Methods for removal of moisture from LNG refrigerant

Patent metadata

Field	Value
Publication number	US-11415348-B2
Application number	US-202016735036-A
Country	US
Kind code	B2
Filing date	Jan 6, 2020
Priority date	Jan 30, 2019
Publication date	Aug 16, 2022
Grant date	Aug 16, 2022

Abstract

Methods and systems for removing moisture from refrigerant that use a desiccant-based moisture removal unit can be used in the production of liquid natural gas (LNG). For example, a method can include: compressing a refrigerant; conveying at least a portion of the refrigerant to a moisture removal unit comprising a desiccant to form dehydrated refrigerant; cooling and condensing the dehydrated refrigerant to provide a cooled dehydrated liquid refrigerant; conveying the cooled dehydrated refrigerant to a heat exchanger; and passing a LNG stream rich in methane through the heat exchanger to cool at least part of the LNG stream by indirect heat exchange with the cooled dehydrated refrigerant.

First claim

The invention claimed is:

1. A system comprising:
a refrigerant compressor;
a refrigerant condenser;
a moisture removal unit comprising a desiccant; and
a heat exchanger that are fluidly connected in a refrigeration circuit in which the refrigerant compressor is upstream of the moisture removal unit, the moisture removal unit is upstream of the refrigerant condenser, the refrigerant condenser is upstream of the heat exchanger, and the heat exchanger is upstream of the refrigerant compressor;
wherein the refrigeration circuit is split into a first stream passing through the moisture removal unit and a second stream passing through a conduit bypassing the moisture removal unit.

2. The system of claim 1 , further comprising a valve capable of directing the second stream through the conduit.

3. The system of claim 2 , wherein the moisture removal unit is removably attached to the refrigeration circuit.

4. The system of claim 1 , wherein the moisture removal unit contains a packed bed of the desiccant.

5. The system of claim 1 , wherein the desiccant is selected from the group consisting of silica, activated charcoal, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof.

6. The system of claim 1 , further comprising:
a refrigerant source fluidly connected to the refrigeration circuit.

7. The system of claim 1 , further comprising a moisture analysis unit downstream of the moisture removal unit, the moisture analysis unit measuring a dew point of a refrigerant within the refrigeration circuit, and the moisture analysis unit comprising a chilled mirror over which the refrigerant is conveyed and formation of condensate upon the chilled mirror is detectable by a change in light reflecting off the chilled mirror.

8. A method comprising:
conveying a refrigerant stream from a refrigerant compressor, a first portion of the refrigerant stream being conveyed to a moisture removal unit containing a desiccant and a second portion of the refrigerant stream being conveyed through a conduit that bypasses the moisture removal unit;
conveying the first portion of the refrigerant stream through the moisture removal unit;
rejoining the first portion of the refrigerant stream with the second portion of the refrigerant stream to form a rejoined refrigerant stream; and
conveying the rejoined refrigerant stream to a refrigerant condenser.

9. The method of claim 8 , wherein the desiccant is selected from the group consisting of silica, activated charcoal, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof.

10. A method comprising:
compressing a refrigerant;
conveying a first portion of the refrigerant after compression thereof through a moisture removal unit containing a desiccant to form dehydrated refrigerant;
conveying a second portion of the refrigerant after compression thereof through a conduit that bypasses the moisture removal unit;
rejoining the first portion of the refrigerant with the second portion of the refrigerant downstream from the moisture removal unit to form a rejoined refrigerant stream comprising the dehydrated refrigerant;
cooling and condensing the rejoined refrigerant stream comprising the dehydrated refrigerant to provide a cooled dehydrated liquid refrigerant;
conveying the cooled dehydrated liquid refrigerant to a heat exchanger; and
passing a liquid natural gas (LNG) stream comprising at least methane through the heat exchanger to cool at least part of the LNG stream by indirect heat exchange with the cooled dehydrated liquid refrigerant.

11. The method of claim 10 , wherein the desiccant is selected from the group consisting of silica, activated charcoal, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof.

12. The method of claim 10 , wherein the LNG stream comprises 87 percent by mole to 97 percent by mole methane.

13. The method of claim 10 , wherein the moisture removal unit is removably attached to a conduit extending between a compressor that compresses the refrigerant and the moisture removal unit.

14. The method of claim 10 , further comprising conveying at least a portion of the dehydrated refrigerant to a moisture analysis unit downstream of the moisture removal unit, the moisture analysis unit measuring a dew point of the dehydrated refrigerant, and the moisture analysis unit comprising a chilled mirror over which the dehydrated refrigerant is conveyed and formation of condensate upon the chilled mirror is detectable by a change in light reflecting off the chilled mirror.

Assignees

• Exxonmobil Upstream Res Co

Inventors

• Kenefake Daryl A
• Tatarzyn Jeffrey
• Amhed Waleed H

Classifications

• F25B2500/14

  the presence of moisture in a refrigeration component or cycle · CPC title

• F25J1/0052

  by vaporising a liquid refrigerant stream · CPC title

• B01D2251/608

  Sulfates · CPC title

• F25J1/025

  Details related to the refrigerant production or treatment, e.g. make-up supply from feed gas itself · CPC title

• F25J1/0022 Primary

  Hydrocarbons, e.g. natural gas · CPC title