Today’s cement industry

	Concrete is used as a material in quantities second only to our use of water
	As much as 1.25 tonnes of CO2 is produced for every tonne of cement
	Around 1600 kg of raw material is needed to produce 1000 kg cement

Portland cement, the basic ingredient in concrete, was first produced and patented in 1824 by a British stonemason. Today around 2800 million tonnes of cement are used every year, with different types manufactured to meet various chemical and physical requirements. Detailed information about the history, manufacture and different types of Portland cement, including a virtual plant tour, is freely available on the website of the Portland Cement Association www.cement.org. Alternatively to read a simple review of the key stages in cement production, click here

Cement production is one of the world’s most energy intensive industries, the release of carbon dioxide during calcination adding to the environmental burden. On average 900 kg of carbon dioxide is emitted for every tonne of cement produced, approximately half coming from the chemical processes involved¹. Recent decades have, however have seen enormous progress in reducing environmental impact and this work continues. By 2020, the industry aims to reduce CO₂ emissions by 10% from 1990 baselines by:

• Using state-of-the-art equipment to improve energy efficiency
• Formulating products to reduce manufacturing energy consumption and the use of natural resources
• Developing new applications for cement and concrete that improve energy efficiency and durability

At the front end of the process burning alternative fuels in the kiln, waste materials such as tyres and used oil, conserves fossil fuels and safely destroys waste material that might otherwise go to landfill. The economics are also advantageous providing further impetus for change. In 2008 over 68% of cement plants in the US and Canada reported using waste fuels² to produce, in combination, more than 10% of the total energy demand of the countries’ cement plants.

Alternative materials can also be profitably used to reduce environmental impact when employed as a replacement for clinker in the final product. Portland blast furnace slag contains up to 70% ground granulated slag, from steel production processes, while Portland flyash cement contains up to 30% replacement material. Use of these waste streams reduces fresh clinker content, thereby decreasing energy consumption and carbon dioxide emissions per tonne of cement. Out of total of 115 operating plants surveyed in a recent report³ 36 reported using blast furnace or iron slag as a raw material, 50 confirming their use of fly or bottom ash from electricity power plants.

To implement these changes and drive efficiency forward the cement industry needs relevant technologies that support detailed process understanding. For example, real-time particle size analysis is a valuable tool for monitoring the finish milling circuit, one of the most energy intensive parts of the process, to minimise energy consumption and maximise product quality. Maintaining product quality, when replacing clinker in the final product is of course essential so tight control is especially important when using alternative raw materials.

¹Elsevier Ltd publication: October 2002 : Greenhouse Gas Control Technologies - 6th International Conference
²PCA publication: U.S and Canadian Labor-Energy Input Survey 2008
³PCA publication : 2008 U.S and Canadian Portland Cement Industry: Plant Information Summary

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