JP2014114989A - Waste incinerator and waste incineration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grate type waste incinerator and a waste incineration method that can suppress amount of generated harmful substances and can perform a low air ratio combustion operation without problems.SOLUTION: A grate type waste incinerator includes: a combustion chamber 2 having a grate and burning waste on the grate; primary air blowing means 9 for blowing combustion primary air from the lower side of the grate into the combustion chamber 2; and high temperature gas blowing means 13 for blowing high temperature gas downwardly from a ceiling of the combustion chamber toward any region from a combustion start region to a main combustion region within the combustion chamber in the incinerator length direction that is a movement direction of the waste on the grate. The high temperature gas blowing means includes high temperature gas blowing flow rate control means 15 for controlling a blowing flow rate of the high temperature gas to a range indicating by the following formula (1) in relationship with height of the combustion chamber: (1) -0.107X+4.70X+3.96≤Y≤-0.199X+8.73X+7.36, wherein Y is the blowing flow rate of the high temperature gas (m/sec) and X is the height of the combustion chamber (m).

Description

  The present invention relates to a grate-type waste incinerator and a waste incineration method for incinerating waste such as municipal waste.

  Grate-type waste incinerators are widely used as incinerators for incinerating waste such as municipal waste. The outline of the configuration of the representative one will be described below.

  The grate-type waste incinerator has a three-stage grate (dry grate, combustion grate, and post-combustion grate) that is arranged in the direction of waste movement at the bottom of the combustion chamber that burns the waste. The secondary combustion chamber is connected to the outlet of the combustion chamber located above the post-combustion grate. The combustion chamber is provided with a waste inlet located above the dry grate. An ash drop port is provided at the downstream side of the post-combustion grate waste in the moving direction. Usually, the secondary combustion chamber is also a part of a waste heat boiler for waste heat recovery, and is in the vicinity of the inlet. Further, a combustion primary air blowing mechanism for blowing combustion primary air from below the grate of each of the dry grate, the combustion grate, and the post-combustion grate is provided.

  In such a grate-type waste incinerator, waste thrown into the combustion chamber from the waste inlet is deposited on the dry grate and dried by air from the bottom of the dry grate and radiant heat in the furnace. At the same time, the temperature is raised and ignition occurs. That is, immediately above the dry grate, a dry region is formed in the upstream space in the waste movement direction, and combustion occurs from the downstream space directly above the dry grate to the upstream space directly above the combustion grate. A starting region is formed. The waste that ignites in the combustion start area and starts combustion is sent from the dry grate onto the combustion grate, and the waste is pyrolyzed to generate combustible gas, and the combustion sent from the bottom of the combustion grate The primary air for combustion burns combustible gas and solid content, and a main combustion region is formed in the space immediately above the combustion grate. Further, unburned components such as fixed carbon are completely burned on the post-combustion grate, and a post-combustion region is formed in a space immediately above the post-combustion grate. Thereafter, the ash remaining after combustion is discharged to the outside from the ash drop opening.

  Thus, in the grate-type waste incinerator, the waste is burned by the primary combustion air blown from below the three-stage grate in the combustion chamber. Further, the unburned portion of the combustible gas contained in the combustion exhaust gas from the combustion chamber receives and burns secondary combustion air in the secondary combustion chamber.

  In a conventional grate-type waste incinerator, the ratio (air ratio) obtained by dividing the amount of air actually supplied into the incinerator by the theoretical amount of air necessary for combustion of the waste is usually about 1.6. . This is larger than 1.05 to 1.2 which is an air ratio necessary for combustion of general fuel. The reason for this is that waste has a higher incombustibility than liquid fuel or gaseous fuel as a general fuel and is inhomogeneous, so the efficiency of air utilization is low, and a large amount of air is required for combustion. Because it becomes. However, if the supply air is simply increased, the amount of exhaust gas increases as the air ratio increases, and accordingly, a larger exhaust gas treatment facility is required.

  If waste can be burned without any problems in a waste incinerator with a reduced air ratio, the amount of exhaust gas will be reduced, and the exhaust gas treatment facility will become compact. As a result, the entire waste incineration facility will be downsized. Equipment costs can be reduced. In addition, since the amount of chemicals used for exhaust gas treatment is reduced, the operating cost can be reduced. Furthermore, since the heat recovery rate of the waste heat boiler can be improved by reducing the amount of exhaust gas, the amount of heat that can not be recovered and discarded to the atmosphere is reduced, and the efficiency of power generation using waste incineration waste heat is reduced accordingly. Can be raised.

  Thus, the advantage of performing the low air ratio combustion is great, but on the other hand, the low air ratio combustion with the air ratio of 1.5 or less causes a problem that the combustion becomes unstable. In other words, when waste is burned at a low air ratio, combustion becomes unstable, CO generation increases, flame temperature rises locally, NOx increases rapidly, and soot is generated in large quantities. As a result, there is a problem that harmful substances in the exhaust gas increase, and waste and ash melt and adhere to the furnace wall due to local high temperatures, and clinker is generated, and the refractory life of the furnace wall is shortened. There is a problem of becoming.

  Under such circumstances, a waste incinerator capable of stably burning at a low air ratio of 1.5 or less has been studied and disclosed in Patent Document 1 (paragraph 0063). ). According to Patent Document 1, high temperature exhaust gas is led out from the outlet side of the secondary combustion region of the waste incinerator, dust is removed, and then mixed with air to be blown into the combustion chamber as a high temperature gas, thereby obtaining the following effects. .

  That is, promoting the thermal decomposition of waste by sensible heat and radiation of high temperature gas, promoting the combustion of combustible gas generated by thermal decomposition of waste by blowing high temperature gas containing oxygen, Gas is blown into the combustion chamber from a nozzle provided on the side wall of the combustion chamber (paragraph 0040), and the flow of the high-temperature gas collides with the upward flow of the combustible gas and the combustion gas generated from the waste. By forming a stagnation region where the flow is slow immediately above, the flow of combustible gas becomes gentle, and there is an effect that stable combustion is performed because the combustible gas is sufficiently mixed with the oxidant component, By blowing high temperature gas into the combustion chamber, it is said that the combustion of waste can be performed stably under low air ratio combustion operation.

JP 2004-84981 A

  In the combustion of waste in a waste incinerator, stable combustion of combustible gas generated by thermal decomposition of the waste suppresses the generation of harmful substances such as CO and NOx generated by the combustion. To make a big contribution. In the waste incinerator described in Patent Document 1, high-temperature gas is blown into the combustion chamber from a nozzle provided on the side wall of the combustion chamber. In this case, the high-temperature gas blown from the side wall exerts the above-described effects evenly over the entire combustion chamber from the vicinity of the side wall to the central part, and is combustible generated from the waste layer under the low air ratio combustion operation. It may not always be possible to stably perform gas combustion.

  In the case of an incinerator with a large amount of waste incineration and a wide combustion chamber width (width in the direction perpendicular to the direction of waste movement on the grate), high-temperature gas blown from the side wall However, it does not reach the vicinity of the center of the combustion chamber, and the above-described combustion promotion effect and combustion stabilization effect cannot be exhibited. Therefore, there is a problem that the low air ratio combustion operation cannot be performed sufficiently. In addition, appropriate blowing conditions for high-temperature gas depending on the size of the incinerator and the shape of the combustion chamber may not always be clear.

  In view of such circumstances, the present invention is not limited to the size of the combustion chamber of the waste incinerator, even when a low air ratio combustion operation with an air ratio of 1.5 or less is performed, from the vicinity of the combustion chamber side wall to the central portion. A fire that can stably burn waste throughout the entire combustion chamber, suppress the generation of harmful substances such as CO and NOx, and perform low-air ratio combustion operations without problems. It is an object to provide a lattice-type waste incinerator and a waste incineration method.

  The inventors have studied a waste incinerator that blows high-temperature gas downward into the combustion chamber from a blow-off port provided in the ceiling of the combustion chamber. The inflow furnace has a downward flow of high-temperature gas and combustible gas and combustion gas generated from the waste. , A slow stagnation area or a circulation area that circulates in the vertical direction directly over the waste layer, regardless of the size of the combustion chamber. It has been found that a combustion promoting effect and a combustion stabilizing effect can be obtained. Furthermore, when hot gas is blown downward from the combustion chamber ceiling blow-in port, it is important to appropriately determine the flow rate of the hot gas to be blown, and the flow rate of the hot gas to be blown can be set according to the height of the combustion chamber. We found it preferable and determined the appropriate range of the hot gas flow rate to match the combustion chamber height by examining the impact on the combustion stability of the waste.

  According to the present invention, the above-mentioned problems are solved by the following first invention with respect to the grate-type waste combustion furnace, and with the second invention with respect to the waste incineration method.

<Grate-type waste incinerator>
(1) 1st invention It is a grate-type waste incinerator, Comprising: The combustion chamber which comprises a grate and burns the waste on a grate,
The primary air blowing means for blowing the primary air for combustion into the combustion chamber from under the grate, and the combustion in the furnace length direction, which is the moving direction of the waste on the grate, from the ceiling of the combustion chamber High-temperature gas blowing means for blowing downward toward an arbitrary region between the combustion start area in the room and the main combustion area, the high-temperature gas blowing means, A grate-type waste incinerator comprising a high-temperature gas blowing flow rate control means for controlling so as to be within a range represented by the following expression (1) in relation to height:

-0.107X ² + 4.70X + 3.96 ≤ Y ≤ -0.199X ² + 8.73X + 7.36 (1)
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)
In the first invention, the high temperature gas blowing means preferably blows high temperature gas having a temperature in the range of 100 to 400 ° C. and an oxygen concentration in the range of 5 to 30% by volume.

  In the first invention, the high-temperature gas blowing means includes a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. It is preferable to provide a high-temperature gas supply source that supplies at least one of them as a high-temperature gas.

<Grate-type waste incineration method>
(2) Second invention A waste incineration method using a grate-type waste incinerator having a combustion chamber, wherein primary combustion air is blown into the combustion chamber from below the grate, and hot gas is introduced from the ceiling of the combustion chamber In the furnace length direction, which is the direction of movement of waste on the grate, it is blown downward toward any region between the combustion start region and the main combustion region in the combustion chamber, and the hot gas blowing flow rate is burned. A waste incineration method characterized by having a range represented by the following formula (1) in relation to the room height.

-0.107X ² + 4.70X + 3.96 ≤ Y ≤ -0.199X ² + 8.73X + 7.36 (1)
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)
In the second invention, the high temperature gas preferably has a temperature in the range of 100 to 400 ° C. and an oxygen concentration in the range of 5 to 30% by volume.

  In the second invention, the hot gas is preferably blown at a flow rate 5 to 20 times the superficial velocity obtained by dividing the flow rate of the combustion chamber gas by the cross-sectional area of the combustion chamber in a plane perpendicular to the furnace length direction.

  In the second invention, the high-temperature gas is a return exhaust gas obtained by returning a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. It is preferable that it is at least one.

  In the present invention, as described above, since the high temperature gas is blown from the ceiling of the combustion chamber, the following effects are obtained.

  High temperature gas is blown downward from the blow-off port provided on the ceiling of the waste incinerator combustion chamber, and the flow velocity of the high temperature gas to be blown is in an appropriate range with respect to the height of the combustion chamber. Combustion gas generated from the material layer collides with the upward flow of combustion gas, and the stagnation region where the gas flow circulates just above the waste layer or the circulation region where it circulates in the vertical direction is the width direction and length of the combustion chamber Since it can be formed over a wide range of directions, a planar combustion region can be established, and the air ratio is 1. regardless of the size of the incinerator, that is, the width and height of the combustion chamber. Even in low air ratio combustion of 5 or less, waste and generated combustible gas can be stably burned. And since combustion is stabilized, the generation amount of harmful substances such as CO and NOx in the exhaust gas discharged from the waste incinerator can be suppressed. Furthermore, the thermal decomposition of waste can be promoted by radiation of a standing flat flame, etc., so the amount of waste supplied to the grate (grate load) and the amount of waste heat supplied to the combustion chamber (furnace) Load) can be increased. For this reason, the volume of the combustion chamber can be reduced relative to the amount of waste incineration, the furnace height of the incinerator can be reduced, and the waste incineration equipment can be made compact to reduce equipment costs and operating costs. Can do.

It is a lineblock diagram showing an outline of a waste incinerator concerning one embodiment of the present invention. 2B is a sectional view in the combustion chamber width direction of the waste incinerator of FIG. 1 for explaining the combustion state in the incinerator, and is compared with the corresponding sectional view of the conventional incinerator of FIG. It is shown as It is a figure which shows the suitable range with respect to the combustion chamber height of the blowing flow velocity of the hot gas injected into a waste incinerator.

  Hereinafter, the present invention will be described in detail according to various embodiments of the present invention. The technical scope of the present invention is not limited by these embodiments, and can be implemented in various forms without changing the gist of the invention. Further, the technical scope of the present invention extends to an equivalent range.

  First, prior to the description of this embodiment, regarding the stabilization of combustion by high-temperature gas injection according to the present invention, the structural comparison between the conventional waste incinerator and the waste incinerator of the present invention, and the present invention obtained. Summarize the effects that can be achieved.

  FIG. 2 (a) of the accompanying drawings shows a combustion state in a conventional waste incinerator (the waste incinerator described in Patent Document 1), and FIG. 2 (b) relates to one embodiment of the present invention. The combustion state in the waste incinerator is shown. With reference to this, the combustion state in the waste incinerator and the conventional waste incinerator and one of the present invention regarding the stabilization of combustion by blowing high-temperature gas are shown. The waste incinerator according to the embodiment will be described in comparison.

  As shown in FIG. 2 (a), the conventional waste incinerator 20 has an inlet 23 in a side wall (a side wall facing in the furnace width direction perpendicular to the moving direction of the waste W on the grate 5) 21. The waste W on the grate 5 is burned by the combustion air A from below. During the combustion of the waste W, the hot gas B is blown obliquely downward from the blow-in port 23 provided on the side wall 21 of the combustion chamber, and the heat rising from the hot gas B and the waste layer W on the grate 5 The upward flow of the combustible gas generated by the decomposition and the combustion gas collide with each other to form a stagnation region where the flow is slow immediately above the waste layer W. Therefore, a combustible gas is burned to form a planar combustion region (planar flame) D. In such a conventional incinerator, stable combustion can be obtained even in a low air ratio combustion operation, but in a combustion furnace having a large combustion chamber width (distance between the side walls), as shown in FIG. Since the hot gas B blown from the blow-in port 21 does not reach the vicinity of the center of the combustion chamber and cannot form a stagnation region in the center, a planar combustion region cannot be formed in the center and is combustible. There is a problem that the property gas is not burned sufficiently and the combustion becomes heterogeneous in the furnace width direction.

  In contrast, as shown in FIG. 2 (b), the waste incinerator 1 according to the embodiment of the present invention is provided with a plurality of inlets 13 in the ceiling width direction in the ceiling 22 and disposed on the grate 5. The object W is burned by the combustion air A from below. When the waste W is burned, the hot gas B is blown downward from the blowing port 13 provided in the ceiling 22, and the upward flow of the hot gas B and the combustible gas and the combustion gas rising from the waste W , A stagnation area where the flow is slow or a circulation area that circulates in the vertical direction is formed immediately above the waste layer W, and the planar combustion area (planar flame) E is set in the furnace width direction and the furnace length direction (the direction of movement of waste). ) Uniformly. Thereby, even in an incinerator having a large furnace width, uniform and stable combustion is possible.

  The waste incinerator of the present invention blows high temperature gas downward into the combustion chamber from the blow port provided in the ceiling of the combustion chamber, and the downward flow of high temperature gas and the rise of combustible gas and combustion gas generated from waste By colliding with the flow, regardless of the size of the combustion chamber, a stagnation region with a slow flow is formed immediately above the waste layer over the entire combustion chamber, and a combustion promoting effect and a combustion stabilizing effect are obtained. Furthermore, by setting the flow rate of the high-temperature gas blown downward from the combustion chamber ceiling inlet according to the combustion chamber height, the combustion promotion effect and the combustion stabilization effect can be reliably obtained regardless of the combustion chamber height. . That is, in the present invention, the following effects are obtained by blowing hot gas downward from the ceiling of the combustion chamber.

  The effect of blowing hot gas downward from the ceiling of the combustion chamber will be described in detail.

  (1) The thermal decomposition of the waste W is promoted by the sensible heat and radiation of the high temperature gas.

  (2) The combustion of the combustible gas generated by the thermal decomposition of the waste W is promoted by blowing a high-temperature gas containing oxygen.

  (3) The hot gas is blown downward into the combustion chamber from the inlet 13 provided in the ceiling 22 of the combustion chamber, the downward flow of the high temperature gas, and the upward flow of the combustible gas and the combustion gas generated from the waste W Facing each other and forming a slow stagnation region or a circulation region in which the flow circulates in the vertical direction directly above the waste layer, the flow of combustible gas becomes gentle, and the combustible gas flows into the primary air for combustion or high temperature. Since it is sufficiently mixed with the oxidant component supplied by the gas, stable combustion is performed. In the stagnation region or circulation region immediately above the waste layer, the combustible gas is stably burned to form a flat combustion region (planar flame), which is present.

  (4) The thermal decomposition of the waste W is promoted by radiation of the standing flat flame.

  Thus, by the actions (1) to (4), the waste W can be stably burned even under the low air ratio combustion operation. And since combustion is stabilized, combustible gas is fully combusted and the generation amount of harmful substances, such as CO and NOx, in the exhaust gas discharged from the incinerator can be suppressed.

  Further, since the thermal decomposition of the waste W can be promoted by radiation of the standing flat flame E or the like, the amount of waste W supplied to the grate 5 (grate load) and the waste supplied to the combustion chamber The amount of heat of W (furnace load) can be increased. For this reason, the volume of the combustion chamber can be reduced with respect to the amount of waste incineration, the furnace height of the incinerator can be reduced, and the waste incineration equipment can be made compact, thereby reducing the equipment cost and operation cost. be able to.

  Next, in the present invention, an upper limit and a lower limit of an appropriate range of the hot gas injection flow rate corresponding to the combustion chamber height are clarified, and a preferable range is determined.

  Opposite the upward flow of combustible gas and combustion gas generated from waste, high temperature gas is blown downward from the ceiling of the combustion chamber to form an appropriate stagnation region or circulation region directly above the waste layer. In order to establish the combustion region, it is necessary to appropriately impinge the hot gas blown into the upward flow from the waste layer, and it is necessary to increase the flow velocity as the combustion chamber height increases. However, if the flow rate is made too high, the high temperature gas blows directly into the waste layer, causing the waste to cool down or scatter the waste, resulting in unstable combustion. , Fly ash increases and is not preferable. Therefore, an upper limit of the flow rate of the hot gas is determined by obtaining a flow rate that does not adversely affect the waste layer. Further, the lower limit of the flow rate of the hot gas is determined from the limit flow rate at which the stagnation region or the circulation region can be formed. In this way, an appropriate range of the hot gas flow rate is determined in accordance with the combustion chamber height.

  As an indicator of the impact on the combustion stability of waste, we determined the appropriate range of the flow rate of high-temperature gas according to the height of the combustion chamber by examining the amount of harmful substances generated. Specifically, for a waste incinerator with a certain combustion chamber height, when the flow rate of high-temperature gas is changed variously, the concentration of harmful substances such as CO and NOx in the exhaust gas discharged from the waste incinerator is investigated, The range of high-temperature gas flow velocity that can suppress the generation of gas, that is, stable combustion, is determined, and the case where the combustion chamber height is different is examined in the same way, and the flow rate of the high-temperature gas relative to the combustion chamber height is The preferred range was clarified. Such a range is a range having an upper limit and a lower limit as shown in FIG. 3 showing the relationship of the flow velocity of the hot gas to the combustion chamber height.

  A line indicating an upper limit and a lower limit of an appropriate range of the hot gas blowing flow rate is as follows as a relational expression between the hot gas blowing flow rate (Y) and the combustion chamber height (X).

Upper limit Y = −0.199X ² + 8.73X + 7.36
Lower limit Y = −0.107X ² + 4.70X + 3.96
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)
The waste incinerator and the waste incineration method of the present invention can be achieved by setting the flow velocity of hot gas to an appropriate range as defined by the relational expression indicating the upper and lower limits with respect to the combustion chamber height. In the incinerator with a wide range of combustion chamber heights, the appropriate blowing conditions of the high temperature gas blown downward from the combustion chamber ceiling inlet are clarified. The combustion of waste is stable even under low air ratio combustion.

  Hereinafter, the basic configuration, each component device, and operation of the grate-type incinerator of one embodiment of the present invention will be described.

  FIG. 1 is a schematic sectional side view showing a waste incinerator according to an embodiment of the present invention. First, a basic configuration of a waste incinerator and an overview of an incineration method according to an embodiment of the present invention will be described, and then details of each component device will be described. In this embodiment, the upstream side of the combustion chamber in the movement direction of the waste in the combustion chamber is referred to as a front portion, and the downstream side is referred to as a rear portion.

<Basic configuration of grate-type incinerator>
The waste incinerator 1 shown in FIG. 1 can make the grate-type waste incinerator equipment compact by stably performing low air ratio combustion by blowing high temperature gas downward from the ceiling or the like. Equipment costs and operating costs can be greatly reduced.

  The waste incinerator 1 according to the present embodiment is disposed on the combustion chamber 2 and on the upstream side (left side in FIG. 1) in the flow direction of the waste in the combustion chamber 2 so as to put the waste into the combustion chamber. This is a grate-type incinerator that includes a waste inlet 3 and a boiler 4 that is provided above the downstream side (the right side in FIG. 1) in the waste flow direction of the combustion chamber 2.

  At the bottom of the combustion chamber 2, there is provided a grate (stoker) 5 that burns while moving the waste. The grate 5 is provided in the order of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c from the side closer to the waste inlet 3, that is, from the upstream side.

  In the dry grate 5a, waste is mainly dried and ignited. In the combustion grate 5b, waste is thermally decomposed and partially oxidized, and combustible gas and solid content generated by the thermal decomposition are combusted. On the post-combustion grate 5c, the remaining unburned matter in the waste is completely burned. The combustion ash after complete combustion is discharged from the ash drop opening 6.

  Wind boxes 7a, 7b, 7c, and 7d are provided below the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c in the combustion chamber 2, respectively. The combustion primary air A supplied by the blower 8 is supplied to the wind boxes 7a, 7b, 7c, 7d through the combustion primary air supply pipe 9, and combusts through the fire grates 5a, 5b, 5c. It is supplied into the chamber 2. The primary air A for combustion supplied from below the grate is used for drying and burning waste on the grate 5a, 5b, 5c, cooling action of the grate 5a, 5b, 5c, Has a stirring action.

  A waste heat boiler 4 is connected to the outlet on the downstream side of the combustion chamber 2, and the vicinity of the inlet of the waste heat boiler 4 is a secondary combustion region 10 for burning unburned gas in the gas discharged from the combustion chamber 2. It has become. In the secondary combustion region 10 which is a part of the waste heat boiler, secondary combustion gas is blown into the unburned gas, and secondary combustion is performed. After this secondary combustion, the combustion exhaust gas is recovered by the waste heat boiler 4. After heat recovery, the combustion exhaust gas discharged from the waste heat boiler is neutralized with acid gas by slaked lime, etc. and dioxins are adsorbed by activated carbon in an exhaust gas treatment system (not shown), and further to a dust removal equipment (not shown). The neutralized reaction product, activated carbon, dust and the like are collected. The combustion exhaust gas that has been dedusted and detoxified by the dust removing device is attracted by an attraction fan (not shown) and released from the chimney into the atmosphere.

  In the grate-type incinerator having such a basic configuration, the waste incinerator 1 according to the present embodiment includes a primary air blowing means for blowing the primary air for combustion into the combustion chamber from under the grate, and a high temperature. High temperature gas blowing means for blowing gas downward from the ceiling of the combustion chamber 2 toward any region between the combustion start region and the main combustion region in the combustion chamber 2 in the furnace length direction, and a secondary combustion gas Secondary combustion gas blowing means for blowing the gas into the secondary combustion region. The hot gas blowing means includes a plurality of hot gas blowing ports, and blows the hot gas against the upward flow of the combustible gas and the combustion gas generated from the waste, so that the stagnation region directly above the waste layer or A circulation region is formed to make the planar combustion region stand.

<Primary air blowing means>
In the present embodiment, the waste incinerator 1 includes a primary air supply system of primary air that serves as combustion air. In the primary air supply system, the primary air A from the air supply source is branched to the wind boxes 7a, 7b, 7c, and 7d of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c via the pipe line 9, respectively. The pipe 9 is provided with a blower 8 and a damper 11 as a flow rate adjusting mechanism.

<High-temperature gas blowing means>
The high temperature gas blowing means includes a high temperature gas supply source 12 provided outside the combustion chamber 2, a high temperature gas injection port 13 for blowing the high temperature gas B into the combustion chamber 2, and the high temperature gas B from the high temperature gas supply source 12. It has a conduit 14 leading to the high temperature gas inlet 13 and a damper 15 as a flow rate adjusting mechanism.

  The hot gas inlet 13 is provided at an arbitrary position directly above the grate within the range from the downstream side (rear part) of the waste grate 5a in the movement direction of the waste to the combustion grate 5b on the ceiling of the combustion chamber 2. . In the example of FIG. 1, in the moving direction of the waste, that is, in the length direction of the incinerator 2, it is provided in three rows immediately above the grate downstream of the dry grate 5a and directly above the grate of the combustion grate 5b. It has been.

  The high temperature gas inlet 13 is also provided at a plurality of locations in the width direction of the incinerator (direction perpendicular to the paper surface in FIG. 1). Therefore, the hot gas inlet 13 is disposed at a plurality of positions in the length direction and the width direction of the incinerator. Further, the direction of the high temperature gas inlet 13 is determined so that the high temperature gas B is blown downward. Thus, the hot gas is blown from the combustion start region toward the main combustion region, which is formed immediately downstream of the dry grate 5a and directly above the combustion grate 5b.

<Secondary combustion gas supply means>
In addition, the waste incinerator 1 of the present embodiment includes a secondary combustion gas (secondary air) supply system that blows the secondary combustion gas into a secondary combustion region 10 corresponding to the vicinity of the inlet of the boiler 4. . The secondary combustion gas supply system feeds the secondary combustion gas C from the secondary combustion gas supply source through the pipe 19 to the secondary combustion gas inlet 16 provided in the secondary combustion region 10. The pipe 19 is provided with a blower 17 and a damper 18 as a flow rate adjusting mechanism. The secondary combustion gas inlet 16 is provided on the peripheral wall of the boiler 4 so as to blow the secondary combustion gas C into the secondary combustion region 10 in the vicinity of the inlet of the boiler 4.

  In the present invention, the configuration of the pipeline for supplying the primary air for combustion, the high-temperature gas, and the secondary combustion gas is not limited to those shown in the drawings, and may be appropriately selected depending on the scale, shape, application, etc. of the incinerator. Can be selected.

<Combustion chamber areas>
In such an incinerator of this embodiment, a waste layer is formed on the dry grate 5a and the combustion grate 5b, and due to the combustion, the space in the combustion chamber 2 is directly above the waste layer. The following areas are formed.

  A dry region is formed in the upstream range of the dry grate 5a, which is positioned directly above the dry grate 5a and below the waste inlet 3, and is combusted from the downstream range of the dry grate 5a. A combustion start region is formed in the upstream range of 5b. That is, the waste on the dry grate 5a is dried in the upstream range, ignited in the downstream range, and combustion starts.

  The waste on the combustion grate 5b carried from the dry grate 5a is thermally decomposed and partially oxidized here, and the combustible gas generated from the waste and the solid content in the waste are combusted. The waste is substantially burned on the combustion grate 5b. Thus, a main combustion region is formed immediately above the combustion grate 5b. Thereafter, the unburned matter such as fixed carbon in the remaining waste is completely burned on the post-burning grate 5c. Thereafter, a post-combustion region is formed on the post-combustion grate 5c.

  Most of the combustible gas generated in the combustion chamber 2 is combusted in the combustion chamber 2, and the remaining unburned gas is secondary corresponding to the vicinity of the inlet of the boiler 4 connected above the post-combustion grate 5c. The gas flows into the combustion region 10 where secondary combustion gas is supplied and secondary combustion occurs.

  When the waste is incinerated, water evaporation occurs first, followed by thermal decomposition and partial oxidation reaction, and combustible gas begins to be generated. Here, the combustion start region is a region where combustion of waste starts and combustible gas begins to be generated by thermal decomposition and partial oxidation of the waste. The main combustion region is a region where waste is thermally decomposed, partially oxidized and burned, combustible gas is generated and burned with a flame, and combustion with a flame is completed ( This is the area up to the burnout point. In a region after the burn-out point, a char combustion region (post-combustion region) in which solid unburnt (char) in the waste is combusted is obtained. In the grate-type waste incinerator, the combustion start area corresponds to the space above the dry grate 5a, and the main combustion area corresponds to the space above the combustion grate 5b.

  Next, an outline of the incineration situation in the apparatus of the present embodiment configured as described above, and actions by blowing in primary combustion air, high temperature gas, and secondary combustion air will be sequentially described.

<Overview of incineration>
First, when the waste is introduced into the waste inlet 3, the falling waste is deposited on the dry grate 5a and is moved onto the combustion grate 5b and onto the post-combustion grate 5c by the operation of each grate. And a waste layer is formed on each grate. Each grate receives the primary air for combustion via the wind boxes 7a, 7b, 7c, 7d, whereby the waste in each grate is dried and burned.

  Wastes are mainly dried and ignited on the dry grate 5a. That is, drying is performed in the upstream region of the drying grate 5a and ignition (combustion start) is performed in the downstream region. On the combustion grate 5b, the thermal decomposition and partial oxidation of the waste are mainly performed, and the combustible gas and the solid content in the waste are combusted. The combustion of the waste is substantially completed on the combustion grate 5b. On the post-combustion grate 5c, unburned components such as fixed carbon in the remaining waste are completely burned. The combustion ash after complete combustion is discharged from the ash drop opening 6. In a state where the waste is burning in this way, a dry region, a combustion start region, a main combustion region, and a post-combustion region are formed in the space immediately above each grate 5a, 5b, 5c.

  As described above, the waste heat boiler 4 is connected to the outlet of the combustion chamber 2, and the vicinity of the inlet of the waste heat boiler 4 is the secondary combustion region 10. Therefore, the unburned gas generated in the combustion chamber 2 is guided to the secondary combustion region 10, where it is mixed and stirred with the secondary combustion gas C, and undergoes secondary combustion. After the secondary combustion, the combustion exhaust gas is recovered by the waste heat boiler 4. After the heat is recovered, the combustion exhaust gas discharged from the waste heat boiler 4 is subjected to neutralization of acid gas by slaked lime and the like, adsorption of dioxins by activated carbon, and further sent to a dust removal device (not shown), Neutralization reaction products, activated carbon, dust, etc. are recovered. The combustion exhaust gas that has been dedusted and detoxified by the dust removing device is attracted by an attracting fan (not shown) and released from the chimney into the atmosphere. In addition, as said dust removal apparatus, dust removal apparatuses, such as a bag filter system and an electrostatic dust collection system, can be used, for example.

  Next, the blowing of the primary combustion air, the high temperature gas, and the secondary combustion gas will be described in detail.

<Blowing primary air for combustion>
The primary air A for combustion passes from the blower 8 through the primary air supply pipe 9 for combustion, and wind boxes 7a, 7b, 7c provided at the lower portions of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c, respectively. , 7d and then supplied into the combustion chamber 2 through the grate 5a, 5b, 5c. The flow rate of the combustion primary air A supplied into the combustion chamber 2 is adjusted by a flow rate adjusting damper 11 provided in the combustion primary air supply pipe 9, and further supplied to each wind box 7a, 7b, 7c, 7d. The flow rate to be adjusted is adjusted by a flow rate adjustment damper (not shown) provided in each supply pipe provided to be branched to each wind box. Further, the configurations of the wind boxes 7a, 7b, 7c, 7d and the combustion primary air supply pipe 9 for supplying the combustion primary air A are not limited to those shown in the figure, but the incinerator scale, shape, application, etc. Can be appropriately selected.

  As the primary air A for combustion, it is preferable to use a gas having a temperature in the range of room temperature to 200 ° C. and an oxygen concentration in the range of 15 to 21% by volume. As the primary air A for combustion, any of air, oxygen-containing gas and return exhaust gas may be used, or a mixed gas thereof may be used.

<Combustion stabilization by hot gas injection>
As seen in FIG. 1, the hot gas B is blown downward toward the waste layer in any region between the combustion start region and the main combustion region in the combustion chamber 2. This is because in order to stabilize combustion, it is preferable to blow 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 region where a large amount of combustible gas exists is from the combustion start region to the main combustion region.

  By blowing the hot gas B downward into the region from the combustion start region to the main combustion region in the combustion chamber 2 and directly downward from the combustion chamber ceiling toward the waste layer W, the hot gas B blown downward is discarded. Opposite the upward flow of combustible gas and combustion gas generated by the thermal decomposition and partial oxidation of the material, both gas flows collide, and in the stagnation area where the flat flow is slow or vertically above the waste layer W A circulating area that circulates occurs. Since these regions have a slow gas flow rate, a flame in which the combustible gas burns is fixed, that is, a planar combustion region (planar flame) is present immediately above the waste layer W, and the combustible gas is present. Is stably burned. As a result, generation of soot can be suppressed while suppressing generation of harmful substances such as CO, NOx, dioxins and the like even in low air ratio combustion. For this reason, low air ratio combustion can be performed without hindrance.

  In addition to the fact that wastes are heated by thermal radiation and sensible heat of high-temperature gas, and thermal decomposition and partial oxidation are promoted, a planar combustion region (planar flame) is present directly above the waste layer. The waste is heated by thermal radiation and sensible heat from the planar combustion region, and thermal decomposition and partial oxidation are further promoted.

<High-temperature gas blowing flow rate>
The hot gas B blown from the hot gas blow-in port 13 is blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber 2 at a blowing flow rate in an appropriate range according to the height of the combustion chamber. It is preferable. An appropriate range in accordance with the combustion chamber height of the hot gas blowing flow rate is a range represented by the following relational expression.

-0.107X ² + 4.70X + 3.96 ≤ Y ≤ -0.199X ² + 8.73X + 7.36 (1)
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)
Combustion gas and combustion generated by pyrolysis and partial oxidation of waste by setting the flow velocity of the hot gas blown downward from the blow-off port of the combustion chamber ceiling to the height of the combustion chamber. Appropriately collides with the upward flow of gas, forms a flat stagnation region of slow flow or a circulation region that circulates in the vertical direction directly above the waste layer W, and establishes a planar combustion region directly above the waste layer W In addition, the combustible gas can be stably burned, and the combustion promotion effect and the combustion stabilization effect can be reliably obtained in the low air ratio combustion operation regardless of the height of the combustion chamber.

  Further, it is preferable that the high-temperature gas blowing flow rate is blown as a flow rate 5 to 20 times the superficial velocity obtained by dividing the flow rate of the combustion chamber gas by the cross-sectional area of the combustion chamber in a plane perpendicular to the furnace length direction. The stagnation region or the circulation region can be formed stably without being affected by the flow.

  The blowing speed of the high temperature gas B is adjusted, for example, by adjusting the blowing amount of the blower that sends the high temperature gas B or the opening degree of the damper 15 as a flow rate adjusting mechanism provided in the pipe 14. It is adjusted by doing.

  When there are a plurality of hot gas gas inlets 13, the hot gas B does not necessarily have to be blown from each hot gas inlet 13 at an equal flow rate, and the scale, shape, application or waste properties, quantity, waste of the incinerator 2 Depending on the layer thickness or the like, the blowing flow rate from each hot gas blowing port 13 can be appropriately changed so as to be different.

  In response to fluctuations in the amount of combustible gas and combustion gas generated from waste in the combustion chamber 2, the hot gas B is injected so that the planar combustion region is fixed immediately above the waste layer without fluctuation. It is preferable to adjust the flow rate. When the state of the planar combustion region changes, the combustion state of the combustible gas changes and the CO concentration, oxygen concentration, etc. in the combustion exhaust gas change, so the CO concentration and oxygen concentration of the exhaust gas discharged from the boiler are monitored as monitoring factors. You may make it adjust the blowing flow volume of the hot gas B according to the measurement and the change.

<Preparation of hot gas>
The temperature of the hot gas B blown from the hot gas blowing ports 13 and 15 is preferably in the range of 100 to 400 ° C, more preferably about 200 ° C. When a gas having a temperature of less than 100 ° C. is blown, the temperature in the furnace decreases, combustion becomes unstable, and the amount of CO generated increases. When a gas exceeding 400 ° C. is blown, the flame temperature in the combustion chamber becomes extremely high, which causes problems such as promotion of clinker generation.

  The oxygen concentration contained in the high temperature gas B is preferably about 5 to 30% by volume, and preferably 5 to 15% by volume. Thereby, the above-mentioned effect is exhibited more effectively, and the reduction of NOx and the reduction of CO of exhaust gas is further promoted.

  As the high-temperature gas B having the above gas temperature and oxygen concentration, a part of the exhaust gas is extracted downstream from the secondary combustion region 10 and returned, a mixed gas of return exhaust gas and air, and a gas containing oxygen. It is preferable to use any one of air and oxygen-enriched air. As the return exhaust gas, it is preferable to return and use a part of the exhaust gas discharged from the waste incinerator, that is, the dust exhausted and neutralized, that is, the exhaust gas discharged from the bag filter. The exhaust gas, the mixed gas of the return exhaust gas and air, the gas containing oxygen, the air, and the oxygen-enriched air are heated by steam generated in the waste heat boiler as necessary, and the temperature and oxygen concentration are The gas is blown into the combustion chamber as a high-temperature gas that satisfies the predetermined condition.

  By adjusting the mixing ratio of the return exhaust gas and air when preparing the high temperature gas, the heating conditions such as the return exhaust gas or the return exhaust gas and air mixed gas, etc., the temperature and oxygen concentration of the high temperature gas are adjusted to the desired ranges.

<High-temperature gas blowing area>
In FIG. 1, the hot gas inlet 13 is installed on the ceiling of the combustion chamber 2 above the dry grate 5 a and the combustion grate 5 b corresponding to the main combustion region from the combustion start region in the combustion chamber 2. Yes. Here, the thermal decomposition reaction of waste occurs at a temperature of about 200 ° C., and is almost completed when the temperature reaches about 400 ° C. In the region where the flammable gas is generated, the hot gas B is blown downward from the ceiling of the combustion chamber 2 directly above the waste layer to form a stagnation region or a circulation region near the waste layer in the furnace. Thus, the planar combustion region is allowed to stand and stable combustion is performed.

  In the example shown in FIG. 1, since the downstream part of the dry grate 5a and the upper part of the combustion grate 5b correspond to the main combustion area from the combustion start area, a high temperature gas inlet 13 is provided above these positions to provide a high temperature gas. B is blowing. Depending on the composition and properties of the waste, the thermal decomposition reaction may be completed at a higher temperature. In this case, a high-temperature gas inlet should also be provided downstream of the position shown in FIG. Is preferred.

<High temperature gas inlet>
The hot gas inlet 13 is provided at an arbitrary position directly above the grate within the range from the downstream side (rear part) of the waste grate 5a in the movement direction of the waste to the combustion grate 5b on the ceiling of the combustion chamber 2. Yes. The hot gas inlets 13 are arranged along a plurality of rows in the width direction and the length direction of the combustion chamber 2. The hot gas inlet 13 may be a nozzle type or a slit type.

  Arrangement position, arrangement number, arrangement interval, blowing direction, shape of blowing port (related to spreading shape of blowing hot gas B), blowing flow rate of blowing hot gas B, blowing flow rate, etc. The setting and operating conditions of the hot gas inlet 13 are set so as to control the state of the planar combustion region to a desired state in accordance with the processing amount, volume, shape, waste property, etc. of the waste incinerator. Adjusted.

  The state of the flow of the high-temperature gas facing the upward flow from the waste is favored so that a planar combustion region is formed over a wide range in the width direction and the length direction immediately above the waste layer in the combustion chamber. In order to control, at least one of the arrangement position, the number of arrangements, the arrangement interval, the blowing direction, the shape of the blowing port, the blowing flow rate and the blowing flow rate of the hot gas is set or adjusted.

  In FIG. 1, a hot gas blowing port 13 is provided on the ceiling of the combustion chamber 2, and the hot gas B is blown downward from here toward the waste layer. Here, as a blowing direction of the high temperature gas B, it is desirable to blow in a blowing direction in an angle range from a perpendicular to the waste layer to 20 °. This is because the flow field generated when the blown hot gas B collides with the combustible gas generated by the thermal decomposition and partial oxidation of the waste and the upward flow of the combustion gas is used as the counter flow field. This is because a suitable counter flow field is not formed when the blowing direction of is in a range larger than 20 ° from the perpendicular to the waste layer.

<Injection of secondary combustion gas>
The secondary combustion gas is blown into the secondary combustion region 10 and the unburned gas from the combustion chamber 2 is subjected to secondary combustion. As the secondary combustion gas, it is preferable to use a gas having a temperature in the range of room temperature to 200 ° C. and an oxygen concentration in the range of 15 to 21% by volume. As the secondary combustion gas, air, a gas containing oxygen, a return exhaust gas, or a mixed gas thereof may be used.

  It is preferable to install one or more secondary combustion gas inlets 16 so as to blow gas in a direction in which a swirling flow is generated in the secondary combustion region. By blowing the secondary combustion gas C in the direction in which the swirl flow is generated in the secondary combustion region 10, the gas temperature and oxygen concentration distribution in the secondary combustion region 10 can be made uniform and averaged. Subsequent combustion is performed stably, generation of a local high temperature region is suppressed, and exhaust gas can be further reduced in NOx. Furthermore, since the mixing of the unburned gas and the oxidant is promoted, the combustion stability is improved and complete combustion can be achieved, so that the exhaust gas can be reduced in CO.

  As the secondary combustion gas C, only the secondary air for combustion supplied by the blower, the gas in which the diluent is mixed with the secondary air for combustion after supply of the blower and the oxygen concentration is adjusted, after passing through the dust removing device Only the return exhaust gas from which a part of the exhaust gas is extracted, or a gas in which the secondary air for combustion and the return exhaust gas are mixed can be used.

  Diluents such as nitrogen and carbon dioxide are conceivable.

  It is preferable to adjust the flow rate of the secondary combustion gas so that the gas temperature in the secondary combustion region 10 is in the range of 800 to 1050 ° C. When the gas temperature in the secondary combustion region 10 is less than 800 ° C., the combustion of the unburned gas becomes insufficient and the CO in the exhaust gas increases. Moreover, when the gas temperature in the secondary combustion area | region 10 exceeds 1050 degreeC, the production | generation of clinker in the secondary combustion area | region 10 will be encouraged, and NOx will increase further.

<Distribution of oxygen amount ratio to achieve low air ratio combustion>
Next, the oxygen amount ratio distribution of the blown gas for realizing the low air ratio combustion in the waste incinerator of the present embodiment will be described.

  Ratio Q1 (=) of oxygen amount per unit time (Y1) supplied by combustion primary air blown into the combustion chamber from below the grate with respect to theoretical oxygen amount (X) per unit time required for combustion of waste Y1 / X) and the ratio Q2 (= Y2 / X) of the amount of oxygen (Y2) per unit time supplied by the high-temperature gas blown into any region between the combustion start region and the main combustion region in the combustion chamber And the ratio Q3 (= Y3 / X) of the oxygen amount (Y3) per unit time supplied by the secondary combustion gas blown into the secondary combustion region is expressed by the following equations (1) and (2): Preferably, each gas is blown so as to satisfy the following expressions (3) and (4). Combustion at a lower air ratio with an air ratio of 1.3 or less by controlling the ratio of blowing each gas so that the following equations (3) and (4) are satisfied. Can be realized.

Q1: Q2: Q3 = 0.75 to 1.10: 0.05 to 0.40: 0.10 to 0.40 (1)
1.0 ≦ Q1 + Q2 + Q3 ≦ 1.5 ………………………………………… (2)
Q1: Q2: Q3 = 0.80 to 1.0: 0.10 to 0.30: 0.10 to 0.30 (3)
1.1 ≦ Q1 + Q2 + Q3 ≦ 1.3 ……………………………………… (4)
Here, the theoretical oxygen amount (X) per unit time required for the combustion of the waste is necessary for the combustion per unit mass of the waste determined from the properties and components of the waste introduced into the combustion chamber. It is determined by the product (Nm ³ / hr) of the amount of oxygen (Nm ³ / kg) and the waste incineration rate (kg / hr) in the incinerator.

  The value of Q1 is the ratio of the oxygen amount per unit time (Y1) supplied by the primary combustion air supplied from below the grate into the combustion chamber to the theoretical oxygen amount, and the primary combustion air Adjust by increasing or decreasing the flow rate. Also, the value of Q2 is adjusted by increasing or decreasing the flow rate of the hot gas blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber. The value of Q3 is adjusted by increasing or decreasing the flow rate of the secondary combustion gas blown into the secondary combustion region.

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

  By setting the above ratios Q1, Q2, and Q3 within the range of the above formula, low oxygen ratio combustion (1.0 ≦ λ ≦ 1.5) (ie, equivalent to low air ratio combustion) is performed in a waste incinerator. Even in this case, the generation 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 greatly reduced.

<Distribution of oxygen amount ratio to realize combustion at a lower air ratio (with an air ratio of 1.3 or less)>
More preferable distribution ratios that can achieve stable low air ratio combustion by suppressing the generation of unburned waste and harmful substances are as follows: Q1: Q2: Q3 = 0.90: 0.15: 015, λ Based on = 1.20, Q1, Q2, and Q3 are adjusted within the above range with λ in the range of 1.1 to 1.3 based on the composition and properties of the waste put into the incinerator.

Specific examples of Q1, Q2, Q3, and λ will be described below.
Q1: Q2: Q3 = 0.90: 0.05: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.10: 0.20, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.20: 0.10, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.25: 0.05, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.05: 0.15, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.10: 0.10, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.15: 0.05, λ = 1.20
Q1: Q2: Q3 = 0.85: 0.10: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.85: 0.20: 0.15, λ = 1.20
Q1: Q2: Q3 = 0.80: 0.15: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.80: 0.20: 0.20, λ = 1.20
Q1: Q2: Q3 = 0.75: 0.20: 0.20, λ = 1.15
Q1: Q2: Q3 = 0.80: 0.15: 0.20, λ = 1.15
Q1: Q2: Q3 = 0.80: 0.10: 0.20, λ = 1.10.
Q1: Q2: Q3 = 0.80: 0.15: 0.15, λ = 1.10
Q1: Q2: Q3 = 0.85: 0.20: 0.25, λ = 1.30
Q1: Q2: Q3 = 0.90: 0.15: 0.25, λ = 1.30
Q1: Q2: Q3 = 1.00: 0.10: 0.20, λ = 1.30
Hereinafter, adjustment criteria for Q1, Q2, and Q3 will be described.

<Adjustment standard of primary air ratio Q1 for combustion>
Q1 is 0.90 for drying and burning normal municipal waste, etc., and Q1 is set when burning waste with low ash content or low moisture, such as plastic. The ratio is reduced to about 0.75 to 0.85, and the ratio Q2 of the hot gas is increased instead.

<Adjustment criteria for high-temperature gas ratio Q2>
To burn waste such as ordinary municipal waste, Q2 is based on 0.15, waste with little ash and moisture, and most combustible, such as plastic, or waste with a large volatile content Q2 is increased to about 0.20 to 0.25. If Q2 is small, the above-described effect of high-temperature gas blowing cannot be obtained sufficiently, and CO increases. If Q2 is increased beyond the above range, low air ratio combustion cannot be achieved, fuel costs for preparing high temperature gas, etc. increase, the temperature in the combustion chamber becomes excessive, and clinker is generated on the inner wall. Or NOx increases, which is not preferable.

<Adjustment standard of secondary combustion gas ratio Q3>
First, as a standard operation standard of a waste incinerator, Q1 and Q2 are determined in consideration of the composition and properties of waste based on the above standard, and then a standard value of Q3 is set. Q3 is adjusted within a range of 0.10 to 0.40 with 0.15 as a reference.

  The combustion state in the secondary combustion region is adjusted by adjusting the value of Q3.

  In actual operation of a waste incinerator, even if it operates with standard operating standards, the combustion status in the incinerator may change, and the amount of harmful substances in the exhaust gas emitted may vary. Therefore, while maintaining the values of Q1 and Q2 determined as described above, adjustment is made to increase or decrease Q3 based on a factor for monitoring the situation in the waste incinerator. By adopting such a combustion control method, even if the combustion situation in the incinerator changes, it can be adjusted so that the combustion is performed stably, and finally harmful substances in the exhaust gas discharged from the waste incinerator The amount can be easily controlled, and the combustion control system of the incinerator can be simplified.

  Here, as the factors for monitoring the situation in the waste incinerator, for example, the exhaust gas temperature near the outlet of the secondary combustion region where the secondary combustion of the unburned gas discharged from the combustion chamber or the boiler outlet is performed, the exhaust gas It is preferable to set any one or more of oxygen concentration, CO concentration, and NOx concentration.

  Measuring means are as follows.

Gas temperature: Temperature sensor (thermocouple, radiation thermometer)
O ₂ concentration in gas: oxygen concentration meter CO concentration in gas: CO concentration meter NOx concentration in gas: NOx concentration meter

  As described above, according to the present invention, a stable stagnation region or a circulation region can be formed in the vicinity of the waste layer in the combustion chamber by blowing high-temperature gas. Regardless of the size of the incinerator, even when low air ratio combustion with an air ratio of 1.5 or less is performed, the stability of combustion is maintained over the entire width and length of the combustion chamber. A waste incinerator and a waste incineration method capable of reducing the generation amount of harmful gases such as CO and NOx are provided. Furthermore, since the combustion can be performed at a lower air ratio than before, the total amount of exhaust gas discharged from the incinerator can be further greatly reduced, and a waste incinerator and a waste incineration method that can improve the recovery efficiency of waste heat are provided. The

  In addition, the thermal decomposition of waste can be promoted by radiation of standing flat flames, etc., so the amount of waste supplied to the grate (grate load) and the amount of waste supplied to the combustion chamber (furnace Load) can be increased. For this reason, the volume of the combustion chamber can be reduced with respect to the amount of waste incineration, the furnace height of the incinerator can be reduced, and the waste incineration equipment can be made compact, thereby reducing the equipment cost and operation cost. be able to.

DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Combustion chamber 5a Dry grate 5b Combustion grate 5c Post combustion grate 13 High temperature gas blowing means

Claims (7)

A grate-type waste incinerator,
A combustion chamber having a grate and burning waste on the grate;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
A high temperature in which hot gas is blown downward from the ceiling of the combustion chamber toward any region between the combustion start region and the main combustion region in the combustion chamber in the furnace length direction, which is the direction of movement of waste on the grate Gas blowing means,
The high-temperature gas blowing means includes high-temperature gas blowing flow rate control means for controlling the high-temperature gas blowing flow rate so as to be in a range represented by the following equation (1) in relation to the combustion chamber height. A grate-type waste incinerator characterized by that.
-0.107X ² + 4.70X + 3.96 ≤ Y ≤ -0.199X ² + 8.73X + 7.36 (1)
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)   The grate-type waste incinerator according to claim 1, wherein the high-temperature gas blowing means blows in a high-temperature gas having a temperature in a range of 100 to 400 ° C and an oxygen concentration in a range of 5 to 30% by volume. .   The high-temperature gas blowing means is configured to heat at least one of a return exhaust gas that has returned a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. The grate-type waste incinerator according to claim 1, further comprising a high-temperature gas supply source that supplies the gas as a gas. A waste incineration method using a grate-type waste incinerator with a combustion chamber,
Blow primary air for combustion into the combustion chamber from below the grate,
Hot gas is blown downward from the ceiling of the combustion chamber toward an arbitrary region between the combustion start region and the main combustion region in the combustion chamber in the furnace length direction, which is the moving direction of waste on the grate,
A waste incineration method characterized in that a high-temperature gas blowing flow rate is in a range represented by the following equation (1) in relation to a combustion chamber height.
-0.107X ² + 4.70X + 3.96 ≤ Y ≤ -0.199X ² + 8.73X + 7.36 (1)
Y: Hot gas blowing flow rate (m / sec)
X: Combustion chamber height (m)   The waste incineration method according to claim 4, wherein the high-temperature gas has a temperature in the range of 100 to 400 ° C and an oxygen concentration in the range of 5 to 30% by volume.   The hot gas is blown at a flow rate 5 to 20 times the superficial velocity obtained by dividing the gas flow rate in the combustion chamber by the cross-sectional area of the combustion chamber in a plane perpendicular to the furnace length direction. The waste incineration method described.   The high-temperature gas is at least one of a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. The waste incineration method according to any one of claims 4 to 6.

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