JP2014211243A - Combustion control system for refuse incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion control system for a stoker type refuse incinerator that can achieve complete combustion while suppressing CO and NOx and preventing generation of clinker by facilitating agitation and mixing inside the furnace without blowing a recycle gas into the furnace at high-speed.SOLUTION: In the combustion control system for a stoker type refuse incinerator, porous pipes each having an outside diameter of between 150 to 300 mm and blowing the recycle gas are disposed parallel to one another in a primary combustion chamber so as to traverse the interior of the primary combustion chamber of the refuse incinerator while being spaced apart from one another with a predetermined interval of 175 to 350 mm pitch.

Description

  The present invention relates to a combustion control device for a waste incinerator.

  Conventionally, a low oxygen method is known as a method for suppressing nitrogen oxides by combustion. This is a method of suppressing NOx by making the inside of the furnace a low oxygen atmosphere. In this method, CO or dioxins may be generated due to incomplete combustion. Therefore, it is common to supply secondary air after the low oxygen atmosphere region to achieve complete combustion of unburned gas. There is known an exhaust gas recirculation method in which a part of the gas is returned into the furnace to form a low oxygen atmosphere to suppress combustion (Non-patent Document 1, etc.).

  Conventionally, a combustion control device that uses an exhaust gas recirculation method to perform two-stage combustion (three-stage combustion when stoker combustion is combined) with recirculation gas and air in order to simultaneously suppress NOx and CO in combustion in a waste incinerator Are known (for example, Patent Documents 1 and 2).

  4 and 5 show a combustion control apparatus for a conventional waste incinerator, and shows an example described in Patent Document 1. FIG. FIG. 4 shows a system diagram of a combustion control apparatus including an incinerator, and FIG. 5 shows an internal structure of the stoker-type waste incinerator of FIG. As shown in FIG. 5, the stalker-type waste incinerator 1A generally includes a trash input hopper 2A, a stalker (dry stalker 3A, combustion stalker 4A, post-combustion stalker 5A), ash discharge chute 19A, etc. , 5A are provided with wind boxes 6A, 7A, 8A, and primary air for combustion is supplied from the primary air blower 9A to each of the wind boxes 6A, 7A, 8A. An upper space of each of the stokers 3A, 4A, and 5A is a primary combustion chamber 10A, and the primary combustion chamber 10A is narrowed down toward the upper side and connected to the secondary combustion chamber 11A. A recirculation gas supply port 50A is provided in the secondary combustion chamber 11A above the primary combustion chamber 10A, and a secondary combustion air supply port 25A is provided above the recirculation gas supply port 50A in the secondary combustion chamber 11A. .

  When waste is introduced into the stoker-type waste incinerator 1A from the waste injection hopper 2A, the primary air A for combustion is supplied below the stokers 3A, 4A, and 5A by the primary air blower 9A according to the amount of waste supplied. The Garbage thrown in from the waste hopper 2A is transported in order on the dry stalker 3A, combustion stalker 4A, and post-combustion stalker 5A, and then goes through drying, gasification combustion, flame combustion, and superficial combustion to become ash, and an ash discharge chute It is discharged from 19A. The combustion gas on the stalker passes through the primary combustion chamber 10A that becomes narrower as it rises, is collected in the secondary combustion chamber 11A, and is completely burned in the secondary combustion chamber 11A.

Exhaust gas containing a lot of moisture from the dry stoker 3A, exhaust gas containing a large amount of unburned CO and HCN and other NOx intermediate products from the combustion stoker 4A, and exhaust gas containing a large amount of excess O ₂ from the post-combustion stoker 5A Therefore, in order to agitate and mix these exhaust gases having different properties, the combustion furnace exhaust gas is heat recovered by the boiler 14A, dust is removed by the dust collector 15A, and the exhaust gas after the acid gas treatment is used. The exhaust gas (recirculation gas) is drawn out as recirculation gas from the recirculation gas supply port 50A to make the inside of the furnace uniform, and then secondary air is blown in from the secondary combustion air supply port 25A to complete combustion. I am letting. 4 and 5, the atmosphere (air) and the recirculated gas are mixed so that the final oxygen concentration of the exhaust gas becomes constant while maintaining the mixing and stirring of the secondary air. To the secondary combustion air supply port 25A. In FIG. 4, symbol F denotes an induction fan, symbol FC denotes a damper control flow rate control device, and symbol O ₂ C denotes an oxygen concentration detection control device.

  Moreover, in the combustion control apparatus described in Patent Document 2, as shown in FIG. 6, combustion air is supplied from the primary air blower 9B in response to the supply of waste to the stoker-type waste incinerator 1B. As in the above Patent Document 1, since the properties of the exhaust gas discharged from the dry stoker 3B, the combustion stoker 4B, and the post-combustion stoker 5B are different, a barrier 60 is provided at the upper part of the stoker, and further, the dry stoker 3B having a lot of unburned gas is provided above. Injects high-temperature air having a relatively high oxygen concentration (about 10 to 18%), and a recirculation gas having an oxygen concentration of about 5 to 8% is passed through a recirculation gas supply pipe 18B to the upper portion of the post-combustion stoker having a high oxygen concentration. The exhaust gas discharged from the front and rear of the barrier 60 is efficiently stirred while being blown, and is completely burned while suppressing NOx. According to this method, the radiant heat from the barrier 60 is also effective for the combustion of dust. In FIG. 6, symbol F is a blower, symbol 14B is a boiler, symbol 15B is a dust collector, symbol 61 is a heat exchanger air heater, symbol 62 is an ejector, and symbol 12B is a chimney.

JP-A-11-294740 JP 2004-239509 A

Edited by Takuma Environmental Technology Study Group, Garbage Incineration Technology Picture and Basic Terms, Revised Supplement, Published by Ohm Co., Ltd., August 25, 2003, p. 216

  However, in the combustion control device for a waste incinerator described in Patent Document 1, in order to uniformly mix the gas in the large furnace, it is necessary to blow in the recirculated gas at a high speed, which increases the power of the blower. It was.

  For example, a large stoker-type waste incinerator may require a recirculation gas blowing speed of 100 m / second or more.

  In the prior art described in Patent Document 2, dust adheres to the barrier and the clinker grows. Therefore, measures are taken to suppress the clinker growth by making the barrier a water-cooled structure. Dust accumulation on the barrier is unavoidable and may interfere with continuous operation.

  The present invention eliminates the above-mentioned problems of the prior art, promotes stirring and mixing in the furnace without blowing recirculated gas at high speed, suppresses CO and NOx, and prevents generation of clinker. The main object is to provide a combustion control device for a stoker type incinerator capable of achieving combustion.

  In order to achieve the above object, the combustion control device for a stoker-type waste incinerator according to the present invention has a pipe-shaped outer diameter of 150 to 300 mm, and a porous tube for blowing out recirculation gas at a predetermined pitch of 175 to 350 mm. It is characterized by being arranged in parallel in the primary combustion chamber so as to cross the primary combustion chamber of the waste incinerator through the gap.

  The predetermined gap between the adjacent porous tubes arranged in parallel is 25 to 50 mm, and the recirculation gas is blown out from the tube surface of the porous tube at a speed of 0.2 to 0.5 m / sec. It is preferable that it is comprised.

  The porous tube is disposed on the drying storker side and the post-combustion stalker side of the primary combustion chamber, leaving an open region with a predetermined width that is wider than the predetermined gap between adjacent porous tubes and through which exhaust gas can flow. It is preferable.

  The porous tubes arranged in parallel are provided in two stages vertically with a predetermined interval, and the upper porous tube is wider than the predetermined gap between adjacent porous tubes and can flow exhaust gas. An open region having a predetermined width is disposed only on the dry stoker side of the primary combustion chamber, and the lower porous tube is wider than the predetermined gap between adjacent porous tubes and has a predetermined width that allows the exhaust gas to flow therethrough. It is preferable that the open areas are disposed so as to remain on the drying and rear combustion stoker sides of the primary combustion chamber.

  The recirculated gas blown into the primary combustion chamber from the porous tube passes through the gap between the adjacent porous tubes while mixing with the exhaust gas from the combustion stalker, and the exhaust gas and the porous gas from the dry stalker side and the post-combustion stalker side are mixed. Since it is slowly mixed at the top of the tube, conversion to NO is suppressed. The recirculation gas blown out from the porous tube does not need to be blown at a high speed, so that the power of the recirculation gas blower is suppressed and the energy recovery amount (power transmission amount) increases. Moreover, there is no adhesion of dust to the porous tube inserted in the furnace. Furthermore, a porous tube can be attached to a conventional furnace, and can be applied to an existing furnace.

1 is a schematic system diagram showing a first embodiment of a combustion control device for a refuse incinerator according to the present invention. FIG. 2 is a cross-sectional plan view taken along II-II in FIG. 1. It is a principal part expanded vertical sectional view which shows 2nd Embodiment of the combustion control apparatus of the refuse incinerator which concerns on this invention. It is a schematic system diagram which shows an example of the combustion control apparatus of the conventional refuse incinerator. It is a principal part expanded longitudinal cross-sectional view of the waste incinerator of FIG. It is a schematic system diagram which shows the other example of the combustion control apparatus of the conventional refuse incinerator.

  Embodiments of a combustion control apparatus for a waste incinerator according to the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic system diagram of a first embodiment of a combustion control apparatus for a refuse incinerator according to the present invention, and FIG. 2 shows a cross-sectional view taken along line II of FIG.

  A waste incinerator 1 shown in FIG. 1 is a stoker type waste incinerator, and is provided at a lower portion of a waste charging hopper 2, a dry stoker 3, a combustion stoker 4, a post combustion stoker 5, and the respective stokers 3, 4, and 5. The air boxes 6, 7, 8 are each provided with a primary air blower 9 for sending air for primary combustion to each of the air boxes 6, 7, 8. A primary combustion chamber 10 for forming a primary combustion zone is provided above the stokers 3, 4, and 5. A secondary combustion chamber 11 that communicates with the primary combustion chamber 10 is provided above the primary combustion chamber 10. It is provided in communication with the central part of the 10 ceiling walls 10a. The combustion chamber of the refuse incinerator 1 is formed by the primary combustion chamber 10 and the secondary combustion chamber 11, and in the primary combustion chamber 10 at the lower part of the combustion chamber, volatile matter is burned and fixed carbon is burned on the stoker. In the secondary combustion chamber 11 above the combustion chamber 10, unburned gas and floating carbon particles are burned.

  An exhaust gas system 13 from the waste incinerator 1 to the chimney 12 includes a flue (gas duct) 16 connecting a boiler 14 and a dust collector 15 such as a bag filter, an induction fan 17 and the like. Although not shown in FIG. 1, an exhaust gas system 13 extending from the waste incinerator 1 to the chimney 12 has an acid gas treatment device for treating harmful acid gases (hydrogen chloride, sulfur oxide), gas reheating. This kind of exhaust gas system, such as a vessel, a denitration device, and a urea water spray device, can be appropriately equipped with known equipment.

  One end of the recirculation gas supply pipe 18 is connected to the flue 16 connecting the dust collector 15 and the induction fan 17, and the other end of the recirculation gas supply pipe 18 is connected to the lower part of the waste incinerator 1. The primary combustion chamber 10 is connected to a porous tube 20 which is preferably arranged at the top. A recirculation blower 21 is interposed in the recirculation gas supply pipe 18. Part of the exhaust gas discharged from the waste incinerator 1 and subjected to dust removal and acid gas treatment is sucked from the flue 16 into the recirculation gas supply pipe 18 by the recirculation blower 21 and blown out from the porous pipe 20.

  A mixed gas supply pipe 25 that supplies a mixed gas of air and exhaust gas is connected to the secondary combustion chamber 11. The mixed gas supply pipe 25 is bifurcated on the upstream side of the mixed gas blower 26, one is a secondary air introduction pipe 25 a for sucking air from the atmosphere, and the other is a flue 16 downstream of the dust collector 15. And an exhaust gas introduction pipe 25b for sucking a part of the exhaust gas. A damper 25c is interposed in the exhaust gas introduction pipe 25b. The oxygen concentration detection control device 27 measures the oxygen concentration in the exhaust gas in the flue 16 of the exhaust gas system 13 to control the opening degree of the damper 25c of the exhaust gas introduction pipe 25b, and controls the flow rate of the exhaust gas flowing through the exhaust gas introduction pipe 25b. Control. The mixed gas supply pipe 25 detects the flow rate of the mixed gas (or air) flowing through the mixed gas supply pipe 25 and controls a damper 25d interposed on the downstream side of the mixed gas blower 26 of the mixed gas supply pipe 25. A flow control device 25e is also provided. By maintaining a constant oxygen concentration in the exhaust gas with such a configuration, generation of CO and dioxins due to incomplete combustion is suppressed. The oxygen concentration detection control device 27 is provided on the upstream side of the boiler 14 in the illustrated example, but may be provided on the downstream side of the dust collector 15.

  The porous tube 20 is a porous tube having an outer diameter of 150 to 300 mm that is open at one end and closed at the other end, and has fine holes communicating from the inner surface of the tube to the outer surface of the tube. Tube 18 is connected.

  It is desirable that the porous tube 20 is made of a cogeneration ceramic that is resistant to thermal shock. The ceramic porous tube 20 receives the heat of combustion and is heated so that the radiant heat from the ceramic porous tube 20 can promote the combustion on the stoker and the gas layer.

  The porous tubes 20 are arranged in parallel, and the pitch (center line interval) P (FIG. 2) is set to 175 so as to form a predetermined gap X (25 to 50 mm) between the adjacent porous tubes 20. It is arranged as ~ 350mm.

  Further, in the example shown in FIGS. 1 and 2, the porous tube 20 has open areas 30 and 31 that allow combustion gas to flow on the dry stoker 3 side and the post-combustion stoker 5 side of the primary combustion chamber 10. It is arranged, leaving behind. The front and rear widths W1 and W2 of the open areas 30 and 31 can be wider than the predetermined gap X between adjacent porous tubes 20, and are preferably 300 to 600 mm.

  The recirculation blower 21 can control the flow rate of exhaust gas by controlling the rotation speed by a control device (not shown). Under the control of the recirculation blower 21, recirculation gas is blown out from the surface of the porous tube 20 at a speed of about 0.2 to 0.5 m / sec. When the flow rate of the recirculation gas blown out from the porous tube 20 is less than 0.2 m / sec, the combustion exhaust gas contacts the porous tube 20 and dust adheres to the porous tube 20 to cause clogging. On the other hand, if it exceeds 0.5 m / sec, the amount of recirculation gas increases so that the power of the recirculation blower 21 increases, and excessive power is consumed. Although not shown, a so-called damper control may be performed by providing a damper in the recirculation gas supply pipe 18 in place of the rotation speed control of the recirculation fan 21.

  The operation and effect of the combustion control apparatus for a waste incinerator having the above configuration will be described below.

The exhaust gas from the combustion stoker 4 contains a large amount of HCN, which is an intermediate product of NOx, and NO is generated when it suddenly comes into contact with the exhaust gas having a high oxygen concentration from the post-combustion stoker 3, but the dry stoker 3 The exhaust gas containing a large amount of moisture from the side of the exhaust gas and the exhaust gas containing a large amount of excess O ₂ from the side of the post-combustion stoker 5 contain almost no HCN or the like, which is an intermediate product of NOx, and are open as it is. 30 and 31 can be allowed to flow into the secondary combustion chamber 11.

  The exhaust gas containing a large amount of intermediate products of NOx from the combustion stoker 4 contains oxygen having a concentration that is difficult to burn and is ejected from the porous tube 20 when passing through the gap X between the adjacent porous tubes 20. Mixed with circulating gas. As a result, rapid contact with the exhaust gas from the post-combustion stoker 3 having a high oxygen concentration is avoided, and the NOx intermediate product is oxidized and reduced so that NOx is not generated, and then the dry stoker 3 and the post-combustion stoker 5 is slowly mixed with the exhaust gas that has passed through the open areas 30 and 31 at the upper part of the porous tube 20, so that the conversion to NOx is suppressed, and air and exhaust gas are mixed from the mixed gas supply pipe 25 at the upper part of the mixing area. By blowing the mixed gas, unburned CO and the like are completely burned.

  Further, the recirculated gas blown out from the porous tube 20 suppresses dust from adhering to the porous tube 20 and suppresses the growth of the clinker.

  JP-A-2001-248830 discloses that a porous ceramic tube is disposed in a secondary combustion chamber and secondary air is ejected from the ceramic tube. In order to suppress NOx before blowing the secondary air, the recirculation gas is slowly mixed with the combustion gas. In the present invention, the blowing of the secondary air is provided in the secondary combustion chamber of the waste incinerator as usual. You may eject from a side wall nozzle (not shown), and you may eject from a porous ceramic pipe | tube similarly to the thing of Unexamined-Japanese-Patent No. 2001-248830.

  Next, 2nd Embodiment of the combustion control apparatus of the waste incinerator concerning this invention is described with reference to FIG.

  As shown in FIG. 3, in the second embodiment, porous tubes 20a and 20b are arranged in two stages with a predetermined interval 32 in the vertical direction. The lower porous tube 20b is wider than a predetermined gap between the adjacent porous tubes 20b and has open regions 30 and 31 having a predetermined width through which exhaust gas can flow. However, the upper porous tube 20a does not directly flow the exhaust gas having a high oxygen concentration from the post-combustion stoker 5 into the secondary combustion chamber 11 as it is, but instead of the lower porous tube 20b. Mixing with the exhaust gas flowing out from the gap gradually into the gap of the upper porous tube 20a and the open area 30 on the dry stalker 3 side and guiding it to the secondary combustion chamber 11 further promotes mixing, and NOx The effect of suppressing the conversion to is increased. The gap 32 between the upper and lower stages of the porous tubes 20a, 20b can be made wider than the gap X (see FIG. 2) of the porous tubes 20a, 20b, and is the same as the width dimension of the open area 31 of the first embodiment. (Height) dimension can be set.

  The present invention is not construed as being limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the first embodiment, the gas blown into the secondary combustion chamber 11 above the porous tube 20 is a mixed gas of air and exhaust gas, but only air may be blown as secondary air. In addition, for example, although not shown, the open areas 30 and 31 may not be provided. In this case, the porous tube 20 is an upper opening of the primary combustion chamber 10 (communication port with the secondary combustion nitrogen 11). Arranged throughout.

1 Waste Incinerator 3 Dry Stoker 4 Combustion Stoker 5 Post Combustion Stoker 10 Primary Combustion Chamber 11 Secondary Combustion Chamber 18 Recirculation Gas Supply Pipe 20 Porous Pipe 30 Open Zone 31 Open Zone

Claims (4)

  Porous pipes having a pipe outer diameter of 150 to 300 mm and for blowing out recirculation gas are arranged in parallel in the primary combustion chamber so as to cross the primary combustion chamber of the waste incinerator through a predetermined gap at a pitch of 175 to 350 mm. Combustion control device for waste incinerator, characterized by being arranged in a shape.   The predetermined gap between the adjacent porous tubes arranged in parallel is 25 to 50 mm, and the recirculation gas is blown out from the tube surface of the porous tube at a speed of 0.2 to 0.5 m / sec. The combustion control device for a waste incinerator according to claim 1, wherein the combustion control device is configured as follows.   The porous tube is disposed on the drying storker side and the post-combustion stalker side of the primary combustion chamber, leaving an open region with a predetermined width that is wider than the predetermined gap between adjacent porous tubes and through which exhaust gas can flow. The combustion control device for a waste incinerator according to claim 1 or 2, wherein the combustion control device is a waste incinerator. The porous tubes arranged in parallel are provided in two stages vertically with a predetermined interval, and the upper porous tube is wider than the predetermined gap between adjacent porous tubes and can flow exhaust gas. An open region having a predetermined width is disposed only on the dry stoker side of the primary combustion chamber, and the lower porous tube is wider than the predetermined gap between adjacent porous tubes and has a predetermined width that allows the exhaust gas to flow therethrough. The combustion control device for a refuse incinerator according to claim 1 or 2, wherein the open area is disposed so as to remain on the drying and rear combustion stoker sides of the primary combustion chamber.

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