Adapting calciners for decarbonisation
The drive to decarbonise cement kiln lines has led to new research that looks at the use of hydrogen and plasma flames in co-firing with biomass. While this new technology requires modifications to the calciner and burner sections, recent R&D investigations open the door for lower-carbon kiln firing. By Tahir Abbas and Michalis Akritopoulos, Cinar Ltd, UK.
Figure 1: the swirling imparted by the tertiary air (TA) to the
upward moving riser duct stream in the calciner is shown by
the fuel particle trajectories injected into the riser duct flow.
The colour of the plots shows oxygen levels (kg/kg) – high
oxygen TA (red) and lower oxygen kiln back-end (blue)
(© Cinar)
Promising developments for new and existing cement plants lie ahead as many countries have committed to decarbonisation, pledging net zero emissions in accordance with the 2015 Paris Agreement and, most recently, reiterated at the COP26 summit in 2021. As a result, several cement multinationals have appointed process ‘decarbonisation directors’, creating dedicated departments to steer the industry towards gradually applying carbon mitigation strategies, covering 2030 interim targets to future 2050 goals.
Currently, calcined clay and alternative/biomass fuels with a lower carbon-to-hydrogen ratio are being considered, followed by other green options focussing on renewables, ie, indirect heating (electric) or direct heating (plasma flame), concentrated solar power, and H2 (green) co-combustion. These measures will enable the cement industry to achieve medium-term CO2 reduction targets.
