JPS6365224A - Burning device - Google Patents

Abstract

PURPOSE:To maintain a steady burning condition and improve the consumption efficiency of fuel by applying a temporary storage method at the time of an operation startup and under low load conditions or wider load fluctuation conditions, and a direct feeding method from a pulverizer under a steady high load state. CONSTITUTION:Coarse coals 2 are fed into and pulverized in a load-pulverizer 51 to become pulverized coals whose grain size is slightly larger than the pulverized coal by a starting pulverizer 4. Under low load conditions such as a startup of boiler or wider load fluctuation conditions, pulverized coals 90% of which are smaller than the grain size of 74mum and finely pulverized 46 having the grain size of 10mum or small are made by operating starting-low load pulverizers 4 in any required number of units, which pulverized coals are fed to start-low load burners 30. If there is a greater boiler load or the range of load fluctuation is relatively small, any required number of load pulverizers 51 are operated to make pulverized coals which are supplied to load main burners 53 to meet the load demand. In a certain load range, both the start-low load burners 30 and the load main burners 53 can be used at the same time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion device that uses fine powder of solid fuel such as pulverized coal, and in particular, the present invention relates to a combustion device that uses fine powder of solid fuel such as pulverized coal, and in particular, the present invention relates to a combustion device that is stable even in terms of odor, such as when starting a boiler and at low load. The present invention relates to a combustion device that can maintain its condition, increase the efficiency of solid fuel use, and reduce oil fuel consumption.

[Background of the invention]

With changes in the fuel supply and demand situation, solid fuels, mainly coal, are increasingly being applied to large-capacity power generation boilers. The background of the present invention will be explained below using coal as an example.

Conventional coal-fired boilers require a crusher such as a ball mill,
Most of them have a coal combustion equipment system mainly consisting of a burner directly connected to the pulverizer, so-called pulverizer direct connection type, and due to the power of coal pulverization and economical reasons, the fineness of 74 μm is 70 to 70 μm. It is operated at around 85% pass.

Furthermore, the pulverized coal pulverized by the pulverizer is transported by primary air and ejected from the burner nozzle into the furnace, and the amount of primary air is determined from the second reason of pulverizer performance. Therefore, the ratio of air to pulverized coal (pulverized coal IA degree) changes depending on the load on the pulverizer, and as the pulverization improves and the load decreases, the pulverized coal concentration becomes thinner, which further affects combustion related to coal properties. Due to the influence of heat, temperature, ambient temperature of the furnace, and combustion air temperature, coal cannot be burned exclusively under low boiler loads, and auxiliary combustion of oil is required.

In addition to the above-mentioned problems, there is also a problem such as coal being unusable during the early stages of startup due to a lack of a heat source for drying the coal inside the crusher.

Furthermore, recently, the proportion of nuclear power generation in the total amount of power generation has been increasing, and therefore the operation of the pulverized coal combustion boiler is also affected by this.

That is, since it is difficult and inefficient to vary the load in nuclear power generation, pulverized coal boilers have been operated at intermediate loads with nuclear power generation as the base load. For this reason, the load on pulverized coal boilers is subject to large fluctuations, and systems are required to be flexible enough to handle these fluctuations.

Under such circumstances, for example, when starting up a pulverized coal boiler,
Alternatively, maintaining the optimum combustion state at the lowest possible load zone or other rapid load change zones requires a crusher, a buffer tank with a large capacity and poor response, that is inherent in the combustion system. As far as extremely ri
It is m.

In contrast to this combustion method that is directly connected to the crusher, there is a storage type combustion method. In this method, pulverized coal that has been pulverized by a pulverizer and adjusted to the desired particle size is stored in a bin regardless of load fluctuations, and the pulverized coal is taken out from the bin according to load fluctuations and transported by airflow to the burner. This is a method in which the fuel is heated and then subjected to combustion.

This method is suitable under conditions where responsiveness is required, such as during start-up, low load, or rapid load fluctuations, but when the boiler load is large and relatively stable, the amount of coal used is large. Also, since there are problems such as ignition and dust explosion when storing a large amount of coal, the above-mentioned method directly connected to the crusher is more suitable.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and includes the following:
The purpose of the present invention is to provide a combustion device that can maintain a stable combustion state even during startup and low load, increase the efficiency of using solid fuel such as coal, and reduce the amount of oil fuel used. It is something.

[A chest of inventions]

In order to achieve the above-mentioned objects, the present invention includes a first solid fuel crushing means, such as a ball mill, which is driven during startup and low load, and a solid fuel such as coal that has been crushed by the first solid fuel crushing means. A fine powder solid fuel having a predetermined particle size distribution by transporting the fuel with a high temperature gas such as a mixture of air and exhaust gas, and an ultra-fine powder solid having a particle size smaller than that of the fine powder solid fuel. Separation means, such as a cyclone separator, which separates the fuel into fuel; A first storage means, such as a bottle, which stores the finely divided solid fuel having a predetermined particle size distribution; and a first storage means, which stores the ultrafine solid fuel. a second storage means consisting of, for example, a bag filter; a start-up/low-load burner that pneumatically transports and combusts the pulverized solid fuel taken out from the first storage means; and the first solid fuel crushing means. a steam-type gas heater for sending high-temperature gas; A hot air furnace attached to the gas heater, a second solid fuel crushing means such as a ball mill, etc., which is driven during startup and normal load other than when the load is low, and the solid fuel crushed by the second solid fuel crushing means. The present invention is characterized by being equipped with a load main burner that pneumatically transports the finely powdered solid fuel using high-temperature gas and directly burns it.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows the schematic configuration of the main parts of the combustion device according to the example.
It is a diagram.

Startup - Coarse coal 2 in low load coal bunker 1 is fed to coal feeder 3
, and is fed into each starting crusher (for example, a pole tube mill, a vertical roll race crusher with a built-in rotary classifier, etc.) 4, and is pulverized. The pulverized coal 5 that has been pulverized by this pulverizer 4 and adjusted to a predetermined particle size (74 μm or more 90% bath) is transported by air flow, and is separated from air by passing through each cyclone separator.
Thereafter, it is distributed and put into each bin 8 by a distributor 7 consisting of a chain conveyor. On the other hand, the air containing the ultrafine coal 46 separated by the cyclone separator 6 is introduced into the bag filter 9, where it is separated into the ultrafine coal 46 and air. A static eliminator 12 is installed in the middle of the connecting pipe 10 that connects the cyclone separator 6 and the distributor 7 and the connecting pipe 11 that connects the distributor 7 and the bin 8 .

This static eliminator! 12, as shown in FIG. 2, is composed of a net 13 made of conductive fine wires, such as copper or nickel, woven at intervals of about 5 to 20III11, and as shown in FIG. Multiple pieces along the falling direction of 5,
They are arranged at predetermined intervals, and each net 13 is grounded.

FIG. 4 shows another example of the static elimination bag [12].

In this example, the conductive plate made of steel or nickel is 20 to 301I.
It is composed of lattice bodies 14 combined at intervals of approximately IIl.

The pulverized coal 5 rubs against each other during transportation and generates static electricity. On the other hand, since a part of the fine powder 5 is floating in the hollow part of the bottle 8, the static electricity of the above-mentioned pulverized coal 5 is discharged in the hollow part and fireworks are generated.

Causes dust explosion. Therefore, the static eliminator mentioned above! 12 removes static electricity from the pulverized coal 5 to prevent dust explosions.

As shown in FIGS. 5 and 6, a large number of cooling pipes 15 are buried in the layer of pulverized coal 5 formed in the bin 8. Each of the cooling pipes 15 is inserted from the outside to the inside of the bottle 8, and is installed with its tip end facing downward (at an inclination angle of about 10 to 30 degrees). In this embodiment, eight cooling pipes 15 are arranged at equal intervals l) in the opening direction, and eight cooling pipes 15 are arranged at equal intervals along the height direction of the bottle 8.
It is set up in three tiers.

As the cooling pipe 15, a natural annular type shown in FIG. 7 or a forced circulation type shown in FIG. 8 is used. Nature W! The annular cooling pipe I5 is a double pipe as shown in FIG. figure)
is filled with.

The forced mm type cooling pipe 15 has a double pipe structure as shown in FIG. 8, and a cooler 16, a refrigerant tank 17, and a pump 18 are attached to the outside of the bottle 8. The cooler 16, the refrigerant tank 17, and the pump 18 are equipped with a temperature sensor 19, such as a thermocouple corner, attached to the outer periphery of the cooling 4vl 5, which is shared with other cooling pipes 15. v
The internal temperature of the pulverized coal 5 is monitored and recorded on the recorder 20. If the temperature inside the layer exceeds 150″C, for example,
A warning bag R121 consisting of a buzzer, lamp, etc. is activated to warn of a rise in temperature within the layer.

The aforementioned Q month’! Zen4Ii! The annular cooling pipe 15 has a structure in which the refrigerant naturally circulates within the system due to the difference in specific gravity, and the high-temperature refrigerant is cooled to a predetermined temperature in the cooler 16 and reused. ). On the other hand, in the forced circulation type cooling pipe 15, the temperature inside the layer 11 is monitored by the temperature detector 9, and when the temperature exceeds a predetermined temperature (for example, 150° C.), the pump 18 is activated to forcefully circulate the refrigerant. It is designed to lower the temperature inside the layer. Furthermore, the pump 18 may be started at predetermined time intervals, in addition to the above-described case of temperature rise.

Furthermore, a heat pipe can also be used as the cooling pipe 15. In this case, the evaporation part side of the P-pipe is pulverized coal 5
The condensation side is placed outside the bottle 8. In any case, the cooling pipe 15 maintains the internal temperature of the pulverized coal 5 at a predetermined temperature or higher.

There is a risk that the pulverized coal 5 stored in the bin 8 will generate heat due to natural oxidation, and especially within the layer, the heat will not be dissipated and will accumulate inside the layer, causing the temperature inside the layer to rise and there is a risk of ignition. . As mentioned above, by burying several cooling pipes 5 in each layer of pulverized coal 5, the temperature inside the layer can be lowered and ignition can be prevented.

Cooling IV1! If 'l is horizontally L co-equipped within the layer,
This may cause blockage and bridge formation of the 1@ powder return 5 in the bin 8, making it impossible to smoothly supply the pulverized coal 5. In the embodiment of the present invention, the cooling pipes 15 are mutually inclined to ensure smooth supply of the pulverized coal 5.

The distributor 7 is of a closed type, and the inside of the distributor 7 is filled with an inert gas such as carbon dioxide gas or nitrogen gas, so that the oxygen concentration is suppressed to about 12% or less. The inert gas is circulated, and as shown in FIG. 1, the inert gas circulation system 22 includes a dust remover 23, a dehumidifier 24, an oxygen concentration detector 25, an inert gas cylinder 26, and a fan 27. It is provided.

The pulverized coal 5 moving along with the circulating inert gas is collected by the dust remover 23 and returned to the distributor 7. If the pulverized coal 5 contains moisture, it may cause blockage or bridge formation, so as described above, the dehumidifier 24 is provided to remove moisture. Also, the oxygen concentration detector 25
The oxygen concentration in the circulating inert gas is constantly monitored, and when the measured oxygen concentration exceeds the set oxygen concentration (for example, 12%), inert gas is supplied from the inert gas cylinder 26 to lower the oxygen concentration. Efforts are being made to prevent ignition. As shown in the figure, an inert gas such as carbon dioxide gas or nitrogen gas is also supplied to the inside of the bottle 8 to create a low oxygen concentration atmosphere.

At the bottom of the bin 8, a metering coal feeder 28, such as a vertical rotary blade feeder or a feeder with an impact meter, is provided. The pulverized coal 5 stored in the bin 8 is sequentially taken out from the metering coal feeder 28 according to the boiler load, and heated to a predetermined temperature (for example, about 80°C) by an air preheater (not shown). It is carried along with the air 29 to each start-up/low load burner 30,
It is used for combustion when starting the boiler, when the load is low, or when the negative 4-hour fluctuation rate is large.

In the supply system of the primary air 29, an air amount measuring device 31 is provided.
As well as a primary air ventilator 32 is provided.

FIG. 9 is a schematic diagram of the start-up/low-load burner 30 used in this embodiment.

As shown in the figure, this start-up/low-load burner 30 includes a primary sleeve 33 for supplying primary air 29 mixed with pulverized coal 5 at a predetermined ratio, and a tip end of the primary sleeve 33. A flame stabilizer 34 is provided, and a gas mixture provided within the primary sleeve 33 and slightly in front of the flame stabilizer 34 swirls the mixed air flow of pulverized coal 5 and primary air 29 to prevent uneven distribution of density. The rotating blade 35 is made of, for example, ceramic and has excellent heat resistance and wear resistance.

Further, this start-up/low load burner 30 includes an opening adjuster 36 for adjusting the opening of the swirl vane 35, and the swirl vane 35 swirls the pulverized coal 5 and the primary air 29 into a mixed air flow. A C/A detector 37 detects the pulverized coal concentration (hereinafter pulverized coal/air, abbreviated as C/A) using, for example, a laser to give a concentration distribution, and the rotating pulverized coal. 5, a power supply device 39 for supplying power to the heating element 38, and the C/A detector 37.
A control signal for adjusting the opening degree of the swirl vane 35 is outputted to the opening degree adjuster 36 in accordance with a detection signal from the power supply device! The control unit 4 outputs the ignition command fN to 39.
0 is attached.

In FIG. 10, a ZrBz/SiC conductive ceramic is used as the heating element 38, and it is connected to pulverized coal 5 and primary air 2.
9 is an ignition characteristic diagram when inserted into a gas mixture flow with No. 9.

In this experiment, the amount of coal supplied was A and B.

Using three types of C with different coal feeding amounts, one of the nozzle exits
In this experiment, the stable ignition region, unstable ignition region, and non-ignition region were investigated by varying the air flow velocity and pulverized coal concentration (C/A).

As is clear from this figure, pulverized coal concentration (
It can be seen that it is necessary to regulate C/A) to 0.5 or more and the primary air flow velocity to 10 m/s or less.

On the other hand, in actual pulverized coal-fired combustion equipment, reliable handling and transportation of pulverized coal cannot be achieved unless the C/A is 0.5 or higher due to the specific gravity of pulverized coal. Are known.

In addition, from the viewpoint of preventing flashback, the air flow velocity at the fuel nozzle is =1
6- Must be maintained at 15 m/s or higher.

In FIG. 9, the inside of the primary sleeve 33 is approximately 15 to 2
The mixed airflow of pulverized coal 5 and primary air 29 supplied at a flow rate of 0 m/s is swirled by swirling vanes 35, and as shown in the figure, pulverized powder is formed near the inner periphery of the tip of the primary sleeve 33. A region with high charcoal concentration (C/A) is formed.

In order to achieve stable ignition, it is necessary to set an appropriate C/A according to the amount of coal feed, as shown in FIG. In this embodiment, the pulverized coal concentration (C/A) is detected using the C/A detector 37, and the controller 40 determines the appropriate C/A based on the detection signal.
The opening degree of the swirling blade 35 is adjusted so that the angle becomes /A.

Note that too much rotation will increase the pressure loss, so C/
A ranges from 0.5 to 2.0, preferably 1.0 to 2.0
What is necessary is to adjust the relationship of the swirling vane 35 so that it is regulated within the range of .

Another factor for stable ignition and flame holding is the air flow rate. In this embodiment, as shown in FIG.
By providing the large diameter portion 41 at the tip of the next sleeve 33, the flow rate of 15 to 20 m/s described above can be reduced to 10 m/s.
It is slowed down below.

Furthermore, by colliding the mixed air flow with the flame holder 34, 41! A circular vortex flow 42 is formed.

The air flow velocity of this circulating vortex flow 42 is 5 m/s in feed value
Since the flow velocity is in the following low flow rate region, a region suitable for ignition and flame holding is formed. For this reason, a region optimal for direct ignition of pulverized coal with a high concentration of pulverized coal and a low flow rate is formed near the exit of the burner.

When the pulverized coal collides with the heating element 38 installed in this area and which generates heat to about 1000 to 1200°C,
The volatile content in the pulverized coal is continuously ignited and 2) forms a flame within the circulating vortex. Further, due to the propagation of this flame, the entire supplied pulverized coal is ignited.

Return to Figure 1 again! The system of baking equipment will be explained below. The exhaust gas introduced from the boiler smoke inlet gas conduit 43 is mixed with the air separated by the bag filter 9 at a predetermined ratio, and is introduced into the steam-type exhaust gas heater 45 by the exhaust gas forcing fan 44. The temperature is raised to a predetermined temperature by high pressure steam 46 from 1).

The exhaust gas whose temperature has been raised in this manner is transferred to the exhaust gas amount measuring device 4.
7, and then supplied to each start-up/low-load crusher 4, respectively.

Apart from the steam type exhaust gas heater 45, a hot air stove 48 is installed, and as fuel for this hot air stove 48, ultra-fine coal 49 with a very small particle size collected by the bag filter 9 is used. directly ignited.

Figure 11 shows the relationship between the particle size of pulverized coal and the ignition energy.As is clear from this figure, when the particle size of pulverized coal becomes ultra-fine coal with a particle size of 10 μm or less, the specific surface area increases and combustion Because the speed increases, it can be ignited with extremely low energy, so it is possible to directly burn ultra-pulverized coal 4G without using oil or gas.

As shown in FIG.
It is also being supplied to

Although not shown, a sensor such as a load cell is installed at the bottom of the bag filter 9 for IQ i'j' f+ , tt
The amount of ultra-fine coal 46 retained in the bag filter 9 can be detected. Then, the ultra-fine coal 46 is usually used for starting the boiler and for low loads.
When the temperature becomes H, the amount of ultra-pulverized coal 46 stored in the bag filter 9 is increased by supplying it to the hot-blast stove 48 or, conversely, by supplying 4G of ultra-pulverized coal to the hot-blast stove 48 for use. When the specified time is reached - ■ Start - Low load burner 30
It is also being supplied to

Coarse coal 2 in the load coal bunker 50 passes through the coal feeder 3, and is charged into each load crusher (for example, a crusher such as a ball mill) 51 to be crushed. This load crusher 51T: 'PiI crushed coal and adjusted to a predetermined particle size (pulverized coal may be crushed in the starting crusher 4 *The particle size may be slightly larger than that of the powder coal) is air-pulverized. It is air-transported while being dried with high-temperature air 52 whose temperature has been raised by a preheater (not shown), and directly introduced into the load main burner 53 for combustion.

When starting the boiler, when the load is low (approximately 10 to 30%) or when the load fluctuation rate is large, start up the required number of low-impact crushers 4 to generate pulverized coal 5 and ultra-fine coal.
16 is made and supplied to the startup/low load burner 30 to cope with boiler startup, low load or high load fluctuation rate, etc. In addition, when the load on the boiler is large or the load fluctuation rate is relatively small, the required number of load crushers 51 are driven to produce pulverized coal, and the load main burner 53 is
It is designed to respond to the required load by supplying it to the customer.

In addition, in a certain load range, the start-up/low-temperature burner 30 and the load main burner 53 can be used together as necessary.

〔Effect of the invention〕

This is because the present invention has the configuration as described above.

When the combustion equipment is started, when there is a low negative load, or when there are large load fluctuations, the highly responsive 141 storage system can be applied, and the solid fuel concentration can be maintained at a high level, eliminating the need for auxiliary combustion of oil and producing low NOx. Efficient combustion including oxidation can be performed. Furthermore, when the load on the combustion device is large and relatively stable, a direct connection system to the crusher can be applied, which does not cause troubles caused by IF storage of pulverized solid fuel, so the safety of the combustion device can be ensured.

Furthermore, when manufacturing the tm powder solid fuel to be supplied to the start-up/low load burner, the ultra-fine powder solid fuel produced is collected and used as fuel for the hot blast furnace. It has high usage efficiency and can reduce the amount of oil fuel used as fuel for the steam type gas heater. Furthermore, since ultrafine powder solid fuel has an extremely large specific surface area and a high combustion speed, it is possible to directly ignite the ultrafine powder solid fuel, which also reduces the amount of oil fuel used. .

[Brief explanation of the drawing]

The figures are all for explaining the combustion device according to the embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of the main parts of the combustion device;
Figures 2 and 3 are a plan view and a sectional view of the static eliminator, Figure 4 is a perspective view of another static eliminator, and Figures 5 and 6 are longitudinal sections showing the arrangement of cooling pipes in the bottle. Fig. 7 is an explanatory diagram of a natural circulation type cooling pipe, Fig. 8 is an explanatory diagram of a forced circulation type cooling pipe, Fig. 9 is a schematic configuration diagram of a start-up/low load burner, and Fig. 10 is an explanatory diagram of a natural circulation type cooling pipe. A characteristic diagram showing the ignition state of coal. FIG. 11 is a characteristic diagram showing the relationship between the particle size of pulverized coal and the ignition energy. 4...Start-up - low load crusher, 5...
Pulverized coal, 6...Cyclone separator 8...
...Bin, 9...Bag filter, 15...
...Cooling pipe, 30...Start-up - low load burner, 3
8...Heating element, 45...Steam exhaust gas heater, 48...Hot stove, 49...Ultra pulverized coal, 51...Load crusher, 53... Main burner for load. Figure 2 Figure 3 Figure 5 Figure 6 Figure 40 and 9 Figure 10 11 \ Amount A 2.00 1000 gold drops! B Capacity C 715 Te = 1\2/ Figure 11

Claims (6)

[Claims] (1) A first solid fuel pulverizing means that is driven during start-up and low load, and the solid fuel pulverized by the first solid fuel pulverizing means is entrained in high-temperature gas and transported by pneumatic flow to obtain a predetermined particle size distribution. separation means for separating the fine powder solid fuel having a particle size distribution from the ultra fine powder solid fuel having a particle size smaller than that of the fine powder solid fuel; and a first storage for storing the fine powder solid fuel having the predetermined particle size distribution. a second storage means for storing the ultrafine solid fuel; a start-up/low-load burner that pneumatically transports and burns the fine powder solid fuel taken out from the first storage means; a steam-type gas heater that sends high-temperature gas to the first solid fuel pulverizing means; and a hot air that combusts the ultrafine solid fuel stored in the second storage means and sends high-temperature gas to the first solid fuel pulverizing means. a furnace; a second solid fuel crushing means that is driven during normal load;
A combustion device comprising: a load main burner that pneumatically transports the pulverized solid fuel pulverized by the second solid fuel pulverizing means using high-temperature gas and directly combusts it. (2) A combustion device according to claim (1), characterized in that a cooling pipe is embedded within the solid fuel layer of the first storage means. (3) In claim (1), the start-up/low-load burner is provided with a heating element made of conductive ceramic, and the pulverized solid fuel supplied to the start-up/low-load burner is A combustion device characterized in that it is configured to be directly ignited by the heating element. (4) In claim (1), the mixture ratio C/A of solid fuel C and air A passing through the start-up/low load burner is regulated to a range of 0.5 to 2.0. A combustion device characterized by: (5) In the claim (1), ultrafine solid fuel conveyance supplies the ultrafine solid fuel stored in the second storage means to the start-up/low load burner. A combustion device characterized in that a passage is provided. (6) In claim (1), a sensor is provided to detect the amount of ultrafine solid fuel stored in the second storage means, and the detection signal is used to detect the A combustion device characterized in that it is configured to switch ultrafine solid fuel supplied to a start-up/low-load burner.