the US department of Energy provides background on particulate control research (for making coal cleaner although the goals would still leave coal the deadliest energy source. Coal kills 1 million per year from air pollution)
To date, most particulate control technologies have been installed to prevent so-called "coarse" particulates from escaping into the atmosphere. Coarse particulates are those with diameters of 10 microns or less (a micron, or micrometer, is 1/25th of a thousandth of an inch); thus, they are referred to as PM10. Power plants typically install either baghouses (essentially large fabric filters) or electrostatic precipitators (devices that use electrical charges to attract particles) to capture solid particles emitted from their coal furnaces.
Today's challenge in particulate control largely focuses on much smaller particles - those with diameters of 2.5 microns or less, or as they are called, PM2.5. PM2.5 particles can be as small as 1/30th the width of a human hair, or smaller. These fine particles are of special health concern, since they can be more easily inhaled deeply into the lungs where they can be absorbed into the bloodstream or remain embedded for long periods of time.
To improve the capabilities of power plants to capture primary particulates, the Energy Department's Fossil Energy program assisted in the development of devices that combine the best features of both a baghouse and an electrostatic precipitator (ESP) in the same compact enclosure. This device removes at least 99.99% of the solid particles in the flue gas of coal-fired power plants. Other projects developed improvements to the efficiency of existing electrostatic precipitators by installing a device that concentrates particles escaping the ESP and recycling them back to the ESP inlet. Another project developed low-cost, non-toxic conditioning agents that are injected in flue gases before they enter the ESP to make the tiny particles more susceptible to capture.
The UK has new technology for cleaning pollution Nano-prorous fibres trap carbon dioxide and other pollutants so they can be removed and recycled back into the production process.
Clean coal retrofits are examined in this pdf Supercritical retrofits might be $700/KWe net. Excludes cost of FGD and SCR.
This pdf compares IGCC and advanced coal options The plant costs for cleaner coal are comparable to nuclear power.
Nuclear power plants are $1600-2000 per KW Nuclear power does not have the particulate or other emissions of coal. As noted in the prior article Japan can reprocess uranium waste without proliferation issues. Nuclear power or renewables are preferable but if we must have coal power then it should be as clean and safe as possible.