If coal is to be “America’s energy future” (see p. 42), the work of the Powder River Basin Coal Users’ Group (PRBCUG) will have a lot to do with making it so. Since 1999, the PRBCUG (see sidebar) has fostered the safe, efficient, and cost-effective use of the fuel as it watched its membership swell from 60 to over 300. More than 320 employees of gencos, equipment suppliers, and engineering contractors came to Electric Power 2006 in Atlanta primarily to network with and learn from the experiences of their peers and customers at this year’s meeting of PRBCUG members (Figure 1).
1. Better safe than sorry. Attendance at this year’s PRBCUG meeting, in the heart of the coal-burning South, was up a bit over last year. Source: POWER magazine
The festivities began one day before the opening of the conference and exhibition, with three half- or full-day workshops and tutorials on various aspects of converting a power plant to burn PRB coal. That evening, following a reception, members were treated to a banquet and an inspirational talk by Cary Mullen, a two-time Olympic downhill skier and still the holder of the sport’s speed record (97 mph).
The main agenda of the annual meeting—sponsored by Benetech Inc.—kicked into high gear the next morning. Charles Kitchens (Figure 2)—project manager of Southern Company’s engineering and construction services and the new chairman of the PRBCUG—welcomed attendees and reminded them that the group’s role isn’t to encourage gencos to use Powder River Basin. Rather, he said, “We work with industry associations to develop best practices [for doing so]. We need to involve as many experts as we can in that process. You in the room have a wealth of knowledge we’d like to capture.”
2. Godfather of coal. Charles Kitchens of Southern Company—a 29-year veteran of the utility industry who has held numerous management posts in engineering, operations, and maintenance at coal-fired plants—is the new PRBCUG chairman. Source: POWER magazine
Kitchens then handed the mike to the keynote speaker, Charles Potter—CEO of Potter Associates International and a 19-year veteran of the utility industry. As opposed to a speech, Potter’s “Who is responsible for safety?” was a very interactive 90-minute discussion of the roles that personal responsibility, attitudes, and behavior play in minimizing accidents and injuries. Next up was the PRBCUG’s presentation of its 2005 Plant of the Year award, which went to TXU Corp.’s Monticello Steam Electric Station (see sidebar).
Subjects other than safety
At this PRBCUG annual meeting, there were enough technical presentations on specific topics to allow attendees to focus on their particular area of interest. To facilitate that specialization, three breakout group meetings—on coal handling; boilers and combustion; and fire protection, safety, and risk management—were held in adjacent rooms on the second and third days of the conference.
Among the more interesting papers presented during the boilers and combustion track was one by David Tillman of DTE Energy’s huge Monroe Power Plant in Michigan. The paper by Tillman and three of his colleagues described why and how Monroe made considerable investments in equipment, O&M programs, and studies whose shared purpose was to optimize the amount of PRB coal in the plant’s fuel blend to maximize profitability.
Another pair of presentations in the other two tracks worth mentioning were “A roadmap to electrical compliance” —by John Klingler, PE, of Klingler Electrical Safety LLC—and “Coal transfer systems: Case studies on how ‘less can do more’ ”—by Andrew Hunter of Benetech. Klingler’s talk was a practical guide to achieving compliance with OSHA electric regulations. Among the topics he covered were qualifications and training, lockout and tagout procedures, hazard risk analysis, recordkeeping, and personal protective equipment. Hunter’s presentation detailed the O&M savings and reductions in coal spillage and dust realized by three PRB-burning utility users of Benetech’s InteliFlo skirtless transfer chute (POWER, October 2005, p. 54.)
Fire prevention on center stage
The fact that coal fires and pulverizer explosions were discussed in all three tracks made clear that safety remains the No. 1 concern of PRB coal users nationwide. Three presentations at the meeting detailed the causes of recent fires at PacifiCorp’s Dave Johnston Power Plant in Wyoming (on the magnetic separator belt) and at Georgia Power’s Plant Scherer and Ontario Power Generation’s Nanticoke Station (in a silo).
According to Richard Hamby of Georgia Power, at Plant Scherer the fire started in one of the silos for Unit 1 on January 31 of last year and burned for four days before it was reported. The CO2 inerting system was able to cool down the fire but not extinguish it, probably due to holes in the silo, which at the time was filled to overflowing. Only after a week did manual firefighting begin, and then at the risk of a coal dust explosion if a large cavity of coal detected in the silo were to collapse.
What caused this fire? A subsequent investigation found that its root cause was the failure of operators to follow a plant procedure that calls for inerting any silo that has stored coal for 10 days. The coal in the silo in question had been stagnant for 24 days when its gas (CO2 and O2) monitor alarms sounded. The investigation also found that a direct cause of the fire was the 12-month shelf life of the alarms’ sensors. Operators heard the alarms but considered them low priority, because frequent repairs of the monitors led them to consider the devices nuisances.
The silo fire at Unit 2 of Nanticoke Station was described by Ken Jobba, production manager for Units 5 through 8 and a former chair of the PRBCUG. At the time of the flash fire—on November 2, 2005—the silo’s bunker had been completely emptied and control room operators had just asked coal yard personnel to refill it. Immediately upon start-up of the conveyors, coal dust in the bunker ignited, sending a fireball through its inspection door. A nearby operator escaped injury by jumping to safety. The plant’s emergency response team extinguished that fire, another one at a pulverizer’s coal feeder, and fires on coal gallery beams within about two hours.
What caused this fire? The root cause, an investigation found, was a series of unfortunate events over the days preceding it. On October 31, an oil leak in a pulverizer for Unit 2 caused an explosion that damaged its cable tray and that of two other pulverizers. Operators took the three pulverizers out of service and placed them in “maintenance mode,” suppressing their alarms. Two days later, the pulverizer that suffered the explosion was returned to service without informing coal yard personnel. Thinking that the silo fed by this pulverizer was completely empty, they began cleaning the area around the chute between it and its silo, manually closed its input gate and opened its outlet gate, and activated the silo’s air blasters and vibrators. Five minutes later, the explosion occurred.
The investigation found that it is common practice among control room operators to put a pulverizer in “feeder maintained” state to prevent it from tripping. The problem is, they do so without being aware of silo coal levels, and even if a “no coal” alarm for a coal feeder inlet pipe or a coal feeder belt is received. Often, the sensors used to detect the absence of coal in feeder inlet pipe are jumpered because they are unreliable. Among the recommendations made to eliminate these problems were:
- Drawing up a procedure for responding to “no coal” alarms.
- Ensuring that a unit’s control room and coal yard are aware at all times of the number of pulverizers in service.
- Designating a pulverizer or its silo as being in “out of service” mode, rather than in maintenance mode, unless work actually is being performed.
- Displaying coal bunker levels and low-level alarms on the unit’s distributed control system screen.
- Improving the reliability of “no coal” detectors.
- Installing explosive-gas detectors on coal silos.
Don’t forget coal pile safety
Fires and explosions can be deadly, but so can the “engulfment” of a bulldozer operator on a coal surge pile. In fact, 19 drivers have lost their lives in that awful way since 1980.
In most of the accidents, the culprit has been a hidden cavity created when coal bridges over a feeder due to compaction, freezing on the surface of the pile, or pile stagnation. The feeding material acts like quicksand, making the edges of the draw hole unstable. Hampered by poor visibility, the dozer operator may unintentionally drive his rig over or near the hole. As he is sucked down, the cab window either breaks under the weight of onrushing coal or is pushed into the cab, engulfing the operator.
Fortunately, there is a simple and cost-effective solution to this problem: make the cab window stronger. The U.S. Labor Department’s Mine Safety and Health Administration (MSHA) has proposed the use of stronger glass for cab windows, and mine operator Massey Energy Co. has responded by adding metal supports to the inside of cab windows and using somewhat stronger glass on the dozers it operates. However, among the disadvantages of the “Massey Subkit” are reduced visibility (especially when backing up), increased noise, and the propensity of the bars to loosen and crack the glass around them.
As described at one of the breakout sessions by Phil Southern, president of Repair King Inc. (Shinnston, W.Va.), his company’s customizable Bodygard system for protecting dozer operators takes the MSHA initiative one step further. Bodygard’s use of polycarbonate for the windows provides more than adequate strength (it can handle 40 psi), as demonstrated by a video of a “near miss” engulfment that Southern played for the attendees.
According to Southern, the polycarbonate—from PPG Industries—used in the Bodygard system is a chemically hardened, preformed product that is installed as easily as glass, by gluing it into a gasket. Compared with standard polycarbonate products, the Bodygard system can be retrofitted to a dozer from any manufacturer and delivers the same benefits—including saving lives.