Method for the recovery and re-use of process gases
The present invention relates to methods and systems for processing an exhaust stream containing a recyclable component mixed with other components and impurities to produce a high purity product that contains all of the recyclable component. One or more waste streams containing none of the recyclable component are also produced. The present invention particularly relates to the recovery of valuable recyclable components used in the manufacture of semiconductor devices.
1. A method for the recovery of process gas, comprising:
scrubbing a gas exhaust stream containing the process gas with water in a first scrubber to obtain a first scrubbed stream;
scrubbing the first scrubbed stream with a water containing solution in a catalyst bed in a second scrubber to obtain a second scrubbed stream;
compressing the second scrubbed stream;
drying the second scrubbed stream in a heat exchanger process;
filtering the second scrubbed stream to obtain a dry compressed stream;
further drying the dry compressed stream to obtain an ultra-dry stream;
cooling the ultra-dry stream to obtain a liquid reflux stream enriched in the process gas and a vapor stream depleted in the process gas;
distilling the liquid reflux stream to recover a substantially pure process gas.
2. A method according to claim 1 , further comprising treating the vapor stream to recover trace amounts of the process gas and a vent stream free of process gas.
3. A method according to claim 1 , wherein the process gas is Xe, Kr, CF 4 , C 2 F 6 , SF 6 , or NH 3 .
4. A method according to claim 1 , wherein the water containing solution is KOH, NaOH or H 2 O 2 .
5. A method according to claim 1 , wherein the catalyst bed is an activated carbon catalyst bed or a hydrophilic activated carbon catalyst bed.
6. A method according to claim 1 , wherein further drying comprises drying in a membrane dryer.
7. A method according to claim 6 , wherein a portion of the dry compressed stream is used as a purge gas for the membrane dryer.
8. A method according to claim 7 , further comprising returning the dry compressed stream used as a purge gas to the first scrubber.
9. A method according to claim 1 , wherein further drying comprises a pressure swing adsorption process using an adsorbent.
10. A method according to claim 1 , cooling the ultra-dry stream comprising cooling to a temperature less than 16 degrees above the freezing temperature of the process gas.
11. A method according to claim 10 , wherein the temperature is less than 3 degrees above the freezing temperature of the process gas.
12. A method according to claim 1 , wherein distilling comprises stripping high volatility impurities from the liquid reflux stream to obtain a substantially pure liquid reflux stream and further comprising vaporizing the substantially pure liquid reflux steam to obtain the substantially pure process gas.
13. A method according to claim 1 , wherein distilling comprises removing high volatility impurities in a first distillation column and removing low volatility impurities in a second distillation column.
14. A method according to claim 1 , further comprising treating the vapor steam to separate any trace amounts of process gas.
15. A method according to claim 14 , wherein treating comprises a pressure swing adsorption process or a molecular sieve.
16. A method according to claim 1 , wherein the gas exhaust stream comes from a semiconductor process.