真空相变加热炉内燃烧特性模拟

Simulation of combustion characteristics in vacuum phase change heating furnace

真空相变加热炉具有排烟温度低、热效率高等特点。针对某油田用300 kW真空相变加热炉内燃烧进行模拟研究,分析不同负荷下炉内温度场、NO_(x)浓度场和速度场的分布特性。结果表明:各负荷在截面高约1.7 m处平均温度均达到峰值,且排烟温度在148.2—177.1℃之间;额定负荷下出口NO_(x)排放质量浓度为52.4 mg/m^(3);在120%负荷下炉内高温区域扩大,NO_(x)排放增大为72.4 mg/m^(3);炉内高温烟气呈螺旋上升状,中心区域可引射烟气回流,从而降低中心火焰温度;该结构炉膛底部存在流体滞留区,通过模拟发现将炉膛底部和燃烧器改为12°倾斜结构,可消除底部滞留区,并在额定负荷下NO_(x)排放质量浓度降低为45.7 mg/m^(3),满足排放标准。为优化真空相变加热炉结构设计提供了参考。

Vacuum phase change heating furnace has the characteristics of low exhaust temperature and high thermal efficiency.The combustion characteristics of 300 kW vacuum phase change heating furnace used in an oilfield were numerically simulated,and the distribution characteristics of temperature field,NO_(x)concentration field and velocity field in the furnace under different loads were analyzed.The results show that the average temperature of each heating furnace load reaches the peak at the section height of about 1.7 m,and the exhaust temperature ranges from 148.2℃to 177.1℃.Outlet NO_(x)emission mass concentration under rated load is 52.4 mg/m^(3).Under 120%load,the high temperature zone in the furnace expands,and the NO_(x)emission increases to 72.4 mg/m^(3).The high temperature flue gas in the furnace is spiraling upward,and the central area can be injected into the flue gas reflux,thereby reducing the central flame temperature.The furnace of this structure has a fluid retention zone at the bottom.By changing the bottom of the furnace and the burner to a 12°inclined structure,the bottom retention zone can be eliminated,and the NO_(x)emission mass concentration under the rated load is reduced to 45.7 mg/m^(3),which meets the emission standards.It provides a useful reference for optimizing the structure design of vacuum phase change heating furnace.