| Combustion of civil bulk coal has caused serious environmental pollution problems.Coal briquette technology is one of the important technologies for pollution control of civil bulk coal.Coal briquette can not only improve the combustion efficiency of coal,but also reduce SO2,NOx,smoke and other pollutants produced by the combustion of bulk coal,which has significant social and environmental benefits.Forming technology and desulfurization technology are key technologies to achieve clean and efficient combustion of coal briquette.The forming,sulfur-fixing mechanism and combustion characteristics of coal briquette were mainly studied.The main results are as follows:(1)In the study of forming of coal briquette,Jincheng coal and Changzhi coal were selected as the main coal types.Starch,bentonite and sodium humate were used as briquette binder.Compressive strength and thermal strength as the main performance indexes of coal briquette.The effects of binder and coal types on briquette strength were studied,and the binding mechanism was analyzed as well.The results showed that starch could significantly improve the compressive strength of coal briquette,bentonite and sodium humate had a significant effect on improving the thermal strength of coal briquette;The better the wettability of the binder on the coal surface,the easier for binder to spread,which increased the contact area between coal and binder,thereby improving the briquette strength;When the mass ratio of Jincheng coal to Dongqu coal was 65:35,the compressive strength and thermal strength could reach 500N/ball respectively;when the mass ratio of Jincheng coal to Xingxian coal was 77:23,the compressive strength and thermal strength reached 503 N/ball and 355 N/ball respectively.(2)In the study of the sulfur-fixing mechanism of coal briquette,Theeffect of different factors(Ca/S molar ratio,temperature,particle size of sulfur-fixing agent)on the sulfur fixation of coal briquette were studied.Effect of combustion atmosphere on sulfur fixation mechanism of coal briquette was mainly studied.The pyrite(Fe S2,the main component of inorganic sulfur in coal)and calcium oxide were used as reactants,air atmosphere and argon atmosphere were used to simulate the aerobic atmosphere of the outer layer and the anaerobic atmosphere of the inner layer of coal briqutte respectively.The mechanism of sulfur fixation in different temperature ranges under the same atmosphere was studied.The results showed that the different sulfur-fixing products were formed in the inner and outer layer of coal briqutte during the combustion process.The sulfur-fixing product was Ca SO4 in the outer layer of coal briqutte,while the sulfur-fixing product was Ca S in the inner layer of coal briqutte.The reaction path of S was Fe S2?Fe1-x S?SO2?Ca SO4 in an aerobic atmosphere while the reaction path was Fe S2?Fe1-x S?Ca S in an anaerobic atmosphere during the reaction process between Fe S2 and Ca O.(3)The self-built thermal balance device was used to study the combustion characteristics of coal briquette.The effect of additives(binder,sulfur-fixing agent,combustion improver)and coal types on the combustion characteristics of coal briquette were investigated,and the emission of pollutants of bulk coal and coal briqutte was tested respectively.The results showed that adding a small amount of binder(mass fraction?1.5%)had little effect on the combustion characteristics of coal briquette;the addition of sulfur-fixing agent(Ca/S molar ratio is 2)caused the increasing of ash of briquette and decreasing of initial combustion rate;Both the combustion improver(1%)and coal blending could significantly improve the ignition characteristic of coal briquette.Compared with bulk coal,the emissions of SOx of coal briquettes made from Jincheng Coal mixed with Dongqu Coal and Xingxian Coal respectively were reduced by 48.97% and 54.17%respectively. |
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