For NaOH alkaline desulfurization, what criteria are used to update the waste liquid?
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During desulfurization using the NaOH alkaline method, an excess of alkali is added in the initial stage, resulting in the formation of sodium sulfite, which accumulates in the absorption solution. Theoretically, the higher the concentration of sodium sulfite, the greater the desulfurization efficiency. Is the waste liquid discharged when sodium sulfite reaches saturation? Should fresh water and fresh alkali solution be added to the waste liquid discharged when the desulfurization efficiency decreases?
Also, when I used ASPEN for simulation, a high concentration of sodium sulfite resulted in lower efficiency; I’m not sure why
It is generally added in stoichiometric amounts; the waste liquid is a mixture, and an auxiliary online pH measurement is used
What does it mean to add substances in stoichiometric amounts? Our teacher said that the amount of S released as waste liquid should be equal to the amount of S absorbed, so as to achieve dynamic equilibrium and maintain the concentration of sulfite. But how is this value calculated in engineering terms?
It’s what your teacher said; however, the addition of the alkaline solution is done in accordance with stoichiometry, that is, MR
Based on the sulfur content in the export product, replace it as soon as it approaches the limit
Is the poster still a student? For high concentrations, it is necessary to design the process as a steady-state one, with continuous addition and continuous discharge; as a result, the discharged waste liquid will contain a certain amount of unreacted base. You can assume an efficiency rate, such as 80%, and then carry out mass balance calculations for the chemical reactions – it’s not complicated
Mm-hmm, thanks for the advice~ There’s one more question: based on the sulfur in/out balance, when the amount of waste liquid discharged is fixed, it’s possible to calculate the concentration of sulfite in the circulating solution after reaching equilibrium. So, what level is this concentration usually maintained at in practice? To avoid crystallization due to too high sulfite concentrations, is it by using a percentage of the saturated concentration of sodium sulfite?