The Research Of Fine Coal And Semi-coke Briquetting And Gasification Characteristics

In recent years, along with the low rank coal, such as pulverized lignite and coke powder production increased year by year. On the one hand,because of its own performance and market demand, pulverized coal and coke powder sales meet difficulties,which brought about by the economic and environmental problems have become increasingly prominent; the other hand, for the gasification of lump coal / coke was in short supply in the state. It was found that the low-level pulverized coal by processing into briquette, underway formed coke which made in low temperature pyrolysis used for gasification, can realize the pulverized coal upgrading classification using, to establish the clean energy system of the sustainable development is of great significance.In this paper,with lignite semi-coke, long-flame coal and anthracite as raw material, independent research of coal-modified binder for forming the body of the binder, by investigating briquette properties after adding different auxiliary binder（sodium silicate, phenolic resin, polyvinyl alcohol, hydroxypropyl methyl cellulose）, to get the optimum binder formula, and determine optimal conditions of briquette forming, drying, carbonization, preparation of high-strength gasification formed coke and using related characterization methods to study the bonding mechanism of briquetting process. Finally, through gasification reaction apparatus for gasification and steam gasification reactivity experiment, established gasification kinetics model.The conclusions can be summarized as follows:（1） Cold and thermal strength of briquette first increased and then decreased with increase of molding moisture, drying time and drying temperature;they tended to increase with increase of molding pressure, final carbonization and holding time; but showed a decreasing trend with increase of heating rate; compared with molding moisture and molding pressure, binder type and content of the mixed molding on coal is more significant. Fine coal and semi-coke briquetting optimum conditions: the ratio of the pulverized coal grain size 0⁰.5mm:0.5¹mm is 80:20, molding moisture 15%, molding pressure 60 MPa, coal modified binder 16% and polyvinyl alcohol 0.3%, the final preparation of the briquette: the cold strength was 3994 N / Ball, falling strength was 97.6%, thermal strength was 3226 N/Ball and thermal stability was 90.12%.（2） The changes of C, O functional group-type during carbonization are: with the increase of the terminal temperature carbonization, aromatic ring- CH began to decline after 600 ℃, aromatic ether C-O-C structure is relatively more stable, the aromatic ring carbonyl carbon C=O has poor thermal stability,its branched chain is easy to heat fracture, fat C-H bond, bridges and side chain, hydrogen bond association – OH keys will gradually diminish step by step. After carbonization, both C- C and C-H together account for over 70% of the total carbon content, the relative content of phenol ether carbon C-O, carbonyl carbon C=O and carboxyl carbon COO- all decline with terminal temperature increases, especially the larger decline of C=O and COO-,from 15.20% and 16.78% down to 3.45% and 8.04% respectively. Under low temperature, coal aromatic carbon net layer configuration is less orderly, raising the carbonization temperature, carbon network structure is more stable.（3） The adsorption and desorption isotherms of coal produced adsorption hysteresis phenomenon, carbonization temperature increased from 120℃ to 700℃, total pore volume and mesoporous of briquette overall decreased, the total pore volume from 0.0288 ml/g fell to 0.0065ml/g and mesoporous volume fell from 0.0291ml/g to 0.0067ml/g, specific surface area increased from 7.0137m₂/g first to 23.1299m₂/g, then fell to 1.5384 m₂/g consistent with micro pore volume changed.（4） Coal carbonization bonding process on the whole is divided into four stages: solid- solid bonding（ 450℃）, solid- gel adsorption（450 550℃）, solid- adhesive curing（550 650℃） and solid- solid carbide（650℃ ^）.（5） Carbon conversion rates of formed coke in different gasification temperature,different steam flow rate and different particle size increased with reaction time increasing, then leveling off; increasing magnitude of XJ3⁸（particle size:3⁸mm）is of little difference; reactivity index R0.5 of formed coke gasification is gradually increased with the increase of gasification temperature, steam flow rate and decrease of coke particle size.（6） Gasification reaction rate of formed coke in different gasification temperature, different steam flow rate and different particle size increased with reaction time were similar, there are obvious inflection point cross P,O and the intersection of M, the curve appears as "mountain" shape. At the inflection point P reached the maximum gasification reaction rate, the gasification reaction can be divided into two stages.（7） Gasification temperature increased from 800℃ to 900℃, the average specific gasification rate B increases obviously; when steam flow rate increased from 430ml/min to 760ml/min, the average specific gasification rate B overall showed an increasing trend; The average specific gasification rate B decreases with the increase of particle size.（8） With gasification temperature increasing, the time needed for 4000ml/g decreased significantly; with the increase of steam flow rate, increasing significantly in gas production rate, steam flow rate when in the range of 430 650 ml/min, improving gas production rate is more significant; with the decrease of the formed coke particle size, gas production rate increased significantly.（9） XJ and HMJ increase first, after the temperature higher than 900℃, the amount of gas is reduced, SCJ and JWJ has been increasing; The total gas volume of different lump coke along with the increase of steam flow rate tend to rise, after 650 ml/min, contining to increase steam flow rate has little effect on the lump coke. Under the same conditions, the total gas volume: HMJ < SCJ <XJ < JWJ;The total gas volume of different lump coke at different particle size change range is between 11.187 13.371L; the total gas volume of different lump coke present the rising trend,with the decrease of the lump coke particle size, but lessly.（10） In addition to JWJ with gasification temperature rises, trend has been reduced, the remaining lump coke gasification at a temperature below 900℃, H₂/CO tended to increase; when the temperature is higher than 900℃, H₂/CO becomes lower;all H₂/CO showed a rising trend, with the increase of steam flow rate, H₂/CO of XJ and SCJ evidently improved; within the scope of the 1⁸ mm size, particle size of lump coke gas content has little impact on H₂/CO.（11） Gasification gas heating value all showed increasing trend with the temperature increasing, JWJ gasification gas heating value is always greater than the others and the increase of the amplitude is also the argest; gasification gas heating value are presented to show a decreasing trend with the increase of the steam flow rate, especially in the most obvious change is in JWJ, gasification gas heating value: SCJ <XJ <HMJ <JWJ; in the case of other conditions fixed, XJ, HMJ and SCJ gasification gas heating value, with the decrease of the lump coke particle size, the overall tended to increase, JWJ showed an decreasing trend, did not exhibit a substantial change.（12） XJ gasification kinetics are availablly been described by shrinking core reaction model SCM（Fp=2） and SCM（Fp=3）, the apparent activation energy were 61.05 k J/mol and 56.90 k J/mol, corresponding to the steam gasification of the Arrhenius equation is as follows:Fp=2:k=22.46exp（-7343.04/T）Fp=3:k=18.90exp（-6843.88/T）...