DESIGN PROJECT ± CHE 3204
CHAPTER 1: INTRODUCTION
CHAPTER 1: INTRODUCTION 1.1 Problem statement statement
The project is about designing a biodiesel plant for the production of 40,000 tons per year of biodiesel from Palm Oil, according to the state-of-art technologies available, and it should include all unit operations starting from crude oil production, pretreatment of oil, transesterification, separation, glycerine treatment and treatment of residues and other wastes. The plant will be producing B100 and it will also operate for 330 days per year. This design has laid emphasis on the technologies adopted by the already existed successful plants around the world and it also conforms to the latest environmental standards. 1.2 Aim of the Design Project 1.2.1 Maurice Ile Durable & Climate Change
The Maurice Ile Durable Fund was created in July 2008, under the aegis of the Ministry of Renewable Energy and Public Utilities to support efforts to promote more efficient use of energy and increase the use of renewable energy. Rs 1.3 billion was provided by Government for financial year 2008-2009, derived from a token MID levy of 15 cents all petroleum products, LPG and coal. The volatility of oil prices and climate change have motivated many governments to explore alternative sources of energy and the focus has been mainly on renewable energy which includes biodiesel. Small Island Developing States (SIDS) such as Mauritius have difficult economic and political choices because of their higher level of vulnerability (Mauritius imported 406 toe of primary energy during the year 2009 for the transportation sector and this amounted to Rs 7,969 million (CSO, 2008)). In view of obtaining carbon credits the Maurice Ile Durable (MID) concept aims at decreasing dependency on fossil fuels. As Mauritius is a non-Annex 1 Country under the Kyoto Protocol, the Clean Development Mechanism (CDM) is the main vehicle to attract carbon financing to the energy sector. Mauritius can benefit from interesting annual cash flow if energy efficiency and renewable energy supply projects including biodiesel production were implemented. 1.3 Evolution of biodiesel
World largest suppliers of Palm oil are Malaysia, which produces 45% of the world¶s supply and Indonesia (39%). The strong growth in Palm oil consumption over the last six years has resulted in Palm oil being the dominant oil in the global market. As Soybean oil prices began to rise in 2001-02, the spread between Palm oil and Soybean oil began to widen, increasing the competitiveness of Palm oil in the world market. Since 2001-02, Palm oil consumption has increased to 13.2 million metric ton, compared to 8.7 MMT increase in Soybean oil consumption. Page 1 of 50
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The Global Biodiesel market is estimated to reach 37 billion gallons by 2016 growing at an average annual growth of 42%. Europe will continue to be the major Biodiesel market for the next decade or so with closely be followed by the US market. Europe is the world¶s largest producer and consumer of biodiesel, yet it consumes much more that is able to produce and therefore imports biodiesel. Higher blending obligations in some European countries (France, Germany, Portugal and United Kingdom) are expected to boost biodiesel consumption in 2011. Imports of biodiesel into Europe were expected to reach over 50,000,000 gallons in 2009. "The global markets for biodiesel are entering a period of rapid, transitional growth, creating both uncertainty and opportunity. The first generation biodiesel markets in Europe and the US have reached impressive biodiesel production capacity levels, but remain constrained by feedstock availability. In the BRIC nations of Brazil, India and China, key government initiatives are spawning hundreds of new opportunities for feedstock development, biodiesel production, and export" said Biodiesel 2020 author Will Thurmond.
Figure 1.0: World biodiesel production and capacity
"A fundamental transition in global fuel production is now happening. In the year 2007, there were only 20 oil producing nations supplying the needs of over 200 nations. By the year 2010, more than 200 nations became biodiesel producing nations and suppliers," said Thurmond. "The world is entering a new era of participation by emerging market nations in global green energy production for transport fuels." 1.4 Existing and future markets
The biodiesel retail price is always higher than that of petrodiesel. The size of the cost difference depends on the size of the biodiesel producers, their feedstock costs, transportation costs, production incentives, tax incentives, and other local variables. Although biodiesel is currently more expensive than petrodiesel, this difference is believed to be diminished with the development of biorefineries, the rising costs of crude oil and government tax subsidies. Pure biodiesel is sold at a price of around $1.50 to $2.00 per gallon. After adding fuel tax, this price goes up by $0.50 per gallon. A combination of 20% biodiesel and 80% diesel costs more per gallon compared Page 2 of 50
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to pure biodiesel. Today, commercial biodiesel is rated at approximately $1.33/gallon if composed of waste-grease. On the Stock Market Exchange it is in the $2-3/gallon range. The lowest bid price is $2. Comparatively the refined diesel rates are at a lower price, ranging between 75-80 per cent per gallon, while crude oil was $25-28/barrel in the beginning of the year. So unless biodiesel prices come down in contrast to diesel, plenty would still have normal diesel as their option. Improving methods to make biodiesel more refined would help bring down its pricing.
Figure 1.1: Chart from William Thurmond, President of Emerging Markets Online and author of Algae 2020: Biofuels Commercialization Outlook, and Biodiesel 2020: A Global Market Survey.
The figure above shows how biodiesel feedstocks (Palm oil, rapeseed oil, and soybean oil) are increasingly following diesel prices. There is a massive overcapacity for biodiesel production in the EU. 1.5 Comparison of biodiesel and its competitors
The advantages of biodiesel as diesel fuel are its portability, ready availability, renewability, higher combustion efficiency, and lower sulfur and aromatic content (Ma and Hanna, 1999; Knothe et al., 2006), higher cetane number, and higher biodegradability (Mudge and Pereira, 1999; Speidal et al., 2000; Zhang et al., 2003). The major disadvantages of biodiesel are its higher viscosity, lower energy content, higher cloud point and pour point, higher nitrogen oxide (NOx) emissions, lower engine speed and power, injector coking, engine compatibility, high price, and greater engine wear. The technical disadvantages of biodiesel/fossil diesel blends include problems with fuel freezing in cold weather, reduced energy density, and degradation of fuel under storage for prolonged periods. One additional problem is encountered when blends are first introduced into equipment that has a long history of pure hydrocarbon usage. Hydrocarbon fuels typically form a layer of deposits on the inside of tanks, fuel filters and hoses. However, this is a minor problem which is easily remedied by proper filter maintenance (Wardle et al., Page 3 of 50
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2003). Table 1.0 below shows the fuel ASTM standards of biodiesel and petroleum diesel fuels. Important operating disadvantages of biodiesel in comparison with petrodiesel are cold start problems, lower energy content, higher copper strip corrosion, and fuel pumping difficulty due to higher viscosity. This increases fuel consumption when biodiesel is used instead of pure petrodiesel. Taking into account the higher production value of biodiesel as compared to petrodiesel, this increase in fuel consumption raises in addition the overall cost of application of biodiesel as an alternative for petrodiesel. Peak torque is lower for biodiesel than petroleum diesel but occurs at lower engine speed. Biodiesels on average decrease power by 5% compared to diesel at rated loads (Demirbas, 2006b). Table 1.0 ASTM standards of biodiesel and petrodiesel fuels
Biodiesel is now mainly being produced from soybean, rapeseed, and palm oils. The higher heating values (HHVs) of biodiesels are relatively high. The HHVs of biodiesels (39 to 41 MJ/kg) are slightly lower than those of gasoline (46 MJ/kg), petrodiesel (43 MJ/kg), or petroleum (42 MJ/kg), but higher than coal (32 to 37 MJ/kg). 1.6 Development of new and relevant process techniques.
Industries are adopting more energy-efficient technologies to improve its profitability and competitiveness (Tehrani et al., 2009). Many researchers are now adopting the two-stage transesterification. In the first stage, esterification of FFA present in waste frying oil is performed using acid to decrease the FFAs to a level less than 1 %. In the second stage, transesterification of the obtained oil is performed using an alkaline catalyst. There can be also the use of Ultrasonic Reactors for biodiesel production. The use of Hielscher¶s ultrasonic reactor technology is a highly cost-effective means of converting a batch biodiesel reaction process to a continuous process since the ultrasonic reactors provide significant operational flexibility and improved recovery times from operational upsets caused in other areas of the process. New process for catalyst-free biodiesel production has recently been introduced by using subcritical acetic acid and supercritical methanol.
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CHAPTER 2: LITERATURE REVIEW 2.1 Oil Extraction Technique 2.1.1 Mechanical Presses
The technique of oil extraction by using mechanical presses is most conventional one. But oil extracted by mechanical presses needed further treatment of filterization and degumming. One more problems associated with conventional mechanical presses are, their design is suited for some particular seeds, and yield affected for other seeds. 2.1.2 Solvent Extraction Technique
It is the technique of removing one constituent from a solid by means of a liquid solvent also called leaching. The process may be employed either for the production of a concentrated solution of a valuable solid material or in order to free an insoluble solid, such as pigment from a soluble material with which it is contaminated. In this process, a chemical solvent such as n-hexane is used to saturate the crushed seed and pull out the oils. After completion of the extraction process the solvent is condensed and reclaimed. 2.1.2.1 Hot Water Extraction
The crushed seeds are mixed with a solvent and incubated in the water bath at a fixed temperature for fixed period of time. Agitation is provided externally for same period of time. After completion of the desired time interval, the contents are allowed to stand at room temperature. The heavier crushed seeds settle down and clear mixture of oil and hexane gets separated by filtration process. 2.1.2.2 Soxhlet Extraction
In comparison to hot water extraction, improved oil yields can also be obtained by using an ingenious device called a Soxhlet apparatus. This apparatus allows extraction of oil from the seed samples by using the distillation extraction method. 2.1.2.3 Ultrasonic Technique
In this process an ultrasonic water bath is used. A container of crushed seeds and solvent is partially immersed in the bath. This is then subjected to ultrasonic vibrations. Colloidal formation indicates extraction of oil from the seeds in the solvent. This method depends upon the surfactant solution, operating temperature and degassing of the solution. 2.1.3 Enzymatic Oil Extraction Technique
Enzymatic oil extraction technique has emerged as a promising technique for extraction of oil. In this process suitable enzymes are used to liberate oil from crushed seeds. Its main advantages are that it is environment friendly and does not produce volatile organic compounds as atmospheric pollutants. One disadvantage associated with this technique is the long process time which is necessary for enzymes to liberate oil bodies. Biodiesel (Greek, bio, life + diesel from Rudolf Diesel) refers to a diesel-equivalent, processed fuel derived
from biological sources. Biodiesel is the name for a variety of ester-based oxygenated fuels from renewable biological sources. It can be made from processed organic oils and fats. Chemically, biodiesel is defined as the monoalkyl esters of long-chain fatty acids derived from renewable biolipids. Page 5 of 50
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2.2 Method of biodiesel production 2.2.1 Pyrolysis
The pyrolysis refers to a chemical change caused by the application of thermal energy in the absence of air or nitrogen. The liquid fractions of the thermally decomposed vegetable oils are likely to approach diesel fuels. 2.2.2 Micro emulsification
Micro emulsions are defined as transparent, thermodynamically stable colloidal dispersion. The droplet diameters in micro emulsions ranges from 100 to 1000 Å. Micro emulsion can be made of vegetable oils with an ester and dispersant (co solvent), or of vegetable oils, and alcohol and a surfactant and a cetane improver, with or without diesel fuels. 2.2.3 Dilution
The dilution of vegetable oils can be accomplished with such material as diesel fuels, solvent or ethanol. 2.2.4
Transesterification
2.2.4.1 Catalytic Transesterification.
The ³Catalytic Transesterification´ process is the reaction of a triglyceride (fat/oil) with an alcohol in the presence of some catalyst to form esters and glycerol. A triglyceride has a glycerin molecule as its base with three long chain fatty acids attached. Acid Catalyzed Transesterification The acid catalyzed process is the reaction of a triglyceride (fat/oil) with an alcohol in the presence of acid catalyst preferably sulphonic and sulphuric acids to form esters (biodiesel) and glycerol. These catalysts give very high yields in alkyl esters, but the reactions are slow, requiring, typically, temperatures above 100°C.The acid-catalyzed transesterification should be carried out in the absence of water, in order to avoid the competitive formation of carboxylic acids which reduce the yields of alkyl esters. Alkaline Catalyzed Transesterification The alkaline catalyzed transesterification process is the reaction of a triglyceride (fat/oil) with an alcohol in the presence of alkaline catalyst such as alkaline metal alkoxides and hydroxides as well as sodium or potassium carbonates to form esters (biodiesel) and glycerol.( For more details see Chapter 3:Process Consideration) Lipase Catalyzed Transesterification This one is the reaction of a triglyceride (fat/oil) with an alcohol in the presence of lipase enzyme as a catalyst to form esters (biodiesel) and glycerol. In lipase catalyzed process no complex operations are needed not only for the recovery of glycerol but also in the elimination of catalyst and soap. 2.2.4.2 Supercritical Methanol Transesterification.
Supercritical methanol is believed to solve the problems associated with the two-phase nature of normal methanol/oil mixtures by forming a single phase as a result of the lower value of the dielectric constant of methanol in the supercritical state.
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2.3 Methyl Ester Wash
After the transesterification reaction, separation of the glycerol, the biodiesel still has high levels of soaps, aggressive pH, excess caustic and other impurities that must be removed via a wash process. The production residues and impurities left in the crude biodiesel after the reaction are dangerous to any combustion system and must be eliminated from the final product. Traditionally, the soap and trace amounts of glycerin are removed by washing with water. This involves mixing water with the biodiesel, agitating them gently, and then allowing them to separate. The soap and glycerin are extracted into the water phase and removed when the water is separated from the solution. As an alternative to water washing, several methods are available to remove soap and glycerin from biodiesel. Recently, several alternative ³waterless´ purification procedures have been used, such as ion exchange resins and Magnesol, a brand named adsorbent. There are several variations to water washing, including washing with deionised water, washing with acidified water, and using a membrane to prevent emulsions with water washing. Studies by Van Gerpen et al. (2003, 2005) have shown that adding acid to the wash water aids in removing soaps. Also, multiple washes are required to achieve satisfactory soap removal. There are different methods for washing biodiesel using water; static washing; agitation or stir washing; mist washing and finally bubbling. 2.3.1 Dry Wash Purification
As an alternative to water washing, several methods are available to remove soap and glycerin from biodiesel. Dry wash purification is a more recent addition to biodiesel purification. Current methods for dry washing the crude fuel include ion-exchange resins (like Amberlite or Purolite) and silicates (like Magnesol or TriSyl). 2.3.2 Ion-exchange purification
An ion exchange resin is an insoluble matrix normally in the form of small (1-2mm diameter) beads, usually white or yellowish, fabricated from an organic polymer substrate. The material has highly developed structure of pores on the surface of with sites which easily trapped and released ions. The trapping of ions takes place only with simultaneous releasing of other ions; thus the process is called ion exchange. 2.3.3 Dry wash process using adsorbent (Magnesol)
Magnesol was one of the first dry wash systems that were introduced, and it is manufactured by the Dallas Group. Magnesol, a synthetic Magnesium Silicate, is an ³adsorbent filter aid´ that ensures biodiesel quality by removing contaminants within methyl esters. Magnesium silicate has a strong affinity for polar compounds. By adsorbing these compounds, magnesium silicate actively filters excess methanol, free glycerin, mono and di-glycerides, metal contaminants, free fatty acids and soap. These materials are then removed from the process through filtration. In a standard biodiesel production process, Magnesol, which is a fine white Page 7 of 50
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powder, is mixed with unwashed biodiesel in a mixing tank for five to 10 minutes. The Magnesol is then removed by settling and filtering. Any used Magnesol is then disposed of. 2.4 Methanol Recovery
The production of biodiesel fuel requires the separation of methanol from the post transesterification product. Often, large quantities of the alcohol is used, to drive the reactions, and therefore it must be recovered for various reasons part economics and part generally responsibility. Methanol recovery from both the biodiesel and glycerol products is imperative to the economics of any biodiesel production facility. Methanol is recovered in a form for re-use in production to reduce the overall methanol costs. There are several different methods of extracting methanol from biodiesel and glycerin: flash evaporation and distillation. 2.4.1 Methanol recovery by flash evaporation
Flash evaporation is a process by which some of a liquid instantly boils after it has been heated and sent through a chamber that has reduced pressure. It is the reduction in pressure that results in some of the liquid vaporizing. Vaporizing a liquid in such a way absorbs heat and can cause the surrounding area to cool drastically. At different stages in biofuel production, a manufacturer may need to remove one liquid from another. In such a case, flash evaporation can be used to remove the more volatile i.e., a liquid that more easily evaporated. 2.4.2 Methanol recovery by distillation
The chosen process for the recovery of methanol was the passing the mixture of glycerol-alcohol through a stripper, which is essentially a distillation column. After the glycerol has been stripped, the methanol was sent to another distillation column where it will be recovered to 100%. More details have been provided in the process consideration unit. The two major types of classical distillation include continuous distillation and batch distillation. 2.5 Glycerol purification
Glycerin is produced as an approximately 11 percent byproduct in the transesterification of triglycerides, which are the predominant feedstock material for producing biodiesel. Glycerin remains one of the most versatile and valuable. The salt content in crude glycerin, stemming from the use of homogeneous alkaline catalysts, often ranges from 5 percent to 7 percent, which makes conventional techniques cost intensive. Almost all biodiesel production today involves homogeneous alkaline catalysts such as sodium methoxide. The transesterification of triglycerides with methanol generates a methyl-ester phase and a glycerin phase. Impurities such as catalyst, soap, methanol and water are preferentially concentrated in the glycerin phase.
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