Air Pollution

Questions & Answers

Problem 1. (PM terminal settling velocity) Calculate terminal settling velocity (V) values for ammonium sulfate ((NH4)2SO4) particles versus particle diameter (d) at: 20°C and 760 mm Hg for dry air. Particle diameter ranges from 0.001 μm ≤d₂ ≤ 10 um. Plot Ve versus da for the described conditions in a plot with Vte on the ordinate and d on the abscissa. Use log scales for both axes. | Solution hints: Follow the steps in example class worksheet problem 2 (Wednesday-Week 4). Calculate Vi by assuming the gas flow is in Stokes region and particles are spherical. Check Stokes region assumption by calculating the particle Reynolds Number (Rep).


Problem 2. (Filtration) A fabric filter will be used downstream of a spray dryer to remove particulate material from a gas stream. Actual concentration of particulate matter is 10 g/m³ upstream of the fabric filter. A pilot plant was built and operated downstream of the spray dryer to characterize the behavior of the filter cake and fabric under actual conditions. Pilot plant data are presented below.


Problem 3. (ESP) A single stage ESP operates with a voltage of 22 kV. The spacing between the collection electrodes of this single channel ESP is 10.0 cm and the anode-cathode spacing for the ESP is 5.0 cm. a) Calculate the electric migration velocity (wp) in m/s at 25°C in air for particles with the diameter 0.05 um, 0.5 µm and 5 µm. Assume the dielectric constant of the particles. Dp². is 10. Pressure is 1 atm. b) What assumption was made in the derivation of the equation for that may not be valid in for the calculation of the solution in a)? How would the calculated wp for the 0.05 µm particles change if we did not use that assumption? No need to calculate the value of wp. just describe the direction of its change (e.g., increases or decreases). c) Assuming the collection plates of the ESP are 3 m tall and 1 m long in the direction of gas flow and the gas velocity is 1.2 m/s. What is the graded collection efficiency of this ESP for the particle diameters in question a)? d) There are several modifications we could make to the ESP design to improve its collection efficiency. List one of those modifications and one tradeoff for implementing that change. (Multiple answers can be correct as long as you justify them). Solution hints -Capo K Ech Eco (Equ. 10 in reading notes) and follow the steps as in 3μ a) Use equation w = similar solved example problem (week 5). b) Check Rec and then calculate collection efficiency accordingly.


12.1


12.4


1. (4 pts) You are asked to evaluate a stack that is emitting PM2.5 at a rate of 220 g/s. The stack is located in an urban area where the surface wind speed is 3 m/s. The stack has an effective stack height of 80 m, and an actual stack height of 50 m. Calculate the ground-level concentration of the pollutant (µg/m³) on a cloudy summer day: a) 800 m directly downwind b) 5,000 m directly downwind


(1 pt) A stack has an effective stack height of 150 m and is emitting PM10 at a rate of 175 g/son a cloudy night with Class D conditions. The wind speed at stack height is 7.6 m/s. Using Figure 20.9, estimate the maximum downwind ground-level concentration (µg/m³) and the distance at which it occurs (m).


5. (3 pts) A student with an active SARS-CoV-2 (Covid-19 coronavirus) infection walks into a classroom without a mask. Prior to the student entering the classroom, the air is free from SARS-CoV-2 viral particles. The student is emitting 1,000,000 viral particles per hour. The classroom has a floor size of 8 m by 7 m, and a ceiling height of 3 m. Assume that there areno other sources of SARS-CoV-2 in the building, that the concentration of SARS-CoV-2 in the outdoor air is zero, and that there is no decay of the virus within the building. The air flow rate coming into the building (infiltration) and leaving the building (exfiltration) is 630m³/hour. a) Calculate the steady-state concentration of viral particles in the classroom if all conditions remain constant (viral particles/m³). b) Assume the viral particle concentration threshold for someone else in the room to catch Covid-19 is 200 viral particles per m³. How long would it take following the entry of the infected student for another student to catch the virus (in minutes)?


Assuming air contains 20% by volume 0; and 80% N3, for combustion of 100 standard cubic feet per minute (sefm) of methane (CH.4) in air. \mathrm{CH}_{4}+2 \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}+2 \mathrm{H}_{0} \mathrm{O} The stoichiometric amount of O; needed for a complete combustion (in scfm) (b) The stoichiometric amount of air needed for a complete combustion (in sefm) (c) The stoichiometric mixture by volume (in % methane in the stoichiometric mixture) (d) The A/F ratio (in a mass/mass ratio)


3. List two active MSWS that are closest to CSU Fullerton. List three closed MSWS that areclosest to CSU Fullerton


Check the answer to problem 3 using Equation 20.6.


1. Which of the following media contains the largest amount of toluene, CeHsCH3 (show your calculations)? (a) 1 million gallons of water containing 5 ppm of toluene (b) 100 cubic meters of soils (bulk density = 1.8 g/cu. cm) with 5 ppm of toluene (c) An empty warehouse (30 m x 15 m x 10 m) with 5 ppmV toluene in air (P = 1 atm and T20 °C).


(1 pt) At an air pollution monitoring station that averages collected data over a 10-minute period, you measure a carbon monoxide concentration of 28 ppm. If the NAAQS secondary standard for CO is 35 ppm with an averaging time of 1 hour, does this location meet the NAAQS secondary standard? Show your work.


5. Briefly introduce Puente Hills Landfills and its closure in 150 - 200 words.


2. From the elemental analysis, a waste mixture contains 15% by weight of ash, and the other portion of the mixture can be represented by a chemical formula of C600h1000O400N10s (a) Use Dulong's formula to estimate the heating value of this waste mixture in Btu/lb,assuming the ash has no heating value. (b) Convert the heating value of the heat mixture into million Btu/ton (c) Use the conversion factors between Btu and kJ and between Ib and kg to convert the heating value of the waste mixture into MJ/kg


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