脱硝副产物硫酸氢铵在飞灰表面沉积与演化特性

空预器堵塞常来源于脱硝副产物硫酸氢铵(ABS)与飞灰的共沉积,通过模拟空预器内温度场,探究ABS与飞灰共存条件下的沉积与演化特性,以期为空预器堵塞防治提供指导.飞灰对烟气中生成的ABS存在捕集和吸附作用,提高了ABS沉积速率与初始生成温度.在100μL/L SO₃与50μL/L NH₃条件下,ABS的初始沉积温度在240～270℃之间.高温段反应篮内无明显的ABS液滴存在,飞灰存在结块现象;低温段反应篮壁面出现少量小液滴,飞灰呈现大颗粒状.ABS沉积将导致飞灰颗粒的积聚和粘附,并在飞灰表面转化为分解温度较高的各种硫酸盐类物质.与低温段硫酸滴在飞灰上演化形成的硫酸盐相比,ABS转化形成的硫酸盐具有较低的相对分解温度.

Deposition and transformation characteristics of SCR by-product ammonium bisulfate on fly ash

The blockage of the air preheater seriously affected the safe and economical operation of coal-fired power plants, which was often caused by the co-deposition of ammonium bisulfate (ABS) and fly ash. By simulating the temperature field in the air preheater, the deposition and transformation characteristics of ABS under the coexistence of fly ash were explored, which can provide guidance for the prevention and control of air preheater blockage. Fly ash had the capturing and adsorbing effects of the ABS generated in the flue gas, which increased the ABS deposition rate and the initial generation temperature. Under the conditions of 100 μL/L SO₃ and 50μL/L NH₃, the initial deposition temperature of ABS was between 240~270℃. There was no obvious ABS droplet in the high-temperature reaction basket, and the fly ash had an agglomeration phenomenon; a part of small droplets appeared on the wall of the reaction basket in the low-temperature stage, and the fly ash was in the form of large particles. ABS deposition would lead to the accumulation and adhesion of fly ash particles, which were converted to various sulfate salts with higher decomposition temperatures on the fly ash surface. Compared with the sulfate formed by the evolution of sulfuric acid droplets on the fly ash at low temperature, the sulfate formed by the conversion of ABS has a lower relative decomposition temperature.