JP6422809B2 - Dust collection method - Google Patents

Description

  The present invention relates to a dust recovery method.

  Dust generated in the steel making process is generally collected by a dust collector or the like. The collected dust is recycled as an iron source by hot metal treatment, a converter, or the like.

  Particularly in converters, a large amount of dust, mainly iron oxide, is generated. This dust is collected by a wet dust collection method using an OG facility (Oxygen Converter Recovery System) which is a facility for cooling, collecting and collecting the converter exhaust gas. Since the dust generated in the converter has a high iron content, various techniques for collecting and utilizing this dust have been proposed from the viewpoint of recycling.

  As the dust collection technique and utilization technique, for example, a method of suppressing and storing oxidation by setting the moisture of dust collected in a converter to a certain ratio or less has been proposed (see, for example, Japanese Patent Laid-Open No. 03-138322). . Further, the dust generated in the converter is separated into coarse particles (coarse dust) and fine particles (fine dust), the coarse dust is used as the converter raw material or hot metal pretreatment raw material, and the fine particle dust is sintered ore or A method for reusing converter dust as a raw material for pellets has been proposed (see, for example, JP-A-2007-9240).

  These methods can be said to meet the requirements in that dust can be collected and reused. However, in the dust recovery system of the above method, the quality of water flowing through the system is not adjusted, and there is a concern about clogging of the water supply pipe, adhesion of deposits, corrosion, and the like. Furthermore, it is desired that the dust recovered from the point of being reused as an iron source has a higher iron content (Fe concentration). However, it is difficult to recover dust having a high iron content by these methods.

Japanese Patent Laid-Open No. 03-138322 Japanese Patent Laid-Open No. 2007-9240

  The present invention has been made based on the circumstances as described above, and its purpose is to effectively suppress the occurrence of equipment problems during dust recovery, and to efficiently produce dust having a high iron content. It is providing the dust collection method which can collect | recover automatically.

  The invention made to solve the above problems includes a step of watering the exhaust gas containing dust by a wet dust collector, a step of separating coarse particles from the dust collection wastewater after the watering step by a classifier, and a thickener. And a step of separating fine particles from fine-grained water after the coarse particle separation step, and collecting dust generated in the converter, wherein the pH of the dust collection wastewater to be treated in the coarse particle separation step is 10 The pH is adjusted to the range of 12 or less and the pH of the fine-grained water to be treated in the fine-grain separation step is in the range of 7 to 9, and the difference between the pH of the dust collection waste water and the pH of the fine-grained water is 3 or more. It is the dust collection method characterized by adjusting so that it may become.

Since the dust collection method adjusts the pH of the dust collection wastewater to be treated in the coarse particle separation step to 10 or more, it effectively suppresses the presence of iron in the dust collection wastewater dissolved as Fe ions, Coarse grains with a high iron content can be recovered. Moreover, since the said dust collection | recovery method adjusts the pH of the dust collection waste_water | drain processed in a coarse grain separation process to 12 or less, the iron content in dust collection waste_water | drain reacts with a hydroxide ion, and Fe (OH) ₂ precipitates. Generation of the resulting deposit can be effectively suppressed. Furthermore, since the said dust collection | recovery method adjusts pH of the fine grain containing water processed at a fine grain separation process to 7 or more, it can fully suppress the corrosion of a thickener. In the dust collection method, the fine-grained water treated in the fine-grain separation step has a pH of 9 or less, and the difference (ΔpH) between the pH of the dust collection wastewater and the fine-grained water is 3 or more. Since adjustment is performed, clogging caused by dust adhesion in the water supply pipe can be sufficiently suppressed.

  Here, the above-mentioned “coarse particles” mean dust having a ratio of particles having a particle size of 50 μm or more of 80% by volume or more. Moreover, the above-mentioned “fine particles” means dust having a ratio of particles having a particle size of less than 50 μm of 80% by volume or more. The “particle size” means the length of the longest string of particles measured by a laser diffraction scattering method.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the malfunction of an installation surface can be suppressed effectively in the case of dust collection | recovery, and the dust which has a high iron content rate can be collect | recovered efficiently.

It is a flowchart which shows the procedure of the dust collection method which concerns on one Embodiment of this invention. It is a block diagram which shows the collection | recovery system of the dust collection method which concerns on one Embodiment of this invention. It is a graph which shows the pH dependence of the total iron amount in the coarse grain of an Example. It is a graph which shows the pH dependence of the amount of metallic iron in the coarse grain of an Example.

  Hereinafter, embodiments of the dust recovery method according to the present invention will be described.

  The dust recovery method shown in FIG. 1 is a method for recovering dust generated in a converter, and includes a step of watering exhaust gas containing dust by a wet dust collector (watering step S1) and a step after the above watering step by a classifier. The step of separating coarse particles from the dust collection wastewater (coarse particle separation step S2) and the step of separating fine particles from the fine particle-containing water after the coarse particle separation step by a thickener (fine particle separation step S3) .

  Impurities are removed from pig iron in converters in the steelmaking process. In the converter, for example, decarburization is performed by removing carbon from the pig iron by blowing oxygen into the pig iron. During the blowing of the converter, exhaust gas containing dust and gas components is generated. The dust recovery method recovers dust from the exhaust gas.

  Examples of the gas blowing type of the converter include an upper blowing type and an upper bottom blowing type.

  Although the amount of hot metal of a converter is not specifically limited, For example, it is 80 to 100 tons.

  Although the hot metal temperature of a converter is not specifically limited, For example, it is 1200 degreeC or more and 1400 degrees C or less.

  Although the hot metal carbon concentration of a converter is not specifically limited, For example, it is 3.5 to 5.0 mass%.

Oxygen-flow-rate of the converter is not particularly limited, for example 2.5Nm ³ / min · t or more 4.2Nm is ³ / min · t or less.

The oxygen accumulation amount of the converter is not particularly limited, but is, for example, 37 Nm ³ / t or more and 52 Nm ³ / t or less.

[Watering process]
In this process, the wet exhaust gas is sprayed on the exhaust gas containing dust generated in the converter. Specifically, as shown in FIG. 2, the exhaust gas A generated in the converter 1 is sent to the wet dust collector 21 of the OG facility 2, and the wet dust collector 21 is sprinkled with the exhaust gas A. It separates into dust collection drainage B containing dust and gas component C. Thus, the dust generated in the converter 1 is collected as the dust collection waste water B in the watering process. The gas component C is sent to the exhaust gas recovery device 23 for processing.

(OG equipment)
The OG facility 2 includes a wet dust collecting device 21, a water tank 22 for storing the dust collecting waste water B, an exhaust gas collecting device 23 for discharging the gas component C, and a pipe connecting them.

  The wet dust collector 21 has a space (chamber) through which the exhaust gas A passes, a sprinkling nozzle installed in the space, a mechanism for collecting the sprinkled water, and a mechanism for collecting the gas component C. In the wet dust collector 21, the exhaust gas A is introduced from the gas inlet at the top of the device, the exhaust gas A is sprinkled, and the dust in the exhaust gas A is collected with water.

  The water tank 22 is a tank that is provided in the lower part of the wet dust collector 21 and temporarily stores the dust collection waste water B discharged from the lower part of the wet dust collector 21.

  In the water tank 22, the dust collection waste water B sent to the classifier 3 is temporarily stored. For example, a water pump (not shown in FIG. 2) is provided in the middle of the water supply pipe between the water tank 22 and the classifier 3 to supply the dust collection waste water B from the water tank 22 to the classifier 3. A method of sending the dust collection waste water B can be used.

  In this step, the exhaust gas A generated in the converter 1 is sent to the wet dust collector 21 and introduced into the wet dust collector 21 from the upper part of the wet dust collector 21. Inside the wet dust collector 21, the exhaust gas A flows from the upper part toward the lower part. In the wet dust collector 21, the exhaust gas A introduced from above is sprinkled by a watering nozzle. The watering can be performed by a spray method using, for example, watering nozzles provided in multiple stages from the top to the bottom.

  It is preferable to use the waste water G after the fine-particle separation process mentioned later from the surface of environmental load or recycling from the water used by the watering of this process. In addition, when using the waste_water | drain G as water to sprinkle, water can be newly replenished as needed.

[Coarse grain separation process]
In this step, the coarse particles D are separated from the dust collection waste water B after the watering step by the classifier 3. Specifically, the dust collection waste water B whose pH is adjusted to be in the range of 10 or more and 12 or less is treated by the classifier 3 to be separated into coarse particles D and fine particles containing water E. Since the coarse particles D contain a large amount of iron, they can be used as they are as an iron source. Moreover, the supernatant after classification is sent to the thickener 4 through the water supply pipe as fine-grained water E.

  The water supply of the fine-grained water E from the classifier 3 to the thickener 4 is, for example, a method using natural flow using a height difference, a water pump (in FIG. 2) in the middle of the water supply pipe between the classifier 3 and the thickener 4. (Not shown), and a method of sending the fine-grained water E with this pump can be used.

(Classifier)
As the classifier 3, for example, a cylindrical supply part to which the dust collection drainage B is supplied, a discharge part for discharging the supernatant in the supply part, and a funnel-shaped bottom part whose center projects downwardly are connected to the lower part of the supply part. The sedimentation tank provided can be used. This sedimentation tank has a recovery port that can collect sediment at the tip of the funnel-shaped bottom.

  When the dust collection waste water B is supplied to the classifier 3, dust having a large particle size in the dust collection waste water B settles at the bottom of the classifier 3. This is because dust having a large particle size has a high sedimentation rate. The settled dust is collected as coarse particles D from the bottom of the classifier 3. The supernatant is recovered as fine-grained water E.

  In addition, the coarse particle D discharged | emitted from the said collection | recovery port can be conveyed to a collection | recovery position using a screw conveyor, a belt conveyor, etc.

The lower limit of the pH of the dust collection waste water B is 10, preferably 10.2, and more preferably 10.5. On the other hand, the upper limit of the pH is 12, preferably 11.9, and more preferably 11.8. When the pH of the dust collection waste water B is less than the lower limit, an oxidation reaction tends to occur in the dust collection waste water B. When this oxidation reaction occurs, iron present in the dust collection waste water B exists in a high proportion in the form of Fe ions, so that the iron content (Fe concentration) in the coarse particles D may be reduced. In addition, when the iron content rate in the coarse grain D is low, there exists a possibility that the efficient reuse as an iron source in a blast furnace or a steelmaking process may become difficult. On the other hand, when the pH of the dust collection waste water B exceeds the upper limit, iron present in the dust collection waste water B reacts with hydroxide ions, and FeOH ₂ (iron hydroxide) is likely to precipitate from the dust collection waste water B. When iron hydroxide is deposited, a deposit is formed, and this deposit adheres to the water supply pipe. This deposit may cause clogging of the water supply pipe between the water tank 22 and the classifier 3.

  As a minimum of temperature of dust collection drainage B, 0 ° C is preferred and 5 ° C is more preferred. On the other hand, the upper limit of the temperature is preferably 50 ° C, more preferably 40 ° C.

  The pH of the dust collection waste water B is preferably adjusted by a water supply pipe from the water tank 22 to the classifier 3 from the viewpoint of workability. The pH may be adjusted with the classifier 3 or the water tank 22, or a water tank for pH adjustment may be provided and used in this water tank.

  The pH of the dust collection waste water B can be adjusted, for example, by introducing an alkaline chemical. Examples of the alkaline agent include alkali metal hydroxides and carbonates. More specifically, sodium hydroxide, slaked lime, calcium carbonate and the like can be mentioned. The said alkaline chemical | medical agent can be thrown into the dust collection waste_water | drain B as aqueous solution. In addition, the said alkaline chemical | medical agent can be used individually or in combination of 2 or more types.

[Fine grain separation process]
In this step, fine particles F are separated from fine particle-containing water E after the coarse particle separation step by thickener 4. Specifically, the fine particles F are separated by the thickener 4 from the fine particle-containing water E adjusted so that the pH is in the range of 7 to 9 and the ΔpH is 3 or more. That is, the fine particles F are recovered by sedimentation from the fine particle-containing water E by the thickener 4. Fine grain F can be used as an iron source, a desiliconizing agent, etc. in a blast furnace or a steelmaking process.

(Thickener)
As the thickener 4, for example, a cylindrical main body portion, a funnel-shaped bottom portion that is connected to the lower portion of the main body portion and protrudes downward at the center, a drainage portion that is positioned on the upper side of the main body portion, and a main body portion are disposed. A coagulation sedimentation tank having a stirring section can be used. This coagulation sedimentation tank has a recovery port capable of recovering the sediment at the tip of the funnel-shaped bottom. The coagulation sedimentation tank can collect the supernatant after fine particle separation from the discharge part.

  In addition, it is preferable that the maximum diameter and height of the said coagulation sedimentation tank are larger than the maximum diameter and height of the said sedimentation tank.

  When the fine particle-containing water E is supplied to the thickener 4, dust having a small particle diameter in the fine particle-containing water E is concentrated and settled by the relatively low speed rotation of the stirring portion of the thickener 4. The dust settled on the bottom of the thickener 4 is collected as fine particles F. The supernatant is discharged as drainage G from the drainage part of the thickener 4. The fine particles F recovered from the thickener 4 may be dehydrated by a filter press. Moreover, it is preferable that the water supply pipe for sending the wastewater G to the watering nozzle of the wet dust collector 21 is connected to the drainage part of the thickener 4.

  As a minimum of pH of fine grain content water E, it is 7, 7.1 is preferred, and 7.2 is more preferred. On the other hand, the upper limit of the pH is 9, is preferably 8.2, and more preferably 7.8. When the pH of the fine-grained water E is less than the lower limit, the pH of the fine-grained water E in the thickener 4 or in the water supply pipe from the classifier 3 to the thickener 4 tends to be acidic. When the pH of the fine-grained water E becomes acidic, there is a risk that equipment damage such as damage to the thickener 4 or damage to the water supply piping from the classifier 3 to the thickener 4 may occur due to corrosion. On the other hand, when the pH of the fine-grained water E exceeds the above upper limit, dust may adhere and the water supply pipe may be clogged. For example, when the waste water G after the fine grain separation step is used as water to be sprinkled in the sprinkling step, clogging may occur in the water supply pipe from the thickener 4 to the water spray nozzle of the wet dust collector 21 or the water spray nozzle.

  The lower limit of the difference (ΔpH) between the pH of the dust collection waste water B and the pH of the fine-grain containing water E is 3, preferably 3.1, and more preferably 3.2. On the other hand, the upper limit of ΔpH is preferably 5, more preferably 4.5, and even more preferably 4. When the ΔpH is less than the lower limit, dust may adhere to the water supply pipe from the classifier 3 to the thickener 4 and the water supply pipe may be clogged. On the other hand, when the above ΔpH exceeds the upper limit, equipment damage such as damage of the thickener 4 due to corrosion and water supply piping from the classifier 3 to the thickener 4 is likely to occur.

  As a minimum of temperature of fine grain content water E, 0 ° C is preferred and 5 ° C is more preferred. On the other hand, the upper limit of the temperature is preferably 50 ° C, more preferably 40 ° C.

  It is preferable to adjust the pH of the fine-grained water E by a water supply pipe from the classifier 3 to the thickener 4 from the viewpoint of workability. The pH may be adjusted by the thickener 4, or a water tank for pH adjustment may be provided and used in this water tank.

  The pH of the fine-grained water E can be adjusted by adding an acidic solution. Examples of the acidic solution include an aqueous acid solution. Specifically, an aqueous solution of an acid such as hydrochloric acid, nitric acid or phosphoric acid is preferably mentioned. In addition, the said acidic solution can be used individually or in combination of 2 or more types.

<Advantages>
In the dust collection method, the pH of the dust collection wastewater to be treated in the coarse particle separation step and the pH of the fine particle-containing water to be treated in the fine particle separation step are adjusted. For this reason, the said dust collection method can suppress effectively generation | occurrence | production of equipment malfunctions, such as clogging in water supply piping and corrosion of water supply piping and a thickener.

  In the dust collection method, the pH of the dust collection waste water to be treated in the coarse particle separation step is adjusted, and the pH of the fine particle-containing water to be treated in the fine particle separation step is adjusted. For this reason, the recovered dust has a high iron content (Fe concentration). In particular, the dust recovery method can recover coarse particles having a very high iron content.

  The dust recovered by the dust recovery method can be used as an iron source in a blast furnace or a steelmaking process. In particular, the recovered coarse particles can be more preferably used as an iron source in a blast furnace or a steelmaking process because the iron content in the coarse particles is high.

[Other Embodiments]
The dust collection method of the present invention is not limited to the above embodiment.

  In the dust collection method, the watering step, the coarse particle separation step, or the fine particle separation step can be performed in multiple stages.

  In the dust collection method, two or more wet dust collectors, two or more classifiers, and two or more thickeners can be used.

  In the dust recovery method, water and additives can be added to the dust collection waste water and fine particle-containing water.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and can be implemented with modifications within a range that can be adapted to the gist of the present invention, all of which are included in the technical scope of the present invention. .

[Examples and Comparative Examples]
Dust generated from the converter was recovered by the following converter dust recovery system. First, pig iron processing (primary refining) was performed using a converter under the conditions shown in Tables 1 and 2. The capacity of the converter was 100 tons. A top-bottom blow was adopted as the converter type. As an upper blowing nozzle for sending oxygen, a nozzle having six holes, a hole diameter of 28.4 mm, and a hole angle of 12 ° was used. As the bottom blowing gas, a mixed gas of CO and Ar (CO / Ar gas) was used. The type of tuyeres into which the bottom blowing gas was blown was a single-layer tube, and the number of tuyere was four. The opening area of the tuyere was 25.8 mm ² . The total opening area of the tuyere was 103.2 mm ² .

  The primary refining was controlled as follows. That is, the required oxygen amount (the amount of oxygen necessary for decarburization of pig iron) was determined by static control according to ordinary methods of those skilled in the art. CaO, the heat-increasing auxiliary material, and the cooling auxiliary material were determined by ordinary methods of those skilled in the art. The dynamic control at the end of the blowing process was carried out by the ordinary method of those skilled in the art.

  The converter dust recovery system includes an exhaust gas recovery device, a wet dust collector, an OG facility having a water tank connected to the lower part of the wet dust collector, a classifier, and a thickener in this order. Moreover, the wet dust collector of OG equipment has a watering nozzle. Water supply pipes are connected between the water tank of the OG facility and the classifier, between the classifier and the thickener, and between the thickener and the water spray nozzle of the wet dust collector. The water supply pipe between the water tank and the classifier and the water supply pipe between the classifier and the thickener include a mechanism for adjusting the pH of the water in the water supply pipe. In addition, a water supply pump is disposed in the middle of the water supply pipe between the water tank of the OG facility and the classifier.

  Next, exhaust gas generated in the converter was sent to the OG facility while performing primary refining, and the exhaust gas was sprinkled with a wet dust collector of the OG facility. Watering was performed by spraying water from a watering nozzle at a water flow rate of 230 t / hr. Watering was performed in a multistage manner using six watering nozzles. By sprinkling water, the exhaust gas was separated into dust collection wastewater containing dust and water and gas components. Dust collection wastewater was collected in a water tank at the bottom of the OG facility, and gas components were sent to the exhaust gas recovery device of the OG facility.

  Next, the collected waste water collected in the water tank was fed to a classifier through a water feeding pipe. At this time, the pH of the dust collection drainage was adjusted using a pH adjustment mechanism provided in the water supply pipe. Tables 1 and 2 show the pH of the dust collection waste water after pH adjustment. Sodium hydroxide and slaked lime were used for pH adjustment.

  Next, the coarse particles were settled and separated from the dust collection wastewater by a classifier, and the coarse particles were collected. The supernatant after the coarse grain recovery was used as fine grain-containing water.

  Next, the fine particle-containing water was fed from the classifier to the thickener through the water feeding pipe. At this time, the pH of the fine-grained water was adjusted using a pH adjustment mechanism provided in the water supply pipe. Tables 1 and 2 show the pH of the fine-grained water after pH adjustment. Hydrochloric acid was used for pH adjustment.

  Next, fine particles were recovered by separating fine particles from the fine particle-containing water using a thickener.

  The drainage from the thickener was sent from the thickener to the watering nozzle of the wet dust collector through the water supply pipe and reused as water for watering.

[Evaluation]
The following evaluation was performed about the Example and the comparative example. The results are shown in Tables 3 and 4. Moreover, the graph which shows the pH dependence of the total iron amount in the coarse grain of an Example in FIG. 3 is shown, and the graph which shows the pH dependence of the metallic iron amount in the coarse grain of an Example is shown in FIG.

(Clogging of water supply piping from the tank to the classifier)
It was confirmed whether or not clogging of the water supply pipe occurred in the water supply pipe from the water tank at the bottom of the OG facility to the classifier. The case where clogging did not occur was evaluated as “good” (A), while the case where clogging occurred was evaluated as “bad” (B). The results are shown in the column “clogging 1” in Tables 3 and 4.

(Clogging in water supply piping from classifier to thickener)
In the water supply pipe from the classifier to the thickener, it was confirmed whether or not the water supply pipe was clogged. The case where clogging did not occur was evaluated as “good” (A), while the case where clogging occurred was evaluated as “bad” (B). The results are shown in the column “clogging 2” in Tables 3 and 4.

(Water pipe from tank to thickener and corrosion of thickener)
It was confirmed whether or not corrosion occurred in the water supply piping from the water tank below the OG facility to the thickener and the thickener. When corrosion does not occur in both the water supply pipe from the tank to the thickener and the thickener is evaluated as “good” (A), and on the other hand, when corrosion occurs in at least one of the water supply pipe from the tank to the thickener and the thickener Was evaluated as “bad” (B). The results are shown in the column of “Corrosion” in Tables 3 and 4.

(Clogging in the water supply piping from the thickener to the water spray nozzle of the wet dust collector)
In the water supply pipe from the thickener to the water spray nozzle of the wet dust collector, it was confirmed whether or not the water supply pipe was clogged. The case where clogging did not occur was evaluated as “good” (A), while the case where clogging occurred was evaluated as “bad” (B). The results are shown in the column “clogging 3” in Tables 3 and 4.

(Coarse and fine component composition)
The composition of the recovered coarse and fine particles was analyzed by inductively coupled plasma emission spectroscopy (lower limit of analysis: 0.01% by mass), and “total iron content (T.Fe)” (% by mass), “metal” The amount of iron (M.Fe) ”(mass%) and the amount of iron oxide (FeO + Fe ₂ O ₃ ) (mass%) were determined. These results are shown in Tables 3 and 4.

<Evaluation results>
From Table 3, in Examples 1 to 15 in which the pH of the dust collection wastewater and the pH of the fine-grained water are adjusted to be within the predetermined ranges, the water supply piping from the water tank to the classifier and the water supply from the classifier to the thickener It can be seen that clogging and corrosion do not occur in the piping. Moreover, in Examples 1-15, it turns out that corrosion of a thickener does not occur. Furthermore, in Examples 1-15, it turns out that clogging does not occur in the water supply piping from the thickener to the water spray nozzle of the wet dust collector or the water spray nozzle of the wet dust collector. From these facts, it can be seen that Examples 1 to 15 do not cause any troubles in equipment when collecting dust.

  From Table 3, FIG. 3 and FIG. 4, according to Examples 1 to 15, coarse particles having a total iron content of 90% by mass or more and a metal iron content of 85% by mass or more and a fine particle having a total iron content of 50% by mass or more Grains can be collected. The coarse particles have a very high iron content and can be suitably used as an iron source.

  Table 4 shows the following. That is, in Comparative Examples 1 to 5 in which the pH of the dust collection wastewater was larger than 12, clogging occurred in the water supply piping from the water tank to the classifier.

  In Comparative Examples 6 to 10 in which ΔpH was less than 3, clogging occurred in the water supply piping from the classifier to the thickener.

  In Comparative Examples 11 to 15 in which the pH of the fine-grained water was less than 7, corrosion occurred in at least one of the water supply pipe from the classifier to the thickener and the thickener.

  In Comparative Examples 16 to 18 in which the pH of the dust collection drainage was larger than 12, clogging occurred in the water supply piping from the water tank to the classifier.

  In Comparative Examples 19 to 21 in which the pH of the fine-grained water was less than 7 and the ΔpH was more than 5, corrosion occurred in at least one of the water supply pipe from the classifier to the thickener and the thickener.

  Comparative Example 22 in which the pH of the dust collection wastewater is greater than 12 and the pH of the fine-grained water is less than 7 is at least one of clogging in the water supply pipe from the water tank to the classifier and the water supply pipe from the classifier to the thickener and the thickener. Corrosion occurred at.

  Comparative Examples 23 and 24, in which the pH of the dust collection wastewater is greater than 12, the pH of the grain-containing water is greater than 9, and ΔpH is less than 3, the water supply piping from the water tank to the classifier, the water supply from the classifier to the thickener Clogging occurred in the piping and the water supply piping from the thickener to the water spray nozzle of the wet dust collector thickener 4 set.

  In Comparative Examples 25 to 28 in which the pH of the dust collection wastewater is less than 10 and the pH of the fine-grained water is less than 7, the water supply piping from the water tank to the classifier, the water supply piping from the classifier to the thickener, and the thickener Corrosion occurred on at least one side.

  As described above, the dust recovery method can effectively suppress the occurrence of equipment problems during dust recovery and efficiently recover dust having a high iron content. The dust obtained by the dust recovery method of the present invention can be used as an iron source in a blast furnace or a steelmaking process.

DESCRIPTION OF SYMBOLS 1 Converter 2 OG equipment 21 Wet dust collector 22 Water tank 23 Exhaust gas recovery device 3 Classifier 4 Thickener A Exhaust gas B Dust collection drainage C Gas component D Coarse grain E Fine grain containing water F Fine grain G Wastewater

Claims (1)

Watering the exhaust gas containing dust with a wet dust collector;
A first separation step of separating the dust from the dust collecting waste water after the shower process by a classifier,
A second separation step of separating dust from the fine-grained water after the first separation step by a thickener, and a method of recovering dust generated in a converter,
In the first separation step , the pH of the dust collection waste water to be treated is adjusted to a range of 10 or more and 12 or less, and coarse particles having a particle size of 50 μm or more are separated by 80% by volume or more,
In the second separation step , the fine particle-containing water to be treated is adjusted to have a pH of 7 to 9 and the difference between the pH of the dust collection waste water and the fine particle-containing water is 3 or more , A dust recovery method characterized by separating fine particles having a ratio of less than 50 μm of 80% by volume or more .

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