JP6270468B2 - Heavy oil-fired boiler combustion method and heavy oil-fired boiler - Google Patents

Description

  The present invention relates to a heavy oil-fired boiler using heavy oil such as asphalt as fuel, and more particularly to a combustion method of a heavy oil-fired boiler and a heavy oil-fired boiler that reduce the amount of dust discharged from the boiler.

  In a conventional oil-fired boiler, liquid fuel is blown into a furnace in a state of being atomized (atomized) with a spray medium such as steam to form a flame and burned. A combustion burner used in such an oil-burning burner includes a burner tip provided at the tip of a supply pipe for liquid fuel and spray medium. This burner tip is capable of injecting atomized fuel from a plurality of ejection holes formed at the tip after mixing and atomizing the liquid fuel and the spray medium.

A heavy oil fired boiler 10B of the embodiment shown in FIG. 6 burns heavy oil such as asphalt, and has a furnace 11 and a combustion device 12B.
The combustion device 12B has a combustion burner 20B in which a plurality of stages (five stages in the illustrated example) are mounted in the vertical direction of the furnace wall. In each stage, for example, four pieces are arranged at regular intervals along the circumferential direction, and the combustion burners 20B in each stage all have the same specifications.

Each combustion burner 20B introduces fuel heavy oil and spraying steam, and mixes heavy oil and spraying steam. As a result, heavy oil is atomized and a mixed fluid containing heavy oil spray particles is injected into the furnace 11 from the combustion burner 20B and burns to form a flame. When a flame is generated in the lower part of the furnace 11 in this way, the combustion gas (exhaust gas) rises in the furnace 11 and is guided to the exhaust gas pipe 37 through the flue 31.
In the figure, reference numeral 13 is a fuel supply pipe, 14 is a steam supply pipe, 32 is a secondary superheater, 33 is a primary superheater, 34 and 35 are evaporators, 36 is a economizer, and 40 is secondary air. (OFA; Over Fire Air), 50 is a two-stage combustion air (AA) supplied from the additional air input unit.

In conventional oil-fired boilers, for example, as disclosed in Patent Document 1 below, in order to suppress nitrogen oxides (NOx) and soot, an internal mixed high-pressure air spray combustion method and a burner tip of an oil burner are provided. Improvements are being made.
In addition, as disclosed in Patent Document 2 below, a technique for improving the air injection method of an internal mixing atomizer is also known in order to achieve high efficiency and low pollution combustion of a slurry-like fuel containing finely divided solids. Yes.

JP 2003-172505 A Japanese Patent Publication No. 8-1288

  By the way, heavy oil fired boilers that use heavy oil such as asphalt have a problem that the amount of dust discharged from the boiler after combustion is large due to the fuel characteristics of heavy oil. . As a measure against such dust, conventionally, a low dust atomizer with an increased consumption rate of steam (atomizing medium) used for atomization is used. However, since this steam uses a part of the steam generated in the boiler, it is not preferable to consume a large amount of steam because it leads to deterioration of boiler efficiency.

  Further, in the conventional heavy oil burning burner 10B, a plurality of combustion burners 20B having the same specifications are arranged in the vertical direction. For this reason, as shown in FIG. 6, the particle trajectory (indicated by a solid line) of the heavy oil spray particles introduced from the lower combustion burner 20B and the heavy oil spray particles introduced from the upper combustion burner 20B. Comparing the particle trajectory (shown with broken lines), the particle trajectory of the heavy oil spray particles introduced from the lower combustion burner 20B becomes longer. As a result, the residence time during which the heavy oil spray particles are in the furnace 11 is also increased. become longer.

From such a background, a combustion method of a heavy oil fired boiler that can suppress the consumption rate of the spray medium consumed for atomization of heavy oil without increasing the amount of discharged dust is desired.
The present invention has been made to solve the above-described problems, and an object of the present invention is to burn a heavy oil-fired boiler capable of suppressing the consumption rate of the spray medium without increasing the dust discharge amount. And providing a heavy oil fired boiler.

In order to solve the above problems, the present invention employs the following means.
A combustion method of a heavy oil fired boiler according to the present invention includes heavy oil fuel and atomized fluid (atomizing medium) introduced into and mixed with a fuel sprayer of a combustion burner, and includes atomized heavy oil spray particles. A combustion method of a heavy oil-fired boiler that injects and mixes a mixed fluid into a furnace together with combustion air , and an oil atomizer is provided at the tip of the fuel sprayer, and the vertical direction of the furnace The particle size of the heavy oil spray particles injected and injected from the combustion burner arranged in a plurality of stages is set so that the upper stage side is smaller than the lower stage side, and the oil atomizer included in the lower stage combustion burner Is characterized in that it is of a larger particle size spray type than the oil atomizer of the upper combustion burner .

According to the combustion method of such a heavy oil fired boiler, the particle size of the heavy oil spray particles injected from the combustion burners arranged in a plurality of stages in the vertical direction of the furnace is the same as that of the heavy oil spray in the furnace. Compared to the lower stage where the particle trajectory of particles is long and the residence time is long, the upper stage side where the particle trajectory of heavy oil spray particles in the furnace is short and the residence time is short is set smaller.
That is, a large particle size spray type atomizer with a low consumption rate of atomized fluid is adopted for the lower combustion burner for a long residence time in the furnace (the combustion time of heavy oil spray particles is long). The combustion burner on the upper stage has a short particle residence time (short combustion time for heavy oil spray particles) and adopts a small particle size spray type atomizer with a high consumption rate of atomized fluid. The consumption rate of the atomized fluid can be suppressed to a necessary and sufficient value for each burner stage without increasing the amount.

  In the above invention, the flow rate of the heavy oil fuel supplied to the combustion burner is preferably set so that the upper side is smaller than the lower side where the residence time in the furnace is long, Burner arrangement and fuel distribution that make effective use of particle trajectories in the furnace. For this reason, the consumption rate of the atomized fluid can be suppressed to a necessary and sufficient value for each burner stage without increasing the amount of dust at the outlet of the boiler.

A heavy oil fired boiler according to the present invention introduces and mixes heavy oil fuel and atomized fluid into a fuel sprayer of a combustion burner, and mixes the mixed fluid containing atomized heavy oil spray particles together with combustion air. A heavy oil fired boiler that injects into a furnace and burns it , and an oil atomizer is provided at the tip of the fuel sprayer, and the combustion burners are arranged in a plurality of stages in the vertical direction of the furnace. And, the heavy oil spray particles injected from the combustion burner are arranged so that the particle size of the lower stage side is larger than the upper stage side, and the oil atomizer of the lower stage combustion burner is the It is characterized by being a larger particle size spray type than the oil atomizer of the combustion burner on the upper stage side .

  According to such a heavy oil fired boiler, the combustion burner is arranged in a plurality of stages in the vertical direction of the furnace, and the heavy oil spray particles injected from the combustion burner have a particle size lower than the upper stage. Is installed so that the residence time in the furnace is long, the large burner type atomizer with low atomization fluid consumption rate is adopted for the lower combustion burner, and the residence time in the furnace is short By adopting a small particle size spray type atomizer with high atomization fluid consumption rate in the upper combustion burner, the consumption rate of atomization fluid is required for each burner stage without increasing the amount of dust at the boiler outlet It becomes possible to suppress to a sufficient value.

  According to the present invention described above, in a heavy oil-fired boiler using heavy oil as a fuel, the amount of dust discharged from the boiler outlet is increased by effectively using the particle trajectory (residence time) in the furnace. In addition, the consumption rate of atomized fluid such as steam can be suppressed to a necessary and sufficient value for each burner stage.

It is a schematic block diagram which shows one Embodiment of the combustion method of the heavy oil-fired boiler which concerns on this invention, and a heavy oil-fired boiler. It is the front view which looked at the combustion burner of the heavy oil fired boiler which concerns on this invention from the inside of a furnace. It is sectional drawing of the combustion burner shown in FIG. It is explanatory drawing which shows the combustion process of the heavy oil spray particle from which a particle size differs, (a) shows the relationship between mass (%) and time, (b) has shown the image of the combustion process. It is a schematic block diagram which shows the modification method of the combustion method of the heavy oil-fired boiler which concerns on this invention, and a heavy oil-fired boiler. It is a schematic block diagram which shows the conventional example of the combustion method of a heavy oil fired boiler, and a heavy oil fired boiler.

Hereinafter, an embodiment of a combustion method of a heavy oil-fired boiler and a heavy oil-fired boiler according to the present invention will be described based on the drawings.
A heavy oil-fired boiler 10 according to the embodiment shown in FIG. 1 is a conventional boiler that uses heavy oil such as asphalt as fluid fuel. The heavy oil fired boiler 10 has a furnace 11 and a combustion device 12. The furnace 11 has a rectangular hollow shape and is installed along the vertical direction. A combustion device 12 is provided at the lower part of the furnace wall constituting the furnace 11.

The combustion device 12 has a plurality of combustion burners 20 mounted on the furnace wall. The combustion burner 20 according to the present embodiment is arranged, for example, five sets, that is, five stages, in the circumferential direction, for example, with four arranged at equal intervals. Note that the arrangement location and number of the combustion burners 20 are not limited to the illustrated configuration.
Each combustion burner 20 is connected to a fuel supply source (not shown) via a fuel supply pipe 13 in order to introduce heavy fuel oil, and the fuel supply pipe 13 has a flow rate for adjusting the fuel supply amount. A regulating valve (not shown) is provided. In addition, each combustion burner 20 is connected to a steam supply source (not shown) via each steam supply pipe 14 in order to introduce atomizing fluid spray steam, and the steam supply pipe 14 has a steam supply amount. A flow rate adjustment valve (not shown) is provided for adjusting the above.

  Therefore, each combustion burner 20 is supplied with heavy fuel oil from the fuel supply source through the fuel supply pipe 13 and is supplied with spraying steam from the steam supply source through the steam supply pipe 14. Therefore, each combustion burner 20 mixes heavy oil and spraying steam to atomize the heavy oil and inject it into the furnace 11 as a mixed fluid containing heavy oil spray particles, and combusts it. To form a flame.

The furnace 11 has a flue 31 connected to the top. In this flue 31, in order to recover the heat of exhaust gas as a convection heat transfer section (heat recovery section), for example, a secondary superheater 32, a primary superheater 33, evaporators 34 and 35, and a economizer in order from the burner side. (Economizer) 36 is provided, and heat exchange is performed between the exhaust gas generated by the combustion in the furnace 11 and water. In addition, about these heat exchangers, the arrangement | positioning, the number, etc. are illustrated, and it does not specifically limit.
The flue 31 is connected to an exhaust gas pipe 37 for discharging the exhaust gas subjected to heat exchange on the downstream side. The exhaust gas pipe 37 is provided with a desulfurization device, an electrostatic precipitator, an induction blower, and a desulfurization device (not shown), and a chimney is provided at the downstream end.

  Therefore, when each combustion burner 20 injects into the furnace 11 a mixed fluid of heavy oil and spraying steam into the combustion apparatus 12, the mixed fluid and air burn in the furnace 11 to generate a flame. When a flame is generated in the lower part of the furnace 11 in this way, the combustion gas (exhaust gas) rises in the furnace 11 and is discharged to the flue 31. The particle trajectory (indicated by solid lines) of the heavy oil spray particles introduced from the lower combustion burner 20 is longer than the particle trajectory (indicated by broken lines) of the heavy oil spray particles introduced from the upper combustion burner 20. Therefore, the time during which the heavy oil spray particles stay in the furnace 11 also becomes longer.

At this time, water supplied from a water supply pump (not shown) is preheated by the economizer 36 and then heated while being supplied to each water pipe (not shown) on the furnace wall via a steam drum (not shown). It becomes saturated steam and is sent to a steam drum (not shown).
Further, saturated steam of a steam drum (not shown) is introduced into the secondary superheater 32 and the primary superheater 33, and is superheated by the combustion gas. The superheated steam generated by the secondary superheater 32 and the primary superheater 33 is supplied to a power plant (such as a turbine) not shown. In the present embodiment, the furnace 11 is described as a drum type (steam drum), but is not limited to this structure.

Next, a configuration example of the combustion apparatus 12 will be described in detail.
The combustion burner 20 of the present embodiment is configured as shown in FIGS. 2 and 3, for example. Reference numeral 21 in the drawing denotes a heavy oil sprayer (fuel sprayer) that atomizes heavy fuel oil and injects it into the furnace 11. An oil atomizer 22 having a plurality of ejection holes 22a is provided at the tip of the heavy oil sprayer 21 in order to atomize and eject the heavy oil fuel by the pressure of the spraying vapor introduced as the atomized fluid. Yes.

Further, a housing tube 23 having an air intake hole 23a is provided on the outer periphery of the heavy oil sprayer 21, and primary air (arrow A1 in the figure) is provided on the outer surface of the tip, that is, in the vicinity of the oil atomizer 22. ) Is provided in a circumferential direction.
The periphery of the housing tube 23 and the swirler 24 is covered with a cylindrical burner throat 26 in order to form an air passage 25 for secondary air (arrow A2 in the figure). Further, an air passage 27 for supplying tertiary air (arrow A3 in the figure) is provided on the outer periphery of the burner throat 26. A variable air damper 28 is provided in the air passage 27.

  In the combustion burner 20 having such a configuration, the heavy fuel oil and the vapor for spraying pass through the heavy oil sprayer 21 to the oil atomizer 22 at the tip, for example, a plurality of large and small jet holes 22a having different diameters. The mixed fluid obtained by atomizing heavy oil is ejected in a predetermined direction (for example, obliquely forward). This mixed fluid first comes into contact with the combustion air passing through the housing tube 23 and the primary air supplied while swirling by the swirler 24, and forms a flame zone while mixing with each other.

On the other hand, the secondary air passing through the gap between the swirler 24 and the burner throat 26 and the tertiary air supplied from the outside of the burner throat 26 are mixed with the unburned components deviating from the flame region due to the primary air, A stable flame zone is formed downstream of the main flame.
At this time, according to the state of the flame and the NOx concentration and oxygen concentration in the exhaust gas, the opening degree of the variable air damper 28 is operated to adjust the supply amount of the tertiary air. Note that the NOx concentration and the oxygen concentration are measured values of a NOx concentration meter and an oxygen concentration meter (not shown) provided at an appropriate rear portion of the flue 31.

In the combustion burner 20 having the above-described configuration, the combustion method described below is adopted in the present embodiment.
That is, the heavy oil fuel and the atomized fluid vapor are introduced into and mixed with the heavy oil sprayer 21 of the combustion burner 20, and the mixed fluid containing the atomized heavy oil spray particles is introduced into the furnace together with the combustion air. In the heavy oil fired boiler 10 to be injected and burned, the particle size of the heavy oil spray particles injected and injected from the combustion burners 20 arranged in a plurality of stages in the vertical direction of the furnace 11 is higher than the lower side. Use a small combustion method.

In the illustrated configuration example, five stages of combustion burners 20 are arranged in the vertical direction, and for example, four pieces are arranged at regular intervals along the circumferential direction.
For such a combustion burner 20, for example, a heavy oil sprayer 21 arranged in two stages on the lower side employs a large particle size spray type with a low steam consumption rate for the oil atomizer 22 and is arranged in two stages on the upper stage side. For the heavy oil sprayer 21 to be used, the oil atomizer 22 adopts a small particle size spray type with a high steam consumption rate. In addition, an oil atomizer 22 in which the steam consumption rate and the spray particle size are intermediate between the large particle size spray type and the small particle size spray type is adopted for the middle one stage. In addition, in the some combustion burner 20 arrange | positioned at each stage, the same oil atomizer 22 is employ | adopted for all.

  As a result, the combustion burner 20 arranged in five stages in the vertical direction of the furnace 11 has a large particle size on the lower stage side where the particle trajectory of the heavy oil spray particles injected into the furnace 11 is long and the residence time is long. And the particle size of the heavy oil spray particles injected into the furnace 11 is short and the particle size is set to be small on the upper stage side with a short residence time. That is, the particle size of the heavy oil particles injected into the furnace 11 is set so as to decrease stepwise from the combustion burner 20 disposed on the lower stage side to the combustion burner 20 disposed on the upper stage side. In other words, the particle size of the heavy oil spray particles injected and injected from the combustion burners 20 arranged in a plurality of stages in the vertical direction is set so that the upper stage with a shorter residence time is smaller than the lower stage with a longer residence time. ing.

If such a combustion method is adopted, the consumption rate of the steam used as the atomized fluid can be suppressed to a value necessary and sufficient for each burner stage, and the dust discharged from the exhaust pipe 37 at the boiler outlet. Does not increase the amount.
This is due to the combustion process of heavy oil spray particles (hereinafter also referred to as “oil particles”) described below with reference to FIG.

  In the first stage of the combustion process shown in FIG. 4 (b), the primary air that the oil particles PL and PS that have flowed out of the heavy oil sprayer 21 into the furnace 11 are introduced around the heavy oil sprayer 21. Furthermore, at the same time, the radiant heat in the furnace 11 is received and the temperature rises rapidly. In the oil particles PL and PS whose temperature has been increased, gasification is performed in which gaseous fuel (volatile matter) G is released by thermal decomposition.

  In the second stage of the combustion process, the oil particles PL and PS move to a higher temperature region in the furnace 11 as time passes, and the gasified gas fuel G burns. Simultaneously with the combustion of the gas fuel G, the particulate char C, which is a residual solid of the oil particles PL and PS, rises in temperature and rises in temperature. This point is the hottest region, combustion of the volatile matter G is completed, and combustion of char C mainly composed of carbon is started.

  Then, in the third stage where the time has passed, the oil particles PL and PS decomposed into the char C and the gas fuel G move the remaining char C due to the disappearance of the gas fuel G in the furnace 11, and the second stage. A lower temperature area is reached. For this reason, the combustion of the char C is performed in a region where the temperature has decreased from the highest temperature region. In the final stage, dust Ca composed of unburned particles and ash is discharged to the outside of the furnace 11.

  As shown in FIG. 4A, the mass (%) of the oil particles PL having a large particle diameter and the oil particles PS having a small particle diameter decrease as the residence time on the horizontal axis elapses. Note that the passage of the residence time means that the particle trajectory becomes longer.

In FIG. 4 (a), the oil particle PS with a small particle size reaches the same state with a short residence time as compared with the residence time when the oil particle PL with a large particle size reaches a state of 50% by mass. Yes. Therefore, even if the amount of steam used for atomization is reduced on the lower side where the residence time is long and the particle size is increased, in the combustion process described above, the combustion is performed to the same state as that of the small particle size because of the longer residence time. Progresses.
Therefore, even if the consumption rate of the steam used as the atomizing fluid is suppressed to a necessary and sufficient value for each burner stage as in the combustion method described above, the amount of dust discharged from the exhaust pipe 37 at the boiler outlet increases. There is no such thing. That is, by effectively utilizing the particle trajectory of the furnace 11 and reliably burning heavy oil spray particles having different particle diameters, an increase in dust discharge can be prevented.

By the way, in embodiment mentioned above, about the combustion burner 20 of 5 steps | paragraphs in the up-down direction, three types of particle diameters which are different in order of large, medium and small from the lower stage side are adopted, but different particle diameters are adopted for each stage. It is good also as a small diameter from the side to the upper stage side.
Further, the number of vertical stages of the combustion burner 20 is not limited to five, and in other plural stages (for example, about 2 to 6 stages), the diameter decreases from the lower stage side to the upper stage side as in the present embodiment. What should I do?

Further, in the heavy oil fired boiler 10A of the modified example shown in FIG. 5, the combustion burner 20A of the combustion device 12A has not only different particle sizes to be injected at each stage, but also the flow rate of the heavy oil fuel to be supplied. The upper side is set to be smaller than the lower side where the residence time in the furnace 11 is long.
Even in this case, burner arrangement and fuel distribution that effectively use the particle trajectory in the furnace 11 are ensured, and even if the fuel ratio injected from the lower stage with a long residence time is increased, the heavy oil spray particles are reliably burned. Increase in dust emission can be prevented. Therefore, the consumption rate of the atomized fluid can be suppressed to a necessary and sufficient value for each burner stage without increasing the amount of dust at the boiler outlet.

Further, the heavy oil-fired boiler 10, 10 </ b> A of the present embodiment is a particle of heavy oil spray particles to be injected into the combustion burner 20, 20 </ b> A that introduces and mixes heavy oil fuel and steam into the fuel sprayer 21. Those having a larger diameter are arranged on the lower stage side, and are arranged so that the particle diameter increases toward the upper stage side. In other words, the residence time in the furnace 11 is long lower side of the combustion burners 2 lower large径噴mist type steam consumption rate 0,20A oil atomizer 22 is adopted, the residence time in the furnace 11 is short upper side steam consumption rate is adopted high small径噴fog type oil atomizer 22 into the combustion burners 2 0,20A.

Thus, the heavy oil-fired boilers 10 and 10A of the burner arrangement in which the heavy oil spray particles are burned by effectively using the particle trajectory in the furnace 11 are used without increasing the amount of dust at the boiler outlet. This makes it possible to keep the steam consumption rate at a sufficient value for each burner stage.
In addition, this invention is not limited to embodiment mentioned above, For example, it can change suitably in the range which does not deviate from the summary, such as utilization of a squeal as a atomization fluid.

10, 10A, 10B Heavy oil fired boiler 11 Furnace 12, 12A, 12B Combustion device 13 Fuel supply pipe 14 Steam supply pipe 20, 20A, 20B Combustion burner 21 Heavy oil sprayer (fuel sprayer)
22 Oil atomizer 22a Ejection hole 23 Housing tube 23a Air intake hole 24 Swirler 25, 27 Air passage 26 Burner throat 28 Variable air damper 31 Chimney

Claims (5)

Heavy oil fuel and atomized fluid are introduced and mixed in the fuel sprayer of the combustion burner, and the mixed fluid containing the atomized heavy oil spray particles is injected into the furnace together with combustion air and burned. A method for burning an oil fired boiler,
An oil atomizer is provided at the tip of the fuel sprayer,
The particle size of the heavy oil spray particles injected from the combustion burner arranged in a plurality of stages in the vertical direction of the furnace is set so that the upper side is smaller than the lower side ,
The method of burning a heavy oil-fired boiler , wherein the oil atomizer of the lower combustion burner is of a larger particle size spray type than the oil atomizer of the upper combustion burner .   2. The method for burning a heavy oil-fired boiler according to claim 1, wherein the flow rate of the heavy oil fuel supplied to the combustion burner is set so that the upper side is smaller than the lower side. .   The combustion of the heavy oil fired boiler according to claim 1 or 2, wherein the oil atomizer of the lower combustion burner has lower steam consumption than the oil atomizer of the upper combustion burner. Method.   The spray particle size of the oil atomizer is determined by a relationship between a residence time of the heavy oil spray particles in the furnace and a mass% of the heavy oil spray particles. The combustion method of the heavy oil fired boiler as described in any one of claim | item 3. Heavy oil fuel and atomized fluid are introduced and mixed in the fuel sprayer of the combustion burner, and the mixed fluid containing the atomized heavy oil spray particles is injected into the furnace together with combustion air and burned. An oil-fired boiler,
An oil atomizer is provided at the tip of the fuel sprayer,
The combustion burner is arranged in a plurality of stages in the vertical direction of the furnace, and the heavy oil spray particles injected and injected from the combustion burner are arranged so that the particle size on the lower stage side is larger than the upper stage side. And
The heavy oil fired boiler , wherein the oil atomizer of the lower combustion burner is of a larger particle size spray type than the oil atomizer of the upper combustion burner .

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