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Coal Specifications

image credit: Photo by Rod Hatt - utility coal plant stack, wet scrubber water vapor
Rod Hatt's picture
Chief, Coal Combustion, Inc.

Having worked with coal quality and combustion issues in the utility industry for over 40 years I have operated Coal Combustion, Inc. for over 17 years providing sound unbiased consulting and...

  • Member since 2005
  • 7 items added with 4,124 views
  • Oct 10, 2022

“Man!, would you look at those krypton levels, how do you expect me to burn that coal”
Things you might hear, even if Superman was running your coal plant.

One day in my life concerning coal quality has struck me more than most. We asked a
group of utility and power plant people what properties of coal they liked and what
caused them concern. As each person provided their response you could see that each
had their own view. Some wanted dust-less coal, others coal that has good flow through
chutes. Many wanted large, lumpy coals, the engineers wanted coal that was dry and
easy to grind. The maintenance folk preferred coal that had low abrasion properties.
The environmental people liked low sulfur and low ash levels. Then, the ash sales
department wanted high ash to dilute the carbon and increase the sales volume. The
fuel purchasing group liked low cost coals. Near the end of the discussion I asked if the
group was describing coal or natural gas. I have worked with power companies that
burn all sorts of coals from lignite and sub-bituminous, dozens of bituminous coals and
high rank coals such as low volatile bituminous and anthracite. In twenty years I have
not come across a coal that would meet everyone’s preferences.

Coal Specifications mean different things to different people.
Ask yourself:

What am I trying to accomplish with coal specifications?
1. Raise the market price I pay for coal.
2. Ensure I am receiving market based pricing.
3. Make life a joy at the plant, (feet up coal).
4. Avoid all problems at plant.
5. Control major problems at plant
6. Control quality from the mine
7. Control product consistency

These and other important business considerations are all influenced
by the use of coal specification. This short paper will attempt to cover
the main objectives in setting coal specifications. These include
which specifications are important. Why there is a difference
between bid and contract specs. How to ensure you are enforcing
your specifications, and several other important aspects of setting
quality parameters.

Coal Quality
There are many influences that determine coal quality. Depositional
environment, geological forces, ground water, mining methodology
and care, coal preparation (washing), and storage all influence the
coal a power plant ultimately uses. Good sampling and laboratory
practices can quantify many quality parameters. An understanding of
coal quality and quality impacts on power plant performance can help
utilities determine what parameters are most important and cause the
most concern. These quality parameters are quantified and set forth
in the specification section of coal contracts and purchase orders
The electric power industry is rapidly changing due to deregulation.
The author was present one hot day in June of this year, when a
southeastern utility company was selling electricity for $5,000.00 per
megawatt with $85.00 cost. Typical power cost range from the mid-teens
at night to about $30.00 on a normal day. The free market place will challenge the power industry in many ways. Fuel is the major cost in electric power. In a regulated industry the cost of fuel was passed on to the customers. Fuels were chosen to minimize
problems such as handling, combustion, ash deposits and other
operational and maintenance concerns.
Tight specifications were used to eliminate or minimize coals that
caused problems. These tight specifications raised the price of fuel
by minimizing competition. Deregulation is on its way. As the power
stations become individual profit centers, plant management must
take a more proactive role in fuel selection. When the plant starts to
take a more active role in the selection process, it develops improved
communication with fuel purchasing as well as a more accurate
overall understanding of coal quality. Fuel cost is always a major
production cost. Understanding how coal quality impacts plant
performance and cost, allows better fuel selection and specification
decisions. The plants need to become more aware of the nature of
coal and implement creative solutions for problems arising from
differing coal quality. The potential of lowering fuel cost is so
significant that most utilities will at least explore their options. How
well plants take advantage of their knowledge, may determine,
whether they will be able to compete in a free market place

Coal Specifications
There are many types of specifications used to describe coal, these

Geological - location, basin, seam, and rank
Physical - heating value, size, moisture, ash, HGI, ash fusion temp
Chemical sulfur, ash chemistry, ultimate and trace elements

The key to the use of these specifications is to understand the
relationships these parameters have on the performance and cost of
making electricity. This should include the impacts on efficiency,
maintenance, load limiters, and forced outage rates. Unfortunately,
even the best computer models are limited in their ability to
accurately predict the costs associated with different quality coals.
The best source of information for this assessment is the plants
experience. The knowledge and sophistication level of the plant
employees will greatly influence the range of acceptable
specifications, and can play a key role in the risk assessment of using
of alternative fuels.
Specifications are meaningful only if there is a strong correlation with
plant performance, cost, load, and or forced outage. If not, why are
you using them?
The following is a short list of the major components at a power plant
that are impacted by coal quality along with several tests used to
measure quality parameters:

Coal Handling – coal size, surface moisture
Pulverization – heating value, HGI, moisture, size

Combustion, NOx – volatile matter, HGI, moisture
Efficiency – moisture, hydrogen
Ash deposits – ash, heating value, sulfur, ash fusion temps.,
ash chemistry, iron, calcium, sodium
Opacity - ash, heating value, sulfur, sodium, ash chemistry

It should be noted that the US does not have a standard to measure
the abrasiveness of coal and therefore it is near impossible to predict
or correlate grinding equipment wear and tear and errosivness of
coals in the laboratory.
Specifications are meaningful only if they are enforced. Are you
using verifiable quality control systems that protect your interests?
Are you confident that the information is accurate and meaningful?

Do you take action if quality parameters fall outside
the spec? Do you differentiate between penalty and rejection specs?
Are you consistent with your enforcement? All of these questions
should be considered, why have specifications if you don’t use them.
Quality specifications can define your coal marketplace, in some
cases they influence the fuel cost as much as transportation. This
leads us to the next section.

Bid verse Contract Specifications
In the best of circumstances, you tell the world you can burn
anything, and then you decide which fuel is the best for you.
You can open up your coal market place by being willing to consider
any fuel specification. The key is to have, in place, the expertise to
evaluate the impacts that each fuel will have on your operation and
costs. This will generally improve the representativeness of the
quality specifications offered, as it allows the mining company to
describe their coal rather than try to fit into your specifications.

Contract specifications are those used to control the quality of a coal
once the price has been established. Many contracts now adjust the
price of coal to the actual specification that the coal was shipped to.
These include adjustments for ash and sulfur in addition to the
heating value adjustments. Several contracts have even attempted
to provide price adjustments for parameters like HGI and Ash Fusion Temperatures.

Contract specifications should represent a given purchase situation and may not correlate to original bid specifications.  You gain the expertise of quantifying the costs of different coal quality be keeping accurate records and by conducting test burns. Your test
burn procedures should be designed to capture this type and quantity
of information.

In conclusion, this short paper has attempted to get you to question
where your specifications came from and how they are set.
Developing a dialogue between the power plant and fuel purchasing
using coal quality information and actual power plant experience is
crucial. Understanding coal quality and the quality control process for
the mining industry is valuable. You can make meaningful
specifications for your particular situation, but remember that
specifications are used in many ways, make them work for you, not
against you. There are differences in the use of bid and contract
specifications, and you should consider how coal quality
specifications impact the cost of doing your business.

Thank you for this opportunity to address this subject.



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Rod Hatt's picture
Thank Rod for the Post!
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