October 09, 2005
Researchers Find Cheaper Way To Reduce Coal Mercury Emissions
Lehigh University researchers have found a cheaper way to reduce mercury emissions from coal plants.
Researchers at Lehigh University's Energy Research Center (ERC) have developed and successfully tested a cost-effective technique for reducing mercury emissions from coal-fired power plants.
In full-scale tests at three power plants, says lead investigator Carlos E. Romero, the Lehigh system reduced flue-gas emissions of mercury by as much as 70 percent or more with modest impact on plant performance and fuel cost.
The reductions were achieved, says Romero, by modifying the physical conditions of power-plant boilers, including flue gas temperature, the size of the coal particles that are burned, the size and unburned carbon level of the fly ash, and the fly ash residence time. These modifications promote the in-flight capture of mercury, Romero said.
Aside: One hears Orwellian talk of "clean coal" as if it is a reality today. But if coal was already so clean there'd be no need for research in how to reduce coal power plant emissions.
Coal-fired power plants are considered to be the biggest sources of mercury emissions. Only now 35 years after the Clean Air Act did the US EPA finally get around to restricting mercury emissions from coal plants.
Coal-fired power plants are the largest single-known source of mercury emissions in the U.S. Estimates of total mercury emissions from coal-fired plants range from 40 to 52 tons.
The U.S. Environmental Protection Agency last March issued its first-ever regulations restricting the emission of mercury from coal-fired power plants. The order mandates reductions of 23 percent by 2010 and 69 percent by 2018. Four states - Massachusetts, New Jersey, Connecticut and Wisconsin - issued their own restrictions before the March 15 action by the EPA.
My take on the Bush Administration mercury reduction regulations is that they came after too many years and do not reduce mercury rapidly enough. Similarly, I fault the Clinton Administration for not already imposing more restrictive standards 10 years ago. Neurotoxins are bad. We should do a lot more about neurotoxins than about the possible threat of global warming. But global warming is a far more fashionable worry.
The trick is to make the mercury become oxidized.
The changes in boiler operating conditions, said Romero, prevent mercury from being emitted at the stack and promote its oxidation in the flue gas and adsorption into the fly ash instead. Oxidized mercury is easily captured by scrubbers, filters and other boiler pollution-control equipment.
Note that computer simulations played a role in identifying operating conditions likely to reduce mercury emissions. This is part of a much larger long running trend where simulations speed up the rate of scientific and technological advance. What I'd like to know: Just how much faster will science and technology be able to advance 20 or 30 years from now due to the ability to rapidly run simulated experiments? Will the rate of advance speed up by orders of magnitue due to simulations alone?
The ERC team used computer software to model boiler operating conditions and alterations and then collaborated with Western Kentucky University on the field tests. Analysis of stack emissions showed that the new technology achieved a 50- to 75-percent reduction of total mercury in the flue gas with minimal to modest impact on unit thermal performance and fuel cost. This was achieved at units burning bituminous coals.
Only about one-third of mercury is captured by coal-burning power plant boilers that are not equipped with special mercury-control devices, Romero said.
Romero estimated that the new ERC technology could save a 250-megawatt power unit as much as $2 million a year in mercury-control costs. The savings could be achieved, he said, by applying the ERC method solely or in combination with a more expensive technology called activated carbon injection, which would be used by coal-fired power plants to reduce mercury emissions. The resulting hybrid method, says Romero, would greatly reduce the approximately 250 pounds per hour of activated carbon that a 250-MW boiler needs to inject to curb mercury emissions.
Reductions of emissions of sulfur and nitrogen oxides causes, as a side effect, a big reduction in mercury emissions as well. So a more rapid tightening of sulfur and nitrogen oxide emissions would also lead to reduced mercury emissions.
Humans have doubled or tripled the amount of mercury in the atmosphere.
Best estimates to date suggest that human activities have about doubled or tripled the amount of mercury in the atmosphere, and the atmospheric burden is increasing by about 1.5 percent per year. Global anthropogenic emissions of mercury are estimated to range between 2000 and 6000 metric tons per year. Electric utilities, municipal waste combustors, commercial and industrial boilers, and medical waste incinerators account for approximately 80 percent of the total amount. Coal-fired utility boilers are the largest point source of unregulated mercury emissions in the United States.
I'd really like to know how much of the mercury in fish is there due to human pollution. Have humans doubled or tripled the amount of mercury in fish? I've yet to come across any reports on research that attempts to quantify the impact of human mercury sources on fish.
Chlorine plants are another major source of mercury.
In 2000, for instance, these chlorine plants reported 79 tons of mercury consumed, according to federal and industry data cited in the report. Fourteen of those tons were emitted or released into the environment; the rest - 65 tons - was officially classified as "unaccounted for" by the US Environmental Protection Agency (EPA).
That's an amount that shocks environmentalists because, by contrast, the nation's 497 mercury-emitting power plants sent 49 tons of the toxin into the air that year, Oceana reports.
A relatively small number of all the chlorine plants still use mercury in the United States and a larger number in Europe use mercury. Why not shut down the old plants or force those plants to shift to mercury-free manufacturing methods?
Indeed, most of the 43 chlor-alkalai manufacturing plants in the US today use advanced mercury-free manufacturing processes that are relatively clean. But nine US factories - and 53 older ones in Europe - still use older "mercury-cell" technology that requires huge quantities of mercury to do the same job, Oceana reports.
One can debate about the effects of green house gases for decades and people have. But mercury is bad for the brain. Why let chlorine or power plants emit much mercury at all?
I didn't know that Chlorine plants were such a major producer of mercury pollution. This
would seem to be an obvious ( and far less disruptive) method of reducing the total mercury
load in the environment than going after coal power plants where 50% of American electrical
power is generated.
I'm with you on the need to clean coal power plants up as well and have long bemoaned the
focus on CO2 or sulfur emissions as mercury is the 'right now' clear and present danger.
Already heavy consumers of fish are affected by mercury. The San Francisco Chronicle some
month ago reported on mercury poisoning resulting from heavy fish intake. As the symptoms
of mercury poisoning include impaired mental acuity I wrote a tongue in cheek letter to
the Chronicle editor suggesting that mercury poisoning maybe very widespread in such 'Blue'
areas as coastal California and Eastern seaboard towns like Boston where seafood is eaten
at much higher rates than in the interior "Red" states and as such Bush might benefit
politically from a reduction in mercury emissions! But seriously when children who like
tuna sandwiches and eat them regularly are being diagnosed with mercury poisoning something
has to be done.
The Bush administration has shied away from forcing 'best available technology' on coal
power plant operators because of the expense and the lack of any short term alternative
energy source other than coal. With the natural gas situation the way it is that may have
been justified. However if there is a low cost and easily installed method to reduce
mercury emissions, as this report suggests, Bush should run with it as it would be both
politically and environmentally beneficial.
Do you have convincing evidence that mercury is
Or are you just returning the claims of environmentalists?
Here is an interesting suggestion. Exposure to mercury
might raise one's levels of metallothionein, which could in
turn reduce the exposure of one's genome to iron and copper.
I am not suggesting that one should expose one's genome to
toxic metal levels. But the ability of the genome to respond
in defensive (and potentially life-extending) ways has *not*
How does one not know that mercury might only be toxic
to a limited set of the population and funds could be
much better spent identifying that population subset?
(rather than cleanup).
Just looking for solutions that actually work and arguing somewhat
outside of the "standard" medical box.
Are you asking if it is known at all that mercury is a neurotoxin? Yes, of course it is known and undisputed.
Recall the "mad hatters"? They were a classic example of workers who suffered from workplace toxin exposure due to mercury used in making hats.
But maybe you know all that and are disputing that the levels added to the environment make a difference? Look at fish tables for mercury ppm concentrations. Yes, the levels in many fish are toxic and one ought to greatly restrict how much one eats of a large variety of fish. Where'd that mercury come from? According to one of the links I used humans doubled or tripled environmental mercury.
Did humans double or triple the mercury in shark and tuna? I'd really like to know. There must be old fish samples in formaldehyde jars that could be tested.
***Why let chlorine or power plants emit much mercury at all?***
Because the utility and chemical companies all have powerful lobbys in Washington, most likely, and those companies don't want to spend any more money to clean up a darn thing.
And most likely they'll ask questions like Robert Bradbury did, perhaps because they don't understand the science behind why mercury is nasty stuff.
I'll copy some info here on what biochemical affects mercury has (yes, I have a chemistry degree and yes it's probably too technical, but):
"Mercury is well documented to cause cell membrane permeability changes, mineral efflux from cells, leaky gut, enzyme blockages, etc. that commonly result in essential mineral deficiencies and imbalances. Mercury causes significant destruction of stomach and intestine epithelial cells, resulting in damage to stomach lining which along with mercury’s ability to bind to SH hydroxyl radical in cell membranes alters permeability and adversely alters bacterial populations in the intestines causing leaky gut syndrome with toxic, incompletely digested complexes in the blood and accumulation of heliobacter pylori, a suspected major factor in stomach ulcers and stomach cancer and candida albicans, as well as poor nutrient absorption.
Mercury’s forming strong bonds with and modification of the -SH groups of proteins causes mitochondrial release of calcium as well as altering molecular function of amino acids and damaging enzymatic process, resulting in improper cysteine regulation, inhibited glucose transfer and uptake, damaged sulfur oxidation processes, and reduced glutathione availability (necessary for detoxification). The essential mineral deficiencies and imbalances have been found to be a major factor in Epilepsy.
Some of the main mechanisms of toxic effects of metals include cytotoxicity; changes in cellular membrane permeability; inhibition of enzymes, coenzymes, and hormones; and generation of lipid peroxides or free radicals- which result in neurotoxicity, immuno toxicity, impaired cellular respiration, gastrointestinal /metabolic effects, hormonal effects, and immune reactivity or autoimmunity. Also mercury binds with cell membranes interfering with sodium and potassium enzyme functions, causing excess membrane permeability, especially in terms of the blood-brain barrier. Less than 1ppm mercury in the blood stream can impair the blood- brain barrier."
One way that mercury, like other heavy metals, is toxic is that it inhibits enzyme function by blocking needed cofactors (cofactors like iron, copper, zinc, etc).
All of the above is solid science, I could find some biochemistry textbooks that talk about this stuff. Needless to say, we don't want lots of mercury in our environment and we certainly don't want it in our seafood. And no one gets away from this one - living in a rich neighborhood far from coal fired power plants doesn't help you, those plants have those huge smoke stacks for a reason. Some of the pollution from those things travel distances you just wouldn't believe.
My wife is pregnant, she can't eat ANY seafood right now, too risky. I don't eat fish except once in a blue moon because of mercury in the fish. Any method that economically and effectively reduces heavy metal output from coal fired plants is a GOOD thing.
Speaking of which, any of you guys heard more news about WOW Energies Inc. and their Cascading Closed Loop Cycle that makes more electricty out of waste heat while dropping flue gasses down to about 120 degrees F? Older articles said that BP and Chevron were interested in testing this technology, and I've read something about Shell doing a project at it's Caroline facility in Canada? testing to see what this can do, but I'm all sketchy on the details.
Anyway, Randall Parker has the original article that I read here on this website talking all about the CCLC, I was just wondering if you guys had heard more about it? I'm thinking that this system when applied to lots of power plants and other industrial waste heat sources, could help answer the question of how do we deal with increased electricity demand in the future without having to build a butt-load more coal fired plants?
P.S. Yes Engineer-Poet, my area of expertise does lie more in the biological field (with some computer science), which explains why I posted a silly-ass thing like "GW/Hr" :)
What's the point in posting replies like that?
Or may be this is a kind of bot, that is posting using the name "Sumyung"?