7(A). A gas stream contains particles of the following: 2 mg for 0-2um size range, 57.6...

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7(A). A gas stream contains particles of the following: 2 mg for 0-2um size range, 57.6 mg for 2- 5um size range, 105 mg for 5-9um size range, 76 mg for 9-15µm size range, 20.5 mg for 15- 25µm size range, and 7.9 mg for >25 um size. A control device is installed to remove the particles before the gas stream is released to the atmosphere. The removal efficiency of the device is 10%, 40%, 70%, 85%, 98% and 100% for 0-2 um, 2-5µm, 5-9µm, 9-15µm, 15-25µm and >25µm particles, respectively. What is the overall removal efficiency of the control device? (5') 7(B). It is estimated that a burning dump emits 3 g/s of NOx. What is the concentration of NOx directly downwind from this source at distances of 0.5, 1, 3, and 5 km on an overcast day with a wind speed of 4 m/s? Assume the dump to be a ground-level point source with no plume rise. Hint: Please refer to the graphs and tables in appendix. (ii) The owner of the dump suggests things would be much better if a 20-m stack were erected on the dump; it could then be considered a point source at an elevation of 20 m. Repeat question (i) for this condition. Is the owner right? (5') (5') 7(A). A gas stream contains particles of the following: 2 mg for 0-2um size range, 57.6 mg for 2- 5um size range, 105 mg for 5-9um size range, 76 mg for 9-15µm size range, 20.5 mg for 15- 25µm size range, and 7.9 mg for >25 um size. A control device is installed to remove the particles before the gas stream is released to the atmosphere. The removal efficiency of the device is 10%, 40%, 70%, 85%, 98% and 100% for 0-2 um, 2-5µm, 5-9µm, 9-15µm, 15-25µm and >25µm particles, respectively. What is the overall removal efficiency of the control device? (5') 7(B). It is estimated that a burning dump emits 3 g/s of NOx. What is the concentration of NOx directly downwind from this source at distances of 0.5, 1, 3, and 5 km on an overcast day with a wind speed of 4 m/s? Assume the dump to be a ground-level point source with no plume rise. Hint: Please refer to the graphs and tables in appendix. (ii) The owner of the dump suggests things would be much better if a 20-m stack were erected on the dump; it could then be considered a point source at an elevation of 20 m. Repeat question (i) for this condition. Is the owner right? (5') (5')

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