Quantity and quality are generally perceived to be on the opposite ends of the spectrum, and it is believed that if you chose one, you must compromise with the other. However, spray drying is one sector that must always deliver the precise size of particles in large amounts. Both quality and quantity matter in spray drying.,
Spray drying technology turns liquids into powders that have specific particle size and moisture content. Spray drying can be used to dry both kind of materials: those that are heat sensitive, and those that are heat resistant. Spray drying uses gas as a medium to quickly dry liquids, and it works in four stages:
Feed Preparation and Concentration
Feedstock preparation is performed prior to introduction of the feed in the spray chamber. Concentration of feed solution is achieved to ensure it can be pumped to chamber. Sometime, the feedstock is heated to alter the physical property of the feed solution.
Spray drying is mainly characterized by atomization of the feedstock. Atomization involves separating the fluids or slurries into fine particles. The Atomisation process breaks-up bulk liquids into droplets. Atomised fluid serves the optimum condition for the moisture to evaporate in a quick and effective way. Atomization of feedstock can be achieved either by rotary atomization or by pressure nozzle. The Dryer can include single to multiple nozzle systems, as per the process design.
How the heating medium i.e. hot air and droplet is contacted is at the heart of overall drying process. In the chamber hot air is drawn through the inlet in specified flow pattern, called air distributor and brought to the droplet which need to be dried. The way through which the hot air and droplet is contacted decides the size, quality and texture of the dried product. The type of the contact between air and droplet is decided by the product quality and position of the atomiser or nozzles.
In the process of moisture removal or evaporation is performed in stages. These stages generally referred to as constant rate drying and falling rate drying. In first stage of the drying, sufficient moisture content is available in the droplet which is ready to evaporate at constant rate. In secondary stage moisture exerts more resistance, compared to the first stage, to evaporate against the hot air and thus process of evaporation slows down results into falling rate of drying. The additional resistance provided in the secondary stage depends on the physical and chemical property of the feed and pore structure of the solid-droplet.
Following complete evaporation of the moisture content from slurry droplet, solids are to be dried in the particulate form and need to be separated from drying medium i.e. hot air and drying chamber. Separation equipment provided after the drying chamber helps to achieve the same. Cyclone separator, wet scrubber, bag filter and electrostatic separator is provided to ensure complete recovery of dried product and to ensure exhaust gas does not contain any environment damaging particulate matter so that air can be safely released in to the environment.
Considering the critical nature of drying, the design and installation of dryers needs skill and experience. At Shachi engineering, we emphasize establish advance simulation and analysis using Computational Fluid Dynamics (CFD) techniques. Our team has many years of expertise in designing of spray dryer with optimum performance and successful delivery of 500+ plant with promised features. To know more about how our spray driers could help your business grow, get in touch with us.