Sintering Machine Flue Gas Internal and External Combined Cycle Purification and Waste Heat Utilization System

Abstract

The present invention belongs to the technical field of flue gas ultra-low emission treatment, and discloses a sintering machine flue gas internal and external combined cycle purification and waste heat utilization system. The system includes a flue gas external circulation subsystem, which has a first main flue connected to the front of the machine air box group; a third main flue connected to the tail of the machine air box group; an external discharge main flue, one end of which is connected to the first main flue and the third main flue, and the other end of which is connected to the external circulation flue and the external discharge branch flue, and the external discharge branch flue is also connected to the chimney; a flue gas internal circulation subsystem, which has a second main flue connected to the middle of the machine air box group, and an intake flue, one end of which is connected to the second main flue and the external circulation flue, and the other end of which is connected to the flue gas sealing hood. Among them, a plurality of air boxes are provided at the bottom of the sintering machine, and the plurality of air boxes are divided into a front of the machine air box group, a middle of the machine air box group and a tail of the machine air box group, and a flue gas sealing hood is arranged above the material surface of the sintering machine. Through the above scheme, the combination of the internal circulation process and the external circulation process is realized, and the respective advantages of the two technologies are integrated to make the best use of advantages and avoid disadvantages.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-low emission treatment of flue gas in the iron and steel industry, and particularly relates to an internal and external combined cycle purification and waste heat utilization system for sintering machine flue gas. Background Technique

[0002] In the iron and steel industry, the pollutant emissions in the sintering process are very large. As an important way to reduce pollutant emissions, various circulation processes have been proposed both at home and abroad. Among them, abroad, there are circulation processes such as LEEP (Low Emission and Energy Optimized Sinter Process), Eposint (Environment Process Optimized Sintering), EOS (Emission Optimized Sintering), and Nippon Steel; at home, enterprises such as Ningbo Iron & Steel, Shagang, Shougang Co., Ltd., Baosteel, Yonggang, Qian'an Steel, and Changgang have respectively implemented their own circulation processes. The technologies adopted by many existing circulation processes are mainly divided into: flue gas internal circulation technology and flue gas external circulation technology.

[0003] The advantages of the flue gas internal circulation technology are as follows: 1. Considering the flue gas pollutant and temperature distribution characteristics of each wind box of the sintering machine, comprehensively considering pollutants such as CO, NO x and SO 2 etc., enabling a series of complex chemical reaction processes of pollutants to occur in the sintering material layer, including secondary combustion heat release of CO, high-temperature decomposition of dioxins, etc.; 2. Taking air from the wind box branch pipe, the operation is flexible, and different wind boxes can be switched to enter the flue gas circulation system at will; 3. The circulating flue gas has a high temperature and a high oxygen content, resulting in a high flue gas circulation rate (up to about 30%) and good waste heat utilization effect of the flue gas. However, the flue gas internal circulation technology has the following disadvantages: The internal circulation process takes air from the wind box branch pipe, resulting in a large amount of engineering changes and high fixed investment.

[0004] The advantages of the flue gas external circulation technology are as follows: Taking flue gas from the flue after the main induced draft fan of the sintering machine, the amount of engineering changes is small and the fixed investment is low. However, the flue gas external circulation technology has the following disadvantages: 1. The circulating flue gas has a low temperature and a low oxygen content, resulting in a low flue gas circulation rate (up to about 20%) and poor waste heat utilization effect of the flue gas; 2. It is impossible to comprehensively consider the flue gas pollutant distribution characteristics of each wind box of the sintering machine, making the concentrations of pollutants such as CO, NO x etc. in the circulating flue gas relatively lower than those of the internal circulation technology, which is not conducive to a series of complex chemical reaction processes of pollutants in the sintering material layer and is not conducive to the purification of relevant pollutants.

[0005] In summary, both the flue gas internal circulation technology and the flue gas external circulation technology have their own advantages and disadvantages. It is particularly important to find a solution that can not only reduce the project volume and investment but also combine the advantages of the internal circulation technology. Summary of the Invention

[0006] To solve the above problems, the present invention provides a sintering machine flue gas internal and external combined circulation purification and waste heat utilization system. A smoke exhaust device is provided at the bottom of the sintering machine, and a flue gas sealing cover is arranged above the material surface of the sintering machine. The smoke exhaust device includes: a front machine wind box group, a middle machine wind box group, and a tail machine wind box group. Each wind box group includes several wind boxes; the system has: a flue gas external circulation subsystem and a flue gas internal circulation subsystem; the flue gas external circulation subsystem includes: a first main flue, a third main flue, and an external smoke exhaust flue. The first main flue is communicated with the front machine wind box group, the third main flue is communicated with the tail machine wind box group, the external smoke exhaust flue includes an external exhaust main flue, an external circulation flue, and an external exhaust branch flue. One end of the external exhaust main flue is respectively communicated with the first main flue and the third main flue, the other end of the external exhaust main flue is respectively communicated with the external circulation flue and the external exhaust branch flue, and the external exhaust branch flue is also communicated with the chimney; the flue gas internal circulation subsystem includes: a second main flue and an intake flue. The second main flue is communicated with the middle machine wind box group, one end of the intake flue is respectively communicated with the second main flue and the external circulation flue, and the other end of the intake flue is communicated with the flue gas sealing cover.

[0007] Optionally, the front machine wind box group, the middle machine wind box group, and the tail machine wind box group are sequentially arranged along the technological process direction of the sintering machine; an external circulation flue valve is arranged on the external circulation flue; the flue gas external circulation subsystem further includes: a denitration device, the intake port of the denitration device is communicated with the external exhaust branch flue, and the outlet port of the denitration device is communicated with the chimney.

[0008] Optionally, along the flue gas flow direction, the second main flue is communicated with the intake flue through a high SO 2 flue; the system further includes: a gas-gas heat exchanger for transferring the heat of the flue gas conveyed by the third main flue to the flue gas conveyed by the high SO 2 flue; a desulfurization reaction device is arranged on the high SO 2 flue for desulfurizing the flue gas conveyed by the high SO 2 flue heated by the gas-gas heat exchanger and conveying the desulfurized flue gas to the intake flue.

[0009] Optionally, the system further includes: an internal circulation bypass flue, which is arranged in parallel with the desulfurization reaction device on the high SO 2 flue.

[0010] Optionally, the system further includes: a first fan for pumping the flue gas conveyed by the second main flue; a second fan disposed on the main exhaust flue for pumping the flue gas conveyed by the first main flue and the third main flue; and a dust collector for dust removal treatment of the flue gas conveyed by the first main flue, the second main flue, and the third main flue. Preferably, the number of the dust collectors is two, namely: a first dust collector for dust removal treatment of the flue gas conveyed by the second main flue, and located in front of the first fan and behind the desulfurization reaction device in the flue gas flow direction; and a second dust collector for dust removal treatment of the flue gas conveyed by the first main flue and the third main flue, and located in front of the second fan in the flue gas flow direction.

[0011] Optionally, the system further includes: an ammonia supply device disposed on the intake flue for inputting ammonia into the intake flue.

[0012] Optionally, the system further includes: a first flue gas mixer. Two intake ports of the first flue gas mixer are respectively communicated with the other end of the second main flue and the outer circulation flue, and an outlet of the first flue gas mixer is communicated with one end of the intake flue.

[0013] Optionally, the system further includes: a first oxygen supply device disposed on the intake flue for supplying oxygen into the intake flue; or a second oxygen supply mixer including an oxygen buffer tank and a second flue gas mixer. The oxygen buffer tank is used for supplying oxygen. Three intake ports of the second flue gas mixer are respectively communicated with the second main flue, the other end of the outer circulation flue, and an outlet of the oxygen buffer tank, and an outlet of the second flue gas mixer is communicated with one end of the intake flue.

[0014] Optionally, the intake flue is communicated with the flue gas sealing hood through a plurality of flue branches. The plurality of flue branches are spaced along the length direction of the flue gas sealing hood. A regulating valve is disposed on the flue branch, and an oxygen concentration analyzer and a pressure detection device are disposed on the flue gas sealing hood corresponding to the flue branch.

[0015] Optionally, the contents of nitrogen oxides and carbon oxides in the flue gas conveyed by the first main flue are greater than those in the flue gas conveyed by the second main flue and the third main flue; the content of sulfur dioxide in the flue gas conveyed by the second main flue is greater than those in the flue gas conveyed by the first main flue and the third main flue; the temperature of the flue gas conveyed by the third main flue is greater than those of the flue gas conveyed by the first main flue and the second main flue.

[0016] The beneficial effects brought by the technical solution provided by the embodiment of the present invention are:

[0017] 1. For the first time, the internal circulation process and the external circulation process are combined to make the best use of their advantages and avoid their disadvantages.

[0018] 2. The internal circulation flue gas avoids taking flue gas from the air box branch pipe and directly takes flue gas from the main sintering machine flue, reducing the engineering quantity and investment.

[0019] 3. Pure O 2 is used to supplement the oxygen content of the circulating flue gas, greatly improving the sintering flue gas circulation rate.

[0020] 4. SCR and SNCR denitrification are organically combined, and the temperature window in the sintering material layer is utilized to realize SNCR denitrification of the sintering machine for the first time.

[0021] 5. Flue gas containing high SO 2 is enriched and removed inside the flue gas circulation system, saving the investment and operating costs of subsequent desulfurization devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a schematic structural diagram of a sintering machine flue gas internal and external combined circulation purification and waste heat utilization system provided by an embodiment of the present invention.

[0023] The symbols in the figure are explained as follows:

[0024] 1 Sintering machine, 2 Gas-gas heat exchanger, 3 Desulfurization reaction device, 4 Bag filter, 5 First fan, 6 Second flue gas mixer, 7 Oxygen buffer tank, 8 Ammonia distributor, 9 Control valve, 10 Oxygen concentration analyzer, 11 Pressure detection device, 12 Flue gas seal cover, 13 Electrostatic precipitator, 14 Second fan, 15 Hot air heating furnace, 16 Ammonia injection system, 17 SCR reactor, 18 Third fan, 19 Chimney, 20 First SO 2 concentration analyzer, 21 Second SO2 concentration analyzer, 22 NO X concentration analyzer, 23 CEMS analyzer, 24 Front section flue of sintering machine, 25 High SO 2 flue, 26 High-temperature flue at the machine tail, 27 Internal circulation bypass flue, 28 Main external discharge flue, 29 External circulation flue, 30 Bypass flue valve, 31 External circulation flue valve, 32 First main flue, 33 Second main flue, 34 Third main flue, 35 External discharge branch flue, 36 Intake flue, 37 Flue branch pipe. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present invention rather than a limitation of the present invention. In fact, those skilled in the art will appreciate that modifications and variations can be made to the present invention without departing from the scope or spirit thereof. For example, features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. Accordingly, it is intended that the present invention cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0026] In the description of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. The terms "connected", "connected to", and "disposed" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate member. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0027] In the prior art, a plurality of wind boxes (i.e., flue gas discharge devices) are provided at the bottom of a sintering machine, and the outlets of the wind boxes are communicated with the main flue of the sintering machine, so that the sintering machine discharges flue gas through the wind boxes. Due to the characteristics of the sintering process, the properties of the flue gas discharged from each wind box are different. Based on considering the pollutant components and temperature distribution characteristics of the flue gas discharged from each wind box, in the embodiments of the present application, the plurality of wind boxes are divided into: a front wind box group, a middle wind box group, and a tail wind box group, and each wind box group includes several wind boxes. Preferably, the plurality of wind boxes are sequentially divided along the process flow direction of the sintering machine.

[0028] Taking a sintering machine equipped with 23 wind boxes as an example to illustrate the wind box groups: The 23 wind boxes are numbered 1#, 2#,..., 22#, 23#, and are arranged in sequence along the sintering process flow direction (i.e., from the feeding end to the discharging end). The 1# - 3# wind boxes correspond to the head position, and the characteristics of the flue gas discharged therefrom are: high oxygen, low temperature, low dust, and low pollutants. This flue gas can be directly discharged into the atmosphere after dust removal; the 4# - 8# wind boxes correspond to the front section position, and the characteristics of the flue gas discharged therefrom are: high CO, NO x ; the 9# - 19# wind boxes correspond to the middle section position, and the characteristics of the flue gas discharged therefrom are: high SO 2; The 20#-23# bellows correspond to the tail position of the machine. The characteristics of the flue gas discharged from the outside are: high temperature. After being dust-removed, this flue gas can be directly discharged into the atmosphere. Therefore, the 1#-8# bellows can be called the front-of-machine bellows group and connected to the first main flue 32; the 9#-19# bellows can be called the middle-of-machine bellows group and connected to the second main flue 33; the 20#-23# bellows can be called the tail-of-machine bellows group and connected to the third main flue 34. In other words, the main flue of the sintering machine is divided into three parts with non-connecting flue gases: the first main flue 32, the second main flue 33, and the third main flue 34. In other embodiments, other divisions can also be made for multiple bellows. For example, multiple bellows can be divided into: the head-of-machine bellows group, the front-segment-of-machine bellows group, the middle-of-machine bellows group, and the tail-of-machine bellows group. Among them, the head-of-machine bellows group and the front-segment-of-machine bellows group are combined and called the front-of-machine bellows group. Corresponding to the aforementioned 23 bellows, the 1#-3# bellows can be called the head-of-machine bellows group and connected to the fourth main flue; the 4#-8# bellows can be called the front-segment-of-machine bellows group and connected to the first main flue 32. As long as it satisfies: the contents of nitrogen oxides and carbon oxides in the flue gas transported by the first main flue 32 are greater than those in the flue gases transported by the second main flue 33 and the third main flue 34, the content of sulfur dioxide in the flue gas transported by the second main flue 33 is greater than those in the flue gases transported by the first main flue 32 and the third main flue 34, and the temperature of the flue gas transported by the third main flue 34 is greater than those of the flue gases transported by the first main flue 32 and the second main flue, this embodiment does not limit this.

[0029] See Figure 1 , The embodiment of the present invention provides a sintering machine flue gas internal and external combined cycle purification and waste heat utilization system, which includes: a flue gas external circulation subsystem and a flue gas internal circulation subsystem.

[0030] The flue gas external circulation subsystem includes: the first main flue 32, the third main flue 34, and the external exhaust flue. One end of the first main flue 32 is connected to the outlets of the air boxes in the front air box group of the machine, and the other end is connected to the front section flue 24 of the sintering machine. One end of the third main flue 34 is connected to the outlets of the air boxes in the tail air box group of the machine, and the other end is connected to the high-temperature flue 26 at the tail of the sintering machine. The external exhaust flue includes: the main external exhaust flue 28, the external circulation flue 29, and the external exhaust branch flue 35. One end of the main external exhaust flue 28 is respectively connected to the first main flue 32 and the third main flue 34 through the front section flue 24 of the sintering machine and the high-temperature flue 26 at the tail of the sintering machine, that is, the flue gas transported by the front section flue 24 of the sintering machine and the flue gas transported by the high-temperature flue 26 at the tail of the sintering machine are mixed and then enter the main external exhaust flue 28. The other end of the main external exhaust flue 28 is respectively connected to one end of the external circulation flue 29 and one end of the external exhaust branch flue 35. The other end of the external exhaust branch flue 35 is also connected to the chimney 19. The other end of the external circulation flue 29 is connected to one end of the following intake flue 36. Thus, a flue gas external circulation path is formed. In other words, the flue gas in the external exhaust flue has two flow paths. One is to be discharged into the atmosphere through the chimney 19, and the other is to enter the intake pipeline 36 to achieve flue gas external circulation. The flue gas internal circulation subsystem includes: the second main flue 33 and the intake flue 36. One end of the second main flue 33 is connected to the outlets of the air boxes in the middle air box group of the machine, and the other end is connected to the high SO 2 flue 25, so that the high SO 2 flue gas of the sintering machine can be led out through the high SO 2 flue 25. Since this part of the flue gas is led out from the second main flue 33 which belongs to the main flue of the sintering machine, that is, the flue gas is directly taken from the second main flue 33, the disadvantages of taking flue gas from the air box branch pipe are avoided, and the project quantity and investment can be reduced. One end of the intake flue 36 is also connected to the high SO 2 flue 25. The other end of the intake flue 36 is connected to the flue gas sealing hood 12. Thus, a flue gas internal circulation path is formed. The flue gas sealing hood 12 is arranged above the material surface of the sintering machine, and it can play a role in evenly distributing the flue gas, and can evenly distribute the flue gas to the material surface in the middle and rear sections of the sintering machine trolley to participate in the sintering process, such as the sintering machine material surface corresponding to the 15# - 23# air boxes.

[0031] By setting the first main flue 32, the third main flue 34, the external exhaust flue, the second main flue 33, and the intake flue 36, the flue gas internal circulation process and the external circulation process of the sintering machine can be combined to realize the integration of the respective advantages of the two technologies, giving full play to strengths and avoiding weaknesses.

[0032] The flue gas of the sintering machine contains a certain concentration of NO xPollutants. To meet the emission standards, the flue gas external circulation subsystem further includes: a denitration device for removing nitrogen oxides in the flue gas, whose inlet is connected to the other end of the external exhaust branch flue 35, and the outlet is connected to the chimney 19, so that the flue gas can reach the ultra-low emission level and then be discharged into the atmosphere by the chimney 19. Specifically, the denitration device includes: a heating furnace, an ammonia injection system 16, an SCR (Selective Catalytic Reduction) reactor 17, and a third fan 18, which are sequentially arranged on the external exhaust branch flue along the denitration process flow. The heating furnace is used to heat the flue gas entering the external exhaust branch flue 35, and it can be a hot air heating furnace 15. The ammonia injection system 16 is arranged after the heating furnace and is used to inject ammonia into the external exhaust branch flue 35 and mix it with the heated flue gas. The SCR reactor 17 is arranged after the ammonia injection system 16 and is used to carry out denitration reaction on the flue gas entering it. The third fan 18 is arranged after the SCR reactor 17 and is used to provide pumping power for the flue gas.

[0033] To adapt to different working conditions, an external circulation flue valve 31 is arranged on the external circulation flue 29. When it is in normal use, this valve is in the open state. According to the different demands for flue gas, the opening degree of this valve can be adjusted. When this valve is in the closed state, the flue gas transported in the external exhaust main flue 28 does not enter the intake flue 36 and is only discharged by the chimney 19.

[0034] Since the flue gas discharged from the chimney 19 directly enters the atmosphere, to make the pollutant indexes of the flue gas reach the emission standards, this system further includes: a CEMS (Continuous Emission Monitoring System) analyzer 23, which is arranged on the external exhaust branch flue 35 near the chimney 19. For example, it can be located on the external exhaust branch flue 35 between the following third fan 18 and the chimney 19. Since the flue gas transported in the first main flue 32 and the third main flue 34 is low-sulfur flue gas and there is basically no situation of SO 2 exceeding the standard, therefore, the CEMS analyzer 23 is mainly used to monitor NO X and the dust concentration. When the NO X concentration exceeds the standard, it is necessary to increase the parameters in the denitration device, such as the ammonia injection amount, to make the flue gas meet the standard; when the dust concentration exceeds the standard, it is necessary to adjust the operation parameters of the following second dust collector to make the flue gas meet the standard. To improve the denitration efficiency, a NO x concentration analyzer 22 is arranged on the external exhaust branch flue 35 in front of the SCR reactor 17 and is used to monitor the NO x concentration of the flue gas entering the SCR reactor 17, so that the ammonia injection amount of the ammonia injection system 16 can be determined according to this concentration. When the NO xWhen the concentration remains high, the ammonia injection amount of the ammonia injection system 16 is increased; otherwise, the injection amount is decreased.

[0035] From the high SO 2 The temperature of the flue gas led out from the flue 25 can reach 160 - 170 °C. Usually, the desulfurization reaction of the desulfurization reaction device 3 requires a certain reaction temperature, such as above 220 °C. And the temperature of the flue gas conveyed by the third main flue 34 is relatively high. In order to make full use of the waste heat of this part of the flue gas and desulfurize the flue gas conveyed by the second main flue 33, this system further includes: a gas-gas heat exchanger 2 and a desulfurization reaction device 3. The gas-gas heat exchanger 2 is used to utilize the heat of the flue gas conveyed by the third main flue 34 to heat the flue gas conveyed by the high SO 2 flue 25, that is, the flue gas conveyed by the high SO 2 flue 25 and the flue gas conveyed by the high-temperature flue 26 at the tail of the machine are exchanged in the gas-gas heat exchanger 2. After heat exchange, the reaction temperature can be reached. Specifically, the heat source inlet and heat source outlet of the gas-gas heat exchanger 2 are arranged on the high-temperature flue 26 at the tail of the machine so that the flue gas conveyed by the high-temperature flue 26 at the tail of the machine enters the gas-gas heat exchanger 2 from the heat source inlet and flows out from the heat source outlet after heat exchange; the cold source inlet and cold source outlet of the gas-gas heat exchanger 2 are arranged on the high SO 2 flue 25 so that the flue gas conveyed by the high SO 2 flue 25 enters the gas-gas heat exchanger 2 from the cold source inlet and flows out from the cold source outlet after heat exchange. The desulfurization reaction device 3 is used to desulfurize the flue gas conveyed by the high SO 2 flue 25 heated by the gas-gas heat exchanger 2 and convey the desulfurized flue gas to the intake flue 36. It is arranged on the high SO 2 flue 25. In this way, the end treatment of sintering flue gas pollutants can be advanced to process control. Inside this system, the flue gas containing high SO 2 is concentrated, and the desulfurization reaction device 3 is embedded inside this system, saving the investment and operation costs of configuring a desulfurization reaction device (or desulfurization device) in the subsequent flue gas purification system. In order to effectively monitor the operation of the desulfurization reaction device 3, this system further includes: a second SO 2 concentration analyzer 21, which is used to monitor the SO 2 concentration in the flue gas treated by the desulfurization reaction device 3. It is arranged on the high SO 2 flue 25 after the desulfurization reaction device 3, for example, it can be on the high SO 2 flue 25 after the following first fan 5. The first fan 5 is located after the desulfurization reaction device 3. When the monitored SO 2 concentration value continuously remains higher than the normal operation value during normal working conditions, an alarm message indicating the failure of the desulfurization reaction device 3 is prompted, and the maintenance personnel need to check whether the desulfurization reaction device 3 fails accordingly.

[0036] When the desulfurization reaction device 3 needs to be overhauled, it is usually shut down for maintenance. At this time, in order to still maintain the normal operation of the flue gas internal circulation subsystem, the system further includes: an internal circulation bypass flue 27, which is arranged in parallel with the desulfurization reaction device 3 on the high-SO 2 flue 25, that is, on the high-SO 2 flue 25 between the cold source outlet of the gas-gas heat exchanger 2 and one end of the intake pipe 36, an internal circulation bypass flue 27 is arranged in parallel. The internal circulation bypass flue 27 is provided with a bypass flue valve 30. When the system operates normally, the valve is in the closed state; when the system needs to be overhauled, the valve is in the open state. On this basis, a desulfurization flue valve can be set in front of the desulfurization reaction device 3. At this time, the valve is in the closed state.

[0037] The SNCR (Selective Non-Catalytic Reduction) denitration reaction temperature range can be 900°C - 1100°C, and the temperature of the sinter ore layer can be 1000°C - 1100°C. The temperature ranges of the two are the same, making the denitration reaction temperature window. In order to further remove NO x The system further includes: an ammonia supply device for inputting ammonia into the intake flue. It is arranged on the intake flue 36, such as near the flue gas seal cover 12 side. In this way, the flue gas containing NO x reacts with NH 3 in the sintering material layer to achieve the organic combination of SCR and SNCR denitration, and improve the removal rate of NO x . Specifically, the ammonia supply device includes: an ammonia tank and an ammonia distributor 8. The ammonia tank is communicated with the intake flue 36, and the ammonia distributor 8 is arranged in the intake flue 36 to make the ammonia entering the intake flue 36 from the ammonia tank evenly distributed in the flue gas, so as to facilitate full mixing with the flue gas.

[0038] Usually, the flue gas contains dust. In order to reduce the adverse effects of dust on the flue and equipment and the pollution to the atmosphere, the system further includes: a dust collector for dust removal treatment of the flue gas transported by the first main flue 32, the second main flue 33 and the third main flue 34. Preferably, the number of dust collectors is two, and the two dust collectors are divided into: a first dust collector and a second dust collector. The first dust collector is used for dust removal treatment of the flue gas transported by the second main flue 33, and it can be arranged on the high-SO 2On the flue 25. In application, the first dust collector can be the bag filter 4, and the dust removal efficiency of the bag filter 4 is above 99.5%, which can remove most of the particulate matters in the flue gas. Since the bag filter 4 usually needs to be shut down for maintenance when it needs to be repaired, in order to still maintain the normal operation of the flue gas internal circulation subsystem, the above-mentioned internal circulation bypass flue 27 is arranged in parallel with the desulfurization reaction device 3 and the bag filter 4 on the high SO 2 On the flue 25, that is, on the high SO between the cold source outlet of the gas-gas heat exchanger 2 and the inlet of the first fan 5 2 An internal circulation bypass flue 27 is arranged in parallel on the flue 25. The second dust collector is used to dust the flue gas conveyed by the first main flue 32 and the third main flue 34, and it can be arranged on the external discharge main flue 28. In application, the second dust collector can be the electrostatic precipitator 13. In other embodiments, the first dust collector can also be used to dust the flue gas conveyed by the first main flue 32 and the second main flue 33, and it is arranged on the inlet flue 36 to dust the mixed flue gas, and the mixed flue gas is the flue gas conveyed by the external circulation flue 29 and the high SO 2 The flue gas after mixing the flue gas conveyed by the flue 25. The second dust collector is used to dust the flue gas conveyed by the third main flue 34, and it is arranged on the external discharge branch flue 35. This embodiment does not limit this.

[0039] To improve the flow power of the flue gas, the system further includes: a first fan 5 and a second fan 14. The first fan 5 is used to pump the flue gas conveyed by the second main flue 33, and it can be arranged behind the first dust collector in the flue gas flow direction. The second fan 14 is used to pump the flue gas conveyed by the first main flue 32 and the third main flue 34, and it can be arranged on the external discharge main flue 28 in the flue gas flow direction and behind the second dust collector.

[0040] To enable the two flue gases to be fully mixed, the system further includes: a first flue gas mixer, which has two inlet ports and one outlet port. The two inlet ports are respectively the first inlet port and the second inlet port. The first inlet port is communicated with the high SO 2 Flue 25, the second inlet port is communicated with the other end of the external circulation flue 29, and this outlet port is communicated with one end of the inlet flue 36. Specifically, the first flue gas mixer includes: a cylinder body and an outlet straight pipe. Two inlet ports are arranged on the upper part of the cylinder body. The outlet straight pipe is arranged in the cylinder body, and a mixing interval is formed between the outlet straight pipe and the cylinder body at a radial distance in the cylinder body. The top end of the outlet straight pipe is located outside the cylinder body for the output of flue gas, and a circulation gap is formed between the bottom end of the outlet straight pipe and the bottom of the cylinder body. The first inlet port is communicated with the high SO 2The flue 25 is connected, the second air inlet is connected to the other end of the outer circulation flue 29, and the rotation directions of the flue gases entering the cylinder body from the first air inlet and the second air inlet are the same, such as counterclockwise or clockwise, so that the two flue gases first rotate downward and then discharge upward, thus enhancing the flue gas mixing effect and enabling the dust to be thrown onto the inner wall of the cylinder body, enhancing the dust removal effect. The way the flue gas enters the cylinder body in each flue can be a tangential way or an arc way, and this embodiment does not limit this. A dust hopper is provided at the bottom of the cylinder body, and the large end of the dust hopper is connected to the bottom of the cylinder body.

[0041] To increase the oxygen content in the flue gas, the system further includes an oxygen supply device, which is arranged on the intake flue 36 and is used to supply oxygen into the intake flue 36, thereby increasing the flue gas circulation rate and enabling the flue gas circulation rate to be increased to more than 65%. Generally, the oxygen supply device includes: an oxygen buffer tank 7 and an oxygen distributor. To reduce the number of devices and make the system structure simple, the system also includes: an oxygen buffer tank 7 and a second flue gas mixer 6. The oxygen buffer tank 7 is used to supply oxygen. The second flue gas mixer 6 has three air inlets and one air outlet. The three air inlets are the first air inlet, the second air inlet and the third air inlet respectively. The first air inlet is connected to the high SO 2 flue 25, the second air inlet is connected to the other end of the outer circulation flue 29, the third air inlet is connected to the oxygen buffer tank 7, and the air outlet is connected to one end of the intake flue 36. The specific structure of the second flue gas mixer 6 can be improved on the basis of the structure of the above first mixer. For example, an additional air inlet, that is, the third air inlet, is added to the cylinder body, and other structures are the same.

[0042] The intake flue 36 is connected to the flue gas sealing cover 12 through a number of flue branches 37. The number of flue branches 37 is arranged at intervals along the length direction of the flue gas sealing cover 12, so as to facilitate the uniform distribution of flue gas on the sintering machine material surface. A regulating valve 9 is provided on each flue branch 37. According to the difference in the permeability of the material layer and the required gas volume in different sintering machine areas, the opening of the regulating valve is adjusted to keep the flue gas pressure stable in the flue gas sealing cover 12 and maintain a slightly negative pressure state to prevent the leakage of flue gas. The slightly negative pressure range can be -150 Pa to 0 Pa. An oxygen concentration analyzer 10 and a pressure detection device 11 are provided on the flue gas sealing cover 12 corresponding to the flue branch 37. If the number of flue branches 37 is 4, 4 oxygen concentration analyzers 10 and 4 pressure detection devices 11 can be provided in total to facilitate the accurate monitoring of the oxygen content and flue gas pressure in each area and provide monitoring parameters for the normal operation of the system.

[0043] The following takes the configuration of 23 wind boxes (numbered 1# to 23# in sequence along the technological process direction) for the sintering machine as an example to illustrate the usage method of the system, which is specifically as follows:

[0044] The main flue of the sintering machine is divided into three non - communicating parts for flue gas, namely: the first main flue 32 corresponding to the 1# - 8# wind boxes, the second main flue 33 corresponding to the 9# - 19# wind boxes, and the third main flue 34 corresponding to the 20# - 23# wind boxes. The flues for transporting flue gas also include: the front - section flue 24 of the sintering machine, the high - SO 2 flue 25, the high - temperature flue 26 at the machine tail, the internal - circulation bypass flue 27, the main external - discharge flue 28, the external - circulation flue 29, and the external - discharge branch flue 35. The equipment involved in the internal - circulation process includes: the gas - gas heat exchanger 2, the desulfurization reaction device 3, the bag filter 4, the first fan 5, the second flue - gas mixer 6, the oxygen buffer tank 7, the ammonia distributor 8, the flue - gas sealing hood 12, etc. The equipment involved in the external - circulation process includes: the electrostatic precipitator 13, the second fan 14, the SCR reactor 17, the third fan 18, etc.

[0045] There are two paths for the flue gas: The first path of flue gas, the high - SO 2 flue gas is led out through the high - SO 2 flue 25 connected to the second main flue 33. First, it exchanges heat with the high - temperature flue gas at the machine tail through the gas - gas heat exchanger 2. After heat exchange, the high - SO 2 flue gas then sequentially passes through the desulfurization reaction device 3, the bag filter 4, the first fan 5, and then mixes with the following another part of the flue gas in the second flue - gas mixer 6. The mixed flue gas then sequentially passes through the ammonia distributor 8 and the flue - gas sealing hood 12 and reaches the sintering machine surface to participate in the sintering process.

[0046] The second path of flue gas, after the flue gas led out from the front - section flue 24 of the sintering machine connected to the first main flue 32 and the high - temperature flue gas led out from the high - temperature flue 26 at the machine tail connected to the third main flue 34 converge, enters the electrostatic precipitator 13 for dust removal, passes through the main external - discharge flue 28, and then a part of it sequentially passes through the second fan 14, the hot - air heating furnace 15, the ammonia injection system 16, the SCR reactor 17, the third fan 18, and the chimney 19 for external discharge.

[0047] In summary, the beneficial effects brought by the technical solution provided in the embodiment of the present invention are:

[0048] 1. For the first time, the internal - circulation process is combined with the external - circulation process to make the best use of their advantages and avoid their disadvantages.

[0049] 2. The internal - circulation flue gas avoids taking flue gas from the wind - box branch pipes and directly takes flue gas from the main flue of the sintering machine, reducing the engineering quantity and investment;

[0050] 3. Using pure O 2 to supplement the oxygen content of the circulating flue gas, greatly improving the sintering - flue - gas circulation rate;

[0051] 4. The organic combination of SCR and SNCR denitration, taking advantage of the temperature window in the sintering material layer, realizing SNCR denitration of the sintering machine for the first time.

[0052] 5. Enrich the flue gas containing high SO 2 and remove it inside the flue gas circulation system, saving the investment and operating costs of subsequent desulfurization devices.

[0053] As is known by common technical knowledge, the present invention can be implemented by other embodiments without departing from its spiritual essence or essential features. Therefore, the above-disclosed embodiments are illustrative in all aspects and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

Claims

1. A combined external and internal flue gas circulation purification and waste heat utilization system for a sintering machine, with a smoke exhaust device provided at the bottom of the sintering machine, and a flue gas sealing hood arranged above the material surface of the sintering machine. Characterized in that, The smoke exhaust device includes: a front machine wind box group, a middle machine wind box group, and a tail machine wind box group, and each wind box group contains several wind boxes; The system has: a flue gas external circulation subsystem and a flue gas internal circulation subsystem; The flue gas external circulation subsystem includes: a first main flue, a third main flue, and an external smoke exhaust flue. The first main flue is connected to the front machine wind box group, the third main flue is connected to the tail machine wind box group, the external smoke exhaust flue includes an external exhaust main flue, an external circulation flue, and an external exhaust branch flue. One end of the external exhaust main flue is respectively connected to the first main flue and the third main flue, the other end of the external exhaust main flue is respectively connected to the external circulation flue and the external exhaust branch flue, and the external exhaust branch flue is also connected to the chimney; The flue gas internal circulation subsystem includes: a second main flue and an intake flue. The second main flue is connected to the middle machine wind box group, one end of the intake flue is respectively connected to the second main flue and the other end of the external circulation flue, and the other end of the intake flue is connected to the flue gas sealing hood; The front machine wind box group, the middle machine wind box group, and the tail machine wind box group are arranged in sequence along the technological process direction of the sintering machine; An external circulation flue valve is arranged on the external circulation flue; The flue gas external circulation subsystem further includes: A denitration device, the intake port of the denitration device is connected to the external exhaust branch flue, and the outlet port of the denitration device is connected to the chimney; The system further includes: A first oxygen supplement device, arranged on the intake flue, for supplementing oxygen into the intake flue; or A second oxygen supplement and mixing device, including: an oxygen buffer tank and a second flue gas mixer. The oxygen buffer tank is used to supply oxygen, three intake ports of the second flue gas mixer are respectively connected to the second main flue, the other end of the external circulation flue, and the outlet port of the oxygen buffer tank, and the outlet port of the second flue gas mixer is connected to one end of the intake flue.

2. The system according to claim 1, Characterized in that, In the flue gas flow direction, the second main flue is connected to the intake flue through a high-SO 2 flue. The system further includes: Gas-gas heat exchanger, used to transfer the heat of the flue gas conveyed by the third main flue to the flue gas conveyed by the high-SO 2 flue; The desulfurization reaction device is arranged on the high-SO 2 flue, and is used for desulfurizing the flue gas conveyed by the high-SO 2 flue after being heated by the gas-gas heat exchanger, and conveying the desulfurized flue gas to the intake flue.

3. The system according to claim 2, Characterized in that, The system further includes: Inner loop bypass flue duct, which is arranged in parallel with the desulfurization reaction device on the high-SO 2 flue duct.

4. The system according to claim 2, Characterized in that, The system further includes: A first fan, used for pumping the flue gas conveyed by the second main flue; A second fan, arranged on the external exhaust main flue, used for pumping the flue gas conveyed by the first main flue and the third main flue; and A dust collector, used for dust removal treatment of the flue gas conveyed by the first main flue, the second main flue, and the third main flue.

5. The system according to claim 4, Characterized in that, The number of the dust collectors is two, respectively: A first dust collector, used for dust removal treatment of the flue gas conveyed by the second main flue, and is located in front of the first fan and behind the desulfurization reaction device in the flue gas flow direction; And A second dust collector, which is used for dust removal of the flue gas conveyed by the first main flue and the third main flue, and is located in front of the second fan in the flue gas flow direction.

6. The system according to claim 1, wherein, the system further comprises: an ammonia supply device, which is arranged on the intake flue and is used for inputting ammonia into the intake flue.

7. The system according to claim 1, wherein, the system further comprises: a first flue gas mixer, two intake ports of the first flue gas mixer are respectively communicated with the other end of the second main flue and the external circulation flue, and the outlet of the first flue gas mixer is communicated with one end of the intake flue.

8. The system according to claim 1, wherein, the intake flue is communicated with the flue gas sealing hood through a plurality of flue branches, the plurality of flue branches are arranged at intervals along the length direction of the flue gas sealing hood, a regulating valve is arranged on the flue branch, and an oxygen concentration analyzer and a pressure detection device are arranged on the flue gas sealing hood corresponding to the flue branch.

9. The system according to claim 1, wherein, the contents of nitrogen oxides and carbon oxides in the flue gas conveyed by the first main flue are greater than those in the flue gas conveyed by the second main flue and the flue gas conveyed by the third main flue; the content of sulfur dioxide in the flue gas conveyed by the second main flue is greater than those in the flue gas conveyed by the first main flue and the flue gas conveyed by the third main flue; the temperature of the flue gas conveyed by the third main flue is greater than those of the flue gas conveyed by the first main flue and the flue gas conveyed by the second main flue.

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