| With the sustained and rapid development of economy in China, the energy problem became more and more serious; one of the difficulties in our country is the energy conservation and emission reduction. The resources and energy consumption of iron-steel enterprises is large, especially energy consumption in iron-making process is about50%-60%of total energy consumption. Though, many technologies such as CDQ and TRT were used, iron-making energy consumption has improved greatly. But the energy of molten blast furnace (BF) slag has only been used limitedly so far.This study proposed a new method of using coal gasification by molten BF slag to recover energy of molten slag, and this method was researched. The research results as follows.(1) A new heat recovery system was proposed. This system consists of melting gasifier, the2nd gasifier and boiler in order to achieve stepped energy using. The melting gasifier and the2nd gasifier use the endothermic heat of gasification reaction instead of sensible heat to recover the energy of molten blast furnace slag.(2) The possibility of the new heat recovery system was studied. The results indicate that this method is possible and better than conventional methods such as hot water or steam production. The molten BF slag acts as not only thermal media but also good catalyst. The viscosity of molten BF slag can meet the requirement of coal gasification in molten slag.(3) The coal gasification reactions in molten slag at elevated temperature were studied kinetically by the isothermal thermogravimetry using STA409PC thermal analyzer. The results showed that the molten BF slag acts as good catalyst.(4) The hydrodynamics of coal gasification in molten slag was studied with water modeling of melting gasifier. The results showed that circulation appeared in bubbles when velocity of flow is large; this is benefit to the gasification reaction. The residence time reduced with the increase of both flow rates. The residence time of bubble is longest using top blowing. The mixing time of bath is shortest using side blowing. The effect of blowing using more guns is better than single gun, but the distinguished is small.(5) Coal gasification reactivity and operation parameter of this system was studied by the small experiment system. The results showed that the coal gasification in molten BF slag has extensive adaptability to the coals supplied from different origin. The carbon conversion and gasification reaction rate of DATONG coal, FUXIN coal and SHENNAN coal are all high, the calorific value of syngas are all about12000kJ/m3. Especially, the reactive rate of SHENNAN coal which is the representative of coals with high ash and low carbon content, is larger than other two kinds of coal. The system has extensive adaptability to the coal granularity. The carbon conversion of different particle size coals all can achieve100%. The CO2coal rations influence the gasification reactivity. The density of CO and H2reduced with the increase of CO2-coal rations. When the CO2-coal ration is1, the carbon conversion and the time required in the reaction are little different too. Looked through the comparison that, the reaction time is a little shorter when the coal granularity is80. Coal granularity does not influent the CO concentration in the coal gasification process. But H2concentration increased with the increase of the coal granularity when the coal granularity is120-80. The coal granularity has little influence with the calorific value of syngas. The study in the influence of the coal gasification reactions in molten slag at elevated temperature by the CO2-coal ration showed that, The CO2-coal rations influence the gasification reactivity. The density of CO and H2reduced with the increase of CO2-coal rations. The calorific value of syngas reduced too. The carbon conversion increased with the increase of C02-coal rations. And C-H ration reduced at first and then increased. When the CO2-coal ration is1, the carbon conversion is a little low, only with0.88. It is caused by shallow Slag pool. Adjust the Slag pool depth can increase the CO2-coal ration. Injection velocity has impact on the coal gasification reactions in molten slag. When the CO2-coal ration is1, the calorific value of syngas in a lower injection velocity is higher than in a higher injection velocity. CO and H2concentration gasification reaction rate and C-H ration reduce when injection velocity increases. The best temperature of the coal gasification reactions in molten slag is1623K.(6) The coal gasification process in molten slag was calculated and the exergy of this system was analyzed. The results showed that, according to the different gasification agent, this system can produce syngas with different C-H ration. The calorific value of syngas is high. The system has high exergy efficiency and its internal exergy loss rate is about5%. The efficiency of melting gasifier is high and without pollution. Besides, this method can bring huge economic and environmental benefits which are important to the survival and sustainable development of iron-steel enterprises. |
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