JP2000161638A - Method and device for processing waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover the heat by solving a problem of corrosion of boiler tubes when the heat is recovered from waste combustion gas in a boiler. SOLUTION: In a waste processing device, a combustible gas of -20 to 1% in concentration expressed in terms of oxygen at furnace outlet is generated by incompletely burning or partially oxidizing wastes in a partial oxidizing furnace 1 associated with the combustion reaction. Then, the combustible gas is introduced in a dust separator 2 at 250-450 deg.C to keep the dust concentration at <=0.1 g/Nm3, and the dust-separated combustible gas is burned at high temperature in a combustion furnace 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for treating waste.

[0002]

2. Description of the Related Art A method of partially oxidizing municipal waste or industrial waste (hereinafter referred to as "waste"), gasifying the municipal waste, and then burning the waste is proposed in Japanese Patent Application Laid-Open No. Hei 7-35322. An outline of the configuration of a typical example is shown in FIG. 6 of the accompanying drawings.

[0003] In FIG. 6, the waste is partially burned fluidized bed furnace 51.
At a fluidized bed temperature of 450 to 650 ° C and an air ratio of 0.15 to
It is gasified in a reducing atmosphere of about 0.5 and introduced into a secondary combustion furnace 53 via a dust collecting device 52 such as a cyclone or a collision type dust collector. The produced gas is mixed with the secondary air in the secondary combustion furnace 53 and completely burns at a high temperature of 800 to 1000 ° C. At this time, a desalting agent is supplied to suppress the generation of HCl gas,
Perform heat recovery. A dust collection line 54 is provided below the dust collector 52. After a part of the desalinating agent and all or a part of the dust are cooled by the cooler 55, they are returned to the partial oxidation fluidized bed furnace again. It is supposed to be.

[0004]

When waste is partially oxidized and burned in such a burning method, a desalinating agent must be used in a secondary combustion furnace. Therefore, the dust concentration becomes high, which is disadvantageous in dust removal. If the dust concentration in the secondary combustion furnace is not controlled below a certain value, corrosion of the boiler tube due to salts in the dust in the boiler disposed downstream for heat recovery is a problem.

The present invention has been made in order to solve such a problem, and a method and an apparatus for treating waste which can be partially oxidized without causing the above problem and can efficiently recover heat. The task is to provide

[0006]

The first means for solving the above-mentioned problem is that the waste is incompletely burned or partially oxidized in a partial oxidation furnace involving a combustion reaction to reduce the oxygen equivalent concentration at the furnace outlet. A combustible gas having a concentration of 20 to 1% is generated, and the combustible gas is introduced into a dust removing device at 250 to 450 ° C. to reduce the dust concentration to 0.1 g / Nm ³ or less. A waste treatment method characterized by burning at a high temperature in a furnace. Here, “oxygen concentration” is defined as the difference between the oxygen concentration in the atmosphere and the oxygen concentration considered to be consumed by the gas that may be oxidized. For example, oxygen (O ₂ ) is 2% and carbon monoxide (CO) is 4%.
%, ₂ % of hydrogen (H ₂ ) and 1% of methane (CH ₄ ), 4% of carbon monoxide (CO) is oxidized to carbon dioxide (CO ₂ ). O ₂ ), 2% of hydrogen (H ₂ ) consumes 1% of oxygen (O ₂ ), and 1% of methane (CH ₄ ) consumes 2% of oxygen (O ₂ ). Therefore, the “oxygen concentration” in this case is 2− (2 + 1 + 2).
= −3%. This number is an index indicating the degree of combustion of the partial oxidation gas in the atmosphere and the degree of the air ratio in the combustion up to that time. That is, the smaller the numerical value, the higher the potential as a combustible gas.

In the partial oxidation furnace, waste is partially oxidized, and a combustible gas having a relatively low temperature of 250 to 450 ° C. is sent to the inlet of the dust remover. Here, the reason why the temperature at the inlet of the dust removing device is set in the above range is that there is a problem such as tar adhesion below 250 ° C., and above 450 ° C. there is a possibility of dioxin generation and a possibility of clogging due to salt. Because there is. "Concentration in terms of oxygen" at the furnace outlet at this time
Is adjusted so as to be −20 to 1%. The reason is that if the "oxygen concentration" is less than -20%, a problem such as tar adhesion occurs as a strong reducing gas, and if it exceeds 1%, the oxidation of combustible gas is promoted before being introduced into the secondary combustion furnace. This is because This keeps the oxygen concentration at the furnace outlet low and reduces the risk of explosion due to combustible components and oxygen. In addition, since the temperature is relatively low, dust can be removed without excessive cooling via equipment such as a cooling tower. In the dust removing device, the combustible gas is burned in a combustion furnace after the dust concentration is set to 0.1 g / Nm ³ or less, and the temperature can be efficiently increased. The dust removing device at this time may use a bag filter, a ceramic filter, a high-temperature electric precipitator, an inertial precipitator, a high-performance cyclone, a centrifugal precipitator, or the like, depending on the temperature of the combustible gas.

In the case of the method of the present invention, dust is removed by a dust remover so that the dust concentration becomes 0.1 g / Nm ³ or less.
The amount of salt in the dust is reduced, and the possibility of corrosion of the subsequent boiler tubes and the like is drastically reduced.

Further, the emission of harmful gas can be suppressed. Since the combustible gas after partial oxidation in the partial oxidation furnace is mixed with an oxidant in the combustion furnace and burned at a high temperature,
Emission of unburned components such as CO is almost completely suppressed. Also,
Since high-temperature combustion is performed after removing combustible gas, the concentration of aromatic organic compounds due to soot is reduced, and as a result, the concentration of dioxin-like substances, which are incomplete combustion products, is also reduced.

A second means for solving the above-mentioned problem is to use a filter-type dust collector as a dust removing device, and to periodically remove deposits on a filter of the dust collector with a gas having an oxygen concentration of 5% or less. This is the waste disposal method to be removed. Thereby, dust can be efficiently removed and emission of harmful gas is further suppressed. Here, the reason why the oxygen concentration is set to 5% or less is to suppress the oxidation of the combustible gas by oxygen and reduce the risk of unnecessary explosion and combustion. The gas having an oxygen concentration of 5% or less can be obtained by recirculation of exhaust gas, pressure swing adsorption, or membrane separation.

A third means for solving the above-mentioned problem is to use a filtration type dust collector as a dust removing device and periodically remove nitrogen deposits on a filter of the dust collector. It is a waste disposal method. By using nitrogen for removing the deposits, the combustible gas is not oxidized in the dust collector. In addition, unnecessary explosion, combustion, and the like caused by this means are eliminated.

A fourth means for solving the above-mentioned problems is a waste disposal method according to the first to third means, wherein an ignition source is provided in the combustion furnace and combustible gas is continuously burned. It is. The combustible gas is sent to the combustion furnace after being dusted and burned, but by placing an ignition source here, the danger of misfiring, mixing the combustible gas and air again, and exploding is avoided.

A fifth means for solving the above-mentioned problem is the first to fourth means, wherein a boiler is provided in or downstream of the combustion furnace, and heat recovery is performed by the boiler. It is a material processing method. Since high-temperature heat can be efficiently recovered, a high-temperature and high-pressure boiler is possible.

A sixth means for solving the above problems is a partial oxidation furnace for incompletely burning or partially oxidizing waste so as to obtain a combustible gas having an oxygen equivalent concentration at the furnace outlet of -20 to 1%. , Installed in the downstream, 250-450 ° C
And a dust removing device for reducing the concentration of dust in the combustible gas to 0.1 g / Nm ³ or less, and a combustion furnace installed downstream of the combustible gas.

A seventh means for solving the above-mentioned problems is a waste treatment apparatus according to the sixth means, wherein an ignition source is provided in the combustion furnace.

In the partial oxidation furnace, the waste is partially oxidized, and combustible gas having a relatively low temperature of 250 to 450 ° C. is generated at the entrance of the dust remover. At this time, the air ratio is adjusted so that the “oxygen concentration” at the furnace outlet is −20 to 1%. As a result, a combustible gas having a low oxygen concentration and a low risk of explosion or the like is generated. Further, since this combustible gas has a relatively low temperature, dust is removed without excessive cooling by equipment such as a cooling tower. After reducing the dust concentration to 0.1 g / Nm ³ or less in the downstream dust remover connected by a duct or the like from the furnace outlet of the partial oxidation furnace, the combustible gas is burned in the downstream combustion furnace to efficiently raise the temperature. Is done. The dust removing device at this time may use a bag filter, a ceramic filter, a high-temperature electric dust collector, an inertial dust collector, a high-performance cyclone, a centrifugal dust collector, or the like, depending on the temperature of the combustible gas. In the case of this apparatus, dust is removed so that the dust concentration becomes 0.1 g / Nm ³ or less, so that the amount of salt in the dust is reduced, and the corrosion of the downstream boil tube and the like is extremely reduced.

Further, the emission of harmful gas can be suppressed. Since the combustible gas that has been partially oxidized in the partial oxidation furnace is mixed with an oxidant in the combustion furnace and burned at a high temperature, the emission of unburned components such as CO is almost completely suppressed. Further, since high-temperature combustion is performed after removing combustible gas, the concentration of aromatic organic compounds due to soot is reduced, and as a result, the concentration of dioxin-like substances, which are incomplete combustion products, is also reduced.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG.
An embodiment of the present invention will be described based on the above.

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention. In the figure, reference numeral 1 denotes a partial oxidation furnace, to which air for oxidation or air-based gas whose oxygen concentration is controlled by steam or exhaust gas is supplied. Waste is injected into the furnace and ignites to partially oxidize to produce combustible gas. The partial oxidation furnace 1 is connected to a dust removing device 2 for removing dust from the combustible gas, a combustion furnace 3 for burning combustible gas, and a boiler 4 for recovering heat of the burned gas.

In the partial oxidation furnace 1, the temperature inside the furnace may be such that the waste can self-combust and partially oxidize.
Desirably, the temperature is 0 to 800 ° C. In addition, the “oxygen concentration” of the gas generated by the partial oxidation is -20 to 1%.
The air ratio is controlled so that The air ratio at this time is about 0.15 to 0.9. Thereafter, the temperature of the combustible gas is controlled by the residence time in the partial oxidation furnace 1, and is sent to the dust removing device 2 at 250 to 450 ° C. The reason for setting the temperature range is that if the temperature is 250 ° C. or lower, there is a problem of deposits such as tar, and if the temperature is 450 ° C. or higher, there is a problem of dioxin formation and a problem of clogging due to salts such as NaCl and KCl.

Next, the combustible gas is introduced into the dust removing device 2, where the dust is removed to a concentration of 0.1 g / Nm ³ or less. If the dust is removed to this concentration, the amount of salt in the dust is reduced, so that corrosion of the subsequent boiler tube and the like is reduced. FIG. 2 shows the relationship between the dust concentration after dust removal and the service life of the downstream boiler tube. From this figure, it can be seen that if the dust concentration after dust removal is set to 0.1 g / Nm ³ or less, the corrosion of the downstream boiler tube can be suppressed to a level that can be practically used.

It is desirable to use a candle-type ceramic filter as shown in FIG. 3 for the dust removing device 2, but it is also conceivable to use a filter cloth or a honeycomb-shaped ceramic filter having an aperture of 10 mm or less. It is desirable that the removal be performed using a gas having an oxygen concentration of 5% or less or nitrogen in order to suppress the oxidation of the combustible gas and reduce the risk of unnecessary explosion and combustion. Considering the effect of removing the deposits, the conditions of the wiping method are a gas pressure of 1 kg / cm ² or more, a wiping interval of several seconds to several tens of minutes, and a wiping time of 0.02.
It is desirable that the time is about seconds to several tens of seconds.

The combustible gas is introduced into the combustion furnace 3 after being dust-removed by the dust-removing device 2, where the temperature rises to about 1000 ° C. Here, since complete combustion is performed, emission of unburned gas and the like is almost completely suppressed. The combustible gas is
Since the dust has been removed in advance, the concentration of the aromatic organic compound due to soot decreases, and as a result, the concentration of dioxin-like substances, which are incomplete combustion products, also decreases.

In the present embodiment, as a preferred example, a boiler, for example, at a temperature of 300 ° C. or more, 20 a
The water pipe of the high-temperature and high-pressure boiler 4 having a capacity of at least ta is installed.
Heat can be efficiently recovered from the combustion gas. Hot air can be recovered if necessary. Since the dust has been removed in advance, corrosion of the boiler tube due to dust can be suppressed. In the case of recovering heat from a high-temperature field of 600 ° C. or more where the corrosion effect of hydrogen chloride gas increases, a boiler tube using a ceramic material having corrosion resistance may be used to extend the life of the boiler tube. . The exhaust gas after heat recovery passes through a downstream exhaust gas treatment facility (not shown) and is discharged from the chimney.

[0025]

An embodiment of the present invention will be described with reference to FIG.
In this embodiment, the fluidized bed furnace 1 is employed as the partial oxidation furnace of the apparatus shown in FIG. Other parts are the same as those of the apparatus shown in FIG. 1. In FIG. 4, the same parts as those of FIG.

In the apparatus shown in FIG. 4, the fluidized-bed furnace 1 has a fluidized air temperature of 20 to 650 ° C. and a sand bed temperature of 400 to 600 ° C.
Municipal solid waste as waste was supplied to the fluidized bed furnace 1 at 1 t / h, and the air ratio was controlled between 0.2 and 0.8 to partially oxidize to generate combustible gas. The combustible gas was supplied to the dust remover 2 at 250 to 450 ° C., and dust was removed by a candle type ceramic filter. The material of the candle type ceramic filter is SiO ₂ , Al ₂ O ₃ , SiC, cordierite, a composite of the above materials, a ceramic fiber type of an inorganic material similar thereto, or a porous body type. Nitrogen gas was used for the wiping off, the wiping pressure was 4 kg / cm ² , the wiping interval was 5 seconds to 50 minutes, and the wiping time was 0.1 seconds to 20 seconds. This allows
The dust concentration before flowing into the dust removing device 2 is 5 to 20 g / Nm
Those were ³ is dust to 0.1 g / Nm ³ or less.
After the removed dust and the like were collected, they were rendered harmless in a melting furnace and an incinerator. The combustible gas after the dust removal is transferred to the combustion furnace 3
And the temperature was increased to 900 to 1000 ° C. At this time, 350-540 ° C., 50-1
Heat recovery could be performed using the steam of 00 ata.
Although stainless steel, Inconel, and other alloy steels were used as the boiler tube, no significant corrosion was observed, and the corrosion resistance that could be used for several years was confirmed depending on the material. In addition, when hot air was collected, the temperature was 350 to 700 ° C.
It was found that high temperature air could be recovered.

The applicability of the grate furnace shown in FIG. 5 was also confirmed. In the apparatus shown in FIG. 5, a grate furnace 1 was employed as a partial oxidation furnace. Others are the same as the apparatus of FIG. In the grate furnace 1, the temperature of the oxidizing air is set to 20 to 250 ° C., the temperature of the upper part of the grate is set to 500 to 800 ° C., and municipal solid waste is supplied into the furnace. Partial oxidation was performed by operating in between. Combustible gas is 250-450 ° C
And the dust was removed by a candle-type ceramic filter and a honeycomb-type ceramic filter. The material of the ceramic filter is SiO ₂ , A
l ₂ O ₃ , SiC, cordierite, a composite of the above materials, or a ceramic fiber type or a porous type of inorganic materials similar thereto. Nitrogen gas was used for the cleaning, the cleaning pressure was 3 kg / cm ² , the cleaning interval was 10 seconds to 20 minutes, and the cleaning time was 0.05 seconds to 1 minute.
The range was 5 seconds. As a result, the dust concentration before flowing into the dust removing device 2 was from 1 to 5 g / Nm ³ to 0.1 g / Nm ^3.
g / Nm ³ or less. After the removed dust and the like were collected, they were subjected to detoxification treatment in a melting furnace and an incinerator.
The combustible gas after dust removal is burned in the combustion furnace 3 to 900 to 11
The temperature was raised to 00C. In the combustion furnace 3, a flammable gas was continuously burned by using a pilot burner (not shown) with an ignition source constantly in order to avoid a danger such as an explosion. This burner uses natural gas or kerosene as fuel, and has a burner with an output of tens of thousands kcal / h to hundreds of thousands of kcal / h. At this time, 540 ° C., 100 at
Heat recovery could be performed using the vapor of a. Although stainless steel, Inconel and other alloy steels were used as boiler tubes, no significant corrosion was observed, and stable operation was confirmed for one year or more.

[0028]

As described above, according to the present invention, since the partially oxidized gas is removed at a relatively low temperature and then burned in a combustion furnace to obtain a high temperature, the gasified waste can be obtained. Processing can be performed efficiently, and heat recovery by installing a high-temperature and high-pressure boiler can be performed efficiently. Further, emission of harmful gases such as dioxin and furan can be suppressed. Further, the entire plant can be simplified and the required installation area can be reduced as compared with the conventional technology.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a dust concentration and a service life of a boiler tube.

FIG. 3 is a schematic view of a candle-type ceramic filter that can be employed in the dust removing apparatus of the apparatus in FIG. 1;

FIG. 4 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an apparatus showing a modification of the apparatus in FIG. 4;

FIG. 6 is a schematic configuration diagram of a conventional waste disposal apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Partial oxidation furnace 2 Dust remover 3 Combustion chamber 4 Boiler

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiji Kinoshita 1-1-2 Marunouchi, Chiyoda-ku, Tokyo, Japan Inside the Nippon Kokan Co., Ltd. (72) Inventor Hajime Akiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan F-term in Honko Co., Ltd. (reference) 3K078 AA05 AA08 AA09 BA03 CA21 CA24

Claims (7)

[Claims] The waste is incompletely burned or partially oxidized in a partial oxidation furnace involving a combustion reaction to produce a combustible gas having an oxygen equivalent concentration at the furnace outlet of -20 to 1%. A method for treating waste, comprising introducing a gas into a dust remover at 250 to 450 ° C. to reduce the dust concentration to 0.1 g / Nm ³ or less, and burning the combustible gas removed at a high temperature in a combustion furnace. . 2. The method according to claim 1, wherein a filter-type dust collector is used as the dust remover, and the deposits on the filter of the dust collector are periodically wiped off with a gas having an oxygen concentration of 5% or less. Waste treatment method as described. 3. A waste filter according to claim 1, wherein a filter-type dust collector is used as a dust-removing device, and deposits on a filter of the dust collector are periodically removed with nitrogen gas. Processing method. 4. The method for treating waste according to claim 1, wherein an ignition source is provided in the combustion furnace to burn combustible gas continuously. 5. The waste treatment according to claim 1, wherein a boiler is disposed in the combustion furnace or downstream of the combustion furnace, and heat recovery is performed in the boiler. Method. 6. A partial oxidation furnace for incompletely burning or partially oxidizing waste so as to obtain a combustible gas having an oxygen equivalent concentration at a furnace outlet of -20 to 1%, and a partial oxidation furnace installed in the downstream thereof, An apparatus for treating waste, comprising: a dust remover for reducing the concentration of dust in the combustible gas at 450 ° C. to 0.1 g / Nm ³ or less; and a combustion furnace installed downstream of the dust remover. 7. An apparatus for treating waste according to claim 6, wherein the combustion furnace is provided with an ignition source.