Emissions Characteristics Of SO₂ And NO_x During Catalytic Combustion Of Coal Gangue And Coal Slime

This paper selects coal gangue and coal slime as raw materials for experiment,and the catalytic combustion characteristics of coal gangue and coal slime in air and O₂/CO₂ atmosphere were studied by the thermogravimetric analyzer.The emission characteristics of SO₂and NO_xduring the combustion of coal gangue and coal slime were also analyzed by the tube furnace and flue gas analyzer.In addition,the ashes obtained from combustion of coal gangue and coal slime were characterized by SEM,BET,XRD and FTIR,and the ash melting point of the ashes obtained from catalytic combustion were also determined.The mechanism of the combustion of coal gangue and coal slime was also discussed.The main results were as follows:(1)During the combustion of coal gangue and coal slime,adding Mo/MS,Mo/HZSM-5 catalyst could reduce the ignition point,burn-out temperature and apparent activation energy both in air and in O₂/CO₂ atmosphere;and the ignition temperature,burn-out temperature and apparent activation energy were lower in air atmosphere than in that in O₂/CO₂.(2)During the combustion of coal gangue and coal slime in air and O₂/CO₂atmosphere,the addition of Mo/MS and Mo/HZSM-5 could reduce the SO₂ emission concentration and the conversion rate,and shorten the release time.The SO₂ emission could be inhibited more obviously when adding Mo/HZSM-5 during combustion of coal gangue at 500-700?and 1000?both in air and in O₂/CO₂ atmosphere.During coal slime combustion,adding Mo/MS at 600?in air could inhibit SO₂emission more effectively;while under O₂/CO₂ atmosphere,SO₂ emission could be inhibited better at 1000?when adding Mo/MS.(3)During the combustion of coal gangue and coal slime in air and O₂/CO₂atmosphere,the addition of Mo/MS and Mo/HZSM-5 could reduce the NO_x emission concentration and NO_x conversion rate,and shorten the release time.Adding Mo/HZSM-5 to coal gangue during combustion at 700-1000?under air and O₂/CO₂ atmosphere could inhibit NO_x emission better.In air,adding Mo/MS to coal slime during combustion at 700?and 1000?could inhibit NO_x emission effectively;and under O₂/CO₂ atmosphere,adding Mo/MS to coal slime during combustion could inhibit NO _x emission obviously at 800?.(4)A series of analyses including SEM,BET,FTIR,XRD,and ash melting point detection were determined for the ashes obtained from combustion of coal gangue and coal slime with addition of Mo/MS and Mo/HZSM-5.It was found that the properties of the ashes obtained from combustion of coal gangue and coal slime were similar in air and O₂/CO₂ atmosphere.XRD analysis showed that the main minerals in the ash obtained from combustion with Mo/MS and Mo/HZSM-5 catalyst were quartz,anhydrite,hematite,mullite and scheelite,and addition of Mo/MS and Mo/HZSM-5led to the formation of mullite and scheelite at 900?.FTIR analysis showed that there was no significant change for the functional groups of the ashes contained from the combustion of coal gangue and coal slime with Mo/MS and Mo/HZSM-5.The ash melting point of ash after catalytic combustion of coal gangue and coal slime was1390-1402?,and the addition of Mo/MS and Mo/HZSM-5 have no obvious effect on the ash melting point of the ashes.This study will provide the theoretical basis for the selection of catalysts during the catalytic combustion of coal gangue and coal slime,and provide guidance for the clean and efficient utilization of them.