Heat exchanger units are a key component of the Bayer process. In a such a demanding energy process, these units recovery heat from the system to use it again so alumina extraction from the bauxite continues happening at a competitive price.
As an inherent part of the process, reactive silica from the bauxite precipitates in the tube side of the HEX units reducing the capacity to recover heat from the system. These HEX units have to be washed periodically with diluted sulphuric acid to dissolve the scale formation consequently recover the levels of heat transfer coefficient.
Diluted sulphuric acid also attacks the metal surface and in some circumstances with critical mass loss that compromises the integrity of the tube. Once the tube integrity is compromised, maintenance cost and alumina losses are incurred. A low carbon steel material, such as Superhex will minimise the corrosion attack consequently reduce the losses.
Corrosion Measured by Electrochemistry and Mass Loss has been obtained from Plant Trials