the increase of the residence time of the solid in the pressing zone.

Such conditions (trial 7: 60 rpm for the screw rotation speed, 5.0 kg/h for the inlet flow rate of whole plant, and 20.3 kg/h for the inlet flow rate of water) are favourable to an efficient contact between the liquid and the solid inside the extractor (8.2 for the L/S ratio), and to the liquid/solid separation (156 s for the residence time of the solid inside the separator).

Taking into account the oil content in the foot of the filtrate (12% of the oil from whole plant), the oil yield is then 53%, and the residual oil content of the cake meal is only 13% of dry weight.

electric current of the twin-screw extruder. SME is the specific mechanical energy consumed by the motor per unit weight of sunflower whole plant. -F and C are the experimental mean residence times of the filtrate and the cake meal, respectively.

Comparison of the experimental and modeled mean residence times of the filtrate and the cake meal (trials 1 to 3).

Comparison of the dry solid mass collected along the barrel after the sudden shutdown of the extruder with that calculated by the model (trial 6).

Prediction of the residence time of the solid in the three successive zones of the extruder: example of its evolution with the inlet flow rate of sunflower whole plant (S S = 75 rpm, and Q W = 24.5 kg/h).

  Biorefinery of sunflower whole plant by thermo Biorefinery of sunflower whole plant by thermo--mechanical fractionation in twin mechanical fractionation in twin--screw extruder: screw extruder: representation of liquid/solid transport inside the barrel representation of liquid/solid transport inside the barrel Ph. Evon 1 *, P.Y. Pontalier 1 , L. Rigal 1 , L. Prat 2 1 Université de Toulouse; INP; Laboratoire de Chimie Agro-industrielle (LCA); ENSIACET, F-31029 Toulouse, France 2 Université de Toulouse; INP; Laboratoire de Génie Chimique (LGC); ENSIACET, F-31029 Toulouse, France * Tel.: (33)(0)5 62 44 60 80 -Fax: (33)(0)5 62 44 60 82 -e-Mail address: Philippe.Evon@ensiacet.fr Schematic modular barrel and screw configuration of the Clextral BC 45 (France) twin-screw extruder ( = 80°C for thermal induction).

[ 3 ]

 3 Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Aqueous extraction of oil from sunflower seeds in batch reactor: reorganization of the mixing in three formulated fractions. 98 th AOCS Annual Meeting & Expo, AOCS, Québec City, QC, Canada (2007).

  T2F = trapezoidal double-thread screw. C2F = conveying double-thread screw. C1F = conveying simple screw. BB = bilobe paddle-screw. DM = monolobe paddle-screw. CF1C = reversed simple screw. -The numbers following the type of the screw indicate the pitch of T2F, C2F, C1F and CF1C screws and the length of the BB and DM screws.

  the screw profile makes possible to define three successive zones: (i) The grinding zone consists of a succession of 10 monolobes paddles (DM), and 5 bilobe paddles (BB). It ensures the conditioning and the grinding of the sunflower whole plant. (ii) The extracting zone begins with the water injection. It is composed of a second series of 5 bilobe paddles (BB) to mix the liquid and the solid.

[ 4 ]

 4 Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Direct extraction of oil from sunflower seeds by twin-screw extruder according to an aqueous extraction process: feasibility study and influence of operating conditions. Ind. Crops Prod., 26 (3), 351-359 (2007). [5] Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Aqueous extraction of residual oil from sunflower press cake using a twin-screw extruder: feasibility study. Ind. Crops Prod., 29 (2-3), 455-465 (2009). [6] Prat L., Guiraud P., Rigal L. and Gourdon C., A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder. Chem. Eng. Process., 41 (9), 743-751 (2002).

[ 1 ]

 1 Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Transformation of sunflower whole plant by twin-screw extrusion technology according to an aqueous process. Proceedings of the 15 th European Biomass Conference & Exhibition, Berlin, Germany, 2094-2098 (2007). [2] Rosenthal A., Pyle D.L. and Niranjan K., Aqueous and enzymatic processes for edible oil extraction. Enzyme Microb. Technol., 19 (6), 402-420 (1996).


Ph Evon

V Vandenbossche

P Y Pontalier

L Rigal

New process for the biorefinery of sunflower whole plant by thermo-mechanical fractionation and aqueous extraction in a twin-screw extruder

Fractionation of sunflower whole plant is carried out with water in a twin-screw extruder. An extract and a raffinate are produced in a single step. Oil extraction yield is 55%. Lipids are extracted in the form of two oil-in-water emulsions: the higher hydrophobic phase and the lower one. Stability of both hydrophobic phases is ensured by the presence at interface of surface-active agents co-extracted: phospholipids and proteins. Pectins and non pectic sugars complete the dry matter of the lower hydrophobic phase. Hydrophobic phases may have applications for non food uses: biolubricants market, transport of active principles (odours, colours, bactericides, antifungals), and treatment of hydrophilic surfaces. They can be also used for oil production because their demulsification with ethanol is efficient. Oil recovery produces also a precipitate containing proteins with tensioactive properties. The extract contains also a hydrophilic phase (aqueous phase). This largest phase is an extract of the soluble constituents from whole plant: proteins from kernel, pectins from pith and head, and hemicelluloses from stalk. Valorization of hydrophilic phase is difficult because it is much diluted. Nevertheless, it would be potentially recyclable for aqueous extraction. It would be also possible to use it for the production of proteins with surface-active properties and pectins. The raffinate (cake meal) is rich in fibres and proteins with thermoplastic properties. It would be suitable for use in animal feeds and for energy production. It is also a natural composite, and it can be manufactured into biodegradable agromaterials by compression moulding. Panels can be used as inter-layer sheets for pallets or for the manufacturing of containers. Oleic sunflower whole plant (15 mm homogenate) (La Toulousaine de Céréales, France): 8.8% of moisture content. -6.5% of mineral content; 26.8% of oil content; 10.7% of protein content; 40.9% of fibers content (cellulose, hemicelluloses and lignins).

Twin-screw extruder:

The aqueous extraction process is an environmentally cleaner alternative technology to the solvent oil extraction process from oilseeds [1-2]. It enables the simultaneous production of an oil-in-water emulsion (hydrophobic phase) and a protein isolate (hydrophilic phase) in the same process.

The implementation of a co-rotating twin-screw extruder allows the aqueous extraction of sunflower oil [3][4]. However, no filtrate is obtained without the addition of fibers upstream from the filtration module. Two lignocellulosic residues were tested successfully: the wheat straw and the sunflower depithed stalk.

The aqueous extraction of sunflower oil is still effective starting from the whole plant [5]. Wringing out the mixing is even easier because of the natural abundance of fibers in the sunflower stalk (until 80%).

Direct application of the fractions obtained after aqueous extraction in the twin-screw extruder as bases for industrial products is investigated in this study. The feasibility of an aqueous extraction process for the biorefinery of sunflower whole plant using a co-rotating twin-screw extruder is confirmed. Aqueous extraction of sunflower oil is chosen as an environment-friendly alternative to the solvent extraction.

The co-rotating twin-screw extruder behaves like a thermo-mechanical reactor. It is equipped with a filtration module to obtain separately an extract and a raffinate. This only apparatus is used to carry out three essential unit operations in a single step and in a continuous mode: (i) conditioning and grinding of sunflower whole plant, (ii) liquid/solid extraction, and (iii) liquid/solid separation.

The process can be considered as an original and powerful solution for fractionation and value-adding to sunflower since the obtained fractions may have applications as bases for industrial products. Lipids are extracted in the form of two different oil-inwater emulsions: (i) the higher hydrophobic phase, and (ii) the lower hydrophobic phase.

Stability of both hydrophobic phases is ensured by the presence at interface of surface-active agents coextracted during the aqueous process: (i) phospholipids, and (ii) proteins. Pectins and non pectic sugars complete the dry matter of the lower hydrophobic phase.

Hydrophobic phases may have applications for non food uses: (i) the biolubricants market, (ii) the transport Matter assessment for the thermo-mechanical fractionation of sunflower whole plant conducted with the Clextral BC 45 twin-screw extruder (60 rpm for the screw rotation speed; 5.0 kg/h for the inlet flow rate of sunflower whole plant; 20.3 kg/h for the inlet flow rate of water). DM, dry matter; L, lipids; P, proteins.

Crushing (Electra VS 1 hammer mill fitted with a 15 mm screen)

Fractionation of sunflower whole plant is carried out with water in a twin-screw extruder.

An extract and a raffinate are produced in a single step. Oil extraction yield is 53%, and protein extraction yield is 46%.

Thermo-mechanical fractionation (Clextral BC 45 twin-screw extruder)

Water (404.8 kg)

Filtrate

Pressure filtration

Cake meal (190.5 kg;65.2 kg DM,8.6 kg L and 4.4 kg P) Foot (20.5 kg; 6.5 kg DM, 2.9 kg L and 0.9 kg P) Clarified extract

High-pressure homogenisation and centrifugation

Higher hydrophobic phase (35.6 kg; 10.4 kg DM, 8.1 kg L and 1.6 kg P) Hydrophilic phase (237.0 kg; 5.6 kg DM, 0.3 kg L and 1.4 kg P) Lower hydrophobic phase (21.3 kg;4.4 kg DM,2.6 kg L and 0.7 kg P) of active principles (odours, colours, bactericides, antifungals), and (iii) the treatment of hydrophilic surfaces.

They can be also used for oil production because their demulsification with ethanol or with ethanol/ether mixture (3/1) is efficient. Oil recovery produces also a precipitate containing proteins with tensioactive properties.

The extract contains also a hydrophilic phase (aqueous phase). This largest fraction is an aqueous extract of the soluble constituents from whole plant: (i) proteins from kernel, (ii) pectins from pith and head, and (iii) hemicelluloses from stalk.

Valorization of hydrophilic phase is difficult because it is much diluted. Nevertheless, it would be potentially recyclable for aqueous extraction. It would be also possible to use it for the production of proteins with surface-active properties and pectins.

The raffinate (cake meal) is rich in fibers and proteins with thermoplastic properties. It would be suitable for use in animal feeds and for energy production. It is also a natural composite, and it can be manufactured into biodegradable agromaterials by compression moulding (until 11.5 MPa for the stress at break, and 1.04 for the corresponding mean apparent density).

Panels can be used as inter-layer sheets for pallets or for the manufacturing of containers by assembly of panels.

  Schematic modular barrel and screw configuration of the Clextral BC 45 (France) twin-screw extruder ( = 80°C for thermal induction).

[ 1 ]

 1 Rosenthal A., Pyle D.L. and Niranjan K., Aqueous and enzymatic processes for edible oil extraction. Enzyme Microb. Technol., 19, 402-420 (1996). [2] Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Aqueous extraction of oil from sunflower seeds in batch reactor: reorganization of the mixing in three formulated fractions. 98 th AOCS Annual Meeting & Expo, AOCS, Québec City, QC, Canada (2007).

  T2F = trapezoidal double-thread screw. C2F = conveying double-thread screw. C1F = conveying simple screw. BB = bilobe paddle-screw. DM = monolobe paddle-screw. CF1C = reversed simple screw. -The numbers following the type of the screw indicate the pitch of T2F, C2F, C1F and CF1C screws and the length of the BB and DM screws.

  0 kg; 91.2 kg DM, 24.5 kg L and 9.8 kg P)

  Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Direct extraction of oil from sunflower seeds by twin-screw extruder according to an aqueous extraction process: feasibility study and influence of operating conditions. Ind. Crops Prod., 26 (3), 351-359 (2007). [4] Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Aqueous extraction of residual oil from sunflower press cake using a twin-screw extruder: feasibility study. Ind. Crops Prod., 29 (2-3), 455-465 (2009). [5] Evon Ph., Vandenbossche V., Pontalier P.Y. and Rigal L., Transformation of sunflower whole plant by twin-screw extrusion technology according to an aqueous process. Proceedings of the 15 th European Biomass Conference & Exhibition, Berlin, Germany, 2094-2098 (2007).

New process for the biorefinery of sunflower whole plant by ther New process for the biorefinery of sunflower whole plant by thermo mo--mechanical mechanical fractionation and aqueous extraction in a twin fractionation and aqueous extraction in a twin--screw extruder screw extruder

	Ph. Evon 1-2 *, V. Vandenbossche 1-2 , P.Y. Pontalier 1-2 , L. Rigal 1-2
	1 Université de Toulouse; INP; LCA (Laboratoire de Chimie Agro-industrielle);
	ENSIACET, 4 Allée Emile Monso, F-31029 Toulouse, France
	2 INRA; LCA (Laboratoire de Chimie Agro-industrielle); F-31029 Toulouse, France
	* Tel.: (33)(0)5 62 44 60 80 -Fax: (33)(0)5 62 44 60 82 -e-Mail address: Philippe.Evon@ensiacet.fr