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.
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 MulitDAC™ pressure system is the most 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
|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) |
MultiDAC Pressure System:
- Medium phase to dense phase conveying
- Low headroom requirement also allowing for easy maintenance
- Low capital and maintenance costs due to one valve per hopper and a small diameter carbon steel conveying line
- Low operating cost from less component wear and power consumption due to the low conveying velocity of the system, especially when conveying materials with more than 50% silica and alumina. Channel back elbows are installed with the line changes direction for increased wear resistance.
- Constant air mass flow provides stable system operation and reduced wear during purge cycles
- No outlet gates required on the transfer vessel
- Feeder size is calculated to minimize material hang-up and provide optimal flow into the conveying line
- No ash/air separation equipment on silo reduces maintenance cost
Medium phase to dense phase conveying
|Max Distance: ||1500 ft (450 m) |
|Maximum Capacity: ||130 TPH |
|Mass Ratio ash : air: ||25-60 |
|Air Velocity: ||900 – 2700 ft/min (5-15 m/sec) |
|Maximum Conveyor Line Pressure: ||20 – 60 psi (140 – 415 kPa) |
|Maximum Prime Over Pressure: ||100 psi (690 kPa) |
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.
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.
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.