Published: July 04, 2008 09:06 pm         

Changes coming at LMU

‘Suspicious emissions’ prompt switch to low sulfur coal

Looking for ways to keep utility rates low and customers happy while still maintaining plant efficiency, Logansport Municipal Utilities made a switch at its power plant to high sulfur coal — a lower quality and therefore lower cost variation that still produces enough heat to meet the plant’s needs.

But that change was made nearly two years ago, and with no other operation changes since then, LMU superintendent Paul Hartman has been stumped recently by what he calls “suspicious emissions” coming from the plant’s stack.

“We’ve been using the higher sulfur coal for a while now and we haven’t always had these problems,” he said. “So we’re looking at why is this happening now.”

Hartman said the smoke coming from the stack at the power plant generally comes out clear, but he and others have noted changes recently. After he, members of the Logansport Utility Service Board and other city officials have received phone calls from concerned city residents, Hartman has been looking into the problem.

Hartman said the problem has nothing to do with particulate coming from the plant’s stack and he isn’t aware of any health problems that could be caused by the dark-colored smoke, but he said LMU was still trying to address residents’ concerns.

“People don’t want to see it and that’s fine,” he said. “That’s all part of giving the best service we possibly can.”

LMU replaced its smoke stack in October, hoping to cure the problem, but while the change helped temporarily, dark-colored smoke has returned in recent weeks to the Logansport skyline.

Board member John Davis raised the issue at the June meeting, and since then Hartman has brought in a combustion engineer to look at the operations at the plant.

Hartman said the engineer recommended no major modifications to the plant’s combustion process, so Hartman is now looking at the high sulfur coal as the culprit.

The fuel source is the only major change at the 52-year-old plant in more than a decade, said Jon Flory the instrumentation and control technician. But in that time, the combustion process has changed only slightly.

Flory explained that coal, which is trucked into the plant daily by the 25-ton load, is burned in one of the plant’s two boilers. Each boiler is connected to a generator, and the heat generated by burning the coal boils water to create steam that turns turbines inside the generators.

The process creates roughly 35 percent of the energy LMU sells to its 13,000 countywide customers. LMU buys the remainder wholesale from Duke Energy.

Flory, who has worked for LMU for 11 years, said he monitors the automated process with the use of computers housed in a central office inside the plant. Flory and other technicians can check and regulate boiler temperatures from the office and make adjustments to the process when necessary.

Hartman said LMU’s process has been modified to near maximum efficiency and very little usable material is left over once the coal is reduced to ash.

The process of dealing with the ash is also efficient, said Flory. As the coal is moved through the boilers on conveyor belts, the majority of the ash falls out into hoppers. What is left in the exhaust is pulled out in an electrostatic precipitator, which was installed in the early 1990s.

The precipitator works by positively charging the dirt and dust particles inside the exhaust. As it moves up the stack, negatively charged plates on the walls of the unit collect the particles so that the exhaust leaving the stack contains only about 5 to 10 percent particulate, which is just a fraction of the 40 percent allowed by law.

“If we turned the precipitator off, we’d have black smoke coming out in about five or 10 minutes,” said Flory.

Flory said he hasn’t seen any change recently in the percentage of particulate leaving the stack that would have caused the smoke to change colors.

“At this point we’re looking pretty hard at a change to the fuel source,” said Hartman. “We’re changing to a fuel that’s more expensive. We’ve been trying to avoid that. Any time we have to use a more expensive coal, we have to pass that expense on to the customers.”

Hartman said the switch to low sulfur coal will likely not be made until August because it will take that long to process a new order with the coal distributor. Once the change is made, Hartman said, customers can expect anywhere from a 10 to 20 percent rise in their monthly electric bills.

The major difference, Hartman said, is in the amount of oxygen getting into the combustion process.

To this point, Hartman said LMU has not considered a change in the type of fuel used at the plant as changing the setup from coal to a different fuel would also be very costly. However, if the problem persists, Hartman said LMU would look at all remaining options.

“Between the fuel and the combustion, we hope that solves any kind of emission problem,” he said.

Carla Knapp can be contacted at (574) 732-5150 or via e-mail at carla.knapp@pharostribune.com



Have questions?

For more information about the power plant, call LMU superintendent Paul Hartman at (574) 753-6231.