Separating SO2 and HCl mixed gases
Thread Content
How to separate a mixture of SO2 and HCl gases
Hydrogen chloride has a boiling point of -85 degrees at standard pressure, while sulfur dioxide has a boiling point of -10 degrees. Based on the boiling point difference, the most effective separation method is low-temperature distillation; however, for these two media, selecting the appropriate materials and process flow is a challenging task. Hydrogen chloride dissolves very easily in water, while sulfur dioxide also dissolves in water but to a limited extent in acidic water. By using dilute hydrochloric acid to absorb the gas mixture, hydrogen chloride can be essentially completely dissolved in water, whereas the amount of sulfur dioxide that can be absorbed is limited, thus allowing for its separation. This approach also imposes strict requirements on the selection of equipment materials.
:(Originally, there was a absorption tower with three stages of water washing at the front and three stages of alkaline washing at the back; hydrochloric acid was produced on the front side while sodium sulfite was produced on the back side. However, hydrochloric acid is difficult to sell due to the presence of reducing sulfur dioxide, which limits its range of applications. Now, design companies are proposing a compression system for separation based on differences in boiling points; it remains to be seen what the actual results will be.)
Adsorption is the best approach – it saves energy. You can try using various adsorbents; however, since both molecules are polar, it might be difficult to find suitable adsorbents. How about trying pressure swing adsorption first?
First, you need to know whether you need one thing, or both. Generally speaking, washing is the conventional method, while pressure swing adsorption is the best choice under environmental considerations
I am very interested in the low-temperature distillation separation of hydrogen chloride and SO2. Have you carried out any work in this area?