Operational study of a 200,000 tonne/yr partial oxy-fuel combustion CO2 capture project for cement production

• An oxy-fuel calciner system for CO 2 capture in the cement industry is presented. • Industrial tests conducted under three combustion modes: air, hybrid and oxy-fuel. • Operational parameters were compared between oxy-fuel and air combustion. • The system achieved a flue gas with 82.7 vol% CO 2 and a product purity of 99.95 wt%. Oxy-fuel combustion presents a viable pathway for achieving near-zero carbon emissions in cement production, significantly reducing flue gas volume while enhancing CO 2 concentration to minimize capture costs. However, elevated CO 2 concentration impede raw meal decomposition in calciner, constituting a constraint for oxy-fuel combustion application. This study evaluated the world’s first industrial-scale 200,000 tonne/yr partial oxy-fuel combustion (oxy-fuel calciner) system in the cement sector, operational in China since 2024. The newly built oxy-fuel calciner operates with flexible transitions between air combustion, oxy-fuel combustion and hybrid combustion conditions, while the original rotary kiln and the pre-existing calciner remain to operate in air combustion condition. Operational results of the oxy-fuel calciner system indicated an average preheater outlet flue gas CO 2 concentration of 82.7 % in oxy-fuel combustion condition, marking a 47.5 % increase over air combustion, with a daily output of 667 tonnes of 99.95 % pure CO 2 production. To mitigate the inhibitory effects of high CO 2 on carbonate decomposition, calciner temperatures required elevation by 27–32 °C, achieving a raw meal calcination rate of 90–93 %. Notably, preheater outlet flue gas temperatures averaged 203 °C, 33 °C lower than air combustion, due to reduced gas volumes despite higher calciner temperatures. Real-time monitoring detected O 2 concentration variations, with air combustion at 1.7–2.6 %, hybrid combustion at 2.4–4.2 % and oxy-fuel operation at 2.0–5.2 %. The study also revealed that increased oxygen utilization exacerbates thermal and pressure instabilities, particularly impacting clinker free-CaO control in kiln operation.