Acid and Oleum Cooling

The circulating streams of acid in the IPAT and FAT need to be cooled before admission to the towers since they get heated while passing through by heat of absorption of SO3 and heat contained depending upon the specific heat which will be dependent upon its composition mainly on the percentage of SO2, SO3, Nj and O2 entering the towers. 

In the case of the drying tower, the acid stream absorbs moisture from the air and this adds the heat of dilution. However, due to the flow of air at a temperature lower than that of the add, the resultant temperature of the exit acid stream is only maiginally more by about 3-5 C. This depends on the relative humidity (moisture content in the air) and the air flow rate. 

Generally the following are considered to be the optimum tanperatures at the inlets of the respective towers. 

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. 

IPAT coolers have more of pipes since more heat is to be removed. 

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Sulphur melters and burner, water treatment plant internal, heat exchangers between converter passes (de-scaling of tubes), plate heat exchangers for acid and oleum cooling. Special emphasis is laid on those units having abnormal pressure drops and less efficiency (converter, acid towers, heat exchangers, etc.). 

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