Vulcan PMRU Portable Mercury Reclamation Unit in Moberly, MO, USA
- Moberly, MO
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Vulcan® PMRU Portable Mercury Reclamation Unit - The Vulcan® PMRU Portable Mercury Reclamation Unit separates mercury from contaminated wastes and then recovers the mercury in our proprietary reclamation system. This proven technology can be witnessed at our on-site commercial demonstration unit. Our dedicated staff has successfully transformed several mercury-contaminated wastes into recyclable feedstock. These wastes include cement kiln dust, activated carbon and bottom ashes from various power plants. The base unit utilizes the following major components to accomplish these tasks:
Material Feed System:
feed storage silo and multiple screw conveyors
Primary Treatment Unit:
indirect fired rotary desorber with combustion chamber, burners and seals
Dry Material Discharge:
screw conveyor and pugmill mixer
industrial dust collector and two-stage condensing unit
The Vulcan® PMRU is designed to remediate 5 to 20 tons per hour of mercury-contaminated wastes in a versatile and portable system. All equipment is mounted onto three (3) highway-legal trailers for flexibility of treatment locations. A key design consideration is complete control of operational parameters in each component to tune the system for the most effective operation for a specified contaminate. Once this has been established, the system can be controlled automatically.
The system works on the premises of low-temperature thermal desorption (LTTD), also known as low-temperature thermal volatilization, and thermal stripping, whereby mercury and mercury-containing compounds are vaporized using heat. The temperature must be maintained above the boiling point of elemental mercury but under the auto-ignition temperature of the substrate. In cases where the mercury contained in the substrate is a compound or the substrate is heat-sensitive, special precautions may have to be taken.
Vaporized mercury and the sweep gas draft into an industrial dust collector to separate entrained particulate matter from the vapor stream to adhere to local and federal dust pollution control regulations. Any dust with high mercury content can be reprocessed. After reducing the dust content, the vapors are drafted into the first stage condenser.
Gas enters a shell and tube heat exchanger (gas pre-cooler) where ambient water absorbs excess heat. The purpose of the first stage condenser is to reduce the duty of the second stage condenser, a refrigerated "air dryer." Once the gas is cooled, it enters into the second stage condenser, which "dries" the sweep gas by condensing any moisture and mercury.
Material Feed System
Pre-prepped materials (typically cement kiln dust or activated carbon) are stockpiled in a 200 ton capacity storage silo which sits atop an incline screw conveyor. The incline screw conveyor lifts the material to be fed into a high-temperature feed screw. This high-temperature feed screw is bolted to the desorbers breeching, allowing material to drop directly onto the hot shell of the desorber.
Primary Treatment Unit
The primary treatment unit is a 60" diameter x 37' long indirect fired rotary desorber. An external furnace envelops this rotating drum and the flames from 10 industrial burners provide up to 8.5 MMBtu/hour of heat. Heat radiates from the flames to the shell and to the materials travelling the length of the desorber. As the contaminated wastes travel the length of the drum, the temperature increases past the vaporization point of the mercury. Vaporized mercury and sweep gases draft counter-currently to the reclamation system.
Industrial Dust Collector
Exhaust gases carrying entrained solids from the rotary desorber are routed to an industrial dust collector (cyclone, baghouse or multi-clone, depending on the application) to reduce particulate matter emissions and reduce fouling in the downstream condensers.
Two Stage Condensing Unit
Once the gas is separated of particulate matter, the exhaust gases are cooled in the first stage condenser, the gas pre-cooler. This gas pre-cooler consists of a shell and tube heat exchanger and an air-cooled heat exchanger loop. Gases travel counter-currently to a glycol water mix in a shell and tube heat exchanger. Heat exchanged from the hot gases to the water is removed by an ambient air cooler. The now cooler mercury-containing vapors then travel to the second stage condenser.
The second stage condenser is a refrigerated "air dryer." Mercury and water vapor containing gases travel over a bank of mechanically refrigerated coils where they are cooled below ambient conditions. Due to the high vapor pressure of mercury, the cold gases may still contain parts per million of mercury. These are polished off by a traditional activated carbon column. Activated carbon can be re-treated for mercury as the rate of adsorption is much lower than the rate of exhaustion.
Optional Control House
The PLC (programmable logic control) operating system for the entire plant can be operated remotely from stand-alone control panels or in a heated and air-conditioned control house. Both options are NEMA 4 rated for continuous outdoor duty.
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