Amodern,
advanced instrumentation and control (I&C) system, an integral part
of any power station, plays a major role in the profitable operation
of a plant. In a previous IEA Clean Coal Centre review by Nalbandian
(2001) on the status of I&C in existing coal-fired power plant,
brief references were made to the effects of upgrading such systems.The
following environmental and fuel cost benefits were reported following
the upgrading of a vintage I&C system in a 500 MWe coal-fired unit:
Up to one per cent improvement in efficiency
which yields significant savings in fuel costs as well as reducing air
pollutant emissions One additional benefit include up to one per cent
reduction in both greenhouse gases and solid wastes 1.1 per cent increase
in availability resulting in additional capacity (kWh/y) for sale hence
improving plant profitability.
This report provides an overview of
power plant instrumentation that are used to measure the values of relevant
parameters, and control systems, which maintain the optimum operation
of the power generation components such as boilers and turbines. All
I&C devices can be included in one of the following categories:
Sensors (including signal conversion equipment) Controllers (including
associated control logic and operator interface stations) Actuation
devices (including positioners).
The I&C chain begins with sensors
that carry meascontrollers where a control strategy is activated based
on the received values and the response moves to final actuating control
elements. This loop repeats over and over during plant operation through
a complex and multilevel communication schemes.
When a project is proposed for upgrading
I&C, in general, management insists on some form of return-on investment
analysis before expending the capital. In some upgrades, specific promises
are made such as ‘the changes are expected to improve heat rate
by, for example,‘200 kJ/kWh’ or‘loadfollowing ability
will be enhanced by 20 per cent’ or ‘steam temperature control
will be improved by 2°C’.Most utilities may go a step further
and translate these promises into expected cost savings. Some even try
to audit the actual versus expected savings, after the upgrade project
is completed. However, those that try, typically, concede failure as
they cannot quantify the improvements due to lack of baseline conditions
and information, if a baseline was established to begin with.
Apart from the technical solutions
implemented and achieved as a part of a plant automation upgrade, there
are also non-technical factors that are crucial if I&C upgrade projects
are to be carried out successfully including: Detailed analysis of the
processes involved; a joint pre-study (feasibility study), which includes
evaluating plant disturbances and performing test runs.
Readiness/willingness on the part of
the operating staff to perform critical reviews of existing control
methods, to change This write up is based on a detailed study undertaken
by IEA Coal Research. The report is called: Upgrading instrumentation
and control in coal-fired plant Herminé Nalbandian CCC/80, ISBN
92-9029-395-0, 52 pp, January 2004
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