Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/19—Fluorine; Hydrogen fluoride
  • C01B7/191—Hydrogen fluoride
  • C01B7/195—Separation; Purification

Definitions

• the present invention meets these needs by producing (1) an aqueous HF solution with low dissolved organic content, as well as (2) a highly concentrated HF solution, also with low dissolved organic content.
• the present invention is directed to methods and systems used to remove HF from a fluorocarbon containing process stream, and thereby forming an isolated aqueous HF solution having both a high HF concentration and low organic content.
• the process stream is scrubbed with a hot aqueous HF solution, wherein the temperature is kept at or above the dewpoint of the organic materials in the process stream, thereby preventing the dissolving of the organic materials into the isolated HF solution.
• the term "low organic content” refers to the amount of organic material remaining in the isolated aqueous HF solution as processed according to the present invention.
• the low organic content of the HF solution is less than about 500 ppm, preferably less than about 250 ppm, more preferably less than about 150 ppm, and most preferably less than about 100 ppm of organics components.
• the present invention provides methods and systems used for the removal of HF from organic process streams by means of a scrubber system designed to operate at a bottom temperature zone higher than the dewpoint condensing temperature of the organic mixture.
• the scrubber system comprises two sections; where the bottom section is scrubbed with an aqueous HF solution having a preselected concentration of HF, and the top section is scrubbed with an aqueous HF solution having a lower HF concentration than the bottom section's HF solution.
• the bottom section is operated at a temperature that is above the dewpoint condensing temperature of the organic components in the process stream being scrubbed.
• the present invention comprises a method and system in which a recycled aqueous HF solution (e.g., up to about 38% wt. HF) is contacted with an HF laden liquid organic stream to extract the HF content from the organic stream.
• a recycled aqueous HF solution e.g., up to about 38% wt. HF
• the resulting HF solution typically achieves an HF content greater than the azeotrope composition of 38% wt.
• Figure 1 shows a two-stage scrubber system useful in one process of the present invention.
• Figure 2 shows a liquid extraction unit operation useful in one process of the present invention.
• an embodiment of this invention is directed to a method and system used to remove HF from an organic product stream, using a scrubber system designed to operate at a bottom temperature zone which is higher than the dewpoint condensing temperature of the organic mixture.
• the scrubber system comprises two sections; wherein the bottom section (1) is scrubbed with aqueous HF solution operating at a higher temperature than the dewpoint condensing temperature of the organic mixture, and wherein the top section (2) is operating with an aqueous HF solution having lesser concentration than the bottom section's HF solution.
• This method and system provides a resulting aqueous HF solution which is substantially free of dissolved organics, while maintaining a high overall HF removal efficiency.
• the resulting aqueous HF solution will have a significant market outlet and it can be transported using conventional containers employed for aqueous acid service.
• the present method and system generally will limit the resulting aqueous HF solution to no more than about 38% wt. HF, due to the formation of an HF/water azeotrope composition at about this concentration level.
• This embodiment of the invention comprises a method and system in which a recycled aqueous HF solution (e.g., up to about 38% wt. HF) is contacted with an HF laden liquid organic stream to extract the HF content from the organic stream.
• a recycled aqueous HF solution e.g., up to about 38% wt. HF
• the resulting HF solution typically achieves an HF content greater than the azeotrope composition of 38% wt.
• the HF is fed to multi-stage vapor-liquid equilibrium separator.
• This device separates the HF and water mixture into two vapor streams, a first stream having an HF content greater than the 38% wt. of the azeotrope composition of HF and water (e.g., greater than 50% wt. HF); and a second aqueous HF stream having an HF content near, but still above the 38% wt. HF azeotrope composition (e.g., greater than about 40% wt. HF).
• the second aqueous HF stream (near but above the 38% wt. HF azeotrope composition) is recycled to extract more HF as described above.
• the first vapor stream rich in HF content and above the azeotrope composition of 38% wt. HF (e.g., greater than 50% wt. HF), is condensed or absorbed with water or absorbed with condensing steam to form a commercially desirable, highly concentrated, aqueous HF solution, having a concentration, for example, greater than about 40% wt. HF.
• the absorbing step is carried out in a multi-stage absorber where the emerging HF solution is kept hot (e.g., near or above the dewpoint of the organics) to eliminate dissolving organic in the product HF solution.
• the vapor leaving the multistage absorber will contain organic and a significant amount of HF. This organic stream can be recaptured and recycled to extract the HF content as described above.
• This method will afford a resulting aqueous HF solution which is substantially free of dissolved organics and has a higher HF concentration, while maintaining high overall HF removal efficiency from the organic stream.
• the resulting aqueous HF solution will have wider market outlet and can be transported with conventional container for aqueous acid service.
• a 38% HF solution at about 150°F is circulated to the top section of the second stage of the two-stage scrubber system. Most of the HF in the organic stream is removed by this hot circulating HF solution.
• the resulting hot HF solution contains a low level, i.e., less than about 500 ppm, preferably less than about 250 ppm, more preferably less than about 150 ppm, and most preferably less than about 100 ppm of dissolved organics. This material may be isolated from this stage of the two-stage scrubber system and is suitable for sale or other use as desired.
• liquid fluorocarbon organic mixture (3) having a dewpoint condensing temperature of 90°F and containing 200 lb/hr HF, is combined with a small recycle stream of organics and HF (27).
• the resultant stream (20) is mixed with 1,500 lb/hr 39% wt. recycle HF solution (25). It is then phase separated at below 50°F.
• this system is known as a liquid extraction unit operation. The extraction can be conducted as a single stage as described, or it can be of multi-stage contactors to enhance the extraction efficiency.
• This solution (24) is then heat economized, cooled, and recycled (25) to extract more HF from the incoming liquid organic stream.
• the overhead vapor gas (23) is sent to a multi-stage absorber with optional condenser.
• Water or steam (26) is introduced at various locations of the absorber to absorb or condensed HF into 50% wt. solution (28). If higher concentration is desired, then less water or steam is added.
• the bottom of the absorber is kept above 150°F to strip off the organics.
• the resulting hot HF solution product (28) contains a low level of dissolved organic and can be sent out for sales after cooling.
• the vapor (27) leaving the multistage absorber will contain organic and significant amount of HF.
• This organic stream (27) can be re-captured and recycled to extract its HF content.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Gas Separation By Absorption (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Extraction Or Liquid Replacement (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

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• 2011
  • 2011-09-26 US US13/245,394 patent/US9309116B2/en active Active
• 2012
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• 2017
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