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Combating corrosion in Ammonium sulphate Plant

We react sulfuric acid with ammonia ⇦ this on eBay or Amazon [affil links] hydroxide to form ammonium sulphate. The problem is that the sulfuric acid is very destructive on the super structure of the plant (both steel and concrete). What can we do to combat this?

Chris Scheepers
Vasco Industrial Commodities - Richards Bay, KZN, South Africa
2005

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First of two simultaneous responses -- 2005

Hi Chris,

Very many moons ago I was visiting ERCO, the electric reduction Company, now called Albright and Wilson, where they had problems with attack on beams and the interior 'ceiling' or roofing.

They tried all the paints ... even expensive vinyl ones.

Their solution? Dead cheap. Dead effective, too. .... was to use ordinary pitch or tar.

Then I had to provide some ducting for sulfuric but this was before the days of the dual laminates ... and due to the temperature from the hotplates where the sulfuric was
bubbling merrily, I used Polypropylene ... and the UV PP
didn't exist then. (they were probably boiling away concentrated sulfuric at around 320 degrees C.)

The ducting had to go outdoors ... so I copied ERCO and used ordinary black pitch ... and many, MANY years later,
someone said to me that Why in the Heck did that Guy use
Asphalt? The proof, of course, is in the pudding. It worked l,000%.

But Chris, what about ventilation? The medium concentrations of sulfuric will attack nearly anything ...
and at the Delco Remy plants and G.M. in Oshawa, they use
36% sulfuric for making car batteries... no problems due to good PVC ventilation and l2 micron horizontal mist eliminators.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

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Second of two simultaneous responses -- 2005

The same thing occurs with municipal swimming pools due to free chlorine corrosion of the overlying roof structures, whether it's timber, steel or concrete, it brings failure.

Since you are reacting H2SO4 + 2NH4OH => 2H2O + N2H8SO4, and presumably reacting in excess of ammonium hydroxide, the sulfuric acid should be completely reacted, and what you're seeing is therefore corrosion from ammonium sulphate particulates, reacting with free atmospheric moisture, in a reverse reaction back into volatilized sulfuric acid.

The solution is either to cover your reaction chamber and treat the fumes with slaked lime or some neutralizing base, or air condition your factory, using full dehumidification.

Robert Marmaduke
Anthae - Olympia, Washington, USA