Heating Sulphuric Acid (H2SO4)

Well, all wetted materials should be resistant to hot.conc.sulphuric acid, and don't splash any around, i.e. make sure it's contained at the pressures expected.

What sort of quantities, please? "What you don't have can't leak." - Dr. Trevor Kletz, safety guru.

Consider graphite heat exchangers.

It's been a while, but as I recall the acid hoods used in semiconductor production typically used a quartz tank with resistive heaters around the outside of the tank. Tank capacity was only about 8-10 gallons, though, so this may be outside your requirements. Another method to consider is using outboard heaters but this involves piping and pumps.

However you go on this, please take exhaust requirements into consideration and get input from the Environmental Health/Safety folks, especially since they'll have some pretty good ideas about containment, spills, etc.

Logan

Dear APPANNA,

I apologize but it seems to me that, if you have to ask us that question, you should not be doing the procedure. Sulfuric acid (H2SO4) is incredibly corrosive. You would need to know how to handle HAZMAT, if you don't, then don't.

The only thing worse than Sulfuric acid is hot Sulfuric acid. If you don't have Hazardous Material handling and training, you should NOT play with this. How about a nice erector set?

Seriously, you can very easily hurt yourself and others. Please do not play with this.

/Ari (Orpheuse)

Hmm, a nice simple way to heat H₂SO₄ (aq) is to use a more concentrated solution and add enough water to dilute it to the required concentration. The reaction H₂SO₄ mixing with water is extremely exothermic and will easily reach the boiling temperature of water. So you control the rate at which water is added and limit the volume of water to just what is needed. Maybe you could start with oleum or 98% conc. to save on the transport volumes, and dilute it locally, as part of the dilution process at the last stage you conserve the heat of reaction to use for your process.

I think you just answered most of his homework problem. As one of the other participants already said, if he was doing this for real he wouldn't need to ask the question - at least we sincerely hope he is not doing this for real.

However, in my experience the acid was always added to the water in order to carefully control the reaction rate. The result is usually a smooth uneventful change in acidity of the mixture. However, adding the water to the acid tends to cause all the water added to react almost instantly, sending a splattering fountain of hot acid into the air. Very bad for the complexion.

I am not a chemical engineer, but to my knowledge this is the fastest, simplest, easiest, cheapest, and safest way to get hot diluted sulfuric acid. Resistive heaters or some such thing may be needed to maintain the temperature if it needs to be stored hot for any length of time.

Thanks to all of your reply., which are informative.

I have some more information regarding the requirement.

presently 5000litres capacity rubber lined tank is used to hold the

acid and they are using a crude method of heating a 9"dia corrosion

resistant alloy pipe dipped in th acid at one end and heated by gas burner at the other end by conduction method.

Purpose is to spray the hot acid to leach the sand used in foundries.
rgds

It should be noted that sulfuric acid becomes more corrosive at lower concentrations. Actually anything below 90% conc. is considered corrosive. There are only a handful of materials compatible with sulfuric acid. Some materials that come to mind are High Density Polyethylene (HDPE) and Alloy 20.

The idea of adding concentrated acid to warm water is a great idea. As long as you can meet the target concentration and temperature. A material and energy balance will tell you how much water you will need and at what temperature.

-David

If acid is concentrated, it becomes a strong oxidizer, and will destroy HDPE.

As he is using a rubber lined tank, it can be presumed that the acid is dilute.

From memory, alloy 20 is fine at all concentrations.

I would be inclined to use a shell and tube heat exchanger with the acid passing through the tubes and probably gas firing in the shell.

Temperature control needs to be good. You do not want to risk local boiling, vapor pockets etc.

This stuff is dangerous, even when dilute and must be treated with the greatest respect.

Dear Mr. orpheuse,physics orof,chemE119 and others,

thanks a lot for your inputs. Of course I will bear in mind all the safety and statutory

advise presented and directed by Mr. Orpheuse.

When I started this thread I was not aware that there were other related threads already in Cr 4 on sulphric acid.

Those who have not seen it , may browse throgh threads 16138 and 16510

in the month of Jan 2008.
Thanks once again