JPS59134412A - Combustion of mixed firing burner for ignition of sintering furnace - Google Patents

Abstract

PURPOSE:To contrive to obtain the excellent ignitionality, to reduce the loading quantity of heat, and yet to improve the quality of sintered ore by a method wherein the distribution ratio among primary, secondary and tertiary airs are specified. CONSTITUTION:The amount of primary air, which is blown-in together with pulverized coal, is rendered to be 20-30%, that of secondary air, which is used for mixing gaseous fuel and pulverized coal, is rendered to be 10-20% of theoretical amount of air, and tertiary air, which is added for combustion, is supplied by the amount so as to suffice the realization of a predetermined air fuel ratio. Concretely, the loading quantity of pulverized coal and/or C-gas (or mixed firing ratio) is determined based upon the values measured with thermometers. For example, the loading quantity of heat is set so as to keep the mean ingition surface temperature of sintering raw material within the range 900-1,000 deg.C. If said temperature tends to be higher, the loading quantity of pulverized coal is reduced, while, if lower, the quantity is increased. After that, the theoretical amount of air is calculated based upon the determined quantity of pulverized coal or C-gas so as to determine to distribution ratio among primary, secondary and tertiary airs in order to control the amounts of the primary, secondary and tertiary airs.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to combustion of a gaseous fuel (e.g., evaporated coke oven gas, f-mouth gas, mixture of blast furnace gas, etc.) and pulverized coal in a co-firing burner provided in a sintering ignition furnace. Regarding the method.

In recent years, research has been progressing on the use of co-firing burners of pulverized coal and gaseous fuel in sintering ignition furnaces. The background to this is the desire to avoid using cheap pulverized coal as much as possible. are getting it.

In Figures 1 and 2, 1 is a guide tube attached to the wall of the ignition furnace, and there are burner tiles 2 concentrically inside the guide tube.
is provided, and its population 2a faces the inside of the ignition furnace. Further, a C gas conduit 3 is provided at a position outside the furnace so that the axis of the burner tile 2 is the same, and into which gaseous fuel as a secondary fuel, such as coke oven gas, is blown. On the outside of the C gas conduit 3, there are a pulverized coal-water air conduit 4, a secondary air conduit 5,
and tertiary air conduit 6 are arranged in a superposed manner in this order.

The conduits 3, 4.5 communicate with the burner tile 2, and their tips are constricted portions. Further, swirl vanes 7 are provided inside the conduit 3 and in the annular gap between the conduits 4 and 5, respectively.
．． 8 is arranged so that C gas and secondary air are smoothly co-fired with pulverized coal. Further, the tertiary air conduit 6 communicates with a gap 9 between the burner tile 2 and the guide cylinder 1, and in the front part of the gap 9, closing parts 10 are provided at intervals in the circumferential direction. There is. Opening angle θ of this closed portion 10
1 is 35 to 50 degrees, preferably about 40 degrees, and the opening angle θ2 of the unoccluded portion 11 is 15 to 25 degrees, preferably about 20 degrees.
It is said that By providing such a closing part 10, 3
The combustibility of the secondary air and the fuel blown out from the burner tile 2 is enhanced.

Here, (1) primary air A1 is for transporting pulverized coal Me,
(2) The secondary air A2 becomes C due to the turbulence generated by the swirling vanes.
In order to achieve smooth mixing of gas and pulverized coal, (3) tertiary air A3 is used as combustion air.

By the way, this type of co-firing burner itself is still in the experimental stage, and there are many unknown points. In addition, pulverized coal is cheaper than coke oven gas (hereinafter referred to as C gas), so it is desirable to use as much pulverized coal as possible; 8 According to numerous tests conducted by the present inventors, the use of a certain amount of C gas is unavoidable.
It has been found that the gas co-firing ratio, that is, the amount of C gas (keat)/the amount of pulverized coal (kcal), can be lowered to about 10%. Still, although the layer thickness of the sintering raw material in the sintering machine varies within the range of 450-480 mm, the distance between its surface and the burner is approximately 800 mm. It is important for the ignitability of the raw material that the tip of the flame reaches the surface of the raw material within this interval, and if the distance is longer or shorter than this, the ignitability will deteriorate.

However, as mentioned above, although the C gas co-combustion rate can be determined through various experiments, the reality is that the distribution of primary to tertiary air amounts is unknown even if it can be determined. And, it is empirically determined that the 1st to 3rd order
It has been found that there are various problems when the distribution ratio of the amount of air is always the same during operation. In other words, when the amount of pulverized coal and C gas used increases or decreases (increases or decreases the mixed combustion ratio) in order to adjust the amount of heat input into the sintering ignition furnace during operation, the air distribution ratio remains constant and the desired air Even if the amount of air is changed to match the fuel ratio, an increase or decrease in the air-fuel ratio will result in excess or deficiency in the amount of primary and secondary air to the burner, which will interfere with the pulverized coal discharge speed and turbulent swirling effect, causing burner failure. It became clear that the frame shape was inappropriate, resulting in wasted heat input and unstable sintered ore quality.

In order to deal with this problem, the inventors repeated experiments on many basic and actual machines, and found that
We have discovered that the tertiary air distribution ratio is important in achieving optimal ignition and combustibility, as well as in reducing the C gas co-combustion ratio to 10%, which was previously thought to be the limit, and developed the present invention. was completed.

That is, in the present invention, when burning a mixed combustion burner of gaseous fuel and pulverized coal installed in a sintering ignition furnace, the amount of primary air to be blown in together with pulverized coal is set to 20% of the theoretical amount of air.
~30 cm, the amount of secondary air for mixing gaseous fuel and pulverized coal is 1
It is characterized in that the air amount corresponding to a predetermined air-fuel ratio is supplemented with tertiary combustion air.

To explain the present invention more specifically, the primary to tertiary air distribution ratios can be appropriately selected based on the gaseous fuel co-combustion rate.

In this case, the theoretical air amount A. In contrast, it is necessary to set the primary to tertiary air amount AI + A2 + A3 as per water fertilizer.

A, = αAo α = 0.2 ~ 0.3 - (
i) A2-βAOβ=0.1~0.2 =-(2
)A 3 ”mAg (αAo+βAO)”Ao(
m-α-β) m: air-fuel ratio (3) Then, within this range of primary to tertiary air distribution ratio, the primary to tertiary air distribution ratio is Change the air volume for each name.

Primary air as carrier air for pulverized coal is
1.2 to 4.0 Nm3 per kg is required. Even if it is more or less than this value, the flow rate will fluctuate due to sedimentation during the transport process, making combustion unstable. The air amount for this is the theoretical air amount (C gas 4.
75 Nm'/'Nm3 + pulverized coal 8Nm3/'9)
However, in the present invention, the pulverized coal discharge speed at the burner tip is set to 25 to 37%. i5
In terms of ml sec, the primary air amount is set to 20 to 30% of the theoretical air amount in order to improve ignition and combustibility.

When the primary air amount is less than 20 inches, the pulverized coal discharge speed is
If it is less than 5m/sec, there is a risk of explosion due to backfire, and if it exceeds 30%, the pulverized coal discharge speed will be 37.5m/sec.
ml sec, a combustion delay occurs, the flame becomes unstable, and there is a risk of misfire.

The secondary air amount is 10 to 20% of the theoretical air amount. This numerical range defines the concentration ratio of C gas and secondary air, and when it exceeds 20%, the ignitability of C gas deteriorates, and when it is less than 10%, the swirling effect decreases.

The tertiary air amount is determined by the predetermined air-fuel ratio as shown in equation (3).

In addition, Fig. 4 and Fig. 5 show a co-firing burner different from Fig. 1 and Fig. 2. Fig. 4 is a schematic sectional view, and Fig. 5 is a view taken along the line V-V. All the symbols are the same as in FIGS. 1 and 2.

FIG. 3 shows an example of combustion control. A plurality of co-combustion burners 50, for example six, are arranged in parallel at intervals in the width direction of the ignition furnace 51, and when igniting and burning the sintered raw material 52, the ignition/combustion state in the ignition furnace 51 or the temperature in the width direction of the furnace is controlled. In order to know the distribution, thermometers 53, 53, etc. consisting of oniba radiation thermometers are installed along the width of the furnace. 54 is a noglet, 55 is an A-let roller, 56 is a wind box,
57 is a side plate, and 58 is a main processing unit.

In controlling using such a control device, the thermometer 53
The amount of pulverized coal and/or C gas input (co-combustion rate) is determined based on the actual measured value. For example, the amount of heat input is set so that the average temperature of the ignition surface of the sintering raw material is 900 to 1000°C. If the temperature tends to be high, the amount of pulverized coal used is decreased, and if the temperature tends to be low, the amount of pulverized coal is increased.

Next, the theoretical air amount is calculated based on the determined amount of pulverized coal or C gas, the primary to tertiary air distribution ratios are determined, and the air amounts are controlled. In this case, the tertiary air amount is determined based on the air-fuel ratio.

By the way, using 6 burners, the C gas co-firing rate was 10
%, the air-fuel ratio is 1.1, and the primary to tertiary air distribution ratio is 1st = 25%, 2nd - 15%, tertiary - 60%,
The following table shows the comparison results between the present invention example and the comparative example, in which the average temperature of the ignition surface of the sintered raw material was controlled to be 900 to 1000°C.

In addition, the comparative example has a C gas co-combustion rate of 10%, an air-fuel ratio of 1, 1.
The initial settings were 25% for primary air, 25% for secondary air, and 50% for tertiary air, and only the amount of fine charcoal and C gas was manually adjusted.

The results show that the amount of heat input can be reduced and the quality of the finished sintered ore is improved.

As described above, according to the present invention, since the primary to tertiary air distribution ratio is specific, excellent ignition combustibility can be exhibited, the amount of input heat can be reduced, and the quality of sintered ore can be improved.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing an example of the structure of a co-combustion burner, Fig. 2 is a view taken along the line ■-■, Fig. 3 is a schematic diagram of the combustion control device, and Fig. 4 is a co-combustion burner with different aspects. side view, No. 5
The figure is a schematic cross-sectional view. 1...Guide tube, burner tile, 7, 8...
Swirling vane, 50... Mixed combustion burner, 51... Ignition furnace,
53...Thermometer, Me...Pulverized coal, A1...Primary air, A2...Secondary air, A3...Tertiary air.

Claims (1)

[Claims] (1) When burning the gaseous fuel and pulverized coal co-fired burner installed in the sintering ignition furnace, the amount of primary air that is blown in together with the pulverized coal is 20 to 30% of the theoretical air amount. A sintering ignition furnace characterized in that the amount of secondary air for mixing gaseous fuel and pulverized coal is 10 to 20%, and the amount of air corresponding to a predetermined air-fuel ratio is supplemented with tertiary air for combustion. Combustion method of mixed combustion burner.