The Research And Development Of Three-way Additive For Reducing Pollutants In FCC Flue Gas

The FCCU is one of the important units used to convert the heavy oil into light oil and produce the high quality gasoline and chemical industry feedstocks in refineries. However, there are some un-friendly environmental polluters, such as SO_x, NO_x and CO in the flue gases. 6%-7% of the total SO_x emission and 10% of the total NO_x emission in the air are from refineries, and most of them are from FCCU. Because of the special physical-chemical atmosphere in the regenerator of FCCU, so far, there are few technologies which use only one catalyst or additive to remove these polluters simultaneously in the world.The studies on reducing the SO_x, NO_x and CO in the flue gas are mainly as follows: flue gas washing, new regenerator designing, SO_x additives, NO_x additives, CO combustion promotors and so on. According to the SO_x and NO_x and CO additives action mechanism theory, we used MgO-Al₂O₃-CuO-CeO₂-Pd as active components and selected appropriate active carrier and adhesive to make a additive for reducing SO_x and NO_x and CO in flue gas simultaneously, and carried out industrial experiment.A series of active components were tested in a minisize quart tube reactor. The result shows that the active component MgO-Al₂O₃-CuO-CeO₂-Pd has the better effect for reducing the amounts of SO_x, NO_x and CO in flue gas, and has high regeneration activity. CuO is efficacious in reducing the amounts of NO_x in flue gas. The CeO₂ is efficacious in reducing the amounts of SO_x in flue gas. In addition, adding Pd to the additive can greatly improve the effect of reducing the amounts of NO_x and CO in flue gas. The ways of bringing CeO₂ into the additive have influence on the performance of reducing SO_x and regeneration efficiency. The SO_x additive efficiency used Co-precipitation is about 15% higher than that used impregnant, and the regeneration efficiency used Co-precipitation is about 7% higher than that used impregnant. The type of adhesive and active matrix has great influence on SO_x additive efficiency, and the adhesive has great influence on the physical and chemical properties of the additive. The CO concentration in flue gas has great influence on the efficiency of NO_x additive, the NO_x additive efficiency increases observably with the increasing of CO concentration in flue gas. The O₂ concentration in flue gas has disadvantage of NO_x additive efficiency and the NO_x additive efficiency decreases observably with the increasing of O₂ concentration. The efficiency of reducing the SO_x, NO_x and CO improves with the amounts of additive increasing.The result of the fixed bed micro-reactor shows: when the amounts of the additive is no more than 5% in the FCC catalyst the activity of the FCC catalyst is almost not decreased. Pilot tests showed: using the feedstock and catalyst of FCCU I and II in Jinan corporation, when the amount of the additive was 2.5% in the FCC catalyst, the amounts of SO_x, NO_x and CO in flue gas were reduced more than 70%, 50% and 90% respectively, compared with the amounts of SO_x, NO_x and CO in flue gas when no additive was added in FCC catalyst. The concentration of sulfur in cracking gas increased, the concentration of sulfur in coke decreased, and it had no disbennifit for the products distribution, gasoline and diesel oil .The results of industrial experiment on FCCU I in Jinan corporation shows that, the additive invented by LPEC has better performance on reducing the amounts of SO_x and NO_x in combustion gases. Keeping the amount of the additive in FCC catalyst as 2.5%, the SO_x and NO_x amounts in flue gas were reduced 68.2% and 45.3% respectively, the operations, product qualities and products distribution were not badly affected.