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Show A REFINERY DATA and SULFUR MEASUREMENT 1.0 Routine Measurement of RFG Sulfur At present there bas not been a standard technique tbat bas been routinely available to tbe refiners for tbe analysis of total sulfur and specific sulfur compounds. The accepted practice between botb tbe refiners and tbe SCAQMD bas been to use HzS measurements to approximate the total fuel gas sulfur. The primary reason for this is tbat the existing analytical techniques are not capable of consistently measuring the other sulfur compounds at tbe low levels tbat are now of interest. Improvements in the analytical tecbniques for low (100 ppmv or less) levels of the individual sulfur species were investigated. Some nonroutine laboratory analyses were obtained from some of the refiners whicb detailed many of tbe sulfur compounds in addition to HzS. 2.0 Existing Refinery Data A summary of tbe detailed fuel gas analyses from the WSP A refiners is shown in TABLE 1. From tbese data, it is apparent tbat tbere are great variations in the levels of individual hydrocarbon and sulfur compounds even within specific refineries. CompositiOns vary according to the source of the gas and the manner in whicb tbe individual source fuel gas streams are tied together. Some refiners bave one large RFG system, while otbers have multiple smaller systems. The overall size of the systems in given WSP A refineries varied in tbe apprOximate range of 20 to 90 MMSCFD (Million Standard Feet3 / Day). The analyses in TABLE 1 indicate tbat most of tbe individual unit fuel gas streams contained larger tban anticipated amounts of COS and mercaptan (RSH) species. For instance, a number of delayed coker fuel gas samples sbowed that most of tbe sulfur in those streams is not HzS. The WSP A refineries typically have 50 to 150 psig amine absorption units (usually DEA or MEA) to treat sour fuel gases. These treatment schemes achieve about 30-70 ppm of total sulfur on predominately HzScontaining fuel gases. In gases generated from heavy oil cracking units the emuent fuel gases contain much higher levels of other sulfur compounds (such as COS and mercaptans - RSH's) and average about 100-300 ppmv total sulfur. Overall, the amine units achieved about a 99.5+ % reduction of tbe inlet sulfur, which is predominately HzS. 3.0 Analytical Techniques Recently, sopbisticated tecbniques have been more fully developed wbicb can yield ·speciated· sulfur data. A brief investigation of the measurement techniques and instruments tbat are available was made. Presently the online measurement of individual sulfur species in fuel gases at levels ~100 wppm is not routinely done in refineries. To make such a measurement, a sample must first be drawn and then transported to an analytical laboratory. A number of problems can develop when RFG samples are drawn and not analyzed immediately. For instance, proper sample containers must be used to minimize chemical reactions between the sulfur compounds and the container. One refiner bas found that epoxy-lined bombs provide fairly consistent results compared with even Teflon-lined ones. One testing company had good success only with silanized glass sample bombs. In addition to the reactivity of the sample bomb surfaces, time is also an important factor. The longer a sample is allowed to sit prior to analysis, the more the sulfur compounds will continue to react and interact to form different sulfur species, tbus distorting the accuracy of the analysis. The eventual aim in gas sulfur analysis is to develop an online instrument to minimize these problems. The Western Researcb Corp. of Calgary and Core Labs of Houston have written manuals and publisbed papers -4- |