mutiple hearth furnace for sale

Multiple Hearth Furnace (MHF)

GEMCO Energy is dedicated to providing global customers with excellent quality multiple hearth furnaces. Our product range includes multiple hearth furnaces with 4 to 14 hearths, catering to various industrial applications of different scales and requirements.

Long service life

Low operation costs

Ease of maintenance

High automation degree

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A multiple hearth furnace (MHF) is an efficient calcination device designed specifically for heavy industrial applications. Its unique working principle is based on transferring the thermal energy generated during combustion to a heat transfer medium, achieving the efficient utilization of thermal energy. The core feature of this device lies in its multi-chamber structure, composed of multiple combustion chambers. The combustion processes in each chamber are independent and can be controlled separately, thereby enhancing the overall efficiency of combustion.

multiple hearth furnace shell
multiple hearth furnace shipping from factory
bottom of a multiple hearth furnace
multiple hearth furnace structural design

Multiple Hearth Furnace Design

The multiple hearth furnace is a vertical cylindrical device, constructed by stacking a series of horizontal insulated hearths from bottom to top. A rotatable central shaft stands in the center of the multiple hearth furnace, and at each hearth, there is a rabble arm connected to the central shaft. These rabble arms have a certain number of rabble teeth, typically around 100mm in length. By rotating the central shaft, the rabble arms can agitate the material, guiding it in a spiral path through the hearth. The thickness of the material layer in the hearth is usually maintained at around 120mm. Auxiliary fuel burners are also located at each hearth.

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GEMCO MHF Features

Excellent Gas Tightness

  • The connection between the central shaft and the furnace adopts water seals or sand seals, effectively preventing the leakage of combustible gases from the furnace and ensuring safe operation.
  • The furnace’s inlet and outlet are equipped with high-temperature-resistant double rotary valves, further enhancing the system’s gas tightness and operational reliability.

Multi-Fuel Compatibility

  • The burner design is flexible, supporting a variety of fuels, including natural gas, propane, gasoline, and more.
  • Users can choose the most suitable fuel type based on cost, availability, or environmental requirements to meet their specific needs.

Sturdy and Durable Components

  • The base of the central shaft adopts roller bearings, ensuring a lifespan exceeding 100,000 hours and guaranteeing long-term stable operation of the equipment.
  • Graphite bearings are used at the top for easy replacement, reducing maintenance costs.

Accurate Temperature Control

  • In a multiple hearth furnace, the calcination process in each hearth is conducted independently. Through a set of independently controlled valves, the firepower and temperature in each hearth can be adjusted separately.
  • Each hearth can be adjusted as needed, ensuring highly precise temperature control to meet different process requirements.
  • The maximum operating temperature can reach 1150°C, making it suitable for various high-temperature industrial calcination applications.

Outstanding Mechanical Performance

  • The cooling air flows upward along the central shaft, and after cooling the rabble arms, it transforms into hot air, which is then discharged from the furnace top. This can be utilized for other processes or reused as preheating air.
  • The meticulously designed mechanical structure ensures outstanding performance, enhancing energy efficiency.

MHF Working Principle

the central shaft of a multiple hearth furnace
details of multiple hearth furnace
the inner refractory liner of multiple hearth furnace

The multiple hearth furnace consists of the furnace body, refractory lining, central shaft, rabble arms, transmission system, and is equipped with multiple combustion chambers. The furnace body, comprising the furnace shell and hearths, is the core part of the entire multiple hearth furnace.

The furnace shell is welded from steel plate coils into a cylindrical shape. It is reinforced with circular rings made of channel steel welded onto the cylinder. The hearths are constructed using high-alumina refractory bricks, and multiple hearths are stacked to form the entire multiple hearth furnace. The high-alumina refractory bricks in the hearths are specially designed and shaped according to the furnace structure.

The temperature of each hearth varies, with temperatures ranging from approximately 300°C to 1000°C from top to bottom.

During the operation of the multiple hearth furnace, the drive motor powers the gearbox, and through gear transmission, rotates the central shaft. The rabble arms, fixed on the central shaft, rotate along with the shaft. Raw materials are fed into the first hearth from the top of the furnace.

The fallen raw materials are swept into the second hearth by the rabble arms, and this process continues layer by layer until reaching the bottom discharge outlet. The materials are then conveyed out by a spiral cooling conveyor.

Gas and preheated air, delivered through the central shaft, are separately introduced into the combustion chambers of each hearth through pipelines. The heat generated by combustion in the combustion chambers heats and processes the materials inside the hearths. A significant amount of waste gas and dust continuously accumulates at the upper part of the furnace. The induced draft fan, installed on the waste gas pipeline, extracts the waste gas and dust through the dust removal outlet.

The central shaft cooling fan injects cold air into the central shaft and cools the central shaft and rabble arms (the central shaft is a hollow shaft). The heated air is then introduced from the top air duct into the nozzles, which, in turn, enter the combustion chambers. This process heats the gas in the combustion chambers, ensuring efficient combustion and achieving energy-saving effects.

Multiple Hearth Furnace Applications

activated carbon products

Activated Carbon Production / Regeneration

metal ores

Metal Ore Calcination

clay ores

Clay Calcination

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