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<br />001128 <br /> <br />Draft - 9/81 <br /> <br />Retorting. Though the methods of moving shale through the <br />retort vessel and of collecting the pyrolysis products vary from <br />process to process, retorting is basically a process of heating <br />the shale to 900'F. The heat causes pyrolysls of the kerogen, <br />which results in the distillation of condensable tars, oils and <br />water, and of noncondensable gases. The sensible heat contained <br />in the spent shale may be partially dissipated by cooling di- <br />rectly with water. In the first case, the plant's thermal effi- <br />ciency will be somewhat higher and water consumption will be <br />somewhat lower than in the second case, though steam generated <br />from wetting the spent shale can in some cases be recaptured and <br />~tilized (Union Oii, for example, as reported in Eyring Research <br />N Institute and Sutron Corporation, 1976, p. IV-6). <br />~ Of special interest is the water evolved during retorting. <br />This includes water produced in combustion, the moisture on the <br />shale surface, and the thermal decomposition products of the car- <br />bonate minerals in the shale (Probstein and Gold, 1978, p. 152). <br />The proportion of each to the total amount evolved, the absolute <br />amount evolved, and the amount recapturable are dependent to some <br />extent on the type of retorting process used. To the extent to <br />which such water is capturable and can be recycled, dependence on <br />outside water sources is di~inished. Unfortunately, many reports <br />have not made clear whether their reported water consumption rep- <br />resents a gross requirement or a net requirement. This omission <br />makes it difficult to determine the net demand on external water <br />sources, inasmuch as it has been estimated that the water pro- <br /> <br />duced during retorting may be as much as 1,090 acre-feet per year <br /> <br />3 <br /> <br />. <br />