CN111569623A - Internal and external circulation system and circulation method for sintering flue gas - Google Patents
Internal and external circulation system and circulation method for sintering flue gas Download PDFInfo
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- CN111569623A CN111569623A CN202010270716.9A CN202010270716A CN111569623A CN 111569623 A CN111569623 A CN 111569623A CN 202010270716 A CN202010270716 A CN 202010270716A CN 111569623 A CN111569623 A CN 111569623A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/54—Nitrogen compounds
- B01D53/56—Nitrogen oxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
Abstract
The invention provides an internal and external circulation system for sintering flue gas, which comprises: the device comprises an internal circulation device, an external circulation device and a desulfurization and denitrification device; the internal circulation device is connected with a middle front section flue of a 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 external circulation device is connected with a machine head flue and a middle and rear section flue of the main flue of the sintering machine to obtain second purified flue gas, one part of the second purified flue gas circulates into the sintering machine, and the other part of the second purified flue gas enters the desulfurization and denitrification device; the flue gas from the middle and rear section flues and the flue gas from the middle and front section flues enter the external circulation device after heat exchange; the invention also provides an internal and external circulation method of the sintering flue gas. The invention improves the circulation rate of the sintering flue gas from 20% to more than 60%, improves the utilization rate of waste heat, reduces the concentration of NOx in the flue gas, realizes two-stage CO removal reaction, and saves a large amount of investment and operation cost.
Description
Technical Field
The invention belongs to the technical field of ultralow emission of flue gas in the steel industry, and particularly relates to an internal and external circulation system and a circulation method for sintering flue gas.
Background
The discharge amount of pollutants in a sintering process in the steel industry is large, a sintering flue gas circulation technology is taken as an important mode for reducing the discharge amount of the pollutants, and various circulation processes are proposed at home and abroad, wherein the processes such as LEEP, Eposint, EOS, new-day iron and the like are available at home and abroad; domestic enterprises such as Ning steel, sand steel, first steel stock, Bao steel, permanent steel, migrating steel, long steel and the like are respectively implemented.
The current flue gas circulation technology of the sintering machine is roughly divided into two technical modes: the flue gas internal circulation technology and the flue gas external circulation technology.
The flue gas internal circulation technology is characterized in that: 1. considering the smoke pollutants and the temperature distribution characteristics of each air box of the sintering machine, the pollutants can generate a series of complex chemical reaction processes in a sintering material layer, including secondary combustion heat release of CO, high-temperature decomposition of dioxin and the like, SO that SO can be theoretically reduced2NOx, and other pollutants. However, according to the circumstances, since the sintering process is accompanied by numerous physical and chemical reactions and the process is very complicated, the internal circulation does not achieve the desired effect and also brings about some other problems. 2. Air is taken from the air box branch pipes, the operation is flexible, and different air boxes can be switched randomly to enter the flue gas circulation system. However, the engineering quantities of equipment, steel structures, civil engineering, valve instruments and the like are large, so that the investment is high and the overhaul workload is large. 3. Compared with the external circulation process, the internal circulation process has the advantages of high temperature and high oxygen content of the circulating flue gas, high flue gas circulation rate (about 30 percent) and good flue gas waste heat utilization effect.
The flue gas external circulation technology is characterized in that: 1. flue gas is taken from a flue behind the sintering main exhaust fan, so that the engineering change is small, and the fixed investment is low; the flue gas circulating system is better than a flue gas internal circulating system in the aspect of popularization degree in the industry; 2. the process flow is simple, the number of valves and meters is small, and the overhaul workload is small; 3. because the temperature of the flue gas after sintering the main exhaust fan is low (generally between 130 ℃ and 150 ℃), the heat utilization effect is general; the oxygen content of the flue gas is relatively low, so that the emission reduction rate of the sintering flue gas is low (about 30 percent).
In conclusion, the flue gas internal circulation technology and the flue gas external circulation technology have respective advantages and disadvantages, and a process technology capable of improving the flue gas circulation rate and improving the utilization rate of the flue gas waste heat does not exist.
Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide an internal and external circulation system and a circulation method for sintering flue gas, which at least solve the problems of low waste heat utilization rate and insufficient circulation rate when the sintering flue gas is subjected to internal circulation or external circulation independently at present.
In order to achieve the above purpose, the invention provides the following technical scheme:
an internal and external circulation system for sintering flue gas, the internal and external circulation system comprising: the device comprises an internal circulation device, an external circulation device and a desulfurization and denitrification device;
the internal circulation device is connected with a middle front section flue of a 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 external circulation device is connected with a machine head flue and a middle and rear section flue of the main flue of the sintering machine, and is used for purifying the machine head flue gas and the middle and rear section flue gas of the main flue of the sintering machine to obtain second purified flue gas, wherein one part of the second purified flue gas circulates into the sintering machine, and the other part of the second purified flue gas enters the desulfurization and denitrification device; the flue gas from the middle and rear section flues and the flue gas from the middle and front section flues enter the external circulation device after heat exchange;
and the desulfurization and denitrification device is used for performing desulfurization and denitrification treatment on the second purified flue gas.
In the sintering flue gas internal and external circulation system, preferably, the first purified flue gas and the second purified flue gas are mixed by a flue gas mixer and then recycled to the sintering machine; the flue gas mixer is connected with the sintering machine through a co-circulating flue, and the mixed flue gas is conveyed into the sintering machine through the co-circulating flue by the flue gas mixer.
In the sintering flue gas internal and external circulation system, preferably, the internal circulation device comprises a gas heat exchanger and a built-in combustion furnace which are arranged on an internal circulation flue; one end of the internal circulation flue is connected with a middle front section flue of the sintering machine, the other end of the internal circulation flue is connected with the flue gas mixer, and 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;
preferably, the flue gas from the middle front section flue and the flue gas from the middle rear section flue exchange heat through a gas heat exchanger, and a first valve is arranged on the internal circulation flue in front of the gas heat exchanger;
preferably, a combustion-supporting flue is arranged on the internal circulation flue behind the built-in combustion furnace, and the combustion-supporting flue is connected to the inlet of the built-in combustion furnace from the internal circulation flue;
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;
further preferably, the internal circulation flues in front of and behind the built-in combustion furnace are provided with CO concentration analyzers.
In the sintering flue gas internal and external circulation system, preferably, flue gases from a head flue of the sintering machine and a middle-rear section flue of the sintering machine are mixed in an external discharge flue and then purified to obtain second purified flue gas, the second purified flue gas enters the flue gas mixer through the external circulation flue, and the flue gas sequentially enters the sintering machine through the external discharge flue, the external circulation flue and the co-circulation flue to complete external circulation of the flue gas;
the external circulation device comprises a machine head electric dust remover arranged on an external discharge flue and used for purifying the mixed flue gas in the external discharge flue, a third fan is arranged on the external discharge flue behind the machine head electric dust remover, 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;
preferably, an overhaul flue is further arranged between the middle front section flue and the outer circulating device and used for circulation and cyclic utilization of the middle front section flue gas when the inner circulating device is overhauled, and a second valve is arranged on the overhaul flue.
In the sintering flue gas internal and external circulation system, preferably, the internal and external circulation system further comprises a ring cooling device, the ring cooling device comprises a ring cooling machine, and the ring cooling machine is connected to the inlet of the flue gas mixer through a ring cooling flue.
In the sintering flue gas internal and external circulation system, preferably, the internal and external circulation system further comprises an ammonia gas injection system and an oxygen gas supply device which are sequentially arranged on the co-circulation flue along the flue gas circulation direction;
preferably, the oxygen supply device comprises an oxygen distributor connected to an outlet of the oxygen buffer tank, and oxygen ejected from the oxygen distributor enters the co-circulation flue;
preferably, the oxygen is pure oxygen, and the purity of the oxygen reaches more than 98%.
In the sintering flue gas internal and external circulation system, preferably, the internal and external circulation system further comprises a plurality of sealing covers, the flue gas supplemented by oxygen enters the plurality of sealing covers through a plurality of branch pipelines respectively, the inner cavities of the sealing covers are communicated with the charge level of the sintering machine, and the plurality of branch pipelines are provided with flue gas regulating valves for regulating the flue gas entering the sealing covers;
preferably, the sealing cover is fixed above the material level of the middle section of the sintering machine, one end of each of the machine head flue, the middle front section flue and the middle rear section flue is respectively connected with different air boxes of the sintering machine, flue gas in the circulating flue of the sintering machine enters the middle section of the sintering machine from the sealing cover, and flue gas in the sintering machine enters the machine head flue, the middle front section flue and the middle rear section flue from different air boxes;
preferably, the seal cover is provided with a pressure detection device and an oxygen concentration analyzer, the oxygen concentration analyzer is connected with the oxygen supply device, and the oxygen supply process is automatically controlled according to the oxygen concentration in the seal cover.
In the sintering flue gas internal and external circulation system, preferably, 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 by the desulfurization reactor and the denitrification reactor and then discharged by the chimney;
preferably, a CEMS analyzer and a fourth fan are arranged in front of the chimney and are respectively used for testing pollutant components in the smoke before emission and induced air.
A sintering flue gas internal and external circulation method comprises the following steps:
step one, flue gas heat exchange comprises the following steps:
flue gas in a middle front section flue and flue gas in a middle rear section flue of the sintering machine exchange heat;
step two, flue gas internal circulation, external circulation and emission include:
after heat exchange, enabling the flue gas in the middle-front section flue to enter an internal circulation device for removing and burning CO to obtain first purified flue gas, and enabling the first purified flue gas to enter the sintering machine through internal circulation; and mixing the flue gas in the middle-rear section flue and the flue gas in the machine head flue, then feeding the mixture into an external circulation device for flue gas purification to obtain second purified flue gas, then feeding one part of the second purified flue gas into the sintering machine through external circulation, and discharging the other part of the second purified flue gas from a chimney after desulfurization and denitrification.
In the internal and external circulation method of the sintering flue gas, preferably, the method further comprises the following steps of supplying ammonia gas and oxygen gas to the sintering flue gas:
mixing the first purified flue gas entering the internal circulation and the second purified flue gas entering the external circulation by additional supplemented ammonia gas and oxygen gas, and then entering the sintering machine;
preferably, the first purified flue gas and the second purified flue gas are mixed with flue gas generated by a circular cooling device before ammonia gas and oxygen gas are supplied, and the flue gas of the circular cooling device is used for supplying oxygen to the flue gas of an internal and external circulation system so as to realize reutilization;
preferably, the method is completed by the system.
Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:
compared with the traditional sintering flue gas which is subjected to internal circulation or external circulation independently, the internal and external circulation system and the circulation method for the sintering flue gas have the following excellent effects:
1. compared with the traditional flue gas circulation technology, the method adopts pure oxygen to supplement the oxygen content of the flue gas, and improves the circulation rate of the sintering flue gas from 20 percent to more than 60 percent;
2. the circular cooling flue gas is introduced into the flue gas circulating system, so that the characteristics of cleanness and high temperature of the circular cooling flue gas are fully utilized, the temperature of the circular flue gas is increased, and the utilization rate of waste heat is increased;
3. an SNCR denitration reaction is carried out by utilizing a material bed temperature window of a sintering machine, so that the concentration of NOx in the flue gas is reduced;
4. and the two-stage CO removal reaction is realized by respectively utilizing material bed temperature windows of the built-in combustion furnace and the sintering machine. The high-concentration CO is changed into valuable, the resource utilization is realized, the CO concentration is reduced, the combustion latent heat of the CO is fully released, the flue gas temperature is increased, and the flue gas waste heat utilization rate is increased.
5. Removing a part of dioxin by utilizing the high temperature of the sintering material layer and the high temperature of the built-in combustion furnace;
6. the process control of the sintering flue gas is combined with the tail end treatment, the comprehensive treatment is realized, and a large amount of investment and operation cost are saved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:
FIG. 1 is a process flow diagram of an internal and external circulation system of sintering flue gas according to an embodiment of the present invention.
In the figure: 1. sintering machine; 101. a machine head flue; 102. a middle front section flue; 103. a middle and rear section flue; 2. a sealing cover; 3. a pressure detection device; 4. an oxygen concentration analyzer; 5. adjusting a valve; 6. an oxygen uniform distributor; 7. an oxygen buffer tank; 8. an ammonia gas injection system; 9. a flue gas mixer; 10. a first valve; 11. a second valve; 12. a gas heat exchanger; 13. a CO concentration analyzer; 14. a built-in combustion furnace; 15. a first fan; 16. a second fan; 17. a circular cooler; 18. a nose electric dust remover; 19. a third fan; 20. a third valve; 21. a desulfurization reactor; 22. a denitration reactor; 23. a fourth fan; 24. a CEMS analyzer; 25. a chimney; 26. an internal circulation flue; 27. an exhaust flue; 28. an external circulation flue; 29. circularly cooling the flue; 30. a combustion-supporting flue; 31. a circulating flue (also referred to as a co-circulating flue).
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected" and "connected" used herein should be interpreted broadly, and may include, for example, a fixed connection or a detachable connection; they may be directly connected or indirectly connected through intermediate members, and specific meanings of the above terms will be understood by those skilled in the art as appropriate.
The sintering material has uneven distribution of flue gas heat of the sintering machine in the sintering process of the sintering machine,the temperature of the flue gas of the head air box (i.e. the head) of the sintering machine is lower and is generally below 150 ℃, the temperature of the middle section and the rear section of the air box of the sintering machine is gradually increased, but the total heat of the flue gas of each air box of the sintering machine is conserved. Meanwhile, the flue gas pollutant SO of the sintering machine2The concentrations of pollutants such as NOx, CO and the like present the situation that the flue gas of different windboxes has different emission characteristics. The air box is divided into different flue gases according to different pollutants and temperatures in the air box, so that the cyclic utilization rate of sintering flue gas can be improved.
The invention divides the air boxes of the sintering machine into three paths, the flue gas of a plurality of air boxes (such as 1# -3# air boxes) of the machine head is correspondingly conveyed to the machine head flue of the main flue of the sintering machine, and the machine head flue generally has the following characteristics: the temperature is low, and the temperature of the flue gas does not exceed 150 ℃; the flue gas of a plurality of bellows (such as 4# -13# bellows) of the middle and front section is correspondingly conveyed to the middle and front section flue of the main flue of the sintering machine, and the flue gas in the middle and front section flue has the following characteristics: the flue gas with high CO and NOx concentrations belongs to the flue gas with high CO and NOx concentrations, namely the CO and NOx concentrations in the flue gas in the middle front section are higher than those in the machine head flue and the flue gas in the middle rear section; the flue gas of a plurality of wind boxes (such as 14# -22# wind boxes) at the middle and rear sections is correspondingly conveyed to a middle and rear section flue of a main flue of the sintering machine, and the flue gas in the middle and rear section flue has the following characteristics: belongs to high-temperature flue gas, and the temperature of the flue gas is not lower than 270 ℃; the low-temperature flue gas in the middle front section flue and the high-temperature flue gas in the middle rear section can improve the preheating utilization rate through gas-gas heat exchange. The machine head flue, the middle front section flue and the middle rear section flue of the sintering machine form a main flue of the sintering machine.
The "front" and "rear" in the present invention are positional relationships shown based on the direction of smoke transmission.
As shown in fig. 1, according to an embodiment of the present invention, there is provided an internal and external circulation system for sintering flue gas, the internal and external circulation system comprising: the device comprises an internal circulation device, an external circulation device and a desulfurization and denitrification device;
the internal circulation device is connected with a middle front section flue 102 of a main flue of the sintering machine 1, and is used for removing CO from middle front section flue gas of the main flue of the sintering machine 1 to obtain first purified flue gas, and then the first purified flue gas is circulated into the sintering machine 1.
The external circulation device is connected with a machine head flue 101 and a middle and rear section flue 103 of a main flue of the sintering machine 1, the external circulation device and the internal circulation device exchange heat in a crossed manner, the external circulation device is used for purifying machine head flue gas and middle and rear section flue gas of the main flue of the sintering machine 1 to obtain second purified flue gas, one part of the second purified flue gas circulates into the sintering machine 1, and the other part of the second purified flue gas enters the desulfurization and denitrification device and is discharged into the atmosphere after being subjected to desulfurization and denitrification treatment. One part of the second purified flue gas is recycled and the other part of the second purified flue gas is discharged to the atmosphere because the recycling rate of the flue gas cannot reach 100 percent, and the flue gas needs to be continuously discharged outwards, so that the sintering machine 1 is prevented from entering too much flue gas which cannot be effectively utilized. The internal circulation device and the external circulation device both comprise a circulation flue 31, and the internal circulation and the external circulation of the flue gas are completed through the circulation flue 31. The circulation flue 31 is a flue shared by the internal circulation device and the external circulation device, and also serves as a common circulation flue.
And the desulfurization and denitrification device is used for performing desulfurization and denitrification treatment on the second purified flue gas.
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 components mixed by the flue gas mixer 9 are more uniform, thereby being convenient for recycling and improving the flue gas circulation rate. The flue gas mixer 9 conveys the mixed flue gas into the sintering machine 1 through the circulation flue 31.
In the embodiment of the present invention, one end of the internal circulation flue 26 is connected to the middle front flue 102 of the sintering machine 1, and the other end is connected to the flue gas mixer 9, and the flue gas from the middle front flue 102 of the sintering machine 1 forms internal circulation of the flue gas through the internal circulation flue 26 and the circulation flue 31.
The internal circulation device comprises a gas heat exchanger 12 and an internal combustion furnace 14 which are arranged on an internal circulation flue 26; the middle front section flue 102 and the middle rear section flue 103 exchange heat through 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 is increased from 100 ℃ to 180 ℃, the temperature of the flue gas in the middle rear section flue 103 is reduced from 280 ℃ to about 200 ℃, effective utilization of high-temperature flue gas heat is realized, the middle front section flue gas after heat exchange enters the built-in combustion furnace 14 for combustion, and CO in the flue gas is removed for the first time; a first valve 10 is arranged on the internal circulation flue 26 in front of the gas heat exchanger 12, and is used for controlling the opening and closing of the flue gas in the middle front section flue 102.
Preferably, a combustion-supporting flue 30 is arranged on the internal circulation flue 26 behind the built-in combustion furnace 14, the combustion-supporting flue 30 is connected to the inlet of the built-in combustion furnace 14 from the internal circulation flue 26, the CO content of the flue gas in the middle front section is high, CO can be removed on one hand through combustion, and on the other hand, heat is released after combustion, so that the temperature of the flue gas is increased; the flue gas after combustion still contains high oxygen content, and a combustion-supporting flue 30 is arranged in the flue gas to support combustion of the built-in combustion furnace 14; still preferably, a first fan 15 is arranged on the combustion-supporting flue 30, a second fan 16 is arranged between the built-in combustion furnace 14 and the flue gas mixer 9, and both the first fan 15 and the second fan 16 are used for inducing air. Further preferably, the internal circulation flues 26 in front of and behind the built-in combustion furnace 14 are provided with CO concentration analyzers 13 for detecting and analyzing the CO concentration in the flue gas before and after passing through the combustion furnace.
Compared with the common heating furnace, the common heating furnace is provided with the heating furnace chambers around the flue, and the coke oven gas or the blast furnace gas generates high-temperature gas after being combusted in the heating furnace chambers, and then enters the flue to be mixed with the upstream flue gas, so that the purpose of heating the flue gas is achieved. When the built-in combustion furnace 14 is adopted, the igniter and the combustion-supporting flue 30 are both inserted into the internal circulation flue 26, and the ignition and combustion are carried out in the internal circulation flue 26 to heat the flue gas. The igniter may be plasma ignited or other ignition means. The in-line burner 14 has the following advantages:
1. the coke oven gas or the blast furnace gas is combusted in the flue, and compared with the combustion in a hearth outside the flue, the heat dissipation of the combustion can be greatly reduced;
2. the average concentration of CO in the flue gas of the middle front section flue 102 is 10000mg/m3While the average CO concentration in the windbox of the sintering machine 1 is only 5300mg/m3The combustion center temperature of the built-in combustion furnace 14 is about 1200 ℃, so that CO in the smoke of the middle and front sections can be easily ignited, the CO can be combusted to release heat, on one hand, high-concentration CO in the smoke is ignited, a large amount of heat is released, the temperature of circulating smoke is favorably improved, and the utilization rate of the waste heat of the smoke is improved; at the same time, CO is also reducedThe concentration is discharged, and waste is changed into valuable. The circulating system can reduce the concentration of CO in the discharged flue gas by about 20 percent.
3. The combustion reaction of dioxin is carried out in the combustion center of the built-in combustion furnace 14, and part of the pollution gas dioxin can be removed.
The high-temperature flue gas passing through the built-in combustion furnace 14 is divided into two paths, one path of the high-temperature flue gas is led back to the built-in combustion furnace 14 through the combustion-supporting flue 30 for supporting combustion, the amount of the flue gas led back into the built-in combustion furnace 14 is generally a fixed value, the flue gas amount can be only used for igniting 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 CO in the flue gas, and the amount of the combustion-supporting flue gas is influenced by the upstream flue gas amount and the flue; and the other path enters the flue gas mixer 9 through the second fan 16 and the subsequent internal circulation flue 26 and circulates to the inner material surface layer of the sintering machine 1 to participate in the sintering process again.
In the specific embodiment of the invention, the flue gas from the head flue 101 of the sintering machine 1 and the rear flue 103 of the sintering machine 1 is mixed in the external discharge flue 27 and then purified to obtain the second purified flue gas, the second purified flue gas enters the flue gas mixer 9 through the external circulation flue 28, and the flue gas sequentially enters the sintering machine 1 through the external discharge flue 27, the external circulation flue 28 and the circulation flue 31 to complete the external circulation of the flue gas.
The external circulation device comprises a machine head electric dust remover 18 arranged on an external discharge flue 27 after the flue gas is mixed, a third fan 19 is arranged on the external discharge flue 27 behind the machine head electric dust remover 18, one part of second purified flue gas obtained after passing through the third fan 19 enters the flue gas mixer 9 through an external circulation flue 28, and a third valve 20 is arranged on the external circulation flue 28 and used for controlling the flow of the flue gas; the other part enters a desulfurization and denitrification device. When the sintering flue gas internal and external circulation system normally operates, the flue gas in the machine head flue 101 and the flue gas in the middle and rear section flue 103 after heat exchange are mixed and then enter the machine head electric dust remover 18 for purification and dust removal, and then enter the external circulation flue 28 and the desulfurization and denitrification device respectively.
Preferably, an overhaul flue is further arranged between the middle front section flue 102 and the outer circulating device and used for circulation and cyclic utilization of middle front section flue gas during overhaul of the inner circulating device, and a second valve 11 is arranged on the overhaul flue. When equipment workpieces in the internal circulation device need to be overhauled, the first valve 10 of the middle front section flue gas is closed in advance, the second valve 11 is opened, the flue gas in the middle front section flue 102, the flue gas in the machine head flue 101 and the flue gas in the middle rear section flue 103 are mixed in the external discharge flue 27 and then enter the machine head electric dust remover 18 for dust removal and purification, second purified flue gas is obtained, then one part of the purified flue gas enters the flue gas mixer 9 through the external circulation flue 28 at the rear part, and the other part of the purified flue gas enters the desulfurization and denitrification device. The purpose of the maintenance flue is to ensure that the sintering machine 1 can still normally operate during the maintenance of the sintering flue gas circulation system.
In the specific embodiment of the present invention, the desulfurization and denitrification apparatus includes a desulfurization reactor 21, a denitrification reactor 22 and a chimney 25 which are sequentially arranged 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, the stack 25 is also preceded by a CEMS analyzer 24 and a fourth fan 23 for testing the pollutant components in the flue gas before emission and induced air, respectively. The CO concentration analyzer 13 arranged in the internal circulation device and the CEMS analyzer 24 in the desulfurization and denitrification device are used for testing the content of pollutant components in the flue gas, and the operation parameters of the system can be adjusted according to the test result so as to prevent the concentration of the pollutant in the flue gas at the outlet of the chimney 25 from exceeding the standard.
In the specific embodiment of the invention, 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 aggregate generated by the sintering machine 1, and the ring cooling flue gas is flue gas generated in the cooling process of the mineral aggregate; the annular cooler 17 is connected to the inlet of the flue gas mixer 9 via an annular cooling flue 29. The flue gas in the circular cooler 17 has the characteristics of low dust concentration and high oxygen content (about 21%), the first section and the second section of circular cooling flue gas in the circular cooler 17 are generally used for waste heat power generation (high heat content), the invention utilizes the third section of circular cooling flue gas, the temperature of the circular cooling flue gas is about 200 ℃, the temperature is proper, and the high oxygen content can be used for supplementing oxygen to the circulating flue gas in an internal and external circulating system.
In the embodiment of the present invention, the internal and external circulation systems further include an ammonia gas injection system 8 and an oxygen gas supply device sequentially disposed on the circulation flue 31 along the flue gas circulation direction. Preferably, the oxygen supplying device comprises an oxygen distributor 6 connected to the outlet of the oxygen buffer tank 7, and oxygen ejected from the oxygen distributor 6 enters the circulating flue 31; preferably, the oxygen is pure oxygen, and the purity of the oxygen reaches more than 98%. The oxygen content of the flue gas entering the material surface layer of the sintering machine 1 can be more than 18 percent through the oxygen supply device (when the oxygen content is more than 18 percent, the sintering production is not influenced). By using the pure oxygen supply process, the flue gas circulation rate can reach more than 60 percent, and is higher than the 20 percent flue gas circulation rate of the traditional flue gas circulation process.
The ammonia gas injection system 8 is used for supplementing ammonia gas into the circulating flue 31 so that the flue gas containing NOx and NH are mixed in the sinter bed3SNCR reaction occurs to remove NOx. The SNCR denitration reaction temperature range is 900-1100 ℃, is consistent with the sintered ore bed temperature (1000-1100 ℃) and has a reaction temperature window. In addition, in the sinter bed, a combustion reaction of a part of CO also occurs, which is called secondary CO removal. In addition, the combustion reaction of the dioxin in the high-temperature sintering material layer is utilized, the dioxin is burnt and decomposed, and a part of the dioxin can be removed.
In the specific embodiment of the invention, the internal and external circulation system further comprises a plurality of sealing hoods 2, the flue gas after oxygen supply enters the plurality of sealing hoods 2 through a plurality of branch pipelines respectively, the inner cavity of each sealing hood 2 is communicated with the charge level of the sintering machine 1, and the plurality of branch pipelines are provided with flue gas regulating valves 5 for regulating the flue gas entering the sealing hoods 2. Preferably, the sealed hood 2 is fixed above the middle section charge level of the sintering machine 1, one end of the machine head flue 101, the middle front section flue 102 and the middle rear section flue 103 are respectively connected with different air boxes of the sintering machine 1, 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 hood 2 and enters the machine head flue 101, the middle front section flue 102 and the middle rear section flue 103 from different air boxes respectively. Preferably, the seal 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 adjustment according to the oxygen concentration in the seal cover 2. In the embodiment of the invention, four branch pipelines are arranged, each pipeline is provided with a flue gas regulating valve 5, and the opening degrees of the regulating valves 5 are different according to the air permeability and the air demand difference of material layers in different areas, so that the flue gas pressure is kept stable in the sealing cover 2, the micro-negative pressure state is maintained, and the flue gas is prevented from leaking. In order to ensure real-time monitoring of the flue gas pressure, four pressure detection devices 3 are arranged on the sealing cover 2.
In order to further understand the internal and external circulation system of the sintering flue gas, the invention also provides an internal and external circulation method of the sintering flue gas, which comprises the following steps:
step one, flue gas heat exchange comprises the following steps:
opening a first valve 10, and carrying out gas-gas heat exchange on the flue gas in a middle front section flue 102 and the flue gas in a middle rear section flue 103 of the sintering machine 1 through a gas heat exchanger 12 to heat the flue gas in the middle front section and cool the flue gas in the middle rear section;
step two, flue gas internal circulation, external circulation and emission include:
after heat exchange, the flue gas in the middle-front section flue 102 enters an internal circulation device to remove combustion CO, so as to obtain first purified flue gas, a part of the first purified flue gas is introduced into the combustion-supporting flue 30 through the first fan 15 and then enters the built-in combustion furnace 14, and the other part of the first purified flue gas is introduced into the flue gas mixer 9 through the second fan 16.
Meanwhile, the flue gas in the middle-rear section flue 103 and the flue gas in the machine head flue 101 are mixed and then enter the external circulation device for flue gas purification to obtain second purified flue gas, then a part of the second purified flue gas is initiated by the third fan 19 and enters the flue gas mixer 9 through the external circulation flue 28, and the other part of the second purified flue gas is induced by the fourth fan 23 after passing through the desulfurization reactor 21 and the denitration reactor 22 and then is discharged from the chimney 25.
In addition, the circular cooling flue gas in the circular cooling machine 17 enters the flue gas mixer 9 through the circular cooling flue 29, the first purified flue gas, the second purified flue gas and the circular cooling flue gas are mixed in the flue gas mixer 9, and then enter the sealing cover 2 after passing through the ammonia supply of the ammonia injection system 8 of the circulating flue 31 and the oxygen supply of the oxygen uniform distributor 6, and then enter the charge level of the sintering machine 1 to participate in the sintering process; at this time, CO is further combusted in the sintering machine 1, dioxin is decomposed, SNCR reaction is performed, and NOx is removed. The flue gas generated by the material surface layer of the sintering machine 1 enters different air boxes again, and the internal and external circulation process is continued.
In addition, when the internal circulation device is maintained, the first valve 10 is closed in advance, the second valve 11 is opened, 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 dust remover 18 in the external circulation device, then one part of the flue gas enters the external circulation flue 28, and the other part of the flue gas enters the desulfurization and denitrification reaction and is discharged.
In conclusion, the sintering flue gas internal and external circulation system and the circulation method have the following excellent effects:
1. compared with the traditional flue gas circulation technology, the method adopts pure oxygen to supplement the oxygen content of the flue gas, and improves the circulation rate of the sintering flue gas from 20 percent to more than 60 percent;
2. the circular cooling flue gas is introduced into the flue gas circulating system, so that the characteristics of cleanness and high temperature of the circular cooling flue gas are fully utilized, the temperature of the circular flue gas is increased, and the utilization rate of waste heat is increased;
3. an SNCR denitration reaction is carried out by utilizing a material bed temperature window of a sintering machine, so that the concentration of NOx in the flue gas is reduced;
4. and the two-stage CO removal reaction is realized by respectively utilizing material bed temperature windows of the built-in combustion furnace and the sintering machine. The high-concentration CO is changed into valuable, the resource utilization is realized, the CO concentration is reduced, the combustion latent heat of the CO is fully released, the flue gas temperature is increased, and the flue gas waste heat utilization rate is increased.
5. Removing a part of dioxin by utilizing the high temperature of the sintering material layer and the high temperature of the built-in combustion furnace;
6. the process control of the sintering flue gas is combined with the tail end treatment, the comprehensive treatment is realized, and a large amount of investment and operation cost are saved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The utility model provides an inside and outside circulation system of sintering flue gas which characterized in that, inside and outside circulation system includes: the device comprises an internal circulation device, an external circulation device and a desulfurization and denitrification device;
the internal circulation device is connected with a middle front section flue of a 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 external circulation device is connected with a machine head flue and a middle and rear section flue of the main flue of the sintering machine, and is used for purifying the machine head flue gas and the middle and rear section flue gas of the main flue of the sintering machine to obtain second purified flue gas, wherein one part of the second purified flue gas circulates into the sintering machine, and the other part of the second purified flue gas enters the desulfurization and denitrification device; the flue gas from the middle and rear section flues and the flue gas from the middle and front section flues enter the external circulation device after heat exchange;
and the desulfurization and denitrification device is used for performing desulfurization and denitrification treatment on the second purified flue gas.
2. The internal and external circulation system for sintering flue gas as claimed in claim 1, wherein the first purified flue gas and the second purified flue gas are mixed by a flue gas mixer and then recycled into the sintering machine; the flue gas mixer is connected with the sintering machine through a co-circulating flue, and the mixed flue gas is conveyed into the sintering machine through the co-circulating flue by the flue gas mixer.
3. The internal and external circulation system for sintering flue gas as claimed in claim 2, wherein the internal circulation device comprises a gas heat exchanger and an internal combustion furnace arranged on the internal circulation flue; one end of the internal circulation flue is connected with a middle front section flue of the sintering machine, the other end of the internal circulation flue is connected with the flue gas mixer, and 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;
preferably, the flue gas from the middle front section flue and the flue gas from the middle rear section flue exchange heat through a gas heat exchanger, and a first valve is arranged on the internal circulation flue in front of the gas heat exchanger;
preferably, a combustion-supporting flue is arranged on the internal circulation flue behind the built-in combustion furnace, and the combustion-supporting flue is connected to the inlet of the built-in combustion furnace from the internal circulation flue;
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;
further preferably, the internal circulation flues in front of and behind the built-in combustion furnace are provided with CO concentration analyzers.
4. The internal and external circulation system for sintering flue gas as claimed in claim 2, wherein flue gas from the head flue of the sintering machine and the middle and rear section flues of the sintering machine is mixed in an external discharge flue and then is purified to obtain second purified flue gas, the second purified flue gas enters the flue gas mixer through the external circulation flue, and the flue gas enters the sintering machine through the external discharge flue, the external circulation flue and the co-circulation flue in sequence to complete external circulation of the flue gas;
the external circulation device comprises a machine head electric dust remover arranged on an external discharge flue and used for purifying the mixed flue gas in the external discharge flue, a third fan is arranged on the external discharge flue behind the machine head electric dust remover, 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;
preferably, an overhaul flue is further arranged between the middle front section flue and the outer circulating device and used for circulation and cyclic utilization of the middle front section flue gas when the inner circulating device is overhauled, and a second valve is arranged on the overhaul flue.
5. The internal and external circulation system for sintering flue gas as claimed in claim 2, wherein the internal and external circulation system further comprises a ring cooling device, the ring cooling device comprises a ring cooling machine, and the ring cooling machine is connected to the inlet of the flue gas mixer through a ring cooling flue.
6. The internal and external circulation system for sintering flue gas as claimed in any one of claims 2 to 5, wherein the internal and external circulation system further comprises an ammonia gas injection system and an oxygen supply device which are arranged on the co-circulation flue in sequence along the circulation direction of the flue gas;
preferably, the oxygen supply device comprises an oxygen distributor connected to an outlet of the oxygen buffer tank, and oxygen ejected from the oxygen distributor enters the co-circulation flue;
preferably, the oxygen is pure oxygen, and the purity of the oxygen reaches more than 98%.
7. The internal and external circulation system for sintering flue gas as claimed in claim 6, wherein the internal and external circulation system further comprises a plurality of sealing hoods, the flue gas after oxygen supply enters the plurality of sealing hoods through a plurality of branch pipelines respectively, the inner cavities of the sealing hoods are communicated with the charge level of the sintering machine, and a flue gas regulating valve is arranged on each branch pipeline and used for regulating the flue gas entering the sealing hoods;
preferably, the sealing cover is fixed above the material level of the middle section of the sintering machine, one end of each of the machine head flue, the middle front section flue and the middle rear section flue is respectively connected with different air boxes of the sintering machine, flue gas in the circulating flue of the sintering machine enters the middle section of the sintering machine from the sealing cover, and flue gas in the sintering machine enters the machine head flue, the middle front section flue and the middle rear section flue from different air boxes;
preferably, the seal cover is provided with a pressure detection device and an oxygen concentration analyzer, the oxygen concentration analyzer is connected with the oxygen supply device, and the oxygen supply process is automatically controlled according to the oxygen concentration in the seal cover.
8. The internal and external circulation system for sintering flue gas as claimed in claim 1, wherein the desulfurization and denitrification device comprises a desulfurization reactor, a denitrification reactor and a chimney which are arranged and communicated in sequence along the flue gas transmission direction, and the second purified flue gas is treated by the desulfurization reactor and the denitrification reactor and then discharged by the chimney;
preferably, a CEMS analyzer and a fourth fan are arranged in front of the chimney and are respectively used for testing pollutant components in the smoke before emission and induced air.
9. A sintering flue gas internal and external circulation method is characterized by comprising the following steps:
step one, flue gas heat exchange comprises the following steps:
flue gas in a middle front section flue and flue gas in a middle rear section flue of the sintering machine exchange heat;
step two, flue gas internal circulation, external circulation and emission include:
after heat exchange, enabling the flue gas in the middle-front section flue to enter an internal circulation device for removing and burning CO to obtain first purified flue gas, and enabling the first purified flue gas to enter the sintering machine through internal circulation; and mixing the flue gas in the middle-rear section flue and the flue gas in the machine head flue, then feeding the mixture into an external circulation device for flue gas purification to obtain second purified flue gas, then feeding one part of the second purified flue gas into the sintering machine through external circulation, and discharging the other part of the second purified flue gas from a chimney after desulfurization and denitrification.
10. The method for internal and external circulation of sintering flue gas as claimed in claim 9, wherein the method further comprises steps of ammonia gas supply and oxygen gas supply of sintering flue gas:
mixing the first purified flue gas entering the internal circulation and the second purified flue gas entering the external circulation by additional supplemented ammonia gas and oxygen gas, and then entering the sintering machine;
preferably, the first purified flue gas and the second purified flue gas are mixed with flue gas generated by a circular cooling device before ammonia gas and oxygen gas are supplied, and the flue gas of the circular cooling device is used for supplying oxygen to the flue gas of an internal and external circulation system so as to realize reutilization;
preferably, the method is performed using the system of any one of claims 1-8.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113390269A (en) * | 2021-05-25 | 2021-09-14 | 鞍钢股份有限公司 | Sintering machine flue gas recycling system and method |
| CN113390270A (en) * | 2021-05-26 | 2021-09-14 | 鞍钢股份有限公司 | Iron ore sintering method and device for reducing emission of sulfide and nitride |
| CN114485196A (en) * | 2022-03-28 | 2022-05-13 | 华北理工大学 | Method for carrying out denitration in sintering process by using various flue gases |
| CN117109323A (en) * | 2023-10-16 | 2023-11-24 | 星远智维邯郸环境科技有限公司 | Device for reducing CO in sintering flue gas and treatment method |
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2020
- 2020-04-08 CN CN202010270716.9A patent/CN111569623A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113390269A (en) * | 2021-05-25 | 2021-09-14 | 鞍钢股份有限公司 | Sintering machine flue gas recycling system and method |
| CN113390270A (en) * | 2021-05-26 | 2021-09-14 | 鞍钢股份有限公司 | Iron ore sintering method and device for reducing emission of sulfide and nitride |
| CN114485196A (en) * | 2022-03-28 | 2022-05-13 | 华北理工大学 | Method for carrying out denitration in sintering process by using various flue gases |
| CN114485196B (en) * | 2022-03-28 | 2022-07-01 | 华北理工大学 | Method for denitration in sintering process by using various flue gases |
| CN117109323A (en) * | 2023-10-16 | 2023-11-24 | 星远智维邯郸环境科技有限公司 | Device for reducing CO in sintering flue gas and treatment method |
| CN117109323B (en) * | 2023-10-16 | 2024-02-02 | 星远智维邯郸环境科技有限公司 | Device for reducing CO in sintering flue gas and treatment method |
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