Spray Dryer

Description:

Spray drying is a highly efficient method designed to convert a liquid or slurry into a dry powder by atomising the material into a hot gas stream. This process is ideal for drying thermally-sensitive materials or products that require a consistent, fine particle size, such as maltodextrin in the starch industry. Spray drying is the preferred method for materials that need to transition from a slurry to a dried powder form while maintaining the integrity and quality of the product.

In the spray drying process, the slurry is atomised into small droplets that are then introduced into a hot air stream within the drying chamber. As these droplets fall from the top to the bottom of the chamber, the water rapidly evaporates, leaving behind small granular particles that are collected at the bottom. To enhance energy efficiency, the feed can be pre-heated before entering the drying chamber. The hot air, heated indirectly, is drawn into the system by a fan equipped with a bag filter at the top, which captures fine powder particles from the cooled exhaust air. The hot air cools down as it absorbs the high latent heat required to evaporate the moisture from the slurry. Additionally, fine powder produced during spray drying can be continuously recycled and mixed with the feed to improve drying efficiency.

Spray dryers typically employ either spray nozzles or atomisers to disperse the liquid or slurry into the hot air, resulting in a broader particle size distribution. The drying time in this method is significantly shorter than other drying techniques due to the maximised heat transfer area provided by the atomised droplets. The design and features of spray dryers can be customised to meet the specific needs of different applications, ensuring optimal performance.