Air Toxics Hot Topic Hour Yesterday underscores the Potential impact on Power Plants

Air Toxics Hot Topic Hour Yesterday underscores the Potential impact on Power Plants

The Hot Topic Hour May 15 on Air Toxics covered the regulations, the technical parameters and the solutions. The conclusion is that nickel, selenium and certain other metals are important and their fate needs to be considered separately from particulate or mercury. In fact some mercury solutions could create problems with the other metals.

For example, John Pavlish of EERC says that while mercury in activated carbon is relatively stable, selenium and certain other metals will leach from the carbon. On the positive side, the carbon will pick up 50 to 90 percent of the selenium, but if some if it will leach into groundwater then the problem is transferred.

Editors note: To clarify the importance of this leaching, it would be worthwhile to compare the quantity of selenium removed by a $10 million FGD wastewater system to the quantity which would leach from an ACI landfill. If there is any parity, then there is a problem.

There were five experts providing presentations. Their biographies and pictures are shown at

Bios and Photos Air Toxics Hot Topic Hour May 15, 2008

John gave a very through coverage of generation of air toxics in coal combustion and their capture by various technologies. His conclusion is that it is relatively easy to remove 95 percent of the metals. Some of the new air permits are being written around 99 percent capture and that could prove difficult.

Bob McIlvaine spent a few minutes talking about the Lesser Quantity Emission Rate (LQER). The LQER never surfaced but was prepared in the early 1990s by EPA. It set the yearly emissions which would trigger MACT based on toxicity. So HCl was 10 tons, nickel 0.2 tons and selenium 0.2 tons. Some metals such as cadmium were 0.01 tons. Here is a comparison of annual emissions for the average plant vs. this threshold.

HCl lbs/plant—100,000 lbs vs. 20,000 lb threshold

Nickel lbs/plant—1400 lbs vs. 200 lb threshold

Selenium lbs/ plant—860 lbs vs. 200 lb threshold

What this shows is that the average power plant is likely to trigger MACT for a number of metals. HCl is relatively benign but the average power plant emits 50 tons/yr. Even without the LQER it exceeds the 10 ton threshold for any toxic.

John Pavlish stressed the variable quantities of toxics in coal. He singled out Gulf Coast lignite for its high selenium content.

John Walke of NRDC gave a very well organized and clear coverage of the very complex toxic regulatory history. He explained the reasons why the odds are high against the mercury vacature decision being overturned. He said that one possibility is a toxics rule proposal in 2009 with promulgation in 2010. Compliance for existing units could be as far out as 2012, although NRDC would be arguing for 2011-12. New units would be faced with complying based on the date of the proposal. In the interim they must comply with the case-by-case MACT in Section 112g. Existing units could face a case-by-case MACT hammer under 112j. MACT is defined as equally to the “best controlled similar source regardless of cost.” However, even better performance may be required through a concept labeled “beyond the floor.” If a better technology is available, then it would be considered. However, cost must be considered for this better option.

John fielded questions about the potential for the Carper bill to be enacted quickly. He was not optimistic. However, he did advise that we watch the fate of CAIR. If this is struck down in a ruling to be issued in the next month then there will be substantial pressure on Congress to pass a new law.

Steve Jaasund of Lundberg explained that wet precipitators do a very effective job in capturing the submicron metal particulates. He was asked about cost. Metal casings are required because of the sparking. High nickel alloys are three times the cost of 2205 alloy. One option is to accept a shorter lifetime and keep down the capital expense.

Bob Ashworth of ClearStack displayed mercury and other air toxic capture achievements of a gasifier which can be attached to an existing coal-fired boiler. The unit can also cope with up to 20 percent biomass. The design is targeted as a low cost retrofit for pc boilers which can meet SO₂, NO_x, and toxic goals.

Rod Truce of Indigo addressed the removal of air toxics through the use of an agglomerator ahead of the precipitator. The submicron metals are attached to larger particles and then caught in the precipitator. The capital cost is a nominal $15/kW and involves inserting a small section in the ductwork.

The individual power points can be immediately viewed in the Mercury Decision Tree using the following links.

John Pavlish - EERC

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Multi-pollutant Reduction Needs

Continuing Decision Process For: Multi-pollutant Reduction Needs

Toxic Emissions by Utility Coal-fired Boilers -Trace Metals in Combustion Systems by John Pavlish, EERC, Air Toxics Hot Topic Hour May 15, 2008

http://www.mcilvainecompany.com/Mercury_Decision_Tree/subscriber/Tree/DescriptionTextLinks/EERC - John Pavlish.pdf