JP2009085551A - Fluidized bed device for firing liquid fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of NOx and burn liquid fuel without reducing the viscosity even when the fuel is highly viscous by burning liquid fuel with a high nitrogen content or highly viscous liquid fuel in a fluidized bed at low temperatures. <P>SOLUTION: The fluidized bed device for firing the liquid fuel F is equipped with: a furnace body 1 having a furnace wall 1a and a furnace bottom 1b; an aeration nozzle 2 disposed on the furnace bottom 1b; a wind box 3 for fluidized air provided on a lower face side of the furnace bottom 1b for providing fluidized air A to the aeration nozzle 2; a flow medium accumulated on the furnace bottom 1b; and a liquid fuel injection nozzle 5 provided to the furnace wall 1a for supplying the liquid fuel F to the inside of the furnace. A fluidized bed 4 is formed in a lower region inside the furnace by injecting the fluidized air A to a flow medium layer on the furnace bottom 1b from the aeration nozzle 2, and the liquid fuel F with a high nitrogen content or the highly viscous liquid fuel F is injected from the liquid fuel injection nozzle 5 on the fluidized bed 4 in a liquid condition and burned at low temperatures in the fluidized bed 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used in a fluidized bed incinerator or a fluidized bed boiler in which fuel is combusted in a fluidized bed, and particularly in a high nitrogen-containing liquid fuel or spray combustion in which a large amount of NOx is generated. By supplying high-viscosity liquid fuel that cannot be finely atomized without heating to a fluidized bed and burning it at a low temperature in the fluidized bed, the amount of NOx generated during combustion of the liquid fuel is suppressed. The present invention relates to a fluidized bed apparatus for combustion of liquid fuel that can be burned without lowering the viscosity even if the liquid fuel has a high viscosity.

In general, fluidized beds composed of a fluid medium such as silica sand are used for the purpose of burning solid fuel such as municipal waste, industrial waste, sewage sludge, coal, etc., and it is difficult to use as a fuel by ordinary combustion methods. It is widely used because it can be burned from high moisture to flame retardant, and two or more types of fuel can be mixed.
In a fluidized bed apparatus having a fluidized bed, incombustible materials such as stone, glass, and metal contained in the solid fuel may stay in the fluidized bed, causing a fluid flow failure of the fluidized medium. Since continuous combustion cannot be performed, it is necessary to discharge non-combustible material together with a part of the fluidized medium from the lower part of the fluidized bed, and the structure has a discharge port for the fluidized medium and a discharge channel at the lower part (for example, , See Patent Document 1).

  2 and 3 each show an example of a conventional fluidized bed apparatus. The fluidized bed apparatus shown in FIG. 2 uses an air supply method for the fluidized bed, and the flow shown in FIG. The bed apparatus uses a diffuser plate as a method for supplying air to the fluidized bed.

That is, in the fluidized bed apparatus of FIG. 2, a plurality of diffuser tubes 12 provided with a large number of diffuser nozzles 11 are arranged in parallel in a fluid medium layer such as silica sand formed in a lower region in the furnace body 10. The fluidized air A is ejected from the diffuser nozzle 11 of each of the diffuser tubes 12 into the fluidized medium layer, so that the fluidized bed 13 made of a fluidized medium such as silica sand is formed in the lower region of the furnace body 10. It is configured.
Further, the fluidized bed apparatus of FIG. 3 is provided with a downwardly inclined diffuser plate 14 provided with a large number of diffuser nozzles 11 in a lower region in the furnace body 10 and at a position below the diffuser plate 14. By providing a wind box 15 for feeding the fluidized air A to the diffuser nozzle 11 and ejecting the fluidized air A from the diffuser nozzle 11 of the diffuser plate 14 into the fluidized medium layer formed on the diffuser plate 14, A fluidized bed 13 made of a fluid medium such as silica sand is formed on the diffuser plate 14.

  In each of the fluidized bed apparatuses, fluidized air A is blown into a fluidized medium layer made of a fluidized medium such as silica sand to cause the fluidized medium to flow to form a fluidized bed 13, and a furnace wall into the fluidized bed 13. The solid fuel F ′ is supplied from the fuel input port 16 formed in the above and fluidized and combusted, and the incombustible material in the solid fuel F ′ is caused to flow down to be discharged from the discharge port 17 together with a part of the fluid medium (shown in the figure). (Omitted).

  By the way, in the conventional fluidized bed apparatus, since both have the non-combustible material and the fluid medium outlet 17 and the discharge channel, if a large amount of liquid fuel is burned in the fluidized bed 13, the temperature is high. The liquid fuel that has been heated and fluidized easily is transferred to the fluid outlet 17 and the fluid medium in the discharge flow path, is unburned and discharged, and causes problems such as external combustion. It was. Due to such problems, the fluidized bed apparatus having the above-described structure has not been used for the combustion of liquid fuel.

  In the combustion of sewage sludge containing a lot of water, there are many cases in which liquid fuel such as heavy oil is blown into the fluidized bed as an auxiliary combustion when the amount of heat is insufficient. In this case, since the purpose of the liquid fuel is to assist combustion, the amount of combustion is small and there is almost no leakage from the lower part, and there is no particular problem.

  On the other hand, spray combustion using a spray burner (not shown) is used for combustion of liquid fuels such as kerosene, light oil, and heavy oil. Because of spray combustion, atomization of droplets is the life of combustion. In order to promote this atomization, liquid fuels with high viscosity, such as C heavy oil, residual oil, asphalt, etc., are vaporized. In general, it is heated by a heater (not shown) or an electric heater (not shown), and the kinematic viscosity is reduced to about 20 cSt or less, which can be atomized, and spray combustion is performed by a spray burner. Is.

However, the combustion of the liquid fuel by the spray burner is spray combustion, so it must be a high temperature combustion, and there is a limit to reducing the amount of NOx generated. In such spray combustion, methods such as two-stage combustion, exhaust gas recirculation, and steam blowing are adopted as measures for reducing NOx, but when the nitrogen content in the liquid fuel is high (nitrogen content is 0.25 wt%) In the above case), it is difficult to reduce the amount of NOx generated to 150 ppm (O ₂ = 4% conversion) below the national regulation level by combustion technology alone. The only way to do this is to reduce the nitrogen content in the fuel, or burn it with heavy oil and then denitrate it with a catalytic denitration device.

Therefore, there is no case where liquid fuel is used as a main fuel for combustion using a fluidized bed, and in the combustion of high viscosity liquid fuels such as C heavy oil, residual oil, and asphalt, it is used for the purpose of low NOx countermeasures. The current fluidized bed equipment has not been developed yet.
JP-A-6-241427

  The present invention has been made in view of such problems, and the object thereof is to supply a high-nitrogen-containing liquid fuel or a high-viscosity liquid fuel to the fluidized bed and perform low-temperature combustion in the fluidized bed. Thus, it is an object to provide a fluidized bed device for combustion of liquid fuel that can suppress the generation of NOx and can burn even a high-viscosity liquid fuel without lowering the viscosity.

  In order to achieve the above object, an invention according to claim 1 of the present invention comprises a furnace body having a furnace wall and a furnace bottom, an aeration nozzle disposed on the furnace bottom, and a lower surface side of the furnace bottom. A liquid comprising a fluidized air windbox for supplying fluidized air to the air nozzle, a fluid medium stored on the furnace bottom, and a liquid fuel injection nozzle provided on the furnace wall for supplying liquid fuel into the furnace A fluidized bed apparatus for fuel combustion, wherein fluidized air is ejected from the aeration nozzle to a fluidized medium layer on a furnace bottom to form a fluidized bed in a lower region in the furnace, and from the liquid fuel injection nozzle It is characterized in that a high-nitrogen-containing liquid fuel or a high-viscosity liquid fuel is jetted onto the fluidized bed in a liquid state and burned at a low temperature in the fluidized bed.

The fluidized bed apparatus for combustion of liquid fuel according to the present invention uses a high-nitrogen liquid fuel that generates a large amount of NOx or a high-viscosity liquid fuel that cannot be atomized unless the temperature is raised to a high temperature by spray combustion. Since low temperature combustion is performed in the fluidized bed, the amount of NOx generated during the combustion of the liquid fuel can be greatly suppressed, and NOx reduction that cannot be achieved by spray combustion using a conventional spray burner can be achieved. As a result, the use of the fluidized bed apparatus for combustion of liquid fuel according to the present invention can greatly suppress the amount of NOx generated even when heavy oil having a nitrogen content of 0.25 wt% or more is burned. Equipment and the like are not required, and fuel costs and exhaust gas treatment costs can be reduced.
Moreover, since the fluidized bed apparatus for combustion of liquid fuel according to the present invention burns high-viscosity liquid fuel in a fluidized bed without spray combustion, even a high-viscosity liquid fuel that is difficult to atomize is used. It is only necessary to lower the viscosity of the high-viscosity liquid fuel to such a level that it can be transported by piping, and the liquid fuel can be burned with high viscosity. As a result, the fluidized bed apparatus for combustion of liquid fuel according to the present invention does not need to reduce the viscosity of the high-viscosity liquid fuel to about 20 cSt as in spray combustion, until the viscosity reaches about 500 cSt that can be transported by a pump. Since only heating is required, heating with electricity or steam becomes unnecessary or less, and energy saving can be achieved.
Further, in the fluidized bed combustion apparatus for liquid fuel according to the present invention, since the liquid fuel is injected from the liquid fuel injection nozzle in a liquid state, the burner nozzle is periodically contaminated with unburned carbon like a spray burner. There is no need to replace the burner nozzle with a cleaned one.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a fluidized bed apparatus for combustion of liquid fuel A according to an embodiment of the present invention. The fluidized bed apparatus for combustion is used in a fluidized bed incinerator, a fluidized bed boiler, etc., and the amount of NOx generated The high-nitrogen-containing liquid fuel F with a large amount is burnt at a low temperature in the fluidized bed 4 so that the amount of NOx generated during the combustion of the liquid fuel F is greatly suppressed, and good fine particles are obtained unless heated to a high temperature. The high-viscosity liquid fuel F that cannot be converted into fuel is burned in the fluidized bed 4 without spray combustion, so that the high-viscosity liquid fuel F can be burned with high viscosity.

That is, the fluidized bed apparatus for combustion of the liquid fuel F comprises a furnace body 1, a diffuser nozzle 2, a fluidized air wind box 3, a fluidized bed 4, a liquid fuel injection nozzle 5, and the like, as shown in FIG. The fluidized air A is ejected from the air diffuser 2 to the lower region in the furnace to form a fluidized bed 4 made of a fluid medium such as silica sand, and the liquid fuel F is fed from the liquid fuel injection nozzle 5 in a liquid state. Injected onto the fluidized bed 4 and combusted in the fluidized bed 4.
For this reason, this fluidized bed apparatus for combustion eliminates the flow passage of the fluid medium at the lower part of the furnace body 1 so that the liquid fuel F does not sag and is discharged to the outside, and the fluid medium from the lower part of the furnace body 1 during operation. The structure is such that no extraction is performed.
This combustion fluidized bed apparatus blows a fine fluidized medium from the fluidized bed 4 and discharges it from the middle or upper part of the furnace body 1, and only the reduced amount of the fluidized medium that has been scattered and discharged into the furnace. It is configured to be replenished.
Further, in this fluidized bed apparatus for combustion, secondary air is supplied in the upper region (combustion chamber) in the furnace so that the combustion gas in the furnace and the unburned components in the combustion gas are completely burned. It has become.

The furnace body 1 is formed in a bottomed cylindrical shape or a bottomed rectangular tube shape by a furnace wall 1a and a furnace bottom 1b having a refractory wall structure, and a portion corresponding to the upper layer portion of the fluidized bed 4 of the furnace wall 1a. Is formed with a fluid medium outlet 6 for extracting a part of the fluid medium when the combustion fluidized bed apparatus is operated.
Further, a fluidized medium discharge port 7 is formed in the lower part of the furnace wall 1a of the furnace body 1 for discharging the fluidized medium in the furnace when the operation of the fluidized bed apparatus for combustion is stopped. The fluid medium outlet 7 is sufficiently sealed so that the liquid fuel F injected into the fluidized bed 4 does not leak during operation of the combustion fluidized bed apparatus. It is closed so that the fluid medium and liquid fuel F do not leak, and when the fluidized bed apparatus for combustion is stopped, the fluid medium is opened and the fluid medium in the furnace can be discharged.
In the above embodiment, the furnace body 1 has a fire wall structure. However, the furnace body 1 is not limited to the fire wall structure, and depending on the amount of heat, a water cooling wall structure or a cooling inner pipe can be used. It is good also as an equipped structure.

The aeration nozzle 2 is for ejecting fluidized air A to the fluidized medium layer stored on the furnace bottom 1b of the furnace body 1 to form a fluidized bed 4 made of a fluidized medium such as silica sand in the lower region of the furnace. Is.
That is, the air diffusion nozzle 2 is formed of a metal material having excellent heat resistance, wear resistance, and the like, and is disposed in the furnace bottom 1b of the furnace body 1 in a penetrating state at a predetermined interval. The space between the air diffusion nozzle 2 and the furnace bottom 1b is sealed so that the liquid fuel F does not leak.

  The fluidized air wind box 3 is attached to the furnace bottom 1b so as to cover the lower surface of the furnace bottom 1b of the furnace body 1, and the fluidized air A supplied from a blower (not shown) is supplied to each diffuser nozzle 2. Can be supplied to.

  The liquid fuel injection nozzle 5 is provided at a position higher than the fluidized bed 4 of the furnace wall 1 a of the furnace body 1 and is supplied from a fuel tank (not shown) by a pump (not shown) and a fuel supply pipe 8. The liquid fuel F can be uniformly injected onto the fluidized bed 4 in a liquid state. From this liquid fuel injection nozzle 5, a high nitrogen content liquid fuel F and a high viscosity liquid fuel F (C heavy oil, residual oil, asphalt, etc.) are injected. The supply amount of the liquid fuel F is determined by detecting the temperature in the furnace by a temperature detector (not shown) and controlling a control valve (not shown) provided in the fuel supply pipe 8 based on the detected temperature. It is done by.

Next, the operation of the fluidized bed apparatus for combustion of the liquid fuel F described above will be described.
In the fluidized bed apparatus for combustion, the fluidized medium discharge port 7 is closed to prevent the fluidized medium from flowing out, and in this state, the fluidized air A supplied to the fluidized air windbox 3 is diffused by the aeration nozzle. When ejected from 2 into the furnace, the fluid medium in the furnace is caused to flow, and a fluidized bed 4 is formed in the lower region of the furnace.
In this state, when the high-nitrogen-containing liquid fuel F or the high-viscosity liquid fuel F is uniformly injected from the liquid fuel injection nozzle 5 onto the fluidized bed 4 in a liquid state, the liquid fuel F is combusted at a low temperature in the fluidized bed 4. The

At this time, since the liquid fuel F is combusted in the fluidized bed 4 at a low temperature, even if the liquid fuel F contains high nitrogen, the amount of NOx generated is small, and the NOx reduction that cannot be obtained by the burner combustion is reduced. I can plan. As a result, even with a heavy nitrogen-containing heavy oil having a nitrogen content of 0.25 wt% or more, a denitration device or the like is unnecessary, and fuel costs and exhaust gas treatment costs can be reduced. Further, even with a high nitrogen-containing liquid fuel F having a nitrogen content of 0.35 to 04 wt%, combustion of 150 ppm (O ₂ = 4% conversion value) or less is possible, and NOx close to the results in a reduction combustion furnace. It becomes possible to suppress to the generation level.
Further, since the liquid fuel F is burned not in the spray combustion but in the fluidized bed 4, even if it is a high viscosity liquid fuel F that is difficult to atomize, the viscosity is such that the high viscosity liquid fuel F can be transported with a pump. The liquid fuel F can be burned with a high viscosity. As a result, it is not necessary to reduce the viscosity of the high-viscosity liquid fuel F to about 20 cSt as in spray combustion, and it is only necessary to heat the high-viscosity liquid fuel F to a viscosity of about 500 cSt that can be transported by a pump. In addition, heating with electricity or steam becomes unnecessary or less, and energy saving can be achieved. In addition, it is not necessary to replace the burner nozzle with a clean burner nozzle that is contaminated with unburned carbon, such as a spray burner.

The combustion gas generated by the combustion of the liquid fuel F in the fluidized bed 4 goes up in the furnace and is completely supplied by the secondary air supplied into the furnace in the upper flow area (combustion chamber) in the furnace. After being combusted, it is discharged from the furnace body and sent to downstream equipment (such as an exhaust gas treatment device).
Further, the fluidized medium, which has become finer due to the flow, is blown up to the upper region in the furnace and discharged together with the combustion gas from the furnace body 1 or extracted from the fluidized medium outlet 6. Therefore, the fluid medium is supplied into the furnace by a reduced amount from a fluid medium inlet (not shown) provided in the upper part of the furnace body 1.

  As described above, in the fluidized bed apparatus for combustion of the liquid fuel F, good atomization cannot be obtained unless the liquid fuel F or spray combustion containing a large amount of NOx is heated to a high temperature. Since the high-viscosity liquid fuel F is supplied to the fluidized bed 4 and burned at a low temperature, the generation of NOx generated during combustion can be suppressed, and even the high-viscosity liquid fuel F is low. It can be burned without viscosity.

It is a schematic longitudinal cross-sectional view of the fluidized bed apparatus for combustion of the liquid fuel which concerns on embodiment of this invention. It is a schematic longitudinal cross-sectional view of the conventional fluidized bed apparatus. It is a schematic longitudinal cross-sectional view of the other conventional fluidized bed apparatus similarly.

Explanation of symbols

  1 is a furnace body, 1a is a furnace wall, 1b furnace bottom, 2 is a diffuser nozzle, 3 is a fluidized air wind box, 4 is a fluidized bed, 5 is a liquid fuel injection nozzle, A is fluidized air, and F is a liquid fuel.

Claims (1)

  A furnace body having a furnace wall and a furnace bottom, an aeration nozzle disposed on the furnace bottom, a fluidized air wind box provided on the lower surface side of the furnace bottom and supplying fluidized air to the aeration nozzle, and a furnace A fluidized bed combustion apparatus for liquid fuel comprising a fluid medium stored on the bottom and a liquid fuel injection nozzle provided on the furnace wall for supplying liquid fuel into the furnace, wherein The fluidized air is jetted into the upper fluidized medium layer to form a fluidized bed in the lower region of the furnace, and the liquid fuel containing high nitrogen or the liquid fuel with high viscosity is liquidized from the liquid fuel injection nozzle in the liquid state. A fluidized bed apparatus for combustion of liquid fuel, characterized in that it is jetted onto a fluidized bed and combusted at a low temperature in the fluidized bed.

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