Abstract: Importing hotwind to the direct-discharged chimney of flue gas desulphurization(FGD),in which secondary dehydration device is installed,could lower the outlet moisture content and solve the problem of chimney rain effectively.In order to examine the influence of hotwind on the flow characteristics and optimize the structure of the chimney dehydration device to match the dehydration capacity and running resistance,discrete phase model,RNG k-ε double-equation turbulence model and component transport model based on calculation fluid dynamics (CFD)were adopted to build a hydrodynamic model to describe the flow field inside the chimney.The variation of temperature,velocity,pressure and moisture content in the chimney with and without hotwind and the optimal angle of blade of the rotating-stream tray were obtained by the numerical simulation.With hotwind added,the outlet temperature rises 3 K,outlet velocity is increased 0.6 m·s^-1,outlet pressure is decreased 55 Pa,outlet moisture content is reduced 29 mg·m^-3,and the optimal angle of blade is 45°.Compared with the angle of 42° in applications,the optimal angle makes the running resistance decrease 108 Pa with negligible increase in moisture content. The simulation results are in the range for practical use,verifying the rationality and feasibility of the simulation.The simulation provides theoretical bases for optimizing the internal structure of chimney and directing the sample locations in the project.

Key words: hotwind, wet flue gas desulphurization, direct-discharged chimney, dehydration, CFD simulation, optimization

摘要： 在安装有二次脱水装置的湿法脱硫直排烟囱内引入热风,可进一步降低烟囱出口含水率,有效解决烟囱飘雨问题。为考察热风对气流流动特性影响,进而优化脱水装置结构,使脱水效果与运行阻力达到最佳匹配,基于CFD方法,采用离散相模型、RNG k-ε双方程湍流模型和组分输运模型组合建立了描述直排烟囱内部流场的流体动力学模型,对其进行了数值模拟,获得了加热风前后烟囱内温度、速度、压强和含水率的变化规律。结果表明,加热风后,烟囱出口处温度上升3 K,速度增加0.6 m·s^-1,压强降低55 Pa,含水率减小29 mg·m^-3,旋流板最佳叶片角度是45°。模拟结果均处于工程实际监测数据波动范围内,验证了模拟合理性和可行性,为优化直排烟囱内部结构和指导工程实际现场取样点提供了理论依据。

关键词: 热风, 湿法烟气脱硫, 直排烟囱, 脱水, CFD模拟, 优化