January 31, 2008

Carbon Cost and Availability were only Two of Many Mercury Issues Discussed in the Mercury Hot Topic Hour

More than 80 people participated in the Mercury Control Hot Topic Hour on January 31. There was a good mix among questions and answers generated from participants and review of highlights of the DOE NETL Mercury Conference and EUEC Conference.

Some of the questions from the utilities are thought provoking. One was triggered by a paper given Thursday at EUEC by Brian Rupp of AEP. He believes there is opportunity to separate the flyash for sale in the first precipitator field and then subsequently capture the carbon in the second. Participants discussed ways to maximize the salable flyash. Don Hug of Clyde Bergemann advised that this is possible but a limiting factor is the precipitator efficiency requirement.

Full scale activated carbon injection (ACI) tests on PRB at AEP were not surprising but bituminous and lignite showed deviations from expectations. In one case longer term deterioration in performance was possibly due to the change in flyash on the collection plates. Mercury and chlorine in the coal varied by orders of magnitude.

Gordon Criswell of PPL Montana indicated that testing of carbon injection ahead of the wet particulate/SO₂ scrubber showed substantial removal of mercury.

Otter Tail Power is faced with mercury control for an existing unit with a pulse jet filter and no scrubber as well as on a new unit with an SCR, pulse jet filter and a wet scrubber. Sid Nelson of Sorbent Technologies explained how the brominated activated carbon acts as a catalyst. Some of the mercury it does not capture will be oxidized and removed in the scrubber. So Otter Tail could minimize carbon consumption in the new unit with the combined capture in the filter and scrubber.

Excerpts from the DOE NETL Mercury Conference were used as a launching pad for further discussion. The full text of these papers can be found at

http://www.netl.doe.gov/publications/proceedings/07/mercury/index.html#overview

George Offen of EPRI provided papers at both the NETL and EUEC conference. Some of the areas where EPRI is helping move the technology involve

• Hot-side ESP SO₃ injection performance on mercury control
• Cost-acceptable options for 90 percent compliance
• PM emission increases (NSR?)
• Potential bromine impacts - boiler, FGD, products
• Other metals - As, Se, ….
• Confidence in technology - expand experience base and validate models
• Improve process, reduce impacts, lower costs
• Prevent re-emissions and control fate of Hg in FGD
• Improve sorbent technology/understanding
• Injection limits for ash use in concrete
• Novel - for high T or high SO₃; with low ash impact or easily separable from ash; better Hg
• Lower cost

Alstom described progress with their Mercure sorbent additive at NETL

• Baseline measurements

-Native capture is 27%-50% by AH/ESP and 23 percent by FGD

-Not all of oxidized mercury was captured by FGD

-A large amount of oxidized mercury was reduced to elemental in FGD

• Parametric testing during sorbent injection

-90% of uncontrolled mercury emission was captured at 0.8 lb/MMacf

-90% of input mercury was captured at 0.5 lb/MMacf

• Balance-of-plant impact

-No stack opacity increase during injection

-No leaching of mercury from flyash

• Continued ash sales/utilization

-75% of uncontrolled mercury can be removed before ash sales loss

-88% of input mercury may be removed before ash sales loss

There was a good discussion of costs and availability of carbon. Sid Nelson of Sorbent Technologies raised the question as to whether carbon could reach $2/lb and noted a recent 70 percent increase by Norit and Calgon Carbon. Calgon Carbon presented data showing hundreds of millions of pounds of increased capacity beyond 2012. On the other hand, Jean Bustard of ADA-ES showed data at EUEC projecting as much as 1 million lb/yr requirement in 2015 if there were new Federal rules. It was agreed that there is flexibility. Brominated carbon will capture more mercury. You can add an extra step in the production to impregnate carbon. So each pound of brominated carbon may be the equivalent of two pounds of untreated activated carbon. However, it was also pointed out that the bromination does not always increase efficiency.

Alternative technologies that may not be competitive at $1/lb AC may be more than competitive at $2/lb. So you do have the classic price-sensitive demand.

McIlvaine indicated that the Chinese demand would be another factor and displayed the analysis by Naiqiang Yan (appears separately in this Alert).

Other Technologies were also discussed Based on Presentations Made at the Two Conferences

A URS two year demonstration of the Johnson Matthey gold catalyst is about to begin at LCRA.

GE partially gasified coal for 70 percent mercury removal is 75 percent less costly than ACI.

Alstom KNX, with bromine, added with the coal results in high removal but some re-emission problems. One of the utilities participating in the Hot Topic Hour volunteered successful KNX testing and no re-emission at his plant.

NaHS from B&W improves wet FGD mercury capture by 10-25 percent without adverse effects or re-emission.

PowerSpan Eco at First Energy at 30 MW achieves 80-85 percent removal of mercury.

Mazyck has demonstrated (at lab scale) a photocatalytic sorbent with 99 percent removal using silica titania material.

Praxair PAC from pulverized coal is very effective at the 1-MW level. Tests are continuing with the promise of lower cost than AC.

Corning’s honeycomb mercury absorber achieved 90 percent removal in long term testing.

BASF (Englehard) mineral-based mercury sorbents derived from flyash and sorbents from molecular sieve materials perform well compared to brominated PAC in some tests but not others. BASF is continuing the research and is optimistic.