Fluidized Bed

Fluidized Bed Technology

Fluid 1 (2)

General

Fluidized beds have long served the chemical processing industry as a unit operation. This type of combustion system has only recently begun to see application in hazardous and solid waste incineration. Fluidized bed incinerators may be either circulating or bubbling bed designs. They are primarily used for sludges or shredded solid materials. To allow for good distribution of waste materials within the bed and removal of solid residues from the bed, all solids generally require pre-screening or crushing to a size less than 2 inches in diameter.  Fluidized bed incinerators offer high gas to solids ratios, high heat transfer efficiencies, high turbulence in both gas and solid phases, uniform temperatures throughout the bed, and the potential for in situ acid gas neutralization by lime or carbonate addition. However, fluid beds also have the potential for solids agglomeration in the bed if salts are present in waste feeds and may have a low residence time for fine particulates.

Advantages

  • Offering high gas to solids ratios

  • High heat transfer efficiencies

  • High turbulence in both gas and solid phases

  • Uniform temperatures throughout the bed

  • No mechanical moving parts, and relatively good durability

Disadvantages & Limitation

  • High potential for solids agglomeration in the bed

  • Cannot accept solid waste greater than 50mm in diameter (due to fluidized bed blockage)

  • High power consumption (large air volume and high pressure)

  • Professional technicians shall be trained

  • High maintenance cost

  • Low thermal stability due to short waste residence time (<30 seconds)

  • Complexity of system is very high

  • Short waste residence time leads to CO peaks, increasing dioxin levels

  • High investment cost

  • Pre-treatment of solid waste is a must

  • Unscheduled shutdowns are inevitable