{"title":"A robust optimization framework for forest biorefineries design considering uncertainties on biomass growth and product selling prices","authors":"Bruno Theozzo, Moises Teles dos Santos","doi":"10.1016/j.compchemeng.2023.108256","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108256","url":null,"abstract":"<div><p>The dependence of biomass growth on uncontrolled environmental factors and the lack of confidence in product selling price estimation imposes challenges for the efficient design of biorefineries, especially for forest systems, which present complex and long-termed growth behavior. The present work proposes the expansion of an optimization framework for forest biorefineries design to handle uncertainties on both biomass productivity and product selling prices. A robust formulation is proposed under a box and polyhedral uncertainty set formulation allowing its conservatism degree to be controlled. A case study of a eucalyptus biorefinery in Brazil illustrates the model's capabilities. The canonical worst-case approach to uncertainties on selling prices leads to a null optimal Net Present Value (NPV) and, on biomass growth, leads to a design that uses a 70% excess of lands. Scenarios of a controlled degree of conservatism lead to designs closer to the uncertainty-free optimal NPV of 136 bi BRL.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"175 ","pages":"Article 108256"},"PeriodicalIF":4.3,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3267509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jinhyeun Kim , Christopher Luettgen , Kamran Paynabar , Fani Boukouvala
{"title":"Physics-based Penalization for Hyperparameter Estimation in Gaussian Process Regression","authors":"Jinhyeun Kim , Christopher Luettgen , Kamran Paynabar , Fani Boukouvala","doi":"10.1016/j.compchemeng.2023.108320","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108320","url":null,"abstract":"<div><p>In Gaussian Process Regression (GPR), hyperparameters are often estimated by maximizing the marginal likelihood function. However, this data-dominant hyperparameter estimation process can lead to poor extrapolation performance and often violates known physics, especially in sparse data scenarios. In this paper, we embed physics-based knowledge through penalization of the marginal likelihood objective function and study the effect of this new objective on consistency of optimal hyperparameters and quality of GPR fit. Three case studies are presented, where physics-based knowledge is available in the form of linear Partial Differential Equations (PDEs), while initial or boundary conditions are not known so direct forward simulation of the model is challenging. The results reveal that the new hyperparameter set obtained from the augmented marginal likelihood function can improve the prediction performance of GPR, reduce the violation of the underlying physics, and mitigate overfitting problems.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"178 ","pages":"Article 108320"},"PeriodicalIF":4.3,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2823496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An Efficient Reinforcement Learning Approach to Optimal Control with Application to Biodiesel Production","authors":"Shiam Kannan , Urmila Diwekar","doi":"10.1016/j.compchemeng.2023.108258","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108258","url":null,"abstract":"<div><p>Optimal control problems are one of the most challenging problems in optimization. This paper presents a new and efficient Reinforcement Learning approach to optimal control problems based on the Batch Q-learning algorithm. To improve the convergence of the RL algorithm, we use k-dimensional uniformity of advanced sampling procedures, namely employing Hamersley sequences (HSS). HSS is used to randomly sample the state variables and discrete controls from the action space for the RL optimal control problem. The Neural-fitted Q-iterative algorithm is applied to solve an optimal control problem for a first-order state dynamical system. A real-world application of optimal temperature profile determination for biodiesel production in a batch reactor is presented. We present the comparison of our HSS-RL algorithm with that of the maximum principle.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108258"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1751388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Zone-wise surrogate modelling (ZSM) of univariate systems","authors":"Srikar Venkataraman Srinivas, Iftekhar A Karimi","doi":"10.1016/j.compchemeng.2023.108249","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108249","url":null,"abstract":"<div><p>Many complex systems display distinctly different behaviors across regions, zones, or sub-domains. A single surrogate may not suffice in modelling such systems. A better approach would be to identify the various zones and model them individually. In this work, we propose a zone-wise surrogate modelling (ZSM) algorithm to identify various zones in a system's input domain based on a user-specified acceptable goodness of fit and recommend the best surrogate for each identified zone from a library of potential surrogates. We have assessed ZSM on ten case studies involving complex 1-D functions and compared its modelling performance against some non-linear and piecewise models. We also show how ZSM can help in global optimization using five complex multimodal functions and found that a ZSM-based approach successfully identifies the true global optima of these functions. In future, we aim to extend ZSM for the modelling and optimization of complex multi-input single-output (MISO) systems.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108249"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3451000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Numerical investigation of hydrogen production from low-pressure microwave steam plasma","authors":"Oytun Oner, Ibrahim Dincer","doi":"10.1016/j.compchemeng.2023.108230","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108230","url":null,"abstract":"<div><p>Hydrogen is recognized as a suitable energy carrier that can facilitate the storage and transport of renewable energy. In this context, hydrogen production from microwave-excited steam plasma is one of the least researched techniques and lacks numerical study due to the complex plasma kinetics and difficullty of the simulation process. Therefore, in this study, a kinetic model is developed for steam plasma, considering forty-one reactions and fourteen species. Two-dimensional microwave steam plasma is modeled using COMSOL Multiphysics software for the first time. At a microwave power of 800 W, plasma formation and hydrogen production from low pressure (1 Torr) and high temperature (150 °C) steam plasma are numerically studied within the time domain of 10<sup>−10</sup> to 10<sup>−4</sup> s. The presented results demonstrate that the maximum electron density reaches 5 10<sup>17</sup> <em>m</em><sup>−3</sup> at 10<sup>−4</sup>s, and 16.8% of the water molecules dissociate to form various species. The conversion rate of water molecules to hydrogen is calculated as 24%. According to the thermodynamic evaluations, the proposed system's energy and exergy efficiencies are 10.31% and 10.14%, respectively, with a hydrogen production rate of 0.68 μg/s. Furthermore, the effect of the applied microwave power on plasma properties and hydrogen production is parametrically studied. Despite the proportional relationship between the input power and hydrogen production, no correlation is found between microwave power and system efficiency.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108230"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1820234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A dynamic model of tablet film coating processes for control system design","authors":"Cecilia Pereira Rodrigues , Carl Duchesne , Éric Poulin , Pierre-Philippe Lapointe-Garant","doi":"10.1016/j.compchemeng.2023.108251","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108251","url":null,"abstract":"<div><p>Aqueous film coating is a common and important step in the production of most pharmaceutical tablets. Controlling this process is beneficial to maintain stable and optimal operation and the use of a model capable of describing its main physical phenomena is fundamental for control system design. This paper presents the development of a dynamic macro scale model of a pan coater based on energy and mass transfer equations. Model complexity is kept low to simplify parameterization and allow for real-time applications, such as the development of system observers to estimate critical unmeasured variables. Pilot plant data from seven batches, ran according to designed experiments, are used for model calibration and validation. The final model adequately captures the global trajectories of the main process variables; mean differences between experimental and simulated values are below 2 °C for the outlet gas and tablet bed temperatures, and 2% for the outlet gas relative humidity.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108251"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1694867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian Langner , Elin Svensson , Stavros Papadokonstantakis , Simon Harvey
{"title":"Flexibility analysis using boundary functions for considering dependencies in uncertain parameters","authors":"Christian Langner , Elin Svensson , Stavros Papadokonstantakis , Simon Harvey","doi":"10.1016/j.compchemeng.2023.108231","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108231","url":null,"abstract":"<div><p>In this work, we present a novel approach for considering dependencies (often called correlations) in the uncertain parameters when performing (deterministic) flexibility analysis. Our proposed approach utilizes (linear) boundary functions to approximate the observed or expected distribution of operating points (i.e. uncertainty space), and can easily be integrated in the flexibility index or flexibility test problem. In contrast to the hyperbox uncertainty sets commonly used in deterministic flexibility analysis, uncertainty sets based on boundary functions allow subsets of the hyperbox which limit the flexibility metric but in which no operation is observed or expected, to be excluded. We derive a generic mixed-integer formulation for the flexibility index based on uncertainty sets defined by boundary functions, and suggest an algorithm to identify boundary functions which approximate the uncertainty set with high accuracy. The approach is tested and compared in several examples including an industrial case study.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108231"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1751386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A scalable optimization framework for refinery operation and management","authors":"Mayank Baranwal , Mayur Selukar , Rushi Lotti , Aditya A. Paranjape , Sushanta Majumder , Jerome Rocher","doi":"10.1016/j.compchemeng.2023.108242","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108242","url":null,"abstract":"<div><p>End-to-end refinery management is a complex scheduling problem requiring simultaneous optimization of coupled subprocesses at several stages. In the specific context of this paper, a planner needs to ascertain (i) how best to store incoming crude at a port, (ii) schedule its transfer, after dewatering, to downstream refinery tanks, and (iii) schedule further processing in the crude distillation units (CDUs). The movement and storage of crude is subjected to various physico-chemical and operational constraints. The resulting optimization problem is combinatorial in nature and scales exponentially with the number of tanks, types of crude, and modes of operation. The problem becomes particularly challenging with stochasticity in crude receipt, requiring the planner to modify their decisions in real-time. In this paper, we develop a scalable, hierarchical framework to address the end-to-end refinery management for throughput maximization. The framework relies on an innovative approach to decoupling the decision-making at port and refinery, reducing significantly the complexity of the overall optimization problem. The proposed approach also results in a significant improvement over the schedules generated by an expert human planner for throughput maximization. It takes only a few minutes to execute the entire optimization routine, over a 30 day planning window, on a standard computer, making it possible to use implement our approach in a time-critical, real-time operational setting.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108242"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1820126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Light Attention-Mixed-Base Deep Learning Architecture toward Process Multivariable Modeling and Knowledge Discovery","authors":"Yue Li , Lijuan Hu , Ning Li , Weifeng Shen","doi":"10.1016/j.compchemeng.2023.108259","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108259","url":null,"abstract":"<div><p><span><span>A Light Attention-Mixed-Base Deep Learning Architecture (LAMBDA) is developed to simultaneously achieve process knowledge discovery and high-accuracy multivariable modeling. By organizing multiple network bases and a novel light attention mechanism in a special way, the proposed LAMBDA is capable to learn different factors affecting the chemical process outputs, i.e. the basic dynamic characteristics, transient disturbances and other unknown factors. Besides, a development procedure embedding a hyperparameter optimization framework—Optuna is performed to optimize the network architecture. Compared with baselines including </span>FNN<span>, CNN<span>, LSTM and Attention-LSTM, the new architecture displays an outstanding fitting capacity on the discharge </span></span></span>flowrates modeling of an actual deethanization process. The process knowledges extracted from the LAMBDA model parameters are also illustrated, which are valuable in the development of advanced process tasks. The proposed LAMDBA can fit any number of outputs without degrading the knowledge discovery ability, making itself potential in the modeling of complex chemical processes.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108259"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2622920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Physics Informed Piecewise Linear Neural Networks for Process Optimization","authors":"Ece Serenat Koksal , Erdal Aydin","doi":"10.1016/j.compchemeng.2023.108244","DOIUrl":"https://doi.org/10.1016/j.compchemeng.2023.108244","url":null,"abstract":"<div><p>Constructing first-principles models is usually a challenging and time-consuming task due to the complexity of real-life processes. On the other hand, data-driven modeling, particularly a neural network model, often suffers from overfitting and lack of useful and high-quality data. At the same time, embedding trained machine learning models directly into the optimization problems has become an effective and state-of-the-art approach for surrogate optimization, whose performance can be improved by physics-informed machine learning. This study proposes using piecewise linear neural network models with physics-informed knowledge for optimization problems with neural network models embedded. In addition to using widely accepted and naturally piecewise linear rectified linear unit (ReLU) activation functions, this study also suggests piecewise linear approximations for the hyperbolic tangent activation function to widen the domain. Optimization of three case studies, a blending process, an industrial distillation column, and a crude oil column are investigated. Physics-informed trained neural network-based optimal results are closer to global optimality for all cases. Finally, associated CPU times for the optimization problems are much shorter than the standard optimization results.</p></div>","PeriodicalId":286,"journal":{"name":"Computers & Chemical Engineering","volume":"174 ","pages":"Article 108244"},"PeriodicalIF":4.3,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1694863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}