2.4 You wish to design a plant to produce 100 tons/day of ethylene glycol from ethane, air, and water. The plant has three reactor stages, ethane dehydrogenation, ethylene oxidation, and ethylene oxide hydration. (a) What are the reactions? (b) Both dehydrogenation and hydration have nearly 100% selectivity (with recycle of unre- acted reactants), but ethylene to ethylene oxide has only 70% selectivity with an old catalyst and 90% selectivity with a new and expensive catalyst. How many tons/day of ethane do we need to supply to this plant with each of these catalysts? (c) Ethylene to EO has a heat of reaction of -25 kcalfmole, and the undesired byproducts are exclusively CO2 and H2O. [You can look up the heat of combustion of ethylene.] What is the rate of heat removal in watts with the two catalysts? (d) If all this heat is used to produce low-pressure steam (from 25°C at 1 atm), approximately how many tons of steam per day can be produced? (e) Could the heat from this reaction be used to provide heat in the other two reactions? Where else could it be used? (f) Sketch a flow diagram of this plant including reactors and separation units.
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A fuel gas containing 95 mole\% methane and the balance ethane is burned completely with 25\% excess air. The stack gas leaves the furnace at $900^{\circ} \mathrm{C}$ and is cooled to $450^{\circ} \mathrm{C}$ in a waste-heat boiler, a heat exchanger in which heat lost by cooling gases is used to produce steam from liquid water for heating, power generation, or process applications. (a) Taking as a basis of calculation 100 mol of the fuel gas fed to the fumace, calculate the amount of heat (kJ) that must be transferred from the gas in the waste heat boiler to accomplish the indicated cooling. (b) How much saturated steam at 50 bar can be produced from boiler feedwater at $40^{\circ} \mathrm{C}$ for the same basis of calculation? (Assume all the heat transferred from the gas goes into the steam production.) (c) At what rate ( $k$ mol/s) must fuel gas be burned to produce 1280 kg steam per hour (an amount required elsewhere in the plant) in the waste heat boiler? What is the volumetric flow rate $\left(\mathrm{m}^{3} / \mathrm{s}\right)$ of the gas leaving the boiler? (d) Briefly explain how the waste-heat boiler contributes to the plant profitability. (Think about what would be required in its absence.)
Currently, Perlis Power Plant is supplying electricity in Perlis. In order to generate electricity, the coals are fired inside the combustion chambers. One of the combustion chambers in this plant is fed with a fuel gas containing 20.0 mole% methane and the balance ethane is completely burned with 25.0% excess air. The combustion reactions for this process are shown below: CH4 + 2O2 → CO2 + 2H2O C2H6 + 7/2 O2 → 2CO2 + 3H2O The gases leave the combustion chamber at 900°C and are cooled to 450°C in a waste heat boiler, in which the heat from the gases is used to produce steam from liquid water. The temperature of the water fed (liquid) to the waste heat boiler is 40°C. (a) Draw and completely label a flowchart of this process. (b) Taking a basis of 100.0 mol of fuel gas fed to the combustion chamber, calculate the moles of gases out from this chamber. (c) Evaluate the amount of heat (kJ) that must be transferred from the gas to the water in the waste heat boiler to accomplish the indicated cooling. (d) How much saturated steam at 50.0 bar can be produced from the same basis of calculation? (Assume all the heat transferred from the gas goes into the steam production.)
Adi S.
A 2.20 g sample of the Ethane C2H6 gas was mixed with excess oxygen gas and a combustion reaction occurred to obtain water in liquid aggregate and carbon dioxide state. The combustion reaction occurred at a constant calorimeter under standard conditions. After the reaction was completed, the temperature in the calorimeter rose by 1.3 K. The heat capacity of the calorimeter is 88.8 kJ/K. 1. Write a balanced response to the burning process that took place. 2. Consider the change in standard enthalpy, ΔH, for a 1 molar reaction of ethane. Show calculations. 3. Explain how you would calculate ΔHf for C2H6(g) given the values of: ΔHf for CO2(g) ΔHf for H2O(g) Numerical calculations are not required. 4. Determine what the missing data is to calculate the change in the fire enthalpy, ΔHc, of ethane at 100°C. 5. Is a difference between ΔHo and ΔUo expected for the reaction formulated in section a? Explain.
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