Membrane and Desalination Technologies - TCE Moodle Website

262 L.K. Wang et al.
Electrode
Rinsing
Solution
Concentrating Solution
K K K
A A A
Cl –
Cl –
+
+
H
H
Raw Solution
C D C D C
(a) concentration of CD before spray-drying for energy and cost-saving; and (b) recycling of
NF permeate for reuse in the fermentation reactor, in turn, for the elimination of wastewater
discharge (37).
5.7. Production of Ethanol from Food Materials Using UF, Fermentation,
CMR, and MF
H +
Cl –
K: Cation-exchange Membrane
A: Anion-exchange Membrane
C: Concentration Cell
D: Dilution Cell
There is need to increase the utilization of agricultural crops in many developed countries
to reduce surpluses and improve the farm economy, rather than flooding the world with
surplus grains. In many cases, the surplus grains become solid waste.
A great deal of interest today is focused on ethanol production by the fermentation of
biomass which includes: (a) starch materials such as corn, wheat, barley, and potatoes; (b)
saccharine materials such as sugar cane, sugar beets, molasses, and fruits; and (c) cellulose
materials such as wood, corn stalks, straw, and other agricultural biomass.
In the conventional fermentation process shown in Fig. 6.23, the starch materials, such as
corn, wheat, and potatoes, must be converted to fermentable sugars by cooking with enzymes.
The pretreated fermentable sugars are then fed into a fermentation reactor where yeast, acid,
and enzyme are added and ethanol and carbon dioxide gas are produced.
When saccharines, such as sugarcane, beets, and molasses are used as feedstock to an
ethanol production system, the saccharine materials can be converted by yeast into ethanol
and carbon dioxide gas directly in the fermentation reactor without a preliminary enzymatic
cooking treatment. On the other hand, when cellulose materials, such as wood, corn stalks,
hay, and straw, are used as feedstock, the cellulose must be broken down to fermentable
Cl –
H +
Diluting Solution
Cl –
Electrode
Rinsing
Solution
Concentrating Solution
Fig. 6.22. Electrodialysis system using both cation- and anion-exchange membranes.