Abstract:

The high-concentration NaHSO₃ solution was prepared by using wet flue gas desulfurization intermediate product CaSO₃,chlor-alkali industrial by-products Na₂SO₄ and waste sulfuric acid via two-step method.This method can simplify the subsequent treatment process and reduce energy consumption of the traditional preparation process of NaHSO₃ solution.The concentration of NaHSO₃ was selected as a major indicator to guide experiments to prepare a high concentration NaHSO₃ solution by two-step method.Firstly,the effects of CaSO₃ amount,reaction temperature,reaction time and mass fraction of CaSO₃ suspension on the concentration of dilute NaHSO₃ were investigated.Secondly,the effect of dilute NaHSO₃ concentration on the high concentration NaHSO₃ solution was investigated.The results showed that when the amount of CaSO₃ was 0.068 mol,the reaction temperature was 13 ℃,reaction time was 30 min and the mass fraction of CaSO₃ solution was 25% in the experiment,the diluted NaHSO₃ solution with 198.2 g/L can be prepared.When the mass concentration of diluted NaHSO₃ solution was 170 g/L,the mass concentration of high concentration NaHSO₃ solution can reached 270.4 g/L,which was close to saturation.This two-step method for preparation of high concentrated NaHSO₃ solution not only saves energy,but also provides a feasible path for the utilization of CaSO₃,which can brings a significant financial benefit.

Key words: wet flue gas desulfurization, CaSO₃, NaHSO₃, metathesis, two-step method