Researchers at Lehigh's Energy Research Center have received a U.S. patent for an adjustable coal-flow control system that reduces air pollution from coal-fired power-plant boilers while enabling the plants to boost combustion efficiency and cut operating costs.
Harun Bilirgen, ERC research scientist and lead researcher in the project, said the new system balances coal and air flows to a boiler's burners, minimizing emission of carbon monoxide (CO) and achieving more efficient combustion.
The ERC researchers are among the first, said Bilirgen, to quantify the benefits of balancing air and coal flows.
The ERC group conducted tests on a full-size (225-megawatt) boiler that burns Eastern bituminous coal and has experienced high levels (25-30 percent) of unburned carbon in its fly ash and episodes of high CO emissions.
Pipe-to-pipe coal-flow imbalances as high as 50 percent were recorded in the test boiler, Bilirgen said, adding, "Our measurements showed that the periods of elevated CO emissions coincided with the coal-flow rate fluctuations."
The power plant installed the ERC's adjustable coal-flow control system at each three-way splitter junction.
Each system, said Bilirgen, "consisted of a specially designed riffler with adjustable coal-flow control elements positioned just upstream of the riffler. These elements were designed to make it possible to balance coal flows without affecting the primary air flow balance. This was done while the pulverizer was on-line."
After the installation of the patented ERC system, said Bilirgen, coal-flow imbalances dropped from roughly 50 percent to approximately 6 percent "with no measureable changes occurring in the individual primary air flow rates."
The ERC system succeeded in reducing unburned carbon in the fly ash as well as average CO stack emissions.
"These reductions," said Bilirgen, "made it possible to reduce the average economizer oxygen level and increase unit load by a few megawatts.
"Operating with a lower economizer oxygen level resulted in a reduced unit heat rate, less fan power, and a lower furnace NOx level with a lower required ammonia injection rate.
"Working with an engineer from the plant, we estimated the financial benefits resulting from the operational improvements. A very conservative analysis shows these were in excess of $400,000 per year."
Edward Levy, director of the ERC, said the project led by Bilirgen was the fourth field installation of the ERC's new coal-flow control system and the first to measure heat rate, emissions impacts, costs and benefits.
"By all measures, this technology has turned out to be extremely beneficial from an operational point of view and cost effectiveness," Levy said.
The other members of Bilirgen's group were Carlos Romero and Nenad Sarunac, who are associate directors of the ERC.
ERC researchers recently received another patent for an invention that more accurately measures the air pollution emitted from a power-plant boiler. The new technology was developed with engineers from PPL Corp.
Posted on Tuesday, April 05, 2005