Sintering offgas purification system

Abstract

The application discloses a sintering flue gas purification system, which comprises a circulating fluidized bed furnace, a primary air duct, a secondary air duct, a sintering flue gas preheating device and a bypass air duct; the circulating fluidized bed furnace is internally provided with a wind distribution plate, the lower portion of the wind distribution plate is a primary air chamber, and the upper portion of the wind distribution plate is a secondary air chamber; the primary air duct is communicated with the primary air chamber; the secondary air duct is communicated with the secondary air chamber; the sintering flue gas preheating device heats the sintering flue gas in the secondary air duct; the bypass air duct is communicated with the secondary air duct and the primary air duct, the sintering flue gas heated by the sintering flue gas preheating device in the secondary air chamber can enter the primary air duct, the sintering flue gas in the secondary air duct and the sintering flue gas preheating device can be directly heat-exchanged, the sintering flue gas in the primary air duct and the sintering flue gas preheating device can be indirectly heat-exchanged, the temperature of the sintering flue gas in the primary air duct and the secondary air duct is simultaneously improved; the temperature of the sintering flue gas in the secondary air duct and the primary air duct can be prevented from exceeding the bonding temperature of iron oxide dust by limiting the temperature of the sintering flue gas preheating device.

Description

Technical Field

[0001] This invention relates to the technical field of sintering flue gas application technology, and in particular to a sintering flue gas purification system. Background Technology

[0002] Sintering flue gas mainly originates from the sintering process in steel production, which involves sintering iron ore into blocks at high temperatures on a sintering machine. This process emits flue gas containing pollutants such as sulfur dioxide and dust. The high-temperature flue gas generated in the sintering process can be used as a heat source for CFB boilers for power generation or heating.

[0003] However, sintering flue gas has a complex composition and requires purification. Among them, the circulating fluidized bed (CFB) purification device for sintering flue gas is an emerging industrial waste gas purification device with advantages such as large waste gas treatment capacity, no secondary pollution, low cost, and recovery of waste heat from the waste gas.

[0004] If the temperature of the sintering flue gas is too low, the temperature inside the circulating fluidized bed boiler will be low, which is not conducive to the complete combustion of pulverized coal in the circulating fluidized bed boiler, thus reducing boiler efficiency. If the temperature of the sintering flue gas is too high, the iron oxide dust present in the sintering flue gas will adhere to the surface of the air cap and flue pipe wall of the circulating fluidized bed boiler at high temperature. This leads to severe corrosion of the sintering flue gas flue. In addition, after a period of use, the boiler air cap will become severely blocked, requiring shutdown for cleaning. This results in a short operating cycle and low availability of the sintering flue gas circulating fluidized bed purification device.

[0005] Therefore, how to ensure that the temperature of the sintering flue gas entering the circulating fluidized bed meets the requirements is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a sintering flue gas purification system that ensures that the temperature of the sintering flue gas is neither too low nor too high, so that the temperature of the sintering flue gas entering the circulating fluidized bed meets the requirements.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A sintering flue gas purification system includes: a circulating fluidized bed furnace, wherein an air distribution plate is provided inside the circulating fluidized bed furnace, a primary air chamber is located below the air distribution plate, and a secondary air chamber is located above the air distribution plate; a primary air duct connected to the primary air chamber; a secondary air duct connected to the secondary air chamber; a sintering flue gas preheating device for heating the sintering flue gas in the secondary air duct; and a bypass air duct connecting the secondary air duct and the primary air duct, wherein the sintering flue gas heated by the sintering flue gas preheating device in the secondary air duct can enter the primary air duct.

[0009] Preferably, in the above-mentioned sintering flue gas purification system, the bypass ventilation duct is connected between the sintering flue gas preheating device and the circulating fluidized bed furnace.

[0010] Preferably, in the above-mentioned sintering flue gas purification system, a bypass fan is provided on the bypass ventilation duct, and the bypass fan is used to introduce the sintering flue gas heated by the sintering flue gas preheating device in the secondary air duct into the primary air duct.

[0011] And / or, a one-way valve is provided on the bypass ventilation duct, and the one-way valve is directed to flow unidirectionally from the secondary air duct to the primary air duct.

[0012] Preferably, in the above-mentioned sintering flue gas purification system, when a bypass fan is installed on the bypass ventilation duct, it also includes a temperature detection device and a fan control system.

[0013] The temperature detection device is connected to the fan control system, and the temperature detection device is used to detect the temperature inside the primary air duct;

[0014] The fan control system is connected to the bypass fan, and the fan control system controls the start and stop of the bypass fan;

[0015] If the temperature of the sintering flue gas in the primary air duct detected by the temperature detection device is lower than a first preset value, the fan control system controls the bypass fan to start, and the bypass fan operates at a preset power.

[0016] If the temperature of the sintering flue gas in the primary air duct detected by the temperature detection device is greater than the second preset value, the fan control system controls the bypass fan to shut down.

[0017] The first preset value is less than the second preset value, and the second preset value is less than the bonding temperature of iron oxide dust in the sintering flue gas.

[0018] Preferably, in the above-mentioned sintering flue gas purification system, the fan control system also controls the power variation of the bypass fan.

[0019] Preferably, in the above-mentioned sintering flue gas purification system, the heating temperature of the sintering flue gas in the secondary air duct by the sintering flue gas preheating device can be a third preset value.

[0020] The first preset value is greater than the third preset value.

[0021] Preferably, in the above-mentioned sintering flue gas purification system, the primary air duct is a bent pipe;

[0022] The bending direction of the primary air duct can be vertical and / or horizontal.

[0023] Preferably, in the above-mentioned sintering flue gas purification system, the primary air duct includes a first section, a second section, and a third section connected in sequence;

[0024] One end of the first segment is connected to the primary air chamber, the other end of the first segment is connected to the second segment, the other end of the second segment is connected to the third segment, and the second segment is inclined relative to the third segment;

[0025] The bypass ventilation duct is connected to the third section.

[0026] Preferably, the above-mentioned sintering flue gas purification system further includes a separator connected to the top of the circulating fluidized bed furnace, the bottom of the separator being connected to the circulating fluidized bed furnace via a return feeder, and the top of the separator being connected to the flue.

[0027] The sintering flue gas preheating device is installed on the flue.

[0028] Preferably, in the above-mentioned sintering flue gas purification system, the sintering flue gas preheating device is an electric heating device or a circulating pipeline heating device.

[0029] This invention discloses a sintering flue gas purification system. By setting a sintering flue gas preheating device on the secondary air duct and connecting the secondary air duct with the primary air duct, the sintering flue gas in the secondary air duct can directly exchange heat with the sintering flue gas preheating device, while the sintering flue gas in the primary air duct can indirectly exchange heat with the sintering flue gas preheating device. This simultaneously increases the temperature of the sintering flue gas in both the primary and secondary air ducts.

[0030] Furthermore, by limiting the temperature of the sintering flue gas preheating device, the temperature of the sintering flue gas in the secondary air duct can be prevented from exceeding the bonding temperature of the iron oxide dust. Moreover, the heat exchange between the sintering flue gas in the secondary air duct and the sintering flue gas in the primary air duct ensures that the temperature of the sintering flue gas in the primary air duct will not exceed the bonding temperature of the iron oxide dust. In other words, by limiting the temperature of the sintering flue gas preheating device, the temperature of the sintering flue gas in both the primary and secondary air ducts can be raised simultaneously, while effectively limiting the excessively high temperature of the sintering flue gas in both the primary and secondary air ducts. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the sintering flue gas purification system disclosed in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the primary air duct of the sintering flue gas purification system disclosed in an embodiment of the present invention.

[0034] Among them, 1-circulating fluidized bed furnace, 2-separator, 3-flue, 4-primary air device, 5-secondary air device, 6-bypass device, 7-fan control system, 8-temperature detection device;

[0035] 11-Air distribution plate, 12-Air cap, 21-Return feeder, 22-Separator outlet flue, 31-Sintering flue gas preheating device, 41-Primary air duct, 411-First section, 412-Second section, 413-Third section, 42-Primary air fan, 51-Secondary air duct, 52-Secondary air fan, 61-Bypass ventilation duct, 62-Bypass ventilation fan. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0037] It should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0038] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0039] Hereinafter, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0040] Sintering flue gas mainly originates from the sintering process in steel production, which involves sintering iron ore into blocks at high temperatures on a sintering machine. This process emits flue gas containing pollutants such as sulfur dioxide and dust. The high-temperature flue gas generated in the sintering process can be used as a heat source for CFB boilers for power generation or heating.

[0041] However, sintering flue gas has a complex composition and requires purification. Among them, the circulating fluidized bed (CFB) purification device for sintering flue gas is an emerging industrial waste gas purification device with advantages such as large waste gas treatment capacity, no secondary pollution, low cost, and recovery of waste heat from the waste gas.

[0042] If the temperature of the sintering flue gas is too low, the temperature inside the circulating fluidized bed boiler will be low, which is not conducive to the complete combustion of pulverized coal in the circulating fluidized bed boiler, thus reducing boiler efficiency. If the temperature of the sintering flue gas is too high, the iron oxide dust present in the sintering flue gas will adhere to the surface of the air cap and flue pipe wall of the circulating fluidized bed boiler at high temperature. This leads to severe corrosion of the sintering flue gas flue. In addition, after a period of use, the boiler air cap will become severely blocked, requiring shutdown for cleaning. This results in a short operating cycle and low availability of the sintering flue gas circulating fluidized bed purification device.

[0043] Based on the above problems, this embodiment discloses a sintering flue gas purification system, including: a circulating fluidized bed furnace 1, a separator 2, a flue 3, a primary air device 4, a secondary air device 5, a bypass device 6, a fan control system 7, and a temperature detection device 8.

[0044] The circulating fluidized bed furnace 1 includes a dense phase zone (not shown in the figure) and a dilute phase zone (not shown in the figure), which are arranged along the height direction of the circulating fluidized bed furnace 1. An air distribution plate 11 and an air cap 12 are provided at the bottom of the circulating fluidized bed furnace 1. Below the air distribution plate 11 is the primary air chamber. The air cap 12 is installed on the air distribution plate 11, allowing the air from the primary air chamber to enter the circulating fluidized bed furnace 1, specifically the dense phase zone, and forming a circulating fluidized bed above the air distribution plate 11. Above the air distribution plate 11 is the secondary air chamber. The distinction between "above" and "below" in this text refers to the vertical orientation of the circulating fluidized bed furnace 1.

[0045] The dense phase region and the dilute phase region are connected. The dilute phase region is connected to the separator 2. The bottom of the separator 2 is connected to the dense phase region through the return feeder 21. The top of the separator 2 is provided with a separator outlet flue 22, which is connected to the flue 3. In this embodiment, the separator 2 can be a cyclone separator.

[0046] The primary air device 4 includes a primary air duct 41 and a primary air fan 42.

[0047] The primary air duct 41 is connected to the primary air chamber of the circulating fluidized bed furnace 1, and the primary air fan 42 is installed on the primary air duct 41 to provide power for the primary air in the primary air duct 41.

[0048] The sintering flue gas, which serves as primary air, can enter the primary air chamber of the circulating fluidized bed furnace 1 through the primary air duct 41 under the action of the primary air fan 42, and then be mixed with the coal in the circulating fluidized bed furnace 1 and burned.

[0049] The secondary air device 5 includes a secondary air duct 51 and a secondary air fan 52.

[0050] The secondary air duct 51 is connected to the secondary air chamber above the air distribution plate 11 of the circulating fluidized bed furnace 1, and the secondary air fan 52 is installed on the secondary air duct 51 to provide power for the secondary air in the secondary air duct 51.

[0051] The sintering flue gas, which serves as secondary air, can enter the secondary air chamber of the circulating fluidized bed furnace 1 through the secondary air duct 51 under the action of the secondary air fan 52, supplementing the oxygen required for coal combustion.

[0052] The temperature of sintering flue gas introduced into the sintering flue gas purification system is usually in the range of 120℃ to 160℃. If sintering flue gas in this range is directly introduced into the circulating fluidized bed furnace 1, the furnace temperature of the circulating fluidized bed furnace 1 will be low, which is not conducive to the combustion of pulverized coal and will result in incomplete combustion of pulverized coal, which will reduce the combustion efficiency of the boiler.

[0053] Based on this, the sintering flue gas purification system of this embodiment has a sintering flue gas preheating device 31, which can heat the sintering flue gas in the secondary air duct 51 so that the temperature of the sintering flue gas in the secondary air duct 51 meets the temperature requirements.

[0054] In an optional embodiment, the sintering flue gas preheating device 31 is installed on the flue 3. For example, the sintering flue gas preheating device 31 is installed on the flue 3 via a threaded connector.

[0055] The sintering flue gas preheating device 31 can be an electric heating device or a circulating pipeline heating device. In some embodiments, the sintering flue gas preheating device 31 is a circulating pipeline structure, which includes a sintering flue gas pipeline and a heating pipeline. The sintering flue gas pipeline is connected to the secondary air duct 51, and the heating pipeline is wound around the sintering flue gas pipeline, or the liquid pipeline and the sintering flue gas pipeline are both coiled around the flue 3. The heating pipeline can be filled with a high-temperature liquid or gas, thereby utilizing the high-temperature liquid or gas to exchange heat with the sintering flue gas, achieving the purpose of heating the sintering flue gas.

[0056] The sintering flue gas preheating device 31 in this embodiment adopts a circulating pipeline structure and uses circulating gas or liquid for heating, which simplifies the structure and enables heat exchange using gas or liquid in the sintering flue gas purification system, thereby realizing energy reuse.

[0057] The sintering flue gas preheating device 31 adopts an electric heating device, which facilitates the control and adjustment of the sintering flue gas heating temperature by the sintering flue gas preheating device 31.

[0058] It is important to know that the iron oxide dust contained in the sintering flue gas will adhere to the pipe wall of the air duct at high temperatures (350℃-400℃), and the iron oxide dust will corrode the pipe wall after a long period of accumulation.

[0059] Based on this, in this embodiment, the sintering flue gas entering the secondary air duct 51 is heated by the sintering flue gas preheating device 31, and its temperature can be raised to a third preset value. In this example, the third preset value can be about 250°C. The temperature of the sintering flue gas in the secondary air duct 51 is raised to 250°C, which can ensure that the sintering flue gas entering the circulating fluidized bed furnace 1 meets the combustion requirements in the furnace of the circulating fluidized bed furnace 1, and can prevent the accumulation of high-temperature iron oxide dust in the secondary air duct 51, which would affect the service life of the secondary air duct 51.

[0060] The third preset value in this embodiment can be set according to different needs, and the third preset value is not greater than the bonding temperature of iron oxide dust in sintering flue gas.

[0061] Based on the above technical solution, the sintering flue gas purification system of this embodiment connects the secondary air duct 51 and the primary air duct 41 through a bypass device 6. In this example, the bypass device 6 includes a bypass air duct 61 and a bypass fan 62.

[0062] One end of the bypass ventilation duct 61 is connected to the sintering flue gas preheating device 31 in the secondary air duct 51 and the secondary air chamber of the circulating fluidized bed furnace 1. It should be understood that the bypass ventilation duct 61 is located between the sintering flue gas preheating device 31 and the circulating fluidized bed furnace 1, so that the sintering flue gas entering the bypass ventilation duct 61 is the sintering flue gas heated by the sintering flue gas preheating device 31.

[0063] The other end of the bypass ventilation duct 61 is connected to the primary air duct 41. Optionally, the bypass ventilation duct 61 is connected to the side of the primary air duct 41 near the circulating fluidized bed furnace 1. In this way, the heat exchange between the sintering flue gas in the primary air duct 41 and the outside can be reduced, so that the temperature of the sintering flue gas entering the circulating fluidized bed furnace 1 is more accurate.

[0064] The side ventilation fan 62 is installed on the side ventilation duct 61 and can introduce the sintering flue gas in the secondary air duct 51 into the primary air duct 41.

[0065] The bypass device 6 connects the primary air duct 41 and the secondary air duct 51, and can introduce part of the heated sintering flue gas in the secondary air duct 51 into the primary air duct 41, so that the heated sintering flue gas in the secondary air duct 51 mixes with the sintering flue gas in the primary air duct 41, thereby heating the sintering flue gas in the primary air duct 41 and increasing the temperature of the sintering flue gas in the primary air duct 41. This is beneficial to the combustion of pulverized coal in the circulating fluidized bed furnace 1, and thus helps to improve the combustion efficiency in the circulating fluidized bed furnace 1.

[0066] In some alternative embodiments, the sintering flue gas purification system may also include a one-way valve (not shown in the figure), which is disposed on the bypass duct 61 and the one-way valve is unidirectionally directed from the secondary air duct 51 to the primary air duct 41.

[0067] A one-way valve is installed on the bypass ventilation duct 61 to allow unidirectional flow from the secondary air duct 51 to the primary air duct 41. This prevents the sintering flue gas in the primary air duct 41 from flowing into the secondary air duct 51, which would affect the temperature of the sintering flue gas in the secondary air duct 51 and consequently affect the combustion efficiency in the circulating fluidized bed furnace 1.

[0068] In some embodiments, the primary air duct 41 is a bent pipe, and the bending direction of the primary air duct 41 can be vertical or horizontal.

[0069] The bend in the primary air duct 41 reduces the flow velocity of the sintering flue gas (including the sintering flue gas entering from the sintering machine and the sintering flue gas entering from the bypass duct 61) within the primary air duct 41. This results in a more uniform mixing of the sintering flue gas entering from the sintering machine and the sintering flue gas entering from the bypass duct 61, preventing the adhesion of iron oxide dust caused by uneven temperature of the sintering flue gas within the primary air duct 41. Furthermore, it prevents uneven coal combustion caused by uneven temperature of the sintering flue gas within the circulating fluidized bed furnace 1, thus helping to ensure the stability of combustion within the circulating fluidized bed furnace 1.

[0070] For example, the primary air duct 41 includes a first section 411, a second section 412, and a third section 413.

[0071] Among them, the first segment 411, the second segment 412 and the third segment 413 are connected in sequence to form a whole. It should be understood that the first segment 411, the second segment 412 and the third segment 413 are different positions of the primary air duct 41.

[0072] One end of the third section 413 is connected to the outlet of the sintering flue gas, for example, one end of the third section 413 is connected to the outlet of the sintering machine; the other end of the third section 413 is connected to the second section 412, the other end of the second section 412 is connected to the first section 411, and the first section 411 is connected to the primary air chamber.

[0073] The aforementioned primary air fan 42 is installed on the third section 413, and the bypass ventilation duct 61 is connected to the end of the third section 413 away from the primary air fan 42.

[0074] The second segment 412 is inclined relative to the third segment 413. Optionally, the second segment 412 is perpendicular to the third segment 413. For example, the third segment 413 is a horizontally arranged pipe, and the second segment 412 is a vertically arranged pipe. The first segment 411 is inclined relative to the second segment 412. Optionally, the first segment 411 is parallel to the third segment 413, and the second segment 412 is perpendicular to both the first segment 411 and the third segment 413.

[0075] In this embodiment, the bypass ventilation duct 61 is connected to the third section 413. Thus, under the action of the second section 412, the flow velocity of the sintering flue gas in the primary air duct 41 can be reduced, making the sintering flue gas entering from the sintering machine and the sintering flue gas entering from the bypass ventilation duct 61 mix more evenly. This prevents the adhesion of iron oxide dust caused by uneven temperature of the sintering flue gas in the primary air duct 41, and also prevents uneven coal combustion caused by uneven temperature of the sintering flue gas in the circulating fluidized bed furnace 1. In other words, it helps to ensure the stability of combustion in the circulating fluidized bed furnace 1.

[0076] It should be noted that the shape of the primary air duct 41 in this embodiment can also be understood as the direction of the primary air duct 41, and can be set according to different needs, and is not limited to the shape limited above.

[0077] The sintering flue gas purification system in this embodiment also includes a temperature detection device 8 and a fan control system 7.

[0078] The temperature detection device 8 is used to detect the temperature inside the primary air duct 41. Optionally, the temperature detection device 8 detects the temperature at the location between the inlet / outlet ventilation duct 61 and the circulating fluidized bed furnace 1. In some embodiments, the temperature detection device 8 can be a temperature sensor or a thermometer, etc. It is understood that any device capable of temperature detection can be used as the temperature detection device 8 in this embodiment.

[0079] The temperature detection device 8 extends inside the primary air duct 41, thereby improving the accuracy of temperature detection by the temperature detection device 8.

[0080] Temperature detection device 8 is connected to fan control system 7, and fan control system 7 is connected to bypass fan 62. It can be understood that fan control system 7 can obtain the temperature value detected by temperature detection device 8 and can adjust the start and stop of bypass fan 62 according to the obtained temperature value.

[0081] This embodiment discloses the specific control process of the fan control system 7: If the temperature of the sintering flue gas in the primary air duct 41 detected by the temperature detection device 8 is lower than the first preset value, the fan control system 7 controls the bypass fan 62 to start, and the bypass fan 62 operates at a preset power; If the temperature of the sintering flue gas in the primary air duct 41 detected by the temperature detection device 8 is higher than the second preset value, the fan control system 7 controls the bypass fan 62 to shut down.

[0082] In this embodiment, the first preset value is less than the second preset value, and the second preset value is less than the bonding temperature of the iron oxide dust. In the example, the first preset value can be 290℃, and the second preset value can be 350℃. Since the temperature in the secondary air duct 51 after being heated by the sintering flue gas preheating device 31 can be maintained at 250℃, it can be understood that the first preset value is greater than the third preset value. Therefore, in this embodiment, the first preset value is set to 290℃, which can reduce the number of times the bypass fan 62 starts and stops. When the temperature of the sintering flue gas provided by the sintering machine is low, the bypass fan 62 can be kept in a continuous working state.

[0083] It should be noted that the power of the bypass fan 62 in this embodiment can be kept constant to maintain the proportion of sintering flue gas entering the primary air duct 41 from the secondary air duct 51. That is, the proportion of sintering flue gas entering the primary air duct 41 from the secondary air duct 51 and the sintering flue gas provided by the sintering machine in the primary air duct 41 remains constant, thereby ensuring the stability of the amount of sintering flue gas supplied by the secondary air duct 51 to the circulating fluidized bed furnace 1, and also ensuring the stability of the amount of sintering flue gas supplied by the primary air duct 41 to the circulating fluidized bed furnace 1, which is convenient for maintaining the combustion stability of the circulating fluidized bed furnace 1.

[0084] Of course, the power of the bypass fan 62 in this embodiment can also be adjusted. The power of the bypass fan 62 can be adjusted in real time according to the actual operating load. Adjusting the power of the bypass fan 62 achieves the regulation of the temperature inside the primary air duct. This means adjusting the proportion of sintering flue gas entering the primary air duct 41 via the bypass fan 61, thereby changing the temperature of the sintering flue gas inside the primary air duct 41. By adjusting the power of the bypass fan 62, the temperature of the sintering flue gas inside the air duct is ensured to not exceed 350℃ within the full load range, thereby reducing dust adhesion in the sintering flue gas, reducing clogging and corrosion of the air cap, and improving the operating cycle of the device.

[0085] Based on the structure of the sintering flue gas purification system described above, during operation: sintering flue gas enters the purification system from the sintering machine via an induced draft fan (not shown in the figure). A portion of the sintering flue gas, under the action of the primary air fan 42, enters the primary air chamber of the circulating fluidized bed furnace 1 below the air distribution plate 11 through the primary air duct 41, passes through the air cap 12, and enters the interior of the circulating fluidized bed furnace 1, where it mixes with the pulverized coal and is then burned. The sintering flue gas entering the primary air duct 41 mixes with the sintering flue gas entering through the secondary air duct 51 and the bypass air duct 61, allowing the temperature of the sintering flue gas entering the primary air chamber to be between 220℃ and 260℃. A portion of the sintering flue gas enters the secondary air duct 51 under the action of the secondary air fan 52. After being heated by the sintering flue gas preheating device 31 (optionally, the temperature is raised to about 250°C), a portion of it enters the secondary air chamber above the air distribution plate 11 of the circulating fluidized bed furnace 1 to supplement the oxygen required for the combustion of pulverized coal in the circulating fluidized bed furnace 1. The other portion enters the primary air duct 41 through the bypass air duct 61 and mixes with the sintering flue gas in the primary air duct 41.

[0086] Typically, 40%-60% of the sintering flue gas enters the circulating fluidized bed furnace 1 through the air chamber. The combustion temperature inside the circulating fluidized bed furnace 1 is usually controlled between 850℃ and 900℃. The combustion particles and flue gas enter the separator 2 through pipes. After separation in the separator 2, over 95% of the particles fall to the bottom of the separator 2 and are returned to the circulating fluidized bed furnace 1 via the return feeder 21. A very small portion of fine particles and dust flows out from the separator outlet flue 22 at the top of the separator 2 and enters the tail flue 3. The tail flue 3, from top to bottom, includes, but is not limited to, devices such as SNCR, SCR, and economizers. After exiting the flue 3, the flue gas enters subsequent dust removal and desulfurization devices, and is finally discharged into the atmosphere through a chimney.

[0087] As can be seen from the above process, the sintering flue gas purification system of this embodiment sets up a sintering flue gas preheating device 31 on the secondary air duct 51 and connects the secondary air duct 51 with the primary air duct 41. Therefore, the sintering flue gas in the secondary air duct 51 can directly exchange heat with the sintering flue gas preheating device 31, and the sintering flue gas in the primary air duct 41 can indirectly exchange heat with the sintering flue gas preheating device 31. At the same time, the temperature of the sintering flue gas in the primary air duct 41 and the temperature of the sintering flue gas in the secondary air duct 51 are increased.

[0088] Furthermore, by limiting the temperature of the sintering flue gas preheating device 31, the temperature of the sintering flue gas in the secondary air duct 51 can be prevented from exceeding the bonding temperature of the iron oxide dust. Moreover, the heat exchange between the sintering flue gas in the secondary air duct 51 and the sintering flue gas in the primary air duct 41 ensures that the temperature of the sintering flue gas in the primary air duct 41 does not exceed the bonding temperature of the iron oxide dust. In other words, by limiting the temperature of the sintering flue gas preheating device 31, the temperature of the sintering flue gas in both the primary air duct 41 and the secondary air duct 51 can be raised simultaneously, and the excessively high temperature of the sintering flue gas in both the primary air duct 41 and the secondary air duct 51 can be effectively limited.

[0089] The sintering flue gas purification system in this embodiment has a simple method for controlling the temperature of the sintering flue gas, and the control effect is effective.

[0090] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sintering flue gas purification system, characterized in that, include: A circulating fluidized bed furnace (1) is provided with an air distribution plate (11), the air distribution plate (11) is located below a primary air chamber and above a secondary air chamber. A primary air duct (41) is connected to the primary air chamber; A secondary air duct (51) is connected to the secondary air chamber; Sintering flue gas preheating device (31), the sintering flue gas preheating device (31) is used to heat the sintering flue gas in the secondary air duct (51); A bypass ventilation duct (61) is provided, which connects the secondary air duct (51) and the primary air duct (41). The sintering flue gas heated by the sintering flue gas preheating device (31) in the secondary air duct (51) can enter the primary air duct (41). The heating temperature of the sintering flue gas in the secondary air duct (51) by the sintering flue gas preheating device (31) is lower than the adhesion temperature of the iron oxide dust in the sintering flue gas, thus limiting the temperature of the sintering flue gas in the primary air duct (41) and the secondary air duct (51) to be too high. A bypass fan (62) is provided on the bypass ventilation duct (61). The bypass fan (62) is used to introduce the sintering flue gas heated by the sintering flue gas preheating device (31) in the secondary air duct into the primary air duct (41). The primary air duct (41) is a bent pipe; The primary air duct (41) includes a first section (411), a second section (412), and a third section (413) connected in sequence. One end of the first segment (411) is connected to the primary air chamber, the other end of the first segment (411) is connected to the second segment (412), the other end of the second segment (412) is connected to the third segment (413), and the second segment (412) is inclined relative to the third segment (413); A primary air fan (42) is provided on the third section (413), and the bypass ventilation duct (61) is connected to the third section (413), and the connection position is located between the primary air fan (42) and the second section (412); It also includes a temperature detection device (8) and a fan control system (7); The temperature detection device (8) is connected to the fan control system (7), and the temperature detection device (8) is used to detect the temperature of the primary air and secondary air mixed in the primary air duct (41); The fan control system (7) is connected to the bypass fan (62), and the fan control system (7) controls the start and stop of the bypass fan (62); If the temperature of the sintering flue gas in the primary air duct (41) detected by the temperature detection device (8) is lower than the first preset value, the fan control system (7) controls the side ventilation fan (62) to start, and the side ventilation fan (62) operates at a preset power. If the temperature of the sintering flue gas in the primary air duct (41) detected by the temperature detection device (8) is greater than the second preset value, the fan control system (7) controls the bypass fan (62) to shut down. The first preset value is less than the second preset value, and the second preset value is less than the bonding temperature of iron oxide dust in the sintering flue gas.

2. The sintering flue gas purification system according to claim 1, characterized in that, The bypass ventilation duct (61) is located between the sintering flue gas preheating device (31) and the circulating fluidized bed furnace (1).

3. The sintering flue gas purification system according to claim 1, characterized in that, The fan control system (7) also controls the power variation of the bypass fan (62).

4. The sintering flue gas purification system according to any one of claims 1 to 3, characterized in that, It also includes a separator (2) connected to the top of the circulating fluidized bed furnace (1), the bottom of the separator (2) being connected to the circulating fluidized bed furnace (1) via a return feeder (21), and the top of the separator (2) being connected to the flue (3). The sintering flue gas preheating device (31) is installed on the flue (3).

5. The sintering flue gas purification system according to claim 4, characterized in that, The sintering flue gas preheating device (31) is an electric heating device or a circulating pipeline heating device.

6. The sintering flue gas purification system according to any one of claims 1 to 3, characterized in that, A one-way valve is provided on the bypass ventilation duct (61), and the one-way valve is unidirectionally directed from the secondary air duct (51) to the primary air duct (41).

7. The sintering flue gas purification system according to any one of claims 1 to 3, characterized in that, The bending direction of the primary air duct (41) can be vertical and / or horizontal.

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