Biofuels. Lec 2: Biodiesel-Part 1

Transcription

1 Biofuels Lec 2: Biodiesel-Part 1 Dr.-Eng. Zayed Al-Hamamre 1 Content Diesel Fuel Biodiesel SVO and Oilseed Processing Production Methods 2

2 Energy Use What do we use energy for? Heating & Cooling Lights, appliances, cooking, household uses Manufacturing Transportation 3 3 Transportation Fuels Two fuels dominate the transportation fuel market: Diesel Biodiesel can be used to supplement or replace diesel fuel Gasoline Diesel Fuel Facts - Widely available - Diesel engines are common - Refining and transportation infrastructure is well developed - Consumers know about diesel 4 4

3 Diesel Fuel Recent Developments New diesel fuel standards (low sulfur diesel) New diesel burns cleaner (good) Lubricity is reduced (bad) Retail diesel prices have increased Why? Demand has been growing Refining capacity is strained Transportation capacity is strained Higher fuel quality standards 5 5 Characteristics of Petroleum Diesel Produced from petroleum Product of distillation of crude oil Amber in color Immiscible High boiling point of > 300 F (> 149 C) Property of DOE, reprinted with permission 6 6

4 Characteristics of Petroleum Diesel Low vapor pressure: 0.40 mmhg Flash point between 100 F & 160 F (38 C & 71 C) Specific gravity between 0.82 & 0.95 Vapor density > 1 Exposure: Irritation to eyes Damage to respiratory system Class B fires Copyright 2008, TEEX/ESTI 7 7 History of Biodiesel Using vegetable oil as fuel in diesel engines isn't a new idea. Rudolf Diesel's first engines were built to run on peanut oil in Since then many researches have taken place to improve the performance of the biodiesel when it s burned in the engine. 8

5 What is Biodiesel? Alternative Fuel derived from from renewable sources like new and used vegetable oils and animal fats Contains no petroleum but be blended with petroleum diesel Produced domestically from renewable resources Biodegradable, Decays in natural conditions (approximately the same as sugar); 9 What is Biodiesel? Nontoxic Fuel; practically does not contain some sulfur and cancerogenic benzene Biodiesel can be blended with diesel fuel o Low-level blends ( 20% biodiesel) can be used in almost any existing diesel engine o High-level blends (>20% can be used in most new diesel engines Biodiesel be produced in small or large quantities o Small-scale producers generally use vegetable oil Provides significant reduction in harmful emissions in an atmosphere at burning, both in engines of internal combustion, and in technological units; 10

6 What is Biodiesel? Only used in diesel engines Immiscible Lower energy content than Diesel o Biodiesel: 118,296 BTUs per gallon o No. 2 Diesel: 129,500 BTUs per gallon Source: National Biodiesel Board Energy Lifecycle o 3.2 units of energy are produced for each energy unit used Source: NREL 11 What is Biodiesel? Will biodiesel damage my engine? No if the biodiesel meets the standards of ASTM 6751 One exception: Biodiesel can damage certain natural rubber engine components over time Older engines may require the replacement of fuel lines and some gaskets These components are unlikely to fail immediately but may fail with increased biodiesel use 12 12

7 Characteristics of Biodiesel Liquid varying in color Immiscible High boiling point of F ( C) Low vapor pressure: < 2 mmhg Flash point 199 F (93 C) Has high temperature of ignition (more than 100 С), that makes its use rather safe Specific gravity between 0.86 & 0.90 Vapor density > 1 Less hazardous in terms of flammability Increases cetane number of fuel and its greasing ability, that essentially increases a resource of the engine; Biodiesel-Blended Fuels Can be used alone / blended B20: 20% biodiesel B99: 99% biodiesel B100: pure biodiesel Mixing biodiesel fuels: - At the plant - Splash mixed in tanker trucks - Line-mixed Property of DOE, reprinted with permission 14 14

8 SVO and WVO Straight Vegetable Oil is not biodiesel This includes Waste Vegetable Oil Diesel engines can be modified to run on vegetable oil Some users who have modified engines have reported long term problems using SVO Biodiesel can be used in any diesel engine with no modifications to the vehicle SVO and WVO To get a diesel engine to run off of straight vegetable oil a conversion needs to be done to the vehicle; o A parallel fuel system is required. o start the vehicle off of diesel, and once it heats up, the coolant from the engine can be used to heat the vegetable oil. o Once the vegetable oil is heated to a certain temperature, and its viscosity is lower, then can switch to using the vegetable oil. Raw vegetable oil requires all sorts of engine, tank, and fuel line modifications 16

9 SVO and WVO Main Problems: o These fuels are too thick. The must be thinned to function in a diesel engine How? By heating or a by chemical reaction (the chemical reaction is the biodiesel production) Problem is worse the lower the temperature Modified engines still typically use SVO in conjunction with diesel for start up and shut down No government incentives for SVO and WVO 17 Types of Oil seeds Major U.S. Oilseed Crops Soybean Cottonseed Sunflower Canola/Rapeseed Flaxseed Safflower Other oil producing crops - Corn - Peanut - Camelina Palm Olive Coconut 18 18

10 Types of Oil seeds Crop Ave. Oil Content Soybeans 22% Canola 40% Flaxseed 38% Safflower 35% Sunflower 42% Mustard 36% Oilseed Processing The Oilseed Processing Industry: Separates the whole seed into 2 or more products The difference between the cost of the seed and the value of the products created is the crushing margin o Two General Methods Solvent Extraction Standard technology for facilities with daily capacities of greater than 300 tons per day Commonly used in conjunction with some form of mechanical extraction o Mechanical Extraction Typically used for facilities with daily capacities of less than 150 tons per day 20 20

11 Simple extraction of materials Biomass Extraction Purification Usage Palm oil press 21 Solvent Extraction Nearly all commercial soybean processors use solvent extraction technology 22 22

12 Solvent Extraction The basic process: Seed Preparation Removal of foreign objects Removal of seed hulls or shells for some seeds Pre-Pressing Seed is crushed through a mechanical press Pre-Pressing removes some oil from high oil content seeds Solvent Extraction The basic process: Solvent Application Solvent (hexane) is applied to the pre-pressed material The solvent bonds to the oil in the material Solvent & oil mixture is removed from the meal The oil is then separated from the solvent which is reused in the process 24

13 Solvent Extraction Benefits: Solvent Extraction is capable of recovering of 99% of the oil contained in the seed Lowest cost per ton for commercial processing Challenges: Large capital investment Not feasible for small-scale processing Environmental concerns Super Critical Oil Extraction Most efficient method. Uses carbon dioxide at critical pressure and temperature (CO2 is almost a liquid). Carbon dioxide. Rapid diffusion of the oil. Very expensive process. 26

14 Mechanical Extraction The basic process: Seed Preparation Removal of foreign objects Removal of seed hulls or shells for some seeds Extraction Seed is processed by a mechanical press Removing 65-80% of oil contained in the seed Mechanical Extraction Required Equipment Mechanical Press Power source for the press Seed Bins Meal Bins Oil Tanks Pumps, Filters, Plumbing 28 28

15 Example On-Farm Example: If you plant 100 acres of canola, with an average yield of 1,100 lbs per acre, your production is approximately 55 tons The 55 tons of seed will yield approximately: - 4,200 gallons of oil - 36 tons of meal * Assuming: The seed has 38% oil content and press recovers 75% of the oil content in the seed. Acres : A unit of land area equal to hectare Example On-Farm Example: If you plant 100 acres of safflower, with an average yield of 800 lbs per acre, your production is approximately 40 tons 30 30

16 Biodiesel = FAME Fatty Acid Methyl Esters (FAME) Fatty acids taken from oils or fats Reacted with MeOH Washed, dried to remove impurities Must comply with fuel standards (U.S., European, etc.) Variety of blends, from B5 to B100 FAME 31 Chemistry of Oils and Fats Fatty acids are long-chain carboxylic acids A glycerol bonded to 3 fatty acids is called a triglyceride Oils/fats contain triglycerides and unbonded, or free, fatty acids (FFA s) A Fatty Acid A Triglyceride 32

17 Biodiesel Production Process Source: Brent Schulte, University of Arkansas. Biomass Magazine April Production Methods 1. Direct use and blending simplest method, 80% of petroleum heat content, ready available feed stock, viscosity too high, reactivity of unsaturated hydrocarbons 2. Micro emulsions Utilizes alcohol solvents to reduce viscosity, causes carbon and laquer deposits on engine parts 3. Thermal cracking Yields both biodiesel and gasoline, biodiesel produced similar to petroleum, negates emissions benefits 34

18 Production Methods 4. Transesterification Most common production method can be used as a continuous process, more easily meets biodiesel fuel standards, expensive alcohol catalyst Uses vegetable oils and animal fats as feed stocks The reaction of a fat or oil with an alcohol to form esters (biodiesel) and glycerol 35 Base-catalyzed Transesterification Most common process Most economical Low pressure (20psi) Low temperature (150 o F) No intermediate steps High conversion rate (98%) 36

19 Base-catalyzed Transesterification Possibility of formation soap if there is a high free fatty acids (FFAs) content in triglycerides. Excessive water can hydrolyze to form FFAs. Recycling of catalyst is challenging and not cost effective. Glycerol is in the crude form and has very little value. 37 Transesterification First observed in 1850 s One main reaction for biodiesel production Exchanges an ester s functional group Must be catalyzed, either base or acid R (below) is methyl, and it replaces glycerol group Viscosity is reduced significantly Transesterification 38

20 Schematic of the Transesterification process Biodiesel 100% Glycerin 39 Transesterification Reaction Triglyceride Fatty Acid Chain Biodiesel Glycerol Catalyst (KOH) Methanol Glycerol 40

21 Free Fatty Acids Interfere With Biodiesel Production Soap Methanol Free Fatty Acid Glycerol Catalyst (KOH) Methanol Glycerol 41 Formation of Soap Formation of soap inhibits the separation process and also deactivate the catalyst. Source: Gerpen et al., Biodiesel Production Technology 42

22 Hydrolysis of Triglycerides At high temperature, water can hydrolyze triglycerides and form free fatty acids (FFAs). Source: Gerpen et al., Biodiesel Production Technology 43 Acid-catalyzed Transesterification Acid catalyzed transesterification is very slow compared to basecatalyzed transesterification. Suitable for oil that has higher FFAs. This process uses strong acid to catalyze esterification of the FFAs and transesterification of triglycerides. The process does not produce soap with high FFAs because no metal is present. Esterification of FFAs is generally faster but produces water. Source: Gerpen et al., Biodiesel Production Technology 44

23 Enzyme-Catalyzed Transesterification Use enzymes to produce esters from triglycerides. Relatively longer period of reaction. Expensive to produce because of the cost of enzymes. No commercial plant using enzymes to produce biodiesel. Catalyst separation issue can be solved easily. 45 Supercritical Transesterification Liquid is defined as supercritical when its temperature and pressure are above critical points. Supercritical temperature and pressure for methanol are 240 o Cand 1140 psia, respectively. No Catalyst is required but can be used. 46

24 Biodiesel Feedstocks Traditional The most common form of Biodiesel is that made by the transesterification of vegetable oils In the US, soybeans provide the most common feedstock In Europe, rapeseed [canola] provides the most common feedstock Other Common Feedstocks Sunflower oil is commonly used in France and Eastern Europe Palm Oil is common in Malaysia Used cooking oil is quickly becoming a common feedstock Tallow is also becoming common and contains highly Saturated Fatty Acid Triglycerides. 47 Feedstock Selection Material FFA Content Cost Refined oils (soybean, etc.) 0-1% High Waste oils (fry grease) 2 7 % Low Animal fat (lard) 5 30 % Low Yellow grease 7 30 % Moderate Brown grease > 30 % Very Low Source: Kemp, William H. Biodiesel Basics and Beyond. p

25 Effect of Water Content and FFA Source: Ayhan Demirbas, Biodiesel: a realistic fuel alternative for diesel engines 49 High FFAs Feedstocks Put excess catalyst to form soap and soaps are stripped using centrifuges ( caustic stripping ). Acid-catalysis followed by base-catalysis process. Acid catalyzed transesterification. 50

26 Procedure for High FFA Feedstocks Measure FFA level. Add 2.25 g methanol and 0.05 g sulfuric acid for each gram of free fatty acid in the oil or fat. Agitate for one hour at 60-65ºC. Let the mixture settle. Methanol-water mixture will rise to the top. Decant the methanol, water, and sulfuric acid layer. Take bottom fraction and measure new FFA level. 51 Source: Gerpen et al., Biodiesel Production Technology Catalyst Selection Acid or base catalyst Base is faster, more economic With high FFA, base catalyst will produce soap Base catalyst also produces glycerol as coproduct Acid catalysis can fix the soap problem Most commercial processes use base catalysis 52

27 Methanol Vs. Ethanol Ethanol is more expensive than methanol. Lower ethyl ester conversion. Ethanol is difficult to recycle. Viscosity of the ethyl ester is slightly higher than that of methyl ester. Cloud and pour points are slightly lower than that of methyl ester. 53 Production 1. Oil Extraction or Clean and heat biolipid (WVO ) 2. Titration the WVO sample. (Optimal PH7) 3. Determine the Amount of Methanol and Catalyst 4. Mix the bioalcohol and catalyst in exact amount 5. Combine methanol/caustic with biolipid at 50 C, mix and heat for several hours (Transesterification Process) 6. Separate biodiesel and glycerol and remove (recovery) alcohol 7. Crude Biodiesel Purification 54

28 Production Pre-Reaction Equipment Oil Storage Tank Alcohol Storage Tank Catalyst Storage Biodiesel Reactor Pumps, Filters, Plumbing Production Post-Reaction Equipment Settling tanks and/or Separating Equipment Washing Equipment Drying Equipment Biodiesel Storage Tank Glycerin Storage Tank Pumps, Filters, Plumbing 56 56

29 Biodiesel Processor Micro Scale Biodiesel Processor (100 gallons or less per batch) Small Scale Biodiesel Processor ( gallons or less per batch) 57 Commercial Processing Unit for Home Made Biodiesel 58

30 Biodiesel Processor Processing 4,200 Gallons 40 gallon processor: 105 batches 60 gallon processor: 70 batches 100 gallon processor: 42 batches Industrial Biodiesel System ton/year Client: Brasil Ecodiesel 59 Industrial Biodiesel System ton/year Client: Brasil Ecodiesel May, Eastern Biofuel

31 Production 61 Final Products Biodiesel On-Farm Use Blended Fuels 100 lbs. of Soybean oil +10 lbs Methanol = 100 lbs. Soy biodiesel +10 lbs of Glycerol Fuel Quality Important Vehicle Modifications May need to replace natural rubber fuel lines and gaskets 62 62

32 Final Products Crude Glycerin No Ready Market for Crude Glycerin Quantity produced is 10% to 20% of biodiesel production Contains Methanol & Catalyst Possible Uses: Compost Fuel Oil Refine to Pharmaceutical Grade Glycerin Biodiesel Final Product 64

33 Biodiesel Final Product Biodiesel 100% Glycerin 65 Biodiesel Final Product BioDiesel is here 66

34 Washing and Drying 67 Biodiesel Emissions Compared to petroleum diesel, reduced emission of: --Unburned hydrocarbons --Carbon monoxide --Particulate matter --Sulfur oxides Overall ~50% less than that for diesel fuel 68

35 Biodiesel Emissions Biodiesel reduces most 20% problematic emissions 10% 0% NOx (greenhouse) -10% emissions are increased -20% -30% Led to regulatory -40% problems with TCEQ -50% Can be addressed with -60% -70% NOx reducing additives Change in emission Percent Biodiesel NOX PM CO VOC Source: U.S. EPA 69 Biodiesel Emissions Think about the environment 70

36 Biodiesel Emissions 71 Biodiesel Advantages Produced from renewable materials eco friendly / closed CO cycle. Local & self production less reliance on foreign oil. Contains practically no sulfur (0.001%) non toxic. Considerably decreases emissions (up to 50%). Easily decomposes does not harm soil or ground water. Biodiesel is not hazardous material (flashpoint above 110 C). Eligible as fuels under international standards & specifications (world-wide). Eligible for CDM (Clean Development Mechanism - Kyoto Treaty) 72

37 Biodiesel Benefits High energy return and displace petroleum based fuels. Biodiesel reduces life-cycle greenhouse gas emissions. Biodiesel reduces tailpipe emissions except NO x. Biodiesel improves air quality and has positive impact in human health. Biodiesel improves engine operation and easy to blend. Source: NREL, Biodiesel Handling and Use Guide 73 Biodiesel Drawbacks Biodiesel can be corrosive to rubber materials. Biodiesel cannot be stored in concrete lined tanks Biodiesel is not necessarily more economic than regular diesel. Depend on the plants, their related processes and, other incentives. Biodiesel can last up to 6 months. In 6-12 months need to be treated. 74

38 Biodiesel Storage Biodiesel should be stored 5-10 degrees F above cloud point. Above ground fuel systems should be protected with insulation, agitation, heating systems, or other measure. Test Method Cloud Point ASTM D2500 Pour Point ASTM D97 Cold Filter Plug Point IP 309 B100 Fuel o F o C o F o C o F o C Soy Methyl Ester Canola Methyl Ester Lard Methyl Ester Edible Tallow Methyl Ester Inedible Tallow Methyl Ester Yellow Grease 1 Methyl Ester Yellow Grease 2 Methyl Ester Biodiesel Transportation Should not be contaminated Trucks or railcars should be washed from previous load to prevent mixing with leftover residuals or water. In cold weather can be shipped in several ways Hot for immediate delivery ( F) Hot ( F) in railcars for delivery within 7-8 days Frozen in railcars equipped with steam coils Blended with winter diesel, kerosene or other low cloud point fuel 76