Optimization Technology Research Of The Limestone/Gypsum Wet Flue Gas Desulphurization System

At present, coal-fired power plants are the main SO2 emitters in China. With the improvement of environmental concerns, the government formulates the stricter SO2 emission standard. In the existing desulfurization technology, limestone/gypsum wet flue gas desulfurization system (WFGD) is the most widely used desulfurization process in our country. The desulfurization device is a high energy consumption system and increases the operating costs of the power plants while it meets standard of environmental protection. Along with the further work of energy-saving and emission reduction in the power industries, exploiting the optimization potentiality of desulfurization system and improving the design quality and operating level have the vital and practical significance. In this paper, several researches are carried out on a WFGD system to improve the operation reliability and economy, which including the internal flow and resistance characteristics of desulfurization absorption tower, optimization of mist eliminator vanes, characteristics model of desulfurization efficiency and operation optimization, condition monitoring for the desulfurization system based on data mining and so on.Two-phase flow between flue gas and droplets in absorption tower directly affects the function of desulfurization in WFGD. In this paper, the flow and resistance characteristics of a 600MW WFGD are studied. Standard k-ε model and discrete particle model (DPM) are separately selected for the flue gas and droplet phase. Simulation results show that the spray of slurry can rectify the flue gas flow. The velocity field and pressure field become more uniform after adding spray, but the total resistance increases. Furthermore, in order to make the flow field in absorption tower more uniform, some optimization design for original inner structure of tower by CFD are carried out. Two feasible schemes such as changing the entrance angle of flue gas and adding a salver are raised, and the role of two schemes are compared.The flow characteristics of the folded vane and corrugated vane eliminator are analyzed by numerical simulation. The laws of the structure parameters and operational parameters to mist eliminator performance are discussed, and the structure parameters include vane space, vane turning angle and vane length and operational parameters include inlet velocity of flue gas, droplet size. The corrugated plate has higher separation efficiency and lower pressure drop compared to the folded plate. A new optimization design method of the vane structure of eliminator is provided based on numerical calculation and the least squares support vector machine model (LSSVM). A prediction model for removal efficiency and pressure drop is established applying least square support vector regression from the results of numerical computation. Based on the prediction model, a mist eliminator parameters optimization model is created employing improved NSGA-II algorithm. The optimal solution and data analysis showed the model can direct the optimum design of mist eliminator and can overcome the numerical simulation consuming long time.Due to the failure situations caused by blocking and wear phenomenon for the pH sensor of WFGD, the soft sensor model for slurry pH value is proposed based on the improved sparseness LSSVM algorithm which has higher accuracy and is suitable for online measuring requirements. The research on characteristics model of desulfurization efficiency is carried out. An on-line residual prediction model of desulfurization efficiency is established based on the static model by test data and improved AOSVR algorithm, which has strong correction capability. The results of sensitivity analysis show this on-line desulfurization efficiency model can improve the prediction accuracy and generalization ability. Based on the desulfurization efficiency prediction model, the model of operation cost which can be controlled for desulfurization system is proposed and the optimization operation methods of the main energy-wasteful equipment of the desulfurization system are studied.The data clustering algorithm is introduced to the optimization operation and condition monitoring for WFGD. A dynamic fuzzy clustering method is presented based on iterative model of entropy and K-means (EKFCM) to select initialization parameters of the fuzzy cluster.The optimum objective condition is obtained by EKFCM algorithm in a certain operation condition, which composes the objective operation condition database.And the LSSVM model is established to ensure the optimum objective condition in the certain condition. Using FCM clustering algorithm, a model is presented to monitor the slurry quality based on the extraction feature of the slurry quality. The standard modes of the slurry quality are collected in the various states by FCM clustering algorithm and then it’s diagnosed according to the biggest subordinate principle. A fuzzy quantitative detection index of the slurry quality is put forward which can be used for analysis of the slurry quality.