Study On Preparation Of Gasification Briquette From Xinjiang Long Flame Coal

Considering the shortage of lump coal for the Yili Xintian coal gas project,the large amount of excess pulverized coal and tar slag are difficult to deal with,etc.This paper takes preparation of gasification briquette from Xinjiang long flame coal as a research topic.The influence of molding technology,preparation parameters of starch binder,type and proportion of binder and tar slag on the properties of briquette were studied.Cold compressive strength?SCC?,drop strength(S₂₅),thermal strength?BTS?and thermal stability(BTS₊₁₃)were used as indicators to characterize the preparation process.Infrared analysis of the samples was conducted to investigate the effect of changes in briquette functional groups on the properties of briquette.Finally,the pyrolysis kinetic parameters of coal and briquette were studied,and the main conclusions obtained after research were as follows:1.It is difficult for long flame coal to be formed separately because of the coal quality.The addition of Fugu char and Nilka gas coal in pulverized coal can significantly increase the SCC of briquettes,besides,Nilka gas coal has a large increase in SCC of briquette.Molding pressure affects the density of briquette,which has an important influence on the SCC and BTS of briquette.There are many oxygen functional groups,large internal pores and strong hydrophilic ability of long flame coal,which results in higher molding moisture of briquette.Forming moisture can wet the coal surface and promote the bonding of binder and pulverized coal.The properties of briquette can be maximized with suitable forming moisture.The residual water content of briquette also affects the SCC of briquette,and the strength is best around 10%.2.Long flame coal has the characteristics of colloid,which can shrink or expand with the change of water content.In the process of direct drying,the briquette is contracted by the internal skeleton,and the internal crack in the briquette leaded to the decrease of the strength.Prolonging the aging time is beneficial to the combination of the binder and the pulverized coal,and the strength and stability of the briquette is optimized when the aging time is 4 days.3.The strength and stability of briquette is affected by the process of alkalization starch synthesis.The appropriate NaOH concentration,reaction time and temperature are beneficial to the improvement of briquette performance,and the performance of the briquette is optimized at the conditions of 0.9%,120 min and 70 ^oC,respectively.The larger the starch concentration,the smaller SCC of briquette is.The oxygen-containing functional groups such as hydroxyl and carboxyl groups in briquette have a negative effect on SCC,in which the effect of carboxyl groups is greater than hydroxyl groups.Through central composite design,it was found that the reaction temperature and reaction time of alkalized starch had a significant influence on the overall performance of briquette.The fitting equation can accurately predict the test optimal conditions:reaction temperature 75 ^oC,reaction time 135 min,starch concentration 6%and NaOH concentrations were 0.9%.Under the optimum synthesis conditions,the SCC,BTS,S₂₅and BTS₊₁₃13 of briquettes were 638.1,390.4 N 98.5%and 97.4%,respectively.4.Adding binder into long flame coal can improve the SCC of briquette,but it is difficult to meet the technical requirements by adding a single binder.Organic binder can significantly increase the SCC of briquette.The use of composite binders can simultaneously increase the SCC and BTS of briquettes,and SCC of briquette can reach a maximum under the conditions of suitable starch,humic acid and bentonite addition amount.Through Plackett-Burman's experimental design,it was found that different binders have significant influence on different indicators,among which bentonite has a significant influence on briquettes.Through orthogonal optimization design,the optimum scheme of briquette was obtained as follows:starch 1%,humic acid 2%,bentonite 7.5%,molding pressure 25.6 MPa,molding moisture 15.5%,aging time 4days.The optimum parameters of briquettes performance were SCC 667.8N,BTS357.1N,S₂₅ 99.8%and BTS₊₁₃13 98.2%,respectively.5.Increased of tars slag and solvent?Isopropyl alcohol?addition,briquette strength was reduced.Through the design of orthogonal test,the impact on the performance of briquette from large to small:gas coal,H₂O,solvent and tar slag,among which the gas coal has significant effect on the performance of briquette.The optimal preparation parameters were gas coal 26%,H₂O 12%,solvent 2.5%and tar slag 3.5%.Under the optimal scheme,the SCC,BTS,S₂₅ and BTS₊₁₃ of the briquettes were 593.1 N,288.6 N,98.8%and 94.5%,respectively.