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Spray drying is a method of drying products by evaporating the solvent present inside. This method is most effective for obtaining powders and granular products.

The features of spray drying

Saturated or hydrothermally pre-treated foods are dried faster, it saves time and energy. The processing of the product takes place with the help of nozzles and rotating discs, which ensure that the product is sprayed into the drying chamber. The product is then dried by contact with air, gases or steam. Gases are formed by combustion of fuel, steam is formed as a result of overheating. Any of these substances increases the evaporation surface due to the intensive exchange of mass and heat with the product itself. Dried product particles are sprayed and deposited on the walls of the chamber, and part of the product remains on the dust separators, where air also penetrates, preventing the product from being unprocessed.

The dried particles may have a monolithic, spongy or hollow structure. It depends on drying mode and the original structure of the product itself.

Spray Drying Methods

Spray drying has several methods that differ in individual parameters:

  1. Cold drying is successfully used in drying a substance that turns into a liquid state after heating, and turns into a solid state after cooling. Such products are loaded into the chamber only in heated condition, and lose moisture only when exposed to cold air flow. Water evaporates not due to exposure to air, but due to the heat exchange of the product itself.
  2. Pre-drying means the product is initially subjected to heat treatment. Thus, the product is sprayed and dried faster, it saves time and energy, reduces production costs and improves the useful properties of the product itself.
  3. Ultrasonic drying is a way to process heat sensitive products. It retains most of the nutrients.

An obligatory condition for drying the product is the possibility of its supply to the spraying device using a pump and pressure.

The advantages of spay drying

There have the following advantages of the spray drying process:

  1. Reducing the time of the drying process. It is finished within fifteen- thirty seconds. All the useful substances of the product are preserved at the same time, and it does not lose its original properties and vitamins, and does not oxidize.
  2. It is easy to operate the spray dryer. The control consists in selecting parameters on the panel: the particle size, the residual moisture, the product weight, the temperature.
  3. The processed product is ready to use and it does not require additional processing, such as grinding etc. The degree of solubility of the product is very high.
  4. The simplification of the production process when no additional tools and equipment are required to achieve full readiness of the product. There is no need in grinding and drying machine, and cleaning equipment anymore.
  5. No need many of workers. The equipment performs a wide range of work without requiring much attention, since the drying process is fully automated.
  6. The absence of corrosive processes on the inner surface of the drying chamber as a result of complete drying of the product particles.
  7. The wide range of drying temperature.
  8. The possibility of processing complex products with a sticky structure, which are not subjected to grinding with conventional mills.
  9. The impossibility of losing a large amount of processed product in the event of an engine stop. The product is evenly distributed in the drying chamber, which has a reliable seal.
  10. The possibility of producing a multi-component product by pre-mixing the necessary substances in liquid form. It is also possible to simultaneously spray different substances directly in the chamber dryer.
  11. The safety of processing ensures the impossibility of getting harmful substances into a production workshop, thereby not harming human health.

The disadvantages of spray drying

The using of spray dryers has not only advantages, but disadvantages as well:

  1. The need of using chamber dryers with large overall dimensions to dry the product with air supply from one hundred to one hundred and fifty degrees.
  2. The high cost of spray drying equipment for drying the product in a liquid state.
  3. The high electrical energy consumption is required. Cause without a good preliminary heat of the drying chamber the quality of drying decreases, and the product turns out to be spoiled.
  4. A small mass of the final product, which takes on a powdery form, which forces the manufacturer to look for additional means to make it heavier, for example, briquettes.

The spray drying method is successfully used not only in the food industry, but also in the chemical and pharmaceutical industries. Using this method, powders, medicines, egg-white mixtures and other products are successfully obtained.