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Textbook: Introduction to Environmental Engineering (3rd Edition) Chapter 1.2, Problem 1DQ3 Some years after the Donora episode, the local paper lamented that “The best we can hope is that people will soon forget about the Donora episode.” Why did the editors of the paper feel that way? Why did they not want people to remember the episode? (3-4 detailed and explained sentences please) 1.2.3 The Donora Episode It was a typical Western Pennsylvania fall day in 1948, cloudy and still. ${ }^{6}$ The residents of Donora, a small mill town on the banks of the Monongahela River, did not pay much attention to what appeared to be a particularly smoggy atmosphere. They had seen worse. Some even remembered days when the air was so thick that streamers of carbon would actually be visible, hanging in the air like black icicles. So the children's Halloween parade went on as scheduled, as did the high school football game Saturday afternoon, although the coach of the opposing team vowed to protest the game. He claimed that the Donora coach had contrived to have a pall of smog stand over the field so that, if a forward pass were thrown, the ball would completely disappear from view and the receivers would not know where it would reappear. But this was different from the usual smoggy day. By that night 11 people were dead, and ten more were to die in the next few hours. The smog was so thick that the doctors treating patients would get lost going from house to house. By Monday almost half the people in the small town of 14,000 were either in hospitals or sick in their own homes with severe headaches, vomiting, and cramps. Pets suffered most, with all the canaries and most of the dogs and cats dead or dying. Even houseplants were not immune to the effects of the smog. There were not enough emergency vehicles or hospitals able to assist in a catastrophe of this magnitude, and many people died for lack of immediate care. Firefighters were sent out with tanks of oxygen to do what they could to assist the most gravely ill. They did not have enough oxygen for everyone, so they gave people a few breaths of oxygen and went on to assist others. When the atmosphere finally cleared on 31 October, six days of intense toxic smog had taken its toll, and the full scope of the episode (as these air quality catastrophies came to be known) became evident. The publicity surrounding Donora ushered in a new awareness and commitment to control air quality in our communities. Health workers speculated that, if the smog had continued for one more night, almost 10,000 people might have died. What is so special about Donora that made this episode possible? First, Donora was a classical steel belt mill town. Three large industrial plants were on the river-a steel plant, a wire mill, and a zinc plant for galvanizing the wire-the three together producing galvanized wire. The Monongahela River provided the transport to world markets, and the availability of raw materials and dependable labor (often imported from eastern Europe) made this a most profitable venture. During the weekend when the air quality situation in town became critical, the plants did not slow down production. Apparently, the plant managers did not sense that they were in any way responsible for the condition of the citizens of Donora. Only Sunday night, when the full extent of the tragedy became known, did they shut down the furnaces. Second, Donora sits on a bend in the Monongahela River, with high cliffs to the outside of the bend, creating a bowl with Donora in the middle (Figure 1.2 on the next page). On the evening of 25 October, 1948, an inversion condition settled into the valley. This meteorological condition, having itself nothing to do with pollution, simply limited the upward movement of air and created a sort of lid on the valley. Pollutants emitted from the steel plants thus could not escape and were trapped under this lid, producing a steadily increasing level of contaminant concentrations. Chapter 1 Identifying and Solving Environmental Problems (A) Figure 1.2 Donora was a typical steel town along the Monongahela River, south of Pittsburgh, with (A) high cliffs creating a bowl and (B) three steel mills producing the pollutants. The steel companies insisted that they were not at fault, and indeed there never was any fault implied by the special inquiry into the incident. The companies were operating within the law and were not coercing any of the workers to work in their plants or anyone to live in Donora. In the absence of legislation, the companies felt no obligation to pay for air pollution equipment or to change processes to reduce air pollution. They believed that, if only their companies were required to pay for and install air pollution control equipment, they would be at a competitive disadvantage and would eventually go out of business. The tragedy forced the State of Pennsylvania and eventually the U.S. government to act and was the single greatest impetus to the passage of the Clean Air Act of 1955, although it wasn't until 1972 that effective federal legislation was passed. In Donora and nearby Pittsburgh, however, there was a sense of denial. Smoke and poor air quality constituted a kind of macho condition that meant jobs and prosperity. The Pittsburgh press gave the news of the Donora tragedy equal billing to a prison breakout. Even in the early 1950 s 1.2 Case Studies 15 (B) Figure 1.2 Continued. there was a fear that, if people protested about pollution, the plants would close down and the jobs would disappear. And indeed, the zinc plant (thought to be the main culprit in the formation of the toxic smog) shut down in 1957, and the other two mills closed a decade later. Donora, however, lives on as the location of the single most significant episode that put into motion our present commitment to clean air. Discussion Questions 1. Some years after the Donora episode, the local paper lamented that "The best we can hope is that people will soon forget about the Donora episode." Why did the editors of the paper feel that way? Why did they not want people to remember the episode?

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Construct a process flow diagram for the methylene chloride production process according to the process description given below: Methane reacts with chlorine to produce methyl chloride and hydrogen chloride. Once formed, the methyl chloride may undergo further chlorination to form methylene chloride (CH2Cl2), chloroform, and carbon tetrachloride. A methyl chloride production process consists of a reactor, a condenser, a distillation column, and an absorption column. A gas stream containing 80.0 mole% methane and the balance chlorine is fed to the reactor. In the reactor a single-pass chlorine conversion of essentially 100% is attained, the mole ratio of methyl chloride to methylene chloride in the product is 5:1, and negligible amounts of chloroform and carbon tetrachloride are formed. The product stream flows to the condenser. Two streams emerge from the condenser: the liquid condensate, which contains essentially all of the methyl chloride and methylene chloride in the reactor effluent, and a gas containing the methane and hydrogen chloride. The condensate goes to the distillation column in which the two component species are separated. The gas leaving the condenser flows to the absorption column where it contacts an aqueous solution. The solution absorbs essentially all of the HCl and none of the CH4 in the feed. The liquid leaving the absorber is pumped elsewhere in the plant for further processing, and the methane is recycled to join the fresh feed to the process (a mixture of methane and chlorine). The combined stream is the feed to the reactor.

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Consider the reaction below for the production of benzene via homogeneous thermal dealkylation of the toluene in the temperature range of $700{ }^{\circ} \mathrm{C}$ to $950{ }^{\circ} \mathrm{C}$. \[ \begin{array}{l} \mathrm{C}_{7} \mathrm{H}_{8}+\mathrm{H}_{2} \rightarrow \mathrm{C}_{6} \mathrm{H}_{6}+\mathrm{CH}_{4} \\ -r_{\text {tol }}=3 \cdot 10^{10} e^{25,614 / T[K]} C_{T o l} C_{H_{2}}^{0.5}\left[\frac{\mathrm{mol}}{\mathrm{m}^{3}} \cdot \mathrm{s}\right] \\ \end{array} \] Where concentrations of reactants are in $\mathrm{mol} / \mathrm{L}$ reactor and the temperature is in $\mathrm{K}$. The heat of reaction is $-52.0 \mathrm{~kJ} / \mathrm{mol}\left(\right.$ at $900^{\circ} \mathrm{C}$ ) and $-50.5 \mathrm{~kJ} / \mathrm{mol}\left(\right.$ at $\left.700{ }^{\circ} \mathrm{C}\right)$, and the average specific heats of the reactor feed and effluent are $3.3216 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}\left(\right.$ at $\left.950{ }^{\circ} \mathrm{C}\right)$ and $3.042 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}\left(\right.$ at $\left.700{ }^{\circ} \mathrm{C}\right)$. a. If feed enters the reactor at $700{ }^{\circ} \mathrm{C}$ and $25 \mathrm{bar}$, solve the material and energy balances for a plug flow reactor to determine the volume of reactor needed to give $90 \%$ conversion of toluene. Do not use a process simulator for this portion The feed to the reactor comprises $80 \mathrm{kmol} / \mathrm{hr}$ of toluene and $320 \mathrm{kmol} / \mathrm{hr}$ of hydrogen. Plot the conversion and temperature profiles in the reactor versus reactor volume. b) If the reactor above is packed with inert ceramic spheres with a diameter of 5 mm and a bed voidage of 0.45, determine the pressure drop across the reactor. Additionally, the reactor length-to-diameter ratio is now set to 8:1 and you can use an average process gas viscosity of 26.8·10-6 kg/m·s. Average gas density can be calculated using the ideal gas law.

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Phase Diagram The following diagram corresponds to a closed system, comprised of a pure substance. See section 16.11 "Phase Diagrams" in Zumdahl "Chemical Principles" 8th ed., pp 694-699 The letter labels closest to the points marked with a dot refer specifically to those points. The other letter labels refer to the region of the graph in which they lie. Match the following: sublimation occurs -- but no fusion normal gas and/or liquid present at equilibrium -- but no solid normal gas region solid region normal liquid region supercritical fluid region gas, liquid and solid all may be present at equilibrium normal freezing point critical point Take a moment to review your choices above, before submitting! No letter should be chosen more than once. Which of the following solid substances can be liquefied simply by increasing the pressure suffciently? ice $\left(\mathrm{H}_{2} \mathrm{O}\right)$ dry ice $\left(\mathrm{CO}_{2}\right)$ sulfur $(\mathrm{S})$ diamond (C) graphite (C) There is only one known pure substance which, as a liquid, cannot be frozen by cooling alone at 1 atm pressure. Which is it? water $\left(\mathrm{H}_{2} \mathrm{O}\right)$ helium $(\mathrm{He})$ hydrogen $\left(\mathrm{H}_{2}\right)$ nitrogen $\left(\mathrm{N}_{2}\right)$ mercury $(\mathrm{Hg})$ For the substance represented by the above phase diagram, at any point at which the solid and liquid are in equilibrium, which phase is more dense? liquid solid The pressure at point $\mathbf{F}$ is called the critical pressure. is atmospheric pressure. is called the supercritical pressure

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