Solid Fuel Derived From MSW And Its Application In Steel Ore Sintering Process

At present,the annual output of municipal solid waste?MSW?was about 200 million tons,the huge amount of MSW will endanger the ecological safety.MSW usually contain a lot of organics,and MSW pyrolysis could recover its energy.Sintering is one of most important processes during the iron and steel production,about 75-80%energy in the sintering process is provided by solid fuel such as coal or coke breeze.Hence,the application of fuel derived from MSW in the sintering process was proposed,which could not only reduce the consumption of the fossile solid fuel,but also provide a new method of treating MSW.In this paper,the influence of pyrolysis parameters such as final pyrolysis temperature,heating rate and holding time on the distribution of pyrolysis products was investigated,and found that the variation tendency of fixed carbon,volatile matter and heating value of fuel derived from MSW under different pyrolysis parameters.Then,the optimum pyrolysis parameters of preparing fuel suitable for the sintering process from MSW were obtained.On the basis of sinter pot tests,the influence of replacing fuel derived from MSW to coke breeze on the qualities of the sintered ore such as tumble strength index,shatter strength index,yield,productivity and vertical sintering speed was understood.Moreover,the main pollutants emission was online recorded under with and without fuel derived from MSW.Lastly,the mechanism of affecting the qualities of the sintered ore was discovered on the basis of temperature profile in the sintering bed,and the microstructure of the sintered ore.The main works are described as following:?1?The effect of pyrolysis parameters on the yields and properties of semi-coke?MSW-derived char?,tar and gas are investigated.The results shows that with the increase of final pyrolysis temperature,MSW-derived char yield is decreased,while the gas yield is increased.However,the heating value of MSW-derived char has a decreasing trend.With the increase of heating rate,the decomposition of tar and MSW-derived char is promoted,which results in an increase of gas yeild.Longer holding time could contribute to the volatile release,and makes a slight decrease of the MSW-derived char yeild.Finally,the experimental results show that the properties of MSW-derived char obtained at the final pyrolysis temperature of 500?,pyrolysis rate of 10?/min and holding time of 1hour is more close to thoses of coke breeze.The heating value of MSW-derived char is25.47 MJ/kg,and the yields of char,liquid and gas are 29.70%,50.01%and 20.29%respectively.?2?The effects of fuel derived from MSW substitution ratio on the qualities of sintered ore are studied.The results indicate that with the substitution ratio of fuel derived from MSW replacing coke breeze increase,the vertical sintering speed and the productivity are increased,while the cold strength and yield are decreased.However,when the substitution ratio is appropriate,the qualities of the sintered ore are not deteriorated.When the substitution ratio of fuel derived from MSW is 20%,the tumble strength index is 62.58%,the yield is 75.38%and the productivity is 1.536 t/?m²·h?,which meet the quality requirements.At the same time,CO₂ and SO₂ emission is reduced,while the emissions of CO and NO_x are increased.The flue gas recirculation was suggested to reduce CO and NOx emission.?3?The mechanism of fuel derived from MSW affecting the qualities of sintered ore are discovered.Fuel derived from MSW could burn faster than coke breeze as a result of its high porosity and lage surface area,which causes the reduction of fuel combustion efficiency.Moreover,the fast combustion of fuel derived from MSW reduces the temperature of sinter bed and shortens the duration of temperature for mineral melting,which suppress calcium ferrite formation and decrease the quantity of sintered ore.When fuel derived from MSW substitution ratio was varied from 0%to 20%,the content of calcium ferrite would decrease from 44.59%to 35.65%.Especially,the content of needle calcium ferrite was sharply decreased from 23.14%to 16.31%.