JPH09119606A - Blast furnace gas mixed firing coal fired boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a boiler efficiency, increase the safetiness of flue instruments and reduce the generating amount of NOx by a method wherein a blast furnace gas compartment is arranged between the thick mixture compartment of pulverized coal. and the thin mixture compartment of the same while respective compartments are provided with downward angles. SOLUTION: In a lower coal/blast furnace gas combination stage 13, an AUX compartment 18, charging auxiliary combustion air, a thin mixture compartment 17, low in the concentration of pulverized cloal, a blast furnace gas compartment 16 and a thick mixture compartment 15, high in the concentration of pulverized coal, are arranged sequentially from the lowr part. On the other hand, an arrangement in an upper coal/blast furnace gas combination stage 11 is reversed to the arrangement in the lowr stage. Respective compartments of the coal/blast furnace gas combination stages 11, 13 are installed so as to have downward angles to elongate the staying period of time of respective fuels and air in a furnace 2. According to this method, the generating amount of NOx can be restrained in a low degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace gas co-firing coal (pulverized coal) -fired boiler for a business / in-house power generation facility, and more particularly to a combustion device thereof.

[0002]

2. Description of the Related Art Conventionally, when blast furnace gas was used as a fuel for a boiler, it was mostly co-firing with heavy oil or natural gas, but in recent years, a co-firing boiler of blast furnace gas and coal (pulverized coal combustion) is also planned. It became so.

In the conventional co-firing of heavy oil (or natural gas) and blast furnace gas, in order to effectively decompose CO, which is the main component of the blast furnace gas, a compartment for the blast furnace gas is provided as shown in FIG. Most were placed at the bottom of the burner box.

On the other hand, a coal-fired (pulverized coal combustion) boiler which suppresses the generation of NO _x is arranged as shown in FIG. That is, in order to reduce NO _x , one coal compartment is divided into two blocks, a dense air-fuel mixture compartment with a high pulverized coal concentration and a light air-fuel mixture compartment with a low pulverized coal concentration, and between the two blocks. , A separate compartment is provided to divide the rich mixture combustion flame and the light mixture flame.
It consisted of a relatively tall wind box.

[0005]

Since the blast furnace gas has a low flame combustion temperature, the residence time in the furnace required for completion of combustion must be long. However, in the case of blast furnace gas, due to the composition of the fuel, the amount of exhaust gas generated per calorific value of the fuel is large, so the superficial velocity in the furnace becomes faster, and compared with the case of mono-fuel combustion of heavy oil, natural gas, coal, etc. The residence time is rather shortened. Therefore, in a mixed-fired boiler of blast furnace gas and coal (pulverized coal), the amount of ash in the ash increases as the residence time in the furnace shortens, and from the viewpoint of boiler efficiency, flue equipment (air preheater, dust collector) There is also a problem in terms of the safety of the reactor, desulfurization equipment, denitration equipment, etc.

That is, in a coal (pulverized coal) / blast furnace gas co-firing boiler, when the blast furnace gas compartment is arranged at the lowest stage and complete combustion is performed at an air ratio of 1.0 or more, the amount of gas generated per calorific value is very large. Therefore, the superficial velocity of the upper part of the coal (pulverized coal) combusting section is increased to inhibit the combustion of the pulverized coal itself, and as a result, the incombustible material of the pulverized coal, that is, the unburned matter in the ash is increased in the furnace.

As a combustion method for suppressing this phenomenon, it is unavoidable to reduce the air ratio in the lowermost blast furnace gas compartment to suppress the gas from being blown up from the lower part of the furnace. However, since the self-combustibility of blast furnace gas itself is worse than that of other fuels, it is not desirable to greatly reduce the air ratio from the viewpoint of suppressing misfire.

[0008]

In order to solve the above-mentioned conventional problems, the present inventor has introduced a blast-furnace gas co-firing coal-fired boiler in which a mixture of pulverized coal and air and blast furnace gas are put into a boiler furnace and burned. In the above, a compartment for introducing blast furnace gas was placed between a compartment for introducing a rich mixture with a high pulverized coal concentration and a compartment for introducing a light mixture with a low pulverized coal concentration, and each compartment was inclined downward. This is to propose a blast furnace gas co-firing coal-fired boiler characterized by the above.

According to the present invention, the blast furnace gas compartment is provided in the part of the separate compartment which is disposed between the rich air-fuel mixture compartment and the light air-fuel mixture compartment in the conventional pulverized coal burning burner.
The following effects occur.

1) Since the blast furnace gas compartment, which was conventionally arranged at the bottom, is divided and arranged in each of the pulverized coal charging compartments, which are usually provided in plural sets,
The blowing up of exhaust gas from the lower part of the burner is reduced, and the generation of unburned matter in ash is suppressed.

2) The flame of coal (pulverized coal) reliably holds flame of blast furnace gas which is likely to misfire.

3) The coal burner itself is a low NO _x burner that forms a rich air-fuel mixture and a light air-fuel mixture, and the generation of NO _x is suppressed.

The present invention also tilts each compartment downward so that the flame is downward and the residence time in the furnace is long.

[0014]

1 is a vertical cross-sectional view showing a blast furnace gas co-firing coal-fired boiler according to an embodiment of the present invention, and FIG. 2 is a front view showing a wind box arrangement of a main burner (1) in FIG. It is a figure and a partial side view.

First, referring to FIG. 1, in the blast furnace gas co-firing coal-fired boiler of this embodiment, a main burner (1) is provided on a side surface of a furnace (2), and a superheater (3), a reheater (4), etc. are provided at an upper portion. A heat exchanger (5) such as a economizer is installed in each rear flue (7). The fuel injected in the main burner (1) burns in the furnace (2) and becomes exhaust gas, which is discharged to the outside through the rear flue (7) and the exhaust gas duct (6).

Next, an example of the main burner (1) will be described with reference to FIG. This main burner (1) consists of the LFA stage (14), the lower coal / blast furnace gas combination stage (1
3), heavy oil stage (12), upper coal / blast furnace gas combination stage (11) and OFA stage (10). The heavy oil stage (12) is arranged in the center,
This is to ignite and burn the boiler furnace and ignite coal (pulverized coal) at the time of initial startup, and it is not necessary to have other ignition / ignition means, and when burning coal and blast furnace gas. Has stopped.

In the lower coal / blast furnace gas combination stage (13), auxiliary combustion air is introduced in order from the bottom, the AUX compartment (18), the pulverized coal concentration low mixture mixture compartment (17), and the blast furnace gas compartment ( 16) and a dense mixture compartment (15) with a high pulverized coal concentration. Also the upper coal
The arrangement of the blast furnace gas combination stage (11) is the opposite of that of the lower stage. This arrangement may be the same for the upper and lower stages, but the ignition of the coal will be better if the rich mixture compartment (15) is placed closer to the heavy oil stage (12).

In this embodiment, as shown in the right half of FIG. 2, the coal / blast furnace gas combination stage (11),
Install each compartment of (13) at a downward angle,
Each input fuel and air is made to stay for a long time in the furnace (2).

In this way, the blast furnace gas co-firing coal-fired boiler of the present embodiment maintains the low NO _x effect, which is the characteristic of the conventional coal-burning burner that combines a rich mixture and a light mixture, and pulverized coal.・ It is intended to reduce unburned matter in ash by stable combustion of blast furnace gas.

[0020]

According to the present invention, in the co-firing boiler of coal (powdered coal) and blast furnace gas, the unburned content in ash is reduced by the optimum configuration of the burner air box, so that the boiler efficiency is improved and the flue equipment The safety can be improved. Further, since it also has the function of the conventional pulverized coal burning low NO _x burner that combines a mixture of dark and light, the amount of NO _x generated can be suppressed to a low level.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing a blast furnace gas co-firing coal-fired boiler according to an embodiment of the present invention.

FIG. 2 is a front view and a partial side view showing a wind box arrangement of a main burner (1) in FIG.

FIG. 3 is a front view showing an example of a burner air box of a conventional blast furnace gas mixed burning heavy oil fired boiler.

FIG. 4 is a front view showing an example of a burner wind box of a conventional pulverized coal burning boiler.

[Explanation of symbols]

 (1) Main burner (2) Furnace (3) Superheater (4) Reheater (5) Economizer (6) Exhaust gas duct (7) Rear flue (10) OFA stage (11) Upper coal / blast furnace Gas combination stage (12) Heavy oil stage (13) Lower coal / blast furnace gas combination stage (14) LFA stage (15) Rich mixture compartment (16) Blast furnace gas compartment (17) Light mixture compartment (18) AUX compartment

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F23D 17/00 103 F23D 17/00 103

Claims (1)

[Claims] Claim: What is claimed is: 1. In a blast furnace gas mixed firing coal-fired boiler in which a mixture of pulverized coal and air and a blast furnace gas are introduced into a boiler furnace and burned, a compartment in which a dense mixture having a high pulverized coal concentration is introduced and a pulverized coal concentration A blast-furnace gas co-firing coal-fired boiler characterized by arranging a compartment for injecting blast furnace gas between a compartment for injecting a low light air-fuel mixture and sloping each compartment downward.