Study On Coal Gasification Slag Loaded Metal Oxides For Removing NO_x From Coke Oven Gas

Coal gasification slag（CGS）is a by-product of the coal gasification process.It has received widespread attention from the community about post-processing issues.However,few attempts have been made so far with concerning the efficient utilization of CGS.To achieve“zero emissions”from coal gasification technology,it is necessary to effectively utilize coal gasification slag resources.For this purpose,this paper attempts to use the waste coal gasification slag as a carrier for the first time,loading different metal oxides（Cu,Mn,V）as active ingredients,screening out the best active components,and preparing SCR catalyst with excellent performance.The catalysts were characterized by XRD,BET,XPS,NH₃-TPD,H₂-TPR,and so on.The NH₃-SCR experiment was carried out by using a fixed bed reactor.The relationship between denitrification activity and active component loading,reaction temperature,carrier and atmosphere was studied.The sulfur resistance of the catalyst was studied.The feasibility of coal gasification slag as denitration catalyst carrier was discussed.The main conclusions of this paper are as follows:（1）The gasification slag with high carbon content has developed pore structure and good sulfur tolerance.It is similar to coal-based activated carbon structure,and coal gasification slag can be used as SCR catalyst carrier.（2）Through the active component and selection of coal gasification slag carriers,it was found that the denitrification activity of V1/CGS₃ was the best in the temperature range of 180-280°C,which was related to the residual carbon content,specific surface area and pore structure of the carrier.The effects of V1/CGS₃ catalyst preparation conditions（calcination temperature and pre-oxidation temperature）on SCR activity were investigated.The optimum preparation conditions for the V1/CGS₃catalyst are as follows:calcination temperature 500°C and pre-oxidation temperature 250°C.（3）V₂O₅ is an important component of the V1/CGS₃ catalyst for NO removal.At a certain temperature,with the increasing of vanadium content（0.8-7%）,the NO conversion rate first increases and then decreases.The V1/CGS₃ catalyst shows the best denitrification performance.（4）The optimum temperature range for the catalyst is 240-290°C.The NO conversion rate increases with the increase of the reaction temperature,and the NO conversion rate reaches 95%at 240°C.The effect of temperature on SCR activity is that increasing the temperature will exacerbate the thermal reaction of the molecule,and more molecules will reach the activated state,thereby improving the NO conversion rate.（5）The V1/CGS₃ catalyst has good N₂ selectivity and stability.The results show that the selectivity of N₂ is over 97%in the NH₃-SCR process.At 260°C,the NO conversion rate of V1/CGS₃ catalyst is still about 100%within 30 h in the presence of water and sulfur dioxide.（6）NH₃ and O₂ are essential reaction components for the SCR process.The presence of H₂O has an inhibitory effect on the SCR reaction,and the presence of SO₂ promotes the SCR reaction.SO₂promotion is attributed to the formation of SO₄^2-on the catalyst surface,which increases NH₃ adsorption and promotes the reaction of NH₃ with NO.