The Study On The Preparation Of Civil Briquette And Combustion Characteristics

Briquette technology is one of the important technologies of clean coal. The promoting, the production and use of civil clean briquette has great economic benefits and environmental benefits. The core technology of briquette lies in the combustion characteristics of briquette and briquette binder.It is found from the experiments that humic acid has an excellent bonding effect of Tangshan briquette. 5% of the amount can meet the requirements of high strength. The compressive strength, the drop strength, thermal strength are high. However, If humic acid was used as the binder, the amount needed is high. And the bonding effect of Zhongyuan briquette is not very good. Bentonite is not suitable to be used as the main part of briquette binder. The compressive strength and the drop strength are low. The strength of cold state is still difficult to meet the requirements even put 3% of the bentonite into the briquette. But the thermal strength is high. The calcium lignosulphonate has a good effect on the compressive strength and drop strength for Zhongyuan briquette. However, the calcium lignosulphonate has a bad effect on Tangshan briquette. And the thermal strength is bad. Starch is a good binder for Zhongyuan briquette and add 0.5% can obtain good bonding effect under cold state. For the Tangshan coal, the bonding effect of starch is poor. Cold strength is still low even add 1.5% of starch. So it is difficult to meet the general requirements of briquette for cooking. And high temperature strength is low when starch is used as binder. Immersion strength and renewed dry strength can be better if starch was modified.An optimized formula of binder for Zhongyuan briquette is 0.2% of starch and 0.3% of calcium lignosulfonate. So the strength of cold can be better when the cost is lower. Besides, 2.5% of bentonite can be added so that the thermal strength will be higher. The Tangshan briquette adds 5% of humic acid can meet the general requirements for cooking briquette strength properties.It is found from the briquette combustion characteristics experiments that the addition of a small amount of binder for briquette had no significant effect on combustion characteristics. The most important factors which affects combustion characteristics of briquette is the properties of raw coal. Compared with the Korean anthracite, Shenhua bituminous coal with high volatile is good for improving the combustion haracteristics of briquette. So the ignition speed is fast, combustion time is short, intensity is higher in the early stage and lower in the late stage. Add 40% of Shenhua coal will bring a small amount of white smoke and Potassium Permanganate can reduce the smoke.The combustion process of briquette be explained by the shrinking core model. Put the briquette into the briquette stove, the briquette rapidly warming and then reach the temperature of briquette stove. The briquette combustion controlled by surface reaction at first. The speed of combustion is fast. However the control area is just a short time. Then the effect of internal diffusion is more and more important. Briquette combustion is gradually turning to be controlled by internal diffusion. Right now, about 40%~50% organic matter of the briquette was burning out. The surface produce a certain thickness of coal ash. Then the briquette burning out beyond diffusion control. The briquette burning under diffusion control cost most of the time. But at the same time, nearly half of the organic matter in briquette burned out before the briquette enter diffusion control region.With the increase of temperature, diffusion controlled area increases, and so is the speed of briquette combustion. Pressure effects more on the coal combustion at low temperature, effects less at higher temperature. Coal is the most important coal briquette combustion properties. Ash can also affect the combustion characteristics by affecting internal diffusion.Briquette combustion under the surface reaction control in the early stage. We can reduce the rate of combustion by changing the shape of the briquettes, diameter, raw coal, oxygen etc. Then the coal is gradually turning to the internal diffusion control. Through changing the shape, diameter, the minerals in coal, oxygen etc., the diffusion rate can be changed. so the combustion rate of coal can be controlled. So that, the coal briquette has a longer burning time and better combustion intensity.