dispersion dryer in a machine plant for drying powders and fibres | © Allgaier Process Technology 2022
Flash Dryer - Model: Dispersion Dryer
Drying of powders, filter cakes and fibers in seconds

Flash Dryer - Model: Dispersion Dryer

Drying bulk materials with very high product moisture poses a significant challenge. The Allgaier Flash Dryer (based on the fluidized bed dryer design) tackles this task in just one drying step without product recirculation. With the spray dryer, it is possible to process fine and highly moist powders or filter cakes that disintegrate during drying and can be pneumatically conveyed out of the dryer.

dispersion dryer in a machine plant for drying powders and fibres | © Allgaier Process Technology 2022

Functioning principle of spray drying

The Allgaier industrial Flash Dryer consists of a vertical cylindrical housing divided by a perforated air distribution plate. The drying gas enters through a nozzle below the air distribution plate and flows upward in a spiral motion. The moist product is fed onto a rapidly rotating centrifugal wheel (optional) through a feed pipe and dispersed by the airflow. By using various centrifugal tools, lumpy wet materials are efficiently disintegrated. The intensive circulation of product and hot gas stream allows for optimal heat and mass transfer, ensuring a significantly more efficient drying process compared to conventional stream dryers. The dried end product is separated and discharged from the gas stream using a cyclone and/or a fine dust filter.


Applications of spray dryers

Stream dryers are suitable for processing all materials that can be pneumatically conveyed in a dry state. Spray drying is used in the following areas:

  • Food industry: Food products such as dextrose, starch derivatives, and spices.
  • Chemical industry: Sensitive substances like dyes, pigments, fiberglass, and plastics.
  • Paper industry: For example, cellulose or shredded paper/cardboard products.
  • Mineral industry: Salts, peat, limestone powder, and gypsum.
  • Pharmaceutical industry: Active ingredients, additives, fillers, and excipients.
  • Recycling: Various filter cakes or film scraps.
dispersion dryer for drying powders and fibers in a production hall | © Allgaier Process Technology 2022

Heating of Flash Dryers

Flash dryers can be heated through direct heating methods such as gas burners/electric heating elements or indirect systems like steam/thermal oil heat exchangers.

Combined Drying and Cooling in Spray Dryers

The combination of drying and cooling within a fluidized bed dryer is not feasible. If product cooling to low temperatures is required according to the process, the use of a downstream cooling unit (depending on the nature of the drying material) can be considered.

Possibilities for Energy Recovery and Efficiency Enhancement

After the drying material has been separated using the exhaust-side cyclone and/or exhaust filter, the warm but cleaned exhaust air stream can be passed through a heat exchanger. This allows for the thermal energy of the exhaust air stream to be used for preheating the drying gas. Depending on the individual process parameters, high-temperature heat pumps can also be integrated into this energy recovery concept to heat the hot gas stream. For more information, please refer to this link.

allgaier employees in front of a dryer in a production hall | © Allgaier Process Technology 2022
Together we determine your potential for energy savings with a view to a high benefit and a short amortization period.
Daniel Mössinger - Machine & Plant Project Planning Drying Technology

Advantages of Flash Dryer Model "Fluidized Bed Dryer"

  • Strong Performance: Direct drying of very moist and lumpy products without pre-treatment.

  • Gentle Product Treatment: Very gentle drying process due to co-current regime.

  • Versatile Applications: Can be used as an economical pre-dryer in multi-stage drying systems.

  • Compact Design: Optimal investment costs due to compact and space-saving construction.

  • Maximum Flexibility: Ability to use all common heating media such as natural gas, saturated steam, hot water, electric heat, or thermal oil.

  • Minimal Process Costs: Low operating costs due to high water evaporation capacity and heat recovery from the dryer exhaust.

allgaier employee performs series of tests on a machine in the technical center | © Allgaier Process Technology 2022
dispersion dryer in a machine plant for drying powders and fibres | © Allgaier Process Technology 2022
dispersion dryer in a machine plant for drying powders and fibres | © Allgaier Process Technology 2022

Limitations of Spray Dryers

Despite the versatile applications of spray dryers/fluidized bed dryers, there are also limitations to this dryer model. Specifically, for products that cannot be dried to the desired residual moisture within the short drying time or for materials with lumps/coarse particles that cannot be dispersed by the disintegration tool. Due to the wide range of machine offerings at Allgaier, these challenging areas of Flash Dryers can be addressed by utilizing other methods such as fluid bed dryers, drum dryers, or rolling bed dryers, which may provide an ideal solution.

FAQ - Frequently asked questions

What is a Flash Dryer?

A Flash Dryer is a drying unit used to rapidly dry moist and sometimes lumpy materials at high temperatures. The material is continuously fed into the drying chamber and comes into contact with a hot gas stream injected into the dryer. The hot gas quickly evaporates the water in the feed product, resulting in drying that takes seconds or even fractions of a second. Flash dryers are used in various industries and are particularly useful for materials that are sensitive to heat and cannot be exposed to prolonged heating.

At what temperatures does a Flash Dryer operate?

The drying temperature of a Flash Dryer depends on various factors, including the type of material being dried, the moisture content of the material, the method, and the requirements of the application. However, temperatures between 100°C and 400°C are typically used.

It is important to note that the drying temperature needs to be carefully monitored to ensure that the material is dried evenly and completely without being overheated or damaged.

What is the size of a Flash Dryer?

The size of a Flash Dryer varies depending on the application and capacity. Spray dryers can be manufactured in different sizes and configurations to meet the requirements of specific applications.

Smaller spray dryers can be produced on a laboratory scale with a diameter of approximately 20 cm. However, larger industrial Flash Dryers can be several meters wide and tall. The capacity of such dryers can range from a few kilograms to several tons per hour.

How long does it take to deliver a Flash Dryer?

The delivery time for a machine can depend on several factors, such as the size and complexity of the dryer, the availability of materials or components, and the distance to the delivery location. The manufacturing workload of the manufacturer and the specific requirements of the customer regarding drying processes also play a crucial role in the delivery time.

In general, the production and delivery of a spray drying machine can take several months, depending on the specific requirements and conditions. Before placing an order, it is important to ensure that all necessary specifications and requirements for the application and material are clarified to ensure that the equipment can be properly tailored to the needs.