JPH0835780A - Clean heating burning furnace for non-oxidizing substance-type refractory, burning method and controlling method thereof - Google Patents

Abstract

PURPOSE:To provide a clean heating burning furnace for a non-oxidizing substance-type refractory, a burning method and a controlling method thereof wherein unmanned burning operation is intended, by achieving energy-saving with the aid of both the uniform heating of an object to be burned and the reduction of a burning cycle and automatically controlling the burning step from the heating of the object to be burned to the cooling of the burned object. CONSTITUTION:A plurality of radiant tubes 11 are disposed inside a furnace 1, and a plurality of radiant tube burners 3 opposed to the radiant tubes 11 are provided outside the furnace. Further, the interior of the furnace 1 is put into the non-oxidizing atmospheric condition, and the furnace is provided with a substitution burner 4 which can be used as a heat source for heating in the initial starting step, an after-burner 5 for self-combustion of flammable gas vaporized from an object W to be burned, an inactive gas nozzle 16 for blowing N2 into the furnace in order to maintain the interior of the furnace in the non- oxidizing atmosphere at the time of cooling the high-temperature burned object, a program controller 17 for automatic control, and a sequencer 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oxidizing firing furnace for a non-oxide refractory material, a firing method and a control method therefor. -A non-oxidizing firing furnace for a non-oxide refractory material, which automatically controls the temperature rise to cooling of an object to be fired by constructing a la and a sequencer, and a firing method and its control method Regarding

[0002]

2. Description of the Related Art Non-oxide refractory materials containing carbon (graphite) or carbon as a part of their composition are usually produced by firing or heat-treating a raw material composition at a temperature of 500 ° C. or higher.

Raw material composition of such non-oxide refractory material
(Subject to be burned), because the oxidation reaction proceeds at high temperature, for example, at 500 ° C. or higher, during firing, (1) the subject to be burnt is packed in a muffle, and the void is filled with a packing coke, Method of firing by oxidative combustion, (2) Air-fuel ratio of 0.
Method of firing in reducing combustion atmosphere lowered to 8-0.65, (3)
An electric heating and firing method in an N ₂ atmosphere has been conventionally known.

[0004]

By the way, the conventional method described above is used.
In the firing method of (1), since the muffle and the coke for packing are used, not only the thermal conductivity is poor and the thermal efficiency is poor, the firing cycle is long, and the workability of filling the burned material is low. There was a problem that was bad.

In the conventional firing method of the above (2), combustion control management troubles (problems such as local heat and air leaks) are likely to occur, and the combustion efficiency of fuel is poor, so that exhaust gas treatment There are drawbacks such as high cost of the device and combustion control device. The conventional electric heating and firing method (3) in N ₂ atmosphere has drawbacks such as poor radiation heat transfer efficiency, high firing energy and N ₂ consumption, and high running cost. .

The present invention has been made in view of the above-mentioned problems and drawbacks in the conventional firing method. The purpose of the present invention is, firstly, that the object to be fired is packed in a muffle,
A uniform heating and firing cycle of the object to be fired by adopting a firing method that does not use packing coke etc. and uses direct combustion heating with a displacement burner and radiant heating with a radiant tube at low temperature Is to achieve energy saving, and second, by replacing the atmosphere in the furnace with a non-oxidizing atmosphere such as N ₂ only at the time of high temperature cooling,
The aim is to reduce the consumption of inert gas such as N ₂ , and thirdly, by constructing a program controller and a sequencer, it is possible to automatically control from the temperature rise to the cooling of the burned material. Intended for unmanned firing.

[0007]

The present invention includes the above-mentioned first to third aspects.
In order to achieve the purpose of, in a non-oxidizing firing furnace for non-oxide refractory materials, a plurality of radiant tubes are arranged inside the furnace, and outside the furnace,
A plurality of radiant tube burners corresponding to the above plurality of radiant tubes are additionally provided, and the inside of the furnace is made a non-oxidizing atmosphere, and a replacement burner serving as a heating heat source at the start of the start, An afterburner for self-combusting a flammable gas volatilized from the fired product is attached (Claim 1), and each of the plurality of radiant tube burners has a heat exchange section. (Claim 2), an inert gas or neutral gas blowing nozzle, a program controller, and a sequencer for maintaining the inside of the furnace in a non-oxidizing atmosphere at a high temperature for cooling the object to be fired. Is attached (Claims 3 and 4).

In addition, the method for firing a non-oxide refractory material according to the present invention is as follows: (1) The atmosphere in the furnace is used in combination with a radiant tube burner, which is a main heating heat source, at the initial stage of raising the temperature of the material to be fired. Is heated with a replacement burner that replaces the weakly reduced combustion gas, and (2) is subsequently fired by radiant heating with a radiant tube placed in the furnace, and (3) the cooling temperature of the fired material after firing is high. Sometimes, the inside of the furnace is maintained in a non-oxidizing atmosphere (claim 5),
In addition, (4) the volatile combustible gas generated from the material to be fired by the heating and firing of (1) and (2) is self-combusted by an afterburner and incinerated (claim 6) .

Furthermore, the method for controlling the firing of the non-oxide refractory material according to the present invention is as follows: The radiant tube burner which is the main heating source for raising the temperature according to the program pattern of the program controller. In order to increase the combustion turn-down ratio of −, (A) If the upper and lower limit deviation set temperature is exceeded during the temperature rise of the object to be fired, ON-OFF (ON-OFF) combustion control is performed, and (B) Kee
When the upper limit absolute set temperature is exceeded at p, PID alternating combustion control is performed with a plurality of radiant tube burners installed as a pair, and ignition of the afterburner against volatile combustible gas generated from the object to be fired and (C) Ignition burner and ultra vision are installed to detect self-burning frame.
The afterburning self-combustion signal is controlled so that the inside of the furnace can be automatically maintained in a non-oxidizing atmosphere in the cooling high temperature region (Claim 7), and (D) keep completion time signal. Main gas shutoff valve is "closed", control valve (air) is "fully open", cooling program EN
The inside of the furnace is cooled by a radiant tube until the combustion blower of D is stopped (Claim 8). As means of (A) to (D) above, the program control and the automatic operation sequence are constructed. It is characterized by performing (claim 9).

The present invention will be described in detail below. In the present invention, a conventional 900 ° C. (Max: 950 ° C.) radiant tube burner is used as a main heating source, and a radiant tube is used to cover the radiant tube burner. The fired product is fired by radiation heating.・ Non-oxidizing atmosphere in the furnace (atmosphere in the low temperature range) is replaced by a replacement burner at the initial temperature rise
Replace with (weakly reducing replacement combustion gas). (Note that the furnace atmosphere (air) during the initial temperature rise of the object to be fired
The substitution bar - but replacing the weak reducing substituted combustion gas supplied from the burner, then the combustible gas from the fired material by heating (CmHn, H _2, C, etc.) is volatilized, the volatile flammable gas By reacting with the air in the furnace atmosphere, it becomes a furnace atmosphere in which the reducibility is further enhanced. )

The radiant tube burner is controlled by the upper and lower limit temperature deviation (low temperature range) signal of the program controller.
ON-OFF combustion is performed, and the object to be fired is heated in combination with the replacement burner.・ The upper limit alarm The combustion control in the absolute temperature range adopts the PID alternating combustion method that pairs multiple radiant burners. -The combustible gas volatilized from the material to be fired is incinerated by an afterburner installed outside the furnace.

After the self-combustion of the above flammable gas is completed,
After keeping at 900 ° C. for a certain period of time, the fuel is stopped, and then an inert gas (N ₂ ) is supplied into the furnace from this high temperature region (900 ° C.) to 400 ° C. through an inert gas nozzle.・ The cooling of the material to be fired shall be performed by the radiant tube supplied with the cooling air, and shall be continued until the cooling program “END”. The temperature at which the material to be fired does not cause an oxidation reaction
Cooling program "END" up to (for example, temperature of about 200 ℃)
After that, the air to be fired can be supplied to cool the object to be fired.

[0013]

EXAMPLE Next, an example of the non-oxidizing firing furnace according to the present invention will be described with reference to FIG. In FIG. 1, solid arrows indicate air and fuel pipes, and dotted arrows indicate signals for control.

Each reference numeral of the non-oxidizing firing furnace according to the present invention shown in FIG. 1 will be described together with its operation. In FIG. 1, reference numeral 1 is a furnace body, and 2 is an airtight door for filling out the burned material W. 3 is a radiant tube burner which is a main heating heat source, and plural units are installed.

Reference numeral 4 denotes a replacement burner for making the inside of the furnace a non-oxidizing atmosphere at low temperature. The weak reducing combustion gas from the replacement burner 4 and the radiant tube burner 3 are used in combination, It serves as the heat source for the initial heating of the start. The reduction combustion from the replacement burner prevents combustion of combustible materials in the furnace and prevents explosion. Reference numeral 5 is an afterburner for incineration of the volatile combustible gas generated by heating the object W to be fired, and 6 is an ignition burner for igniting and burning the volatile combustible gas.

Reference numeral 7 is a combustion air blower, and 8 is a combustion air pressure switch (PS). 9 is a main gas cutoff valve for fuel gas (LPG), and 10 is a fuel gas pressure switch (PS). Both the combustion air pressure switch 8 and the fuel gas pressure switch 10 have their lower limit pressures set, and the fuel gas (LPG) main gas shutoff valve 9 is "closed" in the event of an abnormality such as a power failure or gas leak. It is a safety device for

The combustion gas of each radiant tube burner 3 directly heats the material W to be burned by radiant heat in the radiant tube 11, and subsequently heat-exchanges with combustion air in the heat exchange section 12 and then exhausts it. It is introduced into the exhaust hood 14 through the pipe 13 and is discharged from the exhaust pipe 15 together with the after combustion gas. The after-combustion gas is a gas obtained by burning a volatile combustible gas generated by heating the material W to be fired, and is a volatile gas conduit.
It is a gas in which the volatile combustible gas discharged from 33 is self-combusted by the afterburner 5.

Reference numeral 16 is an inert gas nozzle, and after extinguishing the afterburner 5, N ₂ is supplied into the furnace from the inert gas nozzle. The supply of this N ₂ is for maintaining the inside of the furnace in a non-oxidizing atmosphere during cooling, and the material W to be fired is
This is for cooling to 400 ° C. The extinguishing of the after-burner 5 means that the volatilization from the combustible material in the material W to be fired is completed.

Reference numeral 17 is a program controller (on / off servo PID type), which is a programmed SV (Set Value).
Adjust the control valve 19 so that the output value and the PV (Process Value) input value for actual temperature measurement of the thermocouple 18 are equal,
It is configured to control the combustion amount of each radiant tube burner 3.

Reference numeral 20 is a pressure equalizing valve installed for each radiant tube burner 3 and, according to the combustion air pressure,
The fuel gas is configured to be proportionally controlled at the same pressure. twenty one
Is a sequencer, and is constructed as shown in the following (1) to (6) so as to be automatically controlled and managed from the start to the completion of the program by the control signal of the program controller 17. .

(1) Each radiant tube burner 3 has
A gas solenoid valve (VG) 22, an ignition transformer (TR) 23, and an ultravision (UV) 24 are installed respectively, and the construction contents of the sequencer 21 are the upper and lower limit temperatures of the program temperature SV value of the program controller 17. If the measured temperature PV value exceeds the alarm deviation, the gas solenoid valve 22 is opened / closed to perform ON-OFF combustion, and if the PV value exceeds the upper limit alarm absolute temperature of the program SV value, multiple radiant Tube burner 3 as a pair and PID
Alternating combustion is carried out, and the turndown ratio 1 to 1/3 of the radiant tube burner 3 is greatly increased to 1 to 1/6 to OFF, thereby enabling uniform temperature control in the furnace. Has been done.

(2) The replacement burner 4 has a gas solenoid valve (VG) 2
5, Air solenoid valve (VA) 26, Ignition transformer (TR) 27 and Ultravision (UV) 28 are installed respectively and program control
Combustion control is performed by opening and closing the gas solenoid valve 25 and the air solenoid valve 26 with the time signal of LA17. (3) The ignition burner 6 for the afterburner 5 includes a gas solenoid valve (VG) 29, an ignition transformer (TR) 30, and an ultravision (U).
V) 31 are installed respectively, the gas solenoid valve 29 is opened and closed by the time signal of the program controller 17, and the afterburner 5 is ignited by the ignition burner 6. The afterburner 5 detects the self-combustion flame by the ultravision 31.

(4) The inert gas nozzle 16 has a solenoid valve (VN) 32
Is installed, and the solenoid valve 32 is opened by the signal of the Ultravision 31 that senses that the nature of the afterburner 5 is completed, and N is maintained in order to maintain a non-oxidizing atmosphere in the furnace during cooling. ₂ is blown from the inert gas nozzle 16 to prevent the object W to be fired from being oxidized. The N ₂ blowing stop causes the solenoid valve 32 to be “closed” by a time signal which predicts the degree of the temperature drop of the scheduled program controller 17.

(5) Keep Completion Program The fuel gas (LPG) main gas shutoff valve 9 is "closed" and the control valve 19 is "fully opened" by the time signal, and each radiant tube is opened.
Only air is supplied to the bubbler 3 to cool the material W to be fired. (6) By the cooling completion program time signal, the combustion air blower 7 is stopped and the program becomes “END”.

[0025]

As described in detail above, the present invention employs a radiant heating and radiant heating calcination means, and by automatically controlling the radiant heating and calcination means, it is possible to uniformly heat the object to be fired, and the firing cycle. The energy saving effect can be achieved.

Further, the furnace atmosphere at the time of temperature rise (the furnace atmosphere in the low temperature range) is replaced with the weak reducing combustion gas, while the furnace temperature is raised from the high temperature range (900 ° C.) to the 400 ° C. range. Since only an inert gas is supplied into the inside, N is less than that in the conventional technique (3) “electric heating firing method in N ₂ atmosphere”.
It is possible to reduce the consumption of inert gas such as ₂ . Moreover, by constructing a program controller and a sequencer, it is possible to automatically control from the temperature rise to the cooling of the material to be fired, and to achieve unmanned firing.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of an oxidation-free firing furnace according to the present invention.

[Explanation of symbols]

 1 Furnace Body 2 Airtight Door 3 Radiant Tube Burner 4 Replacement Burner 5 Afterburner 6 Ignition Burner 7 Combustion Air Blower 8 Combustion Air Pressure Switch 9 Main Gas Cutoff Valve 10 Fuel Gas Pressure Switch 11 Radiant tube 12 Heat exchange section 13 Exhaust pipe 14 Exhaust hood 15 Exhaust tube 16 Inert gas nozzle 17 Program controller 18 Thermocouple 19 Control valve 20 Pressure equalizing valve 21 Sequencer 22 Gas solenoid valve 23 Ignition transformer 24 Ultravision 25 Gas solenoid valve 26 Air solenoid valve 27 Ignition transformer 28 Ultravision 29 Gas solenoid valve 30 Ignition transformer 31 Ultravision 32 Solenoid valve 33 Volatile gas conduit W Burned object

Claims (9)

[Claims] 1. A non-oxidizing firing furnace for a non-oxide refractory material, wherein a plurality of radiant tubes are arranged inside the furnace and a plurality of radiant tubes corresponding to the plurality of radiant tubes are provided outside the furnace. A tube burner is additionally provided, and the inside of the furnace is made into a non-oxidizing atmosphere, and a replacement burner that serves as a heating heat source in the initial stage of the start, and an afterburner that self-combusts a combustible gas volatilized from the material to be fired An oxide-free firing furnace for non-oxide refractory materials, characterized by being provided with. 2. The non-oxidizing firing furnace for a non-oxide refractory material according to claim 1, wherein the radiant tube burner is provided with a heat exchange section. 3. The non-oxidizing firing furnace according to claim 1, further comprising a nozzle for maintaining a non-oxidizing atmosphere in the furnace when the object to be fired is cooled at a high temperature. Oxidation-free refractory non-oxidizing furnace. 4. The non-oxidizing refractory non-oxidizing material according to claim 1, wherein the non-oxidizing firing furnace is provided with a program controller and a sequencer. Firing furnace. 5. A method of firing a non-oxide refractory material, comprising: (1) weakly reducing the atmosphere in the furnace in combination with a radiant tube burner, which is a main heating heat source, at the initial stage of raising the temperature of the material to be fired. The object to be fired is heated with a replacement burner that replaces with combustion gas,
Subsequently, radiant heating is performed in a radiant tube arranged in the furnace, and (3) cooling of the object to be fired after baking is maintained in a non-oxidizing atmosphere in the furnace at a high temperature. Method of firing refractory materials. 6. The non-volatile composition according to claim 5, wherein the volatile combustible gas generated from the object to be fired is self-combusted by an afterburner by the heating and firing of the above (1) and (2), and then incinerated. Oxide refractory material firing method. 7. A method for controlling the firing of a non-oxide refractory material in the non-oxidizing firing furnace according to claim 4, which is a radiant as a main heating source for raising the temperature according to a program pattern of a program controller. In order to increase the combustion turn-down ratio of the tube burner, (A) ON / OFF (ON-OF
F) Combustion control, and when (B) Keep exceeds the upper limit absolute set temperature, PID alternating combustion control is performed with multiple radiant tube burners installed as a pair, and volatile combustible generated from the burned material (C) Ignition burner and Ultravision are installed to detect afterburner ignition and self-burning flame against volatile gas. A method for controlling the firing of a non-oxide refractory material, which is characterized in that it is controlled so that it can be automatically maintained. 8. The control method according to claim 7, wherein the main gas shutoff valve is “closed” and the control valve (air) is “fully opened” by the keep completion time signal, and the cooling program is executed.
A method for controlling the firing of a non-oxide refractory material, characterized in that the furnace body is cooled by a radiant tube until the blower for END combustion air is stopped. 9. The control method according to claim 7, further comprising program control and construction of an automated operation sequence.