Method and apparatus for producing high-pressure nitrogen

Abstract

A method and apparatus for producing a high-pressure gas from an air separation unit is provided, in which the method includes the steps of introducing a cold air feed into a distillation column system under conditions effective for separating the cold air feed into a first air gas and a second air gas; withdrawing the first and second air gases from the distillation column system and warming said first and second air gases in a main heat exchanger, wherein the first air gas is withdrawn from the distillation column system at a medium pressure; splitting the first air gas into a first fraction and a second fraction; expanding the first fraction in a turbine; and compressing the second fraction in a booster to a pressure that is higher than the medium pressure, wherein the booster is powered by the turbine

We claim: 
     
         1 . A method for producing a high-pressure gas from an air separation unit, the method comprising the steps of:
 introducing a cold air feed into a distillation column system under conditions effective for separating the cold air feed into a first air gas and a second air gas;   withdrawing the first and second air gases from the distillation column system and warming said first and second air gases in a main heat exchanger, wherein the first air gas is withdrawn from the distillation column system at a medium pressure;   splitting the first air gas into a first fraction and a second fraction;   expanding the first fraction in a turbine; and   compressing the second fraction in a booster to a pressure that is higher than the medium pressure, wherein the booster is powered by the turbine.   
     
     
         2 . The method as claimed in  claim 1 , further comprising the step of warming the expanded first fraction. 
     
     
         3 . The method as claimed in  claim 2 , wherein the expanded first fraction is warmed in a second heat exchanger against the boosted second fraction. 
     
     
         4 . The method as claimed in  claim 2 , wherein the expanded first fraction is warmed in the main heat exchanger. 
     
     
         5 . The method as claimed in  claim 4 , wherein the boosted second fraction is cooled to ambient temperature using a dedicated cooler. 
     
     
         6 . The method as claimed in  claim 5 , wherein the dedicated cooler is a water cooler. 
     
     
         7 . The method as claimed in  claim 1 , wherein the first fraction and the second fraction are withdrawn at an intermediate location of the heat exchanger, such that the first fraction and the second fraction are partially warmed in the main heat exchanger. 
     
     
         8 . The method as claimed in  claim 7 , further comprising the step of warming the expanded first fraction in the main heat exchanger, and wherein the boosted second fraction is at ambient temperature at an outlet of the booster. 
     
     
         9 . The method as claimed in  claim 1 , wherein the second fraction is withdrawn at an intermediate location of the heat exchanger and the first fraction is withdrawn at a warm end of the heat exchanger, such that the first fraction is fully warmed and the second fraction is partially warmed. 
     
     
         10 . The method as claimed in  claim 9 , further comprising the step of warming the expanded first fraction in the main heat exchanger, and wherein the boosted second fraction is at ambient temperature at an outlet of the booster. 
     
     
         11 . The method as claimed in  claim 1 , wherein the distillation column system comprises at least one distillation column. 
     
     
         12 . The method as claimed in  claim 1 , wherein the distillation column system comprises a double column. 
     
     
         13 . The method as claimed in  claim 1 , wherein the first air gas is nitrogen and the second air gas is oxygen. 
     
     
         14 . An apparatus for producing a high-pressure gas from an air separation unit, the apparatus comprising:
 a main heat exchanger having a warm end and a cold end;   a distillation column system in fluid communication with the cold end of the main heat exchanger, wherein the distillation column system is configured to receive a cold air feed from the cold end of the main heat exchanger and separate the cold air feed into a first air gas and a second air gas, wherein the distillation column system is also configured to send the first air gas to the cold end of the main heat exchanger;   a turbine in fluid communication with the main heat exchanger, wherein the turbine is configured to receive a first fraction of the first air gas after warming in the main heat exchanger;   a warm booster in fluid communication with the main heat exchanger, wherein the warm booster is configured to receive a second fraction of the first air gas after warming in the main heat exchanger thereby providing a high-pressure gas that is at a pressure greater than an operating pressure of a column within the distillation column system,   wherein the turbine is configured to power the warm booster.