[S.Bawa]

Hi all, great site, lots of interesting information

I'm struggling to reverse calculate a problem that I have the partial accepted answer to, but am not able to figure out one of the numbers. I'm trying to calculate the emissions of the various haz chemicals per the MSDS, in an alkaline cleaner for  a pretreatment paint line wash tank.

Tank Size: 4.41 m^2
Worst Case emission estimate: solution 150 F (65.5 C)
The tank consists of 2.5% concentration in solution of product ABC
According to MSDS product ABC is 30% potassium hydroxide (+ others as well)
From Perry's at 65.5 C the vapor pressure of H20 is 191.815 mm Hg

So far so good.

The accepted equation I have is:

Potassium Hydroxide = 2.62 x 10^(-4) kg/m^2/s x 4.41m^2 x 1000 g/kg x 0.025 (ABC in soln) x 0.30 (conc in ABC)
= 8.67 x 10(-3) g/s

I can't figure out where this 2.62 x 10^(-4) kg/m^2/s number was derived from. This number is used for the other emission calculations for the different products in ABC (ie phosphoric acid, potassium silicate etc.) based on their % concentration in ABC soln, so it appears to be a constant or a coefficient based on either the temperature/vapor pressure of water at this temperature.

I've been trying to use Langmuir's equation, but I have not been able to reproduce the 2.62 x 10^(-4) kg/m^2/s or the final answer of 8.67 x 10(-3) g/s

---------------------------------------------------------------------------------------------------------------
The rate of free evaporation of vapor atoms from a clean surface per unit area in vacuum, Mc, is given by Langmuir's equation:

      Mc=5.85*10^(-2)*P*(M/T)^0.5     g*cm^(-2)*s^(-1)

Where    P=vapor pressure of evaporant under saturated vapor conditions at temperature T, torr or mmHg.
   M=molecular weight of evaporant material
   T=absolute temperature, K 

-----------------------------------------------------------------------------------------------------------------


Any help is appreciated. Is this the wrong equation? Or is this information already in a table somewhere?

Thanks,