To limit global warming, worldwide CO2 emissions must be reduced. This common goal was formulated by the United Nations in the Paris Climate Agreement. This has implications for industrial production. Energy-intensive sectors such as the cement industry are working to decarbonize their processes. Among other things, it needs replacements for fossil fuels. Green cement is the goal. There are several ways to improve the life cycle assessment in production.
Why does cement production need to become more sustainable?
The production of cement accounts for around 8 percent of global CO2 emissions. To meet the targets of the Paris Climate Agreement, this figure has to be reduced by at least 30 percent by 2030. Mainly responsible for this is the chemical process of calcination, accounting for around 50 percent of the CO2 emitted during the complete cement production process. Firing the rotary kiln accounts for around 35 percent. The remaining 15 percent is divided between the other steps in the process including logistics. In the production of cement, emissions can only be reduced through process optimization and the use of additives. More and more countries are now defining targets for greater climate protection. Failure to meet these targets could result in financial penalties. But more and more customers and consumers also want green cement: Modern manufacturers therefore make sure that their product is produced in a climate-friendly way and protects the environment. This helps their business partners and clients to reduce their carbon footprint as well. In the industry, there are currently several ways to reduce pollutant emissions.
- Using alternative fuels
- Reducing coal dust
- Burning with higher oxygen content
- Reducing clinker content
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The burning of cement clinker is energy intensive. Temperatures of more than 1400 degrees Celsius must be reached in the rotary kiln in conventional processes. For some years now, cement manufacturers have been looking for substitutes for fossil fuels. Waste that is not suitable for high-quality recycling can serve as an alternative fuel. In this way, they become part of the circular economy and do not end up unused in a landfill, where decomposition processes also release CO2. In addition to organic waste such as sewage sludge, plastic, for example, can be used as a fuel. The handling of alternative fuels is challenging, as the waste does not have a constant composition. This makes correct dosing difficult. When transporting the waste to the kiln, bridging and blockages can occur if the material has a low weight and a high volume. Problems with material flow and variable fuel quality can also cause unwanted variations in burner flame and temperature. In unfavorable cases, residues are produced that affect the quality of the cement. The industry has already developed solutions to these problems: In professional test centers, the quality and flow properties of the waste can be measured and evaluated before it is used as fuel. The production lines are optimized for materials with different densities and qualities. |
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Learn more about Qlar's alternative fuels testing capabilities |
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Pulverized coal is no longer the primary fuel used to produce cement in modern plants. However, as the calorific value of alternative fuels fluctuates, fossil fuels are still needed to compensate. In addition, waste cannot be used to fire the kilns itself, only once the target temperature is reached is utilization possible. Since pulverized coal is still needed to compensate for fluctuations and to free-burn the kiln when it is fouled by deposits, the fuel must be metered in smaller quantities and fed variably to the process. As a result, the cement industry achieves a reduction in coal dust and thus lower CO2 emissions to protect the environment. |
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The oxyfuel process can reduce CO2 emissions in the production of cement. Instead of air, pure oxygen is used for burning. This facilitates the subsequent capture of the climate-damaging carbon dioxide. The CO2 no longer leaks into the atmosphere but is collected and stored. In addition, the required temperature is achieved with less fuel when firing with pure oxygen, which has a favorable effect on the energy balance. However, the process is technically complex. If the oxygen content is too low and combustion is incomplete, toxic carbon monoxide can be produced. Under certain circumstances, the quality of the products may also be impaired. To minimize this risk, the oxyfuel process also requires precise and reliable metering of the material. |
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Most processes for improving the life cycle assessment in the production of cement are aimed at reducing fossil fuels. However, the greater proportion of CO2 is produced by chemical processes during the conversion of limestone into clinker. One of the industry's goals is to reduce the clinker content by adding additives. For example, extra-fine ground limestone and small-grind concrete are used, as well as fly ash, granulated blast furnace slag and slag. Key properties of the cement-based building material concrete are cohesiveness, strength and hardness. They should not suffer from the reduction of the clinker content, so that a high product quality can still be guaranteed. The mixing systems in cement production must meter and combine the different raw materials in an exact ratio so that high-quality concrete is later produced. |
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Conclusion: These are the challenges of the future
The world's population is growing. Globally, there is still a lot of construction going on. Demand for green cement and concrete as building materials is therefore unlikely to decline. At the same time, climate protection is becoming increasingly important to limit global warming. The production of cement must become greener in order to protect the environment. In Europe in particular, many cement plants have started to look for substitutes for fossil fuels and to invest in low-emission production. Worldwide, however, there is a major modernization backlog. Pressure on manufacturers to reduce emissions will continue to increase. The more companies focus on green production and greater sustainability, the scarcer alternative fuels will become. Particularly in countries with high recycling rates, the quality of the available material will fall as a result.
This is a challenge for the manufacturers of the machine components: The plants for the production of cement must be designed for the use of a wide variety of bulk materials. The composition of alternative fuels can vary greatly. The admixture of additives in cement production requires the highest accuracy. The quality of concrete as a building material must not suffer. With modern systems, exact metering must be ensured even under more demanding conditions. Expertise and experience are therefore essential to find good solutions for the future.
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