JP2001141215A - Refuse treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refuse treatment system in which easily recoverable gas having a high carbon dioxide gas concentration can be exhausted. SOLUTION: The refuse treatment system comprises a thermal decomposition unit for decomposing refuse thermally to generate thermal decomposition gas and thermal decomposition residue, a melting unit for combusting the thermal decomposition gas and thermal decomposition residue to generate molten slag, and a unit for treating exhaust gas from the melting unit. The refuse treatment system further comprises an oxygen gas generator for generating oxygen gas being supplied to the melting unit, means for supplying oxygen gas generated from the oxygen gas generator to the melting unit, and means for circulating a part of exhaust gas from the melting unit to the thermal decomposition unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment apparatus, and more particularly to a waste treatment apparatus in which a pyrolysis gas generated by thermally decomposing waste and a pyrolysis residue are burned into molten slag.

[0002]

2. Description of the Related Art In recent years, the amount of general waste such as municipal waste and industrial waste such as waste plastic has been increasing more and more, and it has become a problem to secure landfill disposal sites. Since the generation of dioxins due to the incineration of materials has also become a problem, proper disposal of these wastes is essential. Therefore, as a device to solve these problems, waste is heated and pyrolyzed in a low oxygen gas atmosphere, and the pyrolysis gas and pyrolysis residue mainly composed of char are led to the melting furnace. A waste treatment apparatus that reduces the amount of waste and suppresses the generation of dioxin by burning them in a melting furnace to form molten slag has been put into practical use.

[0003] Furthermore, the problem of global warming is increasing, and accordingly, it is necessary to suppress the generation of carbon dioxide gas. Many electric utilities have developed a method of recovering and removing carbon dioxide gas from the exhaust gas of a thermal power plant. Development has begun.
In addition, since the amount of carbon dioxide gas generated from waste treatment equipment reaches 80 million tons per year, not only thermal power plants but also carbon dioxide gas emitted from waste treatment equipment will be reduced in the future. Is required.

[0004]

However, in the conventional waste treatment apparatus, since air is used for combustion of the waste, the concentration of carbon dioxide gas in the exhaust gas generated by this is as low as about 3 to 15%. is there. In order to recover such a low-concentration carbon dioxide gas, it is necessary to once separate and recover only the carbon dioxide gas from other gases contained in the exhaust gas. As a method for separating carbon dioxide gas, chemical absorption method, adsorption method, etc. have been put into practical use for specific applications.However, in order to separate low-concentration carbon dioxide gas from a large amount of exhaust gas, heat energy etc. Since these methods consume large amounts of energy, it is difficult to put these methods into practical use.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a waste treatment apparatus capable of discharging exhaust gas having a high carbon dioxide gas concentration which can be easily recovered. Make it an issue.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have obtained oxygen from the pyrolysis gas and the pyrolysis residue generated in the pyrolysis apparatus. The inventors have found that the concentration of carbon dioxide gas in the exhaust gas can be increased by supplying and burning the fuel and returning a part of the exhaust gas to the pyrolysis device, and reached the present invention.

That is, the present invention firstly provides a pyrolysis apparatus for pyrolyzing waste to produce pyrolysis gas and pyrolysis residue, and burning the generated pyrolysis gas and pyrolysis residue. Oxygen gas for generating oxygen gas to be supplied to a melting device in a waste treatment device having a melting device for generating molten slag and an exhaust gas treatment device for treating exhaust gas discharged from the melting device A generator, means for supplying oxygen gas generated by the oxygen gas generator to the melting device, and means for returning a part of the exhaust gas discharged from the melting device to the thermal decomposition device are provided. Secondly, the gist of the present invention is a waste treatment apparatus characterized by comprising a device for recovering carbon dioxide gas from exhaust gas released into the atmosphere in the above-mentioned device.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, the pyrolysis device in the waste treatment device of the present invention is:
It is a device that heats and thermally decomposes waste to generate a pyrolysis residue mainly composed of pyrolysis gas and char. Examples of the pyrolysis device include a fluidized bed type pyrolysis device and a rotary kiln type pyrolysis device. No.

In a pyrolysis apparatus, waste gas discharged from a melting apparatus to be described later is refluxed and waste is heated and pyrolyzed in a reducing atmosphere, but when a fluidized bed type pyrolysis apparatus is used as the pyrolysis apparatus. Preferably, the oxygen gas is mixed with the exhaust gas to adjust the oxygen gas concentration in the exhaust gas, and the waste is partially burned to maintain the temperature of the sand layer at a predetermined temperature. When mixing the oxygen gas with the exhaust gas, the oxygen gas generated by the oxygen gas generator described later is supplied, and the reflux gas of the exhaust gas discharged from the melting device is adjusted and mixed. In addition, when a device for performing pyrolysis by heating waste by indirect heating, such as a rotary kiln-type pyrolysis device, it is not necessary to supply oxygen gas.

[0010] Next, the melting device is to generate a molten slag by burning the pyrolysis gas generated by the pyrolysis device and the pyrolysis residue. A melting furnace and the like can be mentioned. Oxygen gas generated by an oxygen gas generator described later is supplied to the melting device, and the pyrolysis gas and pyrolysis residue are burned using oxygen gas as a combustion gas. From the viewpoint of safety, it is preferable that a part of the exhaust gas generated from the melting device is returned to the melting device, and a mixed gas of oxygen gas and the exhaust gas is used as a combustion gas. At this time, the pyrolysis gas and the pyrolysis residue can be burned in an oxygen gas-enriched state by adjusting the mixing ratio of the oxygen gas and the exhaust gas.

The oxygen gas generator generates oxygen gas to be supplied to the melting device. Examples of the oxygen gas generator include a cryogenic separation method, an adsorption method (PSA method), a membrane separation method, and a chemical separation method. An apparatus employing an adsorption method or the like can be given.
Among these apparatuses, it is preferable to use an apparatus employing a cryogenic separation method or an adsorption method because oxygen gas can be produced at low cost. The oxygen gas generated by the oxygen gas generator is supplied to the melting device and, if necessary, to the thermal decomposition device as described above.

Means for supplying the oxygen gas generated by the oxygen gas generator to the melting device include an oxygen gas circulation fan and the like. Further, as means for refluxing a part of the exhaust gas discharged from the melting device to the thermal decomposition device,
An exhaust gas recirculation fan may be used. The exhaust gas to be returned to the thermal decomposition device may be the exhaust gas itself discharged from the melting device, the exhaust gas treatment device described below from which dust and air pollutants have been removed, or the exhaust gas from which moisture has been removed.

[0013] The exhaust gas treatment device is a device for treating the remaining exhaust gas that is recirculated to the thermal decomposition device out of the exhaust gas discharged from the melting device. The exhaust gas treatment device is an electric or filtration type collection device. Examples include a dust device, a white smoke prevention device, a denitration device, a dioxin removal device, a smoke washing device, a slaked lime activated carbon supply device, and the like, which may be selected as necessary.

As a device for recovering carbon dioxide gas from exhaust gas discharged into the atmosphere, a known device, for example, a device that chemically absorbs an alkanolamine solution or a potassium carbonate solution, methanol, polyethylene glycol, carbonate Examples of the device include a device that physically absorbs the liquid with an absorbent such as propylene, a device that causes absorption with a zeolite, and a carbon-based solid adsorbent.

According to the waste treatment apparatus of the present invention, the concentration of carbon dioxide gas in the exhaust gas discharged from the melting device can be extremely high, for example, about 90%. No need to separate,
It can be collected as it is. In addition, since the pyrolysis gas and the pyrolysis residue are burned using the oxygen generated by the oxygen gas generator or the mixed gas of the oxygen gas and the exhaust gas as needed as the combustion gas in the melting device, air is used as the combustion gas. The exhaust gas amount is, for example, 1/5
To a degree. Furthermore, since a part of the exhaust gas discharged from the melting device is returned to the thermal decomposition device, nitrogen oxides (NOx, N ₂ O, etc.) in the exhaust gas are almost reduced by the thermal decomposition device in a reducing atmosphere. Therefore, nitrogen oxides in the exhaust gas are also significantly reduced.

Hereinafter, a waste disposal apparatus according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a flowchart showing one embodiment of the waste disposal apparatus of the present invention. In FIG. 1, a waste treatment apparatus includes a waste supply apparatus 1, a fluidized bed type pyrolysis apparatus 2 using fluidized sand as a heat medium, and a swirling flow type melting apparatus having a primary combustion chamber 4 and a secondary combustion chamber 5. 3, a heat exchanger 6, an exhaust heat recovery device 7, a gas cooling device 10, a dust collection device 11 as an exhaust gas treatment device, an induction blower 12, and a carbon dioxide gas recovery device 13 that chemically absorbs carbon dioxide gas in this order. They are connected by piping. An oxygen gas generator 8 employing a cryogenic separation method is connected to the heat exchanger 6, and the oxygen gas generator 8 includes an oxygen gas circulation fan 16,
It is connected to the pyrolysis device 2, the primary combustion chamber 4, and the secondary combustion chamber 5 by a pipe via the heat exchanger 6, and
An exhaust gas recirculation fan 9 is provided in a pipe branched from the downstream side of the exhaust heat recovery device 7, and the exhaust gas recirculation fan 9 is connected to the thermal decomposition device 2, the primary combustion chamber 4, and the secondary combustion chamber 5.

The waste to be treated is crushed if necessary,
After being subjected to pretreatment such as drying, it is quantitatively supplied from the waste supply device 1 to the thermal decomposition device 2. The exhaust gas recirculated from the exhaust gas recirculation fan 9 and the oxygen gas generated by the oxygen gas generator 8 and sent to the heat exchanger 6 by the oxygen gas circulation fan 16 and heat-exchanged there are supplied to the thermal decomposition device 2. Here, the waste is partially burned, and the temperature of the sand layer is maintained at 450 to 700 ° C. At this temperature, the waste is thermally decomposed in a reducing atmosphere to generate a pyrolysis gas and a pyrolysis residue mainly composed of char. Generate. The exhaust gas recirculation fan 9
Nitrogen oxides in the exhaust gas refluxed to the thermal decomposition device 2 from the gas are reduced by the thermal decomposition device 2 and are greatly reduced. Then
The pyrolysis gas and the pyrolysis residue generated by the pyrolysis device 2 are supplied to the melting device 3, and in the primary combustion chamber 4, the pyrolysis gas and the pyrolysis residue are generated by the oxygen gas generation device 8 and heat exchanged by the heat exchanger 6. The mixed gas with the recirculated exhaust gas is burned at 1200 to 1500 ° C. as a combustion gas to melt ash. The molten ash is cooled by water or air and discharged from the primary combustion chamber 4 as a molten slag 14. on the other hand,
The unburned matter is further sent to the secondary combustion chamber 5, where oxygen gas generated by the oxygen gas generator 8 and heat-exchanged by the heat exchanger 6 is supplied to complete combustion. After the exhaust gas discharged from the secondary combustion chamber 5 is recovered in the exhaust heat recovery device 7, a part of the exhaust gas is returned to the thermal decomposition device 2 and the melting device 3 by the exhaust gas recirculation fan 9. After the temperature of the remaining exhaust gas is reduced by the gas cooling device 10, the dust 15 is removed by the dust collecting device 11, and further, guided to the carbon dioxide gas collecting device 13 by the induction blower 12, and the carbon dioxide gas is collected. After being released into the atmosphere.

[0018]

As described above, according to the present invention, the oxygen gas is supplied to the melting device and a part of the exhaust gas discharged from the melting device is returned to the pyrolysis device. High exhaust gas can be discharged from the melting device, and carbon dioxide gas can be easily recovered without separation from the exhaust gas,
The emission amount of carbon dioxide gas, which causes global warming, can be reduced. In addition, since oxygen gas is used as the combustion gas, the amount of exhaust gas is extremely small as compared with the case where air is used, thereby reducing energy loss for heat recovery. Furthermore, since the amount of exhaust gas is also reduced, the exhaust gas treatment device can be reduced in size, whereby power consumption is reduced, unnecessary heating of air is not required, and energy consumption can be reduced.
In addition, by circulating the exhaust gas to the thermal decomposition apparatus, the nitrogen oxides are reduced and greatly reduced, so that the denitration apparatus is unnecessary or can be largely reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the waste disposal apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waste supply apparatus 2 Pyrolysis apparatus 3 Melting apparatus 4 Primary combustion chamber 5 Secondary combustion chamber 6 Heat exchanger 7 Exhaust heat recovery apparatus 8 Oxygen gas generator 9 Exhaust gas recirculation fan 10 Gas cooling apparatus 11 Dust collection device 12 Induction blower 13 carbon dioxide gas recovery device 14 molten slag 15 dust 16 oxygen gas circulation fan

 ────────────────────────────────────────────────── ─── Continued on the front page (71) Applicant 000001834 Sanki Kogyo Co., Ltd. 1-4-1, Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Katsuyuki Mukai 23 Uji Kozakura, Uji-shi, Kyoto In-house (72) Inventor Ayako Shimoide 23 Uji Kozakura, Uji-city, Kyoto Prefecture Unitika Central Research Laboratory (72) Inventor Katsuhito 1-12-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Kurimoto Steel Works, Ltd. (72) Inventor Keiji Kishii 1-1-1 Sonoyama, Otsu City, Shiga Prefecture Toray Engineering Co., Ltd. (72) Koji Masui 1-4-1 Yurakucho, Chiyoda-ku, Tokyo Sanki Kogyo Co., Ltd. Terms (reference) 3K061 AA05 AA07 AA11 AA23 AB02 AB03 AC01 BA10 CA07 FA10 FA21

Claims (2)

[Claims] 1. A pyrolysis apparatus for thermally decomposing waste to generate a pyrolysis gas and a pyrolysis residue, and a melting device for burning the generated pyrolysis gas and the pyrolysis residue to produce a molten slag. An oxygen gas generator for generating oxygen gas to be supplied to a melting apparatus in a waste treatment apparatus provided with an apparatus and an exhaust gas processing apparatus for processing exhaust gas discharged from the melting apparatus; and an oxygen gas generator. A waste treatment apparatus comprising: means for supplying the oxygen gas generated in the step (a) to the melting device; and means for returning a part of the exhaust gas discharged from the melting device to the pyrolysis device. 2. An apparatus for recovering carbon dioxide gas from exhaust gas discharged into the atmosphere.
A waste treatment device as described in the above.