Apparatus and process for liquefaction of natural gases

Claim 2

The process of claim 1 wherein the natural gas mixture in step (1) is at a pressure in the range from about 350 to about 750 psia.

Claim 3

The process of claim 1 wherein the natural gas mixture in step (1) is maintained at a pressure so that the plot of the temperature vs. enthalpy of the mixture approaches a straight line.

Claim 4

separating the minor, methane-nitrogen gas fraction from the major liquid fraction and recovering the major liquid fraction as product, performing in sequence the following steps (4) through (10) thereby providing series flow through the operations of steps (4) through (10),

Claim 5

combining the minor, methane-nitrogen gas fraction with an isentropically expanded, methane-nitrogen refrigerant gas mixture produced subsequently in step (10) to form the combined gas mixture,

Claim 6

The process of claim 1 wherein the flow rate of the combined methane-nitrogen gas mixture in step (1) is from about 2 to about 4 times the flow rate of the natural gas mixture in step (1), expressed as moles per hour.

Claim 7

employing the entire combined gas mixture formed in step (4) to cool the natural gas mixture in step (1),

Claim 8

The process of claim 1 wherein the compressed, methane-nitrogen refrigerant gas mixture from step (7) is at a pressure from about 400 to about 600 psia.

Claim 9

A process of claim 3 wherein the combined nitrogen-methane refrigerant gas stream charged to step (1) is maintained at a pressure in relationship to the temperature of the cooled compressed refrigerant gas stream to be expanded in step (10) so that the work expanded refrigerant gas leaving the expansion engine will thermodynamically balance the process.

Claim 10

heat exchanging the heated, combined gas mixture from step (1) with a compressed and cooled methane-nitrogen refrigerant gas mixture obtained subsequently in step (8) whereby the heated, combined gas mixture is further heated to a temperature in the range from about -50* to about 300*F.,

Claim 11

compressing the further heated, combined, methane-nitrogen gas mixture from step (6) to provide a compressed, methane-nitrogen refrigerant gas mixture,

Claim 12

The process of claim 1 wherein the compression of step (7) is effected in a plurality of stages and the gas is cooled interstage.

Claim 13

cooling the compressed refrigerant gas mixture from step (7),

Claim 14

The process of claim 1 wherein the natural gas mixture is subjected to purification for the removal of water, carbon dioxide, hydrogen sulfide and high freezing point hydrocarbons.

Claim 15

The process of claim 8 wherein the purification is effected by treatment with adsorbents and the minor portion of the combined gas mixture removed in step (10) is employed to purge and regenerate the adsorbents.

Claim 16

employing the compressed and cooled methane-nitrogen refrigerant gas mixture from step (8) in the heat exchange of step (6) whereby the compressed and cooled refrigerant gas mixture is further cooled,

Claim 17

substantially isentropically expanDing in a work recovery engine the further cooled methane-nitrogen refrigerant gas mixture from step (9) whereby mechanical energy is obtained, the refrigerant gas mixture is still further cooled and the isentropically expanded, methane-nitrogen refrigerant gas mixture is formed,

Claim 18

The process of claim 1 wherein the minor portion of the combined gas mixture removed in step (11) is charged to a separate work recovery engine whereby mechanical energy is obtained and employed at least to compress partly the major portion of the combined gas mixture.

Claim 19

removing from the process prior to the compression of step (7) a minor portion of heated the combined gas mixture produced in step (1) which minor portion is substantially equal in magnitude to the minor methane-nitrogen gas fraction formed in step (2), and

Claim 20

A continuous process for the liquefaction of natural gas which comprises the steps of: adjusting the pressure of the incoming gas to a range from about 350 to about 750 pounds psia; passing said pressurized gas through a plurality of molecular sieves and subsequently through a bed of activated carbon to remove water, carbon dioxide, hydrogen sulfide and heavy hydrocarbons from said pressurized gas; cooling and liquifying a predominant portion of said pressurized gas in a countercurrent heat exchanger-liquifier; substantially isenthalpically reducing the pressure of the cooled effluent from the heat exchanger-liquifier further to cool it and thereby flashing a minor vapor fraction while liquifying completely the balance of the natural gas to form a major liquid fraction; collecting the major liquid fraction as product and returning the flash fraction to a point where it is combined with an isentropically expanded refrigeration gas fraction produced subsequently in order to form a combined gas; passing all of said combined gas countercurrently to the incoming gas in said heat exchanger-liquifier at a flow rate of 2 to 4 times that of the feed gas stream whereby the combined gas effluent from the heat exchanger-liquifier is waRmed; separating the warmed effluent from said heat exchanger-liquifier into a major refrigeration gas fraction and a minor regeneration-fuel gas fraction; sequentially passing all of the refrigeration gas fraction in series flow: through a countercurrent heat exchanger precooler wherein it is heated; to a compressor system wherein it is compressed to a pressure in the range from about 400-600 psia; through said heat exchanger precooler, wherein it is cooled; through an expansion engine, wherein it is isentropically expanded at a temperature and pressure sufficient to maintain the gas in the gaseous state in said expansion engine to form the isentropically expanded refrigeration gas, and whereby mechanical energy is obtained and the pressure of the refrigeration gas fraction is reduced thereby further cooling such fraction; combining the further cooled, reduced pressure, isentropically expanded refrigeration gas effluent from said expansion engine with said flash gas at a point prior to entry into said heat exchanger-liquifier; purging said molecular sieves and activated carbon with the regeneration-fuel gas fraction; utilizing the regeneration-fuel gas fraction subsequent to the purging to furnish fuel for a gas driven turbine which provides a minor portion of the mechanical energy necessary to drive said compressor system, employing the mechanical energy obtained from the isentropic expansion to provide a major portion of the mechanical energy necessary to drive the compressor system.

Claim 21

The process of claim 11 wherein the regeneration-fuel gas fraction subsequent to purging is utilized to furnish fuel for steam generation which steam in turn is used to provide a portion of the mechanical energy necessary to drive the compressor system.

Claim 22

employing the mechanical energy obtained from the work recovery engine at least to compress partly the combined refrigerant gas mixture in step (7).