Rising populations put huge stresses on natural resources. Extraction and depletion of raw materials and waste created throughout the supply chain of products have enormous environmental and ...socioeconomic impacts. One way to reduce these impacts is through the move towards the circular economy (CE). CE aims to solve resource, waste, and emission challenges confronting society by creating a production-to-consumption total supply chain that is restorative, regenerative, and environmentally benign. This article highlights research challenges and identifies process systems engineering (PSE) research opportunities to assist in the understanding, analysis and optimization of CE supply chains. A motivating example on the supply chain of coffee is introduced to illustrate the challenges of the transition towards a CE and to propose PSE research opportunities.
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•A survey of the state-of-the-art process systems engineering (PSE) approaches for process intensification.•An overview of the development of various process intensification ...technologies.•Survey of recent advances in modeling, design, and synthesis of intensified systems.•Assessment methods for the controllability/operability/safety performance of intensified process systems.
Process intensification offers the potential to drastically reduce the energy consumption and cost of producing chemicals from both bulk and distributed feedstocks. This review article aims to offer an extensive survey on state-of-the-art process systems engineering (PSE) approaches for process intensification. From both academic and industrial perspectives, this paper provides an overview of the development of various process intensification technologies, specifically those under the categories of separation, reaction, hybrid reaction/separation, and alternative energy sources. A current status analysis in the areas of modeling and simulation is then provided. An indicative list of PSE publications specialized on process intensification is presented to illustrate the progresses made so far towards the deployment of novel process intensification technologies. We also highlight some recent advances for the modeling, design, and synthesis of intensified systems, as well as for the assessment of their controllability/operability/safety performance. Key open questions in these areas include: (i) how to systematically derive intensified designs, and (ii) how to ensure the operability and optimality of the derived intensified structures while delivering their expected functionality.
•A review of recent progress on the conceptual synthesis of intensified processes with state-of-the-art process systems engineering (PSE) approaches.•A survey of current work on the ...control/operability/safety assessment methods for process intensification designs.•Major challenges and future research opportunities discussed towards the synthesis of operable process intensification systems.
Process intensification (PI) has been gaining increasing momentum in the chemical engineering research community and the chemical/energy industry. While many PI alternative technologies and their conventional counterparts exist, systematic approaches and tools to decide on the most promising intensified process solutions are currently rather lacking. Process Systems Engineering (PSE) can contribute uniquely to this challenge by leveraging process synthesis, design, analysis, and optimization tools. However, key open questions in this area still remain, including: (i) how to efficiently address the combinatorial design space and systematically deliver intensified designs, and (ii) how to ensure the operablility performances of the derived intensified structures at an early design stage. This paper provides a brief review of recent progress towards the synthesis of operable process intensification systems, highlights major challenges, and discusses future research opportunities.
Machine learning-based model predictive control (ML-MPC) has been developed to control nonlinear processes with unknown first-principles models. While ML models can capture nonlinear dynamics of ...complex systems, the complexity of ML models leads to increased computation time for real-time implementation of ML-MPC. To address this issue, in this work, we propose an explicit ML-MPC framework for nonlinear processes using multi-parametric programming. Specifically, a self-adaptive approximation algorithm is first developed to obtain a piecewise linear affine function that approximates the behaviors of ML models. Then, multi-parametric quadratic programming (mpQP) problems are formulated to generate the solution map for states in discretized state–space. Furthermore, to accelerate the implementation of explicit ML-MPC, a neighbor-first search algorithm is developed. Finally, an example of a chemical reactor is used to demonstrate the effectiveness of the explicit ML-MPC.
•An explicit MPC framework for MPCs using a general class of ML models.•A self-adaptive algorithm for approximating ML models with the desired accuracy.•Neighbor-first search algorithm for accelerating implementation of explicit ML-MPC.•Improvement of computational efficiency demonstrated in a chemical process example.
•Multi-fluid model with heterogenous condensation in supersonic separator was built.•Interphase slip and droplet behavior of heterogenous condensation were studied.•Dew point depression and water ...removal rate of supersonic separator were predicted.•Both heat transfer coefficient and residence time of droplets must be considered.•Optimal radius is 0.85 μm and water removal rate is 87.82% when pin = 250 kPa.
Supersonic separation is a novel technology. A multi-fluid slip model for swirling flow with homogenous/heterogenous condensation and evaporation processes in the supersonic separator was built to estimate the separation efficiency. This model solves the governing equations of compressible turbulent gas phase and dispersed homogenous/heterogenous liquid phase considering droplet coalescence and interphase force. Its prediction accuracy for condensation and swirling flows was validated. Then, the flow field, slip velocity and droplet trajectory inside the separators with different swirl strengths were investigated. The maximum values of radial slip velocity are 29.2 and 8.26 m/s for inlet foreign droplet radius of 1.0 and 0.4 µm. It means the larger foreign droplet has a better condensation rate. However, the residence time of larger foreign droplet in core flow is shorten. Thus, the inlet radius of foreign droplet has to be moderate for best separation efficiency. Finally, the dehydration performances of separator were evaluated. The optimal radius of inlet foreign droplet to maximize the dehumidification and efficiency was found. For the separator with swirl strength of 22%, the optimal radius is 0.85 µm at inlet pressure of 250 kPa, where the maximum dew point depression is 42.41 °C and the water removal rate is 87.82%.
•Process intensification synthesis for dividing wall columns and complex distillation sequences.•Phenomena-based representation via the Generalized Modular Representation Framework.•Gibbs free ...energy-based driving force constraints to intensify mass/heat transfer performance.•Mixed-integer nonlinear optimization to generate optimal and intensified process solutions.•Application on an industrial methyl methacrylate purification process.
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In this work, we present a process intensification synthesis approach for the design of dividing wall columns based on the Generalized Modular Representation Framework. A superstructure-based representation is developed to represent chemical process alternatives leveraging modular phenomenological building blocks (i.e., pure heat exchange module, mass/heat exchange module). Novel process structures, including but not limited to dividing wall columns, can be systematically generated to enhance process cost and/or energy performance without pre-postulation of equipment design. To describe the possible liquid-vapor and liquid-liquid phase behaviors of the multi-component mixture, rigorous physical property calculations (e.g., UNIQUAC) are explicitly incorporated. The synthesis model is formulated as a single mixed-integer nonlinear optimization problem. The applicability and versatility of the proposed framework is showcased via an industrial case study on methyl methacrylate purification by Dow Global Technologies. Two new dividing wall column designs are obtained, both of which can achieve equipment size reduction and substantial energy savings compared to the original patent design.
•High-fidelity dynamic modeling of a reactive distillation (RD) system.•Design-dependent explicit/multi-parametric model predictive control under disturbances.•Simultaneous design and control via ...mixed-integer dynamic optimization.•Case study on design and control optimization of a methyl tert-butyl ether RD system.
We present a detailed dynamic model for a reactive distillation system, based on which we develop design-dependent explicit optimal control strategies. A mixed-integer dynamic optimization formulation is then proposed integrating design, control and operational components, the solution of which allows us to derive explicit closed-loop strategies that maintain stable and operable conditions in the presence of process disturbances. The simultaneous approach is illustrated with the design of a methyl tert-butyl ether reactive distillation system example as a part of the developed model library in the RAPID SYNOPSIS project.
Enhancing the lifetime of organic light-emitting diodes (OLEDs) is essential for their industrial application. Here, the influence of different driving schemes and interfacial barrier on the ...degradation rate of the deep blue fluorescent OLEDs is investigated. The results reveal that the driving schemes, which are constant current driving, constant voltage driving, and pulsed current driving schemes, strongly affects the lifetime of OLEDs. The lifetime of LT 90 (90% drop of the brightness) under constant voltage driving is the shortest (156 h) due to the high equivalent resistance. On the contrary, the LT 90 of the OLED under pulsed current driving is the longest (807 h), which is attributed to a low built-in electric field resulted from the decreased accumulation of carriers. Meanwhile, through decreasing the interfacial barrier by doping light emitting layer in electron transporting layer and/or hole transporting layer to modulate the charge accumulation at the interface, the lifetime of OLEDs under pulsed current driving was further increased. The LT 90 of the device increases by 1.84 times to as long as 1483 h, which is the record to the best of our knowledge. This work sheds light on the mechanism of increasing the lifetime of OLEDs and facilitates their industrial application.
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