Method to maximize lng plant capacity in all seasons

Abstract

As described herein, a method and system for operating a liquefied natural gas (LNG) plant are provided. The method and system also provide for domestic natural gas production. In the present methods and systems, substantially all of the natural gas produced from a well or formation is processed to form LNG; a portion of the LNG produced is regasified; and the regasification is utilized to cool the inlet air to the gas turbines in the LNG plant, either directly or indirectly.

1 . An integrated liquefied natural gas (LNG) and domestic gas production system comprising:
 (a) an inlet stream comprising natural gas;   (b) a refrigeration system for reducing the temperature of the natural gas and condensing the natural gas to produce LNG;   (c) a gas turbine for driving a compressor for the refrigeration system;   (d) a vaporization heat exchanger for regasifying a portion of the LNG and cooling a heat transfer fluid;   (e) a second heat exchanger for reducing the temperature of inlet air entering the gas turbine with the heat transfer fluid; and   (f) an outlet stream comprising the regasified portion of the LNG.   
     
     
         2 . The integrated system of  claim 1 , wherein a gain in energy efficiency by reducing the temperature of the inlet air entering the gas turbine compensates for an amount of energy required to produce the portion of the LNG regasified in step (d). 
     
     
         3 . The integrated system of  claim 1 , wherein the heat transfer fluid of step (d) takes additional heat or refrigeration from auxiliary sources. 
     
     
         4 . The integrated system of  claim 1 , wherein the portion of the LNG regasified is in a range from 10% to 20% by weight. 
     
     
         5 . The integrated system of  claim 1 , wherein the second heat exchanger comprises a cooling coil at an inlet of the gas turbine. 
     
     
         6 . The integrated system of  claim 1 , wherein the heat transfer fluid comprises methanol, ethanol, propane, an ethylene glycol and water mixture, or any combination thereof. 
     
     
         7 . The integrated system of  claim 1 , wherein the temperature of the inlet air entering the gas turbine is reduced by 10 to 40° F. from the ambient temperature of the LNG production system. 
     
     
         8 . The integrated system of  claim 1 , wherein the temperature of the inlet air entering the gas turbine is reduced from an ambient temperature in a range from about 60 to about 120° F. to a temperature in a range from about 45 to about 55° F. 
     
     
         9 . The integrated system of  claim 1 , wherein the temperature of the inlet air entering the gas turbine is reduced to a temperature in a range from about 45 to about 55° F. 
     
     
         10 . The integrated system of  claim 1 , wherein an efficiency of the gas turbine is increased by at least 3% by reducing the temperature of the inlet air from 90 to 50° F. 
     
     
         11 . The integrated system of  claim 1 , wherein the regasified portion of the LNG is supplied to a natural gas pipeline. 
     
     
         12 . The integrated system of  claim 1 , further comprising a pre-treatment unit for removing contaminants from the inlet stream comprising natural gas. 
     
     
         13 . The integrated system of  claim 1 , further comprising a fractionation apparatus after a first stage in the refrigeration system for removing heavier hydrocarbons from the natural gas. 
     
     
         14 . The integrated system of  claim 1 , further comprising a tank for storing the LNG and the LNG that is regasified is supplied from the tank. 
     
     
         15 . An integrated method for operating a liquefied natural gas (LNG) plant, the method comprising:
 (i) cooling and condensing a natural gas stream in a refrigeration system to produce liquefied natural gas (LNG);   (ii) operating a gas turbine to drive a compressor for the refrigeration system;   (iii) regasifying a portion of the LNG;   (iv) reducing the temperature of inlet air entering the gas turbine by exchanging heat with the regasified portion of the LNG directly or indirectly; and   (iiv) supplying at least a portion of the regasified portion of the LNG to an outlet pipeline.   
     
     
         16 . The method of  claim 15 , wherein a gain in energy efficiency by reducing the temperature of the inlet air entering the gas turbine compensates for an amount of energy required to produce the portion of the LNG regasified in step (iii). 
     
     
         17 . The method of  claim 15 , wherein the temperature of inlet air is reduced by exchanging heat indirectly with the regasified portion of the LNG using an intermediate heat transfer fluid. 
     
     
         18 . The method of  claim 15 , wherein the portion of the LNG regasified is in a range from 5% to 25% by weight. 
     
     
         19 . The method of  claim 15 , wherein the temperature of the inlet air entering the gas turbine is reduced by at least 20° F. from the ambient temperature of the LNG plant. 
     
     
         20 . The method of  claim 15 , wherein the temperature of the inlet air entering the gas turbine is reduced from an ambient temperature in a range from about 80 to about 120° F. to a temperature in a range from about 42 to about 60° F. 
     
     
         21 . The method of  claim 15 , wherein the temperature of the inlet air entering the gas turbine is reduced to a temperature in a range from about 45 to about 55° F. 
     
     
         22 . The method of  claim 15 , wherein an efficiency of the gas turbine is increased by at least 3% by reducing the temperature of the inlet air from 90 to 50° F. 
     
     
         23 . The method of  claim 15 , further comprising a step of supplying the regasified portion of the LNG to a natural gas pipeline for domestic gas production. 
     
     
         24 . The method of  claim 15 , further comprising a step of recycling the regasified portion of the LNG to the natural gas stream in step (i). 
     
     
         25 . The method of  claim 15 , further comprising a step of sub-cooling a refrigerant in at least one stage of the refrigeration system by heat exchanging with from 10% to 90% by weight of the regasified portion of the LNG. 
     
     
         26 . The method of  claim 15 , further comprising a step of pre-treating the natural gas stream prior to step (i) to remove contaminants from natural gas stream. 
     
     
         27 . The method of  claim 15 , further comprising a step of fractionating the natural gas stream after a first stage in the refrigeration system to remove heavier hydrocarbons from the natural gas stream. 
     
     
         28 . The method of  claim 15 , further comprising a step of collecting water condensed from reducing the temperature of the inlet air in step (iv). 
     
     
         29 . The method of  claim 28  wherein the water is of drinking water quality and is supplied a local area. 
     
     
         30 . The method of  claim 15 , further comprising a step of using the regasified LNG supplied to the outlet pipeline to supply a domestic natural gas market. 
     
     
         31 . The method of  claim 15 , further comprising a step of blending the regasified LNG with natural gas to provide a blended gas meeting pipeline specifications for domestic gas production. 
     
     
         32 . A process for creating natural gas for a local gas market and liquefied natural gas (LNG) for transport comprising:
 a) cooling and condensing a natural gas stream in a LNG facility comprising a refrigeration system to produce LNG;   b) regasifying a portion of the LNG;   c) reducing the temperature of inlet air entering the refrigeration system by exchanging heat with the regasified portion of the LNG either directly or indirectly;   d) shipping the LNG to a remote location; and   e) supplying at least a portion of the regasified portion of the LNG to an outlet pipeline for the local gas market.