Research On New Technology Of Pre-desulfurization And Comprehensive Utilization Of By-products In The Sintering Process Based On Ammonia Additives

Iron ore sintering process is an important part of the iron and steel production process,and also a major source of pollution in the iron and steel industry.On the basis of strengthening the end treatment technology,the process and new approaches of energy conservation and emission reduction at the source are expanded.Reducing the main pollutants such as SO₂ of sintering flue gas and promoting the realization of ultra-low emission and green sustainable development of iron and steel industry are of great strategic significance to build iron and steel plant into a national tourist attraction and promote the development concept of“green water and green mountains are golden mountains and silver mountains”.In this paper,a new method of pre-desulfurization in the sintering process based on ammonia additives（urea）is researched.At the same time,a new technology for the comprehensive utilization of ammonium sulfate as a by-product of the desulfurization reaction is developed,and a pre-desulfurization-by-product comprehensive utilization process system in the sintering process is established.It lays an important theoretical foundation for the development process of iron and steel enterprises that use high-sulfur ore sintering to produce a large amount of SO₂ in the sintering flue gas+terminal low-cost,high-efficiency sintering flue gas step-by-step treatment technology.Through the development of urea desulfurization technology in sintering process,the sintering cup experiment was optimized.And the effects of urea addition amount,adding position range and adding mode on sintering mineral quality index and SO₂emission in sintering flue gas were explored.The results show that the best effect is spraying 0.10 wt.%urea solution in the thickness of 200 mm above 80 mm away from the grate bar.The output and quality index of sinter are at the same level as the benchmark experiment.Under these conditions,the flue gas desulfurization efficiency of sintering process can reach more than 90%.Under the optimal laboratory parameter conditions,industrial trials of optimization of desulfurization technology in the sintering process based on ammonia additives were carried out.When spraying a 40%urea solution with a concentration of0.11 wt.%at the cloth position compared to the belt position of the mixer,the urea utilization rate increased from 29.38%to 62.50%,the SO₂content decreased obviously,and the average value after stabilization was 229.17 mg?m^-3,to reduce the burden on the end flue gas treatment and reduce the end treatment cost.Through the chemical characteristic analysis of air box branch bulk and electric field dust removal ash after desulfurization of ammonia additives,the effect of different washing conditions on S and alkali metal leaching rate in sintered desulfurization dust ash was studied.Ammonia additives desulfurized after sintering dust ash in the S content is high,sulfur content S 1.0%,but also contains a large number of K,Na and Cl and other elements;The best experimental conditions for washing and leaching:temperature is 35°C,stirring time is 30 min,solid liquid ratio is 1:4,stirring speed is200 r?min^-1,grinding particle size is-0.074 mm,at this time the washing S leaching rate can reach up to 85.23%,and K leaching rate up to 97.05%.After the filtrate is concentrated by evaporation,cooled and crystallized,and evaporated to dryness,a content of K₂O was 60.44%,content of S was 15.60%,and content of Cl was 0.57%can be obtained as an agricultural potassium sulfate product that meets the requirement of GB/T 20406-2017.At this time,potassium The total conversion rate reached 73.57%.This paper reveals the mechanism of the rational use of urea,the location and method of adding urea to the reduction of SO₂ in the sintering process.In industrial applications,the reasonable distribution of urea in the predetermined area of the material layer is realized,and the by-products of the desulfurization process of the sintering process are comprehensively utilized.The process has the advantages of easy modification,stable operation,low cost,high efficiency and comprehensive utilization of by-products.It is suitable for high-sulfur sintering enterprises to reduce the emission of sintering flue gas pollutants and achieve ultra-low emission goals.