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The resulting powder solid is usually collected in a drum

The gas (often air) is usually heated by a burner as it is forced into the main chamber.A spray dryer is a piece of commercial equipment for rapidly removing moisture from a liquid to produce a solid in powder form. It is usually desirable to retain a liitle moisture within the powder particle at the end of the process - known in the trade as Residual Moisture.Spray dryers can dry a product very quickly compared to other methods of drying.

They also turn a solution, or slurry into a dried powder in a single step, which can be advantageous for profit maximization and process simplification. Drying Chambers are of similar construction to storage silos, large open vessels, their volumes being determined by the required heat exposure time for the feed materials being dried. The feed solution is atomised into the chamber to form droplets, on contact with the hot air the liquid evaporates leaving a powder.

Common spray dried products include instant coffee, milk powder, paint powder, egg powders, resins and detergents. Basically a spray dryer consists of a large chamber through which extremely hot air (or a different gas) is passed through, a feed pump truck mounted line pumps and an atomiser. It is used in widely in food processing and the pharmaceutical industry.On initial contact with the hot gas the visible powder particles are case hardened, a hard outer surface with a molten inner. The initial liquid can either be a solution (a dissolved solid) or an insoluble solid in suspension in the liquid - sometimes called a slurry. Droplet sizes can range from 20 to 180 micrometres depending on the nozzle. A typical example would be for products such as milk, where it’s often economically prudent to put evaporation technologies into the feed system to raise the feed solids as much as possible. The amount of time it takes for the particle to fall the length of the chamber is called residence time.The feed solution is fed into a spray dryer through an nozzle atomising device that breaks down the feed solution into individual spheres.

The resulting powder solid is usually collected in a drum of cyclone.In their basic form, spray dryers undertake the complete process from accepting liquid feed at one end and packing into sacks or other containers at the other end ready for transportation. Spray drying is an evaporation process and the most common method of producing powder especially for heat sensitive materials.Spray drying systems come in many different shapes and sizes can look remarkably different but they all work in basically the same way. As the particle falls down the length of the chamber contact with the hot air draws the liquid from the rest of the particle. Often on larger plants various processes are added both up and down stream to moderate the processing costs as much as possible. A nozzle is usually used to make the droplets as small as possible, maximising heat transfer and the rate of water vaporisation

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