Description A BURNING SYSTEM FOR EMULSIFIED FUEL

Technical Field

[1] The present invention relates to a system for burning emulsified fuel, which is adapted to promptly produce water in oil (W/O) type emulsified fuel, which includes water dispersed in liquid-phase petroleum oil fuel, and to burn the emulsified fuel. Background Art

[2] The term emulsification generally refers to the uniform dispersion of some liquid in the form of fine particles in another liquid immiscible with the first liquid. However, in this specification, the term emulsification means a process of mixing liquid fuel (liquid-phase petroleum oil resulting from the purification of crude oil, diesel oil, kerosene, heavy oil, gasoline, or the like) with water in various ways, thus forming water in oil (W/O) type emulsified fuel, and the mixed fuel, comprised of liquid fuel and water homogeneously dispersed therein, is referred to as emulsified oil (the rate of water added to liquid fuel is set to be 30% or less according to the kind of liquid fuel, and the burning conditions are improved with an increase in the amount of the water).

[3] Since emulsified fuel can improve combustion efficiency, it is an effective way of saving energy. Further, the emulsified fuel can suppress the generation of air-polluting substances, and thus it is useful in terms of reducing environmental contamination. The principle of the emulsified fuel will be described in brief as follows.

[4] - In the combustion of fuel, as the volume of each particle of supplied (sprayed) fuel decreases, the contact area with air is increased and the burning time is decreased, which is beneficial.

[5] - In emulsified fuel, water dispersed in liquid fuel is overheated and is abruptly vaporized at a certain instant in the course of combustion of the water, thus increasing the volume of the water, and thus a microburst occurs in a liquid oil drop (water particles are dispersed in the liquid oil drops). As a result, the liquid oil drops are dispersed and scattered, thus making the oil drops fine.

[6] As it is known that the emulsified fuel is advantageous in terms of energy savings and environmental contamination, the Ministry of Environment of the Republic of Korea announced performance criteria and a facility laboratory procedure for the prevention of air pollution (an auxiliary burning apparatus: an apparatus for decreasing or suppressing the exhaust of air-polluting substances by promoting or aiding the combustion of fuel in ways such as emulsification), and is encouraging the use thereof.

[7] A conventional system for burning emulsified fuel, which is adapted to prepare emulsified fuel and to burn the emulsified fuel, will now be described below.

[8] Although there are many types of burning systems for emulsified fuel, a typical burning system is comprised of a liquid fuel tank, a water tank, an auxiliary burning unit for preparing emulsified fuel from liquid fuel and water, a reservoir tank for storing the emulsified fuel, and a boiler for burning the emulsified fuel, wherein the auxiliary burning unit is comprised of a casing having an emulsification chamber therein, and an impeller disposed in the emulsification chamber for mixing and thus emulsifying the liquid fuel and the water through agitation.

[9] Consequently, when the impeller is operated and the liquid fuel in the liquid fuel tank and the water in the water tank are transferred to the casing, the liquid fuel and the water are emulsified in the course of passing through the emulsification chamber, resulting in emulsified fuel. The emulsified fuel is stored in the reservoir tank and then supplied to the boiler.

[10] However, the above-mentioned conventional burning system has the following problems.

[11] - The emulsified fuel may have different emulsification states, such as the rate of addition of water to liquid fuel, depending on the conditions at the time of manufacture, such as the manufacturing environment, thereby creating different burning conditions in the boiler. The most universal measure for optimizing the burning conditions is to increase the air supply, so that the emulsified fuel is provided with many opportunities to come into contact with air when the burning conditions deteriorate.

[12] Although the measure can produce some effects in terms of improvement in the burning conditions, the effects cannot satisfy the expected value, and the measure cannot be a fundamental solution.

[13] - In the manufacture of emulsified fuel, since liquid fuel and water are emulsified simply by mixing and agitating them using an impeller, it takes a considerable amount of time to produce the emulsified fuel. This consequently makes the continuous production of emulsified fuel and the prompt supply of the emulsified fuel to a boiler impossible.

[14] Furthermore, since the produced emulsified fuel has a very unstable emulsified state, it is necessary to use an emulsifying agent (such as a surfactant) to stabilize the emulsified state. Disclosure of Invention Technical Problem

[15] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a system for burning emulsified fuel, which is able to maintain a rate of addition of

water to liquid fuel at the optimal value and thus improve burning conditions in such a way that the conditions for burning the emulsified fuel are detected by measuring the amount of emitted air-polluting substances, and thus the amount of water (the rate of addition of water to liquid fuel) supplied to an auxiliary burning tank from a water tank is controlled according to the conditions for burning the emulsified fuel.

[16] Another object of the present invention is to provide a high performance auxiliary burning apparatus for use in a system for burning emulsified fuel, which is able to promptly produce emulsified fuel having a stable emulsified state in such a way that liquid fuel and water are primarily mixed with each other in the course of being transferred to an emulsification chamber, and are then secondarily converted into fine particles in the emulsification chamber by shearing, striking, compression, and expansion actions, causing emulsification, and to supply the emulsified fuel to a boiler. Technical Solution

[17] In order to accomplish the above objects, the present invention provides a system for burning emulsified fuel, including: a liquid fuel tank for containing liquid fuel therein, a water tank for containing water therein, an auxiliary burning tank, which is adapted to disperse the water supplied from the water tank throughout the liquid fuel supplied from the liquid fuel tank, thus preparing emulsified fuel containing fine water particles dispersed therein, and a boiler for burning the emulsified fuel supplied from the auxiliary burning unit, and a feed- water control unit, which is adapted to increase the amount of water supplied to the auxiliary burning unit when the amount of emitted air-polluting substances exhausted from the boiler exceeds a set value, and to decrease the amount of water supplied to the auxiliary burning unit when the amount of emitted air-polluting substances exhausted from the boiler is equal to or less than the set value.

[18] In a preferred embodiment, the feed- water control unit may include: a sensor disposed in a chimney of the boiler to measure the amount of emitted air-polluting substances; a flow control valve mounted on a water pipe that transfers the water from the water tank to the auxiliary burning unit; and a control unit for controlling the operation of the flow control valve such that the amount of water flowing through the water pipe is increased when a measured value input from the sensor exceeds the set value, whereas the amount of water flowing through the water pipe is decreased when the measured value, input from the sensor, is equal to or less than the set value.

[19] In a preferred embodiment, the sensor may include one or more selected from a group consisting of a dust sensor, a carbon monoxide sensor, a nitrogen oxide sensor and a sulfur oxide sensor.

[20] In a preferred embodiment, the auxiliary burning unit may include: a casing, which is provided at a region thereof with an inlet port and is provided at another region

thereof with an outlet port for supplying the emulsified fuel to the boiler, and which includes a cylindrical emulsification chamber therein, a raw material transport pipe, which is connected to the inlet port at an end thereof, and is branched into two branch pipes, wherein the liquid fuel from the liquid fuel tank and the water from the water tank are supplied to respective branch pipes, a mixer disposed in the raw material transport pipe to primarily mix the raw material, a stator provided on an inner circumferential surface of the emulsification chamber, which includes a recessed part comprised of a plurality of recesses and a protrusion part comprised of a plurality of protrusions defined between the recesses, wherein the protrusion part includes orifices formed in the protrusions to compress the raw material, a rotor disposed in an inner circumference of the stator, which includes a plurality of circumferential blades at opposite ends thereof, to secondarily mix the raw material while shearing the raw material, in conjunction with the stator, a shaft on which the rotor is mounted, and a motor for rotating the shaft.

[21] In a preferred embodiment, each the orifices of the stator may be gradually increased in inner circumference, moving forwards towards an outlet from an inlet, into which the raw material is introduced.

[22] In a preferred embodiment, the rotor may include orifices having the form of fine holes, which are formed in the blades to compress the raw material.

[23] In a preferred embodiment, each of the orifices of the rotor may be gradually increased in inner circumference, forwards towards an outlet from an inlet, into which the raw material is introduced.

[24] In a preferred embodiment, the rotor may include a first rotor part, which includes the blades at an end thereof, a second rotor part, which includes the blades an end thereof, and a rotor socket, interposed between the first rotor part and the second rotor part, to couple both of the rotor parts to each other, wherein the rotor socket includes a plurality of grooves in an outer circumferential surface thereof, thus forming a plurality of blades therebetween.

[25] In a preferred embodiment, each of the blades of the rotor socket may be inclined in the rotating direction of the rotor at a predetermined angle.

Advantageous Effects

[26] As described above, according to the present invention, an amount of emitted air- polluting substances exhausted from a boiler is measured, and the measured value is compared with the set value. After the comparison, the rate of addition of water to liquid fuel is controlled in such a way that the water supply is increased when the measured value exceeds the set value, whereas the water supply is decreased otherwise. Accordingly, the present invention makes it possible to maintain desirable

burning conditions, effectively saves energy, and efficiently suppresses the generation of air-polluting substances.

[27] In addition, according to the present invention, liquid fuel supplied from a liquid fuel tank and water supplied from a water tank are primarily emulsified in a raw material transport pipe using a mixer, and are then secondarily emulsified in an emul- sification chamber of a casing using shearing, striking, compression and expansion actions caused by a recess part, a protrusion part, the orifices of a stator and blades, and the orifices of a rotor. Consequently, it is possible to quickly produce W/O type emulsified fuel that is stably emulsified and thus enables the prompt supply of the emulsified fuel to the boiler. Brief Description of the Drawings

[28] FIG. 1 is a schematic view showing a construction of a system for burning emulsified fuel, according to the present invention;

[29] FIG. 2 is a fragmentary cross-sectional view showing an auxiliary burning unit of the burning system of FIG. 1;

[30] FIG. 3 is a cross-sectional view of a casing of FIG. 2;

[31] FIG. 4 is a cross-sectional view taken along line A-A of FIG. 3;

[32] FIG. 5 is an enlarged view of circle B of FIG. 4;

[33] FIG. 6 is a half cross-sectional view of a rotor of FIG. 2;

[34] FIGS. 7[A] and 7[B] are a right side view of a first rotor part and a left side view of a second rotor part of FIG. 6;

[35] FIG. 8 is a perspective view of a rotor socket of FIG. 6; and

[36] FIG. 9 is a block diagram showing a feed- water control unit of the system for burning emulsified fuel of FIG. 1.

[37] < Description of the elements in the drawings>

[38] 100: heavy oil tank (liquid fuel tank)

[39] 120: diesel oil tank (liquid fuel tank)

[40] 200: water tank

[41] 300: auxiliary burning unit

[42] 310: casing

[43] 311: emulsification chamber

[44] 312: inlet port

[45] 313: outlet port

[46] 320: raw material transport pipe

[47] 330: mixer

[48] 340: stator

[49] 341: recess part

[50] 342: protrusion part

[51] 343: orifice

[52] 343i: inlet of orifice

[53] 343o: outlet of orifice

[54] 350: rotor

[55] 35 Ia: first rotor part

[56] 35 Ib: second rotor part

[57] 352: rotor socket

[58] 354: blade

[59] 356: orifice

[60] 356i: inlet of orifice

[61] 356o: outlet of orifice

[62] 359: blade

[63] 360: shaft

[64] 370: motor

[65] 400: boiler

[66] 450: chimney

[67] 500: feed- water control unit

[68] 510: sensor for measuring air-polluting substances

[69] 522: flow control valve

[70] 530: control unit

[71] 622: water pipe

[72] G: groove

[73] S: crush section

Best Mode for Carrying Out the Invention

[74] A preferred embodiment of the present invention will now be described in further detail with reference to an example and the accompanying drawings.

[75] FIG. 1 is a schematic view showing a system for burning emulsified fuel according to the present invention.

[76] As shown in FIG. 1, the burning system according to the invention includes a liquid fuel tank for containing liquid fuel, a water tank 200 for containing water, an auxiliary burning unit 300 for preparing W/O type emulsified fuel from the liquid fuel and the water, which are supplied from the liquid fuel tank and the water tank 200, a boiler 400 for burning the emulsified fuel, prepared by the auxiliary burning unit 300, and a feed- water control unit 500 (see FIG. 9) for controlling the amount of water supplied from the auxiliary burning unit 300, according to the amount of air-polluting substances discharged and emitted from the boiler 400.

[77] As shown in FIG. 1, the liquid fuel tank is divided into a heavy oil tank 110, for containing heavy oil, and a diesel oil tank 120, the heavy oil contained in the heavy oil tank 110 and the diesel oil contained in the diesel oil tank 120 being transferred to the auxiliary burning unit 300 through a liquid fuel transport pipe, which communicates the heavy oil tank 110 and the diesel oil tank 120 with the auxiliary burning tank 300.

[78] Here, the liquid fuel transport pipe includes a main pipe 611, with an end thereof being connected to the auxiliary burning unit 300, and a pair of branch pipes 612a and 612b, which are branched from the main pipe 611 and connected to the heavy oil tank 110 and the diesel oil tank 120, respectively. The branch pipes 612a and 612b are provided with control valves 710a and 710b, respectively, which are adapted to open or block respective branch pipes 612a and 612b in order to supply the heavy oil or the diesel oil to the auxiliary burning unit 300, as desired. In addition, although not shown in the drawing, the branch pipes 612a and 612b may be further provided with respective pumps when it is impossible to transfer the liquid fuel using only the force of gravity because of the relatively low position of the liquid fuel tank.

[79] For reference, in the preparation of emulsified fuel and the burning thereof, the heavy oil is used at normal times, and the diesel oil is used when it is desired to extinguish the burning in the boiler 400, wherein, after the burning has been performed using the heavy oil for a predetermined period of time, the burning is performed using the diesel oil, followed the extinction of the burning.

[80] As shown in FIG. 1, the water tank 200 is connected to a water source (a source for water supply) through a service pipe 621 so that the water is supplied to the water tank 200 and is stored therein. In order to allow the stored water to be supplied to the auxiliary burning unit 300, the water tank 200 is connected to the auxiliary burning tank 300 through a water pipe 622.

[81] The service pipe 621 is provided with a control valve 720, which functions to interrupt or allow the supply of water to the water tank 200, and the water pipe 622 is equipped with a water pump 810, which functions to transport the water from the water tank 200 to the auxiliary burning unit 300 using pressure. In this case, where the supply of water can be fulfilled only by the force of gravity, thanks to the water tank 200, positioned at a relatively high level, the water pump may be omitted.

[82] FIG. 2 is a fragmentary cross-sectional view of the auxiliary burning unit 300.

[83] The auxiliary burning unit 300 serves to quickly prepare emulsified fuel, which is stably emulsified by dispersing water throughout the liquid fuel, thus preparing emulsified fuel containing ultrafine water particles dispersed therein, and then immediately to supply the emulsified fuel to the boiler 400. As shown in FIG. 2, the auxiliary burning unit 300 includes a casing 310 having an emulsification chamber 310 defined therein, a raw material supplying unit for primarily emulsifying the liquid fuel

and water (a preparatory procedure executed before the main emulsifying operation) and then supplying it to the emulsification chamber 310, and an emulsification unit for secondarily emulsifying (the main emulsifying operation), the raw material (liquid fuel and water) supplied from the emulsification chamber 311 thus producing emulsified fuel and the emulsified fuel then being supplied to the boiler 400.

[84] FIG. 3 is a cross-sectional view showing the casing 301, and FIG. is a cross- sectional taken along line A-A of FIG. 3.

[85] As shown in FIGS. 3 and 4, the casing 310 is configured to have an emulsification chamber 311 having a cylindrical shape, which is provide at an end thereof with an inlet port to allow the raw material supplied from the raw material supplying unit to be introduced into the emulsification chamber 311, and is provided at the other end thereof with an outlet port 313 to allow the emulsified fuel prepared by the emulsification unit to be discharged from the emulsification chamber 311.

[86] The inlet port 312 and the outlet port 313 are positioned at respective opposite ends of the emulsification chamber 311, and the outlet port 313 is connected to the boiler 400 through an emulsified fuel transport pipe 603 to allow the prepared emulsified fuel to be supplied to the boiler 400.

[87] As shown in FIG. 2, the raw material supplying unit is comprised of a raw material transport pipe 320 and a mixer 330. The liquid fuel (heavy oil or diesel oil) from the heavy oil tank 110 or the diesel oil tank 120 and the water from the water tank 200 are supplied to the raw material transport pipe 320, where the liquid oil and the water are collectively supplied to the emulsification chamber 311. The mixer 330 functions to primarily emulsify the liquid fuel and water in the course of flowing along the raw material transport pipe 320.

[88] The raw material transport pipe 320 is comprised of a stem part and a branch part branched from the stem part, thus forming an approximately Y -shaped pipe. The stem part is comprised of a junction tube 321, in which the liquid fuel and water merge with each other and flow, and the branch part is comprised of branch tubes 322a and 322b which are integrally coupled to one end of the junction tube 321.

[89] Here, the junction tube 321 is connected to the inlet port 312, and the branch tubes

322a and 322b are connected to the main pipe 611 and the water pipe 622, respectively, in order to allow the liquid fuel and the water to be supplied thereto.

[90] The mixer 330 is comprised of a screw 331 disposed in the junction tube 321 and extending longitudinally, and screw driving means for rotating the screw 331 at high speed.

[91] Preferably, the screw 331 has an optimized configuration with respect to the shape and position of the blade, such that a complicated and irregular stream, such as agitation or a change in direction, is rapidly and continuously generated in the junction

tube 321, thus ensuring the efficient emulsification of the liquid fuel and water.

[92] The screw driving means is comprised of a motor 332 and power transmission means for transmitting a turning force, generated by the motor 332, to the screw 331. The power transmission means is comprised of a drive gear 333 mounted on a shaft of the motor 332, and a driven gear 334 mounted on a shaft of the screw 331 and engaged with the drive gear 333.

[93] The motor 332 is disposed outside the junction tube 321 to be at a right angle with the longitudinal axis of the screw 331, and the shaft of the motor 332 passes through the junction tube 321 in such a way as to prevent leakage therebetween. The drive gear 333 and the driven gear 334 are of a bevel gear type.

[94] As shown in FIG. 2, the emulsification unit is comprised of a stator 340, a rotor

350, and rotor driving means. Of course, the rotor 350 is disposed in the emulsification chamber 311, and the stator 340 is disposed around the rotor 350 with a predetermined spacing therebetween.

[95] As shown in FIGS. 3 and 4, the stator 340 functions to provide the inner circumferential surface of the emulsification chamber 311 with a crushing section S where the raw material, introduced through the inlet port 312, collides with the stator, and is thus crushed (emulsification) while passing through the emulsification chamber 311. The stator 340 is comprised of a recess part 341 and a protrusion part 342.

[96] In this case, the recess part 341 is constituted by a plurality of recesses which are formed in a repeating arrangement on the inner circumferential surface of the emulsification chamber 311 in circumferential and longitudinal directions at predetermined intervals, and the protrusion part 342 is constituted by inner surface regions of the emulsification chamber 311, defined between the recesses of the recess part 341.

[97] Each of the recesses of the recess part 341 is formed in an approximate rectangular shape, and the recesses of the recess part 341 are disposed to be aligned with each other in circumferential and longitudinal directions. Further, in order to allow the raw material, introduced into the recess part 341 in the course of the collision, to flow into the adjacent recess without bypassing the emulsification chamber 311, elongated orifices 343 are formed between the respective recesses.

[98] FIG. 5 is a fragmentary enlarged view of circle B of FIG. 4, which shows the orifices 343 of the stator 340.

[99] The orifices 343 of the stator 340 are through-hole type fine holes which are formed to communicate the adjacent recesses of the recess part 341 with each other. The fine holes are classified into horizontal fine holes, which are adapted to connect the horizontal rows of recesses (rows of recesses positioned to be at at right angles with the circumferential direction of the emulsification chamber of FIG. 3) to each other, and vertical rows of fine holes adapted to connect vertical rows of recesses (rows of

recesses positioned to be parallel to the inner circumferential direction of the emul- sification chamber of FIG. 3) to each other.

[100] As shown in FIG. 5, both the horizontal fine holes and the vertical fine holes are configured such that the inner circumference of each of the horizontal and vertical fine holes is gradually decreased toward the inlet 343i from the outlet 343o thereof (a cross section of the horizontal fine hole is shown in FIG. 3).

[101] Consequently, the raw material, introduced through the inlet 343i of the orifice 343, is compressed in the course of passing to the outlet 343o, and is then expanded at the time of flowing out of the outlet 343o. All the while passing through the crush section S , the raw material repeatedly undergoes compression and expansion.

[102] For reference, the horizontal fine holes are oriented such that the inlets 343i of the horizontal fine hole faces the upstream direction of the flow of raw material from the inlet port 312 to the outlet port 313 (the direction P of FIG. 3), thus allowing the raw material to be introduced through the inlet 343L Meanwhile, the vertical fine holes are oriented such that the inlets 3431 of the vertical fine holes face the direction opposite the rotating direction of the raw material caused by the rotating action of the rotor 350 (the direction Q of FIG. 4), thus allowing the raw material to be introduced through the inlet 342i.

[103] FIG. 6 is a half-sectional view showing the rotor 350.

[104] As shown in FIGS. 2 and 5, the rotor 350 is a rotating cylindrical body disposed in the stator 340, which is comprised of a first rotor part 351a, a second rotor part 351b and a rotor socket 352.

[105] FIG. 7[A] is a right side view of the first rotor part 351a, and FIG. 7[B] is a left side view of the second rotor part 351b.

[106] The first rotor part 351a and the second rotor part 351b are constructed in such a way that a boss 353 is centrally formed at the center of either one of the both ends of each of the rotor parts, a plurality of blades 354 is externally formed along the outer circumference of the boss 353 at predetermined intervals, a plurality of elongated recesses is formed in the outer circumferential surface of the boss 353, and the first rotor part 351 and the second rotor part 351b are coupled to each other with the rotor socket 352 interposed therebetween such that the other ends of the first and second rotor parts (where the blades are not formed) face each other.

[107] As a result, the rotor 350 is provided at opposite ends thereof with the blades 353.

[108] As shown in FIG. 7, each of the first rotor part 351a and the second rotor part 351b includes orifices 356 formed therein, in order to permit the compression and expansion of the raw material, like the stator 340. Of course, the orifices 356 of the first rotor part 351a and the second rotor part 351 are configured such that the inner circumference of the orifice is decreased toward the outlet 356o, through which the raw material flows

out, from the inlet 356i, through which the raw material enters. All of the inlets 355i are oriented to face the direction opposite the rotating direction Q of the rotor 350.

[109] FIG. 8 is a perspective view showing the rotor socket 352.

[110] As shown in FIGS. 6 and 8, the rotor socket 352 is comprised of a circular plate

357, and a cylindrical body 358 integrally fitted into the center of the circular plate 357.

[I l l] The circular plate 357 is disposed between the first rotor part 351a and the second rotor part 351b, and has an outer circumference slightly larger than that of the first rotor part 351a and the second rotor part 351b.

[112] The cylindrical body 358 functions to couple the first rotor part 351a and the second rotor part 351b in such a way that the opposite ends of the cylindrical body 358 are inserted into the inner circumferential surfaces of the ends of the first rotor part 351a and the second rotor part 351b, wherein the ends of the first rotor part 351a and the second rotor part 351b are not provided with the blades 353. The outer circumference of the cylindrical body 358 is sized to closely fit the rotor parts, and the inner circumference of the cylindrical body 358 is sized to be larger than the boss 353.

[113] As shown in FIG. 8, the circular plate 357 is provided at outer surface thereof with a plurality of grooves G at predetermined intervals, thus forming a plurality of blades 359 between the grooves. Here, the grooves G are formed such that the blades 359 are inclined in the rotating direction Q of the rotor 350 at a predetermined angle.

[114] As shown in FIG. 2, the rotor driving means is comprised of a shaft 360 and a motor 370 for rotating the shaft 360. One end of the shaft 360 passes through the casing 310 to be disposed in the emulsification chamber 311, and is fitted into the bosses 353 of the first rotor part 351a and the second rotor part 351b. On this occasion, the shaft 360 is coupled to the first rotor part 351a and the second rotor part 351b using keys, and is thus rotated therewith. The other end of the shaft 360 is coupled to the shaft of the motor 370.

[115] As shown in FIG. 1, the boiler 400 is comprised of a boiler body 410, a fuel supplying unit 420, to which the emulsified fuel is supplied from the auxiliary burning unit 300 through an emulsified fuel transport pipe 630, a blower mechanism 440, for supplying combustion air, and a chimney 450, through which exhaust gas, generated during the burning process is discharged. Since the general construction of the boiler 400 is previously known in the art, a detailed description thereof will be omitted herein.

[116] FIG. 9 is a block diagram showing the feed- water control unit 500.

[117] The feed- water control unit 500 functions to control the quantity of water supply in such a way that when the amount of air-polluting substances (an amount of emitted air- polluting substances) contained in exhaust gas discharged from the chimney 450 of the

boiler 400 exceeds a set value (for example, the amount of emitted air-polluting substances when the rate of addition of water to liquid fuel is the optimal value), the amount of water supplied to the auxiliary burning unit 300 is increased, whereas, when the amount of emitted air-polluting substances is equal to or less than the set value, the amount of water supplied to the auxiliary burning unit 300 is decreased. In other words, a deviation in the amount of emitted air-polluting substances from the set value signifies that the burning conditions are bad, because the rate of addition of water to liquid fuel is not at the optimal value. Hence, it is necessary to maintain the rate of addition of water to liquid fuel at the optimal value (in the optimal range?) by controlling the water supply. At this point, the rate of addition of water to liquid fuel is 30% or less as mentioned above, and the amount of supplied water is of course increased or decreased within this range.

[118] As shown in FIG. 9, the feed- water control unit 500 is comprised of a sensor 510, disposed in the chimney 450 of the boiler 400 to measure the amount of emitted air- polluting substances, a flow control valve 520 mounted on the water pipe 622 to control the volume of water flowing in the water pipe 622, and a control unit 530, which is operated in such a way that, after the comparison of a measured value input from the sensor 510 for measuring air-polluting substances with the set value, when the measured value exceeds the set value, the flow control valve 520 opens to increase the amount of water flowing through the water pipe 622, whereas, when the measured value is equal to or less than the set value, the flow control valve 520 closes to decrease the amount of water flowing through the water pipe 622.

[119] Here, the sensor 510 for measuring air-polluting substances may include one or more of a dust sensor 511, a carbon monoxide (CO) sensor 512, a nitrogen oxide (NOx) sensor 513, and a sulfur oxide (SOx) sensor 514. Although not shown in the drawings, the sensor 510 may further include an oxygen (02) sensor for measuring the amount of oxygen discharged from the chimney 450, even though oxygen does not belong to the group of air-polluting substances. This is because an increase in the amount of emitted oxygen signifies bad burning conditions.

[120] The flow control valve 520 is a kind of solenoid valve, which is comprised of a plunger for opening and closing the water pipe 622, a valve housing for allowing the plunger to be linearly moved, a coil disposed between the valve housing and the plunger, which is converted into an electromagnet and thus retracts the plunger, thereby opening the water pipe 622, when current is applied under the control of the control unit 530, and a spring, which is restored to its normal position, thus closing the water pipe 622, at the time of deactivation of the coil.

[121] The operation of the present invention, which is constructed as described above, will now be described.

[122] When the burning system according to the present invention is operated, the branch pipe 612b that communicates the diesel tank 110 with the main pipe 611 is fully closed by the associated control valve 710b while the branch pipe 612a that communicates the heavy oil tank 120 with the main pipe 611 is opened.

[123] Consequently, the diesel in the diesel tank 110, that is, the liquid fuel, flows through the branch pipe 612a and the main pipe 611, and is then introduced into a raw material transport pipe 320 through the branch tube 322a. Meanwhile, the water in the water tank 200 flows through the water pipe 622, and is then introduced into the raw material transport pipe 320 through the branch tube 322b, to which the water pipe 622 is connected.

[124] The liquid fuel and the water, which are introduced into the raw material transport pipe 320, are mixed with each other using the screw 331 of the mixer 330, rotating at high speed, and are then introduced into the emulsification chamber 311 through the inlet port 312. At this point, the primary emulsification of the raw material is fulfilled.

[125] The raw material, which is introduced into the emulsification chamber 311, is transferred to the outlet port 313 through the crush section S . During this procedure, the raw material is repeatedly sheared by the blades 354 of the rotor 350 mounted on the shaft 360, which is rotated at high speed using the turning force of the motor 370 and the blades 359 formed on the rotor socket 352, and repeatedly collides with the recess part 341 and the protrusion part 342 of the stator 340. Subsequently, the raw material is compressed while passing through the orifices 343 of the stator 340 and the orifices 356 of the rotor 350, and is then expanded after flowing out of the orifices 343 and 356. In this way, the raw material undergoes repetitive compression and expansion, thereby achieving secondary emulsification.

[126] At this point, the raw material is emulsified, resulting in ultrafine particles due to the shearing action by the blades 354 and 359 and the striking action by the recess part 341 and the protrusion part 342. Furthermore, with the aid of the compression and expansion by the orifices 343 and 356, the water is stably dispersed in the liquid fuel. As a result, the raw material becomes a stable W/O type emulsified fuel without the addition of an emulsifying agent.

[127] The emulsified fuel, which is discharged from the emulsification chamber 311 through the inlet port 313, is transferred to the boiler 400 through the emulsified fuel transport pipe 630, and is then burned in the boiler 400. At this point, exhaust gas generated during the burning procedure is discharged into the chimney 450.

[128] At this time, the sensor 510 of the feed- water control unit 500 measures the amount of emitted air-polluting substances contained in the exhaust gas discharged into the chimney 450, and outputs the measured value to the control unit 530.

[129] The control unit 530 compares the measured value with the set value. At this point,

when the measured value exceeds the set value, the control unit 530 determines that a large amount of air-polluting substances is generated due to bad burning conditions, and outputs a control signal to the flow control valve 520 to thus operate the flow control valve 520, thus increasing the opening degree of the water pipe 622. [130] Consequently, the amount of water introduced into the raw material transport pipe

320 is increased, and thus the rate of addition of water to liquid fuel is also increased, thereby further improving the burning conditions. [131] Meanwhile, when the measured value is equal to or less than the set value, the control unit 530 also outputs a control signal to the flow control valve 520 and thus operates the flow control valve 520, thus decreasing the opening degree of the water pipe 622.

Industrial Applicability [132] As described above, the present invention can provide a boiler which can maintain desirable conditions for burning emulsified fuel, thus ensuring efficient energy savings and the prevention of air pollution. [133] Further, the present invention can provide an economical boiler, which can rapidly produce and continuously supply emulsified fuel without the need for the addition of an additional emulsifying agent.