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CHALLENGES IN PROCESS SCALE-UP OF SERPENTINITE CARBONATION TO PILOT SCALE

CHALLENGES IN PROCESS SCALE-UP OF SERPENTINITE CARBONATION TO PILOT SCALE. Martin Slotte. Introduction. This presentation involves the evaluation of technical challenges when scaling up a carbon dioxide sequestration process based on mineral carbonation from laboratory scale to pilot scale

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CHALLENGES IN PROCESS SCALE-UP OF SERPENTINITE CARBONATION TO PILOT SCALE

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  1. CHALLENGES IN PROCESS SCALE-UP OF SERPENTINITE CARBONATION TO PILOT SCALE Martin Slotte Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  2. Introduction • This presentation involves the evaluation of technical challenges when scaling up a carbon dioxide sequestration process based on mineral carbonation from laboratory scale to pilot scale • Challenges in process scale-up of serpentinite carbonation to pilot scale, Slotte et. al. (CAPOTE 2012 proceedings) • Total lime kiln gas compression for CO2 mineral sequestration Slotte et. al. (ECOS 2013 under review) Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  3. Background • Problem: Increasing atmospheric CO2 levels • (One) option: Carbon dioxide capture and storage (CCS) • Underground storage • Not applicable everywhere, including Finland • Ocean storage • Also not applicable in Finland • CO2 mineral sequestration (a.k.a. CCU) • An interesting alternative Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  4. Process • The process considered is the CCU process under development at Åbo Akademi University • The process involves • the production of magnesium hydroxide, Mg(OH)2, from magnesium silicate based material using ammonium sulphate salt, followed by • carbonation of the Mg(OH)2 in a pressurised fluidised bed reactor at ~500°C, 20-30 bar CO2partial pressure • recovery of the ammonium sulphate salt Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  5. CO2 mineral sequestrationTHE ÅAU ROUTE Mg-extraction Mg(OH)2 production MgCO3 production Magnesium silicate mineral (e.g. serpentinite) CO2 lean gas Ammonium-hydroxide Ammonia HEAT NH3 + H2O AS* + Mg-silicate reactor Pressurised fluidised bed > 20 bar, > 500°C Magnesium- (and iron) extraction Mg(OH)2 MgSO4 etc. MgCO3+ MgSO4 AS Ammoniumsulphate recovery AS Ammonium- sulphate SiO2m.m. CO2 richflue gas Iron oxide (→ iron/steel industry) *Ammonium sulphate Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  6. Pilot plant for serpentinite carbonation • Pilot plant envisioned for a ~200 t/d lime kiln located in south-western Finland • Pilot plant intended to process 600 kg/h kiln gas containing 21 %-vol (dry) CO2 • The process layout needs to be evaluated with the availability of standard components taken into account • Continuous process • Recycling of chemicals • Hot kiln gas to be used as heat source for the endothermic reactions, currently the gas is quenched from 460°C to 260°C Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  7. System layout Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  8. Exergy production and consumption • Several exergy producing and consuming units • Waste heat from the lime kiln is needed to close the exergy balance Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  9. Technical challenges • Still several variable properties such as: • Density, viscosity and solid fraction of liquids • Size, shape and hardness for solids • Mineral quality • Material related challenges • Corrosive nature of liquids • High temperatures • High pressures • Volumes Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  10. Serpentinite reactor • Major problems • Multi-stage reactor • Drying of AS solution • Mixing of solid AS with serpentinite particles • Heating of mixture to ~400°C • Reaction stage takes 20-60 min • Continuous reactor, possibly a rotary kiln • Minor problems • Heating to be done with hot exhaust gas from the lime kiln • Cannot be direct contact heat exchange (gas/solid particle) due to interference with conversion reaction • Material transport into and inside reactor • Reaction gases utilised in later stages » gas tight reactor Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  11. Precipitation tanks • Major problems • Control of precipitated crystal size • temperature control • pH control • Different optimal conditions for tank 1 & 2 • pH 9 and 50°C in tank 1 and pH 11.5 and 80°C Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  12. Exhaust gas compression • Major problems • ~20-30 bar CO2 partial pressure needed leading to ~80 bar total gas pressure • Compressor intercoolers needed for efficient compression • Exhaust gas contains SOx and other impurities that can cause problems • Suitable size compressor not commercially available • Use of high pressure turbocharger + compressor Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  13. Exhaust gas compression exergy study • Exergy analysis is used as the tool for the evaluation of different compression strategies. • The goal of the analysis is to find the strategy which requires the least of external exergy fed to the process and the one in which the least amount of exergy is destroyed. • Several different compressor configurations are compared and evaluated based on the exergy balance and financial costs. Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  14. Full exhaust gas compression model Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  15. Four-stage compression exergy study Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  16. Three, four and five-stage compression comparison Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  17. Compression strategy comparison based on temperature Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  18. Pressurized fluidized bed reactor • Major problems • Optimal Mg(OH)2 particle size for efficient carbonation • Bubbling vs. circulation bed • In Finland there several manufacturers of FBR but no PFBR manufacturers but due to small size a custom built PFBR is feasible • Minor problems • High-pressure reactor in otherwise mostly non-pressurised process • Pressure vessel regulation Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  19. Conclusions • Several component and material related problems still to be solved • More lab tests needed to refine the process steps • Minimising the loss of AS and recovering the AS are important • Process water balance and treatment needs to be studied • Heat and energy integration of the process with the lime kiln to be done Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

  20. Acknowledgments • The authors want to acknowledge the Academy of Finland’s Graduate School of Energy Efficiency and Systems (2012-2015) for the financial support for the research • Experience Nduagu, InêsRomãoand Johan Fagerlundof ÅA are acknowledged their insights into carbon dioxide storage by mineralization process. • The authors would also like to acknowledge Nordkalk and in particular Thomas Nyberg and MatiasErikssson • Finnish CCSP CLEEN OY motivating this pre-study Thank you for your attention Åbo Akademi University | Domkyrkotorget 3 | 20500 Åbo

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