Exhaust treatment

With an exhaust gas treatment system, I think a mesh mist eliminator is sufficient, rather than a fiber mist eliminator. Mesh mist eliminators are cheaper than fiber mist eliminators and have lower resistance.

We don’t have screen filters here; instead, we use the sodium carbonate-lime double-alkali method to treat the exhaust gases

Mechanism of desulfurization by the double-alkali method: (1) Absorption reaction: Na2CO3 + SO2 → Na2SO3 + CO2; (2) Na2SO3 + SO2 + H2O → 2NaHSO3; (3) 2NaOH + SO2 → Na2SO3 + H2O. Among these, equation 1 represents the reaction in which soda ash solution absorbs SO2 during the startup phase, equation 2 is the main reaction equation during operation, and equation 3 is the main reaction when the pH of the regeneration solution is high. ⑵Regeneration reactions: 2NaHSO3 + Ca(OH)2 → Na2SO3 + CaSO3·1/2H2O + 3/2H2O. (4) Na2SO3 + Ca(OH)2 + 1/2H2O → 2NaOH + CaSO3·1/2H2O. (5) Equation 4 represents the main regeneration reaction, while equation 5 describes the regeneration reaction that occurs when the pH of the regeneration solution is high. ⑶The oxidation reaction: The absorption solution also contains Na2SO4, which is formed as a result of Na2SO3 in the absorption solution being oxidized by the oxygen present in the flue gas. The reaction is as follows: 2Na2SO3+O2→2Na2SO4

Factors affecting the process: 1. Effect of pH value: ① At high pH values, it is mainly NaOH or Na2CO3 that absorb SO2; the reactions Na2CO3+SO2→Na2SO3+CO2 and 2NaOH+SO2→Na2SO3+H2O proceed at a rapid rate and with high efficiency. ②As the concentration of Na2SO3 in the solution increases gradually, the pH value drops at a slightly faster rate. The dominant reaction is Na2SO3 + SO2 + H2O → 2NaHSO3, and there is sufficient desulfurization capacity; therefore, the efficiency remains stable at this stage. ③As the pH value continues to decrease, the amount of Na2SO3 in the solution as well as its desulfurization capacity decrease, and the efficiency starts to drop. Therefore, the appropriate pH value is around 7. (At low sodium ion concentrations, the desulfurization efficiency is greatly affected by the pH value; as the sodium ion concentration increases, the efficiency no longer changes significantly.) ) 2. Effect of Na+ concentration: At low sodium ion concentrations, the desulfurization capacity is low and the efficiency is poor; whereas at high sodium ion concentrations, the desulfurization capacity is higher and the efficiency is better. However, as the sodium ion concentration increases, the reaction is controlled by mass transfer. 3. Effect of the SO42- ratio: ① Under a constant sodium ion concentration, that is, with a constant total sulfur content, an increase in the SO42- ratio inevitably reduces the amount of sulfite, thereby decreasing the effective sodium ions and diminishing the desulfurization efficiency. When sulfate ions account for 20% of the total amount of sulfite and sulfate ions, the solubility products of calcium sulfite at 25°C, 45°C, and 55°C are respectively 2.318*10-7, 1.451*10-7, and 1.130*10-7; the solubility product of calcium sulfate is 1.464*10-6, 7.845*10-7, and 6.165*10-7 respectively. When sulfate ions account for 80% of the total amount of sulfite and sulfate ions, the solubility products of calcium sulfite at 25°C, 45°C, and 55°C are respectively 2.621*10-7, 2.091*10-7, and 1.592*10-7; the solubility product of calcium sulfate is 1.269*10-5, 1.095*10-5, and 8.984*10-6 respectively (referring to the solubility products during coprecipitation). Effect of pH value: At low concentrations of sodium ions, the desulfurization efficiency is greatly affected by the pH value; as the concentration of sodium ions increases, this effect becomes less significant. Effect of sodium ion concentration: At low sodium ion concentrations, the desulfurization capacity is low and the efficiency is poor. At high sodium ion concentrations, it has a greater desulfurization capacity and higher efficiency. However, as the sodium ion concentration increases, the reaction is controlled by mass transfer. Effect of sulfate proportion: Under a constant sodium ion concentration, that is, with a constant total sulfur content, an increase in the proportion of sulfate ions inevitably reduces the amount of sulfite, and as a result, the effective sodium ions decrease, which in turn affects the desulfurization efficiency. Effect of liquid-to-gas ratio: The desulfurization efficiency increases as L/G increases, but the magnitude of this increase gradually decreases.