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FE Review for Environmental Engineering Problems, problems, problems Presented by L.R. Chevalier, Ph.D., P.E. Department of Civil and Environmental Engineering Southern Illinois University Carbondale

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AIR FE Review for Environmental Engineering

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Estimate the amount of soda ash required per m 3 of exhaust gas to neutralize 20,000 g/m 3 of SO 2 at 20° C.

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Review governing reaction Determine the mass of soda ash needed from mole ratio

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The neutralization reaction is: MW: SO 2 = 64 Na 2 CO 3 = 106

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The mass of soda ash is then: Therefore, for each m 3 of exhaust gas, we require 33.1 mg Na 2 CO 3

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Consider a box model for an air shed over a city 1 x 10 5 m wide with a mixing depth of 1200 m. Winds with no SO 2 blow at 4 m/s against one side of the box. SO 2 is emitted in the box at a rate of 20 kg/s. If SO 2 is considered to be conservative, estimate the steady state concentration in the air shed. Report your answer in g/m 3.

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Draw a schematic of your system Consider mass balance

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Solution L W = 1 x 10 5 m H = 1200 m wind u = 4 m/s C o = 0 g/m 3 wind u = 4 m/s C e =? Emission 20 kg/s

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wind u = 4 m/s C o = 0 g/m 3 wind u = 4 m/s C e =? Emission 20 kg/s C e = C o +(qL)/(uH) L W = 1 x 10 5 m H = 1200 m

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wind u = 4 m/s C o = 0 g/m 3 wind u = 4 m/s C e =? Emission 20 kg/s C e = C o +(qL)/(uH) L W = 1 x 10 5 m H = 1200 m

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Consider the emission of SO 2 from a coal fired power plant, at a rate of 1,500 g/s. The wind speed is 4.0 m/s on a sunny afternoon. What is the centerline concentration of SO 2 3 km downwind (Note: centerline implies y=0). Stack parameters: Height = 130 m Diameter = 1.5 m Exit velocity = 12 m/s Temperature = 320°C (593° K) Atmospheric conditions: P=100 kPa T=25° C (298° K)

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Review data Estimate effective stack height Determine stability class Calculate sy and sz Review terms and apply governing equation

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H = effective stack height = h + H = 130 m + 15.4 m = 145.4 m

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Atmospheric stability class: Class B s y = ax 0.894 = 156(3) 0.894 = 416.6 m s z = cx d + f = 108.2(3) 1.098 + 2 = 363.5 m

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Simplify the Gaussian dispersion model to describe a ground level source with no thermal or momentum flux, which is the typical release that occurs at a hazardous waste sites. In this situation, the effective plume rise, H, is essentially 0.

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Consider soil under a single story house that emits 1.0 pCi/m 2 ·s of radon gas. The house has 250 m2 of floor space, and average ceiling height of 2.6 m, and an air change rate of 0.9 ach. Estimate the steady state concentration of radon in the house, assuming that the ambient concentration is negligible. For radon, k = 7.6 x 10 -3 hr -1

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Volume = (250 m 2 )(2.6 m) = 650 m 3 Q/V = 0.9 Ventilation rate = Q = (650 m 3 )(0.9) = 585 m 3 /hr C i = 0 E = (1.0 pCi/m 2 ·s)(250 m 2 )(3600 s/hr) = 900000 pCi/hr Review data Review SS equation

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