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Show absorptive efficiencies. UOP recommended the Benfield "hot-pot" (K2C03) scrubbing process, but no removal efficiencies have been made available. 2.4 Hydrogenation I Hydrolysis Well proven by some vendors, mostly in natural gas service, but some recent experience has been gained with gases more similar to RFG. Can be very effective at converting the two difficult species, RSH ( :II 98 %) and COS (:II 87 %), to HzS; which can then be removed very efficiently with many other processes (e.g., amine). Some of the potential problems are olefin saturation and CO methanation in the hydrogenation beds, and high capital and operating costs. 2.5 Compression The mainly advantage to compression would be to increase the efficiency of existing amine or physical solvent units. The principal drawback is higher energy consumption. Compression might combine well with a Hydrogenation / Hydrolysis unit upstream of an existing amine unit. Computer simulation shows that inlet fuel gas compression would be cost effective for lower pressure (circa 80-90 psia or less) RFG streams. Typically, coker fuel gas is delivered at a lower pressure and it usually contains the highest amount of the difficult sulfur compounds. Compression is probably not cost effective for fuel gas amine units that already operate at 130-150 psia or above. 3.0 RFG Sulfur Removal Schemes All of the refineries utilize amine systems, but the capacities and configurations of the numerous individual systems vary widely. In addition, the compositions of hydrocarbon, sulfur, and other compounds in different fuel gas streams can be very different depending on their source. Due to this great diversity in the fuel gases themselves and their systems, there does not appear to be a single solution to reducing RFG sulfur levels. Real solutions will be ~ry refinery-, stream-, and unit-specific. The different sulfur removal processes that were investigated vary considerably in their abilities to remove specifiC sulfur compounds. In general, HzS is the easiest one to reduce, and COS, heavier mercaptans (RSH's) and DMDS are the most difficult. Most of the processes considered have little or no pilot data or track record in refinery fuel gas service. It is economically prudent for the WSP A refiners to perform some sort of pilot or in-plant testing prior to investing capital. Some of the refiners have already begun testing programs. First, it must be established whether particular processes are applicable to the specific refinery in question, and then the specific removal efficiencies must be determined. 3.1 Development of the "Base Case" Based on the WSP A refinery data collected in TABLE 1, Bechtel generated a "typical" RFG compositional analysis and typical amine unit operating conditions. Performance evaluations and "budget" cost estimates were solicited from over twenty vendors in the gas desulfurization field. Very few data were obtained for existing amine unit inlets, and this composition was estimated. Base case operating condition ranges were developed to cover the variations between plants and given to the vendors as follows : -9- |