Mercury Breakdown: Sources and Cutting Edge Technology
The mercury that ends up in the fish that we love to eat comes from a variety of different sources. Approximately one third of the mercury in the environment comes from natural sources. It is released from the earth’s crust by volcanic activity and weathering and erosion of rocks and minerals. The other two thirds of the mercury is mostly from coal burning power plant, municipal and medical waste incinerators, and especially in Minnesota, taconite processing. The included chart shows where the man made mercury emissions in Minnesota are coming from and how much the different sources are putting out.
Due to the large percentage of mercury emissions attributed to power plants, the EPA has set new regulations which will require more effective mercury removal technologies. The Clean Air Mercury Rule will reduce electric utility mercury emissions by nearly 70 percent from 1999 levels when fully implemented. Current technologies such as settling, flocculating, and coagulating will not achieve the requirements set by the EPA according to members of the Electric Reliability Coordinating Council.
A new advancing technology being tested and implemented is activated carbon injection. New systems will inject specialized carbon materials into the power plant ductwork ahead of particulate removal equipment to adsorb mercury from the flue gas before it can be emitted to the atmosphere. Carbon is especially useful for capturing (adsorbing) gas phase mercury due to the many active sites on it surface. To increase the amount adsorbed, the carbon is often treated with a halogen such as Bromine. Brominated activated carbons have shown mercury capture rates approaching 95% in PRB fuel systems, which would meet the EPA regulations if widely implemented.
Comments
Carbon injection seems like a very easy fix. What are the major drawbacks to this method because it sounds very effective and easy. All a plant would have to do is add the carbon in to the gas stream and then be able to remove it with their current particulate removal system. Is that right or am i oversimlifying it?
Posted by: Brent Haekenkamp | March 3, 2008 12:44 PM
What is PRB?
How much carbon is needed to remove the mercury? What is the absorption capacity?
Where has the technology actually been used - has it made it out of the trial stage and into actual production?
One more question - what part of the taconite process releases mercury - is it fuel use to make the pellets, or is it in the mined materials?
Posted by: Steve Sternberg | March 4, 2008 4:00 PM
Is PRB, Powder River Basin coal?
Mercury in taconite production can come from two sources: the mine and the fuel used. Within the mine, mercury comes from ore hauling, screening, crushing, conveyer transfers, and stockpile wind erosion. Mercury is also found in natural gas, coal, and pet coke that can be used in the indurating furnaces. I am not sure where the majority of the mercury comes from.
Posted by: Simon Larson | March 8, 2008 8:51 PM
I have seen in tv news reports about the potential health hazards about the release of mercury from the energy efficient compact fluorescent light bulbs (CFLs) and other fluorescent bulbs. According to the EPA, CFLs contain an average of 5 milligrams of mercury, depending on manufacturer. If these bulbs are not disposed of properly, such as hazardous waste collection, they may be broken in the landfill and release the mercury.
http://www.epa.gov/bulbrecycling/faqs.htm
Posted by: Becky Walechka | March 23, 2008 3:18 PM