Canadian Biomass Magazine

Controlling moisture in biomass

July 5, 2013
By Canadian Biomass

July 5, 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

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