Effect Of Alkali(Alkaline Earth) Metals On The Precipitation Of Several Gas Products In The Process Of Pyrolysis Of Zhundong Coal

Zhundong coal predicted reserves are ranked first in China,its high moisture,low ash melting point,low ignition point,higher burning rate,low mining costs and other characteristics decide it is excellent power coal.The research on the pyrolysis reaction and gas product precipitation characteristics has an important role on the advantages of its reserves,the improvement of the utilization efficiency and its efficient and clean use.Based on the status quo that alkali and alkaline earth metal elements in coal may cause contamination and fouling of equipment in the process,but also show a catalytic effect on the gasification process.This article aiming at the characteristics of high alkali metal and alkaline earth metal content in Zhundong coal,the addition method of alkali metal and alkaline earth metal was studied by means of experiment and simulation.The effects of different addition methods and alkali metal and alkaline earth metals with different additions on the pyrolysis of coal and the precipitation of gas products under different heating conditions were studied.The reaction characteristics and influence were discussed.TG-FTIR experamental platform was used to study the effects of alkali metal and alkaline earth metal additives(Na2CO3,CaO and the mixture of the two)on the desorption of pyrolysis properties and gas products of Zhundong coal were investigated under three additions of 2wt%,5wt%and 10wt%.The results show that in the case of mechanical mixing,the addition of sodium carbonate reduces the yield of CH4,promotes the release of CO,increases the volatile release characteristic parameter and the maximum weight loss.CaO can promote the thermal loss during pyrolysis,increases the production of CO,and the addition of Na2CO3and CaO increases the temperature at the peak of the weight loss rate and promotes the release of CO2 and CO.The remaining mass of the sample was the smallest in the amount of 5wt%.Na2CO3 and CaO shows a certain synergistic effect.In the pyrolysis reaction under the experimental conditions,the amount of heat release before and after dewaxing is basically the same.The addition of Na2CO3 reduces the amount of heat release.The experiment was carried out by adding the additive to the Zhundong coal by means of a fixed-bed experiment.The effects of additive on the isothermal pyrolysis of coal and the precipitation of gas products were analyzed by the detection and kinetics of CO,CH4,CO2 and H2 production.The results show that the addition of additives reduce pyrolysis activation energy and Na2CO3 and CaO showed the synergistic catalytic effect,and the catalytic effect was most obvious at 750 ? pyrolysis.Based on the Gibbs minimum free energy theory,the chemical reaction equilibrium is calculated for the pyrolysis process of Zhundong coal,the results show that the yield of CO2 and CH4 is reduced from 500? to 700? and the yield is stable from 700? to 850?.The yields of CO and H2 increase with the increase of pyrolysis temperature,750? tends to be stable.Zhundong coal itself and the added sodium element in the pyrolysis temperature of 800?in the form of Na(g);Na2CO3,CaO and the mixture of the two pyrolysis promote the production of H2.