Query of sizing fan capacity

[silebi66]

Dear Eng-tips members:

The fan with exhaust air flow capacity = 35000m3/hr to be used to exhaust the TDI (toluene diisocyanate) fugitive emissions vapor with
feeding concentration 150 ppm TDI/Feeding flow rate=300m3/hr.Haven't said that , the PEL of TDI (permissible exposure limit) = 0.005 ppm
in a confined space 48m3.

I tried to verify the fan capacity is large enough to make this TDI concentration in the factory meet with PEL(0.005ppm).

First, I tried to get the Air changer rate per hour of this fan,

N = Q*60/V0
V0=A*H
Where
N = ideal number of air changes per hour , m3/hr
Q = the volume flow rate of air, m3/hr
V0= the space volume, m3
H = average height of the ceiling m3

From this formula, in our factory V0=48m3, Q=35000m3/hr
,so N=729.


But, if I assume the TDI ) fugitive emissions 0.1 Lpm(liter per minute),its required ACH
(air changer per hour) is form 19000~3900000.

Here the following is another calculation.

Q=G/C
Q:fan capacity [m3/hr]
G: TDI fugitive emission rate (0.1LPM = 0.036kg/hr, TDI density=6kg/m3) [kg/hr]
W= G*1000
Cermissible exposure limit of TDI = 0.005ppm)

Q=24.45*10^3*W/[C*M]]

M=molecular weight of TDI=175

So, I got Q=1005943 m3/hr which is bigger than vendor provide Q=35000 m3/hr


I have trouble to decide the emission rate of TDI in our plant is.


I really appreciated for any suggestion and help.

Thank you so much.

 

[chicopee]

Do a search of the Local Exhaust Ventilation forum. I posted a first order differential equation several months ago addressing the removal of exhaust gases within a garage. If you don't find it in a few days let me know.

 

[chicopee]

See thread #1043-310173

 

[chicopee]

A better thread to your OP is 1043-272680