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Removing nitrogen from and subsequently liquefying natural gas stream

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专利汇可以提供Removing nitrogen from and subsequently liquefying natural gas stream专利检索,专利查询,专利分析的服务。并且A natural gas containing substantial nitrogen is refrigerated to below minus 120*F in usual propane-ethylene refrigeration system using a cascade arrangement. Vapor and liquid thus obtained are separated and the liquid passed into the tubes of a refrigeration heat exchanger. The vapor and liquid, which has been further refrigerated, as a liquid, are recombined to effect uniform distribution of the vapors into the further refrigerated liquid for a flow through the heat exchanger tubes. Thus, admixed liquid and vapor streams are further refrigerated by heat interchange with bottoms from a fractionation zone into which the feed has been flashed, thus reboiling the fractionation zone bottoms. The nitrogen to be separated and some hydrocarbon, e.g., methane, are taken as overhead from the fractionation zone. Also, the overhead is used to refrigerate the liquid first obtained when refrigerating the feed after separation of vapors therefrom. Further, refrigeration of the recombined vapor and liquid is effected by flashing the natural gas containing fractionation zone bottoms in several stages, using liquid obtained upon a first flashing of said bottoms to refrigerate the recombined vapor and liquid streams described and using vapors from each flashing step practiced upon the fractionation zone bottoms to further refrigerate in order the liquid first separated from the feed after separation of vapors therefrom and the incoming feed gas resulting in a fuel gas containing some nitrogen. The remainder of the several times flashed fractionation bottoms is now substantially at atmospheric pressure and constitutes liquefied natural gas substantially free from nitrogen which is the product of the process. A controls system designed to render the system essentially automatic and to keep it in balanced operation is described.,下面是Removing nitrogen from and subsequently liquefying natural gas stream专利的具体信息内容。

1. IN A PROCESS FOR REMOVING NITROGEN AS AN IMPURITY FROM NATURAL GAS COMPRISING REFRIGERATING SAID GAS, GENERATING A LIQUID PORTION AND A VAPOR PORTION, SEPARATING THE VAPOR AND LIQUID PORTIONS FROM EACH OTHER AND FURTHER REFRIGERATING THE SEPARATED LIQUID PORTION IN A FIRST REFRIGERATION ZONE, THE IMPROVEMENT COMPRISING THE STEPS OF
1. COMBINING THE THUS REFRIGERATED LIQUID PORTION WITH SAID VAPOR PORTION AND COOLING THE COMBINED PORTION IN A SECOND REFRIGERATION ZONE UNDER CONDITIONS TO SUBSTANTIALLY LIQUEFY THE COMBINED PORTION,
2. REDUCING THE PRESSURE OF SAID SUBSTANTIALLY LIQUEFIED MIXTURE OBTAINED IN STEP (1) TO FLASH THE LIQUEFIED COMBINED PORTION INTO A VAPOR PORTION AND A LIQUID PORTION AND INTRODUCING THE FLASHED MIXTURE INTO A FRACTIONATION ZONE,
2. reducting the pressure of said substantially liquefied mixture obtained in step (1) to flash the liquefied combined portion into a vapor portion and a liquid portion and introducing the flashed mixture into a fractionation zone,
2. A process according to claim 1 wherein the remaining portion of said liquid stream removed from said separation zone is further flashed to obtain nitrogen-containing gas therefrom and a final liquefied natural gas substantially free from nitrogen, and further wherein said vapor stream obtained from said separation zone upon use as a refrigerant in said first refrigeration zone is removed as a fuel gas containing nitrogen.
3. A process according to claim 1 wherein said fractionation zone is operated under conditions in which the upper portion of the fractionation zone is at a temperature in the range of -200* to -300*F and the bottom portion of the fractionation zone is at a temperature in the range of -50* to -250*F, and the temperature of the combined vapor and liquid stream after refrigeration in said second refrigeration zone is at a temperature in the range of -50* to -225*F.
3. subjecting said flashed mixture to temperature and pressure conditions in said fractionation zone sufficient to separate substantially all of the nitrogen as a vapor overhead stream and a bottoms liquid stream substAntially free of nitrogen,
3. SUBJECTING SAID FLASHED MIXTURE TO TEMPERATURE AND PRESSURE CONDITIONS IN SAID FRACTIONATION ZONE SUFFICIENT TO SEPARATE SUBSTANTIALLY ALL OF THE NITROGEN AS A VAPOR OVERHEAD STREAM AND A BOTTOMS LIQUID STREAM SUBSTANTIALLY FREE OF NITROGEN,
4. PASSING SAID VAPOR OVERHEAD STREAM OBTAINED IN STEP (3) IN HEAT EXCHANGE RELATIONSHIP WITH SAID SEPARATED LIQUID PORTION IN SAID FIRST REFRIGERATION ZONE TO COOL AND FRIGERATE SAID LIQUID PORTION,
4. passing said vapor overhead stream obtained in step (3) in heat exchange relationship with said separated liquid portion in said first refrigeration zone to cool and refrigerate said liquid portion,
4. A process according to claim 1 wherein the temperature of the liquid bottoms stream separated from said fractionation zone in step (3) is in the range of -75* to -300*F and the stream is flashed by reducing the pressure sufficiently to a pressure in the range of 50 to 300 psia to form a vapor portion and liquid portion.
5. passing a portion of said bottoms liquid stream obtained in step (3) in heat exchange relationship with said combined portion in said second refrigeration zone and returning same to a lower portion of said fractionation zone as a source of reboiling heat,
5. PASSING A PORTION OF SAID BOTTOMS LIQUID STREAM OBTAINED IN STEP (3) IN HEAT EXCHANGE RELATIONSHIP WITH SAID COMBINED PORTION IN SAID SECOND REFRIGERATION ZONE AND RETURNING SAME TO A LOWER PORTION OF SAID FRACTIONATION ZONE AS A SOURCE OF REBOILING HEAT,
6. REDUCING THE PRESSURE OF THE REMAINDER OF SAID BOTTOMS LIQUID STREAM OBTAINED IN STEP (3) TO FLASH SAME INTO A VAPOR PORTION AND A LIQUID PORTION AND INTRODUCING THE FLASHED STREAM INTO A SEPARATION ZONE,
6. reducing the pressure of the remainder of said bottoms liquid stream obtained in step (3) to flash same into a vapor portion and a liquid portion and introducing the flashed stream into a separation zone,
7. removing a liquid stream from said separation zone and passing a portion of said stream in heat exchange relationship with said combined portions in said second refrigeration zone and returning same to an upper portion of said separation zone as reflux, and
7. REMOVING A LIQUID STREAM FROM SAID SEPARATION ZONE AND PASSING A PORTION OF SAID STREAM IN HEAT EXCHANGE RELATIONSHIP WITH SAID COMBINED PORTIONS IN SAID SECOND REFRIGERATION ZONE AND RETURNING SAME TO AN UPPER PORTION OF SAID SEPARATION ZONE AS REFLUX, AND
8. REMOVING A VAPOR STREAM FROM SAID SEPARATION ZONE AND PASSING SAME IN HEAT EXCHANGE RELATIONSHIP WITH SAID LIQUID PORTION IN SAID FIRST REFRIGERATION ZONE.
8. removing a vapor stream from said separation zone and passing same in heat exchange relationship with said liquid portion in said first refrigeration zone.
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