Flue gas desulfurization tower, in which a sodium hydroxide solution is added to absorb sulfur trioxide
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In the exhaust gas desulfurization tower, a sodium hydroxide solution is added to the tower; it is sprayed from top to bottom using a pump, thereby absorbing sulfur trioxide. The solution then returns to the desulfurization tower. Based on the pH value, the solution containing sulfur trioxide is discharged through this pump – one pump continues to spray the solution upward while another pumps it out via a valve – as waste liquid. There is a problem: could the sodium hydroxide solution be pumped out at the same time? How can this be controlled so that the sodium hydroxide solution is not pumped out along with the waste liquid?
This is a mixture, so inevitably some of it will be carried away
In the sodium-alkali method for desulfurization, at a pH of 6.5, sodium sulfite is used to absorb sulfur dioxide, resulting in the formation of sodium bisulfite. Sodium bisulfite has no ability to absorb SO2; therefore, sodium hydroxide is added, which reconverts it back into sodium sulfite. SO2 + H2O → H2SO3; H2SO3 + Na2SO3 → 2NaHSO3; NaHSO3 + NaOH → Na2SO3. When the density reaches 1.2, a portion of the desulfurization solution is removed; this solution contains sodium sulfite, sodium bisulfite, and a small amount of sodium sulfate.
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How should this desulfurization liquid be handled? Can it be discharged directly?
By selecting an appropriate addition location and controlling the pH value of the circulating liquid, it is possible to prevent NaOH solution from being carried out of the system. According to current environmental regulations, desulfurization liquid must not be discharged; if it cannot be used in other systems, then an evaporation system needs to be considered.
Just one tower? Does sulfur dioxide in exhaust fumes have a strong smell? What concentration should the sodium sulfite solution be prepared at? Absorbed to 1.2?