Heat extraction, catalyst regenerator

The first step in regenerating the coated, inactive nickel sulfide catalysts is to remove the reactants and products of the catalytic reaction aloi with the extraneous material coating the catalyst. In most cases, extraction of the catalytic mass with solvents, or purging with steam is adequate for this clean-up. The more resistant film of coke or tar is then removed by oxidation with air under carefully controlled conditions to avoid over-heating the catalyst. During this oxidation, the nickel sulfide is usually oxidized to NiO. This NiO is then reduced and sulfided in the same manner as in the initial preparation of the catalyst. 

Regenerated catalyst solution is extracted via a nozzle located about midway on the oxidizer-settler vessel. This solution is recirculated back to the absorber column. The portion fed to the venturi-mixer is first heated to 120°F to ensure that the absorber is operated above the hydrocarbon dew point of the inlet gas. 

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