Heat exchange and heat exchange process

Abstract

Heat exchange process comprising sequential cooling a first fluid by indirect heat exchange with a second fluid and comprising the following steps: introducing the first fluid sequentially into at least two concentric U-tube bundles defining at least a first heating zone and a second heating zone respectively, introducing a second fluid onto the shell side of the U-tube bundles, each heating zone partially separated from the other by a wall, the first heating zone being a colder zone and the second heating zone being a hotter zone, the tube bundle of the first colder heating zone being made of a low alloy steel and the tube bundle of the second hotter heating zone being made of a temperature and corrosion resistant alloy, withdrawing the cooled second fluid and the heated first fluid. The invention also concerns a heat exchanger for use in the above process.

1 . Heat exchange process comprising sequentially cooling a first fluid by indirect heat exchange with a second fluid and comprising the following steps:
 introducing the first fluid sequentially into at least two concentric U-tube bundles defining at least a first heating zone and a second heating zone respectively,   introducing a second fluid onto the shell side of the U-tube bundles, each heating zone partially separated from the other by a wall, the first heating zone being a colder zone and the second heating zone being a hotter zone, the tube bundle of the first colder heating zone being made of a low alloy steel and the tube bundle of the second hotter heating zone being made of a temperature and corrosion resistant alloy,   withdrawing the cooled second fluid and the heated first fluid.   
   
   
       2 . Heat exchange process according to  claim 1 , wherein the first fluid is steam and the second fluid is reformed gas. 
   
   
       3 . Heat exchange process according to  claim 1 , wherein the temperature and corrosion resistant alloy is austenitic nickel/chromium/iron alloy. 
   
   
       4 . Heat exchange process according to  claim 2 , wherein the heated first fluid is superheated steam. 
   
   
       5 . Heat exchanger for use in the process of  claim 1 , comprising a plurality of U-tubes securing a heat exchange surface for allowing heat transfer between a first and a second fluid, the U-tubes arranged in at least two sequential concentric tube bundles, the tube bundles defining at least a first and second heating zone respectively, each heating zone partially separated from the other by a wall, the first heating zone being a colder zone and the second heating zone being a hotter zone, the tube bundle of the first colder heating zone being made of a low alloy steel and the tube bundle of the second hotter heating zone being made of a temperature and corrosion resistant alloy. 
   
   
       6 . Heat exchanger according to  claim 5 , wherein the heat exchanger has three tube bundles, the third bundle being placed in the middle between the first and the second bundles. 
   
   
       7 . Heat exchanger according to  claim 5 , wherein the temperature and corrosion resistant alloy is austenitic nickel/chromium/iron alloy. 
   
   
       8 . Heat exchanger according to  claim 5 , wherein the heat exchanger has baffles of the disc and doughnut type. 
   
   
       9 . Heat Exchanger according to  claim 6 , wherein the tubes of the third bundle placed in the middle are of low alloy steel and the baffles and rods holding the baffles in place and the walls of the middle bundle are of temperature and corrosion resistant alloy. 
   
   
       10 . Heat exchanger according to  claim 5 , wherein the wall separating the heating zones is of metal and is positioned to divide the flow of the second fluid into several streams by passage through openings in the wall.