A carbon adsorption system has been proposed to treat a stream of contaminated a

Question

A carbon adsorption system has been proposed to treat a stream of contaminated air flowing at 17090 ft3/min (T=104 degrees fahreneit, P=1atm) that contains 1000 ppm hexane vapor. Assume that we can recover 95% of the inlet hexane as liquid hexane, which can be reused. (some hexane vapor is lost into the exhaust air when we switch beds, and some hexane liquid is lost into the wastewater stream). If hexane costs $1.50 per liquid gallon (which has a density of 5.50 lb/gal), calculate how much money we can potentially save by this operation. Give your answer in $/year assuming that the plant runs 24 hours per day, 240 days per year.

Explanation / Answer

ft^3 = 0.0283 cubic meter.

17090 ft^3 = 0.0283*17090 m^3 = 483.647 m^3

1000ppm = 1000*483.647 *10^-6 m^3 =0.4836 m^3.

PV= nRT 1atm * 483.6 L = n* 0.0821*377

n= 15.625 moles per minute.

no of moles saved per minute= 0.95*15.625 = 14.845 moles.

1 mole hexane = 86.18 gram/mole

14.845 moles = 1279.34 grams = 1.941 L

1 lb= 453.592 grams

1 gallon= 3.785 litres

density = 659.11 grams/L

1.50/3.785 gives 0.39630 US dollars/L

1.941L * price per L = 0.7692 US dollars per minute.

24*60*0.7692 dollarper day= 1107.68 dollar per day

240*1107.68 dollars per year by considering 240 days = 265843.83 dollarsper year

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