What are some of the main companies for pollution control equipment for plants?

Question

I am talking about scrubbers for removing SO2, particulate, and other acid gases from the gas stream? Also I am asking about spray dryers, bag filters, or anything else you guys know of. These could be used in coal-fired power stations, refineries, glass manufacturing plants, or sintering plants just to name a few.

Answer 1

'Siemens' comes to mind. They are a large vendor/developer for water, atmospheric pollutants, and nuclear operational equipment.

Answer 2

There are many companies that make these products.  Browse http://www.powermag.com/

That's an industry magazine for power generators and related businesses.