Boiler types horizontal shell boilers

For shell boilers, superheaters may be one of three types, depending upon the degree of superheat required. The first and simplest is the pendant superheater installed in the front smokebox (Figure 23.7). The maximum degree of superheat available from this would be around 45°C. The second pattern is again installed in the front smokebox but with this, the elements are horizontal U tubes which extend into the boiler smoketubes. The degree of superheat from this pattern is around 80°C. Third, a superheater may be installed in the reversal chamber of the boiler. A wetback chamber presents problems with lack of space, and therefore a semi-wetback, dryback or water-cooled wall chamber may be considered. Maximum degree of superheat would be around 100°C. 

KETTLE-TYPE BOILERS. A kettle-type boiler, or reboiler as it is called when connected to a distillation column, is shown in Fig. 15.11. A horizontal shell contains a relatively small tube bundle, two-pass on the tube side, with a floating head and tube sheet. The tube bundle is submerged in a pool of boiling liquid. 

Many types of firetube boilers are being supplied to industry. One type is the horizontal return tubular boiler (Fig. 6.6). In this unit, the products of combustion travel across the shell and back through the tubes within the pressure vessel. These units are usually horizontally brick-set. 

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