Patent Publication Number: US-2010126059-A1

Title: Water emulsion production apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of PCT Application No. PCT/JP2008/063208, filed Jul. 23, 2008, which was published under PCT Article 21(2) in Japanese. 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-191346, filed Jul. 23, 2007, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for producing a water emulsion such as a water emulsion fuel. 
     2. Description of the Related Art 
     A water emulsion fuel of a water-in-oil type (W/O type) is known to be combusted based on the following principle. That is, when water emulsion fuel is sprayed into a combustor, oil droplets of the fuel is heated and combusted. At the same time, water particles contained in the oil droplets are heated by radiation heat. The temperature of the water particles reaches a boiling point and the water particles are micro-exploded, which secondarily atomize the surrounding oil droplets. Thus, the fuel is instantaneously atomized into ultrafine particles, and the contact area of the fuel with air increases to cause nearly complete combustion to be achieved. This inhibits unburnt carbon and NOx from being generated in combustion exhaust gas. Furthermore, the increase in the contact area with the air enables a reduction in excess air required for combustion. This provides significant energy saving effect. 
     Conventionally, in order to produce a two-phase water emulsion fuel containing a fuel (heavy oil, light oil, kerosene, BDF, or gasoline) and water, a method is mainly used in which a mixture of the fuel and water is mechanically stirred with a screw, a mixer, shearing, or an ultrasonic homogenizer to disperse water particles (disperse phase) in the fuel (continuous phase). 
     For example, Jpn. Pat. Appln. KOKAI Publication No. 2006-111666 describes an emulsion fuel production apparatus comprising an injection nozzle to inject a mixture containing a fuel and water in the circumferential direction of a stirring container and to form a first swirling flow in the mixture in the stirring container, and a stirring blade to form, below the first swirling flow, a second swirling flow with a smaller diameter than the first swirling flow. 
     Water is particularly insoluble in a fuel such as light oil and A-type heavy oil which are significantly different from water in density, and thus, the water is easily subjected to phase separation. The method of mechanically stirring the mixture comprising fuel and water has a disadvantage that water particles with a wide particle size distribution ranging from about 1 μm to about 30 μm are formed in the fuel and large water particles aggregate and settle out in a short time, resulting in phase separation. The water emulsion fuel phase-separated in such a manner cannot be used as a fuel particularly during start-up. Therefore, an emulsifier is commonly used to prevent the mixture from undergoing phase separation into the fuel and water. 
     The apparatus using mechanical stirring as described above is large and complicated, leading to high cost of the apparatus. Furthermore, owing to the use of the emulsifier, the apparatus is disadvantageous in terms of cost-effectiveness. Moreover, even with use of the emulsifier, phase separation into fuel and water may occur in a short time. Thus, it is actually difficult to install the stirring apparatus in line with the combustor. 
     On the other hand, Jpn. Pat. Appln. KOKAI Publication No. 6-42734 describes an emulsion production apparatus comprising a water injection nozzle to inject pressurized water located at one end of a mixing/stirring chamber and a fuel injection nozzle to inject pressurized fuel located at the other end of the mixing/stirring chamber opposed the water injection nozzle. 
     However, misty water and misty fuel injected through the two opposite nozzles are very unlikely to collide with each other. Thus, it is expected to be impossible to produce water emulsion in which fine water particles are dispersed in the fuel. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a water emulsion production apparatus which has a simple configuration and can be reduced in size, and which makes it possible to produce a water emulsion with fine water particles dispersed in oil in a low cost without using an emulsifier, and which can be installed in line with a combustor or the like. 
     A water emulsion production apparatus according to the present invention comprises: a water emulsion container; a pump for applying a pressure to an oil-water mixture; an injection nozzle injecting the oil-water mixture supplied through the pump into the water emulsion container; and a collision plate which is arranged opposed to the injection nozzle in the water emulsion container and with which the oil-water mixture injected through the injection nozzle is caused to collide. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1A  is a diagram showing the configuration of a water emulsion fuel production apparatus according to a first embodiment of the present invention, and  FIG. 1B  is a plan view of  FIG. 1A ; 
         FIG. 2A  is a diagram showing the water emulsion fuel production apparatus according to a second embodiment of the present invention, and  FIG. 2B  is a cross-sectional view along the line B-B′ in  FIG. 2A ; 
         FIG. 3  is a diagram showing the water emulsion fuel production apparatus according to a third embodiment of the present invention; 
         FIG. 4A  is a diagram showing the water emulsion fuel production apparatus according to a fourth embodiment of the present invention, and  FIG. 4B  is a plan view of  FIG. 4A ; 
         FIG. 5  is a diagram showing the water emulsion fuel production apparatus of a dispersal arrangement type according to a fifth embodiment of the present invention; 
         FIG. 6  is a diagram showing the water emulsion fuel production apparatus of a dispersal arrangement type according to a modification of the fifth embodiment of the present invention; and 
         FIG. 7  is a diagram showing the water emulsion fuel production apparatus of a one-pass type according to a sixth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A theory relating to a water emulsion production apparatus according to the present invention will be described. 
     As understood from the description in Background Art, if fine water particles can be dispersed in fuel, stable water emulsion can, in theory, be produced without the use of an emulsifier (surfactant). The theoretical rationale for this can be approximately described based on the Stokes equation (1) expressing the movement velocity (settling velocity) of particles: 
         Vp=a   2 ×(ρ 0 −ρ 1 )× G/ 18×ρ 0 ×υ  (1) 
     where Vp is the movement velocity (m/sec) of particles, (a) is the particle size (of water) (m), ρ 0  is the density (kg/m 3 ) of the continuous phase, ρ 1  is the density (kg/m 3 ) of the disperse phase, υ is the kinematic viscosity (m 2 /sec) of the continuous phase, and G is the gravitational acceleration (9.8 m/sec 2 ). 
     Equation (1) shows that a smaller water particle size (a) enables a reduction in the movement velocity (settling velocity) of the particles, which suppresses phase separation over an extended time period. In the present invention, the target water particle size is 1 μm or less (submicron), preferably 500 nm or less, more preferably 100 nm or less. 
     In order to form fine water particles, water droplets should be collapsed. A collapse mechanism for water droplets is generally considered as follows. When water droplets are injected into a fluid, the tips of water droplets tend to be shaped like spheres owing to surface tension. However, when the water droplets push aside the stationary fluid, a stagnation point is created in a central portion of the fluid. The pressure in this portion becomes higher than that in the other portions. The pressure can be determined based on the Bernouli theorem (2): 
         P= (σ V   2 /2) 1/2    (2) 
     When the pressure P becomes higher than the surface tension of water droplets, the water droplets start to deform from the stagnation point and finally collapse into smaller water particles. Here, the surface tension of water forming a free surface is 72 dyne/cm (surface tension of light oil is estimated to be about 30 dyne/cm). For example, if water particles with a particle size of 1 μm are present in light oil, the internal pressure P of the water particles is 408×10 4  dyne/cm 2 , which is higher than the pressure of surroundings by 4 bar. Therefore, application of a pressure equal to or higher than the internal pressure causes the water droplets to be destroyed into fine water particles. 
     The water emulsion production apparatus according to the present invention pressurizes and injects an oil-water mixture through an injection nozzle so that the mixture is collided with a collision plate to destroy water droplets into finer water particles. Then, the kinetic energy of the injected oil-water mixture can be converted into pressure at a high efficiency close to 100%. As a result, submicron water particles can be formed. Water emulsion containing such fine water particles is prevented from undergoing phase separation over an extended time period even without containing an emulsifier. Thus, the water emulsion production apparatus according to the present invention can be arranged in line with a combustor, for example. Preferably, the operations of injecting an oil-water mixture through the injection nozzle such that the mixture is collided with the collision plate are repeated. Then, finer water particles can be efficiently formed, and water emulsion can be maintained over an extended time period. Furthermore, the water emulsion production apparatus according to the present invention has a simple configuration and can thus be reduced in seize. Even if the capacity of the apparatus is increased, the apparatus is prevented from being complicated. Consequently, the water emulsion production apparatus according to the present invention is very cost-effective. 
     A first embodiment of the present invention will be described below with reference to the drawings. 
       FIG. 1A  is a diagram of a water emulsion fuel production apparatus according to the first embodiment of the present invention.  FIG. 1B  is a plan view of  FIG. 1A . The water emulsion fuel production apparatus is installed beside a boiler, a cogeneration system, a ship or car engine, or the like to supply water emulsion fuel in line to the combustor. The basic structure of the water emulsion fuel production apparatus according to the present invention remains almost unchanged regardless of the combustor in which the water emulsion fuel production apparatus is installed. 
     A water emulsion container  10  made of stainless steel is configured to store produced water emulsion fuel. The water emulsion container  10  is, for example, cylindrical. The shape of the water emulsion container  10  is not limited to a cylinder but may be a rectangular column. The water emulsion container  10  may be a vertical type or horizontal type. The capacity of the water emulsion container  10  can be set to any value depending on the combustor used so that the value ranges from a small value of about one litter to a large value for ships and electric generators. 
     An injection nozzle  11  is inserted in the top of the water emulsion container  10  to inject a high-pressure fuel-water mixture toward the interior of the water emulsion container 10. The injection nozzle  11  has a nozzle diameter of, for example, 0.1 mm to 1.0 mm. The mounting position of the nozzle and the shape, direction, and number of nozzle holes can be appropriately adjusted in accordance with the intended use. Although not shown, a nozzle configured to inject oil only and a nozzle configured to inject water only may be arranged. 
     In the water emulsion container  10 , a collision plate  12  is supported opposite the injection nozzle  11  so that the injected fuel-water mixture is collided with the collision plate  12 . The distance between the nozzle hole of the injection nozzle  11  and the collision plate  12  is set to 1 mm to 50 mm. As the distance is shortened, a pressure drop of the injected fuel-water mixture can be suppressed. The shape of the collision plate  12  is not particularly limited, and a flat shape, a conical shape, or a spherical shape, for example, may be used. A flat collision plate  12  is advantageous for converting the kinetic energy of the injected fuel-water mixture to a pressure. A conical or spherical collision plate  12  is advantageous for efficient dispersion of water droplets in fuel. 
     A mixture supply line  13  is connected to the injection nozzle  11 . A pump  14  and a switching valve  15  are arranged in the mixture supply line  13 . The mixture supply line reaches a mixing tank  16 . The mixing tank  16  is provided with a mixer to mix fuel and water. Then, the fuel-water mixture is pressurized with the pump  13  to a pressure of 5 MPa to 40 MPa. If the water emulsion container  10  has a large capacity, the fuel-water mixture may be pressurized with the pump  13  to a pressure of 50 MPa or more. 
     A fuel supply line  18  provided with a fuel supply solenoid valve  17  and a water supply line  20  provided with a water supply solenoid valve  19  are connected upstream from the mixing tank  16 . 
     A circulation line  21  is connected to the water emulsion container  10 . Thus, the water emulsion fuel in the water emulsion container  10  can be circulated to the injection nozzle  11  through the switching valve  15  and the pump  14 . A stirrer (not shown) may be arranged in the way of the circulation line  21 . 
     Moreover, an air valve  22  configured to charge air may be arranged in the way of the circulation line  21  as required. Charging of air through the air valve  22  makes it possible to produce water emulsion fuel containing atomized air as well as atomized water. When such water emulsion fuel is sprayed into a combustor, an action that air dissolved in the water emulsion fuel is instantaneously expanded to diffuse the fuel is also obtained. Thus, fuel droplets which are easily combusted with oxygen in air can be utilized, so that more nearly complete combustion can be achieved. This leads to improved combustion efficiency and cleaned exhaust gas. 
     Charging of air through the air valve can be employed not only to produce water emulsion fuel but also to modify only the fuel. That is, if the fuel is modified so as to contain atomized air by charging air through the air valve into the fuel and injecting the pressurized fuel through the injection nozzle to collide with the collision plate, the air is expanded in the combustor and fuel droplets which are easily combusted with oxygen in air can be utilized. This leads to improved combustion efficiency and cleaned exhaust gas. 
     Alternatively, with respect to a liquid other than fuel (such as water, mixed water, washing water, and sterile water), if a method of charging air into the liquid through the air valve and injecting the pressurized liquid through the injection nozzle so as to collide with the collision plate is employed, a liquid containing atomized air can be produced. 
     A water emulsion fuel supply line  23  is connected downstream from the water emulsion container  10  and to a combustor such as a boiler or a car engine. A pressure regulating valve  24  and a trap  25  are arranged in the water emulsion fuel supply line  23 . The bottom of the trap  25  is connected to the bottom of the water emulsion container  10  via a return pipe  26 . A pump  27  is arranged in the return pipe  26 . 
     The pump  14 , the switching valve  15 , the mixing tank  16 , the fuel supply solenoid valve  17 , and the water supply solenoid valve  19  are desirably controlled by a controller  30 . Data processed by the controller  30  such as flow rates of fuel and water is transmitted to an administrative server (not shown) as required. 
     The water emulsion fuel production apparatus according to the present invention may be of an integral type in which the components are integrated together or a separate type in which the components are separated from one another. Alternatively, in a simpler configuration, the fuel supply solenoid valve  17 , the fuel supply line  18 , the water supply solenoid valve  19 , and the water supply line  20  may be omitted from the water emulsion fuel production apparatus. In this case, water emulsion fuel is produced by feeding a fuel-water mixture of a predetermined mixing ratio into the water emulsion fuel container  10 , and performing injection and collision while circulating the fuel-water mixture via the circulation line (and a stirrer arranged in the way of the circulation line as required). 
     Now, the operation of the water emulsion fuel production apparatus will be described. The fuel in the fuel supply line  18 , the flow rate of which is controlled by the fuel supply solenoid valve  17 , and the water in the water supply line  20 , the flow rate of which is controlled by the water supply solenoid valve  19 , are supplied to the mixing tank  15  at a predetermined flow ratio. In the mixing tank  15 , the fuel and the water are mixed by the mixer. The fuel-water mixture is fed from the mixing tank  15  to the pump  14 , where the mixture is pressurized to a pressure of 5 MPa to 40 MPa. The pressurized mixture is injected through the injection nozzle  11  and collided with the collision plate  12 . 
     In the present invention, the injection nozzle  11  applies kinetic energy higher than the internal pressure of water droplets to an injected flow of the fuel-water mixture. When the injected flow is collided with the collision plate  12 , the kinetic energy of the injected flow is converted into pressure. Thus, the water particles (disperse phase) are atomized into ultrafine particles, which are dispersed in the fuel (continuous phase). The size of the water particles has a correlation with the injection pressure. That is, as the pressure is higher, finer water particles can be formed. The present invention enables to easily produce water particles of particle size of 1 μm or less (submicron) by using the means of colliding the injected flow of the fuel-water mixture with the collision plate  12 . 
     The upper space in the water emulsion container  10  is used as a mixing section where the injected fuel and water are mixed together. In the mixing section, a film of the sprayed fuel is formed around the atomized water particles resulting from the collision with the collision plate  12 . Thus, water emulsion fuel in which the disperse phase of the water particles is dispersed in the continuous phase of the fuel is quickly produced. The produced water emulsion fuel is stored in a storage section  51 . If no phase separation has occurred, almost only the water emulsion fuel is stored in the water emulsion container  10 . However, if a fuel-water mixture containing micelle colloid of water particles is formed, it retains in a retention section  52  located under the storage section  51 . The water emulsion fuel containing large-sized water particles retained in the retention section  52  is not suitable for use in the start-up of the combustor. Thus, the water emulsion fuel in the retention section  52  is not supplied to the combustor. Note that, although no partition is arranged in the water emulsion container  10  in  FIGS. 1A and 1B , a partition may be arranged in the water emulsion fuel container  10  if turbulent flow of the liquid is caused by vibration or the like. 
     It is desirable to repeat an operation comprising switching the switching valve  15  to cause the water emulsion fuel in the water emulsion container  10  to be injected through the injection nozzle  11  via the pump  14  so that the fuel is collided with the collision plate  12 . That is, a single collision of the injected flow of the fuel-water mixture with the collision plate  12  may result in formation of water particles of particle size 1 μm or more. Furthermore, as time elapses, even submicron water particles may be formed into micelle colloids of particle size 1 μm or more. 
     In contrast, repetition of circulation of the water emulsion fuel causes the water particles in the water emulsion fuel to be more significantly atomized. The circulation line  21  may be continuously or intermittently used except during the new supply of fuel or water as described below. As a result, phase separation into fuel and water can be prevented over an extended time period. 
     The water emulsion fuel in the water emulsion fuel container  10  is supplied in line to the combustor such as a boiler or a car engine through the fuel supply line  23 . The trap  25  is arranged as required if the distance between the water emulsion fuel container  10  and the combustor is so long that the micelle colloids may settle out. Micelle colloids trapped by the trap  25  are returned to the retention section  51  of the water emulsion fuel container  10  via the return pipe  26 . Thus, in start-up, possible ignition failure is prevented that is caused by supplying the water emulsion fuel containing water particles formed into micelle colloid to the combustor. 
     A supply start sensor  31  and a supply stop sensor  32  may be arranged in the water emulsion fuel container  10 . When the amount of water emulsion fuel in the water emulsion fuel container  10  is decreased because of the use in the combustor, the fuel supply start sensor  31  is turned on. As a result, the switching valve  15  is switched to open the fuel supply solenoid valve  17  and the water supply solenoid valve  19 . Thus, new supplies of fuel and water are mixed in the mixing tank  16 . The fuel-water mixture is then injected through the injection nozzle  11  via the switching valve  15  and the pump  14 , and collided with the collision plate  12 . Consequently, new water emulsion fuel is generated and stored in the water emulsion fuel container  10 . When the amount of water emulsion fuel in the water emulsion fuel container  10  is increased to reach the level of the supply stop sensor  32 , new supplies of fuel and water are stopped. 
     Then, combustion tests were carried out using a boiler comprising an A-heavy oil burner so that water was heated. By way of an example, the water emulsion fuel production apparatus according to the present invention was used to combust water emulsion fuel prepared in a ratio of A-heavy oil to water of 8:2 for two hours. In a comparative example, only A-heavy oil was used as fuel and combusted for two hours. The combustion tests were carried out to compare boiler efficiency. 
     When boiler output is Q1 and the amount of heat supplied is Q2, the boiler efficiency η is expressed by: 
       η= Q 1 /Q 2. 
     Here, Q1 and Q2 are defined as follows: 
         Q 1 =Qw ( Wt 2 −Wt 1), 
     where Qw is an amount of water supplied [L/min], Wt1 is an inlet water temperature, and Wt2 is an outlet water temperature. 
         Q 2 =Hu×Gf,    
     where Hu is a quantity of heat generated by A-heavy oil, and Gf is a fuel flow rate; for the water emulsion fuel in the present example, the actual fuel flow rate is multiplied by 0.8. 
     The fuel flow rate of the A-heavy oil in the comparative example was 9.572 L/H on an average. The inlet water temperature Wt1 (average value) was 16.75° C., whereas the outlet water temperature Wt2 (average value) was 65.75° C. In this case, Q1/Q2 is as follows: 
     
       
         
           
             
               
                 
                   
                     Q 
                      
                     
                         
                     
                      
                     1 
                      
                     
                       / 
                     
                      
                     Q 
                      
                     
                         
                     
                      
                     2 
                   
                   = 
                     
                    
                   
                     
                       
                         Qw 
                          
                         
                           ( 
                           
                             65.75 
                             - 
                             16.75 
                           
                           ) 
                         
                       
                       / 
                       Hu 
                     
                     × 
                     9.572 
                   
                 
               
             
             
               
                 
                   = 
                     
                    
                   
                     5.119 
                      
                     
                         
                     
                      
                     Qw 
                      
                     
                       / 
                     
                      
                     
                       Hu 
                       . 
                     
                   
                 
               
             
           
         
       
     
     The flow rate of the water emulsion fuel in the example was 9.786L/H on an average. The inlet water temperature Wt1 (average value) was 18.4° C., whereas the outlet water temperature Wt2 (average value) was 64.0° C. In this case, Q1/Q2 is as follows: 
     
       
         
           
             
               
                 
                   
                     Q 
                      
                     
                         
                     
                      
                     1 
                      
                     
                       / 
                     
                      
                     Q 
                      
                     
                         
                     
                      
                     2 
                   
                   = 
                     
                    
                   
                     
                       
                         Qw 
                          
                         
                           ( 
                           
                             64.0 
                             - 
                             18.4 
                           
                           ) 
                         
                       
                       / 
                       Hu 
                     
                     × 
                     9.786 
                     × 
                     0.8 
                   
                 
               
             
             
               
                 
                   = 
                     
                    
                   
                     5.825 
                      
                     
                         
                     
                      
                     Qw 
                      
                     
                       / 
                     
                      
                     
                       Hu 
                       . 
                     
                   
                 
               
             
           
         
       
     
     The above results indicate that the use of the water emulsion fuel had increased efficiency by 5.825/5.119=1.137, that is, about 14%, compared to the use of the A-heavy oil. 
     Furthermore, the effect of reducing carbon dioxide, NOx and hydrocarbon (HC) was confirmed, which is known as the advantage of the use of water emulsion fuel. 
     Similarly, combustion tests were carried out for an engine using water emulsion fuel prepared in a ratio of light oil to water of 8:2 or light oil only was used. Then, the water emulsion fuel was determined to be effective for increasing the efficiency and reducing carbon dioxide, NOx and hydrocarbon (HC). 
     In the above-described examples, the apparatus according to the present invention is used to produce water emulsion fuel containing heavy oil and water or light oil and water. However, the present invention may be used for various applications. For example, for water emulsion fuel containing heavy oil and water or light oil and water, the mixing ratio of water may be increased up to 50%. Additionally, it is possible to produce not only water emulsion fuel containing heavy oil and water or light oil and water but also water emulsion fuel containing heavy oil, water, and glycerin or light oil, water, and glycerin. Glycerin is generated as a by-product of BDF fuel and cannot presently be effectively utilized, and is thus incinerated. However, the apparatus according to the present invention enables glycerin to be effectively utilized in water emulsion fuel containing glycerin. Since glycerin is soluble in water, a mixture of fuel and (water+glycerin) may be supplied. Moreover, not only heavy oil and light oil but also various oil components may be used to produce water emulsion. 
     Now, water emulsion fuel production apparatuses according to other embodiments of the present invention will be described. 
       FIG. 2A  is a diagram showing the configuration of a water emulsion fuel production apparatus according to a second embodiment.  FIG. 2B  is a cross-sectional view taken along the line B-B′ in  FIG. 2A . 
     Produced water emulsion fuel is stored in a storage section  101  inside a water emulsion fuel container  100 . Injection nozzles  112  supported by a support  111  and collision plates  113  located opposite the respective injection nozzles  112  are arranged in a liquid in the water emulsion fuel container  100 . As shown in  FIG. 2B , four sets of the injection nozzle  112  and the collision plate  113  are arranged on the circumference at intervals of 90°. Furthermore, two units each of which includes the four sets of the injection nozzle  112  and the collision plate  113  are arranged one above the other. In this manner, a total of eight sets of the injection nozzle  112  and the collision plate  113  are arranged to improve the efficiency of produce of water emulsion fuel. Furthermore, as shown in the lower part of  FIG. 2B , one or more of the collision plates  113  may be slightly inclined to the injection nozzle  112 . Then, a swirling flow may be generated in the liquid in the water emulsion fuel container  100 , which serves to achieve proper stirring. 
       FIG. 2A  shows three fuel and water supply systems F 1 , F 2 , and F 3  optionally used, which will be described below. 
     The injection nozzles  112 , arranged in the liquid in the water emulsion fuel container  100 , are connected to a mixture supply line  121 . If the first or second fuel and water supply system F 1  or F 2  is used, a high-pressure pump  122  is arranged upstream from the mixture supply line  121 . The high-pressure pump  122  is driven by a motor  123 . 
     If the first fuel and water supply system F 1  is used, fuel from a fuel supply line  131  and water from a water supply line  132  are mixed in a mixing tank  133 , and then, the fuel-water mixture is pressurized by the high-pressure pump  122  and injected through the injection nozzles  112  via the mixture supply line  121 , and the mixture is collided with the collision plates  113  to thereby produce water emulsion fuel. 
     If the second fuel and water supply system F 2  is used, fuel and water are pre-mixed in a tank  135 , and the fuel-water mixture is pressurized by the high-pressure pump  122  and injected through the injection nozzles  112  via the mixture supply line  121 , and the mixture is collided with the collision plates  113  to thereby produce water emulsion fuel. 
     On the other hand, if the third fuel and water supply system F 3  is used, a circulation line  125  through which the liquid in the water emulsion fuel container  100  is circulated is connected to the mixture supply line  121 . A high-pressure pump  126  is arranged in the circulation line  125 . The high-pressure pump  126  is driven by a motor  127 . If the third fuel and water supply system F 3  is used, fuel from a fuel supply line  136  and water from a water supply line  137  are metered and fed directly into the water emulsion fuel container  100 , and the fuel-water mixture is pressurized by a high-pressure pump  126  and injected through the injection nozzles  112  via the mixture supply line  121 , and the mixture is collided with the collision plates  113  to thereby produce water emulsion fuel. This cyclic operation is continued until water emulsion fuel suitable for combustion is produced. 
     Note that, even when the first or second fuel and water supply system F 1  or F 2  is used, it is possible to use the high-pressure pump  126  arranged in the circulation line  125  together with the high-pressure pump  122  arranged upstream from the mixture supply line  121 . 
     The water emulsion fuel produced by the above-described operation is supplied to the combustor such as an engine or a boiler through a water emulsion fuel supply line  141 . When the operation for manufacturing water emulsion fuel is stopped, a stirring apparatus  142  is preferably used to stir the liquid in the water emulsion fuel container  100  so as to maintain the mixing ratio of the water emulsion fuel constant. The stirring apparatus  142  is driven by a motor  143 . Although a screw is used as the stirring apparatus  142  in  FIG. 2A , a low-pressure pump may be used instead of the screw. 
       FIG. 3  is a diagram showing the configuration of a water emulsion fuel production apparatus according to a third embodiment of the present invention. In the apparatus, valve and pump operations for supplying fuel and water are manually performed. The apparatus is used to produce a small amount of water emulsion fuel and is inexpensive. 
     Produced water emulsion fuel is stored in a storage section  201  inside a water emulsion fuel container  200 . Injection nozzles  212  supported by a support  211  and collision plates  213  located opposite the respective injection nozzles  212  are arranged in a liquid in the water emulsion fuel container  200 . A fuel supply line  221  provided with a manual valve  222  is connected to the water emulsion fuel container  200 . A scale  223  is attached to a side surface of the water emulsion fuel container  200 . The user supplies fuel up to a predetermined fuel line (OL) while looking at the scale  223 . 
     A water tank  230  is arranged at the top of the water emulsion fuel container  200 . A water supply line  231  provided with a manual valve  232  is connected to the water tank  230 . A scale  233  is attached to a side surface of the water tank  230 . The user supplies fuel up to a predetermined water line (WL) while looking at the scale  233 . The water tank  230  is connected to the water emulsion fuel container  200  via a manual valve  234 . 
     A high-pressure pump  251  driven by a motor  252  is arranged at the bottom of the water emulsion fuel container  200 . The user switches on and operates the high-pressure pump  251 , while opening the manual valve  234  to supply water little by little. When the level in the water emulsion fuel container  200  reaches the predetermined water line (WL), the user closes the manual valve  234 . 
     The liquid in the water emulsion fuel container  200  is pressurized by the high-pressure pump  251 . The pressurized liquid is injected through the injection nozzles  212  via the circulation line  253  and collided with the collision plates  213 . As a result, water emulsion fuel is produced. This cyclic operation is continued until water emulsion fuel suitable for combustion is produced. The produced water emulsion fuel is supplied to the combustor such as a boiler through a water emulsion fuel supply line  255 . 
     Even when the operation for manufacturing water emulsion fuel is stopped, the water emulsion fuel can be used by using a low-pressure pump  254  for stirring to suck, eject, and stir the liquid in the water emulsion fuel container  200 . 
     A setting retardant may be used to retard the settling of water particles. Thus, the stirring carried out by the low-pressure pump  254  may be reduced or eliminated. The settling retardant may be waste engine oil or waste edible oil. The amount of settling retardant added is in the range of 0.2% to 1% of the amount of water emulsion fuel and is set in accordance with the type of fuel and the mixing ratio of water. For example, if A-heavy oil is used in a water mixing ratio of 30%, the addition amount of the settling retardant is set to about 0.5%. The settling retardant may be fed directly into the water emulsion fuel container  200  or fed into a fuel tank in advance. 
       FIG. 4A  is a diagram showing the configuration of a water emulsion fuel production apparatus according to a fourth embodiment of the present invention.  FIG. 4B  is a plan view of  FIG. 4A . The apparatus is of a tandem type including two water emulsion fuel containers. The water emulsion fuel containers are automatically controlled so as to be switched for operation. The apparatus is installed beside, for example, a boiler that uses a large amount of water emulsion fuel. 
     Produced water emulsion fuel is stored in a storage section inside each of two water emulsion fuel containers  300 A and  300 B. Injection nozzles  312  supported by a support  311  and collision plates  313  located opposite the injection nozzles  312  are arranged in a liquid in each of the water emulsion fuel containers  300 A and  300 B. Similarly to  FIG. 2A , two units each of which includes the injection nozzles  112  and the collision plates  113  are arranged one above the other. 
     Fuel is fed from a fuel supply line  331  through a flow meter  332  to one of the water emulsion fuel containers. Water is fed from a fuel supply line  333  through a flow meter  334  to one of the water emulsion fuel containers. The liquid levels in the water emulsion fuel containers  300 A and  300 B are monitored by respective level sensors  302 A and  302 B. 
     A high-pressure pump  351  connected to a circulation line  355  for the water emulsion fuel containers  300 A and  300 B is arranged below the water emulsion fuel containers  300 A and  300 B. The high-pressure pump  351  is driven by a motor  352 . The liquid in the water emulsion fuel container is pressurized by the high-pressure pump  351 . The pressurized liquid is injected through the injection nozzles  312  via the circulation line  355  and is collided with the collision plates  313 . As a result, water emulsion fuel is produced. The water emulsion fuel in the water emulsion fuel containers  300 A and  300 B is stirred and uniformly mixed by a low-pressure pump  356 . For simplification, a line through which the low-pressure pump  356  sucks and ejects the water emulsion fuel from the water emulsion fuel containers is omitted from  FIG. 4A . A stirrer such as a screw may be used instead of the low-pressure pump  356 . 
     The water emulsion fuel in the water emulsion fuel containers  300 A and  300 B is supplied to the combustor such as an engine or a boiler through the water emulsion fuel supply line  361 , the flow meter  362 , and a trap  363  with a stirrer. If the water emulsion fuel is supplied to the engine, return fuel from the engine is returned to the trap  363 . The water emulsion fuel trapped by the trap  363  is returned to the water emulsion fuel containers  300 A and  300 B through a return line  366 . 
     Various components are controlled by a controller  370 . The controller  370  includes an inverter  371 . Operation conditions for the controller  370  are input into an operation panel  372 . 
     An example of the operation of a water emulsion fuel production apparatus according to the present embodiment will be described. 
     First, fuel is supplied to the water emulsion fuel container  300 A. When the level sensor  302 A detects that the fuel reaches the predetermined level, the fuel supply is stopped. At the same time, the high-pressure pump  351  is driven to start supplying water. The start and stop of the fuel supply and water supply is subjected to sequence control by the controller  370 . 
     With the liquid in the water emulsion fuel container  300 A circulated, the liquid pressurized by the high-pressure pump  351  is injected through the injection nozzles  312 . The liquid is collided with the collision plates  313  to thereby produce water emulsion fuel. Note that, if viscous fuel such as C-heavy oil is used or the water emulsion fuel production apparatus is installed beside a furnace, a large-sized engine, and a large-sized boiler which are not affected by a large particle size of water, the liquid in the water emulsion fuel container need not be always circulated. 
     The operation for manufacturing water emulsion fuel is alternately performed in the two water emulsion fuel containers  300 A and  300 B. Emulsion fuel is also fed alternately from the two water emulsion fuel container  300 A and  300 B to the combustor. 
     The operation and management of pumps, motors, solenoid valves, and inverters, and measurements and data transfers by flow meters and pressure gauges are controlled by the controller  370 . Various data is transmitted to an administrative server as required. 
     In  FIGS. 4A and 4B , two water emulsion fuel containers are used. However, three or more water emulsion fuel containers may be used as required. Furthermore, although not shown in the drawings, the line may be switched to a line that uses normal fuel in case of emergency and when the apparatus is stopped for maintenance. 
       FIG. 5  is a diagram showing the configuration of a distributively arranged water emulsion fuel production apparatus according to a fifth embodiment of the present invention. In the apparatus, distributively arranged two water emulsion fuel containers  400 A and  400 B are connected in line. The apparatus is installed beside a ship engine or the like which has no sufficient space to install the integral apparatus shown in  FIGS. 4A and 4B  and which uses a relatively large amount of fuel. 
     The fuel in a fuel tank  431  may be supplied directly to the ship engine or the like through a fuel supply line  432  and bypass switching valve  461  and  462 , so that the fuel can be combusted in the conventional manner. 
     When water emulsion fuel is produced, the bypass switching valves  461  and  462  are switched. The fuel in the fuel tank  431  is fed to a mixing tank  440  through the fuel supply line  432 , the bypass switching valve  461 , and a flow meter  433 . The water in a water tank  435  is fed to the mixing tank  440  through a water supply line  436  and a flow meter  437 . In the in-line arrangement, the amount of water fed from the water tank  435  is adjusted in proportion to the amount of fuel fed from the fuel tank  431 . The fuel-water mixture mixed in the mixing layer  440  is passed a high-pressure pump  451  for the first pass, the water emulsion fuel container  400 A for the first pass, a high-pressure pump  452  for the second pass, and the water emulsion fuel container  400 B for the second pass. Injection nozzles  412  supported by a support  411  and collision plates  413  located opposite the injection nozzles  412  are arranged in the liquid in each of the water emulsion fuel containers  400 A and  400 B. The fuel-water mixture is pressurized by the high-pressure pump  451  and injected through the injection nozzles  412  in the water emulsion fuel container  400 A, and the mixture is collided with the collision plates  413  to thereby produce water emulsion fuel. Moreover, the water emulsion fuel exited the water emulsion fuel container  400 A is pressurized by the high-pressure pump  451  and injected through the injection nozzles  412  in the water emulsion fuel container  400 A, and the mixture is collided with the collision plates  413  to thereby produce water emulsion fuel containing finer particles. 
     The produced water emulsion fuel is fed through the bypass switching valve  462  and a trap  465  to a combustor  460 , where the fuel is combusted. If the combustor  460  is an engine, return fuel is returned to the trap  465 . 
     The operation and management of pumps, motors, solenoid valves, and inverters and measurements and data transfers by flow meters and pressure gauges are controlled by a controller  470 . 
     Fuel such as C-heavy oil having a high viscosity and a high specific gravity is used for large-sized ship engines. Even after the produce of the emulsion, the fuel can be used without problems provided that water particles settle out relatively slowly and have a particle size of about 5 to 10 μm. Thus, water emulsion fuel can be efficiently produced by connecting the plurality of water emulsion fuel containers  400 A and  400 B in line. 
       FIG. 6  is a diagram showing the configuration of a distributively arranged water emulsion fuel production apparatus according to a modification of the fifth embodiment of the present invention. The apparatus has the configuration similar to that shown in  FIG. 4  except that water emulsion fuel is produced by circulating the liquid in the distributively arranged two water emulsion fuel containers  400 A and  400 B using the high-pressure pump  451 . 
       FIG. 7  is a diagram showing the configuration of a one-pass type water emulsion fuel production apparatus according to a sixth embodiment of the present invention. This apparatus produces water emulsion fuel by only one injection of a fuel-water mixture. The apparatus is installed beside a combustor such as an engine, a boiler, and a furnace which are not affected by a relatively nonuniform size of water particles in water emulsion fuel. The apparatus is installed as close to the combustor as possible, and produced water emulsion fuel is immediately combusted in the combustor. 
     Fuel may be supplied directly to a combustor  560  through a fuel supply line  531 , a flow meter  532 , and bypass switching valves  561  and  562 , so that the fuel can be combusted in the conventional manner. 
     When water emulsion fuel is produced, the bypass switching valves  561  and  562  are switched. Fuel is supplied through the fuel supply line  531 , the flow meter  532 , and the bypass switching valve  561 . Water is supplied through a water supply line  535  and a flow meter  536 . The fuel-water mixture is pressurized by a high-pressure pump  551  and is fed to a water emulsion fuel container  500 . Injection nozzles  512  supported by a support  511  and collision plates  513  located opposite the injection nozzles  512  are arranged in the liquid in the water emulsion fuel container  500 . The fuel-water mixture pressurized by the high-pressure pump  551  is injected through the injection nozzles  512  in the water emulsion fuel container  500 , and collided with the collision plates  513  to thereby produce water emulsion fuel. The produced water emulsion fuel is fed through the bypass switching valve  562  to the combustor  560 , where the fuel is combusted. The operation and management of pumps, motors, solenoid valves, and inverters and measurements and data transfers by flow meters and pressure gauges are controlled by a controller  570 . 
     A circulation line  521  may be connected to the water emulsion fuel container  500 . Moreover, return fuel from the engine may be returned to the water emulsion fuel container  500  through a return line  563 .