US 11,378,333 B2Granted

System and method for separating methane and nitrogen with reduced horsepower demands

AssigneeBCCK Holding Company

InventorRayburn C. Butts

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Abstract

A system and method for removing nitrogen from natural gas using two fractionating columns, that may be stacked, and a plurality of separators and heat exchangers, with horsepower requirements that are 50-80% of requirements for prior art systems. The fractionating columns operate at different pressures. A feed stream is separated with a vapor portion feeding the first column to produce a first column bottoms stream that is split into multiple portions at different pressures and first column overhead stream that is cooled and separated into vapor and liquid portions to control subcooling of the vapor portion prior to feeding the second column. Heat exchange between first column and second column streams provides first column reflux and reboil heat for a second column ascending vapor stream. Three sales gas streams are produced, each at a different pressure.

Claims23

Dependent claims

A system for removing nitrogen and for producing a methane product stream from a feed stream comprising nitrogen, methane, and other components, the system comprising:

a first separator wherein the feed stream is separated into a first separator overhead stream and a first separator bottoms stream;
a first splitter for splitting the first separator overhead stream into a first portion and a second portion;
a first fractionating column wherein the first and second portions of the first separator overhead stream are separated into a first column overhead stream and a first column bottoms stream;
a second splitter for splitting the first column bottoms stream into four portions;
a second fractionating column wherein the first column overhead stream is separated into a second column overhead stream and a second column bottoms stream;
a second separator wherein the second column bottoms stream and a fourth portion of the first column bottoms stream are separated into a second separator overhead stream and a second separator bottoms stream;
a first mixer to mix the second separator bottoms stream and a third portion of the first column bottoms stream to form a first mixed stream;
a first heat exchanger wherein the feed stream is cooled upstream of the first separator and the first portion of the first separator overhead stream is cooled upstream of the first fractionating column through heat exchange with the first separator bottoms stream, a first portion of the first column bottoms stream, a second portion of the first column bottoms stream, the first mixed stream, and the second column overhead stream;
wherein the first portion of the first column bottoms stream is a high pressure sales gas stream having a pressure between 315 and 415 psia;
wherein the second portion of the first column bottoms stream is an intermediate pressure sales gas stream having a pressure between 115 and 215 psia;
and
wherein the first mixed stream is a low pressure sales gas stream having a pressure between 45 and 115 psia.

9 more elements

A method for removing nitrogen from a feed stream comprising nitrogen and methane, the method comprising the steps of:

separating the feed stream into a first separator overhead stream and a first separator bottoms stream in a first separator;
dividing the first separator overhead stream into a first portion and a second portion in a first splitter;
separating the first and second portions of the first separator overhead stream into a first column overhead stream and a first column bottoms stream in a first fractionating column operated at a pressure between 315 and 415 psia;
dividing the first column bottoms stream into a first portion, a second portion, a third portion, and a fourth portion in a second splitter;
separating the first column overhead stream into a second column overhead stream and a second column bottoms stream in a second fractionating column operated at a pressure between 45 and 115 psia;
separating the second column bottoms stream and the fourth portion of the first column bottoms stream into a second separator overhead stream and a second separator bottoms stream in a second separator;
mixing the second separator bottoms stream and the third portion of the first column bottoms stream to form a first mixed stream in a first mixer;
cooling the feed stream upstream of the first separator and cooling the first portion of the first separator overhead stream upstream of the first fractionating column through heat exchange with the first separator bottoms stream, the first portion of the first column bottoms stream, the second portion of the first column bottoms stream, the first mixed stream, and the second column overhead stream in a first heat exchanger;
wherein the first portion of the first column bottoms stream is a high pressure sales gas stream having a pressure between 315 and 415 psia;
wherein the second portion of the first column bottoms stream is an intermediate pressure sales gas stream having a pressure between 115 and 215 psia;
and
wherein the first mixed stream is a low pressure sales gas stream having a pressure between 45 and 115 psia.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/714,110Filed 13 Dec 2019
Published: US 2021/0180863 A117 Jun 2021
Granted: 5 Jul 2022
Term ends: Not estimatedThe source records don’t support an estimate.

Classification19 codes

F25J 3/0257
Characterised by the separated product stream: separation of nitrogen
F25J 3/0209
Characterised by the feed stream: natural gas or substitute natural gas
F25J 3/0233
Characterised by the separated product stream: separation of CnHm with 1 carbon atom or more
F25J 3/0238
Characterised by the separated product stream: separation of CnHm with 2 carbon atoms or more