Page 65 - Hub4 Magazine Issue 51
P. 65

Vortex Assists Sanitation Efforts at a Waste-
to-Energy Facility
In 2007, a county sanitation district approached Vortex to discuss a process need in their waste- to-energy power plant. Under their previous process, the plant used manually actuated slide gates to isolate a hopper, filled with incinerator bottom ash and fly ash, from a drag chain conveyor. When the gate is opened, hot ashes discharge into the drag chain conveyor. As the hot ashes convey, they cool before being evacuated from the process.
Of the pre-existing slide gates, the plant had two primary complaints:
• Thoughthegatesweremanuallyactuated,theydidnot actuate well. A sledge hammer was needed to drive the gates closed. To be reopened, each gate required maintenance and downtime. These processes were cumbersome, labor-intensive and were performed weekly.
• Thegatesoftenleakedsteamandmaterialstoatmosphere. When steam is leaked to atmosphere, it reduces the efficiency of the steam generator – which also reduces the total output of electricity. Because some municipal solid wastes also contain hazardous materials, this can create health and safety concerns if ashes are leaked to atmosphere.
The Vortex Aggregate Gate was recommended as the solution to each of these problems.
Gate Specifications:
• Size:18in|455mm
• Pneumaticallyactuated,usingadouble-actingaircylinder actuator.
• Ratedforhandledmaterialtemperaturesof400°F|205° C (max.) continuous service.
• Bonnetsealtohindermaterialsfrommigratingintothe bonnet area.
• Returnpantocontainfinematerials.
• Valvebody,blade&materialcontactareasconstructed from 304 stainless steel, to resist oxidation & corrosion.
• Bladerollersconstructedfrom304stainlesssteel&bronze.
• Roller spacers & bonnet blade guides constructed from 25% glass-filled TeflonTM.
• Sideseals,endseal&upperbonnetsealconstructedfrom high-heat rubber belting.
• AircylindersealsconstructedfromVitonTM,for temperature resistance.
• Aircylinderequippedwithamagneticpiston,to accommodate magnetic reed switches for blade position indication.
By introducing pneumatic actuation, the Vortex Aggregate Gates are able to be opened and closed quickly, simply, and without significant manpower.
On the opening stroke, each gate’s bonnet seal acts as a “squeegee” to force materials remaining along the blade to fall away into the process line below, rather than migrating into the bonnet area.
When using a return pan, on the top part of the gate, a solid
bonnet cover is used. On the bottom part of the gate, the return pan replaces the lower bonnet cover. As materials migrate into the bonnet area, rather than building up, they are deposited down onto the return pan, to be reintroduced into the material flow stream.
Benefits of a return pan include:
• An inexpensive way to prevent dusting to atmosphere. This improves housekeeping and workplace safety, and prevents product loss.
• An effective solution to prevent material build-up in the bonnet area, which could otherwise cause gate actuation issues.
Today, this waste-to-energy power plant operates six Vortex Aggregate Gates, all of similar design. July 2018 - Issue 51
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