洁净煤技术

2020, v.26;No.126(02) 43-49

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基于EDM、PDF和FR/ED模型的煤粉燃烧过程适应性研究
Study on the adaptability of EDM,PDF and FR/ED models to pulverized coal combustion process simulation

程晓磊;
CHENG Xiaolei;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

摘要(Abstract):

还原气氛下煤粉反应过程兼具燃烧和气化的特点,是煤粉实现低氮燃烧的关键因素,合适的化学反应模型是准确模拟该过程的基础。笔者基于煤粉双锥燃烧器,对比了EDM模型、PDF模型和FR/ED模型在氧化气氛和还原气氛的模拟结果,通过与试验结果的对比验证,确定了不同反应气氛适合的化学反应模型。研究结果表明,3种模型在煤粉着火位置和逆喷传播距离的预测上存在差别,PDF模型起火点更靠近燃烧器逆喷喷口,EDM模型一次风和煤粉喷出经过一段升温过程后逐渐燃烧,FR/ED模型的升温过程更长,壁面低温区域接近前锥长度一半;使用FR/ED模型模拟时燃烧器内平均温度最高,EDM模型次之,PDF模型最低; EDM模型中未考虑CO反应,燃烧器内基本无CO存在,PDF模型高CO浓度区域集中在煤粉燃烧初期,燃烧器出口CO含量较低,FR/ED模型化学反应动力学参数在煤粉燃烧整个区域内均有较高CO浓度存在。由于考虑了焦炭与氧气气化反应的影响,FR/ED模型模拟燃烧器内氧含量明显低于EDM和PDF模型,当过量空气系数为1.2时,燃烧器出口处氧含量为7.0%,明显低于EDM模型的11.1%和PDF模型的12.0%,燃烧器出口处CO含量为3.5%,明显高于EDM(0)和PDF模型(0.8%);过量空气系数为0.5时,EDM模型对CO成分的预测结果偏差较大,燃烧器出口CO浓度为0.05%,采用PDF和FR/ED模型时燃烧器出口CO含量分别为5.73%和10.7%。从模拟结果与试验结果的对比来看,在氧化气氛下,主要发生煤粉的燃烧反应,EDM模型和PDF模型在温度、CO含量上的预测较为准确,与试验数据偏差较小,FR/ED模型偏差较大;在还原性气氛下,EDM模型模拟的结果几乎不生成CO和H2,并不适合还原性气氛,PDF模型和FR/ED模型有较合理的还原气氛模拟结果,两者的差别在于还原性气体的生成位置,PDF模型喷口位置CO浓度较高,出口浓度偏低,FR/ED模型随着煤粉反应流程的进行,CO浓度逐渐升高,出口浓度更接近试验结果。综合考虑,氧化气氛下双锥燃烧器适合采用EDM模型和PDF模型进行模拟,还原气氛下适合采用FR/ED模型进行模拟。
The reaction process of pulverized coal in reducing atmosphere has both the characteristics of combustion and gasification,which is the key factor of low-NOxcombustion for pulverized coal.The appropriate chemical reaction model is the basis for accurate simulation of the process. In this paper,the numerical simulation accuracy was studied based on the double cone burner by comparing results of EDM model,PDF model and FR/ED model under the conditions of oxidation atmosphere and reducing atmosphere.Also,by comparing with the experimental results,the chemical reaction models suitable for different reaction atmosphere were determined. The results show that,there are differences among the three models in the prediction of pulverized coal ignition position and back-flow injection distance.The ignition point of PDF model is closer to the back-flow injection nozzle of burner.For EDM model,the primary air and pulverized coal gradually burn after a period of temperature rise process,and the temperature rise process for FR/ED model is longer,and the low-temperature area of wall nearly covers half of the front cone length.When FR/ED model is used to simulate the combustion process,the average temperature is the highest,the EDM model is the second,and the PDF model is the lowest.The CO reaction is not considerd in the EDM model,and there is almost no CO in the burner. The high CO concentration area for PDF model is concentrated in the early stage of pulverized coal combustion,and the CO content at the outlet of burner is low. While The kinetic parameters of chemical reaction in FR/ED model,the high CO concentration in the whole area of pulverized coal combustion is found.Considering the effect of gasification reaction of coal and oxygen,the oxygen content in the burner simulated by FR/ED model is significantly lower than that of EDM and PDF model.When the excess air coefficient is 1.2,the oxygen content at the burner outlet is 7.0%,which is significantly lower than 11.1%of EDM model and 12. 0% of PDF model. The CO content at the burner outlet is 3. 5%,which is significantly higher than ~ 0% of EDM model and 0.8% of PDF model.When the excess air coefficient is 0.5,the prediction results of the EDM model for CO composition are quite different.The CO concentration at the burner outlet is 0.05%.The CO content at the burner outlet is 5.73% and 10.7%,by using PDF and FR/ED models,respectively.Through the comparison between simulation and experimental results for the oxidation atmosphere,the combustion reaction of pulverized coal mainly occurs. The prediction of temperature and CO content of EDM model and PDF model is more accurate,and the deviation of FR/ED model is larger with less deviation from the test data.Under the reducing atmosphere,the simulation results of EDM model hardly generate CO and H2,which is not suitable for reducing atmosphere,while the PDF model and FR/ED model have reasonable simulation results.The difference is mainly the generating position of reducing gas.The CO concentration at the nozzle of PDF model is higher than that at the outlet,while the CO concentration of FR/ED model increases gradually with the process of pulverized coal reaction,which is closer to the test results.Considering comprehensively,EDM model and PDF model are suitable for the simulation of biconical burner in oxidation atmosphere,and FR/ED model is suitable for the simulation in reduction atmosphere.

关键词(KeyWords): 煤粉燃烧;数值模拟;还原气氛;双锥燃烧器;部分气化
pulverized coal combustion;numerical simulation;reducing atmosphere;double cone combustor;partial gasification

Abstract:

Keywords:

基金项目(Foundation): 天地科技股份有限公司科技创新创业资金专项项目重点项目(2018-TD-ZD001)

作者(Author): 程晓磊;
CHENG Xiaolei;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

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DOI: 10.13226/j.issn.1006-6772.20022805

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