JPS60140013A - Microwave heating process - Google Patents

Abstract

PURPOSE:To provide a microwave heating process with a better thermal efficiency and having no danger of explosion by a method wherein a combustive condition of dried powder material is sensed to adjust a feeding amount of microwave and supplying amount of air. CONSTITUTION:Powder material A is agitated by an agitator device 3 and heated by a microwave from a wave guide pipe 2. In case that a heating is rapidly progressed, the danger of explosion is found, so that the powder material A of non-dried condition is fed at the feeding port 7 automatically in response to the condition of combustion in the heating furnace 1 sensed by a sensor 20, a temperature in the heating furnace 1 is decreased and at the same time the generated heat made by a combustion is utilized for a drying of the non-dried powder material A. In this case, the control device 21 controls the microwave oscillator 22 in response to the output value from the sensor 20 to adjust a microwave power and at the same time the opening or closing of the lid 10 is controlled to adjust the air supply volume. With this arrangement, it is possible to get a microwave heating process without any risk of explosion.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is a method for drying a powdery material such as a powdery material containing a liquid or a solidified substance of the powdery material using microwaves and then combusting it. The present invention relates to a microwave heating method.

[Background of the invention]

Generally, a rotary kiln method is used as a method for drying and burning a powdery material containing a liquid because it is suitable for continuously drying and burning a large amount of powdery material. In this rotary kiln system, a cylindrical pipe is rotated, and a stirring blade inside the drum (also used as a feeder) is used to scrape up and drop powder as the drum rotates, and the powder is repeatedly transferred and dried while coming into contact with hot air, and then combusted. It is something that makes you Electrically heated high temperature gas or the like is used as a heating source for this drying/combustion.

However, as mentioned above, in this rotary kiln system, the pipes are rotated to heat, burn, and transport the powder at the same time, so as the combustion progresses, the powder loses moisture and becomes more concentrated as the combustion progresses. It's easy to fly up. Therefore, the emitted exhaust gas contains a considerable amount of fine powder. Therefore, the exhaust gas is collected with a cyclone before being exhausted, but it cannot be completely removed, so it is often necessary to install a filter in the exhaust system to prevent the fine powder from being released into the atmosphere. . Moreover,
If a cyclone or filter is installed, it is necessary to keep the cyclone or filter at a temperature that does not cause condensation so that it can function fully at all times. Furthermore, powdery materials generally have poor thermal conductivity, and since they are heated by supplying high-temperature gas etc. from the outside, thermal efficiency is poor, and a large heating device must be used to completely dry and burn the powdery materials. .

Therefore, it has the disadvantage that it requires excessive equipment for drying and burning powdery materials.

In addition, unlike the rotary kiln method mentioned above, which has the advantage of not scattering the powder, there is also a method in which the powder is placed in an oven or the like and statically heated and dried using an external heating device. It is used. However, if some types of powder with particles with a diameter of several inches or less are heated and dried in a static state, the powder will solidify and the entire powder that enters the open will become one large lump. , it has the disadvantage that subsequent work becomes difficult.

Therefore, in recent years, microwaves have been used as a heat source, and stirring blades have been used to stir the powder during heating drying and combustion to prevent the powder from forming large lumps, and to prevent the powder from scattering when stirring the powder. A microwave heating device as shown in Figure 1 has been proposed, which does not cause this. That is, the heating furnace 1.2, which is conductive and has a cylindrical shape, receives microwaves sent from a microwave oscillator (not shown) via circuit elements such as an isolator, a power monitor, a matching device, and a partition window discharge detector. A waveguide 2 serving as a microwave irradiation port for irradiating the inside of the heating furnace 1 is connected. A stirring device 3 having stirring blades 3a at the lower end is provided in the center of the heated furnace 1. This stirring device 3 is supported by a bearing 4 and is configured to be rotated slowly by a motor 5.The rotation of this stirring device 3 rotates stirring blades 3a, thereby heating and drying and burning powder. Prevents things from clumping. Further, a choke 6 is provided on the bearing 4 to prevent microwaves from flowing into the bearing 4, thereby preventing the bearing 4 from being damaged. Further, the heating furnace 1 is provided with a charging lower for charging the powder material A to be dried into the heating furnace 1, and an exhaust port 8 for exhausting gas such as steam generated within the heating furnace 1. The inner diameters of these input lower and exhaust ports 8 are each one of the wavelength of the microwave used.
/2 or less to prevent microwaves from leaking. Furthermore, an air supply port 9 is provided at the bottom of the heating furnace 1 for supplying air necessary for combustion. This air supply port 9 is provided with a lid 10 that can be attached and removed in the direction shown by the arrow A in the figure, and this lid 10 has the function of opening and closing the air supply port 9't.

Complete heating, drying, and combustion of a powder material using the conventional microwave heating apparatus shown in FIG. 1 is performed as follows. That is, the air supply port 9 is partially covered with the lid 10, and the powder A, such as a liquid powder or a powder solid, is introduced from the input lower, and then the stirring device 3 is driven and the stirring blades 3a are fed. Microwaves are irradiated from the waveguide 2 while rotating slowly nine times. The microwave irradiated from the waveguide 2 is absorbed by the powder A, and the powder A generates heat and dries. During this drying, the stirring blade 3a slowly rotates 9 times, so
Even if the powder A is solidified, it does not become a single lump and is returned to a fine powder. In addition, since the stirring blade 3a rotates slowly, the dry powder A is not scattered and the exhaust port 8
The only gas emitted from the tank is the gas evaporated from the powdery material containing the powdery material. When the powder A is further irradiated with microwaves after the drying of the powder is completed, the temperature of the powder A rises and it starts to burn. Since a large amount of oxygen is required for this combustion, the lid 10 of the air supply port 9 is opened to supply combustion air and the like. During the combustion of this powdered material, a considerable amount of heat is generated as a result of the combustion, and the combustion rate rapidly increases. Therefore, the conventional heating method using a microwave heating device has the disadvantage that there is a risk of explosion if the powdery material generates a large amount of flammable gas.

Furthermore, in conventional microwave heating devices, the generated heat is rapidly released to the outside from the exhaust port 8 along with the exhaust gas, which results in wasteful release of energy and has the disadvantage of poor thermal efficiency. .

[Purpose of the invention]

An object of the present invention is to provide a microwave heating method that is thermally efficient and has no risk of explosion.

[Summary of the invention]

The present invention heats and dries the powdered material put into a heating furnace while stirring it, detects the combustion state of the dried powdered material, and detects when the combustion state of the dried powder exceeds a predetermined combustion state. The aim is to improve thermal efficiency by adjusting the amount of air supplied, automatically adding an appropriate amount of undried powder, and drying and burning it while stirring.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 2 shows a microwave heating device used in the microwave heating method according to the present invention.

Components in the figure that are denoted by the same reference numerals as those in the conventional example shown in FIG. 1 are the same parts and have the same functions. In the figure, the difference from the conventional example shown in FIG. 1 is that a sensor 20 is provided at the exhaust port 8 to determine the combustion state of the powdery substance A. Further, 21 is a control device, and 22 is a microwave oscillator.

A microwave heating method using the microwave heating device configured as described above is as follows.

[First stage] The υ motor 5 is rotationally driven by a control signal from the control device 21, and the powdery material A is stirred by the stirring device 3. At this time,
At the same time, the powder A is irradiated with microwaves through the waveguide 2 to heat the powder.

When the temperature of the powder A increases, the liquid contained in the powder A evaporates and is discharged from the exhaust port 8.

In this way, the powder A is gradually dried. At this time, the powder A is stirred by the stirring blade 3a, so that it is prevented from solidifying and is dried uniformly.

[Second stage] Next, when the sufficiently dried powder A is further irradiated with microwaves, the powder A is combusted. Since this powder A requires a large amount of oxygen to burn, open the lid 10 of the air supply port 9,
Supply air. When the combustion of the powder material A begins, a considerable amount of heat is generated as a result of the combustion, and the synergistic effect of this combustion heat causes the combustion to rapidly increase. If the combustion progresses rapidly, the heating furnace 1 has a closed structure even though the exhaust port 8 is provided, so there is a risk of explosion due to the rapid expansion of the internal pressure, which is not preferable.

Therefore, according to the combustion state inside the heating furnace 1 detected by the sensor 20, new undried powder A is automatically introduced from the charging lower to lower the temperature inside the heating furnace 1 and at the same time reduce the heat generated due to combustion. It is used to dry the newly introduced undried powder material A.

At this time, the control device 21 controls the microwave oscillator 22 to adjust the microwave power based on the output value from the sensor 20, and also controls the opening and closing of the lid 10 to adjust the amount of air supplied. Note that this sensor 20 may be a temperature sensor, humidity sensor, pressure sensor, or the like.

This second step of charging the undried powder may be repeated several times if the amount of residue generated due to combustion is small, and can be repeated as necessary.

[Third stage] Next, when powder A burns, its volume becomes VI.

17'20, the amount of powder in the heating furnace 1 can be kept constant even if undried powder A is introduced during combustion. However, if the operation continues for a long time, the amount of residue will gradually increase, and the capacity to feed the undried powder A will gradually decrease. The injection of powder A is stopped, and the amount of microwave and air supply is controlled to burn all of the powder.

[Fourth stage] Next, after all the combustion is completed, the residue is discharged from the heating furnace 1,
Complete the entire process.

Note that it is not possible to expect the same effect even if the control device 21 performs the third stage operation continuously in the final state of the second stage.

Therefore, according to this embodiment, the undried powder can be burned with high efficiency and without the risk of explosion.

〔Effect of the invention〕

As explained above, according to the present invention, the thermal efficiency is increased over the entire length,
Moreover, it can be burned without the risk of explosion.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional microwave heating device, Fig. 2 is a block diagram of a microwave heating device used in the microwave heating method according to the present invention, and Fig. 3 is a flow diagram showing implementation FJk of the present invention. . 1... Heating furnace, 2... Waveguide, 3... Stirring device,
7...Inlet port, 8...Exhaust port, 9...Air supply port, 2
0...Sensor, 21...Control device, 22...Microwave oscillator. Agent Tatsuyuki Unuma (and 1 other person) (11) Figure 1

Claims (1)

[Claims] (1) Powder containing liquid or powdered combustible solids is heated and heated by irradiating it with microwaves while stirring.
A first step of drying the powder, and when the drying state of the powder reaches a predetermined state, a new powder is supplied, and the amount of microwave irradiation and the amount of supplied air are controlled and agitated. The second step is to gradually heat and dry the bricks, and when the amount of powder sequentially supplied in the second step reaches a predetermined value, the supply of new powder is stopped and the inside of the furnace is and a third step of completely burning the powdery material.