Biomass plant credits efficient operation to use of highly accurate digital meters
Delano Energy Co., a subsidiary of Thermo Electron, turns waste wood into electricity to power southern California homes and businesses. The plant is licensed to deliver power to the Southern California Edison grid at levels below 50 MW. Higher levels require compliance with public utilities regulations, so Delano must monitor output to keep it at or below 49.9 MW. Operators constantly monitor output and many other aspects of the facility, including transformer and motor loads to keep the plant running as efficiently as possible. The plant has two generating units, built at different times. Analog instruments are used in the older unit, but the newer unit uses digital BarGraph instruments from Weschler Instruments, Cleveland, Ohio. Digital BarGraphs make it possible to detect small but important differences, such as 49.9 MW vs. 50.1 MW, which would be difficult to measure on an analog meter. One benefit of the digital displays is their ability to assist operators in heading off potential equipment problems before they compromise production.
Another is the ability to run the unit as profitably as possible up to the maximum production threshold. The BarGraphs help prevent penalties for importing Volt Amps Reactive (VAR) power from the grid. The waste comes from a variety of sources including urban areas and agricultural waste from orchards. The Delano facility employs 50 people at its two units. Unit one entered operation in 1990 and Unit Two started in June 1993. Both units use atmospheric fluidized bubbling bed technology with sand heat transfer. An air blower throws sand around the water tubes, enhancing combustion efficiency. Much of the facility operation is automated. Conveyors are equipped with load cells that automatically speed up or slow down as necessary and the emission control system adds ammonia to the flue gas as necessary to cut NOx. Many safety features are also automated. Two computer systems work together to achieve optimum results. Plant operators have noted definite advantages to the BarGraphs, which are used on the main control panel and in outlying motor control centers (MCC) of Unit Two.
On the main control panel, they are used to monitor power output from the generator along with the status of the many transformers in the unit. The instruments monitoring power output give readings with two points to the right of the decimal place. By knowing these values so precisely, operators can adjust various elements of the combustion process to produce the most efficient burn possible. The instruments monitoring transformers show the number of watts, volts and amps going through each transformer. Since operators know exactly how hard they are driving the transformers, they can operate them at optimum performance without exceeding design limitations.
Weschler digital BarGraphs in the MCCs perform local monitoring of the motors used throughout the unit to ensure the equipment is running within specified voltages and currents. If a reading is out of range, it could indicate imminent equipment failure or need for maintenance. Readings are charted over time for trends. A motor that is failing may draw a few additional amps each day. Precise readings allow operators to see trends quickly, before small fluctuations become big problems. Operators said the BarGraphs are especially useful in monitoring the power factor of the generating unit to improve generating efficiency and avoid VAR penalties, with a goal of keeping a steady stream of power flowing to the grid. The tighter the tolerances the machinery can be held to, the more profitable the plant, and Delano credits Weschler?s digital BarGraphs with helping achieve tight tolerance without exceeding design limits.