Hollow fiber membrane contact apparatus and process

Abstract

The present invention provides a perfluorinated thermoplastic hollow fiber (14) membrane gas-liquid shell side contactor (10) and a process for manufacturing the contactor (10) is described. The present invention also provides a device including a gas-liquid contactor (10) for producing ozonated water.

Description

FIELD OF THE INVENTION [0001] This invention relates to a hollow fiber membrane contactor for phase contact applications. The contactor is made from perfluorinated alkoxy polymeric materials, has a high packing density providing high useful contacting area, and the ability to operate with liquids of low surface tension. BACKGROUND OF THE INVENTION [0002] Liquid-gas contactors are used to transfer one or more soluble substances from one phase to another. Examples of conventional contactors are packed towers, plate columns and wetted wall columns. In these systems, gas absorption of one or more components from a gas stream is accomplished by dispersing the gas as bubbles in packed towers and plate columns in a countercurrent flow to a liquid stream. Absorption efficiency is controlled apart from solubility considerations by the relative rate of the flows and the effective surface area of the gas flow bubbles. In wetted wall contactors the gas stream flows past a downward flow of liqui...

AI Technical Summary

Benefits of technology

[0030] In another aspect of this invention, the shell volume containing the hollow fibers is free of apparatus which promotes turbulent liquid flow within the shell.

Problems solved by technology

Primary among these is the fact that the individual gas and liquid flows cannot be varied independently over wide ranges.

Tray columns are prone to such problems as weeping at low gas flows and flooding at high liquid flows.

Packed towers can flood at high flow rates.

The use of low liquid flow rates in a packed tower can lead to channeling and reduced effective surface area Excessive frothing or foam formation can lead to process inefficiency.

Wetted wall contactors have inherently low mass transfer coefficients, and can flood at high gas flow rates.

As the conditions of the application to which the membrane is being used become more severe, the materials that can be used becomes limited.

For example, the organic solvent-based solutions used for wafer coating in the microelectronics industry will dissolve or swell and weaken most common polymeric membranes.

Being chemically inert, the Poly(PTFE-CO-PFVAE) and FEP polymers are difficult to form into membranes using typical solution casting methods as they are difficult to dissolve in the normal solvents.

Since these chemicals are toxic and dangerous, transport, storage and proper disposal of these chemicals pose serious health and safety hazards to the workers in this industry.

While HF water can easily be produced, a good source for ozonated water has been a challenge.

However, to replace aggressive etch baths, much higher ozone concentration is needed.

This device is characterized by undesirably limited gas mass transfer through the hollow fibers.

Dissolved oxygen in ultrapure water is another problem in semiconductor device manufacturing.

Potential problems associated with uncontrolled oxide growth are prevention of low temperature epitaxy growth, reduction of precise control of gate-oxide films, and increased contact resistance for VIA holes.

Probably because of the impracticality of such a step, this radial stretching step is missing from the disclosed process.

This is a tedious, labor intensive process.

These developers could not be degassed with typical microporous membranes because the liquid would intrude the pores at the pressures used and permeate, causing solution loss and excess evaporation.

While (TFE) membranes would work in these applications, presumably because of their lower surface tension, they are difficult to process into hollow fibers.

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