Issue Date: March 16, 2015
Bromine Comes To The Rescue For Mercury Power Plant Emissions
A one-time environmental malefactor is now considered state of the art in preventing air pollution.
Bromine and its derivatives have taken it on the chin in the past few years. Critics have decried a brominated pesticide, methyl bromide, for its potential to damage Earth’s protective ozone layer and brominated flame retardants, such as hexabromocyclododecane, for their deleterious health effects.
But now bromine appears to be an environmental savior because of its ability to reduce mercury emissions from the smokestacks of coal-fired power plants. In fact, consultants predict that demand for mercury-reducing bromine additives, such as calcium bromide and hydrogen bromide, should rise dramatically.
Chemtura and ICL, major manufacturers of bromine compounds, expect to gain. Also hoping to benefit are companies such as Cabot and Calgon Carbon that supply activated carbon treated with bromine. Another bromine maker, Albemarle, is competing in both sectors.
At the same time, suppliers of alternative technologies, including Novinda and ADA-ES, want to break the lock bromine appears to have on mercury mitigation by pointing to the corrosive effects bromine could have on power plant equipment.
Bromine’s emergence as a star mercury abater was sudden. “Until 2013, it appeared that activated carbon would be the most widely used technology to capture mercury in power plant smokestacks,” says Robert McIlvaine, president of McIlvaine Co., a power industry consulting firm.
When injected into a power plant’s flue gas, activated carbon uses its millions of tiny pores to absorb mercury that is released from coal when it is burned. But treated with bromine, the carbon does double duty by oxidizing mercury and capturing more of the neurotoxin than the untreated variety does. Bromine compounds can also be used on their own—either sprayed onto coal or injected into flue gas—to oxidize mercury into a more easily captured and less harmful form.
The regulatory motivation to get mercury out of coal plant smokestacks is simple. Without any controls, U.S. coal-burning utilities, responsible for nearly 40% of the country’s electricity, would emit 48 tons of the neurotoxic element annually.
After many setbacks, U.S. regulations requiring the removal of 90% or more of mercury emissions from power plant smokestacks should finally go into full force in 2016, barring further regulatory hiccups or court delays. Those regulations and similar rules already in effect in 16 U.S. states are creating what market observers are calling a multi-billion-dollar-per-year mercury emission control market.
“Bromine compounds will be part of most every coal power plant’s technology strategy,” says Corey Tyree, energy and environment director at Southern Research Institute, an engineering research organization. “Most utilities will be selecting it in one form or another,” adds Tyree, who has supervised emission control at coal power plants operated by Southern Co.
Eight years ago, McIlvaine was predicting a 350 million-lb-per-year market for activated carbon, but today the opportunity appears somewhat smaller because many power plant operators are looking to include bromine compounds in their emission controls. By contrast, bromine use is set to rise exponentially.
James Glauser, associate director of consulting firm IHS Chemical, says bromine use in mercury mitigation was “negligible” until 2011, when he calculated U.S. power plant operators used a little more than 2 million lb. By 2018, when all U.S. regulations are expected to be in effect, plant operators will use more than 27 million lb of bromine, he predicts.
Today, mercury abatement accounts for only about 2% of all bromine used worldwide, Glauser says. Flame retardants for plastics, in contrast, account for about half of all bromine use. But long term, bromine for mercury control could grow substantially if other countries adopt similar rules, Glauser suggests.
Craig Rogerson, chief executive officer of Chemtura, doesn’t see mercury mitigation becoming as large a bromine market as flame retardants. But he does see the business turning into a “significant outlet” for bromine.
In fact, mercury mitigation is just the business opportunity Chemtura is eager to embrace because it is not burdened by the contentious issues facing certain types of flame retardants, Rogerson says. In addition, he is counting on other large coal-using countries to adopt bromine-based control technology.
As nations ratify the United Nations Minamata Convention, a treaty designed to reduce mercury emissions globally, Rogerson anticipates supplying China, a country that burns five times more coal than the U.S., as well as Japan, India, and other coal-burning countries.
In a recent call with investors, Stefan Borgas, CEO of Israel-based ICL, called China a real opportunity. “In China, the demand, if there is regulation at the same level as in the U.S., should be at least as big as in the U.S.” More bullish than IHS’s Glauser, Borgas predicted that U.S. demand for bromine for emission control could be as high as 45 million lb per year.
Jack Carmical, a product manager at Albemarle, credits U.S. legislation signed into law in 2004 for initially helping to build demand for bromine. The American Jobs Creation Act provided a $6.00 tax credit to utilities for each ton of calcium bromide-treated coal they burned in their plants. “That was a real boon to bromine suppliers,” Carmical says.
Research from the Environmental Protection Agency, coal utilities, and chemical suppliers showed that mercury could also be removed by directly treating flue gas with bromine-treated activated carbon. Seeing an opportunity, in 2008 Albemarle bought Sorbent Technologies, putting it in the business of also supplying brominated activated carbon.
“We’re treatment agnostic,” Carmical says. “We’ll supply whatever works best for the utilities, whether it’s treated activated carbon or calcium bromide alone.”
The overall market for activated carbon may not be as big as the 350 million lb hoped for nearly a decade ago, admits Michael Pealer, a market manager for Calgon Carbon. But, “it’s still a good time to be in the activated carbon business,” he says.
The carbon can be treated in a variety of ways to suit individual utility needs, Pealer points out. Some activated carbons are treated with both bromine and other techniques so the carbon doesn’t destroy the value of fly ash, a leftover of coal combustion. A number of utilities sell the fly ash as a cement replacement to concrete makers.
Other treatments preserve the value of gypsum recovered in power plant equipment meant to capture another air pollutant, sulfur dioxide. Many utilities sell the recovered gypsum to wallboard makers.
Still, bromine alone or with activated carbon does have at least one significant drawback. According to the Electric Power Research Institute, a consortium of utilities, bromine is an oxidant that “poses a threat for accelerated corrosion” in metal plant equipment. The institute is studying how the corrosion occurs and looking for ways to mitigate it.
Some utility customers are so wary of bromine’s corrosion potential that they might forgo it or use as little as they can to get the job done, says Bart Kalkstein, vice president of activated carbon producer Cabot. For these firms, Cabot promotes activated carbon that incorporates both lower amounts of and a more benign bromine chemistry. Customers that use a bromine-treated carbon can cut sorbent consumption by as much as 80% compared with the untreated variety, he points out.
Others suggest completely different technologies. “If utilities have a corrosion issue, they need to look at an alternative,” argues Thomas K. Gale, technology development director at Novinda. Gale’s firm markets a metal sulfide reactant contained in an amended silicate particle that doesn’t corrode metal, he says. The metal sulfide reacts with mercury to form stable mercuric sulfides that are captured in plant pollution control equipment.
Utilities might also look to ADA-ES for another alternative. The firm has developed an elemental mercury oxidizer, called M-Prove, which it claims is significantly less corrosive than calcium and hydrogen bromide. Although the firm is reluctant to identify the oxidizer, company patents suggest it is based on iodine.
But at this point, the trend seems to be with brominated treatments in one form or another. Such treatments have made possible 90% or greater mercury emission reductions at lower cost than could have been imagined a decade ago, notes emission control guru McIlvaine. And because of that success, utilities can expect even tougher mercury emission regulations in the future, he says.
That’s an opinion that should be music to the ears of bromine suppliers. At least for now, they have found a promising new market free of environmental stigmas.
- Chemical & Engineering News
- ISSN 0009-2347
- Copyright © American Chemical Society