Study On Reactions And Behaviors Of Alkali Metals In The Blast Furnace Smelting Process

The balance of the alkali metals were investigated and studied the on the basis of ShiGang BF'production conditions and reaction mechanism and distribution law of alkali metals were studied in BF via the experimental analogue equipment. The research showed: The alkali metals loads of ShiGang BFs were high, between 5.2 kg/tFe to 5.5kg/tFe. Among it, the alkali metals amount in the sinter was about 69%, either pellet or coke was about 10%, other charges were little. The total removing alkali rate of ShiGang BFs were 73% to 79%. Among it, removing alkali metals rate of slag is 68% to 77% and top gas is 5%. The accumulation rates of the alkali metals of ShiGang BFs were 0.227kg/tFe·h to 0.282kg/tFe·h and BFs were in accumulation age. Thus it suggested that ShiGang critical alkali metals load is 4.0 kg/tFe.In the high temperature smelting zone the alkali metals silicate decomposed into the alkali metals evaporation and the alkali metals evaporation adhered on charges and the adsorption amount was as much as 2.1%. The amount of adsorption in chemical reservation zone was 2.8% and the low temperature prereduction zone is about 0.3%The size of charges can affect the amount of the alkali metals absorption. When the size decreased from 17mm to 11mm, the alkali metals absorption amount would increase from 0.3% to 1.3%. The alkali metals adhering on charges had a catalytic effect on melting reaction of coke. When K2O% was above 1.5 that CRI would be increased 23% and CSR would be decreased 40%. The alkali metals also can accelerate the reduce reaction and increase RDI of the iron ore. When K2O% was above 2.56% the RDI of sinter would be increased 30% and when K2O% was above 1.5% the RDI of pellet would be increased 15%To choose an appropriate chemical composition of slag, both removing alkali metals and desulphurization should be considered. According of experimental results it suggested ShiGang BF slag should be that basicity was 1.0, SiO2% was 37%, MgO% was 12% and Al2O3% was 15%. On the basis of the ShiGang BF slag chemical compositions, when basicity (CaO/SiO2) chaged to about 1.0 that the rate of removing alkali metals was 26% and the [S] was 0.027%; When SiO2% equaled to about 37% that the rate of removing alkali metals was 21% and the [S] was 0.026%; When Al2O3% equaled to about 15% that the rate of removing alkali metals was 24% and the [S] was 0.0275%. Because of technique progress, the quantity of slag decreased which resulted in the rate of removing alkali metals decreasing. It was the main reason of the alkali metals hazard to ShiGang BFs.