Experimental Study On Combustion Characteristics And Pollutants Emissions Of Pulverized Coal In High Temperature Fixed Bed

Coal is most important fossil energy. For a long time, it has played an important role in the human energy structure. According to the existing energy situation in China, the coal’s main position in China’s energy consumption in the near future will not change. However, the massive coal combustion can cause serious environmental problems. In order to make use of coal resources more efficient and environmentally friendly, the study of coal combustion and pollutants emissions has profound significances.Thermo-gravimetric analyzer is the most common equipment to investigate on characteristics of pulverized-coal furnace. And because of limitations of gradually heating, TGA cannot get combustion dynamics at the particular temperature. The temperature in pulverized-coal furnace can be up to 1400℃. In real environment of the furnace, with the exception of outlet of burner around which oxygen concentration is higher（is 21%）, other region low oxygen and oxygen inequality would happen. And the effect of atmosphere of air（simulation of high oxygen concentration around outlet of the burner） and low oxygen in high-temperature condition on the characteristics of pulverized coal combustion was studied by self-made bench which could achieve thermal gravimetric measurement at constant temperatures and simulate atmosphere of flue gas. And at the same time NO and SO₂ were measured. The results show that under the constant temperature environment the curves of burning weight loss of pulverized coal have an inflection between combustion of volatile and char, and with the decrease of coal rank, this phenomenon is more obvious. Under air atmosphere, with the temperature increased, burnout time is shortened, characteristics of combustion of pulverized coal are improved and more volatile is released. But when the temperature reaches 1450℃, raising temperature dose not significantly increases produce of the volatiles. Under high temperature and air atmosphere, with increase of degree of coalification, NO cumulative emissions increase. With temperature increased, the peak value of NO instantaneous releasing increases and NO emissions are accelerated, but increasing temperature has a limited impact on raising the produce of fuel-NO. Under the high temperature of 1250℃-1550 ℃and in air atmosphere, the curves of SO₂ generation showed bimodal pattern in the main. With temperature rising SO₂ cumulative emissions slightly presented downward trend.Under low oxygen atmosphere, Temperature has less effect on the early stage of combustion at above 1300℃. There is smaller rise of the combustion rate when the same amount of oxygen concentration is increased at 1300 ℃than that at 800℃. Under low oxygen and high temperature atmosphere, when water vapor concentration reaches a certain value（10%） in early stage of combustion, its effect on the devolatilization and combustion is more obvious. Under high temperature when CO2 concentration increased to 15%, the results show if it continues to increase CO2 concentration, the combustion rate will be decreased. Under low oxygen conditions when environment temperature is raised, NO instantaneous formation peak forward and NO emissions are mainly concentrated in early reaction. NO emissions are mainly concentrated in early reaction which means the proportion of volatile NO is larger when improving oxygenconcentration. Under the conditions of low oxygen and high temperature, the higher the rank of coal is, the less the heterogeneous reductions are and the more the cumulative emissions are. The existence of water vapor and CO2 can reduce NO emission in a certain concentration range. When Pulverized coal is put into high temperature environment suddenly, the curves of SO₂ emission rate which has only one peak at 800 ℃and 1000 ℃are different from the curves with two peaks at 1200 ℃and 1400 in low℃-oxygen environment（5%O2）. And the peak value rises as the temperature increases. The peak morphology of the SO₂ release curves are mainly decided by the temperature, but affected by high concentration of CO2. With the increase of O2 concentration, more SO₂ releases at the stage of char combustion at 1400℃. The SO₂ initial releasing peak increases firstly and then decreases with the addition of CO2 concentration in high-temperature and low-oxygen environment. Meanwhile, the curves of SO₂ release rate have one peak when the percent of CO2 concentration was 45%.