W型燃煤锅炉掺烧酒糟的数值模拟

Numerical simulation of W-type coal boiler blended with distiller′s grains

燃煤锅炉掺烧生物质具有改造成本低、调峰灵活、运行安全等特点,实现生物质高效利用的同时,对于碳减排有积极作用。目前已经开展了大量燃煤锅炉中掺烧污泥等物质的试验与模拟研究,但鲜见燃煤锅炉中掺烧酒糟的数值模拟研究。为了研究燃煤锅炉中掺烧酒糟对炉内温度场、组分浓度场以及NO_(x)排放等的影响,采用计算流体力学软件FLUENT中的涡耗散模型模拟煤粉与酒糟颗粒的混燃。结果表明,数值模拟具有可靠性;在满负荷下,模拟得到的出口氧量、飞灰含碳量及NO_(x)排放与相同条件下的试验结果吻合较好。酒糟掺烧质量分数分别为0、3%、6%、8%、10%的模拟计算结果显示,掺烧酒糟后,燃烧器喷口附近着火距离缩短,但炉膛整体温度场无明显变化。掺烧酒糟对炉膛内的O2体积分数分布无太大影响,由于受酒糟含水量的影响,水蒸气体积分数在燃烧器喷口附近有所提升。掺混酒糟对NO_(x)排放的影响较明显,这是掺混燃料氮含量和生物质挥发分释放造成的还原性氛围交互作用的结果。

Biomass co-firing in coal-fired power plants has the advantages of low conversion cost,flexible peak shaving,and safe operation,which has a positive effect on carbon emission reduction and can realize the efficient utilization of biomass.At present,a large number of experiments and simulation studies have been carried out on the blending of sludge and other substances in coal-fired boilers,but there are few numerical simulation studies on the blending of distiller′s grains in coal-fired boilers.In order to study the influence of blending distiller′s grains in coal-fired boilers on the temperature field,component concentration field and NO_(x) emission in the furnace,the mixed combustion of pulverized coal and distiller′s grains was simulated by numerical simulation and the vortex dissipation model in computational fluid dynamics software FLUENT.The results show that the simulation method is reliable.Under full load,the simulated outlet oxygen,carbon content of fly ash and NO_(x) emission are in good agreement with the experimental results under the same conditions.The simulation results of 0,3%,6%,8%and 10%of the mass fraction of distiller′s grains show that the ignition distance near the nozzle of the burner is shortened,but the overall temperature field of the furnace does not change significantly.The concentration distribution of O2 in the furnace is not significantly affected by the blending of distiller′s grains,the concentration of H2O is increased near the burner nozzle due to the influence of distiller′s grains water content.Blending distiller′s grains have a significant impact on NO_(x) emission,which is the result of the interaction of reducing atmosphere caused by the nitrogen content of blending fuel and the release of biomass volatiles.