Modeling And Optimization Of Wet Flue Gas Desulfurization Process

With the development of our country’s economy, the demand for electricity is increasing rapidly. At present, as the low penetration of new energy power plants in the power market, thermal power plants is still dominant. The increase of power load will lead to a sharp increase in the amount of flue gas discharged from the power plant. And flue gas can easily lead to acid rain which will speed up the corrosion of building, acidize soil and affect the growth of plants. Besides, flue gas will also induce the burst of chronic respiratory disease and reduce the body’s immune system which has a direct impact on human health. In order to solve the contradiction between the increasing demand of the load and the protection of the atmosphere environment, most of the power plants are equipped with the desulfurization system, which carry on desulphurization processing to the flue gas discharged from the power plant. Therefore, how to make the power plant desulfurization system efficient, stable and economic operation has become a research hotspot. This paper provides ideas and theoretical guidance to solve the two problems of wet flue gas desulfurization, one problem is theoretical modeling and analysis of complex desulphurization system, another is improving the contradiction between desulfurization efficiency and operation cost, which can achieve the stable, economy, sustainable operation of desulfurization system under the premise of environmental protection standards.On the basis of a comprehensive understanding of the technology and principle of wet desulfurization, this paper takes wet limestone flue gas desulfurization system as the research object, the main contributions of this paper are as follows:1. Introduce the structure of typical limestone wet flue gas desulfurization system and its subsystem which includes flue gas heat exchanger system, sulfur dioxide absorption system, limestone preparation system, gypsum dewatering system and wastewater treatment system. Then describe the desulfurization technology and the principle of desulfurization, which provides a theoretical basis for the subsequent theoretical analysis.2. Discussions are made on the operating parameters that affect the desulfurization efficiency in the limestone wet flue gas desulfurization process. Desulfurization rate are compared under the changes of calcium to sulfur ratio, liquid-gas ratio, pH value and the concentration of inlet flue gas. Multi-factor response test based on response surface methodology was designed and by utilizing the Box-Behnken Designs central composite design model we get a model that describes the relationship between operating parameters and the desulfurization efficiency. The impact caused by the interaction of the system parameters were discussed and analysis was made on the variance of the factors. The results show that liquid-gas desulfurization ratio is the main factor that affects the response and the interaction between liquid-gas desulfurization ratio and calcium to sulfur ratio also affects the desulfurization ratio greatly.3. Based on the desulphurization efficiency model, establish desulfurization economic model when take material consumption, energy consumption and gypsum income of the system into consideration. Then using variable weight particle swarm optimization algorithm to solve this optimizing problem with multiple constraints. The result shows that this model can obtain the best parameters combination which can be the guidance of actual operation of the system and achieve the lowest operation cost under the premise of environmental protection standards.4. Take absorption tower as the research object, complete the modeling and numerical simulation of absorption system by the method of distributed parameter model. Study the main chemical reactions and participants in the absorption tower, then divide the absorption tower into two parts including absorption area and slurry tank. In addition, based on reaction and mass transfer process, establish an absorption tower distributed gas liquid solid three-phase coupled mass transfer and reaction model. The distribution of the components in the absorption tower and its dynamic change status can be obtained through the solution of the model. Result shows that this absorption tower distributed gas liquid solid three-phase coupled mass transfer and reaction model can accurately describe the absorption tower desulfurization status, which can provide mathematical model base for dynamic simulation optimization.