Rotary kiln is one of ZK's chief products, and lime rotary kiln is mainly used for calcining lime. This article mainly introduces the rotary kiln for lime production, the feeding limestone for rotary kiln, and fuel for rotary kiln.

The rotary kiln for lime production

The lime rotary kiln consists of a rotating cylinder inclined at an angle of 3° to 4° to the horizontal direction. Limestone is fed into the upper end while fuel and combustion air are fired into the lower end. The limestone will be calcinated with a temperature around 1300 ℃. During the process limestone decomposition, release of CO_2, then become quicklime.

The chemical formula is as below

              Heat       

CaCO3  →→ CaO + CO2

Quicklime is discharged from the kiln into a lime cooler, where it is used to preheat the combustion air. Quicklime will be cooled with temperature around 100℃.

Many kilns have internal features to recover heat from the kiln gases and to preheat the limestone, while permitting the passage of air.

The feeding limestone for rotary kiln

Lime calciniation kiln can accept a wide range of sizes from 60mm down to dust, feature of the tumbling bed in the kiln is that larger stones migrate towards the outside of the bed, while smaller ones concentrate at the centre of the bed. So the larger stones being exposed to higher temperatures and avoids over- calcination of the finer fractions.

Because of the ease with which they can be controlled, rotary kilns can produce a wider range of reactivity and lower CaCO3 levels than shaft kilns. The variability, however, tends to be greater than that of shaft kilns.

Relatively weak feed-stones, such as shell deposits, and limestone that decrepitates, are unsuitable as feed to shaft kiln but may prove to be acceptable for rotary kilns.

Fuel for rotary kiln

Rotary kilns can be fired with a wide range of fuels. As heat transfer in the calcining zone is largely by radiation, and as the infra-red emissivities increase in the sequence gas, oil and solid fuel, the choice of fuel can have a marked effect on heat usage. Radiation and convection losses  from  the kiln  are high relative to other designs of lime kiln.

A feature of rotary kiln is that sulphur from the fuel, and, to a lesser extent from the limestone, can be expelled from the kiln in the kiln gases, without over-burning the lime, by a combination of controlling the temperature and the % CO in the calcining zone. Thus high reactivity, low sulphur limes can be produced using relatively inexpensive high sulphur fuels – subject to any emission limits for SO2 in the exhaust gases.

ZK is a professional lime kiln manufacturer, and we look forward to your inquiry.