Method for removing a foulant from a gas stream with minimal external refrigeration

Patent metadata

Field	Value
Publication number	US-10882001-B2
Application number	US-201715450674-A
Country	US
Kind code	B2
Filing date	Mar 6, 2017
Priority date	Mar 6, 2017
Publication date	Jan 5, 2021
Grant date	Jan 5, 2021

Abstract

A process for removing a foulant from a gas stream. The gas stream is cooled in a series of heat exchangers, causing a portion of the foulant to desublimate and become entrained in a cryogenic liquid. This foulant slurry stream is pressurized, cooled, and separated into a pressurized foulant solid stream and the cryogenic liquid stream. The pressurized foulant solid stream is melted to produce a liquid foulant stream. Heat exchange processes, both internal and external, are provided that close the heat balance of the process. In this manner, the foulant is removed from the gas stream.

First claim

The invention claimed is:

1. A process for removing a foulant from a gas stream, the process comprising:
cooling the gas stream having the foulant in a first heat exchanger to a first temperature that is above a frosting point of the foulant to form a cooled gas stream;
cooling the cooled gas stream in a second heat exchanger against a cryogenic liquid stream to a second temperature that is below the frosting point of the foulant, wherein a portion of the foulant within the cooled gas stream de-sublimates, thereby forming a foulant depleted gas stream and a solid foulant stream, the solid foulant stream becoming entrained in the cryogenic liquid stream, forming a foulant slurry stream;
withdrawing the foulant slurry stream from the second heat exchanger;
withdrawing the foulant depleted gas stream from the second heat exchanger;
pressurizing the foulant slurry stream and cooling the foulant slurry stream across a third heat exchanger to produce a pressurized foulant slurry stream that is at or exceeds the triple point of the foulant;
separating the pressurized foulant slurry stream into a pressurized foulant solid stream and the cryogenic liquid stream;
melting the pressurized foulant solid stream in a melting heat exchanger to produce a liquid foulant stream;
heating the liquid foulant stream in the first heat exchanger to form a warmed foulant fluid stream;
providing the warmed foulant fluid stream to a side inlet of a distillation column, wherein the distillation column separates the warmed foulant fluid stream into a cooled liquid overhead foulant stream and a warmed cryogenic liquid stream;
providing the cooled liquid overhead foulant stream to the melting heat exchanger to warm the pressurized solid foulant stream, causing the cooled liquid overhead foulant stream to cool into an overhead foulant stream, wherein a portion of the overhead foulant stream is recycled to a top inlet of the distillation column, while the remainder of the overhead foulant stream is removed;
providing a portion of the warmed cryogenic liquid stream to a recycle warming heat exchanger, while the balance of the warmed cryogenic liquid stream is cooled across the first heat exchanger to become a cooled cryogenic liquid recycle stream, wherein the recycle warming heat exchanger warms the portion of the cooled cryogenic liquid stream before returning the portion of the warmed cryogenic liquid stream to a bottom inlet of the distillation column;
providing a first portion of external refrigeration to the first heat exchanger and the third heat exchanger using a first reverse Rankine refrigeration cycle having a first refrigerant, wherein the first reverse Rankine refrigeration cycle comprises the steps of:
a. compressing the first refrigerant;
b. condensing the first refrigerant;
c. expanding the first refrigerant;
d. vaporizing the first refrigerant;
wherein step (b) occurs in the first heat exchanger, at a third temperature near the foulant triple point such that the first refrigerant condenses,
wherein step (d) occurs in the third heat exchanger;

whereby the foulant is removed from the gas stream.

2. The method of claim 1 , wherein the cooled cryogenic liquid recycle stream recombines in a location comprising the second heat exchanger, the third heat exchanger, or the foulant slurry stream.

3. The method of claim 1 , wherein the foulant depleted gas stream is warmed across the first heat ex-changer.

4. The method of claim 1 , wherein step (b) also includes a supplemental ambient heat exchange process before the first heat exchanger.

5. The method of claim 1 , wherein step (d) also includes the first heat exchanger.

6. The method of claim 1 , wherein the first refrigerant comprises ethane, methane, propane, R14, refrigerants, or combinations thereof.

7. The method of claim 6 , wherein a storage tank is provided to store excess amounts of the first refrigerant.

8. The method of claim 1 , wherein a second portion of external refrigeration is provided to the first heat exchanger using a second reverse Rankine refrigeration cycles having a second refrigerant, wherein the second reverse Rankine refrigeration cycle comprises the steps of:
a. compressing the second refrigerant;
b. condensing the second refrigerant;
c. expanding the second refrigerant;
d. vaporizing the second refrigerant;
wherein step (b) occurs in the first heat exchanger;
wherein step (d) occurs in the first heat exchanger.

9. The method of claim 8 , wherein step (b) also includes a supplemental ambient heat exchange process.

10. The method of claim 8 , wherein the second refrigerant comprises ethane, methane, propane, R14, refrigerants, or combinations thereof.

11. The method of claim 8 , wherein step (b) also includes at least two ambient heat exchangers in parallel before the first heat exchanger.

12. The method of claim 11 , wherein the at least two ambient heat exchangers operate at different pressures, the different pressures matching different portions of a heat exchange process curve for the second refrigerant.

13. The method of claim 1 , wherein the foulant product is provided to a separation vessel and separated into an overhead vapor foulant product stream and a bottoms liquid foulant product stream; the bottoms liquid foulant product stream is removed and pressurized; the overhead vapor foulant product stream is removed, compressed, and then warmed across the first heat exchanger and recombined with the bottoms liquid foulant product stream and pressurized and cooled across the first heat exchanger.

14. The method of claim 1 , wherein the foulant product is provided to a separation vessel and separated into an overhead vapor foulant product stream and a bottoms liquid foulant product stream; the bottoms liquid foulant product stream is removed and pressurized; the overhead vapor foulant product stream is warmed across the first heat exchanger, compressed, cooled across the first heat exchanger, and then combined with the bottoms foulant product stream before being pressurized and warmed across the first heat exchanger.

15. The method of claim 1 , wherein the cryogenic liquid comprises 1,1,3-trimethylcyclopentane, 1,4-pentadiene, 1,5-hexadiene, 1-butene, 1-methyl-1-ethylcyclopentane, 1-pentene, 2,3,3,3-tetrafluoropropene, 2,3-dimethyl-1-butene, 2-chloro-1,1,1,2-tetrafluoroethane, 2-methylpentane, 3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-methylpentane, 4-methyl-1-hexene, 4-methyl-1-pentene, 4-methylcyclopentene, 4-methyl-trans-2-pentene, bromochlorodifluoromethane, bromodifluoromethane, bromotrifluoroethylene, chlorotrifluoroethylene, cis 2-hexene, cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene, dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl ether, dimethyl ether, ethyl fluoride, ethyl mercaptan, hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan, isopentane, isoprene, methyl isopropyl ether, methylcyclohexane, methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine, octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane, sec-butyl mercaptan, trans-2-pentene, trifluoromethyl trifluorovinyl ether, vinyl chloride, bromotrifluoromethane, chlorodifluoromethane, dimethyl silane, ketene, methyl silane, perchloryl fluoride, propylene, vinyl fluoride, or combinations thereof.

16. The method of claim 1 , wherein the foulant comprises carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons with a freezing point above a temperature of the cryogenic liquid, or combinations thereo

Assignees

• Baxter Larry
• Mansfield Eric
• Hoeger Christopher
• Hall Labs Llc

Inventors

• Baxter Larry
• Mansfield Eric
• Hoeger Christopher

Classifications

• F25J2205/90

  Mixing of components · CPC title

• B01D2258/0283

  Flue gases · CPC title

• B01D2257/404

  Nitrogen oxides other than dinitrogen oxide · CPC title

• F25J2205/30

  using a washing, e.g. "scrubbing" or bubble column for purification purposes · CPC title

• F25J2210/70

  Flue or combustion exhaust gas · CPC title