September 14, 2006

One generalization that can be made is that for modest removal requirements and optimum conditions there are systems which are commercially available. If you want a commercially available system for very high removal with difficult conditions then there are at least some situations where systems are not commercially available. This leaves a lot of space in between and this is where the controversy rages. Both sides of this argument were presented.

EPRI view on commercially available:

Email yesterday from George Offen of EPRI

Bob,

Thank you for ……..late response, I'm on travel. We've delivered
our message in a number of places that we don't believe Hg controls are
commercially ready in the sense that that phrase is normally used. Very
briefly, some of the reasons are:

·        no long-term experience,

·        no demonstrated ability to achieve a uniform reduction (i.e., state-wide x%
reduction independent of fuel, APCD, etc.) as would be required to meet
such a rule;

·        too many surprises still (why do we not get Hg capture at PRB plants with SD/BH when we inject halogens to mimic low-sulfur E. Bit plants;

·        why does a medium chlorine E. Bit plant with SCR present just 50% Hg++ to the FGD);

·        what do we do for high-S coals; etc.

 

I presume the utility attendees will ask similar questions …….George

 

A number of States and regulatory authorities have tried to define “commercially available.” Here is part of a Colorado Fact Sheet.

For undemonstrated or new (different) technologies, the technology must be commercially available and applicable to the intended purpose. In other words, it must be commercially obtained or is otherwise available within the common sense meaning of the term

Another State regulation used the terminology of “has been permitted or commercially applied.” ACI has been permitted and is being applied at Presque Isle. So is it commercially available?

McIlvaine believes that a different approach to the definition is necessary. A unit would be commercially available if there is greater than 99% probability that it will achieve the operating and performance goals within the anticipated time and cost limits. This approach is necessary to deal with the variations in coal and equipment. A technology may be commercially available for a plant with certain coals and equipment but not available for plants with different coals and equipment.

With this background the meeting progressed with presentations by nine different companies most of whom are ready to make guarantees and provide commercial systems or products.

The conference was two hours in length and did not begin to do justice to the quantity of information provided by the presenters. All of the material has been incorporated into the Mercury Decision Tree and can be viewed directly from the links below.

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Vosteen Consulting has granted a license to Southern Company. Tests will be conducted at one of the 4 x 660 MW units at the Miller plant starting next month. Bromine can be injected to substantially increase the oxidation of mercury. It has advantages as compared to chlorine. Vosteen was unable to participate in the meeting but supplied the latest information which has been posted to the Mercury Decision Tree. (The Mercury and FGD Decision Trees share the data on the scrubber enhancement).

The GE integrated approach starts with better distribution of the flyash and reliance on some mercury reduction through the carbon in the flyash. Reduced temperature in the precipitator and other optimization techniques result in up to 80% Hg removal across the precipitator with less sorbent injection. Advantages in low NO_x and higher efficiency are the multi pollutant advantages.

Tony Licatta explained that Babcock Power has multiple approaches to mercury reduction. Sodium tetrasulfide (Na₂S₄) is a low cost control option with up to 90% Hg removal at less than 3 lbs/Macf. It can be injected upstream of a baghouse or ESP. Na₂S₄ is working on a number of waste to energy plants. The company also distributes the activated Lignite HOK which is being used on two German coal/lignite-fired boilers. 85% mercury removal is being obtained at dosage rates of 6 to 9 lbs/Macf.

Tony Favale of Hitachi presented data on a new catalyst that provides high rates of mercury oxidation while maintaining a low rate of conversion of SO₂ to SO₃.

Michael Durham of ADA-ES Inc. covered the performance of various carbons based on very extensive full scale demonstrations. The company also has 10 commercial contracts.

Mineral based mercury sorbents derived from flyash and sorbents from molecular sieve materials perform well compared to bromated PAC according to data discussed by Stan Mack of Engelhard (now BASF).

Sorbent Technologies has demonstrated that brominated PAC can be successful with a range of coals and dust collector types. Good results have even been obtained with hotside ESPs according to Sid Nelson.

MinPlus is a mineral sorbent with high mercury capture. It has been used along with the Mobotec combustor modification and is slated for full scale use at Taconite Harbor.

Praxair supplies a system which allows the utility to manufacture the activated carbon from its own coal supply. Substantial cost reductions are possible says David Thompson.