Rotary kiln

The rotary kiln (DRO ) is a furnace for continuous processes in chemical engineering.

  • 3.1 Direct heated DRO
  • 3.2 Indirectly heated DRO

Types

A distinction is made between directly and indirectly heated rotary kilns.

  • Is directly heated, that the heat supply of the furnace is within, for example, by burners. The product is in direct contact with the flue gas.
  • Heated indirectly means that the supply of heat from outside of the reaction chamber is transmitted through the torque tube wall. These ovens allow a precisely specified product space atmosphere.

Structure directly heated rotary kilns

A directly heated rotary kiln is usually of the following components:

  • An inlet housing to the task or to the filling of the materials to be treated continuously
  • The rotating tube
  • A discharge housing or furnace head
  • A burner equipment
  • The lining of refractory materials
  • Storing two or more supports, wheels and axles
  • The longitudinal positioning control with Axial
  • The drive by gear and sprocket or by frictional entrainment on driven rollers
  • The seals on the oven inlet and outlet to seal the rotating rotary tube furnace head against the fixed parts

Structure indirectly heated rotary kilns

An indirectly heated rotary kiln is usually of the following components:

  • An inlet housing, usually only one feed screw with shield
  • The rotating tube
  • The discharge casing
  • The sealing systems, sealing the product space atmosphere from the air, often with the use of barrier gas
  • Storage, traditionally associated with race and rollers, modern with large ball bearings
  • The drive by means of compact gear and sprocket
  • The isolated outward muffle provides that the amount of heat required, usually by flue gas or heating elements

Furthermore, internals may be present, which mainly affect the transport of solids in rotary kilns. Lifters for example, provide a trickling of the feed through the hot gas atmosphere and improve the transfer of heat. Storage rings at the discharge increase volumetric efficiency in the oven. Chain fittings are particularly suitable in wet feedstock to avoid caking or eliminate.

Procedural features

The rotating pipe is slightly inclined in the longitudinal direction along the inside in the oven to bring about the rotation of the furnace tube of the transport material from the inlet side to the outlet side.

On the basis of length and internal diameter (in each case several feet possible) Rotary kilns are also suitable for the treatment of non-homogeneous materials. The starting materials can have very different consistency and lumpiness. For example, solids, sludges and barrels can be introduced.

A rotary kiln is a high quality capital goods with a cost of usually several million euros. As a rule, rotary kilns 24 hours a day, 7 days a week to be operated in 50 or 51 weeks of the year. The continuous operation ( " continuous opera " ) from cheer to parking the furnace for maintenance and repairs furnace campaign is called.

Because the most difficult thermal conditions and sensitive to rapid temperature fluctuations lining the continuous operation of a rotary kiln must not be suddenly interrupted. In the event of a power failure or damage to the drive emergency devices shall consist ( auxiliary drive or emergency operating ) that allow further rotation of the oven if necessary until his discharge. For rotary kilns, which are to remain in full load suddenly with hot materials, often suffer extraordinarily expensive damage caused by the unilateral action of heat of the residual goods: The dreaded " banana" can arise that no longer irreversible Krumm If the torque tube and no longer work.

Applications of rotary kilns

Directly heated DRO

  • Cement production
  • Lime burning
  • Waste incineration (especially hazardous wastes )
  • Melting of ceramic glass / frit
  • Drying of rock products used in asphalt plants or concrete mixing plants
  • Melting of metals ( for example, for the reduction of nickel ore )
  • Pigment production
  • Activated carbon activation
  • Generating method for the processing of steel mill flue dust and other zinc -makers
  • Iron ore reduction

Indirectly heated DRO

  • Müllpyrolyse ( Burgau, Contherm Hamm- Uentrop )
  • Floor cleaning ( for example, from oil- contaminated soil, dioxins, furans, mercury)
  • Altreifenpyrolyse ( CBp Cyprus)
  • Disposal of hazardous biomass
  • Degassing of products (for example, grill carbon production )
  • Pigment production
  • Hydrofluoric acid production
  • Tonerdekalzinierung
  • Charcoal production

Sources

  • Process engineering
  • Physico- technical process
  • Metallurgical furnace
Leblanc process Gasket Concrete plant Polychlorinated dibenzodioxins
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