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Investigations for the environmentally friendly production of Na₂CO₃ and HCl from exhaust CO₂, NaCl and H₂O

Forster, Martin
Journal of cleaner production 2012 v.23 no.1 pp. 195-208
ammonia, calcium chloride, carbon dioxide, energy, fossil fuels, hydrochloric acid, sodium carbonate, sodium chloride, temperature, water
The conventional Solvay ammonia soda process is a net producer of CO₂ and produces large quantities of ecologically doubtful side products. Therefore a possible solution for this problem was investigated. Theoretical and experimental data are given which show the feasibility of a modified ammonia soda process which delivers Na₂CO₃ and HCl by using exhaust CO₂, NaCl and H₂O. This modified ammonia soda process would not produce the byproduct CaCl₂ as in the conventional Solvay ammonia soda process, would be completely recyclable and could be driven by solar thermal energy. Low maximum reaction temperatures of T ≤ 800 K and an estimated achievable solar efficiency of 10% show that this cycle is not only environmentally friendly but also energetically interesting. Kinetic constants of the main reactions are given which are similar to the ones in the conventional process. The principle of a simple solar thermo-chemical reactor is described. Preliminary economical considerations show that this new process might even be competitive when driven by solar thermal energy instead of using fossil fuels. If this novel process would be implemented worldwide approximately up to 3 × 10⁷ tonne of CO₂ could be omitted annually compared with the conventional Solvay ammonia soda process. This would correspond to 0.15% of the annual release of all anthropogenically produced CO₂.