LI Lulu;YAO Xuan;ZHANG Man;JIN Yan;YANG Hairui;

• 1:College of Electrical and Power Engineering
• 2:Taiyuan University of Technology
• 3:Department of Energy and Power Engineering
• 4:Tsinghua University

Abstract：

Wet desulfurization technology is mostly adopted in large and medium-sized coal-fired power plants,which results in a large amount of water evaporation in the desulfurization process. For 600 MW units,the flue gas discharged after wet desulfurization carries more than 200 t/h of water vapor. Water vapor and low-temperature waste heat in desulfurization wet flue gas are important parts of water resources and energy loss in coal-fired power plants. In order to reduce the moisture content in flue gas,effectively recover the moisture and waste heat in flue gas,and solve the problems such as chimney corrosion, " gypsum rain" and " white smoke" caused by condensation of water vapor in wet flue gas,a three-dimensional steady-state CFD model was built based on fluent software to simulate the condensation process of flue gas after wet desulfurization. Taking the optimized condensation chamber as the calculation object,the energy,mass and momentum exchange between gas-liquid two-phase flows were fully considered. The influence of the structure of the condensation chamber itself and the gas-liquid two-phase parameters on heat and mass transfer was comprehensively discussed. The results show that there is an optimal spacing between the two spray layers,and the optimal spacing in the simulation is 1 m. This spacing can make the residence time of liquid droplets in the condensation chamber and the gas-liquid contact uniformity reach a higher level at the same time. Within a certain range of flue gas velocity,the flue gas velocity is high,the residence time of flue gas in the condensation chamber is short,the contact time between gas and liquid is short,and the degree of heat exchange is poor. The flue gas flow rate is low,the flue gas Reynolds number is small,the turbulent flow is weak,and the amount of air treated per unit area per unit time is small,therefore,there is an optimal flue gas flow rate. The research shows that the optimal flue gas flow rate is 3.5 m/s. Proper increase of liquid-gas ratio,reasonable reduction of droplet diameter,reduction of spray liquid temperature and increase of nozzle angle can effectively ensure the uniformity of flow field,improve the gas-liquid contact strength and enhance the heat and mass transfer effect between gas and liquid. However,increasing the liquid-gas ratio requires a larger amount of water,which is not conducive to saving water and energy. Reducing the temperature of spray liquid can increase the temperature difference of heat exchange,but a lower cooling water source is required. Increasing the nozzle angle has limited effect on improving condensation. Among them,the most effective method is to reduce the droplet diameter. Using a nozzle with good atomization degree,the droplet diameter is less than 210 μm,which can condense wet flue gas from 323 K to 311. 75 K. For600 MW units,at least 80 t of water resources and 6.59 MW of energy can be recovered per hour,so as to achieve the goal of water saving and energy saving, " white elimination" and dust removal integration.

Key Words： desulfurization wet flue gas;condensation;heat and mass transfer;three dimensional steady state numerical simulation

Abstract:

Keywords:

Foundation: 国家重点研发计划资助项目(2019YFE0102100)

Authors: LI Lulu;YAO Xuan;ZHANG Man;JIN Yan;YANG Hairui;

DOI: 10.13226/j.issn.1006-6772.CFB20042801

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