Lng facility with integrated ngl extraction technology for enhanced ngl recovery and product flexibility

Abstract

Process for efficiently operating a natural gas liquefaction system with integrated heavies removal/natural gas liquids recovery to produce liquefied natural gas (LNG) and/or natural gas liquids (NGL) products with varying characteristics, such as, for example higher heating value (HHV) and/or propane content. Resulting LNG and/or NGL products are capable of meeting the significantly different specifications of two or more markets.

1 . A process for producing liquefied natural gas (LNG), said process comprising: 
 (a) operating an LNG facility in a first mode of operation to thereby produce a first LNG product;    (b) adjusting at least one non-feed operating parameter of the LNG facility so that the LNG facility operates in a second mode of operation; and    (c) operating the LNG facility in the second mode of operation to thereby produce a second LNG product, wherein said first and second modes of operation are not carried out during start-up or shut-down of the LNG facility, wherein said operating of steps (a) and (c) optionally includes producing first and second natural gas liquids (NGL) products respectively, wherein the average higher heating value (HHV) of the second LNG product is at least about 10 BTU/SCF different than the average HHV of the first LNG product and/or the average propane content of the second NGL product is at least about 1 mole percent different than the average propane content of the first NGL product.    
   
   
       2 . The process of  claim 1 , wherein said adjusting of step (b) includes transitioning said LNG facility from said first mode of operation to said second mode of operation without ceasing the production of LNG.  
   
   
       3 . The process of  claim 1 , wherein said adjusting of step (b) includes adjusting at least one operating parameter of a distillation column of the LNG facility.  
   
   
       4 . The process of  claim 3 , wherein said operating parameter of said distillation column includes at least one operating parameter selected from the group consisting of column feed composition, column feed temperature, column overhead pressure, reflux stream flow rate, reflux stream composition, reflux stream temperature, stripping gas flow rate, stripping gas composition, and stripping gas temperature.  
   
   
       5 . The process of  claim 3 , wherein said operating of steps (a) and (c) includes using said distillation column to separate a stream into a relatively more volatile fraction and a relatively less volatile fraction, wherein said first and second LNG products comprise at least a portion of said relatively more volatile fraction and/or said first and second NGL products comprise at least a portion of said relatively less volatile fraction.  
   
   
       6 . The process of  claim 5 , wherein said first and second LNG products comprise at least a portion of said relatively more volatile fraction and said first and second NGL products comprise at least a portion of said relatively less volatile fraction.  
   
   
       7 . The process of  claim 1 , wherein said operating of steps (a) and (c) includes cooling a natural gas feed stream, separating the cooled natural gas feed stream into a first relatively more volatile fraction and a first relatively less volatile fraction using a first distillation column, and further cooling at least a portion of the first relatively more volatile fraction to thereby produce at least a portion of the first and second LNG products.  
   
   
       8 . The process of  claim 7 , wherein said operating of steps (a) and (c) includes separating at least a portion of the first relatively less volatile fraction into a second relatively more volatile fraction and a second relatively less volatile fraction using a second distillation column.  
   
   
       9 . The process of  claim 8 , wherein said operating of steps (a) and (c) include further cooling at least a portion of the second relatively more volatile fraction to thereby produce at least a portion of said first and second LNG products.  
   
   
       10 . The process of  claim 8 , wherein said first and second NGL products comprise at least a portion of the second relatively less volatile fraction.  
   
   
       11 . The process of  claim 7 , wherein at least a portion of said cooling of the natural gas feed stream is carried out using a first refrigeration cycle employing a first refrigerant having a mid-boiling point within about 20° F. of the boiling point of pure propane at atmospheric pressure.  
   
   
       12 . The process of  claim 11 , wherein at least a portion of said further cooling of the first relatively more volatile fraction is carried out using a second refrigeration cycle employing a second refrigerant having a mid-boiling point within about 20° F. of the boiling point of pure methane at atmospheric pressure.  
   
   
       13 . The process of  claim 12 , wherein at least a portion of said further cooling of the first relatively more volatile fraction is carried out using a third refrigeration cycle employing a third refrigerant having a mid-boiling point within about 20° F. of pure ethylene at atmospheric pressure.  
   
   
       14 . The process of  claim 13 , wherein said first, second, and third refrigerants are pure component refrigerants.  
   
   
       15 . The process of  claim 1 , wherein said operating of steps (a) and (c) includes using a first distillation column to separate a first stream into a first relatively more volatile fraction and a first relatively less volatile fraction and using a second distillation column to separate at least a portion of said first relatively less volatile fraction into a second relatively more volatile fraction and a second relatively less volatile fraction.  
   
   
       16 . The process of  claim 15 , wherein said first and second LNG products comprise at least a portion of the first and second relatively more volatile fractions.  
   
   
       17 . The process of  claim 15 , wherein said first and second NGL products comprise at least a portion of the second relatively less volatile fraction.  
   
   
       18 . The process of  claim 15 , wherein said at least one non-feed operating parameter is an operating parameter of the first and/or second distillation column.  
   
   
       19 . The process of  claim 17 , wherein said first distillation column is refluxed with at least a portion of the second relatively more volatile fraction.  
   
   
       20 . The process of  claim 19 , wherein said adjusting of step (b) includes adjusting the temperature and/or flow rate of the reflux into the first distillation column.  
   
   
       21 . The process of  claim 1 , wherein the average HHV of the second LNG product is at least about 10 BTU/SCF different than the average HHV of the first LNG product.  
   
   
       22 . The process of  claim 1 , wherein the average propane content of the second NGL product is at least about 1 mole percent different than the average propane content of the first NGL product.  
   
   
       23 . The process of  claim 1 , wherein the average HHV of the second LNG product is at least about 20 BTU/SCF different than the average HHV of the first LNG product.  
   
   
       24 . The process of  claim 1 , wherein the average propane content of the second NGL product is at least about 2 mole percent different than the average propane content of the first NGL product.  
   
   
       25 . The process of  claim 1 , wherein said first LNG product is produced over a first production time period of at least one week, wherein said second LNG product is produced over a second production time period of at least one week, wherein said first and second production time periods are separated by a transition time period of less than one week.  
   
   
       26 . The process of  claim 1 , wherein said transition time period is less than one day.  
   
   
       27 . A method of varying the heating value of LNG produced from an LNG facility, said method comprising: 
 (a) cooling natural gas by indirect heat exchange to thereby produce a first cooled stream;    (b) using a first distillation column to separate at least a portion of the first cooled stream into a first relatively more volatile fraction and a first relatively less volatile fraction;    (c) cooling at least a portion of said first relatively more volatile fraction to thereby produce LNG; and    (d) adjusting at least one operating parameter of the first distillation column to thereby vary the higher heating value (HHV) of the produced LNG by at least about 1 percent over a time period of less than about 72 hours.    
   
   
       28 . The method according to  claim 27 , wherein said at least one operating parameter of the first distillation column is selected from the group consisting of temperature of the first cooled stream, composition of the first cooled stream, and overhead pressure of the first distillation column.  
   
   
       29 . The method according to  claim 27 , wherein said at least one operating parameter of the first distillation is a non-feed operating parameter.  
   
   
       30 . The method according to  claim 27 , wherein step (d) includes adjusting the overhead pressure in the first distillation column.  
   
   
       31 . The method according to  claim 27 , wherein step (d) includes adjusting the temperature of the first cooled stream prior to introduction into the first distillation column.  
   
   
       32 . The method according to  claim 31 , wherein step (d) includes reducing the temperature of the first cooled stream to thereby lower the HHV of the produced LNG.  
   
   
       33 . The method according to  claim 32 , wherein said first cooled stream has a temperature in the range of from about −125 to about −50° F. when introduced into the first distillation column, wherein step (d) includes reducing the temperature of the first cooled stream by at least about 1° F.  
   
   
       34 . The method according to  claim 32 , wherein said first cooled stream has a temperature in the range of from about −115 to about −65° F. when introduced into the first distillation column, wherein step (d) includes reducing the temperature of the first cooled stream by at least about 3° F.  
   
   
       35 . The method according to  claim 27 , wherein step (b) includes introducing a predominately vapor stripping gas stream into a lower section of the first distillation column.  
   
   
       36 . The method according to  claim 35 , wherein said at least one operating parameter of the first distillation column is selected from the group consisting of flow rate of the stripping gas stream, temperature of the stripping gas stream, composition of the stripping gas stream, temperature of the first cooled stream, composition of the first cooled stream, and overhead pressure of the first distillation column.  
   
   
       37 . The method according to  claim 35 , wherein step (d) includes varying the flow rate of the stripping gas stream to the first distillation column.  
   
   
       38 . The method according to  claim 35 , wherein step (d) includes lowering the flow rate of the stripping gas stream to the first distillation column to thereby lower the HHV of the produced LNG.  
   
   
       39 . The method according to  claim 35 , wherein said first cooled stream has a temperature in the range of from about −125 to about −50° F. when introduced into the first distillation column, wherein said stripping gas stream has a temperature in the range from about −50 to about 100° F. when introduced into the first distillation column, wherein step (d) includes lowering the temperature of the stripping gas stream by at least 5° F. to thereby lower the HHV of the produced LNG.  
   
   
       40 . The method according to  claim 27 , wherein step (b) includes introducing a predominately liquid reflux stream into an upper section of the first distillation column.  
   
   
       41 . The method according to  claim 40 , wherein said at least one operating parameter of the first distillation column is selected from the group consisting of flow rate of the reflux stream, temperature of the reflux stream, composition of the reflux stream, temperature of the first cooled stream, composition of the first cooled stream, and overhead pressure in the first distillation column.  
   
   
       42 . The method according to  claim 40 , wherein step (d) includes varying the flow rate of the reflux stream to the first distillation column.  
   
   
       43 . The method according to  claim 40 , wherein step (d) includes increasing the flow rate of the reflux stream to the first distillation column to thereby lower the HHV of the produced LNG.  
   
   
       44 . The method according to  claim 40 , wherein step (d) includes varying the C 2+  content of the reflux stream.  
   
   
       45 . The method according to  claim 40 , wherein step (d) includes increasing the C 2+  content of the reflux stream from an initial C 2+  content to an adjusted C 2+  content to thereby lower the HHV of the LNG product.  
   
   
       46 . The method according to  claim 45 , wherein said adjusted C 2+  content is at least about 10 percent more than the initial C 2+  content on a molar basis.  
   
   
       47 . The method according to  claim 45 , wherein said initial C 2+  content is less than about 75 mole percent and said adjusted C 2+  content is at least about 25 mole percent.  
   
   
       48 . The method according to  claim 40 , wherein step (d) includes varying the temperature of the reflux stream.  
   
   
       49 . The method according to  claim 40 , wherein said first cooled stream has a temperature in the range of from about −125 to about −50° F. when introduced into the first distillation column, wherein said reflux stream has a temperature in the range from about −180 to about −80° F. when introduced into the first distillation column, wherein step (d) includes lowering the temperature of the reflux stream by a least about 5° F. to thereby lower the HHV of the produced LNG.  
   
   
       50 . The method according to  claim 40 , wherein step (d) includes varying the flow rate of the LNG stream to the first distillation column.  
   
   
       51 . The method according to  claim 40 , wherein step (d) includes increasing the flow rate of the LNG stream to the first distillation column to thereby lower the HHV of the produced LNG.  
   
   
       52 . The method according to  claim 27 , further comprising: 
 (e) using a second distillation column to separate at least a portion of said first relatively less volatile fraction into a second relatively more volatile fraction and a second relatively less volatile fraction.    
   
   
       53 . The method according to  claim 52 , further comprising: 
 (f) introducing at least a portion of said second relatively less volatile fraction into an upper section of said first distillation column as a reflux stream.    
   
   
       54 . The method according to  claim 52 , further comprising: 
 (g) adjusting at least one operating parameter of the second distillation column to thereby vary the HHV of the produced LNG.    
   
   
       55 . The method according to  claim 54 , wherein said at least one operating parameter of the second distillation column is selected from the group consisting of temperature of said first relatively less volatile fraction introduced into the second distillation column, composition of said first relatively less volatile fraction introduced into the second distillation column, and overhead pressure in the second distillation column.  
   
   
       56 . The method according to  claim 54 , further comprising: 
 (h) introducing at least a portion of said second relatively less volatile fraction into an upper section of said first distillation column as a reflux stream, wherein step (g) includes varying the C 2+  content of the reflux stream.    
   
   
       57 . The method according to  claim 27 , wherein step (a) includes using a first refrigeration cycle employing a first refrigerant comprising predominantly propane to cool at least a portion of the natural gas.  
   
   
       58 . The method according to  claim 57 , wherein step (c) includes using a second refrigeration cycle employing a second refrigerant comprising predominantly ethane, ethylene, and/or methane to cool at least a portion of the first separated stream.  
   
   
       59 . The method according to  claim 58 , wherein said second refrigerant comprises predominately methane.  
   
   
       60 . The method according to  claim 59 , further comprising: 
 (i) using a third refrigeration cycle employing a third refrigerant comprising predominately ethane and/or ethylene to cool at least a portion of the first cooled stream and/or at least a portion of the first separated stream.    
   
   
       61 . The method according to  claim 27 , wherein step (d) includes varying the HHV of the produced LNG by at least about 3 percent over a time period of less than about 24 hours.  
   
   
       62 . The method according to  claim 27 , wherein step (d) includes varying the HHV of the produced LNG by at least 5 percent over a time period of less than 12 hours.