JP2002212630A - Method of measuring atmospheric gas concentration in heating furnace and heating furnace - Google Patents

Abstract

(57) [Problem] To propose a method for accurately measuring the concentration of a component gas in an atmosphere in a heating furnace by using existing equipment. SOLUTION: In a heating furnace having, as a heating source, a regenerative burner in which a pair of burners provided with a heat storage element are arranged to face each other, the burners of each pair of the regenerative burners are alternately burned. Exhaust gas in the furnace is sucked from the burner during combustion, the exhaust gas is introduced into the regenerator, heat in the exhaust gas is collected in the regenerator, and the recovered heat is used for heating the combustion air of the burner during combustion. Then, when operating the heating furnace, a part of the exhaust gas sucked from the burner is led to an analyzer to measure the component concentration in the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring an atmospheric gas concentration in a heating furnace and a heating furnace.

[0002]

2. Description of the Related Art For example, a heating furnace for steel products reheats a steel slab roughly rolled in a lump mill or a continuously cast slab to a final product at a predetermined temperature suitable for the rolling. It is mainly used when The heating furnace is roughly classified into a batch type and a continuous type, but each has an advantage and a disadvantage, and thus is selectively used according to its purpose. Above all, continuous heating furnaces are widely used in steel mills and the like because they are suitable for mass production in recent years.

[0003] As shown in Fig. 1, a typical example of this continuous heating furnace is a pre-tropical zone 1 and a heating zone 2 in order from the steel material charging side.
In general, the heating zone 2 and the soaking zone 3 are heated and maintained at a predetermined temperature by the burner 4. Then, the steel material 5 introduced from the charging door 1a into the pre-tropical zone 1 is moved on the transport path 6 and is carried out of the furnace through the heating zone 2 and the leveling zone 3 through the extraction door 3a on the exit side of the leveling zone 3. During this time, it is heated to a predetermined temperature. The exhaust gas generated by the combustion of the burner 4 is in the pre-tropical zone 1
From the flue 7 provided on the inlet side of the furnace. Reference numeral 7a denotes a recuperator for exchanging sensible heat of flue gas into sensible heat of burner combustion air, and 7b denotes a damper for controlling furnace pressure.

Here, since the continuous heating furnace heats the steel material to a temperature suitable for the subsequent rolling process, it is naturally necessary to strictly control the furnace temperature. It is also important that the atmosphere in the furnace be strictly controlled in order to maintain the surface of the steel material being heated in a good state. For example, when the oxygen concentration in the furnace atmosphere increases, the surface oxidation, nitridation, or decarburization of the material to be heated such as a steel material charged into the furnace is promoted, and if the rolling is performed as it is, the surface quality of the product is deteriorated. Will be. Therefore,
In order to improve or maintain product quality, it is necessary to suppress an increase in the oxygen concentration in the furnace atmosphere. For that purpose, it is important to accurately measure the oxygen concentration in the furnace atmosphere.

[0005] In addition to the oxygen concentration, it is significant to accurately measure the concentration of nitrogen, carbon monoxide, nitrogen oxide, and the like in the furnace atmosphere. That is, nitrogen affects the nitridation of the steel surface, carbon monoxide can be used to detect incomplete combustion of the burner, and nitrogen oxides are necessary for controlling environmental emission standards.

Japanese Patent Application Laid-Open No. 62-40312 discloses that each probe for measuring the oxygen concentration and the CO concentration in a heating furnace is freely movable, and the concentration is measured at a plurality of measurement positions. It is disclosed to correct and control the air ratio of the burner by determining the concentration value.

However, in order to measure the concentration, it is necessary to newly provide a drive system and a control system, so that the cost required for the initial investment increases and the maintenance thereof is complicated. In a heating furnace having a configuration in which attached equipment is complicated, it is often difficult to newly provide a drive system and a control system due to a problem of arrangement space.

In Japanese Patent Application Laid-Open No. 9-53120, a partition wall is provided in the furnace width direction inside the furnace wall on the extraction side of the heating furnace and below the skid, and the partition wall and the extraction-side furnace wall are connected to each other. In the meantime, it is disclosed that in a heating furnace having an oxygen concentration meter and an exhaust pipe for exhausting the atmosphere gas out of the furnace, the flow rate in the exhaust pipe is controlled while measuring the oxygen concentration using the oxygen concentration meter. I have.

However, in order to perform measurement using an oxygen concentration meter between the partition wall and the extraction furnace wall, it is necessary to insert a probe from the hearth or the furnace wall. The probe may be damaged or clogged due to the drop and accumulation of the like, so that it is difficult to perform a reliable concentration measurement for a long time. Further, when the probe is inserted from the furnace wall, the probe is exposed to a high-temperature region in the furnace and bends, so that a measurement point may be shifted or damaged.

[0010]

SUMMARY OF THE INVENTION Therefore, the present invention
An object of the present invention is to propose a method capable of accurately measuring the concentration of a component gas in an atmosphere in a heating furnace by using existing equipment. Another object of the present invention is to provide a heating furnace capable of measuring the concentration of a component gas in the atmosphere inside the heating furnace.

[0011]

In recent years, a regenerative burner has been used as a heating source of a continuous heating furnace, and heat in exhaust gas is reused for preheating combustion air for the burner. Operations are taking place. That is, as shown in FIG. 2, the regenerative burner is, for example, a pair of burners 40a and 40b disposed face to face between both side walls of the heating furnace soaker 3.
And dual passages 41a and 41b for guiding combustion air from outside the furnace to the respective burners 40a and 40b, and for guiding exhaust gas in the furnace to the outside of the furnace through the respective burners. And the heat storage bodies 42a and 42b disposed in the In this regenerative burner, when the burner pairs are alternately burned, for example, as shown in FIG. 2A, the burner 40a is supplied with combustion air from a shared passage 41a and a fuel 43a.
When the burner 40a is burned, the exhaust gas in the furnace is sucked from the burner 40b opposed to the burner 40a, and the exhaust gas is passed through the regenerator 42b to recover the heat.
And discharge it outside the furnace.

Next, after the combustion operation of the burner is switched, and at that time, the switching valve 44 of the shared passage 41a and 41b is switched to change the connection of the air and exhaust gas to the above-mentioned conduit, and FIG. As shown, in supplying the combustion air from the shared passage 41b to the burner 40b via the heat storage body 42b, the heat recovered in the heat storage body 42b in the step shown in FIG. The combustion air is supplied while preheating is performed, and at the same time, the fuel 43b is supplied to burn the burner 40b. At the same time, the exhaust gas in the furnace is sucked from the burner 40a opposed thereto, the exhaust gas is passed through the regenerator 42a to recover heat, and then guided to the shared passage 41a to be discharged out of the furnace. By repeating the above-described steps shown in FIGS. 2A and 2B, for example, every several tens of seconds to perform heating, a heating furnace operation with little heat loss is realized.

In the operation of a heating furnace using such a regenerative burner, the exhaust gas of the regenerative burner is sucked at a high speed, so that exhaust gas distributed in the furnace width direction is sucked over a wide range. The inventors focused on this phenomenon, and since the exhaust gas in the furnace sucked from the regenerative burner reproduced the atmosphere inside the furnace well, we measured the component concentration of the exhaust gas sucked from the regenerative burner. By doing so, they found that the component concentration in the furnace atmosphere was accurately measured, and completed the present invention.

That is, the gist configuration of the present invention is as follows. (1) In a heating furnace having a regenerative burner in which a pair of burners provided with a heat storage body are arranged facing each other as a heating source, the burners of each pair of the regenerative burners are alternately burned and non-burned. The exhaust gas in the furnace is sucked from the burner at the time, the exhaust gas is introduced into the regenerator and the heat in the exhaust gas is collected in the regenerator, and the recovered heat is used for heating the combustion air of the burner during combustion. In operating the heating furnace, a part of the exhaust gas sucked from the burner was guided to an analyzer,
A method for measuring the concentration of an atmosphere gas in a heating furnace, comprising measuring the concentration of a component in an exhaust gas.

(2) In the above item (1), the measured value of the component concentration of the exhaust gas sucked from the regenerative burner is used as a representative value of the component concentration in a zone in a heating furnace provided with the regenerative burner. Method for measuring the concentration of atmospheric gas in a heating furnace.

(3) As a heating source, a regenerative burner having a pair of burners provided with regenerators is provided so as to face each other. Exhaust gas in the furnace is sucked from the burner during combustion,
An exhaust gas is introduced into the heat storage body, heat in the exhaust gas is recovered in the heat storage body, and the recovered heat is used for heating combustion air of a burner during combustion, and the operation is performed. A probe for sampling a part of the exhaust gas and an analyzer for measuring a component concentration of the collected exhaust gas are provided in the middle of a path for discharging the exhaust gas from the burner through a heat storage unit when the combustion is not performed. heating furnace.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the method of the present invention will be described.
This will be described in detail with reference to the drawings. Now, as shown in FIG. 2, in the regenerative burner, the exhaust gas sucked from the burner 40a or 40b is guided to the outside of the furnace through the shared passage 41a or 41b, and the exhaust gas is sucked as shown in FIG. It is done on the route. That is, dual-use passages 41a and 41b extending from a plurality of sets of regenerative burners are combined into exhaust gas ducts 8a and 8b provided for each of the burner groups on one side and the other side of the furnace wall, and further, these exhaust gas ducts 8a and 8b Into a single conduit 9, which communicates with the flue 7 of the heating furnace via a suction fan 10. Then, the exhaust gas is guided to the flue 7 by the suction force of the suction fan 10 via the shared passages 41a and 41b, the exhaust gas ducts 8a and 8b, and the conduit 9, and discharged to the outside of the furnace.

In the exhaust gas discharging path described above, in the example shown in FIG.
A part of the exhaust gas flowing through the conduit 9 is sampled from the probe 11 and the concentrations of various components are measured using the analyzer 12 with respect to the sampled exhaust gas. As described above, the various measured concentration values thus obtained show well the distribution of the atmosphere in the furnace, particularly in the furnace width direction. It can be used as a representative value.

Here, the average oxygen concentration in the furnace was measured for a case where the exhaust gas sucked from the regenerative burner was sampled and the oxygen concentration was measured, and a case where the oxygen concentration was measured via a probe inserted from the furnace wall. The error for was investigated. As shown in FIG. 4, when the exhaust gas sucked from the regenerative burner was sampled and the oxygen concentration was measured, the difference from the actual average oxygen concentration in the furnace was found to be extremely small. That is, by examining the exhaust gas sucked from the regenerative burner, it is possible to measure the component concentration in accordance with the actual furnace atmosphere. In addition, the average oxygen concentration in the furnace was obtained by closing the extraction door and the charging door and (air entering the furnace) ≒ 0 Nm ³
It is a calculated value of the oxygen concentration in the furnace, which is theoretically obtained from the gas flow rate, the component, and the air ratio supplied to the burner under the condition of the furnace pressure setting of / h. Other conditions will be described in detail in Examples described later.

Further, as shown in FIG. 3, it is desirable that the position where the exhaust gas sucked from the regenerative burner is collected is located downstream of the regenerator of the regenerative burner. Because the exhaust gas from which heat is recovered by the regenerator is naturally lower than the furnace temperature, inserting the probe downstream of the regenerator prevents the probe from being exposed to a high-temperature atmosphere, and its durability. This is because the life can be extended.

In the above case, a case where a continuous heating furnace is used has been described. However, the present invention is advantageously applicable to a batch heating furnace, a rotary hearth heating furnace, and the like.

[0022]

EXAMPLE A steel slab having a thickness of 220 mm, a width of 1200 mm and a length of 9800 mm was introduced using the continuous heating furnace (transport path height: 0.5 m from the furnace bottom) shown in FIG. 1230 ℃
Operation was performed until heating. The specifications of the four sets of regenerative burners arranged in the soaking zone of the heating furnace are as follows. Note Combustion capacity: 2,000,000 (kcal / H. Burner) Combustion load: 10 to 100% Combustion switching time between a pair of burners: 60 s / time Exhaust gas suction rate: 60 to 90%

In the operation of the heating furnace described above, after the exhaust gas sucked from the regenerative burner is passed through the regenerator, a part of the exhaust gas is collected from the probe 11 inserted on the way of the conduit 9,
The analyzer 12 was used to measure the oxygen concentration of the collected exhaust gas. The furnace oxygen concentration measurement range is 0 to 21 vol.
%, And the ambient temperature in the pipe 9 is 200 ° C.
Met. As a comparison, the oxygen concentration was measured via a probe inserted from a furnace wall in a solitary zone.

The results of comparing these measured concentration values with the average oxygen concentration in the furnace are shown in FIG. 4. In the case of measuring with the exhaust gas sucked from the regenerative burner according to the present invention, the average oxygen concentration in the furnace was measured. The deviation from the value was less than 0.5%. On the other hand, when the oxygen concentration was measured via the probe inserted from the furnace wall, the error from the average oxygen concentration in the furnace was 1 to 3%.

[0025]

As described above, according to the present invention,
Since the concentration of components in the furnace atmosphere can be measured accurately,
High quality products can be produced by controlling the furnace atmosphere based on the measured values. Further, the method for measuring the component concentration in the atmosphere in the heating furnace according to the present invention can be easily performed using existing equipment, does not require new equipment investment, and can be realized at low cost. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the structure of a continuous heating furnace.

FIG. 2 is a view showing a structure of a regenerative burner.

FIG. 3 is a diagram showing a discharge path of exhaust gas from a regenerative burner.

FIG. 4 is a diagram comparing measured values of the in-furnace oxygen concentration by various methods and the average in-furnace oxygen concentration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pre-tropical 1a Loading door 2 Heating furnace 3 Uniform tropical 3a Extraction door 4 Burner 5 Conveyance path 6 Steel material 7 Flue 7a Recuperator 7b Damper 8a, 8b Exhaust gas duct 9 Conduit 10 Suction fan 11 Probe 12 Analyzer 40a, 40b Burner 42a , 42b heat storage

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ichiro Sugimoto 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (without address) Inside Mizushima Works, Kawasaki Steel Corporation (72) Inventor, Masahiro Furukawa Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama 1-chome (without address) Mizushima Works, Kawasaki Steel F-term (reference) 3K023 QA03 QB02 QC05 SA01 4K056 AA08 BA02 BB01 CA02 DA27 DA32 FA15 4K063 AA08 BA02 CA02 CA03 DA34

Claims (3)

[Claims] 1. A heating furnace having a regenerative burner in which a pair of burners provided with a regenerator is provided facing each other as a heating source. In a heating furnace, the burners of each pair of regenerative burners are alternately burned, Exhaust gas in the furnace is sucked from the burner during non-combustion, the exhaust gas is introduced into the regenerator and heat in the exhaust gas is collected in the regenerator, and the recovered heat is used for heating the combustion air of the burner during combustion. Utilizing and operating the heating furnace, a part of the exhaust gas sucked from the burner is guided to an analyzer to measure the component concentration in the exhaust gas, and the concentration of the atmosphere gas in the heating furnace is measured. Measuring method. 2. The method according to claim 1, wherein the measured value of the component concentration of the exhaust gas sucked from the regenerative burner is used as a representative value of the component concentration in a zone in a heating furnace provided with the regenerative burner. A method for measuring the concentration of atmospheric gas in a heating furnace. 3. A regenerative burner in which a pair of burners provided with a regenerator is disposed facing each other as a heating source,
While alternately burning each pair of burners of the regenerative burner, the exhaust gas in the furnace is sucked from the non-burning burner, the exhaust gas is introduced into the regenerator, and the heat in the exhaust gas is recovered in the regenerator, The collected heat is used for heating the combustion air of the burner during combustion, and the operation is performed. In a heating furnace, the exhaust gas in the heating furnace is discharged from the burner during non-combustion via a heat storage body in the course of a path. A heating furnace provided with a probe for sampling a part of the exhaust gas and an analyzer for measuring a component concentration of the collected exhaust gas.