Sulfur Recovery – GT-SPOC™ & Tail Gas Treating
GT-SPOC: Rethinking Sulfur Recovery
GT-SPOC is a unique technology developed and tested by ConocoPhillips and is now exclusively licensed worldwide by GTC Technology. GT-SPOC is a selective partial oxidation catalytic combustion of hydrogen sulfide via a “modified Claus” process. GT-SPOC offers substantially reduced footprint, and lower capital costs compared to conventional Claus processes.
As with traditional Claus designs, sour gas from the amine regeneration and sour water stripper off-gas, or both, is mixed with air or oxygen and sent to the GT-SPOC unit. Instead of the traditional combustion section, GT-SPOC utilizes GT-CataFlame™, a catalytic combustion section which allows the reaction to occur at exceptionally high space velocities, and very short contact time. These reaction conditions also enable the destruction of hydrocarbons and ammonia. H2S and SO2 then react with each other to produce sulfur and water.
H2S + 1½ O2 → SO2 + H2O
2H2S + SO2 → 3/x Sx + 2H2O
3H2S + 1½ O2 →3/x Sx + 3H2O
The gas exits the SPOC section and enters a waste heat boiler where heat is recovered, sulfur is condensed, and medium pressure steam is generated. Unreacted gases are reheated in a proprietary reheating section before introduction to the first Claus reactor. Following this, the sulfur is condensed before reheating and introduction into the second Claus reactor. Low pressure steam is generated as the sulfur condenses. The number of Claus catalyst stages depends on the acid gas concentration and desired level of sulfur recovery required.
The GT-CataFlame section avoids a traditional problem with Claus units where start-up, shut-down and variations in the hydrocarbon content create excess SO2 or soot, depending on the air ratio, creating a cascade of operating issues downstream. In the With GT-SPOC the air demand for the partial oxidation of fuel gas is similar to the air demand for the partial oxidation of H2S. This allows for a seamless transition between fuel gas and acid gas, allowing for easy start-up and shut-down.
The reduction or elimination of COS, and CS2 formation also allows a reduction in Claus reactor bed size, allowing for the entire unit to be collapsed to a single vessel.
A number of variations on this technology that can be applied, depending on the acid gas concentration, ammonia content, and specific situations. A variety of tail-gas treating options are also available, including caustic treating.
Normal Operating Ranges
- H2S concentration from 25 – 97%
- NH3/H2S ratio of up to 42%
- Recoveries from 98.5 to 99.99%
- The compact SPOC reactor volume allows for a significantly reduced unit footprint compared to conventional “modified Claus”
- Lower capital cost
- Easier start up and shut down
- Destruction of ammonia, BTX, cyanide and heavy hydrocarbon
- Significant reduction in unit warm up/cool down times
- Reduction in interconnecting piping and equipment
The GT-SPOC process offers the inherent benefits of the “modified Claus” process, along with the advantage of a partial oxidation section which minimizes undesirable byproduct formation.
GT-SPOC is applicable for treating amine and sour water sour streams typical in refinery, and gas processing and coke oven plants.