Paraho retorted

P r ho. The Paraho retorting technology is similar to the PETROSIX technology except that it can be operated in the direct heat (DH) mode. The unique feature of the Paraho technology is the two levels of heat input (Fig. 4). In the IH mode, the air blower shown in Figure 4 is replaced by a recycle gas heater. The Paraho DH operation has been carried out neat Rifle, Colorado since the 1970s operations to produce asphalt (qv) from shale oil are continuing. 

Figure 17.29. Moving bed reactors for cracking and recovery of shale oil. (a) Kiviter retort, USSR 200-300 tons/day [/. W. Smith, in Meyers (Ed.), Handbook of Synfuels Technology, McGraw-Hill, New York, 1984], (b) Paraho retort for shale oil recovery (Paraho Oil Shale Demonstration, Grand Junction, CO).

In this paper the chemistry of Paraho retorted shale, the nature of the thermo-chemical reactions that can contribute to its cement-like properties, and the chemistry of the leachates obtained from permeability studies will be presented. Although civil engineering information now exists which permits the disposal of retorted shale in an environmentally acceptable manner, a better understanding of the thermal reactions of retorting and the chemical composition of retorted shale may suggest changes in retorting operations which would further lessen any possibly adverse environmental impact. 

Figure 4. Compaction test results. Paraho retorted shale, semiworks plant— direct heat 1.5-in. maximum size fraction.

Many studies have been made concerning the mean chemical analysis of Paraho retorted shale(7). Although it is important to know this chemical composition, it is not helpful in assessing the components responsible for the cement-like properties. Much emphasis has been placed upon the formation of reactive oxides, such as free lime and magnesia, from carbonate decomposition. Although free lime can be formed under laboratory conditions(8), it has not been detected in the retorted shale used in the field studies. Although free lime was not detected,... 

Data shown in Table II consists of materials which can contribute to salinity, toxic elements had not been considered. More recently, the U. S. Environmental Protection Agency has proposed an extraction procedure to determine hazardous wastes. Results obtained using the proposed EPA extraction procedure are shown in Table III for Paraho retorted shale. The low... 

Detailed laboratory and field studies have shown that Paraho retorted shale can be compacted easily is not subject to dusting, erosion, or auto-ignition and can be handled to create structures of very low permeability. A basis for these beneficial properties can be found, in part, by an examination of the chemical and physical properties of the retorted shale. For example, it is believed that the strengths achieved are caused by the hydration of magnesia, reactions of the gypsum minerals, and the compaction of the silty-gravel mix. 

UNISHALE B. The UNISHALE process, like the Paraho process, uses lump feed and countercurrent flows, and can be operated ia either the DH or IH mode. The UNISHALE B process is an IH process that uses hot recycled gas as the heat-transport medium (Fig. 6). The unique feature of the UNISHALE processes is the rock pump. The soflds move upward through the retort as the vapors are moving downward. The rock pump was used ia the UNISHALE technology at Parachute, Colorado to produce more than 0.64 x 10 m (four million battels) of cmde shale oil. Operations were shut down in 1991. 

Solids. Proper handling and disposal techniques can obviate potential problems associated with the soHd waste-retorted shale. Retorted shale disposal and revegetation have posed no adverse environmental impacts at the Unocal Parachute Project (62). EarHer studies carried out using Paraho and Lurgi retorted shales indicated that these materials behave as low grade cements (63,64) and can be engineered and compacted into high density materials (Pig. 11) and water impervious stmctures (Table 15). 

Reaction Parameter Studies. Experiments were carried out with conventional shale oil [direct retorted Paraho shale oil) for the purpose of studying the effects of reaction parameters in hydrotreating under supercritical conditions. In one group of experiments, the space velocity was varied (1.6, 3.2, and 5)... 

The raw Colorado shale oil used in this study was provided by DOE s Laramie Energy Research Center (LERC). It was prepared in the Paraho tests in a surface retort operated in the so-called indirectly heated mode. As received, it was an emulsion containing 6% water and about 0.5% fine particles in the shale oil. Heating this mixture to 170°F broke the emulsion most of the water and fines settled out after standing at... 

Although the nature of retorted shale certainly depends upon the nature of the geological deposit from which the raw oil shale was mined, it depends, to a large extent, also upon the retorting technology used to process the raw oil shale. The information presented in this paper is obtained from the Paraho Oil Shale Demonstration carried out from 1973 to 1976 Cl). 

The Paraho semi-works retort is a cylindrical vessel, having a 2.5 m internal diameter and is capable of processing about 250-300 tonnes of raw oil shale per day. A schematic of the Paraho direct mode operations is shown in Figure 1. Raw shale, crushed and screened to +1.0 cm to -10.0 cm, enters the top of the retort, passes through the retort under the influence... 

Most of the material used in the retorted shale disposal research was produced by the Paraho semi-works retort operating in the direct mode operation. Another mode of operation, an indirect mode, was also studied. In the indirect mode, air is not introduced into the retort. Internal combustion does not occur none of the organic carbon remaining on the retorted shale is utilized. Process heat for the indirect mode operation is supplied by heating the recycle gas in an external heater. 

During the recent Paraho operations, the potential problem of retorted shale disposal was recognized. A seven-stage retorted shale research program, jointly supported by the U. S. Bureau of Mines, was carried out using both laboratory and field studies (4). Highlights of this retorted shale research program... 

Because the disposal of retorted shale is, ultimately, a field exercise, this paper will discuss the experimental design and data from field studies which have been carried out. Laboratory experimentation and data will be used to complement the results of field studies. Two field studies, compaction and permeability, were carried out during the Paraho research operations. 

Jones, J. B., Jr., "The Paraho Oil Shale Retort," 9th Oil Shale Symposium, Colorado School of Mines, Golden, CO, 1976. 

Holtz, W. G., "Disposal of Retorted Shale from the Paraho Oil Shale Project," U.S. Department of Interior, Bureau of Mines, J0255004, 1976. 

The crude shale was produced by Paraho Development Corp. over the three year period from 1976 to 1978. Paraho s Anvil Point, Colorado works utilizes a vertical direct heat retort to recover the oil from crushed shale (1). 

---