Acid Coolers Failing

I think further description is needed.

Are the tubes failing within the body of the tubes, or at welded/brazed/soldered/mechanical joints?

What is the fluid on the other side; and what are all the temperatures?

Some other metal or alloy may be better than SS316 or SS316-L.

Plastics/glass/fiberglass might be good for piping, but because of low thermal conductivity not good for heat-exchange surfaces.

Could the cooling be done by some kind of spray process rather than by other liquids?

Etc.

the tubes are failing within the body and the fluid on the other side is portable water and the acid temperature feeding the cooler is 120 degrees celcius the the water temperature is 20 degrees celcius. the flow rate of acid ranges from 275 meter cubic an hour to 300 meter cubic an hour. spray cooling wont be that effective because we dealing with a tube and shell anodic protected cooler

the tubes are failing from the body the cooling medium is water at 20 degrees celcius, the acid inlet is 120 degrees celcius and the flow rate is 300 cubic meter an hour,

the cooler is tube and shell anodic protected cooler.

Why 316? Why not ceramics or carbon/graphite?

...or borosilicate glass?

http://www.coleparmer.com/techinfo/ChemComp.asp

316 Stainless is a poor choice for Sulfuric acid. If the failure rate has changed from what the norm was. I would look at aeration problems that were not there before. Or maybe some process that's been added that aerates it. It would be best to change the tubes to Durimet or Hasteloy B or C.

Alloy 20 would be ideal as it was specifically developed for use with sulfuric acid.

Titanium tubes with anodic protection is specified for sulphuric acid anodizing for heat exchangers.

For 75 - 100% H₂SO₄, titanium has a "severe effect" according to the Cole Parmer compatibility database (and I believe this). We are not talking about anodizing here, merely heat exchange.

Explain yourself, sir.

If you are from India, I can help. We got a concentrated acid dilution plant with heat exchanger for cooling from a Mumbai based Company. 316L material is not at all suitable for such high concentration.

All the previous replies are pertinent and correct when they state that 316-L is a poor choice for heat exchanger tubes in contact with 98% sulfuric acid. CN7M, otherwise known as Alloy 20 is the right stuff. Yes, it costs more, but the lifetime, and trouble-free expectation is well worth what you are losing in production now.

I think you are refering to an anodic protected Acid Cooler. These coolers usually have a narrow range of operation between 94% - 98.5%.

Check with the Mfr. on the anodic protection settings as this is critical.

I presume you are talking about a heat exchanger and two fluids.

If you are running concentrated sulphuric acid in a tube, mild steel is the best solution. It will not corrode in the inside of the tube. The outside however could be an issue, you should use a high PH solution not to form rust, or some other fluid like Glicol or else.

Don't think of diluting the acid ,it will dissolve the tube in no time.

in this case the cooling medium is water and the flow rate of the acid is 275meter cubic an hour the feed temperature of acid is 120 degrees celcius, mild steel at this flow rate and temperature will be eaten up in no time may be i agree with alloy 20 but the expense is just high,

In this case the temperature is the issue and probably also the flow rate. I have never handled concentrated acid at 120°c so maybe you are right.

We have stored concentrated sulphuric acid in MS tanks for years, but the temperature never exceeded 35°C. After many years we have found a slight corrosion on the top acid level of the tank probably due to the humidity.

thats true

Hi,

We are facing also facing same problems on our main acid cooler in sulphuric acid plant supplied by monsanto having four cathode. Although passivation system always remain online & maintained at 300mv. The inlet acid temp. is 78 & outelet temp. is 60 deg. cent. The flow is 900 m3/hr.

Regards

Rajesh