Experimental Study On The Effect Of Coal Combustion Characteristics Of Alkali Metal In High-alkali Coal

The coal of Xinjiang Zhundong area belongs to high sodium(~ 5%) coal, the following factors for the design of coal boiler burned Zhundong coal is extremely important: alkali metal existing in coal, the rules of influence of alkali metal to ignitability and burnout of coal combustion, the effect of alkali metal to contamination and slagging of coal etc.In this paper, on a laboratory scale, using high temperature sintering equipment, by adding different proportion of NaCl to study reaction characteristics and catalytic effect of different coal with alkali metal Na(Xinjiang Zhundong coal #1, #2, #3, the underground coal #6, #7); using thermal TGA- DTA analysis equipment, through the study of characteristics of coal ignitability and burnout of combustion to get the combustion characteristics of Zhundong blended coal #4, #5.By testing the composition of 500℃blending coal ash of Zhundong coal #4, #5, and using of thermodynamic equilibrium calculation software Factsage to calculate the viscosity of blended coal ash under different temperature, through the use of ash melting point tester to test the melting temperature of 815℃coal ash of Zhundong blended #4, #5 and different proportion of them and get fouling and slagging basic characteristics of Xinjiang Zhundong blended coal.This paper is also on 3MW thermal state test platform to conduct test of firing experiment of Xinjiang Zhundong high sodium coal(coal #4, #5, 5:5 blended coal #4:#5) and to analysis fouling and slagging situation on high temperature heating surface and to get conclusions as follows:Alkali metal Na has catalytic effect to combustion reaction of Zhundong coal #1 ~ #3 and the underground coal #6 ~ #7 when added alkali metal salt NaCl,especially catalytic role showing in the late period of burning.As a result of high content of alkali metals in Zhundong coal #5,with the increase of coal #5 blended in Zhundong coal, the combustion reaction is accelerated, combustion is intensified, the ignition point Ti, the maximum weight loss temperature Tmax began to decrease, the presence of Cl is seriously affects the release of sodium and potassium in coal. Combustibility index Cb and burnout index Hj have linearly increasd with the ratio increased of Zhundong coal #5 in the blended coal.The slagging degree of regional and furnace heat load region of the 50% #4:#5 mixed coal is the most severe, followed by Zhundong coal #5, finally Zhundong coal #4,it is related to the low temperature eutectic area of Al2O3-SiO2- CaO three phase diagram. Combined with the catalytic of alkali metal and the fouling and slagging characteristics of Zhundong high alkali coal #5, The ratio of Zhundong high alkali coal #5 blended in Zhundong coal #4 coal should be less than 40%.