Glycerin as Anti-Freeze Agent for Coal

December 1, 2016 |

By Dennis Zeedyk, Glycerin Traders, Lee Enterprises Consulting
Special to The Digest

Anyone who has produced biodiesel knows that glycerin can set up like wax if the process is over-catalyzed and/or animal fats are used as feedstocks. More than one of us has shoveled our share of “hard” glycerin.   As a result, many biodiesel producers find it surprising that one of the larger domestic users for 80% crude glycerin is the coal industry – which uses the glycerin for its winter anti-freeze properties.

As one can see in the attached chart, a 70% blend of glycerin with 30% water is still liquid at -40 degrees Celsius. How is this possible? The key is the almost complete removal of excess fats/oils/soaps from the glycerin as they are what causes the glycerin to “gel up”. The excess methanol must also be removed to < 1%. This is not because the methanol affects freezing, but because its inclusion in the glycerin means a low flash point, making unacceptable for both transportation and handling.

Once the 80% processed glycerin arrives at the railcar loading station, it is blended with water to achieve the required freezing point. The amount of water needed to blend in is based on whether the coal train is going north (to lower temperatures) or south (to higher temperatures), the time of the year (middle of the winter vs. late winter), and the weather forecasts. Some coal companies prefer a mixture that is good to -10 Fahrenheit while others desire that it prevent the coal freezing at a lower temperature. If it is early March, and spring is coming soon, many will allow for a higher freezing point temperature. If it is early January and the load is headed to North Dakota with a forthcoming blizzard, most would require the glycerin anti-freeze blend for a lower freezing point.

Chart 1: Freezing Point & Glycerin Percentage


Source: Wikipedia

It comes as surprise to some that the coal industry is so particularly “quality conscious” for a product that is simply being sprayed on coal and inside railcars to prevent freezing. Normally acceptable limits for glycerin to be used in the coal industry are listed below. Buyers are adamant that there not be any sulfate salts in the glycerin. Thus, sulfuric acid cannot be used for adjusting the pH of glycerin as the salts precipitate out of the glycerin over time, building up in tanks and plugging lines, filters, etc. MONG (primarily fatty acids) must be held to 1% or less as this is what typically causes the glycerin to “gel up.”

Table 1: Typical Buyer Specifications for Glycerin Anti-Freeze

Glycerin 80% minimum
Methanol 1% maximum
Water 10% – 13%
Ash (no sulfuric salts) 5% – 7%
MONG (fats/oils/soaps) 1% maximum

Source: Glycerin Traders LLC

While the exact amount of glycerin used by the coal sector is unknown, it definitely fluctuates year-to-year based on the harshness of winters, with hard winters seeing more glycerin usage and easy winters seeing less. Additionally, coal facilities always desire to end a winter season with their tanks empty. Thus, the last few days of a cold weather often mean lots of inventory checking and calculating, jockeying around with late requests for “one more truck,” or the cancellation of trucks that were previously scheduled.

The “coal anti-freeze effect” is large. It certainly impacts glycerin prices. By analyzing monthly prices and creating an average monthly price over the past 11 years, a seasonal pattern has developed. July through September are seasonally low prices, with upward trends beginning in October as coal plants start buying, or at least glycerin producers (biodiesel plants) start storing glycerin in anticipation of the higher prices. As one can see by the chart below, prices continue to increase into December and remain somewhat steady through March, after which prices normally decrease from about 9.4 cents per pound (cpp) to about 6.6 cpp for the summer. This drop of 2.5 – 3 cpp from winter to summer seems to be a normal seasonal adjustment. Another factor in this equation, is that many biodiesel plants slow down production in the winter. Thus, production is being reduced at exactly the same time when large users need more glycerin.

Chart 2: Average Glycerin Price by Month, 2006-2016


Source: The Jacobsen

Over the past few years, many biodiesel producers question the wisdom of relying on a market associated with the coal industry. Some people ask whether the coal industry is dying.

So, are there any mines left to use glycerin?” Yes. While many coal mines may have fallen aside, coal use in electricity production is approximately 33% of the remaining power plants. Having a reliable fuel source in the winter is absolutely necessary. This means that in the winter, coal must be loose and flowable in order to be fed into the kilns. They cannot be large, 40-ft ice blocks, which cannot be broken apart and fed into a conveying system. Appropriate and cost-effective anti-freeze agents, like glycerin, are an absolute requirement. Currently, an even bigger issue is the mild winters over the past few years. This has obviously caused less glycerin to be consumed, further depressing prices. There is more glycerin is on the market at the end of the winter, going into the spring.

So, what is the bottom line? The important takeaway is that glycerin from biodiesel plants, once properly processed, has many uses – feed, export and further refining. There is a large domestic market that uses watered down glycerin as an anti-freeze agent about four months each year. Although seasonal and dependent on weather conditions, coal mine demand for glycerin is a large market that will allow the industry to get rid of a great deal of its surplus. This allows for starting each new year with lower amounts in inventory and ready market to stable users.

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