Title: 7.3b How Corn is Processed to Make Ethanol | EGEE 439: Alternative Fuels from Biomass Sources
Headings: 7.3b How Corn is Processed to Make Ethanol
7.3b How Corn is Processed to Make Ethanol
7.3b How Corn is Processed to Make Ethanol
Click here for a text alternative to figure 7.10a
Click here for a text alternative to figure 7.10b
Grinding
Figure 7.11: Hammermill for dry grinding of corn.
Cooking and Liquefaction
Figure 7.12: Corn starch mixed with water is being poured into a sauce mixture; as it heats, it will thicken to form a sauce or gravy.
Figure 7.13: The three option types for liquefaction processing of corn mash.
Click here for a text alternative to figure 7.13
Three processes
Process Type 1
α-amylase added; incubated at 85-95ºC
Process Type 2
Jet cooker 105-120ºC for 2-7 minutes
Flash Tank to 90ºC; add α-amylase for 3 hours
Process Type 3
α-amylase added
Heating/Jet cooking @ 150ºC
Flash tank to 90ºC ; add more α-amylase
Credit: BEEMS Module B5
Click here for a text alternative to figure 7.14a
Figure 7.14b: Schematic of a β-amylase.
Saccharification
Figure 7.14c: Schematic of a glucoamylase (aka a ϒ-amylase).
Table 7.2: Different enzymes used in starch depolymerization. (Credit: MF Chaplin and C. Bucke, Enzyme Technology, Cambridge University Press, 1990)
Fermentation
Distillation and Increase of Ethanol Concentration
Figure 7.15: Distillation unit for increasing concentration of ethanol.
Figure 7.16a: The first unit is the dehydrator to remove water while the second unit is having the water removed.
Click here for a text alternative to figure 7.16a
The diagram shows 95% EtOH vapor from distillation going into Unit 1: a high pressure dehydrating bed. Out of that 60-85%, EtOH goes to the final product while 15-40% of the EtOH enters unit 2, a low-pressure vacuum regenerating bed. Out of this, the wet EtOH Vapor goes back to distillation.
Credit: BEEMS Module B5
Figure 7.16b: The units switch places because the second bed of zeolite had the moisture removed and now acts as a dehydrator.
Figure 7.17: How the sieve works to keep water in and ethanol out.
Figure 7.18a: Product recovery diagram of ethanol and other products.
Click here for a text alternative to figure 7.18a
Product recovery diagram of ethanol and other products. From fermentation, CO 2 is recovered along with Beer: 12-13% Ethanol. From there distillation occurs. This recovers 95% ethanol which goes through a molecular sieve to become 100% ethanol and goes into denatured ethanol storage with gasoline. From distillation whole stillage is also recovered. This goes into separation/centrifugation and yields thin stillage and WDG. The thin stillage is either recycled or it goes into the evaporator and becomes syrup. The WDG and syrup are combined to become WDGS. The WDGS goes into the dry and becomes DDGS.
Credit: BEEMS Module B5
Figure 7.18b: Product separation/recovery terminology.
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The image defines terminology.
Whole Stillage (waste liquid from distillation) goes to centrifuge or filter presses.
Thin Stillage (liquid from centrifuge) is recycled or evaporated to make
Syrup (solubles) which are added to the
WDG (Wet distillers grains) which are then dried to make
DDGS (Distiller Dried Grains with Solubles)
Credit: BEEMS Module B5

Content: A screen at the bottom allows particles that are small enough to leave the unit and keep in the larger particles to continue to be hammered until all the material is in the correct size range. The grinding helps to break the tough outer coatings of the corn kernel, which will increase the surface area of the starch. Once the corn is broken down, it is mixed/ slurried with heated water to form a mash or slurry. Figure 7.11: Hammermill for dry grinding of corn. Credit: Feed Machinery
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Cooking and Liquefaction
Once the corn slurry (mash) is made, it goes through cooking and liquefaction. The cooking stage is also called gelatinization. Water interacts with the starch granules in the corn when the temperature is >60°C and forms a viscous suspension. Have you ever cooked with cornstarch to make thick gravy?