JPS581177B2 - Control device for industrial furnace with preheating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling the flow of combustion gas inside an industrial furnace equipped with a preheating device that heats objects to be heated, such as steel materials, with combustion gas.

The heating furnace with a preheating device that has already been proposed aims to improve the fuel consumption rate of the heating furnace (the amount of heat required per sieve of heat-treated steel material, Kcal). A device equipped with a preheating device, in which the combustion waste gas sucked and pressurized from the heating furnace is injected into the steel material in the preheating device through a nozzle, and the heating furnace and preheating device are communicated with each other so that the steel material can be transported. It is.

If combustion gas flows through the communication portion between the heating furnace and the preheating device, the heating efficiency will decrease and the unit consumption of the furnace will deteriorate for reasons described below.

In order to solve such problems, as disclosed in Japanese Patent Laid-Open No. 48-76123 by the applicant, a nozzle is provided in the communication part between the heating furnace and the preheating device communicating with it. There is prior art in which a jet film is formed by a nozzle.

In this prior art, although it is possible to prevent the flow of combustion gas in the communication part between the heating furnace and the preheating device and to provide independence between the heating furnace and the preheating device to a certain extent, the combustion gas in the communication part It is not possible to precisely control the distribution of the current to a desired value, for example zero.

Therefore, the main object of the present invention is to provide a device that can accurately adjust the flow rate of combustion gas in a communication section between an industrial furnace such as a heating furnace and its preheating device to a desired value, for example, zero. It is.

Therefore, the main object of the present invention is to provide a control method and apparatus that can adjust the flow rate of combustion gas in a communication section between an industrial furnace such as a heating furnace and its preheating device to zero.

FIG. 1 is a system diagram of an embodiment of the present invention.

First, the preheating device additional heat furnace will be explained.

The burner 11 of the heating furnace 10 mixes fuel and combustion air and burns the mixture.

The preheating device 20 is communicated with the steel charging side of the heating furnace 10 through the communication portion 12 .

The steel material 13 is charged from the charging port 21 of the preheating device 20 by a conveying device (not shown) such as a walking beam or a pusher, and passes through the communication portion 12 to the extraction port 14 of the heating furnace 10.
It is transferred condylarly to the

Combustion gas discharged from the heating furnace 10 is led to a heat exchanger 23 through a conduit 22, and is further sucked and pressurized by a high temperature blower 24.

This heat exchanger 23 functions to preheat the combustion air of the burner 11 and recover waste heat.

The suctioned and pressurized combustion gas is supplied to the upper and lower headers 25 and 26 of the preheating device 20.

The high temperature combustion gas supplied to this header 25.26 is
It is sprayed at high speed from a large number of spray nozzles 27,28.

The ejection nozzles 27 and 28 are used to heat the steel material 1 in the preheating device 20.
3 and are arranged at appropriate intervals above and below 3, respectively.

Therefore, the injected high-temperature, high-speed combustion gas is injected onto both the upper and lower surfaces of the steel material 13 to preheat the steel material 13.

The preheated combustion gas passes through the flue 30 and is dissipated from the chimney 31.

In this way, the steel material 13 is heated to, for example, about 300°C by the preheating device 20, and further heated to, for example, 1150-1250°C by the heating furnace 10.

In connection with this preheating device-added heating furnace, a well-known furnace pressure control device is provided in order to uniformly heat the steel material 13 by preventing blow-out of the flame inside the furnace and suction of cold air outside the furnace.

This furnace internal pressure control device includes a pressure detector 42 and a controller 43.
and a damper 45 for adjusting furnace pressure.

The pressure detector 42 is installed in the heating furnace 10 and generates a signal corresponding to the internal pressure of the heating furnace 10, and supplies the signal to one input end of the subsequent controller 43.

The other input end of the controller 43 is given a predetermined set value signal 44 corresponding to a predetermined furnace pressure.

A furnace pressure regulating damper 45 is inserted into the flue 30 .

The furnace pressure regulating damper 45 is operated by the output signal of the controller 43, whereby the furnace pressure of the heating furnace 10 is controlled to follow the furnace pressure corresponding to the set value signal 44.

The controller 43 is a conventionally known controller.

The furnace pressure regulating damper 45 is a conventionally known automatic valve that is composed of a combination of a damper and an operating device such as an air cylinder or an electro-hydraulic operating device.

Here, the combustion gas in the furnace has the following two disadvantageous distribution modes (
1), (2): (1) a part of the combustion gas from the heating furnace 10 passes through the communication part 12, and also the remaining combustion gas is injected through the conduit 22 into the preheating device 20; , are dissipated together through the flue 30; (2) heating furnace 1;
A portion of the combustion gases injected into the preheating device 20 through the conduit 22 from the combustion chamber 2 re-enters the furnace 10 through the communication portion 12, while the remainder is dissipated through the flue 30.

These distribution modes (1) and (2) will be explained in detail below.

First, regarding the distribution mode (1), the steel material 1 in the preheating device 20
The endothermic amount Q1 of No. 3 is expressed by the following equation (1).

Q1=K1・α1(Tct Tst)”(i)K1・
... Coefficient α1 determined by the shape and surface area of the steel material 13 ... Heat transfer coefficient TG1 ... Temperature TS1 of the combustion gas injected from the jet nozzles 27 and 28 ... Surface temperature of the steel material 13 in the preheating device 20 The heat transfer coefficient α1 in equation (1) has the relationship of the following equation (2), α1 = F (x + λ, v, γ) − (2)
X...Coefficient determined by the arrangement of the injection nozzles 27, 28, etc. λ...Thermal conductivity of the combustion gas injected from the injection nozzles 27, 28■...Thermal conductivity of the combustion gas injected from the injection nozzles 27, 28 Velocity γ...Kinematic viscosity coefficient of combustion gas injected from the ejection nozzles 27, 28 In this equation (2), there is a relationship in which the heat transfer coefficient α1 decreases as the ejected gas velocity {circle around (2)} decreases.

Incidentally, the combustion gas within the heating furnace 10 originally tends to flow easily to the preheating device 20 through the communication portion 12.

Therefore, once the gas flows out through the communication portion 12 as in the flow mode (1), the velocity of the ejected gas from the ejection nozzles 27 and 28 decreases significantly.

Therefore, the heat transfer coefficient α1 becomes smaller (see equation (2))
.

Therefore, the amount of heat Q1 absorbed by the steel material 13 decreases (see equation (1)), making it impossible to increase the temperature of the steel material 13 within the preheating device 20, and the unit consumption of the furnace worsens.

Next, the case where the above-mentioned flow mode (2) of combustion gas in the furnace occurs will be described.

The heat absorption amount Q2 of the steel material 13 in the heating furnace 10 is calculated by the following formula (3
).

K2... Coefficient φ2 determined by the shape, surface area, etc. of the steel material 13... Radiation absorption rate σ... Stefan-Holmann constant TG2... Temperature Ts of combustion gas in the heating furnace 10
2...Surface temperature of the steel material 13 in the heating furnace 10 In the distribution mode (2), relatively low temperature combustion gas in the preheating device 20 returns to the heating furnace 10 through the communication part 12, thereby increasing the temperature of the heating furnace. The combustion gas temperature TG2 in 10 decreases.

As the gas temperature TG2 decreases, the amount of heat absorbed by the steel material 13 Q
2 decreases (see equation (3)).

That is, it becomes impossible to increase the temperature of the steel material 13 in the heating furnace 10, and the unit consumption of the furnace deteriorates.

From the above explanation, the flow of combustion gas in the communication section 12 is as follows:
It is understood that this worsens the unit consumption of the furnace.

Therefore, according to a certain concept of the present invention, a combustion gas flow control device is provided in order to eliminate the flow of combustion gas in the communication portion 12 as much as possible and improve the basic unit.

This flow control device includes a pressure difference detector 53 and a meter 54.
and an adjustment damper 56.

The pressure difference detector 53 detects a pressure difference between the pressure on the heating furnace 10 side of the communication section 12 and the pressure on the preheating device 20 side, and generates a signal corresponding to this pressure difference.

The output signal from the pressure difference detector 53 is applied to one input end of the controller 54.

The other input of the controller 54 is provided with a set value signal 55 corresponding to zero pressure difference.

The controller 54 has substantially the same configuration as the controller 43 described above, and is well known to those skilled in the art.

An adjustment damper 56 is inserted on the suction side of the high temperature blower 24.

The controller 54 responds to the signal from the pressure difference detector 53 by
actuating the regulating damper 56 and thus the jet nozzle 27;
By changing the amount of combustion gas ejected from 28, the pressure difference between the heating furnace 10 side and the preheating device 20 side of the communication portion 12 becomes zero.

In this way, the flow of combustion gas in the communication portion 12 is always blocked.

Here, the adjustment damper 56 is the furnace pressure adjustment damper 45 described above.
has substantially the same configuration as, and is well known to those skilled in the art.

The embodiment shown in FIG. 1 also has the following functions.

That is, if the rolling mill (not shown) following the heating furnace 10 stops during operation, the rolling pitch changes and the transfer speed of the steel material 13 changes, or the dimensions and shape of the steel material 13 change, , the amount of combustion gas in the furnace fluctuates.

However, even in such a case, the pressure inside heating furnace 10 and the pressure inside preheating device 20 are always maintained equal.

Therefore, combustion gas is prevented from flowing through the communication portion 12, and the unit consumption of the furnace is improved.

FIG. 2 is a system diagram of another embodiment of the present invention.

This embodiment is similar to that of FIG. 1, but is characterized in that a flow rate detector 61 is used in place of the pressure difference detector 53 of FIG. 1 in the combustion gas flow control device.

The flow rate detector 61 is inserted into the communication section 12 and the communication section 1
2 (i.e. the direction of the flow of combustion gas flowing through the heating furnace 1
0 side to the preheating device 20 side or from the preheating device 20 side to the heating furnace 10 side) and the flow rate thereof, and generates a signal corresponding to the flow direction and the flow rate.

The signal from flow sensor 61 is applied to one input of a conventional controller 63.

A set value signal 64 corresponding to a flow rate of zero is given to the other input end of the controller 63.

The controller 63 operates the adjustment damper 65 in response to the signal from the flow rate detector 61 so that the amount of combustion gas flowing through the communication portion 12 becomes zero.

Note that the heating furnace 10 and preheating device 20 that were actually constructed
Inside the furnace, a pressure gradient occurs in the length direction of the furnace depending on their type and shape, and flames inside the furnace may blow out or cold air outside the furnace may enter.

According to another aspect of the invention, therefore, the controllers 54, 6
By slightly changing the set value signals 55, 64 applied to the input terminals of the fuel cell 3, a small amount of combustion gas is allowed to flow through the communication portion 12, thereby solving the above-mentioned technical problem.

Such control schemes should also be construed as falling within the scope of the following claims.

It is pointed out that the present invention can be applied not only to heating furnaces but also to various other industrial furnaces.

As described above, according to the present invention, the pressure inside the industrial furnace 10 is detected by the pressure detector 42, and the opening degree of the furnace pressure regulating damper 45 provided in the middle of the flue 30 is determined based on the detected output. is controlled by the regulating means 43, 44 and the industrial furnace 10
The pressure inside the furnace can be maintained at the desired value.

Furthermore, the pressure difference detector 53 or the flow rate detector 61 detects the differential pressure between the industrial furnace 10 and the preheating device 20 or the gas flow rate in the communication section 12, and based on the detection results, the suction/pressure raising means from the industrial furnace 10 is detected. Adjustment damper 5 inserted in the middle of the flow path leading to the jet nozzles 27 and 28 via 24
6, 65 are controlled by the adjusting means 54, 55; 63, 64, so that the differential pressure between the industrial furnace 10 and the preheating device 20 or the gas flow rate in the communication section 12 can be maintained at a desired value.

For example, by reducing the differential pressure between the industrial furnace 10 and the preheating device 20 to zero, or by reducing the gas flow rate in the communication section 12 to zero, the operation of preheating and heating the object to be heated 13 with high efficiency can be stably maintained. will definitely be achieved.

Therefore, even when operating conditions fluctuate due to changes in the amount of heated material 13 per hour, etc., a good fuel consumption rate can always be achieved.

It is possible to accurately achieve a differential pressure between the industrial furnace 10 and the preheating device 20 at a non-zero predetermined value, or a gas flow rate in the communication section 12 at a non-zero predetermined value.

This allows a small amount of combustion gas to flow through the communication portion 12.

Therefore, depending on the type and shape of the industrial furnace 10 and the preheating device 20, pressure gradients may occur in the length direction of the furnace, causing flames inside the furnace to blow out or cold air outside the furnace to enter. will be prevented.

Moreover, (a) the response speed of the control system that controls the opening degree of the furnace pressure regulating damper 45 provided in the flue 30 based on the detection output from the pressure detector 42 that detects the furnace internal pressure in the industrial furnace 10; (b) The suction/pressure boosting means 24 from the industrial furnace 10 based on the output from the pressure difference detector 53 or the flow rate detector 61
The response speed of these two control systems (a ) and (b) do not interfere with each other, and a stable control operation is achieved.

[Brief explanation of drawings]

FIG. 1 is a system diagram of one embodiment of the present invention, and FIG. 2 is a system diagram of another embodiment of the invention. 10... Heating furnace, 11... Burner, 1
2...Communication part, 13...Steel material, 14.
... Extraction port, 20 ... Preheating device, 21.
...Charging port, 22... Conduit, 23...
... Air preheating heat exchanger, 24 ... High temperature blower, 25 and 26 ... Header, 27 and 2
8...Blowout nozzle, 30...Flute, 3
1... Chimney, 42... Pressure detector, 4
3 and 54 and 63... Controller, 44 and 55 and 64... Setting value signal, 45...
... Furnace pressure adjustment damper, 53 ... Pressure difference detector, 56 and 65 ... Adjustment damper, 61 ...
...Flow rate detector.

Claims (1)

[Claims] 1. An industrial furnace 10, and a means 2 for sucking and pressurizing combustion gas from the industrial furnace 10.
4, and jet nozzles 27 and 28 for injecting the combustion gas sucked and pressurized by the suction/pressurization means 24 to the object to be heated 13, and the object to be heated 13 is preheated by the thermal energy of the injected combustion gas. A control device for an industrial furnace with a preheating device includes a preheating device 20 that connects the industrial furnace 10 and the preheating device 20 to each other to allow the conveyance of the object to be heated 13. A pressure detector 42 that detects the internal pressure, a damper 45 for adjusting the furnace internal pressure inserted in the middle of the flue 30 from which the combustion gas from the preheating device 20 is discharged, and the pressure detector 4
the industrial furnace 10 in the communication section 12; a pressure difference detector 5 that detects the pressure difference of the combustion gas on the side and the preheating device 20 side;
3, and an adjustment damper 5 inserted in the middle of the flow path from the industrial furnace 10 to the jet nozzles 27 and 28 via the suction/pressure boosting means 24.
6; and adjusting means 54 and 55 for controlling the opening degree of the adjusting damper 56 in accordance with the output from the pressure difference detector 53. 2 Industrial furnace 10 and means 2 for sucking and pressurizing combustion gas from this industrial furnace 10
4, and has an injection nozzle 27, 28 that injects the combustion gas sucked and pressurized by the suction/pressurization means 24 to the object to be heated 13, and preheats the object to be heated 13 by the thermal energy of the injected combustion gas. A control device for an industrial furnace with a preheating device includes a preheating device 20 that connects the industrial furnace 10 and the preheating device 20 to each other to allow the conveyance of the object to be heated 13. A pressure detector 42 that detects the internal pressure, a damper 45 for adjusting the furnace internal pressure inserted in the middle of the flue 30 from which the combustion gas from the preheating device 20 is discharged, and the pressure detector 4
1,000 adjustment stages 43 and 44 that control the opening degree of the furnace pressure regulating damper 45 so that the furnace internal pressure of the industrial furnace 10 becomes a predetermined value according to the output from the furnace 2, and the combustion gas passing through the communication section 12. A flow rate detector 61 that detects the flow rate of
5; and adjusting means 63 and 64 for controlling the opening degree of the adjusting damper 65 in accordance with the output from the flow rate detector 61.