Refrigerant and nitrogen recovery

Abstract

Systems, devices, and methods for recovering mixed refrigerant and/or nitrogen within liquefaction systems are provided. The systems, devices, and methods facilitate recovering mixed refrigerant (MR) and/or nitrogen vapor that can leak from a compressor, separating the MR from the nitrogen, and reusing the MR and/or the nitrogen within the liquefaction system. Recovering and reusing MR and/or nitrogen can minimize loss of MR and nitrogen which can lower the total operating cost of a liquefaction system. Additionally, recovering the MR, rather than burning it, can reduce environmental emissions by reducing the amount of MR that is burned.

What is claimed is: 
     
         1 . A liquefaction system, the system comprising:
 a first compressor;   a recovery system in fluid communication with the first compressor, the recovery system comprising
 a first heat exchanger configured to receive a first vapor comprising mixed refrigerant and nitrogen from the first compressor and to convert the first vapor to a mixture of nitrogen rich vapor and a hydrocarbon rich liquid, the first heat exchanger having at least one cooling element configured to receive a cold fluid that provides refrigeration to the first vapor, and 
 a separator configured to receive the mixture of hydrocarbon rich liquid and nitrogen rich vapor from the first heat exchanger, and to separate the hydrocarbon rich liquid and the nitrogen rich vapor. 
   
     
     
         2 . The liquefaction system of  claim 1 , further comprising a nitrogen removal assembly positioned upstream of the first heat exchanger, the nitrogen removal assembly being configured to produce the first vapor from a second vapor comprising mixed refrigerant and nitrogen, wherein the first vapor possesses less nitrogen than the second vapor. 
     
     
         3 . The liquefaction system of  claim 2 , wherein the nitrogen removal assembly includes an adsorption bed. 
     
     
         4 . The liquefaction system of  claim 1 , further comprising a nitrogen removal assembly positioned downstream of the separator, the nitrogen removal assembly being configured to receive the nitrogen rich vapor from the separator and to remove a portion of the nitrogen from the nitrogen rich vapor. 
     
     
         5 . The liquefaction system of  claim 1 , wherein the first compressor includes a seal assembly that is configured to receive at least a portion of the nitrogen rich vapor from the separator. 
     
     
         6 . The liquefaction system of  claim 5 , further comprising a second compressor in fluid communication with the separator, the second compressor being configured to receive the at least a portion of the nitrogen rich vapor from the separator and to urge the at least a portion of the nitrogen rich vapor to the seal assembly. 
     
     
         7 . The liquefaction system of  claim 1 , further comprising a second heat exchanger in fluid communication with the compressor, the second heat exchanger being configured to receive a methane-containing vapor and to convert the methane-containing vapor to a methane-containing liquid. 
     
     
         8 . The liquefaction system of  claim 7 , wherein the cold fluid comprises at least a portion of the methane-containing liquid. 
     
     
         9 . The liquefaction system of  claim 1 , further comprising a pump configured to receive the hydrocarbon rich liquid from the separator and to pump the hydrocarbon rich liquid to a storage vessel. 
     
     
         10 . A method of operating a liquefaction system, the method comprising:
 receiving a seal gas including hydrocarbons at a seal assembly of a first compressor;   receiving a nitrogen vapor at the seal assembly of the first compressor;   receiving, at a first heat exchanger, a first vapor including at least a portion of the seal gas and at least a portion of the nitrogen vapor;   transferring a cold fluid to a cooling element of the first heat exchanger;   transferring heat from the first vapor to the cold fluid, thereby creating a mixture of nitrogen rich vapor and a hydrocarbon rich liquid; and   separating the hydrocarbon rich liquid from the nitrogen rich vapor at a separator positioned downstream of the first heat exchanger.   
     
     
         11 . The method of  claim 10 , further comprising:
 receiving the nitrogen rich vapor at a second compressor;   compressing the nitrogen rich vapor using the second compressor; and   delivering at least a portion of the nitrogen rich vapor to the seal assembly of the first compressor.   
     
     
         12 . The method of  claim 11 , further comprising:
 receiving, at the second compressor, a portion of the nitrogen vapor from the first compressor; and   combining the portion of the nitrogen vapor received at the seal assembly with the nitrogen rich vapor.   
     
     
         13 . The method of  claim 10 , wherein the seal gas is a mixed refrigerant. 
     
     
         14 . The method of  claim 10 , further comprising:
 receiving a methane-containing vapor at a second heat exchanger; and   removing heat from the methane-containing vapor within the second heat exchanger, thereby creating the cold fluid.   
     
     
         15 . The method of  claim 10 , further comprising:
 receiving a second vapor at a nitrogen removal assembly positioned upstream of the first heat exchanger, the second vapor comprising at least a portion of the seal gas and at least a portion of the nitrogen vapor; and   removing a portion of the nitrogen vapor from the second vapor, thereby generating the first vapor.   
     
     
         16 . The method of  claim 10 , further comprising:
 receiving the nitrogen rich vapor at a nitrogen removal assembly positioned downstream of the separator; and   remove a portion of the nitrogen from the nitrogen rich vapor.   
     
     
         17 . The method of  claim 10 , further comprising:
 receiving the hydrocarbon rich liquid at a pump; and   pumping the hydrocarbon rich liquid to a storage vessel.