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CN-122029144-A - Apparatus and condensation method

CN122029144ACN 122029144 ACN122029144 ACN 122029144ACN-122029144-A

Abstract

An apparatus and method for condensing gaseous monomer from a hot gas stream containing gaseous monomer is described. Gaseous monomers tend to undergo thermally initiated polymerization when condensed. The method includes contacting a hot gas stream flowing through a condenser in a first direction with at least one liquid jet comprising liquid monomer directed substantially against the first direction. The contacting is effective to condense the monomer in a condenser. The liquid and gaseous monomers are selected from vinyl monomers, methacrylates, and methacrylic acid.

Inventors

  • Anthony. Andrew Hutchins
  • Paul Hugh Ethan
  • Adam James Clark

Assignees

  • 三菱化学英国有限公司

Dates

Publication Date
20260512
Application Date
20240815
Priority Date
20230818

Claims (20)

  1. 1. A process for condensing gaseous monomers from a hot gas stream comprising said monomers, said monomers being susceptible to thermally initiated polymerization upon condensation, said process comprising contacting said hot gas stream flowing through a condenser in a first direction with at least one liquid jet comprising liquid monomers directed substantially against said first direction, said contacting being effective to condense said monomers in said condenser, wherein said liquid monomers and said monomers are selected from the group consisting of vinyl monomers, methacrylates, and methacrylic acid.
  2. 2. The method of claim 1, wherein the gaseous monomer is produced in a reactor and the condenser is adapted to receive a hot gas stream from the reactor.
  3. 3. An apparatus for condensing gaseous monomer from a hot gas stream comprising the gaseous monomer, the gaseous monomer being susceptible to thermally initiated polymerization upon condensation, the apparatus comprising a condenser having a hot gas inlet adapted to receive a hot gas stream and a monomer condensate outlet, the condenser being arranged such that monomer upon condensation moves towards the outlet of the condenser, a liquid-gas separation vessel in fluid communication with and downstream of the condenser, and at least one reverse injector positioned and designed to direct a liquid jet comprising liquid monomer into the condenser in a direction countercurrent to the direction of the hot gas stream passing through the condenser.
  4. 4. The process of claim 1 or 2 or the apparatus of claim 3, wherein the reactor is a depolymerization reactor effective to depolymerize a polymer into monomers, more typically a pyrolysis reactor.
  5. 5. The method of any of claims 1,2, or 4, wherein the condenser has a hot gas inlet adapted to receive the hot gas stream from the reactor and a monomer condensate outlet.
  6. 6. The process of claim 5 wherein the condenser has a temperature at its outlet below the boiling point of the monomer being condensed and typically below the boiling point at the location of the injection outlet in the condenser.
  7. 7. The method of claim 5 or 6, wherein the temperature in the condenser increases from its outlet toward its inlet.
  8. 8. The method of any of claims 5, 6 or 7, wherein the temperature in the condenser is below the boiling point of the monomer between the point where the hot gas stream contacts the liquid monomer counter-currently and its outlet.
  9. 9. A method according to any one of claims 1, 2 or 4 to 8 or an apparatus according to claim 3, wherein the condenser is arranged such that the monomer, once condensed, moves towards the outlet of the condenser, typically via the wall of the condenser.
  10. 10. The method of any one of claims 1,2 or 4 to 9 or the apparatus of claim 3, 4 or 9, wherein the liquid-gas separation vessel is positioned to receive liquid condensate flowing through the condenser and any further gaseous components, wherein the receiving is typically effected under the influence of gravity.
  11. 11. The method of any one of claims 1,2 or 4 to 10 or the apparatus of claims 3, 4 or 9 to 10, wherein the gas inlet of the condenser is located above both the reversing injector inlet and the condenser outlet such that condensed liquid on the wall of the condenser flows down the wall of the condenser to the outlet.
  12. 12. A method or apparatus according to any preceding claim, wherein the counter-flow liquid jet direction is predominantly in a direction opposite to the main hot gas flow direction.
  13. 13. A method or apparatus according to any preceding claim, wherein the relative direction of the hot gas flow and the liquid jet flow varies by at most +/-10 °, more typically by at most +/-5 °, most typically by at most +/-3 °, wherein precisely opposite relative directions are considered to be the angle of meeting of the flows, i.e. 0 °.
  14. 14. The method or apparatus of any preceding claim, wherein the hot gas stream is directed in a downward direction and the counter-current liquid jet is directed in an upward direction.
  15. 15. A method or apparatus according to any preceding claim, wherein at least 50% v/v, more typically at least 75%, most typically at least 95% v/v of the liquid jet is directed from the jet nozzle in a direction substantially countercurrent to the direction of the hot gas flow, wherein said direction may vary by up to +/-10 ° as described above.
  16. 16. A method or apparatus according to any preceding claim, wherein the liquid jet is treated by thermal cooling and/or by the addition of a stabiliser, typically the liquid in the liquid jet comprises a stabiliser, more typically the stabiliser is dissolved therein.
  17. 17. The method or apparatus of any preceding claim, wherein the concentration of stabilizer in the liquid spray is from 0 to 2500ppm, more typically from 10 to 1000ppm, most typically from 100 to 250ppm.
  18. 18. The method or apparatus of any preceding claim, wherein the concentration of monomer in the condensate from the hot gas stream is at least 60% w/w, more typically at least 70% w/w, most typically at least 80% w/w.
  19. 19. The method or apparatus of any preceding claim, wherein the concentration of monomer in the condensate of the hot gas stream may range from 60 to 100% w/w, more typically from 80 to 99% w/w, most typically from 90 to 95% w/w.
  20. 20. The method or apparatus of any preceding claim, wherein the concentration of monomer in the liquid spray is at least 60% w/w, more typically at least 70% w/w, most typically at least 80% w/w.

Description

Apparatus and condensation method Technical Field The present invention relates to a method of condensing a hot gas stream. And in particular to condensing a hot monomer gas stream comprising (meth) acrylate and (meth) acrylic acid that is susceptible to polymerization upon condensation by using reverse spraying. The invention also relates to a device implementing such a process. Background Polymer recovery is now being performed by various means. One technique that has proven effective for recycling waste polymer waste is pyrolysis. This may involve mixed and single polymer waste streams. PMMA and its various copolymers are used in a variety of applications including protective screens, signage, paints, coatings, fittings, panels, furniture, kitchen and toilet furniture, and automotive parts. After pyrolysis after end of life or other depolymerization process for regenerating (meth) acrylate and (meth) acrylic acid monomers, a crude monomer stream may be generated. Such monomer streams are unique and present special processing challenges. This stream has a high monomer concentration compared to the production of monomer from reactants of the prior art and also has variable impurities depending on the waste polymer input. Such impurities include ethyl acrylate, methyl acrylate, and methyl isobutyrate. Hot (meth) acrylate and (meth) acrylic acid monomer streams, such as alkyl (meth) acrylates, e.g., methyl methacrylate, tend to polymerize when condensed, especially at high concentrations. Polymerization can lead to fouling of process equipment and connection components, resulting in plant downtime and cleaning, and thus loss of processing time. Furthermore, the cleaning material itself may pose environmental challenges in terms of disposal. Thus, there is a need for a method of condensing and stabilizing such hot gases, as well as suitable equipment, to increase the feasibility of a polymer recovery process for the production of crude hot monomer (meth) acrylate or (meth) acrylic acid gas. US2004/0046270 uses a spray cooler with cooling liquid for hot gas mixtures containing (meth) acrylic acid. The spray is co-current with the hot gas stream and the cooling liquid is atomized in the cooling spray by means of an impingement atomizer. The hot gas mixture is relatively dilute with an acrylic acid content of up to 30%. The impact atomizer aims to solve the problem of the nozzle of the spray cooler being blocked. Atomizers of the cooling liquid produce droplet sizes of 0.1 to 0.5 mm. There is no teaching of application to higher concentration hot gas monomer streams. US2004/0129021 relates to a process for separating a (meth) acrylic acid monomer stream in a rectification column. As the vapor rises to the top of the column, it is cooled to form condensate. The cooling process uses a spray condenser in a side-spray arrangement with a discontinuous cooling gas flow. The spray angle may be 90-180 deg., but the main direction of the spray is horizontal with respect to the direction of the downward flowing air stream. The droplet diameter is less than or equal to 1000um. Once ejected from the nozzle, the cooling flow is a spray rather than a continuous liquid jet. Furthermore, the spray cooler is located in the separation vessel, not in the condenser. This can lead to problems with the polymerization of the sprayed and condensed hot gases on the container walls. EP1097742 discloses the condensation of monomers including MMA. A multi-stage condenser arrangement for initial condensation followed by further condensation of the gas vapor from the first condenser is described. Showering in a condenser is disclosed, but the direction of the showering is not indicated, and appears to be the same as the direction of the vapor to be condensed (fig. 5). US2009/0173618 uses steam injection to assist in the separation in the polycondensation reaction. The spray condenser vapor is phenol or phenol-containing vapor. The steam jet creates a vacuum to assist in separating the product from the polycondensation reaction. The applicability to monomer condensation is not disclosed. Surprisingly, it has been found that the condensation achieved by directing the liquid monomer injected in reverse towards the hot gas monomer stream is surprisingly effective in stabilizing and condensing the hot gas monomer stream and preventing polymerization. Reversing ejectors are known in other fields for assisting in the treatment of hot gases. The use of reverse jet liquid to scrub hot gases is described in US 3,803,805. The gas stream is corrosive and the process is said to be particularly useful for the efficient separation and removal of particulate and gaseous components from a hot gas stream. US20160317964A1, mendo corporation, relates to a counter-current scrubber, i.e. a counter-current ejector. The application also teaches a co-current scrubber embodiment, emphasizing that the reversing ejector is not critical to the disclosed invention. The i