12
Aug 2022
Drying of a Chemical Intermediate by Agitated Thin Film Drying
For drying of natural or chemical products several technologies are available on the market. It varies from belt dryers, drum dryers, freezing dryers to spray dryers etc. Many customers approach Technoforce for a drying process of a product that is going from development into industrial production, or to seek a better technology than their existing one. Better could mean higher quality, less residual moisture, lower drying temperature, or higher energy efficiency. In many cases the Technoforce Agitated Thin Film Dryer is the best solution to achieve the desired goal.
Phograph 1: Powder after drying in ATFD
The Technoforce Agitated Thin Film Dryer (ATFD) consists of a vertical cylinder fitted with a heating jacket. The feed material is pumped continuously to the feed nozzle on top of the equipment. By gravity it flows down and is spread uniformly to a thin film on the inner wall of the ATFD by a fast-rotating agitator. The heating jacket is heated by steam or thermal oil and transfers the heat to the evaporator. From the feed film, the volatiles evaporate. Vapors travel to an external condenser while the feed material turns into slurry, sludge, paste and finally dry powder that is collected at the bottom. To ease the powder collection, the dryers are often run under atmospheric pressure, however solutions for vacuum drying including semicontinuous discharge via a double chamber receiver are also available.
Rotor design is crucial to be successful in the drying process. Different rotor types are available with different properties:
– Fixed clearance rotors with a defined clearance/gap between rotor blade tip and evaporator wall. The blades may be rigid or hinged and are usually made from stainless steel.
Phograph 2: Fixed clearance blade in ATFD
– Zero clearance rotors have hinged blades that touch the evaporator wall. During the process the product film typically works as a kind of lubricant between blade an evaporator, however a small amount of wear and tear particles is usually found in the bottom product. In some cases, this can be avoided using PTFE tips for the blades. This design transfers mechanical force into the film, breaking up any build-up of solids on the evaporator.
Phograph 3: Zero clearance blade in ATFD
In our pilot plants in Nashik/India or Geleen/The Netherlands we can offer our customers bench scale and pilot scale drying trials in our continuous ATFD systems. We are happy to send a process questionnaire to be filled by the customer beforehand to speed-up the project.
In this specific case, a customer approached Technoforce to replace their existing spray dryer for a chemical intermediate which was not flexible enough for variations of feed rates and consumed too much energy. After successful pilot trials we could design an ATFD plant skid fulfilling these requirements.
Phograph 4: Typical ATFD skid
Technoforce has already designed and built several hundred skids of process intensification technology for oils and fats applications, fine chemistry, polymers, food and pharma products and other industrial sectors. We also offer other evaporation technologies like Short Path Distillation, Agitated Thin Film Evaporation and Drying in a horizontal ATFD, Falling Film, Rising Film and Forced Circulation Evaporation, as well as Liquid-Liquid Extraction in