JP4121645B2 - Method and apparatus for recovering heat from waste - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for recovering heat from waste.
[0002]
[Prior art]
Japanese Laid-Open Patent Publication No. 9-159132 proposes a method in which municipal waste or industrial waste (hereinafter referred to as “waste”) is partially oxidized, gasified, and burned. An outline of the structure of a typical example is shown in FIG. 5 of the accompanying drawings.
[0003]
In FIG. 5, the combustion exhaust gas generated by burning garbage in the combustion furnace is cooled to 450 to 650 ° C. by the heated water 20 from the economizer 16 in the waste heat boiler 12 and removed by the filter 13. . Part or all of the combustion exhaust gas that has exited the filter 13 is supplied to the heating furnace 14, and is heated in the heating furnace 14 by reheating using the auxiliary fuel 21, and the steam superheater 15 is further removed from the waste heat boiler 12. Overheated to about 500 ° C. with saturated steam 22 from. Furthermore, waste heat is recovered from the combustion exhaust gas by the economizer 15 and the air preheater 17. Thereafter, the combustion exhaust gas is exhausted from the chimney 19 through the induction fan 18.
[0004]
[Problems to be solved by the invention]
When treating combustible materials in such a combustion method, if the dust concentration after dust removal by the filter cannot be controlled below a certain value, it may be caused by salt in the dust in the boiler disposed at a later stage for heat recovery. Boiler tube corrosion becomes a problem. Further, if the amount of unburned flue gas generated in the combustion furnace is small, waste heat cannot be efficiently recovered in the subsequent heating furnace.
[0005]
The present invention has been made to solve such problems, and a method and apparatus for recovering heat from waste that can be partially oxidized and efficiently recovered without causing the above problems. The issue is to provide.
[0006]
[Means for Solving the Problems]
First means for solving the above-mentioned problems, by partial oxidation furnace with a combustion reaction waste, the furnace temperature to 4 5 0 to 800 ° C., by controlling the air ratio to 0.15 to 0.9 Combustible gas is generated by incomplete combustion or partial oxidation, the combustible gas is introduced into a ceramic filter at 450 to 650 ° C., and dust is removed to a dust concentration of 0.1 g / Nm ³ or less. Is introduced into a wet gas treatment device to reduce the hydrogen chloride concentration in the combustible gas to 20 ppm or less, and the treated combustible gas is burned at a high temperature in a combustion furnace, and is disposed in the combustion furnace or downstream of the combustion furnace. A method for recovering heat from waste, characterized in that heat is recovered from gas burned in an installed boiler.
[0007]
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 sent at the ceramic filter inlet. Here, the reason why the temperature at the ceramic filter inlet is set in the above range is that if it is less than 450 ° C., there is a possibility of explosion due to re-ignition in the downstream pipe or combustion furnace, and if it is above 650 ° C., salt in the dust This is because there is a problem of clogging of the dust removing device. Air ratio of the partial oxidation furnace at this time is to adjust the air ratio so that 0.15 to 0.9. The reason is that if the air ratio is less than 0.15 , problems such as tar adhesion occur as a strong reducing gas, and if it exceeds 0.9 , the oxidation of the combustible gas is promoted before being introduced into the combustion furnace. is there. This keeps the oxygen concentration at the furnace outlet low and reduces the risk of explosion due to combustible components and oxygen. As described above, since the temperature of the combustible gas is relatively low at the ceramic filter inlet, dust can be removed without excessive cooling through equipment such as a temperature reducing tower. Thereafter, the combustible gas is introduced into a wet gas processing apparatus. Here, the hydrogen chloride content in the combustible gas is removed, the hydrogen chloride concentration in the combustible gas is set to 20 ppm or less, and the combustible gas is burned in the combustion furnace, so that the temperature can be efficiently increased. The boiler disposed in the combustion furnace or downstream of the combustion furnace can efficiently recover heat from the combustion gas, and a high-temperature and high-pressure boiler becomes possible.
[0008]
In the case of the method of the present invention, dust is removed by the ceramic filter so that the dust concentration is 0.1 g / Nm ³ or less, so the amount of salt in the dust is reduced. After that, since the combustible gas is introduced to the wet gas treatment device and hydrogen chloride in the gas is removed, the generation of hydrogen chloride gas is reduced even if it is burned at a high temperature. Corrosion is drastically reduced. Parts that had to use materials with high corrosion resistance can be switched to inexpensive materials.
[0009]
Furthermore, harmful gas emissions can be suppressed. Since the combustible gas after being partially oxidized in the partial oxidation furnace is mixed with an oxidant in the combustion furnace and burned at a high temperature, discharge of unburned components such as CO is almost completely suppressed. In addition, since the combustible gas is dedusted and then burned at a high temperature, the concentration of the aromatic organic compound resulting from soot is lowered, and as a result, the concentration of dioxins that are incomplete combustion products is also reduced.
[0010]
The second means for solving the above problem is a heat recovery method from waste, in which the deposit on the ceramic filter is periodically removed with a gas having an oxygen concentration of 5% or less. Thereby, dust can be efficiently removed and emission of harmful gas is further suppressed. Here, the oxygen concentration is set to 5% or less in order to suppress the oxidation of the combustible gas with oxygen and reduce the risk of unnecessary explosion and combustion. This gas having an oxygen concentration of 5% or less can be obtained by exhaust gas recirculation, pressure swing adsorption or membrane separation.
[0011]
A third means for solving the above-mentioned problem is a heat recovery method from waste in which the deposit on the ceramic filter is periodically removed with nitrogen gas in the first means . By using nitrogen to remove deposits, the combustible gas does not oxidize in the dust collector. In addition, unnecessary explosions and combustion caused by this means are eliminated.
[0012]
A fourth means for solving the above-mentioned problem is a method for recovering heat from waste in the second or third means described above, wherein the temperature of the burned-out 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 a large amount of gaseous components that tend to condense and become liquid when cooled from the temperature state. If they become liquid, they may adhere in the dust removing device, causing troubles such as eye clogging. Therefore, it is preferable to control the gas temperature for dropping off.
[0013]
A fifth means for solving the above problem is a method of recovering heat from waste in the first to fourth means by disposing an ignition source in the combustion furnace and continuously burning the combustible gas. The combustible gas is sent to the combustion furnace after being dedusted and combusted. By always providing an ignition source here, the danger of misfiring and the explosion of the combustible gas and air is avoided.
[0015]
Sixth means for solving the problems is the furnace temperature to 4 5 0 to 800 ° C., the combustible gas is incomplete combustion or partial oxidation of waste by controlling the air ratio to 0.15 to 0.9 A partial oxidation furnace to be generated, a ceramic filter installed downstream and removing dust in the combustible gas at 450 to 650 ° C. to 0.1 g / Nm ³ or less, and hydrogen chloride in the combustible gas after dust removal A waste gas treatment apparatus having a concentration of 20 ppm or less, a combustion furnace installed downstream thereof, and a boiler disposed in the combustion furnace or downstream of the combustion furnace. It is a heat recovery device.
[0016]
A seventh means for solving the above-mentioned problem is the heat recovery apparatus for waste from the sixth means, in which an ignition source is disposed in the combustion furnace.
[0017]
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 ceramic filter inlet. At this time, the air ratio is adjusted so that the air ratio in the partial oxidation furnace is 0.15 to 0.9 . Thereby, combustible gas with low oxygen concentration and few dangers, such as an explosion, is produced | generated. Moreover, since this combustible gas is comparatively low temperature, dust is removed without excessive cooling by facilities, such as a temperature reduction tower. After setting the dust concentration to 0.1 g / Nm ³ or less in the downstream ceramic filter connected from the furnace outlet of the partial oxidation furnace by a duct or the like, the combustible gas is introduced into the downstream wet gas processing apparatus. Here, after removing the hydrogen chloride content in the combustible gas and setting the hydrogen chloride concentration in the combustible gas to 20 ppm or less, the combustible gas is burned in the downstream combustion furnace and efficiently heated. In the case of this apparatus, dust is removed so that the dust concentration is 0.1 g / Nm ³ or less, so the amount of salt in the dust is reduced. After that, the hydrogen chloride in the gas is removed by introducing it to the wet gas treatment equipment, so that the hydrogen chloride gas can be kept at a low concentration even if it is burned at a high temperature. Corrosion in the downstream equipment, especially in the boiler tube after the combustion furnace Consideration can be reduced. Parts that had to use materials with high corrosion resistance can be switched to inexpensive materials. In addition, by setting the air ratio in the partial oxidation furnace to a value within a certain range, fluctuations in the potential of the generated combustible gas are reduced, and stable operation is possible.
[0018]
Furthermore, harmful gas emissions can be suppressed. Since the combustible gas after being partially oxidized in the partial oxidation furnace is mixed with an oxidant in the combustion furnace and burned at a high temperature, discharge of unburned components such as CO is almost completely suppressed. In addition, since the combustible gas is dedusted and then burned at a high temperature, the concentration of the aromatic organic compound resulting from soot is lowered, and as a result, the concentration of dioxins that are incomplete combustion products is also reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.
[0020]
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, and the partial oxidation furnace 1 is supplied with air for oxidation or air-based gas whose oxygen concentration is controlled by steam or exhaust gas. Things are thrown into the furnace, ignited and partially oxidized to produce combustible gas. The partial oxidation furnace 1 is sequentially connected 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. .
[0021]
In the partial oxidation furnace 1, the furnace temperature can waste self combustion, and well as long as the partial oxidation is desirably 4 5 0 to 800 ° C.. In addition, the air ratio in the partial oxidation is controlled, and the air ratio at this time is set to 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 the combustible gas is sent to the dust removing device 2 at 450 to 650 ° C. The reason for setting this temperature range is that there is a risk of re-ignition or explosion in the downstream at 450 ° C. or lower, and there is a problem such as eye clogging in the dust removing device due to melting of salt in the dust at 650 ° C. or higher. .
[0022]
Next, the combustible gas is brought to the dust removing device 2, and the dust removing device 2 removes dust to a concentration of 0.1 g / Nm ³ or less. If dust is removed to this concentration, the amount of salt in the dust is reduced, so that corrosion of the boiler tube and the like in the subsequent stage is reduced. It can be seen that if the dust concentration after dust removal is 0.1 g / Nm ³ or less, the corrosion of the downstream boiler tube can be suppressed to a practical level.
[0023]
Although it is desirable to use a candle-type ceramic filter as shown in FIG. 2 for the dust removing device 2, it is also possible to use a filter cloth or a honeycomb-shaped ceramic filter having an opening of 10 mm or less. It is desirable to perform the removal with a gas having an oxygen concentration of 5% or less, or nitrogen in order to suppress oxidation of the combustible gas and reduce the risk of unnecessary explosion and combustion. Considering the effect of peeling off the deposits, the conditions for the removal method are a gas pressure of 1 kg / cm ² or more, a removal interval of several seconds to several tens of minutes, and a removal time of about 0.02 seconds to several tens of seconds. It is desirable.
[0024]
After the dust is removed, the combustible gas is introduced into the wet gas processing device 3 and the concentration of a neutralizing agent such as caustic soda is changed as necessary to treat the hydrogen chloride concentration to 20 ppm or less.
[0025]
The combustible gas is processed by the wet gas processing apparatus 3 and then introduced into the combustion furnace 4 where the temperature rises to about 1000 ° C. Since complete combustion is performed here, discharge of unburned gas and the like is almost completely suppressed. In addition, since the dust is previously removed from the combustible gas, the concentration of the aromatic organic compound resulting from soot is lowered, and as a result, the concentration of the dioxin substance that is an incomplete combustion product is also reduced. Further, if the ignition source is provided in the combustion furnace, the combustible gas burns continuously, so that it is possible to avoid the risk that the combustible gas and air mix again and explode due to misfire.
[0026]
In the present embodiment, as a preferable example, a boiler, for example, a water pipe of a high-temperature and high-pressure boiler 5 having a temperature of 300 ° C. or higher and 20 at or higher is installed at the subsequent stage of the combustion furnace 4, and heat can be efficiently recovered from the combustion gas. . High temperature air can be recovered as required. Since dust removal is performed in advance, corrosion of the boiler tube due to dust can be suppressed. When recovering heat from a high temperature field with an exhaust gas temperature of 600 ° C. or more where the corrosion effect of hydrogen chloride gas increases, a boiler tube made of a ceramic material having corrosion resistance may be used to extend the life of the boiler tube. . The exhaust gas after heat recovery is discharged from the chimney through a downstream exhaust gas treatment facility (not shown).
[0027]
【Example】
An embodiment of the present invention will be described with reference to FIG. In this embodiment, a fluidized bed furnace 1 is employed as the partial oxidation furnace of the apparatus shown in FIG. Others are the same as the apparatus of FIG. 1, and in FIG. 3, the same code | symbol is attached | subjected to FIG. 1 and a common part.
[0028]
In the apparatus shown in FIG. 3, fluidized air temperature is set to 20 to 650 ° C. and sand layer temperature is set to 400 to 600 ° C. in the fluidized bed furnace 1, and municipal waste as waste is supplied to the fluidized bed furnace 1 at 1 t / h. Was partially oxidized by operating between 0.2 and 0.8 to produce a 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, or a ceramic fiber type of an inorganic material similar thereto, or a porous body type. Down using a re-circulating oxygen concentration of 5% or less and suppressing gas and nitrogen gas exhaust gas to pay, brushing pressure 3~7kg / cm ^2, 5 seconds to 50 minutes brushing intervals, brushing time 0. The range was 1 second to 20 seconds. Accordingly, those dust concentration before flowing into the filtration apparatus 2 was 5 to 20 g / Nm ³ is dust to 0.1 g / Nm ³ or less. The removed dust and the like were detoxified in a melting furnace and an incinerator after collection. The combustible gas after dust removal was introduced into the wet gas treatment device 3 to remove hydrogen chloride. What was 400 ppm of hydrogen chloride concentration at the inlet of the wet gas treatment apparatus was removed up to 20 ppm. Thereafter, the combustible gas after the treatment was burned in the combustion furnace 4 to raise the temperature to 900 to 1000 ° C. At this time, it was possible to recover heat using steam at 350 to 540 ° C. and 50 to 100 at the subsequent boiler 5. In addition, although inexpensive stainless steel was used as the boiler tube, no significant corrosion was observed, and depending on the material, corrosion resistance that could be used for multiple years was confirmed. Moreover, when high temperature air was also collected, it was found that high temperature air at 350 to 700 ° C. could be collected.
[0029]
In addition, the applicability in the grate furnace shown in FIG. 4 was also confirmed. In the apparatus shown in FIG. 4, a grate furnace 1 is used as a partial oxidation furnace. Others are the same as FIG. 1 apparatus. In this grate furnace 1, the oxidizing air temperature is set to 20 to 250 ° C., the grate upper temperature is set to 500 to 800 ° C., and municipal waste as waste is supplied into the furnace, and the air ratio is 0.3 to 0.9. Partial oxidation was performed by operating in between. 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 and a honeycomb type ceramic filter. The material of the ceramic filter is SiO ₂ , Al ₂ O ₃ , SiC, cordierite, a composite of the above materials, or a ceramic fiber type of an inorganic material similar to the above, or a porous body type. Nitrogen gas was used for the removal, and the removal pressure was in the range of 3 to 7 kg / cm ² , the removal interval of 10 seconds to 20 minutes, and the removal time of 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. The removed dust and the like were detoxified in a melting furnace and an incinerator after collection. The combustible gas after dust removal was introduced into the wet gas treatment device 3 to remove hydrogen chloride. What was the hydrogen chloride concentration of 250 ppm at the wet gas processing apparatus was removed up to 20 ppm. Thereafter, the combustible gas after the treatment was burned in the combustion furnace 4 to raise the temperature to 900 to 1100 ° C. In the combustion furnace 4, in order to avoid dangers such as explosion, a combustible gas was continuously burned with a constant ignition source using a pilot burner (not shown). This burner uses natural gas or kerosene as a fuel, and a burner having an output of several tens of thousands kcal / h to several hundred thousand kcal / h is disposed. At this time, heat recovery could be performed by using a steam of 540 ° C. and 100 ata in the subsequent boiler 5. As the boiler tube, stainless steel, Inconel and other alloy steels that are not very corrosion resistant were used, but no significant corrosion was observed, and stable operation for over a year was confirmed.
[0030]
【The invention's effect】
As described above, in the present invention, the partially oxidized gas is dedusted at a relatively low temperature, and hydrogen chloride is reduced by a wet gas processing apparatus and then burned in a combustion furnace to obtain a high temperature. Therefore, heat recovery from gasified waste can be performed efficiently, and at the same time, corrosion due to hydrogen chloride is suppressed, so even a boiler tube using inexpensive steel can be used as a high-temperature and high-pressure boiler. Heat recovery by installing 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. In addition, by setting the air ratio in the partial oxidation furnace and the dust concentration at the time of dust removal within a certain range, there is no concern about corrosion of the boiler tube or 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.
2 is a schematic view of a candle-type ceramic filter that can be used in the dust removing apparatus of FIG. 1; FIG.
FIG. 3 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention.
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 removal apparatus 3 Wet gas processing apparatus 4 Combustion chamber 5 Boiler

Claims (7)

Waste in the partial oxidation furnace with combustion reaction, and the furnace temperature to 4 5 0 to 800 ° C., controlled and incomplete combustion air ratio from 0.15 to 0.9, or by partial oxidation combustible gas The combustible gas is introduced into a ceramic filter at 450 to 650 ° C. to remove dust to a concentration of 0.1 g / Nm ³ or less, and the combusted gas after dust removal is introduced into a wet gas treatment device. The concentration of hydrogen chloride in the gas is set to 20 ppm or less, the treated combustible gas is burned at a high temperature in a combustion furnace, and heat is generated from the gas burned in the combustion furnace or in a boiler disposed downstream of the combustion furnace. A method of recovering heat from waste, characterized in that it is recovered. The method for recovering heat from waste according to claim 1, wherein deposits on the ceramic filter are periodically removed with a gas having an oxygen concentration of 5% or less. The method for recovering heat from waste according to claim 1, wherein deposits on the ceramic filter are periodically removed with nitrogen gas. The method for recovering heat from waste according to claim 2 or 3, wherein the temperature of the burned-out gas is substantially the same as or higher than the combustible gas in the ceramic filter . The method for recovering heat from waste according to any one of claims 1 to 4, wherein an ignition source is provided in the combustion furnace and the combustible gas is continuously burned. Installing a furnace temperature to 4 5 0 to 800 ° C., and the partial oxidation furnace to produce a combustible gas to the air ratio is incomplete combustion or partial oxidation control to waste from 0.15 to 0.9, thereafter flow A ceramic filter that removes the dust concentration in the combustible gas at 450 to 650 ° C. to 0.1 g / Nm ³ or less, and a wet gas treatment device that reduces the hydrogen chloride concentration in the combustible gas after dust removal to 20 ppm or less, And a waste heat recovery apparatus, further comprising: a combustion furnace installed downstream thereof; and a boiler disposed in the combustion furnace or downstream of the combustion furnace. The apparatus for recovering heat from waste according to claim 6, wherein the combustion furnace is provided with an ignition source .

Images