Product Description
3.3. Working principle of double alkali method of desulfurization liquid
The desulfurization liquid adopts the external circulation absorption method. Sodium carbonate is added to the circulation tank at one time to make the desulfurization liquid (circulating water), and the circulation pump is driven into the desulfurization tower for dust removal and desulfurization. The desulfurized liquid that has absorbed SO2 falls into the bottom of the tower and flows into the regeneration tank, and undergoes a regeneration reaction with the new lime slurry. The reacted slurry flows into the precipitation regeneration tank for precipitation. When the precipitate in a precipitation regeneration tank is full, the slurry is switched to another. A sedimentation regeneration tank, and then manually or by submersible sewage pump to clean up the sedimentation sediment in this regeneration tank, the waste residue is dried and transported out for treatment. The regenerated supernatant flows into the circulating tank. The desulfurized liquid in the circulating tank that is regenerated and supplemented with fresh lye is still driven into the desulfurizing tower by the circulating pump. After being atomized by the nozzle, it fully contacts the smoke and then flows into the regenerating tank. When the pH of the liquid drops to a certain level, fresh alkali is added to restore the absorption capacity of the circulating desulfurization liquid.
The double-alkali method theoretically consumes only lime and does not consume sodium-alkali, but the desulfurization slag with water will cause the desulfurization liquid to lose some sodium ions, and the oxygen in the flue gas will oxidize part of Na2SO3 to Na2SO4 (in the circulating spray process , Na2SO4 cannot absorb SO2), so a small amount of soda ash or waste lye must be added to the circulation tank.
The basic chemical principle can be divided into two parts: desulfurization process and regeneration process.
Absorb SO2 in the tower
Na2CO3 + SO2 = Na2SO3 + CO2 (1)
Na2SO3 ＋ SO2 ＋ H2O ＝ 2NaHSO3 （2）
2NaOH ＋ SO2 ＝ Na2SO3 + H2O （3）
Among them, formula (1) is the reaction equation of SO2 absorption by the soda ash solution at the start-up stage, formula (2) is the main reaction formula of the running process, and formula (3) is the main reaction formula when the pH of the regeneration liquid is high.
Regenerate with hydrated lime
Ca （OH） 2 + Na2SO3 + 1 / 2H2O = 2NaOH ＋ CaSO3 · 1 / 2H2O
Ca (OH) 2 + 2NaHSO3 = Na2SO3 + CaSO3 · 1 / 2H2O + 3/2 H2O
In the lime slurry (lime reaches saturation), NaHSO3 quickly reacts with Ca (OH) 2 to release [Na +], [SO32-] reacts with [Ca2 +], and the resulting CaSO3 precipitates in the form of hemihydrate Thus [Na +] is regenerated. Na2CO3 is just a kind of starting alkali. It actually consumes lime after starting. In theory, it does not consume soda ash. Recycling with desulfurizing agents such as Na2SO3.
