Waste-to-energy technology comes to U.S. biopower market

By Anna Simet | May 18, 2012

North Carolina-based Quality Recycling is bringing to the American electricity market a boiler technology that has a 99.9 percent total carbon burn out, and produces clean water and inert ash that can be used as a soil substitute, with zero landfilling as a result.

The Rotating Cascading Bed Combustor technology is the most tested boiler ever built in the U.S., and possibly the world, according to Doug King, president of Quality Recycling. He said the company has tested 61 different fuels with the U.S. EPA, everything from sewage sludge to coal to municipal solid waste, and the results have indicated the emissions are cleaner than natural gas.

King said the design works similarly to how a clothes dryer works. “A clothes dryer operates at about 15 rpms (rotations per minute) and our system rotates at 17 rpms,” he said. “We enter a piece of fuel through the combustion chamber over 300 times, whereas most boilers only enter it one time for a certain number of seconds or minutes.”

In the RCBC, fuels are burned in cascading contact with sorbents and recirculating inert solids to form byproducts that prevent gaseous emissions. A sorbent, such as limestone, reacts with sulphur and hydrogen chloride to form calcium sulphates and chlorides that are removed as nonhazardous ash. Sorbent chemical reactions take place at combustion temperatures low enough to greatly retard formation of nitrogen oxides, and because of the fuel recycling systems, extended combustion gas and sorbent contact assures complete combustion of fuels and waste.

King said the company is currently working on boiler installations in the Ukraine and Nigeria, as well as two projects in Tennessee, which will be the first ones in the U.S. One system generates 6 MW per 150 tons of trash, according to King.  “And the byproduct is dirt. The difference between the RCBC and others that is nobody has the high percentage of carbon burn out we do, nobody has a totally inert byproduct, and we have less than 1 percent fly ash.”