Simultaneous conversion of CO2 and alkaline solid wastes to value-added products.
For many industries that emit dilute CO2 streams, (for example hard-to-abate processes such as the production of cement, iron and steel, bio-gas and liquefied natural gas), the ability to safely capture and store carbon remains a priority. However, carbon capture and geological storage technologies still face many significant challenges, including high CO2 capture costs and uncertainty on CO2 storage.
Additionally, coal-fired power generation and many other industrial processes generate around two billion tonnes of alkaline residues each year and more than 90 billion tonnes in total since industrialisation. These wastes are frequently stored in waste piles or landfills and can be a potential environmental hazard.
We have developed an integrated CO2 absorption and mineralisation process which can capture CO2 from dilute sources and subsequently convert CO2 and alkaline solid wastes to construction materials such as cement and geopolymer.
Our technology uses chemical absorbents to capture CO2 from dilute streams to form a CO2-rich solution which then reacts with Ca/Mg containing solid wastes. Carbonation reactions occur between wastes and the CO2-rich solution, from which CO2 is precipitated as carbonate and the chemical absorbent is regenerated.
The technology is cost effective for emission reduction and utilisation of CO2 and solid wastes. The benefits of the technology include:
- The carbonation reaction is exothermic, and no additional energy is needed for the solvent regeneration and CO2 compression.
- The mineralisation process does not require steam extraction from the power station and can be carried out independently, having a high operational flexibility.
- Geological storage is not needed, and the CO2 captured is safely stored as the stable carbonate.
- Less absorbent degradation and equipment corrosion occurs at low temperatures which will reduce costs for absorbent makeup, plant maintenance and treatment of waste generated, and less waste generated.
- The alkaline wastes are neutralised and the resulting products have improved commercial values.
This integrated technology could be readily deployed in industries that produce both CO2 and alkaline wastes, for example:
- cement plants
- iron and steel mills
- fossil fuel-based power plants.
It could also be deployed in natural gas production, bi-gas industry, aluminium smelters and hydrogen production where alkaline wastes from other processes can be incorporated.
Know-how on materials selection and process assessment.
The team has been working on the technology development for more than four years. Technical feasibility and economic benefits have been demonstrated on the bench scale.