Direct Alloying Of Abandoned Denitration Catalyst

In our country,Coal-fired power plants produce abandoned denitration catalyst about250,000 cubic meters per year,with a mass of about 140,000 tons.The existing processes have long process flow,high cost and serious environmental pollution for the recycling of TiO₂ and V₂O₅ in the abandoned denitration catalyst.The Ti and V are directly alloyed in the steel making process,and the resource recovery of vanadium and titanium elements is realized.The problems of slag selection,alloy matrix selection and reducing agent selection involved in the direct alloying process were studied by thermodynamic calculation.A thermodynamic equilibrium experiment was carried out at 1600?with the optimum slag composition and aluminum content.The slag composition change and viscosity change during the whole reduction process of the direct alloying were studied.The phase change of the slag during the cooling process was calculated,and the relationship between the change of slag viscosity and the precipitation of solid phase material were found.The time required for the direct alloying process was clarified.The kinetic parameters of the reduction process of the abandoned denitration catalyst were obtained by Freeman-Carroll method.According to the thermodynamic calculation,the CaO content in the initial slag was 16wt%,the CaF₂ content was 37 wt%,the Na₂O content was 2 wt%,and the mass ratio of aluminum to slag was 0.35.Industrial pure iron was selected as the alloy matrix.According to the thermodynamic equilibrium experiment,the titanium content in the steel can reach 3.1 wt%,which is 80%of the thermodynamic calculation value.Most of the TiO₂ and V₂O₅ in the slag are reduced and then enter the iron liquid to form an iron-titanium-vanadium alloy.Recycling of vanadium and titanium in the denitration catalyst was realized.The direct alloying process reaches equilibrium in approximately 45 minutes.In the whole reduction process the slag viscosity is less than 0.3 Pa·s with good flowability,which can meet the requirements of the slag viscosity of the alloying process.According to the thermodynamic calculation of the slag,CaAl₄O₇ and CaAl₁₂O₁₉9 began to precipitate at around 1400?.The increase of solid phase material during the cooling process leads to an increase of the slag viscosity directly.The viscosity of the slag after reduction is significantly higher than that before reduction,and the viscosity is obviously affected by the Al₂O₃ content.The apparent activation energy of the reduction process was E=243.33 KJ/mol and the reaction order number n=0.13 by the Freeman-Carroll method.