Absorption and separation of off-gases from the chlorination process (containing HCl, SO2, SOCl2, and trace organic compounds)
Thread Content
This post was last edited by sunjl1981 on 2013-1-6 at 20:17. I’m a beginner and have a question I’d like to ask everyone; please give me some advice. In the chlorination process, SOCl2 is used as an acylation reagent; the exhaust gas contains HCl, SO2, unreacted SOCl2, as well as a small amount of organic vapor that has not been condensed. Currently, the initial plan is to use a secondary graphite falling film absorption tower to absorb HCl gas, thereby producing process waste acid, and then to employ an alkaline absorption tower in series to absorb SO2 and produce Na2SO3. The questions I would like to ask are: 1. What is the impact of a small amount of SO2 gas and SOCl2 gas on the absorption of HCl gas? What concentration of HCl can be achieved through secondary falling film absorption? Approximately how much HCl will enter the alkaline absorption tower? Or, what is the separation efficiency of HCl and SO2 that can be achieved? 2. What is the impact of other non-condensable gases, such as N2, on absorption? Thank you all for your help! hcbbs !! .
It is recommended to first condense the organic vapor, and then pass it through a primary graphite falling film absorption tower to absorb HCl gas; in this process, SOCl2 + H2O = SO2 + 2HCl. The HCl gas is then absorbed in a secondary graphite falling film absorption tower, and further absorption takes place in an exhaust gas absorption tower. The acidic water is sent back to the secondary graphite falling film absorption tower. The SO2 absorbed by the exhaust gas absorption tower is absorbed using ammonia to produce thiamine mother liquor.
Thank you for your reply. Currently, we are considering using two-stage falling film absorption: in the first stage, 60–70% of the HCl is absorbed, while the remaining HCl is absorbed in the second stage. The resulting dilute HCl is then sent back to the first-stage falling film absorber. The current problem is that it is not clear what the effect of SO2 gas has on the falling-film absorption of HCl, as well as the residue of SO2 gas in the HCl solution.
Hello, last year I worked for an amino acid manufacturer on a project of the same type as what you mentioned. After using it for a year, no problems arose at all. If you’re interested, you can contact me at 15962864400
If the proportion of SO2 in the gas phase is not high, it will be absorbed simultaneously, resulting in a mixed acid of hydrochloric acid and sulfurous acid. Separation is troublesome.