Pollution Control And Heat Recovery From The Flue Gas Of Fluid Catalytic Cracking Units

With the government departments at all levels of environmental regulation to increasethe sulfur dioxide and nitrogen oxide emission regulation, the refinery of flue gas emissionrequirements more and more high. According to the "discharge standard of pollutants forpetroleum refining industry"(Draft) of sulfur dioxide in catalytic cracking unit maximumallowable emission concentration limit of dust emission concentration allows400mg/Nm3,50mg/Nm3, NOx limit values for the maximum allowable emission concentration limit for200mg/Nm3. At present,2800000tons/year refinery FCC CO boiler exhaust SO2flue gasunder normal circumstances is about2600mg/Nm3(dry basis), dust emission concentration isabout180mg/Nm3(dry basis), the concentration of nitrogen oxide emissions of about500mg/Nm3(dry basis), has far exceeded the emission standards, and with the increase ofprocessing high sulfur crude the concentration of exhaust, sulfur dioxide and nitrogen oxidesemissions will rise further. So the desulfurization and denitration imperative for the refineryFCC unit of CO boiler.Firstly, on the desulfurization of refinery catalytic cracking unitdenitrification transformation device before operation and flue gas emission was analyzed,found the device running several problems: catalytic CO boiler flue gas side of large runningresistance, high temperature flue gas in part through the bypass vent, heat wasted; catalyticCO boiler flue gas temperature is high, the boiler the thermal efficiency is low.This paperintroduces some denitrification technology: high temperature, low temperature selectivecatalytic reduction of SCR by SCR selective catalytic reduction, selective non catalyticreduction (SNCR), combination method (SNCR+SCR), ozone oxidation technology. Alsointroduces several foreign catalytic cracking flue gas desulphurization: non regenerative wetwashing process American Belco company (EDV), non renewable wet washing processAmerican Exxon company (WGS), renewable moisture washing process USA Belcocompany (Labsorb), the Canadian renewable wet desulfurization process in Cansolv company(Cansolv), and domestic several dust desulfurization technology: dual alkali, organic amine,inorganic ammonia removal desulfurization process, double circulation model turbulentVenturi dust desulfurization technology.Through the comparison of domestic and abroad andscheme of denitration technology scheme and dust removal and desulfurization technology analysis, combined with the actual situation of the refinery, and ultimately to the refinerycatalytic device can meet the construction of desulfurization and denitrification systemoperation needs, can achieve energy saving, high efficiency, long cycle operation purpose,finally selected denitrification using SCR (high temperature) denitration technology,desulfurization by wet turbulent ammonia flue gas desulfurization technology, and supportingthe additional catalytic flue gas desulfurization wastewater treatment technology to treatwastewater generated dust.At present, has completed the transformation of waste heat boilers, desulfurizationdenitration module construction is underway. From the current transformation effect, the gasvolume greatly reduced, energy consumption is decreased obviously, but the temperature ofthe furnace is increased, the combustion condition has been greatly improved. Although thevolume of self-produced steam had no obvious change, but the steam temperature increasedsignificantly, significantly improve the heat transfer effect. The tail exhaust temperature isdecreased. Furnace wall reinforcement, pressure bearing ability is improved greatly, becausethe tail flue gas circulation even caused reduction of cross section, the flow resistanceincreases and the furnace wall can bear. Desulfurization denitration module for underconstruction, further data accumulation of specific desulfurization and denitrification effect.