Trombone Coolers

12 Other Types of Heat Exchangers 9.12.1 Trombone Coolers 

Banks of pipes over which cooling water is sprayed. There is a basin below the bank of pipes and has a pump for circulating water. The unit acts like a cooling tower— but without a fan—and any leaking pipe can be easily seen and attended. But it should have enclosure sheets all around to prevent any accident due to such leaks. The basin is supplied with fresh make-up water, and is purged out if TDS increases beyond 4000 ppm to reduce scale formation on the pipes. Cost of power required for ID fan is saved. 

It occupies more space— both on floor and vertically. They were used for sulphuric acid plants earlier, but are now replaced by PHE or shell and tube heat exchangers. 

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Acid Coolers. Cast Hon trombone coolers, once the industry standard (101), are considered obsolete. In 1970, anodically passivated stainless steel sheU and tube acid coolers became commercially available. Because these proved to have significant maintenance savings and other advantages, this type of cooler became widely used. Anodic passivation uses an impressed voltage from an external electrical power source to reduce metal corrosion. 

Trixylenyl phosphate, 22 493, 494 Trombone coolers, 23 779 Trommsdorf Effect, 16 281-282 in styrene polymerization, 23 382 Trona, 5 785t... 

If the plant has only one acid circulation tank, then all the exit streams from the towers get mixed. Separate add pumps or a common acid pump can supply acid to the towers through separate cooling arrangements. These are in the form of trombone coolers (rows and columns of Cl pipes over which water spray trickles down) having more cooling area for DT than FAT. 

Cast iron is not attacked by hot acid and hence trombone coolers (rows of Cl pipes over which cooling water is sprayed for trickling down) are used for cooling sulfuric acid from 75-80 °C to 55-60 °C in the plants. 

The Ballestra group uses a combination of U-tube cooler and a shell-and-tube heat exchanger for the cooling of S02/air with ambient air. MM and Mazzoni supply a vertical double-hairpin heat exchanger (a so-called trombone cooler) with air cooling. 

Design a double hairpin ("trombone") cooler to cool the S02/air ex sulphur furnace to a temperature of 430with ambient air flowing counter-current through the jacket of the trombone cooler inlet cooling air temperature 30 "C, outlet 250 C. Mean SOi/air flow velocity in tube 25 m/s, mean cooling air velocity in jacket 20 m/s. 

A closer look at a 180 TPD S.A. plant at Ankleshwar, Gujarat of M/s. Shree Sulphuric Acid. In the foreground one can see the Trombone Cooler for 25 % oleum. 

Cooling system for oleum—MS trombone type coolers with water spray falling down on the pipes or plate heat exchangers with special Viton gaskets. 

Plate heat exchangers instead of trombone-type coolers for acid cooling were more efficient and had less breakdowns. 

Plate heat exchangers and cooling towers which can control the temperature of absorbing liquor in a better manner to minimise pollution (instead of trombone-type coolers). 

Plate heat exchangers can recover heat from hot sulphuric acid as hot water earlier designs of trombone-type acid coolers wasted all the heat). The hot water can be obtained at a temperature within three to five degrees of the temperature of the incoming hot acid stream and hence can be used elsewhere in the premises. 

Oleum An additional absorption tower with Oleum circulation pump, trombone type or PHE type Oleum Coolers, dedicated cooling tower etc. 

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