The working principle of baking soda (sodium bicarbonate) used for flue gas desulfurization

Sodium bicarbonate (baking soda, NaHCO₃) can be used as an adsorbent for flue gas desulfurization. It removes acidic pollutants in the flue gas through chemical adsorption. At the same time, it can also remove some inorganic and organic trace substances through physical adsorption. Spray the fine sodium bicarbonate powder directly into the high-temperature flue gas, and the sodium bicarbonate decomposes at high temperature to produce sodium carbonate Na₂CO₃, H₂O and CO₂.

NaHCO₃ + HCl → NaCl + H₂O + CO₂
2NaHCO₃ + SO₂ + ½ O₂ → Na₂SO₄ + H₂O + 2CO₂
NaHCO₃ + HF → NaF + H₂O + CO₂

Generally, the flue gas temperature is between 140 and 250 °C. Due to the high activity of sodium bicarbonate adsorbents, a slight excess of sodium bicarbonate (stoichiometric factor between 1.1 and 1.3) is usually sufficient.

Due to transportation and storage, sodium bicarbonate raw materials are usually coarse particles (D50 value is about 200 microns). To achieve higher reactivity, the adsorbent must have a larger specific surface area. Therefore, the sodium bicarbonate must be ground to a certain fineness before being injected into the flue gas pipe. For example, to remove SO₂, the fineness of sodium bicarbonate must reach D90 <20μm; and to remove HCl, only D90 <35μm is required. If the system is operated correctly, it can remove more than 95% of SO₂; the removal rate of HCl can even reach 99%.