On-line Monitoring Of Performance Targets And Optimization Of Control Strategy For Limestone Wet Flue Gas Desulphurization

Based on limestone-gypsum wet flue gas desulphurization (WFGD) technology with forced oxidation absorber, two parts of optimization of performance targets and control strategy are thoroughly studied. According to on-line monitoring data that is obtained in the practical operation process, and taking No.11 FGD site in Taiyuan Second Thermal Power Plant (TSTPP) as an example, this paper explicitly introduces the methods and steps of optimization.Firstly, typical process procedures, chemical reaction mechanism, distribution of main measure points, main operating parameters and main control systems are introduced briefly, and this paper gives a conclusion that slurry pH value, calcium-sulfur mole ratio and liquid-gas ratio are irrelevant parameters, and other parameters can be uniquely ascertained by them. Besides, some conclusions that most control systems are executed with feed forward and feed back control strategy and more complicated systems are executed with series circuit control strategy are obtained. Secondly, models of technical performance targets including SO2 removal efficiency and outlet SO2 concentration and models of economical performance targets including the consumption of limestone, electricity and water are established. Besides, this paper deduces the practical models at the time between 21:00, Mar.28th, 2007 and 3:00, Mar.29,2007 on No.11 FGD site in Taiyuan Second Thermal Power Plant by utilizing least square linear or nonlinear regression methods, and solves the optimum values of pH value, calcium-sulfur mole ratio and liquid-gas ratio by multi-object programming method. At last, taking No.11 FGD site in Taiyuan Second Thermal Power Plant as an example, the paper explicated analyzes the control strategy of slurry pH value control system and boost up fan pressure control system, ascertains the model of coupling system by mechanism modeling and makes a simulation study. In addition, because of the feature of delay and inertia, this paper executes optimization and simulation study using Smith estimating and compensating method with the result of excellent performance of slurry pH value in dynamic response.This study combines with theory and practice according to operating data, the models of performance targets and control systems are valuable in simulating study with limestone-gypsum wet flue gas desulphurization technology, and the optimum operating parameters that are obtained can guide operators in practical operating, besides, the methods and processes also could give a tip in the optimization study with other desulphurization technologies.