DEGREE PROJECT IN TECHNOLOGY, FIRST CYCLE, 15 CREDITS STOCKHOLM, SWEDEN 2019 Experimental Study of Mineral Carbonation of Wollastonite for Increased CO2 Uptake DINA BABIKER MATILDA AHLSTRAND KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT TRITA TRITA-ABE-MBT-19533 www.kth.se Abstract The cement and concrete industry stand for approximately 8% of the global CO2 emissions. The demand of concrete and cement is expected to increase rapidly with the growing world population and increased urbanization. This makes it of the utmost importance for the industry to try to mitigate its emissions. One way to reduce the industry’s environmental impact is by mineral carbonation curing through which CO2 can be sequestered in the concrete. This investigation studied the CO2 uptake of wollastonite (CaSiO3) which can be used for mineral carbonation. The CO2 uptake of different brands of wollastonite powders for different temperatures, pressures and water to solid ratios were tested through carbonation, and the samples were then analyzed through XRD, SEM and particle size analysis. The results showed large differences in CO2 uptake between the brands of wollastonite powders. They also indicate that lower temperatures lead to higher CO2 uptake but also possibly slow down the reaction rate and that higher CO2 pressures seem to increase CO2 uptake though the effect is small. There was significant variation of the effects of the water to solid ratios on CO2 uptake between the tested brands. The morphology of the powders also seemed to be of little relevance as an amorphous and crystalline powder were the two best performing powders, similarly particle size is not indicated by the result to have a large effect on CO2 uptake, though further studies are required to fully determine the effect of the morphology and particle size. Sammanfattning Cement- och betongindustrin står för cirka 8% av de globala koldioxidutsläppen. Efterfrågan på betong och cement förväntas öka snabbt med den växande världsbefolkningen och ökad urbanisering. Detta tyder på hur viktigt det är för industrin att minska sina utsläpp. Ett sätt att minska industrins miljöpåverkan är genom härdning av betongen via mineral karbonatisering, en process som binder in koldioxid i betong. I detta arbete studerades koldioxidupptagningen av mineralen wollastonit (CaSiO3) som kan användas för mineral karbonatisering. Olika märken av wollastonitpulvers koldioxidupptag vid olika temperaturer, koldioxidtryck och vattenhalter testades genom karbonatisering och proverna analyserades därefter genom XRD- analys, SEM-analys och partikelstorleksanalys. Resultaten visade stora skillnader i koldioxidupptagning mellan varumärkena av wollastonitpulver. De visar även att lägre temperaturer leder till högre upptag av koldioxid, men att reaktionshastigheten potentiellt saktar ner vid låga temperaturer. Högre koldioxidtryck verkar öka koldioxidupptagningen men effekten är liten. Det fanns signifikant variation av effekterna av vattenhalterna på koldioxidupptagning mellan de testade varumärkena. Pulvrens morfologi verkade inte ha en stor effekt då ett av de två bäst presterande pulvren var amorft och det andra kristallint. På samma sett verkade partikelstorleken inte ha en stor påverkan på koldioxidupptaget men ytterligare studier krävs för att fullständigt kunna bestämma effekten av morfologin och partikelstorleken. 2 List of Figures Figure 1. A schematic diagram of mineral carbonation equipment and a description of the procedure used for the carbonation experiments of the wollastonite. ...................................... 15 Figure 2: CO2 uptake of the different brand samples when covered........................................ 20 Figure 3: Average CO2 uptake of covered Sinopharm samples at different temperatures....... 21 Figure 4: Average CO2 uptake of covered Alfa Aesar samples at different temperatures ....... 22 Figure 5: Average CO2 uptake of covered Sinopharm samples at different pressures ............ 22 Figure 6: Average CO2 uptake of covered Alfa Aesar samples at different pressures ............ 23 Figure 7: Average CO2 uptake of covered Sinopharm samples at different w/s ratios ............ 24 Figure 8: Average CO2 uptake of covered Alfa Aesar samples at different w/s ratios ............ 25 Figure 9: SEM pictures of wollastonite powders with and without water….………………...27 Figure 10: SEM pictures of wollastonite powders (Sinopharm and Alfa Aesar) after carbonation………….…….…….……….…….…….…….…….…….……………...........…28 Figure 11: X-ray powder diffractogram of the different brands' powder…...………....….…..29 Figure 12: Particle size distribution of the different powders……………………….……......31 3 List of tables Table 1: Details about the different brands of calcium silicate (CaSiO3) used……….…………..14 Table 2: Table showing the different CO2 pressures, temperatures and water to solid ratios tested………………………………………………………………………………………………………………………..16 Table 3: XRD matches for Alfa Aesar …………………………………………….…………………...……….29 Table 4: XRD matches for Macklin …………………………………………………….….……….……..…….30 Table 5: XRD matches for Aladdin …………………………………...…………...……………………...……..30 4 Table of Contents 1. Introduction ......................................................................................................................... 7 1.2 Aim and Objectives .......................................................................................................... 8 1.3 Limitations ........................................................................................................................ 9 1.4 Background .................................................................................................................. 9 1.4.1 Concrete ............................................................................................................... 9 1.4.2 CO2 Emissions of the Concrete Industry ............................................................ 10 1.4.3 Mineral Carbonation Curing .............................................................................. 11 2. Methodology ..................................................................................................................... 13 2.1 Material ........................................................................................................................... 13 2.2 Chemical analysis ........................................................................................................... 14 2.2.1 Carbonation of Wollastonite .............................................................................. 14 2.2.2 SEM and particle size analysis ........................................................................... 17 2.2.3 Experiments performed by other parties ............................................................ 17 2.3 Calculations .................................................................................................................... 18 2.3.1 CO2 Uptake ......................................................................................................... 18 3.3.2 Water content of wollastonite powders .............................................................. 19 3. Results and Analysis ......................................................................................................... 19 3.1 Different Brands ........................................................................................................ 20 Notes and observations: Preparation of samples and brands of wollastonite powder for the full analysis ................................................................................................................. 20 3.2 Temperature ............................................................................................................... 21 3.3 CO2 Pressure .............................................................................................................. 22 3.4 Water to solid ratio .................................................................................................... 23 Notes and Observations: Evaporating water during the carbonation experiments ........... 26 3.5 Analysis ..................................................................................................................... 26 3.5.1 SEM .................................................................................................................... 26 3.5.2 XRD ................................................................................................................... 28 3.5.3 Particle size analysis ........................................................................................... 31 4. Discussion ......................................................................................................................... 32 5 4.2 Sources of Error ......................................................................................................... 34 5. Conclusions ....................................................................................................................... 37 6. Future Studies ................................................................................................................... 38 Acknowledgements .................................................................................................................. 39 References ................................................................................................................................ 40 Appendix 1 - Measured weight, calculated CO2 uptake and calculated