Shale hydrotreating yields

We will consider three processes in more detail to show how the sulfur in the original feedstock material (coal or oil shale) is recovered as elemental by-product sulfur. In this way yields of sulfur per barrel of product can be computed. The three processes will illustrate examples of coal gasification for production of SNG, methanol or indirect liquids, direct liquefaction for production of naphtha and synthetic crude oil and finally, oil shale retorting for production of hydrotreated shale oil. 

Once the synthetic crude oils from coal and oil shale have been upgraded and the heavy ends converted to lighter distillates, further refining by existing processes need not be covered in detail except to note the essential character of the products. The paraffinic syncrude from oil shale yields middle distillates which are excellent jet and diesel fuel stocks. The principal requirements are removal of nitrogen to the extent necessary for good thermal stability of the fuels and adjustment of cut points to meet required pour or freeze points, limited by the presence of waxy straight-chain paraffins. The heavy naphtha from shale oil can be further hydrotreated and catalytically reformed to acceptable octane number, but with considerable loss of volume because of the only moderate content of cyclic hydrocarbons, typically 45-50%. On the other... 

The 650°F+ fraction of the hydrotreated shale oil was processed in in FCC pilot plant, and the results show that it is an excellent feed for a conventional refinery. The resulting FCC yields, activity, and product qualities are quite similar to those derived from normal petroleum gas oils. 

Figure 4. Catalytic cracking yields from hydrotreated feeds. Shale oil arm Arabian Light vacuum gas oil at 975°F (O), shale oil containing 870 ppm N (0), shale oil containing 385 ppm N.

Approximate yields for the hydrotreating and FCC processes are shown in Table X. The whole-oil hydrotreater data are based on results from the large-scale feed preparation run. The FCC data are described above. Since 41 LV % of the raw shale oil is fed to the FCC as hydrotreated 650° F+ bottoms, the FCC pilot plant yields were multiplied by 0.41 and reported as yield to raw shale oil. 

Boiling range (°F) Yield (LV fo of whole hydrotreated shale oil blend)... 

The hydrotreated shale oil is fractionated by distillation methods into gasoline, jet, diesel, and 650°F bottoms (residua). The jet and diesel fuel boiling ranges were determined experimentally to meet flash point and freeze or pour point requirements. Some of the residua was recycled back to the hydrotreater to increase jet and diesel fuel yields. 

The residual hydrotreated shale oil was mixed with regular refinery cat cracker feed at a rate of 3%, with no detectable shifts in yields or other adverse consequences. Similarly, the gasoline range cut had no detectable effects on hydrocracker operations at 1.5% of feed. 

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