Heating System for the use of Bio-Oils for Marine Engines

Biofuel is a fuel made directly or indirectly from organic materials - biomass, consisting of two main sources from plants and animal waste, not from fossil sources such as oil, coal. At present, biofuels account for about 20% of global energy consumption. Particularly there are some countries, the use of biofuels is even bigger, such as Germany, Brazil, India ..., these are the leading countries in proving the availability and superiority of biofuels. Because fossil energy reserves are declining rapidly, as well as their use which has many consequences for habitat, bioenergy is an inevitable development for the future. Some typical types of biofuels that are 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, syngas, solid biomass fuels. 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 transport (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, animal and vegetable fats and oils. The paper presents the heating methods for the use of high-viscosity fuels for diesel engines. 


I. INTRODUCTION
Currently, environmental pollution and exhaustion of energy sources are issues that are of interest to every country in the world.Air pollution is mainly caused by exhaust fumes from vehicles.The more society develops; the more inventive means people will invent to meet the life of modern society.The problem is how to reduce emissions to the lowest level and the energy used for renewable vehicles to replace fossil fuels [1].Major emissions of fossil fuels are SO2, SO3, NOX, CO, CO2, hydrocarbon, particulate matter... SOX not only causes corrosion of equipment but also adversely affects human health, causes acid rain... CO2 gas is the cause of the greenhouse effect.CO is generated by incomplete combustion of the fuel, very dangerous to humans [2]- [4].Hydrocarbon components in the exhaust of diesel fuel, especially aromatic compounds are very harmful to humans and cause cancer.The particulate matter mixed in the exhaust gas also causes strong air pollution, they are difficult to identify, causing respiratory and cardiovascular diseases [5]- [6].The countries in the world today are interested in the issue of economic efficiency and environmental protection, so the general development trend of diesel fuel is to optimize from cetan number, to find ways to reduce the amount of storage [7]- [8].Fluid down, expand fuel sources, create clean, less polluting fuels.In light of this situation, reducing environmental pollution emissions to ensure energy security for each country, diversifying energy sources and reducing dependence on fossil energy is one of the top targets of developed country [9]- [11].Biodiesel fuel used for internal combustion engines is considered one of the important solutions and received great attention of the world [12]- [14].Biofuel is defined as any fuel received from biomass.These include bioethanol, biodiesel, biogas, ethanol (ethanol-biended fuels), bio-dimethyl ether and vegetable oils.Biofuels currently used in transportation are bioethanol, biodiesel and ethanol blended gasoline.Biodiesel fuel used for internal combustion engines is considered one of the important solutions and received great attention of the world [15]- [16].One of the solutions for using biofuels is bio-oil, bio-oil including vegetable oil or animal fat that can be used directly on combustion engines [17]- [19].
The original bio-oil is a fuel consisting of vegetable oil or animal fat obtained from the process of refining grease, whose main constituent is long chain fatty acid, not yet mixed with other fuels to use as fuel for diesel engines, denoted by VO100 (the letter V indicates the name of the vegetable oil) or AF100 (the letter A refers to the name of the animal fat) [20]- [21].The original bio-oil is triglyceride, insoluble in water, containing three hydrocarbon chains linked to a glycerol base, thus having a high specific gravity and high viscosity [22]- [23].Original bio-oil can be plantbased oils including edible types (sesame oil, peanut oil, coconut oil ...) or inedible (cottonseed oil, jatropha oil, rubber seed oil ...) and animal fat.
The main chemical composition of the original bio-oil is the ester of glixerol with saturated fatty acids (palmitic (16: 0) and stearic (18: 0) are the two most common saturated fatty acids) or unsaturated (oleic (18: 1) and linoleic (18: 2) are the most common unsaturated fatty acids.Compared to original biodiesel and fossil diesel fuel, much larger molecular weight bio-oil, the molecular formula of the original bio-oil is in the form of C27-57H54-104O6 [24]- [25].Similar to the original biodiesel and different from diesel fuel, the original bio-oil contains the oxygen content in the molecule, contains very little sulfur and aromatic compounds (Table I) so the original biodiesel and the original bio-oil less harmful to the environment [26]- [27].The physical properties of the original bio-oil have a great influence on the quality of the combustion process, which is characterized by the following parameters: -Specific gravity, viscosity and surface tension are an important attribute of the original bio-oil.These three parameters affect the magnitude of the force that binds the Heating System for the use of Bio-Oils for Marine Engines Dao Nam Cao, Danh Chan Nguyen, and Van Huong Dong Van der Waals molecule.Increasing the length of the carbon chain increases the molecular mass, thus increasing the amount of Van der Waals forces so it also increases the viscosity and vice versa.These properties are critical to the quality of the fuel spray, they are inversely proportional to temperature [28]- [29].The direct use of original bio-oil as an alternative fuel for diesel engines necessarily takes into account the improvement of the above parameters to ensure it is within the allowable range and close to the value of diesel fuel [30]- [31].The advantages of the original bio-oil as an alternative fuel are fluidity, availability, regeneration, containing very little sulfur and aromatic compounds, potentially biodegradable [18]- [32].There is currently no standard for the original bio-oil to be used as fuel for the engine, but to be able to use it, it should be based on some standards for diesel fuel.
However, the main drawback of the original bio-oil is 10 to 17 times higher viscosity than diesel fuel, which has a high density and high surface tension, resulting in poor evaporation, reaction of unsaturated hydrocarbon chains make oil susceptible to degradation.Some test results using the original bio-oil on diesel engines show the appearance of a deposits on a nozzle, degrade lubricating oil.

A. Method of heating fuel by steam
Water and steam use is considered to be the most effective and most widely used of the various types of thermal fluids available with high heat transfer performance and easy to control.However, its main drawback is that at temperatures above 100ºC it starts to boil, becomes steam and can therefore only be used as a pressurized systemlimited to processing and used to ensure safe operation.In order to heat the fuel with steam, it is necessary to arrange a steam generator that meets the requirements, specifically the boiler [15].The steam supplied by the boiler for fuel drying needs accounts for about 60% -80% of the total steam production.After the working process, steam will condense into condensate, returning it to the boiler.The steam after leaving the boiler needs to ensure the following requirements: -Having temperature and pressure suitable for the purpose of use; -Content of harmful substances in the vapor must be within the permitted range; The most popular heating pipe layout is still chicken intestinal tube system In chicken intestinal heating systems, steam delivered to chicken intestines is superheated through the main steam pipe.After a large part of the steam is turned into condensate, the condensate will be returned to the boiler hot water.The disadvantage of heating up the heat in the pipe is the possibility of the pipe running in the oil chamber being flooded with condensation.When joints (solder joints) are exposed or pipes are broken or pores appear in the tube, the oil will enter the tube.The method of heating fuel by steam is usually applied on tankers with the purpose of heating oil in combination with fuel heating in tanks before supplying them to the machine.However, with small diesel engines, it is difficult to arrange a steam heating system.In addition, different heating temperatures are required in each tank, which leads to difficulty in adjusting the temperature of the steam (or pressure).At the same time, on some engines running on heavy fuel HFO, IFO need to attach the temperature sensor or viscosity of fuel right before supplying it to the engine, it may be necessary to arrange warming device Electric or steam has a high temperature to ensure fast heating.

B. Method of heating fuel by thermal liquid
Thermal oils or heat-transfer fluids are widely used to carry heat energy during fuel heating, metalworking and machine tool cooling applications.They are mainly used in high temperature systems and equipment where the optimal operating temperature of heat oil or heat transfer fluid is between 150ºC and 400ºC.This method is safer and more effective than using steam, electricity, or other direct heating methods.The type of thermal oil used is unstable if the temperature is higher than the stable temperature that has been set in advance during the long operating period.This results in the heat oil pipes being broken and therefore a part of thermal oil is oxidized and unstable.As a result, a number of thermal oil system problems pose a danger to the extraction and use process.In practice, however, thermal oil systems are less complex, easier to design and safer than steam supply systems, and maintain and stabilize good temperatures for selected applications.Heat transfer oils are classified into two main groups: coolant, refrigerant, anti-freezing used for cooling inside machinery, handling equipment or engines.Hot oil and thermal oil are used for heat transfer or heat transfer as required.
Heat transfer oil can be classified according to chemical structure into three main groups: • Synthetic substances; • Thermal oil; • Other types of silicon; 1) Synthetic substances Synthetic substances, also called aromatic compounds, are artificial liquids, designed specifically for heat transfer applications.They include structures based on benzene molecules and include diphenyl oxide / biphenyl liquids, diphenylenthanes, dibenzyltoluenes, and terphenyl.Synthetic substances have many advantages in terms of high temperatures and heat transfer compared to hot oils or other common substances.Synthetic substances can obtain safe operating temperatures within a temperature range of 400ºC, while non-synthetic substances only stabilize heat up to a maximum temperature of 300ºC.

2) Thermal oil
Crude oil contains a large mixture of organic compounds, ranging from very light hydrocarbons to very high molecular weight molecules.Thermal oil has significant advantages over synthetic substances in terms of cost and processing processes.In addition, petroleum-based liquids are not formed with dangerous toxins, no unpleasant odors, so hot oils can be easily handled [33].However, hot oils are less stable in heat at high temperatures because they contain a certain amount of unsaturated substances (double bonds) and may have more chemical reactions than petroleum products.refined and prone to oxidation.

3) Other types of silicon
Silicon substrate fluids and to a greater extent glycol hybrid fluid, mainly used in specialized applications requiring compatibility between process and product.The efficiency and cost factor of this group is more disadvantageous when compared to the temperature range with synthetic substances and hot oils making it difficult to choose silicon and other special liquids.most of the application process.
In general, a thermal oil system consists of a heat furnace, heat exchangers, expansion tanks, ventilation and pumping systems.The expansion tanks can be coated with inert gas such as nitrogen to prevent liquid oxidation, but in many cases it releases the atmosphere.

C. Method of heating fuel by electricity.
For an electric heating system, this is done by exposing the oil to conductive parts, mainly conductors.This method overcomes the disadvantages of steam-warming method running in the tube.Electric heating method can be conducted directly or indirectly.Directly feed the fuel by placing the conductor-type thermostats in direct contact with the heating fuel or allowing the fuel to flow through the heating device.Indirect direct heating often uses a type of heat transfer device into the fuel tank.Indirect methods can change the temperature from the outside of the tank by using the tank wall as an intermediate medium to transfer heat into the fuel inside the tank.

1) Directly
Direct heating is the method of placing conductor-type thermostats in direct contact with the heating fuel.The heating element is placed below the lowest fuel level in the tank.The advantage of direct heating method is to achieve almost 100% warming effect.This is because all heat produces direct absorbed fuel.This helps to speed up the heating and minimize heat latency.Without intermediate heat transfer zone, it is possible to reduce heat loss.Disadvantages of direct heating systems such as liquid surface limits, surface areas require large space.In addition, the direct warming process must ensure that the elements are compatible and do not corrode or leak electricity due to heat transfer with direct heating devices.Therefore, the heating device must be designed so that it is not exposed to air during operation as this may lead to destruction of the heating device due to the high temperature in the face area and the Warming must be placed at a certain distance from the bottom of the tank to avoid the accumulation of mud in the tank, which may limit the ability of heat transfer.2) Indirectly heating system Indirect heating uses a method of transferring heat into the fuel tank wall.This method can change the temperature from outside the tank by using the wall of the tank as a means to heat the dryer.The biggest advantage of the indirect heating method is that the reheating process is continuous without removing the tank.Furthermore, indirect fuel drying allows the current density to come into contact with liquids during heating to be reduced by spreading heat over a larger surface area [34].At the same time, the possibility of overheating can be limited by limiting the temperature of the heat transfer medium.However, this method encountered some disadvantages such as increased heat loss and thermal latency.

D. Using heat pipes
Heat pipe is a two-way sealed metal tube which contains a defined amount of liquid, the outer surface of the pipe can be smooth or install a heat sink.The tube is divided into 3 parts: boiling part, heating section, condensation.Boiling part: this part is heated by different heat sources, the liquid in the tube boils and forms saturated steam.
Heat section: saturated steam will move through the heating section to the condensate.
Condensation: saturated steam up to the condensate that releases heat to the surrounding environment and is stopped.The condensate will return to boiling by gravitational force, capillary force or centrifugal force.Correspondingly, we have a field heating tube, capillary heat or centrifugal heat pipe.
The liquids used in heat pipes can be water, ammonia, acetone, fractions, mercury, sodium, potassium, lithium ... depending on the temperature used.The use of heat pipes to heat fuel drying is rarely used because the process of calculating, designing and installing the system is difficult and the thermal capacity is not high but the system is very compact in size so utilize waste heat to serve the needs of small engines.
The method of electrically integrated gas-discharge exhaust is the method in which the fuel is first circulated through the device to utilize exhaust gas then it is pumped back to the tank.Here, the fuel continues to be electrically heated if necessary to reach a certain temperature before supplying it to the engine.The fuel temperature is set in advance, if the fuel after receiving heat from the exhaust gas is lower than this temperature, the electric heater will turn on to dry the fuel to the required temperature.Until now, the method of fuel-type exhaust-gas exhaust method has not been used on vehicles for the following reasons: * Fuel used on combustion engines burned by compression is mostly fossil fuels.In this case there will be the following possibilities for use: -If the engine uses DO oil, it is not necessary to arrange heating system; therefore, fuel DO is often used on small engines.
-If the engine uses HFO or IFO oil, it is necessary to arrange the fuel heating system, and at the same time use fuel DO when starting and turning off the engine ie dual fuel system.Due to this complexity, the dual fuel system is often used for large engines such as thousands of tons of ships.Then, on a ship, a fuel-warming device is usually used with thermal oil or steam, if fast heating is needed, electric heating equipment is required.* Exhaust gas energy is usually only used in the area of heat utilization of exhaust gas boilers or exhaust gas turbines and is only arranged on large transport vehicles equipped with boilers or turbocharged engines.exhaust gas turbine.
For the above reasons, it is difficult for the fuel-type exhaust system to integrate power-exhaust to be applied on large transport vehicles, the duration of long-running engines [35].However, the object that the project aims to is small engines mounted on transport vehicles or agricultural and forestry machines or diesel generators with large use life, short operating time so Without a system to utilize exhaust heat, it is suitable for the type of electric-airdischarge integration that not only helps the engine start cold but also utilizes the waste heat energy of the engine.
With such large vessels, the main engine installed on board is a diesel engine with a large capacity of tens of thousands of horsepower.Exhaust gas discharged by the main engine has a large flow, high pressure and temperature, about 0.35 Mpa and 400 degrees C, carrying large amounts of energy discharged.This energy source accounts for about 20% to 25% of the combustion heat generated in the combustion chamber, in addition to the heat generated by cooling water accounts for about 10% to 16% of the total heat generated in the combustion chamber.If taking full advantage of this energy source, it will contribute to saving fuel and increasing the efficiency of the marine power system.In order to save fuel as well as reduce environmental pollution, people not only seek to improve the thermal efficiency of boilers by reducing heat losses but also to find ways to thoroughly utilize waste heat from the diesel discharged into the environment [36].
The problem of utilizing the energy source of exhaust gas due to engine exhaust has been implemented for a long time for countries with developed shipbuilding industry, including the use of ship exhaust gas boiler.This brings many benefits such as not consuming fuel; Providing saturated steam to FO oil warmers, fresh water distillation, blowing sea valves, serving seafarers' activities and cooking and many other needs; Reduce environmental pollution; Reduce waste disposal costs.With the aim of improving the types of exhaust gas boilers currently used in order to reduce manufacturing costs, facilitate the maintenance, repair, and process of manufacturing in the country is a reasonable step to enhance the ratio localize the shipbuilding industry and reduce new construction costs as well as improve ship operation efficiency.For heavy fuel vessel engines, it is imperative to use steam to heat the burning oil and to serve other needs on board, so the boiler is required to install steam to produce steam.Depending on the type of vessel, the use of the vessel, depending on the actual demand and dependence on the shipowner, on the vessel, it is possible to arrange an auxiliary boiler or an exhaust gas boiler or an auxiliary boiler-exhaust or auxiliary boiler and exhaust gas boiler.

III. CONCLUSION
The uneven development across regions has led to the situation of migration from rural to urban areas with increasing speed.Along with the rapid urbanization and the increase in transportation, the air and urban environment have been seriously polluted, especially in large cities.The level of pollution in big cities is at an alarming level.Therefore, the use of biofuel in gasoline will contribute to improving the environmental pollution by reducing the generation of waste gases in traditional fuels such as CO, SO2, dust particles and CO2.In addition, the development of raw material areas for ethanol production (cassava, sugarcane, algae ...) also contributes to green vegetation which reduces the impact of floods and storms and erosion.Development of biofuels helps countries to be proactive, not dependent on the issue of fuel imports, especially in countries without oil and coal resources.At the same time, curb the increase in oil prices, stabilize the energy profile for the world.The development of biofuels on the basis of utilizing huge biomass resources and being produced from renewable sources will really be a priority option in terms of security energy security for nations.

Fig. 1 .
Fig. 1.Fuel heating system by steam applied to the ship

Fig. 3 .
Fig. 3. Direct heating fuel system by the electricity

Fig. 5 .
Fig. 5. Method of heating fuel by heat pipe

TABLE I :
CHEMICAL COMPOSITION OF BASE BIO-OIL, AND DIESEL FUEL