JPS6261089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a non-oxidizing furnace such as a non-oxidizing heating furnace in continuous plating equipment.

The non-oxidizing furnace used in continuous plating equipment is used to clean the surface of the strip by heating it to a predetermined temperature as a pretreatment for plating.In order to prevent the surface of the strip from oxidizing in the furnace, the burner that is the heating source is is less than 100% air-fuel ratio (usually 90
~96%). For this reason, the fuel is not completely combusted, and unburned fuel is discharged outside the furnace as exhaust gas, which is not only undesirable in terms of energy conservation, but also causes pollution problems.

This invention has been made in view of the above points, and aims to provide a control method for a non-oxidizing furnace that can achieve effective energy use and prevent harmful unburned substances from being discharged outside the furnace through complete combustion of fuel. .

Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 is a system diagram of an example of an apparatus for carrying out the method of this invention, in which numeral 1 is a non-oxidizing heating furnace;
2 is the inlet of the furnace, and 3 is the outlet of the furnace. W is a strip of the object to be heated, and 4 is a conveyance device for conveying the object to be heated. Inside the furnace, there is a first zone 31 in the furnace length direction,
The zone is divided into a second zone 32, . . . , and a fifth zone 35, and each zone is provided with a burner 5, which is a heating device. The high-temperature combustion gas generated in the burner 5 flows through the furnace in the direction opposite to the direction of movement of the object W to be heated (in the direction of arrow Y), and is discharged to the outside of the furnace through the preheating throat 6 connected to the inlet 2 of the furnace. It is configured to be 7 is an infrared thermometer for detecting the temperature of the heated object W at the outlet 3 of the furnace, and 8 is a heated object temperature controller. Further, 9 is a changeover switch, and 10 is a heating control device, one set of which is provided for each zone. The configuration of the heating control device 10 is as shown in FIG. 3, where 11 is a fuel flow controller, 12 is an air-fuel ratio setting device, 13 is an air flow controller, 14 is a fuel pipe, 15 is a fuel flow control valve, and 16 is a fuel flow controller. a fuel flow rate detector; 17 is an air pipe; 18 is an air flow control valve;
19 is an air flow rate detector. Furthermore, 20 is a combustion zone selection device, which is a calculator that generates a combustion zone number signal N when the dimensions of the object W to be heated, the heating temperature, and other heating condition data are input. 21 is a discrimination device that discriminates heating and heating stop of each zone;
It is provided for each zone. The discrimination device 21 is composed of, for example, a high-low discriminator, and compares the combustion zone number signal N from the combustion zone selection device 20 with a signal unique to each zone (for example, "3" for the third zone), and determines whether both are different. Switch the changeover switch 9 to the contact a connected to the output side of the heated object temperature controller 8 in the matched zone and the zone on the exit side of the zone, and to the contact b connected to the input signal 0 in other zones. It is something that makes it work. Reference numeral 22 denotes an air-fuel ratio correction calculation device, which is a calculator that calculates the air-fuel ratio from the fuel flow rate and air flow rate of all the burners during combustion, and calculates the corrected air amount for complete combustion of the fuel.

Next, the method of the present invention using the apparatus with the above configuration will be explained. First, heating condition data such as the dimensions, material, conveyance speed, and heating temperature of the object W to be heated are given to the combustion zone selection apparatus 20 to calculate the combustion zone. Determine the number N. FIG. 1 shows a case where the combustion zone number signal N=3 issued by the combustion zone selection device 20, and each changeover switch 9 is switched as shown in the figure by the operation of the discrimination device 21 of each zone. As a result, in the fourth zone 34 and the fifth zone 35, the input signal to the heating control device 10 is 0, so the burner 5 is extinguished. On the other hand, in the first zone 31 to the third zone 33, the output signal of the heated object temperature controller 8 is given as an equal signal to the heating control device 10 of each zone, and the output signal of the infrared thermometer 7 is The combustion amount of the burner 5 in each of these zones 31 to 33 is controlled to control the temperature of the heated object to a predetermined value. On the other hand, the air-fuel ratio correction calculation device 22 is supplied with detection signals of each fuel flow rate and air flow rate of the burners 5 in the first zone 31 to the third zone 33. The air-fuel ratio correction calculation device 22 calculates a correction (additional) air flow rate for complete combustion of the entire fuel flow rate from these input data, and determines the amount of air entering the combustion zone based on the combustion zone number signal N of the combustion zone selection device 20. In the heating control device 10 of the side end zone, that is, the third zone 33,
The above-mentioned corrected air flow rate is given to the air-fuel ratio setter 12 as an air-fuel ratio correction value. As a result, the third zone 33
The burner 5 is additionally supplied with air for burning the unburned part of the fuel resulting from the combustion of the burners in the first to third zones, so the unburned part in the exhaust gas is
It is completely combusted in the zone, and is effectively used for preheating the objects to be heated that proceed in the fourth and fifth zones, and for heating the objects to be heated in the third zone, and prevents unburned substances from being discharged outside the furnace. It will be done.
The temperature rise curve of the heated object W in the furnace at this time is as shown in Figure 2, and the temperature of the heated object in the fourth and fifth zones is 600, which is the oxidation start temperature of the strip.
Since the temperature is low, at ~700°C or less, no harmful oxidation phenomenon occurs on the strip surface even when combustion air is supplied at an air-fuel ratio of 100%, and non-oxidative heating can be performed without any problems.

In the above embodiment, the burner 5 in the third zone 33
Although correction air for complete combustion is additionally supplied to the burner 5 in the fourth zone 34, which is the front zone of the combustion zone, or to both the burners 5 in the third zone and the fourth zone. Furthermore, an air nozzle for supplying correction air may be provided in each zone separately from the burner 5.

Further, in the above embodiment, the output signal of the heated object temperature controller 8 is directly given to each heating control device 10 as a flow rate setting signal, but the furnace temperature control device 10 is provided with the output signal of the heated object temperature controller 8 in each zone. The present invention can also be applied to the case where the furnace temperature of each zone is controlled in a cascade manner. Further, in the above embodiment, the combustion amount is controlled by using all zones of the combustion zone determined according to the heating conditions of the object to be heated as control zones. The present invention can also be applied to non-oxidation heating furnaces that use combustion control methods other than the above embodiments, such as when the combustion amount is controlled as a control zone and other zones in the combustion zone are burned at the maximum furnace temperature. It is.

As explained above, according to the method of the present invention, the unburned portion of the fuel during the operation of the non-oxidizing heating furnace is burned in the furnace and effectively used for heating the object to be heated, so that the fuel consumption rate is improved, and It is possible to prevent harmful unburned substances from being discharged outside the furnace.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of an apparatus for carrying out the method of the present invention, Fig. 2 is a temperature rise curve of the object to be heated in the furnace, and Fig. 3 is a heating control device for the apparatus shown in Fig. 1. It is a partial system diagram. DESCRIPTION OF SYMBOLS 1... Non-oxidation heating furnace, 5... Burner, 7... Infrared thermometer, 8... Heat target temperature controller, 9... Changeover switch, 10... Heating control device, 12... Air-fuel ratio setting device,
20... Combustion zone selection device, 22... Air-fuel ratio correction calculation device, 31... First zone, 32... Second zone,
33...Third zone, 34...Fourth zone, 35...Fifth zone.

Claims (1)

[Claims] 1. Among multiple zones equipped with burners, a combustion zone is determined near the outlet of the furnace based on the heating conditions of the object to be heated, and all of the combustion zones or an appropriate number of zones on the entrance side are designated as control zones. In a non-oxidizing furnace that controls the amount of combustion in the control zone, air for combustion of unburned matter is supplied to the inlet end zone and/or the front zone of the combustion zone, and the air is used to control the amount of combustion in the combustion exhaust gas. A method of controlling a non-oxidizing furnace characterized by burning unburned matter.