Issues regarding SO2 measurement in WSA exhaust CEMS
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Our plant uses the Topsoe SWA wet process for sulfuric acid production. Recently, the environmental protection authorities conducted an inspection and required the installation of CEMS. The levels are as follows: SO2 at 500–800 mg/m3, and nitrogen oxides at 20–40 mg/m3. Question 1) When acid fog increases, neither of these two values changes. Does this indicate that SO3 cannot be detected? 2) Increasing the heat blower capacity raises the oxygen content and reduces the SO2 content. What principle is at work? 3) Are nitrogen oxides formed by the combustion of nitrogen and oxygen in a combustion furnace? Reaction chemical formula? 4) Could the SO2 infrared sensor in CEMS mistakenly detect SO or SO3 as SO2?
This post was last edited by winter0304 on 2015-11-23 at 16:46. When the air flow rate is increased, the SO2 concentration naturally decreases; it’s similar to diluting wastewater with tap water. That’s why the standards specify a baseline oxygen content of 3%. Many technology providers claim to meet emission standards, but in reality they do not; owners need to keep a close eye on this.
What does CEMS mean? Is it online monitoring? 1. Acid mist is used to monitor SO3; it has nothing to do with sulfur dioxide or nitrogen oxides ； 2. The increase in hot air and oxygen content, along with the decrease in sulfur dioxide, indicates an improved conversion rate of sulfur dioxide, in addition to the dilution effect ； 3. Nitrogen oxides are also related to the presence of ammonia in the raw materials ； 4. Sulfur dioxide and sulfur trioxide cannot be mismeasured.
When acid fog increases, neither of these two values changes. Does this indicate that SO3 cannot be detected? There is no separate detection; increasing the heat fan capacity raises the oxygen content while reducing the SO2 content. What is the principle behind this: are the diluted nitrogen oxides formed by the combustion of nitrogen and oxygen in a combustion furnace? Reaction chemical formula? : That’s what the thermodynamic type is like ； The combustion of nitrogen-containing organic compounds also produces it. 4) Will the SO2 infrared sensor in CEMS mistake SO or SO3 for SO2? No, the detection principles are different ； There is virtually no SO
1) When acid mist increases, neither of these two values changes. Does this indicate that SO3 cannot be detected? SO3 cannot be detected. 2) Increasing the power of the heat blower raises the oxygen content while reducing the SO2 content. What principle is at work? An increase in oxygen content leads to a higher conversion rate ； At the same time, as the gas volume increases, the percentage of SO2 naturally decreases. 3) Are nitrogen oxides formed by the combustion of nitrogen and oxygen in a combustion furnace? Reaction chemical formula? No. 4) Could the SO2 infrared sensor in CEMS mismeasure SO or SO3 as SO2? No
With sufficient oxygen and an increased oxygen-sulfur ratio, the conversion rate naturally increases.
A portion of the hot air from the condenser is directed to the exhaust gases, which helps raise the temperature of those gases and thereby eliminates acid mist and water mist. Under conditions of high exhaust gas temperature and in the absence of a catalyst, it is impossible for SO2 to be converted into SO3.
May I ask the original poster: does your company’s acidic water stripping tower extract ammonia via a side stream? If ammonia is not removed via a side stream, the NOX levels in the exhaust gases should be very high.