BRPI0718179B1 - Wet desulfurization and withdrawal of sinterization combustion gas dust. - Google Patents

Wet desulfurization and withdrawal of sinterization combustion gas dust. Download PDF

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Publication number
BRPI0718179B1
BRPI0718179B1 BRPI0718179-5A BRPI0718179A BRPI0718179B1 BR PI0718179 B1 BRPI0718179 B1 BR PI0718179B1 BR PI0718179 A BRPI0718179 A BR PI0718179A BR PI0718179 B1 BRPI0718179 B1 BR PI0718179B1
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BR
Brazil
Prior art keywords
flue gas
slurry
dust removal
desulphurization
sinter
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BRPI0718179-5A
Other languages
Portuguese (pt)
Inventor
Shen Xiaolin
Shi Hongzhi
Shi Guomin
Liu Daoqing
Lin Yu
Shi Lei
Wang Ruyi
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Baoshan Iron & Steel Co., Ltd.
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Priority to CNB200610117516XA priority Critical patent/CN100534587C/en
Priority to CN200610117516.X priority
Application filed by Baoshan Iron & Steel Co., Ltd. filed Critical Baoshan Iron & Steel Co., Ltd.
Priority to PCT/CN2007/070951 priority patent/WO2008052465A1/en
Publication of BRPI0718179A2 publication Critical patent/BRPI0718179A2/en
Publication of BRPI0718179B1 publication Critical patent/BRPI0718179B1/en

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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00Preliminary treatment of ores or scrap
    • C22B1/14Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16Sintering; Agglomerating
    • C22B1/20Sintering; Agglomerating in sintering machines with movable grates
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/46Removing components of defined structure
    • B01D53/48Sulfur compounds
    • B01D53/50Sulfur oxides
    • B01D53/501Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation 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
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/46Removing components of defined structure
    • B01D53/68Halogens or halogen compounds
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/02Working-up flue dust
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2257/00Components to be removed
    • B01D2257/20Halogens or halogen compounds
    • B01D2257/204Inorganic halogen compounds
    • B01D2257/2045Hydrochloric acid
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2257/00Components to be removed
    • B01D2257/20Halogens or halogen compounds
    • B01D2257/204Inorganic halogen compounds
    • B01D2257/2047Hydrofluoric acid
    • Y02P10/212

Description

(54) Title: HUMID DESULFURIZATION PROCESS AND REMOVAL OF DUST FROM SINTER COMBUSTION GAS.
(51) Int.CI .: B01D 53/50; B01D 53/70; B01D 53/78; C22B 1/16 (30) Unionist Priority: 25/10/2006 CN 2006 10117516.Χ (73) Holder (s): BAOSHAN IRON & STEEL CO., LTD.
(72) Inventor (s): XIAOLIN SHEN; HONGZHI SHI; GUOMIN SHI; DAOQING LIU; YU LIN; SHI LAW; RUYI WANG
1/18
Descriptive Report of the Invention Patent for HUMID DESULFURIZATION PROCESS AND WITHDRAWAL OF DUST FROM SINTER COMBUSTION GAS.
Technical Field [001] The present invention relates to a wet process of desulfurization and removal of dust from sintering flue gas, in particular, with a wet process of desulfurization and removal of dust for metallurgy sintering flue gas iron and steel.
Background of the Invention [002] At the moment, a sintering flue gas has become the main source of SO 2 emissions in iron and steel metallurgy. However, substantially no study has been done on the sintering flue gas desulfurization process in China, thus becoming an obstruction to restrict the development of the iron and steel industry in China.
[003] There are mainly two strategies to resolve the SO2 emission from the sintering gas.
[004] The first strategy is to use fuel with a low sulfur content or to add desulfurizers to the raw sintering materials in order to reduce the emission of SO 2 , for example, Chinese Patent Application CN128541A revealed a desulfurization process by adding ammonia-containing compounds for the raw sintering materials during the course of combustion. However, the desulfurization efficiency of this method is not high due to the uneven distribution of the additives in the material layer, and the non-uniformity of the temperature and concentration field in the combustion zone.
[005] The second strategy is to desulfurize the flue gas from sintering. Flue gas desulfurization technology
Petition 870180010776, of 02/07/2018, p. 4/29
2/18 includes dry flue gas desulfurization and flue gas wet desulfurization. Dry flue gas desulfurization includes fluidized circulation bed, semi-dry flue gas desulfurization by rotary spray, active carbon adsorption, electron beam irradiation and so on. The efficiency of the desulfurization of the circulating fluidized bed and the semi-light flue gas desulfurization by rotary spraying is not high, typically 70 to 75% and the by-product after purification is calcium sulfite which is unstable and difficult to use and the stacking of the calcium sulfite for a long time will lead to a large occupation of spaces and will cause secondary pollution. Active carbon adsorption has been applied in the Japanese steel industry, for example, the No. 3 sintering machine in the Nagoya iron works is installed in a set of sintering flue gas desulfurization and denitrification devices using adsorption of active carbon. This method can achieve a desulfurization efficiency of 95% and a denitrification efficiency of 40%, however, the investment and operating expenses are extremely high due to the expensive active carbon and the complicated purification system and absorption regeneration system. . Japanese Patent JP52051846 discloses an electron beam irradiation process, which can achieve a desulfurization efficiency and denitrification efficiency above 80%, however, the process needs high energy consumption and has the risk of leaking radiation. The various dry sintering flue gas desulfurization processes above cannot significantly remove the fine powder in the flue gas, and have no corresponding measures to recycle the metal in the sinter flue gas.
[006] Compared with the wet sintering flue gas desulfurization process, the dry desulphurization processPetition 870180010776, of 7/7/2018, pg. 5/29
3/18 sintering flue gas is more widely used. Kitakyushu's iron and steel mills in Japan sprayed magnesium hydroxide solution along with the sinter flue gas to convert SO 2 into magnesium sulfate, which was then separated from the sintering process by a purifier. Keihin's iron and steel mills in Japan used an ammonium-ammonium sulphate method to desulfurize the sinter flue gas, which used less ammonia from the coke oven gas to react with SO 2 in the flue gas of the sintering, and so, ammonium sulfate was obtained. First, the ammonium sulfite solution (the concentration was 3%) was used to absorb SO2 to obtain ammonium bisulfite, and then, the absorption liquid was distributed to the coke oven plant to absorb NH 3 in the oven gas. coke, thus generating ammonium sulfite, which was then distributed back to the sintering plant for cyclical use. All sintering plants in Chiba, Mizushima, Kashima, and Kobe in Japan used the flue gas desulfurization method of limestone sintering - gypsum, which was established in the 1970s and used the limestone process - traditional gypsum. However, the instruments of this process have been out of date and construction costs and operating expenses are relatively high. Those skilled in the art consider that foreign processes are complicated, and have low economic efficiency, thus, they are not desirable in China.
[007] Different types of absorption tower, a key instrument for the wet desulphurization process, will lead to different desulphurisation efficiencies, construction costs, operating expenses and systemic operating stability. Currently, the well-known absorption tower widely used in the world in a limestone method - gypsum is the spray tower, which has been
Petition 870180010776, of 02/07/2018, p. 6/29
4/18 widely used in the thermal power unit above 300 MW in the country and abroad. Unlike the flue gas emitted from a coal-fired heater, the sinter flue gas has the following characteristics:
(1) The concentration of SO 2 in the sinter flue gas is relatively low (typically 300 to 1000 mg / Nm 3 ), and its lower limit is always lower than the flue gas concentration from the coal-fired heater after the wet desulfurization; in addition, the flue gas volume of the sinter and the concentration of SO2 in it fluctuate within a wide range. These characteristics require that the flue gas desulfurization of the sinter must use a desulfurization process with high efficiency and low cost. However, the efficiency of the mass transfer of gas - liquid from the spraying tower is not high. In order to remove SO 2 at such a low concentration, it must be ensured that the spray slurry fully covers the section of the absorption tower, and also the coverage rate between the spray layers must exceed 200%, and thus, the corresponding proportion of gas / liquid (W / G) is relatively large (typically W / G is 12 to 20), energy consumption is high and economic efficiency is poor.
(2) Compared to the flue gas from a coal-fired heater, the particle size of the dust particles in the sinter flue gas is relatively smaller, and the proportion of submicron dust is relatively large, however, the tower traditional spraying does not have a high dust removal efficiency within this particle size range.
(3) The sinter flue gas, leaving the electrostatic precipitator (ESP), has a relatively high temperature
Petition 870180010776, of 02/07/2018, p. 7/29
5/18 low (85 to 150 ° C), which makes the gas regenerative gas heater (GGH), in front of the spraying tower, unable to reheat the purified flue gas above 80 ° C. In addition, the complicated components of the sinter flue gas make the working condition of the GGH which is naturally susceptible to getting clogged worse, and thus decreasing the system's usability.
(4) The sinter flue gas components are very complicated and each cubic meter of sinter flue gas contains tens of milligrams up to hundreds of milligrams of HF gas, depending on the sintering ore. In addition, the sinter flue gas has a high content of gaseous HCl and heavy metal, and the dust adhesion capacity is strong. These characteristics of the sinter flue gas present higher requirements in relation to the treatment of residual water and anti-corrosion / anti-fouling properties of the absorption towers and of the entire desulfurization system.
[008] Therefore, in view of the particularity of the sinter flue gas, it is not reasonable or economical to copy the wet desulphurization process and the spray tower widely used in coal-fired power plants in the sintering flue gas desulfurization.
Contents of the Invention [009] The technical problem to be solved by the present invention is to provide a wet process of desulfurization and dust removal from the sinter flue gas, which is characterized by the high efficiency of desulfurization and dust removal for the sinter flue gas, low energy consumption, low operating expense, small space footprint, low construction cost, reliable operation, and so on, in order to weaken the effect of the emission of SO 2 from
Petition 870180010776, of 02/07/2018, p. 8/29
6/18 of the sinter flue gas in relation to the ecological environment and human health, and to alleviate economic loss and pressure in relation to the environmental protection of companies. This process can be applied to different flue gas volumes from sintering, and it can be adapted to change the temperature and flue gas components of the sinter within a wide range.
[010] The technical solution of the present invention includes the following steps:
(1) After the sinter flue gas exiting a dust eliminator is driven by a boost fan, it is first de-fluorinated and cooled, that is, using alkali slurry to substantially remove gaseous HF, HCl and large particulate soot. from the flue gas and lower the flue gas temperature to below 80 ° C;
(2) The flue gas enters a desulfurization absorption tower, and the SO 2 in the flue gas is reacted with an alkali slurry in the absorption tower; and (3) The purified flue gas enters a mist eliminator to remove the droplets in the flue gas and is then reheated before it is discharged from a chimney. [011] Unlike the flue gas from the coal-fired heater, each cubic meter of sinter flue gas contains tens of milligrams to hundreds of milligrams of HF gas, depending on the sintering ore. Gaseous HF is very corrosive, and after being dissolved in water, it will form hydrofluoric acid, a powder which will cause severe corrosion in structural components and anti-corrosion materials within the absorption tower, and cause an extremely large destruction of plastic materials reinforced with fiber (FRP), thus decreasing the operational reliability of the system 870180010776, of 02/07/2018, p. 9/29
7/18 desulfurization theme. In order to be sure that the absorption tower can operate in a continuous manner, to decrease the graduation of the anticorrosion materials in the tower and to provide the ideal reaction conditions for the subsequent desulfurization, it is necessary to defluorize and cool the flue gas before it enter the absorption tower. During this process, the flue gas reacts with fresh alkali slurry from a tank of alkali slurry to substantially remove the gaseous HF; at the same time, the evaporation of the alkali slurry and the process water lower the flue gas temperature to below 80 ° C, thus providing the optimal reaction conditions for subsequent desulfurization. If the absorption tower works at a temperature above 80 ° C for a long time, whatever the anti-corrosion material, it will wear out and age and its service life will be shortened. Therefore, lowering the intake temperature of the absorption tower to below 80 ° C will be in favor of the long-term use of the absorption tower materials, which guarantees the thermal safety of the absorption tower. Since the gaseous HCl in the flue gas also has extremely high solubility, most of the gaseous HCl and large particulate dust can be removed when the flue gas is de-fluorinated and cooled.
[012] After being de-fluorinated and cooled, the flue gas enters the high-efficiency desulfurization absorption tower that is especially possessed by the present process, and reacts with the alkali slurry in the absorption tower to substantially remove SO2. Since the concentration of SO2 in the sinter flue gas is relatively low, if the traditional spray tower is used, it requires extremely high energy consumption to obtain relatively high desulfurization efficiency. Therefore, the present process uses a desulfurization absorption tower Petition 870180010776, of 02/07/2018, p. 10/29
8/18 specially designed treatment, which does not use the conventional recycling and spraying slurry on the top side of the tower, instead the flue gas, after being de-fluorinated and cooled uniformly, enters several tubes gas injection tubes arranged regularly inside the tower from the middle part of the absorption tower, and exhaust vents at the bottom of the gas injection tubes are immersed below the surface of the absorbent slurry. The flue gas generates a strong rotation by means of a swirl device in the gas injection tubes, and then it advances from the exhaust vents into the concentration of slurry in the absorption tower along a tangential direction, and , once thrown, the bubbles collide, rotate, cut and break each other, and are further broken down into the semi-fluid paste, thus accentuating the effect of the gas / liquid contact. This process can achieve a desulfurization efficiency above 95% and a dust removal efficiency above 99%. There are several sets of agitator and oxidation unit at the bottom of the slurry concentration of the absorption tower. The purpose of the agitators is to prevent gypsum deposition at the bottom of the slurry concentration; the function of the oxidation unit is to oxidize the by-product to become a usable gypsum crystal. When the concentration of gypsum slurry at the bottom of the absorption tower slurry concentration reaches the set value, the gypsum slurry is discharged from the bottom of the tower and enters the subsequent water withdrawal system of the gypsum.
[013] The purified flue gas enters a mist eliminator and an excellent droplet separation effect will be achieved here. The flue gas, with the mist removed, is heated again, and then discharged from a chimney.
Petition 870180010776, of 02/07/2018, p. 11/29
9/18 [014] As an improvement of the present invention, the gypsum slurry resulting from desulphurisation is subjected to two-stage water withdrawal, and the moisture content is reduced to below 10%, in which withdrawal water in two stages is performed by centrifugal dehydration by helical conveyor (or hydrocyclone) and vacuum dehydration by belt, respectively.
[015] As an improvement of the present invention, the sinter flue gas is de-fluorinated and cooled in a cooling de-fluoriser, which can guarantee that the flue gas temperature can be lowered to below 80 ° C quickly and the HF gas can be substantially removed from the flue gas.
[016] As another improvement of the present invention, the temperature of the flue gas in step 1) is cooled by the evaporation of the alkali slurry and by the process water successively in the cooling defluorizer.
[017] As another improvement of the present invention, the waste water generated in the cooling deflower is discharged directly into the waste water treatment system. The residual water generated in the cooling defluorizer contains F - , C1 - , soot containing heavy metal and a small amount of calcium sulfite. Since the amount of wastewater is not large, it can be directly discharged into the wastewater treatment system without entering the subsequent absorption tower. Therefore, the effect of chlorine ion and heavy metal accumulation in the desulfurization system is highly reduced, thereby relieving chlorine ion corrosion of subsequent equipment and improving the by-product gypsum quality.
[018] As another improvement of the present invention, water
Petition 870180010776, of 02/07/2018, p. 12/29
10/18 residual discharged from the cooling defluorizer is subject to deposition, pH value adjustment and so on, to separate heavy metal from waste water, and dry heavy metal sludge is subjected to magnetic separation to recover iron in it, and then the recovered iron is returned to the top of the sintering machine to participate in the mineral mixture, and thus, the level of resource utilization of the sintering system is accentuated.
[019] As another improvement of the present invention, in the desulfurization absorption tower of step 2), the cooled and defluorinated flue gas beats a concentration of slurry at a high speed by means of a swirling device in a gas injection tube inside the absorption tower. The flue gas is broken into the slurry and mixed with the slurry, and the desulphurization and dust removal process is complete during highly efficient contact of the gas and liquid. The highly efficient desulfurization absorption tower in step 2) is free of a slurry recycling pump, and therefore, its operating cost is low. In addition, since the gas velocity inside the absorption tower is high, the tower structure is compact and the space footprint of the tower is small. In addition, there are no moving elements or nozzles inside the desulphurization absorption tower, so the tendency of the absorption tower to be blocked and dirty is highly reduced, and the operational reliability of the system is high, and maintenance is also reduced. [020] As another improvement of the present invention, the reheating of the condensation-free flue gas from step 3) is carried out by the residual steam from the sintering of the present system, that is, the residual steam generated during the cooling of the sintering ore. by sintering / circular / cooling machines is
Petition 870180010776, of 02/07/2018, p. 13/29
11/18 introduced into the steam flue gas heater to heat the flue gas to 80 ° C, and then the flue gas is discharged from a chimney. The process that uses the residual steam from sintering to replace the gas heater - conventional regenerative gas (GGH) not only eliminates expensive GGH but also prevents the occurrence of blockage, thereby improving the operational stability of the system and reducing the investment cost .
[021] As the alkali slurry described above, any solutions or slurries prepared by alkaline material that can react with SO2 can be used. The commonly used alkaline desulfurization material is calcium-based absorbent, such as limestone and calcium hydroxide due to its low prices. Other alkaline compounds, such as alkaline sodium-based compounds, alkaline magnesium-based compounds and alkaline ammonium-based compounds, can also be used.
[022] The gypsum in the present patent application refers to any of the sulfates formed by the desulfurization of the above alkaline material.
[023] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared to the prior art:
1. It satisfies the requirement to change the flue gas volume of the sinter, flue gas temperature and SO2 concentration in the flue gas within a wide range, and it can achieve a desulfurization efficiency of over 95 % and a dust removal efficiency of 99%; in particular, it has an excellent dust removal effect for sub-micron dust.
2. The cooling de-fluoriser is established before the
Petition 870180010776, of 02/07/2018, p. 14/29
12/18 absorption tower to lower the absorption gas temperature below 80 ° C and remove most of the HF gas oso. This measure not only provides optimal reaction conditions for the subsequent desulfurization, but also guarantees the thermal safety of the absorption tower, relieving corrosion within the tower and enhancing the operational reliability of the desulfurization system.
3. Since most of the gaseous HCl and dust with large particle is removed in the cooling de-fluoriser, the accumulation effect of chlorine and heavy metal ions in the desulphurization system is highly reduced, thus alleviating corrosion by chlorine from subsequent equipment and improving the gypsum quality of the desulfurization by-product.
4. The small amount of waste water generated in the cooling deflower is treated, which reduces the amount of waste water to be treated. Meanwhile, heavy metal, especially iron, in the wastewater, is recovered and returned to the sintering machine head to participate in the ore mixture, and thus the level of resource utilization of the sintering system is accentuated.
5. Compared with the traditional spray tower, there are no moving elements or nozzles inside the absorption tower used in the present process, and thus, the possibility of fouling is highly reduced.
6. Compared with the traditional spray tower system, there is no recycling pump inside the absorption tower used in the present process, and thus, the operating cost is low. In addition, since the gas velocity inside the absorption tower is high, the structure of the tower is compact and space is small.
7. In the absorption tower used in the present process,
Petition 870180010776, of 02/07/2018, p. 15/29
13/18 since the flue gas spins and advances into the slurry concentration at a high speed, the gas / liquid contact effect is excellent and the efficiency of desulphurisation and dust removal is high.
8. Considering the flue gas characteristics of the sintering, replacing the regenerative gas - gas heater (GGH) with the reheating mode using the residual steam from the sintering not only eliminates expensive GGH but also prevents the occurrence of blockage, thereby improving the operational stability of the system and reducing the investment cost.
Description of the figures [024] Figure 1 is a schematic diagram of the process flow of the present invention.
[025] Figure 2 is a schematic diagram of the process system of the present invention.
Best Embodiment of the Present Invention [026] It can be seen from figure 1 and figure 2 that the sinter flue gas to be treated leaving the electrostatic precipitator (ESP) 6 is primarily driven by an impeller fan 7, and then it enters a cooling de-fluoriser 8 located before the desulfurization absorption tower 9 to be de-fluorinated and cooled. During this stage, the flue gas reacts with a fresh, sprayed alkali slurry from a lime slurry slurry tank 14 to the cooling defluorizer 8, and is then washed by the process water sprayed from a slurry tank. process water 13, to substantially remove the gaseous HF from the sinter flue gas and lower the flue gas temperature to below 80 ° C, thereby providing the optimal reaction conditions for subsequent desulphurisation and ensuring thermal safety of the AbPetition Tower 870180010776, of 02/07/2018, p. 16/29
14/18 sorption. Since the gaseous HCl in the flue gas has extremely high solubility, most of the gaseous and particulate dust HCl can be removed when the flue gas is de-fluorinated and cooled.
[027] The waste water generated in the cooling deflowerer 8 is discharged directly to a wastewater treatment system 15. The waste water generated in the cooling deflowerer 8 contains F - , C1 - , soot containing heavy metal and a small amount of calcium sulfite. Since the amount of wastewater is not large, it can be directly discharged into the wastewater treatment system without entering the subsequent desulfurization tower. Therefore, the effect of chlorine ion and heavy metal accumulation in the desulphurization system is highly reduced, thus alleviating the chlorine ion corrosion of subsequent equipment and improving the by-product gypsum quality.
[028] The waste water discharged from the cooling defluorizer 8 is subject to deposition, pH value adjustment and so on in the waste water treatment system 15 to separate heavy metals from waste water, and the dry sludge heavy metal is subjected to magnetic separation by a magnetic separator 16 to recover iron in it, and the recovered iron is returned to the top of the sintering machine 4 to participate in the ore mixture, and thus the level of utilization of sintering system resources is enhanced. The remaining heavy metals can be additionally used or distributed abroad as required.
[029] The flue gas after being cooled in the cooling deflowerer 8 uniformly enters several gas injection tubes arranged regularly inside the desulfurization absorption towers 9, and rotates downwards inside tubes by means of a disPetition 870180010776 , of 07/02/2018, p. 17/29
15/18 positive of swirling in the gas injection tubes and spray inside the alkali slurry along the tangential direction of vents at the bottom of the gas injection tubes. Due to the special arrangement of the gas injection tubes, the bubbles injected from the tubes generate a strong collision, shear, rotation and rupture effect in the slurry, thus generating a turbulence zone with two gas / liquid phases. intensively interfering and highly mixing, and greatly increasing the gas / liquid mass transfer effect. During this course, the SO 2 in the flue gas dissolves in the liquid phase to withstand a chemical absorption reaction, and the residual dust in the flue gas is also removed when it comes in contact with the liquid. The bubbles in the turbulence zone continue to rise tortuously until they break on the upper part of the slurry surface, and thus the entire flue gas washing process is completed. The resulting calcium sulfite is further oxidized to turn calcium sulfate into the slurry tank in the absorption tower through the air blown by the oxidation air blower 12, and crystallizes to form gypsum. The agitators 5 at the bottom of the tower are operating at all times to prevent the deposition of the gypsum slurry. The desulfurization absorption tower of the present invention can be made of integral fiber-reinforced plastic material (to treat a small amount of flue gas) or coated with carbon steel with fiber-reinforced plastic material (to treat a large amount of gas combustion) in addition to conventional carbon steel coated with glass sheet or coated with rubber. Fiber-reinforced plastic materials have excellent anti-corrosion and anti-fouling properties and are low cost; the configuration of the defluorization and cooling section 8 provides a reliable guarantee for the thermal safety and anti-corrosion safety of the plasticsPetition 870180010776, from 07/02/2018, p. 18/29
16/18 fiber-reinforced optics used in absorption towers.
[030] Desulfurized flue gas leaves absorption tower 9 and enters a condensate eliminator 10 to pass through the gas / liquid separation. The flue gas leaving the condenser eliminator 10 needs to be reheated to 80 ° C in the steam flue gas heater 3 and then discharged into a chimney 1 by means of a discharge fan
2. The steam flue gas reheater uses the residual steam generated by cooling the sintering minerals by the sintering / circular / cooling machines as a reheating source. [031] The flue gas reacts with the alkali slurry in the desulfurization absorption tower 9 to generate gypsum slurry, which enters the gypsum dehydration system 11 and is subjected to dehydration in two stages. Two-stage dehydration is performed by the centrifugal dehydrator with helical conveyor (or hydrocyclone) and by the vacuum belt dehydrator, respectively. Since the SO 2 concentration in the sinter flue gas is relatively low, gypsum production is not high. In order to reduce the discomfort of the gypsum treatment system and facilitate dehydration, intermittent gypsum discharge is used, that is, the density of the gypsum slurry is constantly monitored by a densitometer, and when the gypsum density satisfies the established value, the gypsum slurry is extracted by the gypsum discharge pump from the bottom of the absorption tower and pumped into the gypsum slurry tank, and then it is pumped to a centrifugal dehydrator with helical conveyor (or hydrocyclone) by a gypsum dehydration pump to pass the first stage dehydration, and the gypsum after the first stage dehydration and the thickening is additionally dehydrated by vacuum belt dehydration to a content of
Petition 870180010776, of 02/07/2018, p. 19/29
17/18 about 10% water.
[032] The wet process of desulfurizing and removing flue gas dust is controlled by a distributed control system (DCS).
[033] A pilot scale experimental system for sintering flue gas desulfurization: the flue gas tested is extracted from the gas discharged from a sintering plant, with a temperature of 150 ° C, a flow rate 90,000 m 3 / h, corresponding to a flue gas flow rate under the standard condition of 5.78 x 10 4 (Ndm 3 ) / h. The SO2 concentration in the flue gas is 300 to 800 mg / Nm 3 , the HF concentration is 50 to 90 mg / Nm 3 , the HCl concentration is 80 to 150 mg / Nm 3 , and the dust concentration is 50 up to 120 mg / Nm 3 . After passing through the cooling deflower, the flue gas temperature is lowered to 80 ° C, and, when the original flue gas temperature is 150 ° C, the flow rate of the limestone slurry ejected into the defluorizer. cooling is 120 to 250 kg / h, and the flow rate of the process cooling water is 2 t / h. The cooled flue gas then enters the absorption tower to undergo desulfurization reactions, where the diameter of the tower is 4 m, and the height of the slurry surface is 3.5 m, the total number of gas injection tubes. is 28, and the swirl rotation device is located in the middle of the gas injection tube. The absorbent is 15% of the weight of the lime slurry, where the amount of slurry consumed by the desulfurization reaction is 250 to 500 kg / h, and the amount of lime consumption is 37.6 to 75.2 kg / h . The discharge amount of 20% by weight of gypsum is 0.3 to 0.6 m 3 / h. The oxidation air quantity is 3 m 3 / min and the oxidation air pressure head is 49 kPa. The temperature of the desulfurized flue gas is 50 ° C. After a condensation removal, the water droplet
Petition 870180010776, of 02/07/2018, p. 20/29
18/18 carried by the flue gas is less than 75 mg / Nm 3 , and, when reheated, the temperature of the reheated flue gas rises to 80 to 90 ° C.
[034] The desulfurization efficiency of the above desulfurization system is not less than 95%, the efficiency of defluorization and de-chlorination is not less than 95% and the efficiency of dust removal is 99%. The amount of gypsum slurry discharged from the absorption tower is 0.3 to 0.6 m 3 / h. After dehydration by a horizontal centrifugal dehydrator with helical conveyor, the water content of the gypsum is 50% to 60%. After dehydration by a vacuum belt dehydrator, the water content of the gypsum is less than 10%. The particle size of the resulting gypsum crystal is 46 to 100 pm.
Petition 870180010776, of 02/07/2018, p. 21/29
1/3

Claims (2)

1/2
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(1) the sinter flue gas leaving a dust eliminator (6) is driven by a boosting fan (7), then it is first defluorized and cooled, that is, using alkali slurry to substantially remove gaseous HF, HCl and soot with large particle from the flue gas and to lower the flue gas temperature to below 80 ° C;
(2) the flue gas enters a desulfurization absorption tower (9), and the SO 2 in the flue gas is reacted with an alkali slurry in the absorption tower (9), the flue gas being de-fluorinated and cooled spins and advances into the slurry concentration at a high speed by means of a whirlpool device in a gas injection tube inside the absorption tower, and is broken into the slurry and mixed with the slurry, in which the desulphurization and dust removal process is complete during the highly efficient contact of the gas and liquid; and (3) the purified flue gas enters a condensation eliminator (10) to remove the droplets in the flue gas and is then reheated before it is discharged from a chimney (1).
2. Desulphurization and dust removal process for sinter flue gas, according to claim 1, characterized by the fact that de-fluorization and cooling, in step (1), are carried out in a cooling de-fluoriser (8 ).
3. Desulphurization and dust removal process for sinter flue gas according to claim 2,
Petition 870180010776, of 02/07/2018, p. 22/29
2/3 characterized by the fact that the temperature of the flue gas, in step (1), is cooled by the evaporation of the alkaline slurry and by the process water in the cooling defluorizer (8).
4. Desulphurization and dust removal process for sinter flue gas, according to claim 3, characterized by the fact that the small amount of residual water generated in the cooling defluorizer (8) is directly discharged into a cooling system. wastewater treatment (15).
5. Desulphurization and dust removal process for sinter flue gas, according to claim 4, characterized by the fact that the residual water discharged from the cooling deflowerer (8) is subject to deposition, value adjustment pH and so on to separate heavy metals from waste water, and dry heavy metal sludge is subjected to magnetic separation to recover iron in it, and then the recovered iron is returned to the machine head sintering (4) to participate in the ore mixture.
6. Desulphurization and dust removal process for sinter flue gas, according to claim 1, characterized by the fact that after undergoing two-stage dehydration, the water content of the gypsum slurry produced in the step (2), is reduced to below 10%.
7. Desulphurization and dust removal process for sintering flue gas, according to claim 6, characterized by the fact that the two-stage dehydration of the gypsum slurry is completed by the centrifugal dehydrator with helical conveyor (or hydrocyclone) ) and vacuum belt dehydrator, respectively.
8. Desulphurization and dust removal process for sintering flue gas, according to claim 1,
Petition 870180010776, of 02/07/2018, p. 23/29
3/3 characterized by the fact that the reheating of the flue gas, in step (3), is carried out by the residual steam from the sintering.
9. Desulphurization and dust removal process for sinter flue gas, according to claim 1, characterized by the fact that the alkali slurry, in steps (1) and (2), includes an aqueous solution or slurry semifluid prepared by limestone, calcium hydroxide, and by one or more alkaline compounds selected from the group consisting of alkaline compounds based on sodium, based on magnesium and based on ammonium.
Petition 870180010776, of 02/07/2018, p. 24/29
1. Wet process of desulfurization and dust removal for sinter flue gas, characterized by the fact that it comprises the following steps:
2/2
BRPI0718179-5A 2006-10-25 2007-10-25 Wet desulfurization and withdrawal of sinterization combustion gas dust. BRPI0718179B1 (en)

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CNB200610117516XA CN100534587C (en) 2006-10-25 2006-10-25 Sintering smoke wet method sulphur removing and dust removing technology
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PCT/CN2007/070951 WO2008052465A1 (en) 2006-10-25 2007-10-25 A sintered flue gas wet desulfurizing and dedusting process

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CN104479777A (en) * 2014-11-20 2015-04-01 中国石油大学(北京) Pretreatment method, membrane separation method and system for high-sulfur-content gas
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