Study On Poisoning Mechanism And Regeneration Technology Of SCR DeNO_x Catalyst In Coal-fired Power Plant

The pollution of nitrogen oxides（NO_x） have aroused people’s attention increasingly,selective catalytic reduction（SCR） of NO_x with NH₃ is most efficent among the technologies removaling NO_x in flue gas at present.Catalyst is the core of the SCR technology,its performance impact greatly on SCR system. The current SCR de NO_x devices are usually installed in high temperature and high dust environment in coal-fired power plants, then the activity of catalyst will inevitably reduce as catalyst run under the harsh environment for long-term.While the SCR catalyst deactivation will be directly related to the normal operation of SCR system and the safety of downstream equipment,but also greatly increase the cost of SCR system.Regenerating the deactivation catalyst will be the b est choice in consideration of cost and environment.This paper made the simulation poisoning experiment with alkali metal K,alkali earth metal Ca and heavy metal As on the actual application of coal-fired power plant V2O5-WO₃/Ti O₂ de NO_x catalyst,to explore the mechanism of poisoning and regeneration of K,Ca pois oned catalyst.The main results are shown as follow:（1）The influence of different concentration of KNO₃,KCl and K₂SO₄ on the performance of catalysts were investigated,catalysts before and after poisoning were characterized by XRD,N2 adsorption-desorption,NH₃-TPD,SEM.Results show that K had great effects on activity of catalysts,poisoned catalysts ’ surface area showed slight decline,crystal structure had no obvious change,surface morphology had hardened,but the total surface acidity decreased seriously;The study of regenerating 3 wt% KNO₃ poisoned catalyst show that regeneration liquid had the best effect when the p H of liquid is 1.Pickling made the activity of deactivation catalyst recovered greatly,did not influence the crystal structure of the carrier,had less influence on pore structure,but made the total surface acidity recovered to 94.5% of fresh catalyst.（2）The influence of different concentration of Ca（NO₃）₂,Ca Cl₂ and Ca SO₄ on the performance of catalysts were investigated,catalysts before and after poisoning were characterized by XRD,N2 adsorption-desorption,NH₃-TPD.Results show that Ca had great effects on activity of catalysts too, Ca（NO₃）₂ and Ca Cl₂ are similar with potassium,caused the total surface acidity decreased,but less than potassium at the same concentration. poisoned catalysts’ surface area showed slight decline,crystal structure had no obvious change too.While Ca SO₄ would not only cause the total surface acidity decreased but also s pecificly reduce the surface area and total pore volume. The study of regenerating 5 wt% Ca SO₄ poisoned catalyst show regeneration liquid had the best effect when the concentration of EDTA disodium salt is 6 wt%.This method could clean the pore channels of catalyst and recovery the surface pore structure effectively.It also could activate the surface acide sites but did not change the crystal structure at the same time.（3）The influence of different concentration of As on the performance of catalysts were investigated,catalysts before and after poisoning were characterized by XRD,N2 adsorption-desorption,NH₃-TPD.Results show that As had huge effects on activity of catalysts,trace As made the catalysts ’ activity dropped significantly.When As entered the catal yst,the total surface acidity decreased significanty but the crystal structure,surface area and pore structure had no change.