Drizo process

The reboiler temperatures of plants listed in Table 11-5 are well below the recommended maximums however, higher temperatures are often used. Worley (1967) reported that up to 10 years experience with several hundred TEG units utilizing a reboiler temperature of 4(X)°F has failed to indicate any evidence of measurable losses by degradation. Dew-point depressions in excess of 100°F are reported for these units. A dew point of-9S°F is reported by Smith and Skiff (1990) for a plant employing only 1.5 gal TEG/lb water removed. This represents a dew-point depression of at least 150°F (assuming a minimum contact temperature of 55°F). and was attained by using the Drizo process to regenerate the TEG to 99.999% concentration (10 ppm H2O). 

Condensation of water and condensible hydrocarbons in the regeneration system offgas is a very effective means of preventing the emission of BTEX and WOCs. If no stripping gas is used, the offgas can be almost totally condensed and separated into aqueous and hydrocarbon liquid phases. Part of the liquid hydrocarbon can be recycled to the regenerator as in the Drizo process, or all of it can be recovered as a marketable product. 

Drizo A variation of the glycol process for removing water vapor from natural gas, in which the water is removed from the glycol by stripping with a hydrocarbon solvent, typically a mixture of pentanes and heavier aliphatic hydrocarbons. The process also removes aromatic hydrocarbons. Last traces of water are removed from the triethylene glycol by stripping with toluene in a separate, closed loop. Invented in 1966 by J. C. Arnold, R. L. Pearce, and H. G. Scholten at the Dow Chemical Company. Twenty units were operating in 1990. U.S. Patent 3,349,544. 

Smith and Skiff (1990) repotted that this type of process can achieve concentrations of over 99.99% with triethylene glycol, resulting in potential product gas water dew points in the -100° to -140°F range. In more recent papers. Smith (1993) and Smith and Humphrey (1995) cite upper limit glycol concentrations of 99.997 to 99.999% based on use of the Drizo technology. They report experience with one plant producing treated gas with an indicated... 

Fowler, A., 1975, Super-Drizo, The Dow Dehydration Process, Proc. Gas Conditioning Conf, University of Oklahoma, Norman, OK. 

Another dehydration process is the Drizo gas dehydration process that uses high glycol concentrations to give low due point temperatures and uses a solvent to recover extracted aromatics [30]. Trayed columns with a variety of structured proprietary packings have also been used for dehydration of natural gas in arctic gas production [31]. 

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