JPH11337052A - Temperature control method for furnace with heat storage burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat an object uniformly with good temperature distribution by setting the combustion side holding time of one of a pair of heat storage burners longer than that of the other burner. SOLUTION: Heat storage burners A, B form heat accumulators 13a, 13b by filling a casing, where burners 11a, 11b are formed by providing a burner tile part at the forward end part, with a heat storage material 12. The burner A performs combustion at a level required for sustaining the furnace temperature and heat is recovered from combustion exhaust gas through the heat accumulators 13a of the burner B before the exhaust gas is discharged. At the end of combustion, an on/off valve 23 is closed and on/off valves 33, 44 are closed upon elapsing a combustion side holding time Ta after a specified purge time. A controller 52 then delivers an on/off command signal and a combustion side holding time signal Tb of the burner B in order to open on/off valves 34, 43. Since the time Yb is set longer than Ta, combustion time of the burner B is longer than that of the burner A and uneven heating of an object W is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace temperature control method for a furnace having a regenerative burner.

[0002]

2. Description of the Related Art At least one pair of regenerative burners comprising a combination of a burner and a regenerator is provided, and the pair of regenerative burners is alternately switched between a combustion side and an exhaust side to discharge the combustion exhaust gas of the regenerative burner on the combustion side. A furnace that discharges gas through the regenerator of the regenerative burner on the exhaust side has excellent thermal efficiency because the recovered heat of the combustion exhaust gas by the regenerator can be used effectively for preheating of the combustion air after switching. It has come to be widely used as a furnace.

[0003] As a method of controlling the furnace temperature in a furnace equipped with a regenerative burner, a deviation between the detected furnace temperature in the regenerative burner installation zone and the set furnace temperature is required in response to an increase or decrease in the combustion load or a change in the furnace temperature setting. In general, a flow control combustion system in which the amount of fuel supplied to each burner (and the air flow rate) is adjusted in accordance with the flow rate to maintain the furnace temperature at a set value is adopted.

[0004]

However, in the above-mentioned flow control combustion system, switching of the pair of regenerative burners is performed at regular intervals (for example, 30 seconds) as shown in FIG. The combustion side holding time (≒ burning time) T of the regenerative burner A corresponding to the cycle time is equal to the burning side holding time (≒ time) T of the regenerative burner B. For this reason, for example, when one of the pair of regenerative burners is located at a position away from the furnace inlet and the other is near the furnace inlet, or one of the burners is located above the heat-receiving material on the in-furnace conveyor. When the burner and the furnace body, furnace contents, and obstacles are in different relative positions, such as when the burner is located below the conveyor and the other is below the conveyor, one side of a large heated object is underheated. Alternatively, there is a problem that the temperature distribution of the object to be heated is poor and uneven heating is likely to occur, such as an overheated state, and a part of a large number of small objects to be heated accommodated in a pallet or the like becomes insufficiently heated or overheated. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and provides a furnace temperature control method capable of heating an object to be heated to a good temperature distribution state with less heating unevenness in a furnace having a regenerative burner. The purpose is to do.

[0006]

A furnace temperature control method for a furnace having a regenerative burner according to the present invention comprises at least one pair of regenerative burners each comprising a combination of a burner and a regenerator. Is alternately switched to the combustion side and the exhaust side to discharge the combustion exhaust gas of the regenerative burner on the combustion side through the regenerator of the regenerative burner on the exhaust side, and adjust the amount of fuel supplied to each burner to reduce the furnace temperature. In a furnace temperature control method for a furnace having a regenerative burner that is maintained at a predetermined value, the combustion-side holding time of one regenerative burner of the pair of regenerative burners is set to the combustion time of the other regenerative burner. It is characterized by being longer than the side holding time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a heating furnace including a roller hearth type continuous heating furnace.
The object to be heated W charged into the furnace body 3 from the inlet 2 passes through the heating zones 5, 6 and 7 while being conveyed inside the furnace by the hearth roll 4, undergoes heat treatment, and is sent out of the furnace from the outlet 8. You. On one side wall of the furnace body 3, regenerative burners A and B for the heating zone 5 are provided.
However, regenerative burners A and B for the heating zone 6 and regenerative burners A and B for the heating zone 7 are vertically and horizontally (FIG. 2).
(Left and right in Fig. 1) with the phase shifted.

FIG. 3 shows a piping system of the regenerative burners A and B provided in the heating zone 7, and the regenerative burners A and B are provided with burner tiles at their ends to form burners 11a and 11b. The inside of the heat storage unit 12 is filled
3a and 13b. The fuel supply pipe 21 branches via a fuel flow control valve 22 and includes an on-off valve (fuel valve) 23,
24 are connected to the burners 11a and 11b, respectively. Reference numeral 25 denotes a fuel flow controller, and reference numeral 26 denotes a fuel flow detector. Also, an air supply pipe 3 connected to an air supply blower 30.
1 is branched via an air flow control valve 32 and connected to heat storage units 13a and 13b via on-off valves (air valves) 33 and 34, respectively. 35 is an air flow controller, and 36 is an air flow detector.

Reference numeral 41 denotes an exhaust pipe connected to an exhaust blower or a chimney (not shown).
And is connected to the heat accumulators 13a and 13b via on-off valves (exhaust valves) 43 and 44. Reference numeral 51 denotes a thermocouple for detecting the furnace temperature; 52, a fuel flow signal Fg necessary for maintaining the furnace temperature at a set value in accordance with a deviation between the detected furnace temperature of the thermocouple 51 and a set furnace temperature; Air flow signal Fa
And a controller that issues an open / close command signal to each open / close valve. Each of the above-mentioned on-off valves is composed of an electromagnetic on-off valve, and each of the regenerative burners A and B of the other heating zones 5 and 6 has the same structure and the same piping system as described above.

Next, a furnace temperature control method using the above-described apparatus will be described with reference to FIGS. First, the opening degree of the exhaust gas flow control valve 42 is set and controlled by the exhaust gas temperature or the combustion amount (calculated from the fuel and air flow rates). On the basis of the detected furnace temperature of the thermocouple 51 and the set furnace temperature, the control device 52 executes the fuel flow signal Fg.
To the fuel flow controller 25, the combustion air flow rate signal Fa
To the air flow controller 35, respectively.
An on-off command signal to each on-off valve and a combustion side holding time (combustion switching cycle time) signal Ta (for example, 30 seconds) of the regenerative burner A are output, whereby the on-off valves 33 and 44 are opened, and a predetermined pre-purge time Tw After one second (for example, one second), the on-off valve 23 is opened, and combustion is performed in the regenerative burner A (specifically, the burner 11a) under the combustion amount necessary for maintaining the furnace temperature. After the exhaust heat is recovered through the regenerator 13b of B, the exhaust heat is discharged from the exhaust pipe 41.

At the end of the combustion, the on-off valve 23 is closed, and after a predetermined purge time Tp (for example, one second), the on-off valves 33, 44 are closed due to the elapse of the combustion-side holding time Ta.
The control device 52 outputs an opening / closing command signal and a combustion side holding time (combustion switching cycle time) signal Tb (for example, 3
3 seconds), whereby the on-off valves 34 and 43 are opened, and after a predetermined pre-purge time Tw (for example, 1 second), the on-off valve 24 is opened and the regenerative burner B (specifically, the burner 1) is opened.
In 1b), combustion is performed under the combustion amount necessary for maintaining the furnace temperature, and the combustion exhaust gas passes through the regenerator 13a of the regenerative burner A and is discharged from the exhaust pipe 41 after exhaust heat recovery. At the end of combustion, the on-off valve 24 closes and the purge time Tp
(E.g., 1 second) after the combustion side holding time Tb elapses,
The on-off valves 34, 43 close and the on-off valves 33, 44 open. Hereinafter, the combustion of the regenerative burner A, and then the regenerative burner B, are performed every time the combustion-side holding time Ta, Tb elapses.
Is alternately repeated.

In the above, the combustion side holding time Tb is set to be longer than the combustion side holding time Ta, whereby the combustion time of the regenerative burner B, that is, the amount of combustion heat, is
Heated material heating characteristics by the regenerative burner B, which is larger than the heat of combustion of the regenerative burner A and is insufficiently heated because it is located on the outlet 8 side of the furnace where heat loss is large and below the hearth roll 4 which is an interference. Is corrected, the uneven heating of the object to be heated W is reduced, and the object to be heated can be heated to a favorable temperature distribution state.

In this example, the combustion side holding time Tb is Tb = kTa with respect to the combustion side holding time Ta [where k is a proportionality constant larger than 1]. In the above example, k = 1.1] is calculated, and the proportionality constant k is used in a test operation using a heated object W to which a thermocouple for measuring the temperature of each part is attached when the heating furnace is installed. The determination is made while observing the improvement of the temperature distribution state of the object to be heated W.

Although the above control method has been described for the heating zone 7, the same control may be performed in the other heating zones 5 and 6. In this case, the proportional constant k is set according to each heating zone. Use values. Further, in a heating zone where the temperature unevenness of the object to be heated W is small due to the arrangement of the burners, Tb =
The furnace temperature may be controlled by a normal flow control combustion system of Ta.

The present invention is not limited to the above-described example. For example, the type of the heating furnace may be other than that described above, and a regenerative burner may be provided such that a pair of regenerative burners is provided on the opposed furnace wall. May be arranged other than the above.

In the above-described example, the combustion-side holding time of the regenerative burner on the side of the heating target that is underheated is set longer than the combustion-side holding time of the normal flow control combustion system. The combustion-side holding time of the regenerative burner may be shorter than the combustion-side holding time of the normal flow control combustion method to improve the temperature distribution of the heat target. The type burner is referred to as the "other regenerative burner" according to the present invention, and the regenerative burner that performs combustion on the combustion side holding time by the normal flow control combustion method is referred to as "one regenerative burner" according to the present invention. Equivalent to.

Also, in the above example, the ratio of the pair of regenerative burners on both combustion side holding times (proportional constant k in the above example).
However, instead of this, a predetermined time (for example, several seconds) may be added to or subtracted from the combustion side holding time of one regenerative burner to provide a difference between the two combustion side holding times.

[0018]

As described above, according to the present invention,
In a furnace equipped with a regenerative burner and controlling the combustion amount by controlling the combustion amount by a flow control combustion method, the relative position of each burner part of the pair of regenerative burners with the furnace body, furnace contents, and obstacles Even if there is a difference in the heating performance of the heat storage material between the two burners due to the difference, etc., a difference is provided in the combustion side holding time of both regenerative burners to increase the amount of heating on the underheating side of the heating material or reduce the amount of heating on the superheating side Therefore, the object to be heated can be heated to a favorable temperature distribution state with less uneven heating.

[Brief description of the drawings]

FIG. 1 is a plan view of a heating furnace showing an example of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a piping system diagram (a sectional view taken along line YY in FIG. 2) of the regenerative burners A and B in FIG.

FIG. 4 is a timing chart showing an operation of each device in FIG. 3;

FIG. 5 is a schematic timing chart showing a conventional furnace temperature control method.

[Description of Signs] 1 ... Heating furnace, 11a ... Burner, 11b ... Burner, 13a
... regenerator, 13b ... regenerator, 21 ... fuel supply pipe, 23 ...
On-off valve, 24 ... On-off valve, 25 ... Fuel flow controller, 26 ...
Fuel flow rate detector, 31 ... air supply pipe, 33 ... open / close valve, 34 ...
On-off valve, 35 Air flow controller, 36 Air flow detector, 41 Exhaust pipe, 43 On-off valve, 44 On-off valve, 51
... thermocouple, 52 ... control device, A ... regenerative burner, B ... regenerative burner.

Claims (1)

[Claims] At least one pair of a regenerative burner comprising a combination of a burner and a regenerator is provided, and a pair of regenerative burners is alternately switched between a combustion side and an exhaust side to discharge combustion exhaust gas from the regenerative burner on the combustion side. A method of controlling a furnace temperature of a furnace having a regenerative burner in which a regenerative burner is discharged through a regenerator of a regenerative burner on an exhaust side and the amount of fuel supplied to each burner is adjusted to maintain a furnace temperature at a predetermined value. Characterized in that the combustion side holding time of one regenerative burner of the pair of regenerative burners is longer than the combustion side holding time of the other regenerative burner. Temperature control method.