JPS63282423A - Ignition for burner - Google Patents

Abstract

PURPOSE:To prevent the generation of soot and improve the stability in the ignition by preheating coarse grained particle coal and igniting it in a preheated combustion chamber and injecting from a nozzle the combustion gas and char that are generated to make them contact with the fuel for a main burner. CONSTITUTION:Coarse grained coal used for an ignition burner is heated by a preheating device 3 and then sent to a preheating chamber 4, and there the coal is ignited by an ignitor 5 and burns. The combustion gas and char are injected from an ignition burner nozzle 22 toward the fuel 6 for a main burner to ignite the main burner 21. At this time in the preheating chamber 4, the volatile matters in the coal particles are released completely, but because the flame is short the flame is not rapidly cooled by the combustion of the volatile matter, and it is possible to prevent the generation of soot in the preheating chamber. By using coarse grained coal with diameter in 100 mum-300 mum, the inertia moment from the ignition burner nozzle 22 is increased and the flame is not subject to the effects of the combustion air for the main burner, and the combustion gas and char of the ignition burner are brought to the contact reaction with the fuel 6 for the main burner for sure and the main burner can be ignited positively.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses a pulverized coal fuel suitable for stabilizing the ignition of the main burner, particularly at the burner point of a pulverized coal-fired boiler combustion device. This relates to the burner ignition method used.

[Conventional technology]

In recent years, the demand for pulverized coal-fired boilers has increased rapidly due to the rise in oil fuel prices and price instability.

In this pulverized coal-fired boiler, in addition to coal as the main fuel, light oil is generally used as an auxiliary fuel during ignition, and heavy oil is used during startup.

By the way, recent characteristics of electricity demand are that, along with the growth in nuclear power generation, the difference between the maximum and minimum loads has increased, and thermal power generation has tended to shift from base load to load adjustment; When operated for commercial purposes, the boiler is not always operated at full load, but is often operated at variable loads such as 75% load, 50% load, and 25% load depending on the power demand. In addition, operation is stopped at night and on weekends, so-called daily start-up and shutdown (Da
ily 5tart 3top: DSS) operation, and weekend start/stop (Weekffy 5tart 3top: DSS) operation.
5top: WSS) intermediate load operation is also increasing.

FIG. 3 is a diagram showing a system of such a conventional pulverized coal-fired boiler device. This device includes an oil system consisting of a heavy oil tank 26, a plurality of main burners 21 each connected to the heavy oil tank 26 by oil pipes 27, a raw coal storage bin 14, and a feeder 15 connected to the raw coal storage bin 14. A fine powder comprising a mill 16 connected via a mill 16, a particle classifier 17 provided at the top of the mill 16, and a pulverized coal transport pipe 20 connecting the particle classifier 17 and the plurality of main burners 21. It is mainly composed of the charcoal system. Note that 28 is an oil pump, 19 is a particle conveying air 6, 18 is a particle conveying air fan, and 31 is a furnace.

In such a configuration, when the boiler is started, heavy oil in the heavy oil tank 26 is sent to the main burner 21 via the oil pipe 27 by the oil pump 28, and is ignited and burned by an ignition burner (not shown). After the heavy oil in the main burner is ignited, the boiler load is increased to about 30%,
By increasing the temperature inside the furnace 31 and exchanging heat between exhaust gas and air using an air heater (not shown), air for drying and conveying pulverized coal at a temperature of approximately 200 to 250°C is obtained. After this air is supplied to the mill 16, the mill 16 is operated, and the pulverized coal that has been crushed and dried here is supplied to the main burner 21 through the pulverized coal transport pipe 20, and pulverized coal combustion is started. .

When pulverized coal is added to switch from heavy oil combustion to pulverized coal combustion, the starting burner is always ignited by heavy oil as described above, so there is no ignition delay or increase in unburned content due to pulverized coal injection.

FIG. 4 is a diagram showing the configuration of a pulverized coal burner, which is a conventional main burner. This burner has a central nozzle 32 of the burner.
and an oil-activated burner 24 inserted into the central nozzle 32.
and a sleeve 33 provided concentrically around the center nozzle 32 and through which the secondary air 8 passes. In addition, 6 is the fuel for the main burner, 7 is the air register, 23
is a combustion air wind box, 22 is an ignition burner nozzle, 25 is a flame detector, 31 is a furnace, 30 is a light oil tank,
28 is an oil pump. In such a configuration, in a cold start, first, the oil pump 28 is connected from the light oil tank 30.
An ignition burner, not shown, fueled by light oil delivered by the ignition burner is ignited by an igniter, also not shown, and then an oil-started burner 24 is ignited by the nozzle 22 of said ignition burner. After the oil-started burner is ignited in this way, as described above, after increasing the boiler load, pulverized coal is introduced as the main burner fuel 6 and the combustion is switched to pulverized coal combustion.

Research is being actively conducted to reduce the amount of oil consumed during ignition and startup in the coal-fired boiler, and one method is to switch from conventional oil to coal as the burner fuel during ignition and startup. Attempts have been made, including (1) a method of ultra-finely pulverizing the fuel used;
) Method of preheating and supplying pulverized coal fuel, (3) Fuel ratio (
Methods of using coal with a low FR) are being considered.

[Problem that the invention seeks to solve]

However, compared to the conventional coal-fired boiler, which uses oil as the main fuel,
Although the ratio of oil consumed is decreasing, the ratio of auxiliary fuel cost to main fuel cost is high, and the ratio of auxiliary fuel cost is extremely high, especially for boilers operated with intermediate loads where ignition and startup are frequent. There is.

In addition, the method of igniting using only pulverized coal has a significant ignition delay of the coal particles, resulting in a sudden pressure rise inside the furnace and the discharge of unburned matter, especially light vapor-phase precipitated carbon, out of the furnace. There are problems and it is difficult to apply it to actual machines.

An object of the present invention is to provide a method for increasing the burner point, which can solve the problems of the prior art described above, prevent misfires in an ignition burner containing pulverized coal, and improve ignition stability.

[Means for solving problems]

In order to achieve the above object, the present invention provides a burner ignition method for igniting a main burner with an ignition burner using pulverized coal fuel, in which coarse coal having a particle size of 100 μm or more is used as the pulverized coal fuel; After preheating the charcoal, it is ignited in a pre-combustion chamber, and the combustion gas and char generated at this time are injected from the nozzle of the ignition burner and brought into contact with the fuel of the main burner.

[Effect]

Ignition of coal powder occurs when the amount of heat generated by the chemical reaction of the particles exceeds the amount of heat dissipated by radiation and heat conduction from the particle surface.If the particle size is too small, heat transfer loss becomes large and ignition becomes impossible. On the other hand, if the particle size is too large, the specific surface area of the particles becomes small, making it difficult for chemical reactions to proceed (
This makes it difficult to ignite.

Figure 6 is a diagram showing the relationship between the particle size of coal powder and the ignition temperature.
It has been shown that coarse coal of 130 to 300 μm has the same ignition characteristics as fine coal of 130 μm or less. The present invention has the same ignition characteristics as granulated coal, and when injected from a nozzle as high-temperature carbon particles (hereinafter referred to as char), has a moment of inertia greater than that of granulated coal, and is blown away by the combustion air of the main burner. Coarse grain coal of 100 to 300 μm, which is difficult to burn, is used as fuel for the ignition burner. Particle size is 100μ
If it is less than m, it will be easily blown away by the combustion air and ignition will become unstable.

Incidentally, as is unique to solid fuels, the temperature of char during the combustion process of coal powder is higher than the temperature of the surrounding combustion gas, and the temperature varies depending on the particle size of the coal powder.

FIG. 7 is a diagram showing changes over time in cha temperature according to particle size during the combustion process of coal powder. In the figure, 100 to 1
50mesh (105-149μm) coarse particles are 27
It can be seen that the temperature is higher than that of fine particles of 0 to 325 mesh (44 to 53 μm). The present invention ignites the cough main burner by bringing this coarse particle char, which has a high surface temperature, into contact with the main burner fuel together with the combustion gas.

As the coarse coal used in the present invention, high fuel ratio coal having a fuel ratio (FR) of 2 or more is preferable. FIG. 5 is a diagram showing the relationship between the primary air temperature (m feeding air temperature) and the amount of unburned matter in the ash immediately after ignition for low fuel ratio coal and high fuel ratio coal. In the figure, high fuel ratio coal has a smaller amount of unburned matter in the ash than low fuel ratio coal, and this tendency becomes more pronounced as the secondary air temperature increases. When igniting at a low ambient temperature, the flame is rapidly cooled after ignition and a large amount of soot is generated, so low fuel ratio coal with a high volatile content is more likely to generate soot and the amount of unburned matter in the ash will be larger. When relatively high fuel ratio coal is used, the flame will be short because there is less volatile matter in the fuel.
The amount of heat generated by the combustion of volatile components of fuel particles inside the pre-combustion chamber is small, so excessively high temperatures do not occur, and carbon formation during vapor phase extraction can be reduced.

Further, in the present invention, in order to improve the ignition stability of the main burner and to easily blow out char from the ignition burner nozzle 22, the ignition burner nozzle 22 and the main burner 21 are preferably formed at an angle of 10 degrees or more. , the ignition burner nozzle 22 is preferably arranged above the main burner 21.

According to the present invention, by preheating the coarse coal and then igniting it in the pre-combustion chamber, it is possible to suppress the generation of soot and reduce the amount of unburned matter. Furthermore, by injecting the high-temperature combustion gas generated in the pre-combustion chamber and the coarse char into the fuel of the main burner, a relatively large moment of inertia acts on the coarse char, unlike in the case of granulated coal. , the ignition stability is improved because it is no longer blown away by the combustion air of the main burner.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is an explanatory diagram of a burner ignition method using a pulverized coal ignition burner showing one embodiment of the present invention. Of the symbols used in FIG. 1, those that are the same as those in FIG. 4 have the same structure and function, so their explanation will be omitted. The ignition burner shown in the figure includes a preheating device 3, a precombustion chamber 4 having an igniter 5 connected to the preheating device 3, and an ignition burner nozzle 22 extending from the tip of the precombustion chamber 4 to the tip of the main burner 21. Ten is primarily accomplished from this. In addition, 1 is a coarse coal storage bin, 2
6 is the main burner fuel, and θ indicates the angle between the ignition burner nozzle 22 and the flow of the main burner fuel 6. In such a configuration, the coarse coal for the ignition burner is sent from the coarse coal storage bin 1 to the preheating device 3 by the feeding air 2, and after being heated to 70 to 200 ° C. in the preheating device 3, The fuel is sent to the pre-combustion chamber 4, where it is ignited by the igniter 5 and combusted.

The combustion gas and char in the pre-combustion chamber 4 are injected from the ignition burner nozzle 22 toward the main burner fuel 6, and the main burner 21 is ignited.

FIG. 2 is a longitudinal sectional view of the pre-combustion chamber 4.

This pre-combustion chamber 4 is made of ceramics 13, and is provided with a pulverized coal swirler 9 and an igniter 5 on its inlet side. Note that 12 is a heating device, 10 is a volatile combustion zone,
11 is a char combustion area.

The coarse coal fuel 29 for the ignition burner is swirled in the pre-combustion chamber 4 and then charged into the furnace. The fuel particles introduced into the furnace flow along the furnace wall, are ignited by the igniter 5, and then continue to stably burn along the furnace wall, which has been preheated by an external heating device 12.

At this time, the combustion inside the pre-combustion chamber 4 is divided into a volatile matter combustion zone 10 due to the volatile matter released from the coal particles and a char combustion zone 11, but both the high-temperature combustion gas and the red-hot char exit the pre-combustion chamber 4. After that, it is accelerated by the ignition burner nozzle 22,
The fuel is injected toward the main burner fuel 6 and the main burner 21 is ignited.

According to this embodiment, the volatile content of the coal particles is completely released inside the pre-combustion chamber 4, but since the flame is short, the flame is not rapidly cooled due to combustion of the volatile content, and the pre-combustion chamber 4
The generation of soot can be prevented. Also 100-3
By using 00μm coarse grain coal, the moment of inertia from the ignition burner nozzle 22 is increased, so the combustion gas and char of the ignition burner are reliably transferred to the main burner fuel without being affected by the combustion air for the main burner. can be reacted by contact. Furthermore, since coal is used instead of oil as the ignition and starting fuel, running costs can be reduced, and auxiliary fuel costs can be significantly reduced, especially for boilers operated with intermediate loads. Furthermore, according to this embodiment, since the conventional oil supply system is not required, it is possible to reduce the initial cost and realize coal-only combustion in the industrial boiler.

〔Effect of the invention〕

According to the present invention, after preheating coarse grain coal of 100 to 300 μm, it is ignited in the pre-combustion chamber and the high-temperature combustion gas and char are brought into contact with the main burner fuel, thereby suppressing soot generation and stabilizing ignition. can improve sex. Furthermore, since the boiler can be used to exclusively burn coal, fuel costs can be reduced, especially in boiler combustion equipment operated with intermediate loads.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the burner ignition method according to the present invention, and FIG.
The figure shows a cross section of the pre-combustion chamber of the ignition burner used in the present invention, Figure 3 shows the system of a pulverized coal-fired boiler according to the prior art, and Figure 4 shows the structure of a conventional pulverized coal burner. Figure 5 is a diagram showing the relationship between the conveying air temperature (-air temperature) of coal powder and the amount of unburned matter in combustion ash, and Figure 6 is a diagram showing the relationship between the particle size of coal powder and the ignition temperature. FIG. 7 is a diagram showing the change over time between char and particle temperature according to particle size. 1... Coarse coal storage bin, 2... Conveying air, 3...
Preheating device, 4... Precombustion chamber, 5... Igniter, 2
2...Ignition burner nozzle. Agent Patent Attorney Takeshi Kawakita 6: Main burner fuel 7: Air register 8: Secondary air 14: Raw coal storage bin 15: Feeder 16: Mill 17: Powder classifier 18: Particle conveying air fan 19: Particles Conveying air 20: Pulverized coal transport pipe 21: Main burner 22: Ignition burner nozzle 23: Wind box 24: Oil starting burner 25 = Flame detector 26: Heavy oil tank 27 = Oil piping 28 = Oil pump 30: Light oil tank 31: Furnace 32 : Center nozzle 33 sleeve Fig. 3 Fig. 4 1A -

Claims (3)

[Claims] (1) In a burner ignition method in which the main burner is ignited by an ignition burner using pulverized coal fuel, coarse granulated coal with a particle size of 100 μm or more is used as the pulverized coal fuel, and after preheating the coarse granulated coal, A burner ignition method characterized in that the combustion gas and char generated at this time are injected from a nozzle of the ignition burner and brought into contact with the fuel of the main burner. (2) The burner ignition method according to claim 1, characterized in that the combustion gas and char are injected from above the main burner at an angle of at least 10° with respect to the main burner. (3) A burner ignition method according to claim 1 or 2, characterized in that the main burner is ignited using a pre-combustion chamber having a fireproof and heat-insulating structure and an ignition burner nozzle.