One of the vent gas stream contains hydrochloric acid and we are planning to dispose of it by burning it in a flare. Could anyone help me understand whether it will burn and what is the reaction and what will be the components of product of combustion?
I presume chlorine will be formed - probably worse than hydrochloric acid itself. A couple of references: http://en.wikipedia.org/wiki/Deacon_process
http://www.sumitomo-chem.co.jp/english/rd/report/theses/docs/20040100_p0e.pdf
Since heat is involved, Hydrochloric Acid decomposes
2HCl(aq) → H2 (g) + Cl2 (g)
As a result both hydrogen gas and chlorine gas are evolved
The chlorine gas generated during this combustion will readily recombine with water (another combustion byproduct) to form hypochlorous acid, which will dissociate back into chloride ion upon exposure to UV (i.e. sunlight), giving you back HCl.
This will not work. You could use a scrubber with aqueous sodium bicarbonate or other weak/cheap base.
Dr. Ramsey, kindly i do not agree with you in that, in case Hypochlorous acid is formed. At high temperature it would dissociate releasing Hydrochloric acid and oxygen gas;
2HOCl → 2HCl + O2
Where do the Chloride ions come in? If any is formed, then it is minimal at the aqueous state not gaseous
Regards
Correct, I am referencing the aqueous state, i.e. condensation droplets in the cooled exhaust stream. This will not happen in the hot exhaust.
Never heard of it, that HCl can be burned in a flare stack. It is not a hydrocarbon and as such you cannot burn it. The best option is to pass through a Packed bed Scrubber before venting it to atmosphere.
True @ Chaudhuri hydrochloric acid is not flammable, unless it is burnt in oxygen. There is no way it can burn!
Thanks Jeremiah. The question posted is of practical in nature and what I understood was that he wanted to have a solution before venting it to the atmosphere to avoid air pollution.
Most likely, HCl would decompose at high temperature, dissociate to form H2 and Cl2 gases. The Chlorine gas formed will then dissolve in water to form hydrochloric and hypochlorous acids. The hypochlorous acid will be oxidized to form hydrochloric acid. this leads to acid rains.
I have a similar question, and like Dilip (I presume) it is not about flaring pure HCl, but rather a gas flare that contains small amounts of HCl as a contaminant of the stream. What becomes of it? If there are other things in the gas stream such as small amounts of hydrocarbons, CO or H2, are there other reactions that may take place? Neither Cl2 nor HCl are very promising results.
Thanks!
Does anyone (please) have a reference for the decomposition of HCl to H2 + Cl2, reacting with H2O to give HClO and then in UV light reverting back to HCl + O2?
This is not to dispose of HCl, but rather, HCl is an unfortunate contaminant of the waste gas stream being flared. Due to temp it will not create dioxins, etc., but I need a reference (I think).
Thank-you in advance. I know this thread is ageing, but we all are ; )
- Badges
- Science topic
- Similar topics
- Engineering
- Chemical Engineering