The Preparation Of Coke For Gasification And Intrinsic Correlation Between Its Reactivity With The Structure Evolution

The charateristic riching in the coking coal resources determines the dominant position of the coking industry in Shanxi province.In recent years,the decline demand of the iron and steel has led to the overcapacity of the coking.The coking industry in Shanxi province is facing the crisis of the survival and the challenge of transformation development.Besides,there are also aboundant low quality coking coals in Shanxi province and they are mainly used as thermal coals with lower price.Based on the status above,some independent coking industries use coking oven to produce coke for gasification while producing metallurgical coke.The coke for gasification used for the fixed bed gasification can produce carbon-rich gas,and the coke oven gas is rich in hydrogen.The joint use of gasification gas and coke oven gas as raw materials can produce a variety of downstream products by adjusting the ratio of hydrogen and carbon.In addition,the gasification gas can return furnace and replace partially coke oven gas for heating.And the heat value of the gasification gas is lower than that of coke oven gas,which is convenient for the temperature control of the coke oven and beneficial to reducing the emission of nitrogen oxides.According to the background above,on the basis of blending scheme in a coking plant of Shanxi province,this study prepares the coke for gasification in lab scale and explores the coking condition.Then the effects of blending ratio on the caking ability of the coal blends,the properties and structures of the coke for gasification are investigated.The main results and conclusions are shown as follows:?1?The final temperature and the residence time on the properties of the coke are investigated.The final temperature is the main factor affecting the difference between the properties of the coke for gasification obtained from the laboratory and that from the industrial.The preparation conditions in laboratory simulating industry production of coke for gasification are as the followings:stacking density of 1.10 g/cm³,water content of 10%,temperature programming of 10 ?/min to 300 ? and then 3 ?/min to 1150 ?,final temperature residence time of 30 min.Adjust the ratio of the sub-bituminous coal,the gas coal and fat coal in blends and obtain the blending scheme of coke with higher reactivity compared with the coke from the industial:MSC0.65,WGC0.35,DFC0.00;The cost of the coal blends with the coal blending scheme is 42%lower than that of industrial coal blends;and the reactivity of the coke is 8.33%higher than that of industrial coke for gasification,and 1.91%higher than Jincheng anthracite.?2?The caking abiltiy of coal blends vary with the coal types and ratios in blends.The relative ratio change of the subbituminous coal and gas coal in blends lead to an obviously change of the caking ability.When the caking index of coal blends is higher than 40,the interactions of coals in blends strengthen the caking ability of blends.When the caking index of coal blends is lower than 40,the interactions of coals in blends weakening the caking ability of blends.The higher oxygen conten and the development of the pore structure of the subbituminous coal is deleterious to the caking ability of the coal blends;The volatiles in gas coal play an important role in strengthening the caking ability of the blends;The different components of volatiles in subbituminous coal and gas coal may be the reason for its different role in the caking ability.?3?The coke yield of coal blends is affacted by the volatiles,caking ability,ash content in blends.And,when then caking index is lower than 40,the coke yields vary obviously with the change of the blending ratio.When the caking indext is higher than 40,the coke yield vary slightly with the change of the blending ratio in blends.As the ratio of the fat coal in blends is higher than0.1 and the ratio of the subbituminous coal is lower than 0.55,the S₂₅,TS₊₆6 and the CSR is relatively higher and change slightly with the change of the blending ratio.?4?The reactivity of coke for gasification varies with the coal blending ratio for the change of the structure.The increase of the subbituminous coal in blends is helpful to the development of the pore structure and improves the reactivity of the coke.The increase of the fat coal in blends increase the order of carbon structure of the coke and lead to the decrease of the reactivity of the coke.The properties of coke such as CRI,CSR,S₂₅,TS₊₆6 and the coke yields change obviously before and after 0.1 of the fat coal in blends(the G_R.I.I about40 of the coal blends)is derived from the structure parameters change obviously.The effect of the interactions among coals in blends on the caking ability is different when the ratio of the fat coal in blends is about 0.1.?5?The internal correlation between the structure and the reactivity of coke is revealed by using multivariate linear fitting equation:CRI?%??28?1.26S_BET-8.76L_c-17.38?R²?28?0.91?Considering the factors affecting the reactivity of the coke,a prediction model of the reactivity of coke for gasification is established:CRI?%??28?-.0013G_R.I?10?.0863V_daf?10?1.982MCI-25.434?R²?28?0.97??6?The effect of blending ratio on the reactivity of the steam gasification of the coke is similar to its effect on the reactivity of the CO₂.During the steam gasification,the reacivity of the coke is proportional to the BET surface area and pore volume.The increase of the subbituminous coal and gas coal in blends is helpful to the development of the pore structure,and the role of the subbiuminous coal is more obvious.The increase of the fat coal and gas coal in blends strengthen the water shift gas reaction,and the water shift gas reaction is more obvious when the ratio of the fat coal in blends is about 0.3,which is consistent with the content of catalytic minerals in the coke.