Sugarcane juice can be thought of as a solution of water & sucrose (a disaccharide of glucose & fructose, C12H22O11). Let us look at a material balance around a batch fermenter for sugarcane juice. Consider the following: • The sugarcane juice is 15 wt% sucrose. At this concentration, the specific gravity is 1.061. • Each fermenter is 380 m³ batch fermenter filled to 80% at the beginning of the fermentation. The fermentation is carried out long enough to consume 90% of the sucrose and convert to ethanol. Another 5% is consumed for cell growth (assume this is just sucrose consumption with no water consumption or production). The final 5% is unreacted. The overall cycle time is 72 hours. This is the total time between start of fermentation, end of fermentation, emptying, cleaning, & refilling.) Determine the following: a) The chemical reaction given in the textbook (Example 14.1) is not fully balanced. Present a fully balanced reaction to account for sucrose being fermented to ethanol & CO2. b) Based on the specific gravity of the sugarcane juice what is the effective liquid specific gravity of sucrose? (Consider that the density for the solid is 1.6 g/cm³; you would expect the effective liquid density to be similar but not necessarily the same.) c) Using specific gravity of the sugarcane juice, how much sucrose & water is charged to the fermenter (in both kg & kmole)? What is the sugar concentration at the beginning of the fermentation (in kg sucrose per m³ solution)? d) Assume that at the end of the fermentation the liquid only contains water, ethanol, & residual sucrose; consider the produced CO2 is fully evolved to the gas phase & stripped from the fermentation broth (but only the CO2 goes to the gas & none of the ethanol). How much ethanol & CO2 are created during the fermentation (in kg & kmole)? What are the mass fractions of ethanol, water, & sucrose in the fermentation broth at the end of the fermentation? e) What is the volume of the broth at the end of the fermentation (in m³)? Consider an ideal liquid solution for the volume of ethanol (specific gravity 0.789), water, & residual sucrose (use effective liquid specific gravity found previously). What is the volumetric fraction of ethanol in the water? f) What is the time-average production rate of ethanol (in m³/day)? g) If we want to produce 110 m³/day of ethanol, then how many fermenters are needed?
Sugarcane juice can be thought of as a solution of water & sucrose (a disaccharide of glucose & fructose, C12H22O11). Let us look at a material balance around a batch fermenter for sugarcane juice. Consider the following: • The sugarcane juice is 15 wt% sucrose. At this concentration, the specific gravity is 1.061. • Each fermenter is 380 m³ batch fermenter filled to 80% at the beginning of the fermentation. The fermentation is carried out long enough to consume 90% of the sucrose and convert to ethanol. Another 5% is consumed for cell growth (assume this is just sucrose consumption with no water consumption or production). The final 5% is unreacted. The overall cycle time is 72 hours. This is the total time between start of fermentation, end of fermentation, emptying, cleaning, & refilling.) Determine the following: a) The chemical reaction given in the textbook (Example 14.1) is not fully balanced. Present a fully balanced reaction to account for sucrose being fermented to ethanol & CO2. b) Based on the specific gravity of the sugarcane juice what is the effective liquid specific gravity of sucrose? (Consider that the density for the solid is 1.6 g/cm³; you would expect the effective liquid density to be similar but not necessarily the same.) c) Using specific gravity of the sugarcane juice, how much sucrose & water is charged to the fermenter (in both kg & kmole)? What is the sugar concentration at the beginning of the fermentation (in kg sucrose per m³ solution)? d) Assume that at the end of the fermentation the liquid only contains water, ethanol, & residual sucrose; consider the produced CO2 is fully evolved to the gas phase & stripped from the fermentation broth (but only the CO2 goes to the gas & none of the ethanol). How much ethanol & CO2 are created during the fermentation (in kg & kmole)? What are the mass fractions of ethanol, water, & sucrose in the fermentation broth at the end of the fermentation? e) What is the volume of the broth at the end of the fermentation (in m³)? Consider an ideal liquid solution for the volume of ethanol (specific gravity 0.789), water, & residual sucrose (use effective liquid specific gravity found previously). What is the volumetric fraction of ethanol in the water? f) What is the time-average production rate of ethanol (in m³/day)? g) If we want to produce 110 m³/day of ethanol, then how many fermenters are needed?
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:Sugarcane juice can be thought of as a solution of water & sucrose (a disaccharide of glucose &
fructose, C12H22O11). Let us look at a material balance around a batch fermenter for sugarcane juice.
Consider the following:
• The sugarcane juice is 15 wt% sucrose. At this concentration, the specific gravity is 1.061.
•
Each fermenter is 380 m³ batch fermenter filled to 80% at the beginning of the
fermentation.
The fermentation is carried out long enough to consume 90% of the sucrose and convert to
ethanol. Another 5% is consumed for cell growth (assume this is just sucrose consumption
with no water consumption or production). The final 5% is unreacted.
The overall cycle time is 72 hours. This is the total time between start of fermentation, end
of fermentation, emptying, cleaning, & refilling.)
Determine the following:
a) The chemical reaction given in the textbook (Example 14.1) is not fully balanced. Present a
fully balanced reaction to account for sucrose being fermented to ethanol & CO2.
b) Based on the specific gravity of the sugarcane juice what is the effective liquid specific
gravity of sucrose? (Consider that the density for the solid is 1.6 g/cm³; you would expect
the effective liquid density to be similar but not necessarily the same.)
c) Using specific gravity of the sugarcane juice, how much sucrose & water is charged to the
fermenter (in both kg & kmole)? What is the sugar concentration at the beginning of the
fermentation (in kg sucrose per m³ solution)?
d) Assume that at the end of the fermentation the liquid only contains water, ethanol, &
residual sucrose; consider the produced CO2 is fully evolved to the gas phase & stripped
from the fermentation broth (but only the CO2 goes to the gas & none of the ethanol). How
much ethanol & CO2 are created during the fermentation (in kg & kmole)? What are the
mass fractions of ethanol, water, & sucrose in the fermentation broth at the end of the
fermentation?
e) What is the volume of the broth at the end of the fermentation (in m³)? Consider an ideal
liquid solution for the volume of ethanol (specific gravity 0.789), water, & residual sucrose
(use effective liquid specific gravity found previously). What is the volumetric fraction of
ethanol in the water?
f) What is the time-average production rate of ethanol (in m³/day)?
g) If we want to produce 110 m³/day of ethanol, then how many fermenters are needed?
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