WO2004092648A1

WO2004092648A1 - Method of controlling combustion of waste incinerator and waste incinerator

Info

Publication number: WO2004092648A1
Application number: PCT/JP2004/005232
Authority: WO
Inventors: Minoru Suzuki; Teruo Tatefuku; Hiroshi Yamamoto; Masaaki Nishino; Yasuhiro Miyagoshi
Original assignee: Jfe Engineering Corporation
Priority date: 2003-04-18
Filing date: 2004-04-13
Publication date: 2004-10-28
Also published as: CN100467948C; KR100705204B1; JPWO2004092648A1; KR20060005352A; CN1777776A; JP4479655B2

Abstract

In a method of controlling combustion of a stoker waste incinerator, primary combustion air (A) is blown into a combustion chamber from below a stoker, and a high-temperature gas (B) is blown into a desired region between a combustion start region and a main combustion region. A circulation exhaust gas (C) including, as its part, at least an exhaust gas discharged from the incinerator is blown into above a blow-in position for the high temperature gas (B) or into the downstream side of a gas flow direction. An agitating gas (D) of air, the circulation exhaust gas or a mixed gas of air and the circulation exhaust gas is blown into a secondary combustion region.

Description

Specification

Grate type waste incinerator and its combustion control method

Technical field

The present invention relates to a grate-type waste incinerator for incinerating waste such as municipal waste, industrial waste, sewage sludge, and the like, and a grate-type method suitable for implementing such a combustion control method. Regarding incineration of waste.

Grate-type waste incinerators are widely used as incinerators for incinerating waste such as municipal solid waste. Figure 3 shows a schematic diagram of a typical example. The waste 32 input into the hopper 31 is sent to the drying grate 33 through the chute, dried by the air from below and the radiant heat in the furnace, and heated to ignite. The waste 32 that has ignited and started burning is sent to a combustion grate 34, where it is pyrolyzed and gasified by combustion air sent from below, and partly burns. Further, in the post-combustion grate 35, the unburned components in the waste are completely burned. The ash remaining after the combustion is taken out from the main ash chute 36.

The combustion is performed in the combustion chamber 37, the secondary combustion is performed in the secondary combustion chamber 41, and the combustible gas is completely burned. The exhaust gas from the secondary combustion chamber 41 is sent to the waste heat boiler 43, where it is subjected to heat exchange and then discharged outside via a cooling tower, a bagfill, and the like.

In such a grate-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. It is inevitable that the temperature and the distribution of the concentration of the combustion gas in the combustion chamber 37 become uneven in time and space.

As a method for solving such a problem, Japanese Patent Application Laid-Open No. 11-21044 (Patent Document 1) discloses a method in which a high-temperature gas generated by a regenerative parner is supplied to a main combustion chamber or a secondary combustion chamber of an incinerator. A method of injecting into the next combustion chamber is disclosed. This technology aims to reduce unburned gas and harmful substances containing a large amount of c 〇 and aromatic hydrocarbons in the exhaust gas generated in incinerators. It was done.

Also, Japanese Patent Application Laid-Open No. H11-2708029 (Patent Document 2) discloses that the CO concentration in the combustion exhaust gas generated in a refuse incinerator is determined by a preset value for dioxin reduction. so as to, CO value in the combustion exhaust gas, 0 ₂ values and based on the furnace temperature of the incinerator grate speed incinerator, a method of controlling the combustion air quantity and the furnace temperature cooling air amount is disclosed It has been.

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-211104

[Patent Document 2] Japanese Patent Application Laid-Open No. Hei 11-27078

Conventionally, in a waste incinerator, the ratio (air ratio) obtained by dividing the amount of air actually supplied to the furnace by the theoretical amount of air required for waste combustion (air ratio) is about 1.7 to 2.0. This is larger than the air ratio required for general fuel combustion, which is 1.05 to 1.2. The reason for this is that waste contains more non-combustibles and is inhomogeneous than other liquid or gaseous fuels, resulting in low air use efficiency and a large amount of air required for combustion. It is. However, as the air-to-air ratio increases, the amount of exhaust gas also increases, which requires larger exhaust gas treatment equipment.

If the air ratio is reduced, the amount of exhaust gas will be reduced, and the exhaust gas treatment facility will be compact. As a result, the entire waste incineration facility will be reduced in size and equipment costs will be reduced. In addition, 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 that cannot be recovered and is discarded into the atmosphere can be reduced, the heat recovery rate of the waste heat boiler can be improved, and the efficiency of waste power generation can be increased accordingly.

Thus, although the advantages for low air ratio combustion are great, there is a problem that combustion becomes unstable in low air ratio combustion. In other words, when combustion is performed at a low air ratio, combustion becomes unstable, CO emission increases, the flame temperature increases locally, NOX increases rapidly, soot is generated in large quantities, and the cleansing force is increased. There was a problem that the life of the refractory of the furnace was shortened due to generation and local high temperature. With the combustion techniques described in Patent Document 1 and Patent Document 2, it was insufficient to determine such a problem.

Also, using only air or a mixture of air and exhaust gas from an incinerator as air for cooling the furnace temperature reduces the total amount of exhaust gas because new air is introduced into the furnace. There is also a problem that you can not.

It is also known to use preheated air or oxygen-enriched air to improve combustion stability 安定 reduce unburned components in exhaust gas.However, running costs ゃ increase in equipment costs NO x tends to increase, which poses a practical problem.

-On the other hand, a method of reducing the concentration of unburned components in exhaust gas by devising the form of air blowing into the furnace, as typified by swirling combustion, is generally applied. Improvement requires more air, requires larger exhaust gas treatment equipment, increases running costs and equipment costs, and increases the amount of heat (sensible heat) carried by the exhaust gas. Is low.

Excessive injection of exhaust gas into a region with low fuel concentration, such as the secondary combustion region, may result in unstable combustion due to a decrease in reactivity, which may cause misfire and increase of unburned components in exhaust gas. In particular, when the fluctuation of waste quality is large, such a phenomenon is amplified and appears, which poses a problem in pollution control.

As described above, it is difficult to achieve low pollution (reduction of NOx, CO, etc.) and low cost at the same time by conventional combustion improvement means alone.

The present invention has been made to solve the above-mentioned problems, and can reduce the generation of harmful gases such as CO and N Ox even when combustion at a low air ratio is performed in a waste incinerator, and furthermore, discharge from a chimney. It is an object of the present invention to provide a waste incinerator combustion control method and a waste incinerator that can significantly reduce the total amount of exhaust gas emitted. Disclosure of the invention

The features of the present invention for solving such a problem are as follows.

[1] A method for controlling combustion in a grate-type waste incinerator, in which primary air for combustion A is blown into the combustion chamber from below the grate, and high-temperature gas B is supplied from the combustion start area to the main combustion area in the combustion chamber. Circulating exhaust gas C containing at least part of the exhaust gas discharged from the incinerator above the hot gas B blowing position or downstream in the gas flow direction. A combustion control method for a waste incinerator characterized by injecting a stirrer gas D composed of either circulating exhaust gas or a mixed gas of air and circulating exhaust gas into the secondary combustion zone. M

[2]. A combustion control method for a waste incinerator according to the above [1], wherein the circulating exhaust gas C comprises only exhaust gas discharged from the incinerator.

[3]. In the above [1] or [2], the oxygen amount Q1 per unit time supplied by the primary air for combustion A, the oxygen amount Q2 per unit time supplied by the hot gas B, and the circulation The amount of oxygen per unit time Q3 supplied by the exhaust gas C and the amount of oxygen per unit time Q4 supplied by the stirring gas D are the theoretical amount of oxygen per unit time required for combustion of waste. A combustion control method for a waste incinerator characterized by satisfying the following equations (1) and (2) when 1 is set.

Q1: Q2: Q3: Q4 = 0.75 to 1.20: 0.05—0.20: 0.02 to 0.20: 0.02—0.25 (1) 1.2 ≤ Q1 + Q2 + Q3 + Q4 ≤ 1.5 (2)

[4]. In the above [1] or [2], the amount of oxygen per unit time Q1 supplied by the primary air for combustion A, the amount of oxygen Q2 per unit time supplied by the hot gas B, and the circulation The amount of oxygen per unit time Q3 supplied by the exhaust gas C and the amount of oxygen per unit time Q4 supplied by the stirring gas D are the theoretical amount of oxygen per unit time required for waste combustion. To

A combustion control method for a waste incinerator characterized by satisfying the following equations (3) and (4) when 1 is set.

Q1: Q2: Q3: Q4 = 0.75-1.1: 0.07 to 0.15: 0.02 to 0.15: 0.02 to 0.25 (3) 1.25≤Q1 + Q2 + Q3 + Q4≤1.35 (4)

[5]. In any of the above [1] to [4], while maintaining Q1 and Q2 at predetermined values, Q3 and / or Q4 may be a factor for monitoring the condition in the incinerator. It is a combustion control method for a waste incinerator characterized in that it is adjusted on the basis of the above.

[6]. Above in [5], is factor to monitor the status of the incinerator, in the secondary combustion zone near the outlet to perform secondary combustion of the combustible gas generated in the combustion chamber, the gas temperature, gas 0 ₂ dark time, a combustion control method for waste incinerator, characterized in that at CO concentrations in the gas, any one or more of the NO _x concentration in the gas.

[7]. In any one of the above [1] to [6], the high-temperature gas B is supplied from a position not exceeding 50% of the height of the combustion chamber to a position from a combustion start area to a main combustion area in the combustion chamber. Any of A combustion control method for a waste incinerator characterized by being blown into an area.

[8]. In any of the above [1] to [7], the high-temperature gas B may be located vertically above the surface of the waste layer on the grate within a range of 0.2 to 1.5 m, A combustion control method for a waste incinerator characterized by being blown into an arbitrary region between a combustion start region and a main combustion region in a combustion chamber.

[9]. In any of the above [1] to [7], the hot gas B may be burned in the combustion chamber from a height within a range of 0.2 to 2.5 m vertically above the grate surface. This is a combustion control method for a waste incinerator characterized by being blown into an arbitrary area between the start area and the main combustion area.

[10]. In any one of the above [1] to [9], the high-temperature gas B is applied to an arbitrary region between the combustion start region and the main combustion region in the combustion chamber at a blowing speed of at least 10 m / s or more. A combustion control method characterized by being blown.

[11]. In any one of the above [1] to [10], the flow rate of the circulating exhaust gas C and / or the stirring gas D such that the gas temperature in the secondary combustion region is in the range of 800 to 1050 ° C. This is a combustion control method for a waste incinerator characterized by adjusting the temperature.

[12]. The combustion in a waste incinerator according to any of the above [1] to [11], wherein the stirring gas D is blown so as to form a swirling flow in the secondary combustion region. This is the control method.

[13]. In any of the above [1] to [12], the temperature of the primary combustion exhaust gas passing through the combustion start region or the main combustion region may be higher than the temperature of the primary combustion exhaust gas passing through the post-combustion region. This is a combustion control method for a waste incinerator characterized by adjusting the flow rate of the high-temperature gas B.

[14]. In any one of the above [1] to [13], the high-temperature gas B and / or the circulating exhaust gas may be set so that the temperatures of the main combustion zone and the post-combustion zone are respectively within a range of 800 to 1,050 ° C. This is a combustion control method for a waste incinerator characterized by adjusting the flow rate of C.

[15]. In any one of the above [1] to [14], the oxygen concentration of the high-temperature gas B and / or the oxygen concentration and / or the temperature of each of the main combustion zone and the post-combustion zone are in the range of 800 to 1,050 ° C. A combustion control method for a waste incinerator characterized by adjusting a gas temperature. [16]. Means for injecting the primary air for combustion for injecting the primary air for combustion A from below the grate into the combustion chamber, and an arbitrary area between the combustion start area and the main combustion area in the combustion chamber for supplying the high-temperature gas B A circulating exhaust gas blowing means for blowing circulating exhaust gas C containing at least a portion of the exhaust gas discharged from the incinerator above the blowing position of the high-temperature gas B or downstream in the gas flow direction; A grate-type waste incineration characterized by comprising a stirring gas blowing means for blowing a stirring gas D composed of any one of a circulating exhaust gas or a mixed gas of air and circulating exhaust gas into a secondary combustion region. Furnace.

[17]. The grate-type waste incinerator according to the above [16], wherein the high-temperature gas B injection nozzle is provided at a height not exceeding 50% of the height of the combustion chamber. is there.

[18] In either of the above [16] or [17], the injection nozzle of the hot gas B is placed in the range of 0.2 to 1.5 m vertically above the surface of the waste layer on the grate. A grate-type waste incinerator characterized by being installed at a height position. -

[19]. In either of [16] or [17], the injection nozzle of the hot gas B is positioned vertically above the grate surface within a range of 0.2 to 2.5 m. This is a grate-type waste incinerator characterized by being provided in a country.

[20]. The fire according to any one of the above [16] to [19], wherein an agitating gas D injection nozzle is provided so that a swirling flow is formed in the secondary combustion region. It is a grid type waste incinerator.

[21]. In any one of the above [16] to [20], the primary combustion exhaust gas passing through the combustion start region or the main combustion region may be higher than the primary combustion exhaust gas passing through the post-combustion region. In addition, there is provided a fire-type waste incinerator characterized by having a means for adjusting the flow rate of the high-temperature gas B.

[22] The grate-type waste incinerator according to any of the above [16] to [21], further comprising means for adjusting a flow rate of the high-temperature gas B and / or the circulating exhaust gas C. You.

[23] The grate-type waste incinerator according to any one of the above [16] to [22], further comprising means for adjusting the oxygen concentration and / or the gas temperature of the high-temperature gas B. You. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic side sectional view showing one embodiment of a waste incinerator according to the present invention.

FIG. 2 is a diagram showing an example of a schematic configuration of the air amount adjusting means mixed with the exhaust gas according to the present invention. .

FIG. 3 is a schematic side sectional view showing an example of a waste incinerator according to the related art. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described.

FIG. 1 is a schematic side sectional view showing one embodiment of the waste incinerator 30 according to the present invention.

The waste incinerator 30 shown in FIG. 1 includes a combustion chamber 3, a hopper 1 disposed upstream of the combustion chamber 3 (the left side in FIG. 1) for charging the waste 2 into the combustion chamber 3, This is a grate-type double-flow furnace having the hopper 1 and a boiler 12 continuously provided above the downstream side of the combustion chamber 3 on the opposite side. At the bottom of the combustion chamber 3, there is a grate (strike force) that burns while moving the waste 2. The grate is inclined so that it goes down as it moves away from the hopper 1. This grate has two steps and is divided into three parts. These three grate are called a dry grate 5, a combustion grate 6, and a post-combustion grate 7 from the side closer to the hopper 1. In the drying grate 5, the waste 2 is mainly dried and ignited. The combustion grate 6 mainly performs pyrolysis and partial oxidation of the waste 2 and burns combustible gas. In the combustion grate 6, the combustion of the waste 2 is substantially completed. On the post-combustion grate 7, the slightly unburned unburned waste 2 is completely burned. After complete combustion, the combustion ash is discharged from the main ash chute 15.

Below the dry grate 5, the combustion grate 6, and the post-combustion grate 7, wind boxes 8, 9, 10 are provided, respectively. The primary air for combustion supplied by the blower 13 is supplied to each of the wind boxes 8, 9, 10 through a primary air supply pipe 16 for combustion, and is passed through each grate 5, 6, 7 It is supplied into the combustion chamber 3. The primary air for combustion supplied from below the grate is used for drying and burning the waste 2 on the grate, cooling the grate, and stirring the waste. Having

The secondary combustion area 17 of the waste heat boiler 12 is connected to the exit of the combustion chamber 3 on the opposite side of the hopper 1. In the combustion chamber 3, a barrier (intermediate ceiling) 11 for diverting the combustible gas generated from the waste and the combustion gas is provided near the outlet of the combustion chamber 3, and the combustible gas and the combustion The gas flow is diverted into the main flue 20 and the secondary flue 21. The combustible gas and the combustion gas diverted into the main flue 20 and the sub-flue 21 are led to the waste heat boiler 12 where they are mixed and agitated, and are part of the waste heat boiler 12 Secondary combustion occurs in the secondary combustion zone 17, and the flue gas generated by the secondary combustion is recovered by the waste heat boiler 12. After the heat recovery, the flue gas discharged from the waste heat boiler 12 is sent to the first dust removal device 18 through the duct 14, where the fly ash contained in the flue gas is recovered. Done. The flue gas after being dedusted by the first dedusting device 18 is subjected to neutralization of acid gas by slaked lime and adsorption of dioxins by activated carbon, and further to the second dedusting device 19. Activated carbon is collected. The flue gas that has been dust-removed and rendered harmless by the second dust remover 19 is attracted by the attracting fan 22 and released into the atmosphere from the chimney 23. As the dust removing devices 18 and 19, for example, a bag filling type, a cyclone type, an electric dust collecting type or the like can be used.

In such an apparatus configuration, the present invention blows primary air for combustion into the combustion chamber from below the grate, and blows high-temperature gas into an arbitrary area between the combustion start area and the main combustion area in the combustion chamber, In addition to blowing the circulating exhaust gas containing at least part of the exhaust gas discharged from the incinerator above the hot gas blowing position or downstream in the gas flow direction, air, circulating exhaust gas, or mixed gas of air and circulating exhaust gas The combustion control of the waste incinerator is performed by injecting any one of the above into the secondary combustion zone. In FIG. 1, an intermediate ceiling 1 1, are illustrated a furnace provided with grate force ^s i Korohasu, the present invention has no furnace Ya fire such an intermediate ceiling Needless to say, the present invention can be applied to a furnace having a horizontal grid.

[Injection of primary air for combustion]

Here, as described above, the primary air for combustion passes through the primary air supply pipe 16 for combustion from the blower 13 to each of the dry grate 5, the combustion grate 6, and the post-combustion grate 7, beneath After being supplied to the wind boxes 8, 9, 10 provided in the combustion chamber 3, the air is supplied into the combustion chamber 3 through the grate 5, 6, 7. The flow rate of the primary combustion air supplied into the combustion chamber 3 is adjusted by a flow control valve 24 provided in the primary combustion air supply pipe 16, and the flow rate supplied to each wind box is adjusted. The flow control valves 24 a, 24 b, 24 c, 24 provided for the respective supply pipes 16 a, 16 b, 16 c, 16 d provided in each wind box Regulated by d. The configurations of the wind box and the primary combustion air supply pipe for supplying the primary combustion air are not limited to those shown in the drawings, and may be appropriately selected depending on the scale, m, application, and the like of the incinerator.

[Injection of hot gas]

The high-temperature gas is blown into an arbitrary region in the combustion chamber 3 from a combustion start region to a main combustion region. This is because it is preferable to stabilize combustion by injecting high-temperature gas into a region where a flame exists and a large amount of combustible gas exists. In the grate-type waste incinerator, the area where a large amount of combustible gas exists is from the combustion start area to the main combustion area. 'When the waste is incinerated, first the water evaporates, then the pyrolysis and partial oxidation reactions occur, and the formation of flammable gases begins. Here, the combustion start region is a region where the combustion of the waste starts, and the flammable gas starts to be generated by the thermal decomposition and partial oxidation of the waste. In addition, the main combustion area is the area where waste is thermally decomposed, partially oxidized and burned, and flammable gas is generated and burned with a flame. (Burn-out point). The region after the burn-off point is the char combustion region (β-burning region) where the solid unburned matter (chars) in the waste is burned. 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.

High-temperature gas is blown into the main combustion area from the combustion start area in the combustion chamber 3 to form a stagnation area or swirl area immediately above the waste layer, facilitating the mixing and stirring of combustible gas generated from the waste. Therefore, stable combustion is performed. As a result, it is possible to suppress the generation of harmful substances such as CO, N〇x, and dioxins, and to suppress the generation of soot. Therefore, the amount of air blown into the entire incinerator can be reduced, and low air ratio combustion can be performed.

In addition, since high-temperature gas is blown just above the waste layer, it is heated by heat radiation and sensible heat from the high-temperature gas, and thermal decomposition of waste is promoted. Here, the temperature of the high-temperature gas blown from the gas blow-in port 25 is preferably in the range of 30.0 to 600 ° C. Injecting gas below 300 ° C lowers the temperature inside the furnace, making combustion unstable and increasing CO. Injecting a gas exceeding 600 ° C promotes the production of a cleaning force in the furnace, and has no economic effect corresponding to the high temperature. By setting the temperature of the high-temperature power source within the range of 300 to 600 ° C., a hydrodynamically stable stagnation region is formed just above the waste layer in the furnace, and stable combustion is performed. It is preferable to use a high-temperature gas having an oxygen concentration of about 5 to 18%. As a result, the effects described above are more effectively exhibited, and the reduction of NOx and CO is further promoted.

As the high-temperature gas having the above-mentioned gas temperature and oxygen concentration, it is preferable to use returned exhaust gas or a mixed gas of returned exhaust gas and air. The returned exhaust gas is a part of the exhaust gas discharged from the waste incinerator, and ί ^ returns it to the combustion chamber or the secondary combustion area to use its sensible heat or improve gas mixing in the combustion chamber. It is used to improve the combustion state.

When the return exhaust gas satisfies the predetermined conditions, the return exhaust gas may be directly blown into the furnace, but the return exhaust gas may have a low value and a low oxygen concentration. In this case, high-temperature combustion gas such as burner combustion gas or high-temperature air mixed with high-temperature air produced by a high-temperature air production device or hot blast stove is mixed with the returned exhaust gas so that the temperature and oxygen concentration satisfy the specified conditions. The exhaust gas may be blown into the furnace, or the returned exhaust gas may be heated and blown into the furnace.

When the exhaust gas from the secondary combustion area is returned and used, if the returned exhaust gas has a sufficiently high temperature and a high oxygen concentration, the returned exhaust gas can be used without installing a high-temperature air production device. May be used instead of hot air, and mixed with air and blown. Furthermore, if the temperature and the oxygen concentration of the exhaust gas returned from the secondary combustion region satisfy predetermined conditions, the exhaust gas returned may be directly blown into the furnace as a high-temperature gas.

Examples of the high-temperature air producing device include a heat storage burner, a recuperator, a device in which air or oxygen is mixed with combustion gas from a combustion panner, an oxygen-enriched burner, and the like.

Here, when the return exhaust gas and the high-temperature combustion gas or the high-temperature air are mixed by a gas mixing device to prepare a high-temperature gas, the gas mixing device may be an ejector 29. You. In this case, the combustion gas or the high-temperature air is guided to the exercising apparatus 29, which is used as a driving flow to mix the return exhaust gas while sucking it and blow it into the combustion chamber 3. This eliminates the need for a blower for deriving the returned exhaust gas, thereby simplifying the device configuration and reducing troubles caused by dust and the like contained in the returned exhaust gas.

In FIG. 1, the hot gas injection ports 25 are provided above the dry grate 5 and above the combustion grate 6 corresponding to the main combustion area from the combustion start area in the combustion chamber 3. Here, the thermal decomposition reaction of the waste occurs at about 200 ° C in ^^, and is almost completed when the temperature reaches about 400 ° C. At least one pair of gas outlets is opposed to the area where flammable gas is generated, and the gas is blown in such a way that the gas blowing direction is horizontal or downward. A hydrodynamically stable stagnation region is formed just above and stable burning is performed. In the example shown in FIG. 1, since it corresponds to the rear part of the dry grate 5 and the front part of the combustion grate 6, gas injection ports 25 are provided at these positions to blow high-temperature gas. Depending on the properties and properties of waste 2, the pyrolysis reaction may be completed at a higher temperature. In this case, the gas inlet 25 is also located behind the position shown in Fig. 1 (right side in the figure). Is preferably provided. The number of gas inlets 25 or the number of outlets can be selected as appropriate depending on the scale of the incinerator, dog, application, and the like.

Further, as shown in FIG. 1, the gas injection port 25 is located at a position not exceeding 50% of the height of the combustion chamber in each region of the main combustion region from the combustion start region, more preferably, the height of the combustion chamber. At a height not exceeding 40% of the grate, specifically at a height within the range of 0.2 to 1.5 m vertically above the surface of the waste layer on the grate, or vertically from the grate surface 0.2 π upward! It is preferable to provide at least a pair of gas outlets facing each other at a height within a range of 2.5 m. As a result, a flame stabilizing effect is exhibited by the high-temperature gas blown from the gas injection port 25 just above the waste layer in the combustion chamber, so that a high-temperature region (flame) is kept just above the waste layer in the furnace. Can be. Therefore, thermal decomposition of waste is efficiently performed, and the high-temperature region is far from the ceiling, so that the degree of burning of the ceiling can be reduced. The height of the combustion chamber is the height of the space where the main combustion takes place in each part of the grate, and refers to the height from the grate to the ceiling of the combustion chamber. In FIG. 1, at least a pair of gas injection ports 25 are provided opposite to both side surfaces of the combustion chamber 3, and high-temperature gas is injected from the gas injection ports 25. Here, as described above, the gas blowing port 25 is preferably provided so that the gas blowing direction is horizontal or downward. Combustible gases generated from waste usually flow upward. Therefore, if the direction of hot gas injection is upward, 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 damping the gas flow is reduced. The effect is reduced. On the other hand, if the hot gas is blown in the horizontal or downward direction, a stagnation area between the flammable gas and the high-temperature gas that rises is formed, and the substantial residence time of the gas here increases. The reaction capacity of the flame increases and the flame is extended, reducing the amount of NO x generated. In order to promote such an effect, it is preferable to provide the gas outlet downward.However, if the angle is too large, the high-temperature gas will not reach the entire width of the combustion chamber 3 and will be locally located near the furnace wall. A high-temperature region is formed, and the formation of a cleaning force promotes burnout of the furnace wall. Therefore, it is particularly preferable that the angle is in the range of 10 to 20 ° downward. The factor that reduces harmful substances such as dioxins in incinerator combustion is generally 3 T. These are temperature (Temperature), stirring (Turbulence), and residence time (Time). In particular, when high-temperature gas is blown at high speed, the hot gas jet entrains the surrounding gas. And the residence time (Time) can be improved, and the space temperature in the incinerator can be made more uniform.

The high-temperature gas may be blown into the combustion chamber 3 only from one side surface of the combustion chamber 3. Further, the air may be blown not from the side of the combustion chamber 3 but from the intermediate ceiling or the ceiling. However, in any case, care must be taken to prevent the generation of clean force near the ceiling of the combustion chamber and the burnout of furnace materials.

Further, it is preferable that the high-temperature gas blown from the gas blow-in port 25 be blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber at a blowing speed of at least 10 m / s. The blowing speed of 1 O m / s or more is to ensure a relative speed of at least 10 times the average superficial velocity in the furnace (about max mZs). The blowing speed of the high-temperature gas is determined by, for example, adjusting the mixing ratio of the returned exhaust gas. As a result, a stable stagnation region can be formed just above the waste layer in the furnace, stable combustion is performed, and the generation of harmful substances such as CO, NOx, and dioxins is suppressed, and soot is generated. Can be suppressed. For this reason, the amount of air blown into the entire incinerator can be reduced, and low air ratio combustion can be performed. '

In addition, the flow rate of high-temperature gas blown from multiple blowing nozzles installed so that the temperature of the primary combustion exhaust gas passing through the combustion start area or the main combustion area becomes higher than the temperature of the primary combustion exhaust gas passing through the post-combustion area. Is preferably adjusted. Here, the combustion in the combustion chamber of the incinerator is called primary combustion, and the primary combustion exhaust gas that has passed through the combustion start area or the main combustion area refers to the gas that passes through the auxiliary flue 21 in FIG. The primary combustion exhaust gas that has passed through the post-combustion region refers to a gas that passes through the main flue 20 in FIG. '' By making the combustion state such that the temperature of the primary flue gas that has passed through the combustion start area or the main combustion area is higher than the temperature of the primary flue gas that has passed through the post-combustion area, Thermal decomposition of waste is promoted, and supply of combustible gas to the secondary combustion zone is promoted. In addition, by lowering the temperature of the primary combustion exhaust gas passing through the post-combustion region having a high oxygen content, rapid combustion in the primary combustion region or the secondary combustion region can be suppressed, and low NOx can be achieved. It becomes possible.

Here, the temperature of the primary combustion exhaust gas passing through the combustion start region or the main combustion region, and the temperature of the primary combustion exhaust gas passing through the post-combustion region are within a range of 800 to 150 ° C. It is preferred to adjust to. When the temperature of the primary combustion exhaust gas passing through the combustion start region or the main combustion region exceeds 150 ° C., the generation of the cleaning force in the furnace is promoted. Further, when the temperature of the primary combustion exhaust gas passing through the post-combustion region falls below 800 ° C., the temperature of the secondary combustion region decreases, combustion becomes insufficient, and CO increases.

The primary combustion exhaust gas temperature is adjusted by adjusting the flow rate of the high-temperature gas and / or the circulating exhaust gas blown from a plurality of blowing nozzles. When raising the temperature of the primary flue gas through the combustion start zone or the main combustion zone, the flow rate of the hot gas supplied to this zone is increased by increasing the flow rate [] and decreasing the flow rate of the circulating exhaust gas. In addition, when lowering the temperature of the primary combustion exhaust gas, the flow rate of the high-temperature gas supplied to this region is reduced and the flow rate of the circulating exhaust gas is increased. The temperature of the primary combustion exhaust gas passing through the post-combustion region is adjusted in the same manner.

Further, the temperature of the primary combustion exhaust gas can be adjusted by adjusting the oxygen concentration and / or the gas temperature of the high-temperature gas blown from a plurality of blowing nozzles. When raising the temperature of the primary combustion exhaust gas passing through the combustion start area or the main combustion area, the oxygen concentration of the high-temperature gas supplied to this area is increased and the gas temperature is adjusted. When lowering the temperature of the primary combustion exhaust gas, adjustment is made by decreasing the oxygen concentration of the high-temperature gas supplied to this region and lowering the gas temperature.

The temperature of the primary combustion exhaust gas passing through the post-combustion region is adjusted in the same manner.

Here, it is preferable that the adjustment of the oxygen concentration of the high-temperature gas blown from the plurality of blow nozzles is performed in a range of 5 to 18%. This is to ensure self-maintenance of combustion and controllability of temperature adjustment in the primary combustion region or the secondary combustion region.

The temperature of the high-temperature gas blown from the plurality of blowing nozzles is preferably in the range of 300 to 600 ° C. Injecting gas below 300 ° C lowers the furnace temperature, making combustion unstable and increasing CO. Blowing a gas exceeding 600 ° C promotes the production of clinking power in the furnace, and has no economic effect commensurate with high temperature. By setting the high-temperature gas to a temperature range of 300 to 600 ° C, a hydrodynamically stable stagnation region is formed just above the waste layer in the furnace, and stable combustion is performed.

[Injection of circulating exhaust gas containing at least a part of the exhaust gas discharged from the incinerator] The circulating exhaust gas containing at least a part of the exhaust gas or the air discharged from the incinerator is a part of the high-temperature gas in the combustion chamber 3. It is blown above the blowing position or downstream in the gas flow direction. The downstream side in the gas flow direction means a downstream side with respect to the gas flow direction in the furnace. Further, the gas means flammable gas and combustion exhaust gas mainly generated in the combustion chamber.

Here, as the circulating exhaust gas containing at least a part of the exhaust gas discharged from the incinerator, for example, as shown in FIG. 1, for example, it is discharged from the incinerator 30 and passes through the first dust removal device 18 Gas (gas temperature: about 150 to 200 ° C, oxygen concentration: about 4 to 8%) or after passing through the second dust remover 19 Gas (gas temperature: about 150 to 190 ° C, oxygen concentration: about 4 to 8%) Can be. Further, as the circulating exhaust gas, the exhaust gas discharged from the incinerator 30 may be used as it is, or may be a mixture of air.

When air is mixed with the exhaust gas, the exhaust gas may be mixed while absorbing the bow I using an ejector that uses the air to be mixed as a driving flow, and may be blown into the post-combustion region in the combustion chamber 3. . This eliminates the need for a probe for extracting exhaust gas, which simplifies the device configuration and reduces troubles caused by corrosive gas contained in the exhaust gas.

By blowing the circulating exhaust gas above the hot gas blowing position or downstream in the gas flow direction, the combustion region stabilized by the blowing of the hot gas in the combustion chamber 3 or downstream in the gas flow direction is blown. Lowers the flame temperature on the side, prevents the generation of a wide range of high-temperature areas, and more effectively suppresses the generation of N〇x. Furthermore, by blowing the circulating exhaust gas with a low oxygen concentration (about 4 to 8%), the area above the hot gas blowing position or the downstream side in the gas flow direction is brought closer to the reducing atmosphere, and the generation of NOx is suppressed.

Here, the circulating exhaust gas is blown into a region above the gas stagnation region or a region downstream in the gas flow direction formed by the injection of the high-temperature gas, so that the gas is scattered above the stagnation region or downstream in the gas flow direction. Suppressing the occurrence of local high-temperature regions, that is, averaging the temperature distribution, and further promoting agitation in the region to average the oxygen concentration distribution, thereby achieving even better reduction of NOx Becomes possible.

In addition, the circulating exhaust gas inlet 27 for injecting the circulating exhaust gas above the high-temperature gas blowing position or in the downstream region in the gas flow direction is located above the high-temperature gas blowing port 25 or downstream in the gas flow direction (FIG. 1). In the case just above), it is preferable to install them at a distance of about 10% of the height of the combustion chamber. This is because the generation of NOx is more remarkably suppressed by effectively forming a stable stagnation region and suppressing the generation of a local high-temperature region.

However, a circulating exhaust gas inlet 27 and a high-temperature gas inlet 25 can be formed as an integrated inlet separated by a single partition. In this case, although the effect of suppressing the generation of NOx is slightly inferior to the case described above, the construction cost can be reduced by using the integrated blow-in port, and it is advantageous in terms of securing space.

The circulating exhaust gas inlet 27 is a gas formed by blowing a high-temperature gas. The purpose is to equalize the gas temperature distribution and oxygen concentration distribution above the stagnation region or in the downstream region in the gas flow direction, so that at least one pair faces each other or the gas blowing direction is horizontal or downward. No need to provide.

[Blowing of stirring gas]

A stirring gas consisting of air, circulating exhaust gas, or a mixed gas of air and circulating exhaust gas is blown into the secondary combustion region.

Here, it is preferable that one or a plurality of the stirring gas blowing ports 31 be provided so as to blow gas in a direction in which a swirling flow is generated in the secondary combustion region 17. By swirling the gas into the secondary combustion zone 17, the gas temperature and oxygen concentration distribution in the secondary combustion zone 17 can be averaged, suppressing the generation of local high-temperature zones and further reducing NOx. Can be achieved. Furthermore, the mixing of combustible components and oxygen is promoted, so that the stability of combustion is improved, and complete combustion can be achieved, which makes it possible to reduce C〇.

The stirring gas is, as shown in FIG. 1, only the combustion secondary air supplied by the blower 56, a part of the exhaust gas after passing through the first dedusting device 18, or Either only the circulating exhaust gas, which is obtained by extracting a part of the exhaust gas after passing through the dust removing device 19, or a gas obtained by mixing the secondary air for combustion with the circulating exhaust gas can be used.

Here, it is preferable to adjust the flow rate of the circulating exhaust gas and / or the stirring gas such that the gas temperature in the secondary combustion region 17 is in the range of 800 to 150 ° C. . If the gas temperature in the secondary combustion zone 17 becomes lower than 800 ° C, combustion becomes insufficient and CO increases. Further, when the gas temperature in the secondary combustion region 17 exceeds 150 ° C., the generation of the cleaning force in the secondary combustion region 17 is promoted, and the NO x increases.

The gas temperature in the secondary combustion area 17 can be increased by reducing the flow rate of the circulating exhaust gas, and the gas temperature in the secondary combustion area 17 can be reduced by increasing the flow rate of the stirring gas. Can be done.

Further, the amount of oxygen Q1 per unit time supplied by the primary combustion air blown into the combustion chamber 3 from below the grate, and an arbitrary value between the combustion start area and the main combustion area in the combustion chamber 3 And the amount of oxygen Q 2 supplied per unit time by the high-temperature gas blown into the region of the above, and the circulating exhaust gas blown above the high-temperature gas blowing position or downstream in the gas flow direction. The amount of oxygen per unit time Q3 supplied by the unit and the amount of oxygen per unit time Q4 supplied by the stirring gas blown into the secondary combustion zone are the unit time required for waste combustion. Assuming that the theoretical amount of oxygen per unit is 1, it is preferable to blow the gas so as to satisfy the following expressions (1) and (2), more preferably the following expressions (3) and (4).

Q1: Q2: Q3: Q4 = 0.75 ~: 1.20: 0.05 ~ 0.20: 0.02 ~ 0.20: 0.02 ~ (! 25 (1) 1.2≤Q1 + Q2 + Q3 + Q4≤1.5 ( 2)

Q1: Q2: Q3: Q4 = 0.75 ~: 1.1: 0.07 ~ 0.15: 0.02-0.15: 0.02 ~ 0.25 (3) 1.25≤Q1 + Q2 + Q3 + Q4≤1.35 (4)

Here, the theoretical oxygen amount per unit time required for the combustion of the waste is the amount of oxygen required for the combustion per unit mass of the waste determined from the properties and components of the waste put into the combustion chamber. (Nm ³ / kg) and the incinerator waste incineration rate (kg / hr) (Nm ³ / r). Q 1 is the amount of oxygen per unit time supplied by the primary combustion air supplied from the grate 5, 6, 7 into the combustion chamber 3, and increases or decreases the flow rate of the primary combustion air. Adjust by doing. Further, Q2 is adjusted by increasing or decreasing the flow rate of the high-temperature gas blown into an arbitrary region in the combustion chamber 3 from the combustion start region to the main combustion region. Q3 is adjusted by increasing or decreasing the flow rate of the circulating exhaust gas blown above the hot gas blowing position in the combustion chamber 3 or on the downstream side in the gas flow direction. Q4 is adjusted by increasing or decreasing the flow rate of the stirring gas blown into the secondary combustion region.

In the following, Q1 + Q2 + Q3 + Q4 is described as λ.

By setting the above Ql, Q2, Q3 ₃ Q4 to the range of the above formula, low oxygen ratio combustion (1.2 ≤ ぇ ≤1.5) in waste incinerator (that is, equivalent to low air ratio combustion) In this case, the amount of harmful gases such as CO and NOx can be reduced, and the total amount of exhaust gas discharged from the incinerator can be significantly reduced.

The distribution ratio that achieves stable low air ratio combustion by suppressing the generation of unburned waste and harmful substances is as follows: Q1: Q2: Q3: Q4 = 0.98: 0.10: 0.12: 0.10, etc. Adjust Q1, Q2, Q3, and Q4 within the range of 1.2 to 1.5 based on the composition and properties of the waste to be charged into the furnace based on the standard of 30 . 0 ε · ΐ = ΟΖΌ, ΟΖΌ: 5V0: SVO: 08'0 = ¾ G5 2δ

o ε'ΐ = γ, sro: εΐΌ: ζνο: 08Ό = ο TO οε 'τ = γ, s o: SVQ: oro: os'o = o TO

0 ε · ΐ = γ, Ζ Ό: sro: SVO: 8 Ό = 5 CD z τ¾

0 ε "Τ = Υ, Ό: ΖΙΌ: ξΤΟ: 8 Ό = 5 TO ο ε * τ

oi ο ε 'τ = γ ^ ΓΟ: svo: svo: sfo = oz

0 ε 'T = Y ΟΧΌ: SVO: SIO: 06'0 = o τ o o ε · ΐ = Y, · ο: εοΌ: zvo: ο6 · ο = ¾

ο ε · τ = Υ ^ν εΐΌ: zvo: ςνο: ο6 · ο = 5 T¾

0 S · Τ = Υ, 9Γ0: ZVO ZVO: 06Ό = 0 T¾

0 C "ΐ = Y, SIO: SVO: ΟΓΟ: 06Ό = Q Ζ 5 τδ

0 C 'T = Y, 8Γ0: ZVO: ΟΓΟ: 06 · 0 = ¾

0 ε · Τ = Ύ ^ν 50Ό: ΟΙΌ:? 0Ό: ΟΓΐ = 5 TO

0 'ΐ = Υ, 90Ό: SVO: ΠΌ: 50 = D

0 'ΐ = Y, 80Ό .: εΐΌ: ΠΌ: 0 = D g ε · τ = γ, 9: ΖΤΌ: zvo: scn = o z TO

9 C · T = Y ^ν 80Ό: ΟΐΌ: ZVO: 50'1 =

0 ε "Τ = Υ, n ΟΌ: 80Ό: ΟΐΌ: ζΟ = 5

0 ε Ί = Ύ, 90 Ό: 60 ΟΙΌ: =: 50 = ε¾ ID

9 ε · Τ = Υ ΓΟ: ZVO: ΟΓΟ: 86Ό2 D εδ z δ ΐ 5

9 ε · ΐ = γ ΤΌ: εΐΌ: oro: 86 · ο = ¾

9 S 'T = Υ ^ν ΖΧΌ: 5V0: ΟΓΟ: 86 · 0 = ¾ Z ¾ ΐ¾

O S · T = Y 90Ό: ZTO: ΠΌ: 86Ό = ¾ Z 5

OS · ΐ = γ, 80Ό: ZVO: ZTO: 86Ό = f ¾ Z 5 τδ ο ε · · = γ ^ν οχΌ: zvo: oro: se = ε5 τδ H¾ »0g3 丄 ¾ ne ωγ ^cc

81

ZCZS00 / t700idf / X3d 8 9Z60 / tO0Z OAV Hereinafter, the adjustment criteria for Ql, Q2, Q3, and Q4 will be described.

[Q1 adjustment standard]

To dry and burn ordinary municipal waste, etc., use Q 1 = 0.9 as a standard.When burning low-ash waste or low-moisture waste, for example, plastic, etc., use Q 1 Reduce to 0.75 ~ 0.9, but increase Q2 instead.

[Q2 adjustment criteria]

To burn ordinary municipal solid waste, etc., based on Q 2 = 0.1, waste containing little ash or moisture and mostly flammable, such as plastic, or waste with high volatile content When burning, increase Q 2. If Q2 is small, the effect of high-temperature gas injection described above cannot be sufficiently obtained. If Q2 is increased beyond the above range, low air-fuel ratio combustion cannot be achieved, the fuel cost for generating high-temperature gas will increase, and the temperature inside the combustion chamber will become excessive, resulting in the generation of a cleaning force on the inner wall. Or NOx increases.

[Q3, Q4 adjustment criteria]

First, as standard operating standards for waste incinerators, Q1 and Q2 are determined based on the above standards, taking into account the composition and properties of the waste, and then the standard values for Q3 and Q4 are set.

Here, the combustion state in the combustion chamber is adjusted by adjusting the value of Q3, and the combustion state in the secondary combustion region is adjusted by adjusting the value of Q4. Q3 is adjusted within the range of 0.02 to 0.2 with reference to Q3 = 0.12. Q4 is adjusted in the range of 0.02 to 0.25 based on Q4 = 0.18. Q3 + Q4 shall be adjusted in the range of 0.15-0.4 with reference to Q3 + Q4 = 0.3.

In actual operation of waste incinerators, even when operating according to the standard operating standards, the combustion situation inside the incinerator may change and the amount of harmful substances in the exhaust gas discharged may fluctuate. Therefore, while maintaining the values of Q1 and Q2 determined above, based on the factors monitoring the situation inside the waste incinerator, Q3, Q4, or the sum of Q3 and Q4 Adjust any of By adopting such a combustion control method, even if the combustion situation in the incinerator changes, it is possible to adjust the combustion so as to stably perform combustion, and finally, the harmful effect in the exhaust gas discharged from the waste incinerator The amount of substances can be controlled, and the combustion control system of the incinerator can be simplified.

Here, factors for monitoring the situation in the waste incinerator include, for example, in the combustion chamber 3 In the secondary combustion zone 1 7 near the outlet to perform secondary combustion of the generated combustible gas with the combustion gases, gas temperature, 0 ₂ concentration in the gas, gas C_〇 concentration, any one or more of the NO _x concentration in the gas It is preferable that The specific combination of monitoring agents, for example, (1) gas temperature, (2) 0 ₂ concentration in the gas, (3) gas temperature and 0 ₂ concentration in the gas, (4) gas temperature and gas CO Concentration, (5) gas N 0 _X concentration and gas temperature, and (6) gas N 0 _X concentration and gas CO concentration can be used.

In addition, as a method for adjusting the Q3, when the circulating exhaust gas blown into the post-combustion region in the combustion chamber 3 consists only of the exhaust gas discharged from the incinerator, the flow rate of the exhaust gas is adjusted. When the circulating exhaust gas is, for example, a mixed gas of the exhaust gas discharged from an incinerator and air, the circulating exhaust gas can be adjusted by adjusting the amount of the mixed air.

FIG. 2 shows an example of a schematic configuration of the adjusting means 26 when adjusting the amount of air mixed with the exhaust gas as an adjusting method of Q3. The adjusting means 26 shown in FIG. 2 extracts a part of the exhaust gas after passing through the first dust removal device 18 or a part of the exhaust gas after passing through the second dust removal device 19, and It is provided in the middle of a pipe 28 for blowing the circulating exhaust gas from a circulating exhaust gas inlet 27 provided above the high-temperature gas blowing position of the combustion chamber 3 or downstream in the gas flow direction via the fin 2. The adjusting means 26 includes a gas mixing device 50 for mixing exhaust gas and air, an air supply pipe 51 for supplying air to the gas mixing device 50, and a gas mixing device 50. An air amount control device 58 for controlling the amount of air to be supplied.

The air supply pipe 51 is provided with a blower 56 for taking in air, and a flow control valve 54 for adjusting the amount of air supplied to the gas mixing device 50. Further, the air amount control device 58 determines the amount of air to be mixed with the exhaust gas based on the measurement signal from the measuring means 59 for measuring the monitoring factor, and the flow control valve 5 Control 4 In the case where the circulating exhaust gas blown above the high-temperature gas blowing position or downstream in the gas flow direction consists only of the exhaust gas discharged from the incinerator, the damper provided in the middle of the pipe 28 is opened. The flow rate of the circulating exhaust gas is adjusted by controlling the degree o

In addition, as a method of adjusting the Q4, a stirring gas blown into the secondary combustion region is used. When only air or circulating exhaust gas is used, the adjustment is performed by adjusting the flow rate of the air or circulating exhaust gas. When the stirring gas is a mixed gas of air and circulating exhaust gas, the mixing can be performed by adjusting the amount of air to be mixed or the amount of circulating exhaust gas.

Tables 1 and 2 show an example of how to adjust Q3, Q4, or the sum of Q3 and Q4 in an actual waste incinerator. It shows how to adjust the fluctuation of the amount of harmful substances in the exhaust gas when the monitoring factor fluctuates from the reference value and the value of Q3, Q4, or the sum of Q3 and Q4.

The stirring gas is blown from the side wall near the inlet of the secondary combustion region 17 so as to form a swirling flow on a horizontal plane in a direction opposite to the flow of the atmospheric gas in the post-combustion region.

Here, the waste status of the incinerator is a factor to monitor secondary combustion zone 17 the gas temperature at the exit near 0 ₂ concentration in the gas, gas C_〇 concentration of the NO _x concentration in the gas that it The reference values and the measurement methods are as follows. Gas temperature: 950 ± 50 ° C

Gas 0 ₂ concentration:. 5. 5 ± 0 5%

C 0 concentration in gas: 30 p pm or less on average

(Control so that the instantaneous value does not exceed 10 Oppm)

Gas concentration of NO _x: 10 Oppm less

[Measurement means]

Gas temperature: Temperature sensor (thermocouple, radiation thermometer)

Gas 0 ₂ concentration: oxygen concentration meter

CO concentration in gas: CO concentration meter

Gas in the NO _x concentration: NO _x concentration meter 【table 1】

[Table 2]

When combustible gas generated by waste and pyrolysis in an incinerator is burned within the range of appropriate oxygen concentration and temperature, the generation of harmful substances such as C0N0x DXN (dioxins) is minimized. You.

In Table 1, when the gas temperature near the outlet of the secondary combustion zone 17 is high (case (1)), combustion in the combustion chamber is suppressed, and as a result, combustion in the secondary combustion zone occurs rapidly. Therefore, the gas temperature is considered to be rising. In this case, the CO and DXN concentrations emitted from the incinerator decrease or remain unchanged, but the NOx concentration increases. Therefore, when adjusting only Q3, increase Q3 to increase the amount of oxygen supplied to the combustion chamber, and actively perform combustion in the combustion chamber to perform combustion in the secondary combustion area. To optimize. When only Q4 is adjusted, decrease Q4 and reduce the amount of oxygen supplied to the secondary combustion region so that combustion in the secondary combustion region is performed properly. To adjust the total value of Q3 + Q4, increase Q3 Then, decrease Q4 and increase the total value of Q3 + Q4, or make the combustion in the combustion chamber and the secondary combustion zone properly without change.

Secondary combustion region 17 when the gas 0 ₂ concentration at the outlet near the high (in the case of (2)) is, CO concentration and DXN concentration is discharged from the incinerator is any change is not reduced, NOx concentration is increased Add. Therefore, when adjusting only Q3, increase Q3 to increase the supply of oxygen into the combustion chamber, and increase the consumption of oxygen by actively burning in the combustion chamber. When only Q4 is adjusted, decrease Q4 and reduce the amount of oxygen supplied to the secondary combustion region so that combustion is properly performed in the secondary combustion region. When adjusting the total value of Q 3 + Q 4, increase Q 3, decrease Q 4, and increase the total value of Q 3 + Q 4 Combustion in the next combustion zone is performed appropriately.

Conversely, the secondary combustion zone 17 when the gas 0 ₂ concentration at the outlet near the lower (in the case of (3)) is the NOx concentration exhausted from the incinerator is decreased, CO concentration and: DXN concentration increased Slightly, there is no change. Therefore, when only Q3 is adjusted, Q3 is reduced to reduce the dilution ratio due to the circulating exhaust gas in the combustion chamber and increase the oxygen concentration in the secondary combustion region. If only Q4 is adjusted, increase Q4 to increase the oxygen supply to the secondary combustion zone. When adjusting the total value of Q3 + Q4, decrease Q3, increase Q4, and increase the total value of Q3 + Q4 to properly combust in the combustion chamber and secondary combustion area. Do it.

If the CO concentration in the gas near the secondary combustion zone 17 outlet is high (in the case of (4)), the combustion in the secondary combustion zone is insufficient, and the unburned combustible gas remains. Conceivable. Therefore, when only Q3 is adjusted, Q3 is reduced to increase the temperature in the secondary combustion region, stabilize combustion, and suppress CO emissions. If only Q4 is adjusted, increase Q4 to increase the amount of oxygen supplied to the secondary combustion region so that combustion in the secondary combustion region is performed properly. The total value of Q 3 + Q 4 is increased so that combustion in the combustion chamber and the secondary combustion region is performed properly.

In the case where the gas temperature near the outlet of the secondary combustion zone 17 is low and the concentration of O _{2 in} the gas is high (case (5)), the flow rate of the stirring gas is excessive. It is considered that combustion decreased and combustion became unstable. In this case, the CO concentration emitted from the incinerator and D XN concentration increases. Therefore, Q3 is decreased without increasing or changing Q4, so that combustion in the secondary combustion region is performed properly.

Secondary combustion region 1 7 gas temperature at the exit near the lower (in the case of (6)) is low 0 ₂ concentration in the gas is burned in the secondary combustion zone is suppressed, the gas temperature is decreased It is thought that there is. In this case, the concentration of CO and DXN emitted from the incinerator will increase. Therefore, Q 3 is decreased, the temperature in the combustion chamber is increased to increase the inflow of flammable gas into the secondary combustion area, and Q 4 is increased to increase the supply of oxygen to the secondary combustion area to increase the secondary Properly perform combustion in the combustion zone. The total value of Q 3 + Q 4 should be increased or not changed so that the combustion in the combustion chamber and the secondary combustion region is performed properly.

When the CO concentration in the gas near the outlet of the secondary combustion zone 17 is high and the gas temperature is high ((7)), the combustion in the combustion chamber is incomplete and the combustion in the secondary combustion zone is rapid. Therefore, it is considered that the gas temperature has risen and unburned combustible gas remains. In this case, the concentration of CO and DXN discharged from the incinerator will increase. Therefore, Q3 is increased to lower the temperature in the combustion chamber, and Q4 is increased to lower the temperature of the secondary combustion area while increasing the amount of oxygen supplied to the secondary combustion area to increase the amount of oxygen supplied to the secondary combustion area. Ensure proper combustion.

When the CO concentration in the gas near the outlet of the secondary combustion zone 17 is high and the gas temperature is low (case (8)), the amount of waste supplied decreases and the flow rate of the circulating exhaust gas blown into the combustion chamber becomes excessive. It is considered that the temperature inside the furnace dropped and combustion became unstable. In this case, the CO and DXN concentrations discharged from the incinerator increase. For this reason, Q 3 is reduced to raise the inside of the furnace to stabilize combustion, and Q 4 is increased to increase the amount of oxygen supplied to the secondary combustion region to perform appropriate combustion in the secondary combustion region. To do. The total value of Q 3 + Q 4 should be increased or the combustion in the combustion chamber and the secondary combustion zone should be performed properly without any change.

Secondary combustion region 1 7 high gas concentration of NO _x at the exit near (case (9)) when the gas temperature is high, is suppressed combustion in the combustion chamber, resulting combustion in the secondary combustion zone There the gas temperature rises to be done sharply, it is considered that concentration of NO _x in the gas is increasing. Therefore, if Q 3 is increased to lower the temperature in the combustion chamber and suppress combustion in the combustion chamber, In both cases, Q4 is reduced, and the amount of oxygen supplied to the secondary combustion region is reduced so that combustion in the secondary combustion region is performed properly. The total value of Q 3 + Q 4 should be increased or not changed so that the combustion in the combustion chamber and the secondary combustion region is properly performed.

In the case where the concentration of NO _x in the gas near the outlet of the secondary combustion zone 17 is low but the concentration of CO is high ((10)), combustion in the secondary combustion zone is insufficient and unburned combustible It is considered that the reactive gas remains. Therefore, Q 3 is decreased and the temperature in the combustion chamber is increased to increase the inflow of flammable gas into the secondary combustion area, and Q 4 is increased to increase the amount of oxygen supplied to the secondary combustion area. Combustion in the next combustion zone is performed appropriately. The total value of Q3 + Q4 is increased so that combustion in the combustion chamber and the secondary combustion zone is performed properly.

Secondary combustion region 17 lower gas concentration of NO _x in near the outlet, when CO concentration is low (in the case of (1 1)) is considered state of combustion in the furnace has been carried out properly. In this case, there is no need to adjust, and the total value of Q3, Q4, Q3 + Q4 is maintained as it is.

By controlling as described above, it is possible to effectively reduce the amount of harmful substances such as C0, NOx and DXN discharged from waste incinerators without performing complicated control. Table 3 shows that the actual waste incinerator was used as an example to burn waste with Q1: Q2: Q3: Q4 0.98: 0.10: 0.12: 0.10, etc. The results of measurement of CO concentration, NOx concentration and DXN concentration in exhaust gas discharged from the incinerator are shown. Immediately, as Comparative Examples 1 and 2, in the waste incinerator according to the prior art, the amount of oxygen per unit time supplied by the primary air for combustion blown from below the grate r 1, the main combustion area Table 2 shows the amount of oxygen per unit time r2 supplied by the air blown into the air, the amount of oxygen per unit time supplied by the air blown into the post-combustion region r3, and rl + r2 + r3. The results of measurement of the CO, NOx, and DXN concentrations in the exhaust gas discharged from the incinerator outlet when the settings were made as described above are shown. : Table 3)

As shown in Table 3, in the example, low air ratio combustion (e.g. 1.30) can be achieved, and generation of C〇, ΝΌ χ, and DXN is suppressed. On the other hand, in Comparative Example 1, low air ratio combustion could not be achieved (E '= 1.7), and the generation amount of NOx was large. In Comparative Example 2, when the low air ratio combustion (E, = 1-3) was performed, the amount of NO x generated was low, but the amount of CO was large. This is because the combustion state in the furnace becomes unstable, flammable gases are emitted as unburned CO as unburned, and unburned components such as soot are generated, which also increases the amount of dioxins generated. It is thought that it has become.

Further, the flow rate of the high-temperature gas, the circulating exhaust gas, and the stirring gas may be adjusted by using the ratio to the exhaust gas flow rate discharged from the incinerator. This makes it possible to easily set and adjust the blowing flow rate.

When the above-mentioned waste incinerator is an ash melting furnace integrated with an ash melting furnace-a body-type waste incinerator, all or a part of the above-mentioned circulating exhaust gas and / or stirring gas is discharged from the ash melting furnace. Gas may be used. Further, when the ash melting furnace is a kiln type ash melting furnace equipped with a kiln hood, all or a part of the above-described high-temperature gas and / or stirring gas is attracted through the kiln hood. Air heated in the kiln hood can also be used. By using the exhaust gas from the ash melting furnace or the air heated in the kiln hood, waste heat can be used effectively and energy can be saved. As described above, according to the present invention, when a low air ratio combustion is performed in a waste incinerator, Combustion control method and waste incinerator for a waste incinerator that can maintain the stability of combustion, suppress the generation of local high-temperature regions, and reduce the generation of harmful gases such as CO and NOx Is provided. In addition, a combustion control method and a waste incinerator for a waste incinerator are provided, which can significantly reduce the total amount of exhaust gas discharged from the incinerator because the low air ratio combustion can be performed, and can improve the efficiency of waste heat recovery. O

Claims

The scope of the claims

1. A combustion control method for a grate-type waste incinerator,

Primary air A for combustion is blown into the combustion chamber from under the grate,

High-temperature gas B is blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber,

Blowing the circulating exhaust gas C containing at least a part of the exhaust gas discharged from the incinerator above the blowing position of the high-temperature gas B or downstream in the gas flow direction,

A combustion control method for a waste incinerator, characterized by blowing a stirring gas (D) comprising air, circulating exhaust gas, or a mixed gas of air and circulating exhaust gas into a secondary combustion zone.

2. The combustion control method for a waste incinerator according to claim 1, wherein the circulating exhaust gas C comprises only exhaust gas discharged from the incinerator.

3. The amount of oxygen Q 1 supplied by the primary air for combustion A per unit time,

The amount of oxygen per unit time Q 2 supplied by the hot gas B,

The amount of oxygen per unit time Q3 supplied by the circulating exhaust gas C,

The oxygen amount Q 4 per unit time supplied by the stirring gas D is

The waste according to claim 1 or 2, wherein the following formulas (1) and (2) are satisfied, where the theoretical amount of oxygen per unit time required for combustion of the waste is set to 1. Combustion control method for incinerator.

Q1: Q2: Q3: Q4 = 0.75 to: 1.20: 0.05 to 0.20: 0.02 to 0.20: 0.02 to 0.25 (1) 1.2 ≤ Q1 + Q2 + Q3 + Q4 ≤ 1.5 (2)

4. The amount of oxygen per unit time Q 1 supplied by the primary air for combustion A,

The amount of oxygen per unit time Q 2 supplied by the hot gas B,

The oxygen amount Q 4 per unit time supplied by the stirring gas D is The waste according to claim 1 or 2, wherein the following formulas (3) and (4) are satisfied, where the theoretical amount of oxygen per unit time required for combustion of the waste is set to 1. Combustion control method for incinerator.

Q1: Q2: Q3: Q4 = 0.75 to: 1.1: 0.07 to 0.15: 0.02 to 0.15: 0.02 to 0.25 (3)

1.25≤Q1 + Q2 + Q3 + Q4≤1.35 (4)

5. While maintaining Q 1 and Q 2 at predetermined values,

The combustion control method for a waste incinerator according to any one of claims 1 to 4, wherein Q3 and / or Q4 are adjusted based on a factor for monitoring a condition in the incinerator.

6. is factor to monitor the status of the incinerator, in row intends secondary combustion region near the outlet of the secondary combustion of combustible gas generated in the combustion chamber, the gas temperature, 0 ₂ concentration, CO concentration in the gas in the gas, combustion control method for waste incineration furnace according to claim 5, wherein the medium concentration of NO _x gas' is any one or more.

7. The hot gas B is blown into an arbitrary region between a combustion start region and a main combustion region in the combustion chamber from a height position not exceeding 50% of the height of the combustion chamber. 7. The method for controlling combustion in a waste incinerator according to claim 6.

8. The hot gas B flows vertically from the height of the waste layer on the grate within the range of 0.2 to 1.5 m from the combustion start zone to the main combustion zone in the combustion chamber. 8. The method for controlling combustion in a waste incinerator according to claim 1, wherein the method is applied to an arbitrary area.

9. High-temperature gas B is blown vertically above the grate surface into any area between the combustion start area and the main combustion area in the combustion chamber from a height within the range of 0.2 to 2.5 m. The method for controlling combustion of a waste incinerator according to any one of claims 1 to 7, characterized in that:

10. The high-temperature gas 33 is blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber at a blowing speed of at least 10 m / s or more. Item 10. The combustion control method for a waste incinerator according to any one of Items 9.

11. The flow rate of the circulating exhaust gas C and / or the stirring gas D is adjusted so that the gas temperature in the secondary combustion region is in the range of 800 to L500 ° C. The combustion control method for a waste incinerator according to any one of claims 1 to 10.

12. The combustion of a waste incinerator according to any one of claims 1 to 11, wherein the stirring gas D is blown such that a swirling flow is formed in the secondary combustion region. Control method.

13. The flow rate of the hot gas B is adjusted so that the temperature of the primary flue gas passing through the combustion start zone or the main combustion zone becomes higher than ^^ of the primary flue gas passing through the post-combustion zone. combustion control method _c waste incinerator according to any one of claims 1 to 1 2

14. The flow rate of the hot gas B and / or the circulating exhaust gas C is adjusted so that the temperatures of the main combustion zone and the post-combustion zone are within the range of 800 to 150 ° C, respectively. The combustion control method for a waste incinerator according to any one of claims 1 to 13, wherein:

15. The oxygen concentration and / or gas temperature of the hot gas B is adjusted so that the temperatures of the main combustion zone and the post-combustion zone are within the range of 800 to 150 ° C, respectively. The method for controlling combustion in a waste incinerator according to any one of claims 1 to 14.

16. A means for blowing primary air for combustion, which blows primary air for combustion A into the combustion chamber from below the grate,

High-temperature gas blowing means for blowing high-temperature gas B into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber;

The circulating exhaust gas C containing at least a portion of the exhaust gas discharged from the incinerator Secondary combustion of a circulating flue gas blowing means that blows air above the blowing position or downstream of the gas flow direction, and a stirring gas D consisting of air, circulating flue gas, or a mixed gas of air and circulating flue gas A grate-type waste incinerator, characterized by comprising a stirring gas blowing means for blowing into a region.

17. The grate-type waste incinerator according to claim 16, wherein the high-temperature gas B injection nozzle is provided at a height not exceeding 50% of the height of the combustion chamber.

18. The high-temperature gas B injection nozzle is provided vertically above the surface of the waste layer on the grate at a height within a range of 0.2 to 1.5 m. A grate-type waste incinerator according to claim 17.

19. The hot gas B injection nozzle is provided vertically above the grate surface at a height within a range of 0.2 to 2.5 m, wherein the height is within a range of 0.2 to 2.5 m. Grate-type waste incinerator as described.

20. The grate system according to any one of claims 16 to 19, wherein a stirrer gas D blowing nozzle is provided so that a swirling flow is formed in the secondary combustion region. Waste incinerator.

21. A means is provided for adjusting the flow rate of the hot gas B so that the temperature of the primary flue gas passing through the combustion start zone or the main combustion zone becomes higher than the temperature of the primary flue gas passing through the post-combustion zone. The grate-type waste incinerator according to any one of claims 6 to 20, characterized in that:

22. The grate-type waste incinerator according to any one of claims 16 to 21, further comprising means for adjusting a flow rate of the high-temperature gas B and / or the circulating exhaust gas C.

23. The grate-type waste incinerator according to any one of claims 16 to 22, further comprising means for adjusting the oxygen concentration and / or gas temperature of the high-temperature gas B.