Discussion on the formula for calculating conversion rate
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On page 498 of the book \"Sulfuric Acid Production, Processing, and Equipment Operation Manual\", the formula for calculating the conversion rate is given as follows: x = (a – c) / a / (1 – 1.5c/100) * 100. Here, a represents the SO2 concentration entering the converter, in %； c is the SO2 concentration at the exit of the converter, % ； x represents the conversion rate, in %. It is believed that the value “1.5c” in this formula should be replaced with “0.5c”. For example, using a set of data: assume the total amount of gas is 100 mol, and a is 40%, meaning there are 40 mol of SO2. When the conversion rate reaches 50%, the remaining amount of SO2 is 20 mol. According to the chemical equation, the total amount of gas decreases by 10 mol after the reaction; therefore, c should be 20/(100-10)*100%. However, the result obtained using the formula given in the book is different. Let’s all discuss it
The concentration in the formula is on a SO3-free basis; try calculating by dividing by the amount of SO3. :P The concentrations measured during regular analytical tests are all on a SO3-free basis.
In the \"Manual for Sulfuric Acid Production, Processing, and Equipment Operation,\" the values a and c in the formulas refer to the concentration of SO2
It refers to the concentration of SO2. To calculate the SO2 concentration, the amount of SO3 must first be subtracted from the total amount of gas. :(
This post was last edited by Zhang Ruqing on 2015-5-25 09:05. However, in some papers, the conversion rate is calculated directly by substituting the SO2 concentration at the inlet and outlet of each section into the formula.
When using the above formula, the concentration of SO2 at each inlet and outlet should be the concentration without considering SO3. How were the concentrations of SO2 at the inlet and outlet in each paragraph of the paper you saw determined? If one goes to the trouble of calculating the SO2 concentration when SO3 is present (which has no practical significance), it is simpler and more straightforward to just use the molar amount.
Please send me a copy of your book, thank you. Pfz2867@163.com
Take your example: assume the total amount of gas is 100 mol, with a value of 40% for a, meaning there are 40 mol of SO2. When the conversion rate reaches 50%, 20 mol of SO2 remain. According to the chemical equation, the total amount of gas decreases by 10 mol after the reaction; subtracting the 20 mol of SO3 that is produced from this, the value of c should be 20/(100-10-20)*100%, which yields exactly the same result as that obtained using the formula in the book.
Now that you’ve explained it, I finally understand what you mean
This post was last edited by Zhang Ruqing on 2015-5-25 09:03. I haven’t seen this book; when analyzing SO2, washing with a sulfuric acid bottle beforehand already absorbs SO3. I’m not sure if this book covers this point.
This post was last edited by Zhang Ruqing on 2015-5-25 09:04. What else is there?