JPS6012554B2 - Tunnel furnace control method for reduction firing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a tunnel furnace in which a reduction zone maintained in a reducing atmosphere is provided in a part of the firing zone formed in the longitudinal center of a tunnel-shaped furnace body.

As shown in the attached drawing, a tunnel furnace for reduction firing has a tunnel-shaped furnace body 1 in the longitudinal center thereof, which has an inlet 2 for carrying in the materials to be fired at one end and an outlet 3 at the other end. A firing zone B is configured with a large number of burners 4 arranged in a row, and is installed near the entrance 2. The suction pipe 6 of the a 5 is inserted into the furnace body 1, and the discharge pipe 8 of the blower 7 installed near the outlet 3 is penetrated into the furnace body 1, and both blowers 5 and 7 are driven. A pressure gradient is formed that is high at the loading port 3 side and low at the loading port 2, and an airflow is generated in the furnace body 1 from the loading port 3 side toward the loading port 2 side. Obi B
There is a preheating zone A in which the objects to be fired immediately after being carried in are heated by high-temperature gas flowing in from the preheating zone A, and a preheating zone A in which the objects to be fired immediately after being carried in are heated, and a preheating zone A in which the objects to be fired which have been heated to the maximum temperature in the firing zone B are placed on the side of the outlet 3 of the firing zone B. Each cooling zone C is configured to be cooled by air blown in from outside the furnace, and within the firing zone B, from the loading port 3 side toward the loading port 2 side, a neutral zone B1 maintained in a neutral atmosphere,
The reduction zone B2 is kept in a reducing atmosphere, and outside air is blown into the furnace body 1 by the blower 9 inserted through the discharge pipe 10 to create the reduction zone B2.
The atmosphere in each zone is determined by the air/fuel ratio of each burner. Sexual zone BI is kept at maximum temperature. Then, for each belt castle (illustrated only in return belt B2,
The temperature inside the furnace is detected by the thermocouple 20 and inputted to the temperature calculation device 21. If the temperature deviates from the reference temperature, the servo motor 23 is controlled by the output signal and the damper 22 is
Adjusting the relationship between Automatic control is carried out to keep the air and fuel constant and the ambient temperature constant, for example:
When the furnace temperature in reduction zone B2 or neutral zone BI becomes higher than the reference value and control is performed to reduce the amount of air and fuel ejected from burner 4, the amount of gas generated by combustion will decrease. The pressure in that area decreases, the pressure gradient in the length direction of the furnace body 1 changes, the temperature distribution and the atmosphere concentration distribution are disturbed, and the firing conditions may become unstable.Conversely, the reduction zone B2 or If the temperature inside the neutral zone BI becomes lower than the standard value, the amount of air and fuel will increase,
The reactor pressure rose and the aircraft became unstable.

The present invention aims to eliminate such drawbacks and perform stable reduction firing, and an example thereof will be explained based on the attached drawings.
At I, the outputs of the transmitters 12 and 16 that convert the pressure detected by the pressure detection tubes 11 and 15 that have penetrated into the furnace body 1 into electrical signals are input to the furnace pressure calculation device 13, and the furnace pressure calculation device 13 controls the pressure based on the calculation results of the calculation device 13. The rotation speed of the blower 9 is controlled by a signal issued from the device 14.

When an increase in the pressure inside the furnace in the reduction zone B2 or the neutral zone BI is detected, the rotation speed of the blower 9 is reduced and the
When the amount of air blown into B2 decreases and the pressure inside the furnace decreases, the rotational speed of the proir 9 increases and the amount of air increases, and the pressure inside the furnace near the reduction zone B2 is kept substantially constant.

In the above, instead of detecting pressure fluctuations in the reduction zone B2 or the neutral zone BI and controlling the rotation speed of the blower 9, the output signal of the temperature calculation device 21 to the servo motor 23 that adjusts the greasy degree of the damper 22, or The output signal of the flow meter 25 that detects the fuel supply amount is inputted to the pressure calculation device 13,
By predicting fluctuations in furnace pressure due to fluctuations in the flow rate of fuel or air supplied to burner 4 and controlling the rotation speed of blower 9 based on this, delay time is eliminated and more stable control is performed. Can be done.

Note that the rotation speed of the blower 9 may be kept constant, and the opening degree of a damper provided through the discharge pipe 101 may be adjusted to control the flow rate of air blown into the purification zone B3.

In addition, if the furnace pressure fluctuates significantly, purification zone B3
In addition to controlling the flow rate of air blown into the furnace, it is preferable to control the gas flow over the entire length of the furnace body 1 using blowers 5 and 7 installed at the carry-in port 2 and the carry-out port 3. As specifically explained in the above embodiments, the furnace pressure control method for reduction firing in a tunnel furnace according to the present invention comprises arranging burners in a row in the longitudinal center of a tunnel-shaped furnace body to form a firing zone. In addition, by maintaining the pressure inside the furnace so that the pressure on the carry-in port side is higher than that on the carry-in port side and generating an airflow from the carry-in port side to the carry-in port side, a pre-heating zone is formed on the carry-in port side of the firing zone. , a cooling zone is formed on the carry-out port side, and the inside of the firing zone is sequentially maintained in a neutral atmosphere from the carry-in port side toward the carry-in port side; a neutral zone kept in a neutral atmosphere; and a reduction zone kept in a reducing atmosphere;
In a tunnel furnace divided into a purification zone where air is blown into the furnace to completely burn the reducing gas flowing in from the reduction zone, and an oxidation zone where an oxidizing atmosphere is maintained, the tunnel furnace is configured to respond to pressure fluctuations in the reduction zone or the neutral zone. The gist is to vary the amount of air blown into the purification zone,
The furnace pressure near the reduction zone can be kept substantially constant, and the temperature distribution and atmosphere concentration distribution can be stabilized.

[Brief explanation of the drawing]

The attached drawing shows a cross-sectional view of the furnace body and a block diagram of the control circuit. 1: Furnace body, 2: Loading port, 3: Loading port, 4: Burner, 5,
7, 9: Blower, 11, 15: Pressure detection tube, 13: Furnace pressure calculation device, 14: Control device, A: Pre-preparation zone, B: Firing zone,
C: cooling zone, BI: neutral zone, B2: reduction zone, B3: purification zone, B4: oxidation zone.

Claims (1)

[Claims] 1. Burners are arranged in a row in the longitudinal center of a tunnel-shaped furnace body to form a firing zone, and the pressure inside the furnace body is made higher on the outlet side than on the entrance side. By maintaining the air flow from the carrying-out port side to the carrying-in port side, a preheating zone is formed on the carrying-in port side of the firing zone, and a cooling zone is formed on the carrying-out port side. From the outlet side to the entrance side, the neutral zone kept in a neutral atmosphere, the reduction zone kept in a reducing atmosphere, and purification by blowing air into the furnace to completely burn the reducing gas flowing from the reduction zone. A tunnel furnace divided into an oxidation zone and an oxidation zone maintained in an oxidation atmosphere, characterized in that the amount of air blown into the purification zone is varied in response to pressure fluctuations in the reduction zone or the neutral zone. control method. 2. Forecasting atmospheric pressure fluctuations in the reduction zone based on fluctuations in the amount of fuel or air supplied to the burner in the reduction zone or the neutral zone, and varying the amount of air blown into the purification zone based on this. A method for controlling a tunnel furnace according to claim 1, characterized in that: