Experimental Study On Deactivation Mechanism And Regeneration Of Commercial SCR Catalysts Used In Power Plant

Selective catalytic reduction technology(SCR) is currently the most widely used flue gas de-NOX technology in coal-fired power plant. SCR catalyst is the key element in this system. The chemistry design life of the SCR catalyst is basically 3-4 years. In the late design life, the activity of the catalyst is decreased. At this point, it needs to be replaced or for regeneration. Regeneration not only can greatly reduce the cost of de-NOX, but also can help to avoid environmental pollution caused by waste catalyst. Therefore, the research of SCR catalyst regeneration technology is of great significance. This paper studies the deactivation catalyst in a domestic coal-fired power plant and the deactivation reason, and then adopts different ways of regeneration. Finally, discusses the effect of different regeneration ways with some characterization experiments.This paper analyzes how the temperature and the ratio of ammonia(NH3/NOX), space velocity(AV) and O2 concentration affect the performance of old and new de-NOX catalysts. The results indicate that the activity of the deactivated catalysts and the fresh catalysts have the resemble variation tendency with those conditions. However, the activity of the used catalyst significantly decreases and the turning point of the activity curves is in advance. It reveals that the used catalysts have low adaptability to the varying conditions.This paper respectively researches the specific surface area, morphology, element composition, micro groups and active component valence of fresh and deactivated catalyst by the methods of BET, XRD, XRF, FTIR and XPS, analysis the microscopic properties and surface sediments of the deactivated catalyst.The results reveals that the deactivation of the catalysts in the coal-fired power plants is caused by many reasons together, which includes pore jams caused by the sulfate(CaSO4, NH4HSO4, etc.)?alkali metal poisoning, etc. After the catalyst deactivation, the acidic and redox ability on the surface of the catalyst are falling.Ultrasonic washing, dilute sulphuric acid cleaning and different temperature sulfuration were adopted to the experiment of the deactivation catalyst regeneration. The result reveals that all of the regeneration methods can increase the activity of the used catalysts, among which the latter two methods are better. Ultrasonic washing and dilute sulphuric acid cleaning can wash away the most of the ammonium salt and CaSO4 on the surface of the used catalysts, and acid cleaning can increase the catalyst activity by increasing acid which is similar to the Bronsted acid. And the used catalysts have the same activity with the fresh catalysts at 250~350?.Furthermore, sulfuration at 450 ?further enhance the strong acid sites, which makes the activity of the used catalysts attained 104.6% of the fresh catalyst activityand106.3% of acid cleaning catalysts activity at 380 ?. However, sulfide formed at the time of 450? sulfuration would not be stable,after long time running, the influence on catalysts would drop off.