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Perfect utilization of the steel pickling liquor




I have a continuous steel pickling line.
It discharge 15 ton of spent HCl acid per day with concentration (2.5 - 3)% and with iron salt (30 - 35)% as FeCl3.
we have 3 tanks each tank have 15 ton volume

How can I perfectly utilize the spent HCl acid?
Can I convert the dissolved ferrous chloride to ferric chloride [on eBay or Amazon] and HOW?

Hossam ahmed samieh el sayed mohammed
steel industries - Egypt
2006



2006

Many options are available on the utilization of spent hydrochloric acid.

One option: convert it to pigment grade iron oxide or magnetic iron oxide or ferrite.

T.S.N. Sankara Narayanan
T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)


Is it possible to reuse the spent pickling bath for pickling with fresh addition of acid once the iron chlorides are removed and a dilute acid is got back.

Aravind A Narayan
- Coimbatore, Tamilnadu, India
2006



Yes. It is possible to reuse the spent pickling bath after removal of the iron salts, filtration and removal of the contaminants (all types) and fresh addition of acid to make up the acidity, etc.

But if you compare the price of the acid and the amount you should spend for reusing the spent acid, I don't think that you can save much.

How much volume of spent acid you are generating per day?

T.S.N. Sankara Narayanan
T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)
2006



Sir:
For reuse I have seen two methods. In one (South Africa)the spent acid is sprayed into a natural gas flame resulting in HCl with a concentration of about 17% and the solution is very yellow colored (ferric iron). The other is a distillation process (USA) but large volumes of very dilute (e.g. 2% to 4% HCl) are produced. Both processes use large quantities of energy.

A better solution may be to use the spent acid to make paint pigment or for water treatment. To convert Fe+2 to Fe+3 the pH is raised above 5 and hydrogen peroxide is added. Air can be used which is much cheaper but sometimes can take longer.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA
2006




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