Une nouvelle méthode d'analyse thermique et son application aux procédés papetiers

Une méthode d'analyse des besoins énergétiques de procédé a été employée pour identifier dans une étape préliminaire de conception, les possibilités de modification par rétro installation d'un procédé intégré de pâtes et papiers. Le minimum d'énergie requise (MER) du procédé a été calculé au moyen d'une double représentation dans laquelle une distinction est faite entre la demande thermodynamique du procédé et son implémentation technologique. Les potentiels de récupération d'énergie et d'exergie ont été analysés afin d'améliorer l'intégration du réseau d'utilités du procédé. Une méthode de ciblage faisant usage d'optimisation par programmation linéaire mixte en variable entière a été appliquée pour identifier les meilleures options pour la conversion d'énergie et pour optimiser la production combinée de chaleur et d'électricité. Le remplacement des injections de vapeur aux cuviers de mélange par des échangeurs de chaleur diminuerait le MER de 10% et augmenterait la production combinée de la chaleur et d'électricité par un facteur 1.7. Il serait plus difficile d'améliorer l'efficacité exergétique de la technologie du séchage du papier, mais les résultats indiquent que ceci pourrait apporter un gain additionnel de 12% en électricité

An Improved Linear Programming Approach for Simultaneous Optimization of Water and Energy

An optimization method based on Mixed Integer Linear Programming (MILP) has been developed for simultaneous optimization of water and energy (SOWE) in industrial processes. The superstructure integrates process thermal streams and optimizes the consumption of water while maximizing internal heat recovery to reduce thermal utility consumption. In this paper, additional concepts have been implemented in the superstructure to target the issues of the pulp and paper processes. Non-Isothermal Mixing (NIM) has been considered at different locations in order to reduce the number of thermal streams and decrease the investment cost by avoiding unnecessary investment on heat exchangers. The concepts of restricted matches and water tanks have been added to the superstructure to adapt it to the pulp and paper case studies. The Integer-Cut Constraint (ICC) technique has been combined with the MILP model to generate systematically a set of optimal solutions to support the decision-making for cost-effective configurations

Étude expérimentale d'un système de rétention des particules fines dans un formeur de laboratoire

Désenchevêtrement de l'oxyde de polyéthyl`ne -- Travail expérimental -- Conclusions et implication pour la fabrication du papier -- Bilan de masse sur un formeur à double-toile de laboratoire -- Etude expérimental d'un système de rétention basé sur le Peo effectuée sur un formeur double-toile de laboratoire

Analysis of a biorefinery integration: application to a sulfite wood pulping process

The pulp and paper (P&P) industry in industrially mature countries is facing a long-term crisis. Large and modern manufacturing facilities in tropical regions emerge as new competitors. The constant increase of energy costs has also contributed to the financial difficulties encountered in the industry. To stay viable and sustainable, P&P mills need to elaborate new strategies to increase their revenues. In this context, converting a P&P mill into an integrated forest biorefinery could be the solution to restore the health of the industry and overcome the crisis. Diversifying the industry's product mix by producing bio-energy and bio-materials could be a way to penetrate new markets while maintaining its core production of pulp and paper. Producing bio-materials implies energy consumption and waste heat. The energy management cannot therefore be dissociate from the biorefinery integration in a P&P mill: both energy and mass integration must be considered. The objective of this work is to illustrate the trade-off between conversion of materials and of energy and shows the importance of considering simultaneously the heat recovery through heat exchangers and the combined heat and power production. Process integration techniques have been applied to study a bisulfite mill which produces pulp and three additional by-products: bioethanol, lignosulfonate and yeast. Particular attention was devoted to the integration of the chemical recycling loops which have a significant impact on the process energy balances and therefore influence the choice of biorefinery integration strategies. A key element of the process integration pathway was to consider the heat cascade as a model of the heat exchanger network by decoupling the installed heat exchangers network when analysing the potential effects of the recycling and production strategies at the plant level. Using this model, the optimal integration of a combined heat and power production unit was determined taking into account the simultaneous maximisation of process internal heat recovery. To facilitate the computational formulation of the problem, the overall process was subdivided into several production sub-systems with flow diagrams and flow rates dependant on the main product being manufactured in each sub-system. Mass balance constraints were introduced to model the flow distribution between sub-systems and the hot and cold streams were computed by means of a conventional flowsheeting software. The corresponding hot and cold streams were subsequently integrated at the mill scale level. The pulp production line and energy conversion equipment such as the sulphur boiler, lignin boiler and the biomass boilers were simultaneously optimized

Methodology for process energy analysis: application to a sulfite wood pulping

Creating a consistent thermodynamic database is the first step required to perform a process integration study. A method based on the use of data identification and reconciliation has been developed to model the mass and the energy balances of a pulp and paper sulfite mill. It combines data from different sources: online measurements, monthly report, specifications sheets and uses the data from both the process and the utility side in order to compute the nominal process states that are used to define the heat transfert requirement of the process

Energy integration study of a multi-effect evaporator

In the pulp and paper industry, multi-effect evaporators are used to evaporate water from black liquor solutions to allow its recycle as chemicals and fuel for the process. The thermodynamic principle of the multi-effect evaporator consists in a serie of reboilers operating at different pressures; the water evaporated at one stage is condensed and used as the heat source for another stage. Due to its strong integration with the process, it is worth to analyse the integration of the multi-effect evaporator with the rest of the process. To do so a thermo-economic analysis model of the evaporation system has been developped. The example is based on the evaporation system of a calcium bisulfite pulp manufacturing mill located in Switzerland. This system involves 3 multi-effect evaporators fed at different concentrations of black liquor. A systematic analysis of the system Grand composite curve has been developed to identify pertinent process modifications. From this analysis, several modifications like decreasing the ∆Tmin of a stream, increasing or decreasing pressures of evaporation effects have been evaluated

Analysis of a biorefinery integration in a bisulfite pulp process

Process integration techniques have been applied to study a bisulfite mill which produces pulp and three additional by- products: bioethanol, lignosulfonate and yeast. Particular attention was devoted to the integration of the chemical recycling loops which have a significant impact on the process energy balances and therefore influence the choice of biorefinery integration strategies. This analysis illustrates the trade-off between conversion of materials and of energy and shows the importance of considering simultaneously the heat recovery through heat exchangers and the combined heat and power production

Osmose - User Manual version 2.0

OSMOSE is a platform for the study and design of complex integrated energy systems. The software is developed in the Laboratory for Industrial Energy Systems (LENI) in the Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. The project is motivated by the need of a fexible and performant research tool to study and design energy systems. In this perspective, the general scope of the software is to help the user to develop and compute technology models that combine (a) thermodynamic computations, (b) power and energy integration as well as (c) economic or environomic aspects. OSMOSE , exploits the models by performing (a) sensitivity analysis, (b) optimization and (c) data analysis. The present document is a complete user guide to OSMOSE. In addition, elements of software structure and architecture are exposed. This makes therefore the document useful as an introduction for future developers in the project

Process modeling and integration of fuel ethanol production from lignocellulosic biomass based on double acid hydrolysis

Lignocellulosic biomass is considered as one of the most promising feedstocks for producing fuel ethanol because of its global availability and environmental benefits of its use. In this paper, the process of lignocellulosic ethanol production was investigated at its present state of development. The experimental data from the East China University of Science and Technology were used to develop a process model and evaluate the performance of the whole process design. For the process simulation, all relevant information about the process streams, physical properties, and mass and energy balances were also considered. Energy integration is investigated to identify the best ways to supply heat to the process, realizing also combined heat and power production from wastewater and residue treatment. The sensitivity on ethanol yield and the overall system performance are also investigated