Economic H2S Treating and Sulphur Recovery

Abstract There is an abundance of natural gas being discovered and produced that is slightly sour. According to a US Department of the Environment (DOE) survey that includes Canada, about 80% of current and new gas has a hydrogen sulphide (H2S) concentration of 1% or less. Of course, this must be treated to remove the H2S to meet sales gas specifications. For small scale (less than 50 – 100 kg) and large scale (greater than 20 tonne/d) of equivalent sulphur, current technologies appear reasonable. Conversely, for intermediate range (0.1 – 20 tonne/d) equivalent sulphur, current technology has proven to have high capital and/or operating costs and some processes are difficult to operate. Therefore, there is a need for an intermediate scale (0.1 to 20 tonne/d) process with lower capital and operating cost than those currently available. The applications of such a process range from the removal of H2S from acid gas at low pressure produced from the amine process to high pressure raw sour gas. The elemental sulphur produced should be of sales grade quality such that the handling of the product can fit into the existing sulphur infrastructure and sold into existing markets. Otherwise, disposal of the product becomes costly and in some cases becomes another environmental problem. In answer to this need, Xergy Processing Inc. has developed a gas phase direct oxidation process for the above applications as well as treating heavy oil off-gas, fuel gas, power generation gas. The process has relatively low capital and operating costs and is easy to operate, with no equipment that is unfamiliar to the petroleum industry. Conversion to sulphur depends on the process configuration and pressure but ranges from 80% to 99.9+%, with new catalysts resulting in significant improvement. Introduction There is an abundance of natural gas being discovered and produced that is slightly sour. According to recent US Department of Energy (DOE) and Gas Research Institute (GRI) surveys (Dalrymple et al., 1991; Hugman et al., 1993), up to 25% of current and new natural gas is sour. About 80%of that sour gas has a hydrogen sulphide (H2S) concentration of 1% or less and CO2 concentration of 3% or less. Worldwide, the percentage of gas that is sour may be as high as 30% (Cornot-Gandolphe, 1995). Since sales gas specifications of 4–16 ppm H2S are required, such sour gas must be treated to remove it. Recently, government regulatory bodies have introduced more stringent regulations in certain jurisdictions concerning the release of sulphur as SO2 to the atmosphere. The new regulations imposed will, over time, remove the " grandfathering" provisions that many older plants operate under and will cause the sour gas processing industry to initiate facility modifications and additions in order to substantially reduce sulphur emissions. This means that more small scale sulphur recovery will be required as well as more tail gas clean up in larger existing sulphur units. Aside from natural gas, a reduction of sulphur in refinery distillates is occurring by 2006.