JP4363960B2 - Organic waste gasifier - Google Patents

Description

The present invention relates to an apparatus for thermally decomposing and reforming organic waste such as unused resources and renewable resources, and more specifically, a gas for recovering a hydrogen-rich gas from the organic waste. The present invention relates to a conversion device.

In the past, thinned wood and waste wood were subjected to incineration. In recent years, from the viewpoint of energy saving and effective use of heat, methods for generating electricity using these incineration heat have been studied. Waste plastic has been studied to be thermally decomposed into oil or recycled as a blast furnace reducing material, and has been put into practical use. In addition, although most garbage is incinerated, recently, a method for recovering methane by subjecting it to methane fermentation and a method for generating electricity by this are being put into practical use.

As a method for treating thinned wood and waste wood, a direct combustion method and a gasification method can be considered. The direct combustion method completely burns the above materials, and examples of the incinerator include a stoker furnace, a fluidized bed furnace, a fine powder combustion furnace, and a spouted bed furnace. Only the thermal energy can be recovered and used in the direct combustion system, and hot water or steam is generated by the thermal energy to generate electric power. On the other hand, in the gasification method, the material is partially oxidized with oxygen or air, and the gasification furnace includes a fixed bed furnace, a fluidized bed furnace, a bubbling type fluidized bed furnace, a circulating fluidized bed furnace, and a circulating moving bed. There are furnaces. What can be recovered and used in the gasification system is thermal energy and gas. And hot water and electric power can be obtained using this thermal energy. It is also possible to recover hot water and electric power using the gas as fuel. Although both methods are completed technologies, the scale of equipment is usually large, for example, the throughput in the direct combustion method is at least 40 tons / day, and the throughput in the gasification method is at least 50 tons / day. .

In addition, due to regulatory measures to reduce dioxins generated by waste incineration, simple incineration processing of industrial waste and general waste such as thinned wood and construction waste wood is subject to regulation, and simple incineration processing It is becoming impossible. On the other hand, the promotion of recycling construction waste timber is included in the basic policy of the Construction Recycling Law, and it is forced to recycle construction waste timber.

The daily emissions of industrial waste and general waste such as thinned wood and construction waste wood as described above are usually about 0.5 to 3 tons. In addition, the amount of waste wood in most lumber mills in Japan is about 1 ton / day (Non-patent Document 1). Therefore, even if the above direct combustion method and gasification method are technically applicable, they are not economically profitable.

Organic materials such as wood are pyrolyzed by contacting them with a heat-carrying medium in a pyrolysis reactor, and then the pyrolysis gas is mixed with a reaction medium such as steam and then further heated in the second reaction zone. A gasification method for reforming is disclosed (Patent Document 1). In the method, after the thermal support medium is contacted with the organic material, it is removed from the pyrolysis reactor and heated, and sent to a second reaction zone for use in heating the pyrolysis gas; It is sent again to the pyrolysis reactor and circulated. Refractories and metal materials are listed as the heat carrier medium. In the examples, steel balls are used as the heat-carrying medium, and it is described that the treatment amount of the organic substance is 286 kg / hour (about 6.9 tons / day) for wood (water content). Also, as shown in FIGS. 1 to 3, the pyrolysis reaction and reforming are performed in different containers. Since the pyrolysis reaction and reforming are performed in different containers, the heat carrier medium had to be moved between the different containers. In this method, it is said that the amount of treatment is still too large to be economical for processing industrial waste and general waste such as thinned wood and construction waste wood as well as waste wood in Japanese lumber mills. There was a problem.

Journal of the Japan Institute of Energy, 2003, Vol. 82, No. 6, p. 329 Special table 2003-510403 gazette

The present invention provides a gasifier capable of treating a small amount of organic waste such as thinned wood, driftwood, waste wood, waste plastic, garbage, sludge, cut grass, and paper sludge. As a result, the economic efficiency is improved as compared with the conventional gasifier, and the organic waste that has not been used can be effectively used.

When the waste wood is treated at a treatment amount of 1 ton / day using the method of Patent Document 1, the temperature of the thermal decomposition reaction and gas reforming decreases. In order to maintain this, the heat medium (heat carrier medium) must be further heated. Also, heat dissipation during movement of the heat medium must be prevented. Therefore, it is extremely expensive to supply such heat. Therefore, the present inventors have made various studies to solve this problem. As a result, attention was paid to the material of the heat medium, and it was found that the material was changed to one having a larger constant pressure molar heat capacity, preferably alumina. As a result, the temperature can be maintained in a small gasifier, and a small amount of organic waste can be treated. In addition, by using a gasification furnace provided with a pyrolysis region and a gas reforming region in one container, heat dissipation from the heat medium accompanying movement between containers in the method of Patent Document 1 is prevented, and By simplifying the device accompanying the movement, the company succeeded in further cost reduction.

That is, the present invention
(1) Organic waste is pyrolyzed in a non-oxidizing atmosphere, and the organic waste is pyrolyzed in one container in a gasifier that reforms the generated pyrolysis gas by reacting with steam. A gasification furnace having a region and a region for reforming the generated pyrolysis gas, and the region for thermally decomposing the organic waste has a constant pressure molar heat capacity at a temperature of 25 ° C. of 70 J / K · mol or more. It is an apparatus in which a certain solid heat medium is filled.

As a preferred embodiment,
(2) The apparatus according to the above (1), wherein the solid heat medium has a constant pressure molar heat capacity at 25 ° C. of 70 to 90 J / K · mol,
(3) The apparatus according to the above (1) or (2), wherein the solid heat medium is an alumina ball,
(4) The apparatus according to (3) above, wherein 90% or more of the total number of filled alumina balls has a diameter of 5 to 15 mm,
(5) The gasifier has a region for pyrolyzing organic waste at the lower stage and a region for reforming the pyrolysis gas generated at the upper stage, and heating means outside the gasifier at each stage. The device according to any one of (1) to (4) above,
(6) In any one of the above (1) to (5), the organic waste is selected from the group consisting of thinned wood, driftwood, waste wood, waste plastic, garbage, sludge, cut grass, and paper sludge The described device,
(7) The apparatus according to any one of (1) to (5) above, wherein the organic waste is selected from the group consisting of thinned wood, driftwood and waste wood,
(8) The apparatus according to any one of (1) to (7) above, wherein the temperature of the region where the organic waste is thermally decomposed is 500 to 600 ° C.
(9) The apparatus according to any one of (1) to (8) above, wherein the temperature of the region in which the generated pyrolysis gas is reformed is 900 to 1000 ° C.
(10) The apparatus according to any one of (1) to (9) above, wherein the pressure in the gasification furnace is 0.1 to 0.9 MPa.
(11) A method of gasifying organic waste by pyrolysis and reforming using the apparatus according to any one of (1) to (10) above can be mentioned.

The present invention provides a gasifier capable of treating a small amount of organic waste such as thinned wood, driftwood, waste wood, waste plastic, garbage, sludge, cut grass, and paper sludge. Thereby, economical efficiency improves compared with the conventional gasification apparatus, and it becomes possible to utilize effectively these organic wastes which were incinerated until now and were not used. For example, industrial waste and general waste such as thinned wood and construction waste wood, and waste wood at a lumber mill in Japan can be economically processed to obtain a gas rich in heat and high value-added hydrogen. In addition, these organic wastes that have been disposed of by incineration can be used effectively, so it is possible to reduce harmful substances such as dioxins and carbon dioxide and other global warming substances that were generated during incineration. It can contribute to improvement.

In the gasification apparatus of the present invention, the gasification furnace includes a region for pyrolyzing organic waste and a region for reforming the generated pyrolysis gas in one container. Preferably, the gasification furnace includes a region for pyrolyzing organic waste at the lower stage and a region for reforming the pyrolysis gas generated at the upper stage. Moreover, it is preferable to provide a heating means outside the gasification furnace in each of these regions. The gasification furnace is preferably a retort furnace. Any gasification furnace may be used as long as it can heat fixed bed, moving bed, fluidized bed, and other organic wastes as raw materials. A fixed bed is preferably used.

The gasifier of the present invention is filled with a solid heat medium having a constant pressure molar heat capacity of 70 J / K · mol or more, preferably 70 to 90 J / K · mol at a temperature of 25 ° C., in a region where organic waste is thermally decomposed. Has been. The heat medium is for applying heat to the organic waste and thermally decomposing it. When the constant pressure molar heat capacity of the heat medium is less than the lower limit, organic waste cannot be treated in a small amount. Examples of the heat medium include alumina, silica, magnesium oxide, calcium oxide, and the like. Alumina is preferably used. The shape of the heat medium is not particularly limited, but a ball shape is preferable from the viewpoint of thermal efficiency. The particle diameter of the heat medium is preferably 90% or more of the total number filled in the region to be thermally decomposed, and preferably has a diameter of 5 to 15 mm, more preferably 8 to 12 mm. If the particle size is less than the above lower limit, it becomes expensive, and if it exceeds the upper limit, the gap becomes large when filled and the thermal efficiency is lowered. In the present invention, alumina balls are preferably used.

Organic waste used in the present invention includes thinned wood, driftwood, bamboo, rice straw, rice husk, corn, sweet sorghum, vegetables, fruits, flowers, seaweed, other forests, rivers, dams, and coasts Unused resources such as wood and plants, as well as waste wood, sawmill waste, bamboo waste, pruned branches, cut grass, waste plastic, garbage, food residue, vegetable processing residue, fruit processing residue, sewage sludge, human waste sludge, Village drainage sludge, activated sludge, papermaking sludge and the like can be mentioned. Of these, thinned wood, driftwood, waste wood, waste plastic, garbage, sludge, cut grass, and paper sludge are preferably used. Thinned wood, driftwood or waste wood is particularly preferably used.

The organic waste is only required to have a size that is roughly pulverized. For example, it may be a solid having a plate shape, a rod shape, a sheet shape, or other shapes of 1 mm or more and 15 cm or less. Moreover, as long as it is less than 1 mm, it may be any shape such as granular, powder, and sludge. The water content of the organic waste varies depending on its shape, but is preferably 50% by weight or less, more preferably 30% by weight or less. Since the moisture of the organic waste can be used as steam when reforming the pyrolysis gas, it is sufficient that the moisture can supply the organic waste to the gasification furnace of the present invention without any problem. Therefore, natural drying is sufficient for drying organic waste, and in particular, pretreatment such as forced drying is not necessary.

In the present invention, the organic waste is first heated by a solid heat medium in a non-oxidizing atmosphere in a thermal decomposition region of a gasifier. By the heating, the organic waste is subjected to thermal decomposition and generates thermal decomposition gas. The solid heat medium is preferably heated by a heating means provided outside the gasification furnace in the pyrolysis region. The heating means is preferably an electric heater. The solid heat medium is circulated between a heater provided separately from the pyrolysis region of the gasification furnace, and the heat medium heated to a predetermined temperature by the heater is returned to the pyrolysis region. It can also be used for thermal decomposition of organic waste.

The heating temperature in the pyrolysis region is a temperature at which the pyrolysis reaction of the organic waste is almost completed, and the upper limit is 600 ° C., preferably 570 ° C., and the lower limit is 500 ° C., preferably 530 ° C. By adopting the above range, the amount of gas generated can be increased. If it is less than the said minimum, organic waste will not fully thermally decompose. If the upper limit is exceeded, the amount of gas generated cannot be increased. The upper limit of the pressure during the heating is preferably 0.9 MPa, more preferably 0.3 MPa, and the lower limit is preferably 0.1 MPa, more preferably 0.103 MPa.

Examples of the non-oxidizing atmosphere include inert gases such as nitrogen and helium, and preferably nitrogen is used.

In the present invention, after heating the organic waste as described above, the generated pyrolysis gas is reacted with steam. The reaction is carried out in the reforming region of the gasification furnace of the present invention, and the pyrolysis gas can be reformed to a gas rich in hydrogen. In the reforming, for example, a nickel-based catalyst or the like can be used. Thereby, more hydrogen can be obtained.

The temperature at which the gas reacts with steam has an upper limit of 1000 ° C and a lower limit of 900 ° C, preferably 950 ° C. If it is less than the lower limit, the reforming reaction does not proceed, and if the upper limit is exceeded, the material in the reforming region of the gasifier is adversely affected. The heat necessary for the reforming reaction is preferably supplied by a heating means provided outside the gasification furnace. Examples of the heating means include an electric heater. The pressure in the reforming zone is the same as in the pyrolysis zone.

Steam for reforming the pyrolysis gas is supplied to the pyrolysis gas from the outside in the reforming region. The steam is obtained from industrial water or clean water through a heat exchanger using the heat of the high temperature reformed gas exiting from the reforming region of the gasifier. Alternatively, steam may be obtained by installing a separate boiler. The temperature for supplying the steam is preferably 140 ° C. or higher, and the pressure is preferably 0.376 MPa or higher. Without limitation, the temperature and pressure are, for example, 180 ° C. and 0.9 MPa. The reforming zone can be supplied by spraying continuously or intermittently. Further, it is not always necessary to supply steam from the outside, and it is possible to supply only with water contained in organic waste as a raw material. The amount of steam introduced into the reforming zone together with the pyrolysis gas varies depending on the properties of the organic waste, the properties of the desired gas, etc., but preferably 0.1 kg / organic waste 1 kg to 1 kg / organic waste 1 kg, more preferably 0.2 kg / organic waste 1 kg to 0.6 kg / organic waste 1 kg. If the amount of steam is small, the reforming reaction does not proceed sufficiently, and if it is large, steam is discharged without being reacted, so even if steam is supplied excessively, there is no effect.

The reformed gas leaving the reforming zone of the gasifier is preferably passed through the shift reaction layer. As a result, more hydrogen can be recovered by reacting carbon monoxide contained in the reformed gas with excess steam. The shift reaction is known. For example, a two-stage process is used. In the first stage, an iron-chromium high temperature conversion catalyst is used, and the reaction is preferably carried out at 350 to 500 ° C., so that the residual carbon monoxide concentration in the gas is about 3 to 4% by volume. Next, in the second stage, a copper-zinc based low temperature conversion catalyst is used, and the reaction is preferably performed at 200 to 250 ° C., so that the residual carbon monoxide concentration in the gas is about 0.3 to 0.4% by volume. Further, the pressure during the reaction is preferably 1 MPa or more, more preferably 1 to 3 MPa. The pressure can be usually determined in accordance with the pressure of the process before and after the shift reaction layer.

The gas obtained as described above is preferably cooled with water, and then the gas is purified to concentrate hydrogen to recover hydrogen. A known method can be used as means for purifying the gas to recover hydrogen. For example, pressure swing adsorption method (PSA), membrane separation method, and cryogenic separation method can be mentioned. Of these, PSA is suitable because the gas concentration can be adjusted freely and is inexpensive. In PSA, for example, the concentration of recovered hydrogen can be appropriately controlled by changing the adsorption time, the height of the adsorption layer, and the like. In this way, the gas obtained as described above is separated into hydrogen and other gases to recover hydrogen.

On the other hand, tar and char (carbon and ash) generated when organic waste is heated in a non-oxidizing atmosphere is carried on a heat medium and mechanically discharged from the bottom of the furnace. The tar and char discharged in this way can be burned and used for plant energy or the like. Alternatively, char can be used as a soil conditioner.

The gasification furnace of the present invention is suitable for the treatment of organic waste, and can treat organic waste preferably at 60 to 375 kg / hour, more preferably at 100 to 150 kg / hour. Good. The size of the gasification furnace depends on the amount of organic waste treated, the size and filling amount of the solid heat medium, etc., preferably 500 to 1500 mm in diameter, 3250 to 9750 mm in height, more preferably 1000 mm in diameter, The height is 6500 mm. Preferably, the lower half is the pyrolysis region and the upper half is the reforming region. As the gasifier, a cylindrical vessel made of stainless steel or Inconel is preferably used.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited by these Examples.

(Example)
In the examples, about one-tenth of a small experimental apparatus was used. The apparatus used is as shown in FIG. The material of the gasifier body is Inconel. The gasification furnace A has a cylindrical shape with an inner diameter of 100 mm and a height of 650 mm, 300 mm from the bottom of the gasification furnace is the pyrolysis region 2, and 300 mm from the top is the reforming region 3. In the pyrolysis zone 2, alumina balls D (a constant pressure molar heat capacity at a temperature of 25 ° C is 79.01 J / K · mol) as a heating medium, with a thickness of 30 mm from 120 mm to 150 mm from the bottom of the pyrolysis zone And the two layers are filled with a thickness of 20 mm from 50 mm to 70 mm from the top of the pyrolysis zone. As for the diameter of the alumina balls D, 90% or more of the total number of fillings was 5 to 15 mm. The upper part of the reforming region 3 is filled with a nickel catalyst E. A steam inlet 4 is provided between the thermal decomposition region 2 and the reforming region 3. Further, electric heaters B and C capable of temperature control are installed on the outer walls of the gasification furnace in the pyrolysis region 2 and the reforming region 3, respectively.

(Example 1)
Gasified using construction waste wood (cedar waste). The waste wood is pulverized to 0.75 mm or less. Table 1 shows the properties of the waste wood.

Each value in Table 1 is measured according to the following method.
Moisture and ash: JIS-M8812 (1993)
Total calorific value: JIS-M8814 (1993)
Elemental composition: JIS-M8819 (1997)

Waste wood was intermittently introduced from the raw material supply pipe 1 into the pyrolysis region 2 of the gasifier A at intervals of 30 to 40 seconds every 30 grams by airflow conveyance. For the introduction of waste wood, two valves are provided in series on the upstream side and downstream side of the raw material supply pipe 1 to provide a predetermined space, and after the two valves are closed, first, the upstream side valve is opened. Waste wood is charged between the two valves, then the upstream valve is closed, the space between the two valves is evacuated and then pressurized with helium gas, then the downstream valve is opened, This was done by introducing waste wood into the pyrolysis zone of gasifier A. The introduction operation was performed by a timer program. The pyrolysis region 2 of the gasification furnace A was controlled to a temperature of 550 ° C. by heating an alumina ball as a heat medium with an electric heater B. In the pyrolysis region 2, helium gas was introduced at 0.50 liter / min from the bottom thereof, and the pressure was maintained at a pressure of 0.103 MPa. The waste wood was pyrolyzed, and the generated gas was introduced into the reforming region 3 of the gasification furnace A maintained at the same pressure.

When the gas generated by the above pyrolysis was introduced into the reforming region 3 of the gasifier A, steam was added to the pyrolysis gas at a rate of about 0.3 to 0.5 g / min from the steam inlet 4. The temperature of the reforming region 3 of the gasifier A was 1000 ° C., and the gas temperature at the outlet portion 5 of the reforming region 3 was 947 ° C. The temperature of the reforming region 3 was controlled to be constant by the electric heater C.

The resulting modified gas was cooled to room temperature (25 ° C.) with an air-cooled cooling device. The above gasification operation was performed 5 times for 10 minutes each. The modified gas was obtained on a dry gas basis (excluding helium) in amounts of 77.9 grams / hour, 77.6 grams / hour, 77.1 grams / hour, 77.3 grams / hour, and 77.5 grams / hour, respectively. The composition of the modified gas obtained in each operation is as shown in Table 2.

表2のガス組成はガスクロマトグラフィー(株式会社島津製作所製、GC14A)により測定したものである。

The gas composition in Table 2 was measured by gas chromatography (manufactured by Shimadzu Corporation, GC14A).

(Example 2)
The same procedure as in Example 1 was performed except that steam was not added when introducing the pyrolysis gas into the reforming region 3 of the gasifier A. The generated pyrolysis gas was reformed by the water contained in the waste wood. The temperature of the reforming region 3 of the gasifier A was 1000 ° C., and the gas temperature at the outlet portion 5 of the reforming region was 947 ° C.

Modified gases were obtained in amounts of 100.4 grams / hour, 101.5 grams / hour, and 99.8 grams / hour, respectively. The composition of the modified gas obtained in each operation is as shown in Table 3.

表3のガス組成は表2と同じガスクロマトグラフィーにより測定したものである。

The gas composition in Table 3 was measured by the same gas chromatography as in Table 2.

According to the present invention, economic efficiency is improved as compared with conventional gasifiers, and unused resources and renewable resources that have not been used so far, for example, industrial waste such as thinned wood and construction waste wood, and general waste It became possible to effectively use waste and waste wood from sawmills in Japan. Therefore, the method of the present invention can be used in a wide range of industrial fields. For example, it can be used in forestry, lumbering, livestock, construction, environmental, fuel supply, gas supply, and the like.

It is a figure which shows the outline of the gasification furnace used in the Example.

Explanation of symbols

A: Heating furnace
B: Electric heater in pyrolysis area
C: Electric heater in the reforming zone
D: Alumina ball
E: Nickel catalyst
1: Raw material supply piping
2: Thermal decomposition area
3: Reform area
4: Steam inlet
5: Outlet of reforming area
6: Helium inlet

Claims (6)

In a gasifier that thermally decomposes organic waste in a non-oxidizing atmosphere and reacts the generated pyrolysis gas with steam for reforming, it generates a region where organic waste is pyrolyzed in one container. A gasification furnace having a region for reforming the pyrolysis gas, and in a region for pyrolyzing the organic waste, a solid state whose constant pressure molar heat capacity at a temperature of 25 ° C. is 70 J / K · mol or more A device that is filled with a heat carrier. 2. The apparatus according to claim 1, wherein the solid heat medium is an alumina ball. The apparatus of claim 2, wherein 90% or more of the total number of filled alumina balls has a diameter of 5 to 15 mm. The gasification furnace is provided with a region for pyrolyzing organic waste at the lower stage and a region for reforming pyrolysis gas generated at the upper stage, and a heating means provided outside the gasification furnace at each stage. The apparatus as described in any one of -3. The apparatus according to any one of claims 1 to 4, wherein the organic waste is selected from the group consisting of thinned wood, driftwood, waste wood, waste plastic, garbage, sludge, cut grass, and paper sludge. A method for pyrolyzing and reforming organic waste to gasify it using the apparatus according to any one of claims 1 to 5.

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