Most developed countries rely on a fluid food dehydration method that is known as spray drying. As the name suggests, this is a technique that requires a spray dryer. That device separates dry powder from the fluid in which it had previously been suspended. This is accomplished by spraying a stream of the suspension through hot gas.
Spray drying is considered to be a simple system of evaporation that uses a minimal number of moving parts and achieves a rapid drying time. It uses various different nozzles, spray, and patterns of gas, depending on the expected consistency of the product to be dried, and the type of solid that is involved in the process. This method for removing the fluid means that only a minimal amount of heat exposure to the suspension will occur, which is why it is typically the preferred method for drying the majority of food and pharmaceutical products.
The primary concept behind the spray drying process is to be able to create a powder that is highly dispersible from the solvent’s evaporation. It can typically be accomplished by combining heated cases and sprayed fluid that contains a large surface to mass ratio of droplets that are the same size. This occurs inside the drying chamber so that the solvent evaporation can be maintained uniformly through direct contact.
The technique is used for many different purposes in which there is a desire for free flowing powder. This specific type of dehydration has also become quite popular for products such as detergents and soaps, pharmaceuticals, beverages, egg and milk products, bone and tooth amalgams, plant extracts, coloring, flavorings, resins, plastics, and polymers.
Other forms of drying use ovens, freeze dryers, and rotary evaporators in order to result in a large amount of material that will require further grinding or filtering. This means that the results are not equal in size and shape. However, when spray drying is used, a highly flexible control is provided over a powder’s properties, including their density, size, flow characteristics, and moisture content.
The following are the stages involved in spray drying:
- Feed preparation – this should be made homogenous, able to be pumped, and free of any suspension, impurity solutions, or paste.
- Atomization – here, the feed is transformed into droplets. This stage is critical to the success of the entire spray drying process. The level of atomization dictates the rate at which it will dry.
- Drying – at this point, the moisture evaporates at a constant rate, quite quickly from the particle surface. It is typically followed by a falling rate period in which is managed by the particle surface water diffusion.
- Separation of the moist gas from the powder – this stage is typically practiced in a pollutant and economical way. Bag filters, scrubbers, cyclones, and precipitators remove the fine particles.
When seeking to purchase a used spray dryer, it is important to examine each of its various components. For instance, it is a good idea to look at the combustion chamber and make certain that it is in good condition. This can be considered to be an important indicator of the overall condition of the equipment as the combustion chamber is where the fuel is added to the air in order to start the spray drying process.
It is also advised to decide on the atomization technique type that is applied by the equipment. This could be centrifugal atomization, pressure nozzle atomization, or two-fluid nozzle atomization.
- Pressure nozzle atomization – functions when the fluids are passed through an orifice. It is a highly energy efficient technique and offers the most narrow particle size distribution.
- Centrifugal atomization – functions by sending the fluids across a disk that is rotating. This is a method that is highly resistant to wear and is therefore capable of running for longer periods of time.
- Two-fluid nozzle atomization – functions by combining compressed gas with the feed. This allows for very fine particles to be made and is the least energy efficient among the three types.
It is important to think about a number of issues when considering the purchase of spray dryers. Don’t forget to look into the capacity, manufacturer, age, type, what it had previously been used to do, and what you will be using it for. You can choose from a number of different types of spray dryer, including fluidized, industrial, spin flash, table top, pilot plants, and flash dryers. The type of spray dryer you choose should be based on the work you intend it to accomplish and the components that you are seeking.
By buying a used spray dryer, you can take advantage of highly competitive prices and immediate delivery. Contact Perry Videx to learn more about our large inventory of used spray dryers and to discuss your unique needs.