The projects in question are retrofits of air pollution control equipment at existing plants, and there is an equally active market for air pollution control equipment for new plants, says McIlvaine.
In general, the retrofit activity for flue gas desulphurisation (FGD) and particulates is in the US and Eastern Europe. In the US, the retrofits will be modest this year, but there are hundreds of projects projected to take place in 2012, with the promulgation of a new utility air toxic rule. In the 2012-14 period, the US will be the leading purchaser of air pollution control equipment.
In India, while there are some retrofit projects, there are many projects associated with new coal-fired boilers. 
The main investment in air pollution control in FGD is wet scrubbing using ground limestone, which will require big investments in rotating items such as ball mills, pumps and fans. There are few suppliers of this large equipment, and, as a result, in the past when orders have surged, it is these items which have led to delays. The amount of readily available high quality limestone is also diminishing as existing users have contracted for the supplies available.
Some of the particulate projects will involve upgrades of existing electrostatic precipitators, while others involve replacing the precipitators with fabric filters. This allows more flexibility in fuel selection while still making it possible to meet emission requirements.