Dedicated air distribution system and air distribution method for sludge-co-firing waste incinerator

Abstract

Disclosed in the present invention is a dedicated air distribution system for a sludge-co-firing waste incinerator, the system comprising a furnace chamber, a primary air distribution circulation and a secondary air distribution circulation. The primary air distribution circulation involves a flue gas extraction port in a furnace side wall above the furnace chamber being connected to a first ejector, a primary fan being connected to the first ejector, an outlet of the first ejector being connected to a primary air main pipe, and the primary air main pipe being connected to a plurality of primary air inlets at a lower part of the furnace chamber by means of a plurality of output ports. The secondary air distribution circulation involves a steam drum above the furnace chamber being connected to a second ejector by means of a high-pressure steam pipe, an outlet of the second ejector being connected to a secondary air inlet in a side wall of a rear arch outlet of the furnace chamber, and a secondary fan being connected to the second ejector. By means of determining an ejection momentum of secondary air and an ejection angle matching same, a high-temperature flue gas below a front arch area of the furnace chamber can form an α-shaped flow mode. The present invention has the beneficial effects of significantly improving ignition conditions of solid waste, improving the efficiency, and reducing costs.

Description

A dedicated air distribution system and method for waste incinerators that co-fire sludge. Technical Field

[0001] This invention belongs to the field of combustion technology, specifically relating to a special air distribution system and method for waste incinerators that co-fire sludge. Background Technology

[0002] Currently, the main effective method for harmless treatment of sludge is incineration, which requires the sludge's moisture content to be reduced to below 25%. However, currently, even after mechanical dewatering in wastewater treatment plants, the moisture content of sludge can only be reduced to a maximum of 65%, resulting in a very low calorific value and difficulty in ignition and combustion. Therefore, it is necessary to improve the combustion structure of traditional waste incinerators to allow sludge to be completely mixed with waste for combustion, thereby achieving the harmless treatment of sludge—a win-win situation.

[0003] Chinese utility model patent CN219656083U discloses a sludge and solid waste co-combustion system, comprising a waste incinerator, a high-temperature air preheater, a low-temperature air preheater, a deaerator, a biomass gasifier, a vacuum dryer, and an ejector. The biomass gas outlet of the biomass gasifier is connected to the fuel inlet of an auxiliary burner, which is installed on the waste incinerator. The flue gas outlet of the waste incinerator is connected to the first inlet of the mixer via a second fan. A branch of the low-temperature air preheater outlet is connected to the second inlet of the mixer. The outlet of the mixer is connected to the biomass gasifier. The beneficial effects of this technical solution are as follows: it effectively reduces the energy consumption of the vacuum drying system, ensures stable combustion of low-calorific-value municipal solid waste and sludge, and results in extremely low dust and nitrogen oxide content in the combustion flue gas.

[0004] However, the patent mentioned above uses a biomass gasification furnace, which is expensive and difficult to promote widely. Without installing a biomass gasification furnace, the sludge itself has a high water content, making it difficult to burn and has a low calorific value. When it is simply dehydrated and sent to the waste incinerator for combustion, the low calorific value makes combustion difficult. Therefore, the combustion structure of the waste incinerator must be improved to meet the requirements for stable combustion.

[0005] To address the aforementioned technical challenges, there is an urgent need to develop a combustion structure modification technology for traditional waste incinerators (without requiring the addition of a biomass gasification furnace). This technology would effectively incinerate the mixture of sludge and municipal solid waste, fully utilizing the energy value of the sludge and transforming biomass and municipal solid waste resources into valuable assets. This would truly improve efficiency while maintaining environmental protection, and would have significant potential for widespread application. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the existing technology by providing a dedicated air distribution system for waste incinerators that co-fires sludge, thereby improving the combustion structure of existing waste incinerators. This invention uses optimal secondary airflow, velocity, and injection angle to alter the flow conditions and path of the airflow within the furnace, changing the L-shaped flow path to an α-shaped flow path. This forces the high-temperature airflow to form a large recirculation at the furnace front, facilitating the ignition and combustion of low-calorific-value fuels.

[0007] A second objective of this invention is to provide a dedicated air distribution method for the waste incinerator that co-fires sludge.

[0008] The technical solution adopted in this invention is: a special air distribution system for a waste incinerator that co-fires sludge, comprising a furnace 1, a primary air distribution cycle, and a secondary air distribution cycle. The primary air distribution cycle includes a first ejector 6, a primary air fan 5, and a primary air main duct 7. A circulating flue gas suction port is provided on the upper side wall of the furnace 1 and connected to the first ejector 6. The primary air fan 5 is connected to the first ejector 6. The outlet of the first ejector 6 is connected to the primary air main duct 7. The primary air main duct 7 is connected to several primary air inlets at the lower part of the furnace 1 through several outlets. The secondary air distribution cycle includes a second ejector 3, a steam drum 2, and a secondary air fan 4. A steam drum 2 is provided above the furnace 1 and connected to the second ejector 3 through a high-pressure steam pipe. The outlet of the second ejector 3 is connected to the secondary air inlet on the side wall of the rear arch outlet of the furnace 1. The secondary air fan 4 is connected to the second ejector 3.

[0009] The high-temperature flue gas below the front arch zone inside the furnace forms an α-shaped flow.

[0010] Preferably, the rear arch inclination angle β of the furnace is ≥26° and the front arch inclination angle α is ≥35°.

[0011] The geometric parameters of the furnace front arch should meet the following requirements: the angle δ between the momentum I of the combined gas flow and the front arch should be ≥120°, and the momentum combination angle γ should be ≤30°.

[0012] The secondary air nozzles are circular, numbered 8-10, and have a diameter of 110mm.

[0013] A method for distributing air to a waste incinerator that co-fires sludge is provided. Based on the dedicated air distribution system for the waste incinerator that co-fires sludge, the method adjusts the rear arch inclination angle β and the front arch inclination angle α, and determines the flow rate, ejection velocity, and downward injection angle of the secondary air, so that the high-temperature flue gas below the front arch area in the furnace forms an α-shaped flow.

[0014] When an α-shaped flue gas flow is formed below the front arch area in the incinerator furnace, the rear arch inclination angle β ≥ 26°, the front arch inclination angle α ≥ 35°, the secondary air injection velocity ≥ 50 m / s, the secondary air flow rate is 10-15% of the total air volume (of which the air flow rate accounts for 10% and the steam flow rate accounts for 5%), and the downward injection angle θ ≥ 5 degrees.

[0015] The momentum angle γ of the synthesis gas flow is ≤30°, and the angle δ between the synthesis gas flow rate I and the front arch is ≥120°.

[0016] This application involves adding high-speed secondary air to a traditional waste incinerator to create an α-shaped flue gas path flame incinerator. The α-shaped flame significantly increases the residence time of flue gas in the furnace arch zone, ensuring complete fuel combustion. Simultaneously, due to the α-shaped flow of the flue gas, centrifugal force can be used to throw larger unburned fuel particles back onto the fuel layer for further combustion, further improving combustion efficiency and reducing dust emissions. Currently available literature primarily uses methods that modify the furnace arch structure of the waste incinerator to create an α-shaped path for the high-temperature flue gas to flow back into the furnace and reheat the combusted material multiple times, utilizing the residual heat of the flue gas to make the combustion process more complete. However, this modification method is extremely labor-intensive, costly, and requires long-term shutdowns, making large-scale implementation difficult. The secondary air modification method proposed in this application achieves the same goal but with significantly lower workload and cost, facilitating widespread adoption.

[0017] In summary, compared with existing technologies, the present invention has the following beneficial effects: in terms of economic benefits, it can significantly improve the treatment efficiency of solid waste disposal enterprises, reduce the input costs of enterprises, and thus enhance the region's resource recycling capacity; in terms of social benefits, it can significantly reduce pollutant emissions and reduce harm to the health of the surrounding public; it can be promoted and applied to the entire industry, promote scientific and technological progress, and contribute to the development of efficient solid waste treatment technology. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 shows a diagram of an L-shaped flow flame in the prior art.

[0020] Figure 2 shows the α-shaped flowing flame formed after the improvement of this invention;

[0021] Figure 3 is a schematic diagram of the system structure of the present invention;

[0022] Figure 4 shows the design parameter definition diagram for a flame incinerator based on the momentum flux method;

[0023] Figure 5 is a schematic diagram of momentum synthesis;

[0024] Figure 6 shows the original design of a 750-ton / day waste incinerator;

[0025] Figure 7 shows the layout of the measuring points for the hot test.

[0026] Figure 8 shows the flue gas temperature distribution at the measuring point. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] A dedicated air distribution system for a waste incinerator that co-fires sludge, as shown in Figure 3, includes a furnace 1, a primary air distribution cycle, and a secondary air distribution cycle. The primary air distribution cycle includes a first ejector 6, a primary air fan 5, and a primary air main duct 7. A flue gas suction port is provided on the side wall of the furnace above the furnace 1 and connected to the low-pressure inlet of the first ejector 6 via a pipe. The primary air fan 5 is connected to the high-pressure inlet of the first ejector 6 via a pipe. The outlet of the first ejector 6 is connected to the primary air main duct 7. The primary air main duct 7 is connected to several primary air inlets at the bottom of the furnace 1 via several outlet ports. The secondary air distribution cycle includes a second ejector 3, a steam drum 2, and a secondary air fan 4. The steam drum 2, located above the furnace 1, is connected to the high-pressure inlet of the second ejector 3 via a high-pressure steam pipe. The outlet of the second ejector 3 is connected to the secondary air inlet on the side wall of the rear arch outlet of the furnace 1. The secondary air fan 4 is connected to the low-pressure inlet of the second ejector 3. The primary air main duct 7 has several through holes forming an output port, and the output port is connected to the primary air inlet through a pipe.

[0030] This application fully utilizes the thermal energy of the high-temperature flue gas in the furnace, improving ignition and combustion performance while reducing the nitrogen oxide content in the emitted flue gas, achieving two goals at once. Specifically, the primary air fan 5 employs a high-pressure Roots blower, which draws back the 1000°C high-temperature flue gas (15% by mass) from the furnace through the first ejector 6. In the first ejector 6, the gas mixes with cold air (85% by mass) to form hot gas at over 160°C, which then enters the primary air main duct 7 (eliminating the need for high-pressure steam heating, saving energy). This improves the ignition and combustion performance of the waste fuel. Simultaneously, due to the incorporation of flue gas, the oxygen content is reduced, and the nitrogen oxide content in the flue gas is significantly reduced, resulting in significant environmental performance.

[0031] A steam drum 2 is installed at the top of the furnace 1. High-pressure steam (1 / 3 by mass) with a pressure of 40 kg and a temperature of 300 degrees Celsius is drawn out from the steam drum 2 through a high-pressure steam pipe and introduced into the second ejector 3. Cold air (2 / 3 by mass) provided by the secondary air fan 4 is drawn in and mixed in the second ejector 3 to form a high-speed hot air of 100 degrees Celsius as the secondary air of the waste incinerator. It is injected into the furnace at high speed to form an α-shaped flowing flame.

[0032] The key to this invention is to modify the air distribution method of the waste incinerator by adding high-speed secondary air jets within the furnace 1. Through momentum synthesis, the traditional L-shaped flue gas path of the waste incinerator (as shown in Figure 1) is modified into an α-shaped path (as shown in Figure 2). The resulting novel incinerator design is more suitable for burning mixtures of low-calorific-value dehydrated sludge and municipal solid waste. The main advantages of using an α-shaped flue gas flow path in a flame incinerator burning municipal waste are:

[0033] 1. Because the moisture content of the sludge entering the flame incinerator is much higher than that of the solid waste, the mixed solid waste fuel must be preheated and dried to facilitate ignition. With the formation of the α-shaped path, the high-temperature flue gas is forced to turn downwards below the front arch, forming a recirculation zone. This enhances the heat exchange between the high-temperature flue gas and the waste fuel, strengthens the thermal radiation of the high-temperature flue gas to the solid waste fuel, and is beneficial for fuel ignition;

[0034] 2. The α-type flue gas path forces the combustible gases and hot carbon particles in the flue gas to mix fully with the air, thereby improving combustion efficiency;

[0035] 3. The α-shaped route i) prolongs the flue gas flow path, ii) increases the residence time of high-temperature flue gas in the furnace, iii) reduces the fly ash content in the flue gas, and iv) improves the combustion rate of solid waste fuel.

[0036] The α-shaped flowing flame is achieved by increasing the momentum of the secondary air ejection. By increasing the secondary air ejection velocity and momentum, an α-shaped flue gas channel can be formed within the furnace.

[0037] In order to form an α-shaped flue gas passage in the flame incinerator, the geometric parameters of the front arch of the furnace 1 should meet the following requirements: the angle δ between the gas synthesis gas flow rate I and the front arch should be ≥120°, and the momentum synthesis angle γ should be ≤30°.

[0038] Specifically, the method for achieving an α-shaped flowing flame can be obtained by following the data model and calculation steps.

[0039] S1. Define the key parameters for momentum method design of waste incinerators.

[0040] As shown in Figure 4, where A is the cross-sectional area (m²). 2 ), w is the flue gas velocity (m / s), h is the cross-sectional length or height (m), and I is the momentum flux (N). The width of the incinerator is B.

[0041] Definitions of flue gas velocity and momentum flow rate at the rear arched outlet S1-1

[0042] The momentum flow rate method is based on the momentum vector composition theory. The flue gas velocity at the rear arch outlet is w3, and its direction is consistent with the rear arch inclination angle (β). Therefore, w3 is calculated based on the cross-sectional area A3 = h3 * B at the rear arch outlet (the definition of h3 is shown in Figure 1): (1)

[0043] Where K3 = 0.4, C = 273, and A3 is the cross-sectional area of ​​the rear arch exit (m²). 2w3 is the flue gas velocity at the rear arch outlet (m / s), B is the width of the incinerator, and h3 is the height of the rear arch outlet (see Figure 1). Qy is the flue gas temperature at the rear arch outlet, Vy is the total flue gas volume produced per unit of fuel combustion, and Bj is the fuel consumption of the waste incinerator.

[0044] The momentum flow rate (I3) of the flue gas at the rear arched outlet is calculated as follows: (2)

[0045] In the formula: ; where: C=273, the rest of the definitions are the same as in equation (1).

[0046] S1-2. Definition of flue gas velocity and momentum flow rate at the forward arched outlet.

[0047] The direction of the flue gas velocity (w1) at the front arch outlet is parallel to the inclination angle (α) of the front arch, as shown in Figure 1. Considering the formation of the backflow zone under the front arch, the cross-sectional area of ​​the flue gas flow at the front arch outlet is A1 = h1 * B, and the formula for calculating the flue gas velocity (w1) is as follows: (3)

[0048] Where: K1=0.2, C=273, A1 is the cross-sectional area of ​​the front arch exit (m²) 2 w1 is the flue gas velocity at the front arch outlet (m / s), B is the width of the incinerator, and h1 is the outlet height of the front arch (see Figure 1). Here, Qy is the flue gas temperature at the front arch outlet, Vy is the total flue gas volume generated per unit of fuel combustion, and Bj is the fuel consumption of the waste incinerator.

[0049] The momentum flow rate (I1) of the flue gas at the front arch outlet is calculated as follows: (4)

[0050] Where: C=273, and the rest of the definitions are the same as in equation (3).

[0051] S1-3. Definition of flue gas velocity and momentum flow rate in the arched uncovered area

[0052] The cross-sectional area of ​​the outlet of the uncovered area of ​​the furnace is: A2 = h2 * B, and its flue gas velocity (w2) is vertically upward, which can be calculated as: (5)

[0053] Where: K2=0.4; A2 is the cross-sectional area of ​​the front arch exit (m²) 2 w2 represents the flue gas velocity at the outlet of the uncovered area (m / s), B represents the width of the incinerator, and h2 represents the outlet length of the uncovered area. Here, Qy represents the flue gas temperature at the front arch outlet, Vy represents the total flue gas volume generated per unit of fuel combustion, and Bj represents the fuel consumption of the waste incinerator.

[0054] The flue gas momentum flux (I2) in the area not covered by the furnace arch is calculated as follows: (6)

[0055] Where: C=273, and the rest of the definitions are the same as in equation (5).

[0056] S1-4. Definition of momentum flow rate of secondary wind

[0057] The high-speed secondary air injected from the rear arched outlet can penetrate deep into the front arched region to provide oxygen and enhance the combustion of waste fuel. When injected at high speed, the secondary air possesses considerable momentum, which is crucial for forming an α-shaped flue gas flow path. In this application, the secondary air is considered to be injected at room temperature. The momentum flow rate (I4) of the secondary air is calculated as follows: I4 = P0 × V O ×W O (7)

[0058] Where W0 is the secondary air ejection velocity; P0 = 1.29 * (273 + 100) / 273 kg / m 3 It can be approximated as the density of hot air; V0 is the amount of secondary air injected, in meters. 3 / s.

[0059] S1-5 Principle of Momentum Composition

[0060] As shown in Figure 4, the airflow rates I1 to I4 are orthogonally decomposed, with the leftward direction being positive in the X direction.

[0061] I 1X =I3×cosβ+I4×cosθ-I1×COSα

[0062] In the Y direction, upward is considered positive.

[0063] I 1y =I1×sinα+I2+I3×sinβ-I4×sinθ

[0064] to I 1X和 =I 1y Perform orthogonal momentum synthesis:

[0065] The direction angle γ of the resultant momentum I is:

[0066] The extension of the syngas flow rate I along angle γ makes an angle δ with the front arch. The intersection point of the syngas flow rate I and the front arch is K.

[0067] S1-6 Conditions for forming an α-shaped flue gas flow path

[0068] According to the experiment, in order to form an α-shaped flue gas path in the flame incinerator, the geometric parameters of the front arch should meet the following requirements: the angle δ between the syngas flow rate I and the front arch should be ≥120°, and the momentum synthesis angle γ should be ≤30°.

[0069] S1-7 The prerequisite for forming an α-shaped flue gas flow path through secondary wind proposed in this patent.

[0070] The following conditions must be met: rear arch inclination angle β≥26°, front arch inclination angle α≥35°, secondary air injection velocity≥50m / s, secondary air flow rate is 15% of total air volume (of which air flow rate accounts for 10% and steam flow rate accounts for 5%), downward injection angle θ≥5 degrees; secondary air nozzles are circular, number 8-10, and diameter is 110mm.

[0071] At this point, the angle γ of the synthesis momentum of the synthesis gas flow is ≤30°, and the angle δ between the synthesis gas flow rate I and the front arch is ≥120°, which satisfies the condition for forming an α-shaped flue gas flow path through the secondary wind.

[0072] Verification Instance

[0073] This invention selected a conventional full-size incinerator with a capacity of 750 tons / day for analysis.

[0074] (1) Traditional design

[0075] The original incinerator design is shown in Figure 5 (without secondary air). Effective grate length (L) P The grate width (B) is 10.8m, and the grate front arch coverage length (L) is 16.2m. Q The length of the rear arch (L) is 3.3m. H The length is 7.2m, and the middle part is the coverage length (L). HK The arch is 5.7m long, with a front arch inclination angle (α) of 40°, a rear arch inclination angle (β) of 28°, and a rear arch height of 2.121m.

[0076] Calculation results:

[0077] Table 1. Momentum flux parameters of conventional waste incinerators

[0078] I 1y I 2y I 3y I y 7.2441.3112.6661.21I 1x I 2x I 3x I x 8.620-23.82-15.19

[0079] It is evident from the momentum flux calculations of conventional flame incinerators that the flue gas flow rate within the incinerator is insufficient to meet the requirements for forming an α-type flue gas path. According to the momentum flux method discussed in Section 2.7, the momentum resultant angle (δ) is 64°, far less than the recommended 120°.

[0080] Improved design

[0081] Based on the above design, this invention installs 8 circular nozzles at the rear arched outlet, with a downward tilt angle of 5° and a diameter of 110 mm. The secondary air flow rate is 15% of the total air volume (of which the air flow rate accounts for 10% and the steam flow rate accounts for 5%), and the secondary air velocity is 50 m / s.

[0082] Calculation results:

[0083] Table 2 Momentum flux parameters of the new type of waste incinerator

[0084]

[0085] The corrected momentum synthesis angle (δ) is 131°, and the angle between the direction of the combined momentum flow rate and the horizontal direction (γ) is -8.62°. This satisfies the requirements that the angle between the synthesis gas flow rate I and the front arch is δ≥120° and the momentum synthesis angle γ≤30°, thus forming an α-shaped flame. Experimental verification:

[0086] To determine the design results, a hot-state test was conducted on a 750-ton / day waste incinerator. Analysis data on recent municipal solid waste entering the incineration plant are shown in Tables 4 and 5.

[0087] Table 3 Industrial Analysis of Samples

[0088] M(%)V(%)FC(%)A(%)47.2027.074.3621.37

[0089] Table 4 Elemental analysis of the samples

[0090] [M](%)[C] (%)[H] (%)[O] (%)[N] (%)[S] (%)LHV / kJ.kg-147.2020.412.927.950.370.026730

[0091] Because the waste was placed in the waste pit for about a week before incineration, its moisture content decreased from 47.2% to 30%, increasing the mass of municipal solid waste by 32%. ((1-30%)÷(1-47.2%)=1.32). The calorific value of the waste before entering the furnace is 6730kJ / kg (1610kcal / kg)×1.32=8888.68 (2123kcal / kg).

[0092] The arrangement of measuring points is shown in Figure 6; the arrangement of measuring points for the hot test is shown in Figure 7; and the flue gas temperature distribution at the measuring points is shown in Figure 8.

[0093] To form an α-shaped flame, the flue gas is forced downwards below the front arch to enhance combustion, and then rises towards the incinerator outlet, thus creating an α-shaped flow. Therefore, the temperatures in the α-shaped flue gas loop, i.e., measurement locations 6, 7, 9, 2, and 8, are expected to be significantly higher than at other measurement locations. This is clearly visible in Figure 5. Therefore, it can be confidently concluded that the method developed in this study, based on the momentum flux method, generates an α-shaped flue gas path within the flame incinerator to enhance combustion.

[0094] Furthermore, local temperature analysis of the novel α-type flue gas path incinerator indicates that the municipal solid waste fuel was not fully ignited at measurement location 1, where the temperature should be around 200°C. The temperature of 477°C at location 1 is due to the α-shaped flue gas path, which results in a higher flue gas temperature as it passes through the area below the front arch. This temperature increase is highly beneficial for the successful ignition of low-calorific-value municipal solid waste fuel. The higher temperature at measurement location 2 is because the waste fuel there has already ignited and completely burned. Additionally, the high-temperature flue gas flow through this area causes a sharp temperature rise. The lower temperatures at measurement locations 3, 4, and 5 are because they are in the burnout zone of the incinerator, and the waste fuel does not release a large amount of heat. The very high temperatures at measurement locations 6, 7, 8, and 9 are because these locations are in the strong combustion zone, and the fuel releases a considerable amount of heat.

[0095] The results above clearly show that the temperature values ​​in the annular area and uncovered area under the front arch are higher than in other areas, indicating the formation of an ideal α-shaped flue, consistent with the design results. Therefore, the novel α-shaped flue gas path flame incinerator is both effective and efficient in burning municipal solid waste with high moisture content and relatively difficult-to-burn combustion, especially in the case of sewage sludge.

[0096] This application proposes to use a secondary air intake method to create an α-shaped flow of flue gas. This method does not require changes to the furnace structure of the waste incinerator, is low-cost, and easy to promote on a large scale. As shown in Figures 7 and 8, the secondary air refers to several strong airflows injected at high speed from above the combustion bed into the furnace, which significantly affects the airflow within the furnace and enhances mixing. It can improve the thermal efficiency of the waste incinerator without increasing the total amount of combustion air. At the same time, the high-speed, high-momentum secondary airflow can also guide the flue gas within the furnace, organizing it into a predetermined airflow pattern to prolong the flow path of flue gas and fly ash, and change the degree of furnace filling and the position of the combustion center. When properly arranged, a secondary air curtain can also be formed inside the furnace, trapping fly ash particles in the flue gas. This not only changes the ignition conditions of the fuel but also further reduces various incomplete combustion losses within the furnace, improving the combustion efficiency of waste.

[0097] To fully utilize the turbulent mixing effect of secondary air, it needs a certain initial velocity (or a certain range). However, during hot operation of the incinerator, the furnace is at a very high temperature. At this time, the viscosity of the flue gas increases significantly, making it difficult for secondary air to penetrate. Therefore, the secondary air range calculated using the traditional free jet attenuation formula often differs from reality, sometimes significantly, resulting in the secondary air failing to achieve the expected effect. Based on past engineering experience, the penetration depth of secondary air in a hot state is not only related to velocity but also to its density and flow rate, i.e., to its single-stream momentum flow rate. The greater the single-stream momentum flow rate, the greater the turbulence on the flue gas and the deeper the penetration. Furthermore, it is also related to the ratio of the momentum flow rate of the secondary air to that of the rising flue gas at the grate surface; when this ratio increases, both turbulence and mixing effects are enhanced. Reasonable values ​​for these two physical quantities are crucial for achieving the best practical effect from the secondary air. However, determining the optimal values ​​for these two physical quantities is a complex issue. Therefore, one of the purposes of this paper is to derive a more practical calculation formula based on the momentum design method, and to calculate the optimal ratio of the momentum flow rate of the secondary air to the rising flue gas at the grate surface, thereby changing the flow conditions and flow path of the airflow in the furnace, that is, changing the L-shaped flow path to an A-shaped flow path, forcing the high-temperature airflow to form a large backflow in front of the furnace, which is conducive to the ignition and combustion of low-calorific-value fuels.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A special air distribution system for a waste incinerator with co-combustion of sludge, characterized in that, The system comprises a furnace, a primary air distribution cycle and a secondary air distribution cycle, the primary air distribution cycle comprises a first ejector, a primary air fan and a primary air main pipe, a circulating flue gas suction port is arranged on the upper furnace wall side wall of the furnace and connected with the first ejector, the primary air fan is connected with the first ejector, the outlet of the first ejector is connected with the primary air main pipe, and the primary air main pipe is connected with a plurality of primary air inlets of the lower part of the furnace through a plurality of outlets; the secondary air distribution cycle comprises a second ejector, a steam pocket and a secondary air fan, the steam pocket arranged above the furnace is connected with the second ejector through a high-pressure steam pipe, the outlet of the second ejector is connected with a secondary air inlet of the rear arch outlet side wall of the furnace, and the secondary air fan is connected with the second ejector.

2. The air distribution system for a waste incinerator with co-combustion of sludge according to claim 1, characterized in that, The high-temperature flue gas under the front arch area in the furnace forms an alpha-shaped flow.

3. The air distribution system for a waste incinerator with co-combustion of sludge according to claim 2, characterized in that, The rear arch inclination angle β is greater than or equal to 26°, and the front arch inclination angle α is greater than or equal to 35°.

4. The air distribution system for a waste incinerator with co-combustion of sludge according to claim 3, characterized in that, The geometric parameters of the front arch of the furnace should meet the following requirements: the momentum I of the synthesis gas flow and the front arch included angle δ are greater than or equal to 120°, and the momentum synthesis angle γ is less than or equal to 30°.

5. A special air distribution system for a refuse incinerator with mixed burning of sludge according to claim 4, characterized in that, The secondary air injection port is circular, the number is 8-10, and the diameter is 110 mm.

6. A method of special air distribution for a waste incinerator with co-combustion of sludge, characterized in that, The special air distribution system for the garbage incinerator with mixed burning of sludge based on claim 1 adjusts the rear arch inclination angle β and the front arch inclination angle α, determines the flow rate, the injection speed and the downward injection angle of the secondary air, so that the high-temperature flue gas under the front arch area in the furnace forms an alpha-shaped flow.

7. The method according to claim 6, wherein the air distribution method is used for a waste incinerator with co-combustion of sludge, characterized in that, When the alpha-shaped flue gas flow is formed under the front arch area in the furnace of the incinerator, the rear arch inclination angle β is greater than or equal to 26°, the front arch inclination angle α is greater than or equal to 35°, the injection speed of the secondary air is greater than or equal to 50 m / s, the flow rate of the secondary air is 15% of the total air volume, and the downward injection angle θ is greater than or equal to 5 degrees; the secondary air injection port is circular, the number is 8-10, and the diameter is 110 mm.

8. The method according to claim 7, wherein the air distribution method is used for a waste incinerator with mixed waste and sludge, characterized in that, The momentum synthesis angle γ of the synthesis gas flow is less than or equal to 30°, and the momentum I of the synthesis gas and the front arch included angle δ are greater than or equal to 120°.

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