Patent Publication Number: US-2002011022-A1

Title: Low cost, low pollution and low viscosity fuel oil using heavy oil

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates to a new type of fuel oil with low cost and low viscosity made of heavy oil or residue oil, and more particularly, to low cost, low viscosity and low pollution fuel oil which includes base oil made by adding waste plastic disposal oil made through thermal decomposition to heavy oil or residue oil of high viscosity. The base oil is then provided with water and emulsifier to form water-in-oil emulsion fuel oil, thereby capable of reducing generation of pollutants in the exhaust gas when burnt in a combustion engine. The fuel oil of the present invention is especially suitable as vessel fuel oil.  
       BACKGROUND OF THE INVENTION  
       [0002] In a final stage of oil refining process, heavy oil is produced which is generally divided into three different classes, i.e., heavy oil type A, heavy oil type B and heavy oil type C in accordance with their viscosity. Since heavy oil generates high calory and is relatively inexpensive, a large amount of heavy oil is consumed all over the world for facilities in various industries including large scale heating facilities and large vessels.  
       [0003] When heavy oil, in particular high viscosity heavy oil such as heavy oil C (superheavy oil) or low-grade residue oil, is burnt, a large volume of pollutants, such as, sulphur oxides, nitrogen oxides, carbon monoxide, soot and dust are generated. If no effective antipollution countermeasure is taken, these pollutants can contaminate the environment and pose a serious threat to the ecological system.  
       [0004] Accordingly, the governments of various countries have promulgated various standards regarding the maximum permissible discharge levels of toxic pollutants for facilities which burn heavy oil. The government imposes on the industries strict preventive measures to keep the discharge level below the standard level. As a result, the industries in which heavy oil is used as a fuel generally tend to make substantially large investments to equip heavy oil burning facilities with highly complex and expensive antipollution devices and facilities.  
       [0005] The superheavy oil, such as heavy oil C is required to add heat before being provided to burners or engines to lower the viscosity. In recent years, for high calories and economical reasons, heavier oil is tend to be used for large engines such as vessel engines. Because it is necessary to apply heat for adjusting the viscosity, the use of heavy oil involves increase in work load, equipment cost and operating cost (Journal of the Marine Engine Society in Japan, Vol. 34, No. 10, 1999, pp 647-649).  
       [0006] The inventors of this invention have disclosed engine performances and exhaust gas properties of the oil made by adding waste plastic disposal (WPD) oil to light oil and/or heavy oil. Based on this experience, the inventors have evaluated the oil made by adding the WPD oil to the heavy oil equivalent to the type C heavy oil, without adding heat, with respect to engine performances and exhaust gas properties. As a result of this study, it is confirmed that the viscosity of such heavy oil is decreased because of the WPD oil added, thus the heavy oil C can be used without applying heat. It is also confirmed that there is substantially no adverse effects on the engine performances. Further, soluble organic fraction (SOF) and dry soot (DS) are significantly reduced in the exhaust gas while involving a small degree of increase in nitrogen oxides NO X  concentration (63TH Conference on Marine Engineering, 1999, pp 27-29).  
       [0007] It is known in the art that emulsified fuel oil is effective in reducing generation of soot when burnt in a burner such as a boiler because burning oil particles are further miniaturized by micro-explosion of the water. Further, it is also known that, because it contains water, burning temperature is lowered, resulting in reduction of the nitrogen oxides NO X .  
       [0008] The inventors of this invention have invented the heavy oil emulsifier for forming water-in-oil emulsion fuel oil using the heavy oil such as type C heavy oil or waste oil (Japanese Patent Laid-Open Publication No. 11-5987). When used for land boilers, for example, the water-in-oil fuel oil produced by the invention is effective in substantially suppressing generation of contaminants such as soot, sulfur oxides, nitrogen oxides, carbon monoxides, and sulfide, which are ordinarily contained in the exhaust gas of heavy or superheavy fuel oil.  
       [0009] According to this prior invention, the emulsifier mainly composed of caustic soda and calcium chloride promotes to produce the water-in-oil emulsion by mixing the heavy oil and water. When the resultant water-in-oil fuel oil is combusted in a burner, the temperature of the exhaust gas is lowered, thereby reducing the thermally caused nitrogen oxides NO X . Further, asphaltene (including sulfur content) is neutralized by the added alkaline, thereby reducing sulfur oxides SO X . It was not quite clear, however, whether there is any difference between the combustion in a burner which is virtually under ambient pressure and the combustion in an internal combustion engine which is under high pressure.  
       [0010] It was also unknown as to what influences the inorganic salt such as sodium salt generated by the combustion will exert on the internal combustion engine.  
       [0011] When burning the emulsion fuel oil, water contents react with unburnt carbon, and temporarily gasify to create carbon oxide and hydrogen, and then, gas-fire. Thus, when used in a boiler, for example, radiation of luminous flame caused by solid combustion of carbon tends to be reduced. Further, it is known that because the emulsion fuel oil has a higher water content ratio, radiation of non-luminous flame caused by the vapor is increased while radiation of luminous flame is decreased, thereby offsetting with one another. However, it was unknown as to how the water content affects the performance of the internal combustion engine.  
       [0012] Various reports have been made regarding the application of emulsion fuel oil to diesel engines in cogeneration facilities and land fixed engines as well as to offshore tests for vessels. However, there are many unknown factors, today, as to the combustion of the emulsion fuel oil in the internal combustion engine.  
       [0013] Air Pollution Law regulates exhaust gas produced by fixed onshore facilities. Recently, in Japan, several new laws have been promulgated which regulate soot and smoke in exhaust gas from vessels. Moreover, in September 1997, IMO (International Marine Organization) has adopted MARPOL Agreement Protocol IV, ratification of which is under preparation by each country. Thus, the regulation of the vessel exhaust gas will be soon to start.  
       [0014] Moreover, the regulation by IMO will be effective as of January, 2001 and it is considered that the regulation will be retroactively applied to vessels built after January, 2000. In principle, all vessels are regulated, as to NO X , targets are limited to vessel diesel engines with greater than 130kW. In the regulation, with respect to SO X , the maximum content ratio of sulfur is limited to about 4.5%. With respect to NO X , different limits are provided depending on rotation speeds at rated output power level of the engines. For example, the maximum NO X  level is 17 g/kWh for a rotation speed less than 130 rpm, the maximum NO X  level is 45×n(rpm) −0.2  g/kWh for a rotation speed in the range of 130-2000 rpm, and the maximum NO X  level of 9.84 g/kWh for a rotation speed higher than 2000 rpm.  
       [0015] Under the circumstances, there is an urgent need to reduce nitrogen oxides NO X  in the exhaust gas from vessel engines. To meet this requirements, as a practical measure available to reduce the NO X  in the exhaust gas of vessel engines, the use of emulsion fuel oil added with water is effective as a pretreatment process.  
       [0016] On the other hand, in Japan, Container and Package Recycle Law has been effective since 1997, for regulating various types of waste plastic, which requires various recycling technologies. In this law, material recycles are limited to types of waste that can be collected through specified routes, i.e., to vinyl chloride tubes recycled from pure waste vinyl chloride, fibers recycled from PET (polyester terephthalate) bottles, and pure waste olefin. Since other types of waste plastic collected through regular routes include various mixtures, most widely used technology is a thermal recycle (rather than material recycle) in which the waste plastic is thermally decomposed to plastic oil or plastic gas.  
       [0017] It is expected that the recycle rates of the waste plastic will be further increased. In such recycling processes, mixed plastic will be recycled in such ways that chlorine is recycled to hydrochloric acid through the thermal decomposition, PET bottles is recycled as phthalic acid, gasified components and carbonized refuse will be used as heat source for thermal decomposition, and recycled oil components are refined to be used as recycled oil.  
       [0018] At any rate, it is possible that the recycled plastic oil has quality equivalent to light oil while the cost is lower than that of the light oil. Therefore, effective use of the recycled plastic oil can contribute to our environment in shifting to the resource circulating society. Such an effective use of the recycled plastic oil also has an important meaning to reduce an environmental load.  
       [0019] The inventors of this invention have been studying the characteristics of fuels made by mixing the heavy fuel oil with waste plastic disposal (WPD) oil. The results of the study indicates that the viscosity of such heavy fuel oil is decreased because of the WPD oil added thereto, which promotes easy handling. The results further show that particulate matter such as soluble organic fraction (SOF) and dry soot (DS) are reduced while nitrogen oxides NO X  concentration is slightly increased.  
       [0020] Although different from the quality of the waste plastic, in general, aromaticity in the decomposed oil increases, and thus, CCAI (Calculated Carbon Aromaticity Index) increases as well. Accordingly, a cetane value decreases and an ignition lag increases which promotes premix, thereby reducing the generation of the particulate matter (DS, SOF).  
       [0021] Within the normal engine operation, when engine load increases, the ignition lag slightly decreases, while the maximum pressure increases and exhaust gas temperature rises. Thus, although the particles (DS, SOF) decreases, the nitrogen oxides NO X  concentration increases.  
       [0022] Various studies have been made with respect to methods of reducing the NO X  concentration when using the emulsion fuel for engines. An example of such methods is to regulate the amounts of pumping supply of the fuel and water in response to the engine load (Japanese Patent Laid-Open No. 8-303305). Another example shows a method which has an emulsion fuel valve in a fuel supply line (Japanese Patent Laid-Open No. 11-159361). Further examples include a method of circulating the fuel (Japanese Patent Laid-Open No. 9-329067) and a method of circulating the emulsion fuel (Japanese Patent Laid-Open No. 8-246961).  
       [0023] Japanese Patent Laid-Open No. 9-317587 shows a method in which an instrument for measuring NO X  is provided in an exhaust gas passage for regulating the supply of heavy oil or water to reduce the NO X  concentration. This method has a disadvantage in that additional devices such as the measuring device and control valves have to be installed in the engine, and such devices may be broken, resulting in engine trouble. Further, the emulsion fuel oil must be mixed before spraying in the engine, which further requires additional devices such as mixers and controllers.  
       [0024] To solve the environmental and natural resource problems, Japanese Patent Laid-Open No. 6-346071 discloses a method which forms emulsion fuel oil by adding water and a surface active agent to the mixture of petroleum fluid oil and edible recycled oil to solve environmental problems. Further, Japanese Patent Laid-Open No. 7-11269 shows a method which forms heavy oil emulsion fuel oil by adding water and a surface active agent to the mixture of heavy oil and edible oil. However, it is unknown whether such emulsion fuel oil can be effectively used as engine fuels.  
       SUMMARY OF THE INVENTION  
       [0025] It is, therefore, an object of the present invention to provide low cost, low viscosity and low pollution fuel oil which includes base oil made by adding waste plastic disposal oil made through thermal decomposition to heavy oil or residue oil of high viscosity.  
       [0026] It is another object of the present invention to provide low cost and low pollution fuel oil which can contribute thermal recycling of waste plastic disposal oil and heavy oil or residue oil of high viscosity without inversely affecting the environment.  
       [0027] It is a further object of the present invention to provide a water-in-oil emulsion fuel which is stable for a long period of time and is capable of reducing the emission of pollutants in the exhaust gas of large combustion engines such as used for vessels.  
       [0028] It is a further object of the present invention to provide a method for producing a water-in-oil emulsion fuel product in which dispersed phases of water are substantially uniformly distributed in a dispersion medium of oil.  
       [0029] To achieve the above objectives, one aspect of the present invention is a water-in-oil emulsion fuel for a large size and high power combustion engine. The emulsion fuel oil is comprised of base oil formed by mixing heavy oil and waste plastic disposal thermal decomposition oil in a weight ratio from about 95:5 to about 80:20, thereby decreasing viscosity of the heavy oil without heating, emulsifier made of caustic soda (NaOH) and calcium chloride (CaCl 2 ), and water added to the base oil in a weight ratio from about 5:95 to about 20:80. The base oil, emulsifier and water are sufficiently mixed with one another so that the water substantially and uniformly distributed in the base oil.  
       [0030] In the emulsion fuel of the present invention, the heavy oil is heavy oil type C or low grade residue oil having kinematic viscosity of 500 centi-Stokes or higher at temperature 50° C. The waste plastic disposal thermal decomposition oil is made through a thermal decomposition process of olefin (polyethylene, polypropylene) or polystyrene or a mixture of the olefin and polystyrene, and wherein when the waste plastic include vinyl chloride or vinylidene chloride, a dechlorination process is preceded to the thermal decomposition process on the waste plastic. The waste plastic disposal thermal decomposition oil has kinematic viscosity of 5 centi-Stokes or lower at temperature 30° C. is not solidify when left in air for a long period of time.  
       [0031] Preferably, a weight ratio of the emulsifier relative to the water-in-oil emulsion fuel oil is in a range of 0.01-5 weight percent. Further preferably, the caustic soda (NaOH) and the calcium chloride (CaCl 2 ) in the emulsifier are about the same amounts with each other and mixed with water where a weight ratio of NaOH, CaCl 2  and water is about 25:25:100.  
       [0032] Another aspect of the present invention is a method of producing a water-in-oil emulsion fuel. The method is comprised of the steps of: forming base oil by mixing heavy oil and waste plastic disposal thermal decomposition oil in a weight ratio from about 95:5 to about 80:20, thereby decreasing viscosity of the heavy oil without heating, mixing caustic soda (NaOH) and the calcium chloride (CaCl 2 ) and water to form an encapsulating emulsifier, adding the encapsulating emulsifier to a mixture of the base oil and water wherein said mixture contains base oil and water in a weight ratio from about 95:5 to about 20:80; and mixing encapsulating emulsifier and the mixture of base oil and water so that the water substantially and uniformly distributed in the base oil.  
       [0033] The fuel oil of the present invention is produced by mixing the plastic oil made through thermal decomposition of waste plastic disposal (WPD) with heavy oil or residue oil of high viscosity to form base oil. The base oil is then mixed with water by using inorganic emulsifier including caustic soda (NaOH) and calcium chloride (CaCl 2 ), thereby forming water-in-oil emulsion fuel oil in which particles of water are distributed and encapsulated in particles of oil each having a predetermined diameter. The water-in-oil emulsion fuel oil of the present invention improves the thermal efficiency of the engine without posing any problem and reduces generation of dust, SO X  or NO X  in the exhaust gas.  
       [0034] In the present invention, since the emulsion fuel oil is made by mixing the low cost heavy oil or residue oil with the waste plastic disposal (WPD) thermal decomposition oil, significant cost reduction can be achieved. The water-in-oil emulsion fuel oil of the present invention contributes significant reduction of the particulate matters such as nitrogen oxides NO X , sulphur oxides SO X  and dry soot DS in the exhaust gas.  
       [0035] Further, in the present invention, instead of the surface active agents used in the prior art technology, the emulsifier formed of caustic soda (NaOH) and calcium chloride (CaCl 2 ) are used which promote the phase inversion at the oil surface for producing the water-in-oil emulsion fuel. The emulsion fuel is highly stable and remains unchanged for a long period of time such as one month. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0036]FIG. 1 is a graph showing mixing ratios (vol %) of waste plastic thermal decomposition oil to heavy oil type C or residue oil in a horizontal axis and density (g/cm 3 ) of the mixture in a vertical axis.  
     [0037]FIG. 2 is a graph showing mixing ratios (vol %) of waste plastic thermal decomposition oil to heavy oil type C or residue oil in a horizontal axis and sulfur content ratios (wt %) in the mixture in a vertical axis.  
     [0038]FIG. 3 is a graph showing mixing ratios (vol %) of waste plastic thermal decomposition oil to heavy oil type C or residue oil in a horizontal axis and kinematic viscosity (centi-Stokes) in the mixture in a vertical axis.  
     [0039]FIG. 4 is a graph showing molecular weight distribution of the waste plastic thermal decomposition oil used in the experiment measured by a gas chromatography analyzer.  
     [0040]FIG. 5 is a graph showing the molecular weight distribution of the heavy oil type C used in the experiment measured by the gas chromatography analyzer.  
     [0041]FIG. 6 is a graph showing the molecular weight distribution of the mixture of the heavy oil type C and the waste plastic thermal decomposition oil used in the experiment measured by the gas chromatograph analyzer.  
     [0042]FIG. 7 is a graph showing an engine performance where engine load is shown in a horizontal axis while an ignition delay time is shown in a vertical axis.  
     [0043]FIG. 8 is a graph showing an engine performance where engine load is shown in a horizontal axis while exhaust gas temperature is shown in a vertical axis.  
     [0044]FIG. 9 is a graph showing an engine performance where engine load is shown in a horizontal axis while concentration of DS (dry soot) in the exhaust gas is shown in a vertical axis.  
     [0045]FIG. 10 is a graph showing an engine performance where engine load is shown in a horizontal axis while concentration of nitrogen oxides NO X  in the exhaust gas is shown in a vertical axis.  
     [0046]FIG. 11 is a graph showing an engine performance relative to a water content ratio in the emulsified fuel oil where the water content ratio (wt %) is shown in a horizontal axis while concentration of nitrogen oxides NO X  in the exhaust gas is shown in a vertical axis.  
     [0047]FIG. 12 is a graph showing an engine performance relative to a water content ratio in the emulsified fuel oil where the water content ratio (wt %) is shown in a horizontal axis while concentration of sulphur oxides SO X  in the exhaust gas is shown in a vertical axis.  
     [0048]FIG. 13 is a graph showing an engine performance relative to a water content ratio in the emulsified fuel oil where the water content ratio (wt %) is shown in a horizontal axis while concentration of DS (dry soot) in the exhaust gas is shown in a vertical axis. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0049] The fuel oil of the present invention make use of the superheavy oil with high viscosity, such as heavy oil C or low grade residue oil. An example of viscosity of such heavy oil is 500 centi-Stokes or more at temperature 50° C. As mentioned in the foregoing, the heavy oil must be reduced its viscosity by heating before being supplied to an engine. Because it is necessary to apply heat for adjusting the viscosity, the use of heavy oil involves a relatively complicated heating system, resulting in increase in equipment cost and operating cost. The reduction of viscosity can be achieved by mixing the heavy oil with low viscosity oil such as heavy oil type A. However, it is considered that such a method is not economically favorable today.  
     [0050] In the present invention, the viscosity of the heavy oil is reduced without applying the heat but by adding waste plastic oil. Such plastic oil is made through thermal decomposition of waste plastic disposal (WPD), i.e., recycled plastic. An example of temperature for such thermal decomposition is in the temperature range of 450-550° C. in which waste plastic disposal (WPD) is decomposed and is converted to plastic oil.  
     [0051] There are variety of ways to create the plastic oil. The only requirement of the plastic oil suitable for the present invention is that the waste plastic disposal is first dehydrochlorinated with relatively low temperature such as 300° C. to remove the chloride therefrom and then undergone the thermal decomposition process with temperature such as 450° C. Further, the thermal decomposition plastic oil to be used in the present invention does not require any reforming or refining so long as it has a coefficient of kinematic viscosity of less than 5 centi-Stokes at temperature 30° C. Such a degree of viscosity in the plastic oil can sufficiently reduce the viscosity of the heavy oil.  
     [0052] Typically, the thermal decomposition plastic oil to be used in the fuel oil of the present invention is made through thermal decomposition of olefin (polyethylene, polypropylene) or polystyrene or a mixture of the olefin and polystyrene. When the waste plastic include vinyl chloride or vinylidene chloride, a dechlorination process should be preceded to the thermal decomposition process of the plastic.  
     [0053] Since the thermal decomposition plastic oil is made from waste plastic, it is difficult to maintain the quality of such oil within a limited range such as defined by the national standard JIS (Japanese Industrial Standard). Thus, the thermal decomposition plastic oil of standardized quality is not easily obtainable. Further, since the production scale of the thermal decomposition plastic oil is very small, it is not possible to reform and/or refine the plastic oil with efficient and economical ways.  
     [0054] Thus, at present, the thermal decomposition plastic oil is mainly used as fuel oil for land boilers or as base material to mix with other material. Because the thermal decomposition plastic oil is made by thermally decomposing the high molecular compound, it has relatively high content ratios of benzene, toluene, xylene, and ethylbenzene. Accordingly, the thermal decomposition plastic fuel oil has a high capability as solution, and thus, is most suitable for mixing with the heavy oil or residue oil.  
     [0055] Although such inorganic compound of benzene, toluene, xylene, and ethylbenzene is suitable for solution, when used in an engine as a fuel, because the high level of CCAI (calculated Carbon Aromaticity Index), it increases the ignition lag of the engine. Thus, when the engine load is increased, the temperature of the exhaust gas is risen, resulting in the increase in nitrogen oxides NO X  concentration in the exhaust gas.  
     [0056] One of the means for suppressing the generation of NO X  is to convert the plastic oil to water emulsion. However, such water-in-oil emulsion requires to control the mixing ratio of water and oil depending on the engine load. According to the study made by the inventors of this invention, if the water-in-oil emulsion of fixed mixing ratio is to be used without regard to the engine load, the emulsion must be highly stable and water particles must be equally and uniformly dispersed therein.  
     [0057] The inventors of this invention have further studied the water-in-oil emulsion with use of various types of surface active agents. According to this study, it is found that, to uniformly disperse the water particles, the amount of surface active agents or temperature of the surface active agents must be carefully adjusted depending on the components in the heavy oil and the thermal decomposition plastic oil. Further, a long time is required for mixing the heavy oil, plastic oil, water and surface active agents. Thus, the process using the surface active agents involves the long time and complicated process.  
     [0058] To solve this problem, in the present invention, when mixing base oil (mixture of heavy oil and thermal decomposition plastic oil) and water, water solution mainly constituted of caustic soda (NaOH) and calcium chloride (CaCl 2 ) is added to the base oil. Because of this solution, at the early stage of forming the emulsion, ionized Na+ and OH − and water solution CaCl 2  become continuous phases, thereby distributing oil particles in the water and forming oil-in-water emulsion. Thus, during the mixing process, fatty acid and the like contained in the heavy oil and the thermal decomposition plastic oil are saponified and oriented to the surface to act as surface active agents so that calcium (Ca) gradually ionized and changed the free energy at the surface to form the water-in-oil emulsion by phase inversion. The water-in-oil emulsion produced according to the present invention is highly stable and water particles are equally and uniformly dispersed therein.  
     [0059] According to the water-in-oil emulsion fuel oil of the present invention produced as above using the heavy oil and the thermal decomposition plastic oil, there is no need to apply heat to lower the viscosity or to use any special facility to produce the emulsion. The emulsion fuel oil of the present invention can be used in the existing engines without any adverse effects on the engine performances while achieving substantial reduction in particulate matter such as SOF (soluble organic fraction) and DS (dry soot) as well as nitrogen oxides NO X .  
     [0060] It is considered that such reduction of SOF and DS in the present invention is based on the following reasons. First, the viscosity of the base oil (mixture of heavy oil and plastic oil) is low and thus diameter of the sprayed particles is small. Second, the distributed water particles rapidly expand and explode by the heat in the engine so that the oil particles are further miniaturized. Third, because of water gas reaction between high temperature vapor and carbon, the solid carbon in the emulsion fuel oil is reduced, thereby shifting to gas-fire.  
     [0061] In particular, since the waste plastic oil includes a large amount of ring inorganic compound, the inventors have initially concerned about possible increase in SOF (soluble organic fraction) in the exhaust gas. In reality, however, there was no increase in SOF, which is probably related to the water gas reaction noted above. It is considered that the reduction of NO X  is derived mainly from the fact that the emulsion fuel oil contains relatively large amount of water which lowers the burning temperature.  
     [0062] With respect to the present invention, several experiments have been performed, the results of which are described in the following:  
     [0063] Experiment 1  
     [0064] The inventors have examined the characteristics of the base oil formed by mixing the heavy oil C listed in Table 1 or the low grade residue oil listed in Table 2 with the waste plastic disposal (WPD) thermal decomposition oil listed in Table 3. FIGS.  1  and 2 show the resultant characteristics of the fuel oil of the present invention. The rate of WPD thermal decomposition oil added to the heavy oil C or the residue oil was varied from 0, 10, 20, 30 to 40 vol % (volume percent) and the changes in density (FIG. 1) and the changes in sulfur contents (FIG. 2) were respectively examined. Such changes shown in FIGS. 1 and 2 are normal changes derived from mixing the corresponding oils.  
                           TABLE 1                                   Unit   Value                                                        Density (15° C.)   g/cm 3     0.982           Kinematic Viscosity (50° C.)   mm 2 /s ( = cSt)   177           Carbon Residue   wt %   12.3           Sulphur   wt %   2.56           Ash   wt %   0.02           Nitrogen   wt %   0.25           Higher Calorific Value   kcal/kg   10,220                      
 
     [0065] However, as shown in FIG. 3, the kinematic viscosity of the base oil is significantly decreased especially between the mixing ratios between 10 vol % and 20 vol %. The kinematic viscosity of the heavy oil C is decreased from about 180 centi-Stokes to about 15 centi-Stoke. The kinematic viscosity of the low grade residue oil is decreased from about 510 centi-Stokes to 30 centi-Stokes. The inventors consider that this is because the WPD thermal decomposition oil contains a large amount of aromatic compound which has high affinity with asphaltene, and as such, the content ratio of the saturated components, asphaltene, aromatic compound, and resin in the heavy oil or low grade residue oil, has been changed.  
                           TABLE 2                                   Unit   Value                                                        Density (15° C.)   g/cm 3     0.991           Kinematic Viscosity (50° C.)   mm 2 /s ( = cSt)   510           Carbon Residue   wt %   16.2           Sulphur   wt %   3.18           Ash   wt %   0.02           Nitrogen   wt %   0.32           Higher Calorific Value   kcal/kg   10,100                      
 
     [0066] FIGS.  4 - 6  show molecular weight in the base oil. The molecular weight is measured by a gas chromatography analyzer (GCM8-QP5000). FIG. 4 shows the molecular weight of the WPD thermal decomposition oil, FIG. 5 shows the molecular weight of the heavy oil C, and FIG. 6 shows changes in the molecular weight in the fuel oil made by adding the WPD thermal decomposition oil by 20 vol % to the heavy oil C. These drawings show that the components in the WPD thermal decomposition oil and the heavy oil C have been changed by mixing with one another.  
                           TABLE                                    Unit   Value                                                        Density (15° C.)   g/cm 3     0.939           Kinematic Viscosity (30° C.)   mm 2 /s ( = cSt)   1.189           Styrene monomer   wt %   63.9           Styrene dimer   wt %   11.5           Styrene trimer   wt %   5.7           Toluene   wt %   2.2           Ethyl Benzen   wt %   1.4           Alpha Methyl Styrene   wt %   2.2           Other   wt %   13.1                      
 
     [0067] An engine performance involving the base oil made of the heavy oil C mixed with the WPD thermal decomposition oil (20 vol %) is shown in FIGS.  7 - 10 . In FIG. 7, a horizontal axis is engine load and a vertical axis is an ignition delay time. As can be seen in FIG. 7, when the engine load increases, the ignition delay time decreases. In FIG. 8, a horizontal axis is engine load and a vertical axis is an exhaust gas temperature. As can be seen in FIG. 8, when the engine load increases, the exhaust gas temperature rises.  
     [0068] In FIG. 9, a horizontal axis is engine load and a vertical axis is a concentration of DS (dry soot) in the exhaust gas. As can be seen in FIG. 9, when the engine load increases, the DS concentration decreases. In FIG. 10, a horizontal axis is engine load and a vertical axis is a concentration of nitrogen oxides NO X  in the exhaust gas. As can be seen in FIG. 10, when the engine load increases, the concentration of NO X  in the exhaust gas tends to increase. Within the mixing ratios of 5-20 vol % of the WPD thermal decomposition oil in the heavy oil C, the engine can operate for all of the load. The dry soot (DS) concentration has been decreased with the increase of the load while the nitrogen oxides NO X  concentration has been increased with the increase of the load.  
     [0069] Experiment 2  
     [0070] Water was added to the base oil described with respect to the experiment 1 above with mixing ratios of 0, 5, 10, 15, 20, 25 and 30 (weight percent), respectively. The base oil mixed with the water was further mixed with encapsulating emulsifier shown in Table 4 with a mixing ratio of 0.1 (weight percent) relative to the sum of the base oil and the water, thereby forming the water-in-oil emulsion fuel oil. The value in Table 4 is amounts of caustic soda (NaOH) and the calcium chloride (CaCl 2 ) with respect to water of 100 g. As shown in Table 4, the caustic soda (NaOH) and the calcium chloride (CaCl 2 ) in the encapsulating emulsifier are about the same amounts with each other and mixed with water where a weight ratio of NaOH, CaCl 2  and water is about 25:25:100. The engine performance using the water-in-oil emulsion fuel oil was examined while operating under 75% engine load. The concentration ratios of the dry soot (DS), the nitrogen oxides (NO X ) and the sulfur oxides (SO X ) in the exhaust gas were measured.  
                           TABLE 4                                   Unit   Value                                                        Caustic soda (NaOH)   g   25           Calcium chloride (CaCl 2 )   g   25                      
 
     [0071] In this experiment, for the water mixing (content) ratio of 20 wt % (weight percent) or lower, the engine can operate under all of the engine load. For the water mixing ratio higher than 20 wt %, the engine performance showed instability, requiring adjustments in the fuel. For the water mixing ratio higher than 25 wt %, continuous operation of the engine was no longer possible.  
     [0072]FIG. 11 shows the engine performance relative to the water content ratio in which the water content ratio (wt %) is shown in a horizontal axis while the concentration of nitrogen oxides NO X  in the exhaust gas is shown in a vertical axis. As can be seen in FIG. 11, the NO X  concentration is decreased with the increase of the water. For example, the NO X  is reduced to half (½) when the water content ration is 20 wt %. In FIG. 12, the water content ratio (wt %) is shown in a horizontal axis while concentration of sulphur oxides SO x  in the exhaust gas is shown in a vertical axis. As shown in FIG. 12, the SO X  concentration is decreased with the increase of the water. For example, the SO X  is reduced to ⅔when the water content ratio is 20 wt %. In FIG. 13, the water content ratio (wt %) is shown in a horizontal axis while the concentration of DS (dry soot) in the exhaust gas is shown in a vertical axis. As shown in FIG. 13, the DS concentration is decreased with the increase of the water. For example, the DS is reduced to ¾when the water content ratio is 15 wt %.  
     [0073] Experiment 3  
     [0074] This experiment is to examine the optimum mixing ratios in the water-in-oil emulsion fuel oil. Table 5 shows such optimum mixing ratios of the base oil, water and emulsifier in accordance with the present invention. The water was added to the base oil described with respect to the Experiment 1 above (the mixture of the heavy oil C with the WPD thermal decomposition oil or the mixture of the low grade residue oil with the WPD thermal decomposition oil) with mixing ratio 20 wt % (weight percent). The base oil mixed with the water was further mixed with encapsulating emulsion shown in Table 4.  
                           TABLE 5                           Base Oil   Water   Emulsifier       Base Oil Component   (vol %)   (vol %)   (wt %)                  Heavy Oil C + WPD   95    5   0.01       20 vol %       Heavy Oil C + WPD   90   10   0.03       20 vol %       Heavy Oil C + WPD   85   15   0.06       20 vol %       Heavy Oil C + WPD   80   20   0.10       20 vol %       Heavy Oil C + WPD   75   25   0.14       20vol%       Heavy Oil C + WPD   70   30   0.18       20 vol %       Low Grade Residue Oil +   95    5   0.50       WPD 20 vol %       Low Grade Residue Oil +   90   10   1.56       WPD 20 vol %       Low Grade Residue Oil +   85   15   3.10       WPD 20 vol %       Low Grade Residue Oil +   80   20   5.00       WPD 20 vol %       Low Grade Residue Oil +   75   25   7.25       WPD 20 vol %       Low Grade Residue Oil +   70   30   9.83       WPD 20 vol %                  
 
     [0075] As shown in Table 5, when the water mixing ratios between 5-20 wt % (weight percent) relative to the sum of the weight of the water and base oil, the optimum ratio of the encapsulating emulsifier of Table 4 is in the range between 0.01-5 wt % (weight percent). After one month from forming the water-in-oil emulsion fuel oil in which water particles are uniformly dispersed in the oil, the engine can operate without any problems.  
     [0076] Experiment 4  
     [0077] Other than the water-in-oil emulsion fuel oil prepared for the Experiment 3, water-in-oil emulsion fuel oil was produced by using a nonionic surface active agent and an anionic surface active agent available in the market. A sum of both surface active agents with weight percent of 1 wt % (0.5 wt % of each of the nonionic and anionic surface active agents) is mixed with the base oil. After leaving the resultant emulsion fuel oil for predetermined days (storage periods), the performance of the engine was examined using this emulsion fuel oil. The resultant data of this experiment is shown in Table 6.  
                           TABLE 6                           Water   Storage   Engine       Base Oil Component   (vol %)   (days)   Operation                                                Heavy Oil C + WPD   5   7   Normal       20 vol %       Heavy Oil C + WPD   10   7   Impossible       20 vol %       Low Grade Residue Oil +   5   10   Need       WPD 20 vol %           Adjustment       Low Grade Residue Oil +   10   10   Impossible       WPD 20 vol %                  
 
     [0078] As to the emulsion fuel oil using the base oil including the heavy oil C, after seven days, the engine was not able to operate at any load for the water content ratio of 10 vol %. Similarly, as to the emulsion fuel oil using the base oil including the low grade residue oil C, after ten days, the engine was not able to operate at any load for the water content ratio of 10 vol %. Further, in the case of the base oil using the low grade residue oil, various adjustments were necessary even when the water content ratio is 5 vol %. Especially, when the load is light, it was necessary to proportionally control the flow rate of the fuel oil.  
     [0079] It is considered that the cause of such engine trouble in the foregoing is that the water is not uniformly dispersed in the oil. Such lack of uniformity of the water was occurred during the storage periods.  
     [0080] As has been described above, the water-in-oil emulsion fuel oil produced by the method of the present invention is stored in a fuel tank for a long period of time and can be used for vessel engines without any changes. The fuel oil of the present invention is effective in reducing the toxic substances in the exhaust gas of the engine.  
     [0081] In the present invention, since the emulsion fuel oil is made by mixing the low cost heavy oil or residue oil with the waste plastic disposal (WPD) thermal decomposition oil, significant cost reduction can be achieved. The water-in-oil emulsion fuel oil of the present invention contributes significant reduction of the particulate matters such as nitrogen oxides NO X , sulphur oxides SO X  and dry soot DS in the exhaust gas.  
     [0082] Further, in the present invention, instead of the surface active agents used in the prior art technology, the emulsifier formed of caustic soda (NaOH) and calcium chloride (CaCl 2 ) are used which promote the phase inversion at the oil surface for producing the water-in-oil emulsion fuel. The emulsion fuel is highly stable and remains unchanged for a long period of time such as one month. This method of producing the water-in-oil emulsion can be easily conducted on a ship. It is expected that low viscosity waste oil other than the WPD thermal decomposition oil may also be used. Further, the method of producing the water-in-oil emulsion fuel oil of the present invention can be used in ocean going ships which use fuel oil of different qualities.  
     [0083] The presently disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.