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Even though we held a Mercury Hot Topic Hour just eight weeks ago, it was very valuable to be updated on important new findings in a two-hour session.

Chuck Miller of DOE led off the meeting with an update on the latest developments with sorbents, catalysts, and other controls. He presented various charts which illustrated the advantage of separately evaluating the removal of the elemental mercury from the speciated mercury. The net mercury removal can be affected by potential FGD re-emissions and loss of Hg from FGD in the byproducts. Although Chuck pointed out that USG estimates that the gypsum plants are only responsible for one ton of mercury per year or two percent of the power plant total. DOE /NETL will hold another mercury control conference this December.

Steve Derenne showed impressive mercury removal for the TOXECON system at We Energies Presque Isle. The Mercury CEMS acts as a controller. The activated carbon is controlled over a range of +/- 20% cap. In July the efficiency averaged over 90 percent and the feed rate averaged 1.5 lbs/Mcf. Current activities include resolving problems with the ash silo vent filter, upgrades to the ash mixer, and upgrades to the inlet Hg CEM. Trona will be injected for SO₂ and NO_x removal and the impact on mercury removal measured.

Jean Bustard of ADA/ES showed a chart giving the variations in mercury removal with fabric filters and ESPs depending on the SO₃ content and the sorbent injection rate. It is clear that reducing the SO₃ results in substantial improvement in mercury capture. A portable CEM/IRM has proved easy to use and effective and would seem to be a good solution to the RATA problem. ADA/ES is moving forward with plans to build ACI plants. Jean estimates that 400 million lbs/yr of carbon will be needed in 2010. This forecast is validated by the RFPs issued by four utilities in the past four months seeking a combined total of 200 million pounds per year. These do not cover the carbon needs for many of the 50 ACI systems sold to date.

Rob Nebergall of Norit explained that Norit Americas has a capacity of 85 million pounds of PAC at one plant now. A 30 million pound/yr expansion will start in 2009. Permitting for additional units is in process and a new site will be announced this quarter. Norit is mounting a big effort to develop flyash compatible carbons. Six Norit systems are in operation and seven are being installed. Twenty-three are in the design and procurement stage.

Calgon Carbon has a current capacity of 40 million pounds and is recommissioning a 70 million pound mothballed production line.

Overseas Norit Europe has 40 million pounds of PAC capacity. RWE has a 100 million pound capacity of a char which has a lower mercury removal capability. China is a source but demand in China is straining the supply chain.

Philip Elliott of Steag addressed the mercury removal strategies at a number of power plants owned by Steag. Wet scrubbers and SCR are used at all the plants. Therefore mercury removal is in excess of 60 percent even though in the case of Voerde Units 3/4 elemental mercury represents 75 percent of the total. More than 80 percent of the elemental mercury is oxidized as it passes through the SCR. Until the year 2000 mercury was present in the dewatered wastewater sludge. This resulted in a cost of $125/ton or $812,000/yr just to dispose of the hazardous sludge. So Steag decided to convert the one stage wastewater treatment to a two stage system. The mercury passes through the first stage and is captured in the second. 6,300 tons per year of first stage sludge is sent back to the coal pile. Only 200 tons of hazardous sludge is landfilled. The result is a savings of $700,000 per year.

Jim Jarvis of URS was able to show that the injection of SBS for SO₃ removal has a big effect on mercury capture with activated carbon. What is more surprising is that when SO₃ levels were reduced to just a few ppm the flyash itself, even without ACI, could achieve significant mercury capture.

The individual presentations are in the Decision Trees as shown below. If you would like to view the power points just click on the links.

Enhanced SCR
Other Technologies
Removal in Wet Scrubber
Sorbent Injection Prior to Particulate Device
TOXECON

Selective Separation of Mercury and Other Heavy Metals during FGD Wastewater Treatment

Hans Hartenstein of Steag replied to our question on the HCl pre-scrubber option.

"I don’t think the chloride pre-scrubber is cost effective. There are much better, easier and cheaper ways to ensure full Hg oxidation. One of the best is the addition of small amounts of bromine compounds. Bromine is about 100 times as potent in its oxidation capability of mercury compared to chlorine. This results mostly from the fact that mercury oxidation in the flue gas requires elemental chlorine or elemental bromine. Unfortunately, the elemental chlorine formed by the Deacon reaction is quickly consumed by SO₂. Since the U.S. has a lot of relatively high sulfur coal, this poses a problem, which a chloride pre-scrubber cannot overcome cost effectively. Fortunately, elemental bromine is not consumed in the same way, which makes it extremely effective for quantitative mercury oxidation even in very small quantities. Southern Company as well as EPRI ran independent tests with bromine containing additives and the results were more than convincing. We recently published a paper, which is attached for your reference that outlines in the first portion these issues. The paper itself focuses on what happens to the oxidized mercury once absorbed in the scrubber. Since it needs to go somewhere other than the gypsum and the wastewater, we developed a patented method to bind it in the scrubbing liquor and selectively remove it from the wastewater. It is a very interesting technology, which we think has a lot of application for the U.S. Thanks."

Editor note: the full paper can be viewed at STEAG Presentation. Steag also made a presentation with power points during our Mercury Hot Topic Hour yesterday on this very interesting way to separate the mercury from the FGD sludge and then return the sludge to the boiler. Relative to the cost effectiveness of the HCl pre-scrubber we point out that mercury control is not the only cost consideration. Sale of the acid by-product and most importantly the reduction in materials cost for the SO₂ scrubber are important. Also if the mercury and chlorides are removed prior to the wastewater treatment, the cost of the treatment is greatly reduced. We encourage our subscribers to weigh in on this topic.

As more power plants commit to making gypsum, the need for additional sources diminishes. In particular, where SO₂ levels are high and there are nearby markets for sulfuric acid or fertilizer, there is the possibility that gypsum may not be the lowest cost alternative.

Powerspan is active with projects underway. But consider that Philadelphia Electric has been operating a number of FGD systems using magnesium since the 1970s. Haldor Topsoe and Alstom teamed up to build a 125 MW FGD system a decade ago at a U.S. power plant. This system uses catalyst in a step toward making acid. Haldor Topsoe has a number of these systems operating in non-power plant operations.

Marsulex is very active in bidding and supplying systems FGD to make ammonium sulfate. Amy Evans will be updating participants on the latest developments.

Dilute sulfuric acid is another option, but the attractiveness depends on a purchaser of the acid. The amine scrubbing systems offered by Cansolv and others offer the ability to make concentrated sulfuric acid using technology long proven in the chemical industry.

All these processes and others will be discussed in an intensive one to three hour session next week. The time is flexible because there is no restriction on debate and discussion. Given the importance and differences of opinion on this subject, it is likely that the meeting will be longer rather than shorter. It will all commence at 9:00 a.m. CDT on August 16.

This Utility E-Alert is part of the Utility Upgrade Environmental Tracking System. The system allows you to instantly retrieve project details, profiles of each coal-fired plant worldwide, the right contacts at the OEM and A/E firms and summaries of all the scheduled FGD and SCR projects. You need a user name and password to access this system. If you have forgotten your user name or password or are not sure whether you are eligible to access this system, email: