Mauricio Sales - Academia.edu (original) (raw)

Papers by Mauricio Sales

Research paper thumbnail of A probabilistic deep learning approach for thermal and exergy forecasting in organic Rankine cycles

Computers & Chemical Engineering

Research paper thumbnail of 1 Design of membrane systems

Research paper thumbnail of Comparative Thermodynamic Analysis of the Performance of an Organic Rankine Cycle Using Different Working Fluids

Energies

Today, the study of thermal systems that take advantage of residual thermal sources in the power ... more Today, the study of thermal systems that take advantage of residual thermal sources in the power generation sector is of great importance to mitigate environmental impact and promote sustainable alternatives in this sector. Among these alternatives, the organic Rankine cycle (ORC) is of great relevance since it allows taking advantage of residual energy sources at low temperatures. This work presents a methodology to evaluate the feasibility of using a refrigerant as a working fluid in an organic Rankine cycle based on an exergetic viability index. As a case study, R134a, R600a, R245fa, and R123 refrigerants were considered. A residual thermal source was used that came from the Hybrid Cycle Plant of the Valley of Mexico. Thermodynamic analysis was performed to determine generated power, thermal efficiency, refrigerant mass flow, pinch point temperature difference, specific steam consumption, unused thermal exergy flow, exergy efficiency, and total heat transfer requirement. The weig...

Research paper thumbnail of Interstage Pressures of a Multistage Compressor with Intercooling

Entropy, 2021

This paper considers the criterion of minimum compression work to derive an expression for the in... more This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available.

Research paper thumbnail of Online Monitoring of an Enzymatic Reactor based on Density Measurements

Computer Aided Chemical Engineering, 2018

Abstract In this work, a monitoring strategy is presented to infer unmeasured concentrations and ... more Abstract In this work, a monitoring strategy is presented to infer unmeasured concentrations and estimate the kinetic parameter of inhibition in an enzymatic reactor. The reaction corresponds to the hydrolysis of cellulose to produce glucose, in batch and isothermal conditions. The strategy is based on a softsensor that consists of a model-based state estimator and considering only density measurements. The reactor model and the softsensor performances are validated with experimental data, obtaining satisfactory estimates. The strategy could be extended to other bioreactors.

Research paper thumbnail of A Modeling Framework for Chemical Process Design Through a Computer-Aided System

This paper deals with a modeling environment for systematic chemical process design through a Com... more This paper deals with a modeling environment for systematic chemical process design through a Computer-Aided Modeling System (CAMS), whose potential is highlighted through a case study. In particular, the capability of ICAS-MoT (an integrated modeling environment) to build, analyze, manipulate, solve and visualize mathematical models is shown. Our main interest is to use models for process design and analysis by testing and implementing them as fast as possible (in a reliable and efficient manner), writing the model equations without any programming effort, generating modules that can be exported through a model transfer feature to other simulation engines and/or external software, and implementing several process/model configurations in the same environment. From the application perspective, the modeling, operational analysis and process configuration of an emulsion polymerization reactor is considered. The case study highlights the advantages of using a computer-aided modeling sys...

Research paper thumbnail of A Model-Based Methodology for Integrated Design and Operation of Reactive Distillation Processes

Research paper thumbnail of Intensification of the 2g Bioethanol Production Process

Chemical engineering transactions, 2020

The main objective of the present study is to propose a methodology to evaluate alternatives for ... more The main objective of the present study is to propose a methodology to evaluate alternatives for the synthesis of the second-generation bioethanol production process from lignocellulosic feedstock, in order to reduce amount of waste, energy consumption and production costs. The methodology is based on modelling, synthesis, design and simulation, where the heat integration in the 2G bioethanol production process is a key tool to evaluate the process in technical, economic and environmental terms. As a case study, wheat straw is considered as raw material, and the simulations are performed using a modular process simulator. For the assessment and comparison of the biorefinery alternatives, the selected evaluation criteria are ethanol yield, unit production cost, energy consumption, CO2 emissions and water consumption. The results show the best process alternatives that can lead to greater sustainable ethanol production, supporting better decision making in the synthesis and design of ...

Research paper thumbnail of A Systematic Computer-Aided Framework for Integrated Design and Control of Chemical Processes

Processes DTU Orbit (06/12/2018) A Systematic Computer-Aided Framework for Integrated Design and ... more Processes DTU Orbit (06/12/2018) A Systematic Computer-Aided Framework for Integrated Design and Control of Chemical Processes Chemical processes are conventionally designed through a sequential approach. In this sequential approach, first, a steady-state process design is obtained and then, control structure synthesis that, in most of the cases, is based on heuristics is performed. Therefore, process design and process control and operation considerations have been studied independently. Furthermore, this sequential approach does not adequately answer this question, “How process design decisions influence process control and operation?”. In order to answer this question, it is necessary to consider process controllability and operability issues together with process design tasks (Seferlis and Georgiadis, 2004). In this way, it can be assured that design decisions give the optimum operational and economic performance. Operability issues are addressed to ensure a stable and reliable ...

Research paper thumbnail of A novel Graphical Gibbs Energy-Driving Force Method for the Optimal Design of Non-reactive and Reactive Distillation Columns

A simple Gibbs-Driving force method for designing non-reactive and reactive distillation columns ... more A simple Gibbs-Driving force method for designing non-reactive and reactive distillation columns (non-RDC and RDC respectively) has been developed. Based on the binary driving force diagrams (Gani and Bek-Pedersen, 2000)(Perez-Cisneros and Sales-Cruz) coupled with the equilibrium Gibbs energy plots a systematic graphical method for the design of non-RDC and RDC is proposed. The design method exploits the connection between the driving force values and the equilibrium Gibbs energy to determine the number of stages, the optimal feed location, the heat required at the reboiler and condenser and the minimum reflux ratio. The final design guarantee an optimal operation since the global minimum of the equilibrium Gibbs energy is achieved. The above optimal criteria is equivalent to the maximum entropy condition required for a stable operation of the distillation columns. The method has been applied for the design of two non-reactive systems: a) Benzene-Toluene ideal system and b) propanol...

Research paper thumbnail of Conceptual design of sugarcane biorefinery upgrading molasses to value-added chemicals

Research paper thumbnail of An Integrated Reactive Separation Process for Co-Hydrotreating of Vegetable Oils and Gasoil to Produce Jet Diesel

An integrated reactive separation process for the production of jet diesel from vegetable oils an... more An integrated reactive separation process for the production of jet diesel from vegetable oils and gasoil mixture has been developed. The integrated reactive separation process consider three interconnected sections: 1) a triglyceride hydrolysis section consisting of a catalytic heterogeneous reactor which is used to transform the triglycerides of the vegetable oils or animal fats to the corresponding fatty acids and a coupled decanter-distillation column to separate the fatty acids from glycerol and water; 2) a co-hydrotreating section where a reactive distillation column is proposed to perform the deep hydrodesulfurization (HDS) of gasoil and the hydrodeoxigenation (HDO) and the decarbonilation of the fatty acids simultaneously and 3) a isomerization section where a catalytic reactor is used to produce the jet diesel with the appropriate fuel properties. Through intensive simulations the effect of the different operating variables of the three sections were studied. Results show t...

Research paper thumbnail of Simulation of the Biofuel Production Process from Organic Fraction of Municipal Solid Waste (OFMSW)

31st European Symposium on Computer Aided Process Engineering, 2021

The primary management of the organic fraction of municipal solid waste (OFMSW) was commonly comp... more The primary management of the organic fraction of municipal solid waste (OFMSW) was commonly composting, landfill or incineration, while now the anaerobic digestion of OFMSW offers the possibility of a clean and renewable energy source. This work presents the modelling and simulation of an OFMSW biorefinery to produce biogas, fertiliser and bioethanol. The conceptual design of the biorefinery begins with an anaerobic digestion to degrade OFMSW and produce biogas. The resulting solid fibres and the effluent are sent to the subsequent stages to produce fertiliser from the solid waste and anhydrous bioethanol from the fermentation broth. The process simulations are based on an anaerobic biorefinery capable to treat 1,000 tonnes per day of OFMSW generated in CDMX. The main results show the yields are 73 kg ethanol, 54 kg biogas and 59 kg fertiliser per tonne of dry waste.

Research paper thumbnail of Simulation of a Sugarcane Biorefinery for Food Products

This paper aims to highlight the usefulness of molasses from sugarcane as raw material for the pr... more This paper aims to highlight the usefulness of molasses from sugarcane as raw material for the production of food products. The main goal is to establish the conceptual design and the simulation of a sugarcane biorefinery in terms of process flowsheet diagrams. However, a fundamental issue is the decision of the bioproducts of the biorefinery and their percentage of production in relation to the total amount of sugar extracted by the juice and bagasse from sugar cane. The overall methodology is to determine the technical, economic and environmental feasibility. Here the first stage is presented, where the conceptual design in terms of process diagrams are determined to start performing the technical evaluation (through material and energy balances). It should be noted that modeling and simulation tools will be used for the study of processes, to understand the process at different scales and operating conditions, to achieve the synthesis and process optimization, to monitor and control the process, to maintain the level of production and quality product, to detect and correct failures of the process immediately, and so on.

Research paper thumbnail of 6. Graphical tools for designing intensified distillation processes: Methods and applications

Process Intensification, 2019

Research paper thumbnail of A Gibbs energy-driving force method for the optimal design of non-reactive and reactive distillation columns

Computers & Chemical Engineering, 2019

Highlights  A Gibbs energy-driving Force (GE-DF) method for design of reactive and non-reactive... more Highlights  A Gibbs energy-driving Force (GE-DF) method for design of reactive and non-reactive distillation columns is proposed  The link between the thermodynamic separation efficiency and the optimal thermal feed condition is established  The design method is applied for the separation of two non-reactive and one reactive mixtures  Potential application of the (GE-DF) method for integrated design and control of reactivedistillation columns is revealed

Research paper thumbnail of An Analytic Solution for the Transient Diffusion Problem in a Multi-Layer System

An analytic solution for the dynamic diffusive transport in a multi-layer system has been develop... more An analytic solution for the dynamic diffusive transport in a multi-layer system has been developed. The partial differential equations of the model are subjected to boundary conditions, which may be chosen as any function of the time. The methodology followed here, exploits the simplicity of the separation of variables method and the superposition concept and, an eigenvalue or Sturm-Liouville problem is generated. The computation of the eigenvalues associated to the Sturm-Liouville problem is presented. The analytic solution is evaluated using three different time functionality of the bulk fluid concentration. The results show that the type of time functionality at the boundaries strongly affects the shape of the concentration profile inside of the multi-layer system. In some case, the time functionality of the concentration does not lead to any steady state. The main advantage of the analytic solution, when it is compared with that obtained numerically, is the lower CPU time used ...

Research paper thumbnail of Thermal pretreatment of the solid fraction of manure: Impact on the biogas reactor performance and microbial community

Water Science and Technology, 2006

Application of thermal treatment at 100-140 8C as a pretreatment method prior to anaerobic digest... more Application of thermal treatment at 100-140 8C as a pretreatment method prior to anaerobic digestion of a mixture of cattle and swine manure was investigated. In a batch test, biogasification of manure with thermally pretreated solid fraction proceeded faster and resulted in the increase of methane yield. The performances of two thermophilic continuously stirred tank reactors (CSTR) treating manure with solid fraction pretreated for 40 minutes at 140 8C and non-treated manure were compared. The digester fed with the thermally pretreated manure had a higher methane productivity and an improved removal of the volatile solids (VS). The properties of microbial communities of both reactors were analysed. The specific methanogenic activity (SMA) test showed that both biomasses had significant activity towards hydrogen and formate, while the activity with the VFA-acetate, propionate and butyrate-was low. The kinetic parameters of the VFA conversion revealed a reduced affinity of the microbial community from the CSTR fed with thermally pre-treated manure for acetate, propionate and butyrate. The bacterial and archaeal populations identified by t-RLFP analysis of 16S rRNA genes were found to be identical in both systems. However, a change in the abundance of the species present was detected.

Research paper thumbnail of Computer-Aided Model Based Analysis for Design and Operation of a Copolymerization Process

Chemical Engineering Research and Design, 2006

T he advances in computer science and computational algorithms for process modelling, process sim... more T he advances in computer science and computational algorithms for process modelling, process simulation, numerical methods and design/synthesis algorithms, makes it advantageous and helpful to employ computer-aided modelling systems and tools for integrated process analysis. This is illustrated through the study of a copolymerization process, where operational problems due to their complex nonlinear behaviour are usually encountered, indicating thereby, the need for the development of an appropriate process model that can describe the dynamic behaviour over the complete range of conversion. This will allow analysis of the process behaviour, contribute to a better understanding of the polymerization process, help to avoid unsafe conditions of operation, and to develop operational and optimizing control strategies. In this work, through a computer-aided modelling system ICAS-MoT, two first-principles models have been investigated with respect to design and operational issues for solution copolymerization reactors in general, and for the methyl methacrylate/vinyl acetate system in particular. The Model 1 is taken from literature and is commonly used for low conversion region, while the Model 2 has been derived in this work and covers the complete range of conversion. The performances of the two models are compared with respect to the steady state and dynamic behaviour of the polymerization process. The model analyses highlight the influence of the reaction mechanism, the transport phenomena, the process design and conditions of operation on the polymer grade and the production rate.

Research paper thumbnail of Computer-Aided Modelling of Short-Path Evaporation for Chemical Product Purification, Analysis and Design

Chemical Engineering Research and Design, 2006

A n important stage in the design process for many chemical products is its manufacture where, fo... more A n important stage in the design process for many chemical products is its manufacture where, for a class of chemical products that may be thermally unstable (such as, drugs, insecticides, flavours/fragrances, and so on), the purification step plays a major role. Short-path evaporation is a safe method, suitable for separation and purification of thermally unstable materials whose design and analysis can be efficiently performed through reliable model-based techniques. This paper presents a generalized model for short-path evaporation and highlights its development, implementation and solution through a computer-aided modelling framework, which allows the use of systematic simulation strategies for various types of design/analysis problems. The main features of the model and the modelling framework are highlighted through two case studies: (a) the purification of a reaction mixture containing glycerol, mono-, di-and triglycerides, and (b) the recovery of a pharmaceutical product from a six-component mixture. Validation of the short-path evaporation model is highlighted through the comparison of experimental data from an industrial pilot plant with the simulated results from the model. Also, results from model-based sensitivity analysis and design problem solution are highlighted for two case studies.

Research paper thumbnail of A probabilistic deep learning approach for thermal and exergy forecasting in organic Rankine cycles

Computers & Chemical Engineering

Research paper thumbnail of 1 Design of membrane systems

Research paper thumbnail of Comparative Thermodynamic Analysis of the Performance of an Organic Rankine Cycle Using Different Working Fluids

Energies

Today, the study of thermal systems that take advantage of residual thermal sources in the power ... more Today, the study of thermal systems that take advantage of residual thermal sources in the power generation sector is of great importance to mitigate environmental impact and promote sustainable alternatives in this sector. Among these alternatives, the organic Rankine cycle (ORC) is of great relevance since it allows taking advantage of residual energy sources at low temperatures. This work presents a methodology to evaluate the feasibility of using a refrigerant as a working fluid in an organic Rankine cycle based on an exergetic viability index. As a case study, R134a, R600a, R245fa, and R123 refrigerants were considered. A residual thermal source was used that came from the Hybrid Cycle Plant of the Valley of Mexico. Thermodynamic analysis was performed to determine generated power, thermal efficiency, refrigerant mass flow, pinch point temperature difference, specific steam consumption, unused thermal exergy flow, exergy efficiency, and total heat transfer requirement. The weig...

Research paper thumbnail of Interstage Pressures of a Multistage Compressor with Intercooling

Entropy, 2021

This paper considers the criterion of minimum compression work to derive an expression for the in... more This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available.

Research paper thumbnail of Online Monitoring of an Enzymatic Reactor based on Density Measurements

Computer Aided Chemical Engineering, 2018

Abstract In this work, a monitoring strategy is presented to infer unmeasured concentrations and ... more Abstract In this work, a monitoring strategy is presented to infer unmeasured concentrations and estimate the kinetic parameter of inhibition in an enzymatic reactor. The reaction corresponds to the hydrolysis of cellulose to produce glucose, in batch and isothermal conditions. The strategy is based on a softsensor that consists of a model-based state estimator and considering only density measurements. The reactor model and the softsensor performances are validated with experimental data, obtaining satisfactory estimates. The strategy could be extended to other bioreactors.

Research paper thumbnail of A Modeling Framework for Chemical Process Design Through a Computer-Aided System

This paper deals with a modeling environment for systematic chemical process design through a Com... more This paper deals with a modeling environment for systematic chemical process design through a Computer-Aided Modeling System (CAMS), whose potential is highlighted through a case study. In particular, the capability of ICAS-MoT (an integrated modeling environment) to build, analyze, manipulate, solve and visualize mathematical models is shown. Our main interest is to use models for process design and analysis by testing and implementing them as fast as possible (in a reliable and efficient manner), writing the model equations without any programming effort, generating modules that can be exported through a model transfer feature to other simulation engines and/or external software, and implementing several process/model configurations in the same environment. From the application perspective, the modeling, operational analysis and process configuration of an emulsion polymerization reactor is considered. The case study highlights the advantages of using a computer-aided modeling sys...

Research paper thumbnail of A Model-Based Methodology for Integrated Design and Operation of Reactive Distillation Processes

Research paper thumbnail of Intensification of the 2g Bioethanol Production Process

Chemical engineering transactions, 2020

The main objective of the present study is to propose a methodology to evaluate alternatives for ... more The main objective of the present study is to propose a methodology to evaluate alternatives for the synthesis of the second-generation bioethanol production process from lignocellulosic feedstock, in order to reduce amount of waste, energy consumption and production costs. The methodology is based on modelling, synthesis, design and simulation, where the heat integration in the 2G bioethanol production process is a key tool to evaluate the process in technical, economic and environmental terms. As a case study, wheat straw is considered as raw material, and the simulations are performed using a modular process simulator. For the assessment and comparison of the biorefinery alternatives, the selected evaluation criteria are ethanol yield, unit production cost, energy consumption, CO2 emissions and water consumption. The results show the best process alternatives that can lead to greater sustainable ethanol production, supporting better decision making in the synthesis and design of ...

Research paper thumbnail of A Systematic Computer-Aided Framework for Integrated Design and Control of Chemical Processes

Processes DTU Orbit (06/12/2018) A Systematic Computer-Aided Framework for Integrated Design and ... more Processes DTU Orbit (06/12/2018) A Systematic Computer-Aided Framework for Integrated Design and Control of Chemical Processes Chemical processes are conventionally designed through a sequential approach. In this sequential approach, first, a steady-state process design is obtained and then, control structure synthesis that, in most of the cases, is based on heuristics is performed. Therefore, process design and process control and operation considerations have been studied independently. Furthermore, this sequential approach does not adequately answer this question, “How process design decisions influence process control and operation?”. In order to answer this question, it is necessary to consider process controllability and operability issues together with process design tasks (Seferlis and Georgiadis, 2004). In this way, it can be assured that design decisions give the optimum operational and economic performance. Operability issues are addressed to ensure a stable and reliable ...

Research paper thumbnail of A novel Graphical Gibbs Energy-Driving Force Method for the Optimal Design of Non-reactive and Reactive Distillation Columns

A simple Gibbs-Driving force method for designing non-reactive and reactive distillation columns ... more A simple Gibbs-Driving force method for designing non-reactive and reactive distillation columns (non-RDC and RDC respectively) has been developed. Based on the binary driving force diagrams (Gani and Bek-Pedersen, 2000)(Perez-Cisneros and Sales-Cruz) coupled with the equilibrium Gibbs energy plots a systematic graphical method for the design of non-RDC and RDC is proposed. The design method exploits the connection between the driving force values and the equilibrium Gibbs energy to determine the number of stages, the optimal feed location, the heat required at the reboiler and condenser and the minimum reflux ratio. The final design guarantee an optimal operation since the global minimum of the equilibrium Gibbs energy is achieved. The above optimal criteria is equivalent to the maximum entropy condition required for a stable operation of the distillation columns. The method has been applied for the design of two non-reactive systems: a) Benzene-Toluene ideal system and b) propanol...

Research paper thumbnail of Conceptual design of sugarcane biorefinery upgrading molasses to value-added chemicals

Research paper thumbnail of An Integrated Reactive Separation Process for Co-Hydrotreating of Vegetable Oils and Gasoil to Produce Jet Diesel

An integrated reactive separation process for the production of jet diesel from vegetable oils an... more An integrated reactive separation process for the production of jet diesel from vegetable oils and gasoil mixture has been developed. The integrated reactive separation process consider three interconnected sections: 1) a triglyceride hydrolysis section consisting of a catalytic heterogeneous reactor which is used to transform the triglycerides of the vegetable oils or animal fats to the corresponding fatty acids and a coupled decanter-distillation column to separate the fatty acids from glycerol and water; 2) a co-hydrotreating section where a reactive distillation column is proposed to perform the deep hydrodesulfurization (HDS) of gasoil and the hydrodeoxigenation (HDO) and the decarbonilation of the fatty acids simultaneously and 3) a isomerization section where a catalytic reactor is used to produce the jet diesel with the appropriate fuel properties. Through intensive simulations the effect of the different operating variables of the three sections were studied. Results show t...

Research paper thumbnail of Simulation of the Biofuel Production Process from Organic Fraction of Municipal Solid Waste (OFMSW)

31st European Symposium on Computer Aided Process Engineering, 2021

The primary management of the organic fraction of municipal solid waste (OFMSW) was commonly comp... more The primary management of the organic fraction of municipal solid waste (OFMSW) was commonly composting, landfill or incineration, while now the anaerobic digestion of OFMSW offers the possibility of a clean and renewable energy source. This work presents the modelling and simulation of an OFMSW biorefinery to produce biogas, fertiliser and bioethanol. The conceptual design of the biorefinery begins with an anaerobic digestion to degrade OFMSW and produce biogas. The resulting solid fibres and the effluent are sent to the subsequent stages to produce fertiliser from the solid waste and anhydrous bioethanol from the fermentation broth. The process simulations are based on an anaerobic biorefinery capable to treat 1,000 tonnes per day of OFMSW generated in CDMX. The main results show the yields are 73 kg ethanol, 54 kg biogas and 59 kg fertiliser per tonne of dry waste.

Research paper thumbnail of Simulation of a Sugarcane Biorefinery for Food Products

This paper aims to highlight the usefulness of molasses from sugarcane as raw material for the pr... more This paper aims to highlight the usefulness of molasses from sugarcane as raw material for the production of food products. The main goal is to establish the conceptual design and the simulation of a sugarcane biorefinery in terms of process flowsheet diagrams. However, a fundamental issue is the decision of the bioproducts of the biorefinery and their percentage of production in relation to the total amount of sugar extracted by the juice and bagasse from sugar cane. The overall methodology is to determine the technical, economic and environmental feasibility. Here the first stage is presented, where the conceptual design in terms of process diagrams are determined to start performing the technical evaluation (through material and energy balances). It should be noted that modeling and simulation tools will be used for the study of processes, to understand the process at different scales and operating conditions, to achieve the synthesis and process optimization, to monitor and control the process, to maintain the level of production and quality product, to detect and correct failures of the process immediately, and so on.

Research paper thumbnail of 6. Graphical tools for designing intensified distillation processes: Methods and applications

Process Intensification, 2019

Research paper thumbnail of A Gibbs energy-driving force method for the optimal design of non-reactive and reactive distillation columns

Computers & Chemical Engineering, 2019

Highlights  A Gibbs energy-driving Force (GE-DF) method for design of reactive and non-reactive... more Highlights  A Gibbs energy-driving Force (GE-DF) method for design of reactive and non-reactive distillation columns is proposed  The link between the thermodynamic separation efficiency and the optimal thermal feed condition is established  The design method is applied for the separation of two non-reactive and one reactive mixtures  Potential application of the (GE-DF) method for integrated design and control of reactivedistillation columns is revealed

Research paper thumbnail of An Analytic Solution for the Transient Diffusion Problem in a Multi-Layer System

An analytic solution for the dynamic diffusive transport in a multi-layer system has been develop... more An analytic solution for the dynamic diffusive transport in a multi-layer system has been developed. The partial differential equations of the model are subjected to boundary conditions, which may be chosen as any function of the time. The methodology followed here, exploits the simplicity of the separation of variables method and the superposition concept and, an eigenvalue or Sturm-Liouville problem is generated. The computation of the eigenvalues associated to the Sturm-Liouville problem is presented. The analytic solution is evaluated using three different time functionality of the bulk fluid concentration. The results show that the type of time functionality at the boundaries strongly affects the shape of the concentration profile inside of the multi-layer system. In some case, the time functionality of the concentration does not lead to any steady state. The main advantage of the analytic solution, when it is compared with that obtained numerically, is the lower CPU time used ...

Research paper thumbnail of Thermal pretreatment of the solid fraction of manure: Impact on the biogas reactor performance and microbial community

Water Science and Technology, 2006

Application of thermal treatment at 100-140 8C as a pretreatment method prior to anaerobic digest... more Application of thermal treatment at 100-140 8C as a pretreatment method prior to anaerobic digestion of a mixture of cattle and swine manure was investigated. In a batch test, biogasification of manure with thermally pretreated solid fraction proceeded faster and resulted in the increase of methane yield. The performances of two thermophilic continuously stirred tank reactors (CSTR) treating manure with solid fraction pretreated for 40 minutes at 140 8C and non-treated manure were compared. The digester fed with the thermally pretreated manure had a higher methane productivity and an improved removal of the volatile solids (VS). The properties of microbial communities of both reactors were analysed. The specific methanogenic activity (SMA) test showed that both biomasses had significant activity towards hydrogen and formate, while the activity with the VFA-acetate, propionate and butyrate-was low. The kinetic parameters of the VFA conversion revealed a reduced affinity of the microbial community from the CSTR fed with thermally pre-treated manure for acetate, propionate and butyrate. The bacterial and archaeal populations identified by t-RLFP analysis of 16S rRNA genes were found to be identical in both systems. However, a change in the abundance of the species present was detected.

Research paper thumbnail of Computer-Aided Model Based Analysis for Design and Operation of a Copolymerization Process

Chemical Engineering Research and Design, 2006

T he advances in computer science and computational algorithms for process modelling, process sim... more T he advances in computer science and computational algorithms for process modelling, process simulation, numerical methods and design/synthesis algorithms, makes it advantageous and helpful to employ computer-aided modelling systems and tools for integrated process analysis. This is illustrated through the study of a copolymerization process, where operational problems due to their complex nonlinear behaviour are usually encountered, indicating thereby, the need for the development of an appropriate process model that can describe the dynamic behaviour over the complete range of conversion. This will allow analysis of the process behaviour, contribute to a better understanding of the polymerization process, help to avoid unsafe conditions of operation, and to develop operational and optimizing control strategies. In this work, through a computer-aided modelling system ICAS-MoT, two first-principles models have been investigated with respect to design and operational issues for solution copolymerization reactors in general, and for the methyl methacrylate/vinyl acetate system in particular. The Model 1 is taken from literature and is commonly used for low conversion region, while the Model 2 has been derived in this work and covers the complete range of conversion. The performances of the two models are compared with respect to the steady state and dynamic behaviour of the polymerization process. The model analyses highlight the influence of the reaction mechanism, the transport phenomena, the process design and conditions of operation on the polymer grade and the production rate.

Research paper thumbnail of Computer-Aided Modelling of Short-Path Evaporation for Chemical Product Purification, Analysis and Design

Chemical Engineering Research and Design, 2006

A n important stage in the design process for many chemical products is its manufacture where, fo... more A n important stage in the design process for many chemical products is its manufacture where, for a class of chemical products that may be thermally unstable (such as, drugs, insecticides, flavours/fragrances, and so on), the purification step plays a major role. Short-path evaporation is a safe method, suitable for separation and purification of thermally unstable materials whose design and analysis can be efficiently performed through reliable model-based techniques. This paper presents a generalized model for short-path evaporation and highlights its development, implementation and solution through a computer-aided modelling framework, which allows the use of systematic simulation strategies for various types of design/analysis problems. The main features of the model and the modelling framework are highlighted through two case studies: (a) the purification of a reaction mixture containing glycerol, mono-, di-and triglycerides, and (b) the recovery of a pharmaceutical product from a six-component mixture. Validation of the short-path evaporation model is highlighted through the comparison of experimental data from an industrial pilot plant with the simulated results from the model. Also, results from model-based sensitivity analysis and design problem solution are highlighted for two case studies.