Experimental Study On Coal/steam Gasification Reaction In Molten Blast Furnace Slags

As energy intensive industry,the iron and steel industry has made huge energy consumption.Blast furnace of iron making energy consumption is 67%of total energy consumption.Blast furnace slags as waste contains large amounts of waste heat.Recycling of waste heat from blast furnace slag plays a vital role for energy conservation and energy efficiency improvement in steelmaking industry.At present,the blast furnace slag in the iron making is processed by water quenching.The high grade waste heat of blast furnace slags is not reuse by this method.Therefore,a more effective method is needed in heat recovery from molten blast furnace slags.Chemical method has obvious advantages in terms of blast furnace slag waste heat recovery efficiency,and has been widespread concern.In this paper,based on the advantages of chemical method recycling blast furnace slag waste heat and the China's energy structure,the idea that use of coal-steam gasification reaction recycling blast furnace slag waste heat is proposed.The process coal gasification in the molten slag's theoretical analysis,including the theoretical calculation of blast furnace molten slags physical property,the pulverized coal particle's movement,the heat transfer process between the pulverized coal particles and molten blast furnace slags and the mass transfer process between the pulverized coal particles and molten blast furnace slags,is carried out.The type of coal,coal/slag mass ratio and temperature is researched in the thermogravimetric experiment of coal-steam gasification with molten blast furnace slags.After the kinetic analysis of coal-steam gasification with molten blast furnace slags,the reaction mechanism function is determined and the dynamic model is established.The hot-state experiment of coal-steam gasification in molten blast furnace slags is carried out to research of the type of coal,H2O/C mole ratio and temperature's influence on gasification indexes.The theory analysis of the pulverized coal particle's movement in molten slag bubbles shows that whether coal particles can through gas-liquid interface into the molten slag is concerned with coal particle velocity,particle diameter and the bubble size.The theory analysis of coal particle capture by molten slags shows that the larger the pulverized coal particle size,the easy to capture by slag surface.The heat transfer and mass transfer during coal gasification process provide the corresponding theoretical basis of the coal-steam gasification in molten slags.The thermogravimetric experiment of coal-steam gasification in molten slags is carried out by the isothermal method,and three kinds of coal(FX coal,FS coal,DZ coal)are applied to the experiment.The results show that with the temperature from 1300? to 14000C,carbon conversion rate increases,the early(less than 3min)reaction rate increases,reactivity index increased gradually.As the temperature increases,the effect of temperature on the gasification reactivity decreases.With the increasing coal/slag mole ratio,the carbon conversion and reactivity index increase and gasification reaction completion time gradually shortened.It is shown that the addition of blast furnace slag can improve the coal-steam gasification reactivity.Reactivity index by different type of coal in decreasing order is DZ>FS>FX.The kinetics model is established in different conditions,and the kinetics parameter is solved.As can be seen from the calculation results,Addition blast furnace slag is tend to reduce the coal gasification reaction activation energy,and making it easier for the gasification reaction.The experiment of coal-steam gasification in molten slags is carried out by a small experiment system in different conditions.The experimental results showed that the main components in gasification products include H2,CO,CO2 and CH4.The gas composition under different coal conditions is above 57%except the DZ coal condition,and the maximum is 67.4%.The hydrogen-rich gas is produced.The difference in gas composition,carbon conversion and gas yield is related to the component of coal.The difference of heat value in different coal condition is relatively small.Heat values have not much difference in different coal condition,which indicates that the coal-steam gasification in molten slags has wide adaptability for various rank coals.With the temperature increasing from 1300 ? to 1500 ?,Carbon conversion rate improved by 18.8%;gas yield improved 0.29 Nm3·kg-1;heat value of gas production increased 452.29KJ·Nm3;gasification efficiency improved by 13.3%.Comparing the value of gasification efficiency at relatively different temperature conditions can be obtained that gasification reaction temperature is 1350 °C more reasonable.With the H2O/C mole ratio increasing from 1 to 3,Carbon conversion rate improved by 12.0%;gas production rate inproved 0.57 Nm3·kg-1;gasification efficiency is improved by 10.1%;heat value of gas production decreased by 6.6%.Comparing the value of gasification efficiency at relatively different H2O/C mole ratio conditions can be obtained that gasification reaction H2O/C mole ratio is 1.5 more reasonable.Under the optimal condition,the gasification temperature is 1350?and H2O/C ratio is 1.5:1,the hydrogen gas composition is up to 63.8%,and the gasification efficiency was 94.5%.