A high-temperature flue gas cooling structure suitable for an incinerator and containing low-melting-point salt

Abstract

The present application relates to a kind of high-temperature flue gas cooling structure of high low-melting salt containing suitable for incinerator, including furnace body cooling area structure, cooling water lance and combination nozzle;Furnace body cooling area structure adopts cylindrical contraction form, the ratio D / d of inside diameter before and after contraction is 1.25~1.5;Combination nozzle includes multiple nozzle uniformly distributed in circumference, located 1 / 10 furnace inner diameter D at upstream of furnace body cooling area structure contraction section;Combination nozzle converts the static pressure of cooling air into dynamic pressure, forms annular wall jet and eccentric jet, the direction of two jets is contrary, annular wall jet supports eccentric jet, while both interaction generates local vortex to speed up the mixing of flue gas and cooling air;Cooling water lance is used to reduce the flow of flue gas after cooling, located 1 / 2 furnace inner diameter D at upstream of combination nozzle, lance inclination β takes downward 5°~15°, lance atomizing angle is between 60°~75°.The present application protects furnace wall and improves cooling efficiency, achieves the effect of rapid cooling and avoiding furnace wall salt deposition.

Description

Technical Field

[0001] This invention belongs to the field of high-salt, high-temperature flue gas cooling technology, and relates to a high-temperature flue gas cooling structure with high low-melting-point salt content suitable for incinerators. Background Technology

[0002] Currently, saline organic waste liquids are mostly incinerated using vertical top-fired incineration. The high-temperature flue gas produced after incineration (about 1100℃) simultaneously forms low-melting-point salts. Compared with the ash of traditional coal-fired boilers, the ash melting point is lower (about 650-850℃), and it has extremely strong adhesion in this temperature range. The dust content of the flue gas reaches 20mg / Nm3, which is considered flue gas with a high content of low-melting-point salts. In order to ensure that the molten salts pass smoothly through the incinerator, the flue gas needs to be cooled rapidly so that the molten salts can quickly pass through the high-viscosity temperature range and avoid them adhering to the inner wall of the incinerator, causing corrosion and adhesion.

[0003] In the early days, JOHN ZINK COMPANY, LLC used water spray cooling to cool saline flue gas. This method resulted in a water content of nearly 40% in the flue gas, which made the system prone to caking and blockage after salt discharge. As a result, the unit could only operate at low load and for a limited time.

[0004] Kellert Combustion Technology & Equipment (Shanghai) Cable Co., Ltd. employs a mixed-air (or circulating low-temperature flue gas) cooling method. Specifically, a long cooling space is reserved at the bottom of the furnace body, with cooling air ducts arranged in a dense ring at the same height, spraying low-temperature gas jets towards the center of the furnace. This method effectively protects the furnace walls; however, the limited jet air intensity makes it difficult to penetrate the flue gas, resulting in a slow cooling process for the mainstream flue gas and a correspondingly large cooling space required. Insufficient space can easily cause tailing of the side-exit flue gas, whose temperature is often downstream of the viscous range. In particular, the side-exit flue gas ducts are prone to ash accumulation, requiring multiple air cannons for clearing, which can significantly impact downstream systems. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a high-temperature flue gas cooling structure with high content of low melting point salts suitable for incinerators, which takes into account both protecting the furnace wall and improving cooling efficiency, so as to achieve the effects of rapid cooling and avoiding salt deposition on the furnace wall.

[0006] The solution of the present invention is: a high-temperature flue gas cooling structure suitable for incinerators with high content of low melting point salts, including a furnace cooling zone structure, a cooling water spray gun and a combined spray pipe;

[0007] The furnace cooling zone adopts a cylindrical contraction structure, with the ratio of the inner diameter before and after contraction, D / d, being 1.25 to 1.5.

[0008] The combined nozzle consists of multiple identical nozzles evenly distributed circumferentially along the same height, located at position D, 1 / 10 of the furnace inner diameter upstream of the structural contraction section of the furnace cooling area. External cooling air is delivered to the combined nozzle, which converts the static pressure of the cooling air into dynamic pressure, forming a jet in the direction of the ring wall and a jet deviating towards the center of the furnace. The two jets are in opposite directions, with the jet in the direction of the ring wall supporting the jet deviating towards the center of the furnace. At the same time, the interaction between the two generates local vortices that accelerate the mixing of flue gas and cooling air.

[0009] The cooling water spray gun is used to reduce the flow rate of the cooled flue gas. It is set at the position of 1 / 2 furnace inner diameter D upstream of the combined spray pipe. The spray gun tilt angle β is 5° to 15° downward and the spray gun atomization angle is between 60° and 75°.

[0010] Furthermore, the contraction angle α of the furnace cooling zone structure is taken as 45-60°.

[0011] Furthermore, the outlet height of the furnace cooling zone structure is taken as 1 / 4 to 1 / 3 of the outlet diameter d.

[0012] Furthermore, the jet velocity in the direction of the ring wall and the jet velocity deviating towards the center of the furnace body shall not be less than 35 m / s.

[0013] Furthermore, the number of nozzles in the combined nozzle system must ensure that the jet coverage length in the annular wall direction multiplied by the number of nozzles is greater than the perimeter of the furnace body cross section, where the coverage length is the length at which the average jet velocity decays to 50%.

[0014] Furthermore, the proportion of the jet flow in the ring wall direction to the total cooling airflow is 0.35 to 0.45.

[0015] Furthermore, the jet design angle θ, which is biased towards the center of the furnace body, is selected to be 5° to 30°.

[0016] Furthermore, the external cooling air uses low-temperature circulating flue gas or room-temperature air, with the temperature of the low-temperature circulating flue gas between 120℃ and 180℃.

[0017] Furthermore, the heat absorbed by the water cooling gun does not exceed 50%.

[0018] Furthermore, 3 to 4 cooling water spray guns are evenly arranged circumferentially at the same height.

[0019] The advantages of this invention compared to the prior art are:

[0020] This invention can efficiently cool high-temperature, saline flue gas within a designed area, while effectively protecting the furnace wall and preventing salt adhesion or even blockage. It saves approximately 30% of space compared to similar products, and provides uniform outlet temperature, eliminating the risk of adhesion to downstream systems and promoting long-term system operation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the assembly and working principle of the high-temperature flue gas cooling structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the jet distribution of the combined nozzle of the present invention;

[0023] Explanation of reference numerals in the attached drawings: 1-Structure of the furnace cooling zone, 11-Inlet high-temperature saline flue gas, 12-Outlet low-temperature saline flue gas, 2-Cooling water spray gun, 3-Combined nozzle, 31-Annular wall jet, 32-Local vortex, 33-Eccentric jet. Detailed Implementation

[0024] The present invention proposes a high-temperature flue gas cooling structure suitable for incinerators with high salt content and low melting point. The high-temperature flue gas with high salt content is cooled by means of ambient temperature air or low temperature circulating flue gas (hereinafter referred to as cooling air) or by a combination of cooling and water cooling.

[0025] like Figure 1 As shown, the high-temperature flue gas cooling structure of the present invention includes three parts: furnace cooling zone structure 1, cooling water spray gun 2, and combined spray pipe 3.

[0026] The furnace cooling zone structure 1 adopts a cylindrical contraction form, with a contraction angle α of 45 to 60 degrees, an inner diameter ratio D / d before and after contraction of 1.25 to 1.5, and an outlet height h2 of 1 / 4 to 1 / 3 of the outlet diameter d.

[0027] The combined nozzle 3 includes multiple identical nozzles, with a height h1 set at 1 / 10 of the furnace inner diameter D upstream of the contraction section of the furnace cooling area structure 1, and all nozzles are at the same horizontal height and are evenly distributed along the circumference.

[0028] The working principle of the combined nozzle 3 is as follows: external cooling air is delivered to the combined nozzle 3 by a fan. The combined nozzle 3 converts the static pressure of the cooling air into dynamic pressure, forming a jet in the direction of the annular wall—referred to as the annular jet 31—and a jet deviating towards the center of the furnace body—referred to as the eccentric jet 33. The two jets are in opposite directions. The annular jet supports the eccentric jet, and at the same time, the interaction between the two generates a local vortex 32 that accelerates the mixing of flue gas and cooling air. Figure 2 As shown.

[0029] The combined nozzle 3 can also use low-temperature circulating flue gas instead of room temperature air as cooling air, with the circulating flue gas temperature between 120℃ and 180℃. Compared with using room temperature air, low-temperature circulating flue gas can improve the thermal efficiency of waste heat recovery equipment and reduce the impact of external environmental temperature and humidity changes and dust; however, it will also increase the size of downstream equipment; the choice can be made according to process and economic conditions.

[0030] The design parameters of the combined nozzle 3 depend on the cooling process conditions: the number of nozzles in the combined nozzle 3 depends on the furnace inner diameter D. Specifically, the number of nozzles should ensure that the coverage length of the annular jet 31 (the length at which the average jet velocity decays to 50%) multiplied by the number of nozzles is slightly larger than the perimeter of the furnace cross-section. The preferred number is 6 to 12. The larger the furnace inner diameter D, the more nozzles are needed; the higher the cooling capacity required at the flue gas center, the more nozzles are needed. The proportion of the annular jet 31 to the total cooling airflow is approximately 0.35 to 0.45. A smaller value is used if the cooling capacity required at the flue gas center is low. The design angle θ of the eccentric jet 33 can be selected from 5° to 30°. A smaller value is used if the cooling capacity required at the flue gas center is high. The velocities of the annular jet 31 and the eccentric jet 33 are recommended to be above 35 m / s, and can be appropriately increased if pressure conditions permit.

[0031] This invention can use water cooling to reduce the flow rate of the cooled flue gas. However, considering the need to control the water content in the flue gas, it is not recommended that the heat absorption of water cooling account for more than 50%.

[0032] The cooling water spray gun is set at a height h3 approximately 1 / 2 of the furnace inner diameter D upstream of the combined spray pipe 3. Due to the limitations of the furnace cross-sectional shape and the need to protect the wall surface, the number of spray guns should be minimized. It is recommended to have 3 to 4 guns at the same height. The spray gun tilt angle β can be 5° to 15° downward to improve the volume utilization efficiency. The spray gun atomization angle is recommended to be between 60° and 75°. The cooling area of ​​the flue gas by the cooling water is mainly concentrated in the center of the flue gas flow, and there will be no high viscosity temperature range near the wall surface.

[0033] The present invention will be further described below with reference to the embodiments.

[0034] Example 1

[0035] like Figure 1 , Figure 2 As shown, the high-temperature flue gas cooling structure of this embodiment includes three parts: furnace cooling area structure 1, cooling water spray gun 2, and combined spray pipe 3.

[0036] The furnace cooling zone structure 1 adopts a cylindrical contraction form with a contraction angle α of 60 degrees, a ratio of inner diameter before and after contraction D / d of 1.5, and an outlet height h2 of 1 / 3 of the outlet diameter d.

[0037] The combined nozzle 3 consists of 8 nozzles evenly distributed circumferentially along the same height, and is located at a height h1 upstream of the contraction section of the furnace cooling area structure 1, where h1 is approximately 1 / 10 of the furnace inner diameter D.

[0038] The combined nozzle 3 converts the static pressure of the cooling air into dynamic pressure, which can emit a jet in the direction of the ring wall - referred to as the ring wall jet 31, and a jet biased towards the center of the furnace body - referred to as the eccentric jet 33. The two jets are in opposite directions. The ring wall jet 31 supports the eccentric jet 33. At the same time, the two interact to generate a local vortex 32 to accelerate the mixing of flue gas and cooling air.

[0039] The annular jet 31 accounts for approximately 0.4% of the total cooling airflow; a smaller value is used when the cooling requirement at the center of the flue gas is low. The eccentric jet 33 has a design angle θ of 15°; a smaller value is used when the cooling requirement at the center of the flue gas is high. Both jet velocities are above 35 m / s.

[0040] Water cooling is used to reduce the flow rate of the cooled flue gas, and the heat absorption of water cooling accounts for no more than 50%.

[0041] The cooling water spray gun 2 is set at a height h3 upstream of the cooling air combined spray pipe 3, which is about 1 / 2 of the furnace inner diameter D. There are 4 guns at the same height, with an inclination angle β 10° downward and an atomization angle between 60° and 75°.

[0042] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0043] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A high-temperature flue gas cooling structure suitable for incinerators containing high levels of low-melting-point salts, characterized in that, It includes the furnace cooling zone structure (1), cooling water spray gun (2) and combined spray pipe (3); The furnace cooling zone structure (1) adopts a cylindrical shrinkage form, and the ratio of the inner diameter before and after shrinkage, D / d, is 1.25~1.5; the shrinkage angle α of the furnace cooling zone structure (1) is 45~60°, and the outlet height of the furnace cooling zone structure (1) is 1 / 4~1 / 3 of the outlet diameter d; The combined nozzle (3) includes multiple identical nozzles evenly distributed circumferentially along the same height, and is set at the position of 1 / 10 furnace inner diameter D upstream of the contraction section of the furnace cooling area structure (1); external cooling air is delivered to the combined nozzle (3), and the combined nozzle (3) converts the static pressure of the cooling air into dynamic pressure, forming a jet in the direction of the ring wall and a jet biased towards the center of the furnace body. The two jets are in opposite directions, and the jet in the direction of the ring wall supports the jet biased towards the center of the furnace body. At the same time, the two interact to generate local vortices to accelerate the mixing of flue gas and cooling air. The cooling water spray gun (2) is used to reduce the flow rate of the cooled flue gas. It is set at the position of 1 / 2 furnace inner diameter D upstream of the combined spray pipe (3). The spray gun tilt angle β is 5°~15° downward and the spray gun atomization angle is between 60°~75°. The heat absorbed by the water cooling of the cooling water spray gun (2) does not exceed 50%. The jet velocity in the direction of the ring wall and the jet velocity deviating towards the center of the furnace body shall not be less than 35 m / s; The number of nozzles in the combined nozzle (3) should ensure that the jet coverage length in the annular wall direction multiplied by the number of nozzles is greater than the perimeter of the furnace body cross section. The coverage length is the length at which the average jet velocity decays to 50%. The proportion of the jet flow in the direction of the ring wall to the total cooling airflow is 0.35~0.45; The jet design angle θ, which is biased towards the center of the furnace body, is selected as 5°~30°.

2. The high-temperature flue gas cooling structure for incinerators with high content of low-melting-point salts according to claim 1, characterized in that, The external cooling air uses low-temperature circulating flue gas or room temperature air, with the temperature of the low-temperature circulating flue gas between 120℃ and 180℃.

3. The high-temperature flue gas cooling structure for incinerators with high content of low-melting-point salts according to claim 1, characterized in that, Three to four cooling water spray guns (2) are evenly arranged at the same height along the circumference.

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