Combustion furnace and method of operating a combustion furnace

Abstract

The present invention provides a combustion furnace that can effectively homogenize the distribution of pyrolysis gas flowing into the secondary combustion region, addressing any unevenness in its distribution. [Solution] A combustion furnace that heat-treats a material to be processed in a primary combustion chamber while transporting it in a first direction from upstream to downstream, comprising a side wall gas supply mechanism equipped with a plurality of gas injection nozzles that supply gas to exhaust gas that has passed through an inlet to a secondary combustion chamber provided in the space above the primary combustion chamber, so as to face it from the left and right side walls of the secondary combustion chamber in a second direction that intersects the first direction in a plan view, wherein the side wall gas supply mechanism is provided biased toward the upstream side of the first direction.

Description

Technical Field

[0001] The present invention relates to a combustion furnace that heat-treats an object to be treated while conveying it in a first direction from the upstream side to the downstream side in a primary combustion chamber, and a method of operating the combustion furnace.

Background Art

[0002] As a combustion furnace that heat-treats an object to be treated while conveying it in a first direction from the upstream side to the downstream side in a primary combustion chamber, for example, a stoker-type incinerator that incinerates municipal waste and industrial waste is used.

[0003] The object to be treated introduced into the primary combustion chamber by a feeding mechanism is thermally decomposed in the drying zone in the upper reaches along the conveying direction, mainly burned in the combustion zone in the middle reaches, and solid-burned and ashed in the afterburning zone in the lower reaches. When the pyrolysis gas, which is a high-calorie unburned gas generated upstream of the primary combustion chamber, flows into the secondary combustion chamber provided in the upper space of the primary combustion chamber, there is a bias in the concentration distribution of the pyrolysis gas contained in the exhaust gas passing through the inlet of the secondary combustion chamber.

[0004] Therefore, the combustion temperature on the front wall side of the secondary combustion chamber (the upstream side in the first direction) where the concentration distribution of the pyrolysis gas becomes high increases, and not only is the deterioration due to burnout of the heat-resistant wall and adhesion of clinkers on the front wall side remarkable, but it is also essential to address problems such as the generation of NOX and the discharge of unburned gas.

[0005] Patent Document 1 discloses an incinerator including a primary combustion region for incinerating waste, a denitrating agent supply mechanism for supplying a denitrating agent into an exhaust gas flow path through which the exhaust gas generated in the primary combustion region flows, and a gas supply mechanism for supplying gas into the exhaust gas flow path upstream of the denitrating agent supply mechanism. The gas supply mechanism includes a plurality of pairs of gas injection nozzles installed so as to face each other in the direction of the exhaust gas flow on at least a pair of opposing walls partitioning the exhaust gas flow path, and a first adjustment mechanism capable of adjusting the flow rate ratio of the gas injected and supplied from each of the pairs of gas injection nozzles.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-090563 [Overview of the project] [Problems that the invention aims to solve]

[0007] The incinerator disclosed in Patent Document 1 is configured to agitate the exhaust gas flowing into the secondary combustion chamber by providing multiple pairs of gas injection nozzles facing the front and rear walls along the direction of transport of the material to be processed, and by adjusting the flow rate ratio of the gas injected from each pair.

[0008] However, the concentration distribution of pyrolysis gases in the exhaust gas flowing from the primary combustion chamber to the secondary combustion chamber is very large on the upstream side along the direction of transport of the material being processed. Even when the gas flow rate ratio is adjusted from gas injection nozzles positioned opposite each other on the front and rear walls at the inlet side of the secondary combustion chamber, some of the pyrolysis gases may pass through the gaps between the nozzles installed on the upstream front wall, making it difficult to agitate the exhaust gas to achieve a uniform concentration distribution of pyrolysis gases.

[0009] Furthermore, in order to avoid the generation of dioxins, it is necessary to ensure a target residence time for the exhaust gas in the secondary combustion chamber. However, in reality, the temperature and volume of the exhaust gas, as well as the concentration distribution of pyrolysis gases contained in the exhaust gas, vary greatly depending on the properties and amount of material being incinerated. Therefore, achieving a homogeneous residence time distribution on the horizontal cross-section of the secondary combustion chamber has been extremely difficult.

[0010] In view of the above-mentioned conventional problems, the object of the present invention is to provide a combustion furnace and a method for operating a combustion furnace that can effectively homogenize the distribution of pyrolysis gas flowing into the secondary combustion region. [Means for solving the problem]

[0011] To achieve the above-mentioned objectives, the first characteristic configuration of the combustion furnace according to the present invention is a combustion furnace that heat-treats a workpiece in a primary combustion chamber while transporting it in a first direction from upstream to downstream, and is equipped with a side wall gas supply mechanism that has a plurality of gas injection nozzles that supply gas to exhaust gas that has passed through an inlet to a secondary combustion chamber provided in the space above the primary combustion chamber, so as to face it from the left and right side walls of the secondary combustion chamber, which are in a second direction that intersects the first direction in a plan view, and the side wall gas supply mechanism is provided biased toward the upstream side in the first direction.

[0012] The exhaust gas passing through the inlet to the secondary combustion chamber, located in the space above the primary combustion chamber, is distributed such that the concentration of unburned pyrolysis gas is high on the upstream side in the first direction, and the concentration of burned exhaust gas increases as it moves downstream in the first direction. Therefore, by providing multiple gas injection nozzles that supply gas to the exhaust gas that has passed through the inlet to the secondary combustion chamber on both the left and right side walls of the secondary combustion chamber, which are in a second direction intersecting the first direction in a plan view, and by positioning the gas injection nozzles biased towards the upstream side in the first direction, a large amount of gas is concentrated and supplied to the upstream side in the first direction where the high-concentration pyrolysis gas flows in. This creates a localized horizontal swirling flow in the secondary combustion chamber, enabling efficient stirring of the exhaust gas.

[0013] The second characteristic configuration is that, in addition to the first characteristic configuration described above, the inlet portion is formed in the region that overlaps with the combustion zone in a plan view, among the dry zone, combustion zone, and post-combustion zone that constitute the hearth of the primary combustion chamber.

[0014] When the inlet to the secondary combustion chamber is arranged in this manner relative to the primary combustion chamber, a large amount of high-concentration pyrolysis gas flows in from the upstream side of the first direction of the inlet, enabling efficient stirring of the exhaust gas.

[0015] The third characteristic configuration is that, in addition to the first or second characteristic configuration described above, it includes a front and rear wall gas supply mechanism equipped with a plurality of gas injection nozzles that supply secondary combustion air from both the front and rear walls of the secondary combustion chamber facing each other, located upstream of the side wall gas supply mechanism in the inlet portion, and aligned in plan view along the first direction.

[0016] By supplying secondary combustion air from a direction intersecting the gas supply direction by the front and rear wall gas supply mechanisms, which are installed upstream of the side wall gas supply mechanism, even when exhaust gas with a high concentration distribution of pyrolysis gas flows into the upstream side of the secondary combustion chamber inlet in the first direction, the pyrolysis gas is guided to flow downstream in the first direction, thereby enabling effective exhaust gas agitation.

[0017] The fourth characteristic feature is that, in addition to the first characteristic feature described above, the primary combustion chamber's material transport mechanism is equipped with a stoker mechanism.

[0018] The above-described configuration can be suitably used in an incinerator equipped with a stoker mechanism in the material transport mechanism of the primary combustion chamber, which serves as the combustion furnace.

[0019] The fifth characteristic feature is that, in addition to the second characteristic feature described above, the primary combustion chamber is equipped with a kiln mechanism in the conveying mechanism for the drying zone of the material to be processed.

[0020] The above-described configuration can be suitably used in an incinerator equipped with a kiln mechanism as a conveying mechanism in the drying zone of the material to be processed in the primary combustion chamber.

[0021] The characteristic configuration of the operation method of the combustion furnace according to the present invention is an operation method of a combustion furnace that heat-treats while conveying an object to be processed from the upstream side to the downstream side in a first direction in a primary combustion chamber, and for the exhaust gas that has passed through the inlet to the secondary combustion chamber provided in the upper space of the primary combustion chamber, a side wall gas supply mechanism provided with a plurality of gas injection nozzles that supply gas so as to face each other from the left and right side walls of the secondary combustion chamber in a second direction that intersects the first direction in a plan view, based on the carbon monoxide concentration in the exhaust gas discharged from the secondary combustion chamber, adjusting the gas supply amount or the balance of the gas supply amounts from the plurality of gas injection nozzles arranged along the first direction.

[0022] The carbon monoxide concentration in the exhaust gas discharged from the secondary combustion chamber serves as an indicator of whether the unburned gas components contained in the exhaust gas flowing into the secondary combustion chamber are completely burned. In other words, it serves as an indicator for judging the degree of agitation of the unburned gas components contained in the exhaust gas flowing into the secondary combustion chamber. Therefore, by adjusting the gas supply amount or the balance of the gas supply amounts from the plurality of gas injection nozzles arranged along the first direction based on this indicator, it is possible to promote the agitation of the unburned gas components and reduce the carbon monoxide concentration.

Effects of the Invention

[0023] As described above, according to the present invention, it has become possible to provide a combustion furnace and an operation method of a combustion furnace that can effectively homogenize the bias in the distribution of the pyrolysis gas flowing into the secondary combustion region.

Brief Description of the Drawings

[0024] [Figure 1] It is an explanatory diagram showing the configuration of a stoker-type incinerator which is an example of a combustion furnace. [Figure 2] It is a main part explanatory diagram showing the primary combustion chamber and the secondary combustion chamber of a stoker-type incinerator. [Figure 3] It is a plan view explanatory diagram showing the arrangement of nozzles constituting the side wall gas supply mechanism and the front and rear wall gas supply mechanism arranged at the inlet of the secondary combustion chamber. [Figure 4](a) is an explanatory diagram of the exhaust gas flow simulation corresponding to the gas supply mechanism of the present invention, (b) is an explanatory diagram of the exhaust gas flow on the evaluation surface set downstream of the gas supply mechanism, and (c) is an explanatory diagram of the high-temperature section above 1300°C. (d) is an explanatory diagram of the exhaust gas flow simulation corresponding to a conventional gas supply mechanism. [Figure 5] (a) is a carbon monoxide concentration distribution diagram showing the results of a simulation of the exhaust gas flow corresponding to the gas supply mechanism of the present invention, and (b) is a vector diagram showing the gas flow near the inlet of the secondary combustion chamber. [Modes for carrying out the invention]

[0025] The combustion furnace and the method of operating the combustion furnace according to the present invention will be described below, using a stoker-type incinerator, which is an example of a combustion furnace, as an example.

[0026] [Overall structure of the incinerator] Figure 1 shows a stoker-type incinerator 1. The incinerator 1 includes a platform A into which garbage trucks enter, a garbage pit B for accumulating the garbage collected by the garbage trucks, a garbage input hopper D, a crane mechanism C for transferring garbage from garbage pit B to garbage input hopper D, a stoker-type incinerator body E, a waste heat boiler F, an economizer G, a cooling tower H, a dust collector I, a chimney J, and the like.

[0027] By opening the double-hinged garbage input door K, which is located between platform A and garbage pit B to prevent odor leakage and ensure safety, the garbage collected and transported by the garbage truck is dumped into garbage pit B.

[0028] The waste collected in waste pit B is grasped by a crane mechanism C of the club bucket type, which is operated automatically or by an operator in a control room, and transported to an opening formed at the upper end of the waste input hopper D before being dropped in.

[0029] A dust supply device P is provided at the bottom of the waste input hopper D, and the waste filled in the waste input hopper D is pushed into the incinerator body E. The waste filled in the waste input hopper D functions as a sealing mechanism that blocks the inflow of outside air from the waste input hopper D into the furnace chamber formed in the incinerator body E, and the furnace chamber is maintained under negative pressure.

[0030] The furnace chamber formed in the incinerator body E is equipped with a primary combustion chamber 2 and a secondary combustion chamber 3 for the complete combustion of the exhaust gas produced in the primary combustion chamber 2, and multiple water tubes WT of the waste heat boiler F are embedded in the wall of the secondary combustion chamber.

[0031] As shown in Figure 2, the primary combustion chamber 2 is provided with a stoker mechanism S in which a fixed grate and a movable grate are alternately arranged along the direction of waste transport. The movable grate is driven back and forth relative to the fixed grate by hydraulic mechanisms h1, h2, and h3, thereby agitating and transporting the waste downstream.

[0032] Four wind boxes W1, W2, W3, and W4 are provided at the bottom of the stoker mechanism S, in order from upstream to downstream, and primary combustion air is supplied from a forced-air blower. The upstream region corresponding to wind box W1 of the stoker mechanism S is the dry zone S1, the midstream region corresponding to wind boxes W2 and W3 is the combustion zone S2, and the downstream region corresponding to wind box W4 is the post-combustion zone S4.

[0033] The waste, pushed from the dust supply device P into the primary combustion chamber 2, is mainly heated and dried in the drying zone to generate pyrolysis gas containing water vapor. In the combustion zone, it is further pyrolyzed and gasified, and the carbonized waste from the gasification combustion is then solid-burned in the post-combustion zone, and after being reduced to ash, it falls into the ash chute from the end of the post-combustion zone. In the primary combustion chamber 2, the waste to be processed is transported in a first direction from upstream to downstream while being heat-treated.

[0034] The inlet of the secondary combustion chamber 3 is located in the space above the primary combustion chamber 2. A constricted section is formed in the front wall 20F and the rear wall 20R from the exhaust gas outlet of the primary combustion chamber 2 to the inlet of the secondary combustion chamber 3. A front and rear wall gas supply mechanism 4 is installed in this constricted section, and a side wall gas supply mechanism 5 is installed on the left and right side walls 50R and 50L of the constricted section downstream of the front and rear wall gas supply mechanism 4.

[0035] The exhaust gas flowing into the secondary combustion chamber 3 is agitated by the secondary combustion gas supplied from the front and rear wall gas supply mechanisms 4 and the side wall gas supply mechanisms 5, and complete combustion is promoted by contact with the oxygen gas contained in the secondary combustion gas.

[0036] In this embodiment, air is used as the gas supplied from the front and rear wall gas supply mechanism 4 and the side wall gas supply mechanism 5. However, the gas may be exhaust gas drawn from the primary combustion chamber, recirculated exhaust gas branched from the flue downstream of the dust collector I, or exhaust gas branched from other exhaust gas flow paths, or a mixture of air and each type of exhaust gas.

[0037] The total amount of primary and secondary combustion air should be adjusted so that the theoretical air-to-incineration ratio is approximately 1.3. For example, if all the air is supplied by primary combustion air so that the theoretical air-to-incineration ratio is approximately 1.3, then the gas supplied from the gas supply mechanism 4 may consist only of exhaust gas drawn from the flue. Alternatively, the system may be configured so that approximately 1.0 of the air is supplied by primary combustion air and approximately 0.3 by secondary combustion air.

[0038] Furthermore, a denitrification agent supply mechanism 6 is provided on the left and right side walls downstream of the inlet of the secondary combustion chamber 3 to supply a denitrification agent to the exhaust gas. In order to reduce and remove nitrogen oxides NOx, which are generated by the high-temperature combustion of the exhaust gas in the secondary combustion chamber 3, by a non-catalytic denitrification method (SNCR), a denitrification agent such as ammonia water or urea water is injected and supplied by the denitrification agent supply mechanism 6.

[0039] The non-catalytic denitrification method involves injecting a liquid or gaseous denitrification agent into the exhaust gas in an incinerator and reducing the NOx generated by secondary combustion. When using aqueous ammonia as the denitrification agent, a temperature range of 800°C to 1000°C, preferably 820°C to 860°C, efficiently promotes the reaction between NOx and ammonia.

[0040] The exhaust gas, including pyrolysis gas produced in the primary combustion chamber 2, is completely combusted in the secondary combustion chamber 3 and flows out into the flue. Waste heat is recovered by the waste heat boiler F located in the secondary combustion chamber 3, and the generated steam is used for power generation, etc. The economizer G, cooling tower H, dust collector I, chimney J, etc., are arranged along the flue.

[0041] The economizer G is a heat recovery device that preheats the boiler feedwater using the heat contained in the exhaust gas. The exhaust gas, whose temperature has been reduced by the cooling tower H, is then filtered by the dust collector I and exhausted through the chimney J. An induced draft fan M is connected downstream of the dust collector I to prevent flames and exhaust gases from leaking to the outside from the incinerator and other equipment, and the furnace chamber is maintained under negative pressure.

[0042] [Structure of front and rear wall gas supply mechanism 4 and side wall gas supply mechanism 5] As shown in Figures 2 and 3, the front and rear wall gas supply mechanism 4 is equipped with a plurality of gas injection nozzles 4N that supply secondary combustion air to the exhaust gas that has passed through the inlet of the secondary combustion chamber 3, from the front wall 20F and rear wall 20R of the secondary combustion chamber 3, which are aligned in the first direction in a plan view. The gas injection nozzles 4N are positioned at an angle of 10 to 15° downward with respect to the horizontal direction so as to face the flow of exhaust gas flowing in from the primary combustion chamber 2.

[0043] The side wall gas supply mechanism 5 is equipped with multiple gas injection nozzles 5N that supply secondary combustion air from the left wall 30L and right wall 30R of the secondary combustion chamber 3, which are in a second direction intersecting the first direction in a plan view, to exhaust gas that has passed through a constricted portion that serves as an inlet to the secondary combustion chamber, located in the space above the primary combustion chamber 2. The gas injection nozzles 5N constituting the side wall gas supply mechanism 5 are arranged in a substantially horizontal position and are positioned so as to be biased towards the upstream side in the first direction.

[0044] Both the front and rear wall gas supply mechanism 4 and the side wall gas supply mechanism 5 are provided at the inlet of the secondary combustion chamber 3, with the front and rear wall gas supply mechanism 4 located upstream of the side wall gas supply mechanism 5 in the exhaust gas flow. In this example, constricted sections are formed in the front and rear walls 20F and 20R that constitute the inlet to the secondary combustion chamber 3, but the same applies to a secondary combustion chamber 3 that does not have constricted sections.

[0045] The front and rear wall gas supply mechanism 4 has eight 80A straight nozzles 4N arranged at equal intervals on the front wall 20F, and seven straight nozzles 4N arranged at equal intervals on the rear wall 20R, with three 80A straight nozzles and two 50A straight nozzles in between each of them. The spacing between the nozzles is offset by 1 / 2 in a plan view so that the axial directions of the straight nozzles on the front wall 20F and the rear wall 20R do not overlap.

[0046] According to the above configuration, the amount of secondary combustion gas supplied from the straight nozzle 4N located on the front wall 20F is relatively greater than the amount of secondary combustion gas supplied from the straight nozzle 4N located on the rear wall 20R. Furthermore, the secondary combustion gas supplied from the straight nozzle 4N on the front wall 20F and the secondary combustion gas supplied from the straight nozzle 4N on the rear wall 20R are ejected in such a way that they do not directly collide with each other in the secondary combustion space.

[0047] The side wall gas supply mechanism 5 has six 80A straight nozzles 5N arranged at equal intervals on the left wall 30L and the right wall 30R, respectively, so as to be biased toward the front wall 20F, and is arranged so that the axial directions of the straight nozzles on the left wall 30L and the right wall 30R overlap when viewed from above.

[0048] In other words, the combustion gases supplied from the front and rear wall gas supply mechanisms 4 flow toward the opposing walls in a plan view, while the combustion gases supplied from the side wall gas supply mechanisms 5 flow so as to collide in the center of the secondary combustion space in a plan view. The number and diameter of each straight nozzle can be set as appropriate according to the volume of the secondary combustion chamber, and are not particularly limited.

[0049] The exhaust gas passing through the inlet to the secondary combustion chamber 3, which is located in the space above the primary combustion chamber 2, is distributed such that the concentration of pyrolysis gas is higher on the upstream side in the first direction, i.e., on the front wall 20F side, and the concentration of burnt exhaust gas increases as it moves downstream in the first direction, i.e., on the rear wall 20R side.

[0050] Therefore, by providing multiple gas injection nozzles 5N that supply secondary combustion air to the exhaust gas that has passed through the inlet to the secondary combustion chamber 3 on the left and right side walls 30L and 30R of the secondary combustion chamber, which are in a second direction intersecting the first direction in a plan view, and by arranging the gas injection nozzles 5N biased toward the upstream side of the first direction, that is, toward the front wall 20F side, a large amount of secondary combustion gas is supplied to the upstream side of the first direction into which the highly concentrated pyrolysis gas flows, a horizontal swirling flow is generated in the secondary combustion chamber, enabling efficient stirring of the exhaust gas.

[0051] As in this example, when the inlet to the secondary combustion chamber 3 relative to the primary combustion chamber 2 is formed in the region that overlaps with the combustion zone S2 in a plan view among the dry zone S1, combustion zone S3, and post-combustion zone S3 that constitute the hearth of the primary combustion chamber 2, and a large amount of high-concentration pyrolysis gas flows in from the upstream side of the inlet in the first direction, efficient stirring of the exhaust gas can be achieved.

[0052] Even if the combustion gas flowing into the secondary combustion chamber 3 slips through the gaps between the nozzles 4N that make up the front and rear wall gas supply mechanism 4, or rises without being sufficiently agitated, the flow of secondary combustion gas supplied from the nozzles 5N that make up the side wall gas supply mechanism 5 intersects with the flow of secondary combustion gas ejected from the nozzles 4N. As a result, localized horizontal swirling flows are generated at multiple locations for the exhaust gas rising in the secondary combustion chamber 3, enabling good agitation of the exhaust gas.

[0053] As described above, the front and rear wall gas supply mechanism 4 is configured such that the gas injection nozzles 4N on the front wall 20F and the gas injection nozzles 4N on the rear wall 20R are arranged to supply different amounts of gas. This ensures stirring efficiency even when the concentration distribution of pyrolysis gas contained in the exhaust gas flowing in from the inlet differs between the front wall and the rear wall. In this example, the gas injection nozzles 4N on the front wall 20F are supplied more than the gas injection nozzles 4N on the rear wall 20R, allowing for efficient stirring in the front wall 20F where the concentration distribution of pyrolysis gas is larger.

[0054] Next, we will explain an operating method for adjusting the supply amount of secondary combustion gas in the combustion furnace 1, which heat-treats the material to be processed in a first direction from upstream to downstream in the primary combustion chamber 2. A carbon monoxide sensor GS is provided near the furnace outlet, which is downstream of the secondary combustion chamber 3. A control unit is provided that adjusts the amount of secondary combustion gas supplied from the gas injection nozzles 5N that constitute the side wall gas supply mechanism 5 based on the carbon monoxide concentration detected by the carbon monoxide sensor GS. The control unit adjusts the balance of the amount of secondary combustion gas supplied from the multiple gas injection nozzles 5N so that the carbon monoxide concentration decreases. As described above, while the total amount of secondary combustion gas is set in advance, adjusting the balance of the amount of secondary combustion gas supplied from the gas injection nozzles 5N corresponds to the concentration distribution of pyrolysis gas flowing in from the inlet, thereby promoting complete combustion. It is also possible to use an oxygen gas sensor instead of the carbon monoxide sensor GS. The balance of the amount of secondary combustion gas supplied should be adjusted so that the oxygen gas concentration in the exhaust gas increases. Alternatively, while the total amount of secondary combustion gas is set in advance, the amount of secondary combustion gas supplied to the front and rear wall gas supply mechanisms 4 and the side wall gas supply mechanism 5 can be adjusted by increasing or decreasing the amount of secondary combustion gas supplied to the side wall gas supply mechanism 5.

[0055] In the embodiment described above, an example was explained in which the front and rear wall gas supply mechanism 4 is arranged such that the axial directions of the straight nozzles arranged on the front wall 20F and the rear wall 20R do not overlap in a plan view, with the distance between the nozzles offset by 1 / 2. However, the straight nozzles arranged on the front wall 20F and the rear wall 20R may be arranged so that the axial directions of the straight nozzles overlap in a plan view.

[0056] In the embodiments described above, an example was given in which the gas injection nozzles 5N constituting the side wall gas supply mechanism 5 are arranged in a substantially horizontal position. However, the position of the gas injection nozzles 5N is not limited to a substantially horizontal position, as long as they are arranged in a position that intersects, preferably perpendicular to, the first direction in a plan view. Furthermore, an example was given in which the gas injection nozzles 5N constituting the side wall gas supply mechanism 5 are predominantly located on the upstream side of the side wall in the first direction. However, it is sufficient that the installation density of the gas injection nozzles 5N is higher on the upstream side of the first direction.

[0057] In the embodiments described above, the present invention was explained using an incinerator equipped with a stoker mechanism as the material transport mechanism in the primary combustion chamber as a heat treatment furnace. However, the present invention may also be applied to an incinerator equipped with a kiln mechanism as the material transport mechanism in the drying zone of the primary combustion chamber as a heat treatment furnace.

[0058] [Explanation of Simulation Results] As shown in Figure 4(a), the results when the front and rear wall gas supply mechanism 4 and the side wall gas supply mechanism 5 shown in Figure 3 are applied to the secondary combustion chamber 3 of a combustion furnace 1 equipped with a kiln mechanism in the primary combustion chamber 2 are shown in Figures 4(b), (c) and 5(a), (b). Figure 4(b) is a vector diagram showing the exhaust gas flow when the horizontal plane near the downstream side of the constricted portion is used as the evaluation surface, Figure 4(c) is a distribution map of the high temperature region at 1300°C, Figure 5(a) is a distribution map of the carbon monoxide concentration in the secondary combustion chamber, and Figure 5(b) is a vector diagram showing the exhaust gas flow through the secondary combustion chamber.

[0059] This simulation uses the general-purpose thermal fluid analysis software Fluent ver.23.0 to analyze the gas flow in the secondary combustion chamber, which is the exhaust gas flow path, based on a three-dimensional thermal fluid analysis model at the actual machine scale.

[0060] The analysis model had approximately 6 million meshes. The Realizable k-ε model was used for turbulence, and the DO model was used for radiation. From the component analysis results of the waste material to be treated, the composition and calorific value of the combustible components C (carbon), H (hydrogen), O (oxygen), and N (oxygen) were determined, and the enthalpy of formation corresponding to the composition and calorific value was given as the physical properties of the combustible gas (wood_vol) in the general-purpose software. The combustion of the combustible components of the waste was modeled using an eddy dissipation model and the overall two-step reaction shown in the equation below. wood_vol + a O2→ b CO + c H2O + d N2 (1 formula) CO + 0.5O2 → CO2 (2 formulas)

[0061] As shown in Figure 4(b), localized swirling flows are observed in multiple regions of the exhaust gas on the evaluation surface, indicating a good mixing state. Furthermore, as shown in Figure 4(c), although the high-temperature region of 1300°C is slightly distributed on the front wall at the inlet of the secondary combustion chamber, the exhaust gas is mixed overall, and no localized abnormal combustion is observed.

[0062] Furthermore, as shown in Figure 5(a), it was found that the carbon monoxide concentration downstream of the furnace outlet was extremely low at 1.9 ppm, and as shown in Figure 5(b), it was confirmed that there was no localized bias in the exhaust gas flowing through the secondary combustion chamber.

[0063] It should be noted that the embodiments described above are merely examples of the present invention, and it goes without saying that the specific structure, shape, material, size, etc. of each part can be appropriately modified and designed within the scope of achieving the effects of the present invention. [Explanation of symbols]

[0064] 1: Garbage incinerator 2: Primary combustion chamber (primary combustion region) 3: Secondary combustion chamber (exhaust gas passage) 4: Front and rear wall gas supply mechanism 4N: Gas injection nozzle 5: Side wall gas supply mechanism 5N: Gas injection nozzle 6: Denitrification agent supply mechanism

Claims

1. A combustion furnace that heat-treats a material to be processed in a primary combustion chamber while transporting it in a first direction from upstream to downstream, The system includes a side wall gas supply mechanism equipped with multiple gas injection nozzles that supply gas to the exhaust gas that has passed through the inlet to the secondary combustion chamber, which is located in the space above the primary combustion chamber, from the left and right side walls of the secondary combustion chamber in a second direction that intersects the first direction in a plan view. A combustion furnace in which the side wall gas supply mechanism is provided biased toward the upstream side in the first direction.

2. The combustion furnace according to claim 1, wherein the inlet portion is formed in a region that overlaps with the combustion zone in a plan view among the dry zone, combustion zone, and post-combustion zone that constitute the hearth bed of the primary combustion chamber.

3. The combustion furnace according to claim 1 or 2, further comprising a front and rear wall gas supply mechanism with a plurality of gas injection nozzles that supply secondary combustion air from both the front and rear walls of the secondary combustion chamber facing each other, located upstream of the side wall gas supply mechanism in the inlet portion, and aligned in plan view along the first direction.

4. The combustion furnace according to claim 1, wherein the material to be processed in the primary combustion chamber is provided with a stoker mechanism.

5. The combustion furnace according to claim 2, wherein the conveying mechanism in the drying zone of the primary combustion chamber is equipped with a kiln mechanism.

6. A method for operating a combustion furnace in which a material to be processed is transported in a first direction from upstream to downstream in the primary combustion chamber while undergoing heat treatment, A side wall gas supply mechanism is provided with a plurality of gas injection nozzles that supply gas to exhaust gas that has passed through an inlet to a secondary combustion chamber located in the upper space of the primary combustion chamber, so as to be opposed from the left and right side walls of the secondary combustion chamber in a second direction that intersects the first direction in a plan view, A method for operating a combustion furnace, which adjusts the amount of gas supplied from a plurality of gas injection nozzles arranged along the first direction or the balance of the gas supply amounts based on the carbon monoxide concentration in the exhaust gas discharged from the secondary combustion chamber.

Images