Freeze Conditioning Agents
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Each winter season, the electric utility and steel industries are faced with the problem of unloading
and handling frozen coal and coke. Freezing in loaded rail cars, bunkers and conveying equipment
is a costly, labor intensive problem which can result in perturbations in the respective production of
the two industries. The unloading of frozen coal and coke means, at the very least, an increase in
labor and maintenance costs, as well as the cost of demurrage. Coal with as little as 6% surface
moisture can, when frozen; cohere so strongly that special handling is required to break up the
frozen mass. Over the last twenty years, improvements in the chemical products and techniques
to combat freezing have put a cost effective rein on the problem.
There are currently two principal chemical approaches for dealing with the freezing problem:
Soluble salts as freeze conditioning agents
Organic chemicals as freeze conditioning agents
SOLUBLE SALTS AS FREEZE CONDITIONING AGENTS
Solutions containing the chloride salts of magnesium and calcium are sprayed onto the coal or
coke during car loading at the mine. CaCl2 is also commonly used at the unloading site to loosen
and remove frozen coal which fails to unload from cars. MgCl2 is also a commonly used freeze
conditioner and, typically is used in combination with CaCl2 because it has a lower freezing point in
dilute solutions than the calcium salt. Use of these salts as freeze conditioners has been
challenged in the past on the basis that they can contribute to corrosion of handling equipment
and steam generator heat transfer surface. It has been shown from studies and experience that
this is a relatively minor problem and the potential for corrosion is predictable.
ORGANIC CHEMICALS AS FREEZE CONDITIONING AGENTS
Certain organic chemicals including light oil-based products and glycols can be used as freeze
conditioning agents. They combine with or replace surface moisture on the coal or coke and
modify the crystalline structure of the ice. The weak bond that is created between the ice crystals
at low temperatures reduces the shear or compressive strength of the frozen coal or coke.
Depending on the surface moisture and particle size range of the coal, oil based products can be
used as a freeze conditioner; however, their effectiveness diminishes at lower temperatures. Tests
conducted by U.S. Steel showed no benefits of oil based freeze conditioning agents when
temperatures dropped below 200F. In addition, water insolubility minimizes loss of agent due to
thawing or rain, which tends to reduce water source contamination from coal pile run off. Light
oils used as freeze conditioning agents contain little ash and burn readily. Their use can pose
problems for workers in confided areas, because of the irritating fumes which are emitted and the
slippery conditions which can develop in the work areas, increasing the risk of accidents.
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Another commonly used method of treating frozen coal is to use a blend of water soluble
polyhydroxyalkanes, a group of glycol based chemicals. Because of environmental regulations, use
of glycol is fairly limited to diethylene glycol or a blend using other organic compounds. Glycol
based products are designed for direct application.
BENETECH'S FREEZE CONDITIONING AGENTS
The primary freeze conditioning agents applied by Benetech are a group of polymer products
combined with either magnesium chloride, calcium chloride or a blend of the two. Over the last
several seasons, the dominant product has been the blend, because of its superior performance
characteristics. Even though Benetech does treat with glycol based products if so required by its
client, a shift, by most, away from the glycol based freeze conditioning agents has been driven by
economics and product performance.
The polymer salt products are normally applied at a rate of two pints per tons of coal. An increase
in the application rate is dependent upon the prediction of the weather's severity, estimated travel
time and the unloading location.
The concern over the potential for corrosion can best be addressed by an example. Adding
magnesium at the rate of two pints per ton in a concentration of 22% adds 0.43 lb. chloride per
ton of coal or 215 ppm. Adding calcium chloride at the rate of two pints per ton in a concentration
of 28% adds 0.47 lb. chloride per ton of coal or 235 ppm. This added level of chloride is, in most
cases, inconsequential in terms of the part it plays in the overall chloride level in the coal and the
potential for tube corrosion from chlorides.
Some typical chloride levels in coal, taken from reference texts, are:
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Upper Freeport, Pennsylvania seam
Illinois No. 6
Lewiston-Stockton seam (West Virginia)
Pittsburgh No. 8
Virginia Pocahontas 3
0.00%
0.05%
0.10%
0.11%
0.19%
( 500 ppm)
(1,000 ppm)
(1,100 ppm)
(1,900 ppm)
One commonly held guideline in analyzing the corrosive potential from chloride is that bituminous
coals with more than 0.25% chloride (2,500 ppm) may be particularly troublesome.
Along with the freeze conditioning agents for bulk product application, Benetech offers the freeze
conditioning agents for side-car release and belt de-icing. The belt de-icers are glycol based
products with varying levels of actives. The side-car release agents are chemically designed to
include certain polymers for improved cohesiveness to the car's sides.
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Product bulletins describing the Benetech line of freeze conditioning agents are included as part of
this informational package.
THE BENETECH ADVANTAGE
As a major supplier, the company provides freeze conditioning products and services in all of the
domestic coal mining regions, working with either the mining company or the user. Benetech
provides product, equipment, engineering, monitoring services and application verification. With
its own fleet of tankers, the company can even coordinate emergency shipments within hours of
notification. The company is a subscriber to Accu-weather Forecaster, with a satellite radar
computer stationed at Benetech's corporate headquarters. This technology makes present
weather conditions and forecasts readily available to Benetech's FCA customers.
In summary, Benetech offers a string of advantages to prospective FCA customers.
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Full scope of products and services
Qualified field personnel experienced in application techniques
Company tanker fleet
Competitive pricing
Quality assurance program to monitor application and need
Close proximity of product supply to user facility
Engineering and equipment fabrication
Accu-weather Forecaster( service
Full inventory of FCA application systems and components
A proven off-season preventative maintenance program
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Benetech, Inc. ●1851 Albright Rd. ● Montgomery, IL 60538 ● (630) 844-1300 ● Fax (630) 844-0064
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