Final Senior Design Report

Final Senior Design Report Team 14: GRE-cycle Hannah Albers, Ben Guilfoyle, Melanie Thelen, and Cole Walker ENGR 340--Senior Design Project May 13, 20...
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Final Senior Design Report Team 14: GRE-cycle Hannah Albers, Ben Guilfoyle, Melanie Thelen, and Cole Walker ENGR 340--Senior Design Project May 13, 2015

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Abstract Waste cooking oils (WCOs) contain high levels of triglycerides, which store large amounts of energy. The team designed a biodiesel production plant that uses WCO from restaurants and other businesses as its primary feed source. The plant will be located in Miami, FL as the size of the Miami area will allow significant grease collection for the production of a substantial amount of biodiesel. Based on the number of restaurants in the area and the understanding that grease will not be obtained from every one of these sources, the plant is designed to produce 9.5 million gallons of biodiesel per year. The team assessed the possibility of blending the produced biodiesel at the plant, however it was determined that this was outside the scope of the project. The plant will be used exclusively to produce the biodiesel that will be blended elsewhere. The plant was designed to produce biodiesel through pretreatment, conversion, and product purification steps. The pretreatment reactor was modeled as a plug-flow reactor in UNISIM as this reactor type was sufficient to decrease feed FFA content to the desired range. The transesterification reactor was simulated as a batch and plug-flow reactor, and a plug-flow reactor was selected as optimal. Additional reactor types were considered and eliminated due to higher operating expenses and higher risk of failure. The primary method of product purification is membrane separation and the primary method of methanol recovery is distillation. The biodiesel production process was simulated in UniSim, but has supplemental design calculations for further accuracy. The plant will require methanol, sulfuric acid, and sodium hydroxide to react to process WCO. The methanol used for plant operations will be biomethanol, which is produced by a less energy-intensive process than standard methanol. Upon estimating capital, raw material, and operating costs, if biodiesel is sold for $3.50/gal, which is approximately $0.50/gal lower than the average biodiesel price, the plant receive a 20% rate of return over the 20 year lifespan. With this conservative selling price, our plant will be profitable despite mild market fluctuations. It is important to note that $1.00 per gallon comes from a government subsidy. Without this added dollar, the plant would not be profitable. This indicates that this fuel requires further development to be a profitable enterprise. The plant will profit 4.2 million dollars a year, with 16.5 million dollars in capital costs.

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Table of Contents Abstract ......................................................................................................................................................... 2 Table of Contents .......................................................................................................................................... 3 Table of Figures ............................................................................................................................................ 6 Table of Tables ............................................................................................................................................. 7 1. Introduction ............................................................................................................................................... 8 1.1 Background Information ..................................................................................................................... 8 1.2 Objective ............................................................................................................................................. 9 1.3 Scope ................................................................................................................................................... 9 1.4 Past Project Teams ............................................................................................................................ 10 1.5 Feasibility.......................................................................................................................................... 10 1.6 Comparing Biodiesel and Petroleum Diesel ..................................................................................... 11 1.6.1 Differences in Chemistry ........................................................................................................... 11 1.6.2 Engine Modification .................................................................................................................. 12 1.6.1 Engine Performance ................................................................................................................... 12 2. Design Norms ......................................................................................................................................... 13 2.1 Stewardship ....................................................................................................................................... 14 2.2 Caring................................................................................................................................................ 14 2.3 Transparency ..................................................................................................................................... 14 3. Project Management ............................................................................................................................... 15 Team Responsibilities ......................................................................................................................... 16 Hannah Albers .................................................................................................................................... 16 Ben Guilfoyle ...................................................................................................................................... 16 Melanie Thelen ................................................................................................................................... 16 Cole Walker ........................................................................................................................................ 16 4. Process Overview.................................................................................................................................... 17 4.1 Process Research ............................................................................................................................... 17 4.1.1 Block Flow Diagram .................................................................................................................. 17 4.1.2 Reaction Chemistry .................................................................................................................... 17 4.1.3 Key Variables............................................................................................................................. 19 4.1.4 Design Alternatives .................................................................................................................... 21 4.2 Material Research ............................................................................................................................. 22 4.2.1 Feed Sources .............................................................................................................................. 22 3

4.2.2 Feed Composition Research....................................................................................................... 22 4.2.3 Feed Composition Model ........................................................................................................... 25 4.2.3 Alcohol....................................................................................................................................... 26 4.2.4 Product ....................................................................................................................................... 27 5. Design ..................................................................................................................................................... 28 5.1 Pre-Treatment Section ...................................................................................................................... 28 5.1.1 Water Removal .......................................................................................................................... 28 5.1.2 Filter ........................................................................................................................................... 29 5.1.3 Acid Treatment .......................................................................................................................... 31 5.1.4 Waste Separation........................................................................................................................ 35 5.2 Transesterification Reactor ............................................................................................................... 40 5.2.1 Mass Transfer Limitations ......................................................................................................... 41 5.2.2 Design Alternatives .................................................................................................................... 42 5.2.3 Polymath Kinetic Modeling ....................................................................................................... 45 5.2.4 Design Decision ......................................................................................................................... 46 5.2.5 Catalyst ...................................................................................................................................... 47 5.3 Post-Treatment Section ..................................................................................................................... 48 5.3.1 Glycerin Separation.................................................................................................................... 48 5.3.3 Waste Water Treatment ............................................................................................................. 51 6. Equipment ............................................................................................................................................... 52 6.1 Equipment Listing............................................................................................................................. 52 7. Safety Considerations ............................................................................................................................. 56 7.1 Chemicals.......................................................................................................................................... 56 7.2 Operating........................................................................................................................................... 56 8. Quality Control ....................................................................................................................................... 58 9. Business Plan .......................................................................................................................................... 60 9.1 Market Study..................................................................................................................................... 60 9.1.1 Customer .................................................................................................................................... 61 9.1.2 Competition................................................................................................................................ 61 9.2 Tax Information ................................................................................................................................ 63 9.3 Costs.................................................................................................................................................. 64 9.3.1 Capital Costs .............................................................................................................................. 64 9.3.2 Operating Costs .......................................................................................................................... 66 4

9.4 Profitability ....................................................................................................................................... 67 10. Conclusion ............................................................................................................................................ 70 References ................................................................................................................................................... 71 Appendices Table of Contents .................................................................................................................... 75 Appendix 1. Overall Process Mass Balance and UniSim design ............................................................ 76 Appendix 2. Component Stream Table ................................................................................................... 78 Appendix 3: Settling Tank Calculations ................................................................................................. 79 Appendix 4. Particulate Removal Calculations ...................................................................................... 80 Appendix 5. Competing Biodiesel Plants in Florida............................................................................... 81 Appendix 6. Transesterification Kinetics Calculations ........................................................................... 82 Appendix 7. Membrane Filter Calculations ............................................................................................ 84 Appendix 8. Vessel Cost Details............................................................................................................. 86

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Table of Figures Figure 1: Biodiesel molecule ...................................................................................................................... 11 Figure 2: Petroleum Diesel Molecule ......................................................................................................... 11 Figure 3: Work Breakdown Schedule Organized as Critically Linked Tasks ............................................ 15 Figure 4: Process Overview (above) and Block Flow Diagram (below) .................................................... 17 Figure 5: Triglyceride Molecule ................................................................................................................. 18 Figure 6: Overall Biodiesel Reaction .......................................................................................................... 18 Figure 7: Saponification of Free Fatty Acids to form soap ......................................................................... 20 Figure 8: Water formation in an acid catalyst reaction to convert Fatty acids to biodiesel ........................ 20 Figure 9: Standard Curve of Linoleic Acid ................................................................................................. 24 Figure 10: TLC Plate of Butter, Linoleic Acid and Grease Extract ............................................................ 24 Figure 11. Kinetic comparison of oils with different feed compositions. ................................................... 26 Figure 12:Pre-Treatment Block Flow Diagram .......................................................................................... 28 Figure 13: Maximum Water Content vs Maximum FFA Content .............................................................. 29 Figure 14:Levenspiel Plot of the Pre-Treatment Reaction .......................................................................... 33 Figure 15: Effect of Pre-Treatment Reactor Volume on FFA Composition ............................................... 34 Figure 16: Effect of Trays on Distillation Cost........................................................................................... 38 Figure 17: Overall Cost of the Distillation Column .................................................................................... 38 Figure 18: Methanol Feed Required at Different Reflux Ratios ................................................................. 39 Figure 19: Transesterification of triglycerides to form biodiesel (methyl esters) ....................................... 41 Figure 20: PFR and batch reactor comparison with Polymath with methanol:oil ratio and entering flow rates held constant ....................................................................................................................................... 46 Figure 21: Post-Treatment Block Flow Diagram ........................................................................................ 48 Figure 22: Materials of Construction for Handling Caustic Solution ......................................................... 53 Figure 23: Plant Piping and Instrumentation Diagram ............................................................................... 59 Figure 24: Million barrels of biodiesel produced in the United States per year ....................................... 600 Figure 25: Cash flow diagram of Plant Construction and Operation .......................................................... 69

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Table of Tables Table 1. Fatty acid composition of WCO and various oils., ....................................................................... 25 Table 2: EPA Biodiesel Specifications ....................................................................................................... 27 Table 3. EPA biodiesel specifications met by final design. ....................................................................... 27 Table 4. Pretreatment PFR operating parameters. ...................................................................................... 35 Table 5: Membrane Filter Specifications .................................................................................................... 37 Table 6: Distillation Column Specifications ............................................................................................... 40 Table 7. Transesterification reactor alternatives ........................................................................................ 43 Table 8. Transesterification PFR operating parameters. ............................................................................ 47 Table 9: Relative densities of effluent stream components ........................................................................ 49 Table 10: Equipment and Materials of Construction .................................................................................. 54 Table 11: Vessel Volumes based on Storage Density Contents. An asterisk denotes vessels that are incorporated into the process but are not represented in the process flow diagram .................................... 55 Table 12: Vessel Capital Costs as Calculated by Guthrie Cost Estimation Tool ........................................ 64 Table 13: Plant Development Capital Costs ............................................................................................... 65 Table 14: Hourly Costs of Raw Materials .................................................................................................. 66 Table 15: Hourly Operating Costs .............................................................................................................. 67 Table 16: Income from Products................................................................................................................. 68 Table 17. Rate constants and activation energies for biodiesel production with soybean oil and NaOH catalysis. ...................................................................................................................................................... 82 Table 18. Thermodynamic properties of reactants and products. .............................................................. 83

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1. Introduction 1.1 Background Information Fossil fuels account for approximately 82% of the United States’ energy supply. Though geologists estimate that less than half the total volume of crude in below-ground reserves will be depleted by 20301, it remains a fact that the supply of crude oil continues to decrease as the energy demand necessary to support the rapidly advancing lifestyles around the world increase. Oil has done well to advance human technology to the point where it is today, but the drawbacks of crude oil cannot be ignored. The demand for crude oil has caused wars, damaged the atmosphere, and eventually must be replaced by more sustainable energy sources. Used restaurant grease contains high levels of triglycerides, which store large amounts of energy. According to USA Today2, approximately 3 billion pounds of grease are produced in the United States each year. The average fast food restaurant produces about 150 - 250 pounds of grease every week, says the New York Times3. The disposal of waste grease has been a large burden on restaurants, since grease cannot be processed in a wastewater treatment plant. It must be collected in a grease trap and disposed of in alternative ways. Restaurants recently have been selling their used grease to recycling companies that convert the used grease into fresh cooking oil. Rather than recycling the grease for consumption, the burden of grease waste disposal can be alleviated by instead converting the grease into fuel. Also, in contrast to fossil fuels, biofuels are produced from renewable plant and animal materials such as vegetable oils, grease, or animal fats. Over the past decade, interest in producing biodiesel from oils and grease has grown into a marginally successful industry as the future availability of fossil fuels became uncertain. Additionally, burning biodiesel produces 56-87% less greenhouse gas emissions than conventional diesel4, which makes it a viable and promising option as an alternative to crude oil.

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Institute for Energy Research, 2014 Ron, Barnett. "Restaurants' Grease a Hot Item for Thieves." USA Today 3 Saulny, Susan. "As Oil Prices Soar, Restaurant Grease Theft Rises." The New York Times 2

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Beer, T, T Grant, and PK Campbell. "Biodiesel could reduce greenhouse gas emissions." CSIRO. CSIRO, 27 Nov. 2007.

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1.2 Objective The main objective of this project is to design a biodiesel production plant that will provide a clean alternative to diesel. Petroleum production is unsustainable whereas the supply of restaurant grease is readily available. Obtaining feedstock for the plant will require the participation of restaurants, which currently sell the grease to an outside source in order to dispose of the grease they generate on a daily basis. By establishing the plant in a populous area with a lot of restaurants, a significant amount of biodiesel feedstock will be available. Secondly, the team purposes to make the plant profitable. Biodiesel production will not increase unless there is money to be made in the industry. Despite its environmental implications, production will be limited if it continues to be more economical to use fossil fuels to run our vehicles. By designing a profitable biodiesel plant, the team hopes to prove that biodiesel production is part of the answer for a more sustainable future.

1.3 Scope The team plans to design a production plant in the Miami area that will buy used grease from surrounding restaurants and convert it into pure biodiesel. The size of the Miami area will allow significant grease collection for the production of a substantial amount of biodiesel. Based on the number of restaurants in the area and the fact that grease will not be obtained from every one of these sources, the production of biodiesel is anticipated to be in the hundreds of barrels per day range. This comes from the estimation of available feed at 130,000 kg/day. This calculation can be found in section 4.2.1. Biodiesel is commonly blended with conventional diesel in 50:1, 20:1, or 5:1 diesel to biodiesel ratios. The team assessed the possibility of blending the produced biodiesel at the plant but determined that this was outside the scope of the project. The plant will be used exclusively to produce purified biodiesel that can be blended by an outside source.

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1.4 Past Project Teams Several senior design teams have completed projects pertaining to biodiesel production. In 2001, Team FAME designed a plant that produced biodiesel in a continuous process for missionary transportation services in third world countries. In 2008, Team Rinnova designed a small scale biodiesel batch reactor for home users using feedstock from Calvin College Dining Services. Rinnova met their project goals but included recommendations for a second prototype. Suggested changes included adding a completely electronic control system, using better materials for piping, and installing a coarser filter. The Diesel Crew took these recommendations in 2013-2014 and designed a second prototype for home users. Their design utilized a microwave reactor, unlike the batch reactor designed by Rinnova, as the Diesel Crew was interested in designing a continuous system. Though the scope of this report includes a full-scale plant design, references to these project groups are found scattered throughout this report, particularly in the design alternatives for each plant section. The team will not be directly using other team projects by scaling up the past designs, but will instead take into consideration their design decisions while evaluating alternatives.

1.5 Feasibility The use of biodiesel compared to currently available diesel has both advantages and disadvantages. For one, restaurant grease can be obtained inexpensively, which makes the plant more economically feasible by lowering operating costs. Additionally, biodiesel has positive environmental implications as it produces less hydrocarbons and carbon monoxide than regular diesel when burned5. The proposed process is more sustainable by helping the environment and eliminating waste. The traditional diesel process requires a depletion of Earth’s natural resources to produce the fuel, while biodiesel uses otherwise useless waste as its feedstock.

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"How Much Does Biodiesel Reduce Air Pollutants?" AllegroBiodiesel.

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Despite these advantages, the use of biodiesel instead of traditional diesel does pose some challenges, most notably gelling. In colder weather, some biodiesels solidify into a gel that renders them unusable. This is one reason the plant will be placed in Florida. Considering the warm climate in the state, gelling should not be a concern. Though biodiesel significantly decreases carbon emissions, it is less efficient than normal diesel. It has been found that fuel efficiency is reduced by 10% compared to regular diesel6. Despite these drawbacks, the team feels that the economic and environmental considerations make the proposed process a valuable and feasible project to pursue.

1.6 Comparing Biodiesel and Petroleum Diesel 1.6.1 Differences in Chemistry Figure 1 depicts a typical biodiesel molecule. It is composed of a long carbon atom chain (average of 16-20 carbons) with an ester functional group, shown in blue, on one end.

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Figure 1: Biodiesel molecule

A typical petroleum diesel molecule looks very similar, except it does not have the same ester functional group attached to one end.

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Figure 2: Petroleum Diesel Molecule

The ester group on the biodiesel molecule makes the fuel much less toxic and more biodegradable than petroleum diesel. Enzymes such as esterase recognize the ester group on the biodiesel and begin fatty

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"Biodiesel." fueleconomy.gov. US Department of Energy ”The Chemistry of Biodiesel”. Goshen College 8 ”The Chemistry of Biodiesel”. Goshen College 7

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acid degradation9. This process breaks the molecule down to generate acetyl-CoA, which can be metabolized and thus is biodegradable and non-toxic. Biodiesel is safer for both the environment and human contact due to these characteristics. A biodiesel spill would be much less concerning than a petroleum diesel spill and since biodiesel can be metabolized, it is not as toxic to humans.

1.6.2 Engine Modification Due to the similarity in chemical structure, a diesel engine can run on biodiesel fuel with minor modification. Diesel engines manufactured pre-1993 may contain rubber tubing that may soften with biodiesel fuel and should be replaced with biodiesel-rated components. These are typically made of fluoroelastomers like Teflon and will not degrade with biodiesel10. If the biodiesel fuel is a blend with less than 20% pure biodiesel, there is no need to replace the rubber tubing. There is most likely no need to replace the tubing on a car manufactured post-1993 either, but a mechanic should examine the engine before switching to biodiesel. Also, biodiesel is more viscous than petroleum diesel so it may gel, causing engine issues while trying to start the car11. In cool climates, engines may have to be modified by adding a fuel heating system or using a fuel additive that will lower the viscosity. Viscosity lowering fuel additives are available commercially, such as Wintron®, a Biodiesel Cold Flow Additive12.

1.6.1 Engine Performance Overall the engine performance using biodiesel is comparable to using petroleum diesel; however, some discrepancies occur in fuel efficiency and engine power. The energy content of biodiesel is slightly less than petroleum diesel, so the overall fuel efficiency is approximately 10% less. Also,

McKay, DB, “Degradation of triglycerides by a pseudomonad isolated from milk” “Using Biodiesel Fuel in Your Engine” Penn State Extension. 11 “Engine Modification,” University of Strathclyde Engineering 12 ”Biodiesel Cold Fuel Additives,” Biofuel Systems Group LTD 9

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engine power is reduced by 3 to 5% while using biodiesel since it has less energy per unit volume than petroleum diesel.13 Engine clogging can occur if low-quality biodiesel is used since it will contain more deposits and viscous materials. However, this should not be an engine performance concern if high quality biodiesel is used. Also, care should be taken that the biodiesel does not oxidize and thus polymerize before it is burned, since this may clog a standard diesel engine. As long as the biodiesel is stored properly before being distributed, this should not be a major concern. Proper storage includes storing at moderate temperatures and not allowing the biodiesel to sit for extensive amounts of time before use.14 As mentioned in the introduction, engine emissions are also significantly reduced using biodiesel. Sulfur emissions are in effect non-existent and hydrocarbon emissions are reduced by an average of 50%15. The only trade-off is a slight increase in nitrogen oxide emissions. Nitrogen oxide (NOx) is a greenhouse gas and can cause smog and acid rain16. However, the reduction in the carbon emissions is so beneficial that the slight increase in NOx is negligible.

2. Design Norms Crucial to the sustainability of the proposed plant from both business and ethical standpoints is the promotion and prioritization of certain design norms, three of which are detailed in this report. These norms should be integrated into early planning stages of the plant and throughout the detailed design work, construction, and daily operation to ensure the health, well-being, and integrity of employees and customers alike.

“Using Biodiesel Fuel in Your Engine” Penn State Extension. “Using Biodiesel Fuel in Your Engine” Penn State Extension. 15 “Biodiesel Emissions,” Biodiesel: America’s Advanced Biofuel. 16 ”Nitrogen Oxide,” U.S. National Library of Medicine. 13 14

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2.1 Stewardship From its conception, the biodiesel plant proposal is centered on the importance of environmental stewardship. The proposed biodiesel plant would lower total emissions, generate less hazardous waste, and draw from a readily available and constant feed source of grease and turn something originally considered waste into a desirable product. Furthermore, it becomes increasingly vital in a world of unlimited demand and limited resources to think forward to a time when the nonrenewable resources currently used for energy generation are no longer a feasible option. Additionally, exercising stewardship requires examining the consequences of energy consumption and making every effort to mitigate the problems (greenhouse gas emissions or high volumes of dangerous waste material) faced by the energy industry.

2.2 Caring Once built, the proposed plant would require employees to operate the plant equipment. Caring, one of the design norms, becomes an important attribute of the design engineers for the safety of all employees. From the reactor catalyst selection to the layout of the plant units, care must be exercised to ensure employees aren’t required to put themselves in harm’s way as part of their job description and to ensure safety procedures are established for routine and non-routine tasks. This design norm will be practiced when designing the controls used in the plant and by not introducing dangerous chemicals into the design without taking proper safety measures.

2.3 Transparency The potential for dangerous situations extending beyond the plant property are necessary to internally evaluate and communicate to local government and local citizens who could be negatively affected by the plant. Transparent business practices require full disclosure to employees and citizens of potential hazards, Furthermore, since the final product must meet certain governmental standards to be used in diesel engines, it is important to the team to ensure that the plant meet or even go beyond these 14

standards. No shortcuts or half-measures will be taken in the design process in an attempt to promote the profitability of the design over the quality.

3. Project Management Task deadlines were assigned based on both class and team-specific deadlines. Professor Jeremy VanAntwerp was assigned to the team as a project advisor, and he met with the team every other week to discuss progress and design challenges. Professor VanAntwerp connected the team with Randy and Doug Elenbaas, who served as an industrial consultant. Randy Elenbaas is a chemical engineer employed at Vertellus Specialties, Inc. in Zeeland, Michigan with valuable knowledge of process design and project management. Doug Elenbaas is a professional engineer at El Energy Consulting LLC, with over 30 years of engineering experience. As seen in Figure 3, the project could be divided into three sections with research integrated throughout the process: the main reaction with pretreatment, the main reaction without pretreatment, and post-treatment. This schedule illustrates the team’s method of approach for choosing the most profitable design.

Post-treatment

Tranesterification Reaction

Need for Pretreatment

Research Design Criteria

Research Design Criteria

Design Criteria Design Decision Design Decision

Design Decision Economic Optimization

Figure 3: Work Breakdown Schedule Organized as Critically Linked Tasks

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Team Responsibilities Hannah Albers Hannah was tasked with the transesterification reactor design including catalyst selection, kinetic modeling, reactor type, and reactor sizing. She was also responsible for feed selection and characterization, and recording the team’s weekly progress to be reported to Professor VanAntwerp during regular meetings.

Ben Guilfoyle Ben was tasked with pretreatment design including esterification reaction kinetics, sizing, and design alternatives, and he was also responsible for feedstock research in the Miami area. Ben was also responsible for product purification simulations and worked on economic analysis to prove the plant’s profitability. He is the team’s webmaster and kept the team’s website up to date throughout the year.

Melanie Thelen Melanie was responsible for economic analysis for the optimized plant and UniSim design work. She headed research pertaining to governmental biodiesel standards and regulations and safety, and she kept the team organized by ensuring all class deadlines were met and deliverables were submitted on time.

Cole Walker Cole was tasked with the preliminary pretreatment design including filter selection, membrane design, and batch reactor simulations in SuperPro designer. He was also responsible for financial research pertaining to market trends and plant profitability. Melanie and Cole completed laboratory work with grease samples to help the team better quantify % FFA of restaurant grease for the design.

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4. Process Overview 4.1 Process Research 4.1.1 Block Flow Diagram

Acid Catalyst

WCO

Methanol

Methanol

Basic Catalyst

Pretreatment

Main Chemistry

Purification

Lower free fatty acid content Methanol recovery

Transesterification WCO conversion to biodiesel

Methanol recovery Glycerin separation

Biodiesel

Glycerin

Waste Water

Figure 4: Process Overview (above) and Block Flow Diagram (below)

4.1.2 Reaction Chemistry The precursor to biodiesel molecules is a triglyceride. A triglyceride is an ester composed of three fatty acids connected with a glycerin backbone (see Figure 5. The fatty acids in waste grease can either be saturated (animal fat derivative) or unsaturated (vegetable oil derivative). A glycerin molecule

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consists of three hydroxyl (HO-) groups, which form ester bonds with the carboxyl (-COOH) groups in the fatty acids. Triglycerides can be burned on their own in diesel engines but the three “tails” can become tangled, increasing the viscosity. A highly viscous fuel could congest fuel injectors and other engine internals. Instead, transforming triglycerides into biodiesel molecules will lower the viscosity.

Figure 5: Triglyceride Molecule17

The main reaction that converts a triglyceride to biodiesel is called transesterification. In this process, triglycerides are contacted with methanol, which causes the single carbon-oxygen bonds to break. The methanol then reacts with the free end of the fatty acid to form a methoxy group, creating a biodiesel molecule. Since one triglyceride molecule “frees” 3 fatty acids, 3 molecules of biodiesel are produced for every one triglyceride. As shown in Figure 6, the final biodiesel molecule will have a long carbon chain with an ester group, formed by the addition of the methoxy group. The overall reaction is shown in Figure 6.

Figure 6: Overall Biodiesel Reaction18

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”The Chemistry of Biodiesel”. Goshen College

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Lasry, Sophie, “Renewable Energy”

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where R1, R2, R3 are alkyl groups that can be the same or different. When methanol breaks the carbonoxygen bonds in the triglyceride, the entire backbone molecule remains intact and becomes glycerol—or soap. As seen in the chemical mechanism, a base catalyst is used this reaction and will be discussed in depth in section 5.2.5 Catalyst.

4.1.3 Key Variables The feedstock to be used in the process will be trap grease—that is food waste grease that is unable to be processed as wastewater. The oil portion of the grease may or may not be solid at room temperature but it will contain solid food particles that need to be filtered out. Within trap grease, there are two main types of grease: brown grease and yellow grease. Brown grease is essentially rotten food oil while yellow grease is rendered animal fat and used vegetable frying oil. The most significant difference in regard to biodiesel production is the free fatty acid (FFA) content of the grease. Brown grease contains more than 15% FFA while yellow grease has less than 15%. An increased amount of FFA is undesirable since it decreases the amount of triglycerides that can be turned into biodiesel. However, there are methods of turning FFAs into esters, which will be discussed later. Yellow and brown grease can either be processed simultaneously or separated beforehand. The rest of the grease is composed of triglycerides, which can be directly converted to biodiesel, as seen in Figure 6. The majority of processes involve a pre-treatment of high FFA feedstock with an acid catalyst. An acid catalyst, like sulfuric acid, will convert the FFAs to esters, increasing the overall conversion and product quality. It has been found that feed stocks need to have approximately 1% FFAs or less to provide acceptable product quality19. One problem with pre-treatment is the formation of water as a byproduct of the FFA to ester reaction. This water needs to be removed since it would otherwise contaminate the final product. Another issue with the acid pre-treatment is potential damage to vessels, so an appropriate material of construction needs to be selected for the vessels. This acid pretreatment can be repeated to

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Encinar, “Study of biodiesel production from animal fats with high free fatty acid content”

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lower the FFA level to less than 1% since a lower FFA content indicates a higher overall process conversion to biodiesel. Additionally, FFAs can cause undesirable side reactions in the reactor, such as saponification. Saponification is a soap formation process, as seen in Figure 7.

Figure 7: Saponification of Free Fatty Acids to form soap20

The FFA needs to be removed or converted before contacting with NaOH base in the main reactor to prevent the soap formation. The saponification reaction occurs in the presence of water, so the water formed in the acid catalyst reaction, seen in Figure 8, needs to be removed.

Figure 8: Water formation in an acid catalyst reaction to convert Fatty acids to biodiesel 21

Despite pretreatment, some soap (glycerin, in this case) will inevitably form and pass through to the main reactor. Glycerin separation techniques will be discussed later in this report. Upon completing the pretreatment, the feed is transferred to the main reactor where it is heated to between 50°C and 60°C. The temperature must remain below the boiling point of the chosen alcohol so it remains in the liquid phase without pressurizing the reactor. A solution of alcohol and alkaline catalyst is prepared separately and added to the reactor. The alkaline catalyst is present to speed the reaction of

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”Biotechnology Trends,” Best Biotech ”Water Formation in Biodiesel Production,” Intech Journals

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triglycerides to methyl esters and convert any remaining FFA to soap. An agitator is used for up to one hour to ensure proper mixing, and the new solution settles. After proper separation, there will be a layer of biodiesel at the top of the reactor, and any soap formed will settle at the bottom. Once these layers are separated, biodiesel is ready for use. The variables to be manipulated in this process are: · · · · · · · · ·

Number of pre-treatment cycles (0, 1, or 2) Acid catalyst used in pre-treatment (sulfuric , hydrochloric , or other) Alcohol used in pre-treatment (methanol or ethanol) Ratio of acid catalyst to alcohol Temperature Alkaline catalyst (NaOH, KOH, NaOCH3, metallic Na, or other) Ratio of alkaline catalyst to alcohol Agitator time Settling Time It is important to note that this process assumes a given feedstock where the initial composition

cannot be predicted or manipulated with accuracy.

4.1.4 Design Alternatives In addition to the process described above, there are many alternative processes to convert used grease to biodiesel under development. One option is using a supercritical reactor for processing grease with high FFA compositions. This process operates at high temperature (275°C to 325°C), high pressure, and therefore must take place in pressure-rated reaction vessels. This reactor does not require a catalyst because of the high temperature and pressure, so some separation steps are no longer necessary to purify the downstream product. Furthermore, side-reactions are less of a concern with no catalyst present. Initial FFA content, water formation and subsequent glycerol formation due to the high operating conditions affect the process less. However, the capital and operating costs are very high. This is not a feasible option for a start-up plant of this scope. It would be better implemented as part of a revamp for a current facility since capital costs associated with pressure-rated vessels are higher. Another process is glycerinysis, a process that can handle feed stocks with greater than 10% FFA. Glycerin is heated to 400F and reacted with the FFAs in the feed to form monoglycerides. These monoglycerides can be processed as normal with the triglycerides by using an alkaline catalyst to form 21

biodiesel. Problems with this process include high operating costs due to the high heat, a high-pressure boiler to keep the process in liquid phase, and a vacuum to remove any formed water. Glycerinysis is similar to the process mentioned earlier because the glycerin must be separated at the end, but there is much more glycerin produced in glycerinysis. Finally, the use of solid acid catalyst is an emerging option for processing grease. The mixture of grease and alcohol flows through the solid acid catalyst packed bed reactor. Water is still formed during the reaction though, so the alcohol/water solution separated the end must be distilled to recycle the alcohol. Also, contaminants in the oil like phosphorus and water can foul the catalyst.

4.2 Material Research 4.2.1 Feed Sources The feed grease will be collected from restaurants in the Miami area. In the greater-Miami area there are approximately 10,750 restaurants22. It was also found that an average restaurant produces about 35 lbs of grease per day23. This means that about 375,000 lbs of waste restaurant grease is produced per day in the Miami area. The greater Miami area is 6,137 square miles, which is well within reason to expect the plant’s trucks to be able to collect from the entire area. At the same time, it is not feasible to expect every restaurant to contribute to the plant’s feed stock, so it was estimated that the plant could collect approximately 75% of this waste grease. This leads to the estimation the plant will operate with a feed of 130,000 kg of waste restaurant grease per day.

4.2.2 Feed Composition Research In conjunction with BIOL383L, research was done to analyze the average composition of a sample of restaurant waste grease. The grease was obtained from Johnny's Café where they make both vegetable and animal products in the fryer.

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Knight, Lauren. "How Many Restaurants and Bars are there in Miami?" Rosinski, Alan. "How Much Grease Fast Food Places Put Out." greener ideal

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4.2.2.1 Methods First, the waste grease was heated until homogenous and filtered through a cheesecloth to remove any suspended particles. Then, the grease was washed to reveal a lipid extract phase. A separatory funnel was used along with a chloroform-methanol solution to separate the lipid phase. Thin layer chromatography (TLC) was used to analyze the lipid phase. This method uses a highpolarity silica coated plate and a low-polarity solvent that travels up the plate. A dot of the sample to be analyzed is placed at the bottom of the plate, and the plate is placed in a beaker with a small amount of solvent on the bottom. As the solvent travels up the plate, the movement of the sample depends on its polarity. Standards were created to compare the lipid sample movement to known compounds. Butter was used to simulate triglycerides and linoleic acid was used to simulate free fatty acids. Known concentrations of each of the standards and the lipid extract were run on a TLC column. Then the plates were stained with iodine chips to reveal the spots of sample. The area of the sample spot directly correlates to the concentration of the sample.

4.2.2.2 Results The area of the samples were calculated using a program called ImageJ, which counts the number of pixels in a traced area. Standard curves were generated which compared the known concentration to the number of pixels in the spot.

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Figure 9: Standard Curve of Linoleic Acid

Then the extract was run and the area of the triglyceride spot and FFA spot were compared to the standard curves.

Figure 10: TLC Plate of Butter, Linoleic Acid and Grease Extract

It was determined that this grease contains 29% FFAs. This agrees with literature values, which say that yellow grease contains 4-15% FFAs and brown grease contains 50-100% FFAs24. Yellow grease comes from vegetable oil and brown grease comes from animal fat. Since the sample contains both, 29% is a reasonable result and representative of waste grease from many restaurants that serve both animal and

24

”Brown Grease Feedstock for Biodiesel.” National Renewable Energy Laboratory

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vegetable fried products. This value will be used to determine the amount of pre-treatment needed to reduce the FFA content to less than 1% (the standard for adequate conversion).

4.2.3 Feed Composition Model The variable nature of waste cooking oil (WCO) presents a challenge when modeling feedstock characteristics. Table 1 displays average fatty acid composition of WCO compared to several pure oils with known chemical properties necessary for creating a kinetic model, and all candidates listed in Table 1 have been used by the scientific community as models for WCO. WCO composition best fits within the soybean oil fatty acid percentages. The kinetics of different oils were simulated to quantify the effect of feed composition variations on biodiesel conversion, and these differences were determined to be very significant. Figure 11 compares the conversion of jatrophas oil25 and soybean oil26, which differ by approximately 50% triglyceride overall conversion, all other reaction conditions being the same. This comparison emphasized the sensitivity of feed composition on product yields. Table 1. Fatty acid composition of WCO and various oils.27,28

Fatty Acids

WCO

Soybean Oil

Sunflower Oil

Jatrophas Oil

Linseed Oil

Linoleic Acid

44%

43-56%

44-75%

19-41%

17-24%

Linolenic Acid

5%

5-11%

--

--

35-60%

Oleic Acid

34%

22-34%

14-35%

37-63%

12-34%

Palmitic Acid

14%

7-11%

3-6%

12-17%

4-7%

Stearic Acid

4%

2-6%

1-3%

5-9.5%

2-5%

Given these results, the decision was made to model WCO as soybean oil for the most accurate process model. The free fatty acids also present in the feed were modeled as a combination of the fatty

25

Aransiola, 2013 Noureddini, 1997 27 Abidin, 2013 28 Chempro, Fatty Acids Composition 26

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acid chains that would convert to the methyl ester form when pretreated with methanol and sulfuric acid (e.g. oleic acid converting to methyl oleate).

1

Triglyceride Conversion

0.9 0.8

Jatrophas

0.7

Soybean

0.6 0.5 0.4 0.3 0.2 0.1 0 0

200

400

600

800

1000

1200

1400

1600

1800

2000

PFR Transesterification Reactor Volume (L) Figure 11. Kinetic comparison of oils with different feed compositions.

4.2.3 Alcohol There are two alcohols that would be suitable for this process: methanol and ethanol. The purpose for the alcohol will be discussed in the pre-treatment and transesterification reactor sections. Methanol was chosen over ethanol as the pretreatment alcohol because it is more commonly used and is significantly cheaper than ethanol29. However, methanol is typically produced from natural gas in a petroleum refinery. Not only is this source non-renewable, it is also requires high amounts of energy to produce. This counteracts the purpose of creating a biofuel if a petroleum-based product was used in the process. Therefore, it was determined that a bio-based methanol should be used. Bio methanol is most typically produced by gasifying a variety of organic materials such as wood waste, algae and glycerin—a by product of the biodiesel production process30.

29 30

"Ethanol and Unleaded Gasoline Average Rack Prices." State of Nebraska. 2014. http://www.chemicals-technology.com/features/feature77667/

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4.2.4 Product Table 2 features the federal EPA specifications for 100% biodiesel stock fuel, but a majority of the EPA specifications pertain to compounds that were outside the scope of the feed composition model. Table 3 presents the specifications met by the final process. Table 2: EPA Biodiesel Specifications

Table 3. EPA biodiesel specifications met by final design.

Property Water and sediment Total glycerin Methanol content

Limits 0.050 max 0.24 max 0.2 max

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Simulation Result 0.008 0.22 0.198

Units vol% wt% vol%

5. Design 5.1 Pre-Treatment Section

Figure 12:Pre-Treatment Block Flow Diagram

5.1.1 Water Removal Before the feed can enter the pre-treatment section, the water content needs to be reduced to less than 0.2 wt%31. The most common problem that biodiesel producers face is excessive water in the feed. This will compromise the product quality by limiting reactions and creating unwanted glycerin instead of biodiesel. First, free water will be removed by gravity separation. The feed will sit in a heated storage tank for 24 hours, during which the oil and water will separate and the water (which is heavier than oil) will settle to the bottom. The tank is heated in order to make the oil phase thinner, thus speeding up the separation process. Now, the water content is approximately 0.4 wt%, still double the allotted amount. After the free water has been removed by gravity separation, the oil phase will be moved to an evaporator to remove any entrained water. The evaporator will be heated and agitated for 8 hours. During this time, additional water will be evaporated, lowing the total water content to