Air Heater Equipped Dryers Used in Industry

While there are many types of dryers used in industry today, there are 4 main systems that

implement indirect or direct fired process air heaters. These dryers include: rotary dryers,

pneumatic/flash dryers, spray dryers, and fluidized bed dryers.

Rotary dryers are not only the oldest type of industrial dryer, but they are also the most

common. The nature of the wet material to be dried determines whether an indirect or direct

(gas or oil) fired air heater is used in conjunction with the dryer. If the material is not

chemically sensitive, a direct air heater is used and the dryer is consequently deemed a “direct

rotary dryer”. Some examples of products that are directly fired include: sugar beet pulp,

calcium carbonate, blast furnace slag, zinc and lead concentrates.

All images have been taken from “Best Practice Manual-Dryers”

Pneumatic/Flash Dryers are used in processes where the feed is susceptible to easy/ quick

drying. The material is dried within seconds when it is mixed with heated air and sent through a

drying duct at rapid speeds. Direct fired air heaters are most commonly used with flash dryers.

Filter cakes, sludges, granules, and pastes are a few of the products dried using flash/

pneumatic dryers.

All images have been taken from “Best Practice Manual-Dryers”

Spray dryers are the most widely used drying system in the food and dairy powder industries.

These dryers use an atomizer to feed the liquid into a drying chamber. When the small drops of

liquid enter the chamber, they are subjected to hot air, which turns the feed into power by

means of water evaporation. The hot air is generated, indirect or direct fired air heaters;

depending upon the sensitivity of the feed. Powdered colors, inorganic chemicals, insoluble

organic dyes, and instant mixes in the food and dairy industries are just a few of the items that

require spray drying.

All images have been taken from “Best Practice Manual-Dryers”

Fluidized bed dryers are used across all industries, employing gas or oil fired, indirect or direct

configured air heaters. The hot air is passed through the bed of particles at a velocity high

enough to suspended them and make them flow as if they are fluid. This batch drying process is

used for products that do not vary much in size; cement, clay, pigments, and powders are a few

of the products dried with fluid beds dryers.

All images have been taken from “Best Practice Manual-Dryers”

From pharmaceutical powders to sand ores, these dryers produce many diverse products,

across various industries. However, regardless of the application or the dryer type, each of

these four dryers uses hot air produced from indirect or direct fired air heaters.

For more information on indirect or direct fired process air heaters, please call Stelter & Brinck at 513-

367-9300 or visit www.stelterbrinck.com

Keywords: indirect fired process air heaters, direct fired process air heaters, gas fired heaters, oil fired air

heaters, stelter, brinck, spray dryer, fluid bed dryer, fluidized bed, combustion, flash dryer, rotary dryer.