Study On Explosibility And Combustion Performance Of Coal-sludge Mixed Powder In FINEX Ironmaking Process

FINEX ironmaking is a typical non-blast furnace ironmaking technology.One of the characteristics about the technology is large pulverized coal injection operation.PCI is beneficial to adjust the furnace temperature,increase productivity.Because of the different physical properties of bituminous coal and anthracite coal,there are some differences in explosibility and combustibility,so it’s very important to blend coal reasonably.Another major feature of the FINEX process is the full oxygen injection.Under the condition of full oxygen injection,the explosibility of pulverized coal is one of the main points to be concerned.Sludge is produced in iron and steel enterprises which contains the Fe and C elements.With the increasing attention to the environmental and resource issues,it is particularly prominent to strengthen the utilization of this resources.In this paper,three kinds of pulverized coal and a sludge provided by steel company were used as raw materials to study the explosibility of single coal and blended coal.The influence of physical properties of pulverized coals(particle size,volatile matter),the proportion of sludge,different oxygen concentration and the impact of additives on pulverized coal explosive and its impact mechanism were investigated.Meanwhile,the combustion efficiency of single coal and blended coal is measured by combustion test to explore the influence of reasonable coal blended ratio,pulverized coal’s physical properties(ash,volatile matter)and the proportion of sludge on combustion efficiency.With the safety and economy are considered,the best blended pulverized coal injection scheme was optimized.The main findings can be summarized as follows.(1)The anthracite A1,A2 and bituminous coal B are employed as pulverized coal for injection.The fixed carbon content of the A1 is the highest to 77.72%and low calorific value of the A1 is 31.93kJ/g.The volatile content of B is the highest(30.65%),and the fixed carbon content is the lowest.The TFe content in sludge is relatively high,getting to 59.14%.Also,some minerals which can be utilized for slagging are discovered in the sludge.Therefore,the re-using value can be achieved for the sludge.(2)As for single coal,bituminous coal B has strong explosibility,anthracite A1,A2 and sludge have no explosibility.The explosibility of bituminous coal can be reduced by adding a certain amount of anthracite into the bituminous coal.With the increase of volatile content,the explosibility of coal samples at each particle size level tends to strengthen.For the same coal sample,with the increase of the particle size,the explosibility is weakened.(3)In the addition of sludge,the explosibility is weakened and the sludge has the effect of inhibiting the explosion.The reasonable blended solutions based on explosibility are A1:B(7:3)+10%of Sludge,A2:B(7:3)+10%of Sludge.(4)With the increase of oxygen concentration,pulverized coal explosibility increased.In the addition of MgCO3·5H2O,the return flame length of the three particle size pulverized coal decreases and the maximum fall can reach 61.67%,indicating that MgCO3·5H2O has good anti-explosion effect.(5)The combustion efficiency of bituminous coal B is 84.45%,which is the highest,the combustion of A2 is 58.37%and the combustion of A1 is 50.01%.With the addition of the proportion of bituminous(B),the combustion efficiency increases gradually.The higher the ash content of coal,the lower the combustion efficiency of pulverized coal.When the ash is reduced by 1%,the combustion efficiency can be increased by about 6%～8%.With the increase of the volatile content of the blended coal,the combustion efficiency of pulverized coal is increased.The volatile content of blended coal should be controlled at 18%～25%.(6)The combustion efficiency of binary blended powders(A1,B and sludge)is somewhere in between two kinds of single powder.Moreover,the addition of sludge will negatively affect the combustion efficiency of blended coal.Comprehensively consideration the results,we think that the programs of A2:B(7:3)+10%of Sludge will be the better choice to achieve the reasonable combustion and re-using of sludge.