Why has the cement industry become the main battlefield of carbon reduction in China?

One approach is waste heat recovery.

The high temperatures required for rotary kilns are maintained by the heat generated by burning fossil fuels, 44% of which is wasted. If this waste heat can be recycled and used, it can greatly save fuel and thus reduce carbon emissions. A case study in India showed that using waste heat to generate electricity increased fuel efficiency in cement plants by 5%. However, it should also be noted that the current mainstream use of waste heat is power generation, for carbon reduction, at present, the effect is very limited.

One strategy that looks at the source is to reduce or eliminate fossil fuel use. At home and abroad, fuel substitution and collaborative disposal technologies continue to be explored, and it is expected to achieve "zero consumption" of fossil energy in clinker production.

Lafarge, the world's cement giant, has been working to replace fossil fuels with low-carbon and carbon-neutral fuels since 2013. Carbon neutral fuels are mainly biomass, because the carbon inside the biomass will eventually be released, and the use of fuel will not add carbon to the atmosphere.

3. Carbon Capture & coagulene

The most direct way to deal with the carbon dioxide emitted by calcination of limestone is carbon capture and storage, that is, the carbon dioxide emitted is separated, or can be recycled for direct use, or can be stored deep in the formation, long-term isolation from the atmosphere, and can be converted into minerals for secondary use.

The captured carbon dioxide can be used on-site. When cement is mixed with water, sand, stone, etc., to make concrete, carbon dioxide is applied to control the appropriate reaction conditions, and calcium carbonate is generated, which is stored in the concrete without reducing the performance of the concrete. Canadian company CarbonCure has fully commercialized this technology, which is currently equipped with more than 300 cement plants, and plans to reduce carbon emissions by 500 million tons per year by 2030, which is equivalent to removing 100 million fuel trucks.

However, CarbonCure's technology requires the purification and encapsulation of carbon dioxide from exhaust gases, which is still inconvenient. Australian company Calix has invented a new kiln that could make carbon dioxide harvesting easy. In traditional kilns, raw materials and fuel are mixed together; Calix's kilns, on the other hand, are filled with ground lime and water vapor, which is heated outside the kiln, expelled from the kiln by simple condensation, turning the water vapor into water, and the rest is pure carbon dioxide, which can be captured and reused.

The European Union is so interested in Calix's technology that it has included it in its €20 million research project "Low Emissions Intensity Lime and Cement" (LEILAC).

In 2019, Heidelberg Cement began pilot trials of the technology at a cement plant in Belgium. The pilot test results successfully separated the carbon dioxide and did not increase the fuel input, with no significant negative effects on the product and production plant. According to a Calix press release, an upgraded version of the pilot plant will go into demonstration production in Hanover, Germany, in 2023, and the demonstration plant will be able to capture 20% of the carbon emissions, or 100,000 tons of CO2 per year.

In addition, academia and industry are collaborating to apply cutting-edge scientific advances to improve traditional concrete.

The University of Manchester has teamed up with the UK's Nationwide engineering company to invent graphene-reinforced concrete - Concretene. With better performance and a 30% reduction in carbon emissions, the concrete has already had its first commercial application. In October 2021, Concretene poured an entire 756 square meter floor for a ballroom in Manchester.

So, where does the raw graphene come from? Rice University has found a cheap source: used tires. Rice University has invented a flash process that can turn leftover carbon or old tire debris from the pyrolysis of old tires into mixed layers of graphene, which can be added directly to cement. While solving municipal solid waste, the carbon in the waste is fixed in the concrete.

Carbon reduction not only depends on hard science and technology, information technology can also contribute.

European cement industry giant LafargeHolcim launched the "Factory of Tomorrow" program in 2019, developing a technical information system that integrates robots, artificial intelligence, Predictive Maintenance (Predictive Maintenance), real-time monitoring of the state of the assembly line, according to the development trend of the state of the equipment and possible failure modes. Predictive maintenance planning) and other technologies are integrated organically. Eighty percent of LafargeHolcim's cement plants have been connected to this system, which is estimated to increase plant operating efficiency by 15-20 percent and reduce carbon by 10 percent.

articulation

The cement industry is a major carbon emitter and is of great significance for global carbon reduction. This paper Outlines several directions and paths for carbon reduction in the cement industry: