25MW
Operational Coal Fired Power Plant for Sale
For Conversion to a Biomass Plant for Continued Operation in Place (Midwest US)
The owner of this plant is a municipality opting to get out of the power business, but wants have the operating capacity to remain in place and will bring support to a qualified purchase in pursuit that objective. The owner/seller feels this plant would be ideal for conversion to a biomass plant and will provide support.
This 25MW operational plant consists of 2 each 12.5MW Coal Fire Steam Turbine Generators and 1 each 15MW Gas Turbine Generator (GTG) burning #2 diesel. These units are connected to a 12.5kV distribution system with two step-up transformers to two 69kV lines. These units are on a 37 acre parcel of land owned by the municipality.
The coal plant was designed by Black and Veatch and operational in 1958 and consists of two identical 12.5MW units. Each units includes a top supported Babcock and Wilcox two drum boiler. Each rated at 125,000 lbs per hour and 600 psig and 825°F.
The GTG is a 18MW GE Frame 5 made in 1968. Rated 21,176kVA at 0.85 power factor. The GTG was completely overhauled in 2002. It has had 2,689 hours and 280 starts since overhauled. Evaporative cooling, water injection and NOx control. Also adjacent is a 100,000 gallon fuel tank for #2 diesel oil. The fuel oil needs to be delivered by truck and must have less than .2% sulfur content. The unit has black start capability and can be converted to dual fuel (natural gas and #2). The GTG typically operates 350-500 hours annually as needed for transmission support. From 2003 through 2007 the GTG had a 2.7% capacity and a 99.72% equivalent availability factor.
Permit requirement limit operation to 35.9 tons of nitrogen oxide annually. This is equivalent to approximately 1,360 hours of operation at full load.
The coal is fed to the boiler by Alston stokers and burned on a Detroit Stoker Rotograte traveling grate. Each grate is 15’ 4 ½ ” wide by 18’ net length for a surface area of 276.7 square feet. Each boiler has an economizer for preheating feedwater to the boiler, but does not have a combustion air preheater. At rated capacity, boiler performance data states the efficiency of the boiler at 84.3 percent. The average annual net heat reate of the steam generation plant is 14,500 Btu/kWh. The design grate heat release at 125,000 lbs. per hour steam flow burning coal is an extremely conservative 592,477 Btu/hr.-square foot. If this boiler were converted to burning wood eveh as high as 55% moisture contact, the grate heat release appears to be adequately sized.
The boilers are balanced draft units, each with a single forced draft fan providing combustion air from the ground floor elevation and a single induced draft fan located after the mechanical collectors and the electrostatic precipitators. Flue gas cleaning consists of centrifugal mechanical collectors followed by a three-field electrostatic installed in 1979. Steam from the boiler in each unit is piped to a turbine generator that was supplied by Allis Chalmers and has a nameplate rating of 12,650kW gross. Steam is extracted to four feedwater heaters, and the turbine exhausts to a surface condenser utilizing circulating water from a nearby large lake. The steam turbine drives a Allis Chalmers generator operating at 3,600rpm.
The coal-fired units operate continuously whenever they are available. Typically, during the day, they are operating at high loads, as much as 13MW gross for each unit. Considering the station service requirements of 500kW for unit, the net output is approximately 12.5MW. The current State Operating Permit references a nameplate rating of 12.5MW. During the night, the unit are typically ramped as directed by the ISO. The minimum load for each unit is 4MW gross. Operating the units at minimum load during off peak hours as opposed to shutting them down and restarting has most probably helped the availability of the units.
The plant is currently operated and maintained by a staff of 28 people.
4 – Shift Engineers (1 per
shift)
4 – Boiler Turbine Engineers (1 per shift)
4 – Oilers (1 per shift)
1 – Electrical and Controls Tech.
2 – Generation Techs.
2 – Coal Handlers
3 – Relief Operators
1 – Station Clerk
1 – Environmental Consultant
1 – Station Supervisor
1 – Station Superintendent
4 – Maintenance Generation Specialists
Fuel
Units 1 and 2 are solely fueled by coal. There
is no auxiliary fuel capability. Startup
is accomplished by using waste wood on the boiler grates.
Given the infrequency of plant is accomplished by using waste wood on the
boiler grates. Given the infrequency
of the plant startups, this works quite adequately.
Annually, the City requests proposals from potential coal suppliers. Coal is requested to be sized 2”x 0”. The coal typically has a calorific value of 12,500Btu/lb. and must contain less than 1.5% sulfur in accordance with the current operating permit. Coal is currently transported by ship and stored on a dock immediately north of the plant. There are also rail facilities adjacent to the property that could be developed for fuel delivery. This dock is not owned by the city, but leased from a coal company. There is adequate draft next to the coal pile, so that the ship can unload directly to the storage pile. Generally, the plant purchases sufficient coal to operate the plant for one year. Annual coal requirements vary between 60,000 and 80,000 tons. Coal is loaded into a dump truck from the storage pile using a front loader and transported to the in feed hopper at the Station.
