From Batch Rotary Kiln Testing to Detailed Kiln Design

This article was co-authored by:

Jenny Seim
Technical Writer

Alex Ebben
Process and Sales Engineer

Since 1951, FEECO International has built a reputation as the leader in rotary kiln design and manufacturing. Part of our success is owed to the FEECO Innovation Center, a state-of-the-art testing facility where our team of process experts conduct a variety of thermal tests to assist in establishing process and equipment parameters for commercial-scale production. The design of our commercial kilns is often a direct result of the batch rotary kiln tests conducted in FEECO’s Innovation Center, located in Green Bay, WI (USA).

Why Test with a Batch Rotary Kiln?

The objective of testing with a batch rotary kiln is to determine the time and temperature required to achieve product quality. Testing also helps determine the maximum temperature that the feed can tolerate. Several gas temperatures, shell temperatures and heating rates can be tested to determine the effect of temperature on reaction rate. The results of such tests help define the process parameters for continuous pilot plant test work, and ultimately, the design and manufacturing of a commercial rotary kiln.

FEECO’s batch rotary kiln simulates the conditions in continuous commercial rotary kilns, utilizing high temperatures to cause chemical reactions or phase changes in a material. Each test setup is dependent upon the material, processing goal, and desired end-product. Generally speaking, however, commonly tested processes with the batch kiln include:

Batch Rotary Kiln Specs

The direct-fired batch rotary kiln has a diameter (inside refractory) of 18 inches, with a length of 24 inches. This rotary kiln features a refractory-lined rotary vessel with variable-speed control and instrumentation to provide temperature profiles along the material bed and gas phase. The kiln has a propane-fired burner, with the option for providing an oxidizing or reducing gas environment. The rotary kiln exhaust can be treated with a secondary combustion chamber, wet scrubber, or baghouse for specific pollution control requirements. Finally, the batch kiln is lined with lightweight castable refractory.  The rotary kiln can be operated to heat solids up to 3000ºF (1650ºC) with the firing maintained from highly oxidizing to sub-stoichiometric.

The Innovation Center is also equipped with an indirect batch rotary kiln. The indirect kiln is used when a material cannot come into contact with the combustion gases, and thus the heat is introduced to the outside of the drum shell via gas burners or electric heaters.

The indirect batch rotary kiln has a diameter of 10.5” (0.27 m) and a heated length of 24” (0.61 m). It is generally filled to 8-10% volumetric loading. Dams are located inside the kiln to keep the material within the heated zone. The kiln shell is capable of reaching temperatures up to 1000 °C and is heated by a propane burner underneath the shell. Two thermocouples located near the shell in the furnace are used to measure the shell temperature. Two additional thermocouples are used to measure the bed and exhaust gas temperatures. Finally, the ends of the kiln can be sealed and have an inlet for a purge gas and an outlet port for purge gas exhaust.

Our team of experts is able to capture numerous points of data during testing, and then store the data in a historic database for future reference. The following data is displayed and stored during each batch kiln test:

      • Zone electrical current (continuous indirect)
      • Shell temperatures (indirect)
      • Kiln material temperature (both)
      • Kiln exhaust gas temperature (both)
      • Kiln furnace temperatures (indirect)

Material samples are taken at regular intervals to determine the extent of reaction. The data from the tests, along with the chemical and physical analyses, can be used in determining the necessary commercial kiln size and process operating conditions. The batch kiln can also be used to help determine the conditions for continuous pilot plant tests.

Conclusion

Typical applications for rotary kilns include waste lime recovery, proppant manufacture, clays, thermal desorption of organic / hazardous wastes, mineral roasting, specialty ceramics, plastic processing, gypsum calcining, tire pyrolysis, bauxite calcining, pigments, catalysts, and phosphate productions.

With the multitude of applications and varying materials, it is easy to see how testing in the FEECO Innovation Center may be a valuable investment for a number of process development and scale-up projects for new thermal process technologies.

If you’re interested in rotary kiln testing, contact us today!

About the Authors . . .


Jenny Seim is a technical writer and service specialist.

More About Jenny

Alex Ebben is a Process Sales Engineer and thermal processing expert.

More About Alex