分解炉三次风管与生料管相对位置对分解炉影响的数值模拟

Numerical simulation of effect of relative position between tertiary air duct and raw meal pipe on precalciner

采用数值模拟方法研究了DD分解炉三次风管与上部生料管相对位置变化对炉内流场、温度场及组分浓度场的影响。结果表明,三次风管上移至6.3 m处时,三次风在上部生料冲击下出现了向下的反向旋流效应将O_(2)输运至上部煤粉燃烧区,使得煤粉可以充分燃烧,炉温升高,NO_(x)浓度也随之上升。生料管的下移占据了煤粉燃烧的空间,当生料管移动至7.5 m处时,部分煤粉将绕过生料至炉上部完成燃烧。三次风管上移及生料管的下移都对炉内NO_(x)浓度有很大影响。在一定范围内,三次风管的上移可以降低NO_(x)浓度,但由于O_(2)逐渐远离煤粉燃烧区使得煤粉燃烧会受到严重影响。计算了五种情况下的生料分解率发现,A(T_(1)R_(3))情况下的生料分解率最高,可达87.5%。综合炉内温度、组分分布及生料分解率计算结果在实际应用中推荐A方案,即三次风管与生料管分别位于4.4m和9.3 m时比较合理。

The numerical simulation method is used to study the effect of relative position change of tertiary air duct and the upper raw meal duct in DD precalciner on flow field,temperature field and component concentration field.The results showed that when tertiary air duct rised to 6.3 m,tertiary air had a downward reverse swirling effect under the impact of the upper raw meal,transporting O_(2) to the upper coal combustion zone,which made pulverized coal completely burned and the temperature and NO_(x) concentration in precalciner would increase accordingly.After raw meal pipe moved downward,rawmeal occupied the space where pulverized coal was burned.When raw meal pipe was moved to 7.5 m,part of pulverized coal would bypass raw meal and reached the upper part of the precalciner to complete the combustion.In addition,the upward movement of tertiary air duct and the downward movement of raw meal pipe had a great influence on NO_(x) concentration in precalciner.Within a certain range,the upward movement of tertiary air duct can reduce NO_(x) concentration,but pulverized coal combustion would be seriously affected as O_(2) gradually moves away from pulverized coal combustion zone.Calculating the decomposition rate of raw meal in five cases.It was found that the decomposition rate of raw meal in the case of A(T_(1)R_(3))was the highest,reaching 87.5%.Considering the factors such as the temperature,the distribution of components and the calculation results of raw meal decomposition rate,it was reasonable to recommend the case of A in practical applications.Therefore,it was reasonable when tertiary air duct and raw meal pipe were located at 4.4 m and 9.3 m respectively.