JP3128083B2 - Furnace atmosphere control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discontinuous kiln, and more particularly to an atmosphere control for a discontinuous kiln.

[0002]

2. Description of the Related Art Conventionally, when firing ceramic bodies, it has been desired to appropriately control the atmosphere such as gas components, temperature, and pressure in a furnace. This is because a change in the atmosphere in the furnace has a great effect on the quality of the product to be fired, such as the color and the compaction. As a control device for controlling the atmosphere in the furnace, for example, as shown in FIG. Air is supplied from the blower blower 3 to the burner 2 according to the opening degree of the air damper 5 driven by the motor 4, and the fuel gas cylinder 7 is controlled according to the opening degree of the fuel gas damper 9 driven by the motor 10.
The fuel gas reduced in pressure by the pressure reducing valve 8 is supplied to the burner 2. Air and fuel gas are mixed in the burner 2,
The mixture is ignited as a mixed gas having a substantially approximate stoichiometric air-fuel ratio, and the ignited high-temperature combustion gas is blown into the furnace.

[0003]

However, according to the conventional in-furnace atmosphere control device, the operator manually adjusts the opening of the air damper and the opening of the fuel gas damper, so that the initial opening of both dampers is set. It is difficult to adjust the opening degree and the opening degree at the intermediate time, so that the operation of adjusting the atmosphere in the furnace is complicated. If the opening of the adjustment valves such as the two dampers is not proper, the atmosphere in the furnace becomes unstable due to excess and deficiency of air and fuel, so that the firing of the fired product becomes uneven and the quality of the fired product deteriorates. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is intended to easily adjust a flow rate control valve for air and fuel gas, and to provide a highly reliable furnace atmosphere capable of precise atmosphere control. It is an object to provide a control device.

[0005]

According to a first aspect of the present invention, there is provided a furnace atmosphere control apparatus, comprising: a gas burner mounted on a furnace body; an air passage for supplying air to the gas burner; A fuel gas passage for supplying fuel gas to the gas burner, a valve body of a flow control valve that opens and closes the fuel gas passage, an urging means for urging the valve body of the flow control valve in a closing direction, and A diaphragm partitioned into a loading pressure chamber for introducing the taken-out loading pressure from a loading pressure introduction passage and an atmospheric pressure chamber for introducing atmospheric pressure, wherein the diaphragm opposes the urging means with a decrease in the pressure of the loading pressure chamber. A diaphragm that drives the valve body in a direction to increase the opening of the flow control valve;
Controls the loading pressure in the loading pressure introduction passage
Pressure relief control valve and the loading pressure
Elapsed after the start of firing by controlling the opening of the relief control valve
Air-fuel ratio control that controls the oxygen concentration in the furnace according to time
And a roller .

[0006] The furnace atmosphere control apparatus of the first invention can be provided with a loading pressure relief control valve for controlling the loading pressure in the loading pressure introduction passage, and controls the opening of the loading pressure relief control valve. Air-fuel ratio controller can be provided.

[0007]

According to the furnace atmosphere control apparatus of the present invention, since the mixing ratio of air and fuel gas is automatically controlled by the diaphragm means, the initial setting of the opening of the air flow control valve and the fuel gas flow control valve is performed. Becomes easier.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a shuttle kiln.
And FIG. A gas burner 2 and a temperature sensor 12 for detecting a temperature in a furnace chamber are provided on a side wall of the kiln 1. The air from the blower 3 passes through the air damper 5 and is supplied to the gas burner 2 from the air passage 21. The fuel gas from the fuel gas cylinder 7 is supplied to the gas burner 2 from a fuel gas passage 23 through a pressure equalizing valve 22 as a flow control valve described later. In the gas burner 2, the air and the fuel gas are mixed, and this air-fuel mixture is burned to become a combustion gas and blown out into the furnace chamber.

The supply amount of air is controlled by a temperature controller 14. The motor 4 driven by a command from the temperature controller 14 adjusts the opening of the air damper 5. The supply amount of air is adjusted according to the opening degree of the air damper 5. The mixture ratio of air and fuel gas is controlled by the air-fuel ratio controller 16. That is, the loading pressure taken out of the air passage 21 is guided to the loading pressure chamber 29 of the pressure equalizing valve 22 shown in FIG. The loading pressure in the loading pressure introduction passage 27 is controlled by the loading pressure relief valve 20 shown in FIG. The opening of the loading pressure relief valve 20 is adjusted by a motor 18 driven by a command from the air-fuel ratio controller 16.

As shown in FIG. 2, the inside of the housings 24 and 25 of the pressure equalizing valve 22 is divided into a loading pressure chamber 29 and an atmospheric pressure chamber 31 by a diaphragm 26. A valve body 32 is provided at the tip of a rod 28 integrally attached to the diaphragm 26. The valve 32 controls the flow rate of the fuel gas flowing through the fuel gas passage 23. At the rear end of the rod 28, a coil spring 30 presses the rod 28 in the closing direction so as to close the valve body 32. Thereby, the valve element 3
2 is the pressure Px guided to the loading pressure chamber 29.
And the set pressure of the coil spring 30 and the atmospheric pressure chamber 3
It comes to a position where the atmospheric pressure Po guided to 1 is balanced. Accordingly, when the pressure Px of the loading pressure chamber 29 decreases as the air flow rate increases, the diaphragm 26 rises in FIG. 2 to increase the opening degree of the valve body 32 and increase the fuel gas flow rate.

Next, the relationship between the output of the temperature controller and the air-fuel ratio is shown in FIG. Even if the output of the temperature controller changes, the air-fuel ratio is controlled to approximately the stoichiometric air-fuel ratio, for example. When the opening degree of the relief valve 20 is increased and the pressure Px guided to the loading pressure chamber 29 increases, the air-fuel ratio increases. FIG.
Shows the relationship between the output of the temperature controller and the air flow rate.
When the motor 4 increases the opening of the air damper 5 according to a command from the temperature controller 14, the air flow rate flowing through the air passage 21 gradually increases. The setting of the air flow rate is fixed or programmed in the temperature controller 14 at a position indicated by a dotted line or a solid line shown in FIG.

FIG. 5 shows the relationship between the opening of the loading pressure relief valve and the fuel gas flow rate. As the opening of the loading pressure relief valve 20 increases, the pressure Px of the loading pressure introduction passage 27 increases. Then, as shown in FIG. 2, as the pressure Px in the loading pressure chamber 29 increases, the opening degree of the valve body 32 integrated with the diaphragm 26 decreases, so that the fuel gas flow rate gradually decreases.

FIG. 6 shows the relationship between the elapsed time during firing, the oxygen concentration in the furnace, and the temperature in the furnace. The oxygen concentration in the furnace is relatively high at the beginning, but then decreases gradually and rises again just before the fire is stopped. The furnace temperature gradually rises from the initial stage and reaches the maximum temperature immediately before the fire is stopped. Thereafter, the furnace temperature gradually decreases. The furnace temperature characteristics and the furnace oxygen concentration can be appropriately changed according to the control programs of the temperature controller 14 and the air-fuel ratio controller 16,
The air flow rate and the fuel gas flow rate are controlled in accordance with a time schedule based on the above-described operation based on a desired control program.

[0014]

As described above, according to the furnace atmosphere control apparatus of the present invention, the fuel gas flow rate in the fuel gas passage is automatically controlled by using the pressure equalizing valve as the diaphragm means by the loading pressure guided from the air passage. Therefore, the initial opening of the air flow control valve and the fuel gas flow control valve can be easily set, and the workability of the control valve is improved. Therefore, since the atmosphere in the furnace chamber can be precisely controlled, there is an effect that the characteristics of the article to be fired, such as color and baking, can be finished with high quality.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a furnace atmosphere control apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a pressure equalizing valve used in FIG.

FIG. 3 is a characteristic diagram showing a relationship between an output of a temperature controller and an air-fuel ratio.

FIG. 4 is a characteristic diagram showing a relationship between an output of a temperature controller and an air flow rate.

FIG. 5 is a characteristic diagram showing a relationship between an opening degree of a loading pressure relief valve and a fuel gas flow rate.

FIG. 6 is a characteristic diagram showing the relationship between the elapsed time during firing, the oxygen concentration in the furnace, and the temperature in the furnace.

FIG. 7 is a circuit diagram showing a conventional furnace atmosphere control device.

[Explanation of symbols]

Reference Signs List 1 kiln (furnace body) 2 gas burner 16 air-fuel ratio controller 20 loading pressure relief valve (loading pressure relief control valve) 21 air passage 22 equalizing valve (flow rate control valve) 23 fuel gas passage 26 diaphragm (diaphragm means) 27 loading pressure introduction Passage 28 Rod (diaphragm means) 29 Loading pressure chamber 30 Coil spring (biasing means) 31 Atmospheric pressure chamber 32 Valve body

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F27D 7/02 F27B 17/00 F23N 1/02 104

Claims (1)

(57) [Claims] A gas burner attached to a furnace body; an air passage for supplying air to the gas burner; a fuel gas passage for supplying fuel gas to the gas burner; and a valve body of a flow control valve for opening and closing the fuel gas passage. An urging means for urging the valve body of the flow control valve in a closing direction; a loading pressure chamber for introducing a loading pressure taken out from the air passage from a loading pressure introduction passage; and an atmospheric pressure chamber for introducing atmospheric pressure. a diaphragm which partitions the, a diaphragm means for driving the valve body in a direction to increase the opening of the flow regulating valve against the biasing means due to the pressure drop of the loading chamber, the loading pressure Controls the loading pressure in the introduction passage
Controlling the opening of the loading pressure relief control valve and the loading pressure relief control valve.
Control the oxygen concentration in the furnace according to the elapsed time after the start of firing
And an air-fuel ratio controller .