St. Clair Power Plant

UnitsEdit

A total of seven coal-fired boilers were ultimately built at St. Clair, although only six remain operational.

Units 1–4Edit

Units 1–4 are 163 MW Babcock & Wilcox boilers tied to GE and Allis-Chalmers steam turbines. These are the four original units at St. Clair. Generating units 1–4 are St. Clair's base load units, usually running at full capacity. The flue gases from those units exit through south stack, which was erected in the late 1970s when new electrostatic precipitators were added to these units. When the plant was first built, there were four relatively short stacks, one for each unit.

Unit 5Edit

Unit 5 is St. Clair's only decommissioned unit. Its cyclone boiler produced 300 MW, and was taken out of service in 1979 due to a mechanical problem with the boiler. The stack for unit five was removed in 2012.

Unit 6Edit

Units 6 is a tangentially fired Combustion Engineering dual furnace boiler tied to a Westinghouse turbine. Commissioned in 1961, this unit produces 321 MW.

Unit 7Edit

Unit 7 is also a tangentially fired Combustion Engineering boiler tied to a Westinghouse steam turbine. It was commissioned in 1969. Unit 7 is rated at 451 MW, originally built to produce over 500 MW. This unit is St. Clair's largest generating unit, but has a small electrostatic precipitator, causing problems with the opacity when burning western coal.

Other unitsEdit

An oil-fueled gas turbine Unit 11, rated at 18.5 MWe, was added in 1968. Two smaller oil-fueled internal-combustion generators, totaling 5.4 MWe, were added as units 12A and 12B in 1970.

HistoryEdit

St. Clair Power Plant came online in August 1953, and was the largest in the DTE Energy network. At that time, its capacity was 652 MW. Later, units 5, 6 and 7 were added to meet growing demands for power in Metro Detroit, with St. Clair producing 1571 MW. After the completion of unit 7 in 1969, St. Clair Power Plant was the world's largest. In the middle to late 1970s, the plant was converted to burn Western subbituminous coal. The conversion resulted in lower unit power ratings and necessitated the installation of larger electrostatic precipitators on Units 1–4 and Unit 6. This also included building a new stack for units 1–4. In addition, low NOx burners and overfire air ports have been installed on all of St. Clair's generating units.

On August 11, 2016 at around 6:30 pm local time, a generation unit at St. Clair Power Plant caught fire. This led to a complete shutdown of all units at the plant. No injuries were reported as a result of the fire. The fire took 15 hours to extinguish. Fire equipment was borrowed from across St. Clair County, from Detroit and nearby Canadian fire departments.

DTE plans to retire the plant some time between 2020 and 2023.

Operational dataEdit

St. Clair is a base load power plant, dispatched after DTE Energy's Fermi 2 nuclear unit and the neighboring Belle River coal-fired power plant. Between 1999 and 2003, St. Clair's capacity factor averaged 57%, plant heat rate averaged 10,449 Btu/kWh, and the equivalent forced outage rate averaged 18%.

Connections to power gridEdit

The plant is connected to the power grid by 2 double circuit 345,000 and 5 120,000 volt transmission lines, owned and operated by ITC Transmission. The St. Clair has one 345 kV line (St. Clair-Lambton #1) and one 230 kV line (St. Clair-Lambton #2) that interconnect with Hydro One across the St. Clair River in Ontario, Canada. One of the wires of a 345 kV line enters a substation at the Belle River Power Plant.

Environmental impactEdit

The St. Clair and Belle River Complex, along with the rest of Detroit Edison's generating facilities are ISO 14001 certified.

Sulphur dioxideEdit

With its oldest unit dating back to the 1950s, the plant was ranked 74th on the United States list of dirtiest power plants in terms of sulphur dioxide emissions per megawatt-hour of electrical energy produced in 2006. Sulphur emissions could be lowered by using flue-gas desulfurization units, better known as SO₂ "scrubbers", like those of Lambton Generating Station across the St. Clair River. Currently, these scrubbers are being installed at DTE's Monroe Power Plant, and may eventually be added at the St. Clair site as well.

Waste waterEdit

All of the waste heat generated by the plant (about twice its electrical output) is released into the St. Clair River. This water is used in large condensers to cool the used steam back to its liquid form. Water used in the condensers is treated, filtered, and replaced back into the river. Other water used on site for cleaning boilers and to drive the turbines is treated in settling ponds where ash and particulate are suspended from the water. The water is purified and pumped back to the river. The particulate is taken to the St. Clair/Belle River ash landfill a few miles north.