JP2000161637A - 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 in terms of oxygen at a furnace outlet is generated by incompletely burning or partially oxidizing wastes in a partial oxidizing furnace 1 associated with the combustion reaction, the combustible gas is introduced in a dust separator 2 at 450-650 deg.C to keep the dust concentration at <=0.1 g/Nm3. Then, the combustible gas is introduced in a wet type gas processing device 3, the concentration of hydrogen chloride in the combustible gas is kept at <=20 ppm, and the processed combustible gas is burned at high temperature in a combustion furnace 4.

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 waste and then burning the waste is proposed in Japanese Patent Application Laid-Open No. 9-159132. An outline of the configuration of a typical example is shown in FIG. 5 of the accompanying drawings.

[0003] In FIG. 5, flue gas generated by burning refuse in a combustion furnace is cooled to 450 to 650 ° C. in a waste heat boiler 12 by heated water 20 from a economizer 16, and filtered by a filter 13. Dust is removed. The filter 1
Part or all of the flue gas that has exited 3 is supplied to a heating furnace 14, where the temperature is raised in the heating furnace 14 by reheating using an auxiliary fuel 21, and the steam superheater 15 is further discharged from the waste heat boiler 12. Superheated to about 500 ° C. with saturated steam 22. Furthermore, the combustion exhaust gas is saved by the economizer 15 and the air preheater 1
At 7, waste heat is recovered. Thereafter, the combustion exhaust gas is exhausted from the chimney 19 via the induction blower 18.

[0004]

In the case of treating combustibles in such a combustion method, if the concentration of dust after removal of dust by a filter cannot be controlled to a certain value or less, it is disposed at a subsequent stage for heat recovery. In boilers, corrosion of boiler tubes due to salts in dust is a problem. Also,
If the unburned portion of the combustion exhaust gas generated in the combustion furnace is small,
The waste heat cannot be efficiently recovered by the heating furnace in the subsequent flow.

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 remover at 450 to 650 ° C. to reduce the dust concentration to 0.1 g / Nm ³ or less. A method for treating waste, comprising introducing into a device a hydrogen chloride concentration in the combustible gas of 20 ppm or less and burning the treated combustible gas at a high temperature in a combustion 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,
When oxygen (O ₂ ) is 2%, carbon monoxide (CO) is 4%, hydrogen (H ₂ ) is 2%, and methane (CH ₄ ) is 1%,
Carbon monoxide (CO) 4% is oxidized to carbon dioxide (C
O ₂ ) consumes 2% oxygen (O ₂ ), likewise 2% hydrogen (H ₂ ) consumes 1% oxygen (O ₂ ), and 1% methane (CH ₄ ) consumes 2% % Oxygen (O ₂ ). Therefore, the “oxygen conversion 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.

[0007] In the partial oxidation furnace, waste is partially oxidized, and a combustible gas having a relatively low temperature of 450 to 650 ° C is sent at the entrance 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 if the temperature is lower than 450 ° C., there is a possibility of explosion due to re-ignition in a downstream pipe or a combustion furnace,
If the temperature is higher than 650 ° C., the salt in the dust is melted, and there is a problem that the dust removing device is clogged. At this time, the air ratio is adjusted so that the “oxygen conversion concentration” at the furnace outlet is −20 to 1%. The reason is that "oxygen conversion concentration" is -20.
If it is less than 1%, a problem such as tar adhesion occurs as a strong reducing gas, and if it is more than 1%, the oxidation of the combustible gas is promoted before being introduced into the combustion furnace. This keeps the oxygen concentration at the furnace outlet low and reduces the risk of explosion due to combustible components and oxygen. In the case of the system of the present invention, since the “oxygen concentration” is kept in a constant value range as described above, the fluctuation of the potential of the combustible gas is reduced, and stable operation can be performed. In addition, since the temperature is relatively low, dust can be removed without excessive cooling via equipment such as a cooling tower. Thereafter, the combustible gas is introduced into a wet gas processing device. Here, the amount of hydrogen chloride in the combustible gas is removed, the concentration of hydrogen chloride in the combustible gas is reduced to 20 ppm or less, and then the combustible gas is burned in a combustion furnace, so that 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 removing device so that the dust concentration becomes 0.1 g / Nm ³ or less.
The amount of salt in the dust is reduced. After that, the combustible gas is led to the wet gas treatment device to remove hydrogen chloride in the gas, so even if it is burned at a high temperature, the generation of hydrogen chloride gas is reduced, and the downstream equipment, especially in the boiler tube etc. at the subsequent stage of the combustion furnace, etc. Corrosion is drastically reduced. Parts or the like that had to use materials having high corrosion resistance can be switched to inexpensive materials.

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 problem is a waste treatment method according to the first or third means, wherein the temperature of the scavenging gas is substantially the same as or higher than the combustible gas in the dust removing device. is there. When the partially oxidized exhaust gas is treated at 450 ° C. to 650 ° C., it contains many gaseous components that are easily condensed and become liquid if cooled even slightly from that temperature state. If they become liquid, they may adhere to the inside of the dust remover, causing troubles such as eye clogging. Therefore, it is preferable to control the temperature of the gas for wiping off.

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

A sixth means for solving the above-mentioned problem is the first to fifth means, wherein a boiler is provided in a combustion furnace or downstream of the combustion furnace, and heat is recovered 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 seventh 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%. , Set in the downstream, 450-650 ° C
And a wet gas processing device for reducing the concentration of hydrogen chloride in the combustible gas after dust removal to 20 ppm or less, and a dust removal device for reducing the concentration of dust in the combustible gas to 0.1 g / Nm ³ or less. A waste treatment apparatus characterized by having a combustion furnace.

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

In the partial oxidation furnace, the waste is partially oxidized, and a combustible gas having a relatively low temperature of 450 to 650 ° 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 a downstream dust removing device connected by a duct or the like from a furnace outlet of the partial oxidation furnace, the combustible gas is introduced into a downstream wet gas processing device. Here, the hydrogen chloride content in the combustible gas is removed, and the hydrogen chloride concentration in the combustible gas is reduced to 20 p.
After that, the combustible gas is burned in a downstream combustion furnace, and is efficiently heated to a high temperature. 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 the present 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. After that, it is led to a wet gas treatment device to remove hydrogen chloride in the gas,
Even when the fuel is burned at a high temperature, the concentration of the hydrogen chloride gas can be suppressed to a low level, and it is possible to reduce consideration for corrosion in downstream equipment, particularly, in a boiler tube or the like at a later stage of the combustion furnace. Parts and the like that had to use a material having high corrosion resistance can be switched to an inexpensive material. Further, by setting the “oxygen concentration” to a value within a certain range, fluctuations in the potential of the combustible gas generated are reduced, and stable operation is possible.

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.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings.

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, which is supplied with air or a gas mainly containing air whose oxygen concentration is controlled by steam or exhaust gas for oxidation. An object is charged into the furnace and ignites to partially oxidize to produce combustible gas. The partial oxidation furnace 1 is connected in order with a dust removing device 2 for removing dust from the combustible gas, a wet gas processing device 3, a combustion furnace 4 for burning combustible gas, and a boiler 5 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 removal device 2 at 450 to 650 ° C. The reason for setting the temperature range is that if the temperature is 450 ° C. or lower, there is a risk of re-ignition or explosion in the wake, and if the temperature is 650 ° C. or higher, there is a problem that the salt in the dust is melted and eyes are clogged in the dust removing device. .

Next, the combustible gas is introduced to 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. It can be seen that if the dust concentration after dust removal is 0.1 g / Nm ³ or less, 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. 2 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.

After the combustible gas is removed, the combustible gas is introduced into the wet gas treatment device 3 where the concentration of the neutralizing agent such as caustic soda is changed as necessary to reduce the concentration of hydrogen chloride to 20 ppm or less.

The combustible gas is introduced into the combustion furnace 4 after being treated by the wet gas treatment apparatus 3 and the temperature thereof is raised to about 1000 ° C. Here, complete combustion takes place,
Emission of unburned gas and the like is almost completely suppressed. Further, since the combustible gas has been subjected to dust removal in advance, the concentration of the aromatic organic compound due to soot is reduced, and as a result, the concentration of dioxin-like substances, which are incomplete combustion products, is also reduced. Further, if the ignition source is provided in the combustion furnace, the combustible gas burns continuously, so that the danger of misfiring, mixing of the combustible gas and air, and explosion can be avoided.

In the present embodiment, as a preferred example, a boiler, for example, at a temperature of 300 ° C. or more and 20 a
The water pipe of the high-temperature and high-pressure boiler 5 with a pressure 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.

[0027]

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. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the apparatus shown in FIG. 3, 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 removing device 2 at 450 to 650 ° 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. For cleaning off, recirculate exhaust gas to reduce oxygen concentration to 5
% And a nitrogen gas, the sweeping pressure was 3 to 7 kg / cm ² , the sweeping interval was 5 seconds to 50 minutes, and the sweeping time was 0.1 seconds to 20 seconds. Thereby, the dust concentration before flowing into the dust removal device 2 is 5 to 20 g /
Those were Nm 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 dust removal was introduced into the wet gas treatment device 3 to remove hydrogen chloride. The concentration of hydrogen chloride at the inlet of the wet gas treatment device of 400 ppm was removed to 20 ppm. Thereafter, the combustible gas after the treatment was burned in the combustion furnace 4 to increase the temperature to 900 to 1000 ° C. At this time, 350-
Heat recovery was performed using steam at 540 ° C. and 50 to 100 ata. Although inexpensive stainless steel was used for the boiler tube, no significant corrosion was observed.
Corrosion resistance that can be used for several years was confirmed for some materials.
In addition, when hot air was collected, 350-700
It has been found that it is possible to recover high-temperature air at ℃.

Further, the applicability of the grate furnace shown in FIG. 4 was confirmed. In the apparatus shown in FIG. 4, 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 450-650 ° 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 wiping, the wiping pressure was 3 to 7 kg / cm ² , the wiping interval was 10 seconds to 20 minutes, and the wiping time was 0.05 seconds to 15 seconds. Thus, what is dust concentration before entering the dust collector 2 was 1 to 5 g / Nm ³ is dust to 0.1 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 was introduced into the wet gas treatment device 3 to remove hydrogen chloride. The concentration of hydrogen chloride at the inlet of the wet gas treatment device of 250 ppm was removed to 20 ppm. Thereafter, the combustible gas after the treatment was caused to flow in the combustion furnace 4 to increase the temperature to 900 to 1100 ° C. In the combustion furnace 4, a pilot burner is used to avoid dangers such as explosions.
(Not shown), the combustible gas was continuously burned with the ignition source always on. This burner uses natural gas or kerosene as fuel and has an output of tens of thousands of kcal / h to hundreds of thousands of kc.
Al / h burners were provided. At this time, heat recovery could be performed in the subsequent boiler 5 using steam at 540 ° C. and 100 ata. In addition, stainless steel, Inconel, and other alloy steels, which have not much corrosion resistance, were used as boiler tubes, but no significant corrosion was observed, and stable operation was confirmed for one year or more.

[0030]

As described above, in the present invention, the partially oxidized gas is removed at a relatively low temperature, the hydrogen chloride is reduced by a wet gas treatment device, and the gas is burned in a combustion furnace to increase the temperature. As a result, gasified waste can be treated efficiently, and at the same time, boiler tubes using inexpensive steel materials etc. can be used as high-temperature and high-pressure boilers because corrosion by hydrogen chloride is suppressed, Moreover, heat recovery by installing such a high-temperature and high-pressure boiler can also be performed efficiently. Furthermore, emission of harmful gases such as dioxin and furan can be suppressed. Also, "oxygen equivalent concentration"
By setting the dust concentration at the time of dust removal within a certain range, there is no need to worry about corrosion of the boiler tube and the like, and stable operation can be performed.

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

FIG. 3 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an apparatus showing a modification of the apparatus in FIG. 3;

FIG. 5 is a schematic configuration diagram of a conventional waste treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Partial oxidation furnace 2 Dust remover 3 Wet gas processing unit 4 Combustion chamber 5 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 (8)

[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%. The gas is introduced into a dust remover at 450 to 650 ° C. to reduce the dust concentration to 0.1 g / Nm ³ or less, and then the combustible gas is introduced to a wet gas treatment device to reduce the concentration of hydrogen chloride in the combustible gas to 20 ppm or less. And burning the treated combustible gas 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 2, wherein the temperature of the flushing gas is substantially the same as or higher than the temperature of the combustible gas in the dust remover. 5. The waste disposal method according to claim 1, wherein an ignition source is provided in the combustion furnace to burn combustible gas continuously. 6. The waste treatment according to claim 1, wherein a boiler is disposed in the combustion furnace or downstream of the combustion furnace, and the heat recovery is performed in the boiler. Method. 7. A partial oxidation furnace for incompletely combusting or partially oxidizing waste so as to obtain a combustible gas having an oxygen equivalent concentration of -20 to 1% at a furnace outlet, and a partial oxidation furnace installed in the downstream thereof, A dust remover for reducing the concentration of dust in the combustible gas at 650 ° C. to 0.1 g / Nm ³ or less, a wet gas treatment device for reducing the concentration of hydrogen chloride in the combustible gas after dust removal to 20 ppm or less, and An apparatus for treating waste, comprising an installed combustion furnace. 8. An apparatus for treating waste according to claim 7, wherein the combustion furnace is provided with an ignition source.