Chemical and Biological Engineering ETDs

Publication Date

10-11-1978

Abstract

This study demonstrates the technical feasibility of purifying concentrated organic solutions by the cyclic indirect freezing process with in-situ washing and in-situ melting operations. The key to a successful purification in the freezing process is a near plug flow displacement of unfrozen liquor from the bed in an in-situ washing operation. To be successful, a freezing step has to be initiated uniformly and a high permeability bed has to be formed uniformly throughout the freezing conduits. In the study, a nucleation technique based on pressure induced supersaturation has been used to accomplish a uniform initiation and a pressure induced freezing operation has been used to control the morphology of the solid bed formed. The following three methods have been adopted in the study:

1. In Method A, an ultrasonic nucleation and a pressure induced freezing are used.

2. In Method B, a pressure induced nucleation and a pressure induced freezing are used.

3. In Method C, a pressure induced nucleation and a temperature induced freezing are used.

Feeds containing 80% to 95% para-xylene have been purified and produced 98.5% to 99.7% para-xylene with recoveries ranging from 32% to 49%. It is noted that the pressure induced nucleation and the pressure induced freezing have significantly simplified the equipment used and the operational procedures. The process should be applicable to any mixture that exhibits an eutectic type phase diagram. Two examples are cited to show the pressures to be applied in nucleation steps:

1. With a cooling medium maintained at 48.5 ° F and without a liquid agitation, a feed containing 90% para-xylene can be spontaneously nucleated when the pressure applied is raised to 6500 psi.

2. A spontaneous nucleation of a 90% para-xylene solution takes place when the solution is agitated by circulating the liquid at a rate of 50 cc per minute and the applied pressure is raised to 3000 psi.

Sponsors

The National Science Foundation

Document Type

Thesis

Language

English

Degree Name

Chemical Engineering

Level of Degree

Masters

Department Name

Chemical and Biological Engineering

First Committee Member (Chair)

Chen-Yen Cheng

Second Committee Member

Richard Wilson Mead

Third Committee Member

Frank Lynn Williams

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