I have a dryer under vacuum conditions (~ 20 mmHga). The distillate has a small high boiling carboxylic acid content that will freeze under condensing conditions. I intend to spray a chilled 1% caustic solution into the vapor in vessel (L/D ~ 1.25) to accomplish the following tasks:
Condense/adsorb/dissolve the high boilers, Desuperheat the water vapor ~190 F, (248 --> 60 F)
then
Condense the water, leaving a noncondensible fraction of ~ 8%.
I currently have this modeled as a single stage flash with a 150 to 1 mass ratio of circulation rate to vapor load.
What approach to adjusting the results should I take to set:
a) the minimum circulation rate, b) the droplet size to meet condensing & desuperheating process requirements c) and min-max subcooling of the liquid spray? i.e after the liquid is subcooled enough to absorb all the heat, what incremental safety factor in subcooling should be applied to assure sufficient heat sink for the condensing vapor?
Conceptually I was thinking the initial cocurrent spray took care of all of 1 and 2 and ~ 60-80% of task 3. Then I was thinking I could use packing or a sprayed mist eliminator to approach the desired outlet temperature at the outlet of the vessel for a 90+% efficiency but there is a risk of molten material buildup on the mist eliminator.
Can I expect to do a reasonable job in such an open single stage device without the outlet contact device or will efficiency be too low and droplet transit time too high?