System and method of cooling

Abstract

A cooling system and method for use in industrial plants are disclosed. A hot fluid stream is first cooled in an air-cooled stage to an intermediate temperature, and then to a final temperature in a water-cooled stage. The two-stage cooling method, which has advantages over either air-cooling or water-cooling alone, is well-suited for applications or locations where water use is restricted due to economic or environmental concerns.

What is claimed is:  
     
         1 . A cooling system for use in an air separation plant, comprising: 
 an air-cooled stage downstream from an equipment in said air separation plant for cooling a hot fluid stream associated with said equipment to a first temperature; and    a water-cooled stage downstream from said air-cooled stage for cooling said hot fluid stream further to a second temperature.    
     
     
         2 . The cooling system of  claim 1 , wherein said water-cooled stage comprises a water-cooled device, a water source, and a pump for delivering a water coolant stream from said water source to said water-cooled device.  
     
     
         3 . The cooling system of  claim 2 , wherein said water source is at least one of an evaporative water tower or an open body of water.  
     
     
         4 . The cooling system of  claim 2 , further comprising a chiller downstream from said water source but upstream of said water-cooled device.  
     
     
         5 . The cooling system of  claim 1 , wherein said air-cooled stage comprises a non-evaporative air cooler.  
     
     
         6 . The cooling system of  claim 1 , wherein said air-cooled stage comprises a heat exchange section, an air cooler, and a pump for circulating a coolant stream between said heat exchange section and said air cooler; said heat exchange section being configured for heat exchange between said hot fluid stream and said coolant stream.  
     
     
         7 . The cooling system of  claim 6 , wherein said water-cooled stage comprises a water-cooled device, a water source, and a pump for delivering a water coolant stream from said water source to said water-cooled device.  
     
     
         8 . The cooling system of  claim 7 , wherein said water source is at least one of an evaporative water tower or an open body of water.  
     
     
         9 . The cooling system of  claim 7 , further comprising a chiller downstream from said water source but upstream of said water-cooled device.  
     
     
         10 . The cooling system of  claim 1 , wherein said air-cooled stage and said water-cooled stage are coupled in series to a heat exchange section and a circulating pump, said air-cooled stage being downstream from said heat exchange section to provide air cooling of said hot fluid stream to said first temperature.  
     
     
         11 . The cooling system of  claim 10 , wherein said air-cooled stage is a non-evaporative air cooler and said water-cooled stage is an evaporative water tower.  
     
     
         12 . The cooling system of  claim 10 , further comprising a chiller downstream of said water-cooled stage but upstream of said heat exchange section.  
     
     
         13 . The cooling system of  claim 1 , wherein said equipment is selected from the group consisting of a compressor and a compressor/expander system.  
     
     
         14 . A method of cooling for use in an air separation plant, comprising: 
 (a) cooling a hot fluid stream associated with an equipment in said air separation plant to a first temperature using an air-cooled stage; and    (b) cooling said hot fluid stream further to a second temperature in a water-cooled stage downstream from said air-cooled stage.    
     
     
         15 . The method of  claim 14 , wherein said water-cooled stage comprises a water-cooled device, a water source, and a pump for delivering a water coolant stream from said water source to said water-cooled device for cooling said hot fluid stream to said second temperature.  
     
     
         16 . The method of  claim 15 , wherein said water source is at least one of an evaporative water tower or an open body of water.  
     
     
         17 . The method of  claim 14 , wherein said air-cooled stage is selected from the group consisting of a fin fan air cooler and a liquid circulating circuit; said liquid circulating circuit comprising a heat exchange section, an air-cooled device and a pump for circulating a liquid coolant between said heat exchange section and said air-cooled device.  
     
     
         18 . The method of  claim 14 , wherein said air-cooled stage is operated at a higher approach temperature higher than said water-cooled stage.  
     
     
         19 . The method of  claim 14 , wherein said equipment is selected from a compressor, compressor/expander system, and a refrigeration unit condenser.  
     
     
         20 . The method of  claim 14 , wherein said hot fluid stream is a process stream exiting from said equipment or a coolant stream heated by heat exchange with said process stream.  
     
     
         21 . A method of cooling for use in an industrial plant comprising: 
 (a) cooling a hot fluid stream originating from an equipment in said industrial plant to a first temperature using an air-cooled stage, said equipment being selected from the group consisting of a compressor and a compressor/expander system; and    (b) cooling said hot fluid stream from said first temperature to a second temperature using a water-cooled stage.    
     
     
         22 . The method of  claim 21 , wherein said hot fluid stream is a compressed air stream from a first compressor, and said method further comprises introducing said compressed air stream at said second temperature into a second compressor.  
     
     
         23 . The method of  claim 21 , wherein said industrial plant is an air separation plant, and said hot fluid stream is a compressed air stream from a compressor.