Preparation Of Metallurgical Waste Slag Modified Catalyst And Study On Low Temperature SCR Denitrification Performanc

The world’s energy sources today are mainly obtained through the consumption of fossil fuels,and with the development of society the demand for energy is increasing,while the massive consumption of fossil energy will be accompanied by a series of environmental problems.China’s energy structure is characterised by"coal-rich,oil-poor and gas-poor",with coal resources still occupying a major position in the future.As a low-grade fossil energy source,the combustion process of coal produces a large amount of particulate matter,SO₂,NO_x and other air pollutants as well as the greenhouse gas CO₂,which is one of the main sources of pollution in today’s society and poses a great threat to human health and the ecological environment.As the country pays more and more attention to the cause of environmental protection,the corresponding policy standards have been tightened and become increasingly stringent,putting forward high requirements for flue gas control technology.This paper focuses on NO_x,an air pollutant,and uses selective catalytic reduction（SCR）technology to control and solve the NO_x emission problem.Due to the poor low temperature denitration performance of existing commercial catalysts and their inability to operate under SO₂ containing conditions for extended periods of time.Therefore,research and development of catalysts with low temperature SCR denitration performance and some sulphur resistance is the key to solving the NO_x emission control problem.Iron-based catalysts are widely used in NH₃-SCR reactions,while a large amount of waste sludge containing iron-oxygen compounds in China’s smelting industry is not effectively treated and utilised.For this reason this paper uses cold rolled sludge,titanium sponge ferromanganese sludge,bar pellet sludge,vanadium containing tailings and iron concentrate powder,which are commonly found in the smelting industry,as research objects.The waste sludge was modified by sulfuric acid impregnation,calcination and loading with metal（Mn,Ce,CO）oxides.The prepared samples were evaluated for activity and resistance to sulphur and water.The relationship between the denitration performance of the sludge catalyst and its physicochemical properties was also investigated by characterization methods such as XRD,SEM,H₂-TPR,NH₃-TPD,BET and XPS.The results showed that the cold rolled sludge had 100%denitration conversion at 280°C(working conditions:200 ppm NO,200 ppm NH₃ and 3.00 vol%O₂,N₂ as equilibrium gas,total flow rate of 300 ml/min and GHSV of 30,000ml·g^-1·h^-1,the subsequent test conditions were consistent with this condition)after acid leaching and calcination treatment.The bimetallic element loaded cold rolled sludge series catalyst with a controlled metal oxide loading mass fraction of 10%.In the case of cold rolled sludge loaded with metal（Mn,Ce,CO）oxides and calcined treatment,the cold rolled sludge loaded with the best proportion of Mn and Co oxides can reach more than 90%denitration at 80-180°C.The cold rolled sludge loaded with the best proportion of Mn and Ce oxides can reach more than 90%conversion at 100-180°C and up to 98%denitration at 140°C.A series of acid-impregnated cold-rolled sludge catalysts loaded with metal（Mn,Ce,CO）oxides were prepared and the activity evaluation showed that the acid-impregnated cold-rolled sludge loaded with manganese oxides was the best and generally had excellent low temperature SCR activity,with the best sample achieving 100%denitration conversion at 60°C-180°C.The acid impregnated cold-rolled sludge series catalysts were found to have good sulphur and water resistance through the sulphur and water resistance tests.In addition,bar pellet sludge,vanadium-bearing tailings and iron concentrates were subjected to acid leaching and calcination,and modifications to different sludges by acid leaching were compared.It was noted that the bar pellet sludge withγ-Fe₂O₃ as the main component showed superior denitration performance even when it contained alkali metal element impurities,which provided a direction to find more suitable ores,slags,sludge etc.for acid leaching modification.Because acid leaching cold-rolled sludge loaded with manganese oxide compounds has excellent low temperature denitration properties,titanium sponge ferromanganese sludge with Fe（70.7%）and Mn（6.8%）as the main components was acid leached and calcined to modify the treatment.The denitration performance curve of iron-manganese slag calcined at 500°C was found to be M-shaped,with the performance rising,then falling,then rising and then falling again with increasing temperature,reaching74.4%conversion at 80°C and 83.4%conversion at 200°C respectively.After acid impregnation of ferromanganese sludge,the low temperature activity of this series of catalysts was destroyed due to the reaction of sulphuric acid with the low temperature active material manganese oxide to form sulphate,but as with other sulphuric acid treated waste sludge,improved denitration performance within 200 to 320°C,reaching 94%denitration performance at 220°C.