Studies On Modeling And Advanced Control Technologies Applied To Two Chemical Processes

The modeling and process control problems for two chemical plants (manufacturing phenylpyruvic acid and butadiene) are studied in this dissertation.The enzymatic L-phenylalanine process developed by Nanjing University of Technology, including two parts: the synthesis processes of phenylpyruvic acid and the transfer-ammonia reaction for producing L-phenylalanine, is a typical batch chemical process. The problem of modeling and process control for synthesis of phenylpyruvic acid was studied in this thesis. It consists of the kinetics of the double carbonylation of benzylchloride, modeling and control for the reaction process of phenylpyruvic acid, and modeling of the crystal size distribution for the crystallization process of phenylpyruvic acid sodium salt. All of these projects are very useful to the industrialization of the L-phenylalanine process.The butadiene plant belonged to Yangzi Branch of SINOPEC is a big chemical industrial process, including extraction distillation, compression, and normal distillation workshop sections. By making use of the chance in which the control device was changed from conventional instrument to distributed control system, the modeling was studied, and a new advanced control system was developed. This part of work has been brought into use in the industrial plant, and has acquired notable economic benefit. Furthermore, in order to obtain the field data, a communication approach was proposed, which made the web communication low costed, and provided the bases of modeling and process control.The textual content is divided into three parts.The first part is an overview with regard to modeling and process control in chemical engineering, given in Chapters 1 and 2.The second part is a research concerning the production of phenylpyruvic acid in the L-phenylalanine process, including the Chapters 3, 4 and 5. L-phenylalanine is a very important raw material in medicine and food industries, which can't yet be produced industrially in China at the present time. The main reason is that theproducing cost is too high, therefore the product is short of market competition. The enzyme method synthesis technique of L-phenylalanine developed by Nanjing University of Technology possess the prospect for industrial scale production, and the phenylpyruvic acid process, especially the bouble carbonylation reaction of benzylchloride, is the most important procedure.In Chapter 3, by means of mechanism and statistics hybrid method, the kinetics model of the double carbonylation of benzylchloride is built up. In Chapter 5, with artificial neural network and regression hybrid method, a intrinsic model is established from the limited experimental data. This model reflects the operation performance of the reaction preferably. Depending on the model, a control scheme is proposed based on internal model control and inferential control. Elemental simulation has vindicated the feasibility of this control scheme. In Chapter 4, the modeling problem of the crystal size distribution (CSD) for the crystallization process of phenylpyruvic acid sodium salt was studied. The CSD reflects the operation quality of the crystallization process, and should be controlled strictly. An assumption is brought forward that the whole reactor is decomposed into two perfect mixed hypo-reactors connected in series and with backmixing between them, therefore the problem was settled that crystals are not uniformly distributed. Then, the continuous crystal size distribution was treated to be in discretization, and the difficult was avoided for solving the partial differential equation of crystal number equilibrium. Finally, a CSD model was built up, which is quite simple and easy to solve. The model can be used to predict the CSD of the crystallization process, therefore possesses distinguished practical value, and the same ideology could afford to be used to the crystallization process of phenylalanine salt.The third part including Chapters 6, 7, and 8 is concerning a study on modeling and process control for a butadiene plant...