Prospectus

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DST-1 Tray Blowing Expected Benefit toMembers:

Traditional Research Idea

The probability of sieve tray or valve tray blowing is increased as designs move to higher vapor velocities. The tray designer needs additional information to confidently design trays to avoid “blowing.” A large economic incentive exists to avoid field erected columns. In order to reduce the column diameter, the designer needs to be able to confidently design at higher vapor velocities using higher (36 inch) tray spacing.

Present Situation and Proposed Research: Within the body of F.R.I. information, there are no guidelines or correlations to predict the loss of a liquid layer on the tray. As vapor rates increase, increased spray action causes more liquid to be blown into the downcomer. Since there is a fixed amount coming onto the tray, there is a loss of liquid on the tray. Simulator work is proposed to understand the relative importance of high vapor velocity, low hole area, downcomer design, and high tray spacing on the blowing mechanism.

An improved tray will then be tested under a range of distillation conditions. Proposed Internals and Test System: One sieve tray design with 36-inch tray spacing and design features to prevent blowing. The systems will be xylenes and C6/C7. Estimated Unit Time: Simulator Required. Column: Three weeks for each system. Estimated Additional Costs (Beyond Unit Time): None

Background and Discussion: Blowing is defined here as the loss of liquid inventory on the tray. Conditions of high vapor velocity and low liquid rate promote blowing. If sufficient liquid is lost on the tray, the downcomer seal can be lost and vapor will travel up the downcomer causing flooding. Inlet weirs have been shown by FRI to prevent the loss of downcomer seal, but the installation of inlet weirs remains uncommon in modern tray design. The loss of liquid on the tray also leads to loss of tray efficiency and can result in dramatic failure of the column to perform any separation. FRI information should be developed to allow the designer to understand tray design features or conditions which are prone to “blowing”.

PROSPECTUS

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