Method and apparatus for recycling heptafluoroisobutyronitrile
A method and device for purifying heptafluoroisobutyronitrile and a dilution gas from a used gas mixture comprising heptafluoroisobutyronitrile, a dilution gas and arcing by-products. The method comprising the steps of (a) contacting the used gas mixture with at least one adsorbent material to generate a gas stream depleted in arcing by-products; (b) contacting the gas stream depleted in by-products with a first membrane to obtain a first permeate stream rich in the dilution gas, and a first retentate stream rich in heptafluoroisobutyronitrile; (c) contacting the first permeate stream rich in the dilution gas with a second membrane to obtain a second permeate stream rich in the dilution gas and a second retentate stream rich in heptafluoroisobutyronitrile; and (d) combining the first and second retentate streams rich in heptafluoroisobutyronitrile.
1. An apparatus for purifying heptafluoroisobutyronitrile and a dilution gas from a used gas mixture comprising heptafluoroisobutyronitrile, a dilution gas and arcing by-products, the apparatus comprising
at least one adsorbent unit configured to remove a first group of arcing by-products from the used gas mixture, yielding a stream depleted from by-products;
a first membrane separation unit configured to separate the used gas mixture depleted from arcing by-products into a first permeate stream and a first retentate stream, wherein the first membrane separation unit comprises a first membrane unit feed inlet, a first membrane unit permeate gas outlet and a first membrane unit retentate gas outlet, wherein the first membrane unit feed inlet is downstream from the at least one adsorbent unit;
a second membrane separation unit configured to separate the first permeate stream into a dilution gas mixture and by-products, wherein the second membrane separation unit comprises a second membrane unit feed inlet, a second membrane unit permeate gas outlet and a second membrane unit retentate gas outlet, wherein the second membrane unit feed inlet is downstream from the first membrane unit permeate gas outlet; and
a metal organic framework material unit downstream of the first membrane separation unit.
2. The apparatus of claim 1 , further comprising a compressor unit disposed upstream from first membrane separation unit for compressing the gas stream depleted of by-products.
3. The apparatus of claim 1 , wherein the first and/or second membrane separation unit comprises a membrane selected from the group consisting of polyimides, polyamides, polyamide-imides, polyesters, polycarbonates, polysulfones, polyethersulfone, polyetherketone, alky substituted aromatic polyesters, and blends of polyethersulfone, aromatic polyimides, aromatic polyamides, polyamide-imides, fluorinated aromatic polyimide, polyamide and polyamide-imides.
4. The apparatus of claim 1 , further comprising at least one adsorbent unit downstream from the second membrane separation unit.
5. The apparatus of claim 4 , wherein the adsorbent unit absorbent is selected from the group consisting of molecular sieves, soda lime, and activated alumina.
6. The apparatus of claim 1 , wherein the apparatus further comprises a metal-organic framework material unit downstream from the first membrane separation unit.
7. A method of purifying heptafluoroisobutyronitrile and a dilution gas from a used gas mixture comprising heptafluoroisobutyronitrile, a dilution gas and arcing by-products, the method comprising:
contacting the used gas mixture with at least one adsorbent material to generate a gas stream depleted in arcing by-products;
contacting the gas stream depleted in by-products with a first membrane and a metal organic framework material unit downstream of the first membrane separation unit to obtain a first permeate stream rich in the dilution gas, and a first retentate stream rich in heptafluoroisobutyronitrile;
contacting the first permeate stream rich in the dilution gas with a second membrane to obtain a second permeate stream rich in the dilution gas and a second retentate stream rich in heptafluoroisobutyronitrile; and
combining the first and second retentate streams rich in heptafluoroisobutyronitrile.
8. The method of claim 7 , wherein the method further comprises contacting the used gas mixture with a particle filter to remove particulate matter.
9. The method of claim 7 , wherein the method further comprises contacting the combined retentate streams rich in heptafluoroisobutyronitrile with a humidity filter.
10. The method of claim 7 , wherein the method further comprises contacting a dehumidified stream rich in heptafluoroisobutyronitrile with an adsorbent material.
11. The method of claim 7 , wherein the dilution gas comprises CO 2 and O 2 .
12. The method of claim 7 , wherein the method further comprises contacting the second permeate stream rich in the dilution gas with a metal-organic framework material to obtain a gas stream depleted in CO.
13. The method of claim 7 , wherein the first and/or second membrane is selected from the group consisting of polyimides, polyamides, polyamide-imides, polyesters, polycarbonates, polysulfones, polyethersulfone, polyetherketone, alky substituted aromatic polyesters, and blends of polyethersulfone, aromatic polyimides, aromatic polyamides, polyamide-imides, fluorinated aromatic polyimide, polyamide and polyamide-imides.