JPH0333962B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is a method for drying and further burning powdery substances such as powdery substances containing liquid or solidified substances using microwaves. 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. This rotary kiln system rotates a cylindrical pipe while stirring the powder inside the drum (which also serves as a feeder).As the drum rotates, the powder is stirred up and dropped, and it 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, this rotary kiln system rotates the pipe to heat, burn, and transport the powder at the same time, so as the combustion progresses, it loses moisture and further becomes pulverized as it burns. Things tend to fly up. Therefore, the exhaust gas that is discharged 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, etc. in the exhaust system to prevent the fine powder from being released into the atmosphere. . Moreover, when a cyclone, filter, etc. are provided, it is necessary to keep the cyclone, filter, etc. at a temperature that does not cause dew condensation so that the cyclone, filter, etc. always function perfectly. 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 large heating equipment 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 millimeters or less are heated and dried in a static state, the powder will solidify and the entire powder that enters the oven 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 FIG. 1 has been proposed which does not cause this. That is, the heating furnaces 1 and 2, which are conductive and have a cylindrical shape, receive 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. Furthermore, in the center of the heating furnace 1, there is provided a stirring device 3 having stirring blades 3a at its lower end. This stirring device 3 is supported by a bearing 4 and is configured to rotate slowly by a motor 5.
This rotation of the stirring device 3 rotates the stirring blades 3a,
This prevents the powder from clumping during heating, drying, and combustion. 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. The heating furnace 1 also has an input port 7 for charging the powder material A to be dried into the heating furnace 1 .
An exhaust port 8 is provided for exhausting gas such as steam generated inside. The inner diameter of these input port 7 and exhaust port 8 is 1/2 of the wavelength of the microwave used.
The settings are as follows to prevent microwave leakage. 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 is removable in the direction shown by the arrow A in the figure.
has the function of opening and closing the air supply port 9.

The heating, drying, and combustion of a powdered material using the conventional microwave heating apparatus shown in FIG. 1 is carried out as follows. That is, the air supply port 9 is partially closed with a lid 10, and the powder A such as a powder containing liquid or a powder solid is introduced from the input port 7.
Thereafter, microwaves are irradiated from the waveguide 2 while the stirring device 3 is driven to slowly rotate the stirring blades 3a. 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 rotates slowly, so that even if the powder A is solidified, it does not become a single lump but is returned to a fine powder. Furthermore, since the stirring blades 3a rotate slowly, the dried powder A is not scattered, and the gas discharged from the exhaust port 8 contains only the gas evaporated from the powder, which does not contain any powder. When the powder A is further irradiated with microwaves after the drying of the powder is completed, the temperature of the powder A increases 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, heating methods using such conventional microwave heating devices have the disadvantage that there is a risk of explosion when it comes to powdery materials that generate large amounts of flammable gas. .

Furthermore, in the case of conventional microwave heating devices, the generated heat is rapidly released to the outside from the exhaust port 8 together 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 powdered material put into a heating furnace while stirring it, detects the combustion state of this dried powdered material, and detects when the combustion state 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. Also,
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 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, the powder A is simultaneously irradiated with microwaves through the waveguide 2, and the powder is heated.
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. This powder A
Since a large amount of oxygen is required for combustion, the lid 10 of the air supply port 9 is opened to 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 too quickly, there is a risk of explosion due to rapid expansion of internal pressure, which is undesirable since the heating furnace 1 has a closed structure even though the exhaust port 8 is provided. Therefore, according to the combustion state inside the heating furnace 1 detected by the sensor 20, a new undried powder material A is automatically introduced from the inlet 7 to lower the temperature inside the heating furnace 1. The heat generated by combustion is used to dry the newly added undried powder A.
At this time, the control device 21 controls the microwave oscillator 22 based on the output value from the sensor 20 to adjust the microwave power, 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 stage of introducing the undried powder A is
When the amount of residue generated due to combustion is small, the process may be repeated several times, and can be repeated as necessary.

[Third stage] Next, when powder A is burnt, its volume decreases to 1/10
Since the amount decreases to ~1/20, the amount of powder in the heating furnace 1 can be kept constant even if undried powder A is added during combustion. However, if the operation continues for a long time, the amount of residue will gradually increase, and the amount of undried powder A that can be fed will gradually decrease. The injection of powder A is stopped, and the microwave and the amount of air supplied are controlled to completely burn the powder.

[Fourth stage] Next, when the entire mixture is combusted, the residue is discharged from the heating furnace 1, and the entire process is completed.

Note that in the final state of the second stage, the control device 2
It goes without saying that the same effect can be expected even if the operation of the third stage is performed continuously according to No. 1.

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

〔Effect of the invention〕

As explained above, according to the present invention, thermal efficiency can be improved and combustion can be performed without the risk of explosion.

[Brief explanation of the drawing]

Figure 1 is a configuration 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 an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Heating furnace, 2... Waveguide, 3... Stirring device, 7... Input port, 8... Exhaust port, 9... Air supply port, 20... Sensor, 21... Control device, 22 …
...Microwave oscillator.

Claims (1)

[Claims] 1. A first step of heating and drying a powdery material such as a powdery material containing a liquid or a powdery combustible solid material by irradiating microwaves while stirring the powdery material, and heating and drying the powdery material such as a powdery material containing a liquid or a powdery combustible solid material, and a step of heating and drying the powdery material such as a powdery material containing a liquid or a powdery combustible solid material. When the condition is reached, there is a second step in which a new powder is supplied, and the amount of microwave irradiation and the amount of air supplied are controlled to heat and dry the powder while stirring; Microwave heating is characterized by a third step in which the supply of new powder is stopped when the amount of powder in the furnace reaches a predetermined amount, and the powder in the furnace is completely burned. Method.