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EP-4741368-A1 - STYRENE RESIDUE RECYCLE PROCESSES AND RELATED SYSTEMS

EP4741368A1EP 4741368 A1EP4741368 A1EP 4741368A1EP-4741368-A1

Abstract

Systems and methods for purifying styrene monomer may include a styrene prefractionation system, a styrene finishing system, and a residue recycle processer. The residue recycle processer may heat and separate a residue stream from the styrene finishing system to produce a residue recycle stream with lower concentrations of C 9 and C 10 aromatic hydrocarbons therein compared to the residue stream. The residue recycle stream may be recycled back to the styrene prefractionation system. Such systems and methods for purifying styrene monomer may have less energy consumption, lower polymerization inhibitor dosage, less air pollution, and/or less equipment fouling.

Inventors

  • HUBBELL, DOUGLAS STUART

Assignees

  • Technip Energies France

Dates

Publication Date
20260513
Application Date
20241111

Claims (15)

  1. A system comprising: a styrene finishing system configured to receive a first portion of a styrene-rich stream from a styrene prefractionation system and produce a styrene monomer product, a residue stream, and a net heavy by-product stream; a residue recycle processor configured to process a second portion of the styrene-rich stream from the styrene prefractionation system and the residue stream from the styrene finishing system to produce an overhead vapor stream and a residue recycle stream; and wherein the styrene finishing system is further configured to receive the overhead vapor stream; and wherein the styrene prefractionation system is configured to receive the residue recycle stream from the residue recycle processer.
  2. The system of claim 1, wherein the residue recycle stream comprises 15 wt% or less of styrene and 0.10 wt% or greater of a polymerization inhibitor.
  3. The system of any preceding claim, wherein the second portion of the styrene-rich stream comprises 90 wt% or greater of styrene.
  4. The system of any preceding claim, wherein the residue recycle processor comprises a residue recycle reboiler and a residue recycle drum, wherein the residue recycle reboiler is configured to receive and heat the second portion of the styrene-rich stream from the styrene prefractionation system and the residue stream from the styrene finishing system as a combined stream to produce a partially vaporized stream, wherein the residue recycle drum is configured to receive and separate the partially vaporized stream to produce the overhead vapor stream and a bottoms liquid stream, and wherein at least a portion of the bottoms liquid stream is the residue recycle stream.
  5. The system of claim 4, wherein the system is further configured to mix a portion of the bottoms liquid stream with the residue stream and/or the second portion of the styrene-rich stream upstream of the residue recycle reboiler.
  6. The system of any preceding claim, wherein the styrene finishing system comprises one or more distillation finishing columns, one or more reboilers, and one or more drums.
  7. The system of any preceding claim, wherein the overhead vapor stream is a first overhead vapor stream, wherein the bottoms liquid stream is a first bottoms liquid stream, and wherein the styrene finishing system comprises: a distillation finishing column configured to receive the first portion of the styrene-rich stream from the styrene prefractionation system and the first overhead vapor stream from the residue recycle processor and to produce a second overhead vapor stream and a second bottoms liquid stream; and a residue reboiler and a residue flash drum in series configured to receive the second bottoms liquid stream and to produce a third overhead vapor stream and a third bottoms liquid stream, wherein the system is configured to split the third bottoms liquid stream to produce the residue stream and the net heavy by-product stream.
  8. A method comprising: purifying a first portion of a styrene-rich stream from a styrene prefractionation system in a styrene finishing system to produce a styrene monomer product, a residue stream, and a net heavy by-product stream; separating at least a portion of the residue stream using a second portion of the styrene-rich stream as a stripping agent to yield an overhead vapor stream and a bottoms liquid stream; recycling the overhead vapor stream to the styrene finishing system; and recycling at least a portion of the bottoms liquid stream as a residue recycle stream to the styrene prefractionation system.
  9. The method of claim 8, wherein the residue stream comprises 15 wt% or less of styrene and 0.10 wt% or greater of a polymerization inhibitor.
  10. The method of claim 8 or 9, wherein the second portion of the styrene-rich stream comprises 90 wt% or greater of styrene.
  11. The method of any one of claims 8-10, wherein the second portion of the styrene-rich stream is up to 25 wt% of the styrene-rich stream.
  12. The method of any one of claims 8-11, wherein a percent reduction of alpha-methylstyrene in the residue recycle stream compared to the residue stream is 50% or greater.
  13. The method of any one of claims 8-12, wherein a percent reduction of divinylbenzene in the residue recycle stream compared to the residue stream is 40% or greater.
  14. The method of any one of claims 8-13, wherein a weight ratio of the residue stream to the net heavy by-product stream is 0.5:1 to 10:1.
  15. The method of any one of claims 8-14, wherein a weight ratio of the second portion of the styrene-rich stream to the residue stream is 0.1:1 to 10:1.

Description

Technical Field The present disclosure relates generally to chemical processing and, more particularly (although not necessarily exclusively), to purifying styrene monomer with less energy consumption, lower polymerization inhibitor dosage, less air pollution, and/or less equipment fouling. Background Styrene monomer manufacturing produces a crude styrene stream from a dehydrogenation section. The compounds lighter than styrene may be stripped in one or more distillation columns, hereinafter collectively referred to as a styrene prefractionation system. The remaining stream, including styrene monomer and less volatile impurities, is fed to a styrene finishing system, which typically starts with a distillation finishing column that has a reboiler and condenser, operates under vacuum, and recovers a final styrene monomer product as distillate. The heavier impurities in this stream include C9 aromatic hydrocarbons (such as propylbenzene and methylstyrene isomers), C10 aromatic hydrocarbons (such as diethylbenzene and divinylbenzene isomers), multiple-ring aromatics that are less volatile than styrene (primarily condensation products of styrene, including stilbene), and styrene polymer. One or more types of polymerization inhibitor compounds are added typically to the styrene prefractionation system to reduce the loss of styrene to polymer (polystyrene) during distillation. The inhibitors that are slow to react but provide extended inhibition time are also referred to as retarders. These inhibitors typically have nitrogen in their molecules. Because the net residue of a styrene process may be burned to recover its fuel value, use of these polymerization inhibitors may result in emissions of harmful nitrogen oxides to the environment. The bottoms stream from the distillation finishing column is typically partially vaporized in a residue reboiler (e.g., a steam-heated exchanger) and fed to a residue flash drum where the vapor is separated from the liquid and fed back to the distillation finishing column. This residue flash drum liquid contains most of the low-volatility (heavy) by-products of the styrene process, as well as residual styrene, typically at a concentration of about 5.0 wt%. A portion of this liquid from the residue flash drum may be optionally recycled to the styrene prefractionation system upstream of the styrene finishing system to reuse residual active polymerization inhibitors, especially the retarder. The rest of the liquid is the net heavy by-product stream (residue) of the styrene process. Summary One or more embodiments include a system comprising: a styrene finishing system configured to receive a first portion of a styrene-rich stream from a styrene prefractionation system and produce a styrene monomer product, a residue stream, and a net heavy by-product stream; a residue recycle processor configured to process a second portion of the styrene-rich stream from the styrene prefractionation system and the residue stream from the styrene finishing system to produce an overhead vapor stream and a residue recycle stream; and wherein the styrene finishing system is further configured to receive the overhead vapor stream; and wherein the styrene prefractionation system is configured to receive the residue recycle stream from the residue recycle processer. One or more embodiments include the system of the previous paragraph, wherein the residue recycle stream comprises 15 wt% or less of styrene and 0.10 wt% or greater of a polymerization inhibitor. One or more embodiments include the system of any previous paragraph, wherein the second portion of the styrene-rich stream comprises 90 wt% or greater of styrene. One or more embodiments include the system of any previous paragraph, wherein the residue recycle processor comprises a residue recycle reboiler and a residue recycle drum, wherein the residue recycle reboiler is configured to receive and heat the second portion of the styrene-rich stream from the styrene prefractionation system and the residue stream from the styrene finishing system as a combined stream to produce a partially vaporized stream, wherein the residue recycle drum is configured to receive and separate the partially vaporized stream to produce the overhead vapor stream and a bottoms liquid stream, and wherein at least a portion of the bottoms liquid stream is the residue recycle stream. One or more embodiments include the system of any previous paragraph, wherein the styrene finishing system comprises one or more distillation finishing columns, one or more reboilers, and one or more drums. One or more embodiments include the system of any previous paragraph, wherein the overhead vapor stream is a first overhead vapor stream, wherein the bottoms liquid stream is a first bottoms liquid stream, and wherein the styrene finishing system comprises: a distillation finishing column configured to receive the first portion of the styrene-rich stream from the styrene prefractionation system