The electrified commercial cement kiln

Last year, the US signed into law the Inflation Reduction Act (IRA) of 2022, the most significant climate legislation in US history. The IRA will provide some US$500bn in new spending and tax breaks, with nearly US$400bn directed towards carbon emissions reduction and funding clean energy. A reported US$5.8bn is earmarked for industrial decarbonisation.

For the cement sector it represents a great opportunity in North America to invest in new technology to decarbonise and cement kiln electrification is set to be a high priority. The Natural Resources Defense Council Inc (NRDC) has sent a letter in support if the Department of Environment (DoE), urging the agency to use these funds in part for commercial-scale demonstration projects such as the trial of electric cement kilns. Additionally, the Californian Energy Commission (CEC) has budgeted US$100m in funding for industrial facilities to purchase and deploy electrification technologies.

A successful push towards decarbonisation in California is going to be key in encouraging other states to follow suit in the USA. Following a new law in 2021, all cement used in California will need to reach net zero emissions by 2045, at the latest. The California Air Resources Board (CARB) is directing the cement industry away from fossil fuel usage, on which it has become dependent in California. Kiln electrification is seen as a golden opportunity to abandon coal and petcoke kilns in favour of clean energy sources to drive electric kilns.

Europe heads development for electrification
In Europe kiln electrification is likely to be achieved on a commercial scale at perhaps an even quicker pace. CEMEX announced in May 2022 that it was working with Finnish start-up Coolbrook to test its patented Roto Dynamic Heater (RDH) technology which aims to replace fossil-fuelled kilns with cleanly-generated electricity. It is argued that 45 per cent of the carbon emissions from cement production are derived from fossil fuels, which could be immediately eliminated if the electric kiln proves widely adoptable on an industrial scale. Coolbrook and CEMEX aim to have their first electric kiln in operation by 2024 and in use for commercial purposes.

In related developments, Swedish pioneering firm SaltX Technology recently announced that its Electric Arc Calciner (EAC) has successfully produced ‘green quicklime’ in June 2022. The SaltX project used a 300kW plant, but it has a way to go before scaling up to commercial production.

“SaltX has succeeded in producing clinker with the same clinker mineral characteristics as conventional clinker but using electric plasma heating instead of a traditional kiln,” reported WHD Microanalysis, a company that has analysed the material.

Generating heat via plasma generators and microwave energy has still to be developed beyond the pilot plant. Vattenfall and Cementa (Heidelberg Materials) may make the breakthrough at the Gotland cement plant in Slite, Sweden. Cementa are aiming to achieve zero CO₂ emissions from its cement products by 2030 with full-scale electrified cement production in its CemZero project.

Elsewhere, VTT Technical Research Centre in Finland is developing an electrically-heated rotary kiln with Kumera with partners Finnsementti and Nordkalk. This year has seen the project test cement raw powder and pulp mill lime in a 12m kiln.

Meanwhile, AGICO Cement (China) has been developing a heated kiln with silicon carbide as the heating element. A total of 48 silicon carbide rods are electrified to generate heat along the kiln and heat is transferred to material through the kiln wall.

A benefit of the electrification process is “the much higher concentrations of CO₂ in the flue gases than found in combustion heating, from an estimated 25 per cent concentration to close to 100 per cent,” according to Energy Efficiency In Industrial Processes (EEIP). This would make capturing carbon in the flue gases easier.

Smokeless thermal efficiency can also be achieved and there would be no storage equipment for fuel or fuel transport costs.

However, the use of electricity will be vastly increased in seven of the eight scenarios developed by EEIP where cement production is fully electrified. The demand for renewable electricity will be six-times the 2015 electricity demand, reports ECF, New Processes. The electric kiln is not a new idea. It was operated successfully by North Star Cement before the manufacturer closed down in 2014. It is the generating of cheap electricity that the industry needs to see at the same time as developing a commercial electrified kiln.

Summary
Kiln electrification will only form one part of the possible solutions for a decarbonised cement industry. The electrified kiln would cut CO₂ emissions which would be a huge saving for EU cement producers looking at approximately EUR75/t of CO₂ emission charges. Battery storage could well be required to enhance the electric kiln and to optimise usage at peak electricity tariff usage periods. It is with such methods that the cement industry might not only achieve decarbonisation but could also achieve the necessary six per cent rise in cement production to meet the growing cement demand expected from larger populations by 2050.