Coal

Mine-mouth facility operates efficiently

Issue 10 and Volume 100.

Mine-mouth facilityoperates efficiently

In its first year of operation, one of the nation`s newest coal-fired power plants reports more than 91 percent availability and a production cost of just over 1 cent per kWh. This plant, Neil Simpson Unit 2, began commercial operation in August 1995, 22 months after construction began. It is owned and operated by Black Hills Power and Light Co. and was constructed by Black and Veatch. The 80 MW plant is located just outside of Gillette, Wyo., at the mouth of the Wyodak coal mine, the source of some of the lowest cost coal in North America. The mine is owned by Wyodak Resources Development Corp., a subsidiary of Black Hills Corp. The plant, which is designed to burn coal with a sulfur content ranging from 0.2 to 1.2 percent, features emissions controls that make it one of the cleanest operating plants in the region, said Tom Stalcup, Neil Simpson Station complex`s plant manager.

During its first year of operation, the plant`s emissions averaged 0.20 pounds per million Btu (lb/MBtu) SO2 and 0.23 lb/MBtu NOx, well within the limits allowed by the plant`s permit. Black Hill`s goal is to reduce SO2 to about 0.17 lb/MBtu, said Bob Jordon, Neil Simpson Unit 2`s operation and maintenance supervisor. The use of Babcock & Wilcox low-NOx burners (four per pulverizer) and a dry scrubber make these relatively low emission levels possible. To be near the mine mouth, the plant had to be located about 40 miles away from the nearest river, making water a premium. Stalcup said total plant water consumption is only 120 gallons per minute (gpm). The scrubber uses about 80 gpm (all lime is hydrated on-site) and the boiler uses about 20 gpm.

The plant is cooled by a closed-loop, air-cooled condenser which consumes 20 gpm of water. According to Jordan, the saturated steam leaves the turbine at approximately 140 F (minus 22 inches Hg vacuum) and is piped over to the condenser. The condenser is equipped with very large fans that cool the steam just enough to condense it. The condensate is then collected in a tank and circulated back to the boiler. By locating the plant at the mine mouth, Black Hills eliminated the cost of fuel transportation, as well as the need to keep a large coal reserve on hand. The plant burns 1,400 to 1,500 tons of coal per day at full power and keeps only a five- to six-day supply of mined coal on hand at any time, said Stalcup.

Operating efficiency also contributes to the plant`s low-cost production. Stalcup said 98 percent of the plant`s equipment can be controlled from its state-of-the-art control room. Plant personnel do not have to leave the control room to position valves, open/close breakers, etc. Black Hills has trained each of the 15 plant operators as plant mechanics. Using plant operators to perform maintenance tasks has resulted in fewer contract personnel being brought in to assist with outage maintenance activities and decreased the number of permanent employees. The plant`s maintenance staff consists of only two mechanics, two electricians and two instrument technicians. These six individuals are shared with the Neil Simpson Unit 1 plant, an 18 MW coal-fired unit located at the same site.

Sister site

Since construction went well and plant performance has been good and is expected to improve (95 percent or better availability), Black Hills Corp. is planning to construct an identical plant at the same location. This sister plant will be operated as an independent power producer. Jordon said the company hopes to be able to produce electricity for less than 1 cent per kWh with this second plant. Plans call for construction of the proposed plant to begin in 1997, with the project entering commercial operation by 1999. Electricity will be marketed by power marketing subsidiary, Calpine Power Services Co., to customers throughout the West.

M By Teresa Hansen, Associate Editor

Utility R&D fell in 1995

Total 1995 research, development and demonstration expenditures for 100 major investor-owned U.S. electric utilities was $498 million, reflecting a decline of $115 million or 19 percent from the previous year and continuing a downward trend started in 1994, according to U.S. Electric IOU Research, Development & Demonstration Expense Comparisons 1995 from TECC Group Inc.

The report is based on 1995 R&D expenditure information from IOUs serving retail customers and spending at least $100,000 annually on research. More information is available at (303) 742-8168.