JP2002195519A - Method and system for gasifying/melting refuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated method and system for gasifying/melting refuse in which various kinds of refuse are subjected to from gasification to melting in the same furnace without generating NOx or dioxines through a simple and small system. SOLUTION: The system for gasifying/melting refuse comprises a plasma furnace having an inner space arranged with one or a plurality of pairs of torch electrode being applied with power from a DC plasma power supply wherein refuse thrown into the furnace is gasified and inorganic components are melted and slagged while performing plasma discharge by means of one or a plurality of pairs of torch electrode under a state where a plasma working gas, nitrogen gas, argon gas, or the like, is supplied into the furnace. The system further comprises means for supplying high temperature steam into the inner space of furnace, and means for generating power using gas produced from the plasma furnace wherein at least a part of generated power is supplied to the DC plasma power supply. Furthermore, forward ends of the torch electrodes are disposed above the molten slag level in the inner space of furnace on the opposite sides of a refuse throw-in opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated waste gasification and melting method for performing various processes from gasification to melting of various wastes such as municipal garbage, industrial waste, sewage sludge, and waste plastics in the same furnace and the method. Related to the device.

[0002]

2. Description of the Related Art Various wastes such as municipal solid waste and sewage sludge have been incinerated in an incineration facility, and the resulting incinerated ash and dust have conventionally been disposed of in landfills. However, due to the problem of depletion of landfill sites and the problem of groundwater pollution due to elution of harmful heavy metals, the necessity for weight reduction, volume reduction and detoxification by melting is increasing. In order to solve such a problem, a pyrolysis gasification and melting system combining a pyrolysis gasification furnace such as a fluidized bed or a rotary kiln and an ash melting furnace has been proposed. In such a pyrolysis gasification and melting system, the waste is heated to about 450 ° C. in a reducing atmosphere in a pyrolysis furnace to separate the residue and the pyrolysis gas. Up to 1 due to combustion of pyrolysis gas
By burning to 400 to 1500 ° C., the ash is dissolved and discharged as slag. However, in such a pyrolysis gasification melting system,
Since the pyrolysis gasification furnace such as a fluidized bed or a rotary kiln and the ash melting furnace for melting the residue into slag are separately provided, the entire apparatus becomes large. Most of the pyrolysis gas is consumed in the ash melting furnace and cannot be reused. On the other hand, a coke bed type melting furnace using a blast furnace has been proposed as a technology integrating a pyrolysis section and a melting section. In this technique, coke and limestone are mixed and introduced together with waste such as garbage from the upper part of a blast furnace-shaped melting furnace, and oxygen-enriched air is blown from a furnace bottom tuyere. As a result, the garbage thrown in is dried at the top of the furnace and then goes down to the bottom of the furnace,
Pyrolysis and combustion are sequentially performed, and ash is melted at the bottom of the furnace to be discharged as slag. However, such a technique involves mixing and inputting coke and limestone together with waste, which leads to an increase in the amount of molten slag and an increase in apparatus configuration.

[0003] There is also a technique in which waste is incinerated in a stoker type or fluidized bed incinerator and then collected fly ash and the like in the exhaust gas are melted in an ash melting furnace. However, even in this technology, there are cases where a high-temperature combustion method is adopted in order to reduce dioxins. However, measures such as fire grate burnout and measures to suppress clinker generation due to a high temperature in the furnace are required. Further, since it is difficult to sufficiently stir and mix the combustion gas in the secondary combustion section, there is a limit to stably simultaneously reducing dioxins, CO, NOx, and the like. On the other hand, there is also a technique for actively burning by introducing oxygen-enriched air or the like into the secondary combustion section. However, even in this technique, when the temperature in the secondary combustion section rises in an oxygen-enriched state, NOx generation is promoted. Is concerned.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention gasifies various kinds of wastes, which do not generate NOx or dioxin, have a simple apparatus configuration and can be reduced in size, in the same furnace. It is an object of the present invention to provide an integrated waste gasification / melting method and an apparatus for performing the process from melting to melting.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is directed to a method for gasification and melting of wastes in which waste is gasified to melt in the same furnace. A plasma working gas, preferably a nitrogen gas, a non-oxygen gas such as an argon gas is flowed into a furnace space through a plasma torch, plasma arc discharge is performed, and waste is charged into the arc discharge region. From gasification to melting in the same furnace. In this case, supplying high-temperature steam of at least 300 ° C. or more to the arc discharge region has high gasification promotion and gasification gas reforming effects, and a plasma power supply for performing the plasma arc is a DC power supply. And a DC power source generated by gasification gas generated in the furnace.
The supply amount of the high-temperature steam is H ₂ O / C (molar ratio).
= 0.5 to 10 (C is the carbon content (mol) in the object to be treated) is preferable from the viewpoint of energy self-sufficiency.

A fifth aspect of the present invention relates to an apparatus suitable for performing gasification and melting of waste, wherein one or a plurality of pairs of torch electrodes to which a DC plasma power supply is applied are arranged in a furnace space. A plasma furnace is provided, and a plasma working gas, preferably a non-oxygen gas such as a nitrogen gas or an argon gas, is supplied via a plasma torch, and plasma discharge is performed by the one or more pairs of torch electrodes. In addition, gasification of the waste put into the furnace and formation of molten slag of the inorganic material are performed. In this case, the plasma furnace is provided with a means for supplying high-temperature steam to the furnace space because the gasification promotion effect and the gasification gas reforming effect are high, and power generation is performed using the gasification gas generated from the plasma furnace. Preferably, at least a part of the power generation amount of the power generation facility is supplied to the DC plasma power supply. More preferably, the plasma furnace is a plasma furnace in which a tip of a torch electrode is disposed above a molten slag surface in a furnace space with a waste input port interposed therebetween.

According to this invention, gasification in the gasification furnace and the use of molten slag of the inorganic material are possible by using the direct current plasma as the gasification heat source, and the size of the furnace itself can be reduced. In particular, by applying nitrogen plasma as a plasma working gas, combustibles in waste can be gasified without loss.

In the present invention, it is preferable to gasify in an atmosphere (oxygen-free or low-oxygen) substantially free of oxygen such as nitrogen, argon, and water vapor. Since it is not a method, it can contribute to reduction of the amount of exhaust gas and improvement of the calorific value of the gasified gas.

Furthermore reforming gasification gas by injecting hot steam into the furnace as a gasification promoter, i.e. H ₂ gas, high efficiency recovery of CO gas are possible, the result becomes more of the gasification gas as High calorie is possible.

[0010] The plasma furnace used in the present invention is a twin furnace in which the tip of the electrode torch is disposed adjacent to the waste input port from the bottom electrode plasma furnace which generates a plasma arc between the electrode torch and the bottom electrode. A torch type plasma furnace is preferred. The reason for this is that the object to be treated according to the present invention contains a large amount of combustibles such as garbage and industrial waste (industrial waste), and since these combustibles (organic substances) are not conductive, the distance between the plasma torch and the furnace bottom electrode is low. If it accumulates in a bulky state, plasma instability (plasma extinguishing) and the like will occur, making it impossible to treat waste smoothly. Similarly, in the electric resistance furnace, since it uses Joule heat, it is suitable for heating conductive materials, but heats non-conductive organic substances by radiant heat by a plasma frame as in the present invention. It is impossible.

Further, regarding the temperature range of the high-temperature steam, when gasification of organic substances is considered, the decomposition start temperature of hydrocarbon is about 250 ° C., and the gasification rate is improved by increasing the temperature. It suffices that it be at least ℃. That is, the role of steam in the present invention is to promote gasification and water gasification reaction by cooking chars in which organic matter is carbonized. The former has a proper temperature range of 800 to 900 ° C, and the latter has a proper temperature range of 800 to 1000 ° C. It has been. Originally, the presence of steam at the temperature in the gasification and reforming field would promote these reactions.

In the presence of high-temperature gas due to plasma, raising the temperature of steam contributes to improvement of energy efficiency. However, as in the present invention, there is energy for producing high-temperature steam such as waste heat recovery. Taking this into consideration, the necessity of high-temperature steam of 800 ° C. or more is not necessarily high, and a temperature not lowering (not lowering) the decomposition initiation temperature of 250 ° C., specifically 300 ° C. or more, preferably 400 ° C. to 800 ° C. High temperature steam is sufficient.

The suitable amount of the high-temperature steam to be supplied is different depending on the kind of the waste and the operating temperature, but it is preferable that H ₂ O / C (molar ratio) is in the range of 0.5 to 10. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples. FIG. 1 is a schematic diagram showing an integrated waste gasification and melting apparatus for performing various processes from gasification to melting in the same furnace according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a plasma furnace which constitutes an integrated waste gasification / melting furnace for performing waste from gasification to melting in the same furnace, and a pair of torches 12, 12 to which a DC plasma power supply 11 is connected. Is inserted into the furnace symmetrically on the left and right sides of the waste inlet 13 provided at the upper center of the furnace and vertically suspended, and its tip is set to be slightly above the storage surface of the molten slag. The annular torch electrode 12a and the ejection tube 12b are formed in a concentric double tube structure so that a plasma working gas such as nitrogen gas is ejected from the center of the tubular torch electrode 12.

A furnace wall 14 constituting the plasma furnace 1
_Is, Al ₂ O 3 -SiC Shitsushoyui bricks, constituted by _ZrO 2 -C Shitsushoyui bricks or ZrO ₂ based electroforming brick, etc., the upper surface of the cylindrical interior space 15 into a flat dome,
The bottom surface is formed in a flat mortar shape, a molten metal discharge port 17 is provided at the center bottom of the flat mortar portion 16, and a molten slag discharge tub 19 is extended to a side wall forming a storage surface 18 for the molten slag.

A large number of steam jet nozzles 20 are arranged around the side of the plasma processing space (inner space) above the tip of the torch 12 so that high-temperature steam is jetted toward the center of the processing space. I do. Further, a gasified gas discharge passage 21 is formed at a position outside the plasma torch 12 on the upper surface of the flat dome-shaped furnace wall, and the gasified gas passage connected to the discharge passage 21 may form the path (1). Alternatively, the path (2) may be formed.

That is, the path (1) is a cogeneration type power generation path, in which a gas power generation facility 3 such as a gas engine or a gas turbine is attached via a gasification gas purifying and dehumidifying apparatus 2.
Further, a boiler 4 for collecting waste heat (using heat of exhaust gas or the like) of the gas engine or the gas turbine is attached downstream of the power generation equipment 3.
Produces high temperature steam of ~ 500 ° C. The high-temperature steam is led to a steam nozzle 20 on the furnace side. A part of the electric power of the gas power generation equipment 3 is used for the DC power supply 11 of the plasma furnace.

Further, the gasified gas may be constituted as a gas power generation device in which fuel cells are combined as shown in the route (2). That is, the path (2) is a fuel cell type power generation path, and a gas power generation facility 7 including a fuel cell via a gasification gas purification / purification device 5 (including a reforming operation if necessary) and a dehumidification device 6 if necessary. The remaining purified gas is used for industrial fuel 8 and chemical raw material 9. Then, a part of the industrial fuel is burned in the boiler 4 to generate high-temperature steam of about 400 to 500 ° C., and the high-temperature steam is guided to the steam nozzle 20 on the furnace side. A part of the electric power of the gas power generation equipment 7 is used for the DC power supply 11 of the plasma furnace 1 in the same manner as the path (1).

Next, the operation of the embodiment will be described. First, nitrogen gas was flown into the plasma furnace 1 and high-temperature steam at 400 ° C. or higher was further flowed from the steam nozzle 20 to set the furnace temperature to 300 ° C. or higher and in an atmosphere of a non-oxygen state. By applying a DC plasma power supply 11 to the two torch electrodes 1 and 12,
A plasma arc is generated between 2 and 12. In this state, by injecting the waste from the waste inlet 13, the organic components in the waste generate thermal decomposition for gasification due to the radiant heat of the high-temperature gas due to the plasma region which is plasma-discharged from both sides thereof. At the same time, the high temperature gas generated in the plasma region raises the steam to a high temperature steam of 800 ° C. or higher. When the steam becomes a high-temperature steam of 800 ° C. or more, gasification promotion and water gasification reaction due to the cooking of the char carbonized by the organic component are promoted, and the generation of dioxin is suppressed.

During this time, high-temperature steam of 300 ° C. or more is constantly supplied. The amount of the supply varies depending on the kind of waste and the operating temperature, but preferably H _{2 is used.}
A controller 30 for controlling the amount of waste input and the amount of steam supply so that O / C (molar ratio) = 0.5 to 10 (C is the carbon content (mol) in the waste). Should be provided. Then, the inorganic residue separated from the organic matter without being gasified is further heated by plasma discharge.
When the temperature is raised to 00 ° C. or higher, the molten metal becomes molten slag, and metals such as iron mixed in the inorganic material are also melted and stored as molten metal below the molten slag. Then, the molten slag is discharged from the slag discharge tub 19, and the molten metal is discharged from the bottom discharge port 17, respectively, while continuing to gasify and melt the waste. Further, as described above, the gasified gas discharged from the gasified gas discharge passage is generated by the gas power generation equipment and a part thereof is supplied to the DC power supply. Is also as described above. Further, since the gasification and melting treatment is performed in a reducing atmosphere close to low oxygen or oxygen-free, NOx is not generated.

[0021]

As described above, according to the present invention, NO
Obtain an integrated waste gasification / melting method and apparatus for performing various processes from gasification to melting of various types of waste that can be simplified and reduced in size without generating x or dioxin in the same furnace. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an integrated waste gasification and melting apparatus for performing various processes from gasification to melting in the same furnace according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma furnace 2 Gasification gas purification dehumidifier 3 Gas power generation equipment 4 Boiler 5 Gasification gas purification / purification equipment 6 Dehumidifier 7 Gas power generation equipment including a fuel cell 8 Industrial fuel 9 Chemical raw material 11 DC plasma power supply 12 Torch 13 Waste Inlet 17 Molten metal outlet 19 Molten slag discharge tub 20 Steam jet nozzle 21 Gasified gas discharge passage

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09B 3/00 C10J 3/00 L 4G075 C02F 11/10 F23G 5/16 ZABZ C10J 3/00 5/46 ZABZ F23G 5/16 ZAB B09B 3/00 ZAB 5/46 ZAB 303K (72) Inventor Satoshi Okuno 12 Nishikicho, Naka-ku, Yokohama-shi Mitsubishi Heavy Industries, Ltd. Yokohama Works (72) Inventor Ryuichi Horiya 12 Nishikicho, Naka-ku, Yokohama-shi Address Mitsubishi Heavy Industries, Ltd.Yokohama Works F-term (reference) BA02 BA03 BA22 BA26 CA02 CA11 CA21 CA24 4D004 AA46 CA27 CA29 CB33 CC03 DA02 DA03 DA06 DA10 4D059 AA03 BB0 4 BF02 BK30 EA10 EB10 4G075 AA37 CA47 EB43

Claims (9)

[Claims] In a waste gasification and melting method for performing waste from gasification to melting in the same furnace, a plasma working gas (nitrogen gas, argon gas, etc.) is supplied to a furnace space via a plasma torch (electrode). While flowing
A method for gasification and melting of waste, comprising performing plasma arc discharge, charging waste into the arc discharge region, and performing the process from gasification to melting in the same furnace. 2. At least 300 ° C. in said arc discharge zone.
The waste gasification and melting method according to claim 1, wherein the high-temperature steam is supplied. 3. The plasma power source for forming the plasma arc is a DC power source, and the DC power source is a DC power source generated by a gasified gas generated in the furnace. The waste gasification and melting method as described in the above. 4. The supply amount of the high-temperature steam is H ₂ O /
2. The method according to claim 1, wherein C (molar ratio) is in the range of 0.5 to 10 (C is the carbon content (mol) in the object to be treated).
The waste gasification and melting method as described in the above. 5. An integrated waste gasification and melting apparatus for performing waste from gasification to melting in the same furnace, wherein one or more pairs of torch electrodes to which a DC plasma power supply is applied are arranged in the furnace space. While performing plasma discharge with the one or more pairs of torch electrodes in a state in which plasma working gas (nitrogen gas, argon gas, etc.) is supplied through a plasma torch in the furnace. A waste gasification / melting apparatus characterized in that gasification of waste put into the furnace and melting of slag of inorganic components are performed. 6. The waste gasification and melting apparatus according to claim 5, wherein said plasma furnace is provided with means for supplying high-temperature steam to said furnace space. 7. A power generation facility for generating power using gasified gas generated from the plasma furnace, wherein at least a part of the power generation of the power generation facility is supplied to the DC plasma power supply. Item 6. A waste gasification and melting apparatus according to Item 5. 8. The waste gasification / melting apparatus according to claim 5, wherein the power generation equipment includes a steam turbine, a gas turbine, a gas engine, a fuel cell, and the like, and a gas reforming equipment is attached as necessary. . 9. The plasma furnace according to claim 5, wherein the tip of a torch electrode is disposed above a molten slag surface in a furnace space with a waste inlet inserted therebetween.
The waste gasification and melting apparatus as described in the above.