A new bed material for use in circulating fluidised bed (CFB) boilers can improve the efficiency of waste and biomass combustion while cutting operation and maintenance costs, researchers have found.
In a joint project, Sweden’s Chalmers University of Technology and German utility E.ON found that replacing the traditional silica sand with metal oxides in a CFB boiler produced several advantages, including more uniform and efficient combustion, increased overall efficiency, lower carbon monoxide emissions and a decrease in problems associated with ash fouling.
The researchers attributed the positive effects to the new material’s oxygen-carrying properties, which allow it to distribute oxygen evenly inside the combustion chamber when mixed and circulated with the fuel.
Testing with the new bed material was conducted between November 2014 and May of this year in a 75 MW CFB boiler at the Händelöverket combined heat and power (CHP) plant in Norrköping, Sweden. The plant is one of the country’s largest CHP installations, with waste and biomass making up 95% of its fuel.
E.ON said it aims to begin using the new bed material in two boilers in Norrköping by the end of this year, and is eyeing several other plants for a scale-up to commercial operation. The utility is also planning a service offering that will help its customers transition to the new material.
Bengt-Åke Andersson, Adjunct Professor in combustion technology and Senior Specialist at E.ON, added: ‘This is the biggest improvement I have experienced. A little like placing a turbo charge to the process.’
‘It is too early to speculate in the exact gains but it is clear that the profit margin of each CHP boiler will improve significantly,’ the researchers said in a statement.
Fredrik Lind, PhD at the Department of Energy and Environment and project coordinator at Chalmers University of Technology, added: ‘We are now sure that we are able to significantly lower the operational and maintenance costs in most of the thousands of fluidised bed combustor plants that are currently in use internationally.’
The material also enables CFB boilers to burn non-traditional fuels such as coarse waste, which ‘could become crucial in the future, if we are to meet our climate goals,’ Lind said.