Internal and external circulation system and circulation method for sintering flue gas

Abstract

The application provides a sintering flue gas internal and external circulation system, which comprises an internal circulation device, an external circulation device and a desulfurization and denitrification device; the internal circulation device is connected with the middle and front flue of a sintering machine main flue to obtain first purified flue gas, and then the first purified flue gas is circulated into the sintering machine; the external circulation device is connected with the machine head flue and the middle and rear flue of the sintering machine main flue to obtain second purified flue gas, and the second purified flue gas is partly circulated into the sintering machine and partly enters the desulfurization and denitrification device; the flue gas from the middle and rear flue exchanges heat with the flue gas from the middle and front flue and then enters the external circulation device; the application also provides a sintering flue gas internal and external circulation method. According to the application, the sintering flue gas circulation rate is increased from 20% to more than 60%, the waste heat utilization rate is increased, the NOx concentration in the flue gas is reduced, two-stage CO removal reactions are realized, and a large amount of investment and operation cost is saved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultra-low emission of flue gas in the steel industry, and particularly relates to a sintering flue gas internal and external circulation system and a circulation method. BACKGROUND

[0002] The pollutant emission amount of the sintering process in the steel industry is large, and the sintering flue gas circulation technology is an important way to reduce pollutant emission. Many circulation processes have been proposed at home and abroad, among which there are LEEP, Eposint, EOS and Nippon Steel processes abroad, and Ninggang, Shasteel, Shougang, Baosteel, Yonggang, Qiangang and Changgang enterprises at home have all implemented them respectively.

[0003] At present, the sintering machine flue gas circulation technology is roughly divided into two technical ways: flue gas internal circulation technology and flue gas external circulation technology.

[0004] The flue gas internal circulation technology has the following characteristics: 1. The flue gas pollutant and temperature distribution characteristics of each wind box of the sintering machine are considered, so that the pollutants undergo a series of complex chemical reaction processes in the sintering material layer, including the secondary combustion of CO and the high-temperature decomposition of dioxin, which theoretically reduces the emission concentration of SO2, NOx and other pollutants. However, according to the operation situation, the internal circulation does not achieve the expected effect due to the complex process accompanied by numerous physical and chemical reactions in the sintering process, and also brings some other problems. 2. The air is taken from the wind box branch pipe, which is flexible and can switch different wind boxes into the flue gas circulation system at will. However, it also causes large engineering quantities of equipment, steel structure, civil engineering, valves and instruments, resulting in high investment and large maintenance workload. 3. Compared with the external circulation technology, the internal circulation technology has high temperature and high oxygen content of the circulating flue gas, high flue gas circulation rate (about 30%), and good flue gas waste heat utilization effect.

[0005] The flue gas external circulation technology has the following characteristics: 1. The flue gas is taken from the flue gas after the main sintering exhaust fan, which has small engineering changes and low fixed investment. It is better than the flue gas internal circulation system in the industry promotion degree. 2. The process flow is simple, the number of valves and instruments is small, and the maintenance workload is small. 3. Due to the low temperature (generally between 130-150℃) of the flue gas after the main sintering exhaust fan, the heat utilization effect is general. The oxygen content of the flue gas is relatively low, so the sintering flue gas emission reduction rate is low (about 30%).

[0006] In summary, the flue gas internal circulation technology and the flue gas external circulation technology have their own advantages and disadvantages, and there is no process technology that can both improve the flue gas circulation rate and improve the flue gas waste heat utilization rate.

[0007] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art. SUMMARY

[0008] The sintering flue gas internal-external circulation system and circulation method can at least solve the problem of low waste heat utilization rate and insufficient circulation rate when the sintering flue gas is internally or externally circulated alone.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0010] A sintering flue gas internal-external circulation system, the internal-external circulation system comprising: an internal circulation device, an external circulation device and a desulfurization and denitrification device;

[0011] The internal circulation device is connected with the middle-front section flue of the sintering machine main flue, and is used for removing CO from the middle-front section flue gas of the sintering machine main flue to obtain first purified flue gas, and then the first purified flue gas is circulated into the sintering machine;

[0012] The external circulation device is connected with the machine head flue and the middle-back section flue of the sintering machine main flue, and is used for purifying the machine head flue gas and the middle-back section flue gas of the sintering machine main flue to obtain second purified flue gas, part of the second purified flue gas is circulated into the sintering machine, and the other part enters the desulfurization and denitrification device; the flue gas from the middle-back section flue exchanges heat with the flue gas from the middle-front section flue and then enters the external circulation device;

[0013] The desulfurization and denitrification device is used for desulfurization and denitrification treatment of the second purified flue gas.

[0014] In the sintering flue gas internal-external circulation system as described above, preferably, the first purified flue gas and the second purified flue gas are mixed by a flue gas mixer and then circulated into the sintering machine; the flue gas mixer is connected with the sintering machine through a co-circulation flue, and the flue gas mixer delivers the mixed flue gas to the sintering machine through the co-circulation flue.

[0015] In the sintering flue gas internal-external circulation system as described above, preferably, the internal circulation device comprises a gas heat exchanger and an internal combustion furnace arranged on an internal circulation flue; one end of the internal circulation flue is connected with the middle-front section flue of the sintering machine, and the other end is connected with the flue gas mixer; the flue gas from the middle-front section flue of the sintering machine forms internal circulation of the flue gas through the internal circulation flue and the co-circulation flue;

[0016] Preferably, the flue gas from the middle-front section flue exchanges heat with the flue gas from the middle-back section flue through a gas heat exchanger, and a first valve is arranged on the internal circulation flue in front of the gas heat exchanger;

[0017] Preferably, a combustion-supporting flue is arranged on the internal circulation flue behind the internal combustion furnace, and the combustion-supporting flue is connected from the internal circulation flue to the inlet of the internal combustion furnace;

[0018] Preferably, a first fan is arranged on the combustion-supporting flue, and a second fan is arranged between the built-in combustion furnace and the flue gas mixer.

[0019] Further preferably, a CO concentration analyzer is arranged on the inner circulating flue in front of and behind the built-in combustion furnace.

[0020] In the sintering flue gas internal-external circulation system as described above, preferably, the flue gas from the sintering machine head flue and the sintering machine middle-late section flue is mixed in the external exhaust flue and then purified to obtain second purified flue gas, and the second purified flue gas enters the flue gas mixer through the external circulation flue, and the flue gas enters the sintering machine in turn through the external exhaust flue, the external circulation flue and the common circulation flue, thereby completing the external circulation of the flue gas.

[0021] The external circulation device comprises a head electric dust collector arranged on the external exhaust flue, which is used for purifying the mixed flue gas in the external exhaust flue, and a third fan arranged on the external exhaust flue behind the head electric dust collector, and a part of the second purified flue gas obtained after passing through the third fan enters the flue gas mixer through the external circulation flue.

[0022] Preferably, a maintenance flue is arranged between the middle-front section flue and the external circulation device, which is used for the circulation and recycling of the middle-front section flue gas when the internal circulation device is maintained, and a second valve is arranged on the maintenance flue.

[0023] In the sintering flue gas internal-external circulation system as described above, preferably, the internal-external circulation system further comprises a ring cooling device, and the ring cooling device comprises a ring cooler connected to the inlet of the flue gas mixer through a ring cooling flue.

[0024] In the sintering flue gas internal-external circulation system as described above, preferably, the internal-external circulation system further comprises an ammonia gas injection system and an oxygen supply device arranged in turn on the common circulation flue along the flue gas circulation direction.

[0025] Preferably, the oxygen supply device comprises an oxygen uniform distributor connected to the outlet of an oxygen buffer tank, and the oxygen gas injected from the oxygen uniform distributor enters the common circulation flue.

[0026] Preferably, the oxygen gas is pure oxygen gas, and the purity of the oxygen gas is above 98%.

[0027] In the sintering flue gas internal-external circulation system as described above, preferably, the internal-external circulation system further comprises a plurality of sealing covers, and the flue gas after oxygen supply enters the plurality of sealing covers through a plurality of branch pipes respectively, the inner cavities of the sealing covers are in communication with the material surface of the sintering machine, and flue gas regulating valves are arranged on the plurality of branch pipes respectively, which are used for regulating the flue gas entering the sealing covers.

[0028] Preferably, the sealing cover is fixed above the material surface in the middle section of the sintering machine, and one end of the head flue, the front middle section flue, and the rear middle section flue are respectively connected to different air boxes of the sintering machine. The flue gas in the circulating flue of the sintering machine enters the middle section of the sintering machine through the sealing cover, and the flue gas in the sintering machine enters the head flue, the front middle section flue, and the rear middle section flue through different air boxes.

[0029] Preferably, the sealing cover is equipped with a pressure detection device and an oxygen concentration analyzer. The oxygen concentration analyzer is connected to the oxygen supply device and automatically controls the oxygen supply process according to the oxygen concentration inside the sealing cover.

[0030] In the sintering flue gas internal and external circulation system as described above, preferably, the desulfurization and denitrification device includes a desulfurization reactor, a denitrification reactor and a chimney arranged sequentially and connected along the flue gas transmission direction, and the second purified flue gas is discharged through the chimney after being treated by the desulfurization reactor and the denitrification reactor.

[0031] Preferably, a CEMS analyzer and a fourth fan are installed before the chimney, respectively for testing the pollutant components in the flue gas before emission and for induced draft.

[0032] A method for internal and external circulation of sintering flue gas, the method comprising the following steps:

[0033] Step 1, flue gas heat exchange, includes:

[0034] Heat exchange between the flue gas in the front and middle sections of the sintering machine and the flue gas in the rear sections;

[0035] Step two, flue gas internal circulation, external circulation, and emission, includes:

[0036] After heat exchange, the flue gas in the middle and front flue enters the internal circulation device to remove CO from the combustion, resulting in first purified flue gas. The first purified flue gas then enters the sintering machine through internal circulation. The flue gas in the middle and rear flue and the flue gas in the head flue mix and then enter the external circulation device for flue gas purification, resulting in second purified flue gas. A portion of the second purified flue gas then enters the sintering machine through external circulation, while the other portion of the second purified flue gas is discharged from the chimney after desulfurization and denitrification.

[0037] In the sintering flue gas internal and external circulation method described above, preferably, the method further includes ammonia and oxygen supply steps for the sintering flue gas:

[0038] The first purified flue gas entering the internal circulation and the second purified flue gas entering the external circulation are mixed with additional ammonia and oxygen before entering the sintering machine.

[0039] Preferably, the first and second purified flue gas is mixed with the flue gas produced by the ring cooling device before being supplemented with ammonia and oxygen, and the flue gas of the ring cooling device is used to supplement oxygen to the flue gas of the internal and external circulation system to realize recycling.

[0040] Preferably, the system of the method is completed.

[0041] Compared with the closest prior art, the technical scheme provided by the present application has the following excellent effects:

[0042] Compared with the traditional sintering flue gas internal or external circulation, the sintering flue gas internal and external circulation system and the circulation method have the following excellent effects:

[0043] 1. Compared with the traditional flue gas circulation technology, the present application uses pure oxygen to supplement the oxygen content of the flue gas, and the sintering flue gas circulation rate is increased from 20% to more than 60%;

[0044] 2. The ring cooling flue gas is introduced into the flue gas circulation system, and the clean and high-temperature characteristics of the ring cooling flue gas are fully utilized to increase the temperature of the circulating flue gas and improve the waste heat utilization rate;

[0045] 3. Utilize the sintering machine material layer temperature window to carry out SNCR denitration reaction, and reduce the NOx concentration in the flue gas;

[0046] 4. Utilize the built-in combustion furnace and the sintering machine material layer temperature window respectively to realize two-stage CO removal reaction. The high-concentration CO is turned into treasure and is resourcefully utilized, which not only reduces the CO concentration, but also fully releases the latent heat of combustion of CO, increases the flue gas temperature, and thus improves the flue gas waste heat utilization rate.

[0047] 5. Utilize the high temperature of the sintering material layer and the high temperature of the built-in combustion furnace to remove part of dioxin;

[0048] 6. Combine sintering flue gas process control with end treatment, and comprehensively treat, which saves a large amount of investment and operation cost. BRIEF DESCRIPTION OF DRAWINGS

[0049] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and the explanation thereof, to explain the present application, and do not constitute an improper limitation of the present application. Among them:

[0050] Figure 1 The process flow diagram of the sintering flue gas internal and external circulation system of the embodiments of the present application.

[0051] In the figure: 1, sintering machine; 101, machine head flue; 102, middle front section flue; 103, middle rear section flue; 2, sealing cover; 3, pressure detection device; 4, oxygen concentration analyzer; 5, regulating valve; 6, oxygen uniform distributor; 7, oxygen buffer tank; 8, ammonia gas injection system; 9, flue gas mixer; 10, first valve; 11, second valve; 12, gas heat exchanger; 13, CO concentration analyzer; 14, built-in combustion furnace; 15, first fan; 16, second fan; 17, ring cooler; 18, machine head electric dust collector; 19, third fan; 20, third valve; 21, desulfurization reactor; 22, denitration reactor; 23, fourth fan; 24, CEMS analyzer; 25, chimney; 26, internal circulating flue; 27, external flue; 28, external circulating flue; 29, ring cooling flue; 30, combustion-supporting flue; 31, circulating flue (also known as co-circulating flue). DETAILED DESCRIPTION

[0052] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0053] In the description of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and do not require the present application to be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The terms "connected", "connected" used in the present application should be understood broadly, for example, it can be fixed connection, or detachable connection; it can be directly connected, or indirectly connected through intermediate components, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0054] During the sintering process of the sintering material in the sintering machine, the sintering machine flue gas heat is not evenly distributed, among which the sintering machine head air bellow (i.e. machine head) flue gas temperature is relatively low, generally below 150℃, the temperature of the middle and rear sections of the sintering machine air bellow gradually increases, but the total heat of the flue gas of each air bellow of the sintering machine is conserved. At the same time, the concentrations of the sintering machine flue gas pollutants SO2, NOx, CO and other pollutants show different emission characteristics in different air bellows. According to the different pollutants and temperatures in the air bellow, different flue gases can be divided, which can improve the sintering flue gas recycling rate.

[0055] This invention divides the sintering machine's air boxes into three paths. The flue gas from multiple air boxes at the machine head (e.g., air boxes 1-3) is correspondingly transported to the machine head flue of the main flue of the sintering machine. The machine head flue typically has the following characteristics: low temperature, with the flue gas temperature not exceeding 150℃. The flue gas from multiple air boxes in the middle and front sections (e.g., air boxes 4-13) is correspondingly transported to the middle and front sections of the main flue of the sintering machine. The flue gas in the middle and front sections typically has the following characteristics: high CO and NOx concentrations, i.e. The CO and NOx concentrations in the flue gas in the front and middle sections of the sintering machine are higher than those in the head flue and the rear flue. Flue gas from multiple air boxes (e.g., air boxes 14-22) in the rear section is transported to the rear section of the sintering machine's main flue. The flue gas in the rear section typically has the following characteristics: it is high-temperature flue gas, with a temperature not lower than 270℃; the low-temperature flue gas in the front section and the high-temperature flue gas in the rear section undergo gas-to-gas heat exchange, which improves preheating utilization. The head flue, front and middle sections of the sintering machine, and the rear flue form the main flue of the sintering machine.

[0056] In this invention, "front" and "back" refer to the positional relationship based on the direction of flue gas transmission.

[0057] like Figure 1 As shown, according to an embodiment of the present invention, a sintering flue gas internal and external circulation system is provided, the internal and external circulation system comprising: an internal circulation device, an external circulation device, and a desulfurization and denitrification device;

[0058] The internal circulation device is connected to the middle and front section of the flue 102 of the main flue of the sintering machine 1. The internal circulation device is used to remove CO from the flue gas in the middle and front section of the main flue of the sintering machine 1 to obtain the first purified flue gas, and then the first purified flue gas is circulated back into the sintering machine 1.

[0059] The external circulation device is connected to the head flue 101 and the middle and rear flue 103 of the main flue of the sintering machine 1. The external circulation device and the internal circulation device exchange heat crosswise. The external circulation device is used to purify the head flue gas and the middle and rear flue gas of the main flue of the sintering machine 1 to obtain the second purified flue gas. Part of the second purified flue gas is circulated back into the sintering machine 1, and the other part enters the desulfurization and denitrification device. After desulfurization and denitrification treatment, it is discharged into the atmosphere. The reason why part of the second purified flue gas is recycled and part is discharged into the atmosphere is because the flue gas recycling rate cannot reach 100%, and it needs to be continuously discharged to avoid the sintering machine 1 from entering too much flue gas that cannot be effectively utilized. Both the internal circulation device and the external circulation device include a circulating flue 31, through which the internal and external circulation of flue gas is completed. The circulating flue 31 is a flue shared by the internal circulation device and the external circulation device, and is also called a common circulating flue.

[0060] The desulfurization and denitrification unit is used to treat the second-stage purified flue gas for desulfurization and denitrification.

[0061] The first purified flue gas and the second purified flue gas are mixed by the flue gas mixer 9 and then recycled into the sintering machine 1. The flue gas mixed by the flue gas mixer 9 is more uniform in composition, facilitating recycling and improving the flue gas recycling rate. The flue gas mixer 9 delivers the mixed flue gas to the sintering machine 1 through the circulating flue 31.

[0062] In a specific embodiment of the present application, one end of the inner circulating flue 26 is connected to the middle-front section flue 102 of the sintering machine 1, and the other end is connected to the flue gas mixer 9. The flue gas from the middle-front section flue 102 of the sintering machine 1 forms an inner circulation of flue gas through the inner circulating flue 26 and the circulating flue 31.

[0063] The inner circulating device includes a gas heat exchanger 12 and an inner combustion furnace 14 arranged on the inner circulating flue 26. The middle-front section flue 102 and the middle-back section flue 103 are heat exchanged by the gas heat exchanger 12. The gas heat exchanger 12 is a gas-gas heat exchanger. After heat exchange, the temperature of the flue gas in the middle-front section flue 102 increases from 100℃ to 180℃, and the temperature of the flue gas in the middle-back section flue 103 decreases from 280℃ to about 200℃, achieving effective utilization of high-temperature flue gas heat. The middle-front section flue gas after heat exchange enters the inner combustion furnace 14 for combustion, removing CO in the flue gas for the first time. A first valve 10 is arranged on the inner circulating flue 26 in front of the gas heat exchanger 12, for controlling the opening and closing of the flue gas in the middle-front section flue 102.

[0064] Preferably, a combustion-supporting flue 30 is arranged on the inner circulating flue 26 behind the inner combustion furnace 14. The combustion-supporting flue 30 is connected from the inner circulating flue 26 to the inlet of the inner combustion furnace 14. The middle-front section flue gas has a high CO content, which can be removed by combustion, and the heat released after combustion can increase the temperature of the flue gas. The flue gas after combustion still contains a high oxygen content, and the combustion-supporting flue 30 is arranged here to support the combustion of the inner combustion furnace 14. More preferably, a first fan 15 is arranged on the combustion-supporting flue 30, and a second fan 16 is arranged between the inner combustion furnace 14 and the flue gas mixer 9. Both the first fan 15 and the second fan 16 are used for air induction. Further preferably, CO concentration analyzers 13 are arranged on the inner circulating flue 26 in front of and behind the inner combustion furnace 14, for detecting and analyzing the CO concentration in the flue gas before and after the combustion furnace.

[0065] Compared with a common heating furnace, the common heating furnace is arranged around the flue with a heating furnace chamber. Coke oven gas or blast furnace gas is combusted in the heating furnace chamber to produce high-temperature gas, which then enters the flue to mix with the upstream flue gas, achieving the purpose of flue gas temperature rise. When the inner combustion furnace 14 is used, the igniter and the combustion-supporting flue 30 are inserted into the inner circulating flue 26, igniting and combusting in the inner circulating flue 26 to heat the flue gas. The igniter can use plasma ignition or other ignition methods. The inner combustion furnace 14 has the following advantages:

[0066] 1. The coke oven gas or blast furnace gas is combusted in the flue, which can greatly reduce the heat loss of combustion compared with the combustion in the hearth outside the flue;

[0067] 2. The average concentration of CO in the flue gas of the middle and front section flue 102 is 10000mg / m 3 , while the average concentration of CO in the blast box of the sintering machine 1 is only 5300mg / m 3 , and the combustion center temperature of the built-in combustion furnace 14 is about 1200℃, which can easily ignite the CO in the middle and front section flue gas and make the CO burn and release heat. On the one hand, the high concentration of CO in the flue gas is ignited to release a large amount of heat, which is beneficial to improve the circulating flue gas temperature and improve the utilization rate of flue gas waste heat; at the same time, the CO emission concentration is also reduced, and waste is turned into treasure. The CO concentration in the exhaust flue gas can be reduced by about 20% through the circulating system of the present application.

[0068] 3. The combustion reaction of dioxin in the combustion center of the built-in combustion furnace 14 can also remove a part of the pollution gas dioxin.

[0069] The high-temperature flue gas after the built-in combustion furnace 14 is divided into two paths. One is introduced back to the built-in combustion furnace 14 by the combustion flue 30 for combustion support. The amount of flue gas introduced back to the built-in combustion furnace 14 is generally a fixed value, and the amount of flue gas can ignite the coke oven gas or blast furnace gas in the built-in combustion furnace 14. Then the ignited blast furnace gas or coke oven gas ignites the CO in the flue gas, and the amount of combustion support flue gas is affected by the amount and temperature of the upstream flue gas. The other path is through the second fan 16 and the subsequent internal circulating flue 26 into the flue gas mixer 9 to circulate to the material surface layer of the sintering machine 1 to participate in the sintering process again.

[0070] In the specific embodiment of the present application, the flue gas from the machine head flue 101 of the sintering machine 1 and the middle and rear section flue 103 of the sintering machine 1 is mixed and purified in the external exhaust flue 27 to obtain the second purified flue gas. The second purified flue gas passes through the external circulating flue 28 and enters the flue gas mixer 9. The flue gas successively passes through the external exhaust flue 27, the external circulating flue 28 and the circulating flue 31 into the sintering machine 1 to complete the external circulation of the flue gas.

[0071] The outer circulation device comprises a machine head electric dust collector 18 arranged on the outer flue 27 after the flue gas mixing, and a third fan 19 arranged on the outer flue 27 behind the machine head electric dust collector 18; a part of the second purified flue gas obtained after passing through the third fan 19 enters the flue gas mixer 9 through the outer circulation flue 28, and the outer circulation flue 28 is provided with a third valve 20 for controlling the flow of flue gas; the other part enters the desulfurization and denitrification device. When the sintering flue gas inner and outer circulation system is in normal operation, the flue gas in the machine head flue 101 and the flue gas in the heat-exchanged middle and rear flue 103 are mixed and then enter the machine head electric dust collector 18 for purification and dust removal, and then enter the outer circulation flue 28 and the desulfurization and denitrification device, respectively.

[0072] Preferably, a maintenance flue is further arranged between the middle and front flue 102 and the outer circulation device, which is used for the circulation and recycling of the middle and front flue gas during the maintenance of the inner circulation device, and the maintenance flue is provided with a second valve 11. When the equipment workpiece in the inner circulation device needs to be maintained, the first valve 10 of the middle and front flue gas is closed in advance, and the second valve 11 is opened; the flue gas in the middle and front flue 102, the flue gas in the machine head flue 101 and the flue gas in the middle and rear flue 103 are mixed in the outer flue 27 and then enter the machine head electric dust collector 18 for dust removal and purification to obtain the second purified flue gas, and then a part of the second purified flue gas enters the flue gas mixer 9 through the rear outer circulation flue 28, and the other part enters the desulfurization and denitrification device. The purpose of arranging the maintenance flue is to ensure that the sintering machine 1 can still operate normally during the maintenance of the sintering flue gas circulation system.

[0073] In the specific embodiment of the present application, the desulfurization and denitrification device comprises a desulfurization reactor 21, a denitrification reactor 22 and a chimney 25 arranged in sequence and communicated along the flue gas transmission direction, and the second purified flue gas is discharged through the chimney 25 after being treated by the desulfurization reactor 21 and the denitrification reactor 22; preferably, a CEMS analyzer 24 and a fourth fan 23 are further arranged in front of the chimney 25, which are respectively used for testing the pollutant components in the flue gas before emission and for inducing air. The CO concentration analyzer 13 arranged in the inner circulation device and the CEMS analyzer 24 in the desulfurization and denitrification device are both used for testing the content of pollutant components in the flue gas, and according to the test results, the operating parameters of the system can be adjusted to prevent the concentration of flue gas pollutants at the chimney 25 outlet from exceeding the standard.

[0074] In the specific embodiment of the application, the internal and external circulation system further comprises a ring cooling device, the ring cooling device comprises a ring cooling machine 17, the ring cooling machine 17 is used for cooling the mineral material generated by the sintering machine 1, and ring cooling flue gas is flue gas generated in the process of cooling the mineral material; the ring cooling machine 17 is connected to the inlet of the flue gas mixer 9 through a ring cooling flue 29. The flue gas in the ring cooling machine 17 has the characteristics of low dust concentration and high oxygen content (about 21%), and the first section and the second section of the ring cooling flue gas in the ring cooling machine 17 are generally used for waste heat power generation (high heat), and the third section of the ring cooling flue gas is used in the application. The temperature of the ring cooling flue gas is about 200 DEG C, the temperature is appropriate, and the high oxygen content can be used for oxygen supplement of the circulating flue gas in the internal and external circulation system.

[0075] In the specific embodiment of the application, the internal and external circulation system further comprises an ammonia injection system 8 and an oxygen supplement device arranged in the circulating flue 31 in sequence along the circulating direction of the flue gas. Preferably, the oxygen supplement device comprises an oxygen distributor 6 connected to the outlet of the oxygen buffer tank 7, and the oxygen sprayed from the oxygen distributor 6 enters the circulating flue 31; preferably, the oxygen is pure oxygen, and the oxygen purity reaches more than 98%. Through the oxygen supplement device, the oxygen content of the flue gas entering the material surface layer of the sintering machine 1 is greater than 18% (when the oxygen content is greater than 18%, the sintering production is not affected). Through the use of pure oxygen supplement process, the flue gas circulation rate can reach more than 60%, which is much higher than the flue gas circulation rate of 20% in the traditional flue gas circulation process.

[0076] The ammonia injection system 8 is used for supplementing ammonia gas into the circulating flue 31, so that the flue gas containing NOx reacts with NH3 in the sintering material layer to remove NOx. The SNCR denitration reaction temperature range is 900 DEG C-1100 DEG C, which is consistent with the temperature of the sintering material layer (1000 DEG C-1100 DEG C), and has a reaction temperature window. In addition, a part of the combustion reaction of CO also occurs in the sintering material layer, which is called the second CO removal process. In addition, by using the combustion reaction of dioxin in the high-temperature sintering material layer, the dioxin combustion decomposition also removes a part of the dioxin.

[0077] In the specific embodiment of the present application, the internal and external circulation system further comprises a plurality of sealed covers 2, the flue gas after oxygen supply enters the plurality of sealed covers 2 through a plurality of branch pipes respectively, the inner cavity of the sealed cover 2 is in communication with the material surface of the sintering machine 1, and a flue gas regulating valve 5 is arranged on each of the plurality of branch pipes, for regulating the flue gas entering the sealed cover 2. Preferably, the sealed cover 2 is fixed above the middle material surface of the sintering machine 1, one end of the machine head flue 101, the middle front flue 102 and the middle rear flue 103 is connected with different air boxes of the sintering machine 1 respectively, and the flue gas in the circulating flue 31 of the sintering machine 1 enters the middle section of the sintering machine 1 from the sealed cover 2 and enters the machine head flue 101, the middle front flue 102 and the middle rear flue 103 through different air boxes respectively. Preferably, the sealed cover 2 is provided with a pressure detection device 3 and an oxygen concentration analyzer 4, the oxygen concentration analyzer 4 is connected with an oxygen supply device, and the oxygen supply process is automatically controlled through PID regulation according to the oxygen concentration in the sealed cover 2. In the embodiment of the present application, four branch pipes are arranged, and a flue gas regulating valve 5 is arranged on each pipe, the opening degrees of the regulating valves 5 are different according to the differences in the air permeability of the material layer and the required gas amount, so that the flue gas pressure is kept stable in the sealed cover 2 and a micro negative pressure state is maintained, thereby preventing the flue gas from leaking. In order to ensure real-time monitoring of the flue gas pressure, four pressure detection devices 3 are arranged on the sealed cover 2.

[0078] In order to further understand the sintering flue gas internal and external circulation system of the present application, the present application further provides a sintering flue gas internal and external circulation method, comprising the following steps:

[0079] Step one, flue gas heat exchange, comprising:

[0080] The first valve 10 is opened, the flue gas in the middle front flue 102 and the flue gas in the middle rear flue 103 of the sintering machine 1 first pass through the gas heat exchanger 12 for gas-gas heat exchange, so that the middle front flue gas is heated and the middle rear flue gas is cooled;

[0081] Step two, flue gas internal and external circulation and discharge, comprising:

[0082] After heat exchange, the flue gas in the middle front flue 102 enters the internal circulation device to remove combustion CO, to obtain first purified flue gas, part of the first purified flue gas is introduced into the combustion flue 30 through the first fan 15 to re-enter the built-in combustion furnace 14, and the other part is introduced into the flue gas mixer 9 through the second fan 16.

[0083] At the same time, the flue gas in the middle rear flue 103 and the flue gas in the machine head flue 101 are mixed and then enter the external circulation device to purify the flue gas, to obtain second purified flue gas, and then the second purified flue gas is introduced into the flue gas mixer 9 through the third fan 19, and the other part is introduced into the flue gas mixer 9 through the fourth fan 23 after passing through the desulfurization reactor 21 and the denitration reactor 22, and then discharged from the chimney 25.

[0084] In addition, the ring cooling flue gas in the ring cooler 17 enters the flue gas mixer 9 through the ring cooling flue 29, and the first purified flue gas, the second purified flue gas and the ring cooling flue gas are mixed in the flue gas mixer 9, and then the flue gas enters the sealing cover 2 after the ammonia supply of the ammonia injection system 8 of the circulating flue 31 and the oxygen supply of the oxygen distributor 6, and then enters the sintering machine 1 layer to participate in the sintering process; at this time, CO is further combusted in the sintering machine 1, dioxin is decomposed, SNCR reaction is carried out, and NOx is removed. The flue gas generated in the sintering machine 1 layer enters different wind boxes to continue the internal and external circulation process.

[0085] In addition, when the internal circulation device is maintained, the first valve 10 is closed in advance, and the second valve 11 is opened, and the flue gas in the machine head flue 101, the middle front section flue 102 and the middle rear section flue 103 is mixed and then enters the machine head electric precipitator 18 in the external circulation device, and then part of the flue gas enters the external circulation flue 28, and the other part enters the desulfurization and denitrification reaction and is discharged.

[0086] In summary, the sintering flue gas internal and external circulation system and the circulation method have the following excellent effects:

[0087] 1. Compared with the traditional flue gas circulation technology, pure oxygen is used to supplement the oxygen content of the flue gas, and the sintering flue gas circulation rate is increased from 20% to more than 60%;

[0088] 2. The ring cooling flue gas is introduced into the flue gas circulation system, the characteristics of the ring cooling flue gas are fully utilized, the temperature of the circulating flue gas is increased, and the waste heat utilization rate is increased;

[0089] 3. The SNCR denitrification reaction is carried out by utilizing the sintering machine layer temperature window, and the NOx concentration in the flue gas is reduced;

[0090] 4. Two-stage CO removal reactions are realized by utilizing the built-in combustion furnace and the sintering machine layer temperature window respectively. The high-concentration CO is turned into treasure and is resourcefully utilized, which not only reduces the CO concentration, but also fully releases the latent heat of combustion of CO, increases the flue gas temperature, and thus improves the flue gas waste heat utilization rate.

[0091] 5. A part of dioxin is removed by utilizing the high temperature of the sintering layer and the high temperature of the built-in combustion furnace;

[0092] 6. The sintering flue gas process control is combined with the end treatment, and the comprehensive treatment saves a large amount of investment and operation cost.

[0093] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sintering off-gas internal and external circulation system, characterized in that, The internal-external circulation system comprises: an internal circulation device, an external circulation device and a desulfurization and denitrification device; the internal circulation device is connected with the middle-front section flue of the main flue of the sintering machine, and is used for removing CO from the middle-front section flue gas of the main flue of the sintering machine to obtain first purified flue gas, and then the first purified flue gas is circulated into the sintering machine; the internal circulation device comprises a gas heat exchanger arranged on the internal circulation flue and an internal combustion furnace; a combustion-supporting flue is arranged on the internal circulation flue behind the internal combustion furnace, and the combustion-supporting flue is connected from the internal circulation flue to the inlet of the internal combustion furnace; the external circulation device is connected with the machine head flue and the middle-late section flue of the main flue of the sintering machine, and is used for purifying the machine head flue gas and the middle-late section flue gas of the main flue of the sintering machine to obtain second purified flue gas, part of which is circulated into the sintering machine, and the other part enters the desulfurization and denitrification device; the flue gas from the middle-late section flue is heat-exchanged with the flue gas from the middle-front section flue and then enters the external circulation device; the external circulation device comprises a machine head electric dust collector arranged on the external flue for purifying the mixed flue gas in the external flue, and a third fan is arranged on the external flue behind the machine head electric dust collector, and part of the second purified flue gas obtained after passing through the third fan enters a flue gas mixer through an external circulation flue; the flue gas mixer is connected with the sintering machine through a common circulation flue, and the flue gas mixer delivers the mixed flue gas to the sintering machine through the common circulation flue; the first purified flue gas and the second purified flue gas are mixed in the flue gas mixer and then are circulated into the sintering machine; the desulfurization and denitrification device is used for desulfurization and denitrification treatment of the second purified flue gas; the desulfurization and denitrification device comprises a desulfurization reactor, a denitrification reactor and a chimney which are sequentially arranged and communicated along the flue gas transmission direction, and the second purified flue gas is treated in the desulfurization reactor and the denitrification reactor and then is discharged through the chimney; the internal-external circulation system further comprises an ammonia gas injection system and an oxygen supply device which are sequentially arranged on the common circulation flue along the flue gas circulation direction; the internal-external circulation system further comprises a plurality of sealing covers, the flue gas after oxygen supply enters the plurality of sealing covers through a plurality of branch pipes respectively, the inner cavities of the sealing covers are communicated with the material surface of the sintering machine, and flue gas regulating valves are arranged on the plurality of branch pipes for regulating the flue gas entering the sealing covers; the sealing covers are fixed above the middle section material surface of the sintering machine, one end of the machine head flue, the middle-front section flue and the middle-late section flue is connected with different air boxes of the sintering machine respectively, the flue gas in the circulation flue of the sintering machine enters the middle section of the sintering machine from the sealing covers, and the flue gas in the sintering machine enters the machine head flue, the middle-front section flue and the middle-late section flue from different air boxes respectively.

2. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The inner circulating flue is connected with the middle front section flue of the sintering machine at one end and with the flue gas mixer at the other end, and the flue gas from the middle front section flue of the sintering machine forms an inner circulation of flue gas through the inner circulating flue and the common circulating flue.

3. The sintering flue gas internal and external circulation system as claimed in claim 2, wherein, The flue gas from the middle front section flue and the flue gas from the middle rear section flue are heat exchanged through a gas heat exchanger, and a first valve is arranged on the inner circulating flue in front of the gas heat exchanger.

4. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, A first fan is arranged on the combustion-supporting flue, and a second fan is arranged between the built-in combustion furnace and the flue gas mixer.

5. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, CO concentration analyzers are arranged on the inner circulating flues in front of and behind the built-in combustion furnace.

6. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The flue gas from the sintering machine head flue and the sintering machine middle rear section flue is mixed and then purified in the outer flue, to obtain second purified flue gas, which enters the flue gas mixer through the outer circulating flue, and the flue gas enters the sintering machine in sequence through the outer flue, the outer circulating flue and the common circulating flue, to complete the outer circulation of the flue gas.

7. The sintering flue gas internal and external circulation system as claimed in claim 6, wherein, A maintenance flue is further arranged between the middle front section flue and the outer circulating device, for the circulation and recycling of the middle front section flue gas during maintenance of the inner circulating device, and a second valve is arranged on the maintenance flue.

8. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The inner and outer circulating system further comprises a ring cooling device, which comprises a ring cooling machine connected to the inlet of the flue gas mixer through a ring cooling flue.

9. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The oxygen supply device comprises an oxygen distributor connected to the outlet of an oxygen buffer tank, and the oxygen sprayed from the oxygen distributor enters the common circulating flue.

10. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The oxygen is pure oxygen with a purity of more than 98%.

11. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, The sealing cover is provided with a pressure detection device and an oxygen concentration analyzer, the oxygen concentration analyzer is connected to the oxygen supply device, and the oxygen supply process is automatically controlled according to the oxygen concentration in the sealing cover.

12. The sintering flue gas internal and external circulation system as claimed in claim 1, wherein, A CEMS analyzer and a fourth fan are further arranged in front of the chimney, for testing the pollutant components in the flue gas before emission and for inducing air respectively.

13. A method of internal and external circulation of sintering flue gases, characterized in that, The method is completed by using the system according to any one of claims 1-12, and comprises the following steps: Step one, flue gas heat exchange, comprising: heat exchange of the flue gas in the middle front section flue and the flue gas in the middle rear section flue of the sintering machine; Step two, flue gas inner circulation, outer circulation and emission, comprising: after heat exchange, the flue gas in the middle front section flue enters the inner circulating device to remove combustion CO, to obtain first purified flue gas, which enters the sintering machine through inner circulation; the flue gas in the middle rear section flue and the flue gas in the head flue are mixed to enter the outer circulating device for flue gas purification, to obtain second purified flue gas, and then part of the second purified flue gas enters the sintering machine through outer circulation, and the other part of the second purified flue gas is desulfurized and denitrified and then emitted from the chimney.

14. The sintering flue gas internal and external circulation method as claimed in claim 13, characterized in that, The method further comprises steps of ammonia gas supply and oxygen supply for sintering flue gas: The first purified flue gas entering the inner circulation and the second purified flue gas entering the outer circulation are mixed with additional supplied ammonia gas and oxygen and then enter the sintering machine.

15. The process of claim 14 wherein the sintering flue gas is internally and externally circulated. The first purified flue gas and the second purified flue gas are mixed with flue gas generated by a ring cooling device before being supplemented with ammonia and oxygen, and the flue gas of the ring cooling device is used to supplement oxygen for the flue gas of the internal and external circulation systems to achieve reuse.

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