POWER August 2017 - 49

COAL
A Proactive Program to Mitigate
Coal Dust Reduces the Risk of
Explosions
Coal, by its very nature, is a dusty fuel. That poses a serious risk at coal-fired
power plants, because coal dust can be highly explosive. However, actions
can be taken to reduce the risk. Implementing strict administrative
controls is a good first step, but combining that with other passive and
active control measures may be the best way to ensure a plant avoids catastrophe
in the long run.
Jason Schwartz
O
n February 7, 2008, the
Imperial
Sugar refinery in Port Wentworth,
Ga., exploded, ultimately killing 14
people and injuring 38. The resulting investigation
determined that the explosion was
fueled by massive accumulations of combustible
sugar dust throughout the packaging
building at the plant.
After that incident, industrial facilities all
over the U.S. took notice. Whether sugar,
flour, wood, plastics, or coal, uncontrolled
industrial dust is a significant explosion risk.
Utilities with coal generation facilities, rightly
concerned with the safety implications,
worked to develop plans to mitigate the combustible
dust risk at their coal-fired plants.
The concern was driven in part by the
fact that many plants have converted from
Appalachian coal to Powder River Basin
(PRB) coal for its noteworthy environmental
benefits. However, there is a significantly
increased risk of dust explosions in these
converted plants due to the possibility of
spontaneous combustion and the higher explosive
severity of PRB coal.
People who take safety seriously don't
wait around for regulations to change. They
work to mitigate the risk of combustible dust
disasters regardless of whether or not they
are meeting present regulatory guidelines.
A good first step is to conduct an audit of
the current combustible dust risk level at your
coal-fired plants. That establishes a baseline
for risk and helps management understand
what is required to ensure safe operations. To
improve working conditions and protect lives
of employees, a plan for plant upgrades and a
cost estimate for projects is needed.
Evaluating Problems
Acensium was brought in to perform an audit
for a major southern utility's coal plants
August 2017 | POWER
in 2010. Acensium's leadership had significant
experience in PRB coal conversions
and meaningful expertise in mitigating coal
dust risks, which was a driving factor in the
company's selection. The utility assigned
a corporate project manager to work with
Acensium in planning the project and budgeting
the upgrades over a 7-year period.
Together, the team performed onsite evaluations
of each plant targeted for upgrades.
Data was compiled on all problems identified
at each plant, a technical plan to implement
solutions was developed, and a budget
was created to carry out the plan. The process
culminated with a central meeting of
all the coal-handling managers from each
plant. The meeting lasted approximately
two full 8-hour days.
At the client's insistence, improvements
were prioritized based on safety impact-not
the revenue ranking of each plant. The outcome
was $180 million in budgeted safety
improvements designed to shrink the risk
presented by coal dust in each unique situation.
A schedule was developed to implement
upgrades across the plants, and the program
was launched in the spring of 2011.
Getting Coal Dust Under Control
The plan to effectively manage coal dust
at each facility was comprised of three key
components. The approach to dust management
for material-handling systems followed
a path from administrative controls, to passive
engineering controls, and then to active
engineering controls.
Administrative Dust Control. One
of the initial priorities was to create a culture
in the material-handling department in
which the danger of combustible dust was
understood, and simple, everyday actions
were carried out to reduce that risk. Those
www.powermag.com
1. Button it up. Little changes, like closing
chute inspection hatches, can go a long
way in reducing dust throughout a plant. Courtesy:
Acensium
actions included closing chute inspection
hatches (Figure 1), closing doors to material
handling buildings, and completing more
frequent walkdowns during operation. Typically
a large portion of combustible dust can
be controlled through culture change and its
ensuing positive actions.
Passive Dust Control. The second priority
was to implement a foundational change
in how the general material stream was handled
at each plant. That included replacing
end-of-life equipment in the transfer systems
in order to capture nominal coal particles
before moving on to containing submicron
dust. Acensium informed the customer that
transfer point technology had advanced significantly
since most of the plants had been
constructed, and that transfer point features
and materials had been developed to allow
better material control and prevent spillage,
while extending maintenance intervals.
In the mid 1980s, Alan Huth first conceived
a hood-and-spoon arrangement for
material handling transfers. The concept of
the hood was employed to consolidate the
material flow as it left the delivery belt with
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POWER August 2017

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