The VAX Vibratory Ash Extractor is the latest innovation in United Conveyor Corporation’s system portfolio. Increased awareness of environmental issues has accelerated the trend for new technology that reduces the water consumption and increases plant efficiency. The VAX system is the latest evolution in dry bottom ash technology which delivers superior heat recovery, lower installed cost, higher reliability and less maintenance compared with conventional moving belt designs.
The VAX dry bottom ash system incorporates patented fluidized bed vibratory technology to produce maximum combustion and cooling. The VAX design is simple, yet effective. Unlike alternative mechanical bottom ash systems, there are no moving belts or hinged joints exposed to the boiler that can become damaged from large slag falls or soot blower lances. The result is system reliability and reduced risk of an unplanned outage.
The VAX Advantage:
- Zero Water Usage
- Greater Boiler and Plant Efficiency
- Dependable Performance
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VAX Vibratory Ash Extractor:
- Dependable Performance – Design is simple yet durable to withstand large clinkers
- Increased Heat Recovery and Boiler Efficiency – Fluidized ash increases combustion and heat recovery to the boiler compared to a moving belt design. Up to 90% of all heat contained in the bottom ash is recovered and delivered to the boiler
- Fully Automated Controls – Controls are integrated with the DCS to optimize conveying and combustion air flow capacities (ie. faster during soot blowing). The result is controlled accumulated of ash on the conveyor deck, maximizing heat recovery and efficient ash transfer to downstream equipment
- Reduced Risk of Sudden Failure – Heavy-duty, semi-circular deck is designed to absorb disruptive impacts caused by large slag falls
- Extended Service Life and Safety – All moving parts are located outside of the boiler flue gas environment for long life operation
- Reliable Dry Seal – A multi-layered composite made of high temperature, flexible sealing and insulation fabrics accommodate thermal boiler expansion
- Low Energy Consumption – Operates with a low horsepower drive and positive pressure cooling fan
- Low Maintenance – Designed around springs and an eccentric drive with no moving parts exposed to corrosive boiler environment. Regular maintenance can be performed with the boiler on-line
- System Options – Include hydraulic isolation doors between the transition hopper and boiler throat and roll-out wheels to provide easy access to the boiler during outages
- No water troughs, piping or seal plates
Is the vibratory technology proven and reliable? [+]
Vibratory conveying technology has proven itself in extreme temperature, abrasive applications for over 50 years. There are more than 1000 installations in over 35 countries. There are multiple Mass Burn Bottom Ash installations using similar vibratory conveying that have been in operation for 30+ years and running continuously for 7+ years. Similarly, glass cooling applications run continuously for roughly 7 years.
Is the storage capacity sufficient during soot blowing?[+]
During soot blowing, the VAX system will increase its conveying capacity (speed) and cooling airflow commensurate with the increased ash volume. The conveying speed is governed by the peak to peak displacement and frequency of the ash conveyor trough. These parameters are controlled by the Distributed Control System, or PLC, for the boiler.
How does the VAX fluidized bed increase heat recovery and boiler efficiency compared to the moving belt design?[+]
The vibrating fluidized bed forces air over the entire surface of the ash particle for maximum, continued combustion and cooling. Alternative moving belt systems draw air from the conveyor sides which flows over the ash pile, exposing only the top particles to combustion air.
How is the air flow controlled for fluidization, combustion and cooling?[+]
A velocity pressure signal and, where required, an air temperature signal are forwarded to the boiler DCS or PLC. An algorithm is used to calculate the target velocity pressure commensurate with the particular operating condition and be output to the VFD controlling the ash conveyor forced draft cooling air fan speed. When operating with normal design ash fall rates the cooling fan would have a lower speed than that corresponding to the sootblow operating condition. The boiler DCS or PLC would output a signal to the VFD for the particular operating condition. Although the algorithm would incorporate velocity pressure values, the settings are field adjustable and may have any and as many values as desired so long as they do not exceed the limiting air flow rate to the boiler.
What noise emission has the conveyor?[+]
Typical noise level is less than 85 dBA at one meter distance.
How is energy absorbed from large slag falls?[+]
The VAX incorporates a counterbalance system that is designed to provide complete damping of all vibration with no energy transmitted to the foundation.
– 27”, 33”, 54”