JP2001082704A - Device and method for burning solid waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion device to completely decompose dioxin generated due to combustion of RDF(refure derived fuel), minimize dropping of an RDF component to a furnace bottom, and besides perform uniform combustion of the RDF. SOLUTION: By using a combustion device formed such that mixture fluid of fuel and air is fed to a burner 4 and combustion air to completely burn incomplete combustion gas of fuel by the burner 4 is charged through an air charge port 13 for two-stage combustion, crushed RDF(refure derived fuel) is fed to an air charge port 13 for two-stage combustion by air 26 for conveyance. Since the RDF charged in a furnace 5 through the air charge port 13 is burnt at a combustion temperature high enough to decompose dioxin, no dioxin is discharged to the outside of a system. Since the height level of the air charge port 13 is a region where the ascending flow speed of combustion gas in the furnace 5 is highest, a ratio of the crushed RDF falling on a furnace bottom is decreased to the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for burning solid waste fuel (RDF) and a method for burning the same, and in particular, to a combustion facility such as a boiler capable of burning solid waste fuel with high efficiency and low pollution. About.

[0002]

2. Description of the Related Art With the increase in the amount of urban refuse generated, the development of a treatment method has become a major issue. As one garbage disposal method, garbage is treated as RDF with a predetermined treatment.
There is a movement to utilize it for energy reuse. Since the RDF is formed into a mass of the order of centimeters,
In many cases, a means is used which is incinerated exclusively in a small fluidized bed combustion furnace and a part of the combustion energy is recovered as steam or electricity.

[0003] Examples of the properties of RDF are shown in Table 1. As shown in Table 1, RDF has a high volatile content, and has high ignitability and combustibility. However, since RDF has a high chlorine content, it is necessary to pay attention to generation of dioxin and corrosion of heat transfer tubes.

[0004]

[Table 1]

[0005]

SUMMARY OF THE INVENTION RDF in a small combustion furnace
There is a fundamental problem that needs to be improved in the following points. a) Since the combustion temperature is low, there is a limit in controlling the amount of dioxin generated when burning RDF containing a large amount of chlorine. b) The steam generation method using a small combustion furnace is disadvantageous in terms of economic operation because the generated steam temperature and pressure are low and the thermal efficiency is low, and the amount of CO ₂ generated per recovered energy is large, which causes environmental degradation. Also.

[0006] As a means for burning RDF in a large-sized combustion device, there is a method in which coal or the like is used as a main fuel and mixed therewith. However, this method has the following technical problems. a) When the method of supplying RDF together with coal to the coal pulverizer and pulverizing it is used, RDF has an adhesive property and cannot be easily pulverized by the pulverizer. Increases the risk of spontaneous ignition and explosion due to the properties of the minute.

[0007] b) In order to solve the above problem, it is conceivable to inject RDF pulverized to a predetermined fineness into a fine powder solid fuel supply channel. However, since RDF is sticky, RDF is crushed. There is a limit to reducing the particle size.
Therefore, when the RDF is charged into the furnace from the burner region where the rising gas flow rate in the furnace is low, the RDF particles fall to the furnace bottom. The unburned matter in the falling object at the bottom of the furnace sinks into a water seal section provided at the lower part of the furnace bottom or accumulates on the ash conveyor section. At this time, for example, particles that have fallen from a region of about 400 to 500 ° C. in the burner region to a region of 300 ° C. at the furnace bottom entrance have a high possibility of generating dioxin, and become water in the water seal portion and ash on the ash conveyor. It is more likely to be present in wastewater and waste, and does not lead to environmental improvements.

[0008] RDF together with the main fuel from the upper burner of the furnace equipped with the multi-stage burner, where the gas flow rate in the furnace is relatively high
The problem of b) above is alleviated by charging the furnace into the furnace, but the burner stage varies depending on the operation.
If the burner stage of the DF is fixed, there is a restriction on the furnace operation. In order to eliminate the restrictions on the operation, it is also possible to connect RDF supply pipes to all the burners and to switch the burners for supplying the RDF in accordance with the operation. However, when the RDF is supplied to the lower burner in such a configuration, the above-described problem of the RDF particles falling to the furnace bottom occurs.

Further, when the method of supplying RDF to a specific burner is used, the main fuel such as coal and RDF are not uniformly mixed in the furnace, so that the combustion gas locally has a high chlorine concentration. It causes corrosion of the heat transfer tube for heat recovery to increase.

[0010] An object of the present invention is to completely decompose dioxin generated by the combustion of RDF, minimize the drop of RDF components to the furnace bottom, and uniformly burn RDF. It is an object of the present invention to provide an RDF combustion apparatus and an RDF two-stage combustion method.

[0011]

SUMMARY OF THE INVENTION The above-mentioned object of the present invention is as follows.
A furnace, a burner provided with a mixed fluid of solid fuel such as pulverized coal and combustion air provided on the furnace wall, and complete combustion of incomplete combustion gas of fuel supplied into the furnace from the burner Crushed in a two-stage combustion air flow path for supplying combustion air and a two-stage combustion combustion device provided with a two-stage combustion air inlet from the two-stage combustion air flow path provided in the furnace wall. The problem can be solved by an RDF combustion device in which a gas transfer passage for transferring RDF by gas is connected to a two-stage combustion air inlet.

The crushed RDF gas transport passage is connected to the two-stage combustion air passage to mix the crushed RDF with the two-stage combustion air and then transported to the furnace outlet, or the RDF gas transport flow. An outlet of the passage is provided at the two-stage combustion air inlet, and the crushed RDF is introduced into the furnace together with the two-stage combustion air supplied from around the carrier gas.

[0013]

A) As shown in FIG. 4, the combustion temperature of the RDF such as municipal waste is increased by a two-stage combustion combustion device to a high enough combustion temperature to decompose dioxin, so that dioxin is discharged out of the system. It is effective in preventing. b) As shown in FIG. 4, the position of the height at which the two-stage combustion air inlet of the two-stage combustion combustion device is arranged is the position where the rising flow velocity of the combustion gas in the furnace of the combustion device is the highest. Therefore, the ratio of the crushed RDF falling to the furnace bottom can be minimized. c) In general, the two-stage combustion air introduced into the two-stage combustion combustion device is always supplied while the furnace is in operation, and there is no restriction on the operation of RDF combustion. d) Since the combustion device for two-stage combustion is designed so that the air for two-stage combustion supplied into the furnace is uniformly mixed with the combustion gas rising from the burner, the combustion gas generated from the RDF is also reduced. The uniform distribution in the furnace also solves the problem of heat transfer tube corrosion due to localized high concentrations of chlorine in the combustion gases.

[0014]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example in which the distorted RDF is supplied from the two-stage combustion air inlet 13 into the furnace 5 through the gas passage for the two-stage combustion air supply of the pulverized coal-fired boiler. The pulverized coal, which is the main fuel, is pulverized by the mill 3, guided to the burner 4 and charged into the furnace 5. The primary air for fuel transport is supplied from the primary air fan (PAF) 1 through the air preheater 2 to the burner 4 together with the pulverized coal in the mill 3, and the two-stage combustion air is supplied to the forced air fan (FDF) 6.
Through the air preheater 2 and the wind path 7, a part of which is supplied to the furnace 5 from a burner wind box 9 and the rest from a two-stage combustion wind box 12. The supply amount of the two-stage combustion air is adjusted by dampers 8 and 11 provided in the wind path 7 and sent to the wind boxes 9 and 12, respectively.

The RDF is supplied from a RDF lump storage bunker 21 to a crusher 23 by a supply device 22 and is broken into a predetermined particle size, and then temporarily stored in an RDF particle storage bunker 24. The feeder 22 and the crusher 23 are used for the RDF grain storage bunker 2.
The operation is performed continuously or batchwise so that level 4 is within a predetermined range. The RDF particles in the RDF particle storage bunker 24 are guided from the metering device 25 to the two-stage combustion air path 7 by the conveying air 26, mixed with the two-stage combustion air, and then passed through the two-stage combustion wind box 12. From the stage combustion air inlet 13 to the furnace 5
It is thrown into.

In the pulverized coal-fired boiler shown in FIG.
The transport air temperature before and after mixing with the two-stage combustion air must be lower than the RDF ignition temperature so that the particles do not ignite during transportation, and the flow velocity and structural surface must be such that the RDF particles do not accumulate on the wind path 7 or wind box 12. Consideration is necessary.

FIG. 2 shows an example in which the crushed RDF is supplied from the two-stage combustion air inlet 13 into the furnace 5 through the air transfer passage 27 dedicated to the RDF transfer of the pulverized coal-fired boiler. In the combustion system of the pulverized coal-fired boiler shown in FIG. 2, the same devices and members as those shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

In the pulverized coal-fired boiler shown in FIG. 2, instead of guiding the same RDF particles as those shown in FIG. Directly lead to combustion air inlet 13, RD
It is thrown into the furnace 5 from the F inlet 27.

In this embodiment, it is possible to prevent the RDF from accumulating in the flow path only by controlling the temperature of the conveying air.
The wind box 12 can apply the design concept of the prior art. Also,
This example can be easily applied simply by modifying not only a new boiler but also a conventional pulverized coal-fired boiler.

FIG. 3 shows a structural example around the two-stage combustion air inlet 13 applied to the boiler of FIG. In this example, the two-stage combustion air is supplied to the furnace 5 in the wind box 12 while being divided into outer air and inner air. The RDF inlet 27 is provided at the center of the inner peripheral air flow path 14, and the RDF particles are charged into the furnace 5 while being surrounded by the two-stage combustion air. In the example shown in FIG. 3, an air swirler 16 is provided in the outer peripheral air passage 15.

In the embodiment shown in FIGS. 1 to 3 described above, the advantage of supplying RDF from the two-stage combustion air inlet 13 will be further described.

In the two-stage combustion method, combustion air is supplied to the burner 4 and the downstream two-stage combustion air inlet 13 for low NOx combustion.
And burner 4 and combustion air inlet 13
This is a method for burning the fuel to be charged into the furnace 5 from. At this time, in order to completely burn the unburned gas rising from the burner 4, the two-stage combustion air introduced into the furnace 5 from the combustion air inlet 13 is designed optimally in its flow rate and injection position. You. As a result, the two-stage combustion air has a uniform distribution at the outlet of the furnace 5.

By placing the RDF in the flow of the air for two-stage combustion and putting it into the furnace 5, the RDF can also have a uniform distribution in the furnace 5. In addition, since a sufficient distance from the two-stage combustion air inlet 13 to the outlet of the furnace 5 is secured for the least combustible coal among the planned coals, the ignition temperature is as low as 200 ° C. Excellent R
For complete combustion of the DF, the two-stage combustion air inlet 13
The length from to the exit of the furnace 5 is a sufficient length.

Here, the planned coal will be described. In order to stably supply coal as fuel for the boiler used,
We use coal imported from multiple coal-producing countries and mines,
Since there is a difference in flammability due to the difference in the properties of coal, if the difference is large, the desired performance cannot be obtained with the boiler to be used, so a trial run is performed in advance, and a combustion test of a plurality of coal types is performed. Confirm that the required performance is met. The “plural coal types” are “planned coals” that are planned to be used in advance.

[0025]

According to the present invention, the RDF particles are uniformly supplied to the region where the ascending gas flow rate is high at a high temperature, so that the dioxin generated by the combustion of the RDF is completely decomposed, and the dioxin is discharged outside the system. It is possible to prevent discharge, further minimize the fall of the RDF to the furnace bottom, and uniformly burn the RDF.

[Brief description of the drawings]

FIG. 1 is a diagram showing a solid waste combustion apparatus according to an embodiment of the present invention. Is shown.

FIG. 2 is a diagram showing a solid waste combustion apparatus according to an embodiment of the present invention.

FIG. 3 is a structure around a two-stage combustion air inlet of the combustion apparatus of FIG. 2;

FIG. 4 is a diagram showing an example of a gas temperature and a rising gas flow rate in a furnace in a two-stage combustion type boiler.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Primary air fan 2 Air preheater 3 Mill 4 Burner 5 Furnace 6 Push-in air fan 7 Airway 8 Burner air damper 9 Burner wind box 11 Two-stage combustion air damper 12 Two-stage combustion wind box 13 Two-stage combustion Air inlet 14 Inner air passage 15 Outer air passage 16 Outer air swirler 21 RDF lump storage bunker 22 Feeder 23 Crusher 24 RDF particle storage bunker 25 Metering and feeding device 26 Transport air 27 RDF inlet

Continued on the front page (72) Inventor Shunichi Tsumura 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside Babcock Hitachi Kure Factory (72) Inventor Koji Masura 6-9 Takaramachi Kure City, Hiroshima Prefecture Inside Babcock Hitachi Kure Factory (72) Inventor Takehiro Kobayashi Inside Babcock Hitachi, Ltd. 2-4-1 Hamamatsucho, Minato-ku, Tokyo (72) Inventor Toshikazu Nakajima 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Co., Ltd. F Term (reference) 3K046 AA01 AA20 AB03 AC06 BA01 BA04 BA05 FA06

Claims (6)

[Claims] 1. A furnace, a burner provided on the furnace wall to which a mixed fluid of solid fuel and combustion air is supplied, and complete combustion of incomplete combustion gas of fuel supplied from the burner into the furnace. Crushed solid waste in a combustion device equipped with a two-stage combustion air flow path for supplying combustion air for blasting and a two-stage combustion air inlet from the two-stage combustion air flow channel provided on the furnace wall An apparatus for combusting solid waste, wherein a gas transport passage for transporting waste fuel by gas is connected to a two-stage combustion air inlet portion. 2. A gas conveying passage for crushed solid waste fuel is connected to a two-stage combustion air inlet through a two-stage combustion air passage. Solid waste combustion equipment. 3. The solid waste combustion apparatus according to claim 1, wherein an outlet of a gas transfer passage for the crushed solid waste fuel is provided at a two-stage combustion air inlet. 4. A solid waste fuel, characterized in that crushed solid waste fuel is introduced into a furnace from a two-stage combustion air inlet using the solid waste combustion apparatus according to claim 1. Burning method. 5. The crushed solid waste fuel is transported to a two-stage combustion air supply channel by a carrier gas, mixed with the two-stage combustion air, and then supplied to a furnace. A method for burning a solid waste fuel according to the above. 6. The crushed solid waste fuel is transported to a two-stage combustion air inlet with a carrier gas, and is introduced into the furnace together with the two-stage combustion air supplied from around the carrier gas. The method for burning solid waste fuel according to claim 4, wherein: