Sudeep Sar, FLSmidth, explains how the use of supplementary cementitious materials and alternative fuels has made modern quality control and automated sampling & analysis systems a prerequisite for ensuring both process consistency and a lower environmental footprint.
The production of clinker is the most carbon-intensive part of the cement-making process; it is also the most costly. Reducing the clinker factor to the lowest allowable within specification is therefore a key aspect in reducing the cement industry’s carbon emissions, as well as its production costs.
Every ton of cement produced with a higher-than-specified clinker factor wastes money. On the flipside, every ton of cement produced which does not meet the target clinker factor risks rejection. Traditionally, cement producers would err on the side of caution and include more clinker than strictly necessary to ensure they met specification.
For example: A cement plant produces CEM I cement with a specified clinker factor of 95 – 100%. The closer the plant can get to the lower end of that range, the lower its OPEX and environmental footprint will be. In fact, a 3000 tpd cement plant that brings the clinker factor of its cement down by just one percentage point would reduce its emissions by 23 tpd of CO2 – the equivalent emissions of a VW Passat driving around the world 4.6 times.
The average global clinker-to-cement ratio is currently about 0.81 with the balance made up by gypsum and supplementary cementitious materials (SCM), including industrial by-products, such as blastfurnace slag and flyash, calcined clay and natural pozzolans. The clinker-to-cement factor could reasonably be reduced to a global average of <0.60 by 2030.
Another key element in strategies to decarbonise the cement industry is the use of alternative fuels that have the potential to deliver 12% of the cumulative CO2 emissions savings required of the cement industry to meet the two-degree scenario under the Paris Agreement. Their use poses challenges, however.
Alternative fuels are inherently inconsistent with the potential to impact clinker mineralogy and the reactivity of cement. As the International Energy Agency (IEA) notes: “…developing strategies for easier use of alternative fuels in cement kilns, e.g., automatic alternative fuel assessment and adjustment of kiln operating conditions is one of the major concerns in enabling the widespread use of alternative fuels.”
Data drives good decision-making
At every stage of the cement-making process, operators are making decisions that impact the final quality of the product, the productivity of the plant, its carbon footprint and, ultimately, its profitability. As the old adage goes, however, “you can only manage what you can measure” – high-quality decision-making relies on access to high-quality data.
Digital technologies are a vital weapon in the cement plant operator’s arsenal, opening up the opportunity to maximise both fuel and clinker substitution, without impacting the quality of the cement.
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Read the article online at: https://www.worldcement.com/special-reports/05112021/quality-control-at-the-foundation-of-sustainability/