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Description of Dry Mill Process

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Ethanol is a corn-based alcohol with a

chemical formula of C2H5OH. Because of its

chemical formula, it burns cleaner thangasoline but it is a less efficient fuel. Ethanol

is used as a fuel additive and as an alternative

to gasoline. E10 is a mix of 10% ethanol and90% gasoline. It is used as an alternative toMTBE to prevent engine knocking.

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Engine knocking is damaging to the engine

because the pistons dont run smoothly due

to an explosion in the chamber. The ethanolprevents this by retarding the

combustion. This low amount of ethanol

doesnt affect cars and can be run in any kindof vehicle.

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Ethanol is also mixed as E85, 85% ethanol

and 15% gasoline. This formula is used as an

alternative fuel to reduce the amountgasoline we use. E85 requires a special

engine as it is corrosive and will destroy a

regular engine. Many car companies are nowmaking flex fuel vehicles (FFVs) which can runon either E85 or regular gasoline.

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There are three methods for

creating ethanol: dry milling, wet

milling, and ethanol productionfrom cellulosic biomass. Dry

milling is the most commonproduction method in the UnitedStates.

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Wet milling breaks down the corn andutilizes each part creating many more

byproducts then dry milling. Cellulosicbiomass production is still being

researched but it is expected to be themost energy efficient and cost efficient

method if it reaches mass production.

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Issues like noise, odors, traffic,visual, and economic effects impactthe areas surrounding ethanolplants. These five main issues are

important factors to consider whenchoosing the location of ethanolplants.

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The Clean Fleet Guide is a link toinformation about Flex FuelVehicles.We have researched anddiscussed many of these issues with

representatives from ethanolproduction companies in Indiana,Wisconsin, and Minnesota.

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When looking at the social impacts of an

ethanol plant it is important to think of

where it is located. Location iseverything! If a plant is built within a city

or town, these issues become even more

of a factor. On the other hand if anethanol plant is constructed on the

outskirts of a city or town these are not

much of an issue.

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The majority of corn arrives at the site via rail

car delivered byWisconsin and Southern

Railroad approximately three times per week.Nearby corn arrives by truck. Automated

unloading systems can be self-operated bythe truck driver and the rail cars are typically

unloaded during low truck traffic times.

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A fifteen thousand bushel per hour grain

system screens the corn for rocks and cobs

before being sent to one of two 225,000-bushel storage bins. To begin processing, the

corn is transferred to a "day bin" and meteredto the hammermill by a computer-controlled

weigh belt feeder, then ground andpneumatically conveyed to the slurry tank for

enzymatic processing.

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The addition of water, heat and enzymes

break the ground corn into fine slurry. The

slurry is heated for sterilization and ispumped to a Liquefaction tank where other

enzymes are added to convert the starchesinto glucose sugars. Next the corn slurry is

pumped into one of three fermenters whereyeast is added to begin the forty-eight to fifty

hour batch fermentation process.

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ICM's process utilizes a vacuum distillation

system to divide the alcohol from the corn

mash. Both streams are routed to thedehydration equipment. 145 proof alcohol

exiting the distillation stripper then exits therectifier at 190 proof and is dried to 200 proof

in an ICM designed molecular sieve.

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Mash streams from the distillation stripper

are pumped to one of several decanter type

centrifuges for dewatering. The water, "thinstillage" is pumped to a steam driven

evaporator to produce a thick syrup. Thesolids stream exiting the centrifuge, "wet

cake" are conveyed to the DDG dryer.

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Syrup from the evaporator and wet cake fromthe centrifuge are conveyed to the DDGS naturalgas fired rotary dryer. This unit removes

moisture and produces the golden drieddistillers grains with solubles (DDGS). Multiplepasses produces a ten percent moisture product(DDGS) and one pass drying produces a fiftypercent moisture product (DWG). BSE will havethe capability to produce either product on adaily basis.

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The ten percent DDGS is pneumatically

conveyed to flat storage to cool and readied

for shipment via jumbo rail car or hopperbottom trucks. Fifty percent moisture DWG is

shipped locally via "moving floor" trucks.

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There are two, seven hundred fifty thousand

gallon denatured ethanol storage tanks on

site. The tanks were built to code and utilizethe covered top floating roof design which

incorporates the appropriate relief valves.Additional smaller tanks were erected for

denaturant storage and temporary storage.There are truck and railcar load-out facilities.

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The fermenter produces carbon dioxide gas

that can be processed into salable product.

ICM's design will collect the gases andremove impurities with a packed water

scrubber. Additional transfer fans will need tobe added pending the specifications of the

future CO2 vendor. At this time BSE plans tolook at CO2 recovery as a future venture.

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The principal products produced at our

ethanol plant are ethanol and distiller grains.

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