Ethane recovery and ethane rejection methods and configurations

Patent metadata

Field	Value
Publication number	US-9557103-B2
Application number	US-201113996805-A
Country	US
Kind code	B2
Filing date	Dec 15, 2011
Priority date	Dec 23, 2010
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

Contemplated plants for flexible ethane recovery and rejection by allowing to switch the top reflux to the demethanizer from residue gas to the deethanizer overhead product and by controlling the flow ratio of feed gas to two different feed gas exchangers. Moreover, the pressure of the demethanizer is adjusted relative to the deethanizer pressure for control of the ethane recovery and rejection.

First claim

What is claimed is:

1. A method of flexibly recovering ethane from a feed gas, comprising:
expanding the feed gas in a turbo expander to produce a partially expanded feed gas;
cooling and additionally expanding a first portion of the partially expanded feed gas to produce a second reflux;
cooling a second portion of the partially expanded feed gas to produce a partially condensed feed stream;
separating the partially condensed feed stream into a vapor stream and a liquid stream;
expanding the vapor stream and the liquid stream prior to feeding into a demethanizer;
using a demethanizer side reboiler in cooling a third portion of the partially expanded feed gas to produce a cooled feed stream;
combining the cooled feed stream with the partially condensed feed stream;
feeding into the demethanizer a top reflux and the second reflux below the top reflux, wherein the demethanizer produces a demethanizer bottom product and a demethanizer overhead product;
feeding at least part of the demethanizer bottom product to a demethanizer to produce a demethanizer bottom product and a demethanizer overhead product; and
feeding a portion of the demethanizer overhead product back to the demethanizer as the top reflux during ethane recovery, and feeding a portion of the demethanizer overhead product back to the demethanizer as the top reflux during ethane rejection;
wherein flow of the third portion of the partially expanded feed gas to the demethanizer side reboiler is decreased relative to flow of the first portion and the second portion of the partially expanded feed gas during ethane rejection.

2. The method of claim 1 , wherein the demethanizer is operated at a higher pressure than the deethanizer during ethane recovery, and wherein the demethanizer is operated at a lower pressure than the demethanizer during ethane rejection.

3. The method of claim 1 , wherein a propane recovery of at least 99% is achieved during ethane recovery and during ethane rejection.

4. The method of claim 1 , wherein an ethane recovery of at least 95% is achieved during ethane recovery.

Assignees

• Mak John
• Fluor Tech Corp

Inventors

• Mak John

Classifications

• F25J2200/78

  Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column · CPC title

• F25J2215/60

  Methane · CPC title

• F25J3/0228

  characterised by the separated product stream · CPC title

• F25J2240/02

  Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream · CPC title

• F25J2215/62

  Ethane or ethylene · CPC title