JP2016114316A - Method for igniting heavy fuel oil burning boiler and heavy fuel oil burning boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for igniting heavy fuel oil burning boiler capable of performing simultaneous ignition of several kinds of fuel oil and restricting a consumption efficiency of atomized medium without increasing a discharging amount of soot dusts.SOLUTION: This invention relates to a method for igniting a heavy oil burning boiler 10 for feeding heavy fuel oil and fine particle fluid into a fuel spraying unit of a combustion burner 20 and mixing them to make mixed fluid including fine heavy fuel oil sprayed particles into a furnace 11 together with combustion air. In regard to the heavy oil sprayed particles injected and fed from each of the combustion burners 20 of a plurality of stages arranged in a vertical direction of the furnace 11 while a plurality of kinds of fuel oil including fuel oil with residual carbon elements of 10% or more as heavy fuel oil are ignited simultaneously, combustion characteristic of heavy fuel oil sprayed particles injected and fed from one or a plurality of stages of combustion burners 20 arranged at the upper stage is set to be higher than that of the heavy fuel oil sprayed particles injected and fed from one or a plurality of stages of the combustion burners 20 arranged at the lower stage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heavy oil fired boiler that uses heavy oil such as asphalt as fuel, and more particularly, combustion of a heavy oil fired boiler that reduces the amount of dust discharged from a boiler that simultaneously burns multiple types of fuel oil The present invention relates to a method and a heavy oil fired 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 conventional heavy oil-fired boiler 10A shown in FIG. 5 burns heavy oil such as asphalt, and has a furnace 11 and a combustion device 12A.
The combustion device 12A has a combustion burner 20A 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 equal intervals along the circumferential direction, and the combustion burners 20A in each stage all have the same specifications.

Each combustion burner 20A 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 20A 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.
Furthermore, the following Patent Document 3 discloses a technique related to improving the fuel injection method in the entire oil-fired boiler for the same fuel oil.

JP 2003-172505 A Japanese Patent Publication No. 8-1288 JP 2014-35126 A

  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 10A, a plurality of combustion burners 20A having the same specifications are arranged in the vertical direction. For this reason, as shown in FIG. 5, the particle trajectory (indicated by a solid line) of the heavy oil spray particles introduced from the lower combustion burner 20A and the heavy oil spray particles introduced from the upper combustion burner 20A. Comparing the particle trajectory (shown with broken lines), the particle trajectory of the heavy oil spray particles introduced from the lower combustion burner 20A 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.
Some boilers may burn multiple types of fuel oil at the same time, but there is no clear guideline on how to add fuel oil.

From such a background, in heavy oil fired boilers that simultaneously burn different types of fuel oil, the spray medium that does not increase the amount of dust discharged and is consumed for atomization of heavy oil A combustion method and heavy oil fired boiler that can suppress the consumption rate of the oil are desired.
The present invention has been made in order to solve the above-described problems, and the object of the present invention is to be applied to a boiler that simultaneously burns a plurality of types of fuel oil and consumes the spray medium without increasing the amount of dust emission. An object of the present invention is to provide a heavy oil-fired boiler combustion method and a heavy oil-fired boiler that can suppress the rate.

In order to solve the above problems, the present invention employs the following means.
The combustion method of a heavy oil fired boiler according to the present invention is to introduce a heavy oil fuel and atomized fluid into a fuel atomizer of a combustion burner, mix them, and burn a mixed fluid containing atomized heavy oil spray particles A method of burning a heavy oil-fired boiler that is injected into a furnace together with industrial air and combusts, and simultaneously burns a plurality of oil types including fuel oil having a residual carbon content of 10% or more as the heavy oil fuel The heavy oil spray particles injected and injected from the combustion burners arranged in a plurality of stages in the vertical direction of the furnace are injected and injected from one or more stages of the combustion burners arranged on the upper stage side. The flammability of the heavy oil spray particles is set to be higher than the flammability of the heavy oil spray particles injected from one or more stages of the combustion burner arranged on the lower stage side. .

  According to the combustion method of such a heavy oil fired boiler, the heavy oil spray particles injected and injected from the combustion burners arranged in a plurality of stages in the vertical direction of the furnace are one or more stages arranged on the upper stage side. The combustion property of the heavy oil spray particles injected from the combustion burner is set higher than the combustion property of the heavy oil spray particles injected from the one or more stages of combustion burners arranged on the lower side. For this reason, low (bad) heavy oil spray particles injected from the lower combustion burner are injected with high (good) heavy oil spray particles injected from the upper combustion burner. In comparison, the particle trajectory of heavy oil spray particles in the furnace becomes longer, and the residence time in the furnace becomes longer.

  That is, the residence time in the furnace is short (the combustion time of heavy oil spray particles is short), and the combustion oil on the upper stage is sprayed with highly combustible heavy oil spray particles, and the residence time in the furnace is Heavy oil spray particles having low combustibility are sprayed into a long lower combustion burner (the combustion time of heavy oil spray particles is long). For this reason, since a long residence time and combustion time in the furnace are secured for heavy oil spray particles with low flammability that do not burn before reaching the boiler outlet and are likely to become unburned, the boiler outlet An increase in the amount of dust can be suppressed, and the consumption rate of the atomized fluid can be similarly suppressed.

により算出される燃焼性評価指標の大小により判断するとよい。このように、重質油噴霧粒子の燃焼性について、算出した燃焼性評価指標の値から燃焼性の高低（良し悪し）を判断すれば、すなわち、チャー収率（残留炭素成分量）及びチャーの燃焼速度から燃焼性評価指標を算出して燃焼性を判断すれば、各重質油噴霧粒子の燃焼性に関する評価精度を向上させることができる。 In the above invention, the level of combustibility is:

Judgment may be made based on the magnitude of the flammability evaluation index calculated by. As described above, regarding the combustibility of the heavy oil spray particles, if the combustibility level (good or bad) is judged from the calculated combustibility evaluation index value, that is, char yield (residual carbon component amount) and char If the combustibility evaluation index is calculated from the combustion speed and the combustibility is judged, the evaluation accuracy regarding the combustibility of each heavy oil spray particle can be improved.

  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 and burns into a furnace, and simultaneously burns a plurality of oil types including fuel oil with a residual carbon content of 10% or more as the heavy oil fuel, and the vertical direction of the furnace The combustion burner that is arranged in a plurality of stages and injects and inputs the heavy oil spray particles, respectively, includes one or more upper burners arranged on the upper stage side, and one or more lower burners arranged on the lower stage side. And the combustion property of the heavy oil spray particles injected from the upper burner is set higher than the combustion property of the heavy oil spray particles injected from the lower burner. Is.

  According to such a heavy oil-fired boiler, the combustion burner that is arranged in a plurality of stages in the vertical direction of the furnace and injects and inputs heavy oil spray particles, respectively, has one or more upper burners arranged on the upper stage side. One or a plurality of lower burners arranged on the lower stage side, and the combustibility of the heavy oil spray particles injected from the upper burner is the combustion of the heavy oil spray particles injected from the lower burner It is set higher than sex. Therefore, heavy oil spray particles with low (bad) flammability injected from the lower burner are compared with heavy oil spray particles with high flammability (good) injected from the upper burner. As a result, the particle trajectory of heavy oil spray particles becomes longer and the residence time in the furnace also becomes longer.

  That is, the residence time in the furnace is short (the combustion time of heavy oil spray particles is short), and the heavy burner oil spray particles with high combustibility are sprayed into the upper burner and the residence time in the furnace is long (heavy (The combustion time of the fine oil spray particles is long.) The lower burner is charged with heavy oil spray particles with low combustibility. A long furnace residence time and combustion time is ensured for low heavy oil spray particles. Therefore, an increase in the amount of dust at the boiler outlet can be suppressed, and the consumption rate of the atomized fluid can be similarly suppressed.

により算出される燃焼性評価指標の大小により判断するとよい。このように、重質油噴霧粒子の燃焼性について、算出した燃焼性評価指標の値から燃焼性の高低（良し悪し）を判断すれば、すなわち、チャー収率及びチャーの燃焼速度から燃焼性評価指標を算出して燃焼性を判断すれば、各重質油噴霧粒子の燃焼性に関する評価精度を向上させることができる。なお、チャーとは、燃料油を熱分解させた後の固体残存物質のことである。 In the above invention, the level of combustibility is:

Judgment may be made based on the magnitude of the flammability evaluation index calculated by. In this way, with regard to the combustibility of heavy oil spray particles, if the combustibility level is judged from the calculated combustibility evaluation index value (good or bad), that is, the combustibility evaluation from the char yield and char combustion rate. If an index is calculated and combustibility is judged, the evaluation accuracy regarding the combustibility of each heavy oil spray particle can be improved. In addition, char is a solid residual substance after thermally decomposing fuel oil.

  According to the present invention described above, in a heavy oil-fired boiler that simultaneously burns a plurality of oil types including fuel oil having a residual carbon content of 10% or more as heavy oil fuel, particle trajectory (residence time) in the furnace. It is possible to suppress the amount of dust discharged from the boiler outlet without increasing the consumption rate of the atomized fluid such as steam by effectively burning the low-combustibility fuel as long as possible. .

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 explanatory drawing which shows the combustion process of heavy oil spray particle | grains. 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 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 simultaneously burns a plurality of heavy oils such as asphalt as fluid fuel. The heavy oil fired boiler 10 has a furnace 11 and a combustion device 12. The furnace 11 is installed along the vertical direction with a hollow shape of, for example, a square cylinder, and a combustion device 12 is provided at the lower part of the furnace wall constituting the furnace 11.

  The heavy oil in this embodiment is defined as heavy oil having a residual carbon component of 10% or more. That is, the heavy oil in this embodiment limits heavy oil using the value of the residual carbon which is an analysis item of industrial analysis, and specifically means heavy oil equal to or higher than C heavy oil.

The combustion device 12 has a plurality of combustion burners 20 mounted on the furnace wall. The combustion burner 20 of the present embodiment is arranged, for example, five sets, that is, five stages in the vertical direction, for example, in which four burners 20 are arranged at equal intervals along the circumferential direction. 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 denitration device, an electric dust collector, an induction blower, and a desulfurization device (not shown), and a chimney is provided at the downstream end.

  Therefore, in the combustion apparatus 12, when each combustion burner 20 injects a mixed fluid of heavy oil and spraying steam into the furnace 11, in the furnace 11, the mixed fluid and air burn 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 this embodiment is configured, for example, as shown in FIGS. 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 ejection 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.

Now, in the heavy oil fired boiler 10 provided with the combustion burner 20 of the structure mentioned above, the combustion method demonstrated below is employ | adopted in this embodiment.
That is, in the present embodiment, 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 used for combustion. In a heavy oil-fired boiler 10 that is injected and burned into the furnace 11 together with air, a plurality of oil types including fuel oil having a residual carbon content of 10% or more are burned simultaneously as heavy oil fuel. In the present embodiment described below, two types of heavy oil fuels (fuel oil A and fuel oil B) are used, and one of the fuels is relatively inferior (lower) in combustibility than fuel oil B. Oil A, and the other is fuel oil B that is relatively more combustible (higher) than fuel oil A.

  The heavy oil spray particles injected and injected from the combustion burner 20 having a plurality of stages arranged in the vertical direction of the furnace 11 are injected and injected with the heavy oil spray particles of the fuel oil B from the upper combustion burner 20. In addition, heavy oil spray particles of the fuel oil A are injected and injected from the combustion burner 20 on the lower stage side. As a result, the combustibility of the heavy oil spray particles injected from the upper combustion burner 20 is higher than the combustibility of the heavy oil spray particles injected from the lower combustion burner 20.

  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. Further, in the illustrated configuration example, the fuel oil A is supplied to the combustion burner 20 at the lower stage 2 (hereinafter referred to as “lower burner 20N”), and the combustion burner at the upper stage 3 (hereinafter referred to as “upper burner”). The fuel oil B is supplied to the fuel 20. Accordingly, in the combustion burner 20 arranged in five stages in the vertical direction, heavy oil spray particles having low combustibility are injected and injected from the lower burner 20N of the lower two stages, and the combustibility from the upper burner 20P of the upper three stages. Heavy oil spray particles are injected and injected, for example, low-burning heavy oil spray particles are injected from the lower three-stage lower burner 20N, and combustibility is injected from the upper two-stage upper burner 20P. There is no particular limitation such as injection of heavy oil spray particles having a high particle size.

  As a result, the heavy oil spray particles of the low combustibility fuel oil A injected from the lower burner 20N of the lower two stages are injected into the highly burnable fuel oil injected from the upper burner 20P of the upper three stages. Compared with the heavy oil spray particles of B, the particle trajectory of the heavy oil spray particles in the furnace 11 becomes longer, so the residence time in the furnace also becomes longer. Specifically, the heavy oil spray particles of the fuel oil A injected from the lower burner 20N are burned through a particle locus as shown by a solid line in FIG. For this reason, the heavy oil spray particles of the fuel oil A have a longer particle trajectory in the furnace 11 than the heavy oil particles of the fuel oil B that burns through the particle trajectory as shown by the broken line in FIG. The residence time of is also increased. Thus, the heavy oil particles of the fuel oil A whose residence time in the furnace 11 is extended also has a longer combustion time.

  Therefore, when two types of fuel oil A and fuel oil B having different combustibility are burned simultaneously in the furnace 11, the heavy oil of the fuel oil A having low combustibility from the lower burner 20N having a long residence time and combustion time. Combustion before reaching the boiler outlet by spraying the spray particles and spraying heavy oil spray particles of fuel oil B with high combustibility from the upper burner 20P having a short residence time and short combustion time. Long staying time in the furnace and combustion time are secured for heavy oil spray particles of fuel oil A, which is likely to become unburned and not combustible, so that the increase in the amount of dust at the boiler outlet can be suppressed. it can.

FIG. 2 is an explanatory diagram showing a combustion process of heavy oil spray particles, in which the horizontal axis represents the residence time in the furnace, and the vertical axis represents the fuel weight. That is, FIG. 2 shows the change in the fuel weight with the passage of the same residence time in the two types of fuel oil A and fuel oil B described above.
The fuel oil A and the fuel oil B having the same fuel weight are vaporized and thermally decomposed in the high-temperature furnace 11 at the initial stage of the residence time in the furnace injected into the furnace 11. The volatile matter generated in this way burns and char remains. Such combustion of the volatile matter becomes remarkable in the fuel oil B having high combustibility (the change in decrease in the fuel weight is large). In other words, the fuel oil B having high combustibility contains a large amount of volatile matter. Therefore, the char yield is such that β of the fuel oil B is lower than α of the fuel oil A.

  This char yield is the weight ratio of char to the weight of fuel charged. Such char yield has been conventionally used for primary evaluation of heavy oil combustibility, and fuel oil with higher combustibility tends to be a small value because the proportion of volatile matter is larger.

After the volatile matter is generated and burned, the remaining char burns. Such char combustion proceeds until reaching the boiler outlet during the residence time in the furnace.
In the illustrated example, in the case of the fuel oil A, the combustion of the char proceeds from the state of the char yield α, and is discharged in a state where the unburned portion weight ratio of the boiler outlet to the injected fuel weight is αm. On the other hand, in the case of the fuel oil B, the combustion of the char proceeds from the state of the char yield β, and is discharged in a state where the unburned fuel weight ratio at the boiler outlet with respect to the injected fuel weight is βm. Note that the slope of change in the fuel weight within the furnace residence time from the char yields α, β to the unburned component weight ratios αm, βm is referred to as char combustion characteristics that differ for each fuel oil.

By the way, the combustibility of the heavy oil described above, that is, the combustibility of the heavy oil spray particles is high or low from the magnitude of the combustibility evaluation index calculated based on the following equation from the char yield and the char combustion speed. Judge (good or bad). In this case, if the combustion evaluation index is large, it is evaluated that the combustibility of the heavy oil spray particles is low.

In this formula, in addition to the above-mentioned char yield, a combustibility evaluation index is calculated taking into account the combustion rate of char. The char yield used here can be the yield of residual carbon in industrial analysis, but if the value can be obtained by a rapid pyrolysis device such as Curie Point Pyrolaser, the accuracy will be improved. Can do. The burning rate is a value obtained by, for example, a char burning characteristic test using a differential thermogravimetry apparatus. That is, this combustion rate is a char combustion characteristic that is different for each fuel oil described based on FIG. 2, and the fuel weight from char yield α, β to unburned component weight ratio αm, βm within the residence time in the furnace. Change (slope).
In addition, although the average burning rate is used for the burning rate in this case, the burning rate of the unburned char (region where the burning rate is close to 1) may be used.

  Therefore, in the combustion process shown in FIG. 2, if the residence time of the low-combustible fuel oil A in the furnace is lengthened, the unburnt weight ratio can be reduced to approach the fuel oil B. That is, increasing the residence time of the fuel oil A in the furnace means moving the boiler outlet in FIG. 2 to the right side, so that the unburned weight ratio αm is changed to αn according to the extension of the residence time in the furnace. Can be reduced to

In addition, if a combustion evaluation index that takes into account the char combustion rate (combustion characteristics) is adopted, not only the amount of remaining char but also the combustibility (the amount of char that burns within the residence time in the furnace) means the quality of char. Since the reflected evaluation becomes possible, the evaluation accuracy regarding the combustibility of each heavy oil spray particle is further improved.
The unburned fraction ratio αn of the fuel oil A after extending the residence time in the furnace is the same as the unburned fraction ratio βn of the fuel oil B depending on the char combustion characteristics of the fuel oil A and the fuel oil B, the extended time, and the like. In some cases, depending on various conditions, it may reverse and fall below the unburned fraction βn.

If the increase in the amount of dust at the boiler outlet can be suppressed in this way, it is not necessary to increase the amount of atomized fluid (spray medium) such as steam used for atomization of fuel oil for the purpose of dust control. An increase in the consumption rate of the atomized fluid can be suppressed.
When three or more kinds of heavy oils having different flammability are burned simultaneously, heavy oil spray particles of heavy oil having the lowest flammability are injected from one or more stages of combustion burners 20 located on the lower side. One or a plurality of stages of combustion burners 20 on the lower stage side so that heavy oil spray particles of heavy oil having the highest combustibility are injected from one or more stages of combustion burners 20 located on the upper stage side. From this to the one or more stages of combustion burners 20 on the upper stage side, the combustibility of the heavy oil spray particles injected and injected may be sequentially increased. That is, when three types of heavy oil are burned simultaneously, the combustibility of the heavy oil spray particles injected from the combustion burner 20 may be increased in the order of the lower region, the middle region, and the upper region.

Thus, according to the present embodiment described above, in the heavy oil-fired boiler 10 that simultaneously burns a plurality of oil types including fuel oil having a residual carbon content of 10% or more as heavy oil fuel, the furnace 11 By effectively utilizing the particle trajectory (residence time) in the fuel, the fuel with low combustibility is burned for as long as possible, that is, the heavy oil spray particles of the heavy oil fuel with low combustibility are burned at the lower combustion burner. By injecting from 20 and securing a long residence time in the furnace, it becomes possible to suppress the amount of dust discharged from the boiler outlet without increasing the consumption rate of atomized fluid such as steam. Such a heavy oil-fired boiler 10 and its combustion method of this embodiment can be applied to a boiler of a swirl combustion system or an opposed combustion system.
In addition, this invention is not limited to embodiment mentioned above, For example, utilization of air is possible as atomization fluid, For example, it can change suitably in the range which does not deviate from the summary.

DESCRIPTION OF SYMBOLS 10 Heavy oil fired boiler 11 Furnace 12 Combustion device 13 Fuel supply piping 14 Steam supply piping 20 Combustion burner 20N Lower burner 20P Upper burner 21 Heavy oil sprayer (fuel sprayer)
22 Oil atomizer 24 Swirler 31 Flue

Claims (4)

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,
Combusting a plurality of oil types including fuel oil having a residual carbon content of 10% or more as the heavy oil fuel,
The heavy oil spray particles injected from the combustion burners arranged in a plurality of stages in the vertical direction of the furnace are injected from the combustion burner of one or more stages arranged on the upper stage side. A heavy oil-fired boiler characterized in that the combustibility of the oil spray particles is set higher than the combustibility of the heavy oil spray particles injected from one or more stages of the combustion burner arranged on the lower side. Combustion method. The level of flammability is

The combustion method for a heavy oil-fired boiler according to claim 1, wherein the determination is based on the magnitude of the flammability evaluation index calculated by: 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,
Combusting a plurality of oil types including fuel oil having a residual carbon content of 10% or more as the heavy oil fuel,
The combustion burner, which is arranged in a plurality of stages in the vertical direction of the furnace and injects and inputs the heavy oil spray particles, respectively, is one or more upper burners arranged on the upper stage side and one or more arranged on the lower stage side. A lower burner of the stage, and the combustibility of the heavy oil spray particles injected from the upper burner is set higher than the combustibility of the heavy oil spray particles injected from the lower burner. A heavy oil-fired boiler characterized by that. The level of flammability is

The heavy oil-fired boiler according to claim 3, which is determined based on the magnitude of the flammability evaluation index calculated by:

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