Choosing the right drying system is a significant investment and critical to your process. It is essential to know the variations between the different dryer options. The heat source is one of the most common differences. Read on and consider the following reasons why we often recommend a steam tube dryer over a direct heat dryer.
Steam Tube Drying vs. Direct Heat Drying: What’s the Difference?
Steam Tube Drying
Steam tube dryers perform as if it were a rotating tube with a shell heat exchanger. The drum is fitted with a high-pressure chamber that distributes steam into tubes running the length of the drum. Because its applications are for low-temperature processes, the equipment required for thermal destruction is reduced or eliminated.
Steam Tube Dryers Are the Most Efficient Industrial Dryer
The most efficient of all the dryers, the steam tube dryer has very little air being exhausted – making the stack loss significantly reduced. The air pollution control system is also much smaller in a steam tube dyer and, since only a minor amount of air is used to sweep out the water vapors, the exhaust volume is a fraction compared to that of a direct heat dryer.
Steam Tube Dryers are also one of the easiest dryer types to operate. Once the steam pressure is set, the unit will take what it needs to do the job. Think of it as having a set-it-and-forget-it technology.
A steam tube dryer is used extensively in processing high-moisture organic materials such as distiller’s grain, gluten feed from the wet milling industry, oilseeds, and a variety of sludges.
How Does an Industrial Steam Tube Dryer Work?
Material is fed into the drum and tumbles over the outside of the inner tubes. Inside those tubes, steam is collapsing to condensate. The latent heat from the steam—about 850 BTUs per pound—provides the heat energy for drying. The condensate from the steam is removed through a rotary joint. It is then taken back to the boiler for regeneration.
Direct Heat Drying
How Does A Direct Heat Rotary Dryer Work?
A direct heat rotary dryer uses a hot gas which is induced into a rotary drum. Its heat source may be as simple as a steam coil in low-temperature applications, or it can have a burner for higher temperatures. The burner may combust into a chamber or it may fire directly into the dryer drum. We use the term direct-fired when there is no combustion chamber.
Direct heat dryers typically work best when the burner system can operate with a minimal amount of excess air or near stoichiometric balance of the gas and air. This allows the dryer to minimize the air required to carry the thermal energy.
Wet material is fed into the same end of the drum (parallel flow) or the opposite end of the drum (counterflow) and is picked up and showered (or veiled) into the hot gas stream. The thermal energy is transferred from the hot gas to the material, which heats the solids and the water, ultimately evaporating the water. The primary heat transfer is by convection.
If your product is not affected by heat from the burner flame or the products of combustion, then a direct-fired unit will provide an efficient drying solution through the full utilization of all three heat transfer methods: radiation, convection, and conduction.
Why Choose a Steam Tube Dryer over a Direct Heat Dryer?
Developed more than 100 years ago, the Louisville Steam Tube Dryer has always been a quality choice for drying high moisture organic by-products such as brewers’ and distillers’ spent grain. Today, this same dryer technology serves thousands of applications.
What Materials Does an Industrial Steam Tube Dryer Process?
A steam tube drying system is our recommended choice for drying and processing inorganic and organic chemicals and other bulk solid materials including, but not limited to:
- Dried distillers grains (DDG, DDGS)
- Wet corn (fiber, grits, meal)
- Wood chips
- Soda ash
- Paper mill sludge
- Oil Seed (soy, sunflower, canola)
- Soy meal
- Chemical products
- Petrochemical products (TA, PTA)
- Lithium processing
- Copper concentrate
All our dryers, including the steam tube system, are built in our state-of-the-art factory using proven technologies. Our in-house design team of engineers have vast experience in every type of process and industry; thus, our customers always receive a drying system that is custom fit for their operation.
5 Benefits of A Steam Tube Drying System
#1: More Cost-Effective
Louisville Steam Tube Dryers have been proven superior to other types of indirect-heat dryer installations in which hot gas, rather than steam, is used as the heat source. We provide solutions with the Lowest Cost per Revolution throughout our industries. Maintenance savings alone have often prompted the replacement of other dryer systems with the steam tube dryer.
#2: Better Quality
A steam tube dryer is classified as an ASME vessel. Thus, the requirements for its construction are more stringent than for other dryers.
#3: More Efficient
The steam tube dryer generally operates at a lower temperature than other dryers and rotates at a slower speed. Material tumbles gently around tubes that rotate with the shell, eliminating the friction forces that other types of dryers require.
#4: Easier Maintenance
Louisville Steam Tube Dryers enjoy a longer lifespan than most other dryers and require very little maintenance.
#5: Environmentally Friendly
Steam Tube Dryers are environmentally friendly. Since the steam tube dryer utilizes the latent heat of steam to drive the drying process, only a small amount of sweep air is required to remove the water vapor driven off the product generated in the drying process. Typically, the method uses less than about 30% of the exhaust gas required for a direct heat dryer.
Purchasing A Steam Tube Dryer
Because choosing the right drying system is a major investment and critical to your process, you should be sure you are getting the best equipment available. The Louisville Dryer Company manufacturing facilities hold esteemed accreditation by the American Society of Mechanical Engineers (ASME) and The National Board of Boiler and Pressure Vessel Inspectors.
We extend personal attention and service to each customer, ensuring that their rotary processing equipment needs are efficiently met. If you are interested in learning more about the Louisville Dryer Company Steam Tube Drying System and its applications, please reach out directly to Hank Lawson, our Senior Process Engineer. He would be happy to listen and discuss the best options available for your application.
Call (800) 735-3163 or fill out our online contact form to get started.