JPH06228620A - Combustion control method in hot stove - Google Patents

Abstract

PURPOSE:To improve the combustion efficiency in a hot blast stove by adjusting the calorific value of a combustion gas for heating at the time of accumulating the heat in the hot air stove for blast furnace over at the initial stage, intermediate stage and latter stage of the combustion. CONSTITUTION:Into a combustion chamber 8 in the hot blast stove 1 for blasting the high temp. air to a tuyere in the blast furnace, blast furnace exhaust gas BFC containing CO and high calorific gas COG of coke oven gas, converter gas, etc., are mixed and fed, and checker bricks 2 are heated by the burnt generated heat. In this case, heat medium 10 is heated in heat exchanger 4 in a flue duct 3 with the high temp. exhaust gas in a hot blast stove 1, and the blast furnace gas BFG for burning the hot blast stove and the coke oven gas COG are heated with the heat medium 10 and also, by heating the air for supplying into the hot blast stove with the heat exchangers 6A-6C, the heated air is fed to the combustion chamber 8 in the hot blast stove 1. In this case, the mixing ratio of the high calorific coke oven gas COG added in the blast furnace gas BFG in order to supply into the combustion chamber 8, is gradually decreased or gradually increased over at the initial stage, intermediate stage and latter stage of the combustion, and at the end stage of combustion, the lower temp. air without preheating is used as the air for combustion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method in a hot stove which is an auxiliary facility of a steelmaking blast furnace.

[0002]

2. Description of the Related Art A hot blast stove, which is a heating device for blowing blast furnace, is usually provided for each blast furnace with at least three hot blast furnaces. When the amount of heat stored in the hot stove that supplies hot air to the checker brick decreases, one of the hot stoves that was newly burning is switched to the blast furnace. I am trying to start supplying hot air.

As the fuel, a gas obtained by mixing a blast furnace gas with a high calorie gas such as a coke oven gas or a converter gas is used.
FIG. 4 is a flowchart showing the heat exchange system of the hot stove.
As shown in FIG. 4, an exhaust gas heat exchanger 4 is provided in the flue pipe 3, and the sensible heat of the exhaust gas is recovered by this heat exchanger 4, and the blast furnace gas heat exchanger 5 and the combustion air heat exchanger 5 are collected. Exchanger 6
Blast furnace gas BFG and combustion air A through A, 6B and 6C
The IR is being preheated. That is, the heat exchanger 4 provided in the flue
By increasing the sensible heat of the blast furnace gas, which becomes the fuel of the hot blast stove, and the combustion air with the sensible heat of the exhaust gas recovered by the above, it is possible to reduce the mixing amount of the high-calorie gas corresponding to this increased sensible heat. ing.

On the other hand, the gas combustion temperature control in the furnace top dome portion 7 is performed as protection management for the refractory bricks of the hot-blast stove 1, but the heat absorption amount of the side wall refractory bricks 9 of the combustion chamber 8 and the exhaust heat recovery heat amount in the flue. , The gas combustion temperature control method in the hot stove 1 is performed by increasing or decreasing the calories of the fuel gas or increasing or decreasing the excess air amount during combustion so as to maintain the target temperature. In the figure, 11 is a chimney, 1
2 is a heat medium circulation pump, 13A, 13B and 13C are air preheating valves, and 14A, 14B and 14C are blowers.

[0005]

When high-temperature air is blown to the blast furnace, the required amount of heat is supplemented by increasing the mixing ratio of the high-calorie gas during combustion in the hot blast stove, which increases the gas combustion temperature. Therefore, it is necessary to suppress the rise in the gas combustion temperature from the viewpoint of protecting the dome bricks. For this reason,
Combustion control is generally performed by reducing the high-calorie gas mixture ratio or increasing the excess air amount. However, after the middle of combustion, when the heat absorption amount of the refractory bricks on the side wall of the combustion chamber decreases and the heat recovery amount of exhaust heat increases, the rise of the combustion temperature of the dome gas becomes too large. If the amount of heat storage becomes insufficient and the amount of excess air is increased, the amount of heat dissipated by the excess air will increase and the combustion efficiency will deteriorate.

[0006]

The present invention has been made in order to advantageously solve the above-mentioned problems of the prior art.
The summary is as follows. (1) The mixing ratio of the high calorie gas to the blast furnace gas is increased in the early stage of combustion, the mixing ratio is gradually decreased from the early stage of combustion to the middle period, the mixing ratio is gradually increased from the middle period of combustion to the latter period, and the combustion air is mixed in the latter period. Combustion control method in a hot stove, characterized in that preheating of the air is stopped and combustion is performed with low-temperature air.

(2) From the early combustion stage to the latter combustion stage, the combustion pattern is set such that the mixing ratio of the high-calorie gas to the blast furnace gas is initially increased, gradually decreased from the initial period to the middle period, and gradually increased from the middle period to the latter period. In addition, in the latter stage of combustion, a sequence for setting the air preheating valve for combustion air preheating provided in the exhaust heat recovery device is set, and combustion is performed in the hot stove characterized by performing combustion based on the pattern and the sequence. Control method.

[0008]

The change in the gas combustion temperature of the furnace top dome portion 7 in the hot-blast stove 1 is caused by the change in the heat absorption amount of the sidewall refractory bricks 9 and the change in the exhaust heat recovery heat amount. That is, when hot air is supplied to the blast furnace in the air blowing step, the temperature of the sidewall refractory bricks 9 decreases. Therefore, in the combustion process, heat is consumed to heat the low-temperature side wall refractory bricks in the early stage of combustion, and the gas combustion temperature at the dome of the furnace top remains low and rises with the passage of combustion time.

On the other hand, after the middle stage of combustion, the temperature of the sidewall refractory brick reaches the target dome portion temperature, and the checker brick 2
Since the heat storage of the exhaust gas increases and the exhaust gas temperature rises, the exhaust heat recovery heat amount in the exhaust gas heat exchanger increases, the preheat amount of the fuel gas and the combustion air also increases, and the combustion temperature of the dome portion excessively rises.

Therefore, in the present invention, as shown in FIG. 1, in the initial stage of combustion, the mixing ratio of the high-calorie gas to the blast furnace gas is increased and the air preheating valve for preheating the combustion air is opened to increase the exhaust heat recovery amount. By doing so, the gas combustion temperature is raised to promote heat storage in the checker brick. That is, No. 1 shown in FIG. Explaining 1 hot blast stove, the air preheat valve 13A provided in the heat exchanger 6A for combustion air is opened, and the heat medium (solid line 10 in the figure) heated to high temperature by exchanging heat with the heat exchanger 4 for exhaust gas is blast furnace. Gas heat exchanger 5 and combustion air heat exchanger 6
It is supplied to A to preheat the fuel gas and the combustion air, and in combination with the increase in the mixing ratio of the high-calorie gas, the heat accumulation in the checker brick is promoted.

However, when the side wall refractory bricks 9 and the top dome portion 7 of the combustion chamber 8 are heated to a high temperature due to high temperature combustion due to an increase in the mixing ratio of the high-calorie gas and an increase in the amount of exhaust heat recovery, the adverse effects thereof appear. From the middle to the middle period, the mixture ratio of the high-calorie gas is gradually reduced to prevent the temperature of the furnace top dome portion 7 from excessively rising.

In the middle of combustion, the exhaust gas temperature is lowered by gradually reducing the mixing ratio of the high-calorie gas in order to suppress the gas combustion temperature. Since the heat storage amount tends to be insufficient, the mixing ratio of the high-calorie gas is gradually increased from the middle stage of combustion to the second stage to prevent the heat storage amount from decreasing.

In the latter stage of combustion, the exhaust gas temperature rises as the mixing ratio of the high-calorie gas increases, and the exhaust heat recovery amount also increases. As a result, the harmful effect of the excessive rise in the gas combustion temperature appears. Take measures to stop preheating. That is, the air preheat valve 13A of FIG. (1) The preheating of the combustion air supplied to the hot stove 1 is stopped, and combustion is switched to low temperature air to prevent the combustion gas temperature from rising excessively. By this measure, it is possible to prevent an increase in heat dissipated by excess air, and further, in another hot stove No. 2 or No. The heat medium circulation amount to the heat exchanger 6B or 6C for air for 3 increases, and the No. 2 or No. 3 Exhaust heat can be recovered in a hot stove.

[0014]

EXAMPLE The present invention was carried out in an installation having three internal combustion hot blast stoves per one blast furnace. Blast furnace gas (800 kcal /
Coke oven gas for Nm ³ (4800 kcal /
The mixing ratio of Nm ³ ) and the opening / closing control of the air preheating valve were performed according to FIG. The results are shown in FIGS. 2 and 3.

FIGS. 2 and 3 show the amount of O _{2 in the} exhaust gas and the hot-air stove combustion efficiency before the implementation of the present invention (H3 year average) and when the present invention was implemented (H4 May-September). In Although,
According to the present invention, the amount of O ₂ in the exhaust gas can be greatly reduced because the excess air heat dissipation is reduced by keeping the gas combustion temperature of the furnace top dome constant. Furthermore, the amount of fuel gas can be limited as a result of recovering the released heat as effective heat by rapidly burning it in the early stage of combustion, and the combustion effect can be greatly improved.

[0016]

As described above, according to the present invention, the combustion capacity of the hot blast stove can be effectively utilized, and efficient and stable high temperature air blowing becomes possible. Needless to say, the present invention has the same effect not only in the internal combustion hot stove but also in the external combustion hot stove.

[Brief description of drawings]

FIG. 1 is a diagram exemplifying a pattern of a coke oven gas mixture ratio and opening / closing control of an air preheating valve according to the present invention.

FIG. 2 is a graph showing changes in the amount of exhaust gas O _{2 in the} example of the present invention.

FIG. 3 is a graph showing the transition of hot stove combustion efficiency in the example of the present invention.

FIG. 4 is a flowchart showing a heat exchange system of a hot stove.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot-blast stove 2 Checker bricks 3 Flue tube 4 Exhaust gas heat exchanger 5 Blast furnace gas heat exchanger 6A, 6B, 6C Combustion gas heat exchanger 7 Top dome part 8 Combustion chamber 9 Side wall refractory brick 10 Heat medium 13A , 13B, 13C Air preheating valve 14A, 14B, 14C Blower

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akira Katayama 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corp. Kimitsu Steel Co., Ltd.

Claims (2)

[Claims] 1. A mixing ratio of a high calorie gas to a blast furnace gas is increased in an early stage of combustion, the mixing ratio is gradually decreased from an early stage of combustion to a middle period, and the mixing ratio is gradually increased from a middle period of combustion to a second stage of combustion, and combustion is performed in a latter stage of the combustion. A combustion control method in a hot stove, characterized in that preheating of the working air is stopped and combustion is performed with low-temperature air. 2. The combustion pattern is set such that the mixing ratio of the high-calorie gas to the blast furnace gas is increased in the initial period, gradually decreased in the initial period to the middle period, and gradually increased in the intermediate period to the latter period from the early stage to the latter period of the combustion. Also, in the latter half of combustion, a sequence for closing the air preheating valve for combustion air preheating provided in the exhaust heat recovery device is set, and combustion is performed based on the pattern and the sequence. Method.