Evaluation of the Exxon CFZ and CNG-Claus Process for the Treatment of SubqualityNatural Gas. Final Report, May-November 1991

摘要

Vast quantities of subquality natural gas exist which are unsuitable forconventional gas treating. The CFZ technology developed by Exxon Production Research and the TPC technology developed by CNG Research Company can be integrated to process subquality natural gas. These low temperature processes can produce pipeline spec natural gas from subquality gas containing more than 10% carbon dioxide and any amount of hydrogen sulfide. The CO2 can be separated as a high pressure stream suitable for re-injection, reducing CO2 emissions to the atmosphere, or as high purity CO2 for commercial applications. Two cases are examined at a scale of 20 MMSCFD: an Exxon gas with 66% carbon dioxide, 20% methane, and a GRI generic gas with 18% carbon dioxide, 80% methane. Process flow diagrams and economics are developed. Breakeven allowances for raw gas cost are established, i.e., the raw gas cost at which plant net revenues would be zero. Breakeven allowances range from ($0.34) to $1.79/MSCF of raw gas for low-high product price scenarios and a simple five year capital payback period. The results indicate that 20 MMSCFD is too restrictive a scale for widespread application of the technology. Economies of scale realized for raw gas flows greater than 100 MMSCFD allow a much broader application of the integrated technology. Simple extrapolation of economics to 250 MMSCFD yield breakeven allowances of $0.30 to $2.18/MSCF raw gas. The process achieves virtually 100% sulfur recovery at costs competitive with conventional Claus plus tail gas processes.