What if… you were asked to explore the example problems in this chapter to learn the effects of varying the different parameters? This sensitivity analysis can be carried out by either downloading the examples from the web or by loading the programs from the CD-ROM supplied with the text. For each of the example problems you investigate, write a paragraph describing your findings.
(a) What if you were asked to give examples of the material in this book that are found in everyday life? What would you say? Before solving the problems, state or sketch qualitatively the expected results or trends.
(b) Example 4–1. What would be the error in k if the batch reactor were only 80% filled with the same concentrations of reactants instead of being completely filled as in the example? What generalizations can you draw from this example?
(c) Example 4–2. How would your reactor volume change if you only needed 50% conversion to produce the 200 million pounds per year required? What generalizations can you draw from this example?
(d) Example 4–3. What would be the reactor volume for X = 0.8 if the pressure were increased by a factor of 10 assuming everything else remains the same? What generalizations can you draw from this example?
(e) Example 4–4. How would the pressure drop change if the particle diameter were reduced by 25%? What generalizations can you draw from this example?
(f) Example 4–5. What would be the conversion with and without pressure drop if the entering pressure were increased by a factor of 10? Would the optimum diameter change? If so, how? What would the conversion be if the reactor diameter were decreased by a factor of 2 for the same mass flow rate?
(g) Example 4–6. Load the Living Example Problem 4–6 from the CD-ROM. How much would the catalyst weight change if the pressure was increased by a factor of 5 and the particle size decreased by a factor of 5 (recall α is also a function of P0)7 Use plots and figures to describe what you find.
(h) Example 4–7. Load the Living Example Problem 4–7 from the CD-ROM. How would the results change if the pressure were doubled and the temperature was decreased 20 °C?
(i) Example 4–8. Load the Living Example Problem 4–8 from the CD-ROM. Vary parameters (e.g., kc), and ratios of parameters (k/kc), (kiCM)/Ke), etc., and write a paragraph describing what you find. What ratio of parameters has the greatest effect on the conversion X = (fA0 — FA)/FM ?
(j) Example 4–9. Load the Living Example Problem 4–9 from the CD-ROM. The temperature is to be lowered by 35 °C so that the reaction rate constant is now (1/10) its original value, (i) If the concentration of B is to be maintained at 0.01 mol/dm3 or below, what is the maximum feed rate of B? (ii) How would your answer change if the concentration of A were tripled?
(k) Web Module on Wetlands from the CD-ROM. Load the Polymath program and vary a number of parameters such as rainfall, evaporation rate, atrazine concentration, and liquid flow rate, and write a paragraph describing what you find. This topic is a hot Ch.E. research area.
(I) Web Module on Reactive Distillation from the CD-ROM. Load the Polymath program and vary the parameters such as feed rate and evaporation rate, and write a paragraph describing what you find.
(m) Web Module on Aerosol Reactors from the CD-ROM. Load the Polymath program and (1) vary the parameters such as cooling rate and How rate, and describe their effect on each of the regimes: nucleation, growth and flocculation. Write a paragraph describing what you find. (2) It is proposed to replace the carrier gas by helium
(i) Compare your plots (He versus Ar) of the number of A1 particles as a function of time. Explain the shape of the plots.
(ii) How does the final value of dp compare with that when the carrier gas was argon? Explain.
(iii) Compare the time at which the rate of nucleation reaches a peak in the two cases [carrier gas = Ar and He]. Discuss the comparison.
Data for a He molecule: Mass = 6.64 x 10−27 kg, Volume = 1.33 x 10−29 m3, Surface area = 2.72 x 1019 m2, Bulk density = 0.164 kg/m3, at normal temperature (25 °C) and pressure (1 atm).
(n) Vary some of the operating costs, conversions, and separations in Figure 4–10 to learn how the profit changes. Ethylene oxide, used to make ethylene glycol, sells for $0.56/lb„ while ethylene glycol sells for $0.38/lbm. Is this a money-losing proposition? Explain, (o) What should you do if some of the ethylene glycol splashed out of the reactor onto your face and clothing? (Hint: Recall www.siri.org) (p) What safety precautions should you take with the ethylene oxide formation discussed in Example 4-6? With the bromine cyanide discussed in Example 4-9?
(q) Load reactor lab on to your computer and call up D1 Isothermal Reactors. Detailed instructions with screen shots are given in Chapter 4 of the Summary Notes. (1) For LI Nth Order Reactions. Vary the parameters n, E, T for a batch, CSTR, and PFR. Write a paragraph discussing the trends (e.g., first order versus second order) and describe what you find. (2) Next choose the “Quiz” on membrane at the top of the screen, and find the reaction order (3) and turn in your performance number.
Performance number:---------------
(r) The Work Self Tests on the Web. Write a question for this problem that involves critical thinking and explaining why it involves critical thinking. See examples on the Web Summary Note for Chapter
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