Clean Air Engineering Sorbent Trap Blog

Public blog for sorbent trap monitoring issues

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Utility Information Collection Request (ICR), Take II.

The EPA announced their latest version of the Electric Utility ICR on November 10th. Is it any different than the one they proposed in July? Some initial comments regarding the latest version of the ICR.

Get more EPA information in Docket ID No. EPA-HQ-OAR-2009-0234, available at http://www.regulations.gov/  (copy and search for this docket no.)

Also, for a more complete description of the July, 2009 version of the ICR, go HERE.

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The Penalty for Success

This is an interesting example of how difficult it is to get your hands around global environmental issues. It’s almost never black and white, and success in one arena may lead to steps backwards somewhere else.

This Friday’s issue of the journal Science contains a report that implicates nitrous oxide (N2O), a.k.a. laughing gas, as a major contributor to depletion of stratospheric ozone. This report is based on a study done by the U.S. National Oceanic and Atmospheric Administration (NOAA) that calculates the potency of ozone-depleting chemicals based on recent data.

The fact that N2O is ozone-depleting is old news. The fact that it’s potency is 1/60th as strong (and gaining) as CFC-11 is new news. The team leader of the study, Dr. A.R. Ravishankara, claims that this means that nitrous oxide is now a bigger threat to future stratospheric ozone depletion than are CFCs.

Ironically, what we’re seeing is an indirect result of the success of the 1987 Montreal Protocol. This international treaty has resulted in a dramatic reduction over the last 20 years in CFCs, halons and other chlorine- and bromine-containing substances that attack ozone. As a result, N2O, which was consciously left out of the Montreal Protocol, has become a larger fraction of ozone-depleting substances.

Making matters worse, the chlorine from CFCs actually works against N2O in depleting ozone (and vice versa). Now, as there are less and less CFCs to go around, this balance starts shifting and the effectiveness of N2O in attacking ozone increases. Add to this the fact that laughing gas sticks around in the atmosphere for decades, and you start to see why Dr. Ravishankara isn't laughing when he says that N2O will be the largest ozone-depleting contributor for the rest of the century.

The real story yet to come will be how policy-makers will address this, or if they will address this (note that the NOAA report does not discuss policymaking). The majority of N2O comes from microbial breakdown of nitrogen-containing compounds, such as manure and fertilizer. The split between naturally-occurring and man-made N2O is about 2:1, i.e., one-third of the total comes from human activities such as fertilization and livestock production.

Although humans do generate some N2O from a few clear targets such as fossil fuel combustion, the bulk comes from more diffuse sources like agriculture and deforestation-related activities. Thus, significant reductions will not be possible through conventional tailpipe controls.

There is a double benefit to figuring out a way to address this, however. As you may recall, N2O is also listed as a greenhouse gas and is covered by the U.N.'s Kyoto Protocol. Thus, even though anthropogenic emissions of N2O have been growing steadily (roughly one percent every four years according to the report), there are now two significant drivers to limit these emissions.

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The Dark Side of Global Warming...after carbon dioxide, what's the second largest contributor to human-induced global warming?

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Utility Boiler ICR - An Overview

Related Links: EPA Download Page  Search for Docket No. EPA-HQ-OAR-2009-0234 (Should provide four documents)

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Text-to-Speach Synthesis Software...Solution for Non-Readers?

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Pitot tubes REVEALED...the simple story behind the pitot tube.

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Bing versus Google. A test drive of MS Bing using it to search for tech terms relative to mercury testing.

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You don't need to measure moisture when doing a 30B RATA on a sorbent trap Hg system.

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A way around the sample volume "box" in Method 30B.

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Even the best stack testers can get tripped up by the nuances of Method 30B's QA/QC requirements.

If you're part of the CleanAir network, download the referenced spreadsheet HERE.

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If there’s no mercury to measure, does anybody care?

So, we’re mobilizing to do a 30B RATA on a CleanAir MET-80 system that’s installed in a stack where the mercury concentration is typically LESS than 0.05 ug/dscm. This low of a concentration is pushing us to do test runs of 6 hours, maybe longer. Even then, getting enough mercury to measure and pass all of the method QA/QC requirements is iffy.

Someone mentioned to me a section in 30B that supposedly eliminates the need for a rigorous RATA at these levels. In section 8.2.4 of the method, it states “For the purposes of relative accuracy testing…, when the stack gas Hg concentration is expected to be very low (<0.5 ug/dscm) you may estimate the Hg concentration at 0.5 ug/dscm” This section deals specifically with the procedure for determination of target sample volume. However, they tell me that it also means that, in general, if you can just demonstrate that the concentration is below 0.5 ug/dscm, then that is good enough. Then, as long as the CEMS result is no greater than 1.5 ug/dscm, then the RATA criteria of being within +/- 1.0 ug difference is satisfied.

I think this is a low road approach, and that a rigorous measurement is in order when the technology is there to do it. What do you think? Leave your comments below.

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Reid Gardner Job Plan Update

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Portland Cement MACT May Breathe New Life into Mercury Monitoring

A recently proposed EPA rule may rekindle the mercury CEMS and sorbent trap market... On April 21, 2009, the USEPA proposed to reduce mercury emissions from Portland cement kilns. There are currently 93 portland cement plants operating 163 kilns and associated clinker coolers in the U.S. that are expected to be affected. These plants represent the fourth-largest source of mercury air emissions in the U.S. The proposal, known as a Maximum Available Control Technology standard, or MACT standard, would set the nation’s first limits on mercury emissions from existing Portland cement kilns and would strengthen the limits for new kilns. The EPA believes that the proposed new source MACT "floor" is approximately 30 percent lower than the not-to-exceed standard EPA promulgated in December 2006, which was 41 µg/dscm. The proposed MACT standards also would set limits for emissions of total hydrocarbons (THC), particulate matter (PM), and sulfur dioxide (SO2) from cement kilns of all sizes, and would reduce hydrochloric acid (HCl) emissions from large kilns. Under the proposed amendments, existing kilns would be expected to add one or more control devices to meet MACT, most likely a wet scrubber and activated carbon injection (ACI). Each kiln would also be required to install continuous emissions monitoring systems (CEMS) to monitor mercury, THC and HCl. Direct PM monitoring would not be required; instead, bag leak detectors (BLDs) would be required to monitor performance of all baghouses. Existing facilities will have three years after the promulgation to comply with the new emission limits for mercury, THC, PM, and HCl. This is the maximum period allowed by law. Most facilities will need this time, since they will likely have to install new emissions control devices to comply with the emissions limits. For new sources (i.e., those that started construction after December 5, 2005), the compliance date will be the date of publication of the final rule or startup, whichever is later. Generally, mercury emissions from cement kilns reflect the amounts of mercury in the feedstock and fuel inputs of the kilns. The EPA assumes that nearly all the mercury entering a kiln eventually leaves as a stack emission. Usually, up to 80% of the mercury emissions result from trace contaminants of mercury present in the limestone, which typically comes from a quarry located adjacent to the plant. Mercury is also found as a trace contaminant in the other inputs to the kiln such as silica, alumina, and iron, as well as the coal and petroleum coke used to fuel the kilns. Since the mercury content of the feed and fuels is believed to vary significantly from day-to-day, cement kilns do not emit mercury uniformly. This variation is compounded in modern preheater and preheater/precalciner kilns that have in-line raw mills. Consequently, short term emission tests would not be expected to provide a good indication of long term mercury emissions from cement kilns. Therefore, the proposed rule will require plants to install either instrument based or sorbent trap based mercury monitoring systems that meet either the requirements of PS-12A or PS-12B. These performance specifications are being added into 40 CFR 60, Appendix B as part of the proposed rule changes (they had been removed after CAMR was vacated The EPA states that they “see no technical basis to say that [mercury CEMS or sorbent trap monitoring systems] will not work as well on a cement kiln as they do on a utility boiler. In addition, we are aware that there are 34 cement kilns that have operating continuous mercury monitors in Germany.” We'll see if the rest of the industry agrees. The proposed rule is currently in the midst of a 60-day comment period that expires on or about June 20th. After that, we’ll have to see what, if any changes the EPA makes before publishing the final rule. Stay tuned…