| The technology of coal gasification using molten blast furnace slag as heat carrier is a new fashion to recovery the waste heat of blast furnace slag in the steel enterprise efficient.Coal and gasification agent inject into molten bath with carrier gas is the main process of this technology,and the coal gasification with heat and mass transfer to molten blast furnace slag will happen in the molten bath.During the process,the bubble behavior will effect the process of multiphase flow and coal gasification chemical reaction in the molten bath directly,and the bubble behavior also be effected by some structure and operation parameter.Therefore,the simulation of the process of multiphase flow and coal gasification chemical reaction in the molten bath is signification to the development of the technology of coal gasification using molten blast furnace slag as heart carrier.In this paper,the Eulerian-Eulerian model for multiphase flow coupled with coal gasification chemical reaction has been improved to simulate the self-made top-submerged lance molten furnace by the ANSYS FLUENT.The main research work and conclusion listed as follow:(1)This paper established the physical and mathematical model of top-submerged lance injection.And the numerical simulation and experiment of top-submerged lance injection have been carried out,and the comparison of their result testify the accuracy of established model.(2)This paper investigates the gas-liquid flow in molten bath.According to the bubble behavior in molten bath,there are four stages for it:initial expansion stage,bubble detachment stage,freedom lift up stage and bubble rupture stage;when the flow field in molten bath fully developed,the gas fraction decrease with the increasing of molten bath deep;during the injection process the area near the nozzle and lower the molten bath will first generate two symmetric heliciform flow regime,and then the flow regime in whole molten bath will become irregular because of the bubble lifting up and rupturing;as time goes on,the gas fraction in molten bath,the average velocity and turbulence energy of molten slag will decrease before it increase to maximum,and then it will keeping fluctuate in a range.(3)The orthogonal experiment using numerical simulation is employed to optimize gas-liquid flow and mix process;the effect of the various factors on the gas-liquid flow and mix process in top-submerged lance molten furnace are the ratio of two pipe diameter,the nozzle deep and the gas inject rate;the optimal conditions obtained by analysis is:A3B3C4,that is,with the ratio of two pipe diameter is 20:1,the nozzle deep is 200mm,the gas inject rate is 800L/h,and compared to the experimental condition,the gas-liquid flow and mix process of optimal condition is more reasonable.(4)To numerical simulation the whole coal gasification process in furnace,the model of coal gasification is added into the previous top-submerged lance injection model;the numerical simulation and experiment of coal gasification have been carried out,and the comparison of their result testify the accuracy of established model;meanwhile this paper also investigates the distribution of gas component in molten bath and the effects of steam to coal ratio on the syngas,the results listed as follows:coal and steam will react as soon as they inject into the molten bath and will be exhausted near the nozzle;the distribution of CO and CO2,steam and H2 is to the contrary in molten bath;CO2 and H2 will concentrate in the center of bubble,and H2 and steam will concentrate in the edge of bubble;with increase of S/C ratio,the fraction of H2 and CO2 in syngas increase while the fraction of steam CO decrease;the CO in syngas generated under optimal condition is more than experimental condition,but the H2 and CO2 is less than experimental condition,meanwhile the heating value of syngas generated under optimal condition is larger than experimental conditional. |
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