Elementary Principles of Chemical Processes, Binder Ready Version
Elementary Principles of Chemical Processes, Binder Ready Version
4th Edition
ISBN: 9781118431221
Author: Richard M. Felder, Ronald W. Rousseau, Lisa G. Bullard
Publisher: WILEY

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Chapter 9, Problem 9.21P

Ethyl alcohol (ethanol) can be produced by the fermentation of sugars derived from agricultural products such as sugarcane and com. Some countries without large petroleum and natural gas reserves—such as Brazil—have found it profitable to convert a portion of their agricultural output to ethanol for fuel or for use as a feedstock in the synthesis of other chemicals.

In one such process, a portion of the starch in com is converted to ethanol in two consecutive reactions. In a saccharification reaction, starch decomposes in the presence of certain enzymes (biological catalysts) to form an aqueous mash containing maltose (C12H22O11, a sugar) and several other decomposition products. The mash is cooled and combined with additional water and a yeast culture in a batch fermentation tank (fermentor). In the fermentation reaction (actually a complex series of reactions), the yeast culture grows and in the process converts maltose to ethanol and carbon dioxide:

   C 12 H 22 O 11 + H 2 O 4 C 2 H 5 O H + 4 C O 2

The fermentor is a 550,000 gallon tank filled to 90% of its capacity with a suspension of mash and yeast in water. The mass of the yeast is negligible compared to the total mass of the tank contents. Thermal energy is released by the exothermic conversion of maltose to ethanol. In an adiabatic operating stage, the temperature of the tank contents increases from an initial value of 85°F to 95°F. and in a second stage the temperature is kept at 95°F by a reactor cooling system. The final reaction mixture contains carbon dioxide dissolved in a slurry containing 7.1 wt% ethanol, 6.9 wt% soluble and suspended solids, and the balance water. The mixture is pumped to a flash evaporator in w hich CO2is vaporized, and the ethanol product is then separated from the remaining mixture components in a series of distillation and stripping operations. Data

• One bushel (56 Ibm) of com yields 25 gallons of mash fed to the fermentor, which in turn yields 2.6 gallons of ethanol. Roughly 101 bushels of com is harvested from an acre of land.

  1. A batch fermentation cycle (charging the fermentation tank, running the reaction, discharging the tank, and preparing the tank to receive the next load) takes eight hours. The process operates 24 hours per day, 330 days per year.
  2. The specific gravity of the fermentation reaction mixture is approximately constant at 1.05. The average heat capacity of the mixture is 0.95 Btu/(Ibm·°F).
  3. The standard heat of combustion of maltose to form CO 2(g) and H 2 O ( l ) is Δ H ^ c ° = 5649 k J / m o l .

  • Calculate (i) the quantity of ethanol (Ibm) produced per batch, (ii) the quantity of water (gal) that must be added to the mash and yeast in the fermentation tank, and (iii) the acres of land that must be harvested per year to keep the process running.
  • Calculate the standard heat of the maltose conversion reaction, Δ H r ° (Btu).

  • Estimate the total amount of heat (Btu) that must be transferred from the fermentor during the reaction period. Take only the maltose conversion into account in this calculation (i.e., neglect the yeast growth reaction and any other reactions that may occur in the fermentor), assume that the heat of reaction is independent of temperature in the range from 77°F (= 25°C) to 95°F, and neglect the heat of solution of carbon dioxide in water.
  • Although Brazil and Venezuela are neighboring countries, producing ethanol from grain for use as a fuel is an important process in Brazil and an almost nonexistent one in Venezuela. What difference between the two countries probably accounts for this observation?
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    Chapter 9 Solutions

    Elementary Principles of Chemical Processes, Binder Ready Version

    Ch. 9 - Prob. 9.11PCh. 9 - Prob. 9.12PCh. 9 - In the production of many microelectronic devices,...Ch. 9 - Prob. 9.14PCh. 9 - Prob. 9.15PCh. 9 - Prob. 9.16PCh. 9 - Prob. 9.17PCh. 9 - Carbon monoxide at 25°C and steam at 150°C are fed...Ch. 9 - Prob. 9.19PCh. 9 - Prob. 9.20PCh. 9 - Ethyl alcohol (ethanol) can be produced by the...Ch. 9 - Prob. 9.22PCh. 9 - Prob. 9.23PCh. 9 - Prob. 9.24PCh. 9 - Formaldehyde is produced commercially by the...Ch. 9 - Prob. 9.26PCh. 9 - Prob. 9.27PCh. 9 - Prob. 9.28PCh. 9 - Prob. 9.29PCh. 9 - A gas mixture containing 85 mole% methane and the...Ch. 9 - Ethylene oxide is produced by the catalytic...Ch. 9 - Cumene (C6H5C3H7) is produced by reacting benzene...Ch. 9 - Ethylbenzene is converted to styrene in the...Ch. 9 - Prob. 9.34PCh. 9 - Prob. 9.35PCh. 9 - Prob. 9.36PCh. 9 - Prob. 9.37PCh. 9 - Coke can be converted into CO—a fuel gas—in the...Ch. 9 - Prob. 9.39PCh. 9 - Prob. 9.40PCh. 9 - Prob. 9.41PCh. 9 - The equilibrium constant for the ethane...Ch. 9 - You are checking the performance of a reactor in...Ch. 9 - Hydrogen is produced in the steam reforming of...Ch. 9 - Prob. 9.45PCh. 9 - Five cubic meters of a 1.00-molar aqueous sulfuric...Ch. 9 - Prob. 9.47PCh. 9 - Prob. 9.48PCh. 9 - Prob. 9.49PCh. 9 - Calcium chloride is a salt used in a number of...Ch. 9 - A dilute aqueous solution of sulfuric acid at 25°C...Ch. 9 - A 2.00 mole% sulfuric acid solution is neutralized...Ch. 9 - A 12.0-molar solution of sodium hydroxide (SG =...Ch. 9 - Citric acid (C6H8O7) is used in the preparation of...Ch. 9 - Ammonia scrubbing is one of many processes for...Ch. 9 - Various uses for nitric acid are given in Problem...Ch. 9 - A natural gas is analyzed and found to consist of...Ch. 9 - Prob. 9.58PCh. 9 - A fuel gas is known to contain methane, ethane,...Ch. 9 - A fuel gas containing 85.0 mole% methane and the...Ch. 9 - A mixture of air and a fine spray of gasoline at...Ch. 9 - The heating value of a fuel oil is to be measured...Ch. 9 - Methanol vapor is burned with excess air in a...Ch. 9 - Methane at 25°C is burned in a boiler furnace with...Ch. 9 - Methane is burned completely with 40% excess air....Ch. 9 - A gaseous fuel containing methane and ethane is...Ch. 9 - A coal contains 73.0 wt% C, 4.7% H (not including...Ch. 9 - A mixture of methane, ethane, and argon at 25°C is...Ch. 9 - Prob. 9.69PCh. 9 - Prob. 9.70PCh. 9 - Prob. 9.71PCh. 9 - A bituminous coal is burned with air in a boiler...Ch. 9 - Prob. 9.73PCh. 9 - A natural gas containing 82.0 mole% CH4and the...Ch. 9 - Prob. 9.75PCh. 9 - Liquid n-pentane at 25°C is burned with 30% excess...Ch. 9 - Methane is burned with 25% excess air in a...Ch. 9 - Methane and 30% excess air are to be fed to a...Ch. 9 - Prob. 9.79PCh. 9 - In Problem 9.79, the synthesis of methanol from...Ch. 9 - Natural gas that contains methane, ethane, and...Ch. 9 - Prob. 9.82PCh. 9 - The wastewater treatment plant at the Ossabaw...

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