Posted on February 23, 2023
Heavy industry accounts for about a quarter of CO2 emissions worldwide. Burning fossil fuels to generate industrial process heat is a key factor. Heating steel blast furnaces to about 1000° C is one example. Heating cement kilns to about 1400° C is another.
Kiln Operations & Reduced Emissions
Researchers have looked at fossil fuel alternatives to firing the kilns. Concentrated solar power (CSP), hydrogen, and electricity are all examples. With electrified kilns, CO2 is still released during calcination. However, it is purer and easier to capture. To achieve plant-wide carbon neutrality, CO2 released by calcination must still occur.
Concentrated solar power (CSP)
Synhelion seeks to decarbonize industrial processes with high-temperature solar heat. With CSP, a mirror array concentrates solar radiation onto a receiver. Concentrated radiation becomes high-temperature process heat exceeding 1500° C.
Synhelion and Cemex plan to construct a carbon-neutral cement plant using CSP.
We’ve discussed fueling kilns with green hydrogen in a previous post. The prospect of hydrogen-powered kilns is exciting because emissions are water, period. More efficient freshwater electrolyzers offer promise. So does the prospect of electrolyzers that can get hydrogen from salt water.
Another approach is to electrify cement kilns. This poses two challenges, however. First, generating the process heat required for calcination. Second,. Do so in an energy-efficient, renewable manner.
One Approach to Kiln Electrification
One entry in the quest for kiln electrification is Coolbrook, a Finnish company. Coolbrook’s game-changing tech replaces fossil fuels with electrification powered by renewable energy.
Coolbrook’s RotoDynamic Heater (RDH) supplies process heat devoid of CO2, NOx and SOx emissions. The design is a product of innovative chemical engineering, turbomachinery, and space science. RDH delivers aerodynamic action through a rotating blade flow. To provide sufficient process heat, the heater directly imparts mechanical energy of its shaft to the heated gas. Air, nitrogen or process gasses get heated to very high temperatures.
As Coolbrook asserts, “With unprecedented benefits like the ability to replace fossil-fuels with clean electrification, RDH is the technology of choice for the heavy industrial production of steel, iron, cement and chemicals.” By 2024, the Finnish company expects to offer large-scale retrofitting of existing cement plants.
Coolbrook ran a pilot of its RDH tech in Finland. In 2022, Coolbrook demonstrated its technology at Brightlands Chemelot in the Netherlands. The demo plant generates process temperatures of 1000° C using 100% renewable electric power.
This means there is still a way to go since calcination requires a peak temperature of about 1400° C to complete the reaction. Coolbrook claims its RotoDynamic tech will ultimately generate 1700°C process heat. Cemex believes in RDH technology. In 2022, the Mexican company and UltraTech Cement signed a memorandum of understanding with Coolbrook. Together, they will build an industrial pilot using RDH tech.
Retrofitting & Scaling
The compact size of the RotoDynamic Heater makes retrofitting a possibility. According to Coolbrook, “The technology can be retrofitted to existing production plants and will be ready for large-scale use in 2024.” The manufacturer asserts that RDH energy efficiency exceeds 90%. Coolbrook also points to the competitive CapEx and OpEx of its technology.
Coupling electrification with carbon capture
Carbon capture and storage (CCS) is becoming increasingly feasible in cement production. This is important because it is an essential complement to kiln electrification. In 2019, Cementa completed a study of electrified cement production. By 2030, HeidelbergCement plans to build a f1.8Mt/yr CCS plant at its Slite cement plant in Sweden.
The CemZero explores electrification, CO2 capture, and more. CemZero consists of three projects running until 2025:
Direct separation of CO2 during calcination
Electrified production featuring the reactivity of cement clinker with secondary additives
Heat transfer via plasma in rotary kilns
The VTT Decarbonate Project is another example. A shipping container houses an electrified kiln 12 meters long. It is wrapped in well-insulated, fixed radiant heating coils. Capacity is 25 kg/hr. In a 2021 test, the unit operated for three days at 1000° C.
Kiln Electrification: An Ultimate Possibility?
Will fusion ever power electrified cement kilns? The International Atomic Energy Agency (IAEA) cites considerable obstacles to energy production via fusion.
However, in December 2022, researchers announced the achievement of a major milestone. For the first time, a fusion process yielded more energy than it consumed. Paul Dabbar of Columbia University’s Center on Global Energy Policy, sees commercially viable fusion within 15 years. Compare that to the cement industry’s carbon neutrality goals for 2050, 37 years away. Maybe, just maybe, commercially viable fusion may be a part of humanity’s future.
Nuclear fusion is the process by which the Sun emits the radiation heating our planet some 93 million miles away. In fusion, two light atomic nuclei come together to form a heavier atom, releasing extreme amounts of energy in the process. Fusion occurs in plasma, a very hot, charged gas consisting of free-moving electrons and positive ions.
Controlling the super-hot plasma is quite a challenge. One way to confine it is to use magnets inside doughnut-shaped reactors. More powerful magnets are key to developing a compact, more energy-efficient reactor. Doubling the magnetic field reduces required plasma volumes by as much as 16 times. Research scientists continue to make progress. MIT Technology Review reports that researchers charged a 10-ton D-shaped magnet until its field strength exceeded a record 20 tesla.
Industry and government leaders responsible for planning decades into the future face daunting decisions. Will fusion or some other revolutionary power source work well with electrification wherever process heat is required?
The Pennsylvania Aggregates and Concrete Association (PACA) reports on industry innovation at SpecifyConcrete.org. We welcome your questions about any current or upcoming concrete project. Please contact us at your convenience.