Subject: FGD is a Big Market for Valves

The sudden spurt in construction of new coal-fired plants and the initiatives to reduce sulfur emissions at existing coal-fired plants in the U.S. and China are creating a big market for valves. In the McIlvaine report Industrial Valves: World Markets the revenue forecasts reflect this opportunity. Hundreds of flue gas desulfurization (FGD) scrubbing systems will be built. The largest systems will recirculate as much as 400,000 gpm.

A variety of valve types and materials of construction are in use, and the chief factors that dictate valve selection are corrosion and erosion resistance, minimum resistance to flow, and positive shutoff in long-term use.

• Hand-operated valves are of the overhead chain wheel type or of the gear assistance type. The following valves are typical hand-operated ones in use in limestone scrubbing systems:

Eccentric plug valves

Lined butterfly valves

Flex check valves

Water knife-gate valves

Water gate valves

• Air-operated or electric-operated control valves are very important for the control of the various liquor streams in accordance with the process control scheme. They are also used for the isolation of equipment, such as pumps. Typical control valves used in a limestone scrubbing system are pinch valves and plug valves.

• Globe valves are used to control the service water, mist eliminator wash, and miscellaneous water flows. A few globe-type valves with favorably formed body passages simulating plug valves have seen service in slurry control.

• Butterfly valves are used as on-off control valves for slurry service lines and in recirculation slurry pump discharge piping.

• Knife-gate valves are used for shutoff and also for modulating service for clear liquor-like streams. The knife-gate valve uses a shearing action in which its thin disk knifes through any deposit on the valve seats. The seat rings can be elastomeric, but the disk is usually stainless steel. A butterfly valve handles less flow than the same size knife-gate valve because the disk remains in the flowstream with a butterfly valve, while the gate is entirely outside the flowstream with a knife-gate valve.

• Plug valves are used for isolation service in water and/or slurry lines. Eccentric plug valves, in which the plug wipes past the seat and is clear of flow in the open position, have given excellent results in limestone scrubbing slurry service.

• Quarter-turn valves, in which the stem rotates without the sliding that permits slurry into the stem packing, are preferred for slurry service.

Each FGD project is tracked weekly in the McIlvaine service Utility Environmental Upgrade Tracking System http://www.mcilvainecompany.com/utilitytracking.htm

The market for valves in all applications in all countries is forecast in Industrial Valves: World Markets http://www.mcilvainecompany.com/water.html#n028

Bob McIlvaine

847-784-0012

www.mcilvainecompany.com