洁净煤技术

2019, (04) 87-93

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双锥燃烧器燃用污泥水煤浆的燃烧特性和数值模拟
Combustion characteristics and numerical simulation of sludge coal water slurry fired by double cone combustor

程晓磊;
CHENG Xiaolei

摘要(Abstract):

为促进城市污泥的资源化利用,解决污泥物理处置中存在的二次污染问题,以及传统污泥干化焚烧中干燥成本高的问题,提出了将污泥浆与煤粉掺混制备污泥水煤浆,利用具有强化燃烧功能的中心逆喷双锥燃烧器燃烧的技术思路。通过热重分析试验对比了煤粉、水煤浆、污泥水煤浆的燃烧特性,并利用数值模拟研究污泥水煤浆在双锥燃烧器上的燃烧特性,通过降低二次风量、提高二次风旋流强度及二次风温度等强化燃烧的措施,研究污泥水煤浆在双锥燃烧器上应用的可行性。污泥水煤浆的基础燃烧特性试验结果表明,水煤浆中水分超过35%,除影响燃料热值外,水蒸发吸热是影响污泥水煤浆燃烧过程着火和燃尽的关键因素。由于水分的存在,水煤浆起始着火温度高于煤粉11. 3℃,燃尽温度低于煤粉13. 6℃,其最大吸热速率为0. 504 k W/kg,占水煤浆最大放热速率的56. 05%,总吸热量为1. 917 MJ/kg,占燃烧放热量的9. 94%;掺烧20%污泥时,污泥水煤浆起始着火温度高于水煤浆12. 3℃,燃尽温度低59. 1℃,水蒸发吸热量为0. 546 kW/kg,比水煤浆燃烧高8. 4%,总放热量为16. 88 MJ/kg,比水煤浆燃烧低12. 5%。通过采用双DPM的离散相数值模拟模型,充分考虑污泥水煤浆燃烧时水蒸发过程的影响,对污泥水煤浆燃烧的数值模拟更接近实际结果。14 MW双锥燃烧器的污泥水煤浆燃烧模拟结果表明,直接使用现有双锥燃烧器无法实现污泥水煤浆的稳定燃烧,仅可燃烧水含量为25%左右的污泥水煤浆。污泥水煤浆中水含量由0增至35%时,平均每提高1%水含量,燃烧器出口温度下降7. 95℃,燃烧器内平均温度下降7. 69℃;水含量为35%时,燃烧器内平均温度降低269℃,燃烧器出口平均温度降低278℃。污泥水煤浆在双锥燃烧器内的燃烧,可通过降低二次风量、增加二次风旋流强度、提高二次风温度等强化燃烧措施实现。二次风旋流强度由1变为2时,燃烧器出口平均温度提高20℃,二次风量减少为理论空气量的0. 6,燃烧出口平均温度提高203℃,综合使用降低二次风量、增加旋流强度和提高二次风温的措施后,燃烧器出口平均温度提高289℃,基本接近该燃烧器燃用煤粉时的燃烧条件,双锥燃烧器基本可达到稳定燃烧污泥水煤浆的目的。
In order to promote the utilization of municipal sludge,and further to solve the secondary pollution problem in sludge physical disposal and the high cost problem of sludge drying combustion in traditional way,a technical idea of preparing sludge-coal-water slurry by mixing sludge slurry with pulverized coal,and using the central reverse injection double cone burner with enhanced combustion function was proposed.The combustion characteristics of pulverized coal,coal water slurry and sludge coal water slurry were analyzed by thermogravimetric analysis experiments.The combustion characteristics of sludge coal water slurry in double-cone burner were studied by numerical simulation.The feasibility of sludge coal water slurry application in double-cone burner was studied by reducing secondary air,increasing secondary air swirl intensity and secondary air temperature.The comparison of basic combustion characteristics of sludge-coal-water slurry shows that the moisture content in sludge-coal-water slurry exceeds 35%,and the fuel calorific value,water evaporation and heat absorption are the key factors affecting the ignition and burnout of sludge-coal-water slurry combustion process.Due to the presence of water,the initial ignition temperature of CWS is 11.3 ℃ higher than that of coal powder,and the burnout temperature is 13.6 ℃ lower than that of pulverized coal.The maximum heat absorption rate is 0.504 kW/kg,accounting for 56.05% of the maximum heat release rate of CWS,and the total heat absorption is 1.917 MJ/kg,accounting for 9.94% of the combustion heat.When 20% sludge is mixed,the initial ignition temperature of sludge CWS is 12.3 ℃ higher than that of CWS,and the burnout temperature is 59.1 ℃ lower than that of CWS.The heat absorbed by water evaporation is 0.546 kW/kg,which is 8.4% higher than that of coal water slurry combustion,and the total heat released is 16.88 MJ/kg,which is 12.5% lower than that of coal water slurry combustion.In this paper,a double-DPM Discrete-Phase numerical simulation model is used to fully consider the influence of water evaporation during sludge CWS combustion,and the numerical simulation of sludge CWS combustion is closer to the actual results.The simulation results of sludge CWS combustion in 14 MW double-cone burner show that the existing double-cone burner can not achieve stable combustion of sludge CWS,only can burn sludge CWS with water concentration of ca.25%,which is not existed in actual form.When the concentration of water in sludge CWS increases from 0 to 35%,the average temperature of burner outlet decreases by 7.95 ℃ and the average temperature of burner interior decreases by 7.69 ℃ with the increase of 1% water concentration.The average temperature of burner interior decreases by 269 ℃ and the average temperature of burner outlet decreases by 278 ℃,when the concentration of water is 35%.The combustion of sludge CWS in a double cone burner can be realized by reducing secondary air flow,increasing secondary swirl intensity and increasing secondary air temperature.When the swirl intensity of secondary air changes from 1 to 2,the average temperature of burner outlet increases by 20 ℃.When the secondary air volume decreases to 0.6 of theoretical air,the average temperature of burner outlet increases by 203 ℃.The average temperature of burner outlet increases by 289 ℃,it is basically close to the burning condition when the burner burns pulverized coal.After comprehensive application,the double-cone combustor can realize the stable combustion of sludge CWS.

关键词(KeyWords): 污泥水煤浆;燃烧;热重分析;数值模拟
sludge coal-water-slurry;combustion;thermogravimetric analysis;numerical simulation

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作者(Author): 程晓磊;
CHENG Xiaolei

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