Simultaneous optimization of energy and materials based on heat exchanger network simulation for diesel hydrotreating units

Research advances on process systems integration and process safety in China

Process systems engineering research focuses on the planning, design, operation, and safety of process systems rather than unit operations. In response to the rapid growth of the chemical process industry in the last 20 years in China, advanced system integration and process safety technologies are investigated and applied for better resource utilization, less environmental impact, and safer working places. In this regard, the review in this article consists of four main achievements: (1) process synthesis, (2) energy system integration, (3) water system integration, and (4) process safety management. The purpose of process synthesis and integration is to improve resource and energy utilization, at the same time lowering by-products and emissions. Optimization is conducted on process structure and operation, following the principles of resource coupling and energy cascade utilization. Typical examples are coupling of coal and hydrogen-rich resources and integration of coal-based polygeneration process of chemicals, electricity, and heat. Energy integration implements the coordinated optimization of total site energy systems. Reviews are made on specific methodologies based on the thermodynamics and applications of design and retrofit in ethylene, oil refining, and synthetic ammonia industries. There are energy savings by 10%–20% and yields increasing by 20%–30%. In addition, waste heat recovery and cold energy utilization are also important research areas. Reviews on the progress of water system integration and its industrial applications are also conducted. It includes the direct reuse, regeneration, and reuse/recycle in water systems and systems with internal water mains. Finally, safety management and technologies are also indispensable technological advancements of the process. The legislation system and the work safety-related standard system have been gradually established and enforced. Process safety research progress is reviewed, and questions are proposed for improving the accident prevention and safety management agenda.

A novel high level canonical piecewise linear model based on the simplicial partition and its application

The piecewise linear (PWL) model has attracted more and more attention in recent research because it can handle complex nonlinearity while maintaining linearity in local regions. A large number of compact representations for PWL modeling have been introduced, such as hinging hyperplanes and its generalized version. However, the existing methods usually give rise to many and complex subregions, which is an issue known as "curse of partitions", and hampered practical applications of PWL models. In this paper, a novel high level canonical PWL model is presented to tackle the curse of partitions. In more detail, an improved simplicial partition strategy with alterable intervals is proposed to improve the model representation capability. The proposed PWL model guarantees an unchangeable topology during training and thus a limited number of subregions after training. Several numerical experiments, and a simulated chemical process, are used to demonstrate the effectiveness of the proposed model.