Max Tschurtschenthaler, ABB, and Joonas Rauramo, Coolbrook, discuss how a pioneering project aimed at replacing fossil fuels with renewable electricity has the potential to slash carbon emissions from cement production and help meet customer demand for CO2-free products.
The global cement sector, like so many other energy-intensive industries that produce materials vital to modern life, finds itself at a crossroads. On the one hand, the production of cement, the second-most consumed material in the world after water, is expected to increase worldwide through the mid-century.
On the other hand, the industry is responsible for 7 – 8% of global carbon dioxide (CO2) emissions, even more than aviation. Cement production is notoriously difficult to decarbonise due to the high temperatures required in the kiln and the emissions produced by the calcination of limestone. According to the International Energy Agency (IEA), the direct CO2 intensity of cement production increased by about 1.5% per year in 2015 – 21; 3% annual declines to 2030 are required to meet the IEA’s ‘Net Zero Emissions by 2050 Scenario’.
Solutions such as reducing the clinker-to-cement ratio (by including a greater uptake of blended cements) and deploying innovative technologies such as electric kilns, carbon capture and storage (CCS), and clinker made from alternative raw materials, must therefore be more of a priority, says the IEA.
A new technology
Now for the good news. First, throughout the industry, ABB sees that more and more companies are focusing investment on reducing emissions to protect their licence to operate. At the recent COP27 climate conference in Egypt, concrete and cement producers joined the First Movers Coalition, a collection of 50+ companies committed to decarbonising seven highly polluting industrial sectors. These first movers pledged to purchase at least 10% near zero carbon cement and concrete by 2030. Second is technology innovation, specifically a joint project involving ABB and the Finnish company Coolbrook to advance technology that helps decarbonise the chemicals, cement, and steel industries, which are collectively responsible for 70%, or six billion tpy, of industrial CO2 emissions.
The solution combines Coolbrook’s RotoDynamic technology (which replaces fossil fuels with renewable electricity), with ABB’s motors, power electronics, and process automation for optimised energy efficiency and operational processes.
By developing and scaling up RotoDynamic technology for use in emission-heavy industries such as cement manufacture, Coolbrook and ABB aim to cut carbon emissions annually by up to 2.4 billion t.
Achieving higher temperatures using electrification
During cement production, the chemical process, whereby limestone is heated and combined with various components to produce clinker,7 is responsible for around 60% of CO2 emissions, while the remainder (around 40%) is released during the combustion of fuels to activate the chemical process.
At present, heavy industry uses polluting fossil fuels for this process because electric heaters are not capable of heating gases to the extremely high temperatures required – up to 1700°C. In traditional electric heaters, the electric current is directed through resistive material to produce heat, which limits the achievable temperature to 500 – 600°C.
Coolbrook’s RotoDynamic Heater (RDH) has the potential to reach temperature levels of 1700°C without burning fossil fuels, enabling it to replace fossil-fired furnaces and kilns with electric heating during the production of cement, steel, iron, and chemicals. The key differentiator here is that the RDH solution is essentially a turbo machine that increases the temperature internally within the gas. The gas is first heated to supersonic velocity and then slowed down very quickly in a diffuser, which converts electric energy to kinetic energy, and then the kinetic energy to thermal energy. By performing this acceleration/deceleration process multiple times, it is possible to achieve significantly higher temperatures compared with existing electric heater solutions.
Unlike existing electric heating technologies, the RDH is a turbo machine, meaning it is compact and can be retrofitted easily in almost any type of brownfield industrial processing facility, including cement plants, where it can be used in multiple applications, such as the pre-heating of feedstocks and heat provision to the pre-calciner, where the majority of the fuel is used. Ultimately, the aim is to replace the burner in the main kiln with the electrification unit, where temperatures reach in excess of 1700°C.