Experimental Study On Combustion And Pollutant Emission Characteristics Of Blended Coals In O₂ / CO₂ Atmosphere

At present,coal blending is an effective measure to realize the economic operation of power plants,reduce pollutant emissions,and improve the rational use of coal resources.O₂/CO₂ combustion technology not only can effectively reduce NO_x and SO₂emissions,but also capture and store CO₂ in flue gas for industrial use,and has broad application prospect.With Yinni lignite,Datong bituminous coal and their blending?60%bituminous coal+40%lignite coal?of a power plant as the research object,the combustion and pollutant emission characteristics of blended coal combustion in O₂/CO₂atmosphere were studied in this paper using thermogravimetric analyzer and the one dimension settling furnace.The combustion characteristics of blended coal were analyzed by thermogravimetric analyzer.The effects of V?O₂?/V?CO₂?volume ratio,lignite blending ratio and heating rate on the combustion characteristics of pulverized coal were discussed.Results showed that the changing rules of the blended coal combustion were the same.With the increase of the blending ratio of lignite,ignition and burnout temperatures reduced and the combustion characteristic index increased.In O₂/CO₂ atmosphere,with the oxygen volume fraction increased from 20%to 50%,ignition temperature and burnout temperature decreased,and the decline is not obvious,comprehensive combustion index increased.In 20%O₂/80%CO₂ atmosphere,the ignition temperature and burnout temperature were about 10?higher than that air atmosphere.In 30%O₂/70%CO₂atmosphere,the ignition temperature of blended coal was 3?higher than air atmosphere.It is correct that the 30%oxygen volume fraction in the O₂/CO₂ atmosphere is the most reasonable volume fraction.With the heating rate increased from 10?/min to 40?/min,the ignition temperature?burnout temperature and combustion characteristic index increased significantly,that is,the combustion characteristics of pulverized coal are sensitive to the heating rate.The pollutant emission characteristics of Yinni lignite,Datong bituminous coal and blended coals were studied on the one-dimensional settling furnace.Also,the effects of the excess air ratio?CO₂ mass concentration?fuel ratio FC/V and temperature on NO and SO₂ emission characteristics were analyzed.Results show that NO and SO₂ emission mass concentrations are increasing and CO emission mass concentrations are decreasing with the excess air ratioincreased from 0.8 to 1.4.The higher mass concentration of CO in flue gas,NO and SO₂ emission mass concentration is the lower.Under O₂/CO₂atmosphere,NO and SO₂ emission mass concentrations are lower about 30%⁴0%and10%than that of O₂/N₂ atmosphere.In O₂/CO₂ atmosphere,as the CO₂ mass concentration increased from 20%to 50%,NO and SO₂ emission mass concentrations are decreasing,and the magnitude of the changes are not large.When the oxygen content is certain,it is not good to simply increase the CO₂ mass concentration to achieve the emission reduction effect of NO and SO₂.With the increasing of temperature,NO and SO₂ emission mass concentrations always increase in O₂/CO₂ and O₂/N₂atmosphere.Different atmosphere and different heating segment,NO and SO₂ emission mass concentration curve slope significantly change.Under the low and high temperature,NO emission mass concentration trends are different with the increasing of the FC/V,while SO₂ emission mass concentration trends are consistent,and gradually increase.