FIG. 3.8.5 The oxychlorination step of the vinyl chloride process with oxygen feed. (Reprinted, with permission, from Smith and Patela, 1992.)
processing introduces a safety problem downstream of the reactor; unconverted ethylene can create explosive mixtures with oxygen.
This problem can be avoided when a small bleed of nitrogen is introduced. Since nitrogen is drastically reduced in the feed and essentially all ethylene is recycled, only a small purge must be vented. This method results in a 20-to-100-fold reduction in the size of the purge compared to a process that uses air as the oxidant (Reich 1976).
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