Standard Rotary Calciner
The rotary calciner design consists principally of an inclined rotating cylinder that is enclosed in a furnace along its active length, featuring gas, oil, dual-fuel burners, or electric heating elements, and can be equipped with gas-tight seals that prevent interchange between the internal atmosphere and local ambient conditions.
Principal of Operation
Material is fed into a rotating cylinder that is externally heated according to process related time versus temperature criteria. As the cylinder rotates, the material is gently tumbled as it flows from the feed end of the cylinder to the discharge end. This action promotes uniform exposure of the product to a defined environment. Various processes employ reaction gases in direct contact with the product to propagate a given reaction or cover gases to protect the product.
Applications that are appropriate for indirect heat calciners involve a wide variety of fine powders, granular materials, pellets and extrudates that require retention times ranging from a few minutes up to several hours, non-contact with products of combustion, special purge or reactant gases and bed temperature profiling.
Heat for the process is transferred through the cylinder wall, resulting in low internal process gas flow rates. The resulting low gas velocity within the cylinder provides for low levels of attrition and particulate entrainment when processing fragile and micron-sized products. The low flow rate gas conditions within an indirectly heated calciner also provide for a significantly smaller and more economical off-gas handling system, than that required for a direct-fired kiln.
Proper selection of the calciner cylinder material is critical and is determined by process temperature, process compatibility and physical size considerations.
In cases where it is necessary to cool the heated material prior to discharge, an integral indirect water spay cooler section can be added to the calciner by extending the length of the cylinder.
Bartlett-Snow rotary calciners are available in 6" to 120" cylinder diameter
The benefits realized by users of Bartlett-Snow™ equipment compared to conventional tunnel kiln or mesh belt style equipment are as follows:
• Maximum Product Uniformity
The material bed is constantly being turned over, all of it is exposed uniformly to its required environment.
• Greater Yields
All of the material is processed; none is overheated or under heated.
• Reduced Process Time Factors
Due to uniform exposure and dynamics of the product, process time requirements are drastically reduced.
• Reduced Capital Costs
With reduced process time requirements, the equipment is smaller and therefore less costly.
• Reduced Floor Space Requirement
Due to reduced process time factors, Bartlett-Snow™ Calciners require less floor space compared to other calcination equipment.
• Reduced Energy Costs
Reduced process time factors result in reduced energy requirements.
• Reduced Operating Costs
Material is inherently conveyed through a rotary calciner, thus eliminating the ongoing replacement cost of material holding containers and automation devices. Since the bed of material is constantly being turned over, solids to gas contact is optimized, minimizing process gas consumption and reducing the size of off-gas treatment systems.