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Controlling moisture in biomass

Jul. 2, 2013, Pittsburgh, PA - Emerson Process Management now offers an integrated solution that enables biomass-fuelled power plants to continually monitor feedstock moisture content and adjust the combustion process for better efficiency.

The solution combines a biomass fuel moisture sensor with Emerson’s Ovation expert control system, which can help reduce maintenance costs as well as boost net yearly MWh production. Biomass fuels vary considerably in their energy content and if it has high moisture content, it will generate less heat and will have a significant effect on energy recovery in steam generators. The traditional method of controlling the combustion process is by monitoring the flue gases and adjusting the combustion air to give the best efficiency. However, rapidly changing fuel quality and boiler characteristics can make maintaining optimum conditions difficult.

Emerson’s new integrated solution continuously monitors fuel for moisture content as it is being fed into the combustion chamber. The Ovation system uses this data to adjust the combustion air to match the characteristics of the fuel based on the master set-point output (MWe steam or pressure), boiler response and the thermal cycle overall. This enables the plant to react much more quickly to changes in fuel moisture content, maximizing combustion efficiency.

For new or existing installations, the system comprises a small skid that takes biomass fuel from the transport system, measures its moisture content using microwave technology and returns it to the transport system. It provides a volumetric evaluation of feedstock humidity every 2-3 minutes.

The moisture sensor is connected via Ethernet to the Ovation system, providing an input to the boiler and thermal-cycle control logic. The data provided is analyzed to provide fast and accurate information on the temperature and moisture content of the feedstock.

Monitoring and controlling combustion air can dramatically influence profits and costs of boiler operations. Excess oxygen does nothing to improve combustion. Instead, it actually serves to reduce boiler efficiency by absorbing heat that could be used in steam production. Ovation helps to modulate the amount of air in the system to provide the exact amount of air that the system needs, ensuring efficient combustion.

“The variable moisture content of biomass fuels presents a challenge for operators who are under pressure to maximize performance from their power plants,” said Bob Yeager, president of Emerson Process Management's Power & Water Solutions business. “With continuous moisture monitoring data incorporated into the Ovation control system, operators can make rapid adjustments to the combustion process to help enable an increase in net yearly MWh production.”

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July 2, 2013  By Emerson Process Management


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