Methods for separating nitrogen

Abstract

According to one or more embodiments, a method for separating nitrogen from hydrocarbon streams, comprising: receiving a hydrocarbon feed stream comprising nitrogen and at least 50% hydrocarbons through an inlet of a housing; separating the hydrocarbon feed stream into a vapor and a liquid in the housing; receiving a cooling medium through an inlet of a first heat exchanger and mass transfer device located at the top of the housing; cooling the vapor with the cooling medium as the vapor flows through the first heat exchanger and mass transfer device to separate nitrogen from the vapor to produce a first product; receiving a heating medium through an inlet of a second heat exchanger and mass transfer device located at the bottom of the housing; and heating the liquid with the heating medium as the liquid flows through the second heat exchanger and mass transfer device to separate liquefied natural gas from the liquid to produce a second product

1 . A method for separating nitrogen from hydrocarbon streams, comprising:
 receiving a hydrocarbon feed stream comprising nitrogen and at least 50 mol % hydrocarbons through an inlet of a housing;   separating the hydrocarbon feed stream into a vapor and a liquid in the housing;   receiving a cooling medium through an inlet of a first heat exchange and mass transfer device located at a top of the housing;   cooling the vapor with the cooling medium as the vapor flows through the first heat exchange and mass transfer device to separate nitrogen from the vapor to produce a first product;   receiving a heating medium through an inlet of a second heat exchange and mass transfer device located at a bottom of the housing; and   heating the liquid with the heating medium as the liquid flows through the second heat exchange and mass transfer device to separate liquefied natural gas from the liquid to produce a second product.   
     
     
         2 . The method of  claim 1 , wherein the first product comprises about 90 mol % to about 99.99999 mol % nitrogen. 
     
     
         3 . The method of  claim 1 , wherein the cooling medium is at least one of the hydrocarbon feed stream, mixed refrigerant, methane, natural gas, and combinations thereof. 
     
     
         4 . The method of  claim 3 , wherein the cooling medium is mixed refrigerant, and wherein the method further comprises:
 compressing the mixed refrigerant;   cooling the mixed refrigerant in a main heat exchanger before receiving the mixed refrigerant through the inlet of the first heat exchange and mass transfer device; and   reheating the mixed refrigerant in the main heat exchanger after cooling the vapor with the mixed refrigerant, wherein the mixed refrigerant is heated while the mixed refrigerant cools the vapor.   
     
     
         5 . The method of  claim 1 , wherein the heating medium is at least one of the hydrocarbon feed stream, mixed refrigerant, methane, natural gas, and combinations thereof. 
     
     
         6 . The method of  claim 5 , wherein the heating medium is the hydrocarbon feed stream. 
     
     
         7 . The method of  claim 6 , further comprising:
 cooling the hydrocarbon feed stream in a main heat exchanger before receiving the hydrocarbon feed stream through the inlet of the second heat exchange and mass transfer device;   cooling the hydrocarbon feed stream in the main heat exchanger after heating the liquid with the hydrocarbon feed stream, wherein the hydrocarbon feed stream is cooled while the hydrocarbon feed stream heats the liquid; and   cooling and expanding the hydrocarbon feed stream before the hydrocarbon feed stream is received through the inlet of the housing.   
     
     
         8 . The method of  claim 1 , wherein the first heat exchange and mass transfer device comprises a first stage and a second stage, and wherein the second heat exchange and mass transfer device comprises a first stage and a second stage. 
     
     
         9 . The method of  claim 8 , wherein:
 the first stage of the first heat exchange and mass transfer device receives the cooling medium and cools the vapor with the cooling medium;   the second stage of the first heat exchange and mass transfer device receives a second cooling medium and cools the vapor with the second cooling medium;   the first stage of the second heat exchange and mass transfer device receives the heating medium and heats the liquid with the heating medium; and   the second stage of the second heat exchange and mass transfer device receives a second heating medium and heats the liquid with the second heating medium.   
     
     
         10 . The method of  claim 1 , wherein:
 a portion of the vapor cooled by the first heat exchange and mass transfer device condenses to become a portion of the liquid; and   a portion of the liquid heated by the second heat exchange and mass transfer device vaporizes to become a portion of the vapor.   
     
     
         11 . The method of  claim 1 , wherein the hydrocarbon feed stream enters a separation section in the housing, wherein the separation section is disposed between the first heat exchange and mass transfer device and the second heat exchange and mass transfer device. 
     
     
         12 . The method of  claim 11 , wherein heat and mass transfer occur in both the first heat exchange and mass transfer device and the second heat exchange and mass transfer device such that no heat transfer and/or mass transfer occur in the separation section. 
     
     
         13 . A method for separating nitrogen from hydrocarbon streams, comprising:
 receiving a hydrocarbon feed stream comprising nitrogen and at least 50 mol % hydrocarbons through an inlet of a housing;   separating the hydrocarbon feed stream into a vapor and a liquid in the housing;   receiving a heating medium through an inlet of a heat exchange and mass transfer device located at a bottom of the housing; and   heating the liquid with the heating medium as the liquid flows through the heat exchange and mass transfer device to separate liquefied natural gas from the liquid to produce a product.   
     
     
         14 . The method of  claim 13 , wherein the product comprises about 0.1 mol % to about 50 mol % nitrogen. 
     
     
         15 . The method of  claim 13 , wherein the heating medium is at least one of the hydrocarbon feed stream, mixed refrigerant, methane, natural gas, and combinations thereof. 
     
     
         16 . The method of  claim 15 , wherein the heating medium is the hydrocarbon feed stream. 
     
     
         17 . The method of  claim 13 , wherein the heat exchange and mass transfer device comprises a first stage and a second stage. 
     
     
         18 . The method of  claim 17 , wherein:
 the first stage of the heat exchange and mass transfer device receives the heating medium and heats the liquid with the heating medium; and   the second stage of the heat exchange and mass transfer device receives a second heating medium and heats the liquid with the second heating medium.   
     
     
         19 . The method of  claim 13 , wherein a portion of the liquid heated by the heat exchange and mass transfer device vaporizes to become a portion of the vapor. 
     
     
         20 . The method of  claim 19 , wherein the housing includes at least one of packed beds and trays.