One common use for rotary kilns is the production of lime (calcium oxide) by calcinating limestone, which requires significant heat to achieve – approximately 900 °C (1,650 °F).  Such high-temperature processes must be handled carefully, and there are several problems that may arise if the kiln is not properly configured for this usage. 

Rotary kiln manufacturers will have their own recommended methods for utilizing the kiln, but the problems which occur tend to be the same.  In this article, we’ll briefly outline common problems that occur when producing lime, and how they may be avoided.

Common Problems Rotary Kiln Manufacturers See from Customers Producing Lime

1.  Underfiring

This is the most common issue seen when producing lime, and there are a few potential reasons for it:

• The limestone particles are too large.  The calcination process requires the limestone particles to be heated uniformly.   The larger they are, the harder this is to achieve.
• Insufficient fuel.  The fuel used to power the reaction should generally be providing greater than 5500Kcals to produce the proper reaction,
• Restricted air supply.  Oxygen is a necessary component in the reaction, so if the air supply is restricted, output will drop.
• Excessive heat.  The temperature of the reaction must be maintained at approximately 900 °C.  If the reaction runs hotter, especially above 1000 °C, it will harm the final product.

2. Shifting calcination zones

The ideal area for calcination to occur is in the center of your rotary kiln.  If the heat zone shifts too far up or down the kiln, it could significantly affect output.  The main reason this could happen is improper airflow.  If the calcination zone is shifting upwards, too much air is being used.  If it’s shifting downwards, there’s too little air. 

However, this can also be caused if there is too much ash building up within the kiln, so take care to remove ash properly.  Poorly burning fuel can also cause the calcination zone to shift.

3. Extended calcination zone

Finally, there’s the possibility that the calcination zone will extend too far in both directions.  This tends to increase the temperature of the reaction, leading to more wasted lime and lowered output.  Carefully manage your fuel and airflow to get the zone back into its proper boundaries.

For more than 20 years, Kiln Technology Company has been a leader among rotary kiln manufacturers, as well as having extensive repair and maintenance experience.  Whether you need a new kiln or need help maintaining your existing equipment, contact us!