Framework of computer-aided sustainable integrated process design and control for reactor systems

Abstract

An integrated process design and control (IPDC) methodology has been developed which is able to identify and obtain an optimal solution for the IPDC problem for chemical processes in an easy, simple and efficient way. However, the developed IPDC methodology does not consider any sustainability aspect in the analysis. This study aims to develop a framework of computer-aided sustainable integrated process design and control (SustainIPDC) for reactor systems. This new framework methodology was developed in order to ensure that the process is more economical, controllable as well as sustainable to meet the product quality specifications. The Sustain-IPDC problem for reactor systems, typically formulated as a generic optimization problem was solved by decomposing it into six hierarchical stages: (i) pre-analysis, (ii) design analysis, (iii) controller design analysis, (iv) economic analysis, (v) sustainability analysis, and (vi) final selection and verification. Using thermodynamics and process insights, a bounded search space was first identified. This feasible solution space was further reduced to satisfy the process design, controller design and economic constraints in stages 2, 3 and 4, respectively. The sustainability aspect was then analyzed in stage 5 to satisfy the sustainability constraints, until in the final stage all feasible solutions (candidates) were ordered according to the defined performance criteria (objective function). The final selected design was then verified through rigorous simulations or experiments. In the first stage, the concept of the attainable region (AR) was used to locate the optimal solution. The target for this optimal solution was defined and selected at the maximum point of the AR diagram. It is expected that the solution target will show higher value of the objective function, hence verifying the optimal solution for the SustainIPDC problem for reactor systems. In addition, the sustainability calculator (called SustainPlus©) was also developed in this study in which the simultaneous calculation of three sustainability indices (one-dimensional, two-dimensional, and three-dimensional) can be performed in one single analysis. Then, the developed methodology were verified by using two different case studies; (i) production of cyclohexanone in a continuous-stirred tank reactor system, and (ii) biomass production in two continuous bioreactor system. Based on two different case studies that have been performed, the results have shown that the optimal solution in terms of design, controller design, economic and sustainability is the best at the highest point of the AR diagram. It also shows that the proposed SustainIPDC methodology is able to find the optimal solution that satisfies design, controller, economics and sustainability criteria in an easy, efficient and systematic way.