气化细灰颗粒在混合器内的沉积特性

Deposition Characteristics of Gasified Fine Ash Particles in the Mixer

混合器是煤气化合成气分级初步净化工艺中的关键设备之一,合成气中细灰颗粒在其内的沉积行为显著影响气化系统的长周期稳定运行。采用颗粒沉积临界速度模型对气化细灰颗粒在混合器中的沉积特性进行了数值模拟,研究了不同颗粒粒径、气体流速及混合器结构对颗粒沉积特性的影响规律。结果表明,在相同入口气速下,气化细灰在混合器内壁面的沉积率随颗粒粒径的增大总体呈下降趋势,粒径5~13μm的颗粒更是如此;粒径1μm的颗粒在Wall4壁面的单位面积沉积量最大;相同粒径颗粒的沉积率随入口气速的变化而不同,但总体上随入口气速的增大而减小;水管出口端面到渐缩套管口端面距离(H)的改变对颗粒在混合器内的沉积率无明显影响;混合器C是一种可有效避免缩口面附近发生堵塞的结构。

The mixer is an important part of the purification system of coal gasification syngas.However,the adhesion of fly ash particles on the wall of the mixer can cause clogging,resulting in a lowered syngas purification efficiency and compromising the gasification efficiency of the gasifier leading to economic losses.In this paper,the deposition characteristics of gasification fine ash particles in the mixer are numerically simulated by using the particle deposition critical velocity model,and the influence of different particle sizes,gas flow rate and mixer structure on particle deposition is studied.At the same inlet gas velocity,the deposition rate of gasified fine ash on the inner wall surface of the mixer generally tends to decrease with the increase of particle size,especially for particles of 5—13μm;deposition per unit area of 1μm particles on the surface of wall4 is the largest.While the deposition rate of different particle sizes varies with the gas flow rate,it generally decreases,and the change of the distance H from the outlet face of the water pipe to the end face of the indented casing mouth has minimal effect on the deposition rate of particles in the mixer.Mixer C is a structure that can effectively avoid clogging near the indented face.