煤粉孔隙率对四角切圆燃煤锅炉飞灰含碳量及结焦特性的影响

Effect of Pulverized Coal Porosity on Dust Carbon Content and Slagging Characteristics of a Tangentially Coal-fired Boiler

研究煤粉颗粒孔隙率对1 000 MW机组燃煤锅炉飞灰含碳量及结焦特性的影响。选定了25℃、75℃、110℃这三个干燥温度对煤粉进行干燥,测试了煤粉颗粒的水分和孔隙率。采用测试得出的孔隙率范围,利用FLUENT软件对该台四角切圆燃煤锅炉炉内燃烧进行了三维稳态数值模拟,其中,模拟焦炭的燃烧采用了intrinsic模型。研究结果表明:(1)煤粉颗粒的孔隙率、比表面积和孔径都随着煤粉加热温度的升高而增大;(2)煤粉颗粒孔隙率越大,炉膛火焰中心位置越低,燃尽风区域的温度也越低;(3)煤粉颗粒孔隙率越大,煤粉颗粒的碰壁率和炉膛出口的飞灰含碳量都会越小;(4)煤粉颗粒孔隙率越大,水冷壁越不易结焦。研究结果为燃煤锅炉运行实践、设计以及改造提供了依据。

In order to investigate the effect of the pulverized coal particles porosity on dust carbon content and slagging in a 1 000 MW unit coal-fired boiler,the pulverized coal was dried at three selected drying temperatures of25 ℃,75 ℃ and 110 ℃,and the moisture and porosity of the pulverized coal particles were tested. Based on the porosity range obtained from the test,3 D steady numerical simulation of combustion in this tangentially coal-fired boiler was carried out by use of Fluent software,in which,the intrinsic model was used to simulate the combustion.It was found that（1） the porosity,surface area and pore diameter of pulverized coal particles increased with the increase of the heating temperature of pulverized coal.（2） the larger the pulverized coal porosity was,the lower the furnace flame center position was,and the lower the temperature in OFA area was.（3） the rate of coal particles with impacting wall and the dust carbon content decreased with the increase of the pulverized coal porosity.（4） the slagging degree of water wall decreased with the increase of the pulverized coal porosity. The results provide the basis for the operation,design and modification of coal-fired boiler.