Method for circularly absorbing SO2 in RFCC (Residue Fluid Catalytic Cracking) regenerative flue gas by utilizing ionic liquid

Abstract

The invention relates to a method for circularly absorbing SO2 in RFCC regenerative flue gas by utilizing ionic liquid, which comprises a flue gas cooling system, an SO2 absorbing and dust collecting system, a desorbing system, an ionic liquid purifying system and an SO2 acid making system. The method comprises the following detailed procedures: the flue gas firstly enters a gas-gas heat exchanger to exchange heat with purified flue gas for cooling, then enters an absorption tower through a flue and makes countercurrent contact with the ionic liquid in the absorption tower; the purified flue gas is exhausted from the absorption tower, enters the gas-gas heat exchanger, exchanges heat with the unpurified high-temperature flue gas to realize temperature rise, and then is exhausted from a chimney; a pregnant solution absorbing the SO2 is filtered; the pregnant solution with the dust filtered enters a desorption tower after passing through a barren and pregnant solution heat exchanger; the pregnant solution is desorbed and regenerated by means of heating by waste heat in the desorption tower; the regenerated absorbing agent (barren solution) returns to the absorption tower for recycle through the barren and pregnant solution heat exchanger, wherein a small part of barren solution needs to be recycled after being purified in the purifying system; the desorbed SO2 saturated steam enters a condenser to be condensed and separated, and then enters the acid making system.

Description

technical field [0001] The invention relates to a method for ionic liquid to circulate and absorb SO2 from RFCC regeneration flue gas, belonging to the fields of environmental engineering and petrochemical industry. Background technique [0002] my country's catalytic cracking unit (RFCCU) SO 2 Emissions seriously exceed the current national standards and may intensify. Existing catalytic cracking units (RFCCU) SO 2 There are three main methods for the control of fuel oil: raw oil hydrotreating, using sulfur transfer catalyst and flue gas desulfurization technology. The desulfurization effect of raw material hydrogenation pretreatment is remarkable, but the cost is high; the use of sulfur transfer catalyst is to add a certain amount of sulfur transfer agent to the RFCC catalyst. Under the oxidizing atmosphere of the RFCC regenerator, the sulfur transfer agent absorbs SOx to form sulfate. Circulate to the reactor, decompose sulfate in reducing atmosphere to generate H 2 S,...

AI Technical Summary

Problems solved by technology

[0004] Traditional wet flue gas desulfurization includes limestone-gypsum method, ammonia method, and sodium-alkali method: limestone-gypsum method has low solubility of absorbent and by-products, which is easy to cause fouling and blockage of system pipes and equipment, high water consumption, and by-products Desulfurization gypsum is not easy to reuse in my country; the ammonia desulfurization process has the problem of aerosol escape, its by-product ammonium sulfite is difficult to oxidize, and the evaporation and crystallization of ammonium sulfate uses high energy consumption; the product after sodium-alkali desulfurization needs to be reduced with calcium hydroxide Regeneration, the regenerated sodium-based desulfurizer can be recycled, but the side reaction product sodium sulfate is difficult to regenerate, and it is necessary to continuously replenish sodium hydroxide or sodium carbonate to the system to increase the consumption of alkali, so that the desulfurization system actually consumes calcium hydroxide. It will also consume sodium alkali, and the final desulfurization product gypsum slurry of the desulfurization system will carry part of Na 2 SO 4 , leading to complex post-treatment of desulfurization by-products and low purity, reducing the quality of by-product gypsum

Ammonia and limestone-gypsum desulfurizers cannot be regenerated, and the regeneration of sodium-alkali desulfurizers actually consumes calcium hydroxide

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