You know MCHM now, but do you know how it’s supposed to work?
A leaky tank at a chemical storage facility near the Elk River on Thursday, Jan. 9 threw a spotlight onto the relationship between the chemical and coal industries.
Coal preparation plants crush and wash coal before it is delivered to clients. Froth flotation chemicals like crude MCHM — 4-methylcyclohexane methanol — can be mixed in during the washing process to separate more ash, or unwanted material, from the coal.
Freedom Industries, the company responsible for the January chemical spill, claims the tank at its Etowah River Terminal facility that leaked spilled a mixture of more than 10,000 gallons of chemicals, made up of 88.5 percent crude MCHM; 7.3 percent PPH, stripped; and 4.2 percent water. The chemical leak, originally thought to only involve crude MCHM, polluted the intake of West Virginia American Water’s treatment facility a mile and a half downstream and forced a do-not-use water order for 300,000 West Virginians in parts of nine counties for as many as 10 days.
Freedom Industries describes the terminal as a “liquid bulk storage and distribution facility” on its website. That means it purchased chemicals from manufacturers then sold them (or mixtures of multiple chemicals) to clients.
To understand the role crude MCHM plays in coal cleaning, a basic understanding of the process is necessary.
Dr. Mike Nelson, chairman of the Department of Mining and Engineering at the University of Utah, has written numerous academic papers on mineral processing plant design. He said coal is a lightweight mineral and is hydrophobic, meaning its surface doesn’t get wet.
A popular coal washing process takes advantage of these properties by separating coal from ash in a large tank of aerated water. Ash can include pyrite (which contains sulfur) and sedimentary rock — two things Nelson said power plants don’t want to burn in their coal.
“(Sulfur) gets converted into sulfur dioxide. That would go up the stack and eventually cause air pollution,” Nelson said. “The ash is undesirable because it gets into the boiler and consumes heat. It also contributed to the solid material that has to be disposed of. Coal is too high in sulfur and ash for the power company, so coal will be washed and processed to remove those undesirable constituents.”
Before coal is washed, it is ground down into a fine powder — Nelson described it as “almost like face powder.” The powdered form of impure coal is then dumped into a flotation cell full of water with air bubbles coming up from below. Gravity pulls the heavier, unwanted materials to the bottom of the tank, while the coal is carried to the top of the tank by the air bubbles.
“It’s real turbulent, so you have a lot of contact between particles and bubbles,” Nelson said. “The coal particles will connect with those bubbles and rise to the top.”
Smaller, more numerous bubbles can separate smaller impurities from the coal. Flotation reagent chemicals like MCHM make it possible for smaller bubbles to form by reducing water’s surface tension.
“There are a lot of different frothers used. MCHM is one of them,” Nelson said. “They are organic compounds that modify the surface tension of the water so it will make a lot more bubbles.
“Froth flotation gets the coal cleaner.”
Chemicals called activators and depressants can also be used to modify the surface tension of minerals, though Nelson said coal typically floats without modification.
“It’s a very complicated corner of chemistry,” Nelson said.
Nelson said froth flotation chemicals like MCHM are used in “proportionately small amounts” compared to water. He estimated about a gallon of frothing chemical is used for every 1,000 to 10,000 gallons of water. Those affected by the Jan. 9 chemical leak may better understand this frother-to-water ratio as 100 to 1,000 parts per million.
Harold Ward, acting director of the West Virginia Department of Environmental Protection’s Division of Mining and Reclamation, offered more details about the typical coal-washing process and pegged a much lower estimate of how much MCHM is used in the process.
Ward said 650 to 1,700 gallons of water per minute are typically used in a coal preparation plant, depending on its size. He said MCHM is injected at a rate of about 80 milliliters per minute.
Ward said the estimates are based on numbers he received from coal preparation plants in West Virginia.
“It’s a drip into the metallurgical process,” Ward said.
In parts-per-million scale, 650 gallons of water mixed with 80 milliliters of MCHM would have a composition of 32.51 parts per million MCHM.
After the washing phase of preparation, the crushed, washed coal is filtered and sometimes dried before it’s shipped to customers by rail, barge or truck. The slurry is pumped to a “thickener” — a cylindrical, open-air well outside the wash plant that spins the slurry around. Rakes in the well help separate the water from the slurry.
The water is skimmed from the top of the slurry and recycled for reuse in the wash plant. The slurry is pumped to slurry impoundments.
Ward said water used in the cleaning process is filtered before it is released through a DEP-permitted outfall into the environment.
“All the water that is discharged from the treatment plants has to be treated to a certain level meant to protect human and biological health,” Ward said.
In testing conducted after the Jan. 9 chemical leak, MCHM was found in the outfalls of three of the 25 West Virginia coal preparation plants that were actively using MCHM at the time of the leak. The three plants’ outfalls had undetectable levels of MCHM in later testing, and Ward said the chemical was never detected in the streams the outflows flow into at any time.
“We have no indication of any of this process affecting the waters of this state,” Ward said.
Ward said most of the MCHM stays with the coal and is shipped with the produced coal wherever it’s bound for. He estimated that “there could have only been 4.7 gallons of MCHM in 100,000 gallons” of coal slurry in a slurry impoundment.
Nelson said he has never smelled the odor of froth-flotation chemicals emanating from coal slurry impoundments, but has smelled the chemicals in wash plants.
Both Nelson and Ward agree that chemicals like MCHM pose the biggest potential risk to the environment and the public during storage and transport. Ward said the “spill bill,” signed into law by Gov. Earl Ray Tomblin on April 1, will help regulators keep a better eye on facilities that store large amounts of chemicals, like Freedom Industries’ Etowah River Terminal.
But Nelson said there are thousands of chemicals whose effects on human health, much like MCHM, are little-known or unknown. And in areas where the political forces are not friendly to environmental regulation, people may never know the effects of those chemicals until the next big accident.
“The bigger problem is we don’t have a good understanding of what they do in human systems,” Nelson said. “It’s expensive to find out and the government hasn’t wanted to pay to find out.
“I don’t think regulations for chemicals have been updated for years,” Nelson said. “And a lot of political jurisdictions are not friendly with more regulations. You may be familiar with that where you live.”
Contact writer Marcus Constantino at 304-348-1796 or email@example.com. Follow him at www.twitter.com/amtino.