Lagan Process

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Cement production firstly requires the production of a material called 'clinker'. This is the material which is produced when limestone and shale/clay mixes are burned in combination at very high temperatures. (>1400oC)

Materials such as limestone and shale that contain appropriate amounts of calcium, silica, alumina and iron oxides are crushed and screened and placed in a rotating cement kiln. Other materials which are typically used include marl, iron ore, clay, sand, bauxite and fly ash.

On-line analytical systems continually fine-tune the chemical composition of the resulting mix of these materials, before they are pulverised and fed to the burning stage of the process.

This consists of the preheating tower, where all the material is precalcined, and passed to the kiln.

Clinkerisation occurs in the burning zone of the rotating kiln, as the material passes through.

Flame temperatures of 2000oC convert the mix into the black nodular material (less than 40mm), known as clinker. >>

Process (continued)

>> The resulting clinker contains the tricalcium silicate and aluminate minerals which are essential to the hydraulic properties of the cement.

Continuous process sampling and X-Ray analysis of the clinker ensures that the burning process is continuously optimised to produce the highest quality clinker.

For each tonne of material that goes into the feed end of the kiln, approximately two thirds of a tonne exits the kiln as nodular clinker.

The clinker is then very finely ground in a large rotating ball mill to produce Portland Cement.

A small amount of gypsum is also added during the grinding process to control the cement's setting characteristics.

While the basic principles of the Cement Manufacturing process have fundamentally changed very little in the past hundreds of years, the technologies employed in order to achieve maximum clinker production per energy expended, coupled with the lowest emissions possible, have continually developed to their current position today.

As a new and modern manufacturing facility, utilising all the state-of-the-art technologies, Lagan Cement are well prepared to face the environmental and production challenges of the coming years.

Lagan Cement has used traditional and alternative fuels to fire its kiln at the Killaskillen plant. The use of alternative fuels does not involve any changes to the actual cement making process.