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Rotary Kiln

Reliable high-tech solution for a variety of continuous and discontinuous processes

The ONEJOON rotary drum furnace is the optimal solution for processes and applications where high mass throughputs are to be heat treated homogeneously at high temperatures. The rotary drum furnace's robust design allows the processing of a wide range of raw materials under various atmospheres. Powdery and lumpy educts, as well as suspensions, can be treated equally well. Two operation modes can be differentiated: Continuous or discontinuous. Later is also called batch operation. Depending on the kiln's design, both operating modes can be carried out by the same kiln. The rotary furnace operates well with a wide variety of atmospheres, such that air and inert gas atmospheres can be deployed equally well. The gas- and dust-tight sealing system developed and patented by us prevents an exchange of atmospheres with the environment and enables the processing of harmful substances.  

Our modularized furnace concept, combined with the long-term, multifaceted experience in heat treatment, make ONEJOON a reliable partner for developing innovative processes. As such, we cooperatively explore new thermal processes with our customers in our in-house test center or consult and support our customers where and when they need it. To quickly realize comprehensive solutions, ONEJOON uses an integrated system and strong partner network, covering the entire process chain, from the rotary kiln over the filling and cooling to the discharging technology. Due to our broad product portfolio, customers can also realize processes that require several different types of furnaces.

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Processes of Rotary Kiln

A wide variety of processes can be realized with an ONEJOON rotary drum furnace.

These include, for example:

These processes can be run continuously or discontinuously (batch-operation).

Plant engineering

The Rotary Drum Furnace in detail

Industrial furnace for treating powders and granules

  • Furnace head with modular ports for integrating various types of product feeding equipment.

    Here: Filling of the furnace via water-cooled charging conveyor screw. Frequently used alternatives are vibratory conveyors or simple conveyor chutes.

  • The inlet area represents the first system boundary to the process chamber and is usually designed with a furnace head and seal. In order to meet the increasingly high demands for tightness, we rely on ONEJOON'S specially developed, patented, technical gas- and dust-tight sealing system.

    For convenient maintenance work, the components in this area can be designed in a mobile way to better access the drum and some of the wearing parts. Furthermore, connections for process control and monitoring are installed here. The required measuring devices, instruments, and other "peripherals" are selected according to customer requirements.

    • Temperature: Standard solutions for T ≤ 1200 °C and customized solutions for T > 1200 °C
    • Material: stainless steel, Inconel, centrifugal casting, advanced materials (quartz glass, carbon-based)


    The rotary kiln is the heart of the oven. Since it integrates the function of heat and mass transfer, it is often the only moving element of the kiln. Its robust design enables the thermal treatment of various products with differing mechanical and chemical properties. Thus, rotary kilns are used for powdery educts, solids, and viscous suspensions. 

    In many industries, the rotary kiln's simple operating principle is confronted with high demands on material properties and behavior. Thus, a wide variety of phase transformations, chemical reactions, and heat and mass transfer processes have to be carried out reliably, without exceeding the tube's critical material values or causing unwanted reactions between the tube and the material bed.

    To ensure product quality at maximum plant safety, ONEJOON focuses on application-specific and customer-specific tube materials, geometries, and process parameters. Thus, inclination angle, speed, tube internals, and filling degrees are designed according to customer specifications.

  • ONEJOON rotary kilns can be designed for temperatures up to 1,200 °C. For special applications, temperatures up to 2,000 °C are also possible. Heating is realized either by electric heaters, gas burners, or an upstream combustion chamber.

    We deploy an integrative system to optimize the entire plant's energy efficiency, thus considering increasingly strict limits, regulations, and growing environmental awareness. This is done by improving the design - based on mechanical and fluidic simulations - as well as operating more efficiently - by using heat exchangers, insulation, and secondary fuels.

  • The rotary drum furnace's heated area is enclosed by the kiln body, an outer housing, and a refractory lining. The furnace body and housing are made of steel or heat-resistant sheets. The refractory lining often consists of heat-resistant fiber insulation that allows surface temperatures below 60 °C. Alternative insulation materials such as vacuum molded parts or stones can be used in a complementary way.

  • Depending on the value-added chain, the product must be cooled before being transferred to the next process step or stored. In principle, various types of media can be used for cooling. In industrial practice, however, an air or water-cooled system is the rule. A combination of both concepts is also possible. ONEJOON uses a cooled drum or other indirectly cooled conveying systems, such as a vibratory conveyor, depending on the application.

  • The furnace is mounted on a base frame to reduce external shocks and achieve maximum stability. By utilizing discrete or continuous mechanisms, the frame can be adjusted in height and inclination. On customer request, this can be automized using a spindle lifting system.

  • Continuous and trouble-free drum rotation is safety-critical due to the high temperatures and the resulting drum tensions. For particularly critical processes, ONEJOON relies on diversified redundancy, using secondary engines. An electric motor with a chain hoist generally functions as the main drive.

  • The outlet area is the last system boundary between the process and heating room and the environment. The product discharge channel is an additional component that discharges the heat-treated product from the process area. Depending on the process, this can be done via simple conveyor systems or highly complex systems, including atmosphere exchange and emergency discharge for products with deviating product quality.

Technical data*

Rotary drum materialStainless steel, Inconel, centrifugal casting, carbon-based, quartz glass
Rotary drum diameter300 - 1,800 mm
Heated rotary drum length2,000 - 16,000 mm
Operating temperatureup to approx. 2000°C
Potential furnace atmospheresnitrogen, hydrogen, air, other gas mixtures, e. g. pyrolysis gas
Throughput ratesup to 3,000 kg/h
Heating typeindirectly, gas or electrically heated, alternatively also via heat recovery
Process managementcontinuous, discontinuous (batch operation) or combination possible
Othergas and dust tight, direct downstream cooling
* other dimensions, materials and various accessories on request
Plant description

How does a rotary kiln work?

Robust design with high-tech finesse

In the chemical industry, the rotary kiln's robust design is contrasted by highly complex chemical and material processes taking place inside the drum. The result is a large set of factors that must be taken into account for process and plant design. Consequently, there are many rotary kiln modifications and countless optional or necessary applications that complement the process. In the following, the product path through the rotary kiln will be outlined in general terms to generate an initial understanding of potential challenges.

Material feeding

Prior to the actual heat treatment, the educt is fed into the furnace. Complexity and the number of necessary conveyors and sensor technology, as well as additional equipment, depend strongly on the material properties, the furnace's operating mode, and the conditions on-site. The filling can take place at discrete times (batch operation) or continuously (continuous operation). In addition, material properties such as transportability or reactivity determine the suitability of different applications. A feed screw, a dosing system, and chambers for calibrating the process atmosphere frequently realize this function.

Process room

The furnace head functions as a system boundary to the process chamber and has ports for various devices for process monitoring and control. These include, for example, thermocouples, optics, and process gas lines. Seals are used to prevent a potentially safety-critical exchange of atmosphere between the process or heating chamber and the environment. The complexity of the sealing system depends strongly on the application. For processes with high requirements regarding atmospheric separation, ONEJOON uses a specially developed and patented dust- and gas-tight multi-chamber system, which reliably operates at over- and negative pressure. This allows the use of protective gas atmospheres such as N2, H2, or O2 as well as the heat treatment of input materials that are harmful to health.

Heat treatment process in the rotary kiln

The actual heat treatment process takes place in the drum (process chamber). Here the material is heat-treated for a defined residence time and according to characteristic thermal profiles that need to be determined. In batch processes, the rotary kiln is filled at discrete intervals before the thermal profile is being followed at a certain rotational speed of the drum. For continuous operations, the mass throughput is defined by the length and diameter of the drum, rotational speed, angle of inclination, and internal fittings geometry.

Both process types can be operated at temperatures up to 1200 °C, depending on the drum material and heating type.  In special cases, temperatures up to 2000 °C are also possible. Depending on the process, the material and gas flow are either equally-oriented (co-current flow) or reciprocated (counter-current flow). For high-quality materials, the furnace is heated indirectly by either electric heaters, gas burners, or an upstream combustion chamber. Insulation, which is located behind the heating elements, enables an ideal heat transfer to the pipe and minimizes heat emissions to the environment.  

An electric motor with a chain drive realizes the characteristic rotational movement of the rotary kiln. The drum is supported by a running ring, which is mounted on the kiln's circumference and runs on rollers. The rollers are fixed to the furnace frame via corresponding bearings. The frame consists of a stable steel framework, which gives the system the necessary mechanical qualities.


After the heat-treatment, the product must potentially be chilled down. The cooling zone consists of either a cooling drum or alternative indirectly cooled conveyor technology, such as a water-cooled vibration channel. Suppose a drum is used, then an open system with a medium flowing around the tube is typically employed. In industrial practice, water or air functions as a cooling medium. The dimensioning of the cooling zone depends primarily on the material's target temperature, the mass throughput, and the product's specific heat capacity.

Product discharge

On the discharge side, a furnace head and a sealing system are again used as system boundaries to the environment. The furnace head has a product discharge shaft through which the heat-treated product leaves the furnace. Depending on the process requirements, the product ejection shaft can be supplemented with additional equipment for atmosphere separation and further processing.

As illustrated, the supposedly simple design of the rotary kiln is contrasted by complex process handling, which significantly influences the product quality and the possible mass throughput. Therefore, the equipment complementing the rotary kiln is critical for high product quality and comfortable operation. This is why ONEJOON systematically develops solutions to optimize the design of rotary kilns. At some customer plants, we installed mobile furnace heads and sealing systems saving 25-30% of the time required for maintenance work. Other applications include temperature measurement of the product or a self-cleaning pipe.

Covers and protectors

If particularly strict limits (e.g., high OEB levels) for contamination or material emissions regarding process or heating chamber have to be complied with, a closed extraction system outside the furnace can be used to complement the sealing system. This ensures the safety of the plant even in the event of a potential incident.

Technical highlights:

ONEJOON rotary drum furnaces offer you a number of advantages: 

  • single-chamber or multi-chamber sealing system
  • technically gas- and dust-tight
  • heating electrically, burner heated or via hot gas (combustion chamber)
  • time optimized maintenance and cleaning concept
  • temperature measurement directly on the product possible
  • variable process gas discharge and supply inside the furnace possible 
  • operation with flammable and non-flammable gases
  • direct or downstream product cooling 
  • on request metal-free product handling in the furnace and the periphery
  • modular design for flexible adaptation to a wide range of requirements and materials
  • higher plant availability for pyrolysis processes through individually designed process optimization / process control
  •  Heat recovery by using exhaust gases from a combustion chamber and thus reduced CO2 emissions (green footprint)
  • ONEJOON is your partner for the design of complete solutions that go beyond the furnace and the directly adjacent periphery (Turn-Key Solution)

Test rotary drum furnace

Our Test Center has a gas-tight test rotary kiln with a heated length of 3,000 mm, a diameter of 300 mm, and a maximum kiln temperature of 1,100 °C, thus offering a wide range of experimentation opportunities and short and long-term tests under production-like conditions. Even an upscaling from laboratory scale to production scale is possible.

>> More Information

Test rotary drum furnace

Our services

Consulting, service, furnace construction and much more.
Just because every customer has special requirements.

Together with our customers, we develop new furnace concepts and then reproduce them in an initial engineering contract. Especially for new developments, this approach in connection with further tests and simulations offers the possibility of risk minimization and time savings in longer-term decision phases.

Our engineers and process technicians are able to develop solutions for pure furnace concepts as well as for turnkey projects. We are also happy to take over the modification and optimization of existing plants for you. The respective scope and degree of detail are to be agreed on a project-specific basis.

Together with you, we will work out the optimal solution for your request.

  • definition of the scope of delivery
  • design of the system based on your specifications
  • configuration of the system from standardised components, customer-specific adaptations
  • presentation of the plant concept
  • preparation of the offer
  • design, production and testing of the system in our factory
  • shipping, assembly, commissioning and acceptance of the plant at your location around the globe
  • preparation of the plant documentation and the CE declaration of conformity
  • poduction support
  • services: plant maintenance, spare parts, repairs, measurements
  • network to adjacent processes

We are looking forward to your request, contact us today!

3 14 Leistungen Produktinformationsblatt 630x695

Selected references

Satisfied customers. The best proof of successful cooperation.

Furnace plants for the calcination of different products

Dates & Facts

  • customer: German company from the chemical industry
  • product: powder for chemical application
  • plant: calciner with downstream cooling
  • year of construction: 2016
  • scope of supply: 3 Rotary Drum Furnaces including filling, emptying and downstream cooling
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Test Center

Development and optimisation of heat treatment processes read more
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Sophisticated furnace solutions with the aid of CFD simulations read more
About us

More than 125 years of expertise in industrial furnace construction

Get to know ONEJOON
Christian Eckart Sales Manager +49 551 820 830 - 715
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