| In the process of coal mining and washing,a large amount of coal slurry will be produced,and its large amount of storage will cause serious harm to the environment and waste of resources.In the slime,its combustible components and mineral components in the ash are worthy of our use.In China,the use of CFBB combustion power generation is one of the effective ways to utilize coal resources.Among them,oxy-combustion technology can effectively capture CO2 and reduce pollutant emissions during combustion,which is a new type of clean combustion technology.In the oxy-combustion mode,the continuous circulation of flue gas and the introduction of raw materials lead to an increase in the content of CO2 and water vapor,which affects the combustion and utilization of fuel.This paper aims to investigate the combustion behavior of coal slime under O2/CO2/H2 O atmosphere and the influence of two gasification reactions on oxyfuel combustion behavior through atmosphere tube furnace test.The main contents and conclusions are as follows:(1)Taking the coal slurry in Shuozhou area as the research object,the combustion characteristics of the slime in O2/N2,O2/CO2,O2/CO2/H2 O atmosphere were studied by using atmosphere tube furnace and testo350 flue gas analyzer.According to the weight loss curve and the smoke release law,the weight loss can be divided into a pyrolysis-combustion coexistence section,a combustion section and a combustion completion section.When the oxygen concentration is between 2% and 30%,the CO emission reaches the maximum at 8% to 10% oxygen concentration,and the incomplete combustion accounts for the largest.Due to the difference in thermophysical and chemical properties of CO2,the reaction devolatilization rate and burnout rate are both reduced and C-CO2 reaction is difficult,and the effect on weight loss is not obvious.Only at lower oxygen concentrations(2%),the effect of C-CO2 gasification on weight loss is more obvious.(2)The combustion characteristics of slime in O2/CO2,O2/H2O/CO2 atmosphere were studied.Through the study of different carbon dioxide concentration and water vapor concentration,it is found that: in the O2/N2 atmosphere and O2/CO2 atmosphere,the totalCO emission is about 6 times in the 2%O2+98%CO2 atmosphere.The two gasification reactions at 850 °C are weak,but the gasification reaction of C-H2 O is greater than the C-CO2 reaction.At three oxygen concentrations(30%,10%,2%),at 2% oxygen concentration,H2 is most released.Controlling the water vapor concentration to 20% or less has little effect on the furnace temperature and the ignition and burnout of the slime.At the same time,the addition of water vapor promotes the C-CO2 gasification reaction,and the two have a certain synergistic effect.(3)The effects of different temperatures on the oxyfuel combustion behavior of coal slurry under O2/CO2/H2 O atmosphere were investigated.The higher the temperature,the faster the weight loss rate,the more intense the reaction,the shorter the weight loss completion time,and the higher temperature(850 ℃→1100 ℃).The combustion reaction and the two gasification reactions proceeded.At 1100 ℃,both gasification reactions reached the reaction temperature,and the weight loss rate was significantly accelerated.At low oxygen concentration(2%),the combustion completion time was advanced by 2/5.At950 °C,C-H2 O has the greatest advantage over C-CO2 reaction,at which time CO release is less and H2 is released more.When the CO temperature rises to 1100 °C,the C-CO2 reaction begins to increase.The purpose of this paper is to clarify the oxyfuel combustion behavior of coal slurry under O2/CO2/H2 O atmosphere,and to reveal the influence of gasification reaction on oxyfuel combustion behavior,which can provide theoretical basis for oxyfuel combustion in actual circulating fluidized bed,in order to achieve low calorific value.Provide research examples and guidance for the clean and efficient use of coal. |
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