What is the key parameter for pH in the sodium-calcium double-alkali desulfurization method?
Thread Content
Based on the chemical reaction principles of the sodium-calcium double-alkali method, when the main component of the spray desulfurization agent is Na2SO3, the amount of NaOH required is twice that needed when the main component is NaHSO3. Therefore, in order to control the concentration of NaHSO3 in the circulating spray desulfurization agent, the pH should be maintained at 5–6. Yet, the pH value in the sodium-calcium double-alkali method as generally mentioned is usually above 9. Why is that?
Reply: According to the chemical reaction principles of the sodium-calcium double-alkali method, when the main component of the spray desulfurization agent is Na2SO3, the amount of NaOH required is twice that needed when the main component is NaHSO3. Therefore, in order to control the content of NaHSO3 in the circulating spray desulfurization agent, the pH should be maintained at 5–6. However, the pH value in the sodium-calcium double-alkali method as generally mentioned is usually above 9. Why is that? NaHSO3 is formed only under acidic conditions, that is, when there is a shortage of alkali; otherwise, when there is an excess of NaOH, Na2SO3 is the compound that forms. There have been many experiments conducted on this topic.
What is the impact of producing sodium sulfate and sodium sulfite on desulfurization?
The 9 mentioned generally refers to the newly prepared solution, while the 5–6 you mentioned is the pH value that the slurry should be kept at during the reaction.