配风方式对燃煤锅炉掺烧污泥影响的数值模拟研究

Numerical simulation study on the effect of air distribution on combustion of coal-fired boiler blended with sludge

燃煤耦合污泥发电技术研究主要聚焦在掺混比等条件的影响,而主燃区过量空气系数等因素的影响规律尚不清晰。鉴于此,采用涡耗散模型对600 MW四角切圆煤粉锅炉掺烧市政污泥进行数值模拟研究,分析了污泥掺混比例、主燃区过量空气系数以及二次风配风方式对燃煤锅炉内污泥掺混燃烧及NOx生成的影响。结果表明:随着污泥掺混比增加,炉膛整体温度下降,影响燃烧稳定性,同时炉膛出口NOx浓度有所降低。当污泥掺混比例增长至20%,炉膛出口温度约下降100 K,NOx浓度减少53.2%。而污泥掺混比例对于炉膛内速度场分布影响较小。随着主燃区过量空气系数由0.72增加至0.96,炉膛出口温度增幅较小,仅增加15 K左右,而NOx浓度则大幅增长,由174.39 mg/m3增长至352.09 mg/m3,约增长50.4%。在本文过量空气系数范围内,考虑温度和NOx浓度,推荐主燃区过量空气系数0.84。不同二次风配风对燃煤锅炉掺烧污泥影响差异较大。5种配风方式下,炉膛出口温度和NOx浓度有较大变化。鼓腰配风下炉膛出口温度最低,为1 289 K,而倒塔配风温度最高,为1 341 K。同时鼓腰配风下NOx浓度较高,为207.77 mg/m3,束腰配风NOx浓度较低,为156.42mg/m3。综合温度和NOx浓度,本文二次风配风推荐采用束腰配风方式。

The present study on coal-fired coupled sludge power generation technology mainly focused on the influence of mixing ratio,but the effects of factors such as the excess air coefficient in the main combustion zone are still unclear.In view of this point,the eddy dissipa⁃tion model was used to simulate the municipal sludge combustion in a 600 MW tangentially fired boiler.The effects of sludge blending rati⁃o,excess air coefficient in the main combustion zone and secondary air distribution mode on the sludge mixing combustion and NOx genera⁃tion characteristics in coal-fired boiler were analyzed.The results show that as the sludge blending ratio increases,the overall temperature of the furnace decreases,which affects the stability of combustion,and the NOx concentration at the outlet of the furnace decreases.When the blending ratio of sludge increases to 20%,the furnace outlet temperature drops by about 100 K,and the NOx concentration decreases by 53.2%.However,the blending ratio has little effect on the velocity field distribution in the furnace.As the excess air coefficient of the main combustion zone increases from 0.72 to 0.96,the furnace outlet temperature increases slightly,only by about 15 K,while the NOx concentration increases significantly,from 174.39 mg/m3 to 352.09 mg/m3,which is about an increase of 50.4%.Within the range of excess air coefficient in this paper,considering temperature and NOx concentration,it is recommended that the excess air coefficient of the main combustion zone is 0.84.The influence of different secondary air distribution on the co-combustion of sludge in coal-fired boilers is quite different.In the five air distribution modes,the furnace outlet temperature and NOx concentration change greatly.The furnace outlet temperature under the condition of air distribution at the waist is the lowest at 1289 K,while the inverted tower air distribution temperature is the highest at 1341 K.At the same time,the NOx concentration of the drum waist air distribution is higher,which is 207.77 mg/m3,and the beam waist air distribution is lower,which is 156.42 mg/m3.Considering the temperature and NOx concentration,the secondary air dis⁃tribution is recommended to adopt the beam waist distribution mode.