Spent shales

Spent shale zone residual carbon burned... 

Major obstacles to large-scale production are the disposal of the spent shale and the vast earth-moving operations. Table 1-7 is a typical analysis of a raw shale oil produced from retorting oil shale. 

When oil shale is retorted, the inorganic portion of the shale expands considerably. The spent shale remaining has no direct commercial value and, ideally, it is placed back in the mine. However, because of the popcorn effect, the volume of spent shale is greater than the volume of the mine from which it was taken. 

API containing. 6-.67% S (wt) (34). It is possible that not all of the sulfur contained in the shale is produced. At least one study indicates that in a retort operation, 82.5 percent of the sulfur contained in the as-mined shale feed is retained in the spent shale (35) ... 

The process considered is the Colony hydrotreated shale oil plant using the TOSCO II pyrolysis retort (4). In this process raw shale, crushed to 1/2" or smaller, is contacted with hot ceramic balls in a rotating drum. Downstream of the retort the balls and spent shale are separated by screening. The balls are then transported by an elevator to a vessel in which they are reheated by direct contact with hot combustion gases. The heated balls are then recycled to the rotating retort. 

Most of the heat used in preheating the shale to reaction temperature would be lost as sensible heat in the hot spent shale, which would be discharged at 1100°-1300°F. 

Leachates from the oil-shale industry and from spent shale dumps Phenols Sulfates V. fischeri (BiotoxMicrotox ) Daphnia pulex (Daphtoxkit F pulex) Brachionus calyciflorus (.Rotoxkit F )... 

In situ retorting offers the possibility of eliminating the problems associated with the disposal of large quantities of spent shale that occur with surface retorting. True in situ (TIS) retorting involves fracturing the shale in place, ignit-... 

Shale oil and a fuel gas have been produced by microwaveheating oil shale in a standard microwave oven in conjunction with experimentation to develop an in situ microwave retorting process. Various grades of oil shale have been subjected to high microwave fields. The derived oil has been submitted to various physical and chemical testing methods, and the chemical composition of the evolved gas has been evaluated. The specific gravity pour point yields of oil, water, gas, and losses and spent shale are compared with parallel data obtained with the Fischer assay procedure. Important differences in oil flow properties and gas composition are discussed in view of microwave interactive theory. 

Crude oil analysis techniques, developed by the Bureau of Mines (9), was used initially to describe the overall quality of the product. Spent shale samples were ashed using a two-day, low temperature procedure. The covered samples were placed in a room temperature furnace, and the temperature was increased to 700°C (370°C) in a near-reductive atmosphere. The sample was uncovered and the temperature was increased to 750°F (300°C) for one more day with air forced over the sample. This method has been suggested to cause the least changes to heat-sensitive mineral components of the shale (17). Actual experience has shown that the time for this procedure can be halved because of the porous nature of the spent shale and the small sample size. Results are presented as weight percent of the pre-retorted sample. 

Average Grade Spent Shale Ash Spent Shale Ash... 

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. 

Preparation and Storage. Much of the preparation work on the standard shale and spent shales has been reported previously (16,20). The raw shale was taken from a 3-ton pile of —1/2 mesh feedstock which was mined from a fresh face of the Dow Mine of the Colony Development Company at the head of Parachute Creek in the Piceance Creek Basin, Colorado. TOSCO II pilot plant operations produced a yield of 37-38 gal/ton. The shale is designated as OS-1 SS-2 is a spent shale from the pilot plant produced from the same feedstock. 

Table II. Results of Homogeneity Tests for Rubidium (Rb) and Strontium (Sr) on the Standard Shale and a Spent Shale...

Problems in Analyzing Samples. The samples encountered in this study fall into three general categories geological (oil shale and spent shale), waters (process waters), and petroleum (shale oil). The chemical treatments required for these materials have been adapted from conventional methods commonly used for the analysis of similar materials. However, analysis of the oil shales has presented several problems not common to other geological materials. 

The focus of this research and other mass balance studies has been on trace elements (1,2,3). However, in future studies on speciation it will be necessary to know the concentrations of the elements present in amounts above 1%. Therefore, analyses of the oil shale and spent shale samples were performed for these elements. Atomic absorption and colorimetry were used for many of these analyses. Some major element results also were obtained by the broad-range instrumental analysis surveys. The comparison of the results obtained by the different techniques shows large discrepancies. 

The analytical results for trace elements appear better than those for the major elements. Table IV is a summary of results for the raw shale (OS-1), and the spent shale from the TOSCO II pilot plant (SS-2), and the spent shale (FS), unacidified water and unfiltered oil from the Fischer assay studies. The spent shale SS-2 is the residue from the retorting of the same raw feedstock from which OS-1 was taken. In the case of the solid samples, the concentrations are from multiple analyses of different splits. In all cases, the relative deviations of multiple analyses lie within 10%. Comparison of these results with those from other laboratories on different splits of the same solid samples show agreement within 2cr SI), The two exceptions are manganese and zinc for which the results reported here are low in comparison with other methods. Analyses of NBS standard coal (SRM 1632) and coal fly ash (SRM 1633) are included also in Table IV. The concentrations in raw and spent shale are similar to those reported by TOSCO except for selenium where their values range from 10-16 ppm (3). 

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