What type of dryer produces a fine powder as the final product?

The production of a fine powder as the final product is most typically associated with a spray dryer. This method works by atomizing a liquid feed into small droplets and spraying them into a hot gas stream, usually air. As the droplets travel through the hot air, the moisture evaporates rapidly, leaving behind solid particles that are collected as a fine powder. The quick evaporation process minimizes heat exposure, preserving the quality of heat-sensitive materials often found in food products.

Drum dryers, on the other hand, involve spreading a liquid on a heated drum surface where it dries and is then scraped off, resulting in flakes or sheets rather than fine powders. Fluid bed dryers are used to dry particulate materials and can produce granular products, but they do not typically achieve the fine powder consistency that a spray dryer does. Vacuum dryers operate under reduced pressure to lower boiling points, thereby drying materials that could be sensitive to heat, but they also do not generally produce a fine powder as efficiently or uniformly as spray drying does.