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topic 6721

Hydrofluoric Acid pickling tank design


(2000)

I am a Chemical Engineering major at Clemson University and I have a design problem for my Materials class. I am required to recommend at least two different materials of construction for a pickling tank that would be able to contain HF at a 10% concentration and at 75 °C. I also have to consider the materials of the other parts that would be used in the pickling process such as baskets, crates, and chains. Any help is appreciated.

Joshua Carpenter
- Clemson, South Carolina


(2000)

Joshua, Let's have a think. For a weak l0% HF solution @ 75°C (or l52°F as they now, unfortunately, say in Canada) surely, going by memory, there are many, MANY material options.

METALLICs ... 3l6 ss, Hastalloy C, Carpenter 20, Titanium

PLASTICS a) PVC but only if frp reinforced b) PP but preferably frp reinforced c) PVDF and d) all the weldable but exotically expensive fluorcarbons such as FEP, Tefzel, Halar

That makes the thermoset mfgs mad so they will say use any good acid resistant resin, ATLAC 382, HETRON 197 or DERAKANE 411 etc.etc.etc

However the thermosets, i.e., fibreglass, maybe be A.OK for just containment but oh, BEWARE! if you scratch the surface and expose them thar nice virgin strands of glass to HF !

Depending on the size of the tank I'd opt for armouring PVC with fibreglass, what to-day is called a Dual Laminate material where the FRP is bonded to the homogenous thermoplastic. PVC by itself is nbg at that temperature but when frp'd, it should be good for an additional l0 degrees or so.

Surely old Clemson Uni has a library and surely you should be able to collate corrosion data from it, eh?. I hope this helps. But 'tis always wise to double-check, isn't it? Cheers !

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



(2001)

As Freeman Newton implied, a library search should give a fair idea of requirements. But, as I've experienced in South Africa, the younger generation don't seem to be trained or guided towards investigative research with facilities available to them. What about contact with suppliers of construction materials in this field? Must be a'plenty in your country!

Agree with FM re dual coating. Initial cost (not sure in your country) usually higher than conventional single layering, however, longer term cost per unit throughout generally considerably lower.

Best wishes for the future and don't give up!

Godfrey Gibson
Visionchem - Port Elizabeth, South Africa


(2003)

A message to Mr Newton,

Is the internet not a reference source? May we agree that it is? Does our Mr. Carpenter need reminders to reference words stored on paper, stored in rowed, sequenced, concrete structures? Is your information untrustworthy? Should we believe more what a book has to say than another human source? Is this all education is? I once heard it is always wise to double check though.

Cheers!

Travis McWilliams
- St. Catharines, ON, Canada


(2003)

The internet is a wonderful source for some things, Mr. McWilliams, but it is not a good reference source for engineering data for a number of reasons including:

1. the relative anonymity of the posters.
2. the fact that pages and their contents are constantly coming and going and being revised without any "edition notes".
3. the probable lack of any organized peer review process.
4. books sell for hundreds of dollars and support in-depth, organized research and meaningful peer review. On the internet to date the cost/demand curve is "infinite demand at zero cost / zero demand at infinitesimal cost" (Pullizzi, Thomas J.----).

The inability of the world so far to come up with a viable economic model to support "publication" of data on the internet means that, while some helpful info may be found, it is certainly no substitute for a textbook or engineering handbook. The media that the data is stored on isn't the issue...we're not making a claim that VCR tapes are more believable than DVDs; it's the informational process involved in publishing a book that is more reliable than the process of strangers posting messages on message boards.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2004)

Stainless pickle acid normally also contains HCl and nitric to complicate your question a bit. Some continuous lines are replacing HF with hydrogen peroxide. I concur that dual laminate to most frequently used in stainless pickle line construction. Some now prefer heavy duty thick wall reinforced thermoplastic tanks. Design should always consider exposure over the life of the vessels. I have also successfully lined larger carbon steel vessels intended for this service with vinyl esters.

John Hausfeld
- Liberty Twp, Ohio



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