空气分级耦合与不耦合多孔壁风工况下煤粉燃烧特性的数值模拟研究

Modeling of Pulverized Coal Combustion Under Air Staged Coupled and Un-coupled With Multi-hole Wall Air

为探究多孔壁风对煤粉燃烧特性及高温腐蚀的影响,利用AnsysFluent软件开展了空气分级耦合与不耦合多孔壁风工况的数值模拟研究,并采用用户自定义函数法编译了焦炭气化反应、硫释放和含硫组分气相反应等模型的宏文件。通过对比2工况的空气动力场、温度场和浓度场,可知:1)多孔壁风可在主燃区和还原区壁面形成新鲜气流,阻止烟气冲刷壁面。2)多孔壁风不会破坏燃烧组织,也不会提高主燃区火焰温度。3)新鲜气流中O2浓度超过1.5%,在壁面附近形成氧化性气氛,将H2S、COS和CS2氧化为SO2,防止高温腐蚀。

In order to investigate the impact of multi-hole wall air on high-temperature corrosion, the pulverized coal combustion and sulfur evolution are modeled using Ansys Fluent software under air staged coupled and un-coupled with multi-hole wall air(CMW and UCMW). The macro files of char gasification, sulfur release and reaction mechanism of sulfur species were compiled into the software using User Defined Function(UDF). The aerodynamic field, temperature field, and concentration field under CMW and UCMW were compared, and some conclusions were obtained. Firstly, with the ejection of multi-hole wall air, a fresh air flow is produced close to the wall in the primary and reduction zones, and thus prevents the gas flow scouring the wall. Secondly, the multi-hole wall air does not damage the combustion, and will not improve the flame temperature in the primary zone. Thirdly, the O2 concentration in the fresh air flow exceeds 1.5%, which means an oxidative atmosphere is formed near the wall. So, the corrosive species near the wall, such as H2 S, COS and CS2, are oxidized to SO2, and thus the high-temperature corrosion is avoided.