A recycling device and treatment method for flue gas emitted from converter of steel plant

Abstract

A device for recycling and utilizing flue gas emitted from a converter in a steel plant and a method for treating the same relate to a device for recycling and utilizing flue gas and a method for treating the same. The present invention is to solve the problems of energy waste and environmental pollution in the prior art when treating flue gas emitted from converter steelmaking. The present invention recycles the flue gas emitted during converter steelmaking, and the flue gas is completely burned in the flue gas reaction unit to release all the heat. A rapid cooling unit is used to recover the heat and convert it into steam for comprehensive utilization by the enterprise. After heat exchange, the temperature of the high-temperature flue gas is reduced to below 140°C, and then it is treated by an SCR‑SNCR coupled denitrifier, a dust collector and a secondary desulfurizer before being discharged into the atmosphere; thereby avoiding air pollution and energy waste, and reducing carbon monoxide emissions from the source. The present invention belongs to the field of energy conservation, environmental protection and flue gas treatment technology in the steel industry.

Description

Technical Field

[0001] The invention relates to a flue gas recovery and utilization device and a treatment method, in particular to a flue gas recovery and utilization device and a treatment method for flue gas emitted from a converter in a steel plant, and belongs to the technical field of energy conservation, environmental protection and flue gas treatment in the steel industry. Background Art

[0002] In converter steelmaking, oxygen top-blowing converter steelmaking process is currently the most commonly used process. After adding materials according to the batching requirements, the oxygen spray gun is inserted into the furnace from the top of the furnace to blow oxygen (high-pressure oxygen flow with a purity greater than 99%) into the furnace, so that it directly reacts with the high-temperature molten iron to remove impurities. The converter will produce a large amount of brown smoke during the oxygen top-blowing process, and its main components are iron oxide dust and high-concentration carbon monoxide gas (converter gas). The concentration of carbon monoxide is parabolically related to the oxygen blowing time.

[0003] After purification, the converter flue gas generated during converter production has two process paths. One path is that when the carbon monoxide concentration is appropriate, this part of the gas enters the gas storage cabinet for storage, recovery, and reuse to become converter gas; the other path is to release and empty it when the carbon monoxide concentration is not appropriate. Since a large amount of carbon monoxide is only generated during the carbon oxidation period (middle period) during converter blowing, and the amount of furnace gas generated in the early stage of blowing and near the end is small and the carbon monoxide content is low and the oxygen content is high, this part of the flue gas cannot be recycled and needs to be released, which is usually called "converter released flue gas". At this time, carbon monoxide is discharged with the characteristics of "unstable concentration and intermittent".

[0004] According to statistics, 120-140m3 of crude steel is recovered for every ton of crude steel produced during converter steelmaking. 3 Converter gas, flue gas emission about 300m 3 The average concentration of carbon monoxide in the flue gas is 6-12%. The national crude steel output is 1.033 billion tons per year, and the annual carbon monoxide released is as high as 18.5-37.9 billion cubic meters, equivalent to 8-16 million tons of standard coal. A large amount of carbon monoxide is emitted into the atmosphere, causing air pollution and energy waste, which is not conducive to energy conservation and emission reduction.

[0005] At present, there are three main ways of venting: one is to vent directly to the air, which is also the method chosen by most steel companies; the second is that some steel companies choose to add ignition devices at the venting port to ignite the gas with high gas concentration; the third is that a few steel companies use co-firing devices to ignite all the gas in the venting part. However, no matter which venting method is used, a lot of energy waste and environmental pollution are generated.

[0006] In summary, how to propose a new flue gas recovery and utilization device and treatment method to address the above technical problems has become an urgent problem to be solved by technicians in this field. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a device and a method for recovering and utilizing flue gas emitted from a converter in a steel plant.

[0008] The technical solution of the present invention is: a device for recycling flue gas emitted from a converter in a steel plant comprises a flue gas emission reaction unit, a rapid cooling unit and a tail gas treatment unit which are sequentially connected through a flue gas exhaust pipeline.

[0009] A low-nitrogen combustion nozzle is installed on the flue gas emission reaction unit, and the low-nitrogen combustion nozzle is connected to a blower through a pipeline, and a heat storage body is installed at the nozzle of the low-nitrogen combustion nozzle.

[0010] The rapid cooling unit is connected with a superheater, a reheater and an economizer in sequence according to the flow direction of the flue gas; the working fluid inlet of the economizer is connected to the desalted water inlet on the rapid cooling unit, and the working fluid outlet of the superheater is connected to the steam outlet on the rapid cooling unit.

[0011] The tail gas treatment unit includes a primary desulfurizer, a dust collector, a secondary desulfurizer and two SCR-SNCR coupled denitrifiers; the primary desulfurizer is installed in the flue gas reaction unit, and the two SCR-SNCR coupled denitrifiers are respectively arranged at the flue gas outlets of the flue gas reaction unit and the rapid cooling unit, the dust collector and the secondary desulfurizer connected in sequence through the exhaust pipe are arranged at the flue gas outlet of the rapid cooling unit, and the secondary desulfurizer is connected to the chimney.

[0012] Furthermore, it also includes a water supply pump, which is connected to the desalted water inlet.

[0013] Furthermore, the tail gas treatment unit also includes an induced draft fan, which is installed on the smoke exhaust pipeline between the secondary desulfurizer and the chimney.

[0014] The present invention also provides a method for treating flue gas emitted from a converter in a steel plant, which is specifically carried out in the following steps:

[0015] Step 1: spraying a mixture of flue gas and combustion-supporting air into the flue gas reaction unit, and the high-temperature flue gas generated after the mixture is burned in the flue gas reaction unit is sequentially passed through a primary desulfurizer and an SCR-SNCR coupled denitrifier for desulfurization and denitrification treatment;

[0016] Step 2: The high-temperature flue gas treated in the flue gas reaction unit enters the rapid cooler device through the exhaust pipe. The high-temperature flue gas first exchanges heat with the desalted water. After the heat exchange, the high-temperature flue gas becomes low-temperature tail gas, and then the low-temperature tail gas flows through the SCR-SNCR coupled denitrifier for denitrification treatment;

[0017] Step 3: The low-temperature tail gas enters the dust collector through the smoke exhaust pipeline, processes the particulate matter in the dust collector, and then undergoes secondary desulfurization in the secondary desulfurizer. Finally, the low-temperature tail gas enters the chimney through the induced draft fan and is discharged to the outside.

[0018] Compared with the prior art, the present invention has the following effects:

[0019] 1. The present invention recycles the flue gas emitted in the converter steelmaking process. The flue gas is completely burned in the flue gas reaction unit 4 to release all the heat, and the rapid cooling unit 7 is used to recover the heat and convert it into steam for comprehensive utilization by the enterprise. The temperature of the high-temperature flue gas after heat exchange is reduced to below 140°C, and then it is processed by the SCR-SNCR coupled denitrifier 6, the dust collector 10 and the secondary desulfurizer 11 and discharged into the atmosphere; thereby avoiding air pollution and energy waste, and reducing carbon monoxide emissions from the source.

[0020] 2. The present invention is specially designed for the characteristics of large flue gas emission and intermittent emission: a heat storage body is installed at the nozzle of the low-nitrogen combustion nozzle 1 to realize the heat storage self-sustaining combustion mode, so that the low-nitrogen combustion nozzle 1 has both pulse combustion characteristics and low-nitrogen combustion characteristics, which solves the problem that the intermittently emitted flue gas cannot be fully burned and is difficult to burn stably; such a design can not only ensure the full combustion of carbon monoxide in the emitted flue gas, but also avoid excessive combustion temperature caused by excessive carbon monoxide concentration, thereby forming an unstable state.

[0021] 3. The present invention reduces gas emission, reduces energy waste, and generates certain economic benefits after the heat of the emitted flue gas is recovered and utilized.

[0022] 4. The present invention eliminates the ignition or co-firing process in the prior art, reduces energy waste and process energy consumption, and thus reduces carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the present invention;

[0024] Figure 2 It is a schematic structural diagram of the rapid cooling unit 7 of the present invention.

[0025] In the figure: 1. low nitrogen combustion nozzle, 2. exhaust gas inlet, 3. blower, 4. exhaust gas reaction unit, 5. primary desulfurizer, 6. SCR-SNCR coupled denitrifier, 7. rapid cooling unit, 7-1. superheater, 7-2. reheater, 7-3. economizer, 8. steam outlet, 9. desalted water inlet, 10. dust collector, 11. secondary desulfurizer, 12. feed water pump, 13. ash remover, 14. induced draft fan, 15. chimney. DETAILED DESCRIPTION

[0026] In order to make the purpose, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] Specific implementation method 1: Combination Figure 1 to Figure 2 The present embodiment is described as follows. A device for recycling flue gas emitted from a converter in a steel plant comprises a flue gas emission reaction unit 4, a rapid cooling unit 7 and a tail gas treatment unit which are sequentially connected via a flue gas exhaust pipeline.

[0028] A low-nitrogen combustion nozzle 1 is installed on the flue gas emission reaction unit 4 , and the low-nitrogen combustion nozzle 1 is connected to a blower 3 through a pipeline, and a heat storage body is installed at the nozzle of the low-nitrogen combustion nozzle 1 .

[0029] The rapid cooling unit 7 is connected with a superheater 7-1, a reheater 7-2 and an economizer 7-3 in sequence according to the flow direction of the flue gas; and the working fluid inlet of the economizer 7-3 is connected to the desalted water inlet 9 on the rapid cooling unit 7, and the working fluid outlet of the superheater 7-1 is connected to the steam outlet 8 on the rapid cooling unit 7.

[0030] The exhaust gas treatment unit includes a primary desulfurizer 5, a dust collector 10, a secondary desulfurizer 11 and two SCR-SNCR coupled denitrifiers 6; the primary desulfurizer 5 is installed in the flue gas reaction unit 4, and the two SCR-SNCR coupled denitrifiers 6 are respectively arranged at the flue gas outlets of the flue gas reaction unit 4 and the rapid cooling unit 7, the dust collector 10 and the secondary desulfurizer 11 connected in sequence through the exhaust pipe are arranged at the flue gas outlet of the rapid cooling unit 7, and the secondary desulfurizer 11 is connected to the chimney 15.

[0031] In view of the characteristics of large flue gas emission and intermittent emission, a special design is made in this embodiment: a heat storage body is installed at the nozzle of the low-nitrogen combustion nozzle 1 to realize the heat storage self-sustaining combustion mode, so that the low-nitrogen combustion nozzle 1 has both pulse combustion characteristics and low-nitrogen combustion characteristics. Such a design can not only ensure that the carbon monoxide in the flue gas is fully burned, but also avoid the excessive combustion temperature caused by excessive carbon monoxide concentration, forming an unstable state.

[0032] In this embodiment, the blower 3 mainly provides combustion air. After the combustion air is pressurized by the blower 3, it is mixed with the flue gas introduced from the flue gas interface 2. The mixed gas burns in the flue gas reaction unit 4. At the same time, under the action of the heat storage body, the temperature stability in the flue gas reactor device 4 is guaranteed.

[0033] Specific implementation method 2: Combination Figure 1 to Figure 2 This embodiment further includes a feed water pump 12, which is connected to the desalted water inlet 9. This arrangement facilitates the desalted water to be transported to the superheater 7-1, the reheater 7-2 and the economizer 7-3 through the desalted water inlet 9, and the high-temperature flue gas exchanges heat with the desalted water to generate high-temperature subcritical steam, which is then sent to users through the steam outlet 8 for unified use.

[0034] Furthermore, the tail gas treatment unit further includes an induced draft fan 14, which is installed on the exhaust pipe between the secondary desulfurizer 11 and the chimney 15. In this way, by adjusting the wind force of the induced draft fan 14 and thus controlling the flue gas flow rate, the high-temperature flue gas can be quickly heat exchanged and cooled to achieve the effect of inhibiting the regeneration of dioxins.

[0035] Furthermore, the tail gas treatment unit further includes a dust collector 13 , which is installed at the bottom of the dust collector 10 .

[0036] Other components and connection relationships are the same as those in the first specific implementation method.

[0037] Specific implementation method three: Combination Figure 1 to Figure 2 This embodiment is described. A method for treating flue gas emitted from a converter in a steel plant is carried out according to the following steps:

[0038] Step 1: spraying a mixture of flue gas and combustion-supporting air into the flue gas reaction unit 4; the high-temperature flue gas generated after the mixture is burned in the flue gas reaction unit 4 passes through a primary desulfurizer 5 and an SCR-SNCR coupled denitrifier 6 in sequence for desulfurization and denitrification treatment;

[0039] Step 2: The high-temperature flue gas treated in the flue gas reaction unit 4 enters the rapid cooler device 7 through the exhaust pipe, and the high-temperature flue gas first exchanges heat with the desalted water, and the high-temperature flue gas after the heat exchange becomes low-temperature tail gas, and then the low-temperature tail gas flows through the SCR-SNCR coupled denitrifier 6 for denitrification treatment;

[0040] Step 3: The low-temperature tail gas enters the dust collector 10 through the smoke exhaust pipeline, processes particulate matter in the dust collector 10, and then undergoes secondary desulfurization in the secondary desulfurizer 11. Finally, the low-temperature tail gas enters the chimney 15 through the induced draft fan 14 and is discharged to the outside.

[0041] In this embodiment, the temperature of the high-temperature flue gas after heat exchange is reduced to below 140° C., and then it is processed by the SCR-SNCR coupled denitrifier 6, the dust collector 10 and the secondary desulfurizer 11 before being discharged into the atmosphere.

[0042] Other components and connection relationships are the same as those in the first or second specific implementation.

[0043] How it works

[0044] The flue gas is introduced into the low-nitrogen combustion nozzle through the flue gas interface 2, the combustion-supporting air is pressurized by the blower 3 and mixed with the flue gas, and the mixed gas is burned in the flue gas reaction unit 4. At the same time, under the action of the heat storage body, the temperature stability in the flue gas reactor device 4 is guaranteed, which solves the problem that the intermittently discharged flue gas cannot be fully burned and is difficult to burn stably.

[0045] The high-temperature flue gas generated after the combustion of the flue gas is first desulfurized by the primary desulfurizer 5 before being discharged from the flue gas reaction unit 4, and then denitrated by the SCR-SNCR coupled denitrifier 6; the high-temperature flue gas treated in the flue gas reaction unit 4 enters the rapid cooling unit to exchange heat with the desalted water; the heated desalted water forms high-quality steam, which is discharged from the steam outlet 8 for users to use, thereby achieving the effect of waste heat utilization; the high-temperature flue gas after heat exchange becomes low-temperature exhaust gas with a temperature below 140°C, is treated with particulate matter by the dust collector 10, and then undergoes secondary desulfurization in the secondary desulfurizer 11, and finally enters the chimney 15 through the induced draft fan 14 and is discharged to the outside.

[0046] The present invention has been disclosed as above in the form of a preferred embodiment, but it is not intended to limit the present invention. Any simple modification, equivalent changes and modifications made to the above implementation cases by any professional and technical personnel who do not deviate from the content of the technical solution of the present invention and based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A recovery and utilization device for the converter off-gas in a steel plant, characterized in that: it includes a off-gas reaction unit (4), a rapid cooling unit (7) and a tail gas treatment unit connected in sequence through a smoke exhaust pipeline; a low-nitrogen combustion nozzle (1) is installed on the off-gas reaction unit (4), and the low-nitrogen combustion nozzle (1) is connected to a blower (3) through a pipeline, and a heat storage body is installed at the nozzle of the low-nitrogen combustion nozzle (1); in the rapid cooling unit (7), a superheater (7-1), a reheater (7-2) and an economizer (7-3) are connected in sequence according to the flow direction of the flue gas; and the working medium inlet of the economizer (7-3) is connected to the desalted water inlet (9) on the rapid cooling unit (7), and the working medium outlet of the superheater (7-1) is connected to the steam outlet (8) on the rapid cooling unit (7); the tail gas treatment unit includes a primary desulfurizer (5), a dust collector (10), a secondary desulfurizer (11) and two SCR-SNCR coupled denitrators (6); the primary desulfurizer (5) is installed in the off-gas reaction unit (4), the two SCR-SNCR coupled denitrators (6) are respectively arranged at the flue gas outlets of the off-gas reaction unit (4) and the rapid cooling unit (7), the dust collector (10) and the secondary desulfurizer (11) connected in sequence through a smoke exhaust pipeline are arranged at the flue gas outlet of the rapid cooling unit (7), and the secondary desulfurizer (11) is communicated with the chimney (15).

2. A recovery and utilization device for the converter off-gas in a steel plant according to claim 1, characterized in that: it further includes a feed water pump (12), and the feed water pump (12) is connected to the desalted water inlet (9).

3. A recovery and utilization device for the converter off-gas in a steel plant according to claim 2, characterized in that: the tail gas treatment unit further includes an induced draft fan (14), and the induced draft fan (14) is installed on the smoke exhaust pipeline between the secondary desulfurizer (11) and the chimney (15).

4. A recovery and utilization device for the converter off-gas in a steel plant according to claim 3, characterized in that: the tail gas treatment unit further includes an ash remover (13), and the ash remover (13) is installed at the bottom of the dust collector (10).

5. A method for treating the converter off-gas in a steel plant, which uses a recovery and utilization device for the converter off-gas in a steel plant according to any one of claims 1-4, characterized in that: the method is specifically carried out according to the following steps: Step 1: Inject a mixture of off-gas and combustion-supporting air into the off-gas reaction unit (4), and the high-temperature flue gas generated after the mixture burns in the off-gas reaction unit (4) is successively subjected to desulfurization and denitration treatment through the primary desulfurizer (5) and the SCR-SNCR coupled denitrator (6); Step 2: The high-temperature flue gas treated in the off-gas reaction unit (4) enters the rapid cooler device (7) through the smoke exhaust pipeline. The high-temperature flue gas first exchanges heat with desalted water, and the high-temperature flue gas after heat exchange becomes low-temperature tail gas. Then the low-temperature tail gas flows through the SCR-SNCR coupled denitrator (6) for denitration treatment; Step 3: The low-temperature tail gas enters the dust collector (10) through the smoke exhaust pipeline, processes particulate matter in the dust collector (10), and then undergoes secondary desulfurization in the secondary desulfurizer (11). Finally, the low-temperature tail gas enters the chimney (15) through the induced draft fan (14) and is discharged to the outside.

Images