How the right analytical strategy can bring CO2-neutral cement within reach

Manufacturing cement has always been a complex, highly technical process requiring tight control of each production step. Now, sustainability is bringing additional challenges, as manufacturers aim for lower energy consumption and greenhouse gas (GHG) emissions, and conservation of natural resources. Indeed, many companies have committed to reducing their CO2 emissions by 30% by 2030 compared with 1990, and are expecting to achieve lifetime neutrality for concrete by 2050.

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Achieving these goals requires continuous adjustments across the whole value chain, from raw materials to final product. Several new solutions to reduce CO2 emissions in cement production are now being explored – in particular, cutting clinker emissions and creating ‘green’ cements. As well as supporting sustainability and circularity targets, these approaches can also deliver cost reductions.

However, process efficiency, energy consumption, emissions, and final product quality are affected by raw materials’ elemental and mineralogical composition and fineness, the intermediates and additives added, and the quality of any alternative fuels. As such, high-quality materials characterization – particularly automated solutions – is more important than ever in making these new solutions successful.

Different approaches to reduce manufacturing emissions from the clinker

Over 85% of the cement industry’s emissions are generated during clinker production. Improved production efficiency, digitalization, alternative fuels, and renewable energy (often with a kiln upgrade) can help reduce these emissions. But 60% of emissions within the 85% still come from chemical reactions when heating limestone. This makes lowering the clinker factor the most effective solution, followed by technologies such as carbon capture, storage and use (CCSU), or co-processing with other businesses nearby.
Improving process & kiln efficiency
Optimizing operating conditions in the raw milling and pyro-processing stages can play a big role in ensuring maximum efficiency. Firstly, to ensure that raw mix particles can be easily combined without hard burning, it’s key for them to be fine enough. Coarse calcite or quartz grains or silica particles lead to large clusters of alite and belite (respectively), making the clinker difficult to grind and diminishing strength.

To ensure their particles are fine enough, cement manufacturers can adjust particle size distribution using lab-based or in-field particle size analyzers, and monitor crystalline phases using X-ray diffraction (XRD). When implemented as part of automated control of the finishing circuit, these solutions enable higher throughputs, reduced energy consumption, and effective use of replacement materials – in turn, this delivers both cost and CO2 reductions.

Stable chemical composition of raw meal can also help enable strong properties in the clinker by ensuring consistent heat profiles in the kiln. To achieve this, manufacturers can adjust the raw meal’s chemical composition in the lab using an X-ray fluorescence (XRF) spectrometer, or in real time using an cross-belt analyzer (neutrons on/off). They can also adjust mineralogy using XRD.

Next to this, controlling the kiln’s oxidizing conditions is also essential: a short, quick heat rise helps enable a strong, grindable clinker and prevent the decomposition of C3S to C2S and free lime. Quenching the clinker rapidly can also help prevent these grindability issues, and is also key to preventing powder formation when Beta-C2S belite converts to Gamma-C2S. XRF, XRD, neutron analyzers, and particle size analyzers can all help control these parameters and optimize the energy-efficiency of your clinker production.

Using alternative fuels
Because they are so energy- and resource-intensive, clinker and cement production have a considerable environmental impact. Waste management solutions such as pre-processing and co-processing can help reduce this environmental impact by enabling improved resource efficiency.

Co-processing involves reducing direct CO2 emissions using alternative fuels that recover the calorific value of waste:
-    biomass fuels such as rice husk and sewage sludge,
-    mixed fuels such as used tires or Refused Derived Fuels  from Municipal Solid Waste,
-    fossil-waste fuels with lower emissions factors.

It allows to reduce indirect CO2 emissions by:
-    avoiding CO2 emissions from open burning or incineration without energy recovery,
-    avoiding methane emissions from dumpsites and landfills without landfill gas capture.

Alternative fuels provide a strong solution to make cement production more circular and environmentally friendly, but they require complete chemical, thermal, and physical characterization. For instance, their moisture and granulometry will affect flame temperature and heat exchange. Their chemical composition must also be monitored to enable optimum kiln availability and avoid corrosion, refractory expansion, thermal shocks, and poor combustion (SO3).

These characterizations can be carried out using X-Ray Fluorescence for chemical and elemental composition (including heavy metals), X-Ray Diffraction for crystallography, amorphous composition, oxidated or reduced forms, and Laser Diffraction for Particle Size analysis to optimize combustion and circulation in the kiln.

The best alternatives to efficiently produce high-performance ‘green’ cements

To produce clinker and traditional Ordinary Portland Cement (OPC), limestone is heated to 1450°C, sparking a chemical reaction that drops a carbon dioxide molecule from the limestone. The chemical reactions in this process release huge amounts of carbon dioxide: for every molecule of limestone that is used to make Portland cement, a molecule of carbon dioxide is released.
One way to reduce these carbon dioxide emissions is to supplement the limestone with materials such as blast-furnace slag from steel production, fly-ash from coal power plants, silica fume, calcined clays, pozzolans, and other industrial waste. Not only does this keep these by-products out of landfill, it also means less clinker is needed, cutting emissions by as much as half.

Enhanced recent blended cement combining limestone with calcined (dehydroxylated) clay to partially replace clinker is a particularly promising solution. The resulting limestone calcined clay cement (LC3) can enable CO2 emission reductions of up to 30-40% compared with OPC, and the calcined clay and limestone promote early hydration. Because clinker and the ratio of calcined clay to limestone both affect the cement’s compressive strength, characterizing their properties is important. This can be done using loss on ignition (LOI), XRF, and XRD.

Alternative Green Cementitious Materials can also be made using geopolymers or calcium sulphoaluminate. This last one can be a ye’elimite-based system or a belite-based system and replace in the first case OPC at a ratio 1:2 and can be used as a 100% replacement of OPC in the second case; CSA clinker is much softer compared to OPC clinker and can be calcinated at 1250°C (instead of 1450°C for Ordinary Portland Cement), saving around  30% in CO2 and 15 20% in fuel and grinding energy vs OPC. On top of this, this special cement distinguishes itself from Portland cement by a high-speed bonding, fast strength development, and a shrinkage reduction.

So we see that CO2 reduction and profit-seeking can both be achieved, specifically with these new approaches. Another factor can still help to achieve both: automation.

Automation: even better monitoring and efficiency

Automation involves carefully monitoring all the variations introduced when manufacturing green and classical cements to keep the process as efficient as possible. By enabling good sampling, regular control checks, and timely feedback, automation can enable maximum product performance and better, cheaper cement. Large, accurate datasets from multiple analyzers and sensors are crucial for future clinker and cement production.
At Malvern Panalytical, we provide a wide range of robust, accurate instruments to support an automated approach. These instruments can be connected to an automated lab or used directly on-line. The consistent and reliable data they provide can help reduce production costs by controlling the chemical composition of raw materials, optimizing fuels and power costs and complying with the required quality of cement. Controlling production through automated, on-line analysis with real-time data also help reduce human error and minimize non-conformities. Malvern Panalytical’s instruments can either be integrated into a third-party automation or fully developed by us. Specifically, the on-line solutions (cross belts CNA and Particle Size Analyser Insitec) address in a unique way the very common sampling representativity issue - sample representativity (size and homogeneity) is key - that is one of the most critical parts of the monitoring and control process.

Finally, on-line automated analyzers are the best solutions for obtaining consistent and reliable data for AI and machine-learning models. Malvern Panalytical’s solutions can contribute to supplying this data – from sampling to analytical measurements – enabling cost savings of up to 5-10%. Our dedicated automation team and expertise in automation even make it possible to integrate automated instruments from other brands, such as automated sample prep machines or robots.

How to move forward

Developing a CO2-neutral cement and concrete sector is certainly a daunting challenge – but the industry and its partners are bringing a wide range of innovative solutions to this task. Together, more efficient manufacturing practices, higher recycling rates, electrification, hydrogen, renewable power, and carbon capture could help cut industrial emissions by about three-quarters by 2050. And that’s just the start: innovation is likely to add more options to this list.

While these solutions will certainly have a cost, requiring the right incentives and infrastructure, they will also enable significant cost savings for cement manufacturers. And international associations also have an important role in communicating the cement sector’s needs to policymakers and coordinating sustainability efforts with those outside the sector. With this support, profit and planet can go hand-in-hand.

At Malvern Panalytical, we’re proud to be part of the solution to the net-zero cement challenge by helping our customers to adapt their processes and ingredients successfully. We believe that our high expertise in the analytical field and our long experience with cement customers allow to get the most of our unique on-line and at-line automated instruments and automation solutions. We can guide you to with the analytical strategy to keep an eye in your process and provide the required consistent and reliable data for increased automation. From the right sampling to the fine control of the major analytical parameters of products all along your process, we can put in place customised solutions for a better quality and green cement at lower cost period. This way, we’re helping contribute to a more sustainable future of cement, in line with our vision and values.

Stay tuned, our next whitepaper will clarify and illustrate the key elements on the analytical strategy to be adopted to improve the environmental approach to cement manufacturing while controlling production costs!

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To find out more about how our solutions contribute to sustainability and cost-control in the cement  industry, please contact us.

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More updates?
The cement industry is set to change dramatically in the years to come. To help the cement industry become more sustainable, cost efficient and automated we have created a series of great insights which we would like to share with you over the coming weeks. 

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