Heat exchanger

Abstract

A shell and tube heat exchanger particularly of enhanced diameter size of use, particularly, in the manufacture of sulfuric acid and having a plurality of an adjacent pair of longitudinal baffle plates located symmetrically and intermittently between and extending the length of the tube bundle. The exchanger is most advantageously made from segments which may be shipped to off-site locations for in situ manufacture of the heat exchanger, particularly when oversized heat exchangers are required when transportation of such large heat exchangers from an off-site manufacturing facility is not possible.

1 . A heat exchanger for exchanging heat between fluids and having a heat exchanger shell and a plurality of parallel tubes of circular cross-section, said tubes all having the same outer diameter, the improvement wherein said tubes are laid out according to the following relationship: 
 (i) said tubes are arranged with their centers located on a set of concentric circular arcs, said set comprising at least first, second and third such arcs, a plurality of tubes on each arc,    (ii) the number of tubes in each arc differs from the number of tubes in each other arc by not more than one,    (iii) the tubes in each arc are spaced uniformly apart along such arc,    (iv) each tube in each arc, other than such end tubes as may be present in some of said arcs, is located circumferentially midway between the two adjacent tubes of each neighboring arc so that the centers of each such three tubes form an isosceles triangle, each tube in each arc being separated from each of said adjacent tubes in each adjacent arc by a diagonal ligament distance h, said distance h being constant for all said tubes, and    (v) the distance between each two adjacent tubes in any said arc is at least as great as twice said diagonal ligament distance h, so that the minimum cross-sectional area for radial fluid flow between adjacent arcs of said set is defined as to its circumferential dimension by the sum of said diagonal ligament distances h between the tubes of said adjacent arcs and is substantially constant independent of the radial position of said arcs,    the improvement wherein said exchanger further comprises a plurality of an adjacent pair of longitudinal baffle plates located symmetrically and intermittently between transverse disc and donut baffles and extending the length of said plurality of tubes.    
   
   
       2 . A heat exchanger according to  claim 1  wherein each said arc extends through 360° so that each arc is a closed circular ring without end tubes, each ring having the same number of tubes as each other ring and is coaxial with said heat exchanger shell.  
   
   
       3 . A heat exchanger according to  claim 1  wherein each said arc extends through 360° so that each arc is a closed circular ring without end tubes, each ring having the same number of tubes as each other ring and is non-coaxial with said heat exchanger shell.  
   
   
       4 . A heat exchanger according to  claim 1  wherein each said arc comprises a plurality of arc segments, each segment extending through 360° divided by said plurality, such that each arc is a part of a closed “petal” shaped ring with end tubes and wherein, each non-adjacent arc has the same number of tubes, and adjacent arcs have a number of tubes differing by not more then one, and each arc is off-centered with said heat exchanger shell.  
   
   
       5 . A heat exchanger according  claim 1  wherein the radius of one of said rings is R n  and the radius of the next ring radially within said ring is R n+1  and said radii are related by the relationship  
     
       
         
           
             
               
                 R 
                 
                   n 
                   + 
                   1 
                 
               
               + 
               
                 b 
                 n 
               
             
             = 
             
               
                 R 
                 n 
               
               ⁢ 
               cos 
               ⁢ 
               
                   
               
               ⁢ 
               
                 α 
                 2 
               
             
           
         
       
     
     substantially within the limit that the radius of the innermost ring is  
     
       
         
           
             
               R 
               min 
             
             ≥ 
             
               
                 Do 
                 + 
                 
                   2 
                   ⁢ 
                   h 
                 
               
               
                 
                   2 
                   · 
                   sin 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     180 
                     ° 
                   
                   Ntr 
                 
               
             
           
         
       
     
     where b n  is the height of a said isosceles triangle between two adjacent tubes in said one ring and one tube in said next ring,  
     
       
         
           
             
               α 
               2 
             
             = 
             
               
                 180 
                 ° 
               
               
                 N 
                 tr 
               
             
           
         
       
       N tr  is the number of tubes per ring,  
       D o  is the outer diameter of said tubes.  
     
   
   
       6 . A heat exchanger according to  claim 5  wherein said tubes are arranged subject to the restriction that 
     
       

       R 
       n 
       −R 
       n+2 
       ≧D 
       o 
       +h 

       so that for the outermost ring R n ,  
       
         
           
             
               
                 θ 
                 n 
               
               ≥ 
               
                 
                   30 
                   ° 
                 
                 - 
                 
                   
                     180 
                     ° 
                   
                   
                     N 
                     tr 
                   
                 
               
             
           
         
       
       where θ n  is the angle between the base and one side of said isosceles triangle between two adjacent tubes, one in the said outermost ring and the nearest tube in the next ring.  
     
   
   
       7 . A heat exchanger according to  claim 1  and including a wall defining said shell extending parallel to and encircling said tubes, and first and second baffles each extending at right angles to said wall and intersecting at least some of said tubes, said first baffle extending to said wall and having an inner opening within the innermost of said rings, and hence being of donut configuration, said second baffle being of disc shape and extending from the centre of said innermost ring outwardly past said tubes and having an annular gap between its periphery and said wall, said first and second baffles alternating with each other to form a disc and donut baffle configuration.  
   
   
       8 . A heat exchanger according to  claim 7  wherein each said baffle intersects all of said tubes.  
   
   
       9 . A heat exchanger according to  claim 2  including two and three sets of said rings, each set containing a plurality of rings, the number of tubes in each ring of one set being different from the number of tubes in each ring of the other sets.  
   
   
       10 . A heat exchanger according to  claim 9  wherein said diagonal ligament distance h in said one set is different from said diagonal ligament distance in said other sets.  
   
   
       11 . A heat exchanger according to  claim 10  wherein the number of tubes in each ring of said one set multiplied by said diagonal ligament distance of said one set is equal to the number of tubes in each ring of said other set multiplied by said diagonal ligament distance of said other sets, so that said minimum cross-sectional area for said one set is equal to said minimum cross-sectional area for said other sets.  
   
   
       12 . A heat exchanger according to  claim 1  including two or three sets of said arcs, each said set containing a plurality of arcs, the number of tubes in each arc of one set being different from the number of tubes in each arc of the other sets.  
   
   
       13 . A heat exchanger according to  claim 12  wherein said diagonal ligament distance h in said one set is different from said diagonal ligament size distance in said other sets.  
   
   
       14 . A heat exchanger according to  claim 1 , wherein said plurality of said longitudinal baffle plates is an odd integer selected from 3 to 15.  
   
   
       15 . A heat exchanger according to  claim 14  wherein said integer is selected from 5, 7 and 9.  
   
   
       16 . A heat exchanger according to  claim 1  wherein said plurality of tubes extend between tube sheet end plates and said plurality of longitudinal baffle plates extend between said tube sheet end plates.  
   
   
       17 . A heat exchanger according to  claim 1  wherein said plurality of tubes within said exchanger has a diameter selected from 3 m to 8 m.  
   
   
       18 . A heat exchanger according to  claim 17  wherein said diameter is selected from 4 m to 6 m.  
   
   
       19 . A plant for the manufacture of sulfuric acid by the oxidation of sulfur dioxide to sulfur trioxide in a catalytic converter and subsequent absorption of said sulfur trioxide in sulfuric acid, said plant comprising an absorption tower, a heat exchanger and said catalytic converter, the improvement comprising a heat exchanger as defined in  claim 1 .  
   
   
       20 . A method of manufacturing a heat exchanger having said tube layout according to  claim 1 , wherein said method comprises 
 (A) providing a plurality of exchanger segments, wherein each of said segments (a) define a segment of an annulus having a longitudinal baffle plate along the radial sides of and extending the length of said segment;    (b) comprise a plurality of tubes of circular cross-section within said segment, said tubes all having the same outer diameter wherein said tubes are laid out according to the following relationship:    (i) said tubes are arranged with their centers located on a set of concentric circular arcs, said set comprising at least first, second and third such arcs, a plurality of tubes on each arc,    (ii) the number of tubes in each arc differs from the number of tubes in each other arc by not more than one,    (iii) the tubes in each arc are spaced uniformly apart along such arc,    (iv) each tube in each arc, other than such end tubes as may be present in some of said arcs, is located circumferentially midway between the two adjacent tubes of each neighboring arc so that the centers of each such three tubes form an isosceles triangle, each tube in each arc being separated from each of said adjacent tubes in each adjacent arc by a diagonal ligament distance h, said distance h being constant for all said tubes, and    (v) the distance between each two adjacent tubes in any said arc is at least as great as twice said diagonal ligament distance h, so that the minimum cross-sectional area for radial fluid flow between adjacent arcs of said set is defined as to its circumferential dimension by the sum of said diagonal ligament distances h between the tubes of said adjacent arcs and is substantially constant independent of the radial position of said arcs; and    (B) welding the requisite number of said segments one to another adjacent said longitudinal baffle plates to produce said heat exchanger having said tube layout and a plurality of adjacent pairs of longitudinal baffle plates located symmetrically and intermittently between and extending the length of said plurality of tubes.    
   
   
       21 . A method according to  claim 20  wherein said requisite number of said segments is an odd number selected from 5 to 15.  
   
   
       22 . A method according to  claim 21 , wherein said requisite number is selected from 5, 7 and 9.  
   
   
       23 . A method according to  claim 20  wherein each of said arcs extends through 360° so that each arc is a closed circular ring without end tubes, each ring having the same number of tubes as each other ring.  
   
   
       24 . A method according to  claim 20  wherein the radius of one of said rings is R n  and the radius of the next ring radially within said ring is R n+1  and said radii are related by the relationship  
     
       
         
           
             
               
                 R 
                 
                   n 
                   + 
                   1 
                 
               
               + 
               
                 b 
                 n 
               
             
             = 
             
               
                 R 
                 n 
               
               ⁢ 
               cos 
               ⁢ 
               
                   
               
               ⁢ 
               
                 α 
                 2 
               
             
           
         
       
       substantially within the limit that the radius of the innermost ring  
       
         
           
             
               
                 R 
                 min 
               
               ≥ 
               
                 
                   Do 
                   + 
                   
                     2 
                     ⁢ 
                     h 
                   
                 
                 
                   
                     2 
                     · 
                     sin 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     
                       180 
                       ° 
                     
                     Ntr 
                   
                 
               
             
           
         
       
       where b n  is the height of a said isosceles triangle between two adjacent tubes in said one ring and one tube in said next ring,  
       
         
           
             
               
                 α 
                 2 
               
               = 
               
                 
                   180 
                   ° 
                 
                 
                   N 
                   tr 
                 
               
             
           
         
       
       N tr  is the number of tubes per ring,  
       D o  is the outer diameter of said tubes.  
     
   
   
       25 . A method according to  claim 20  wherein said tubes are arranged subject to the restriction that 
     
       

       R 
       n 
       −R 
       n+2 
       ≧D 
       o 
       +h 

     
     so that for the outermost ring R n ,  
     
       
         
           
             
               θ 
               n 
             
             ≥ 
             
               
                 30 
                 ° 
               
               - 
               
                 
                   180 
                   ° 
                 
                 
                   N 
                   tr 
                 
               
             
           
         
       
     
     where θ n  is the angle between the base and one side of said isosceles triangle  
     between two adjacent tubes in said outermost ring and one tube in the next ring.  
   
   
       26 . A method according to  claim 20  wherein said exchanger includes a wall defining a shell extending parallel to and encircling said tubes, and first and second baffles each extending at right angles to said wall and intersecting at least some of said tubes, said first baffle extending to said wall and having an inner opening within the innermost of said rings, and hence being of donut configuration, said second baffle being of disc shape and extending from the centre of said innermost ring outwardly past said tubes and having an annular gap between its periphery and said wall, said first and second baffles alternating with each other to form a disc and donut baffle configuration.  
   
   
       27 . A method according to  claim 26  wherein each said baffle intersects all of said tubes.  
   
   
       28 . A method according to  claim 20  wherein said heat exchanger includes two or three sets of said rings, each set containing a plurality of rings, the number of tubes in each ring of one set being different from the number of tubes in each ring of the other sets.  
   
   
       29 . A method according to  claim 20  wherein said diagonal ligament distance h in said one set is different from said diagonal ligament distance in said other set.  
   
   
       30 . A method according to  claim 20  wherein the number of tubes in each ring of said one set multiplied by said diagonal ligament distance of said one set is equal to the number of tubes in each ring of said other set multiplied by said diagonal ligament distance of said other sets, so that said minimum cross-sectional area for said one set is equal to said minimum cross-sectional area for said other sets.  
   
   
       31 . A method according to  claim 20  wherein said heat exchanger includes two or three sets of said arcs, each said set containing a plurality of arcs, the number of tubes in each arc of one set being different from the number of tubes in each arc of the other sets.  
   
   
       32 . A method according to  claim 20  wherein said diagonal ligament distance h in said one set is different from said diagonal ligament size distance in said other sets.  
   
   
       33 . A heat exchanger segment which  
     (a) defines a segment of an annulus having a longitudinal baffle plate along the radial sides of and extending the length of said segment;  
     (b) comprises a plurality of tubes of circular cross-section within said segment, said tubes all having the same outer diameter wherein said tubes are laid out according to the following relationship: 
 (i) said tubes are arranged with their centers located on a set of concentric circular arcs, said set comprising at least first, second and third such arcs, a plurality of tubes on each arc,  
 (ii) the number of tubes in each arc differs from the number of tubes in each other arc by not more than one,  
 (iii) the tubes in each arc are spaced uniformly apart along such arc,  
 (iv) each tube in each arc, other than such end tubes as may be present in some of said arcs, is located circumferentially midway between the two adjacent tubes of each neighboring arc so that the centers of each such three tubes form an isosceles triangle, each tube in each arc being separated from each of said adjacent tubes in each adjacent arc by a diagonal ligament distance h, said distance h being constant for all said tubes, and  
 (v) the distance between each two adjacent tubes in any said arc is at least as great as twice said diagonal ligament distance h, so that the minimum cross-sectional area for radial fluid flow between adjacent arcs of said set is defined as to its circumferential dimension by the sum of said diagonal ligament distances h between the tubes of said adjacent arcs and is substantially constant independent of the radial position of said arcs of use in the method defined in  claim 30 .  
 
   
   
       34 . A heat exchanger segment as defined in  claim 33  which longitudinal baffle plates subtend an angle therebetween, selected from the group consisting of about 72°; 51.5°; 40°; 33°; 28° and 24°.