Problem 5An analysis of the gas in an underground utility vault revealed 30 mg/m3 of hydrogen sulfide, which a workcrew discovered before entering the vault to perform repairs. Due to the permissible exposure limitationof 14 mg/m3, the work team started using a blower to ventilate the vault (cellar). Suppose the vault has a200 m³ capacity and the predicted duration of detention is 15 minutes. determinea) The flow rate of contaminant-free air in (m3/s) to lower the hydrogen sulfide level to a level thatwill allow the work crew to enter the vault?b) How long will it take to lower the hydrogen sulfide level to a level that will allow the work crew toenter?Assume the system behaves as a CSTR and that hydrogen sulfide is nonreactive in the time considered.Note: This is a case of flushing a nonreactive contaminant from a CSTR.
Problem 5
An analysis of the gas in an underground utility vault revealed 30 mg/m3 of hydrogen sulfide, which a work
crew discovered before entering the vault to perform repairs. Due to the permissible exposure limitation
of 14 mg/m3, the work team started using a blower to ventilate the vault (cellar). Suppose the vault has a
200 m³ capacity and the predicted duration of detention is 15 minutes. determine
a) The flow rate of contaminant-free air in (m3/s) to lower the hydrogen sulfide level to a level that
will allow the work crew to enter the vault?
b) How long will it take to lower the hydrogen sulfide level to a level that will allow the work crew to
enter?
Assume the system behaves as a CSTR and that hydrogen sulfide is nonreactive in the time considered.
Note: This is a case of flushing a nonreactive contaminant from a CSTR.
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