From: Childress, Jerry [mailto:jchildress@mcgillairclean.com] Sent: Wednesday, April 24, 2013 3:12 PM To: Holloway, Thomas C. (Tom) Subject: RE: From McGill AirClean Web Site

Tom,

Most of the things that you mentioned below can affect the performance of a DSI/FF emission control system. There are some others as well.

Primary factors affecting acid gas reduction:

1. Temperature

- dry injected calcium hydroxide typically reacts best at lower temperatures while sodium bi

- carb is better at higher temps.

2. Flue gas moisture content

- lime usually reacts better in higher moisture content gas streams. Does not affect bi

- carb that much.

3. Reagent

- particle size and surface area of the reagent. Sometimes it is necessary to mill sodium bi

carb to get the best utilization. Reagent chemistry is also important although most reputable suppliers of either reagent typically have products with good chemistry.

4. Reaction time and mi xing

- good mixing of the reagent and the flue gas is important for higher removal efficiencies. We sometimes provide dry reaction chambers that provide mixing and retention time prior to entering the baghouse.

5. Stoichiometric ratio

- increasing the r eagent feed rate will sometimes improve the removal efficiencies although you can reach a point of diminishing returns. DSI is typically not as efficient at acid gas reduction or reagent usage when compared to a spray

- dry absorber. An SDA still ends up w ith a dry product but the reagents are mixed with water and injected as a slurry or a solution and the flue gas heat evaporates the droplets. We put one of these at a Belden Brick plant in Sugarcreek, Ohio. I think it is the only SDA on brick kilns anywh ere. That facility also has an ESP for particulate control as opposed to a fabric filter. It is probably the only facility at a brick plant with an ESP.

6. Fabric filter

- with a FF there is a secondary reaction opportunity as the flue gas containing r esidual acid gases passes through the dustcake on the bags. A portion of this dustcake will contain unreacted
lime or bi

- carb because you will be injecting at stoichiometric ratios greater than 1:1. So, there will be some additional contact time and reac tions at that point. Maintaining a good dustcake can help with the overall removal efficiencies. The bags should not be over cleaned which destroys too much of the dustcake and decreases the effect of this secondary contact. If the air

- to

- cloth ratio is too high, the baghouse may need to be cleaned too frequently in order to control the system pressure drop. So, the baghouse could be undersized. Felted bags typically provide the best dustcake formation. There are other factors to consider as well when making the fabric selection.

One or more of the above can affect the system performance. It is usually a combination of things that prevent a system from performing properly. If you have a specific site in mind, and could provide me with some informat ion regarding the existing conditions, I would be glad to take a look and make some suggestions.Regards,

Gerald J. Childress, National Sales Manager McGill AirClean LLC 1777 Refugee Road Columbus, Ohio 43207

- 2119 614/829

- 1350, Cell: 614/937

- 1816
Fax: 614/445

- 8759

----- Original Message

----- From: Holloway, Thomas C. (Tom) [ mailto:tcholloway@rti.org ] Sent: Wednesday, April 24, 2013 1:55 PM To: Childress, Jerry Subject: RE: From McGill AirClean Web Site

Jerry,

Thanks for the referral to Norit. I have contacted them for further information about mercury removal efficiency for the brick industry.

Another question has come up from the brick industry that I hope you can help with, specifically what, if anything, ca n be done to improve the performance of an existing control system, in this case a dry sorbent injection system followed by a baghouse, for the control of acid gases (e.g., hydrogen fluoride, hydrogen chloride) and particulate matter. Is it as simple as in creasing the amount of sorbent injected (e.g., lime or sodium bicarbonate) for a given airflow, using a more efficient sorbent formulation, replacing the bags, using larger/more efficient bags, or some other parameter adjustment? Are there
limitations to w hat can be done to improve performance? Any assistance you can provide in answering these questions would be greatly appreciated. Thanks.

Tom Holloway RTI International 3040 Cornwallis Rd., P.O. Box 12194 Research Triangle Park, NC 27709 Phone: (919) 316

- 3733 Fax: (919) 541

- 7155
E

- mail: tcholloway@rti.org