Phillips Petroleum Company

Dunn M Bailey

William R Low

Ernest A Harper, Deceased

Joseph T Karbosky

The inventive process and associated apparatus are ideally suited for the small-scale liquefaction of natural gas. The current invention provides a methodology and apparatus for the liquefaction of normally gaseous material, most notably natural gas, which reduces both the number of process vessels required and also the associated space requirements over convention apparatus while resulting in only a slight decrease in process efficiency.

Conversion of normally gaseous material to liquefied product

A process for simultaneously, cryogenically separating natural gas liquids from a lean natural gas stream and a rich natural gas stream; including, compressing the lean gas feed, cooling the compressed lean gas feed, separating the cooled lean gas feed to form a vapor phase and a liquid phase, expanding the vapor phase lean gas feed, separating the expanded vapor phase lean gas feed to form a second vapor phase and a second liquid phase, fractionating the second vapor phase lean gas feed to form a methane-enriched, low pressure bottoms fraction and a nitrogen-enriched, high pressure overhead fraction, flashing a portion of the methane-enriched bottoms fraction and passing the same in countercurrent, indirect heat exchange with the nitrogen-enriched overhead fraction, to cool the same and produce a vapor phase nitrogen-enriched product and a liquid phase reflux for the fractionator, passing the remainder of the methane-enriched bottoms fraction, the flashed methane-enriched bottoms fraction and the vapor phase nitrogen-enriched fraction in countercurrent heat exchange with the lean gas feed, compressing the rich gas feed, cooling the compressed rich gas feed, fractionating the cooled rich gas feed and the liquid phases separated from the lean gas feed to form a methane-enriched overhead fraction and a natural gas liquids bottoms product and combining the methane-enriched overhead with a portion of the methane-enriched bottoms product from the lean gas feed, prior to the passage of the latter in heat exchange with the lean gas feed. The methane-enriched streams are combined, following their use as heat exchange media, to form a pipeline quality natural gas product and the nitrogen-enriched vapor phase can be utilized as a low BTU fuel gas for the plant.

Cryogenic separation of lean and rich gas streams

In a system for liquefying natural gas containing more than about 1.5 percent nitrogen in which the natural gas is cooled by refrigeration and heat exchange with initial flashing of liquid at a pressure to remove substantialy all of the container nitrogen and with additional stages of flashing of liquid with low pressure flash liquid being passed to liquid natural gas storage and flashed vapors used for heat exchange, recompressed, and combined with the incoming feed the energy requirements of the system are improved by stabilizing the amount of nitrogen recycle in the system by stripping nitrogen from the initial vapor flash with overhead from the stripping heat exchanged within the system to recover its refrigeration and then yielded from the system and with the liquid from the stripping, recycled to the liquid from the initial flashing.

Natural gas liquefaction with nitrogen rejection stabilization

A process for liquefying a natural gas, having a pressure above atmospheric pressure, in which a feed gas is cooled to sequentially lower temperatures, by passing the gas through a plurality of cooling stages, in indirect heat exchange with at least one refrigerant, until the gas is substantially completely condensed in the last of the cooling stages, a fuel gas fraction is withdrawn from the liquefied gas in an amount proportional to the amount of feed gas passing through the cooling stages and, thereafter, the pressure of the remaining liquefied gas is reduced to essentially atmospheric pressure. Apparatus for carrying out the process is also described.

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Bartlesville, OK, United States of America

Dunn M Bailey