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___________________________ Project No.: 0172.09.029.042 DISTRIBUTION

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Project Name: Steam

TELEPHONE CALL RECORD

Outgoing Call Date:

6/14/2012 Time:

9:00 am E T

Company Name: Synthetic Materials Contact Name: John Glasscock

Phone No.: 727

- 367

- 0400

Name: Danielle Lewis

GENERAL SUBJECT : Discuss Dewatering of Fly Ash and Gypsum Solids



### TOPICS DISCUSSED AND ACTION TAKEN

ERG requested a call with Synthetic Materials (SYNMAT) after identifying a 2009 paper written by Alex Hohne (an employee) on the

dewatering of FGD gypsum in combination with fly ash. The paper, titled A Novel Approach to the Handling and Disposal of Coal

Combustion Products

, discusses a process where FGD gypsum and fly ash ca n be dewatered simultaneously using the same vacuum

belt filter. Based on the paper, the vacuum belt filter has two feedboxes, the first receives the FGD gypsum which is partia lly

dewatered by the filter before the fly ash is applied at the second feedbox . The gypsum cake acts as the filter media for the fly ash.

The process generates a layer fly ash cake that sits on top of a the gypsum cake. The cakes can be combined and landfilled together or

mechanically separated and disposed of separately. The pr ocess requires the fly ash sluice to undergo a thickening step to bring the

solids content up to 20 percent , either using a thickener or a cla r ifier, prior to applying the fly ash on top of the gypsum cake for

dewatering.

ERG contacted John Glasscock, President of SYNMAT

, on June 14, 2012 to gain a better understand ing of the system further and ask

specific questions regarding the system application. Mr. Glasscock explained that the theory behind the process is that FGD gy psum

solids contains larger particles that function as a film to prevent the smaller fly ash particles from passing through the vacuum belt

filter media . As the gypsum is dewatered

, it forms a cake on top of the vacuum belt because the larger particles do not pass through

the mesh of the belt. While the fly ash particles would be small enough to permeate the belt filter , the gypsum cake acts as a primary

filter media prevent ing the fly ash particles from reaching the belt filter. Through this process, th e vacuum belt is able to dewater the

fly ash and the gypsum simultaneously

.

SYNMAT feels that this technology is feasible for the power industry and remains a viable option for plants needing to handle both

wet sluiced fly ash and FGD gypsum solids. Mr. Glasscock is not aware of any power plant s that are currently using this technology

in the industry

. SYNMAT does provide operational support to several steam electric power plants for the dewatering of those plants’

FGD gypsum; however, all those plants o perate dry fly ash handling systems and therefore, do not have the need for this technology

. To date, SYNMAT has only demonstrated this technology in their laboratories.

The process of dewatering fly ash in conjunction with FGD gypsum requires the fly as h sluice stream to undergo thickening, via a

clarifier or thickener, to remove some water prior to depositing the solids onto the vacuum belt filter. Mr. Glasscock is not aware of

any plants in the industry that are currently operating a thickener or clar ifier for the purpose of decanting or thickening fly ash sluice.

Mr. Glasscock could not speak to the approximate costs for the thickener/clarifier and whether it would be cost prohibitive to install

due to the potential size requirements to handle a plant’s entire fly ash sluice flow. Mr. Glasscock indicated that this would need to be

evaluated on a case

- by

- case basis.

ERG inquired about several aspects specific to the process put forth by SYNMAT in the article. Regarding the operation of th e

clari fier to thicken the fly ash sluice, ERG asked if the overflow could be reused, treated, or discharge d directly to a pond or POTW.

Mr. Glasscock indicated that this would also need to be evaluated on a case

- by

- case basis depending on each plant’s individua l permit

limitations.

ERG also inquired about the optimal proportion of fly ash solids to FGD solids. From the article it appears as through a sig nificantly

higher amount of FGD solids are required as compared to fly ash solids. Mr. Glasscock indicate d that the system only needs sufficient

gypsum solids to prevent the fly ash solids from bleeding through the vacuum filter. The thickness of this gypsum layer depe nds onNeed to return call by / at/between and

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___________________________ particle size, of both the gypsum and the fly ash. Mr. Glasscock indicated that pla nts can vary the rate at which both the gypsum and

fly ash slurr y are deposited on the filter , as well as the speed of the filter itself

, to change the thickness of both the gypsum layer and

the fly ash layer. Mr. Glasscock stated that dewatering of fly a sh alone is not feasible because it would pass through the filter belt;

therefore, e ither the fly ash slurry would need to be stored until sufficient gypsum slurry is available to operate the vacuum belt filter

or the operation of the FGD process would nee d to be altered to accommodate the fly ash production rate.

The article by Mr. Alex Hohne states that the dewatered fly ash solid and gypsum solid can be mechanically separated and the

resulting gypsum only product is of sufficient quality to market. Mr. Glasscock indicated that this is incorrect; the resulting gypsum

would not be marketable. Instead, the combined dewatered product would most likely be disposed of in a landfill. According to Mr.

Glasscock, i f a plant desires to market its solid gypsum product, it would most likely operate separate dewatering processes

.

ERG inquired about the types of modifications that would be required for a plant that is wet sluicing its fly ash and dewater ing its

gypsum to convert to this type of system. Mr. Glas scock stated that the plant would need to make the following modifications:

**•** Install a thickener/clarifier to increase the solids content of the fly ash slurry;

**•** Install feedlines to transfer the fly ash slurry to the existing vacuum belt filter;

**•** Install a second feedbox on the vacuum belt filter for the fly ash;

**•** Install additional vacuum capacity to extract the additional water; and

**•** Install equipment to handle/treat the overflow from the ash thickener/clarifier

.

Mr. Glasscock stated that he does not foresee any limitations to implementing this type of system at power plants. This system of

dewatering fly ash and gypsum could work for plants producing all types of fly ash so long as a gypsum layer could be created to

prevent the fly ash particles from passing through the belt filter.