Exploring the Dynamics of Natural Sodium Bicarbonate, Sodium Carbonate, and Black Ash in Spray-Dry SO₂ Capture

The viability of spray-dry desulphurisation relative to wet flue gas desulphurisation (FGD) systems is determined by selecting a highly reactive scrubbing reagent. This research evaluated sodium-based reagents from natural and waste by-product sources for treating sulphur dioxide (SO₂). Sodium carbonate (Na₂CO₃) and sodium bicarbonate (NaHCO₃) were obtained from mineral sources, whereas the black ash (BA) (Na₂CO₃.NaHCO₃) was sourced from the pulp and paper industry. The sorbents introduced in slurry form were subject to SO₂ absorption conditions in a lab-scale spray dryer, including an inlet gas phase temperature of 120 to 180 °C, a flue gas flow rate of 21 to 34 m³/h, and a sodium-to-sulphur stoichiometric ratio (SR) (Na:S) of 0.5 to 2. The performance comparison was assessed based on %SO₂ removal efficiency (%_DeSOx) and revealed that NaHCO₃ exhibited the highest overall effectiveness of 62% at saturation. BA was the second-best-performing reagent, achieving a removal efficiency of 56%, and Na₂CO₃ demonstrated the lowest efficiency of 53%. The maximum SO₂ reduction of NaHCO₃ at individual operating conditions was seen at an SR of 1.75 (69%), a reaction temperature of 120 °C (73%), and a gas inlet flow rate of 34 m³/h (80%). In summary, the sodium reagents produced a notable SO₂ neutralisation of over 50% in their unprocessed state, which is within permissible bounds in small- to medium-sized coal-fired power plants considering retrofitting pollution mitigation systems.