Few words about the REACTIV project
Background
Bauxite residue is the main by-product of the alumina sector produced at rates of 6.8 million tons per year in the EU, out of which less than 200 thousand tons of BR per year are reused in industrial processed. Most of the Bauxite Residue is currently landfilled due to the lack of a large-scale, sustainable reuse option. In Europe, the Bauxite Residue production represents about 7 millions tons per year while the clinker production is about 100 millions tons per year currently. Reactiv aims to provide a new sustainable and large scale re-use option for Bauxite Residue.
Bauxite Residue in Cement
The International Aluminium Institute (IAI) has launched the Bauxite Residue Roadmap to maximise the use of bauxite residue in cement and concrete products. The roadmap provides information that addresses concerns, prejudices, technical and legislative barriers to bauxite residue use.
This roadmap has identified six key pathways that can help the industry deliver success:
- 1. Provide solutions to existing barriers and fill knowledge gaps;
- 2. Establish joint research projects between alumina, cement & concrete producers to investigate the use of BR in Portland Cement Clinker (PCC) or Supplementary Cementitious Materials (SCM) for blended cement and develop technical approval documents;
- 3. Demonstrate benefits in carbon dioxide emission reduction that can be achieved using BR in PCC & SCM for blended cements;
- 4. Establish the level of interest & preparedness in incorporating BR in PCC & SCM for blended cements;
- 5. Encourage the use of BR in cement & concrete products to further the circular economy; and
- 6. Promote the use of BR in PCC & SCM for blended cements in sourcing & public procurement policies.
Objective
The objective of the project is to produce cements with a replacement of 30% of the clinker by modified Bauxite Residue. Therefore, the cement industry can potentially consume the total production of the modified bauxite residue in Europe.
In ReActiv modification will be made to both the alumina production and the cement production side of the chain, in order to link them through the new ReActiv technologies. The latter will modify the properties of the Industrial Residue, transforming into a reactive material (with pozzolanic or hydraulic activity) suitable for new, low CO2 footprint, cement products. In this manner ReActiv proposes a win-win scenario for both industrial sectors (reducing wastes and CO2 emissions respectively).
What is SCM?
According to the UNEP’s 2017 report on Eco-efficient cement, one of the main areas that can deliver substantial reductions in global CO2 emissions related to cement and concrete is the increased use of low-CO2 supplements (supplementary cementitious materials or SCMs) as partial replacements for Portland cement clinker. Today’s cements contain on average only around 20% of SCMs substituting Portland cement clinker — mainly limestone, granulated blast-furnace slags (GBFS) and coal burning power plant fly ashes (FA).
GBFS and FA sources of adequate quality are limited globally to about 15–25% of cement consumption. These ranges are determined both by the applicable cement standards and by the local availability of such materials. The utilization of an even higher amount is in principle possible but seems to be unrealistic, due to the decreasing availability of GBFS and FA (limitation of coal use in Europe) and their rising costs.
To further increase OPC substitution alternative low-CO2 SCM systems are been developed, using optimised combinations of calcined clays with ground limestone. Such combinations represent a relatively inexpensive and widely available SCM source capable of replacing up to 50% of clinker while maintaining similar performance to existing cements. Increasing the average level of clinker substitution in cement to reach 40%, for instance, using alternative SCM could avoid up to 400 million tonnes of CO2 emissions annually.
Reactiv aims to convert BR to a novel SCM capable of replacing up to 30% of clinker.
Methodology
This is a 2-steps project.
The first step will be to assess the performances of different processes to transform bauxite residue into an active material suitable for the cement industry. This step will require mainly lab experimental testing.
Performance
The ReActiv project will screen various raw materials (BR available to the project and other accessible mineral and industrial wastes) with different processing technologies in order to produce ‘active’ material which will be tested for production of new cement products. Performance criteria will be not limited to technical standards but will also include financial and environmental KPIs, in order to ensure that scale up technologies are viable and sustainable. Indicatively:
- Technical KPI: Clinker replacement factor >30%, Activity index >80%
- Financial KPI: The cost to produce the new cement versus the strength achieved, €/MPa under constant workability
- Environmental KPI: CO2 kg/t of new cement (<520 kg CO2/t cement)
A major review of achieved results is foreseen at the middle of the project (M24), to decide, based on the performance indicators for each technology, the upscaling to industrial pilots.
Technologies
| Technology | Current status | Delivered at | Market Readiness Level (MRL) / Uptake | |
| De-alkanisation | Validated at pilot scale in the H2020 RemovAL project solely for Na2O removal | Pilot testing at MYTIL’s alumina refinery with optimized conditions for formation of active precursors. | Direct to market (adaptation by alumina producers) | |
| Development of new SCM through BR roasting and fluxing | Validate at bench scale for other BRs (TRL 5) |
| Direct to market – Active Material suitable for new cement products | |
| Iron Rich SCM through BR vitrification | Validated at bench scale (TRL 5) | Industrial Pilot (TRL 7) at KUL rotary EFD induction furnace pilot -1 t/d capacity | Direct to market – Active Material suitable for new cement products | |
| Iron Free SCM through BR carbothermic smelting | Validated at bench scale (TRL 5) {BR smelting at TRL 7 in H2020 RemovAL, ENSUREAL and PF7 ENEXAL projects} | Industrial Pilot at MYTIL’s 1 MVA EAF- 3t/d capacity (TRL 7) | Direct to market – Active Material suitable for new cement products | |
| BR CAC cement | CAC slag has been produced at bench scale (TRL 5) | CAC slag produced at Industrial Pilot, MYTIL’s 1 MVA EAF (TRL 7) | Provide calcium aluminate cement for refractory applications | |
| CSAF- clinker | Validated at lab scale (TRL 4) | Industrial Pilot at LH (TRL 7) | Subject to standardization, prior to market uptake | |
| New blended cement products utilizing the Re-Active SCM | Blended cements with other SCM are in market | Production test of new blended cements at industrial pilots at LH (TRL 7) | Subject to standardization, prior to market uptake |