HCl 35% DRUM VENT SCRUBBER

[roker]

Hello,

If the HCl solution is stored for a long period while the vent scrubber is operating, can it be that in the time of use the concentration of the HCl shall be much lower (or there is no effect since the HCl is chemically bonded to the water?)

regards,
roker

 

[kenvlach]

The concentration of HCl in the solution will be reduced by loss of HCl to the vapor phase. At 20^oC, the HCl vapor pressure of a 35 wt% solution is about 0.1 atm. The rate of decrease in concentration depends upon the surface-to-volume ratio of the solution, temperature, air flow rate, otther dissolved substances (especially, chloride formers such as Ca⁺² & Na⁺), but generally a first order decay:

dC/dt [∝] k_HC

The Henry's Law constant is unfortunately not constant (should be an expression somewhere), but data for the HCl vapor pressure vs. concentration & temperature is given many places, e.g., Table 1 & Fig 1 here:

http://archive.orr.noaa.gov/cameo/hcl.pdf#search="hydrochloric water vapor pressure concentration"