JPS61190280A - Method of controlling furnace pressure of tunnel furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a method for carrying in a trolley carrying objects to be fired through an inlet formed at one end of a long and narrow tunnel-shaped furnace body, and proceeding to an outlet formed at the other end of the furnace body. The present invention relates to a method for appropriately controlling the pressure inside a tunnel furnace in which firing is continuously performed during transport.

Problems to be solved by conventional technology and the invention In a tunnel furnace, gas inside the furnace is discharged from near the delivery port, and air is supplied into the furnace from near the delivery port, and air is brought into the furnace from the port side. A gas flow is generated toward the mouth side, thereby maintaining an appropriate temperature distribution in the longitudinal direction inside the furnace. When you open the door installed at the entrance or exit to transport baked products, the pressure inside the furnace fluctuates rapidly due to the inflow of outside air and the outflow of gas inside the furnace, and the gas flow is disturbed. If the temperature and atmosphere distribution inside the furnace deviates from the appropriate values, it may cause firing defects.Many of the latest tunnel furnaces detect changes in the pressure or temperature inside the furnace and discharge gas from inside the furnace. Automatic control devices that adjust the flow rate or the flow rate of air supplied into the furnace have come to be installed, but automatic control inevitably involves a delay time, and every time the door is opened or closed, the inside of the furnace Since the pressure, concentration and temperature of each gas are unstable for a considerable period of time, improvements have been desired.

For this reason, the applicant of the present application has developed a tunnel in which the gas discharge flow rate and/or air supply flow rate in the furnace can be changed in relation to the opening and closing of the loading entrance or the door that opens and closes the loading exit. Developed a furnace pressure control method and filed a patent application in 1982.
A patent application was filed as No.-221603.

By implementing this control method, pressure fluctuations due to control delays were reduced, making it possible to maintain a stable state inside the furnace. It has been found that the fluctuations can be divided into two stages: the first stage when the door is opened, and the second stage when a trolley enters the loading port or exits from the loading port. To explain this in terms of the carry-out port side, when the door is opened, the gas inside the furnace is discharged from the carry-out port. Since the furnace is on standby, the gas in the furnace is discharged through a narrow gap around the trolley and the objects to be fired placed on it. Therefore, as shown in 1 in Figure 1, the range of decrease in the pressure inside the furnace from the reference value from the time one door is opened until the trolley is completely pulled out from the export port is not that large, and the trolley When the furnace is completely pulled out from the outlet, the gas inside the furnace is exhausted from the entire outlet, so as shown in the figure, the pressure inside the furnace remains higher than the standard value until the door is closed again. However, this kind of two-step change in the pressure inside the furnace also occurs at the loading port side of the cart, and on the loading port side, when the door is opened, the pressure in the furnace once drops from the reference value. When the pressure fluctuates greatly and then the cart carrying the unfired material to be fired is pushed in, most of the entrance is blocked and the range of fluctuation of the furnace pressure with respect to the reference value becomes small.

Purpose of the Invention The present invention provides for adjusting the flow rate of air supplied to the vicinity of the discharge port in the furnace or gas from the vicinity of the discharge port in response to two-stage pressure fluctuations in the pressure inside the furnace due to the opening and closing of the door of the discharge port or the import port. The purpose of this is to further suppress fluctuations in the pressure inside the furnace by controlling the discharge flow rate of the gas, thereby maintaining the inside of the furnace in an extremely stable state.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

The furnace body 1 of the tunnel furnace is in the shape of a long and narrow tunnel with rails 2 laid inside, and a pre-heating zone 1a is located on the left side of the firing body 1b at the center in the longitudinal direction, with a large number of burners 3 arranged in rows on both sides, and a preheating zone 1a is located on the right side. A cooling zone IC is connected to each of the cooling zone ICs, and doors 6 and 7 that are opened and closed by going up and down are provided at the loading inlet 4 formed at the left end and the unloading outlet 5 formed at the right end, respectively. A rail 8 for circulating circulation is laid, and a traverser 10.10 connects both ends of this rail 8 and the inlet 4 and outlet 5 of the furnace body 1'.
The cart 13 loaded with the materials to be fired at the loading position A at the left end of the traverser 10 is transferred to the transfer platform 12 of the traverser 10 and transported to the loading port 4, and when the door 6 rises and opens, the non-rotating button It is pushed into the furnace body 1 by L; 2
When the trolley 13 loaded with baked products passes through the preheating zone 1a, baking zone 1b, and cooling zone 1C and reaches the carry-out port 5, the door 7 opens and a drawer device (not shown) pulls out the 1- The rubber server 10 is pulled out onto the transfer table 12, transferred onto the rail 8 again, and the fired product is unloaded at the unloading position B.

In addition, a discharge blower 14 is installed near the loading port 4 of the preheating zone 1a of the furnace body 1, and its suction pipe 15 penetrates into the furnace. A blower 16 is installed, and its discharge pipe 1 penetrates into the furnace.The discharge blower 14 discharges the gas inside the furnace to the outside of the furnace, and the supply blower 16 discharges the air outside the furnace. is forced into the furnace, and a pressure gradient is formed in the furnace that gradually decreases from the outlet 5 side to the inlet 4 side, and this pressure gradient causes a gas flow from the outlet 5 side to the inlet 4 side. This gas flow causes the temperature distribution in the longitudinal direction of the furnace to match the desired heat curve. Pressure fluctuations detected by the pressure detection tubes 18.19 penetrated into the transmitter 20.21 are converted into electrical signals and input to the calculation device 22.23, and the control device 24.23 receives an output signal based on the calculation result. 2
By changing the output of the blowers 14 and 16 and controlling the rotational speed of the blowers 14 and 16, the flow rate is adjusted and the pressure gradient in the furnace is kept constant. The pressure fluctuation inside the furnace caused by the opening and closing of the door 6.7 for loading and unloading the trolley 13 is corrected by such automatic control, as described above.

After the pressure inside the furnace fluctuates, this is detected and the blower 1
If the flow rate of 4.16 is changed, a certain delay time is required for the pressure in the furnace to restore to an appropriate value, and there is a risk that firing defects may occur due to fluctuations in the temperature or atmosphere in the furnace.

Therefore, in this embodiment, detection devices 26.27, such as limit switches and phototubes, which are activated when the door 6.7 is opened, and detection devices 28. 29 is a trolley 13 on which a fired product is placed.
A detection device 30 that is activated by detecting that the front end of the cart 13 has entered the carry-in port 4 is installed at the carry-out port 5. Each detection device 26 and 28 is provided with a detection device 31 that detects and operates.
．． 30, 27, 29, and 31 are connected to timing pulse generators 32, 33, respectively, and the timing pulses generated in response to the detection signals from each detector are sent to the correction calculation device 34.
35, and the calculated correction value is input to the above-mentioned calculation device 2.
2.23 is connected to input.

Next, the operation of this embodiment will be explained with respect to the outlet 5 side of the furnace body 1. When the detection device 27, 29, 31 detects the completion of opening the door 7 and pulling out the trolley 13, timing pulses corresponding to the detection signal are sequentially input from the timing pulse generator 33 to the correction calculation circuit 35. .

This correction calculation circuit 35 includes, as shown in ■ in FIG.
Data corresponding to temporal fluctuations in the pressure inside the furnace due to the opening and closing of the door and the pulling out of the trolley 13, which have been measured in advance, are stored, and correction values calculated based on this data are input to the calculation device 23 over time. A control value is determined by calculating the correction value and the furnace pressure detected by the pressure detection tube 19, and the control value is input to the control device 25, and the rotation speed of the blower 16 is controlled by the output signal. It is supposed to be done. Therefore, as shown in ■ in Fig. 1, the first
In the step, the rotation speed of the blower 16 is rapidly increased from the reference rotation speed, and then maintained at approximately that level, and the
In the second stage, when the withdrawal of No. 3 is completed, the rotation speed is further increased rapidly and then maintained at approximately that level. When the door 7 is closed, the rotation speed is controlled to return to the standard rotation speed, and as a result, the rotation speed into the furnace is controlled to return to the standard rotation speed. The air supply flow rate changes to maintain the furnace pressure approximately constant. On the side of the loading port 4, the rotation speed of the blower 14 is similarly controlled, the amount of discharged gas in the furnace is changed, and the pressure in the furnace is similarly maintained substantially constant.

61 The following table shows an example of actual measured values of the fluctuation range of the furnace pressure on the outlet side with respect to the reference value by the control method according to the present invention and the conventional control method.

Note that the setting of the pressure distribution inside the furnace differs depending on the furnace.For example, contrary to the above, the furnace pressure on the loading port 4 side may be set higher than the atmospheric pressure. In such a case, when the door 6 is opened, it is necessary to reduce the rotational speed of the blower 14 to reduce the amount of flow flowing out from the loading port 4.

Structure and Effects of the Invention As specifically explained in the above embodiments, the furnace pressure control method for a tunnel furnace of the present invention has a method for controlling the furnace pressure of a tunnel furnace, in which an inlet for a trolley on which a material to be fired is placed is placed at one end, and an outlet at the other end. The gas inside the furnace is discharged from the vicinity of the inlet of the tunnel-shaped furnace body in which the inlet is formed, and the air is supplied into the furnace from the vicinity of the outlet. In a tunnel furnace that is lower than the outlet side, the gas discharge flow rate and the air supply flow rate are both or either of the following:
The gist is to change in relation to the opening and closing of the door that opens and closes the loading entrance or the loading port, the loading or unloading of the trolley, and the blockage, and the changes are made in connection with the opening and closing of the door and loading and unloading of the trolley. Since it is possible to control in response to two-step fluctuations in the pressure inside the furnace and to correct the fluctuations immediately before the fluctuations occur, it is possible to maintain the inside of the furnace in an extremely stable state.

[Brief explanation of drawings]

1 in Figure 1 is a graph showing fluctuations in furnace pressure, ■ in the same figure is a graph showing changes in blower rotation speed, and Figure 2 is a cross-sectional view of a tunnel furnace used to carry out the method of the present invention, showing furnace pressure control. It also includes a block diagram of the circuit. 1: Furnace body 4: Loading port 5: Loading port 6.7: Door 14
．． 16: Blower 18.19: Pressure detection tube 20.21
: Transmitter 22.23: Arithmetic device 24.25: Control device 26.27.28.29.30.31: Detection device
32.33: Timing pulse generator 34.35:
Correction calculation device

Claims (1)

[Claims] The gas inside the furnace is discharged from the vicinity of the loading port of the tunnel-shaped furnace body, which has a loading port for the trolley on which the material to be fired is placed at one end and a loading port at the other end. In a tunnel furnace, the pressure gradient in the furnace is made lower on the inlet side than on the outlet side by supplying air to , a furnace pressure control method for a tunnel furnace, characterized in that the furnace pressure is changed in relation to the opening of a door that opens and closes the loading port or the loading port, loading or unloading of a cart, and blockage.