Prospectus

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PPP-6 Column Draw-Offs Expected Benefit toMembers:

Traditional Research Idea

Side and bottom draw offs are seldom-analyzed components of columns which, when improperly designed and specified, may lead to costly startup problems or operating bottlenecks. Well researched design correlations will aid the designer in correctly sizing these critical components.

Present Situation and Proposed Research: It is proposed that all tests be done in the 4 foot section of the low-pressure column. Tests would be performed using the iC4/nC4 system at 165 psia (a high vapor density system) and o/p xylene (a low vapor density system). The program will include a review of the results of the sponsored research project recently completed with Oklahoma State University to ascertain if any research results obtained in the program might be applicable.

A literature search will be conducted to review the numerous published articles relating to the design of ancillary column details. The FRI Design Practices Committee will be called upon to provide their input and guidance in structuring the details of the program. No simulator work is proposed due to the uncertain effects of surface tension and viscosity on the experimental results.

Proposed Internals and Test System: Existing FRI sieve trays and packing with specially constructed draw off sumps. Estimated Unit Time: Two weeks per device (trays and packing), total of four weeks. Estimated Additional Costs (Beyond Unit Time): Unknown. Background and Discussion: Side and bottoms draw offs are common components of all columns - both trayed and packed. In the case of bottoms draw offs, there is often sufficient liquid residence time to allow degassing of the liquid so that outflow is predictable and operation does not suffer. In the case of side draw offs, however, the "liquid" being drawn is usually aerated and at equilibrium conditions. These two conditions combine with typically shallow liquid levels so that flashing in the throat of the outlet nozzle is a problem. Draw off connections are often sized based on other criteria with no consideration given to the physical conditions or internals inside the column. A benefit of this program is that it will draw attention to these details and underscore their criticality. The data and correlations derived from the program will provide the column designer with tools to enable him to easily consider and incorporate side and bottoms sump and draw off nozzle details into his design.

PROSPECTUS

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