Solvent vessels must be purged before maintenance personnel enter in order to en

Question

Solvent vessels must be purged before maintenance personnel enter in order to ensure that: (1) sufficient oxygen is available for breathing; (2) vapor concentrations are below the flash point; (3) vapor concentrations are below the Occupational Safety and Health Administration (OSHA) limits if breathing apparatus is not to be used. Assuming that a 8 m3 fixed-roof solvent tank has just been drained of all liquid and that the vapor phase is initially saturated at 22 C, estimate the length of purge necessary with 2 m3 / min of gas at 0.1 MPa and 22 C to reach the OSHA 8-hr exposure limit. (c) Chloroform 50 ppm

Explanation / Answer

Moles of Purge gas = PV/RT

P=0.1MPa= 0.986923 atm

V= 2m3/min =2000 liters/min

R= 0.08206atm.lit/gmoleK

T= 22deg.c =22+273.15= 295.15K

n= 0.986923*2000/(0.08206*295.15)=81.4965 moles/min

Density of chlorofom = 1465 kg/m3

mass of chloroform = 8m3* 1465 kg/m3= 11720 kg =11720*1000 gm

Moles of chloroform= 11720*1000/119.38=98487.395 gmoles

gas flow rate= 81.4965moles/min

Length of purge= 98487.395/81.4965 min=1208.486 min

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