JP3989333B2 - Operation method of waste incinerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a waste incinerator that incinerates wastes such as general waste, industrial waste, and sewage sludge.
[0002]
[Prior art]
Grate type or fluidized bed type waste incinerators are widely used as incinerators for incinerating waste such as municipal waste. A schematic diagram of a representative one is shown in FIG. The waste 32 thrown into the hopper 31 is sent to a drying stoker 33 through a chute, dried by air from below and radiant heat in the furnace, and heated to ignite. The waste 32 ignited and combusted is sent to the combustion stalker 34, pyrolyzed and gasified by the combustion air sent from below, and a part is combusted. Further, the unburned matter in the waste is completely burned by the post-burning stoker 35. The ash remaining after combustion is taken out from the main ash chute 36.
[0003]
Combustion is performed in the main combustion chamber 37, and the generated combustion gas is discharged separately 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 matter and contains about 10% or more of oxygen. The exhaust gas passing through the auxiliary flue 40 contains about 8% of unburned gas. These exhaust gases are mixed in the secondary combustion chamber 41, secondary combustion is performed, and the unburned gas is completely burned. The exhaust gas from the secondary combustion chamber 41 is sent to the waste heat boiler 43, and after heat exchange, it is discharged to the outside through a temperature reducing tower, a bag filter, and the like.
[0004]
In such a grate-type or fluidized-bed type waste incinerator, 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. Therefore, it is inevitable that the temperature and the distribution of the concentration of the combustion gas in the main combustion chamber 37 are non-uniform in time and space.
[0005]
As a method for solving such a problem, Japanese Patent Application Laid-Open No. 11-2111044 (Patent Document 1) discloses a method in which high-temperature gas generated by a regenerative burner is blown into a main combustion chamber or a secondary combustion chamber of an incinerator. Is disclosed.
[0006]
Japanese Patent Application Laid-Open No. 11-223323 (Patent Document 2) discloses a method in which a high-temperature gas generated by a heat storage burner is blown into a furnace at a temperature of 800 ° C. or higher. All of these techniques are intended to reduce unburned gas and harmful substances containing a large amount of CO, aromatic hydrocarbons, and the like in exhaust gas generated in an incinerator.
[0007]
[Patent Document 1]
JP 11-2111044 A
[Patent Document 2]
JP-A-11-223323
[0008]
[Problems to be solved by the invention]
However, in the technique disclosed in Japanese Patent Application Laid-Open No. 11-2111044, the oxygen concentration in the high-temperature gas is 20% or more. Therefore, when such a high-temperature gas is blown into the incinerator, it is suddenly generated in the incinerator. There is a risk that the combustion proceeds and a local high temperature region is formed. When a local high temperature region is formed, there is a problem that, for example, the amount of NOx that is a harmful substance increases.
[0009]
In addition, in the technique described in JP-A-11-223323, in addition to the above problems, oxygen-containing gas is blown into the main combustion chamber at a temperature of 800 ° C. or higher. The reaction is promoted, and in some cases, CO may be generated.
[0010]
Thus, in any of the above technologies, it is difficult to sufficiently reduce harmful substances including NOx, CO, and dioxin in exhaust gas when incinerating waste by an incinerator such as a grate type incinerator. There is a problem that there is.
[0011]
Conventionally, in a waste incinerator, a ratio (air ratio) obtained by dividing an actual air amount by a theoretical air amount necessary for combustion of waste is about 1.7 to 2.0. This is larger than 1.05 to 1.2, which is the air ratio required for normal combustion. The reason for this is that the waste contains a large amount of incombustible material and is inhomogeneous, so that a large amount of air is required for combustion. However, as the air ratio increases, the amount of exhaust gas also increases, and a larger exhaust gas treatment facility is required as compared with a normal combustion furnace.
[0012]
If the air ratio is reduced, the amount of exhaust gas is reduced and the exhaust gas treatment facility becomes compact. As a result, the entire waste incineration facility can be miniaturized and the equipment cost can be reduced. In addition, since the amount of chemicals for exhaust gas treatment can be reduced, the operating cost can be reduced. Furthermore, since the amount of heat lost without heat recovery can be reduced, the heat recovery rate of the waste heat boiler can be improved, and the power generation efficiency of waste power generation can be increased accordingly.
[0013]
As described above, although the advantage over the low air ratio combustion is great, there is a problem that the combustion becomes unstable in the low air ratio combustion. In other words, in the conventional combustion technology, when combustion is performed at a low air ratio, the combustion becomes unstable, the generation of CO increases, the flame temperature rises locally, NOx increases rapidly, and a large amount of soot is generated. And clinker is generated, and the lifetime of the refractory in the furnace is shortened due to local high temperatures.
[0014]
Furthermore, in the techniques described in the above two documents, high-temperature air is blown in, but there is a problem that the radiation rate of this high-temperature air is low and the combustion gas cannot be sufficiently heated by radiant heat transfer, For this reason, there has been a problem that there is a limit to the reduction of CO and NOx in the exhaust gas.
[0015]
The present invention has been made in view of such circumstances, and in a method for operating a waste incinerator that blows gas into a combustion chamber, particularly in a low air ratio combustion operation method, provides preferable properties and temperature of the blown gas, And let it be a subject to provide a preferable blowing method.
[0016]
[Means for Solving the Problems]
  The first means for solving the above problem is to perform a low air ratio combustion operation in which the air ratio obtained by dividing the actual air amount by the theoretical air amount necessary for combustion of waste in the waste incinerator is lower than 1.7. In the combustion chamber of a waste incinerator,An operation method of a waste incinerator for blowing a high temperature gas, wherein the high temperature gas contains at least one of carbon dioxide and water vapor, and oxygen, and the temperature [° C.] T is 200 Above, and the concentration of oxygen contained in the hot gas [ vol. %] The relationship with C is in the range represented by the following formula (1), and the high-temperature gas does not increase the amount of CO generated due to unstable combustion of unburned gas in the furnace ( 1) The lower limit of the amount of oxygen and temperature is determined based on the equation, and high-temperature combustion results in excessive thermal decomposition and gasification of waste, and local combustion of unburned gas, resulting in increased NOx generation. The upper limit of the amount of oxygen and the temperature are determined based on the formula (1) so as not to let the oxygen concentration and temperature range of the high-temperature gas be blown into the high-temperature gas, thereby promoting thermal decomposition of the waste and disposing of it. It is a range defined to form a stagnation area in the space above the object to localize a stable flame, to make the combustion of waste uniform and stable, and to suppress the generation of CO and NOx TossThis is a method for operating a waste incinerator (claim 1).
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) ... (1)
[0017]
  In this means, the high temperature gas blown into the combustion chamber contains at least one of carbon dioxide and water vapor. Since the emissivity of carbon dioxide and water vapor is higher than that of nitrogen and oxygen, the heat radiation from high-temperature gas containing these gases causes waste and waste.appearSince the unburned gas is efficiently heated and, as a result, stable combustion is performed even when low air ratio combustion is performed, the generation of CO and NOx can be efficiently reduced.
[0018]
Furthermore, the inventors, in a waste incinerator, CO generated when blowing high temperature gas containing at least one of carbon dioxide and water vapor into the combustion chamber, Nox, and oxygen concentration in the high temperature gas blown into the combustion chamber, The relationship between hot gas temperatures was investigated. As a result, the oxygen concentration in the high temperature gas and the temperature range of the high temperature gas that can simultaneously reduce CO and NOx in the exhaust gas are limited to the region surrounded by the A line, the B line, and the C line in FIG. I found it. When the temperature of the hot gas at the time of being blown into the furnace is T [° C.] and the oxygen concentration in the hot gas is C [vol.
T = exp (8.05-0.23C)
B line is
T = exp (7.40-0.09C)
C line
T = 200
It corresponds to.
[0019]
Blowing high-temperature gas having oxygen concentration and temperature in the area surrounded by A-line, B-line, and C-line into the combustion chamber promotes thermal decomposition of waste and forms a stagnation area in the space above waste Can stabilize a stable flame. Furthermore, since the mixing of the pyrolysis gas is promoted, uniform and stable combustion is promoted, so that the generation of NOx and CO can be greatly reduced.
[0020]
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 unburned gas becomes unstable, and as a result, the generation of CO increases. In the region above line B, high-temperature combustion occurs, the thermal decomposition and gasification reaction of waste is excessively promoted, and as a result of unburned gas burning locally, NOx increases. In the region below the C line, even if the gas is blown, the surrounding gas is not entrained and the stirring effect is small, so that the gas is not sufficiently mixed. As a result, a local high temperature region is generated and NOx increases.
[0021]
For example, 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 high-temperature gas is 15%, the temperature of the high-temperature gas that achieves both low NOx and low CO is in the range of 200 to 400 ° C.
It is effective to use exhaust gas discharged from a combustion furnace as a high-temperature gas containing at least one of carbon dioxide and water vapor.
[0022]
The second means for solving the above-mentioned problem is the first means, wherein the hot gas blowing location / area is a space where the temperature of the blowing location is 400 [° C.] or more and unburned gas exists. (Claim 2).
[0023]
In the combustion chamber, the space where the temperature is 400 [° C.] or more and unburned gas exists is a region where thermal decomposition of waste is promoted, or a region where thermal decomposition of waste is completed, and waste This is a region where unburned gas is generated by the thermal decomposition of and flame is present. For example, in paper waste, thermal decomposition starts at about 250 ° C and completes at about 400 ° C. For plastic waste, thermal decomposition begins at about 400 ° C and completes at about 500 ° C.
[0024]
Even if the hot gas is blown into a region where the thermal decomposition of the waste does not start and only drying is performed, the effect of promoting low NOx and low CO of the exhaust gas is small. That is, it is preferable to blow into a region where a large amount of unburned gas exists. By blowing hot gas into this region, unburned gas is stably combusted. Therefore, in this means, the area | region which blows in high temperature gas is limited to the above-mentioned space.
[0025]
The third means for solving the above-mentioned problem is the first means or the second means, characterized in that the hot gas blowing location / region is from the combustion start region to the main combustion region. (Claim 3).
[0026]
As described above, it is preferable that the high temperature gas is blown into a region where a large amount of unburned gas exists, but in many waste incinerators such as a grate type and a fluidized bed type, a region where a large amount of unburned gas exists is From the combustion start region to the main combustion region. Here, the combustion start region is a region where the combustion of waste starts, and the main combustion region is a region where the combustion of waste is substantially completed. Therefore, it is preferable to blow in the high-temperature gas between the combustion start region and the main combustion region.
[0027]
A fourth means for solving the problem is any one of the first to third means, wherein the amount of hot gas blown is 10% to 70% of the primary air amount. (Claim 4).
[0028]
The primary air is air that is blown for the purpose of burning waste, and is air that is blown in a conventional waste incinerator that does not blow high-temperature gas. Generally, in the case of a grate furnace, it is blown from under the grate, and in the case of a fluidized bed furnace, it is blown from under the fluidized bed.
[0029]
If the amount of hot gas blown is less than 10% of the amount of primary air, the momentum required for gas stirring in the furnace is not sufficient, and the effect of hot gas blowing may not be fully exhibited. In addition, if the amount of high-temperature gas blown exceeds 70% of the primary air amount, the effect of reducing the NOx and CO emissions of the exhaust gas will be saturated, and the meaning of increasing the amount of high-temperature gas blown will not be lost. This is not preferable because the amount is increased and the exhaust gas treatment facility is increased. Therefore, in this means, the amount of hot gas blown is limited to the range of 10% to 70% of the primary air amount.
[0030]
A fifth means for solving the problem is any one of the first to third means, wherein the amount of hot gas blown is 10% to 70% of the theoretical air amount for burning waste. (Claim 5).
[0031]
In the fifth means, the primary air amount is used as a reference value for the amount of hot gas blown in. However, in some cases, the primary air amount is equal to or less than the theoretical air amount necessary to completely burn the waste. There is a case. In such a case, the amount of hot gas blown is set to 10% to 70% of the theoretical air amount for burning the waste. The theoretical air amount is determined from the type of waste.
[0032]
  A sixth means for solving the problem is any one of the first means to the fifth means, and the blowing direction of the high temperature gas is:From the height position not exceeding 1/2 of the main combustion chamber height, it is a blowing direction in the range of 20 ° downward from the horizontal.(Claim 6).
[0033]
Unburned gas generated from the waste usually flows upward. Therefore, if the high temperature gas blowing direction is upward, the flow of the unburned gas and the high temperature gas have velocity components in the same direction, the stirring effect is reduced, and the high temperature gas blowing effect is reduced. On the other hand, when the blowing direction of the high temperature gas is horizontal or downward, the rising unburned gas and the high temperature gas are well stirred, and the high temperature gas blowing effect can be enhanced. In general, it is said that 3T is a factor effective in blowing high temperature gas. These are temperature, stirring (Turbulence), and residence time (Time). In particular, by blowing a high-temperature gas downward, stirring (Turbulence) and residence time (Time) can be improved.
[0034]
A seventh means for solving the above problem is any one of the first to sixth means, wherein hot gas is blown as a swirling flow (Claim 7). .
[0035]
By blowing the hot gas as a swirl flow, the stirring effect can be enhanced and the hot gas blowing effect can be enhanced. “Blowing high-temperature gas as a swirling flow” means that the high-temperature gas itself flowing out from the outlet is a swirling flow, and the flow of the high-temperature gas flowing out from a plurality of outlets is combined into a swirling flow Including cases.
[0036]
An eighth means for solving the problem is any one of the first to seventh means in a waste incinerator having a waste heat boiler, wherein the high-temperature gas is in a waste heat boiler or waste. A method for operating a waste incinerator comprising gas derived from an outlet of a thermal boiler (claim 8).
[0037]
In this means, the gas extracted from the waste heat boiler or from the outlet of the waste heat boiler is used as all or part of the high-temperature gas blown into the combustion chamber. Therefore, since high-temperature exhaust gas can be used for all or part of the gas blown into the combustion chamber, sensible heat in the exhaust gas can be used effectively, and thermal efficiency can be increased.
[0038]
A ninth means for solving the above problem is any one of the first to seventh means in a waste incinerator having an exhaust gas treatment facility, wherein the high temperature gas is upstream of the exhaust gas treatment facility. A waste incinerator operating method (Claim 9) characterized in that it contains a gas having a temperature of 800 ° C. or less derived from the above.
[0039]
Also in this means, the exhaust gas before being cooled by the exhaust gas treatment facility is used as all or part of the high-temperature gas blown into the combustion chamber. Therefore, since the high-temperature exhaust gas can be used for all or a part of the high-temperature gas blown into the combustion chamber, the sensible heat in the exhaust gas can be used effectively and the thermal efficiency can be increased.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram illustrating an example of a waste incinerator that performs a method of operating a waste incinerator that is an example of an embodiment of the present invention. 2 is a main combustion chamber, and on one side (left side in FIG. 2) of this main combustion chamber 1 is provided a hopper 2 for introducing waste 3 into the main combustion chamber 1. Yes.
[0041]
A mesh-like grate (stoker) that burns while moving the waste 3 is provided at the bottom of the main combustion chamber 1 so as to be lowered as it moves away from the hopper 2. The grate is formed with two steps and is divided into three parts. These three grates are called dry stoker 4, combustion stoker 5, and post-combustion stoker 6 from the side closer to hopper 2. In the dry stoker 4, the waste 3 is mainly dried and ignited. The combustion stoker 5 mainly burns the waste 3, but the waste 3 is burned and thermally decomposed, and unburned gas is released together with the combustion gas. Combustion of the waste 3 is substantially completed in the combustion stoker 5. On the post-combustion stoker 6, the remaining unburned matter in the waste 3 is completely burned. The combustion residue after complete combustion is discharged from the main ash chute 7.
[0042]
A wind box 8 connected to a supply pipe for supplying combustion air is provided below each grate.
[0043]
A main flue 9 and a sub flue 10 are provided below and above the main combustion chamber 1 on the side opposite to the hopper 2, and these include secondary combustion of the waste heat boiler 11 that is part of the gas cooling facility. A chamber 12 is connected. An intermediate ceiling 13 for diverting the combustion gas is provided in the main combustion chamber 1 in the vicinity of the outlet of the main combustion chamber 1, and the flow of the combustion gas is divided into the main flue 9 and the sub flue 10. ing.
[0044]
As shown in FIG. 2, waste 3 is put into the main combustion chamber 1 from the hopper 2, and combustion air is supplied to the waste 3 moving on the grate through each supply pipe and the wind box 8. The waste 3 is dried and further combusted.
[0045]
A nozzle 14 is provided on the side wall of the main combustion chamber 1, and a high-temperature gas containing at least one of carbon dioxide and water vapor and oxygen is blown into the main combustion chamber 1 from the nozzle 14. The temperature of the high temperature gas is adjusted to be 200 ° C. or higher and the relationship between the temperature and the oxygen concentration satisfies the above equation (1).
[0046]
In FIG. 2, the nozzle 14 is installed at the upper part of the dry stalker 4 and the upper part of the combustion stalker 5 on the dry stalker side. When the waste 3 is incinerated, moisture first evaporates, and then thermal decomposition and partial oxidation occur. 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, it corresponds to the dry stoker 4 part (rear stage part) and the front stage part of the combustion stoker 5, and therefore a nozzle 14 is provided at these positions to blow high temperature gas. Depending on the type of the waste 3, there are those in which the thermal decomposition reaction is completed at a higher temperature. In this case, it is preferable to provide the nozzle 14 on the rear stage side (right side in the figure) from the position shown in FIG. 2.
[0047]
Further, as shown in FIG. 2, the nozzle 14 is preferably provided at a height not exceeding 1/2 of the main combustion chamber height. The reason is that a high temperature region can be fixed immediately above the waste 3.
[0048]
Moreover, the combustion of the unburned gas can be promoted by blowing the high temperature gas into the space where the temperature is 400 ° C. or higher and the unburned gas exists. Therefore, the nozzle is arranged so that the hot gas is blown into the region where the sub flue gas containing a large amount of unburned gas and the main flue gas are mixed, that is, above the intermediate ceiling 13 and into the entrance of the secondary combustion chamber 12. You may provide in a side wall, a ceiling, the intermediate | middle ceiling 13, and the secondary combustion chamber 12 entrance.
[0049]
The amount of hot gas blown in should be as small as possible when considering exhaust gas treatment. However, when the amount of blowing is reduced, CO is likely to be generated, and complete combustion cannot be performed. For this reason, it is desirable to set it as the blowing amount of 10%-70% of the primary air amount blown from the wind box 8. Thereby, generation | occurrence | production of CO can be suppressed to the extent which is satisfactory. As described above, it is preferable that the amount of hot gas blown is as small as possible within the range in which the purpose is achieved. Therefore, it is preferable to increase or decrease the blowing amount in the range of 10% to 70% of the primary air amount while monitoring the amount of CO or NOx discharged.
[0050]
In particular, when the type of the waste 3 varies, the amount of primary air that is blown may be less than the theoretical air amount necessary for burning the waste 3, and in this case, a large amount of high-temperature gas It is preferable to promote the complete combustion of the waste 3 and prevent the generation of CO.
[0051]
When it is known that the amount of primary air to be blown is small, the amount of hot gas to be blown may be in the range of 10% to 70% of the theoretical air amount necessary for burning the waste 3. Good.
[0052]
In FIG. 2, nozzles 14 are provided on both sides of the furnace, and hot gas is blown from here. The nozzle is preferably provided horizontally or downward. By doing in this way, a stirring action can be caused by the rising unburned gas and the high temperature gas ejected from the nozzle, and combustion of the unburned gas can be promoted. In order to promote the stirring action, the nozzle is preferably provided downward. However, if the angle is set too much, the hot gas does not reach the entire furnace width direction. Therefore, it is particularly preferable that the angle is in the range of 10 to 20 ° downward.
[0053]
Further, in order to exert the stirring action of the high temperature gas in the whole furnace width direction, the high temperature gas blowing speed is set to a range of 20 W [m / s] or more when the furnace width is W [m]. By providing nozzles at opposite positions on both sides of the furnace and performing such high-speed blowing, a stagnation region of unburned gas is formed in the incinerator. As a result, the residence time of the unburned gas in the furnace becomes longer and the reaction time with the high temperature gas becomes longer, so that the reaction is sufficiently performed. In order to form the stagnation region, it is particularly effective to install the nozzle downward.
[0054]
In order to show the arrangement of the nozzles in FIG. 2, an A-A ′ sectional view and a B-B ′ sectional view are shown in FIG. 3. However, in FIG. 3, illustrations of structures not related to the present invention are omitted. In FIG. 3, 15 is a stagnation region, 17 is a furnace wall, 18 is a furnace ceiling, 19 is a hot gas, 20 is a swirling flow part, and 21 is a combustion gas.
[0055]
From a pair of nozzles 14 provided facing the left and right sides of the furnace wall 17, gas is jetted out to become a high-temperature gas 19, which is a cross-sectional view taken along the line AA ′ (a), They collide with each other in the center of the furnace. Therefore, a stagnation region (combustion stable region) 15 in which the movement of the gas in the furnace is slow and stays is formed in the center of the furnace.
[0056]
FIG. 3 (b) shows another embodiment and is a cross-sectional plan view. The nozzles 14 are oriented such that their central axes are parallel to each other and spaced apart from each other by a predetermined distance, and the hot gas 19 passes by a predetermined distance in the center of the furnace. Therefore, a swirl flow part (swirl area) 20 is formed at the center of the furnace.
[0057]
That is, in this embodiment, the stagnation region 15 or the swirling flow portion 20 is formed in the center of the furnace when viewed in plan. Therefore, as described above, the flame is stabilized and the mixing of the gases is promoted.
[0058]
In FIG. 3A, the size of the stagnation region 15 can be controlled by changing the flow rates of the hot gases ejected from the two nozzles 14 in the same manner. Further, by providing a difference in the flow rate of the hot gas ejected from both nozzles 14, the position of the stagnation region 15 in the left-right direction of the furnace can be changed. Further, the position of the stagnation region 15 in the front-rear direction of the furnace can be changed by changing the direction of the nozzle 14 in the same direction in the front-rear direction of the furnace.
[0059]
Further, in FIG. 3B, the size of the swirling flow portion 20 can be changed by changing the interval between the two hot gases 19. In addition, by providing a speed difference between the two high-temperature gases 19, the left-right position of the furnace in which the swirl flow section 20 is formed can be changed. Furthermore, the speed of the swirling flow can be changed by changing the speeds of the two hot gases 19 in the same manner.
[0060]
FIG. 3C is a cross-sectional view taken along the line B-B of FIG. 2, and the hot gas 19 blown out from the nozzles 14 provided downward on the furnace walls 17 on both sides collides with the rising unburned gas 21. Thus, the stagnation region 15 is shown. In the stagnation region 15, a stable diffusion flame is formed as a result of stable combustion. As a result, unlike the prior art, instability of combustion in the combustion start region is not amplified even under low air ratio combustion conditions, soot generation is suppressed, and uniform and stable combustion can be expected.
[0061]
In order to exert a stirring action, it is also effective to blow hot gas into the furnace from the nozzle 14 as a swirling flow.
Moreover, since there is an effect of stabilizing combustion by blowing high-temperature gas so that the gas in the vicinity of the furnace side wall is sufficiently stirred, it is preferable to set the blowing speed to at least 10 [m / s] or more.
[0062]
The flame in the furnace when the high temperature gas is not blown is a luminous flame, but when the high temperature gas is blown into the furnace appropriately according to the above embodiment, the flame in the furnace becomes a clear flame, and the furnace wall It will be possible to observe the hearth. This is considered to be because the temperature distribution in the furnace is averaged and the unburned portion is completely burned. Therefore, it is possible to observe the transparency of the flame in the furnace and use it as a criterion for determining whether or not the hot gas is being blown appropriately.
[0063]
The above embodiment is effective in reducing trace harmful substances such as CO, NOx, and dioxin. Moreover, although the furnace which has the intermediate ceiling 13 is illustrated in FIG. 2, it cannot be overemphasized that this invention is applicable also to the furnace which does not have such an intermediate ceiling. In FIG. 2, the hot gas is blown into the main combustion chamber 1, but the hot gas may be blown into the secondary combustion chamber 12. Further, the hot gas may be blown from one side surface of the furnace. Furthermore, you may make it blow in from an intermediate | middle ceiling or a ceiling instead of from the side surface of a furnace.
[0064]
In these embodiments, it is appropriate to use a mixed gas of circulating exhaust gas and air as the hot gas ejected from the nozzle 14. Circulating exhaust gas means that a part of the exhaust gas discharged from the waste incinerator is returned to the main combustion chamber to recover its sensible heat, reburn the unburned component, and effectively use residual oxygen in the exhaust gas. It is something to do.
[0065]
When the circulating exhaust gas satisfies the limitation of the present invention, the circulating exhaust gas may be blown into the furnace as it is, but the temperature of the circulating exhaust gas that is usually used is lower than 200 ° C. and the oxygen concentration is lower than 10%. For this reason, high-temperature gas that creates high-temperature air using a high-temperature air production system or hot-air furnace, mixes it with the circulating exhaust gas, and has a temperature of 200 ° C or higher and the relationship between oxygen concentration and temperature satisfies equation (1) It is preferable to blow into the furnace.
[0066]
In addition, when the temperature of the exhaust gas from the secondary combustion chamber 12 is sufficiently high and the oxygen concentration is high, it is possible to use this instead of high-temperature air, mix it with air and blow it in without using a high-temperature air production device. Good. Further, if the temperature of the exhaust gas from the secondary combustion chamber 12 is 200 ° C. or higher and the relationship between the oxygen concentration and the temperature satisfies the expression (1), this may be directly blown into the furnace.
[0067]
When exhaust gas generated from an incinerator is used as a high-temperature gas, or exhaust gas generated from an incinerator is used as part of the high-temperature gas, sodium salts and potassium contained in dust contained in the exhaust gas Salt or the like may adhere to the pipe wall and cause corrosion or blockage of the pipe. Moreover, when it blows in in a furnace, without removing dust, the danger that the density | concentration of these hazardous | toxic substances discharged | emitted by the harmful | toxic substance (for example, dioxin) contained in dust will increase on the contrary is also considered.
[0068]
In order to prevent such problems from occurring, it is preferable to remove dust in the exhaust gas. As a dust removal method, a known method such as a filter method or a cyclone method can be used. Some filter systems use filter cloth and others use ceramic filters. If the temperature of the exhaust gas is high, ceramic filters are superior in terms of durability and heat resistance. . A filter cloth processed with metal fibers is also effective depending on the use temperature. A moving bed type dust remover may also be used. The place where dust is removed is preferably as close to the outlet as possible because the piping before dust removal becomes shorter.
[0069]
It is desirable to take out the exhaust gas outlet from a place where the temperature of the exhaust gas is high, and in the case of an incinerator with a waste heat boiler, it is effective to take out from the boiler section. In the boiler section, it is possible to extract high-temperature exhaust gas at 800 ° C. Further, by using such high temperature exhaust gas as a whole or a part of the high temperature gas and blowing it into the furnace, harmful substances contained in the exhaust gas can be effectively removed.
[0070]
As an example of the high-temperature air production apparatus, a pair of heat storage bodies are prepared, the first heat storage body is heated and stored with high-temperature exhaust gas from the combustion burner, and air is put into the second heat storage body that has already been heated and stored. The combustion gas of the combustion burner, recuperator, or combustion burner that generates high-temperature air by switching between heating of the heat storage body by the heat storage body and heating of the heat storage body by the high-temperature exhaust gas and heating of the air by the heat storage body Anything that mixes air can be used.
[0071]
When mixing high-temperature air from a high-temperature air production apparatus or a hot air furnace and circulating exhaust gas, it is preferable to mix them with an ejector apparatus and blow them into the furnace. That is, high-temperature air is guided to an ejector device, and this is used as a driving flow to mix while sucking circulating exhaust gas and blown into the furnace. In this way, an apparatus having a special movable part such as a fan for sucking the circulating exhaust gas is not necessary, so that the apparatus configuration is simplified and dust trouble can be reduced.
[0072]
The region into which the hot gas is blown is preferably lower than ½ of the height from the grate or fluidized bed of the main combustion chamber 3 to the furnace ceiling. In this way, since the flame holding effect appears by the high temperature gas blown from the nozzle immediately above the waste layer in the furnace, a high temperature region (flame) can be established immediately above the waste layer in the furnace. Therefore, the waste is efficiently decomposed and the high temperature region is far from the ceiling, so that the degree of burning of the ceiling can be reduced.
[0073]
In the above embodiment, the example which injected hot gas so that a stagnation area | region and a turning area | region in a furnace may be formed was shown. The fact that this is preferable for the stability of combustion is as described in the specification of the invention of the prior application, but in the present invention, the purpose is to stabilize the combustion from the combustion start region to the main combustion region. Therefore, it is not always necessary to blow in the high temperature gas so as to form the stagnation region and the swirl region.
[0074]
In FIG. 4, the outline | summary of the waste gas circulation system in the waste incinerator which is an example of embodiment of this invention is shown. As shown in FIG. 2, the exhaust gas from the main combustion chamber 1 is guided to the waste heat boiler 11, and after secondary combustion in the secondary combustion chamber 12, which is a part of the exhaust gas, heat exchange is performed in the waste heat boiler 11. It is purified by the exhaust gas treatment facility 22 and diffused from the chimney 23 to the atmosphere.
[0075]
In this embodiment, the exhaust gas is sucked from the upstream side of the exhaust gas treatment facility 22 by the blower 24 and guided to the gas mixing device 25. A high-temperature combustion gas such as a burner combustion gas is introduced into the gas mixing device 25 through a high-temperature combustion gas control valve 26, and dilution air is introduced through a dilution air control valve 27.
[0076]
The gas mixing device 25 mixes exhaust gas, high-temperature combustion gas, and diluted air to generate high-temperature gas. This hot gas is blown into the main combustion chamber 1. The oxygen concentration in the high temperature gas is adjusted by an oxygen concentration adjusting device 29. The oxygen concentration adjusting device 29 adjusts the opening degree of the dilution air adjusting valve 27 so that the oxygen concentration in the high-temperature gas becomes a predetermined concentration. Further, the temperature of the hot gas is adjusted by the temperature adjusting device 28. The temperature adjustment device 28 adjusts the opening degree of the high-temperature combustion gas adjustment valve 26 so that the temperature of the high-temperature gas falls within the range indicated by the equation (1).
[0077]
In this example, since exhaust gas is taken out from the upstream of the exhaust gas treatment facility 22, exhaust gas having a high temperature can be used. However, since the exhaust gas contains dust and has the above-mentioned problems, a dust removing device 30 is provided in the pipe leading to the blower 24, and the exhaust gas purified by removing dust is sent to the blower 24. Yes.
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.
[0078]
Thus, in this embodiment, since it has a function of adjusting the oxygen concentration and temperature in the hot gas blown into the main combustion chamber, the oxygen concentration and temperature in the hot gas blown into the main combustion chamber. Can be kept within an appropriate range. In order to adjust the flow rate and flow rate of the hot gas to be blown, the rotational speed of the blower 24 may be adjusted.
[0079]
FIG. 5 shows a modification of the exhaust gas circulation system shown in FIG. This example is different from the example shown in FIG. 4 in that the place where the exhaust gas is taken out is in the waste heat boiler 11, and the overall function is the same. In this case, higher temperature exhaust gas can be used.
[0080]
In the example shown in FIG. 4 and FIG. 5, an example is shown in which high-temperature combustion gas such as burner combustion gas and dilution air are mixed with circulating exhaust gas. Instead of the high-temperature combustion gas, it can be led to a gas combustion apparatus. In this case, instead of adjusting the dilution air by introducing it into the gas mixing device, the oxygen concentration of the high temperature gas may be adjusted by adjusting the amount of air introduced into the high temperature air production device.
[0081]
【The invention's effect】
As described above, according to the present invention, in a method for operating a waste incinerator that blows high-temperature gas into a combustion chamber, particularly in a low-air ratio combustion operation method, the preferred properties and temperature of the blown high-temperature gas are provided, and A preferred blowing method can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the temperature of a hot gas blown into a furnace and the oxygen concentration.
FIG. 2 is a diagram showing an example of a waste incinerator to which an embodiment of the present invention is applied.
FIG. 3 is a diagram showing a partial cross section of FIG. 2;
FIG. 4 is a diagram showing an outline of an exhaust gas circulation system in a waste incinerator as an example of an embodiment of the present invention.
FIG. 5 is a diagram showing an outline of an exhaust gas circulation system in a waste incinerator as an example of an embodiment of the present invention.
FIG. 6 is a schematic diagram showing an example of a conventional waste incinerator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Main combustion chamber, 2 ... Hopper, 3 ... Waste ... 4 ... Dry stoker, 5 ... Combustion stoker, 6 ... Post combustion stoker, 7 ... Main ash chute, 8 ... Wind box, 9 ... Main flue, 10 ...... Sub flue, 11 ... waste heat boiler, 12 ... secondary combustion chamber, 13 ... intermediate ceiling, 14 ... nozzle, 15 ... stagnation area, 17 ... furnace wall, 18 ... furnace ceiling, 19 ... hot gas (flow), DESCRIPTION OF SYMBOLS 20 ... Swirling flow part (swivel area | region), 21 ... Unburned gas, 22 ... Exhaust gas treatment equipment, 23 ... Chimney, 24 ... Blower, 25 ... Gas mixing apparatus, 26 ... High-temperature combustion gas control valve, 27 ... Dilution air control valve 28 ... Temperature control device, 29 ... Oxygen concentration control device

Claims (9)

In a waste incinerator, a low air ratio combustion operation is performed in which the air ratio obtained by dividing the actual air volume by the theoretical air volume required for combustion of waste is lower than 1.7, and high-temperature gas is introduced into the combustion chamber of the waste incinerator. A method for operating a waste incinerator to be blown, wherein the high-temperature gas contains at least one of carbon dioxide and water vapor, and oxygen, and has a temperature [° C.] T of 200 or more and is included in the high-temperature gas. The oxygen concentration [ vol. %] C is in the range represented by the following formula (1), and the high-temperature gas generates CO due to unstable combustion of unburned gas in the furnace. In order not to increase the amount, the lower limit of the amount of oxygen and the temperature is determined based on the formula (1), the combustion becomes high-temperature combustion, excessively promotes the thermal decomposition and gasification of waste, and causes local combustion of unburned gas Oxygen based on the formula (1) so as not to increase the amount of NOx generated The upper limit of the temperature is determined, and the oxygen concentration and temperature range of the high temperature gas is increased by blowing in the high temperature gas to promote thermal decomposition of the waste and form a stagnation region in the space on the waste. is standing the stable flame, waste method of operating an incinerator you being a range determined as to uniform and stabilize the burning to suppress the generation of CO and NOx in waste.
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) ... (1)   2. The method for operating a waste incinerator according to claim 1, wherein the hot gas blowing place / region is a space where the temperature of the blowing place is 400 [° C.] or more and unburned components exist. How to operate a waste incinerator.   The method for operating a waste incinerator according to claim 1 or 2, wherein a hot gas blowing location / region is from a combustion start region to a main combustion region. Operation method.   The waste incinerator operation method according to any one of claims 1 to 3, wherein the amount of hot gas blown is 10% to 70% of the amount of primary air. How to operate a waste incinerator.   4. The method for operating a waste incinerator according to any one of claims 1 to 3, wherein the amount of hot gas blown is 10% to 70% of the theoretical air amount for burning the waste. A method for operating a waste incinerator. It is an operating method of the waste incinerator of any one of Claims 1-5, Comprising: From the height position where the blowing direction of high temperature gas does not exceed 1/2 of the main combustion chamber height A method for operating a waste incinerator, wherein the blowing direction is 20 ° downward from the horizontal .   The method for operating a waste incinerator according to any one of claims 1 to 6, wherein hot gas is blown as a swirl flow.   The operation method of a waste incinerator according to any one of claims 1 to 7 in a waste incinerator having a waste heat boiler, wherein the high-temperature gas is in a waste heat boiler or a waste heat boiler. A method for operating a waste incinerator comprising gas derived from the outlet of the waste.   The waste incinerator operating method according to any one of claims 1 to 7 in a waste incinerator having an exhaust gas treatment facility, wherein the high-temperature gas is derived from upstream of the exhaust gas treatment facility. A method for operating a waste incinerator characterized by containing a gas having a temperature of 800 ° C or lower.

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