World cement production in 2011 reached 3.6 billion tonnes. This resulted in over 2 billion tonnes of CO2 being produced from both the calcination of limestone and the fuels used (mainly coal and gas) to drive this process.
The global cement sector has been very active in reducing its emissions from cement production. The three levers that have been used are:
- Energy efficiency,
- Alternative fuels or biofuels, and
- Clinker substitution.
Through the combination of these efforts, the emissions per tonne of cement have been reduced by 16 percent from the 1990 levels of 750 kg CO2/ tonne of cement. Further reductions can be achieved through continued action using these three levers but there is a practical limit on the reductions that can be achieved. Hence deep cuts in CO2 emissions from cement production can only be achieved through CCS.
The 2012 IEA Energy Technology Perspectives estimates that the cement sector will need to reduce its emissions by around 1,100 million tonnes CO2 per year from 2050 onwards and that the share of CCS is between 660 and 940 million tonnes per year. CCS is the main contributor to achieving the emission cuts required. The IEA also provides interim targets for 2020 of 11 CCS plants in the cement sector capturing 13 million tonnes of CO2 per year.
So what is happening to deploy CO2 capture in cement production?
From the three most advanced capture technologies there are only two that may be suitable to the cement sector. These are post combustion capture and oxyfuel combustion. Pre combustion is not suitable because it is unable to capture the emissions from the conversion of limestone to lime, the key component of cement. A study by Worrell et al discusses more about the emissions sources from the cement industry.
There have been a number of desktop studies completed on the feasibility of post combustion capture and oxyfuel for cement production. The most detailed ones are the IEAGHG sponsored study completed by Mott MacDonald and the Phase III technical report by the European Cement Research Academy.
What these studies have in common is that they both recognise that post combustion capture can be readily fitted to a cement plant, although there are some challenges related to managing the dust and SOx emissions from the process and meeting the additional heat requirements for the solvent process. This will require an auxiliary boiler and increase the capital and operational costs. Both studies also indicated that oxyfuel may be beneficial for the cement sector but that this would require a more substantial change to the cement plant compared to post combustion capture. Applying oxyfuel will require more research and development as many of the fundamentals of applying oxyfuel to a cement plant need to be better understood. The ECRA Phase III report has provided some results indicating that the challenges associated with air leakage, gas recirculating and heat transfer associated with oxyfuel can be managed, although more detailed work is required.
The next stage of development is to proceed to pilot scale. There are four key activities around the world that are contributing to this.
- The European Cement Research Academy has agreed to proceed with Phase IV of the ECRA CCS Project. This phase will have a dedicated focus on oxyfuel technology and consists of four work packages:They expect to complete these work packages by mid 2015 and the technical advisory board will make a decision to build a demonstration plant at the completion of this phase.
- Further optimisation/ detailing of a 3,000 tpd cement plant
- Concept study for a pilot plant
- Pre-engineering study
- CO2 balance and economic sensitivity analyses.
- Norcem (Norway) is commencing a pilot project at their Brevik cement works. This will involve three separate pilot plants to test three different post combustion capture technologies. The technologies being investigated include Aker Clean Carbon’s amine scrubbing, Alstom’s chilled ammonia process and Alstom’s regenerative carbonate cycle [ECRA Phase III report]. It is expected that this project will commence later this year.
- The Industrial Technology Research Institute (Taiwan) and Taiwan Cement are working together on a calcium looping capture project. They have an operational 1 ton per hour pilot scale facilityat the Hualien cement plant in Eastern Taiwan.
- Skyonic has an operational pilot facility at the Capital Aggregates cement mill in the US. The focus of the Skyonic business model is on the re-use of CO2 to create sodium bicarbonate (baking soda). They currently have a mobile test facility demonstrating their technology by capturing CO2 produced from a cement plant.
These projects are early stage pilot projects applied to cement plants. They are generally at a TRL of 5 to 6. While these are important steps to deploy capture in the cement sector, more focussed effort is required to achieve the 13 Mt of CO2 capture by 2020.
Alternative cements are also being developed (based on Magnesium instead of Calcium) and claim to be able to produce lower CO2 emissions. These may the subject of future insights.
As an interesting aside, the ECRA has developed an animation of a cement plant and have used that animation to illustrate how post combustion capture and oxyfired technology can be applied to cement plants. These are definitely worth a closer look for anyone interested in capture from the cement sector.