CN111203083B - Sintering flue gas desulfurization and denitrification process - Google Patents

Sintering flue gas desulfurization and denitrification process Download PDF

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CN111203083B
CN111203083B CN202010117621.3A CN202010117621A CN111203083B CN 111203083 B CN111203083 B CN 111203083B CN 202010117621 A CN202010117621 A CN 202010117621A CN 111203083 B CN111203083 B CN 111203083B
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flue gas
flue
sintering
desulfurization
circulating
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CN111203083A (en
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王�锋
齐渊洪
王海风
周和敏
严定鎏
林万舟
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Central Iron and Steel Research Institute
CISRI Sunward Technology Co Ltd
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CISRI Sunward Technology Co Ltd
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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
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75—Multi-step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D50/00—Combinations of methods or devices for separating particles from gases or vapours
    • 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
    • B01D53/50—Sulfur oxides
    • 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
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/80—Semi-solid phase processes, i.e. by using slurries
    • 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
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8631—Processes characterised by a specific device
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/001—Extraction of waste gases, collection of fumes and hoods used therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/004—Systems for reclaiming waste heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/008—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases cleaning gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27M—INDEXING SCHEME RELATING TO ASPECTS OF THE CHARGES OR FURNACES, KILNS, OVENS OR RETORTS
    • F27M2003/00—Type of treatment of the charge
    • F27M2003/04—Sintering
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

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Abstract

The invention discloses a sintering flue gas desulfurization and denitrification process, belongs to the field of metallurgical industry, and solves the problems of high investment and high operation cost of the sintering flue gas desulfurization and denitrification process in the prior art. The method comprises the following steps: sintering flue gas of a sintering machine is subjected to a flue gas circulation process, and the flue gas is divided into two parts of flue gas to be subjected to desulfurization and denitrification and circulating flue gas; desulfurizing and pressurizing the flue gas to be desulfurized and denitrated, and then desulfurizing and dedusting the desulfurized flue gas; the flue gas after dust removal is blown into a material layer of the high-temperature section of the circular cooler by a blower of the high-temperature section of the circular cooler to exchange heat with the hot sintering ore and heat up; the flue gas after heat exchange and temperature rise is subjected to coarse dust removal and then enters a denitration reactor for denitration; the denitrated flue gas enters a waste heat recovery unit for cooling, and the cooled flue gas is firstly dedusted and then led out by an induced draft fan; the extracted flue gas is directly discharged from a chimney. The process has low cost and energy conservation, and is suitable for desulfurization and denitrification treatment of sintering flue gas.

Description

Sintering flue gas desulfurization and denitrification process
Technical Field
The invention relates to the field of metallurgical industry, in particular to a sintering flue gas desulfurization and denitrification process.
Background
The sintering flue gas is waste gas containing pollutants generated in the production process of a sintering machine, at present, iron and steel enterprises are carrying out ultralow-emission desulfurization, denitrification and dedusting modification, and SO in the modified flue gas2The concentration is 35mg/Nm3Interior of NOxThe concentration is 50mg/Nm3The concentration of fine particulate matter is within 10mg/Nm3Within.
The existing desulfurization and denitrification processes mainly comprise an active coke desulfurization and denitrification process, a dry (semi-dry) desulfurization and flue gas concurrent heating and denitrification process and a flue gas oxidation desulfurization and denitrification process. The activated coke desulfurization and denitrification process can meet the requirement of ultralow emission, but has high investment and high operation cost; compared with the activated coke desulfurization and denitrification process, the dry (semi-dry) desulfurization, flue gas concurrent heating and denitrification process has less investment, but needs concurrent combustion and heating of the flue gas, consumes a large amount of coal gas, and therefore, has higher denitrification cost; the implementation method of the flue gas oxidation desulfurization and denitration process is simple, but the ozone is used as the oxidant to oxidize NO, so that the emission of ozone is easily caused, and secondary pollution is caused.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a sintering flue gas desulfurization and denitration process, which can solve at least one of the following technical problems: (1) the existing sintering flue gas desulfurization and denitrification process has large investment and high operation cost; (2) secondary pollution exists.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a sintering flue gas desulfurization process, which comprises the following steps:
s1, dividing the sintering flue gas of the sintering machine into two parts of flue gas to be desulfurized and denitrated and circulating flue gas through a flue gas circulating process;
s2, desulfurizing and pressurizing the flue gas to be desulfurized and denitrated, and then dedusting the desulfurized flue gas;
s3, blowing the flue gas subjected to desulfurization and dust removal into a high-temperature section material layer of the ring cooling machine by a blower at the high-temperature section of the ring cooling machine to perform heat exchange with hot sinter and heat rise;
s4, roughly dedusting the flue gas subjected to heat exchange and temperature rise, and then feeding the flue gas into a denitration reactor for denitration;
s5, cooling the denitrated flue gas in a waste heat recovery unit, and dedusting the cooled flue gas and then leading out the flue gas by a draught fan;
and S6, directly discharging the extracted flue gas from a chimney.
Further, in S1, the flue gas recycling process includes two processes: an internal circulation process and an external circulation process;
the internal circulation process takes part of sintering flue gas in the air box as circulating flue gas, and the circulating flue gas directly reaches the sintering machine through a circulating flue; the flue gas in the other bellows is divided into two paths as the flue gas needing desulfurization and denitrification, and the two paths respectively pass through an electric dust collector and a main exhaust fan of the flue A or an electric dust collector and a main exhaust fan of the flue B, and then are combined to a main flue gas pipeline to carry out the steps S2-S6;
the external circulation process divides the sintering flue gas in the air box into two parts which respectively pass through an electric dust remover and a main exhaust fan of the flue A or an electric dust remover and a main exhaust fan of the flue B, then one part of the mixture is taken as the circulation flue gas and reaches the sintering machine through the circulation flue, and the other part of the mixture is taken as the flue gas to be desulfurized and denitrated to carry out the steps S2-S6.
Further, in S4, before the flue gas enters the denitration reactor, the ammonia water supply unit sprays ammonia water into the flue.
Further, in S3, the method further includes that air is used as a cooling medium in the low-temperature section of the circular cooler, the air cools the sintered ore to obtain low-temperature exhaust gas with a temperature higher than 70 ℃, and the low-temperature exhaust gas is sent into a smoke hood on the sintering machine through an exhaust gas circulating fan to be used as a gas source for sintering.
Further, in S6, a part of the extracted flue gas is directly discharged from the chimney, and another part of the extracted flue gas is recycled as the circulating exhaust gas to the high-temperature blowing section of the circular cooler to be mixed with the low-temperature exhaust gas as a gas source for sintering.
Further, in S1, the initial SO of the sintering flue gas2The content is 400-2000 mg/Nm3，NOxThe content is 120-350 mg/Nm3The content of dust is>1g/Nm3。
Further, the sintering flue gas desulfurization and denitrification device adopted by the sintering flue gas desulfurization and denitrification process comprises a sintering machine, a circular cooler, an air box, a flue A, a flue B, a main flue gas pipeline and a chimney; the quantity of the air boxes is multiple, the air boxes are uniformly and symmetrically distributed on two sides of the sintering machine, part or all of the air boxes on one side of the sintering machine are connected with the flue A, and part or all of the air boxes on the other side of the sintering machine are connected with the flue B; the flue A and the flue B are combined and then connected with one end of a main flue gas pipeline, and a desulfurization unit, a denitration reactor and a waste heat recovery unit are arranged on the main flue gas pipeline; the annular cooling machine is arranged between the desulfurization unit and the denitration reactor and comprises a high-temperature section and a low-temperature section; the tail end of the main flue gas pipeline is connected with a chimney.
Furthermore, the wind power generation device also comprises a circulating flue, wherein one end of the circulating flue is connected with part of the wind boxes, and the other end of the circulating flue is connected with the wind cover;
or the circulating flue is also included, and the flue A and the flue B are combined and then connected with the circulating flue and the main flue gas pipeline through a tee joint unit; the other end of the circulating flue is connected with the fan cover.
Furthermore, n branch pipelines are also arranged on the main flue gas pipeline, blowers are arranged on the branch pipelines, and the branch pipelines are connected with the high-temperature section of the circular cooler; the low-temperature section of the circular cooler is connected with the fan cover through the waste gas circulation flue.
Further, a high-temperature dust remover and an ammonia water supply unit are arranged between the circular cooler and the denitration reactor; and a third dust remover and an induced draft fan are also arranged between the waste heat recovery unit and the chimney.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
a) the sintering flue gas desulfurization and denitrification process provided by the invention has the advantages that the flue gas is divided into two parts, one part is flue gas to be desulfurized and denitrified, the subsequent desulfurization and denitrification treatment is carried out, and the other part is used as circulating flue gas and used as a gas source of the sintering flue gas; like this can greatly reduced need the volume of SOx/NOx control flue gas, reduce the load of follow-up sweetener, denitration device etc. can guarantee to the appropriate denitration temperature with the flue gas heat transfer, guarantee the denitration effect, utilize the circulation flue gas as the air supply of sintering flue gas simultaneously, because the circulation flue gas has certain temperature (for example, this part flue gas temperature is 110 ~200 ℃), can reduce the energy consumption of sintering machine through the heat that utilizes this part flue gas, practice thrift the energy consumption > 1%.
b) The desulfurization and denitrification process for the sintering flue gas desulfurization and denitrification process has the advantages that the annular cooler and the main flue gas pipeline are arranged together, the flue gas is heated to the denitrification temperature through heat exchange with hot sintering ores in the annular cooler, so that the denitration is carried out, heating equipment is not required to be additionally used for heating the flue gas to be denitrated, the investment is low, and reasonable utilization of energy is realized.
c) In the sintering flue gas desulfurization and denitrification process, the waste heat of the low-temperature section of the circular cooler is utilized to heat air and then the air is used as an air source of a sintering machine. The energy consumption of the sintering machine can be reduced due to the heat of the gas after heat exchange; through the cold quick-witted circulating fan of ring that passes through on the C flue with the partial flue gas after the denitration recirculating to the high temperature section of the cold machine of ring be used for adjusting the cooling amount of wind of high temperature section, simultaneously, can utilize the temperature of this part flue gas, be favorable to waste heat recovery.
d) The sintering flue gas desulfurization and denitration process provided by the invention can realize multi-pollutant removal, is low in cost, saves the denitration cost by more than 15%, and has great popularization value.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic structural diagram of a sintering flue gas desulfurization and denitrification apparatus according to a first embodiment of the invention;
FIG. 2 is a schematic structural diagram of a sintering flue gas desulfurization and denitrification apparatus according to a second embodiment of the invention;
fig. 3 is a schematic structural diagram of a sintering flue gas desulfurization and denitrification apparatus according to a third embodiment of the invention.
Reference numerals:
1-sintering machine; 2-circular cooler; 3-an air box; 4-a first dust remover; 5-a second dust remover; 6-a first main exhaust fan; 7-a second main exhaust fan; 8-a desulfurization booster fan; 9-a desulfurization unit; 10-a desulfurizing dust remover; 11-main flue gas duct; 12-ring cooler feed inlet; 13-discharge port of circular cooler; 14-a first blower; 15-a second blower; 16-a third blower; 17-a fourth blower; 18-a fifth blower; 19-a high temperature dust remover; 19-1-a first high temperature precipitator; 19-2-a second high temperature precipitator; a 20-ammonia water supply unit; 21-a denitration reactor; 21-1-a first denitrification reactor; 21-2-a second denitrification reactor; 22-a waste heat recovery unit; 23-a third precipitator; 24-a draught fan; 25-a chimney; 26-circulating fan of circular cooler; 27-an exhaust gas recirculation fan; 28-flue gas circulation flue; 29-a fourth precipitator; 30-a circulating fan; 31-a circulating flue; 32-wind shield.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
The invention provides a sintering flue gas desulfurization and denitrification process, which comprises the following steps:
s1, dividing the sintering flue gas of the sintering machine into two parts of flue gas to be desulfurized and denitrated and circulating flue gas through a flue gas circulating process;
s2, enabling the flue gas to be desulfurized and denitrated to pass through a desulfurization booster fan and then enter a desulfurization unit for desulfurization, and performing cloth bag dust removal on the desulfurized flue gas;
s3, blowing the flue gas subjected to desulfurization and dust removal into a high-temperature section material layer of the ring cooling machine from a blower at the high-temperature section of the ring cooling machine through a main flue gas pipeline to perform heat exchange with hot sinter and heat rise;
s4, leading the flue gas subjected to heat exchange and temperature rise out of a smoke hood at the high-temperature section of the circular cooler; the flue gas is subjected to coarse dust removal through a high-temperature dust remover, then enters a denitration reactor for denitration, and before the flue gas enters the denitration, an appropriate amount of ammonia water is sprayed into a flue by an ammonia water supply unit;
s5, cooling the denitrated flue gas in a waste heat recovery unit, and dedusting the cooled flue gas and then leading out the flue gas by a draught fan;
and S6, directly discharging the extracted flue gas from a chimney.
In the above S1, the flue gas circulation process includes two processes: an internal circulation process and an external circulation process.
The internal circulation process is characterized in that part of flue gas in the air box is used as circulating flue gas, and the circulating flue gas directly reaches the sintering machine through a circulating flue and is used as an air source for sintering; the flue gas in other air boxes is divided into two streams as flue gas needing desulfurization and denitrification, and the two streams respectively pass through the electric dust remover of the flue A and the main exhaust fan or the electric dust remover and the main exhaust fan of the flue B to carry out preliminary dust removal so as to prevent subsequent equipment from being blocked, and then are combined to the main flue gas pipeline to carry out the steps of S2-S6.
The external circulation process divides the flue gas in the air box into two parts, the two parts respectively pass through the electric dust remover and the main exhaust fan of the flue A and the electric dust remover and the main exhaust fan of the flue B to perform preliminary dust removal so as to prevent subsequent equipment from being blocked, then one part of the mixed flue gas reaches a sintering machine as the circulation flue gas, and the other part of the mixed flue gas is used as the flue gas needing desulfurization and denitrification to perform the steps S2-S6.
In S3, air is used as a cooling medium in the low-temperature section of the circular cooler, the air cools the sintered ore to obtain low-temperature exhaust gas at a temperature higher than 70 ℃, and the low-temperature exhaust gas is sent into a smoke hood of the sintering machine by an exhaust gas circulating fan, mixed with circulating smoke gas, and used as a gas source for sintering; or the air and the circulating waste gas are mixed for heat exchange and then are sent into a smoke hood on the sintering machine through a waste gas circulating fan to be mixed with the circulating smoke gas to be used as an air source for sintering. Because the low-temperature waste gas not only has the same oxygen content as air, but also has a certain temperature, the low-temperature waste gas can completely replace part of air used for sintering, the energy consumption is saved, and the waste gas discharge amount is reduced.
It should be noted that in S1, the flue gas circulation process ensures that the flue gas circulation volume is greater than 20%, so that the flue gas volume that needs to be desulfurized and denitrated can be reduced, and further it is ensured that the circular cooler can exchange heat with the flue gas that needs to be denitrated to the denitration temperature, thereby ensuring the denitration effect and reducing the denitration cost.
Specifically, in the above S1, the initial SO of the sintering flue gas2The content is 400-2000 mg/Nm3(e.g., 780-915 mg/Nm)3)，NOxThe content is 120-350 mg/Nm3(e.g., 218-236 mg/Nm)3) The content of dust is>1g/Nm3。
Specifically, in the above S2, the desulfurization is performed by a dry or semi-dry method, and SO in the flue gas after desulfurization2Content (wt.)<35mg/Nm3。
Specifically, in the above S2, the dust content in the flue gas after the bag-type dust removal<10mg/Nm3。
Due to the adoption of the flue gas circulation process, the amount of flue gas needing desulfurization and denitration is reduced, the temperature of the flue gas subjected to heat exchange and temperature rise in S4 can be ensured to be higher than 220 ℃, for example, the flue gas subjected to heat exchange and temperature rise is divided into two paths, one path of the flue gas is 330-420 ℃, high-temperature denitration can be performed, the other path of the flue gas is 220-280 ℃, and medium-temperature denitration can be performed.
Specifically, in S4, the denitration reactor is a single denitration tower or two denitration towers, and the NOx content in the flue gas after denitration is reduced<50mg/Nm3。
In the above S5, the temperature of the flue gas at the outlet of the waste heat recovery unit is less than 150 ℃.
Specifically, in the above-mentioned S6, SO is contained in the flue gas2The content is 15-32 mg/Nm3，NOxThe content is 40-45 mg/Nm3The dust content is 5-6 mg/Nm3. Meets the requirements.
In a possible design, in S6, one part of the extracted flue gas is directly discharged from a chimney, and the other part of the extracted flue gas is recycled as circulating waste gas through a circulating fan of the circular cooler to a high-temperature blast section of the circular cooler to be mixed with heat-exchanged air to be used as a gas source for sintering.
Compared with the prior art, the sintering flue gas desulfurization and denitrification process provided by the invention has the advantages that the flue gas is divided into two parts, one part is flue gas to be desulfurized and denitrified, the subsequent desulfurization and denitrification treatment is carried out, and the other part is used as circulating flue gas and an air source of the sintering flue gas; like this can greatly reduced need the volume of SOx/NOx control flue gas, reduce the load of follow-up sweetener, denitration device etc. can guarantee to the appropriate denitration temperature with the flue gas heat transfer, guarantee the denitration effect, utilize the circulation flue gas as the air supply of sintering flue gas simultaneously, because the circulation flue gas has certain temperature (for example, this part flue gas temperature is 110 ~200 ℃), can reduce the energy consumption of sintering machine through the heat that utilizes this part flue gas, practice thrift the energy consumption > 1%.
In the sintering flue gas desulfurization and denitrification process, the waste heat of the low-temperature section of the circular cooler is utilized to heat air and then the air is used as an air source of a sintering machine. The energy consumption of the sintering machine can be reduced due to the heat of the gas after heat exchange; through the cold quick-witted circulating fan of ring that passes through on the C flue with the partial flue gas after the denitration recirculating to the high temperature section of the cold machine of ring be used for adjusting the cooling amount of wind of high temperature section, simultaneously, can utilize the temperature of this part flue gas, be favorable to waste heat recovery.
It should be noted that, the sintering flue gas desulfurization and denitrification device used in the sintering flue gas desulfurization and denitrification process is as follows, referring to fig. 1 to fig. 3, the sintering flue gas desulfurization and denitrification device includes a sintering machine 1, a circular cooler 2, a wind box 3, a flue a, a flue B, a main flue gas pipeline 11 and a chimney 25; the quantity of the air boxes 3 is multiple, the air boxes 3 are uniformly and symmetrically distributed on two sides of the sintering machine 1, part or all of the air boxes on one side of the sintering machine 1 are connected with the flue A, and part or all of the air boxes on the other side of the sintering machine 1 are connected with the flue B; the A flue and the B flue are combined and then connected with one end of a main flue gas pipeline 11, and a desulfurization unit 9 and a denitration reactor 21 are arranged on the main flue gas pipeline; the circular cooler 2 is arranged between the desulfurization unit 9 and the denitration reactor 21; the tail end of the main flue gas duct 11 is connected to a stack 25.
Considering that the amount of flue gas is relatively large during normal production, when the flue gas in the air box 3 is all subjected to a first desulfurization and then denitration process through the main flue gas pipeline 11, the loads of the desulfurization unit and the denitration reactor are relatively large, so that the desulfurization and denitration effects are incomplete, even the denitration effects are extremely poor because the flue gas cannot be heated to the denitration temperature by the circular cooler 2 due to the excessive amount of the flue gas, therefore, the sintering flue gas desulfurization and denitration device further comprises a circulating flue 31, one end of the circulating flue 31 is connected with part of the air box 3, and the other end is connected with the fan housing 32 of the sintering machine, so that part of the flue gas generated in the sintering machine 1 can directly reach the sintering machine 1 through the circulating flue 31, on one hand, the amount of the flue gas which needs to be further desulfurized and denitrated is reduced, on the other hand, the part of the flue gas is used, the temperature and the oxygen concentration of the part of flue gas can be controlled by controlling the number and the number of the bellows, for example, the temperature of the part of flue gas is controlled to be 130-180 ℃, the oxygen concentration is more than or equal to 18%, so that the energy consumption of the sintering machine can be reduced by utilizing the heat of the part of flue gas, the energy consumption is saved by more than 1%, and the quality of the sintered ore can be ensured by controlling the proper oxygen concentration of the circulating flue gas as an air source.
Or, the flue A and the flue B are combined and then connected with the circulating flue 31 and the main flue gas pipeline 11 through a three-way unit, and the other end of the circulating flue 31 is connected with a fan housing 32 of the sintering machine; in this case, a part of the mixed flue gas in the flue a and the flue B reaches the sintering machine 1 through the circulation flue 31, and the other part of the mixed flue gas passes through the main flue gas duct 11 to be further desulfurized and denitrated. Thus, one part of the flue gas generated in the sintering machine 1 reaches the fan housing 32 of the sintering machine 1 through the circulating flue 31, and the other part of the flue gas passes through the main flue gas pipeline 11 to carry out the process of firstly desulfurizing and then denitrating; therefore, on one hand, the amount of flue gas which needs to be further subjected to desulfurization and denitrification is reduced, on the other hand, part of the flue gas is used as an air source of the sintering machine, and as the part of the flue gas has certain temperature, for example, the temperature of the part of the flue gas is 110-135 ℃, the oxygen concentration is less than 18%, the energy consumption of the sintering machine can be reduced by utilizing the sensible heat of the part of the flue gas, and the energy consumption is saved by more than 1%.
Specifically, the circulation flue 31 is sequentially provided with a fourth dust remover 29 and a circulation fan 30, and the flue gas passes through the fourth dust remover 29 and the circulation fan 30 and then reaches the wind shield 32 of the sintering machine 1.
In order to ensure that the flue gas passing through the circulating flue 31 can be uniformly distributed on the charge level, the tail end of the circulating flue 31 is divided into a plurality of branches, for example, 3-10 branches.
Specifically, a first dust remover 4 and a first main exhaust fan 6 are sequentially arranged on the flue A, a second dust remover 5 and a second main exhaust fan 7 are sequentially arranged on the flue B, and the first dust remover 4 and the second dust remover 5 are both used for removing dust, so that the concentration of dust in flue gas is controlled within a certain range, and subsequent equipment cannot be blocked; the first main exhaust fan 6 and the second main exhaust fan 7 are added to ensure that the flue gas enters the subsequent equipment at a certain flow rate.
Specifically, the first dust remover 4 and the second dust remover 5 are electric dust removers.
In order to increase the wind pressure, reduce the resistance and ensure the desulfurization effect, a desulfurization booster fan 8 is arranged in front of the desulfurization unit 9.
Specifically, a desulfurization dust collector 10 is arranged behind the desulfurization unit 9 and is used for further removing dust from the desulfurized flue gas, and in order to ensure the recovery effect of the desulfurization reactant, the desulfurization dust collector 10 is a bag-type dust collector in consideration of the fact that a dry or semi-dry desulfurization method is adopted for desulfurization.
It should be noted that the circular cooler 2 is provided with a circular cooler feed inlet 12 and a circular cooler discharge outlet 13, one side of the circular cooler feed inlet 12 is a high-temperature section, one side of the circular cooler discharge outlet 13 is a low-temperature section, and the main flue gas pipeline 11 is also provided with n branch pipelines, wherein n is controlled to be more than or equal to 5 and more than or equal to 2 in order to ensure that the flue gas is uniformly subjected to heat exchange through a high-temperature section material layer; the branch pipelines are provided with air blowers and are connected with the high-temperature section of the ring cooling machine 2 (specifically, the high-temperature section of the ring cooling machine 2 is provided with a first smoke hood, and the branch pipelines are connected with the first smoke hood); preferably, the n is 3, the 3 branch pipelines are respectively provided with a third blower 16, a fourth blower 17 and a fifth blower 18, and the flue gas dedusted by the desulfurization deduster 10 is blown into the high-temperature material layer of the circular cooler by the third blower 16, the fourth blower 17 or the fifth blower 18; after the flue gas is subjected to heat exchange with the hot sintering ore and temperature rise, the temperature of the flue gas is higher than 250 ℃, and the flue gas is led out from a smoke hood of a high-temperature section of the circular cooler 2 to be subjected to denitration treatment.
Considering that the denitration process can be high-temperature denitration (the temperature is 330-420 ℃) or medium-temperature denitration (the temperature is 220-280 ℃), the gas outlet of the high-temperature section can be one or two.
Specifically, the main flue gas pipeline 11 is further provided with a high-temperature dust collector 19, and flue gas led out from the high-temperature section of the flue gas hood is subjected to coarse dust removal by the high-temperature dust collector 19 and then enters the denitration reactor 21 for denitration.
In order to provide a denitration agent for the denitration process, an ammonia water supply unit 20 is arranged between the high-temperature dust remover 19 and the denitration reactor 21, and before flue gas enters the denitration reactor 21, a proper amount of ammonia water is sprayed into a flue by the ammonia water supply unit 20.
Specifically, a waste heat recovery unit 22, a third dust remover 23 and an induced draft fan 24 are sequentially arranged between the denitration reactor 21 and the chimney 25, a flue C is arranged between the induced draft fan 24 and the chimney 25, the flue C is connected with a certain branch pipeline, and a circular cooler circulating fan 26 is arranged on the flue C; in this way, the denitrated flue gas enters the waste heat recovery unit 22 for cooling; the cooled flue gas is firstly dedusted by the third deduster 23 and then led out by the induced draft fan 24, one part of the led-out flue gas is directly discharged from the chimney 25, and the other part of the flue gas is recirculated to the high-temperature section of the ring cooler 2 through the ring cooler circulating fan 26 on the C flue to adjust the cooling air quantity of the high-temperature section, and meanwhile, the temperature of the part of the flue gas can be utilized, which is beneficial to waste heat recovery.
It should be noted that the circulation volume of the circulating fan 26 of the ring cooling machine is 0-50%, that is, the circulation air volume that can be adjusted by the circulating fan 26 of the ring cooling machine is 0-50% of the air volume led out by the induced draft fan 24.
Considering the exhaust temperature of the denitrated flue gas after passing through the waste heat recovery unit 22>100 ℃ and also for achieving dust emission<10mg/Nm3Therefore, the third dust collector 23 is a bag-type dust collector.
The low-temperature section of the circular cooler 2 is provided with a first air blower 14, a second air blower 15 and a waste gas circulation flue 28 (specifically, the low-temperature section of the circular cooler 2 is provided with a second smoke hood, the waste gas circulation flue 28 is connected with the second smoke hood), the waste gas circulation flue 28 is provided with a waste gas circulation fan 27, the first air blower 14 and the second air blower 15 blow air into the low-temperature section for heat exchange, then the gas temperature is higher than 70 ℃, the gas after heat exchange is circulated to a fan cover 32 of the sintering machine by the waste gas circulation fan 27, and an air source is provided for the sintering machine. The sensible heat of the gas after heat exchange can reduce the energy consumption of the sintering machine.
It should be noted that the windboxes 3 are uniformly and symmetrically distributed on both sides of the sintering machine 1, because the amount of flue gas is large during the production process, if the flue gas is single-strand flue gas, the flue is too thick, and the production site is not easy to install, so the flue gas is divided into two streams, and the two streams are respectively discharged from the windboxes on both sides of the sintering machine and respectively enter the flue a and the flue B.
Considering that the number of the windboxes 3 is too large to cause resource waste, and the requirement on the size of the flue is severe when the number of the windboxes 3 is too small, therefore, the number of the windboxes is controlled to be 18-30, preferably 24-28.
Specifically, the heat recovery unit 22 includes a heat recovery boiler for gas heat exchange and a turbine power generation unit, and the boiler may be single-pressure or double-pressure.
The sintering flue gas desulfurization and denitrification device used by the invention divides the sintering flue gas into two parts by symmetrically arranging the plurality of air boxes, the flue A and the flue B, can avoid the problems of overlarge flue diameter and draught fan power caused by overlarge air volume, and is suitable for being installed on a production site.
The flue gas is divided into two parts by arranging a circulating flue, one part is flue gas needing desulfurization and denitration, and the subsequent desulfurization and denitration treatment is carried out, and the other part is used as circulating flue gas and an air source of sintering flue gas; like this can greatly reduced need the volume of SOx/NOx control flue gas, reduce the load of follow-up sweetener, denitration device etc. can guarantee that the cold machine of ring is with flue gas heat transfer to appropriate denitration temperature, guarantee the denitration effect, utilize the circulation flue gas as the air supply of sintering flue gas simultaneously, because the circulation flue gas has certain temperature (for example, this part flue gas temperature is 120~ 200 ℃), can reduce the energy consumption of sintering machine through the sensible heat that utilizes this part flue gas, practice thrift the energy consumption > 1%. Through setting up with cold machine of ring jointly with main flue gas pipeline, with the flue gas through with the cold hot sintering deposit heat transfer in the machine of ring heat rise to reach the denitration temperature and carry out the denitration, need not additionally use firing equipment to the flue gas heating that needs the denitration, the investment is low, and has realized the rational utilization of the energy.
By arranging the first air blower 14, the second air blower 15 and the waste gas circulating flue, the air can be heated by utilizing the residual heat of the low-temperature section of the circular cooler and then used as the air source of the sintering machine. The sensible heat of the gas after heat exchange can reduce the energy consumption of the sintering machine; through the cold quick-witted circulating fan of ring that passes through on the C flue with the partial flue gas after the denitration recirculating to the high temperature section of the cold machine of ring be used for adjusting the cooling amount of wind of high temperature section, simultaneously, can utilize the temperature of this part flue gas, be favorable to waste heat recovery.
Example one
As shown in fig. 1, the desulfurization and denitrification apparatus for sintering flue gas provided by this embodiment includes a 400m unit2The sintering machine 1 is characterized in that 28 air boxes 3 are respectively arranged on each of the upper side and the lower side of the sintering machine 1, wherein the upper air boxes are compiled into A1-A28 from right to left, the lower air boxes are compiled into B1-B28 from right to left, and the A4-A7, B4-B7, A24-A28 and B24-B28 air boxes are directly connected with a circulating flue 31, so that the circulating amount of flue gas can reach 31 percent, and the oxygen content in the circulating flue gas can reach 31 percent>18% of temperature>180 ℃, so that the energy consumption of the sintering machine can be reduced by utilizing the sensible heat of the part of the flue gas, and the energy consumption is saved>1 percent, and the quality of the sinter can be ensured by controlling the proper oxygen concentration of the circulating flue gas as an air source. The arrangement can lead part of the flue gas generated in the sintering machine 1 to directly pass through the circulating flue 31 and reach the sintering machine 1 as a gas source for sintering; the rest of the air boxes on the upper side of the sintering machine 1 are connected with a flue A, a first dust remover 4 and a first main exhaust fan 6 are sequentially arranged on the flue A, the rest of the air boxes on the lower side of the sintering machine 1 are connected with a flue B, a second dust remover 5 and a second main exhaust fan 7 are sequentially arranged on the flue B, and the flue A and the flue B are combined and then connected with one end of a main flue gas pipeline 11; a desulfurization booster fan 8, a desulfurization unit 9, a desulfurization dust remover 10, a blower (comprising a third blower 16, a fourth blower 17 and a fifth blower 18) at the high-temperature section of the circular cooler 2, the circular cooler 2 (the circular cooler 2 is provided with a circular cooler feeding hole 12, a first air blower and a second air blower are sequentially arranged on the main flue gas pipeline 11,The discharge port 13 of the ring cooling machine, the high temperature section on one side of the feed port 12 of the ring cooling machine, and the low temperature section on one side of the discharge port 13 of the ring cooling machine, therefore, the temperature of the sintered ore corresponding to the fifth blower 18 is the highest, and then the fourth blower 17 and the third blower 16), the high temperature dust collector 19, the ammonia water supply unit 20, the denitration reactor 21, the waste heat recovery unit 22, the third dust collector 23, the induced draft fan 24 and the chimney 25 are arranged.
Specifically, a flue C is arranged between the induced draft fan 24 and the chimney 25, the flue C is connected with a branch pipeline where the fifth blower 18 is located, and the flue C is provided with a circular cooler circulating fan 26.
Specifically, the low-temperature section of the circular cooler 2 is provided with a first air blower 14, a second air blower 15 and a waste gas circulation flue 28, the waste gas circulation flue 28 is provided with a waste gas circulation fan 27, the first air blower 14 and the second air blower 15 blow air into the low-temperature section for heat exchange, then the temperature of the gas is higher than 70 ℃, the gas after heat exchange is circulated to the fan housing of the sintering machine by the waste gas circulation fan 27, and an air source is provided for the sintering machine.
Specifically, the circulation flue 31 is sequentially provided with a fourth dust remover 29 and a circulation fan 30, and the flue gas passes through the fourth dust remover 29 and the circulation fan 30 and then reaches the wind shield 32 of the sintering machine 1.
The sintering flue gas desulfurization and denitrification process provided by the embodiment comprises the following steps: taking the flue gas in the air boxes of A4-A7, B4-B7, A24-A28 and B24-B28 as circulating flue gas, directly passing the circulating flue gas to a sintering machine, and using the circulating flue gas as a gas source for sintering; flue gas in all the other bellows divide into two strands as the flue gas that needs SOx/NOx control, through the electrostatic precipitator and the main air exhauster of A flue, the electrostatic precipitator and the main air exhauster of B flue respectively, tentatively remove dust, prevent to block up subsequent equipment, then merge to main flue gas pipeline and get into the desulfurization unit through desulfurization booster fan (sintering flue gas gets into initial SO before the desulfurization unit)2The content is 915mg/Nm3、NOxThe content is 236mg/Nm3The dust content was 50mg/Nm3) (ii) a The desulfurization unit adopts a semi-dry desulfurization process (SO in the desulfurized flue gas) of a circulating fluidized bed2The content is 32mg/Nm3) (ii) a The desulfurized flue gas is subjected to cloth bag dust removal (the dust content in the flue gas after dust removal is 7 mg/Nm)3) (ii) a Flue gas after desulfurization and dust removalThe high-temperature material layer of the circular cooler is blown into the high-temperature material layer of the circular cooler by blowers (comprising a third blower, a fourth blower and a fifth blower) at the high-temperature section of the circular cooler through a main flue gas pipeline; after the flue gas is subjected to heat exchange with the hot sintering ore and is heated, the temperature of the flue gas reaches 360 ℃, and the flue gas is led out from a smoke hood at the high-temperature section of the circular cooler; the extracted flue gas is firstly subjected to coarse dust removal by a high-temperature dust remover 19, and the dust content in the flue gas after dust removal<50mg/Nm3(ii) a Then the flue gas enters a denitration reactor 21 for denitration, before the flue gas enters the denitration, an ammonia water supply unit 20 sprays a proper amount of ammonia water into the flue, and a high-temperature denitration catalyst is filled in the denitration reactor; denitrated flue gas NOxThe content is 45mg/Nm3(ii) a After denitration, the flue gas enters a waste heat recovery unit for cooling; the temperature of the cooled flue gas is 140 ℃, the cooled flue gas is firstly introduced into a third dust remover for dust removal, and the dust content in the flue gas after dust removal is 6mg/Nm3(ii) a Then the flue gas is led out by an induced draft fan; one part of the extracted flue gas is directly discharged from a chimney, and the other part of the extracted flue gas is recycled to a high-temperature blast section of the circular cooler through a circular cooler circulating fan, wherein the circulating amount is 10% of the discharge amount of an outlet of the induced draft fan; the low-temperature section of the circular cooler uses air as a cooling medium, and the temperature of exhaust gas discharged after heat exchange of the air is 90 ℃; the discharged waste gas is sent into a smoke hood on the sintering machine through a waste gas circulating flue by a waste gas circulating fan and is mixed with the smoke of the circulating flue of the sintering machine to be used as a gas source for sintering.
In this example, the desulfurization rate of the sintering flue gas was 96.5%, the denitration rate was 81%, the dust removal rate was 88%, and the SO content in the flue gas after desulfurization and denitration was found to be2Content, NOxThe content and the dust content meet the requirements, and the denitration cost is saved by more than 15%.
Example 2
As shown in fig. 2, the desulfurization and denitrification apparatus for sintering flue gas provided by this embodiment includes a 360m desulfurization and denitrification apparatus2The sintering machine 1, 28 air boxes 3 on each side of the upper side and the lower side of the sintering machine 1, the upper air boxes are connected with a flue A, a first dust remover 4 and a first main exhaust fan 6 are sequentially arranged on the flue A, the lower air boxes are connected with a flue B, a second dust remover 5 and a second main exhaust fan 7 are sequentially arranged on the flue B, and the flue A and the flue B are combined and then pass throughThe three-way unit is connected with the circulating flue 31 and the main flue gas pipeline 11; the arrangement of the main flue gas duct 11 is the same as that of the first embodiment, and the description thereof is omitted.
Specifically, a circulating fan 30 is arranged on the circulating flue 31, and the flue gas passes through the circulating fan 30 and then reaches a fan housing 32 of the sintering machine 1.
The sintering flue gas desulfurization and denitrification process provided by the embodiment comprises the following steps: the flue gas of sintering machine both sides is earlier removed dust through first dust remover or second dust remover respectively, then passes through first main air exhauster or second main air exhauster respectively, assembles at last and introduces 21% flue gas in the flue as the flue gas that circulates in proper order into the circulation flue and circulates, and remaining 79% flue gas passes through desulfurization booster fan and gets into desulfurization unit and carry out the desulfurization, and the whole step after the desulfurization is the same with embodiment one, does not describe here in detail one by one.
Specifically, the initial SO before the sintering flue gas enters the desulfurization unit2The content was 780mg/Nm3、NOxThe content is 218mg/Nm3The dust content was 49mg/Nm3. The desulfurization unit adopts a baking soda dry desulfurization process, and SO in the desulfurized flue gas2The content is 15mg/Nm3(ii) a The desulfurized flue gas is subjected to cloth bag dust removal, and the dust content in the flue gas after dust removal is 5mg/Nm3(ii) a After the flue gas is subjected to heat exchange with the hot sintering ore and temperature rise, the temperature of the flue gas reaches 350 ℃, the flue gas is subjected to coarse dust removal by a high-temperature dust remover 19, and the dust content in the flue gas after dust removal<40mg/Nm3(ii) a Then enters a denitration reactor for denitration, and the denitrated flue gas NOxThe content is 44mg/Nm3(ii) a After denitration, the flue gas enters a waste heat recovery unit for cooling; the temperature of the cooled flue gas is 130 ℃, the cooled flue gas is dedusted by a third deduster, and the dust content in the dedusted flue gas is 5mg/Nm3(ii) a Then the flue gas is led out by an induced draft fan; one part of the extracted flue gas is directly discharged from a chimney, and the other part of the extracted flue gas is recycled to a high-temperature blast section of the circular cooler through a circular cooler circulating fan, wherein the circulating amount is 12% of the discharge amount of an outlet of the induced draft fan; air is used as a cooling medium at the low-temperature section of the circular cooler, and the temperature of exhaust gas discharged after heat exchange of the air is 88 ℃; the discharged waste gas is sent to the furnace through the waste gas circulating flue by the waste gas circulating fanIn the smoke hood of the sintering machine, the smoke is mixed with the smoke of the circulating flue of the sintering machine to be used as an air source for sintering.
In this example, the desulfurization rate of the sintering flue gas was 98%, the denitration rate was 79.8%, the dust removal rate was 89.8%, and the SO of the flue gas after desulfurization and denitration was 89.8%2The content, the NOx content and the dust content all meet the requirements, and the denitration cost is saved by more than 15%.
Example 3
As shown in fig. 3, the difference between the desulfurization and denitrification apparatus for sintering flue gas provided in this embodiment and embodiment 2 is that the boiler in the waste heat recovery unit 22 is a dual-pressure boiler, so that there are two flue gases with different temperatures entering the waste heat recovery unit 22, that is, there are two flue gas outlets in the high temperature section of the ring cooling machine; two paths of flue gas are led out from a smoke hood of a high-temperature section of the circular cooler 2; one path of flue gas has higher temperature, the flue gas temperature is 400 ℃, the flue gas is subjected to coarse dust removal by a first high-temperature dust remover 19-1, then enters a first denitration reactor 21-1 for denitration, and enters a first heat exchange tube in a boiler in a waste heat recovery unit 22 after denitration; one path of flue gas is low in temperature and is 270 ℃, the flue gas is subjected to coarse dust removal by a second high-temperature dust remover 19-2, then enters a second denitration reactor 21-2 for denitration, and enters a second heat exchange tube in the boiler in the waste heat recovery unit 22 after denitration; the two paths of flue gas discharged from the waste heat recovery unit 22 are mixed into one path, and then dust removal is performed.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (6)

1. A sintering flue gas desulfurization and denitrification process is characterized by comprising the following steps:
s1, dividing the sintering flue gas of the sintering machine into two parts of flue gas to be desulfurized and denitrated and circulating flue gas through a flue gas circulating process; circulating flue gas is used as a gas source of sintering flue gas;
s2, desulfurizing the flue gas to be desulfurized and denitrated by a desulfurization booster fan, and dedusting the desulfurized flue gas; the desulfurization adopts a dry or semi-dry desulfurization method;
s3, blowing the flue gas subjected to desulfurization and dust removal into a high-temperature section material layer of the ring cooling machine by a blower at the high-temperature section of the ring cooling machine to perform heat exchange with hot sinter and heat rise;
s4, roughly dedusting the flue gas subjected to heat exchange and temperature rise, and then feeding the flue gas into a denitration reactor for denitration;
s5, cooling the denitrated flue gas in a waste heat recovery unit, and dedusting the cooled flue gas and then leading out the flue gas by a draught fan;
s6, directly discharging the extracted flue gas from a chimney;
in the step S3, air is used as a cooling medium in a low-temperature section of the circular cooler, and low-temperature waste gas which is obtained after the air cools the sinter and is higher than 70 ℃ is sent into a smoke hood of the sintering machine through a waste gas circulating fan to be used as a gas source for sintering;
in the S6, one part of the extracted flue gas is directly discharged from a chimney, and the other part of the extracted flue gas is recycled as circulating waste gas to a high-temperature blast section of the circular cooler to be mixed with low-temperature waste gas to be used as a gas source for sintering;
the sintering flue gas desulfurization and denitrification device adopted by the sintering flue gas desulfurization and denitrification process comprises a sintering machine (1), a circular cooler (2), an air box (3), a flue A, a flue B, a main flue gas pipeline (11) and a chimney (25); the number of the air boxes (3) is multiple, the air boxes (3) are uniformly and symmetrically distributed on two sides of the sintering machine (1), part or all of the air boxes on one side of the sintering machine (1) are connected with the flue A, and part or all of the air boxes on the other side of the sintering machine (1) are connected with the flue B; the flue A and the flue B are combined and then connected with one end of a main flue gas pipeline (11), and a desulfurization unit (9), a denitration reactor (21) and a waste heat recovery unit (22) are arranged on the main flue gas pipeline (11); the annular cooling machine (2) is arranged between the desulfurization unit (9) and the denitration reactor (21), and the annular cooling machine (2) comprises a high-temperature section and a low-temperature section; n branch pipelines are further arranged on the main flue gas pipeline (11), blowers are arranged on the branch pipelines, and the branch pipelines are connected with the high-temperature section of the circular cooler (2); the low-temperature section of the circular cooler (2) is connected with a fan cover (32) through an exhaust gas circulation flue (28); n is more than or equal to 5 and more than or equal to 2; the tail end of the main flue gas pipeline (11) is connected with a chimney (25); and a waste heat recovery unit (22), a third dust remover (23) and an induced draft fan (24) are sequentially arranged between the denitration reactor (21) and the chimney (25), a C flue is arranged between the induced draft fan (24) and the chimney (25), the C flue is connected with a certain branch pipeline, and a circular cooler circulating fan (26) is arranged on the C flue.
2. The desulfurization and denitrification process for sintering flue gas as claimed in claim 1, wherein in the step S1, the flue gas circulation process comprises two processes: an internal circulation process and an external circulation process;
the internal circulation process takes part of sintering flue gas in the air box as circulating flue gas, and the circulating flue gas directly reaches the sintering machine through a circulating flue; the flue gas in the other bellows is divided into two paths as the flue gas needing desulfurization and denitrification, and the two paths respectively pass through an electric dust collector and a main exhaust fan of the flue A or an electric dust collector and a main exhaust fan of the flue B, and then are combined to a main flue gas pipeline to carry out the steps S2-S6;
the external circulation process divides the sintering flue gas in the air box into two parts which respectively pass through an electric dust remover and a main exhaust fan of the flue A or an electric dust remover and a main exhaust fan of the flue B, then one part of the mixture is taken as the circulation flue gas and reaches the sintering machine through the circulation flue, and the other part of the mixture is taken as the flue gas to be desulfurized and denitrated to carry out the steps S2-S6.
3. The desulfurization and denitrification process for the sintering flue gas as claimed in claim 1, wherein in S4, the ammonia water supply unit sprays ammonia water into the flue before the flue gas enters the denitrification reactor.
4. The desulfurization and denitrification process for sintering flue gas as claimed in any one of claims 1 to 3, wherein in S1, the initial SO of sintering flue gas2The content is 400-2000 mg/Nm3，NOxThe content is 120-350 mg/Nm3The content of dust is> 1g/Nm3。
5. The sintering flue gas desulfurization and denitrification process according to claim 4, further comprising a circulating flue (31), wherein one end of the circulating flue (31) is connected with part of the wind boxes (3), and the other end of the circulating flue (31) is connected with the wind cover (32);
or the flue gas purification device also comprises a circulating flue (31), wherein the flue A and the flue B are combined and then connected with the circulating flue (31) and the main flue gas pipeline (11) through a tee joint unit; the other end of the circulating flue (31) is connected with a fan cover (32).
6. The sintering flue gas desulfurization and denitrification process according to claim 5, wherein a high temperature dust collector (19) and an ammonia water supply unit (20) are further arranged between the annular cooler (2) and the denitrification reactor (21); and a third dust remover (23) and an induced draft fan (24) are also arranged between the waste heat recovery unit (22) and the chimney (25).
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