JP2004169955A - Waste incinerator and method of operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an waste incinerator capable of reducing the generated amount of harmful gases such as CO and NOx even in combustion with low air ratio and a method of operating the incinerator. <P>SOLUTION: In this waste incinerator having a stairstep fire grate, a gas blowing port 14 blowing gas onto waste on a combustion fire grate 5 is provided in the wall of a step part between a drying fire fire grate 4 and the combustion fire grate 5, and a mechanism blowing hot gas is connected to the gas blowing port 14. A nozzle 15 positioned horizontally or facing a diagonal lower side is fitted to the gas blowing port 14. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a waste incinerator for incinerating waste such as general waste, industrial waste, and sewage sludge, and a method of operating the same.
[0002]
[Prior art]
Grate-type waste incinerators are widely used as incinerators for incinerating waste such as municipal solid waste. FIG. 8 shows a schematic diagram of a representative example. The waste 32 put into the hopper 31 is sent to the drying grate 33 through the chute, dried by the air from below and the radiant heat in the furnace, and heated to ignite. The waste 32 that has ignited and started burning is sent to a combustion grate 34, where it is pyrolyzed and gasified by combustion air sent from below, and partly burns. Then, the unburned components in the waste are completely burned by the post-combustion grate 35. The ash remaining after the combustion is taken out from the main ash chute 36.
[0003]
The combustion is performed in the combustion chamber 37, and the generated combustion gas is separated and discharged into the main flue 39 and the sub-flue 40 due to the presence of the intermediate ceiling 38. The exhaust gas passing through the main flue 39 contains almost no unburned components and contains about 10% or more of oxygen. The flue gas passing through the auxiliary flue 40 contains about 8% of combustible gas. These exhaust gases are mixed in the secondary combustion chamber 41, secondary combustion is performed, and the combustible gas is completely burned. The exhaust gas from the secondary combustion chamber 41 is sent to a waste heat boiler 43, and after being subjected to heat exchange, is discharged to the outside via a cooling tower, a bag filter and the like.
[0004]
In such grate-type waste incinerators, when incinerating waste, it is difficult to maintain a constant combustion state in the furnace because the waste consists of many substances with different properties. It is inevitable that the distribution of the temperature and the concentration of the combustion gas in the chamber 37 becomes non-uniform temporally and spatially, and a high-temperature region and a combustion unstable region are locally generated.
[0005]
As a method for solving such a problem, Japanese Patent Application Laid-Open No. H11-211044 (Patent Document 1) discloses a method in which a high-temperature gas generated by a regenerative burner is blown into a combustion chamber or a secondary combustion chamber of an incinerator. It has been disclosed.
[0006]
Japanese Patent Application Laid-Open No. H11-223323 (Patent Document 2) discloses a method in which a high-temperature gas generated by a regenerative burner is blown into a furnace at a temperature of 800 ° C. or more. These techniques are all aimed at reducing flammable gases and harmful substances containing a large amount of CO and aromatic hydrocarbons in exhaust gas generated in an incinerator.
[0007]
[Patent Document 1]
JP-A-11-2111044
[Patent Document 2]
JP-A-11-223323
[Problems to be solved by the invention]
Conventionally, in a waste incinerator, the ratio (air ratio) obtained by dividing the amount of air actually supplied to the furnace by the theoretical amount of air necessary for combustion of waste is about 1.7 to 2.0. This is larger than the air ratio required for general fuel combustion of 1.05 to 1.2. The reason for this is that waste has a large amount of non-combustibles and is inhomogeneous as compared with liquid fuels, so that a large amount of air is required to perform combustion. However, as the air ratio increases, the amount of exhaust gas also increases, and large exhaust gas treatment equipment is required as compared with a general combustion furnace.
[0010]
If the air ratio is reduced, the amount of exhaust gas is reduced, and the exhaust gas treatment facility is made compact. As a result, the entire waste incineration facility can be reduced in size and the facility cost can be reduced. In addition to this, the amount of chemicals for exhaust gas treatment can be reduced, so that operating costs can be reduced. Further, since the amount of heat lost due to the inability to recover heat can be reduced, the heat recovery rate of the waste heat boiler is improved, and accordingly, the power generation efficiency of waste power generation can be increased.
[0011]
As described above, although the advantage for the low air ratio combustion is great, there is a problem that the combustion becomes unstable in the low air ratio combustion. That is, when the fuel is burned at a low air ratio, the combustion becomes unstable, the generation of CO increases, the temperature in the furnace increases locally, the NOx sharply increases, a large amount of soot is generated, and clinker is generated. There is a problem that the life of the refractory of the furnace is shortened due to generation or local high temperature. The combustion techniques described in Patent Literature 1 and Patent Literature 2 were insufficient to solve such problems.
[0012]
The present invention has been made in view of such circumstances, and provides a waste incinerator and a method for operating the incinerator, in which the generation amount of harmful gases such as CO and NOx is reduced even with low air ratio combustion. That is the task.
[0013]
[Means for Solving the Problems]
A first means for solving the above-mentioned problem is a waste incinerator having a stepped grate, wherein a step portion between a dry grate and a combustion grate is provided on a waste grate on the combustion grate. A waste incinerator comprising a gas inlet for injecting gas into the waste incinerator (claim 1).
[0014]
The air blown into the combustion chamber from below the grate mixes and combusts the combustible gas generated by the pyrolysis of waste, and is blown so as to promote its combustion. In the provided conventional incinerator, the gas in the furnace cannot be sufficiently stirred unless a large amount of air is blown at a high speed.
[0015]
In addition, when air or high-temperature gas is blown, even if it is blown into a region where only drying is performed, the effect of promoting low NOx and low CO in exhaust gas is small. That is, it is preferable to blow into a region where a large amount of combustible gas generated by thermal decomposition of waste exists. By injecting gas into this area, the combustible gas is stably burned.
[0016]
For this reason, in the present invention, in order to perform efficient gas stirring with a small amount of gas blowing, a gas blowing port is provided at a step between the dry grate and the combustion grate, and from this gas blowing port, A gas is blown onto the waste in the direction of the waste.
[0017]
In the upstream part of the combustion grate near the step, the waste falls from the dry grate, and the waste is inverted or the lump is loosened. Combustible gas is generated.
[0018]
Therefore, in the present invention, gas is blown from the step between the dry grate and the combustion grate to a location where waste falls from the dry grate. This gas injection promotes the thermal decomposition of waste and generates a large amount of combustible gas. At the upstream part of the combustion grate, the combustible gas and the blown gas are efficiently mixed, and uniform and stable combustion is achieved. Done. Therefore, generation of harmful gases such as NOx and CO can be significantly reduced.
[0019]
Further, since gas is blown into the surface of the waste layer, thermal decomposition of the waste is promoted. For this reason, the waste on the combustion grate is burned out quickly, and the length of the grate required for burning the waste is shortened, so that the incinerator can be made compact.
[0020]
A second means for solving the above-mentioned problem is the first means, further comprising a mechanism connected to a gas blow-in port to blow a high-temperature gas. ).
[0021]
If the gas blown from the step is a high-temperature gas, the waste on the combustion grate is heated by heat radiation from the high-temperature gas and sensible heat, and the thermal decomposition of the waste is promoted. Further, since the high-temperature gas has a high viscosity, the residence time becomes long, and the mixing with the generated combustible gas is promoted.
[0022]
A third means for solving the above-mentioned problem is the waste incinerator according to the first means, wherein a mechanism connected to a gas blowing port for blowing a high-temperature gas containing oxygen is provided. Claim 3).
[0023]
When the high-temperature gas blown from the step portion contains oxygen, the combustion of the combustible gas is promoted, and the amount of generated CO is reduced.
[0024]
A fourth means for solving the above problem is a method of operating a waste incinerator having a stepped grate, the method comprising the steps of: providing a waste grate on a combustion grate through a step between a dry grate and a combustion grate; A method for operating a waste incinerator characterized by blowing gas upward.
[0025]
By blowing gas from the step onto the waste on the combustion grate, the combustible gases on the combustion grate are uniformly mixed and burned, and the generation of harmful gases such as NOx and CO is greatly reduced. At the same time, the amount of air blown into the entire incinerator can be reduced, and low air ratio combustion can be performed.
[0026]
A fifth means for solving the above-mentioned problem is the fourth means, wherein the gas blown from the step onto the waste on the combustion grate is a high-temperature gas, the waste incinerator being characterized in that: (Claim 5).
[0027]
If the gas blown from the step is a high-temperature gas, the waste on the combustion grate is heated by heat radiation from the high-temperature gas and sensible heat, and the thermal decomposition of the waste is promoted. Further, since the high-temperature gas has a high viscosity, the residence time becomes long, and the mixing with the generated combustible gas is promoted.
[0028]
A sixth means for solving the above-mentioned problem is the fifth means, wherein the temperature [° C.] T is 200 or more from a step between the dry grate and the combustion grate, and Concentration of oxygen contained therein [vol. %] Is a method for operating a waste incinerator characterized by injecting a gas having a relationship with C in the range represented by the following formula (Claim 6).
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) (1)
The inventors investigated the relationship between CO and NOx generated in the combustion chamber, the oxygen concentration in the high-temperature gas blown into the combustion chamber from the step, and the temperature of the high-temperature gas in the waste incinerator. As a result, the range of the oxygen concentration in the high-temperature gas and the temperature of the high-temperature gas at which the CO and NOx in the exhaust gas can be efficiently and simultaneously reduced is a region surrounded by lines A, B, and C in FIG. Was found. The temperature of the high-temperature gas at the time of being blown into the furnace is T [° C.], and the oxygen concentration in the high-temperature gas is C [vol. %], The line A is T = exp (8.05-0.23C)
Line B is
T ≦ exp (7.40-0.09C)
Line C is T = 200
Is equivalent to
[0029]
The thermal decomposition of waste is promoted by blowing high-temperature gas having the oxygen concentration and temperature in the area surrounded by the A-line, B-line, and C-line from the step between the dry grate and the combustion grate. Since uniform and stable combustion is promoted, the generation of NOx and CO can be significantly reduced.
[0030]
In the region below the line A, the amount of oxygen is insufficient, and the temperature of the gas to be blown is low, so that the combustion of the combustible gas becomes unstable, and as a result, the generation of CO increases. In the region above the line B, high-temperature combustion occurs, and as a result, the combustible gasification reaction of waste is excessively promoted and the temperature becomes locally high, so that NOx increases. Further, in a region below the line C, the degree of heating of the waste by heat radiation and sensible heat from the blown gas is small, so that thermal decomposition of the waste is not promoted.
[0031]
For example, depending on the composition and properties of the waste, when the oxygen concentration in the high-temperature gas is 12%, the temperature of the high-temperature gas that achieves both low NOx and low CO is in the range of 200 to 550 ° C. When the oxygen concentration in the hot gas is 15%, the temperature of the hot gas that achieves both low NOx and low CO is in the range of 200 to 400 ° C.
[0032]
A seventh means for solving the above problem is any one of the fourth means to the sixth means, wherein a gas blowing amount is 20% to 30% of a primary air amount. (Claim 7).
[0033]
Primary air is air blown from below a grate to burn waste in a grate type waste incinerator.
[0034]
If the amount of gas blown from the stepped portion is less than 20% of the amount of primary air, there is no momentum necessary for stirring the gas in the furnace, so that the gas blowing effect may not be sufficiently exhibited. Further, when the amount of gas blown exceeds 30% of the amount of primary air, the effect of lowering NOx and CO in exhaust gas is saturated, and it is not only meaningless to increase the amount of gas blown, but also the amount of exhaust gas is unnecessarily increased. It is not preferable because it increases the number of exhaust gas treatment facilities. Therefore, in this means, the gas blowing amount is limited to the range of 20% to 30% of the primary air amount.
[0035]
An eighth means for solving the above-mentioned problem is any one of the fourth means to the sixth means, wherein a gas blowing amount is from 20% of a theoretical air amount for burning waste. 30% (claim 8).
[0036]
In the seventh means, the primary air amount is used as the reference value of the gas blowing amount, but in some cases, the primary air amount is equal to or less than the theoretical air amount necessary for completely burning the waste. There is. In such a case, the gas blowing amount is set to 20% to 30% of the theoretical air amount for burning the waste. The theoretical amount of air is determined from the composition and properties of the waste.
[0037]
A ninth means for solving the above problem is any one of the fourth means to the eighth means, wherein a gas blowing direction is horizontal or obliquely downward. (Claim 9).
[0038]
The combustible gas generated from waste usually flows upward. Therefore, when the gas blowing direction is upward, the flow of the combustible gas and the flow of the blowing gas have the same velocity component in the same direction, and the effect of stirring is reduced, and the effect of gas blowing is reduced. On the other hand, when the gas blowing direction is horizontal or obliquely downward, the rising combustible gas and the blowing gas are well stirred, and the gas blowing effect can be enhanced. Generally, the factor that is effective in blowing high-temperature gas is said to be 3T. These are temperature (Temperature), stirring (Turbulence), and residence time (Time). In particular, by blowing high-temperature gas obliquely downward, the stirring (Turbulence) and residence time (Time) can be improved. .
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing a waste incinerator which is an example of an embodiment of the present invention. In FIG. 2, reference numeral 1 denotes a combustion chamber, and on one side (left side in FIG. 2) of the combustion chamber 1, a hopper 2 for charging waste 3 into the combustion chamber 1 is provided.
[0040]
At the bottom of the combustion chamber 1, a grate (stoker) for burning the waste 3 while moving it is provided. The grate is provided to be inclined in the direction of movement of the waste, and is provided in a stepped manner with two steps, and is divided into three parts. These three grate are called a dry grate 4, a combustion grate 5, and a post-combustion grate 6 from the side closer to the hopper 2. The drying grate 4 mainly performs drying and ignition of the waste 3. The combustion grate 5 mainly burns the waste 3, and the waste 3 is burned and thermally decomposed to generate combustible gas. Part of the combustible gas burns, and the rest becomes combustible gas, which is released together with the combustion gas. The combustion of the waste 3 is substantially completed in the combustion grate 5. On the post-combustion grate 6, the unburned portion of the slightly remaining waste 3 is completely burned. The combustion residue after complete combustion is discharged from the main ash chute 7.
[0041]
At the lower part of each grate, there is provided a wind box 8 to which a supply pipe for supplying combustion air is connected.
[0042]
Above the combustion chamber 1 on the opposite side of the hopper 2, a secondary combustion chamber 12 of the waste heat boiler 11 is connected and provided.
[0043]
A gas inlet 14 is provided at the step between the dry grate 4 and the combustion grate 5 so that gas is blown onto the waste on the combustion grate 5. I have. As shown in FIG. 3 and FIG. 4, a plurality of gas inlets are provided in the width direction of the grate at a height of the step portion wall 13 not covered by the waste. A nozzle 15 is attached to 14. The nozzle 15 is directed horizontally or obliquely downward, and gas is blown onto the waste in the moving direction of the waste. In FIG. 3, reference numeral 16 denotes a header tube for distributing the gas blown into each nozzle 15, and reference numeral 3 denotes waste.
[0044]
The gas inlet 14 is not limited to a plurality provided in the width direction of the grate as shown in FIG. 4, but is formed in a slit shape in the width direction of the grate as shown in FIG. You may.
[0045]
Next, a method of operating the waste incinerator having the above configuration will be described. As shown in FIG. 2, the waste 3 is put into the combustion chamber 1 from the hopper 2, and the combustion air is supplied to the waste 3 moving on the grate through the wind box 8 to dry the waste 3. And further burn.
[0046]
In addition, a high-temperature gas is blown onto the waste on the combustion grate 5 from a gas inlet 14 provided on a wall of a step portion between the dry grate 4 and the combustion grate 5. The temperature of the high-temperature gas blown onto the waste is adjusted so that the temperature at the time of the blow is 200 ° C. or more, and the relationship between the temperature and the oxygen concentration satisfies the expression (1).
[0047]
When the waste 3 is incinerated in the waste incinerator shown in FIG. 2, first, moisture evaporates, and then thermal decomposition / partial oxidation reaction occurs. Here, the thermal decomposition reaction occurs at a temperature of about 200 ° C., and is almost completed when the temperature reaches about 400 ° C. In the example shown in FIG. 2, the region where the thermal decomposition reaction occurs corresponds to the upstream portion of the combustion grate 5, and therefore, a gas blowing port 14 is provided at a step between the dry grate 4 and the combustion grate 5. Hot gas is blown onto the waste of the combustion grate 5.
[0048]
The amount of high-temperature gas blown from the gas blowing port 14 is preferably as small as possible in consideration of exhaust gas treatment and the like. However, when the blowing amount is small, complete combustion cannot be performed, and CO is easily generated. For this reason, it is desirable that the amount of gas blown from the gas blowing port 14 be 20% to 30% of the amount of primary air blown from the wind box 8. As a result, the generation of CO can be suppressed to a level that causes no problem. As described above, the amount of the high-temperature gas to be blown is preferably as small as possible within a range in which the object is achieved. Therefore, it is preferable to adjust the blowing amount in the range of 20% to 30% of the primary air amount while monitoring the amount of CO and NOx to be discharged.
[0049]
In particular, when the type of the waste 3 fluctuates, the amount of the primary air to be blown may be smaller than the theoretical air amount required for burning the waste 3, and in this case, a large amount of hot gas Is preferably blown to promote complete combustion of the waste 3 to prevent generation of CO.
[0050]
If it is known that the amount of the primary air to be blown is small, the amount of the hot gas to be blown may be in the range of 20% to 30% of the theoretical air amount required for burning the waste 3. Good.
[0051]
In FIG. 2, high-temperature gas is blown from a gas blowing port 14 provided at a step between the dry grate 4 and the combustion grate 5, and the blowing direction of the high-temperature gas is preferably horizontal or obliquely downward. By doing so, the rising combustible gas and the high-temperature gas ejected from the nozzle cause a stirring action, and the combustion of the combustible gas can be promoted.
[0052]
In the above embodiment, CO, NOx, and dioxin are effective in reducing trace harmful substances. However, when blowing gas into the furnace, further, blowing from the side of the furnace or from the ceiling is also used. Is also good.
[0053]
In these embodiments, when high-temperature gas is blown into the furnace, it is appropriate to use a mixed gas of circulating exhaust gas and air as the high-temperature gas to be blown out from the gas blowing port of the step. Recirculated exhaust gas is exhaust gas discharged from waste incinerators, part of which is returned to the combustion chamber to use its sensible heat, reburn unburned gas, and effectively use residual oxygen in exhaust gas. Or use it.
[0054]
When the circulating exhaust gas satisfies the limitation according to the formula (1) of the present invention, the circulating exhaust gas may be directly blown into the furnace, but the temperature of the circulating exhaust gas used is lower than 200 ° C. In, the oxygen concentration may be lower than 10%. For this reason, high-temperature air is produced by a high-temperature air production device or a hot blast stove, and mixed with the circulating exhaust gas to produce a high-temperature gas having a temperature of 200 ° C. or higher and a relation between oxygen concentration and temperature satisfying the expression (1) And blow it into the furnace.
[0055]
When using exhaust gas from the secondary combustion chamber, if the exhaust gas has a sufficiently high temperature and a high oxygen concentration, the exhaust gas can be used instead of the high-temperature gas without providing a high-temperature air production device. It may be used and mixed with air and blown. Further, if the temperature of the exhaust gas from the secondary combustion chamber is 200 ° C. or higher and the relationship between the oxygen concentration and the temperature satisfies the expression (1), the exhaust gas may be directly blown into the furnace.
[0056]
When the exhaust gas generated from the incinerator is used in its entirety as the high-temperature gas blown into the furnace, or when the exhaust gas generated from the incinerator is used as part of the high-temperature gas, it is contained in the dust contained in the exhaust gas. Sodium salts, potassium salts, and the like may adhere to the pipe wall of the pipe and cause corrosion or block the pipe. If the dust is blown into the furnace without removing the dust, there is a risk that the concentration of the discharged harmful substances may increase due to harmful substances (eg, dioxins) contained in the dust.
[0057]
In order to prevent such a problem from occurring, it is preferable to remove dust in the exhaust gas. As a dust removing method, a known method such as a filter method or a cyclone method can be used. There are a filter method using a filter cloth and a filter method using a ceramic filter. When the temperature of the exhaust gas is high, the ceramic filter is superior in durability and heat resistance. Filter cloth processed with metal fibers is also effective depending on the operating temperature. Further, a moving bed type dust removing device may be used. The place where dust is removed is preferably as close as possible to the exhaust gas outlet because the piping before dust removal becomes shorter.
[0058]
The exhaust gas outlet is desirably provided in a place where the temperature of the exhaust gas is high. In the case of an incinerator with a waste heat boiler, it is effective to extract the exhaust gas from the boiler section. In the boiler section, it is possible to extract high-temperature exhaust gas at 800 ° C.
[0059]
As an example of the high-temperature air producing apparatus, a pair of heat storage elements is prepared, the first heat storage element is heated and stored by high-temperature exhaust gas from the combustion burner, and air is put into the second heat storage element that has already been heated and stored. Then, the air is heated by the regenerator and the regenerator is heated by the high-temperature exhaust gas, and the air is heated by the regenerator. A mixture of gas and air or oxygen, an oxygen-enriched burner, or the like can be used.
[0060]
When mixing the circulating exhaust gas with high-temperature air from a high-temperature air production device or a hot-blast furnace, it is preferable that the mixture is blown into the furnace by mixing with an ejector device. That is, high-temperature air is guided to an ejector device, which is used as a driving flow to mix while circulating exhaust gas is sucked and blown into the furnace. This eliminates the need for a device having a special movable portion such as a fan for sucking the circulating exhaust gas, so that the device configuration is simplified and dust troubles can be reduced.
[0061]
If the circulating exhaust gas removes dust and has a temperature of about 400 ° C. or lower, the exhaust gas can be blown into the furnace using a blower.
[0062]
FIG. 6 shows an outline of an exhaust gas circulation system in an example of a waste incinerator according to an embodiment of the present invention. Exhaust gas discharged from the combustion chamber 1 of the incinerator is subjected to secondary combustion in the secondary combustion chamber 12, then guided to the waste heat boiler 11 for heat exchange, purified by the exhaust gas treatment equipment 22, and discharged from the chimney 23. Released to the atmosphere.
[0063]
FIG. 6 shows a mechanism for injecting high-temperature gas from the gas inlet 14 shown in FIGS. 2 and 3. In this embodiment, the exhaust gas is sucked from the downstream side of the exhaust gas treatment equipment by the blower 24. , A gas mixing device 25. A high-temperature combustion gas such as a burner combustion gas is introduced into the gas mixing device 25 via a high-temperature combustion gas control valve 26, and air for adjustment is introduced via an adjustment air control valve 27.
[0064]
The gas mixing device 25 mixes the exhaust gas, the high-temperature combustion gas, and the adjusting air to generate a high-temperature gas. The high-temperature gas pipe is connected to a gas inlet 14 shown in FIG. 2, and the high-temperature gas is blown into the combustion chamber 1 from the gas inlet 14. The oxygen concentration in the high-temperature gas is adjusted by the oxygen concentration adjusting device 29. The oxygen concentration adjusting device 29 adjusts the opening degree of the adjusting air adjustment valve 27 so that the oxygen concentration in the high-temperature gas becomes a predetermined concentration. The temperature of the high-temperature gas is adjusted by the temperature adjusting device 28. The temperature adjusting device 28 adjusts the opening degree of the high-temperature combustion gas control valve 26 or the opening degree of the adjustment air control valve 27 so that the temperature of the high-temperature gas falls within the range shown by the expression (1).
[0065]
As described above, in this embodiment, since the function of adjusting the oxygen concentration and the temperature of the high-temperature gas blown into the combustion chamber is provided, the oxygen concentration and the temperature of the high-temperature gas blown into the combustion chamber are appropriately adjusted. Range can be maintained. When it is desired to adjust the flow rate and flow velocity of the high-temperature gas to be blown in, adjustment is performed by means such as adjusting the number of revolutions of the blower 24 or adjusting the opening of the high-temperature combustion gas control valve 26 or the adjustment air control valve 27. do it.
[0066]
FIG. 7 shows a modification of the exhaust gas circulation system shown in FIG. This example is different from the example shown in FIG. 6 in that the place where the exhaust gas is taken out is the outlet of the waste heat boiler 11, and since the function as a whole is the same, only the parts different from FIG. 6 will be described. . In the example shown in FIG. 6, since the exhaust gas is taken out from the rear of the exhaust gas treatment equipment 22, dust in the exhaust gas is removed and the exhaust gas is clean. However, the temperature has dropped.
[0067]
In the example shown in FIG. 7, since the exhaust gas is taken out from the outlet of the waste heat boiler 11, high temperature exhaust gas can be used. However, since this exhaust gas contains dust and has the above-mentioned adverse effects, a dust removing device 30 is provided in a piping system leading to the blower 24, and the exhaust gas that has been cleaned by removing dust is sent to the blower 24. I have.
[0068]
In this case, since the temperature of the exhaust gas is high, the high-temperature combustion gas production device and the high-temperature combustion gas control valve 26 can be omitted depending on the temperature of the blown gas.
[0069]
In the example shown in FIGS. 6 and 7, an example is shown in which high-temperature combustion gas such as burner combustion gas and adjustment air are mixed into the circulating exhaust gas. Alternatively, the gas may be led to a gas combustion device instead of the high-temperature combustion gas. In this case, instead of introducing and adjusting the adjusting air into the gas mixing device, the amount of air introduced into the high-temperature air producing device may be adjusted to adjust the oxygen concentration of the high-temperature gas.
[0070]
【The invention's effect】
As described above, according to the present invention, the generation amount of harmful gases such as CO and NOx is reduced even in low air ratio combustion.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the temperature of a gas blown into a furnace and the oxygen concentration.
FIG. 2 is a diagram showing a waste incinerator as an example of an embodiment of the present invention.
FIG. 3 is a view showing a gas blowing port in FIG. 2;
FIG. 4 is a diagram showing an example of an arrangement of gas blowing ports.
FIG. 5 is a diagram showing another example of the arrangement of the gas blowing ports.
FIG. 6 shows an outline of an exhaust gas circulation system in an example of a waste incinerator according to an embodiment of the present invention.
FIG. 7 shows a modification of the exhaust gas circulation system shown in FIG.
FIG. 8 is a schematic diagram showing an example of a conventional waste incinerator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Combustion chamber, 2 ... Hopper, 3 ... Waste, 4 ... Dry grate, 5 ... Combustion grate, 7 ... Main ash chute, 8 ... Wind box, 11 ... Waste heat boiler, 12: Secondary combustion chamber, 13: Wall of stepped portion, 14: Gas inlet, 15: Nozzle, 16: Header pipe, 22: Exhaust gas treatment equipment, 23: Chimney, 24: Blower, 25: Gas mixing device, 26 ... High temperature combustion gas control valve, 27 ... Adjustment air control valve, 28 ... Temperature control device, 29 ... Oxygen concentration control device, 30 ... Dust removal device

Claims (9)

A waste incinerator with a stepped grate, wherein a gas inlet for blowing gas onto the waste on the combustion grate is provided at a step between the dry grate and the combustion grate. And waste incinerator. 2. The waste incinerator according to claim 1, further comprising a mechanism connected to the gas inlet to inject high-temperature gas. 2. The waste incinerator according to claim 1, further comprising a mechanism connected to the gas inlet for injecting a high-temperature gas containing oxygen. A method for operating a waste incinerator having a stepped grate, wherein gas is blown from a step between the dry grate and the combustion grate onto the waste on the combustion grate. How to operate the furnace. The method for operating a waste incinerator according to claim 4, wherein the gas blown into the waste on the combustion grate from the step is a high-temperature gas. The method for operating a waste incinerator according to claim 5, wherein the temperature [° C] T from the step between the dry grate and the combustion grate is 200 or more and oxygen contained therein. Concentration [vol. %] A method for operating a waste incinerator characterized by blowing a gas having a relationship with C in a range represented by the following formula.
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) (1) The method for operating a waste incinerator according to any one of claims 4 to 6, wherein a gas blowing amount is 20% to 30% of a primary air amount. How to operate a waste incinerator. The method for operating a waste incinerator according to any one of claims 4 to 6, wherein a gas blowing amount is 20% to 30% of a theoretical air amount for burning the waste. A method of operating a waste incinerator characterized by the following. The method for operating a waste incinerator according to any one of claims 4 to 8, wherein the gas blowing direction is horizontal or obliquely downward. .

Images