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System for the Use of Alternative Fuels in Cement Production, Part One: Alternative Fuels and Raw Materials

World Cement,

The rising costs of primary fuels and their limited availability, are forcing more and more cement manufacturers to use alternative fuels, leading to a constant increase in the substitution of traditional fuels such as oil, gas, coal and petroleum coke. This necessary change in the clinker production process has now also been made by Ciment’s de l’Atlas in its Beni Mellal plant in Morocco.

While in Europe, and especially in Germany, an average of around 60% of regular fuel is substituted by high quality alternative materials, which are carefully prepared and undergo quality control, the employment of such materials is developing much more slowly in other regions of the world.

Alternative fuels and raw materials

The motivation to substitute regular fuels with alternative fuels and raw materials (AFR) lies in the cost savings and in the reduction of CO2 emissions. By operating an AFR co-processing system, the cement plant not only slashes its fuel costs, but simultaneously reduces the CO2 emission load of the clinker production process through the use of biogenic materials (wood, rice husks, sewage sludge, etc). Moreover, the thermal utilisation of refuse-derived materials, such as fuel and raw material, in the cement manufacturing process ensures the residue-free disposal of waste material that would otherwise pollute the environment or have to be disposed of in special landfill sites.

Stringent demands are imposed on the quality of the substitute fuels, particularly in view of the desired high substitution rates. Apart from assuring continuously high calorific values, the characteristics and contents of the alternative process materials must not negatively affect the operation of the burning process, and above all must not impair the quality of the produced clinker and cement.

Regular monitoring of the constituents and of the production process with regard to chlorine, sulfur content, heavy metals and other harmful substances is absolutely essential. Scrap tyres are often used for starting up with alternative fuels because their high calorific value and homogeneous chemical properties make them a very good substitute for regular fuels. After a certain period of learning and gaining operational experience, the introduction of other, more complex, alternative materials is much easier.

This does involve one particular challenge: designing the material feeding system in a future-proof manner so that it can also be used for other solid alternative fuels, thus avoiding additional capital costs in the future.

As in many other cement markets outside Europe, the initial development of secondary fuel usage in Morocco is also based on the use of scrap tyres with uniform properties and high calorific values. The Beni Mellal plant of Ciment’s de l’Atlas initially burned imported tyre chips as a substitute fuel. It is therefore necessary to store an entire shipload of tyre chips on the plant premises so that the material can be consistently supplied to the process.

Ciment’s de l’Atlas’ Beni Mellal cement plant was constructed by ThyssenKrupp Polysius S.A.S, France (now part of ThyssenKrupp Industrial Solutions) in 2009. Its 3600 tpd kiln system was equipped with a modern calcining system and with a combustion chamber for petroleum coke firing.

Read part one of System for the Use of Alternative Fuels in Cement Production here.

Written by Wolfram Zschiesche and Karl Menzel, Vecoplan FuelTrack. This is an abridged version of the full article, which appeared in the February 2014 issue of World Cement. Subscribers can view the full article by logging in.

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