Views on the revision of the analysis standards for sulfuric acid mist
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This post was last edited by in the blink of an eye on 2019-8-10 at 19:02. Since 2009, when the method for detecting sulfuric acid mist in the sulfuric acid industry was changed from the cotton ball method to ion chromatography (HJ544-2016), it has been difficult for the acid mist at the outlet of the second absorption tower in the vast majority of sulfuric acid plants to meet the requirement of 30 mg/Nm3. The cotton ball method involves using cotton balls to capture sulfuric acid mist and performing acid-base titration; thereafter, the SO2 content is determined by the iodometry method and subtracted from the total amount. Ion chromatography is used to analyze the acid mist captured by the fiberglass filter cartridge and that captured by the impact absorption bottle. The amount of acid mist captured by the fiberglass filter cartridge is not high; it is mainly the high concentration of sulfates in the impact absorption bottle that leads to a significant increase in the test results for acid mist. Some factories add a small amount of antioxidant to the absorbent solution in these impact absorbers, which results in a significant reduction in the amount of acid mist captured by the impact absorbers. In fact, in China’s sulfuric acid industry, some factories use sulfuric acid exhaust gases to produce sodium sulfite; sometimes the content of sodium sulfate in this sodium sulfite product is too high, and the reason for this is that part of the sodium sulfite gets oxidized. An improvement of ion chromatography over the cotton ball method is that it takes into account the interception efficiency of the filter cartridge, using the acid mist intercepted in the impact absorption bottle as a supplement. The raw cotton ball method only uses filter media to trap a portion of the acid mist; on the surface, the ion chromatography method appears to be more effective than the cotton method. In fact, even in ion chromatography, there are still many more factors that have not been taken into account. The acid-retaining capacity formed by the filter media after trapping acid mist has an absorption effect on SO3 vapor and sulfuric acid vapor in the flue gas. When measuring the SO3 absorption rate in the first and second absorption towers of the sulfuric acid plant, the SO3 concentration at the outlet of the tower’s demister is used in the calculations, not the SO3 concentration at the inlet of the demister! The acid retention in the absorber demister contributes to the absorption of SO3 and sulfuric acid vapor.
The EPA acid mist testing method used by the U.S. environmental protection agency is similar to the cotton ball method; it simply involves using the amount of acid mist trapped by the filtering material in the calculations. In an impact absorption bottle, isopropanol is used to absorb SO3, which is then converted into sulfuric acid vapor.
I see, thanks to the original poster for sharing
Antioxidants can be p-phenylenediamine, hydroquinone, or EDTA
I’ve learned about it; now companies are struggling because of these standards.
It is said that the vast majority of this testing method is copied from the United States, but some aspects are not, which has led to the current situation.
Only the absorbent in the impact-type absorption bottle was copied over, but for the results in the EPA test, the sulfuric acid vapor and acid mist values are still taken from those obtained by the fiberglass filter. Even if it were copied verbatim, there wouldn’t be so many problems now.