SiC, not Ti-gr1, for HX in ZLD crystallizer or evaporator?

[davefitz]

Is anyone familiar withthe use of silicon carbide SiC as the material for the heat exchanger plates or tubes in ZLD crystallizers and evaporators?

The cost of Ti-Gr1 seems prohibitive, while the thermal conductivity of SiC is 7 times that of Ti, and it has better anti corrosion behavior.

 

[EdStainless]

Excuse me, Ti tubing will be a fraction of the cost of SiC.
Ti tubing is selling for about 45$/kg, there are a lot of common alloys that more expensive.
We have supplied tubing for crystallizers in both AL-6XN and SEA-CURE. The use a super stainless steel is largely dependent on the pH of the system. High pH is good application for SEA-CURE.

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Plymouth Tube

 

[davefitz]

Thanks EdStainless.

pH in evaps and crystallizers is normally corrected up over 8.5, so perhaps SeaCure may be an alternative, although, the pH of teh bulk mixture may not be the governing parameter if crevice corrosion yields a local pH below 7.

It may be that the reason that SiC is used in europe for FGD components is the acidic pH in the FGD slurry.

 

[EdStainless]

In order for SiC to be corrosion resistant at low pH it will need to sintered, not reaction bonded. I am sure that the effective overall heat transfer coef for SiC tubes will be much worse than for Ti.
Yes, if this is aggressive enough that an alloyed Ti grade or special Ni alloy is needed then the cost may be above that of SiC. But I still find that hard to believe.

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Plymouth Tube

 

[davefitz]

edstainless:
the ZLD crystallizers and evaporators operatoe at a high pH, over 8.5 , in general.

 

[EdStainless]

Depending on the mineral loading I have seen them run anywhere from a pH of 1.5 up to 13.
Materials selection is very touch for these.

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Plymouth Tube