The effect of temperature on material corrosion
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This post was last edited by zjq1962 on 2018-4-8 at 13:31. In a titanium spiral plate heat exchanger, the temperature of the material increases gradually from the center toward the outer rim; the temperature is highest at the outer rim. The concentration of the material remains unchanged. As can be seen from the diagram, the corrosion on the outermost plates as well as on the welds at the ends is quite severe
Generally, the corrosion rate always increases with temperature. As the temperature rises, the diffusion rate increases, accelerating the corrosion reaction.
Screw exchanges that have been in contact with persulfuric acid are highly sensitive to temperature; the corrosion rate can increase exponentially at times, and the operational range is very narrow. In such cases, it’s necessary to choose a different material
Several special materials have been tried, but titanium still has the longest service life
There are also some special materials with better corrosion resistance than titanium, and they are more expensive as well; of course, the specific choice depends on the corrosive environment. Screw-type corrosion margin has advantages, but it increases the amount of steel used significantly. It may be advisable to strengthen the vulnerable areas specifically, such as by thickening them or by using or applying better alloys in those areas.
It is feasible to thicken the outermost layers of the heat exchange plates appropriately, but how can covering be achieved?
Spraying, cladding with corrosion-resistant alloys, or lining with enamel/F4
The best approach is to increase the thickness of the heat exchange plates in the outermost layers. The several methods you mentioned cannot be implemented in spiral plate heat exchangers
If cooling could prevent corrosion, then the heat exchange area could be increased to compensate for the temperature difference; for example, by using two units in parallel.
This post was last edited by zjq1962 on 2018-4-15 at 22:47. The outlet temperature is originally a value required by the manufacturing process. Two units in parallel are used for high flow rates that exceed the processing capacity of a single unit.