JP2000282061A - Apparatus and method for producing fuel gas from waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize partial combustion in a thermal decomposition furnace, and to achieve the shortening of thermal decomposition time. SOLUTION: This apparatus for producing a fuel gas has a thermal decomposition furnace 1 divided to a drying zone 1A, a thermally decomposing zone.1B and a cooling zone 1C each having a prescribed temperature in the interior and for carrying out the drying, the thermal decomposition and the cooling of a waste material respectively by the contact with a flowing gas, and having a conveyer 3 for conveying air-permeable containers 2 storing a waste material to each zone in series, an ash-melting furnace 4 for melting the ash and char discharged from the thermal decomposition furnace 1, a secondary combustion chamber 3 arranged at the downstream of the thermal decomposition furnace 1, a cooler 6 for cooling the gas discharged from the secondary combustion chamber 5, and a gas-purifying device 7 for purifying the gas discharged from the cooler 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an industrial raw material gas which can be used as a raw material gas from waste to gaseous fuel, fuel cell raw material gas, and also chemical raw material gas such as ammonia and methanol.
In particular, the present invention relates to a fuel gas production apparatus suitably applicable to the production of synthesis gas, and a method for producing fuel gas from waste using the same.

As an example of such a fuel gas, H ₂ =
20 to 40, CO = 20 to 40, CO ₂ = 0 to 30% by volume, N ₂ , H ₂ O, calorific value composed of trace inorganic gas 100
There is a gas of 0 to 4000 kcal / Nm ³ .

[0003]

2. Description of the Related Art Recently, synthesis gas (main components are H ₂ , CO, CO
₂ , CH _4, etc.) and using them as fuels and chemical raw materials, and suppressing the generation of dioxins.

In order to produce synthesis gas from waste, use of a fluidized bed pyrolysis furnace or an externally heated pyrolysis furnace can be considered. In the case of a fluidized bed type pyrolysis furnace, see JP-A-10-15631.
4, JP-A-10-67992 and JP-A-10-1
As proposed in US Pat. No. 28288, the waste is crushed and fed to an internal circulating fluidized bed pyrolysis furnace, where the waste is 450-600.
Thermal decomposition is performed by partial combustion at a temperature of ℃, and pyrolysis gas and pyrolysis residue (char, ash, etc.) are supplied to a high-temperature oxidation furnace,
The system promotes gas reforming at high temperatures using oxygen. In the case of an externally heated pyrolysis furnace, the waste is supplied to a degassing channel including the externally heated pyrolysis furnace, and is heated by a heating gas from the outside in an oxygen-free state to perform drying and pyrolysis. The pyrolyzed gas is supplied to a high-temperature reactor to promote gas reforming at a high temperature by partial oxidation using oxygen.

[0005]

When wastes are supplied to a fluidized bed pyrolysis furnace, the wastes have large fluctuations in calories,
In order to operate the fluidized bed stably according to the calorie fluctuation of the input waste, the temperature control in the bed becomes complicated. As a countermeasure, Japanese Unexamined Patent Publication No. Hei 10-128288 provides high calorie and low calorie waste pits, and the amount of heat is made uniform by adjusting the quantity ratio between the two. Is complicated, and it is necessary to prepare wastes of different calories. In this system, pyrolysis gas, tar, steam, char, and ash generated by pyrolysis are all partially burned in a high-temperature oxidation furnace. In this way, when these are all partially oxidized at high temperature, the pyrolysis gas and tar component with a high reaction rate react preferentially, reducing the calorie of the synthesis gas and generating a large amount of incompletely burned char .

On the other hand, when the waste is supplied to an externally heated pyrolysis furnace, since the waste is heated and dried and pyrolyzed by a heating gas from the outside, the heat transfer area with the compressed waste is reduced. The time required for pyrolysis is limited and it takes a long time, and a considerably long pyrolysis furnace is required to reduce the time. Also, in this system, since the supply of waste is performed by a press, it is necessary to seal the press sufficiently to prevent leakage of pyrolysis gas, and there is also a problem with the wastewater treatment method generated by the press. There is.

An object of the present invention is to provide a system capable of solving the above-mentioned problems.

[0008]

Means for Solving the Problems The present inventors conducted the following experiments to grasp the thermal decomposition behavior of dewatered municipal solid waste.

[0009] General municipal waste was dehydrated by pressing to a moisture content of 6% by weight and pyrolyzed.

FIG. 2, FIG. 3 and FIG. 4 are graphs showing the relationship between the generated gas composition and the amount of generated char when the municipal solid waste is pyrolyzed in an oxygen-free atmosphere at a temperature of 500 to 850 ° C. and the pyrolysis temperature. It is. From these graphs, it can be seen that the pyrolysis temperature needs to be kept at a constant value.

FIG. 5 shows that the gas before char separation (mixture of pyrolytic combustible gas, tar, steam, char and ash) and after char separation (mixture of only pyrolytic combustible gas, tar and steam) at high temperature. 7 is a graph showing a relationship between a char generation amount and a partial combustion rate in the case. From this graph, it can be seen that the latter has a smaller amount of char generation.

FIG. 6 shows that after the municipal waste is dehydrated (dried),
It is a graph which shows the material balance at the time of thermal decomposition. From this graph, it can be seen that a dehydration (drying) operation is required to obtain a high calorie synthesis gas.

FIG. 7 is a graph showing an example of a heat balance when pyrolyzing municipal solid waste without dehydration (drying). From this graph, it can be seen that it is inefficient to pyrolyze municipal solid waste because considerable energy is used for drying.

From the above experimental results, in order to obtain a purified synthesis gas having a constant composition, waste is dehydrated and dried as pretreatment,
It is understood that it is necessary to separate char and ash from pyrolysis gas, tar, and water vapor.

In order to improve the thermal conductivity of waste during pyrolysis, the method of enlarging the heat transfer area has many problems, such as an increase in the size of the apparatus. For this purpose, a method in which a heating gas is passed through the waste and heating is performed by gas contact is considered appropriate.

The water vapor generated during drying contains a large amount of organic substances and gives off odors. This steam is 1000 to 13
When reacted with carbon at a high temperature of 00 ° C., as follows:
Organic substances are thermally decomposed and carbon is gasified by water.

Organic substances → H ₂ , CO, N ₂ , CO ₂ , CH _4, etc. C + H ₂ O → CO + H _{2 Based on the} above findings, a ventilating container (can) containing wastes is used as a pyrolysis furnace. It has been found that the above-mentioned problems can be solved by adopting a so-called Kens type furnace equipped with a so-called cans furnace for heating waste by contact with flowing gas and employing the following method.

That is, the apparatus for producing fuel gas from waste according to the present invention comprises a drying zone, a pyrolysis zone, and a cooling zone in which the waste is dried, thermally decomposed and cooled by contact with a flowing gas having a predetermined temperature. A pyrolysis furnace having a transport means for sequentially transporting a gas-permeable container partitioned into zones and containing waste to each zone; an ash melting furnace for melting ash and chars discharged from the pyrolysis furnace; A secondary combustion chamber disposed in the flow, a cooler for cooling gas discharged from the secondary combustion chamber, and a gas purifier for purifying gas discharged from the cooler. .

Further, the method for producing fuel gas from waste according to the present invention is characterized in that the waste is dried and pyrolyzed by being brought into contact with a flowing gas at a predetermined temperature in a drying zone, a pyrolysis zone and a cooling zone in a pyrolysis furnace. Ash and char from the pyrolysis furnace are melted in the ash melting furnace, and the pyrolysis gas component from the pyrolysis furnace is reformed in the secondary combustion chamber, and the gas discharged from the secondary combustion chamber is cooled. Is cooled by a cooler,
The gas discharged from the cooler is purified by a gas purifier.

In the above method for producing a fuel gas, the temperature of the drying zone is 50 to 250 ° C., and the temperature of the pyrolysis zone is 250 to 250 ° C.
It is preferable to set 950 ° C. and the cooling zone temperature to 25 to 250 ° C.

It is preferable to use a gas having an oxygen concentration of 10% or less (preferably 2% or less) discharged from the secondary combustion chamber as a gas flowing through the drying zone, the thermal decomposition zone and the cooling zone.

[0022] Preferably, the steam produced by drying the waste in the drying zone is supplied to an ash melting furnace and / or a secondary combustion chamber.

A high-concentration oxygen gas (preferably having an oxygen concentration of 70% or more) is supplied to the ash melting furnace as an oxidizing medium, and the temperature in the ash melting furnace is set at 1300 to 1800 ° C. (preferably 1350 to 1800 ° C.).
By setting the temperature to 1500 ° C., it is preferable to make the ash and the char into a molten slag.

In the secondary combustion chamber, a high-concentration oxygen gas (preferably having an oxygen concentration of 70% or more) is used as an oxidizing medium, with a partial combustion rate of 0.1%.
1 to 0.6, and 1000 to 130 in the secondary combustion chamber.
Preferably, the temperature is set to 0 ° C.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

The fuel gas producing apparatus includes a drying zone (1A), a pyrolysis zone (1B), and a cooling zone (1C) for drying, pyrolyzing, and cooling waste by contact with a flowing gas having a predetermined temperature. Pyrolysis furnace (1) having a conveyor (3) that sequentially transports the permeable container (2) containing waste and divided into zones (1A) (1B) (1C), and a pyrolysis furnace (1) Ash melting furnace (4) for melting ash and char from
Secondary combustion chamber (5) arranged downstream of (1) and secondary combustion chamber
A cooler (6) for cooling the gas discharged from (5) and a gas purifier (7) for purifying the gas discharged from the cooler (6) are provided.

In front of the pyrolysis furnace (1), a waste hopper (8) is arranged. At the lower end of the hopper (8)
A crushing roller (9) for crushing waste is provided.

Below the hopper (8), a gas permeable container (2) is arranged. The gas-permeable container (2) has a bottom wall formed of a wire mesh, so that gas can flow in the container (2) in the vertical direction.

The pyrolysis furnace (1) is operated through a gate (10) for a total of 8
It is divided into three rooms (11) to (18). 1st most upstream
The chamber (11) contains the air-permeable container (2)
This is a chamber for introducing gas into (1), and gas is not circulated for sealing. A drying zone (1A) is constituted by the second chamber (12), a pyrolysis zone (1B) is constituted by the third chamber (13) to the fifth chamber (15), and the sixth chamber (16) and the A cooling zone (1C) is constituted by the seven chambers (17). A receiving section (19) for the char and ash generated in the pyrolysis zone (1B) is provided below the eighth chamber (18) on the most downstream side. At the bottom of the receiving part (19), a screw conveyor (20) is provided.

Between the pyrolysis furnace (1) and the ash melting furnace (4),
A hopper (21) for storing char and ash supplied from the receiving section (19) by the screw conveyor (20) is provided.

The secondary combustion chamber (5) is provided above the upstream part of the ash melting furnace (4) so as to communicate with the inside of the ash melting furnace (4).

The cooler (6) comprises a gas quenching tower.

The gas purifier (7) comprises a gas washing tower (71) and a fine substance washing tower (72).

The production of fuel gas from wastes is carried out, for example, as follows using the above-mentioned fuel gas production apparatus.

First, the waste is put into a hopper (8), crushed by a crushing roller (9), and then stored in a gas permeable container (2).

Then, a breathable container (2) containing wastes
Is placed in the first chamber (11) of the pyrolysis furnace (1), and the conveyor (3)
, And are sequentially transported to the second chamber (12) to the eighth chamber (18). Each room (1
The residence time of the gas permeable container (2) in (1) to (18) is 20 minutes.

In the second chamber (12) (drying zone (1A)), a part of the gas having an oxygen concentration of 10% or less from the secondary combustion chamber (5) is supplied to two heat exchangers (22) and (23). ) To 100 ° C., and then supply. The waste is dried by contact with this gas.
The water vapor generated by drying the waste is supplied to the second chamber (12) and is discharged together with the exhaust gas used for drying.
Send to (5).

The third chamber (13) to the fifth chamber (15) (the pyrolysis zone (1
B)), a part of the gas having an oxygen concentration of 10% or less from the secondary combustion chamber (5) is cooled to 700 ° C. through one heat exchanger (22), and then supplied. Thermal decomposition of waste by contact with The temperature of the supplied gas is 500 to 9
If the temperature is 00 ° C., the thermal decomposition of the waste can proceed. By pyrolysis, waste is converted into pyrolysis gas components,
Decomposes into char and ash. The pyrolysis gas component is composed of a pyrolysis combustible gas, a tar component, and a water vapor component. The pyrolytic combustible gas is H ₂ , CH ₄ , CO, CO ₂ , C ₂ H ₄ , C ₂ H
_6, a mixed gas of up to about C3, tar are benzene, toluene, naphthalene, a mixture of condensed polycyclic aromatic C ₁₀ -C _20. The ratio of the above decomposition products resulting from the thermal decomposition of waste is as shown in FIG. The pyrolysis gas component is supplied to the third chamber (13) to the fifth chamber (15) and sent to the secondary combustion chamber (5) together with the exhaust gas used for the pyrolysis.

The sixth chamber (16) (cooling zone (1C)) contains the second
As with the chamber (12), the oxygen concentration of the secondary combustion chamber (5)
% Of the gas below 2% through two heat exchangers (22) and (23)
It is supplied after cooling to 00 ° C., and the contact with this gas cools the ash and char produced by the pyrolysis of the waste. The gas supplied to the sixth chamber (16) and used for cooling is then sent to the secondary combustion chamber (5). Room 7 (17)
In the (cooling zone (1C)), the ash and the char are naturally cooled. Thus, if the ash and the char are cooled, spontaneous ignition of the char can be prevented when the ash and the char are transferred to the downstream side. Further, by cooling, the char handling performance is improved, storage can be performed, and it is possible to separately use the char for use.

As described above, when the thermal decomposition of the waste is performed by contact with the flowing gas, the heat transfer rate to the waste is high, and the thermal decomposition can be completed in a short time. Moreover, since the drying and cooling of the waste are performed in the same pyrolysis furnace (1), the entire system can be made compact accordingly. Further, by using a part of the gas discharged from the secondary combustion chamber (5) as the gas for drying, pyrolysis and cooling, energy saving of the whole system can be achieved.

In the eighth chamber (18), the ash and char in the gas-permeable container (2) which have been conveyed are transferred to a receiving portion (19) below the ash and char.
And then empty the air-permeable container (2) into the pyrolysis furnace (1).
Remove from

The ash and char in the receiving section (19) are charged into a storage hopper (21) by a screw conveyor (20),
From here, an appropriate amount is supplied into the ash melting furnace (4).

In the ash melting furnace (4), steam is supplied from the second chamber (12) to carry out water gasification of the pyrolysis char and to thermally decompose organic substances contained in the steam. By supplying oxygen, the temperature in the ash melting furnace was set to 1300
By setting the temperature at 1800 ° C., the ash and the char are made into molten slag. Water gasification of the char and steam occurs, and a portion of the char is gasified. Offensive odor components are also eliminated by high-temperature pyrolysis. Molten slag is recovered as slag through the slag melt separation layer (41), and metal is collected in the same layer (4).
Collect from 1).

From the third chamber (13) to the fifth chamber (15), the secondary combustion chamber
The pyrolysis gas supplied to (5) has a partial combustion rate of 0.1 to
0.6, in other words, the synthesis gas which is thermally decomposed by blowing pure oxygen and rich in CO and H ₂ so that the ratio of the supplied O ₂ amount to the required O ₂ amount is 10 to 60%. It is reformed to. The temperature in the secondary combustion chamber (5) is 1000-
Keep at 1300 ° C. In the secondary combustion chamber (5), the second chamber
The thermal decomposition of the organic substance contained in the water vapor supplied from (12) is also performed at the same time.

The synthesis gas is subjected to water spray quenching to 100 ° C. or lower in a gas quenching tower (6), followed by alkali washing and acid washing in a gas washing tower (71) and fine particulate matter in a fine particulate washing tower (72). It is removed and becomes purified synthesis gas. The purified synthesis gas can be used as it is for a gas engine or the like.

[0046]

[Example] 100 kg of municipal waste with a moisture content of 6% by weight after drying
An example in which the method of the present invention was carried out is shown below.

Conditions: Gas temperature supplied to the pyrolysis zone of the pyrolysis furnace = 700 ° C. Ash melting furnace temperature = 1400 ° C. Secondary combustion chamber gas reforming section temperature = 1200 ° C. Secondary combustion chamber partial combustion rate = 0.2 Composition of obtained synthesis gas; CO = 37, H ₂ = 40, CO ₂ = 12, H ₂ O = 1
[All vol%], 2340 [kcal / Nm3] Other products; slag = 20 [kg], metal = 1.5 [kg]

[0048]

According to the system of the present invention, drying, pyrolysis, and cooling of waste are sequentially performed in three zones in a pyrolysis furnace by contact with a flowing gas at a predetermined temperature, whereby the pyrolysis furnace can be used. It is possible to stabilize the partial combustion and to shorten the pyrolysis time.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a composition of a generated gas and a thermal decomposition temperature.

FIG. 3 is a graph showing a relationship between a composition of a generated gas and a thermal decomposition temperature.

FIG. 4 is a graph showing the relationship between the amount of generated char and the pyrolysis temperature.

FIG. 5 is a graph showing a relationship between a char generation amount and a partial combustion rate.

FIG. 6 is a graph showing a material balance when municipal solid waste is dehydrated and then thermally decomposed.

FIG. 7 is a graph showing a heat balance when municipal solid waste is pyrolyzed without being dewatered.

[Explanation of symbols]

 (1): Pyrolysis furnace (1A): Drying zone (1B): Pyrolysis zone (1C): Cooling zone (2): Air permeable container (3): Conveyor (transportation means) (4): Ash melting furnace ( 5): Secondary combustion chamber (6): Gas quenching tower (cooler) (7): Gas purification unit (71): Gas washing tower (72): Trace substance washing tower

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23G 5/44 ZAB F23J 1/00 B F23J 1/00 B09B 3/00 302E 15/06 F23J 15/00 K (72) Inventor Yoshitoshi Sekiguchi 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi F-term in Tachibashi Shipbuilding Co., Ltd. 3K061 AA04 AA23 AB02 AB03 AC01 AC03 AC19 AC20 BA01 BA08 BA09 BA10 CA07 FA03 FA10 FA12 FA21 NB03 NB30 3K065 AA04 AA23 AB02 AB03 AC01 AC03 AC20 BA01 BA08 BA09 BA10 CA10 CA14 CA16 HA02 HA03 HA05 HA08 3K070 DA04 DA08 DA09 DA13 DA15 DA33 DA37 DA38 DA76 DA85 3K078 AA01 AA08 AA09 AA10 BA03 BA06 CA02 CA09 CA24 4A004 DA10

Claims (7)

[Claims] An air-permeable container which is divided into a drying zone, a pyrolysis zone and a cooling zone for drying, pyrolyzing and cooling waste by contact with a flowing gas having a predetermined temperature, and containing the waste. A pyrolysis furnace having transport means for sequentially transporting to each zone, an ash melting furnace for melting ash and char discharged from the pyrolysis furnace, a secondary combustion chamber arranged downstream of the pyrolysis furnace, and a secondary combustion chamber A fuel gas producing apparatus, comprising: a cooler for cooling gas discharged from a chamber; and a gas purifier for purifying gas discharged from the cooler. 2. Drying, pyrolysis, and cooling of waste are sequentially performed by contact with a flowing gas at a predetermined temperature in a drying zone, a pyrolysis zone, and a cooling zone in the pyrolysis furnace. And the char is melted in the ash melting furnace, the pyrolysis gas component discharged from the pyrolysis furnace is reformed in the secondary combustion chamber, the gas discharged from the secondary combustion chamber is cooled by the cooler, and the gas discharged from the cooler is discharged. A method for producing fuel gas from waste, comprising purifying with a gas purifier. 3. A drying zone temperature of 50 to 250 ° C., a pyrolysis zone temperature of 250 to 950 ° C., and a cooling zone temperature of 2 ° C.
The method for producing fuel gas from waste according to claim 2, wherein the temperature is set at 5 to 250C. 4. The gas according to claim 2, wherein a gas having an oxygen concentration of 10% or less from the secondary combustion chamber is used as a gas flowing through the drying zone, the pyrolysis zone, and the cooling zone. For producing fuel gas from waste. 5. The waste according to claim 2, wherein steam generated by drying the waste in the drying zone is supplied to an ash melting furnace and / or a secondary combustion chamber. Method of producing fuel gas from products. 6. An ash-melting furnace is supplied with high-concentration oxygen gas as an oxidizing medium, and the temperature in the ash-melting furnace is set to 1300 to 1800 ° C., so that ash and char are melted into slag. A method for producing a fuel gas from waste according to any one of claims 2 to 5. 7. A high-concentration oxygen gas as an oxidizing medium is supplied to the secondary combustion chamber at a partial combustion rate of 0.1 to 0.6, and the temperature of the secondary combustion chamber is set at 1000 to 1300 ° C. A method for producing fuel gas from waste according to any one of claims 2 to 6.