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Indirect Contact Dryers

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  • Overview

  • How It Works

  • Design Principles

  • Literature

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Overview

LCI Thin-Film Dryers concentrate slurries, suspensions, and solutions such as catalyst or salt solutions and crude glycerin with indirect heat transfer and mechanical agitation of the thin product film under both vacuum and positive pressure conditions. LCI offers a range of drying technologies from thin-film dryers to large volume segmental disc dryers.

LCI's Thin-film Dryers, the Vertical Dryer, Horizontal Dryer, and the Combi Dryer™ (Vertical and Horizontal designs together), are being used in numerous chemical process facilities worldwide.

The Reactotherm® and the Rovactor® can be operated continuously or batch-wise with residence times ranging from a few minutes to several hours. Units consist of a horizontal shell and a rotor with segmented discs. The Reactotherm adds mixing bars and stationary mixing hooks to provide intensive mixing and kneading. Heat is transferred to the product from the body jackets and the segmented rotor using steam or another thermal fluid.

How It Works

Product enters above the heated zone and is evenly distributed over the unit's inner surface by the rotor. Hinged blade elements transport the viscous material down the thermal surface and promote heat transfer.

Volatile components are rapidly evaporated and flow counter-currently to the solid/liquid flow through the unit. Vapors are ready for condensing or subsequent processing upon existing the dryer.

As the volatiles are evaporated, the solids eventually stop flowing and create masses which the thin-film dryer blades then eject from the wall. The free-flowing solids then fall down the remainder of the evaporator to the discharge section. For horizontal dryers, segmented blades are used to push the solids towards the discharge section.

Nonvolatile components are discharged at the bottom of the thin-film dryer with a specially-designed discharge section. Dryers typically use special rotary or spherical disc valves for solids discharge handling. The solids can also be directly discharged to a bin hopper or vessel depending on the process requirements.

The dryers are indirectly heated by steam or hot oil and can be operated semi-batch wise or continuously.

Its relative short residence time and open, low pressure-drop configuration allow continuous, reliable processing of many heat-sensitive, viscous materials without product degradation.

Design Principles

LCI offers thin-film dryers with the following design configurations.

Rotor Designs
Thin film / Wiped film Rotor Designs
  • Drying for solids-containing streams from which liquid must be evaporated or distilled
  • Transported Flow provides positive transport for dried powder through the horizontal dryer and can be used to adjust residence time
Rotor Orientation
  • Vertical configuration provides reliable, efficient processing of slurries, solutions, and suspensions to free-flowing powders.
  • Horizontal designs are ideal for applications where longer residence times are required for mass transfer and reactions, or where headroom is limited. The longer residence time provides the ability to reach lower residual volatile levels.
Vapor Flow
  • Countercurrent flow is recommended for most drying applications.

Literature

Related Products

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