While it is important to try to be "consistent" with grades, I think we can mostly agree that the point of courses is to educate, rather than demanding compliance to (admittedly artificial, even if self-consistent) rules. If the situation described comes up in the middle of the term, it's awkward to accommodate, because suddenly declaring that students have the option of having their grade determined by just exams could be objected-to on the grounds that if they'd known that, they might not have done the other work... Hard to argue with this, even if we imagine that the intention of homework and labs is to help learn the material, etc.
In the past, I have bent my own rules and given grades based on performance on the final. By this time, I would arrange things so that I'd have less reason to do so... Altogether, out of perhaps 100 such cases in 40 years, I can recall at most 1 or 2 where students were genuinely successful in learning the material while being somewhat disconnected. So, in fact, although some students half-heartedly complained that they'd have not done the homework if they'd been allowed-to, not "allowing" it did them a favor.
So, I have no regrets at bending the rules for a few, although I was not happy that in 98 percent of cases this bending didn't save them.
So, by now, my default for undergrad courses is to "require" homework + for exceptions see me at the beginning of the term, not part-way through... explaining that changing things in the middle easily leads to unfairness... I do give examples of plausible exceptions (about skipping homework, especially, about missing a midterm, ... how can I demand that people not go ski-ing at Thanksgiving?...)
Summary: the goal is education, but/and a significant fraction of students will dis-serve themselves through naivete... But/and I no longer can stomach arguing that enforcement of artificial rules "makes sense". I strongly prefer more defensible positions. :)
Production of Ethanol From Corn Crops September 28, 2017 Homwork #1 ChE 396 – Senior Design I Instructor: Dr. Betul Bilgin Group 5, Tu/Th AM Section Waseem Jaban Arun Joseph Kevin Wu Patrick Yau Department of Chemical Engineering University of Illinois at Chicago TABLE OF CONTENTS Project Charter………………………………………………………….……………………….2 Design Plan……..…………………………………………………………………………..…….3 Introduction……………………………………………………..…………………..…………....4 Objective………………………………………………………………………....………..4 Market Analysis......……………………………………………………..………………...7 Process Description Problem…………………………………………………………………………………..12 Possible Solutions………………………………………………………………………..13 Chosen Solution………………………………………………………………………….17 Design Basis……...…………………………………………………….………………...22 Operating Conditions, Flow rates, and Assumptions……………...….………………….23 Material Balance…………………………………………………………………………24 BFD………………………………...…………………………………………….……....26 PFD……………………………………………………………………………………....27 Equipment Description………………………………………………………………......28 References/Bibliography…………………………………………………………………........31 Page 1 Department of Chemical Engineering University of Illinois at Chicago PROJECT CHARTER OPPORTUNITY The design team’s chemical process synthesis of ethanol through fermentation of corn meets criteria for economical and effective design GOAL Introduce and simultaneously optimize the process of ethanol production through esterification to fit customer specifications OBJECTIVES ● Find a environmentally friendly way to produce ethanol ● Produce ethanol at a high industrial/fuel grade purity for industrial use IN SCOPE ● Designing the process of dry-mill fermentation of corn to produce ethanol ● Comparison and optimization of multiple processes facilitation the production of ethanol CORE TEAM MEMBERS ROLE Waseem Jaban: Design team leader Arun Joseph: Design team member Kevin Wu: Design team member Patrick Yau: Design team member PROJECT STATUS SUMMARY Project Start Date: 9/22/17 Estimated Completion: 9/28/17 Completion Date: 9/27/17 Process Impacted: Ethanol production MILESTONES Project assigned: 9/14/17 Design plan approval: 9/22/17 Literature review and market analysis: 9/23/17 Indirect hydrolysis process selection: 9/26/17 BDF and PDF production: 9/27/17 Submission of project: 9/28/17 OUT OF SCOPE ● Developing waste stream into revenue stream ● Safety considerations ● EPA compliance ASSUMPTIONS ● Reaction conditions ● Unlimited budget ● Process will be running a dry mill hydration of ethanol DELIVERABLES ● Market analysis of ethanol as of 28 September 2017 ● Potential ethanol production methods and alternatives ● Block flow diagram and process flow diagram of our chosen fermentation design DESIGN PLAN Page 2 Department of Chemical Engineering University of Illinois at Chicago INTRODUCTION Page 3 Department of Chemical Engineering University of Illinois at Chicago Objective Chosen by our consulting company to design and prepare an introductory report of the chemical synthesis of ethanol, the purpose of our report is to summarize our final design and extrapolate our results for potential future applications. Ethanol is a grain alcohol utilized for a plethora of processes: medical applications, chemical solvent, synthesis of other compounds, and even a clean energy fuel source. However, the largest single use of ethanol is as an engine fuel and fuel additive. In 2016, U.S. fuel ethanol production soared to more than 15.25 billion gallons. According to Figure 1, the U.S. is the world’s largest producer of ethanol; with Brazil far behind at second, both countries combined produce close to 85% of the world ethanol production . Such long development in production forces us to ponder, why such an increase all of a sudden? Figure 1: Global Ethanol Production  As reported by the U.S. Environmental Protection Agency (EPA) in Figure 2, for 2017 the EPA requirements for conventional renewable fuel blending are finally meeting statutory levels. With the desire for more octane content in gasoline, gasoline refiners have steered away from Page 4 Department of Chemical Engineering University of Illinois at Chicago producing octane from hydrocarbons to “take advantage of ethanol’s superior clean octane properties”. The addition of ethanol to gasoline not only reduces knocking in vehicle engines, but also cuts down on tailpipe emissions of exhaust hydrocarbons, carcinogens like benzene, carbon monoxide, many greenhouse gases, and small particles in the air which may cause complications in the respiratory system if ingested. Ethanol recycling of atmospheric carbon has reduced greenhouse gas emissions enough in the past year to equate to taking 9.3 million cars off the road for an entire year. By focusing more efforts on producing octane through ethanol, refiners have not only found a more cost and energy efficient source of octane, but have also shaped the future of fuel consumption. Automakers are encouraged to produce vehicles which require more fuel efficient ethanol blends which in turn has resulted in the increasing presence of retail stations across the nation offering various blends of ethanol called flex fuels ( 2017 Ethanol Industry...,2, 12, 14, 16, 18, 28, 29). Figure 2: RFS Conventional Renewable Fuel Volume Requirements  However, according to EPA data, auto- manufacturers are slowing down their production of flex fuel vehicles due to the down-scaled Page 5 Department of Chemical Engineering University of Illinois at Chicago fuel economy credits. Fuel economy credit is a miles per gallon credit manufacturers receive from the government for producing vehicles which have high Corporate Average Fuel Economy (CAFE) ratings (high fuel efficiency). In an attempt to push sales of such vehicles, the government multiplies the sale of the vehicles by a certain factor. As reported by EPA, the factor for electric vehicle sales will scale down from 2.0 to 1.5 by 2021 . Beyond being utilized for octane production, the process of producing dry-grind ethanol from corn has several other benefits including the various uses for its co-products. One example is the use of Distiller’s Dried Grains with Solubles (DDGS) for conducting electricity . As a continuously growing sector, efficient design of ethanol production relying on corn crops is increasingly vital. Observations of these trends are outlined in our market analysis of ethanol.The process of ethanol production from corn can be broken down into two main categories; dry grind and wet mill. While dry mill co-products become DDGS and corn distillers oil, wet mill coproducts include corn germ components such fiber, starch, and even gluten which is utilized as animal feed . Though wet milling produces a higher yield of ethanol per corn bushel as well as a larger variety of products, the capital costs involved in dry milling are significantly less than those present in the wet milling process . As exemplified by statistics gathered by the U.S. Department of Agriculture in Figure 3, the vast majority of U.S. ethanol production is facilitated using the dry mill process which is why we structured our design off of the dry-mill fermentation of corn to produce ethanol . Further optimization and identification of problems within our chosen design process thereby impacts multiple industries. Figure 3: U.S. Grain Ethanol Production by Technology Type Page 6 Department of Chemical Engineering University of Illinois at Chicago Market Analysis: According to the U.S Energy Information Administration (EIA), ethanol production reached 13.61 billion gallons, and although there are no current data for the years of 2015 and 2016, a study done by Patricia Batres-Marquez who works at , shows that the ethanol production for the year of 2015 and 2016 are 14.807 billion gallons, and 15.329 billion gallons, respectively. Figure 4: Ethanol Production in the U.S. and Selected States in Billion Gallons Page 7 Department of Chemical Engineering University of Illinois at Chicago According to the latest data collected by EIA, in 2011, the production of ethanol in the U.S was 59 thousands barrels per day, with a consumption rate fairly close to the amount produced. Figure 5: Annual U.S. Ethanol Production and Consumption EIA’s data which was analyzed by Marquez indicate that the U.S monthly consumption averaged to 390.4 million gallons per day in the year of 2016, which is equivalent to 14.25 billion gallons per year. Figure 6: U.S. Annual Gasoline Consumption and Estimated Ethanol Consumption Blended into Motor Gasoline Page 8 Department of Chemical Engineering University of Illinois at Chicago The production outlook for 2017 according to EIA’s data analyzed by Marquez shows the production of ethanol will increase to 43.26 million gallons per day. The data also suggests that the amount of ethanol that is going to be used in motor gasoline will be approximately 39.48 million gallons per day, making it the number one consumption factor. However, the production rate exceeds the consumption rate, which will lead to the need to export the excess ethanol to other countries. The ethanol export rate will have to be around 3.5 million gallons per day. There are two main factors that affect the ethanol price market: oil prices and feed grains. Oil prices affect the price of ethanol simply because of the alcohol fuel’s major contribution in gasoline blending. However, the price of ethanol is also determined by the price of feed grains such as corn which serves to be the most readily available raw material necessary for the production of the commodity. A study was done by Dr. Dan O’Brien and Dr. Mike Woolverton from Kansas State University in the AgMRC Renewable Fuels Newsletter shows clearly how Iowa ethanol prices is related directly to oil prices. Page 9 Department of Chemical Engineering University of Illinois at Chicago Figure 7: Iowa Ethanol and Midwest Gasoline Prices Furthermore, the chart below shows clearly how the three (oil, corn, and ethanol prices) are closely related. Also, According to Dr. Dan O’Brien and Dr. Mike Woolverton “ Corn processing for ethanol is second in size only to the domestic livestock feed market and may become the largest source of demand in three years.” Figure 8: Index of Monthly Crude Oil, Gasoline, Corn, and Ethanol Prices One of the biggest ethanol producing companies in Illinois and in the U.S is Marquis Energy, LLC. The company produces one million gallons of fuel grade ethanol per day, and well over 300 million gallons of ethanol a year. Therefore, we will design our plant to produce 400 million gallons of ethanol per year. The location of the plant is important. It should be close to a large Page 10 Department of Chemical Engineering University of Illinois at Chicago supply of corn like a corn farm, and have access to rail tracks for easy shipment, and/or a nearby interstate highway. Therefore, the ideal location for a plant seems to be in the midwest, where corn crops and water are abundant. It would also be most efficient to have a plant located near a shipping railroad track so the transportation process can be as smooth as possible. The image below shows Marquis Energy plant. The train track lies in the top portion of the image, while the highway (Not shown in the image) lies on the opposite side. Figure 9: Aerial View of the Marquis Energy Plant in Putnam, Illinois (Google Earth) Page 11 Department of Chemical Engineering University of Illinois at Chicago PROCESS DESCRIPTION Problem For fermentation, the reaction that governs this process is the conversion of glucose to ethanol and carbon dioxide byproduct. C6 H 12 O6 →2 C 2 H 5 OH +2 C O2 Now we need a source of this glucose in order to arrive at our product. With fermentation we use biological materials such as corn, sugarcane and other plants containing starch or sugar. Because of our central location and proximity to corn fields we will use corn as our starting material for our ethanol process. When delivered the whole corn cobs are sorted to remove debris and then milled into corn starch, similar to what is at the supermarket.  After being grounded into flour, the starch is then mixed with water and a enzyme (alpha-amylase) and heated to reduce the viscosity of the mixture.  The slurry is now at the liquefaction stage, where the solid portion of the mix is now turned into pure liquid. The slurry is introduced into a pressurized cooker and then heated at 221 °C for a short time and then cooled.  The mixture is again heated for 1-2 hours.  During this time the enzyme added before will now breakdown the starch into dextrins, glucose polymer chains. Page 12 Department of Chemical Engineering University of Illinois at Chicago  After this, another enzyme is added, glucoamylase which decomposes the dextrins into single pieces of glucose ready for the fermentation reaction above.  With the ethanol we want to produce, we intend to sell it to petroleum companies such as BP, Shell and Exxonmobil as an additive in their gasoline. With our product, it provides a home grown solution to produce environmentally friendly gas for American consumers. For gasoline made for the US market, two types of gasoline use ethanol as an additive, E10 and E85. E10 is comprised of 10% ethanol and 90% gas and E85 has a composition of 85% ethanol and 15% regular fuel . For our customers they will need a fairly pure product in order to ensure these ratios in their gasoline, so our final ethanol composition will be 99%. Possible Solution There are many ways to produce ethanol, for varying concentrations and uses, for instance, in synthetic ways such as using ethylene to directly synthesize ethanol through a catalyst. In addition, we can ferment sugar to create it as well in a very similar way beer and spirits are produced. This method is very versatile as the source materials can be anything from corn or sugarcane as the only requirement is that they have glucose within. A solution that can be used is the direct hydration of ethylene to ethanol. Water is introduced to vapor ethylene at an environment of 300॰C and 70 bar in the presence of a catalyst of phosphoric acid and silica.  C H 2=C H 2 + H 2 O→ C2 H 5 OH Page 13 Department of Chemical Engineering University of Illinois at Chicago Afterwards, the reaction mixture is entrained in benzene in order to separate the product from excess water.  The advantages of this process is that the byproducts made are in very limited quantities, the selectivity of ethanol is 97%.  However, the conversion is very low, around 4%.  With such low production, in order to make this pathway usable ethylene must be recycled over and over and must be introduced at high concentration, which ramps up the costs.  Because of the reaction conditions needed, 300॰C and 70 bar, an enormous amount of energy is required, this has to be taken from an outside utility that we pay for. Furthermore, catalyst is continuously lost during operation. Of course, this has to be replaced, shutting down the reactor and putting the plant on idle. Another industrial process to produce ethanol is indirect hydration in a manner very similar to direct hydration. Ethylene is reacted with highly concentrated sulfuric acid with Ag2SO4 as a catalyst, causing an ester to be produced. This method of manufacturing of ethanol involves two unit processes: absorption and hydrolysis. The concentration of the ethylene gases range from 35% to 95% reacting with 94-98% sulfuric acid:  C H 2=C H 2 + H 2 S O 4 → C 2 H 5 O−S O3 H C 2 H 5 O¿ 2 S O 2 C H 2=C H 2 +C 2 H 5 O−S O3 H → ¿ The first reaction produces ethyl hydrogen sulphate, and the second reaction produces diethyl sulphate. Diethyl sulfate C2 H 5 O ¿2 S O2 ¿ is highly toxic and a likely carcinogen and proves to be a substantial obstacle towards the use of this particular process.  Dilution of the resulting solution of sulfuric acid and diethyl sulfate with water allows the ester to hydrolyze to ethanol.  While this process has a very high conversion (85 %) , it suffers from many expensive Page 14 Department of Chemical Engineering University of Illinois at Chicago drawbacks that has limit its use in industry. In particular, the sulfuric acid is at such a high concentration (94-98%) that it corrodes machinery and pipes from its insane acidity.  The continued cost of replacing corroded pipes and equipment would accumulate significantly over the lifespan of a plant. Furthermore, as a way of cost saving excess sulfuric acid is recycled from the end of the process. However, this involves re-concentrating the acid. The easiest way to do this is to heat the acid to boil off water, but a byproduct of this heating is that sulfur dioxide is made, which is toxic and must be dealt with.  Another byproduct of this reaction is diethyl ether, which is also a hazardous material as well as very volatile and poses safety concerns during operation.  C 2 H 5 ¿2 O C2 H 5 O ¿2 S O2 + H 2 O→ C2 H 5 OH +¿ ¿ C 2 H 5 ¿2 O C2 H 5 O−S O3 H + H 2 O →C 2 H 5 OH + ¿ What both of the discussed processes depend on for their viability is the cost of ethylene, which varies due to market fluctuations.  While the price depends on demand the main factor is the cost to produce ethylene. The chemical is made through the cracking of hydrocarbons, therefore the price of ethylene is dependent on the price of hydrocarbon sources such as natural gas and crude oil.  As we know when we fill up our cars, the price of gasoline (and oil) has been on the rise for the past 15-20 years, thus processes such as the two outlined have fallen to the wayside. Figure 10: Ethylene price trend 1988-2012 (Duncan Seddon & Associates PTY. LTD.) Page 15 Department of Chemical Engineering University of Illinois at Chicago With the obsolescence of ethylene to ethanol processes, companies have turn to other ways of producing the needed commodity. In specific we turn to bioprocesses such as fermentation of simple sugars to produce ethyl alcohol. Fermentation relies on the conversion of glucose into ethanol and CO2, using yeast as a natural catalyst to perform this reaction. C6 H 12 O6 →2 C 2 H 5 OH +2 C O2 There are two variants of this process, dry mill and wet mill processing. The main difference between these two pathways is the way the glucose is refined from the source material. Dry mill production involves the preliminary grinding of the starting material (such as corn) into a starch, this is then mixed with water and enzymes that eventually creates glucose.  Wet mill processing differs where by the corn is first bathed in hot water to release all of the starch and then grinded into a pulp.  Afterwards the resulting mixture is separated into 3 parts: fiber, gluten and starch. The starch is then used to make the ethanol. Meanwhile, the fiber and gluten are furthered refined to make separate products that can be sold to further profit.  Page 16 Department of Chemical Engineering University of Illinois at Chicago In both these two processes the fermentation steps are similar. After the corn is broken down into starch it is mixed with water and a enzyme (alpha-amylase) and heated, during this time the enzyme breakdowns the starch into dextrins.  A further process is done where another enzyme is introduced (glucoamylase), this further tears down the dextrins into glucose molecules.  Once at this stage, the mix is pumped into fermentation tanks and yeast added and left to sit for 50-60 hours.  The yeast acts as the catalyst for the reaction, at the end of the duration ethanol and carbon dioxide have replaced the glucose. Once this is finished the ethanol is distilled, separated and stored for sale. When compared to wet mill, dry mill processing is a cheaper solution for ethanol fermentation. This is due to the fact that the wet mill process is more cost intensive compared to the dry mill.  These associated costs go toward making the byproducts of the corn, the gluten and corn germ into marketable products for consumers such as livestock feed and corn oil.  Meanwhile, the dry mill process is tailored to exclusively producing ethanol and the solid byproduct Dried Distillers Grains (DDG) is also sold as feed product as well.  While the dry mill lends to higher ethanol production and lower capital expenses, the wet mill process is more versatile.  If ethanol prices were to plummet a wet mill plant can still weather the low off the sales of their byproducts, while a dry mill plant might have to shut down or lay off workers due to a downturn. Chosen Solution The challenges of producing ethanol from corn crops are the following steps: 1) Grinding. 2) Cooking and liquefaction. Page 17 Department of Chemical Engineering University of Illinois at Chicago 3) Saccharification. 4) Fermentation. 5) Distillation Figure 11: Overview of a Dry Mill Plant Page 18 Department of Chemical Engineering University of Illinois at Chicago Grinding can be done using two different methods, Dry Method, and Wet Method. These two methods will produce two different products. Dry milling which is the simpler process will produce ethanol, CO2, and dried distiller grain with solubles (DDGS). Wet milling will produce feed, corn oil, gluten meal and gluten feed. The most efficient and simple method is the dry milling that will be adopted for this process. It consist of using a hammer mill, or roller mill to grind the corn. The following photo shows how the corn get milled prior to cooking and liquefaction. Figure 12: Illustration of a Hammer mill Page 19 Department of Chemical Engineering University of Illinois at Chicago The cooking stage of the grinded corn, which is referred to as gelatinization. It involved mixing the corn with water at temperatures higher than 60 degree Celsius, pH of range of 5.9-6.2, where ammonia and sulfuric acid are added to maintain the pH level. The process is partially hydrolysis that lowers the viscosity of the mixture. It is essentially breaking up the longer starch chains into smaller chains.  The liquefaction can be done with three similar options. The jet cooker process is chosen for this design, because the most efficient process. The image below describe the three processes. Figure 13: Liquefaction process diagram Page 20 Department of Chemical Engineering University of Illinois at Chicago The common material that is added to the three processes is α-amylase. The α-amylase for liquefaction acts on the internal α (1,4) glycosidic bonds to yield dextrins and maltose (glucose dimers). Glucose is used in the next step to make ethanol. Now that glucose is present, the saccharification process to making ethanol can begin. The optimum conditions for the process are 4.5 pH, and a temperature of 55-65 degree Celsius. The glucose will further hydrolysis to glucose monomers, which are then fermented to produce ethanol and carbon dioxide. The following chemical reaction equation shows that one mole of glucose is converted to two moles of ethanol and carbon dioxide. C6H12O6→2C2H6OH + 2CO2 The reaction takes place in a batch reactor over 2 to 3 days at a temperature of 30 degree celsius. The conversion rate is between 90-95%. To initiate the reaction, yeast is added. The most common yeast is saccharomyces cerevisiae.  Page 21 Department of Chemical Engineering University of Illinois at Chicago The distillation is the last step of this process. The concentration of the ethanol in the mixture is about 15%. The other 85% is water. Water boils at 100 degree Celsius, while ethanol boils at 78 degree celsius. One of the challenges faced when running the mixture in a distillation column to separate the two components is the fact that water and ethanol evaporate at a relatively lower temperature, and therefore, the distillate at the top of the column will contain 95% ethanol and 5% water.  To achieve a concentration of 100% ethanol, the method of dehydration is used. The unit that is used is called a molecular sieve, and the material used in it is called zeolite. The pore size of the zeolite membrane is 0.30 nm, while the size of the water molecule is 0.28 nm and the ethanol 0.44 nm. Therefore, when the mixture is passed through these sieves at high and low pressure, the water molecules will pass through the Zeolite sieves, and ethanol molecules will be isolated.  Figure 14: Ethanol Filtration Using Sieves (BEEMS Module B5) Page 22 Department of Chemical Engineering University of Illinois at Chicago Design Basis The estimated production of ethanol from corns are the followings; One bushel of corn (56 lbs.) will produce 2.8 gal of ethanol, 17 lbs of CO2, and 17 lbs of DDGS (Distillers Dried Grains with Solubles). Bushel of corn: 56 lbs x 62% starch = 34.7 lbs of starch 34.7 lbs starch x 1.11 lbs glucose/lb starch = 38.5 lbs glucose/bu The reaction of glucose to ethanol C6H12O6→2C2H5OH + CO2 180g/mol 2*46 g/mol 38.5 lbs glucose x 92 lbs EtOH/180 lbs glucose = 19.7 lbs EtOH/bu 19.7 lbs EtOH x 1 gal EtOH/6.6 lbs = 3.0 gal EtOH theoretically 100 x (2.8/3.0) = 93% yield of ethanol Page 23 Department of Chemical Engineering University of Illinois at Chicago Operating Conditions, Flow rates, and Assumptions ● The corn particle size pass the mill is (<2 mm) to facilitate the subsequent penetration of water. ● The slurry tank’s pressure and temperature are 4 bar, 110 °C, respectively. ● The liquefaction step will operate at 85 degree celsius. ● The fermentation reactor will convert 99.5% or raw materials to products. ● The first two distillation columns will operate under the pressure of 1.7 and 0.5 bar with a distillate products of 50% ethanol. ● The last distillation column will operate under pressure 5 bar with 92% w/ ethanol purity in the distillate. ● Specifications for all columns in distillation section of process are set to recover more than 99.99% of ethanol in the feed streams. Page 24 Department of Chemical Engineering University of Illinois at Chicago Material Balance The following process shows the overall steps: 1.1 million gallons of ethanol need to be produced everyday to meet the goal of ~400 million gallons produced in one year 1.1x10^6 gal of ethanol x (1 bushel of corn)/2.8 gal of ethanol x 56 lbs corn = 22x10^6 lbs Corn 1.1x10^6 gal of ethanol/24 hours) x 8.35 lbs/gallon = 382708.33 lbs/hour of ethanol Therefore, 22x10^6 lbs of corn is needed to produce ethanol at a rate of 382,708.33 lbs/hour in order to reach our production goal Figure 15: Material Balance Calculations Page 25 Department of Chemical Engineering University of Illinois at Chicago The composition of corn is the following : Figure 16: Corn Composition Component Mass fraction Water .150 Xilose .062 Starch .595 Hemicellulose .131 Cellulose .057 Lignin .005 Based on the above, the following flow rates were calculated: Figure 17: Component Flow Rates BFD Page 26 Department of Chemical Engineering University of Illinois at Chicago The production of ethanol and related processes are in blue; the byproducts of distillation is sent to a centrifuge and process through the systems in grey. This byproduct is non-fermentable material and also known as whole stillage, consisting of suspended grain solids, dissolved materials, and water. The main byproducts produced are Wet Distillers Grains (WDG) which contains unfermented grain residues. WDGS indicates Wet Distillers Grains with Solubles. WDGS, upon drying, creates Distiller’s Dried Grains with Solubles suitable for animal feed and electricity production . Further analysis of this process and reutilization of this waste stream for revenue is out of scope for this report. Page 27 Department of Chemical Engineering University of Illinois at Chicago Process Flow Diagram Equipment and Process Description Page 28 Department of Chemical Engineering University of Illinois at Chicago Milling Process (Red Section) 1: Hammer Mill Mills aggregate material into smaller pieces. Corn is milled to < 2 mm in order to facilitate the mixing process with water in the mixer. Dry milling produces ethanol, CO2, and dried distiller grain with solubles (DDGS). 2: Mixer Water is added into the finely ground corn to saturate the material. Also receives recycled water from the fermentation process. Cooking Process (Orange Section) 3: Slurry Tank Receives slurry from mixer as well as ammonia and sulfuric acid to maintain pH level. 4: Jet Cooker The jet cooker utilizes steam to raise the temperature to 100oC and 4 bar. This sterilizes the slurry and breaks the hydrogen bonds to facilitate water absorption. Also known as gelatinization as the mixture becomes gelatinous. 5: Vacuum Flash Heats slurry to optimize yield, conversion, and avoidance of intractable products. Liquefaction (Yellow Section) 6: Liquefaction Tank At 85oC, alpha-amylase enzymes are added to the starch molecules at .082% dry basis with respect to corn. This decreases viscosity as alpha-1,4 glucosidic amylose and amylopectin linkages are broken. Simultaneous Saccharification and Fermentation (Green Section) Page 29 Department of Chemical Engineering University of Illinois at Chicago 7: Saccharification Tank Starch oligosaccharides are hydrolysed at a rate of 99% into glucose molecules by glucoamylase enzyme. This enzyme is added at .011% dry basis with respect to corn. 8: Mash steam cooler Mash resulting from liquefaction and saccharification are cooled to 35oC to facilitate propagation. 9: Yeast Starter Tank (Propagation) Yeast, or Saccharomices cerevistae, catalyzes glucose at a conversion rate of 99.5% within this tank. The remaining .5% is transformed by reaction. 10: Fermentation Batch Reactor Glucose is converted to ethanol and carbon dioxide. This reaction occurs in batch reactor over two to three days at a temperature of 30oC. Outlet stream from fermenter is beer: contains negligible quantities of acetaldehyde, methanol, butanol, and small quantities of acetic acid, and glycerol. 11: Absorption Column A large quantity of CO2 is produced as a consequence of the reaction taking place in the fermentation batch reactor. Most is purged to the absorption column which recovers ethanol, and the scrubbing water is recycled to the slurry tank. 12: Beer Degasser Drum The remainder of the CO2 produced from fermentation is expunged by heating the beer. Distillation (Blue Section) 13: Stripping Column Page 30 Department of Chemical Engineering University of Illinois at Chicago The fermentation broth is split into two streams. One stream is sent to this column operating at 1.7 bar. 14: Stripping Column The fermentation broth is split into two streams. One stream is sent to this column operating at .4 bar. 15: Rectifying Column The product resulting from the stripping columns are 50% ethanol by weight and sent to the rectifying column at 5 bar. This produces ethanol at 92 wt% purity. Condensing heat of this column supplies energy to the reboiler of the 1.7 bar stripping column. 16: Molecular Sieve This produces anhydrous ethanol at fuel grade purity: 99.8 wt%. Byproduct Processing (Purple Section) 17: Centrifuge Non-fermentable products of the feed (whole stillage) consists of suspended grain solids, dissolved materials, and water. Whole stillage is sent to a centrifuge, where a wet cake (35% of solids by weight) and thin stillage (8% of solids by weight) are obtained. Part of the thin stillage is recycled (backset), and the rest is sent to an evaporator for further processing, which is out of the scope of our report. Page 31 Department of Chemical Engineering University of Illinois at Chicago References 1. Joern, Ernst, and Haldor Topsoee. “Ethyl and Isopropyl Alcohol.” SciFinder, Ger. Offen Patent CODEN:GWXXBX, 1972, scifinder-cas-org.proxy.cc.uic.edu/scifinder /view/scifinder/scifinderExplore.jsf. 2. Arpe, Hans-JuÌˆrgen, and Klaus Weissermel. Industrial Organic Chemistry. 3rd ed., Wiley-VCH, 2012, dlx.b-ok.org/genesis/660000/f357a383b80c419d7169bd992c5107ad/ _as/[Klaus_Weissermel,_Hans-Jurgen_Arpe]_Industrial_Or(b-ok.org).pdf. 3. K, Sam K. “Industrial Alcohol Production from Ethylene and Sulphuric Acid.” Inclusive Science and Engineering, Inclusive Science and Engineering: Science, Engineering & Technology for Business, Research, and Industries, 1 Apr. 2012, www.inclusive -science-engineering.com/industrial-alcohol-production-from-ethylene-and-sulphuric-aci d/. 4. Giada Franceschin, Andrea Zamboni, Fabrizio Bezzo, Alberto Bertucco, Ethanol from corn: a technical and economical assessment based on different scenarios, In Chemical Engineering Research and Design, Volume 86, Issue 5, 2008, Pages 488-498, ISSN 02638762, https://doi.org/10.1016/j.cherd.2008.01.001. 5. 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