WO2003093728A1

WO2003093728A1 - Method of operating waste incinerator and waste incinerator

Info

Publication number: WO2003093728A1
Application number: PCT/JP2003/002623
Authority: WO
Inventors: Minoru Suzuki; Teruo Tatefuku; Satoshi Matsui; Takashi Noto; Masaaki Nishino
Original assignee: Jfe Engineering Corporation
Priority date: 2002-05-02
Filing date: 2003-03-06
Publication date: 2003-11-13
Also published as: EP1500875A1; KR100660757B1; EP1500875A4; KR20040102200A

Abstract

A method of operating a waste incinerator, comprising a step of blowing a high-temperature gas of 200ºC or higher whose temperature, TºC, satisfies exp(7.78-0.18C) ≤ T ≤ exp(7.45-0.11C) in a combustion chamber of waste incinerator, or the like. In the formula, C represents the oxygen concentration (vol.%) of high-temperature gas. This method enables satisfactorily reducing the amount of toxic substances, such as NOx and CO, while performing combustion of low air ratio in a waste incinerator.

Description

TECHNICAL FIELD The present invention relates to a method for operating a waste incinerator for incinerating waste such as general waste, industrial waste, and sewage sludge, and a method for operating this waste incinerator. It relates to a waste incinerator suitable for implementation. BACKGROUND ART Grate or fluidized bed waste incinerators are widely used as incinerators for incinerating waste such as municipal solid waste. Figure 1 shows a typical example. The waste 32 put into the hopper 31 is sent to a drying strike 33 through a chute, dried by air from below and radiant heat in the furnace, and heated to ignite. The refuse 32 that has ignited and started burning is sent to a combustion stove 34 where it is pyrolyzed and gasified by combustion air sent from below, and part of it is burned. In addition, the unburned components in the waste are completely burned by the post-combustion force of 35. The ash remaining after the combustion is taken out of the main ash chute 36.

The combustion takes place in the combustion chamber 37, and the generated combustion gas is discharged separately to the main flue 39 and the secondary flue 40 due to the presence of the intermediate ceiling 38. Exhaust gas passing through the main flue 39 contains little flammable gas and contains about 10 or more oxygen. The flue gas passing through the secondary flue 40 contains about 8 combustible gases. These gases are mixed in the secondary combustion chamber 41, secondary combustion is performed, and the combustible gas power is completely burned. The exhaust gas from the secondary combustion chamber 41 is sent to a waste heat poiler 43, and after being subjected to heat exchange, is discharged outside through a cooling tower, a bag filter and the like.

When incinerating waste in such a grate or fluidized bed waste incinerator, the combustion state in the furnace is constant 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 combustion chamber 37 become non-uniform temporally and spatially.

As a method for solving such a problem, Japanese Patent Application Laid-Open No. 11-211044 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.

Also, Japanese Patent Application Laid-Open No. 11-223323 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. -All of these technologies are aimed at reducing flammable gases and harmful substances containing large amounts of CO and aromatic carbon in exhaust gas generated in incinerators.

However, in the technology disclosed in Japanese Patent Application Laid-Open No. 11-211044, since the oxygen concentration in the high-temperature gas is 0 or more, when such high-temperature gas is blown into the incinerator, it suddenly Combustion may progress and a local high-temperature region may be formed. When local high-temperature regions are formed, for example, the amount of NOX, a harmful substance, increases.

In addition, in the technology described in Japanese Patent Application Laid-Open No. H11-223323, in addition to the above-mentioned problems, since oxygen-containing gas is blown into the combustion chamber at a temperature of 800 ° C or more, thermal decomposition of waste The oxidation reaction is promoted, and in some cases, CO may be generated.

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 with an incinerator such as a grate incinerator. is there. On the other hand, in the conventional waste incinerator, the ratio (air ratio) obtained by dividing the actual air amount by the theoretical air amount required for waste combustion is about 1.7 to 2.0. This is larger than the air ratio required for normal combustion: 1.05-: L.2. The reason for this is that the waste has a large amount of non-combustible and non-homogeneous materials, so 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 compared to a normal combustion furnace.

If the air ratio is reduced, the amount of exhaust gas will be reduced, and the exhaust gas treatment equipment will be compact, As a result, the entire waste incineration facility can be reduced in size and equipment costs can be reduced. Also, the amount of chemicals used for exhaust gas treatment can be reduced, so that operating costs can be reduced. Furthermore, since the amount of heat lost due to heat recovery cannot be reduced, the heat recovery rate of the waste heat poiler can be improved, and the power generation efficiency of waste power generation can be increased accordingly.

Thus, although the advantages for low air ratio combustion are great, combustion becomes unstable in low air ratio combustion. In other words, with conventional combustion technology, burning at a low air ratio results in unstable combustion, resulting in an increase in CO generation, a local increase in the flame temperature, a sudden increase in NOX, and a large amount of soot The temperature of the refractory of the furnace is shortened due to dripping, clinking, and local high temperatures. DISCLOSURE OF THE INVENTION The present invention relates to a method of operating a waste incinerator in which high-temperature gas is blown into a combustion chamber, particularly an operation method capable of sufficiently reducing harmful substances such as ΝΟΧ and CO while performing low air ratio combustion, and an operation method thereof. The purpose is to provide a waste incinerator suitable for performing. This object is achieved by the following methods of operating a waste incinerator i) to: Lv). i) A method for operating a waste incinerator having a process of injecting a high-temperature gas having a temperature T [° C] of 200 ° C or more and satisfying the following equation (1) into a combustion chamber of the waste incinerator.

exp (7.78-0.18C) ≤T≤exp (7.45-0.11C) "-(l)

ii) High-temperature gas containing at least one of carbon dioxide and water vapor and oxygen and having a temperature of 200 ° C or more and satisfying the following equation (2) is burned by a waste incinerator. A method of operating a waste incinerator that has a process of blowing it into the room.

exp (8.05-0.23C) ≤T≤exp (7.40-0.09C) '-(2)

iii) A method for operating a waste incinerator having a process of injecting a high-temperature gas having a temperature T [° C] lower than 200 ° C and satisfying the following equation ( ³ ) into the combustion chamber of the waste incinerator.

exp (7.78-0.18C) ≤T-"(3)

iv) containing at least one of carbon dioxide and water vapor and oxygen, at a temperature of less than 200 ° C. A method for operating a waste incinerator comprising a step of injecting a high-temperature gas having a temperature T [° C] satisfying the following expression (4) into the combustion chamber of the waste incinerator.

exp (8 .05-0. 23C) ≤T- "(4)

Here, C in the equations (1) to (4) represents the oxygen concentration (vol.%) In the high-temperature gas. In addition, such a method of operating a waste incinerator has an exhaust gas circulating device that circulates and blows exhaust gas into the furnace, and the exhaust gas circulating device vigorously mixes air with the exhaust gas to adjust the properties of the high-temperature gas. This can be achieved by a grate-type or fluidized-bed type waste incinerator equipped with a device for adjusting the oxygen concentration and temperature in the high-temperature gas blown from the combustion start zone in the furnace to the main combustion zone. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a conventional waste incinerator.

FIG. 2 is a diagram showing the relationship between the temperature of the high-temperature gas blown into the furnace and the oxygen concentration.

FIG. 3 is a diagram showing one example of the waste incinerator of the present invention.

FIG. 4 is a diagram showing a partial cross section of FIG.

FIG. 5 is a diagram showing an example of an exhaust gas circulation system in the waste incinerator of the present invention. FIG. 6 is a diagram showing another example of the exhaust gas circulation system in the waste incinerator of the present invention. FIG. 7 is a diagram showing the relationship between the temperature of the high-temperature gas blown into the furnace and the oxygen concentration.

FIG. 8 is a diagram showing the relationship between the temperature of the high-temperature gas blown into the furnace and the oxygen concentration.

FIG. 9 is a diagram showing the relationship between the temperature of the high-temperature gas blown into the furnace and the oxygen concentration. BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

The inventors investigated the relationship between the CO and NOx generated in the combustion chamber, the oxygen concentration in the high-temperature gas blown into the combustion chamber, and the temperature of the high-temperature gas in the waste incinerator. That As a result, as shown in Fig. 2, if the oxygen concentration in the hot gas and the temperature of the hot gas are controlled in the region surrounded by the A, B, and C lines, CO and NOx in the exhaust gas can be reduced at the same time. I found what I could do.

Assuming that the temperature of the hot gas at the time of injection into the furnace is T [] and the oxygen concentration in the hot gas is C [vol.], Line A is T-exp (7.78-0.18C), B The line can be expressed as T = exp (7.45-0.1C), and the C line can be expressed as T = 200.

By blowing high-temperature gas with oxygen concentration and temperature in the area surrounded by the Α-line, B-line, and C-line into the combustion chamber, it is heated by the heat radiation from the high-temperature gas and sensible heat to thermally decompose waste. To promote. A stagnation area where flammable gas and combustion air stagnate in the space above the waste can stabilize a stable flame. Furthermore, since the mixing of the combustible gas and the combustion air is promoted, uniform and stable combustion is promoted, so that the generation of NOx and CO can be significantly reduced.

In the region below the line A, the amount of oxygen is insufficient, and the temperature of the gas to be injected is low, so that the combustion of flammable gas becomes unstable, and as a result, the generation of CO increases.

In the region above the B line, high-temperature combustion occurs, and as a result, the thermal decomposition of wastes and the gas reaction are excessively promoted, and the flammable gas burns locally, resulting in an increase in NOX.

In the region below the line C, even if the gas is blown, the effect of entraining and stirring the surrounding gas is small, so that the gas is not sufficiently mixed. As a result, local high-temperature regions occur, and NOX increases.

For example, when the oxygen concentration in the hot gas is 12, the temperature of the hot gas that achieves both low NOx and low CO is in the range of 280-500. 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 330 ° C. In the combustion chamber, the space where 400 or more and flammable gas exists is the area where the thermal decomposition of waste is promoted or the area where the thermal decomposition of waste is completed. This is the area where gas is generated and the cap flame exists. For example, thermal decomposition of paper waste starts at about 250 ° C and completes at about 400 ° C. Pyrolysis of plastic waste begins at about 400 and is completed at about 500 ° C. high temperature Even if gas is blown into an area where thermal decomposition of waste does not start and only drying is performed, the effect of promoting low NOx and low CO in exhaust gas is small. Therefore, it is preferable that the blowing region of the high-temperature gas is 400 ° C. or more, and the space is where the flammable gas exists. As described above, high-temperature gas is preferably injected into the area where a large amount of flammable gas is present. From the combustion start area to the main combustion area. Here, the combustion start region is a region in which combustible gas is generated by thermal decomposition or partial oxidation of the waste, and combustion of the waste starts. The main combustion area is the area in which waste is thermally decomposed, partially oxidized and burned, generates flammable gas, and burns with a flame, and the combustion with the flame is completed. This is the area up to the point (burnout point). Therefore, it is preferable to set the high-temperature gas blowing region from the combustion start region to the main combustion region. In a grate incinerator, the combustion start area is the space above the dry grate, and the main combustion area is the space above the combustion grate.

In general, the primary air is the combustion air blown from the wind box below the grate in the case of a grate furnace, or the air box below the fluidized bed in the case of a fluidized bed furnace. In the present invention, it is preferable that the amount of high-temperature gas blown be 10 to 70% of the amount of primary air for the following reasons. If the amount of high-temperature gas injected is less than 10 times the amount of primary air, the momentum required for stirring the gas in the furnace is not provided, and the effect of high-temperature gas injection may not be fully exerted. If the amount of high-temperature gas blown exceeds 70, which is the primary air flow, the effect of low NOx and low CO2 emissions in exhaust gas will be saturated, and not only will there be no point in increasing the amount of high-temperature gas blown, but also unnecessarily. Increase the amount of exhaust gas, which leads to an increase in exhaust gas treatment equipment. If the amount of primary air used as the reference value for the amount of hot gas blown is less than the theoretical amount of air required for complete combustion of waste, the amount of hot gas blown and the theory of burning waste Preferably, the air volume is 10 to 70. The theoretical air volume is determined based on the nature of the waste.

Combustible gases generated from waste usually flow upward. Therefore, when the hot gas is injected in the upward direction, the flow of the combustible gas and the flow of the hot gas have the same velocity component in the same direction, and the effect of stirring and the effect of retaining the flow of the combustible gas are small. Summer Thus, the effect of hot gas injection is reduced. On the other hand, if the blowing direction of the high-temperature gas is horizontal or downward, the rising flammable gas and high-temperature gas are well stirred, and the flow of the flammable gas can be retained. The blowing effect can be further enhanced.

By blowing high-temperature gas as a swirling flow, the stirring effect can be enhanced, and the blowing effect of high-temperature gas can be further enhanced. Here, “injecting the hot gas as a swirl flow” means that the hot gas itself flowing out of the outlet is a swirl flow or the flow of the hot gas flowing out of a plurality of outlets is a composite. Including swirling flow. The above-described method for operating a waste incinerator according to the present invention includes an exhaust gas circulating device that circulates exhaust gas into the furnace and blows the exhaust gas into the furnace. Grate or fluidized bed waste incinerator equipped with a device that adjusts the properties of oxygen and adjusts the oxygen concentration and temperature in the high-temperature gas blown from the combustion start zone in the furnace to the main combustion zone. Therefore, it can be easily realized.

In this waste incinerator, if a nozzle for blowing high-temperature gas into the furnace is provided at a position that does not exceed 1/2 of the height of the combustion chamber, the high-temperature gas blown from the nozzle just above the waste layer in the furnace Since the gas forms a stagnation zone, the flame can be kept just above the waste layer in the furnace. Therefore, the thermal decomposition of waste is more efficiently performed, and the high-temperature area is further away from the ceiling, thereby reducing ceiling burning. The “combustion chamber height” is the height of the space in which the main combustion takes place, and refers to the height from the grate or fluidized bed to the furnace ceiling or the position where the secondary combustion air is blown.

FIG. 3 shows an example of the waste incinerator of the present invention.

On one side of the combustion chamber 1 (on the left side in FIG. 3), a hopper 2 for charging the waste 3 into the combustion chamber 1 is provided. At the bottom of the combustion chamber 1, a grate (storage force) for burning the waste 3 while moving the waste 3 is provided so as to be inclined downward as the distance from the hopper 2 increases. This grate has two steps and is divided into three parts. These three grate, from the side closer to the hopper 2, the dry strike 4, the combustion strike 5, and after It is called the combustion strike power 6. In drying strike 4, drying and ignition of waste 3 are mainly performed. In combustion strike 5, waste 3 is mainly burned, but waste 3 is burned and thermally decomposed, and combustible gas is released together with the combustion gas. The combustion of the waste 3 is substantially completed in the combustion strike 5. On the post-combustion strike 6, the unburned part of the slightly remaining waste 3 is completely burned. The combustion residue after complete combustion is discharged from the main ash chute 7.

At the bottom of each grate, there is provided a wind box 8 connected to a supply pipe for supplying combustion air.

Below and above the combustion chamber 1 on the opposite side of the hopper 2, a main flue 9 and a secondary flue 10 are provided. These include a waste heat boiler that is part of the gas cooling system; A combustion chamber 12 is provided connected. In the combustion chamber 1, a barrier (intermediate ceiling) 13 for dividing the combustion gas is provided near the exit of the combustion chamber 1, and the flow of the combustion gas is divided into a main flue 9 and a sub-flue 10. Shedding.

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 supply pipes and the wind box 8, and the waste 3 is dried. Burn.

A nozzle 14 is provided on the side wall of the combustion chamber 1, and a high-temperature gas at a temperature of 200 ° C. or more and satisfying the above formula (1) is blown into the combustion chamber 1 from the nozzle 14. The nozzle 14 is installed at the upper part of the drying stove 4 and at the upper left of the combustion stove 5. When waste 3 is incinerated, first, water evaporates, followed by thermal decomposition and partial oxidation. Here, the thermal decomposition reaction occurs at a temperature of about 200, and is almost completed when the temperature reaches about 400 ° C. Nozzles 14 are provided at the part of the drying stove 4 (the latter part) and the former part of the combustion stove 5 to blow hot gas. Depending on the type of waste 3, the pyrolysis reaction can be completed at a higher temperature. In this case, a nozzle 14 may be provided downstream (right side in the figure) from the position shown in FIG. preferable.

As described above, the nozzle 14 is preferably provided at a height not exceeding 1/2 of the height of the combustion chamber.

In addition, as described above, in a space where the temperature is 400 ° C or more and flammable gas exists, By injecting high-temperature gas, combustion of combustible gas can be promoted. Accordingly, the hot gas is blown into the area where the secondary flue gas containing a large amount of combustible 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. May be provided at the side wall, ceiling, intermediate ceiling 13, and entrance to the secondary combustion chamber 12.

The amount of high-temperature gas blown should be as small as possible in consideration of exhaust gas treatment. However, if the injection amount is small, CO is likely to be generated, and complete combustion cannot be achieved. For this reason, as described above, it is preferable that the amount of primary air blown from the wind box 8 be 10 to 70 times. As a result, the generation of CO can be suppressed to an acceptable level. Therefore, it is preferable to control the amount of CO and NOX emitted while adjusting the amount of air blown within the range of 10 to 70 times the amount of primary air. In particular, depending on the type of waste 3, the amount of primary air injected may be less than the theoretical amount of air required to burn waste 3, in which case a large amount of hot gas is injected. However, it is preferable to promote complete combustion of the waste 3 and prevent the generation of CO. If it is known that the amount of primary air to be injected is small, as mentioned above, the amount of hot gas to be injected should be in the range of 10 to 70% of the theoretical air amount required to burn waste 3. You may make it become.

When the nozzle 14 is provided horizontally or downward, the flow of the flammable gas in which the high-temperature gas ejected from the nozzle rises can be retained, and the combustion of the flammable gas can be promoted. In order to promote the stagnation effect, it is preferable to set the nozzle downward.However, if the angle is too large, the high-temperature gas will not reach the entire furnace width direction. It is particularly preferred to do so.

4, to show the arrangement of the nozzles in FIG. 3, A- A 'cross-sectional view (horizontal cross-section: Figure 4A, Figure 4B), BB' of FIG. 3 a cross-sectional view (vertical cross-section: Figure ⁴ C) shows a. In FIG. ⁴ , structures not related to the present invention are omitted.

In FIG. 4A, high-temperature gas 19 is ejected from a pair of nozzles 14 provided in the width direction of the furnace wall 17 and collides with each other at the center of the furnace. Therefore, the movement of the gas in the furnace is slow and a stagnant stagnation region 15 is formed at the center of the furnace, so that combustion is stably performed. FIG. 4B shows another example, in which the nozzles 14 are oriented such that their central axes are parallel to each other. The hot gases 19 are separated by a predetermined distance at the center of the furnace and pass each other at a predetermined distance. Therefore, a swirl zone 20 is formed in the center of the furnace.

In such an example, a stagnation region 15 or a swirl region 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.

In FIG. 4A, the size of the stagnation region 15 can be controlled by changing the flow velocity of the hot gas ejected from the two nozzles 14 in the same manner. Further, by providing a difference in the flow velocity of the high-temperature gas ejected from both nozzles 14, the position of the furnace in the stagnation region 15 in the left-right direction can be changed. Further, by changing the direction of the nozzle 14 in the same direction as the furnace length direction, the position of the stagnation region 15 in the furnace length direction can be changed.

In FIG. 4B, by changing the interval between the two nozzles 14, the size of the swirl area 20 can be changed. Further, by providing a speed difference between the two high-temperature gases 19, it is possible to change the position in the width direction of the furnace where the swirling region 20 is formed. Further, by changing the speed of the two hot gases 19 in the same manner, the speed of the swirling flow can be changed.

In FIG.4C, the vertical cross section of the furnace is shown, but the hot gas 19 blown out from the nozzles 14 provided downward on the furnace walls 17 on both sides collides with the rising combustible gas 21 to form a stagnation region 15. Is shown. In the stagnation region 15, stable combustion is performed as a result of stable combustion. As a result, unlike the prior art, even in the low air ratio combustion, the combustion instability in the combustion start region is not amplified, soot generation is suppressed, and uniform and stable combustion can be expected.

In order to exert a stirring action, it is also effective to blow high-humidity gas into the furnace from the nozzle 14 as a swirling flow.

Further, since blowing the high-temperature gas to sufficiently stir the gas near the furnace side wall also has the effect of stabilizing the combustion, it is preferable to set the blowing speed to at least 10 m / s〗 or more. The flame in the furnace when the high-temperature gas is not blown is a bright flame, but when the high-temperature gas is blown into the furnace properly as described above, the flame in the furnace becomes a transparent flame, and the furnace wall Strike). This is considered to be due to the slow burning of combustible f raw gas due to the injection of high-temperature gas. Therefore, it is also possible to observe the transparency of the flame in the furnace and use it as a criterion for determining whether or not the high-temperature gas is properly blown.

The above embodiment is effective in reducing trace harmful substances such as CO, NOx, and dioxin.

Although FIG. 3 shows a furnace having an intermediate ceiling 13, it goes without saying that the present invention can be applied to a furnace without such an intermediate ceiling. Although high-temperature gas is blown into the combustion chamber 1, high-temperature gas may be blown into the secondary combustion chamber 12. Further, the hot gas may be blown from one side of the furnace. It can also be blown from the middle ceiling or ceiling, rather than from the side of the furnace.

As the high-temperature gas ejected from the nozzle 14, a mixed gas of circulating exhaust gas and air is appropriate. Recirculated exhaust gas is a part of the exhaust gas discharged from a waste incinerator, and returning it to the combustion chamber has the effect of reducing harmful substances and reducing the amount of exhaust gas.

If the circulating exhaust gas satisfies the conditions of the high-temperature gas of the present invention, it may be blown into the furnace as it is, but if the temperature is lower than 200 ° C and the oxygen concentration is low, a high-temperature air production device or hot air High-temperature air is produced by the furnace, mixed with the circulating exhaust gas, and blown into the furnace as a high-temperature gas satisfying the conditions of the present invention.

If the temperature of the exhaust gas from the secondary combustion chamber 12 is sufficiently high and the oxygen concentration is high, it is used as a substitute for high-temperature air without using a high-temperature air production device, and is mixed with air. You can also blow it. 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 above equation (1), the exhaust gas is directly injected into the furnace. You may blow it.

When exhaust gas generated from an incinerator is used, in whole or in part, as high-temperature gas, the sodium salt or hot-water salt contained in the dust contained in the exhaust gas adheres to the pipe wall of the piping, causing corrosion. Otherwise, the piping may be blocked or the piping may be blocked. Also, das If the dust is blown into the furnace without removing it, there is a risk that the concentration of harmful substances emitted may increase due to harmful substances (eg dioxin) contained in the dust. Therefore, it is preferable to remove dust in the exhaust gas. Well-known methods such as a filtration method and a cyclone method can be used for dust removal. There are two types of filter type, one using a filter cloth and the other using a ceramic filter.However, when the exhaust gas temperature is high, the ceramic type filter is more excellent in durability and heat resistance. ing. Filter cloth processed with metal fibers is also effective depending on the operating temperature. In addition, a moving bed type dust remover can be used. The place where dust is removed is preferably as close as possible to the outlet because the piping before dust removal becomes shorter.

It is desirable to take out the exhaust gas from a place where the temperature of the exhaust gas is high. In the case of an incinerator with a waste heat poiler, it is effective to take it out of the poiler. In the boiler section, it is possible to extract high-temperature exhaust gas at 800 ° C. Further, such high-temperature exhaust gas can effectively remove harmful substances contained therein.

As the high-temperature air producing apparatus, a heat storage burner, an apparatus for mixing air or oxygen with a combustion gas from a combustion burner of a hot air stove, a recuperator, or the like can be used. The heat storage burner prepares a pair of heat storage bodies, heats the first heat storage body with the high-temperature exhaust gas from the combustion parner, heats the second heat storage body that has already been heated and stored, and heats it. This is a device that can switch between heating of the heat storage element by high-temperature exhaust gas and heating of air by the heat storage element.

When mixing the high-temperature air from the high-temperature air producing apparatus with the circulating exhaust gas, it is preferable that the high-temperature air is mixed by an ejector and blown into the furnace. In other words, if high-temperature air is guided to the ejector unit and used as a driving flow to mix and suck the circulating exhaust gas and blow it into the furnace, special moving parts such as fans for sucking the circulating exhaust gas can be used. Since no equipment is required, the device configuration is simplified and dust troubles are reduced.

Table 1 shows the properties of the high-temperature gas (oxygen concentration and temperature) blown into the furnace when the high-temperature gas is adjusted by mixing the burner combustion gas, dilution air, and circulating exhaust gas of the hot-blast furnace and blowing into the furnace. The following shows the correspondence between operating factors and operating methods for improving the properties of the high-temperature gas blown into the furnace when it deviates from the scope of the present invention. For example, the oxygen concentration is within the scope of the present invention. If the temperature is lower and the temperature is lower than the range of the present invention, the combustion amount of the combustion burner is increased to increase the temperature of the high-temperature gas to be blown, the exhaust gas circulation amount is reduced, and the dilution air amount (high-temperature gas Is increased so as to be within the scope of the present invention. When the oxygen concentration is lower than the range of the present invention and the temperature is higher than the range of the present invention, the oxygen concentration is increased by increasing only the dilution air amount. ·

As described above, the example in which the high-temperature gas is blown so as to form the stagnation region and the swirl region in the furnace has been described. As described in the prior art, it is preferable that the above-described method be performed in order to stabilize combustion. However, in the present invention, for the purpose of stabilizing combustion in the main combustion region from the combustion start region. Therefore, if the temperature and oxygen concentration of the high-temperature gas are within the range of the present invention, it is not always necessary to blow the high-temperature gas so as to form a stagnation region and a swirl region. FIG. 5 shows an example of an exhaust gas circulation system in the waste incinerator of the present invention.

As shown in detail in Fig. 2, the exhaust gas from the combustion chamber 1 is guided to the waste heat poirer 11, where it is subjected to secondary combustion in the secondary combustion chamber 12, which is a part of the exhaust heat. The waste gas is cleaned by the exhaust gas treatment equipment 22 and released to the atmosphere from the chimney 23.

At this time, a part of the exhaust gas is sucked from the downstream side of the exhaust gas treatment facility by the blower 24 and guided to the gas mixing device 25. A high-temperature combustion gas such as a burner gas is introduced into the gas mixing device 25 through a high-temperature combustion gas control valve 26, and the dilution air is diluted. Introduced via air control valve 27. Then, in the gas mixing device 25, the exhaust gas, the high-temperature combustion gas, and the dilution air are mixed to adjust the high-temperature gas. This high-temperature gas is blown into the combustion chamber 1. The oxygen concentration in the high-temperature gas is adjusted by the oxygen concentration adjusting device 29. In the oxygen concentration adjusting device 29, the opening degree of the dilution air adjusting valve 27 is adjusted so that the oxygen concentration in the high-temperature gas becomes a predetermined concentration. Further, the temperature of the high-temperature gas is adjusted by the temperature adjusting device 28. In the temperature control device 28, the opening degree of the high-temperature combustion gas control valve 26 is adjusted so that the temperature of the high-temperature gas falls within the range represented by the above equation (1). -As described above, the function of adjusting the oxygen concentration and temperature in the hot gas blown into the combustion chamber can be maintained in an appropriate range. When it is desired to adjust the flow rate and flow velocity of the high-temperature gas to be blown, the rotational speed of the blower 24 may be adjusted.

FIG. 6 shows another example of the exhaust gas circulation system shown in FIG. This example differs from the example shown in FIG. 5 only in that the place where the exhaust gas is taken out is the outlet of the waste heat boiler 11.

In the example of FIG. 5, the exhaust gas is taken out from the rear of the exhaust gas treatment equipment 22, so that the dust in the exhaust gas has been removed and the exhaust gas is clean. However, the temperature of the exhaust gas is decreasing.

On the other hand, in the example of FIG. 6, since the exhaust gas is taken out from the outlet of the waste heat poiler 11, the temperature of the exhaust gas is high. However, since the exhaust gas contains dust, the exhaust gas is sent to the blower 24 after the dust is removed by a dust remover 30 provided in a pipe leading to the blower 24.

In the case of FIG. 6, 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.

In the examples shown in FIGS. 5 and 6, the circulating exhaust gas is mixed with a high-temperature combustion gas such as a burner gas and diluted air, and the high-temperature air produced by the above-described high-temperature air production apparatus is mixed with the high-temperature combustion gas. Alternatively, it can be led to a gas combustion device. In this case, instead of introducing and adjusting the dilution air into the gas mixing device, the oxygen concentration of the high-temperature gas can be adjusted by adjusting the amount of air introduced into the high-temperature air production device. Embodiment 2

The present inventors have also proposed that as a method of operating a waste incinerator in which a high-temperature gas is blown into a combustion chamber, the high-temperature gas contains at least one of dioxide carbon and water vapor, such as NO _X and CO. It has been found to be effective in sufficiently reducing harmful substances. This is because the emissivity of carbon dioxide and water vapor is higher than that of nitrogen or oxygen, and waste and combustible gas generated from waste can be efficiently produced by heat radiation from high-temperature gas containing these gases. This is because the fuel is heated, and as a result, stable combustion is performed even when performing low air ratio combustion.

As in the first embodiment, co, which is generated when hot gas is blown into the combustion chamber,

When the relationship between NOx and the oxygen concentration in the high-temperature gas blown into the combustion chamber and the temperature of the high-temperature gas was investigated, as shown in Fig. 7, the oxygen concentration in the high-temperature gas and the temperature of the high- If the temperature is controlled in the area surrounded by the line and the line C, that is, if the temperature of the high-temperature gas is 200 ° C or more and the above equation (2) is satisfied, CO and NOX in the exhaust gas can be simultaneously measured. It became clear that it could be reduced. In FIG. 7, the line is = 63 £ (8.5-0.23C), the line B is T = exp (7.40-0.09C), and the line C is T = 200.

For example, when the oxygen concentration in the hot gas is 12, the temperature of the hot gas that achieves both low ΝΟχ 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.

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.

Like the first embodiment, the high-temperature gas blowing region is a space where the temperature is 400 ° C. or higher and a combustible gas is present, and it is preferable that the high-temperature gas blowing region be from the combustion start region to the main combustion region. '

In addition, if a waste incinerator with a waste heat poirer is used and the high-temperature gas contains gas discharged from the waste heat boiler or from the outlet of the waste heat boiler, the sensible heat in the exhaust gas is used effectively. And increase thermal efficiency.

In addition, using a waste incinerator with exhaust gas treatment equipment, If the gas containing 800 ° C or less derived from the upstream of the facility is included, the sensible heat in the exhaust gas can be effectively removed and the thermal efficiency can be increased as in the above case.

The operation method of the waste incinerator of the present invention can be realized by the waste incinerator shown in FIG. 3 described in the first embodiment. According to the method of the present invention, from the nozzle 14 provided on the side wall of the combustion chamber 1, at least one of carbon dioxide and water vapor and oxygen are contained, the temperature is 200 ° C. or more, and the above equation (2) is satisfied Except for the high-temperature gas being blown into the combustion chamber 1, what has been described in the first embodiment can be applied as it is. -Embodiment 3

In the first and second embodiments, the temperature of the high-temperature gas blown into the combustion chamber was 200 ° C. or higher. We found that there are conditions that can suppress the generation of CO and dioxin even when the content is less than C.

That is, when the waste contains biomass or wood chips, the temperature at which thermal decomposition starts is generally 100 ° C or higher, so even if the temperature is lower than 200 ° C, thermal decomposition occurs and flammable gas is generated. Therefore, if the temperature and oxygen concentration of the hot gas are optimized, the effect of reducing CO and dioxins can be expected. In this case, the effect of reducing NOX is smaller than when the temperature of the high-temperature gas is 200 or more, but NOx can be reduced by installing denitration equipment.

Fig. 8 shows the relationship between the temperature and the oxygen concentration of the high-temperature gas.By blowing the high-temperature gas with the oxygen concentration and temperature in the region surrounded by lines A, B, and C into the combustion chamber, If the temperature is less than 200 ° C and the above equation (3) is satisfied, it is possible to promote the thermal decomposition of the waste and to stably stabilize the flame on the waste layer. Obviously. At this time, the mixed combustion of the combustible gas is promoted, so that uniform and stable combustion is performed, and the generation of harmful substances such as CO and dioxin can be reduced. In Fig. 8, line A has T = exp (7.78-0.18C), line B has C = 21, and line C has T = 200.

The reason why the oxygen concentration is set to 21 or less is that an oxygen enrichment device is required to make oxygen larger than 21, which is not preferable.

Also, when the temperature of the high-temperature gas is lower than 200 ° C., as in Embodiment 2, Inclusion of at least one of carbon dioxide and water vapor in the hot gas is effective for suppressing the generation of CO and dioxin.

In this case, as shown in Fig. 9, the temperature and oxygen concentration of the hot gas are controlled in the region surrounded by the D, E, and F lines, that is, when the temperature of the hot gas is less than 200, It is necessary to satisfy equation (4). In Fig. 9, line 0 is = 62¾) (8.05-0.23, line E is C = 21, line F is T = 200. Note that even when the temperature of the above high-temperature gas is lower than 200 ° C, it is blown. Except for the condition of the high-temperature gas, the description in the first embodiment can be applied as it is.

Claims

The scope of the claims

1. The process of injecting a high-temperature gas at a temperature of 200 ° C or higher and a temperature T [:] satisfying the following equation (1) into the combustion chamber of a waste incinerator:

Operating method of waste incinerator having;

exp (7.78-0.18C) ≤T≤exp (7.45-0.11C)-"(l)

Here, C represents the oxygen concentration (vol.%) In the high-temperature gas. -

2. The method for operating a waste incinerator according to claim 1, wherein the high-temperature gas blowing region is a space where the temperature is 400 ° C or higher and flammable gas exists.

3. The method for operating a waste incinerator according to claim 1, wherein the high-temperature gas injection region extends from a combustion start region to a main combustion region.

4. The method for operating a waste incinerator according to claim 1, wherein the amount of high-temperature gas injected is 10 to 70 times the amount of primary air.

5. The method for operating a waste incinerator according to claim 1, wherein the amount of high-temperature gas injected is 10 to 70 times the theoretical amount of air for burning waste.

6. The method for operating a waste incinerator according to claim 1, wherein the hot gas is blown in a horizontal or downward direction.

7. The method for operating a waste incinerator according to claim 1, wherein high-temperature gas is injected as a swirling flow.

8. A high-temperature gas containing at least one of carbon dioxide and water vapor and oxygen and having a temperature of 200 t: or more and satisfying the following formula (2), T [° C〗] is introduced into the combustion chamber of the waste incinerator. Injecting process, Operating method of waste incinerator having;

exp (8.05-0.23C) ≤T≤exp (7.40-0.09C)-"(2)

Here, C represents the oxygen concentration (vol.%) In the high-temperature gas.

9. The method for operating a waste incinerator according to claim 8, wherein the high-temperature gas blowing region is a space where the temperature is 400 ° C or higher and a flammable gas exists.

10. The method for operating a waste incinerator according to claim ⁸ , wherein the high-temperature gas injection region is from a combustion start region to a main combustion region.

11. The method for operating a waste incinerator according to claim 8, wherein the waste incinerator having a waste heat poiler is used, and the high-temperature gas includes gas derived from the waste heat poiler or an outlet of the waste heat poiler.

12. The method for operating a waste incinerator according to claim 8, wherein the waste incinerator having an exhaust gas treatment facility is used, and the high-temperature gas includes a gas of 800t or less derived from the upstream of the exhaust gas treatment facility.

13. A process of injecting a high-temperature gas at a temperature T [° C] that is less than 200 ° C and satisfies the following equation (3) into a combustion chamber of a waste incinerator:

Operating method of waste incinerator having;

exp (7.78-0.18C) ≤T-"(3)

Here, C represents the oxygen concentration (vol.) In the high-temperature gas.

14. A high temperature gas containing at least one of carbon dioxide, water vapor and oxygen, having a temperature of less than 200 ° C. and satisfying the following formula (4) T [° C.] The process of blowing into the combustion chamber of

Operating method of waste incinerator having; exp (8.05-0.23C) ≤T— (4)

Here, C represents the oxygen concentration (vol.) In the hot gas.

15. Exhaust gas circulating equipment that circulates and blows exhaust gas into the furnace

Having, and said exhaust gas circulation equipment,

A grate equipped with a device that mixes air with the exhaust gas to adjust a high-temperature gas, and that controls the oxygen concentration and the temperature of the high-temperature gas blown from a combustion start region in the furnace to a main combustion region. Or fluidized bed waste incinerator.

16. The waste incinerator according to claim 15, which is provided at a position where the nozzle for injecting the high-temperature gas into the furnace does not exceed 1/2 of the height of the combustion chamber.