JP2002228130A - Combustion furnace or incinerator, and method for reducing discharge of regulated gas content of the furnaces - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve the burden of an exhaust gas treating system and to reduce the size of a boiler by directly suppressing the generation of dioxin and NOx by directly burning exhaust gas discharged from a furnace outlet. SOLUTION: An air area is formed on the furnace outlet side of a combustion furnace or an incinerator. Assisting fuel is blown in the air area so as to use low oxygen concentration high temperature exhaust gas discharged from the furnace as combustion air that is combustible. The air area is formed right before a boiler mounting position on the surface outlet side or in a boiler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion furnace or an incinerator using high-temperature air and a method for reducing the emission control of these furnaces. The present invention relates to a method and apparatus for controlling combustion in a waste incinerator that reduces the concentration of exhaust gas such as dioxin.

[0002]

2. Description of the Related Art Conventionally, in waste incineration stoker furnaces and fluidized bed furnaces, there is a temperature distribution in the secondary combustion part, so DXNs are not decomposed in relatively low temperature parts, and thermal NOx is generated in high temperature parts. Gas is generated, and its removal is an important issue. These harmful gases are mainly removed by an exhaust gas treatment system (especially a reaction bag filter) provided in the outlet path of the furnace.

Further, the exhaust gas from the furnace outlet has a high temperature of 800 ° C. or more, while the heat resistance temperature of the bag filter is 250 ° C.
Therefore, the hot gas from the furnace outlet must be cooled to 250 ° C. or lower while passing through a boiler or a cooler and introduced into the reaction bag filter, during which dioxin resynthesis occurs. .

[0004]

SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, the present invention does not remove dioxin in an exhaust gas treatment system provided in an outlet path of a furnace, but directly removes exhaust gas discharged from the outlet of the furnace. Combustion furnaces or incinerators capable of directly suppressing the generation of dioxins and NOx by burning, thereby reducing the burden and reducing the size of the exhaust gas treatment system provided at the outlet path of the furnace, and It is an object of the present invention to provide a method for reducing exhaust gas regulations of furnaces. Another object of the present invention is to make effective use of waste heat at the furnace outlet side up to the limit.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention blows auxiliary fuel into an air space provided on the furnace outlet side of a combustion furnace or an incinerator, and discharges high-temperature exhaust gas having a low oxygen concentration discharged from the furnace. As combustion air. In this case, the combustion furnace includes a combustion boiler for burning coal, and the incinerator includes a waste incinerator such as a stoker or a fluidized bed.

According to this invention, the auxiliary fuel supplied to the furnace outlet side air space is burned by the high-temperature low-oxygen-concentration air, so that a uniform temperature field is formed. As a result, undecomposed D
Decomposition of XNs becomes possible. Also, due to slow combustion, N
Ox can be reduced. Further, in this method, the high-temperature air generator itself required for the conventional high-temperature air combustion can be omitted.

In order to effectively reduce dioxins and NOx, the high-temperature exhaust gas preferably has a temperature of 800 ° C. or more and an oxygen concentration of about 5 to 11%. However, dioxin is not decomposed at 800 ° C. or lower, and NOx cannot be reduced at an oxygen concentration of 11% or more. Further, if the oxygen concentration is about 5% or less, combustion does not occur even if the auxiliary combustion amount is supplied.

The process leading to the present invention will be specifically described.
Exhaust gas obtained from the furnace outlet side has reduced oxygen concentration in the furnace due to primary combustion and secondary combustion (free board), but since the exhaust gas is at a high temperature, the oxygen concentration is extremely diluted. However, combustion stability is not impaired, and it can be expected that the highest combustion temperature, which is a cause of NOx generation, will be lowered by dilution. Such high-temperature rare-burn combustion reduces the local high-temperature region and enables the formation of a uniform combustion temperature field, thereby realizing a low NOx reduction. In addition, the formation of a combustion field at a temperature of 800 ° C. or higher reduces dioxin. Is also possible. According to the experimental results of the inventor, as shown in FIG. 2, the temperature was 900 to 1200 ° C. and the oxygen concentration was 5 to 5.
It has been found that ~ 11% is preferred.

The invention according to claim 3 relates to an apparatus for effectively carrying out the invention, wherein an air space is provided on the furnace outlet side of a combustion furnace or an incinerator, auxiliary fuel is blown into the air space, and discharged from the furnace. The high-temperature exhaust gas having a low oxygen concentration is used as combustion air to be combustible. In this case, the air space is preferably an air space formed on the furnace outlet side through a partition or a throttle. However, simply supplying the auxiliary combustion amount on the passage does not result in smooth combustion due to lack of oxygen. Therefore, it is preferable that the high-temperature gas is retained at the furnace outlet side via a partition or a throttle and the retained air region is formed in which smooth combustion is formed.

Further, the air space is provided immediately before the boiler mounting position on the furnace outlet side or in the boiler so that the combustion can be utilized for heat absorption of the boiler, so that the boiler functions as a combustion boiler instead of a conventional waste heat boiler. In addition, higher temperature steam is preferably obtained. Further, in the present invention, since the heat flux increases, the boiler can be made compact.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples. FIG. 1 shows a schematic configuration of a stoker-type incinerator according to an embodiment of the present invention, and 11 is a chute (hopper) into which garbage is put.
Although not shown, a feeder is disposed below the chute 1 as a device for quantitatively supplying dust. Reference numeral 2 denotes a stoker, for example, a drying stoker, a burning stoker, and further a burning stoker are sequentially arranged as the garbage enters from the feeder to a later stage, so that the primary air 3 can be introduced from below. Further, an ash removing device 8 such as an ash chute is provided on the back side. Above the stoker 2, a reburning chamber 4 extending upward is provided. The furnace wall on the chute 1 input side (front side) on the inlet side (lower side) of the combustion chamber 4 faces the furnace wall. OFA nozzles (also referred to as overfire air nozzles or secondary air supply nozzles) 14 and 15 are provided on the furnace wall on the ash removal device side (rear side), respectively, and secondary air is supplied to the nozzles 14 and 15. Is controlled by dampers (not shown) provided in the air supply passages. A boiler installation space 5 is formed on the furnace outlet side. The lower side of the boiler installation space 5 is partitioned by the furnace wall 51 on the inlet side, and the outlet side is narrowed by the passage 5b, so that the exhaust gas circulates while staying in the lower space.

An auxiliary fuel supply nozzle 12 is provided at the top of the boiler installation space 5 on the inlet side, and blows the auxiliary fuel toward the lower space where high-temperature exhaust gas stays. A boiler 5a composed of a water pipe structure is attached to the inner wall of the boiler installation space 5. On the outlet passage 5b side of the boiler installation space 5, a cooling tower 7, a reaction dust collector 8 such as a bag filter, an induction ventilator 9, and a chimney 10 are provided in a known manner.

The method of burning waste in such an incinerator will be described below. The refuse introduced into the chutes 11 is quantitatively supplied onto the stoker 3 by a feeder (not shown), and is supplied from below each stoker 2 while being conveyed on the stoker 2 toward the ash chute 18 side. After being sequentially dried, gasified, flame-fired, and ignited by the air 3, the ash after the combustion falls to the ash removal device 8 such as an ash chute. On the other hand, unburned components such as CmHn generated by drying / combustion of the stoker 2 are supplied to the secondary air (from the OFA front side nozzle 14 and the OFA rear side nozzle 15 on the inlet side (lower side) of the reburning chamber 4. Overfire air,
(Hereinafter referred to as OFA).

The exhaust gas, which has become hot and oxygen deficient due to the combustion of the secondary air, is introduced into the boiler installation space 5 from the furnace outlet side, while an auxiliary fuel supply nozzle arranged at the top of the inlet of the boiler installation space 5 From 12, the auxiliary combustion amount is supplied into the boiler installation space 5, and the fuel is burned by exhaust gas composed of high-temperature, low-oxygen-concentration air, so that the local high-temperature region is reduced to form a uniform temperature field. As a result, undecomposed DXNs can be decomposed. Further, NOx can be reduced by slow combustion.

FIG. 2 shows the experimental results based on the present embodiment, in which the oxygen concentration of the primary air supplied from below the stoker is changed to 21-30% oxygen-enriched side, while the temperature is between normal temperature and 200 ° C. Make it variable. Secondary air has an oxygen concentration of 2
The oxygen deficiency is varied from 1 to 8%, while the temperature is varied from room temperature to 600 ° C. In this way, various exhaust gas states having a furnace outlet temperature of 300 to 1200 ° C. and an oxygen concentration of 5 to 21% were generated. Then, in this state, the auxiliary fuel supply nozzle 12 supplied an auxiliary combustion amount of propane gas into the boiler installation space 5 to grasp the combustion state as shown in FIG.

As is apparent from the figure, in the low oxygen region below 800 ° C., a non-combustible region is formed, and the oxygen concentration becomes 15 to 21.
%, The presence of a local combustion zone was observed. However, 8
In the temperature range of 00 ° C. to 1200 ° C. and the low oxygen range of 5% to 11%, burning spreading to the entire boiler installation space was observed together with pale flame. Therefore, according to the present embodiment, the exhaust gas obtained from the furnace outlet side has a reduced oxygen concentration due to primary combustion and secondary combustion (free board) in the furnace.
Since the exhaust gas has a high temperature, even if it is diluted to an oxygen concentration of about 5 to 11%, combustion stability is not impaired, and it can be expected that the highest combustion temperature, which is a cause of NOx generation, is lowered by dilution. Such high-temperature rare-burn combustion reduces the local high-temperature region and enables the formation of a uniform combustion temperature field, thereby realizing a low NOx emission. Is also possible. In particular, the range is as shown in FIG.
It has been understood that the temperature is preferably 850 to 1200 ° C. and the oxygen concentration is preferably 5 to 11%.

[0017]

As described above, according to the present invention, low NOx and dioxin can be reduced by realizing high-temperature uniform air combustion using incinerator exhaust gas as combustion air, and a compact exhaust gas boiler is used for exhaust gas treatment. This leads to a reduction in system addition.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration diagram of a stoker-type incinerator as an embodiment of the present invention.

FIG. 2 is a graph showing a combustion state of exhaust gas in the incinerator of FIG. 1 by a relationship between an oxygen concentration and an exhaust gas temperature.

[Explanation of symbols]

 Reference Signs List 4 Reburning chamber 5 Boiler installation space 12 Stalker 12 Fuel supply amount supply nozzle 14, 15 OFA nozzle 51 Furnace wall 5b Passage 5a Boiler

Continued on the front page F-term (reference) 3K061 AA02 AA11 AB01 AC01 AC19 BA01 BA08 BA09 CA01 HA05 HA18 HA29 3K065 AA01 AA11 AB01 AC01 AC19 BA01 BA08 GA03 GA12 GA14 GA32 3K078 AA01 AA08 AA09 BA03 BA22 BA26 CA21

Claims (5)

[Claims] A combustion furnace characterized in that auxiliary fuel is blown into an air space provided on the furnace outlet side of a combustion furnace or an incinerator, and high-temperature exhaust gas with a low oxygen concentration discharged from the furnace is burned as combustion air. How to reduce regulations for incinerators. 2. A method according to claim 1, wherein said high-temperature exhaust gas has a temperature of 800 ° C. or more and an oxygen concentration of about 5 to 11%. 3. An air space is provided on a furnace outlet side of a combustion furnace or an incinerator, auxiliary fuel is blown into the air space, and high-temperature exhaust gas having a low oxygen concentration discharged from the furnace is burnable as combustion air. Combustion furnace or incinerator characterized by the following. 4. The combustion furnace or the incinerator according to claim 3, wherein the air space is an air space formed on the furnace outlet side through a partition or a throttle. 5. The combustion furnace or incinerator according to claim 3, wherein the air space is provided immediately before the boiler mounting position on the furnace outlet side or in the boiler so that the combustion can be utilized for heat absorption of the boiler.