Cockburn cement is in trouble with the EPA for its emissions of sulphur dioxide and lime dust.
Sulphur dioxide is one thing, but personally I’d be more concerned about the lime dust. Here’s why.
They make the lime (which they use for making cement) by roasting calcium carbonate (which of course is limestone).
The reaction looks like this:
CaCO3 = CaO + CO2
Or, without the symbols:
Limestone = Quicklime + Carbon Dioxide
That is, the limestone is converted into lime (calcium oxide) and carbon dioxide (by being heated to 800°C).
Now since the whole point of the exercise is to make lime, it is obviously in Cockburn’s interest to catch as much of it as they can. The problem is that it is an extremely fine dust, and it is very difficult to capture it all, so some of it is released into the atmosphere, causing problems for the residents of Cockburn.
Well, what happens to the calcium oxide (industrial name “quicklime”) when it is released into the atmosphere? To quote the amazing Harry Hoo, this present “two possibility”
The first is that the quicklime reacts with carbon dioxide and the reaction above simply goes in reverse, so that we will reform the limestone (calcium carbonate). This is a problem of sorts, since we know that limestone is extremely hard and if tiny particles of it get in the wrong places they could have a very abrasive effect.
But the second possibility, and in my view of greater concern, is if it reacts with water vapour in the atmosphere to form hydrated lime:
CaO + H2O = Ca(OH)2
The reason that this is of concern, is that hydrated lime is extremely caustic (alkaline). And unfortunately, of the two reactions, the second reaction is more favoured energetically, so most of the quicklime will be converted to hydrated lime.
I used to use this stuff quite a lot in a previous job, and lost track of how many pairs of trousers and shirts I destroyed with it. It is an extremely fine powder, and so when you get it on your clothes, you don’t notice. But when you wash your clothes, the highly caustic nature of this stuff just burns holes through the fabric. It’s more of a problem with natural fibres, like cotton, but polyester cotton is not immune either.
The other problem with the hydrated lime might occur if you got it on to paint work. It’s not so much a problem on modern cars, with their extremely hard and durable two-pack coatings, but it could certainly be a problem if it deposited onto your house paint, or other painted goods with perhaps an older style of paint on them.
In days gone by caustic soda solutions were a common formulation for paint strippers – and hydrated lime is almost as caustic as caustic soda.
So if you are in the plume of sulphur dioxide from the plant, the chances are you’re also in the plume of the lime, which of course is so fine as to almost be invisible. So if you’re experiencing degradation of painted surfaces (or clothes) at an unacceptable rate, lime may be the culprit.