Main heat exchanger and a process for cooling a tube side stream

Abstract

A process for cooling a tube side stream in a main heat exchanger is described. The process comprises: a) supplying a first mass flow of a tube side stream to a first zone of individual tubes in the tube bundle; b) supplying a second mass flow of the tube side stream to a second zone of individual tubes in the tube bundle, the second zone being offset from the first zone; c) supplying a refrigerant stream on the shell side for cooling the first and second mass flows; d) removing the evaporated refrigerant stream from the warm end of the main heat exchanger; and, e) adjusting the first mass flow of the tube side stream relative to the second mass flow of the tube side stream to maximise the temperature of the removed evaporated refrigerant stream.

1 . A process for cooling a tube side stream in a main heat exchanger having a warm end and a cold end, the main heat exchanger comprising a wall defining a shell side within which a coil-wound tube bundle is arranged around a central mandrel, the process comprising the steps of:
 a) supplying a first mass flow of a tube side stream to the warm end of a first zone of individual tubes in the tube bundle via a first nozzle;   b) supplying a second mass flow of the tube side stream to the warm end of a second zone of individual tubes in the tube bundle via a second nozzle, the second zone being offset from the first zone along a radius extending from the central mandrel to the wall of the main heat exchanger;   c) supplying a refrigerant stream on the shell side for cooling the first and second mass flows to form an evaporated refrigerant stream;   d) removing the evaporated refrigerant stream from the warm end of the main heat exchanger; and,   e) adjusting the first mass flow of the tube side stream relative to the second mass flow of the tube side stream to maximise the temperature of the evaporated refrigerant stream removed in step d)   wherein step e) comprises equalizing the temperature of the first mass flow of the tube side stream at a first axial location relative to the length of the mandrel with the temperature of the second mass flow of the tube side stream at said first axial location by adjusting the mass flow supplied to one or both of the first and second nozzles.   
     
     
         2 . (canceled) 
     
     
         3 . The process of  claim 1  wherein a first temperature sensor generates a first signal indicative of the temperature of the first mass flow and a second temperature sensor generates a second signal indicative of the temperature of the second mass flow and step e) comprises using a controller to adjust the first mass flow of the tube side stream relative to the second mass flow of the tube side stream to equalise the first signal with the second signal. 
     
     
         4 . The process of  claim 1  wherein the first axial location is at or adjacent to the cold end of the main heat exchanger. 
     
     
         5 . The process of  claim 1  wherein the first zone is an inner zone of the tube bundle and the second zone is an outer zone of the tube bundle. 
     
     
         6 . The process of  claim 1  wherein the mass flow through the first nozzle is controllably adjusted using a first valve and the mass flow through the second nozzle is controllably adjusted using a second valve. 
     
     
         7 . The process of  claim 6  wherein one or both of the first and second valves is external to the main heat exchanger. 
     
     
         8 . The process of  claim 6  wherein one or both of the first and second valves is a fail-safe open low pressure drop valve. 
     
     
         9 . The process of  claim 6  wherein one or both of the first and second valves is located at one or both of the warm end and the cold end of the tube side stream. 
     
     
         10 . The process of  claim 1  wherein the first nozzle supplies the tube fluid to the first zone via a first tube sheet and the second nozzle supplies the tube side fluid to the second zone via a second tube sheet. 
     
     
         11 . The process of  claim 1  wherein the tube bundle comprises a warm tube bundle arranged towards the warm end of the main heat exchanger, and a cold tube bundle arranged towards the cold end of the main heat exchanger, each of the warm tube bundle and the cold tube bundle having a warm end and a cold end and the first location is at or adjacent to the cold end of the warm tube bundle. 
     
     
         12 . The process of  claim 11  wherein the tube side stream is a first tube side stream which enters the warm end of the warm tube bundle as a liquid and exits the cold end of the cold tube bundle as a sub-cooled liquid. 
     
     
         13 . The process of  claim 11  wherein the first tube side stream enters the warm end of the warm tube bundle as a gaseous, methane-rich feed which has been liquefied by the time it passes from the warm end of the warm tube bundle into the warm end of the cold tube bundle. 
     
     
         14 . The process of  claim 13  wherein the first tube side stream enters the warm end of the cold tube bundle as a liquid and exits the cold end of the cold tube bundle as a sub-cooled liquid. 
     
     
         15 . The process of  claim 14  wherein the sub-cooled liquid is removed from the cold end of the cold tube bundle of the main heat exchanger before being directed to storage. 
     
     
         16 . The process of  claim 15  wherein the first tube side stream exchanges heat with a predominately liquid light refrigerant stream which is progressively boiled off on the shell side of the cold tube bundle. 
     
     
         17 . The process of  claim 16  wherein evaporated refrigerant removed from the warm end of the shell side of the main heat exchanger is fed to first and second refrigerant compressors in which the evaporated refrigerant is compressed to form a high pressure refrigerant stream. 
     
     
         18 . The process of  claim 17  wherein the high pressure refrigerant stream is directed to a heat exchanger in which it is cooled so as to produce a partly-condensed refrigerant stream which is then directed in a separator to separate out a heavy refrigerant fraction in liquid form and a light refrigerant fraction in gaseous form. 
     
     
         19 . The process of  claim 18  wherein the heavy refrigerant fraction becomes a second tube side stream which is supplied at the warm end of the warm tube bundle as a liquid and exits at the cold end of the warm tube bundle as a sub-cooled heavy refrigerant stream in liquid form. 
     
     
         20 . The process of  claim 19  wherein the sub-cooled heavy refrigerant stream removed at the cold end of the warm tube bundle is expanded across a first expansion device to form a reduced pressure heavy refrigerant stream that is then introduced into the shell side of the main heat exchanger at a location intermediate between the cold end of the warm tube bundle and the warm end of the cold tube bundle, and wherein said reduced pressure heavy refrigerant stream is allowed to evaporate in the shell side, thereby cooling the fluids in the first, second and third tube side streams as they pass through the warm tube bundle. 
     
     
         21 . The process of  claim 20  wherein part of the light refrigerant fraction from the separator becomes a third tube side stream which is introduced into the warm end of the warm tube bundle as a gas and exits at the cold end of the cold tube bundle as a sub-cooled liquid. 
     
     
         22 . The process of  claim 21  wherein the third tube side stream is cooled from a gas to a liquid as it passes through the warm tube bundle and is cooled from a liquid to a sub-cooled liquid as it passes through the cool bundle. 
     
     
         23 . The process of  claim 22  wherein the sub-cooled light refrigerant stream removed from the cold end of the cold tube bundle is expanded through a second expansion device to cause a reduction in pressure and produce a reduced pressure light refrigerant stream. 
     
     
         24 . The process of  claim 23  wherein the reduced pressure light refrigerant stream is introduced into the shell side of the main heat exchanger at its cold end, and wherein said reduced pressure light refrigerant stream is allowed to evaporate in the shell side, thereby cooling the fluids in the first and third tube side streams as they travel through the cold tube bundle as well as providing cooling to the fluids in the first, second and third tube side streams as they travel through the warm tube bundle. 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . (canceled) 
     
     
         29 . (canceled) 
     
     
         30 . (canceled) 
     
     
         31 . (canceled) 
     
     
         32 . (canceled) 
     
     
         33 . (canceled) 
     
     
         34 . (canceled) 
     
     
         35 . (canceled) 
     
     
         36 . (canceled) 
     
     
         37 . (canceled)