Fluidized Bed Ash

United Conveyor Corporation has unparalleled experience and the highest number of reference installations for fluidized bed ash conveying systems. Our comprehensive understanding of fluidized bed ash, high bulk density material, and the complications that may arise in conveying this material, allow us to determine the most effective conveying system for our customer. Mechanical, pneumatic and combination systems are available to ensure optimal performance specific to individual plant needs and customer preference.

Mechanical System (DFC™)

A mechanical system is often the best choice for fluidized bed ash where headroom is restricted under the boiler. This system offers continuous removal, requiring no water and much less horsepower over hydraulic or pneumatic system of comparable capacity. The United Conveyor Corporation DFC (Dry Flight Conveyor) is designed for continuous ash removal through a completely closed trough. Ash from the hoppers drops through the return flights and onto the bottom of the conveyor. The lower flight bars pull the ash along the conveyor trough to the discharge chute. The chute can lead to a storage location and/or pneumatic system for conveying to final disposal point.

Pneumatic Systems

A NUVEYOR® vacuum system is often the best choice for secondary conveying of fluidized bed ash for smaller boiler units in industrial environments such as universities or municipalities. The vacuum system is the simplest secondary system to install and a cost-effective solution ensuring proper ash suspension through conveying lines to the silo.

A NUVA FEEDER® dilute phase pressure system is the preferred method of transport where higher conveying capacities and longer conveying distances are required.

DFC Dry Flight Conveyor:

  • Continuous ash removal minimizes clinkering in hoppers. The DFC is highly recommended when calcium oxide content of the ash is 15% or greater.
  • The enclosed trough can maintain economizer vacuum to reduce clinkering with the use of airlock dump gates on the discharge.
  • Accommodates a variety of ash types and particle sizes, including lumps
  • Several standard modules allow for horizontal, inclined and vertical motion. Accommodates installations with minimum headroom.
  • Designed to withstand high temperature material (up to 800° F) without damage to conveyor
  • Premium construction for highly reliable 24/7 performance
    • Bottom plate of ½” thick abrasion resistant steel and 3/8” thick abrasion resistant side liners minimize wear.
    • Chain links are drop forged from high chrome/magnesium steel with a core hardness of 300-400 BHN. The entire link is then case hardened to 500-650 BHN for wear resistance.
    • Drive shaft runs in self-aligning double-row roller bearings designed for long life. Chain sprockets on the drive shaft are induction hardened to 560 BHN to maximize life.
  • Modular construction reduces cost and design time, improves installation accuracy, and minimizes spare part requirements
  • Low maintenance as a result of low speed operation and wear-resistant components
  • Low horsepower drive assembly minimizes power consumption

NUVEYOR Vacuum System:

  • Ability to stop and restart due to low ash-to-air ratios
  • Low headroom requirements below the fly ash collection hoppers
  • Capable of handling a wide range of ash types
  • Full load/no load control allow system to achieve rated capacity more efficiently
  • Wear sections follow each change in pipeline direction
  • Low maintenance at precipitator and economizer areas
  • Single pneumatic valve under each hopper
  • Single air intake per row
  • One I/O per hopper valve
  • No plugging
  • Proven temperature tolerant design for large particle economizer ash

Performance Specs:

Max Distance: 1500 ft (4500 m)
Maximum Capacity: 80 TPH
Mass Ratio ash : air: 5-22
Air Velocity: 3000 – 5200 ft/min (16-27 m/sec)
Maximum Conveyor Line Pressure: 20 in Hg (530 mm Hg)
Maximum Prime Over Pressure: 22 in Hg (560 mm Hg)

NUVA FEEDER Dilute Phase Pressure System:

  • Dilute to medium phase conveying
  • Long distance conveying without the need for a transfer vessel
  • Capable of high capacity conveying
  • Control system keeps the conveying line filled for longer periods, resulting in high conveying efficiency and lower operating costs
  • Low sensitivity to ash characteristics; capable of conveying larger and more dense particles
  • Proven ability to handle economizer ash
  • Ability to stop and restart system operation without plugging due to moderate ash-to-air ratios
  • Full load control prevents line plugging
  • The use of a bin vent filter reduces maintenance on silo roof
  • Highly stable condition with no pressure surges
  • Ideal for high altitude applications where vacuum systems are not effective

Performance Specs:

Max Distance: 8,000 ft (2,400 m)
Maximum Capacity: 175 TPH
Mass Ratio ash : air: 5-22
Air Velocity: 2,400 – 4,800 ft/min (12-25 m/sec)
Maximum Conveyor Line Pressure: 40 psi (275 kPa)
Maximum Prime Over Pressure: 45 psi (300 kPa)

  1. What are the typical concerns in handling fluidized bed ash pneumatically?[+]
    Fluidized bed ash is very abrasive. Heavy bulk density material, broad size distribution and final disposal point will determine best conveying method.
  2. I have a bed ash system producing ash between 500 – 700 degrees. Does UCC offer equipment to handle these high temperatures?[+]
    Yes. UCC had designed equipment to withstand the rigors of the application and conditions under the screw coolers.
  3. How do you dispose of fluidized bed ash with un-reacted lime?[+]

    There are two main methods:

    Dry Telescopic Spout – A dry telescopic spout fits directly into the truck for disposal.

    Reinjection System (with or without hydration) – By mixing the bed ash with a small amount of water causes the particles to “crack,” exposing un-reacted lime which is injected back into the boiler, therefore less lime is needed and generates cost savings.