JP2004150706A - Method for gasifying waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for gasifying waste capable of recovering valuable metals such as aluminum in a favorable un-oxidized state even when supplying waste of a high calorific value with a hygroscopic lower calorific value of 2000-8000kcal/kg to a fluidized bed of a fluidized bed gasifying furnace when gasifying the waste in the fluidized bed gasifying furnace. <P>SOLUTION: The waste with a hygroscopic lower calorific value of 2000-8000kcal/kg is supplied to the fluidized bed of the fluidized bed gasifying furnace. Fluidized bed fluidized gas containing oxygen and inert gas (for example, one type or more of steam, nitrogen, argon or helium) is supplied to the fluidized bed so as to satisfy 40-220Nm<SP>3</SP>in oxygen quantity and 450-3300Nm<SP>3</SP>in inert gas quantity per ton of the waste. The waste is gasified by controlling a temperature of the fluidized bed at 450-600°C. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention belongs to a technical field related to a waste gasification method, and particularly to a technical field related to a waste gasification method in which waste is gasified by a fluidized bed gasifier.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 10-103633 (Patent Document 1) discloses a technique relating to gasification of waste by a fluidized bed gasifier. This technology uses waste gas with a lower oxygen concentration than air as the fluidizing gas to ensure that a sufficient amount of fluidizing gas is supplied to form a fluidized bed while at the same time introducing waste into a fluidized bed gasifier. The air ratio can be kept low without increasing the amount.
[0003]
[Patent Document 1]
JP 10-103633 A
However, in this method, when high calorific value waste is supplied to a fluidized bed of a fluidized bed gasifier, there is a possibility that phenomena such as poor flow and a high fluidized bed (sand layer) temperature may occur. is there.
[0005]
[Problems to be solved by the invention]
In the conventional gasification method using a fluidized-bed gasifier, as described above, when high-calorific value waste is supplied to the fluidized-bed of the fluidized-bed gasifier, the temperature of the fluidized-bed increases. Particularly, when waste having a high calorific value is supplied to the fluidized bed, there occurs a problem that the temperature of the fluidized bed becomes too high and it becomes difficult to recover valuable metals such as aluminum. As a countermeasure, if the amount of air input to the fluidized bed is reduced to suppress excessive combustion in the fluidized bed and the air ratio is reduced, the fluidized bed (sand bed etc.) cannot be maintained, and the fluidized bed gasifier It becomes difficult to operate properly.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to produce a waste with a low-moisture moisture calorific value of 2000 to 8000 kcal / kg when gasifying waste with a fluidized bed gasifier. When supplying calorific value waste to the fluidized bed of a fluidized bed gasifier, valuable metals such as aluminum are not oxidized in good condition (they are not oxidized and hinder reuse. ) Is intended to provide a method for gasifying waste that can be recovered in (1).
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a waste gasification method according to the present invention includes a waste gasification method according to claims 1 and 2 (a waste gasification method according to the first invention and the second invention). It has the following configuration.
[0008]
That is, the method for gasifying waste according to claim 1 is a method for gasifying waste with gasification of waste having a lower moisture calorific value of 2000 to 8000 kcal / kg in a fluidized bed gasifier. The waste is supplied to a fluidized bed of the fluidized-bed gasifier, and a fluidized-bed fluidized gas containing oxygen and an inert gas is supplied in an amount of 40 to 220 Nm ^{3 in} terms of oxygen per ton of waste and an inert gas amount. And supplying gas to the fluidized bed so as to satisfy 450 to 3300 Nm ³ , and gasifying the waste while controlling the temperature of the fluidized bed to 450 to 600 ° C. (First invention).
[0009]
The method for gasifying waste according to claim 2 is the method for gasifying waste according to claim 1, wherein the inert gas is one or more of steam, nitrogen, argon, and helium (second example). invention).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is implemented, for example, as follows.
Moisture lower heating value: 2000 to 8000 kcal / kg of waste is supplied to a fluidized bed of a fluidized bed gasifier, and a fluidized bed fluidizing gas containing oxygen and an inert gas is supplied to the fluidized bed. At this time, the fluidized bed fluidizing gas is supplied to the fluidized bed so as to satisfy 40 to 220 Nm ^{3 in} terms of oxygen per ton of waste and 450 to 3300 Nm ³ in terms of inert gas. That is, the fluidized bed fluidizing gas is applied to the fluidized bed so as to have an oxygen amount of 40 to 220 Nm ³ and an inert gas amount of 450 to 3300 Nm ³ (all amounts per ton of waste supplied to the fluidized bed). Supply. By doing so, the temperature of the fluidized bed is controlled at 450 to 600C. The waste is gasified while performing such control.
[0011]
The present invention is implemented in such a form. Hereinafter, the operation and effect of the present invention will be mainly described.
[0012]
In order to perform good pyrolysis of waste and gasify it in a fluidized-bed gasifier, and to recover valuable metals such as aluminum in a good, unoxidized state, the fluidized bed of a fluidized-bed gasifier is required. Must be maintained at an appropriate temperature (450 to 600 ° C.). However, in the conventional method, when a waste having a high calorific value is supplied to a fluidized bed of a fluidized bed gasifier, the temperature of the fluidized bed rises excessively and exceeds 600 ° C., and the fluidized bed temperature is adjusted to an appropriate temperature. A problem that it becomes difficult to maintain the This is because the air ratio to the waste is too high, so that the oxygen concentration in the fluidized bed increases and excessive combustion occurs. To prevent this, the air ratio must be kept low. As means for keeping the air ratio low, it is conceivable to simply reduce the supply amount of the fluidizing gas to the fluidized bed or simply increase the supply amount of waste, but if the supply amount of the fluidizing gas is simply reduced, It is not possible to maintain a sufficient fluidized bed (sand layer etc.) flow, which makes it difficult to operate the fluidized bed gasifier properly. In the case of (1), a local high-temperature portion is formed in the fluidized bed and clinker is easily generated, so that good fluidity cannot be obtained.
[0013]
As described above, when the waste having a high calorific value is supplied to the fluidized bed of the fluidized bed gasifier, in order to maintain the temperature of the fluidized bed at an appropriate temperature (450 to 600 ° C.), simply use the fluidized gas. Reducing the supply of waste gas or simply increasing the amount of waste will not be able to maintain the required fluidized bed flow, and will even weaken the essential basic functions of a fluidized bed gasifier. Alternatively, a serious problem of disappearance occurs.
[0014]
Therefore, in the waste gasification method according to the present invention, when the waste having a lower moisture calorific value: 2000 to 8000 kcal / kg is gasified by a fluidized bed gasifier, the waste is treated with the fluidized bed gas. supplies to the fluidized bed furnace, so as to satisfy the 450～3300Nm ³ a fluidized bed fluidizing gas containing oxygen and inert gas at 40～220Nm ³ and inert gas amount in the waste per ton oxygen The waste is supplied to the fluidized bed and the waste is gasified while controlling the temperature of the fluidized bed at 450 to 600 ° C.
[0015]
That is, in the gasification method of waste according to the present invention, when gasification of waste having a low calorific value of moisture: high calorific value of 2000 to 8000 kcal / kg in a fluidized-bed gasifier, only the fluidized gas is used. Instead of reducing the supply amount or simply increasing the waste supply amount, the fluidized bed fluidizing gas containing oxygen and the inert gas is supplied with an oxygen amount of 40 to 220 Nm ³ and an inert gas amount of 450 to It supplies to a fluidized bed so that it may be set to 3300Nm < ³ > (all the amount per 1 ton of waste supplied to a fluidized bed). By doing so, the temperature of the fluidized bed can be controlled at 450 to 600 ° C. Therefore, by supplying such a fluidized bed fluidizing gas, waste is gasified while controlling the temperature of the fluidized bed at 450 to 600 ° C.
[0016]
Therefore, according to the waste gasification method of the present invention, even in the case where waste having a low calorific value of moisture: 2000 to 8000 kcal / kg and a high calorific value is supplied to the fluidized bed of the fluidized-bed gasification furnace. It is possible to maintain the temperature of the fluidized bed at an appropriate temperature (450 to 600 ° C.) while maintaining the required fluidized bed flow without causing the fluidized bed to be inferiorly flown. Can be gasified by good thermal decomposition, and valuable metals such as aluminum can be recovered in a good, unoxidized state.
[0017]
In the waste gasification method according to the present invention, the temperature of the fluidized bed to be controlled is set to 450 to 600 ° C. If the temperature is set to less than 450 ° C, it is difficult to gasify the waste by good thermal decomposition. On the other hand, if the temperature exceeds 600 ° C., valuable metals such as aluminum are excessively oxidized, and it becomes impossible to recover valuable metals such as aluminum in an unoxidized and favorable state.
[0018]
The fluidized bed fluidizing gas containing oxygen and an inert gas has an oxygen amount of 40 to 220 Nm ³ and an inert gas amount of 450 to 3300 Nm ³ (each amount per ton of waste supplied to the fluidized bed). The fluid is supplied to the fluidized bed in order to control the temperature of the fluidized bed to 450 to 600 ° C. That is, when the oxygen amount is less than 40 Nm ³ , the fluidized bed temperature is less than 450 ° C., and when the oxygen amount is more than 220 Nm ³ , the fluidized bed temperature is more than 600 ° C. In any case, the fluidized bed temperature is 450 to 600 ° C. ℃ can not be controlled. When the amount of inert gas is more than 3300 Nm ³ , the fluidized bed temperature is lower than 450 ° C. When the amount of inert gas is less than 450 Nm ³ , the fluidized bed temperature is more than 600 ° C. In any case, the fluidized bed temperature is 450 ° C. It cannot be controlled to ６００600 ° C.
[0019]
As the inert gas contained in the fluidized bed fluidized gas, the type thereof is not particularly limited, and various types can be mentioned. For example, one or more of steam, nitrogen, argon, and helium may be used. Can be mentioned.
[0020]
When gasification of organic waste is carried out, in a fluidized-bed gasifier, combustible gas containing hydrogen, carbon monoxide, and hydrocarbons, char and ash are generated. If the combustible gas, char, ash, and the like generated in the fluidized bed gasifier are subsequently introduced into the melting furnace, the char can be burned to melt the ash. At this time, the combustible gas acts as fuel for the melting furnace and is used. Exhaust gas sent from the melting furnace is recovered by a waste heat boiler and an air preheater, and then discharged to the atmosphere via an exhaust gas treatment device.
[0021]
The waste gasification method according to the present invention can be used in such a waste gasification and waste gasification step in a combustion melting process.
[0022]
In the present invention, the lower calorific value of the moisture of the waste can be obtained from the total calorific value measured by a measuring method using a bomb calorimeter for solid fuel in JIS M8814 by the following equation (1).
[0023]
_{H = H 0 (1-w} ) -6 [9h (1-w) + w] ------------- Equation (1)
However, in the above formula (1), H: moisture lower calorific value (true calorific value) [kcal / kg], H ₀ : total calorific value [kcal / kg], h: in waste material excluding water (dry) (W / w) is the mass ratio of hydrogen in the waste.
[0024]
【Example】
Examples of the present invention and comparative examples will be described below. Note that the present invention is not limited to this embodiment.
[0025]
[Example 1 and Comparative Example 1]
FIG. 4 shows an overview of a fluidized bed gasifier used for gasification of waste and a swirling flow melting furnace for melting and processing products generated in the gasifier according to Example 1 and Comparative Example 1 of the present invention. Show.
[0026]
In FIG. 4, reference numeral 1 indicates a fluidized bed gasifier. The fluidized bed gasifier 1 is provided with a dispersion plate 2 having a large number of gas injection ports 3 at the bottom thereof, and a wind box 4 formed below the dispersion plate 2. When the fluidizing gas is injected upward from the wind box 4 through the gas injection ports 3 of the dispersion plate 2, the sand layer 5 above the dispersion plate 2 flows to form a fluidized bed. The sand in the sand layer 5 is a kind of fluid medium, and is heated at the upper part of the hearth and becomes high temperature.
[0027]
The fluidizing gas introduced into the wind box 4 is supplied by a supply pipe 6 and a supply pipe 7. Steam (one kind of inert gas) is supplied from the supply pipe 6, and air is supplied from the supply pipe 7. Then, the water vapor and the air are mixed in the wind box 4, and the mixed gas is injected upward from the gas injection ports 3 of the dispersion plate 2 as a fluidizing gas, and the sand layer 5 is caused to flow to form a fluidized bed. This fluidizing gas can be said to be a fluidizing gas containing oxygen and an inert gas (steam and nitrogen), that is, a fluidizing gas containing oxygen and steam and nitrogen as inert gas. In addition, as the steam supplied from the supply pipe 6 to the wind box 4, a part of the steam generated by an attached waste heat boiler downstream of the swirling flow melting furnace 10 is used.
[0028]
In this way, a fluidizing gas containing oxygen and an inert gas (steam and nitrogen) is supplied as a fluidizing gas of the fluidized-bed gasifier 1, and the sand layer 5 is fluidized to form a fluidized bed. Then, the fluidized gas is continuously supplied to the fluidized bed (sand layer 5) to continuously form the fluidized bed. The fluidized bed is heated to a high temperature by the fluidized medium (sand) heated at the upper part of the hearth and heated to a high temperature.
[0029]
Along with the supply of the fluidized gas, the waste is quantitatively supplied to the fluidized bed (sand layer 5) from the waste supply port 8 located above the fluidized bed.
[0030]
Thus, the waste is heated by the fluidized bed (sand layer 5), thermally decomposed and gasified. The pyrolysis gas generated at this time is discharged from the upper pyrolysis gas discharge port 9 and introduced into the swirling flow melting furnace 10. In the swirling flow melting furnace 10, air for combustion is supplied to further burn the pyrolysis gas and to melt ash in the pyrolysis gas by using heat generated by the combustion, and discharge this as molten slag. I do.
[0031]
In such gasification of wastes, wastes with a moisture lower calorific value: 2000 to 8000 kcal / kg are used as wastes to be supplied to the fluidized bed of the fluidized bed gasifier 1, and fluidized bed gasification is performed. The amount of oxygen and the amount of inert gas (steam and nitrogen) (both per ton of waste supplied to the fluidized bed) in the fluidized gas supplied to the fluidized bed of the gasification furnace 1 are varied as parameters. Was. Then, the change over time in the temperature of the fluidized bed was measured. The amount of oxygen and the amount of inert gas in the fluidized gas are, more specifically, the amount of water vapor supplied from the supply pipe 6, the amount of air supplied from the supply pipe 7, and the amount of waste supplied to the fluidized bed. By changing one or more of the amounts of
[0032]
FIG. 1 shows an example of the measurement results of the change over time in the temperature of the fluidized bed, and FIG. 2 shows another example.
[0033]
FIG. 1 uses waste (garbage) having a moisture lower calorific value of about 3000 kcal / kg as a waste, and has an oxygen amount in a fluidizing gas of 270 to 550 Nm ³ and an inert gas amount of 1000 to 2100 Nm ^3. (Each amount per ton of waste supplied to the fluidized bed), that is, the fluidizing gas is an oxygen amount: 270 to 550 Nm ³ and an inert gas amount: 1000 to 2100 Nm ³ (both are added to the fluidized bed. (Amount of waste per ton supplied). Except immediately after the start of the supply of the fluidizing gas, the temperature of the fluidized bed (sand layer) exceeds 600 ° C., and the average value of the temperature of the fluidized bed (sand layer) during the supply of the fluidizing gas is 640 ° C., which is also 600 ° C. Is over.
[0034]
FIG. 2 shows a case in which waste (garbage) having a lower moisture calorific value of about 3500 kcal / kg is used as a waste, and a fluidizing gas is an oxygen quantity: 140 to 190 Nm ³ and an inert gas quantity is 1200 to 1400 Nm ³ ( In each case, the amount of waste per ton supplied to the fluidized bed) is the result when supplied to the fluidized bed. The temperature of the fluidized bed (sand layer) during the supply of the fluidizing gas is in the range of 450-600 ° C., the average value of which is 552 ° C., also in the range of 450-600 ° C.
[0035]
FIG. 3 is a diagram in which the conditions (oxygen amount, inert gas amount) in the case of FIG. 1 and FIG. 2 are plotted in a relationship between the oxygen amount and the inert gas amount. That is, the relationship between the oxygen amount and the inert gas amount in the case of FIG. 1 (Comparative Example 1) and the relationship between the oxygen amount and the inert gas amount in the case of FIG. 2 (Example 1 of the present invention) are shown. The conditions in the case of FIG. 1 are plotted with Δ marks, and the conditions in the case of FIG. 2 are plotted with Δ marks (black square marks). Drawing, a region surrounded by a dotted line (----) is a region satisfying the "450～3300Nm ³ in 40～220Nm ³ and inert gas amount in the oxygen amount" is a requirement of the present invention. The conditions (oxygen amount, inert gas amount) in the case of FIG. 1 are outside the above-mentioned region, whereas the conditions (oxygen amount, inert gas amount) in the case of FIG. 2 are in the above-mentioned region.
[0036]
Under the conditions in FIG. 1 (oxygen amount, inert gas amount), the temperature of the fluidized bed (sand layer) is too high (above 600 ° C.), so that the waste can be gasified by good thermal decomposition. However, valuable metals such as aluminum are excessively oxidized, and valuable metals such as aluminum cannot be recovered in a good unoxidized state. On the other hand, under the conditions of FIG. 2 (oxygen amount, inert gas amount), the fluidized bed (sand layer) temperature is maintained at an appropriate temperature (a temperature in the range of 450 to 600 ° C.). The waste can be gasified by good thermal decomposition, and valuable metals such as aluminum can be recovered in a good unoxidized state.
[0037]
[Example 2 and Comparative Example 2]
In the above Example 1 and Comparative Example 1, the case where the conditions (the amount of oxygen and the amount of the inert gas) are plotted in FIG. 3 has been described, but also in the case of other conditions, the dotted line (----) in FIG. The fluidized bed (sand layer) temperature is maintained at an appropriate temperature (a temperature in the range of 450 to 600 ° C.) in the case of the conditions in the area surrounded by , And valuable metals such as aluminum can be recovered in a good, unoxidized state. On the other hand, under the condition outside the area surrounded by the dotted line (----), the fluidized bed (sand layer) temperature is set to an appropriate temperature (a temperature in the range of 450 to 600C). Therefore, it is difficult to gasify the waste by good thermal decomposition, and it is not possible to recover valuable metals such as aluminum in a good, unoxidized state. Failures occur.
[0038]
[Example 3 and Comparative Example 3]
In the above Examples and Comparative Examples (Examples 1-2 and Comparative Examples 1-2), a fluid containing a mixed gas of steam and air, ie, oxygen and an inert gas (steam and nitrogen) as the fluidizing gas. Although the case where the liquefied gas is used has been described, a fluidized gas containing another inert gas and oxygen, such as a fluid containing one or more of nitrogen, argon, and helium, and oxygen instead of the fluidized gas, is used. Also in the case of using the liquefied gas, and also in the case of using the fluidized gas containing only oxygen and water vapor, the dotted line (----) of FIG. In the case of conditions outside the region surrounded by the circles, the fluidized bed (sand layer) temperature is not maintained at an appropriate temperature (a temperature in the range of 450 to 600 ° C.), and therefore, waste is removed by good heat. It is difficult to decompose and gasify In addition, valuable metals such as aluminum cannot be recovered in an unoxidized and good state, or both of these problems occur. On the other hand, a region surrounded by a dotted line (----) in FIG. In the case of the conditions in the above, the temperature of the fluidized bed (sand layer) is maintained at an appropriate temperature (a temperature in the range of 450 to 600 ° C.), so that the waste is gasified by good thermal decomposition. And a valuable metal such as aluminum can be recovered in a good, unoxidized state.
[0039]
In the case of a fluidizing gas containing nitrogen and oxygen, oxygen gas or air is used as an oxygen source, and nitrogen or air is used as a nitrogen source. In the case of a fluidizing gas containing argon in addition to nitrogen and oxygen, argon gas is used as the argon source, and the same oxygen source and nitrogen source as those described above are used. In the case of a fluidizing gas containing only argon and oxygen, an argon gas is used as an argon source and an oxygen gas is used as an oxygen source. In the case of a fluidizing gas containing only oxygen and water vapor, oxygen gas is used as an oxygen source.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the gasification method of the waste which concerns on this invention, when gasifying a waste with a fluidized-bed type gasifier, the low calorific value of moisture: The waste of a high calorific value of 2000-8000 kcal / kg is fluidized bed. Even when the fluidized bed is supplied to a fluidized bed of a gasification furnace, the temperature of the fluidized bed is adjusted to an appropriate temperature (450 to 600) while maintaining the required fluidized bed flow without causing poor fluidization of the fluidized bed. ° C), and the waste can be gasified by good thermal decomposition, and valuable metals such as aluminum can be recovered in a good unoxidized state. .
[Brief description of the drawings]
FIG. 1 is a view showing an example of a measurement result of a temporal change of a temperature of a fluidized bed of a fluidized-bed gasification furnace during a waste gasification treatment according to Comparative Example 1.
FIG. 2 is a diagram showing an example of a measurement result of a temporal change of a temperature of a fluidized bed of a fluidized-bed gasifier during a gasification treatment of a waste according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a relationship between an oxygen amount and an inert gas amount according to Example 1 and Comparative Example 1 of the present invention.
FIG. 4 shows an outline of a fluidized-bed gasification furnace used for gasification of waste and a swirling flow melting furnace for melting and processing products generated in the gasification furnace according to Examples and Comparative Examples of the present invention. It is a schematic diagram.
[Explanation of symbols]
1- Fluidized bed gasifier, 2- Dispersion plate, 3- Gas injection port, 4- Box
5--sand layer, 6-supply pipe, 7-supply pipe, 8--waste supply port,
9-pyrolysis gas outlet, 10-swirling flow melting furnace.

Claims (2)

Moisture lower heating value: A waste gasification method in which waste of 2000 to 8000 kcal / kg is gasified by a fluidized bed gasifier, wherein the waste is formed in a fluidized bed of the fluidized bed gasifier. supplies, oxygen and inert gas is supplied to the fluidized bed so as to satisfy the 450～3300Nm ³ in 40～220Nm ³ and inert gas amount to the fluidized bed fluidizing gas at the waste tonne oxygen containing And gasifying the waste while controlling the temperature of the fluidized bed to 450 to 600 ° C. The waste gasification method according to claim 1, wherein the inert gas is one or more of steam, nitrogen, argon, and helium.

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