By Steve Blankinship, Associate Editor
AmerenUE’s decision to switch to compliance Powder River Basin (PRB) coal for its coal plant fleet has proven to be a good one. Perhaps no better example exists than the Rush Island Plant in Jefferson County, Mo.
Rush Island’s two 650 MW units went into service in 1976 and 1977 operating on high sulfur Illinois Basin coal. But in the 1990s, both units switched to PRB coal rather than install scrubbers to meet sulfur dioxide (SO2) emissions issues that stemmed from the use of local, Illinois-basin coal. Today, Rush Island operates at an annual capacity factor of 84 percent.
With a fleetwide generating capacity of 16,400 MW, AmerenUE operates as Ameren Illinois Utilities in the Illinois deregulated market and as AmerenUE in Missouri’s regulated market. Ameren’s generation portfolio is 84 percent coal, with the company’s Callaway nuclear plant providing 12 percent. Two hydroelectric stations provide 2 percent. The utility also has a several combustion turbines (natural gas represents 2 percent of its fuel mix) with a small amount of oil making up the balance.
AmerenUE also has filed a request with the Nuclear Regulatory Commission for a construction and operating license to build an additional nuclear unit at Callaway.
Both Rush Island boilers are Combustion Engineering T-fired units. The high and intermediate pressure turbine sections are from Alstom and the generators are General Electric. Along with a drop in sulfur dioxide emissions, the plant’s switch to PRB also led to a drop in heating value, from 11,600 Btu/lb. with the Illinois Basin coal to a current heat value averaging 8,400 Btu/lb. for PRB. But the fuel switch did not necessitate any major plant modifications.
For major turbine inspections, the two-unit 650 MW Rush Island station is on a six-year outage cycle. Photo courtesy AmerenUE.
The plant was originally equipped with electrostatic precipitators and has generally not had to turn down to any extent to meet opacity requirements after the switch to PRB. As was the case before the fuel switch, the coal is delivered by rail. The plant also added a barge offload facility several years ago to allow some flexibility for receiving coal from the Mississippi River.
Rush Island has 184 full time employees and normal day-to-day maintenance is performed by workers permanently assigned to the plant. Ameren UE also has a roving maintenance crew of about 35 people to help on special situations and major plant maintenance outages, with any balance of work contracted out.
Tracking a trend of dramatically reducing scheduled maintenance outages for coal plants, which used to be conducted at 18-month intervals, Rush Island’s major maintenance outages for big capital improvement projects are conducted at much longer intervals.
“For major turbine inspections and work of that nature, this plant is on a six-year outage cycle,” said Dave Strubberg, Rush Island plant manager. “We are currently performing at a very robust annual capacity factor. The plant runs pretty much at full load all the time except for turning down at night.”
Strubberg said Ameren bases its plant maintenance protocol on the Plant Reliability Optimization (PRO) originally developed by EPRI in the mid-1990s, but has enhanced that platform. Like many maintenance systems, the philosophy is predicated on performing the right maintenance at the right time to produce the highest capacity factors, the highest effective availability and the lowest forced outage rate.
“We define the work that needs to be done using condition-based predictive maintenance tools,” he said. “You take a lot of oil samples, vibration samples, do a lot of motor testing and infrared thermography.” That testing is applied to Priority 1 (P1) equipment, which includes equipment that has no backup and “will cost you megawatts if your lose it,” he said. “P1 means you need to be calling people out immediately” because the problem is related either to safety or megawatt production. “P2 is something that needs to be worked on in the next available shift.”
Strubberg said that if things are done right, the P1 and P2 jobs should start to trend down. “And we have metrics that show they are,” he said. The plant combines the condition-based maintenance with routine preventative maintenance tasks based on OEM recommendations such as changing air filters, checking oil levels on equipment and “anything the OEM says to do to keep the equipment running at its best,” said Strubberg.
The plant also uses other preventative maintenance practices based on industry and EPRI best practices to mitigate risk. “We are starting to use a scheduling matrix when systems such as boiler feed water, flyash and raw water systems are designated for maintenance on a routine frequency so that necessary tasks on a given system can be completed within the same week.”
In 2003, EPRI expanded its maintenance management system to plant maintenance optimization (PMO) to help utilities plan maintenance jobs properly, including the addition of maintenance planners, plus implement a four-week rolling scheduling for maintenance activities. Strubberg stressed the importance of maintaining maintenance compliance schedules to keep a maintenance supervisor focused on the work that is necessary to keep the plant operating at top performance. The idea was to confer a more comprehensive, almost holistic approach to every maintenance job. That too was rolled into Ameren UE’s fleetwide approach.