by Jenny Knodell, IQS Editor
When it comes to drying large amounts of raw material, there are a number of options for manufacturers to choose from, depending on their budget, space and properties of the material being dried. Industrial dryers are often used to remove moisture from materials such as powders, foods and chemicals for the pharmaceutical, paper, pollution control, food and agricultural industries. If your company is in the market for a new industrial dryer, there are 5 main types for different applications, each with its own advantages and disadvantages.
Dryers that pass material through a large, revolving metal drum and heated by gas, liquid or solid fuel are commonly used in the chemical, food and mineral industries. Rotary dryers have low maintenance costs and allow vast amounts of material with differing particle sizes to dry at one time. However, because these dryers are powered by gas, moisture control is difficult and they often create fire hazards as a result of drying flammable materials. Because the drum can be quite large, these dryers tend to require a lot of space.
In a flash dryer, solid material is mixed with a powerful stream of hot air and rapid drying occurs. Cyclones then separate the solids from the air. These air dryers use much less space in comparison to other dryers, are simple to operate and have a very short drying time. The risk of fire is low, but energy costs are higher. Like all steam dryers, they require smaller, homogenous material.
In a disk dryer, made for smaller amounts of material, solids are steam-heated in a small shaft. Because steam indirectly heats the material, retaining some latent heat from vaporization is possible. Disk dryers are simple and have low maintenance costs. It does, however, have a lower operating temperature, which allows for less material to be dried at one time.
These dryers are most commonly used in the food industry. The material, often grain, enters into an enclosed chamber and is hit with a stream of hot air. Particle sizes in this method must be homogenous, but may be larger. Cascade dryers can be quite expensive equipment, but because they are steam-powered, they generate a significant ROI over time.
Superheated Steam Dryers
This type of drying system is similar to a flash dryer, but uses heated steam that is able to re-circulate, minimizing heat loss. Using this type of dryer doesn’t create any sort of fire hazard, has a high heat transfer, dries materials very quickly, and produces zero air emissions. The machinery costs are high, however, since stainless steel is often used for the pressure vessel. For this reason, superheated steam dryers are fairly uncommon. However, using them allows for significant energy savings, and they offer a significant ROI over time. Any steam dryer needs homogenous material in order to mix.