Remove sulfur compounds present in tail gases from Claus plants and meet air pollution standards.
The high Claus ratio (HCR) process consists of two sections :
• Hydrogenation and hydrolysis of sulfur compounds present in tail gases (COS, CS2, Sx and SO2). Tail gas is heated to about 300°C and, without hydrogen addition, is treated with Co/Mo catalyst. Gas
passes through a waste-heat boiler (WHB) and is cooled to approximately 40°C in a direct contact tower.
• H2S removal and recycle of acid gas to a Claus plant.The gas is washed in a carefully designed amine absorber, and the treated gas is incinerated. Rich amine is processed and recycled.
The process requires adjusting the operating criteria for the Claus unit by increasing the H2S/SO2 tail gas ratio. The operation is very steady and has high service factors that are achieved during upset conditions from upstream units. Hydrogen or reducing gas from external sources are not required in the hydrogenation reactor.
Operating conditions: The pressure drop of the unit is 0.20–0.30 bar and the operating pressure is almost atmospheric. Treated gas contains less than 250 ppmv of H2S.
Economics: Process uses standard equipment and carbon steel almost everywhere. No consumption of reducing gas or caustic chemicals is required. Process analyzers are not mandatory. Reduction in utilities and chemical costs are approximately $1.50/t of sulfur produced. Lower operating and maintenance labor is about one-eighth man per shift.
Licensor: SIIRTEC NIGI