The status of air pollution control technology for coal fired industrial and power plant boilers has been surveyed. Lime and limestone based scrubbers are capable of removing as much as 93% of flue gas SO2 at facilities supplying 800 MW power. A sludge containing SOx ions must be discarded in the process, usually requiring landfill or a settling pond. The Wellman-Lord, thiosorbic, and citrate processes are capable of producing salable products instead of the sludge. They are successful (85 to 90% removal) on demonstration-scale units. The Wellman-Lord process is currently being tested on large-scale coal fired units.
Electrostatic precipitators, the mahor control device for removing particulates, can eliminate 99.5% of the fine particles. Fabric filtration can remove 99.9% and is more efficient in the 0.2 to 2μm size range than ESPs. Utilization of fabric filters is expected to increase significantly from its present 5% of the particulate removal market. Nitrogen oxide concentrations in coal fired systems are usually reduced by modification of the combustion system. No significant NOx reduction on full-scale boilers has yet been reported, but demonstrations are planned over the next few years.
Various process capital and annualized costs are reported for SO2 and particulate removal systems. The status of fluidized bed combustion, fuel desulfurization, conversion of coal to gaseous and liquid fuels, and flue gas denitrification is also discussed. Part A deals with S emission; Part B with NOx, particulates, and combined systems.