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Rate of Mass Deposition of Scaling Compounds from Seawater on the Outer Surface of Heat Exchangers in MED Evaporators
Author(s) -
Omar W.,
Ulrich J.
Publication year - 2006
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.200600050
Subject(s) - seawater , scaling , evaporator , deposition (geology) , heat exchanger , salinity , chemistry , artificial seawater , mass transfer , heat transfer , materials science , chromatography , thermodynamics , physics , geology , paleontology , oceanography , geometry , mathematics , sediment
Abstract The scaling problem in Multi Effect Distillation (MED) evaporators is investigated by the experimental measurement of the deposition rate under different operating conditions. The measurements are conducted in a batch vessel containing artificial seawater, which is allowed to contact the outer surface of a hot pipe under controlled temperature, salinity and pH. The rate of mass deposition is higher at elevated temperature. The salinity of the seawater also influences the scaling process – an increase in salinity from 47–59 g/L leads to an increase of 75.6 % in the deposition rate. Decreasing the pH value of seawater to 2.01 results in a complete inhibition of scaling, whereas the severity of the scaling increases in neutral and basic mediums. Polyacrylic acid is tested as an antifoulant and it was found that its presence in seawater reduces the scaling process. The nature of the heat transfer surface material also plays an important role in the scaling process. It is found experimentally that the rate of scaling is higher in the case of a Cu‐Ni alloy as the surface material of the tube rather than stainless steel.