Fischer assay analyses

Table I. Results of Fischer Assay Analyses on the Standard Shale...

Procedure. Green River site 1 was located 5 mi west of the Rock Springs sites 4 and 5. The oil shale zone of interest, at approximately 346-385 ft, was selected after studying the analysis of cores cut from an earlier well. As determined by Fischer assay, oil yield of the cored section averaged about 21.0 gal/ton. 

A Fischer assay simulates the conversion of oil shale to usable fuels in an above-ground retort. The results of an extensive program of chemical analysis of major and trace elements in spent shale, oil, and water collected from the Fischer assay of a standard oil shale are presented. The concentration of major elements in raw and spent shale can be determined only to 10% in this study. Two criteria show that fluorine and zinc may have been mobilized during the assays. The concentrations of arsenic and selenium in the Fischer assay retort water exceed the maximum permissible concentrations for drinking water. 

Analytical methods are described in (2). Standard methods were employed for total organic carbon (TOC) and Fischer Assay (FA) analyses. Kerogen was isolated by solvent extraction to remove bitumen and acid dissolution to remove mineral matter. Elemental analysis was performed only on kerogen with low ash content (<25% by weight). 

Product Assay. Fischer Assays were performed with samples of Marathon lease material, with both raw shale and with the beneficiated pellets. Spent shale (char) from the assay was subjected to heat value (Btu content) analysis. Results are shown in Table IV. 

The grade of oil shale can be determined by measuring the yield of oil of a shale sample in a laboratory retort. This is perhaps the most common type of analysis that is currently used to evaluate an oil shale resource. The method commonly used in the United States is the modified Fischer assay, first developed in Germany and then adapted by the U.S. Bureau of Mines for analyzing oil shale of the Green River formation in the western United States (Stanfield and Frost, 1949). The technique was subsequently standardized as the American Society for Testing and Materials (ASTM) Method D-3904-80 (ASTM, 1984). Some laboratories have further modified the Fischer assay method to better evaluate different types of oil shale and different methods of oil-shale processing. 

As the test conditions are very similar to conditions inside the gasifier, the analysis is useful for predicting the tar production fi om coals under consideration. Table 3.8 shows results from the Fischer assay for coals of different rank and origin. It can be seen that lower coal rank leads to increasing tar yield, which is in line with the increasing volatile matter. It should be noted that some lignites might have tar yields of up to 25 wt%(wf), which represents a substantial fraction of the overall calorific value. 

In current industrial practice gas chromatographic analysis (glc) is used for quahty control. The impurities, mainly a small amount of water (by Kad-Fischer) and some organic trace constituents (by glc), are deterrnined quantitatively, and the balance to 100% is taken as the acetone content. Compliance to specified ranges of individual impurities can also be assured by this analysis. The gas chromatographic method is accurately correlated to any other tests specified for the assay of acetone in the product. Contract specification tests are performed on product to be shipped. Typical wet methods for the deterrnination of acetone are acidimetry (49), titration of the Hberated hydrochloric acid after treating the acetone with hydroxylamine hydrochloride and iodimetry (50), titrating the excess of iodine after treating the acetone with iodine and base (iodoform reaction). 

Samples must dissolve In chemical assay systems to Insure that all the water is available for analysis, e.g., liquids and solids in Karl Fischer reaction... 

ISO standard 893 covers analysis of alkanesulfonates, specifying assay by gravimetry, alkane monosulfonates by titration or extraction (Sections 2(a) and 2(c), below), neutral oil by petroleum ether extraction of an isopropanol/water solution, pH of a 5% aqueous solution, water by Karl Fischer titration or azeotropic distillation, sulfate by titration with lead nitrate, sulfite by iodometric titration, and chloride by potentiometric titration (99). The value for neutral oil can be checked for losses due to evaporation by confirming that the weight of the sulfonates and other salts in the 2-propanol/water phase plus the water content and weight of neutral oil is equal to 100%. 

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