99 research outputs found
Integrated approach to chemical process flowsheet synthesis
Chemical process synthesis is an open ended step of process design as it deals with the problem of how to develop and integrate the chemical process flowsheet. Over the past four decades, very few systematic procedures have been proposed for the rigorous synthesis of complete chemical process flowsheets. Mathematical design and heuristics from experience of past processes are the two main methods usually employed in process synthesis. Most approaches for new designs use heuristics based on studying reaction and separation systems in isolation. This thesis discusses the development of a new process synthesis systematic procedure and software that integrates a knowledge based system with Aspen HYSYS process simulator, HYSYS optimizer, Aspen Icarus economic evaluator, and databases, utilising knowledge from existing industrial processes to obtain design rules. The proposed generic superstructure for the synthesis and optimization of reaction-separation-recycle systems has been validated. To account for the non-ideal behaviour of reactors, modular simulation is used and an example of the approach is illustrated for a fluidized bed reactor. Preliminary work in customizing Aspen HYSYS to simulate new unit operation has been illustrated. A Visual Basic for Application (VBA) programming code has been developed to link the integrated knowledge based system (IKBS) to Aspen HYSYS. The prototype IKBS has been applied for the selection of reactor-separator-recycle systems for ethylene oxide, ethylene glycol, acetic acid and cumene manufacturing processes as case studies. A wide range of chemical reactors and separators were considered during the selection process and then elimination occurs at different levels leading to the best alternatives being selected for simulation, optimization and economic evaluation in the second phase of the IKBS for future development. The suggested alternative reactor-separator-recycle systems by the IKBS include currently used processes in addition to novel and recommended reactors/separators in industrial research. The proposed integrated knowledge based approach to chemical process flowsheet synthesis is expected to yield a cost effective design methodology for the petrochemical industry.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Steady State Simulation of Plug Flow Reactor (PFR) In Aspen Plus
In this project work, we report Aspen-plus simulation of a cracking reaction viz. conversion of ethane to ethylene and hydrogen using plug flow reactor system. Ethane, which is produced in refineries isn’t stored under normal temperature and pressure and is often sold at a cost lower than its production cost. However, cracking of ethane produces two very important compounds viz. ethylene and hydrogen which has very wide range of applications. Generally, in industry, cracking takes place in a fluidized bed catalytic cracker. In this work, the performance of plug flow reactor was studied to evaluate the process. Two contrastingly different routes were followed leading to the simulation. The first involved was the simulation of an adiabatic plug flow reactor at different operating conditions viz. feed flow rate, feed temperature, reactor temperature and pressure. The variation of diameter and length of the reactors were also studied in the overall performance of the system. Similarly, simulation studies were carried out for isothermal system as well. The performances of both the reactors were compared. It was observed that under a given set of conditions, isothermal plug flow reactor performed comparatively much better than its adiabatic counterpart
Numerical Formulations For Attainable Region Analysis
Student Number : 9611112G -
PhD thesis -
School of Chemical and Metallurgical Engineering -
Faculty of Engineering and the Built EnvironmentAttainable Region analysis is a chemical process synthesis technique that
enables a design engineer to find process unit configurations that can be
used to identify all possible outputs, by considering only the given feed
specifications and permitted fundamental processes. The mathematical
complexity of the attainable regions theory has so far been a major
drawback in the implementation of this powerful technique into standard
process design tools. In the past five years researchers focused on
developing systematic methods to automate the procedure of identifying
the set of all possible outputs termed the Attainable Regions.
This work contributes to the development of systematic numerical
formulations for attainable region analysis. By considering combinations
of fundamental processes of chemical reaction, bulk mixing and heat
transfer, two numerical formulations are proposed as systematic
techniques for automation of identifying optimal process units networks
using the attainable region analysis. The first formulation named the
recursive convex control policy (RCC) algorithm uses the necessary
requirement for convexity to approximate optimal combinations of
fundamental processes that outline the shape of the boundary of the
attainable regions. The recursive convex control policy forms the major
content of this work and several case studies including those of industrial
significance are used to demonstrate the efficiency of this technique. The
ease of application and fast computational run-time are shown by
assembling the RCC into a user interfaced computer application contained
in a compact disk accompanying this thesis. The RCC algorithm enables
identifying solutions for higher dimensional and complex industrial case studies that were previously perceived impractical to solve.
The second numerical formulation uses singular optimal control
techniques to identify optimal combinations of fundamental processes.
This formulation also serves as a guarantee that the attainable region
analysis conforms to Pontryagin’s maximum principle. This was shown by
the solutions obtained using the RCC algorithm being consistent with
those obtained by singular optimal control techniques
Synthesis and design of integrated reaction-separation systems with complex configurations and rigorous models
Chemical engineering, and specially process design, synthesis and intensification, are well positioned to support both society and industry in overcoming present global challenges of environment degradation, energy supply, water scarcity and food supply. These challenges have been translated into industrial problems that involve the design of chemical processes with decreased water and energy consumption, and improved efficiencies. In this context the present study focuses on the simultaneous synthesis and design of reaction-separation systems including complex configuration distillation columns and using rigorous models. The study is considered a further step in this research area, as previous works have usually focused on the synthesis of sub-networks and have used shortcut models. Additionally, among complex configuration, thermally coupled distillation columns are reported to present significant savings in terms of the total annualised cost of the system. Among the available approaches to synthesis and design, a superstructure optimisation approach is used. The procedure involves the construction of a superstructure that includes a reaction superstructure, taken from Ma et al. (Ma et al. 2019) and a separation superstructure, proposed by Sargent and Gaminibandara (Sargent and K. Gaminibandara 1976). The modelling is performed using generalised disjunctive programming (GDP) to produce a logic-based model. This model is then reformulated into a mixed-integer nonlinear programming (MINLP) optimisation problem, where the objective is to minimise the total annualised cost of the process. For the reformulation convex hull and bypass efficiency methods are used. A modified version of the solving strategy presented by Ma et al. (Ma et al. 2019) is used, which involves using the solver SBB in General Algebraic Modelling System (GAMS).
The proposed framework is applied to a case study previously addressed by Zhang et al. (Zhang et al. 2018) and Ma et al. (Ma et al. 2019). Economic models and assumptions made in those studies are maintained in order to evaluate the benefits of including complex configuration columns in the design possibilities. Results present a flowsheet with one PFR reactor and complex configuration distillation columns that are partially thermally coupled. The total annualised cost of the process is 5.85x105 $/yr, which is 6.3% and 4.7% less than the value achieved by Zhang et al. (Zhang et al. 2018)and Ma et al., respectively. Results show that it is both possible and beneficial to consider complex configuration distillation columns, including thermally coupled ones, in the simultaneous synthesis and design of reaction-separation systems using rigorous models.Chevening AwardsAgencia Nacional de Investigación e Innovació
Studies on design and plant-wide control of chemical processes
Master'sMASTER OF ENGINEERIN
Synthesis and design of integrated reaction-separation systems with complex configurations and rigorous models
Chemical engineering, and specially process design, synthesis and intensification, are well positioned to support both society and industry in overcoming present global challenges of environment degradation, energy supply, water scarcity and food supply. These challenges have been translated into industrial problems that involve the design of chemical processes with decreased water and energy consumption, and improved efficiencies. In this context the present study focuses on the simultaneous synthesis and design of reaction-separation systems including complex configuration distillation columns and using rigorous models. The study is considered a further step in this research area, as previous works have usually focused on the synthesis of sub-networks and have used shortcut models. Additionally, among complex configuration, thermally coupled distillation columns are reported to present significant savings in terms of the total annualised cost of the system. Among the available approaches to synthesis and design, a superstructure optimisation approach is used. The procedure involves the construction of a superstructure that includes a reaction superstructure, taken from Ma et al. (Ma et al. 2019) and a separation superstructure, proposed by Sargent and Gaminibandara (Sargent and K. Gaminibandara 1976). The modelling is performed using generalised disjunctive programming (GDP) to produce a logic-based model. This model is then reformulated into a mixed-integer nonlinear programming (MINLP) optimisation problem, where the objective is to minimise the total annualised cost of the process. For the reformulation convex hull and bypass efficiency methods are used. A modified version of the solving strategy presented by Ma et al. (Ma et al. 2019) is used, which involves using the solver SBB in General Algebraic Modelling System (GAMS).
The proposed framework is applied to a case study previously addressed by Zhang et al. (Zhang et al. 2018) and Ma et al. (Ma et al. 2019). Economic models and assumptions made in those studies are maintained in order to evaluate the benefits of including complex configuration columns in the design possibilities. Results present a flowsheet with one PFR reactor and complex configuration distillation columns that are partially thermally coupled. The total annualised cost of the process is 5.85x105 $/yr, which is 6.3% and 4.7% less than the value achieved by Zhang et al. (Zhang et al. 2018)and Ma et al., respectively. Results show that it is both possible and beneficial to consider complex configuration distillation columns, including thermally coupled ones, in the simultaneous synthesis and design of reaction-separation systems using rigorous models.Chevening AwardsAgencia Nacional de Investigación e Innovació
Adsorptive reactor technology for VOC abatement.
Imperial Users onl
Industrial Chemistry Reactions: Kinetics, Mass Transfer and Industrial Reactor Design
Nowadays, the impressive progress of commercially available computers allows us to solve complicated mathematical problems in many scientific and technical fields. This revolution has reinvigorated all aspects of chemical engineering science. More sophisticated approaches to catalysis, kinetics, reactor design, and simulation have been developed thanks to the powerful calculation methods that have recently become available. It is well known that many chemical reactions are of great interest for industrial processes and must be conducted on a large scale in order to obtain needed information in thermodynamics, kinetics, and transport phenomena related to mass, energy, and momentum. For a reliable industrial-scale reactor design, all of this information must be employed in appropriate equations and mathematical models that allow for accurate and reliable simulations for scaling up purposes. The aim of this proposed Special Issue was to collect worldwide contributions from experts in the field of industrial reactor design based on kinetic and mass transfer studies. The following areas/sections were covered by the call for original papers: Kinetic studies on complex reaction schemes (multiphase systems); Kinetics and mass transfer in multifunctional reactors; Reactions in mass transfer-dominated regimes (fluid–solid and intraparticle diffusive limitations); Kinetic and mass transfer modeling using alternative approaches (ex. stochastic modeling); Simulations in pilot plants and industrial-sized reactors and scale-up studies based on kinetic studies (lab-to-plant approach)
Mathematical modelling of a low-temperature hydrogen production process with In Situ CO2 capture
Imperial Users onl
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