Ingetecsa’s Rotary Calciner is based on a rotary drum concept. Most appreciated from our technology are the consistent product quality and the very low energy requirement. We specialise in indirectly heated calciners with temperatures up to approximately 850°C.
Calcination, or calcining, is defined as the process of heating a substance to a high temperature but below the melting or fusing point, causing loss of moisture, reduction, or oxidation, and dissociation into simpler substances. Calcination also takes place to extract metals from ores (Source: Dictionary.com).
Calcining processes occur in applications in the mineral as well as in chemical industries. The temperature at which calcining takes place depends on the (conversion) process. Also, some products can be exposed to the direct heat of combustion gases while other products can’t. Those products require indirect heating or maybe even calcination in the absence of oxygen.
Process
Product enters the drum at the product inlet side. Feeding is typically by a screw conveyor although different feed methods are possible. Product is moving through the drum by gravity to the opposite end. Longitudinal lifting plates refresh the product layer at the hot drum shell. This results in uniform heat transfer and consistent product quality. At the opposite end, product flows out of the drum in the discharge housing. Under the discharge housing is a screw conveyor or rotary valve to create an air lock. The feed rate controls the residence time of the product in the calciner, and with that the conversion rate. If needed can additional end dams vary or fine tune the dwell time in the calciner.
Heating of the product is by contact with the hot drum shell. A ventilator blows ambient air to the burners. The burners are positioned under the drum and produce hot exhaust gases to heat the revolving drum shell on the outside. This heats the product on the inside of the drum. The hot exhaust gases circulate – guided by baffles – between the shroud and the drum towards the product inlet side. Then, an exhaust fan extracts the cooled down off gases. On their way to the stack, the exhaust gases exchange their residual heat with the incoming combustion air. This results in a substantial energy saving.
Process combinations
Process combinations are possible. Often, product requires drying prior to calcining. A solution is to directly couple a rotary drum dryer to the rotary calciner. The off gasses from the calcination process flow directly to the drying kiln where they heat the shell of the dryer. Another combination is reusing the off gasses to heat a flash dryer, such as the conventional Flash Dryer or the Spiral Flash Dryer. In the case of (pre-) drying, the conventional flash dryer is the preferred drying technology when drying temperatures need to be very high.
Example of a combination of a rotary drum dryer and a rotary calciner.
Also, other combinations are possible such as post cooling. The Multi Chamber Cooler has proven to be a very reliable candidate as it is primarily designed to cope with very hot temperatures of even greater than 800°C.
Contact us if you like to know how we can assist you selecting the best configuration for your application.
