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> Great River Energy
Great River Energy
Wear Resistant Lining Extends Pulverizer
Rejects Piping Life
Author information - This article was prepared
through joint efforts between Abresist Corp., Urbana, IN.
and Great River Energy’s Coal Creek Station in Underwood,
N.D. Reprinted with permission from POWER ENGINEERING, October
2007 issue.
Great River Energy’s Coal Creek Station
in Underwood, N.D., is fueled 100 percent by lignite coal.
Because the pyrites and ash from the lignite are abrasive
to the power plant’s pipe lines, Coal Creek had problems
with leaking in its pulverizer reject lines. Plant personnel
searched for a way to mitigate the effects of this leaking
and extend the pipes’ life. They found that wear resistant
basalt- and ceramic-lined piping extended the reject piping’s
life and reduced maintenance requirements.
Coal Creek Station is North Dakota’s largest
power plant, consisting of two units, each rated at about
550 MWs. Unit 1 at Coal Creek Station began commercial operation
in 1979 and Unit 2 in 1980. Each unit burns approximately
11,000 tons of lignite per day from the Falkirk Mine, which
is adjacent to the plant.
Lignite coal contains an abrasive portion of
non-combustible material that is extremely damaging to piping.
Coal Creek had major issues with abrasion in the pyrites rejects
pipes, which required them to be rotated annually. Even with
the annual rotation, the piping still leaked and began to
cause problems within the plant’s pulverizer area. In
addition, repairing the leaks and continually rotating the
pipes increased the company’s maintenance and labor
costs. “It was really getting to be a high maintenance
area,” said Louis Simenson, a maintenance mechanic with
Great River Energy.
Myron Schell, also a maintenance mechanic with
Great River Energy, agreed, “We had leaks in those areas
and, because of the way the previous pipe was designed and
installed, we were down in the water a lot. It (the pyrites
reject pipe) began to wear out faster so the decision was
made to look for other solutions.”
Great River Energy turned to abrasion resistant
linings from Abresist Corp., Urbana, Ind., to help extend
the piping’s life. Abresist Corp. provided more than
2,500 feet of basalt-lined piping and alumina ceramic elbows
for the 16 pulverizers on Units 1 and 2.
The plant’s personnel were already familiar
with Abresist Corp.’s lined pipes because the plant’s
main 12-inch diameter ash line had previously been replaced
with more than 2,000 feet of the company’s 12-inch diameter
basalt-lined pipe.
The new lined pipe and fittings were installed
in the pulverizer reject areas when each pulverizer was brought
down for an overhaul. “We would go in and tear out the
existing line and start putting in the ABRESIST® line,”
Schell said.
Wear Protection and More
The primary benefit from the basalt-lined piping
and ceramic-lined elbows is the wear protection they offer
and the resulting life extension. The power plant also realized
labor savings, decreased pipe maintenance and less downtime.
“In our system, everything is abrasive because we use
jet pumps to pump everything out,” Schell explained.
“We have water that contains abrasive material and we’re
basically wet sanding everything at a high velocity.”
With the new lined pipes and elbows in
the pulverizer reject line, Schell and Simenson intended to
rotate sections of the pipe about every four years to help
even out the wear and give the pipe a longer life. Before
the lined pipes were installed, the previous pipes had to
be rotated more often. “We were rotating the other pipes
every year,” Simenson said. Rotating the pulverizer
reject section of the line required about two to three days
of plant labor. By extending the pipe rotation to every four
years instead of annually, the extra days of labor can now
be spent more productively.
Eight Years and Counting
The basalt-lined piping and ceramic-lined elbows
have been in the Coal Creek Station pulverizer reject line
for eight years without rotation. An inspection was performed
earlier this year and the company was pleased with the outcome.
“We found them (the pipes) to be fine, a little bit
of wear, but after eight years you’re going to have
some wear. We put the pipe back together and were totally
satisfied,” Schell said.
“We were anticipating that we were going
to have to rotate these lines,” Simenson said. However,
plant personnel have decided that they can wait four more
years before rotating the pipes, resulting in a total of 12
years of service before pipe rotation is needed.
The new lined piping and elbows have also reduced
the abrasive wear in critical areas of the line, such as the
elbows. The new elbows of the pulverizer reject line, lined
with ALRESIST® high alumina ceramics, have mitigated abrasion
caused from the material changing direction. “The elbow
is a higher abrasive area because it’s changing the
flow’s direction and you have an impact point. We will
probably have to replace them every five to six years,”
Schell said.
Continuing Confidence
Coal Creek Station needed a solution to its
wear problems in the pulverizer reject areas, something that
could help reduce maintenance costs and labor time. The lined
pipes and elbows from Abresist Corp. have proved to be that
solution.
They have helped Coal Creek Station reduce
its down time, maintenance costs and labor while increasing
the life of the plant’s pipes. The lined piping not
only stopped the initial leakage problem, but it also offered
better overall wear-life on the pipes and allowed the plant
to go for longer periods of time without rotating its pipes.
“Certain pieces of equipment, like the pulverizer, will
come down every four years, so you want to make sure that
the other products in the system will last four years, if
not longer,” Schell said. “The same thing is true
when you bring down a unit that’s been running three
years; you want to be sure that the associated products will
last for at least three years. So, if you can save some dollars
on the material and work with vendors to accomplish all that,
you can keep your operating costs down.”
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