One argument for industrial boilers is to use cheap solid fuels with more contaminants but to turn them into byproducts.  Suez is making hydrochloric acid by burning waste products. So a two stage scrubber and high chlorine coal is an option. What about using more expensive solid fuels and eliminating the investment in pollution control?

Alternatively, increasing the efficiency of your boiler is a cost-effective way to reduce emissions. How good are optimization systems?  What about specific operations such as weighing the coal rather than using volumetric measurements?