Turning cement green with XRD

Sustainability is an increasingly important priority in the cement sector. Despite challenges such as higher fuel prices, the scarcity of supplementary cementitious materials (SCMs), and water and electricity regulations, there are encouraging opportunities. The European Union’s Emissions Trading System is helping to alleviate the shortage of resources and reduce carbon emissions. Moreover, an improved understanding of the impact and performance of alternative fuels and alternative raw materials has opened doors for new processes and materials. Indeed, the solutions for producing green cements and decarbonising the cement industry in the short and medium term are co-processing alternative fuels and reducing the clinker in cement using new SCMs. For that to happen, mineralogical analysis with X-ray diffraction is essential for selecting the proper raw materials and SCMs, optimising pyroprocessing and its intermediate products, controlling blending, and maximising SCMs in the final green cements.

Cement manufacturing is a complex process. The manufacture of ordinary Portland cement starts by mining and then grinding raw materials that include limestone and clay into a fine powder called raw meal. It is then heated to a sintering temperature as high as 1450°C in a cement kiln. The resulting clinker is ground to a fine powder in a cement mill and mixed with gypsum to create cement. The powdered cement is then mixed with water and aggregates to form the concrete that is used in construction.

Cement manufacture is an energy and resource-intensive process. If it were up to the quality managers, only raw meal made from the best part of the limestone quarry would enter the kiln, and only fossil fuels would be used. However, in recent years, sustainability has become an increasingly important priority in the cement sector. New SCMs are being used, such as calcined clays, as well as new alternative fuels (AFs) such as biomass, refuse-derived fuel, municipal solid waste, tyres, sawdust, and many other types of wastes and byproducts.

Mineralogical analysis is currently helping the cement industry to transition to a low-carbon and more circular economy. It is providing the sharp eyed analysis in order to identify solutions for producing greener cements. Fast and automatic full mineralogical analysis using X-ray diffraction (XRD) makes it easier to select the right raw materials for blending. It helps to optimise and control the calcination and clinkerisation processes. It is the only reliable and proven industrial technology capable of quantifying the amorphous content of SCMs and verifying that composition of complex cement meets the required standards.

X-ray diffraction heightens mineralogical awareness

XRD has been around since the 1970s. Today, it is the go-to technique for identifying and quantifying minerals and crystalline phases in a completely automated fashion. In fact, it is the only industrial technique available for quantifying amorphous materials (including some SCMs), which are solids that do not possess order beyond a few nanometres. The lack of order makes these materials extremely reactive and therefore a good SCM that can reduce clinker in cement.

Modern industrial diffractometers tap into the full potential of XRD. Instead of focusing on a specific mineral, they can identify the full mineralogical composition of materials in just a few minutes. This heightened mineralogical awareness can be used to further improve clinker quality, produce new green cements and increase the know-how of entire processing plants. The current use of XRD systems in cement plants focuses on maintaining product quality and ensuring smooth operations while reducing the carbon footprint and overall environmental impact of cement production.

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For more information on X-ray diffractometers, please visit Malvern Panalytical's website here.

Read the article online at: https://www.worldcement.com/special-reports/25112022/turning-cement-green-with-xrd/