HCl Acid Recovery / Regeneration

A. Call U.S. Filter Recovery Services. I saw a presentation over a year ago where they were going to put a plant on line for bulk reprocessing/recovery of HCl. They probably also have technology for reclamation of HCl on-site if the volume is big enough.

A. Dear Daniela,

You can contact HYDROMATIX. Their technology may help you out, as well as they are helping us.

Regards
Joe

A. Hi, Regarding your recouping HCl, I'd like to think that you would get a PARTIAL ... possibly a large 'partial' reduction of the gas stream were you to intercept the fumes and with an inertial (dry scrubber)scrubber approach. This would only partially work as the emitted HCl fumes may be or could be partially gaseous BUT, most definitely, would contain low micron droplets of acid. This inertial approach is much improved/enhanced if one can keep the temperatures down and ergo get improved condensing. I ran across a HCl wire pickling plant where I also happened to design the fume hoods. NO, said that Company, we don't want or need any scrubber'. (This was back in the mid 70's in Ontario, Canada.) I thought that they WOULD have a problem with air pollution and on purpose allowed for an extra length of ducting before the fan ... They DID have a problem.There WAS carry-over.But fortunately as there was enough room/space before the fan, a simple inertial scrubber was installed very easily. This seemed to do the job & I never had a complaint from them. However,the old philosophy dealing with ccid fumes has always been USE A MASS TRANSFER SCRUBBER. My experience indicates that MOST of the fumes and gases in your industry, the Surface Finishing field, are neither GASEOUS NOR FUMES but consist of invisible droplets. Hence, if one can remove said droplets (an absolute breeze for Hard Chrome fumes) WITHOUT 'wetting down and scrubbing with water', then one achieves acid regain. That simple scrubber was a horizontal two stage CT-l20/2 made of PVC which will take out all droplets down to l2 microns. A more advanced unit (which I designed), the so-called LMITS inertial scrubber, will remove droplets down to 3 microns. I did have it once tested at around 85% efficiency in a 0.2 to 0.8 micron spectrum but that was for hot sulfuric emissions and they did wash down constantly with Na0H. (INCO # 2 Research, Port Colborne). . This may not be exactly what you have in mind. Nor would I l00% guarantee a LMITS because some of the HCl will disassociate and be gaseous. But at least I think you could have a very inexpensive partial solution to recouping most of the HCL. Food for thought! Regards,

A. Dear Ms. Ramos,
The idea of recovering acid has always been a concern of mine and wondered about distillation and eventually came across this link
acidrecovery.com/products-and-services/other-products-and-services/distillation-systems.html
which showed that the technology is applicable for spent acids. I also envisioned this method would make it a lot easier to collect and recycle iron which is more profitable than the recovered acid I guess.

Thank you and regards.

A. Dear Suman,

Recovery and treatment is possible depending on the quantity of pickling involved. Distillation of unused acid for reuse, membrane recovery etc are some of the possible solutions.

A. Many times the "Spent" pickle solution can be used at near by waste water treatment plants. The solution is used in a process to clean sewage water. The higher the iron content the better. Many companies will now pay you for the product.

A. Presently I am searching on this topic I found several methods to recover the acid and salts:

-ion exchange

-diffusion dialysis

-electro dialysis

-microbial oxidation of salts fallowed by precipitation

combination of one of other etc......found

A. I undertook thesis regarding treatment of plating chromium waste using pickling waste. Wherein Pickling waste is used to treat Hexavalent chromium compound retained in (carcinogenic in nature) waste water. The sulphates of iron perform reduction reaction in acidic media (both sulphates and acid are present in Pickling waste). Both wastes neutralize each other symbiotically.

A. Hi Nilesh. With full respect I wonder if your inquiry is worded precisely enough? ... I think you might be concerned with maintaining the pickling effectiveness rather than the pH.

Decades ago I heard the assertion that simply adding water to a partially spent pickling acid could improve its effectiveness. In the years since, I've learned that not only might that be true in certain circumstances, but that there is a whole science to the effectiveness of acid based on its dissolved iron, dissolved zinc, pH, acid content and water content. Barlow Campano has graciously provided this site with a technical article, "The Kleingarn Regenerated Spent Acid at Increasing Ferrous (Fe+2) and Ferric (Fe+3) Chloride Content" and a "HYDROCHLORIC ACID PICKLING CHART", that I think you will find helpful! A patient search of the site will reveal several discussions on the topic.

Regards,

A. Hi raj.R,
For the benefit of any readers who generate such waste, we must note that getting the maximum use from the acid via inhibitors, acid extenders, and techniques like the Kleingarn method are a better way to go than trying to recover the iron or re-use the acid. Obviously, you as a trader will be looking at what to do with the waste product rather than how to minimize it, and Ajay Jolly's posting might be of interest.

opinion!  Here in the USA no one dares attempt recycling or re-use of process chemicals anymore. Everything has unintended consequences, and our EPA in an attempt to shut down "midnight dumpers" ruled that the generator of a waste is responsible for it forever, so nobody risks trading it anymore. To my knowledge the whole "Industrial Waste Exchange" business completely collapsed, and treating and burying the waste in a secure landfill is the only non-reckless approach to disposal. If there is in fact an industrial waste exchange that can disabuse me of my ignorance I'd appreciate it.

Regards,

A. Hi raj.R,

There are some uses for pickling acid, as here in Argentina some company is taking used pickling acid and using as an input in the ferric chloride ⇦this on eBay or Amazon [affil links] production. This ferric chloride ⇦this on eBay or Amazon [affil links] , here, is used mostly as a cationic aggregation agent or coagulant.

Some companies that have this type of waste products here use it by oxidizing (totally or partially) it to later co-precipitate other heavy metals in wastewater treatment. This is costly because of the quantity of sludge produced by the iron content in this liquid, and disposal is very expensive.

Hope this helps you in some way. Best regards!

A. If the acid used is Sulfuric, then there is one more technology to recover the iron and reuse the acid, namely crystallization of ferrous sulfate ⇦this on eBay or Amazon [affil links] at low temperature.