Improving the Properties of Pure Vegetable Oils to Use Directly in Diesel Engines

Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel). biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel. In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles). diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils. The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines. Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study. Characteristics of the viscosity, density and the surface tension versus fuel temperature are established. Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.


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Abstract-Some typical types of biofuels widely known today include: bioethanol (bioetanol), biodiesel (biodiesel), green diesel (diesel), biological kerosene (biokerosen-or reactive fuel).biological forces), other biological alcohols (methanol, butanol), bio ether, biogas, synthetic gas, solid biomass fuel.In fact, the two most important biofuels are bioetanol and biodiesel, because of the many properties they have: use for the two most common types of vehicles (gasoline and motor vehicles).diesel engine); has many properties similar to fossil fuels, but cleaner and cleaner; produced from abundant and renewable materials such as sugar, starch and animal and vegetable fats and oils.The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines.Some typical properties such as high viscosity, high surface tension, high density and high cloud point are considered to be improved within this study.Characteristics of the viscosity, density and the surface tension versus fuel temperature are established.Findings of this study provide a basis for calculation and design a heating system of bio-oil fuel and for improving some typical properties of this fuel in order to use directly in diesel engines of small generator sets or diesel engines used in agriculture, forestry fields or in small boats.Index Terms-Biofuels, Properties, Diesel Engines, Heating Method.

I. INTRODUCTION
Biofuels can exist in all three solid, liquid, and gas states, and are also divided into three generations.First-generation biofuels, also known as traditional biofuels, are made from products used in food (such as sugar, starch, cooking oil, animal fat); Second-generation biofuels are produced from agricultural and forestry by-products (waste oil, rubber seed oil, straw, rice husk, organic waste); Third generation biofuels come from non-food sources (such as marine microalgae, jatropha).These types are easy to grow and produce very large oil yield [1][2] [3].Each generation of fuel has its own advantages and disadvantages, for example, the production of fuel from the first generation faces food security and land shortages; Second-generation fuel production does not encounter this disadvantage but the transition from biomass to product is more difficult; Thirdgeneration fuel overcomes all the above disadvantages, but the price is currently at a high level, so breakthrough developments are needed to successfully commercialize.Biofuels can be produced according to many processes, which are as popular as: Fermentation: Often used to produce alcohol, especially important is bioetanol, away from raw materials containing carbohydrates, biomass.Currently, the production of bioetanol mainly comes from starch or molasses.In addition, cellulose is also a potential source of materials.The fermentation process can be used to produce some other liquors such as biobutanol.
Ester exchange: Used to produce biodiesel, biokerosen from animal and vegetable fats and oils: Cracking, hydrocracking catalysts: Producing green fuels (greenfuel) such as gasoline, kerosen, blue diesel -are hydrocarbons away from oil, vegetable fat and biomass.These hydrocarbons burn cleaner, the efficiency of use for engines is higher than fossil fuels.Hydrogenation or decacboxylation: Production of green fuels from biomass, according to the principle of separation of oxygen.Besides, other hormones like nitrogen and sulfur are also separated in this process.Products are hydrocarbons of many different fuel segments (gasoline, kerosen, diesel).
Bioetanol is used to blend with gasoline to produce biogasoline.This is the most commonly used fuel.Pure bioethanol is denoted as E100, when added to gasoline it will be denoted according to the amount given, eg E5 gasoline means bio-gasoline has 5% of bioetanol volume and 95% of fuel volume from petroleum [4] [5].With a blend content of less than 20% by volume of bioetanol, the engine can work well without changing the structure.Biodiesel is used to blend with diesel from petroleum to make biodiesel fuel.Pure Biodiesel symbol is B100, when mixed into diesel, there will be the same symbol rules for bio-petrol, ie, there will also be B5 and B10 fuels for diesel engines [6][7] [8].Also with a content of less than 20% biodiesel (B20), diesel engines can operate well without changing engine structure.Gasoline, kerosen, and green diesel are used to blend into the corresponding petroleum fuels.The advantage is that it has a high calorific value, does not contain sulfur, can be mixed in any proportion Biofuels have many advantages compared to fossil fuels: They can be easily made from biomass; Sustainable development thanks to good regeneration and biodegradability; Do not increase CO2 emissions due to being in the CO2 balance process of the earth; Environmentally friendly: Clean fire, complete fire, does not contain toxic compounds, especially sulfur (S, when burning produces SOx causing acid rain, serious air pollution); Using biofuels will protect public health.It is forecasted that in the next few decades, biofuels will grow at a rapid rate, along with the development of agriculture -the industry that creates products and byproducts as raw materials for biofuel production [11][12] [13].The research also confirmed that the inevitable trend of the fuel economy is to increase market share of biofuels, reduce the exploitation and production of fuels from oil and coal.Bio-oils have become more attractive recently because of their environmental benefits and the fact that they are made from renewable resources.Bio-oils have the potential to replace a fraction of the petroleum distillates and petroleum-based petrochemicals in the near future [14][15] [16].Bio-oil fuels presently does not compete with petroleum-based fuels because they are more expensive.However, with recently increases in petroleum prices, uncertainties surrounding petroleum availability and climate changes, there is renewed interest in using bio-oils in diesel engines [17] [18].The paper presents results obtained from a method applied for improving the properties of pure bio-oil aiming a direct use as a fuel in conventional diesel engines.Some typical properties such as viscosity, surface tension and density are considered to establish the relationship between them with temperature.This will be able to show the range of optimum temperature to heat pure bio-oil.

II. PROPERTIES OF VEGETABLE OILS
Chemically speaking, bio-oils that include vegetable oils and animal fats after removing the water, ash and free acid are esters of fatty acid.The advantages of bio-oils as diesel fuel are liquidity, ready availability, renewability, lower sulfur and aromatic content, and biodegradability [14][19] [20].The main disadvantages of bio-oils as diesel fuel are higher viscosity, higher surface tension, lower volatility, coking on injectors, oil ring sticking, and thickening and gelling of the engine lubricant oil.
Bio-oils derive from many different: from edible vegetable oils and fats (1) such as soybean (which are used the most popularly), sunflower, peanut oils; inedible vegetable oils and fats (2) such as Mahua, castor, palm, sesame, coconut, Jatropha, cottonseed, waste cooking oils or fats of animals; biomass (3) and algae shows promise (4).Properties of some selected bio-oils are given in Table 1 in which abbreviations are presented in Table 2 including the standard test method for determination of these properties.
The main ingredient of vegetable oil and animal fat is Triglyceride, also known as triglyceride, triacylglycerol, TAG, Triacylglyceride derived from glycerol and 3 fatty acids.Triglycerides are formed by combining glycerol with three molecules of fatty acids.The glycerol molecules have three hydroxyl functional groups (HO-).Each fatty acid has a carboxyl functional group (COOH).In triglycerides, the hydroxyl groups of glycerol combine with carboxyl groups of fatty acids to form ester bonds: Triglycerides are the main components of vegetable oils and animal fats.HOCH2CH(OH)CH2OH + RCOOH + RCOOH + R"COOH → RCOOCH2CH (OOCR)CR"+ H2O Three fatty acids (RCOOH, R'COOH, R"COOH) are often different.The length of the chain of fatty acids in natural triglycerides varies but most have 16, 18, or 20 carbon atoms.Natural fatty acids found in plants and animals usually consist only of even numbers of carbon atoms.However, bacteria have the ability to synthesize fatty acid chains with odd and branched carbon atoms.Therefore, ruminant fat has an odd number of fatty acids, such as 15, made by bacteria in the rumen.Many fatty acids are unsaturated (unsaturated) and poly-unsaturated (polyunsaturated) [21] [22].Most natural fats contain a complex mixture of triglycerides so they melt within a wide temperature range.No cooking oil has only one type of saturated or unsaturated.All natural fats and oils include a mixture of all three fatty acids.The viscosity of vegetable oil at a temperature is usually several dozen times higher than that of diesel (particularly for coconut oil the viscosity at 200C is 37 cSt greater than diesel about 7 times), but the curve indicates a very steep viscosity, When the temperature increases, the viscosity of vegetable oil decreases rapidly.The viscosity of the oil greatly affects the viability of the oil in the filter, the quality of the fuel injection and the blending, thus strongly affecting the economy and efficiency of the engine.Cetan index of vegetable oil is smaller than diesel, among the research vegetable oil, coconut oil has Cetan index close to diesel [23] [24].To increase the Cetane index for vegetable oils, it is possible to use a "ProCetane" additive or convert them into esters of vegetable oil.

III. METHODS FOR USE OF VEGETABLE OILS FOR DIESEL ENGINES
A. Biodiesel production Biodiesel, a fuel that has the same properties as diesel but is not made from petroleum but from vegetable oil or animal fat.Biodiezen, or biofuels in general, is a clean energy.Chemically, biodiesel is methyl, ethyl ester of fatty acids.They are non-toxic and easy to resolve in nature.Biodiesel can completely replace diesel oil in internal combustion engines (B100) or blend with diesel diesel in a certain proportion.Biodiezen contains a very small amount of sulfur, 11% oxygen, so it burns cleaner, biodegradable, less polluting water and soil.Compared to the use of gasoline, it reduces 70% CO2 and nearly 30% of toxic gas.Today, when oil resources are dwindling, along with the heavy environmental pollution caused by the greenhouse effect, Biodiezen is a potential replacement for diesel thanks to similar properties and outstanding advantages.Therefore, after studying the extraction of lipids (fatty oil), determining the content of fatty acid components and analyzing the physicochemical parameters of oil quality assessment, building the fat oil base standards of 3 samples.Plant seeds of species: So, Lai, Trom, scientists of the Institute of Ecology and Biological Resources have initially studied the process of esterification of fatty oil into biodiesel to orient the efficient exploitation of the source.Seed oil and enhance the value of using resources from Vietnamese plant resources.Biodiesel can be produced from vegetable oils by extraction, converting fat esters into FAMEs, increasing the solubility and acidity by methanol.Normally, the process of converting oil into biodiezen through a series of steps including preparation of seed oil extract with chemical solvents and then the conversion from fatty oil to biodiezen under the effect of catalysis.Fatty acid methyl esters (FAMEs) including polar phospholipids, free fatty acids and triglycerides in Lai seeds are increased in liquid with evaporation, while reducing the polarity of high energy molecules in Critical lawsuit.This is achieved with direct liquefaction and the conversion of hybrid oil into biodiesel in just one step, with critical methanol with the presence of nitrogen, and optimization of process parameters affecting the reaction.ester metabolism using the membrane induction method (RSM).The induction membrane method (RSM) was used to analyze the influence of factors on the conversion of FAMEs, including: ratio of hybrid oil to methanol, reaction temperature and reaction time.The collected fuel samples were analyzed on ATR-FTIR and GC-MS.A new technology, i.e. transesterification reaction has been applied to produce a renewable fuel ''biodiesel'' derived from various raw materials.These raw materials include the edible and nonedible oils, algae, waste cooking oil, etc.It is named biodiesel because it is derived from biological products and matches petrodiesel in performance.The biodiesel so produced has lesser exhaust emissions in terms of unburnt hydrocarbon, carbon monoxide and particulate matter.Biodiesel can be termed clean fuel as it does not contain carcinogens and its sulphur content is also lesser than the mineral diesel.It possesses high biodegradability and lubricating property which makes it even better fuel.Hence, being a renewable fuel and characteristics similar to petrodiesel, it has the potential to be an alternate for petrodiesel in long run.However, few other properties of biodiesel are of concern and have to be improved to make it usable in neat form (i.e.100% biodiesel) [19][15].These properties are increase in calorific value, engine power, reduced emission of NOx and improvement in low temperature properties.An improvement in oxidation stability is also desired to prevent it from deterioration with time.At present it is compatible in blended form with mineral diesel in the ratio 20 (biodiesel):80 (mineral diesel).Biodiesel has been in use in countries such as United States of America, Malaysia, Indonesia, Brazil, Germany, France, Italy and other European nations.However, the potential for its production and application is much more.The feedstock available for development of biodiesel in these nations is 28% for soybean oil 22% for palm oil, 20% for animal fats, 11% for coconut oil, while rapeseed, sunflower and olive oils constitute 5% each.

B. Heating method
One common type of biofuel today is biodiesel, which is similar in quality to diesel fuel, made from vegetable oil or animal fat.Currently, Vietnam has also achieved initial achievements in the study of processing biodiesel (from sesame oil, basa fish fat, pangasius, waste oil from restaurants, food processing enterprises ... ).Recently, a conversion device has been made in the world so that diesel engines can operate directly with vegetable oil without processing it into biodiesel.Compared with biodiesel, SVO solution has the advantage that there is no need for an industrial-scale treatment plant such as biodiesel, due to the direct use of vegetable oil, it does not increase the price of fuel input.Biodiesel is prone to deterioration in preservation quality, the recommended storage time is less than one year with strict storage, vegetable oil used for SVO only needs to be stored under normal conditions.In some engines, biodiesel can damage rubber and gaskets, whereas no work has been published that publishes similar effects when using SVO.It can be said from these advantages of SVO, we decided to embark on SVO decoding.For example, overseas SVO converters are mainly for recently-produced engines, especially diesel-injection (injection rail) engines, while most cars in our country are old.than.External converters often use heating methods to reduce the viscosity of oil by DO fuel.Therefore, it is necessary to have a fairly strict standard for SVO oil, which leads to a limited amount of oil used for SVO fuel in some categories.SVO reheat converters can directly use vegetable oils for diesel engines, up to 100 HP.In addition to the specifications designed to suit domestic use conditions, the other specifications of this SVO are almost equivalent to external devices.Records of design and manufacture of SVO converters comply with TCVN.The process of fabricating some main assemblies of SVO transducer is also suitable for domestic manufacturing technology conditions.Guidelines for installation, use and maintenance were also compiled by the research team in accordance with the level of domestic use.
In the heat losses of diesel engines, the exhaust heat loss has the largest component.The heat generated by exhaust gas accounts for about 25-30% of the total heat when burning fuel [25] [26].Currently, on medium and large-sized vessels (greater than 1000cv), exhaust gas energy is utilized through auxiliary boiler -exhaust gas to generate steam to serve on-board needs such as heating room, drying Heavy fuel, salt water production ...However, on small vessels, the utilization of exhaust gas energy has not been paid attention to due to the low amount of exhaust gas, the arrangement of salvaged equipment on ships is difficult.towel.
The temperature of air discharged from the engine in different load modes will be different.In the rated mode, the exhaust temperature of the engine types is as follows: 4-stroke uncharged engine: tkx = (300 -410) 0 C 4-stroke engine with turbocharger: tkx = (380 -450) 0 C Two-stroke straight motor: tkx = (360 -380) 0 C Two-stroke engine: tkx = (270 -310) 0 C According to calculations, the amount of exhaust gas brought out of the engine is calculated as follows: or Qkx = GkxCpkx (t1'-t1'') (kW) Gkx: exhaust gas flow, kg / h; Gkx = ge .Ne. (αL0 + 1) ge: useful fuel consumption rate, kg / cv.h Ne: Useful power of engine, cv α: theoretical scanning air coefficient L0: The amount of theoretical air needed to completely burn 1 kg of fuel, kg/kg.ht1'; t1'': temperature of gas discharged into and exhaust gas removed from the salvage system, 0 C Cpkx, Cpkk: specific pressure capacitance of exhaust gas and intake gas, J/kg.K TKx, Tkk: exhaust gas temperature and intake gas, K The direct biodiesel fuel heating system can be applied on small vessels.This method has the advantage of high heat utilization efficiency, the system is simply finished and weak, the reliability is not high, the system can only operate when the main engine is operating, causing hydraulic resistance on discharge road so The calculation and installation are difficult.This method is calculated on the basis of baffle-type heat exchange problem that operates continuously in liquid-gas form.The temperature of biodiesel in and out of heating equipment is t2' and t2' 'respectively, the amount of biodiesel fuel needed is G2 (kg/h), C2 is the specific pressure of biodiesel (kJ/kg.K).As reported in literature, the best way to use coconut oil as a fuel for diesel engine is fuel heating.There are two types of heating system: one-tank system and two-tank system.In two-tank (dual) system, one tank contains raw vegetable oil while the other contains diesel or biodiesel.The engine started with diesel/ biodiesel for the first few minutes while the raw vegetable oil is heated to lower viscosity.The heater can be electrical, engine coolant or engine exhaust gas.When the fuel reaches the required temperature (80-100°C), the engine is switched to run on raw vegetable oil.With the one-tank (single) system, all the fuel is kept in the original tank and the fuel is heated up with a heat exchanger [27].
The cost of both single and dual tanks is the same at around 1000 euros.It is quite much expensive in condition of Vietnam, thus the authors designed and manufactured a heating system following the single tank structure with lower cost.At cold start, the electric heater will be used to warm up the raw vegetable oil in the fuel tank.At normal operating conditions, the oil will be heated up by the heat exchanger that is supplied with exhaust gas from engine.

IV. CONCLUSION
The use of pure vegetable oil as a fuel for diesel engines needs to change some of the engine's structure, not feasible in Vietnam.In order to use vegetable oil as a fuel, it is necessary to apply oil treatment methods to its properties similar to diesel fuel.From the point of view of engine extraction, the basic difference between vegetable oil and Diesel fuel is viscosity and Cetan index.The effect of viscosity and Cetane index of vegetable oil makes the fuel system and combustion process unusually, making the quality of the spraying and burning process less than the economic criteria will decrease.The vegetable oil, after being made into Biodiessel, has properties similar to diesel but the cost of equipment is too high.Mixing vegetable oils with easy-to-find solvents, lowering and heating costsspecifically a mixture with kerosene with high stability, low fuel costs, can make diesel fuel.The heating method is based on a change graph of viscosity according to the temperature of vegetable oil.Viscosity of vegetable oil will decrease when temperature increases.Increasing the temperature to too high changes the thermal state and adversely affects the fuel supply system.On the other hand, this method does not improve the Cetan value of vegetable oil, so this method is only suitable for simultaneous application with other methods.

Fig. 3 .
Fig. 3. Method for direct use of vegetable oil for diesel engines

Fig. 3 .
Fig. 3. Heating system for heavy fuel in marine engine

TABLE I :
PHYSICAL AND CHEMICAL PROPERTIES OF BIO-OILS SAMPLES