CANSOLV systems

HS A family of gas purification processes developed by Union Carbide Corporation, based on the use of proprietary solvents known as UCARSOLs. UCARSOL HS-101, is based on methyl diethanolamine and is used for removing hydrogen sulfide and carbon dioxide from other gases. Ucarsol LH-101 is used in its Cansolv system for flue-gas desulfurization. 

Both of these processes direct the SO2 absorbed from the FCCU flue gas to the refinery SRU, where it is converted to elemental sulfur and added to the marketable sulfur that is generated by the SRU from H2S. Alternately, the SO2 can be converted to sulfuric acid in a dedicated sulfuric acid plant, or in combination with an existing refinery spent acid regeneration unit. When the SO2 is directed to the SRU, 1 ton of SO2 captured in the scrubber is converted to 0.5 tons of marketable elemental sulfur and less than 0.1 ton of sodium sulfate waste is generated per ton of SO2 absorbed. In an acid plant, 1 ton of SO2 generates 1.5 tons of 98% sulfuric acid. Steam is also generated from the conversion of SO2 in both the SRU and the acid plant, which moderates somewhat the steam consumption rate of the solvent regenerator for both the LABSORB and CANSOLV systems. 

Hakka, L. E., and Barnett, A. B., 1991, The CANSOLV System for Removal of SO2 from Gas Streams, unpublished Union Carbide paper, Danbury, CT, December. 

The process diagram illustrates a typical flowscheme for the CANSOLV SO2 Scrubbing System. In it, gas is shown to leave the FCCU battery limits at a hot and dry condition. While a CO boiler and ESP are shown, the FCCU system may... 

FIGURE 16.11 CANSOLV regenerable SO2 scrubbing system process diagram. (With permission from CANSOLV Technologies.)... 

Losses of amine up the stack are undetectable in the CANSOLV SO2 Scrubbing System. Losses from evaporation do not occur because the amine is in salt form in solution, and losses from entrainment are avoided by using trough type distributors instead of spray nozzles to distribute the amine over the packing. In extreme cases where upsets in gas flow are anticipated, a demister may also be used. 

The absorbent in the CANSOLV SO2 Scrubbing System accumulates nonregenera-ble salts [also called Heat Stable Salts (HSS)] and dust that are removed from the gas over time. These contaminants must be removed from the absorbent continuously to avoid excessive build-up. An APU incorporates both an ion exchange unit (IX) for the removal of HSS and a filtration unit for the removal of dust. 

Cansolv , 2009. Cansolv SO2 scruhhing system for sulfuric acid plants, case study refinery acid plant tail gas treatment. Retrieved from http //www.cansolv.com/rtecontent/docu ment/CaseStudy.AcidPlantTailGas.pdf (accessed 05.10.12). 

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