Choosing a mixer lining for a highly corrosive/abrasive feed 1

[NPKresults]

Hello all,
Currently I have been researching suitable materials from which to construct a reactor. The reaction involves finely ground phosphate rock (150mesh) and 80% H2SO4 which is further diluted at the mixer. Obviously this is going to be a hot (150C design temp) and nasty reaction. In the past effort has been made to construct the mixer out of everything short of diamonds (hastalloys, and more expensive). This time around efforts are being made to design an easily replacable mixer out much less costly materials so that it may easily be discarded at most every 3-6 months. My current thought was to construct a mixer shell out of a high silicon (10%+) cast iron (I have read has decent oxidation and reduction resistance) and to line it with a thick (>1") polymer coating. I was thinking about one of the fluoroplastics (PTFE, CTFE, etc). I would appreciate any thoughts on the subject

 

[NPKresults]

I should also mention that the superalloys did not do the job, hastelloy C failed within 3 months, and hastelloy G30 did not last much longer

 

[EdStainless]

With your temp and abrasion I doubt that you will find a polymer liner system that will work. It would need to be a thermoset to have the strength and chemical resistance.

There is no doubt that G30 has better corrosion resistance in your application than any other alloy. If that life was too short then maybe you should look at a Co based alloy such as Ultimet for added wear resistance.
The other thought is to use a metal overlay, either weld or spray. A Co/Cr alloy would be my first thought. You could re-hab the coating regularly before you have failures.

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Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[StoneCold]

Maybe contact CoorsTek ceramics. You might be able to put ceramic linings on an alloy. If you could stop the abrasion of the base metals they should hold up a lot better.

Just a general suggestion.

Regards
Stonecold

 

[NPKresults]

Thanks to both of you for your feedback.

Ceramics are a very tempting choice but after thinking more about it I decided that I would stay away from ceramics----the thought of a plant worker striking it with a BFH is a bit scary and though they shouldn't, it would likely be their first reaction to buildup on the sides.

Currently I am leaning towards a high temp. Chlorobutyl rubber lining (250F max operating temp). While my design maximum is 290F, I have been told that the rubber will not melt, but it will just require more frequent replacement(Every 6 months maximum). The other possibility would be a thick plastic lining. I will alert the forum when I have made a decesion.

 

[unclesyd]

If you decide to go with a wear resistant metals here is some information on Ultimet. We have used if on several pipe systems that were experiencing erosion problems . The 6B material is also good.

http://www.haynesintl.com/Ultimet/er2082pg.htm