Optimization of Slurry PH Value for Limestone Wet Desulfurization Technology
Based on limestone wet desulfurization spray scrubber technology, this paper explicitly introduces the ionization process of water in slurry, deduces controlled range of slurry PH value and equation of slurry PH value in slurry droplet by analyzing the main origin of H+ and OH-, and other factors that influence ionization balance of water in slurry, provides theories for simulation of slurry PH value and optimization in practical operation. Besides, it concludes the reasonable range of slurry PH value by analyzing various factors such as increasing SO2 removal efficiency, decreasing operation cost, dissolution of CaCO3, oxidation of SO32- andHSO3-, and relationship of slurry PH values between slurry surface and the undersurface, provides reference for optimization of slurry PH value in practice. Finally, an optimization experiment of slurry PH value is designed for#11FGD in Taiyuan co-generation power plant, and the slurry PH value is optimized effectively.
Operation strategy optimization of desulfurization system based on data mining
Abstract Desulfurization systems in coal-fired power stations often suffer the problem of high operating costs caused by a rule-of-thumb control strategy, which implies great potential for optimization of the operation. Due to the complex desulfurization mechanism, frequently fluctuating unit load, and severe disturbance, it is challenging to determine the optimal operating parameters based on the traditional mechanistic models, and the operating parameters are closely related to the operational efficiency of the flue gas desulfurization system. In this paper, an operation strategy optimization method for the desulfurization process is proposed based on a data mining framework, which is able to determine online the optimal operating parameter settings from a large amount of historical data. First, Principal Component Analysis (PCA) is used to reduce data redundancy by mapping the data into a new vector space. Based on the new vector space, an enhanced fuzzy C-means clustering (Enhanced-FCM) is developed to cluster the historical data into groups sharing similar characteristics. Taking sulfur dioxide emission concentration as a constraint condition, the system is optimized with economic benefits and desulfurization efficiency as the objective function. When performing optimization, the group that current operating conditions belong to is determined first, then the operating parameters of the best performance are searched within the group and provided as the optimization results. The method is validated and tested based on the data from a wet flue gas desulfurization (WFGD) system of a 1000 MWe supercritical coal-fired power plant in China. The results indicate that the proposed operation strategy can appropriately obtain operating parameter settings at different conditions, and effectively reduce the desulfurization cost under the constraint of meeting emission requirements.
Modeling the absorption of SO2 in a spray scrubber using the penetration theory
A model based on the penetration theory has been developed to calculate the dynamic absorption rate of sulfur dioxide into a droplet of limestone slurry. The model includes both instantaneous equilibrium reactions and reactions with finite rates; limestone dissolution, sulfite oxidation, gypsum crystallization and the hydrolysis reaction of CO2. The model has been used to quantify the mass transfer within a spray scrubber and to estimate the impact of the reactions with finite rate of the SO2 mass transfer. The variations within the physical mass transfer conditions of a spray scrubber have been simulated by assuming high mass transfer coefficients close to the nozzles and low coefficients below the spray region. The developed concentration profiles of the diffusing species and the depth of penetration have been determined for different penetration times. The calculations show that the absorption of SO2 into a limestone spray scrubber to a large extent is liquid-side controlled. Only at the very top of the absorber, where the partial pressure of SO2 is low, is the gas film resistance above 50%. Limestone dissolution close to the gas-liquid interface has been shown to be of significance at low pH and in the parts of the absorber where the internal circulation inside the droplets is low. The impact of the hydrolysis reaction of CO2 on the absorption rate of SO2 has been studied by varying the reaction rate constant. Simulations show that the rate constant has a large impact on local absorption rates. Depending on the length of the contact time between the gas and the liquid, the assumption of an instantaneous hydrolysis reaction has an impact on the overall SO2 absorption rate. (C) 1997 Elsevier Science Ltd. (Less)