June 7, 2007

A good mix of suppliers, utilities, OEMS and A/Es heard several presentations which provided a good comparison of belt filters and basket centrifuges for gypsum dewatering. In addition, insights were provided as to the needs of the wallboard companies. John Halm of USG indicated that his company will pay a premium for solids moisture content below 10 percent. He also said that there was concern about mercury in the gypsum. USG is involved in several mercury  research projects.

The power points have been incorporated into the FGD Decision Tree. Links to the presentations along with summaries are shown below.

Jim McGillicuddy, KPMT

Krauss Maffei basket centrifuges have been used for FGD gypsum dewatering since the 1980s. The most recent installation is Progress Energy Ashville. The capital cost is favorable compared to belt filters for smaller boilers but loses this advantage as the system size increases. The basket centrifuge can deliver 95 percent solids, but at lower thru put than to produce 90 percent solids.

One of the participants questioned the maintenance compared to belt filters. Jim says that the maintenance has proven to be low on many installations. The energy consumption is also less.

Continuing Decision Process For: Products

Presentation at June 7, 2007 Hot Topic Hour

Innovative, Reliable, Efficient Solutions for Mechanical and Thermal Solid / Liquid Separation

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/FGD Gypsum Hot Topic Hour - June 7, 2007 Jim McGillicuddy, KMPT USA.htm

Rod Coombs, RPA Process

RPA has experience with liquid solid separation dating back more than one century through its Filtres Phillippe Group. The company makes large belt filters suitable for FGD applications. Rod says the four fundamental factors to dewatering and washing are

• Temperature

• Particle size distribution "PSD"

• Concentration of gypsum in the slurry

• Concentration of Cl^- in the feed liquor

• Vacuum pump capacity

Continuing Decision Process For: Products

Presentation at June 7, 2007 Hot Topic Hour

Filtres Philippe Horizontal Vacuum Belt Filters for FGD Gypsum Dewatering Horizontal Vacuum Belt Filters for FGD Gypsum Dewatering

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/RPA Process Technologies FGD Presentation Hot topic.pdf

David Carduff, GKD

GKD is a world wide supplier of dewatering belts. Horizontal vacuum belt filters typically utilize a woven belt with characteristics to allow water flow while capturing the gypsum. Fine particles require creative weaves and combinations of mono and multifilaments in the warp and weft. The typical material is polyester (a tough, chemical resistant, and economical material readily weavable). The typical weave design is twill and/or multi-layer with air permeabililty of 25-40 cfm (particle size dependent).

Belts typically last eight months on FGD applications. Life is a function of the particle size distribution. Small particles can penetrate the belt and reduce flow. In China the gypsum particle size is unusually small. As a result some Chinese plants add an additional step to grow the particles prior to dewatering.

Continuing Decision Process For: Products

Presentation at June 7, 2007 Hot Topic Hour

FGD Gypsum Handling

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/RVSD FGD Presentation by J. David Carduff, GKD-USA.pdf
 

Mercury: Commercial and Cost Issues Will Be the “Hot Topic” Discussion June 14

Our last “Hot Topic” discussion on mercury control cost and performance was February 15. A lot has happened since then. At 9:00 a.m. next Thursday, June 14, we will spend one to two hours discussing all the developments in the last few months. We will get an update on the We Energies Presque Isle system, the sorbent injection experience, the progress with catalysts, scrubber additives and novel technologies. We will also review the remaining ACI issues which include:

Site Specific Issues

Hot electrostatic precipitators

SO₃ conditioning

Poor performance of halogenated carbon when firing PRB coal and using spray drier/baghouse

Commercial Issues

Availability of carbon

Carbon cost

Cost of higher performance carbons

Cost of flyash friendly sorbents

Lack of experience

Narrow guarantees

Meeting low mercury limits with high mercury in flue gas

Flyash salability impact

Review of Technical Issues

CUB impacts

Mercury re-emissions

Increased particulate

SO₃ interference

Baghouse impacts

Sorbent distribution

Temperature sensitivity of halogenated carbons

Hopper fires

PAC handling

Variability of mercury content in flue gas

Last but not least, we will explore the potential for chloride pre-scrubbers and the removal of the mercury before it gets to the SO₂ scrubber.