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Show processes will most likely be necessary. The estimated removal efficiencies are approximate and were generated for the base case operating conditions only. The results for this ·typical· case should be used for comparison purposes only. Efficiencies for actual refinery RFG streams will depend on hydrocarbon compoSition, acid gas concentration, pressure, temperature, and the relative and total amounts of the individual sulfur compounds. As shown in the raw refinery database (TABLE 1), variations are extremely wide, and the optimum sulfur reduction scheme can vary also. The generalized findings here need to be ·custom-fit· to each individual refiners situation. D. Costs and Cost Effectiveness Based on the process schemes as outlined in TABLES 2 and 3, and represented schematically in FIGURE 1, Bechtel has generated order-of magnitude installed costs and operating expenses for each process for comparative purposes. 1.0 Estimation Basis In cost estimating the processes presented in this study, Bechtel obtained the purchased costs of individual equipment items such as pumps, heat exchangers, compressors, and fired heaters, obtained from vendor quotes and/or Bechtel equipment cost files. The installed equipment cost is the sum of : the costs of the major purchased equipment, commOdity and bulk materials, and installation labor. The installed battery limits equipment costs were computed and then integrated with other cost items to give total capital costs. The installed equipment costs for each process scheme is the sum of all the individual equipment costs. The cost estimates developed are for screening purposes only and are not intended to provide sufficient information for the selection and detailed engineering of the final optimized process(es). Without further pilot and plant tests, specific design recommendations cannot yet be made. The processes outlined represent a number of feasible alternatives which could apply to various different refinery situations. 2.0 Comparative Budget Estimates The comparative order-of magnitude cost estimate categories and the assumed costs are shown in TABLE 4. For most of the proposed processes, there have been no fuel gas installations and there are no cost or peformance data available. Although the assumed goal in installing additional desulfurization units has been to achieve an overall sulfur content of 40 ppm in the fuel gas, the most cost effective process may not require treatment of the total fuel gas. In fact, it may be possible to achieve the sulfur limit in the fuel gas by treating streams in the refinery with the highest sulfur content. The SCAQMD evaluates the "Cost Effectiveness" of various technologies based on the total annual costs per incremental unit (ton) of pollutant gases removed. They have published a list of "acceptable" expenditures for different pollutants. The guideline figure that they published for SOX in June of 1988 in their AQMP Appendix IV-A is $18,300/ton of SOx. The cost effectiveness factors are shown in the last column of TABLE 4. All of the proposed processes that can theoretically achieve the new SCAQMD 40 ppmv RFG total sulfur limit appear to fall close to this guideline. Therefore, they would appear to be reasonable and cost effective. Some of the processes that were investigated can separate out portions of the fuel gas that might have higher value elsewhere in the refinery. These recoverable components could include hydrogen, C;'s and C,/s (propane, butanes, olefins), and Cs+ (gasoline). The integration of these processes into each individual refinery would vary considerably, and therefore these processes were not cost estimated. -12- |
