Hi Friends,
In earlier posts, we have already discussed about the design and operational suitability of Shell & tube type and Double pipe heat exchangers for Alumina refinery. In present post, we shall focus on highlights of design considerations for Plate Heat Exchangers (PHEs).
In Heat interchange area of Alumina refinery, PHEs are used for transfer of thermal energy from filtered saturated aluminate liquor (Pregnant liquor) to spent liquor going to evaporation / digestion circuit. PHEs are very efficient heat transfer equipment requiring small installation as well as working space compared to Vacuum flash system for similar duty conditions. In brownfield expansion of Alumina refineries, generally PHEs are installed for the purpose because of space limitation in the plant.
The heat transfer coefficient for Pregnant liquor - Spent liquor service is taken at 1600-1850 k.cal/m2.hr.oC for working out the heat transfer area requirement and thereby the number of plates for PHE. Though, there should not be suspended solids in either fluid streams, however, the system is designed for movement of liquor with maximum particle size of 5 mm diameter through PHEs during operation. The Neoprene rubber gaskets are used for fixing the plates in PHEs. The hydrostatic test of PHE is conducted at 1.5 times the design pressure before commissioning the system for taking into normal operation in process circuit.
In my opinion, Vacuum flash system is a better choice over PHEs as it gives extra evaporation free of cost over and above the required heat transfer. Also, it requires less capital investment comparision to PHEs. We will discuss the design aspects of Vacuum flash system in forthcoming post.
Request to flash your views / comments / suggestions ,if any, on design features of PHEs.
Regards.
Kunwar Rajendra
The heat transfer coefficient for Pregnant liquor - Spent liquor service is taken at 1600-1850 k.cal/m2.hr.oC for working out the heat transfer area requirement and thereby the number of plates for PHE. Though, there should not be suspended solids in either fluid streams, however, the system is designed for movement of liquor with maximum particle size of 5 mm diameter through PHEs during operation. The Neoprene rubber gaskets are used for fixing the plates in PHEs. The hydrostatic test of PHE is conducted at 1.5 times the design pressure before commissioning the system for taking into normal operation in process circuit.
In my opinion, Vacuum flash system is a better choice over PHEs as it gives extra evaporation free of cost over and above the required heat transfer. Also, it requires less capital investment comparision to PHEs. We will discuss the design aspects of Vacuum flash system in forthcoming post.
Request to flash your views / comments / suggestions ,if any, on design features of PHEs.
Regards.
Kunwar Rajendra
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