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Fuelled by efficiency

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World Cement,

Dr. Dipl. Eng. Jan Tuma, BEUMER Group, considers the most effective solutions for efficient conveying, storage and feeding of alternative fuels.

Fuelled by efficiency

Cement is the most commonly used building material worldwide, and its popularity is continuously growing. However, manufacturers have to comply with ever stricter environmental regulations in order to keep air pollution under control. Depending on the processes used, around 0.6 – 0.99 t of CO2 are produced per ton of cement. Emissions from the cement sector are estimated to account for 7 – 8% of overall global carbon dioxide emissions.

An approach to sustainably reduce greenhouse gas emissions and production costs is to increase the use of alternative fuels.

Fluid materials like waste oil or solvents as well as solids for example, can be used instead of coal and gas. The majority of the material is composed of municipal and industrial waste, such as plastic, paper, composite material or textile mixes as well as wood pellets. The use of entire or shredded waste tyres is also welcome. The calorific value of the rubber from waste tyres is comparable to that from hard coal, and the iron from the reinforcement can be incorporated mineralogically into cement. This minimises the addition of ferrous corrective substances. Alternative fuels are available in large quantities and at low costs and can be disposed of completely in a safe high-temperature process in the rotary kilns of cement plants. Thus, these materials do not have to be landfilled or otherwise disposed of.

As different materials have different calorific values, complete household waste cannot simply be fed into the combustion process in the kiln. Especially in countries where waste separation is not as developed as it is in Europe, the challenge is huge. How alternative fuels are composed and how they are used often also depends on their availability in a specific region and, in particular, on the economic aspects. In addition, the materials have to fulfil defined quality requirements. Some operators, for example, only use processed waste with a defined minimum calorific value and low heavy metal content. In these instances, the alternative fuels used must have a determined particle size and a density. The moisture content is also an important factor.

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