Process for improving propylene recovery from FCC recovery unit

Patent metadata

Field	Value
Publication number	US-10487271-B2
Application number	US-201815994906-A
Country	US
Kind code	B2
Filing date	May 31, 2018
Priority date	Dec 16, 2015
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

The present subject matter relates generally to processes for propylene recovery. More specifically, the present subject matter relates to processes for enhanced recovery of propylene and liquid petroleum gas (LPG) from the fuel gas produced in fluid catalytic cracking (FCC) units by minimizing the light ends and propylene in the unstabilized gasoline which is used as lean oil for the primary absorber of the FCC gas concentration unit.

First claim

The invention claimed is:

1. A process for the recovery of propylene comprising:
(i) contacting a hydrocarbon feed with a catalyst in a fluid catalytic cracking process to produce a product stream;
(ii) distilling the product stream in a fractionator to obtain heavier liquid products as side/bottom draws and a gaseous top product;
(iii) cooling and condensing the gaseous top product and thereafter, separating the obtained gas-liquid mixture in a receiver to obtain a liquid fraction and a lighter gaseous fraction;
(iv) sequentially sending the gaseous fraction obtained from step (iii) to a wet gas compressor train;
(v) feeding a first portion of the liquid fraction obtained in step (iii) back to the fractionator;
(vi) feeding a second portion of the liquid fraction obtained in step (iii) to at least one heat exchanger to produce a heated stream; and
(vii) feeding the heated stream to a flash drum to produce a flashed light ends stream to be sent back to the wet gas compressor in step (iv) and a bottoms liquid stream wherein the bottoms stream is sent to one or more heat exchangers in step (vi) before routing the liquid stream to FCC gas concentration absorber.

2. The process of claim 1 wherein the one or more heat exchangers heats the liquid fraction from about 38° C. to about 80° C.

3. The process of claim 1 wherein the flashed light ends stream contains nearly 70% of the propylene in the flash drum feed.

4. The process of claim 1 wherein one or more of the heat exchanges uses a waste heat process stream.

5. The process of claim 1 wherein two heat exchangers are used to heat the liquid fraction.

6. A process for the recovery of propylene comprising:
(i) contacting a hydrocarbon feed with a catalyst in a fluid catalytic cracking process to produce a product stream;
(ii) distilling the product stream in a fractionator to obtain heavier liquid products as side/bottom draws and a gaseous top product;
(iii) cooling and condensing the gaseous top product and thereafter, separating the obtained gas-liquid mixture in a receiver to obtain a liquid fraction and a lighter gaseous fraction;
(iv) sequentially sending the gaseous fraction obtained from step (iii) to a wet gas compressor;
(v) feeding a first portion of the liquid fraction obtained in step (iii) back to the fractionator;
(vi) feeding a second portion of the liquid fraction obtained in step (iii) to at least one heat exchanger to produce a heated stream; and
(vii) feeding the heated stream to a split shell flash drum having a first side and a second side wherein the heated stream is sent to the first side of the split shell to produce a first flashed light ends stream to be sent back to the wet gas compressor in step (iv) and a first bottoms stream wherein the bottoms stream is heated and sent to the second side of the split shell flash drum to produce a second flashed light ends stream to be sent back to the wet gas compressor in step (iv) and a second bottoms stream wherein the second bottoms stream is sent to one or more heat exchangers in step (vi) before routing liquid stream to FCC gas concentration absorber.

7. The process of claim 6 wherein the one or more heat exchangers heats the liquid fraction from about 38° C. to about 80° C.

8. The process of claim 6 wherein the flashed light ends stream contains nearly 70% of the propylene in the flash drum feed.

9. The process of claim 6 wherein one or more of the heat exchanges uses a waste heat process stream.

10. The process of claim 6 wherein two heat exchangers are used to heat the liquid fraction.

Assignees

• Uop Llc

Inventors

• Qafisheh Jibreel A
• Cabanaw Boyd E

Classifications

• C10G2400/20

  C2-C4 olefins · CPC title

• C10G70/043

  by fractional condensation · CPC title

• C10G70/041

  by distillation · CPC title

• C10L3/12

  Liquefied petroleum gas {(liquefying by pressure and cold treatment F25J)} · CPC title

• C10L2290/30

  Pressing, compressing or compacting · CPC title