Evaluación de la eficiencia de procesos químicos: Reactor i separación

Treballs Finals de Grau d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Curs: 2017-2018, Tutors: Jordi Bonet Ruiz, Alexandra Elena Bonet RuizChemical sector is one of the big sectors in the world. The shortage of raw materials, the importance in the sustainability, as the environmental requirements, and the increased of competition make the necessity of investigation and application of more efficient and cost-effective processes (Recker et al, 2015). One tool in the search or optimization of process is the use of simulators, which allow us obtaining results quickly and easily in complex processes using simplified models, allowed us to do changes or variations in same process to compare with each other. However, rigorous simulations requires a great effort and therefore it is not suitable for process screening. Due to the shortage of methods that study the efficiency of the process at early process design stages, in this work has been developed a short cut method that allows obtaining the efficiency of the alternative process schemes considering reactor and separation jointly. This method is based on application of DSE (Distillation Sequence Efficiency), to which is added a correction factor to take into consideration the reactor. ETBE (Ethyl Tert-Butyl Ether) production process is used as case study. Analyzing the different alternatives of design of the chosen alternative, trough simulations in AspenPlus®, is determined the feasibility of each of the alternatives suggested. The DSE with the correction factors for the calculation of the efficiency is implemented using FORTRAN® in AspenPlus®

Integrated reaction-separation processes sequencing and screening at early stages of design

Process intensification and selection of the most efficient chemical process provides resources conservation and decreases the energy consumption to minimize CO2 emissions. Distillation Sequence Efficiency (DSE) method is extended to chemical processes also considering the reactors to provide a very simple and useful process design tool. A minimum amount of input data and computation power is required for a fast screening providing a basis for other more rigorous methods, i.e. including a cost assessment. The method considers, in a rough approach but at very early stages of process design, three factors related to environmental impact resources conservation and catalyst costs. The input data required is the vapour-liquid equilibrium represented by a proper thermodynamic model and some other predictable basic thermodynamic data. As it is an early stage approach, the reactor outputs can be assumed at chemical equilibrium minimizing the free Gibbs Energy. The ∞/∞ analysis is used to check the feasibility and calculate the stream flow rates and compositions. The distillation column output streams are at boiling point, and therefore the input data for the DSE method is available, which quantifies the process efficiency and therefore it is related to its environmental impact. A resources conservation factor, considering reactant losses, relates the product quantity generated to the amount that could be generated. A catalyst cost factor, considering catalyst deactivation, relates the feed raw materials to the system with the total feed stream to the reactor. ETBE (Ethyl Tert-Butyl Ether) production process is used as a case study. According to the results, the best alternative is the intensified process, i.e. reactive distillation, followed by the process proposed in the BREF. Other five alternative process schemes values are all in agreement with Recker et al. (2015) cost assessment results. However, there is disagreement between methods only in one case due to catalyst cost

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

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

Multi-scale Optimization Frameworks for Integrated Process and Material Design and Intensification

Meeting energy and chemical production demands while reducing costs and emissions is a grand challenge. Intensified processes which merge multiple tasks while maintaining performance can significantly reduce equipment footprint, energy input and costs. Effectively designing such processes requires balancing competing trade-offs on multiple levels. A multi-scale framework is developed for simultaneous consideration of operational and material decisions by posing the intensified process design problem as an optimization formulation. Models and constraints related to process operations, process performance, product quality and material properties are incorporated into the framework. The framework is applied to intensify the separation and storage of methane (CHv4) from feed-stocks by exploiting the preferential adsorption properties of zeolites. However, meeting constraints on CHv4 loss and purity while maximizing the storage capacity is a challenge requiring consideration of both process and material decisions. The complete dynamic process model and constraints along with adsorption isotherm models are posed as a nonlinear programming (NLP) problem. Adsorption isotherm data on 178 siliceous zeolite frameworks are obtained using Grand Canonical Monte Carlo (GCMC) simulations. An initialization strategy is developed to aid in optimizing the model using which the top candidate zeolites and their corresponding process conditions are determined for different feed compositions. The analysis is extended to obtain target material property maps by extensively sampling the material property space (Henry coefficient, deliverable capacity, isotherm parameters) using a Latin Hypercube based strategy. Data from publicly available zeolite databases are super-imposed onto these maps to identify the top zeolite structures for process performance and feasibility. Another application studied is the design of a process to integrate COv2 capture and syngas pro-duction using methane feedstocks. The energy intensive periodic pressure changes employed for adsorbent-based COv2 capture are avoided by using a CHv4 rich purge feed to strip the adsorbed COv2 which then becomes feed for syngas production. A data-driven constrained optimization algorithm is applied to identify process conditions which satisfy process specifications and product quality requirements and to determine optimal process decisions for different objectives and feedstocks. The importance of the multi-scale optimization approach in designing novel intensified processes is demonstrated through these applications