Catalytic regeneration flue gas denitration technology

The denitration technology of FCC regeneration flue gas mainly includes denitration additives, oxidation method, adsorption method and electron beam method. The electron beam method has the problem of immature technology. The adsorption method is seldom used due to the problems of adsorbent wear and large pressure drop. The selective non catalytic reduction (SNCR) technology is also limited in the application of catalytic cracking flue gas denitration process due to its low removal rate. At present, the most commonly used methods of denitration technology for FCC regeneration flue gas are low temperature oxidation (lotox), selective catalytic reduction (SCR) and denitration additives.

SCR technology is a catalytic reduction of NOx in flue gas with NH3 as reducing agent in the presence of catalyst and oxygen, so that NH3 selectively reacts with NOx in flue gas to generate N2. The catalyst used in SCR process generally contains vanadium, titanium and tungsten, and its operating temperature is generally 350 ~ 375 ℃. SCR method can reduce NOx When the temperature is lower than 300 ℃, SO2 in the flue gas may be converted to SO3 by SCR catalyst and react with ammonia to form ammonium sulfate, which usually causes scaling and blockage in the coal saving section of CO boiler.

Lotox is a kind of low-temperature oxidation technology, in which the mixed gas of oxygen and ozone is added into the flue of regenerator for reaction. In the reaction process, NOx is oxidized to form N2O5 which is easily soluble in water, and HNO3 is generated in the washing process. When this technology is used, the removal rate of NOx is generally 70% ~ 90%. However, the presence of O2 will promote the formation of aerosols in ammonia desulfurization, so lotox denitration technology should not be combined with ammonia desulfurization technology.

The addition of denitration promoter can effectively remove NOx in the regeneration flue gas, and the regenerator does not need to be modified, and the cracking performance of the main catalyst will not be affected. In the presence of C and Co, the active components of denitration additives can promote the conversion of no to N2, so as to reduce NOx in the regeneration flue gas.