Gas separation: processes – With control responsive to sensed condition – Concentration sensed
Reexamination Certificate
2000-04-19
2001-10-23
Smith, Duane S. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Concentration sensed
C095S188000, C095S206000, C095S237000, C096S240000, C096S417000
Reexamination Certificate
active
06306197
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to treatment systems for process exhaust streams containing isopropyl alcohol, and more particularly to a gas scrubbing system and method for removing isopropyl alcohol from a process stream.
BACKGROUND OF THE INVENTION
Isopropyl alcohol (IPA), or 2-propanol, is commonly used as a solvent and/or drying agent in many industrial applications. For example, IPA is used in deionized water in many semiconductor processing facilities to reduce surface tension in a finishing rinse to clean silicon wafers. Both liquid and gas-phase IPA-laden waste streams are often generated. Limitations are placed upon the amount of liquid IPA that may be introduced into the publicly owned treatment works (sewer), often in conjunction with the requirement to pay fees proportional to the amount of organic carbon associated with the IPA being released. In addition, the resultant IPA-laden gas stream must be treated before being discharged into the environment.
A variety of treatment mechanisms have been used to treat IPA-containing gas streams. However, none have provided a cost- and materials-effective solution. Known procedures typically have high consumption rates of water and other materials, require frequent maintenance and cleaning, or require expensive equipment and/or materials.
SUMMARY OF THE INVENTION
The present invention provides a system and method for cost-effective removal of IPA from a gas stream. The invented system includes a gas scrubber unit that receives a process gas stream containing a concentration of IPA in the gas stream and reduces the concentration of IPA therein to below a determined threshold for discharge into the atmosphere. The scrubber includes a reverse osmosis (RO) assembly that significantly reduces water consumption for the gas scrubbing process as compared to conventional once-through systems. The system may be operated at an elevated pH to prevent biofouling from inhibiting the cost-effective operation of the reverse osmosis assembly. The system may also be adapted to soften the water streams used in the system, such as to remove polyvalent cations that may cause scaling of the RO membranes, and to remove and sodium ions, which may cause salting/scaling of the pacing using in the scrubber tower.
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Boyce Allen R.
Ferrigno Michael
Mukhopadhyay Debasish
Alston & Bird LLP
SEH America Inc.
Smith Duane S.
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