JPH0772289B2 - Method and apparatus for recycling hot metal pretreatment dust - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for recycling hot metal pretreatment dust, and particularly to a hot metal pretreatment process using soda ash, lime, carbide or the like as a refining agent. The present invention relates to a method and an apparatus for reusing the generated dust as a refining agent for hot metal.

[Conventional technology]

Generally, hot metal produced in a blast furnace is stored in a transport container such as a hot metal truck and conveyed to a steelmaking plant, or before it is charged into a converter, lime, calcium carbonate, calcium carbide, calcium chloride. , Soda ash and other refining agents are injected into the hot metal for pretreatment. Furthermore, recently, the functionalization of the steelmaking process has progressed, and the hot metal pretreatment process in which the hot metal desiliconization, dephosphorization, and desulfurization processes are separated from the steelmaking process using a converter has been widely adopted. For example, in the dephosphorization step, while adjusting the basicity of slag by adding lime or the like, iron oxide, sintered ore powder, injecting solid oxygen sources such as manganese ore powder,
Alternatively, a method of blowing in gaseous oxygen is often adopted, and a method of simultaneously performing dephosphorization and desulfurization by injecting soda ash is also known.

In these hot metal pretreatment steps, in addition to iron powder and iron oxide, there is a large amount of dust containing unreacted refining agents, etc., from the viewpoint of pollution prevention and effective use of resources from the past,
Much work has been done on collecting and recycling these dusts.

That is, dust containing iron powder and iron oxide is pelletized and reused as an iron source in a blast furnace. However, if dust containing soda ash is reused in a blast furnace, it will adversely affect refractory materials, and even if it is discarded as industrial waste, dust-prevention treatment by water addition is required, and transportation costs and treatment costs increase. Therefore, paying attention to the fact that it contains an effective component as a refining agent, rather it is advisable to reuse it for pretreatment such as dephosphorization, desulfurization, etc. Has been disclosed.

For example, JP-A-51-143507 proposes a method in which dust generated during hot metal desulfurization is collected by a dust collector and then directly charged into a pressure tank for infusion and blown into the hot metal. In Japanese Examined Patent Publication No. 55-21812, the collected dust is temporarily stored in a primary storage tank outside the dust collector and then conveyed by air to a second tank, and the dust cut out from the tank is passed through a weighing hopper. A method of carrying out and reusing as a part of the desulfurizing agent for hot metal is disclosed. Furthermore, in JP-A-61-227116, in order to stably carry out the same method,
A method of drying the collected dust using the heat of the collected exhaust gas is disclosed.

However, experiments conducted by the present inventors have revealed that the above-mentioned conventional technique has the following problems. That is, in the dust collector hopper, the moisture in the dust collecting gas or the moisture in the outside air entering from the leak part such as the inspection port may be absorbed to solidify the dust, and the collected dust is initially 100
Although it is a fine powder having a low bulk specific gravity of ℃ or more, when it is cooled by heat radiation from the outer wall while it is stored in the hopper, the adhesiveness increases, and the dust grows in layers on the inner wall of the hopper. This phenomenon is particularly remarkable in the dust containing soda ash, and is also observed when the exhaust gas is cooled by the heat exchange method without using a large amount of diluted atmosphere or water.

As described above, the dust adhering to the inner wall of the hopper peels off or solidifies, so that the lump of dust is mixed in the hopper, and such a dust is left untreated and the pressure tank for infusion is left untreated. It was also confirmed in the experiments conducted by the present inventors that, when charging into the hot metal, massive dust blocks the outlet of the tank at the time of injecting the dust into the hot metal, and the pretreatment operation must be interrupted.

In this development, when a storage container other than the dust collector hopper is provided as in Japanese Patent Publication No. 55-21812, the same adhesion phenomenon as that of the dust collector hopper is recognized during long-term use.
It was also found to be a source of lumpy dust.

[Problems to be Solved by the Invention]

The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art relating to the reuse of hot metal pretreatment dust, prevent the lumpy dust from being mixed into the infusion tank, and generate dust during stable hot metal pretreatment. Also aims to provide a method and a device which can be reused as a refining agent in a simple process and at low cost.

[Means for Solving the Problems]

The gist of the method for recycling hot metal pretreatment dust according to the present invention is as follows.

(1) In a method of reusing hot metal pretreatment dust, which collects dust dust generated in the hot metal pretreatment step and reuses it as a refining agent, in the dust collector, after collecting the dust from the exhaust gas with a dry dust collector. A step of storing in the hopper, and a step of transporting the dust stored in the hopper to an infusion pressure tank after removing the lumped dust,
And a step of reusing the dust charged in the pressure tank for infusion treatment for hot metal pretreatment alone or together with another refining agent, and a method for reusing the hot metal pretreatment dust. .

(2) The removal of the lump dust from the dust stored in the hopper is performed by a trap or a classification means or a crushing means provided on the way to the pressure tank for the injection, the hot metal pretreatment described in (1) above. How to reuse dust.

(3) The removal of the lumpy dust from the dust stored in the hopper is performed by preliminary crushing before transportation to the pressure tank for infusion using a crushing device installed in the hopper. A method of reusing pretreatment dust.

Further, the gist of the apparatus for recycling hot metal pretreatment dust according to the present invention is as follows.

(4) A dry-type dust collector that collects the dusty dust generated in the hot metal pretreatment step in a reclaiming device of the hot metal pretreatment dust that is collected by a dust collector and reused as a refining agent, A dust hopper for storing the collected dust in the dust collector, a means for transporting the dust stored in the dust hopper to a pressure tank for indicion after removing the lumped dust, and storing the transported dust. A pressure tank for injection
And a blowing device for blowing the dust stored in the pressure tank for infusion, into the hot metal alone or together with other refining agent, to reuse the hot metal pretreatment dust.

(5) The hot metal pretreatment dust according to (4) above, which has a trap or a classifying device or a crushing device that excludes agglomerate dust in the middle of a means for transporting the dust stored in the dust hopper to a pressure tank for infusion. Reuse equipment.

(6) The recycling apparatus for hot metal pretreatment dust according to (4), further including a crushing device for lumpy dust provided in the vicinity of an outlet of a dust hopper that stores the dust collected by the dry dust collecting device. is there.

The present invention has been completed based on the following findings obtained by many experiments by the present inventors.

That is, the properties of the lumpy dust collected during the experiments of the inventors of the present invention are such that most lumps are relatively soft and fragile, and the cause of this is that the dust attached to the inner wall of the hopper and the protrusions inside is laminated. It has grown into a shape and is about 100-200 mm in size, while there are very few lumps that hardened by absorbing a large amount of water. Therefore, if the exhaust gas is cooled by the indirect cooling method and the dust is collected by the dry dust collector, the moisture content of the powdery dust in the hopper is less than 1%, and the injection can be performed as it is. Further, it has been found that the dust in the hopper has a relatively high temperature and the shorter the standing time, the better the fluidity.

Based on these findings, the following facts were found regarding the dust recycling process.

(B) If the lumps in the dust are excluded, the dust in the dust collector hopper can be immediately received in the pressure tank for the injection and blown into the hot metal.

(B) Providing a dust storage hopper other than the dust collector will reduce the temperature of the dust, increase the amount of adhered dust, and cause the generation of lumpy dust.

(C) The dust collected by the dust collector is still warm in the hopper unless it is left for a long time and the fluidity is relatively good, so it should be kept in the dust collector hopper until just before the ingestion.

The present invention has been completed from the above findings, and the steps of the method for recycling hot metal pretreatment dust of the present invention will be described with reference to FIG.

Using an infusion tank (pressurization tank) 10 containing a conventional refining agent such as lime, soda ash, calcium carbonate, calcium carbide, etc., the high temperature dust generated in the hot metal pretreatment step 1 The exhaust gas 2 contained is
Almost all the amount is sucked into the dust collector provided as an environmental measure, but at this time, the temperature is usually 800 to 900 ° C, although it is diluted a little because some of the outside air is also sucked. It is not possible to introduce this into the dry dust collector 4 as it is, because it is impossible due to the heat resistance of the bag filter for collecting dust, so it is necessary to cool it to 100 to 150 ° C. in the preceding stage. There are various methods for cooling the high-temperature exhaust gas, such as dilution cooling with a large amount of outside air, water addition with a mist spray, or a water washing method with a bench yuly scrubber that also serves as dust removal.
In the present invention, it is desirable to install the gas cooler 3 by the indirect cooling method from the viewpoint that it is necessary to avoid mixing of water, which causes solidification, adhesion, and cohesion due to moisture absorption of dust, as much as possible. The indirect cooling method also includes water cooling and air cooling, and the shapes and control methods of the heat transfer parts are different in both methods, but any indirect cooling method can be used as long as it can prevent supercooling of exhaust gas. In the present invention, the introduction of outside air entrained during the exhaust gas suction should be avoided as much as possible from the viewpoint of avoiding the generation of lumpy dust as much as possible due to solidification due to moisture absorption of dust, increase in adhesion and cohesiveness. However, if it is unavoidable, it is necessary to have sufficient capacity for crushing or separating and removing lumps in the recycling process.

The dust-containing dust-containing exhaust gas cooled by the indirect cooling type gas cooler 3 is collected by the dry dust collector 4 in order to avoid moisture absorption as much as in the cooling process, and the exhaust gas 6 and the collected dust 7 are removed into dust. To be separated. The exhaust gas 6 is further dust-removed by a dust remover, and then released into the atmosphere as clean exhaust gas 6.

The collected dust 7 that is separated and collected is stored in the hopper 5 in the temporary dust collector 4, and the temperature of the collected dust 7 at this time is about
Since the temperature was 100 ° C, almost no water adhered to the dust surface, and the crystal water could be suppressed to less than 1% by using the gas cooler 3 of the indirect cooling system. By collecting the collected dust 7 in the hopper 5 in the dust collector, it is possible to prevent a temperature drop due to transfer or the like, but long-term storage is impossible due to the capacity of the hopper 5, and with the passage of time. Since it will promote lump formation due to cooling and increase in adhesiveness and cohesiveness, it should be promptly taken out and reused. At that time, the same applies to the pressurized injection tank 9 for reused dust. For this reason, it is better to transfer it just before use.

At this time, if the collected dust 7 in the dust collector hopper 5 is kept warm and heated by using another heat source, or if the collected dust 7 in the hopper 5 is agitated or fluidized by installing an air ration device. Even better, according to the present invention, it is not necessary in practice and can be omitted for the purpose of reuse at low cost.

One of the features of the present invention is that the lumped dust is excluded when the collected dust 7 stored in the dust collector hopper 5 is transferred to the pressure tank 9 for injection. As a concrete method thereof, a trap, a classifying device, or a crushing device is provided in the middle of the transportation means from the hopper 5 to the pressure tank 9 for infusion as described in detail in Examples below, or crushing is performed near the discharge port of the hopper 5. It was decided to incorporate the device.

As the transportation means, a known powder transportation means such as a belt conveyor, a chain conveyor, an air slide, an air transportation, and a gravity fall may be applied, but it is necessary to consider to prevent the scattering of moisture absorption and falling powder. is there. Examples described later show these examples.

Thus, the collected dust 7 received in the pressure tank 9 for infusion is used alone or in combination with other refining agents in place of the pressure tank 10 for infusion in which the conventional ordinary refining agent is stored in the hot metal pretreatment step 1. It is reused after being exposed to hot metal.

〔Example〕

An embodiment of a method and an apparatus for recycling hot metal pretreatment dust according to the present invention will be described with reference to FIGS. 2 and 3.

Example 1 In the hot metal pretreatment step 1, the hot metal 24 accommodated in the hot metal wheel 24 is sucked with the refining agent from the conventional injection tank 10 through the immersion lance 23 for desiliconization and degassing. Pretreatment of phosphorus, desulfurization, etc., but exhaust gas containing dust at high temperature of 800-900 ℃ generated at that time 2
Are collected in the dust collecting hood 26 and cooled to 100 to 150 ° C. by the indirect cooling type exhaust gas cooler 3, and the dry type dust collector 4
Is separated into collected dust 7 and exhaust gas 6 which have been removed by a bag filter (not shown), and the exhaust gas 6 is a clean gas 17
Is released into the atmosphere as. On the other hand, collected dust 7
Is stored in the dust collector hopper 5, and during long-term use, of the collected dust 7 in the hopper 5, especially the portion in contact with the outer wall of the hopper 5 is cooled and absorbed to become attached dust 29.

The adhering dust 29 peels off during long-term use and falls off as a dust lump.
It is often 30.

Dust lump 30 as it is Pressure tank for ingestion 9
Since the outlet 37 of the tank is closed when it is transferred to, the feature of the present invention is that the dust lump 30 is excluded before the transfer. An example of the case where the trap 13 for dust lumps is provided is shown. The operation is as follows. That is, the roots blower 16 for exhaust pressure reduction of the pressure tank (injection tank) 9 is used to exhaust and reduce the pressure inside the pressure tank 9, and the valve 21 of the air transport pipe 18 is opened to transport the dehumidified gas 14 to the transport pipe 18. Send in. At this time, when the cut-out gate 20 of the dust collector hopper 5 is opened, the collected dust 7 in the hopper 5 is suspended in the dehumidified gas 14 and the transportation pipe 18
It is transported inside and loaded into the injection tank 9. Here, most of the collected dust 7 remains in the injection tank 9, but part of it is mixed with the exhaust gas 28 and the exhaust pipe.
Since it is discharged from 19, the dust remover 15 is provided in front of the roots blower 16 to remove dust and then discharged into the atmosphere as clean exhaust gas 17.

The adhered dust 29 and the like adhering to the inner wall of the dust collector hopper 5 may peel off and become a dust lump 30 and mix into the transportation pipe 18, but these dust lumps 30 are relatively soft.
Therefore, as shown in the figure, a trap chamber 35 having a suddenly large volume is provided in the middle of the transportation pipe 18 to reduce the transportation speed of the hopper dust 7 during air transportation, and a collision plate 12 is provided in the traveling direction to collide with the dust mass. A part of 30 is crushed. The crushed dust lumps 30 that have not been crushed are gravity-sorted and settled due to the rapid change in the gas flow rate, and are collected at the bottom of the trap chamber 35. Therefore, the lumps in the collected dust that flow into the injection tank 9 are removed. To be done.

The fine powdery collected dust 7 transported to the ingestion tank 9 is blown alone or together with another refining agent into the molten pig iron 25 accommodated in the hot metal truck 24 through the ingestion transport pipe 22 to remove phosphorus, It is reused for pretreatment such as desulfurization.

As means for removing the dust lumps 30 during transportation, in addition to the traps, a classifying device 40 having a sieve 39 as shown in FIG. 5 (A) and a driving device as shown in FIG. 5 (B) are used. The crushing device 41 included therein can also be installed.

Example 2 As to the specific method of removing the dust lumps 30 during the transportation of the collected dust 7 from the dust collector hopper 5 to the injection tank 9 in the present invention, as in Example 1, Instead of providing the trap 13 for sinking the dust lumps 30 on the way, a crusher 31 for crushing the dust lumps 30 may be provided at the bottom of the dust collector hopper 5, as shown in FIG.

In this case, an independent drive source is attached to the bottom of the dust collector Hopper 5.
32 and a horizontal shaft 34 equipped with a scraping bar 33 are rotated to remove dust clumps.
By stirring 30 the relatively soft dust mass 30 is easily crushed. Accordingly, the collected dust 7 stored in the dust collector hopper 5 is passed through the crusher 31 at the bottom regardless of whether it is fine dust or dust lumps 30, and the injection tank 9
Therefore, the fine powder dust 7 can be transported to the injection tank 9 by a gravity drop method by using the vertical pipe 36 instead of the air transportation pipe 18. Also in this case, the dust lumps 30 are completely prevented from being mixed in the collected dust 7 conveyed to the injection tank 9, and the transportation pipe 22 for injection from the injection tank 9 to the towing car 24 is closed. The hot metal pretreatment is operated smoothly.

Example 3 An example at the time of reusing dust generated in the hot metal pretreatment step in a hot metal truck using soda ash will be described with reference to FIGS.

Using soda ash as a desulfurizing and refining agent, exhaust gas 2 containing dust generated at a maximum of 850 ℃ in a hot metal car is cooled by an air-cooled plate cooler type heat exchanger that is an indirect cooling gas cooler 3 to 100-130 ℃ After controlled cooling up to, the dust was collected by the dry dust collector 4 using a bag filter.
Table 1 shows examples of the components of the collected dust 7.

As is clear from Table 1, the collected dust 7 is mainly composed of soda ash and has a water content of less than 1%.

The collected dust 7 is the dust collector Hopper 5 shown in FIG.
And cut it out from the hopper 5 through the gate 20
Air transportation was carried out using a 0 mmφ transport pipe, and a trapezoidal trap chamber 35 having a side length of 1.5 m was provided on the way, and a dust lump 30 was removed by providing the collision plate 12 in front of the entrance side. After performing the injection test, the trap chamber 35 was opened and examined. As a result, a large number of dust lumps 30 having a diameter of 5 to 40 mm were found. It is considered that these dust lumps 30 are the dust 29 adhering to the inner wall of the dust collector hopper 5, which has fallen off and mixed, but a simple trap device is used.
It was confirmed to be extremely effective for the separation and removal of.

75 kg / min of the collected dust 7 thus collected in the injection tank 9 in 180 to 220 tons of hot metal 25 in the hot metal wheel 24
The blow-off desulfurization test was conducted at the following speed. FIG. 4 is a diagram comparing the relationship between the amount of desulfurization agent used (kg-Na ₂ CO ₃ / t hot metal) and the desulfurization rate between conventional pure soda ash and the dust collected by the present invention. As is clear from FIG. 4, the collected dust 7 collected by the present invention is used as a desulfurization refining agent,
Although there were variations, it was found that there was almost no difference from the desulfurization rate when conventional pure soda ash was used as a refining agent.

In addition, no abnormal reaction due to water was observed even in the ingestion of only the collected dust, and it was confirmed that the ingestion speed is stable and can be effectively used as a refining agent for hot metal pretreatment as an alternative to pure soda ash. .

The present inventors conducted a dephosphorization test using collected dust subsequent to the desulfurization test, and found that the dephosphorization effect was similar to that when pure soda ash was used, as in the above.

〔The invention's effect〕

The method and apparatus for recycling hot metal pretreatment dust according to the present invention has drawbacks of the prior art, especially during long-term storage in the hopper, which was remarkable at the time of recovering dust containing a component having hygroscopicity such as lime and soda ash. Dry dust collector is used in the recovery process in order to eliminate the problems such as the growth of adhered dust on the inner wall that occurs and the clogging of the outlet due to the dropout, etc. in the injection operation. By dealing with the inclusion of dust lumps, by installing a simple trap device in the middle of air transportation to the infusion tank, or by using a dust collector hopper equipped with a crushing device,
Since the dust lumps were eliminated, the following effects could be achieved.

(A) When used alone or simultaneously with other refining agents by the collected dust, it was possible to carry out the injection without any operational trouble, and the injection speed was stable.

(B) The desulfurization and dephosphorization effects due to the collected dust are comparable to those of the new refining agent in the net content calculation results.

(C) Since the process of the present invention is extremely simple and the apparatus is simple, the equipment cost is low and the manufacturing cost is low.

(D) It was possible to prevent pollution in the factory and effectively use resources.

[Brief description of drawings]

FIG. 1 is a flow chart showing the steps of a method for recycling hot metal pretreatment dust according to the present invention, and FIG. 2 is a partially omitted sectional view showing the arrangement of a recycling method and apparatus in an embodiment of the present invention,
FIG. 3 is a schematic cross-sectional view of an apparatus for transporting collected dust from a dust collector Hopper equipped with a dust lump crushing apparatus used in another embodiment of the present invention to an injection tank through a vertical pipe, FIG. Is a comparison diagram of the desulfurization rate with pure soda ash in the desulfurization test by the collected dust collected during the hot metal pretreatment using the soda ash according to the present invention as a refining agent, FIG. 5 (A),
(B) is a schematic cross-sectional view showing another embodiment having a device for removing dust lumps during the transportation of collected dust from the dust collector hopper to the injection tank, (A) is a classifier, and (B) is This is the case with a crushing device. 1 …… Hot metal pretreatment process 2 …… Exhaust gas containing dust emission 3 …… Exhaust gas cooler 4 …… Dry dust collector 5 …… Dust collector hopper, 6 …… Dust removal exhaust gas 7 …… Collection dust, 8 …… Dust lump Exclusion device 9 …… Injection tank for collecting dust (pressurized tank) 11 …… Dust transport device, 12 …… Collision plate 13 …… Trap for removing dust lumps, 14 …… Dehumidifying gas 15 …… Dust remover, 16 …… Roots blower 17 …… Clean exhaust gas, 18 …… Air transportation pipe 19 …… Exhaust pipe, 20 …… Cutout gate 21 …… Valve, 22 …… Injection transportation pipe 23 …… Injection immersion lance 24 …… Mixer car , 25 …… hot metal 26 …… dust collecting hood, 27 …… valve 28 …… dust exhaust gas, 29 …… adhered dust 30 …… dust lump, 31 …… dust crusher 32 …… driving source, 33 …… Scraper 34 …… Trap chamber, 35 …… Trap chamber 36… Vertical tube, 37 ...... outlet 39 ...... sieve, 40 ...... classifier 41 ...... crushing device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Takeshi 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture (no address) Inside the Mizushima Works, Kawasaki Steel Co., Ltd. (56) Reference JP 62-93308 (JP, A) ) Actual public Sho 60-40574 (JP, Y2)

Claims (6)

[Claims] 1. A method for reusing hot metal pretreatment dust, wherein dust generated in the hot metal pretreatment step is collected by a dust collector and reused as a refining agent, and the exhaust gas is collected by a dry dust collector. After that, a step of storing the dust in the hopper of the dust collector, a step of removing the dust accumulated in the hopper to a pressure tank for injection after removing lumpy dust, and a step of mounting the dust in the pressure tank for injection And a step of reusing the introduced dust alone or together with another refining agent for hot metal pretreatment, a method for recycling hot metal pretreatment dust. 2. The method according to claim 1, wherein the lump dust is removed from the dust stored in the hopper by a trap or a classification means or a crushing means provided on the way to the pressure tank for injection. A method for reusing the described hot metal pretreatment dust. 3. The removal of lumpy dust from the dust stored in the hopper is carried out by preliminary crushing before transportation to the injection pressure tank by a crushing device installed in the hopper. The method for reusing the hot metal pretreatment dust described in (4). 4. A dry-type dust collecting apparatus for collecting the dusty dust generated in the hot metal pretreatment step in a reclaiming device for the hot metal pretreatment dust, which is collected by a dust collector and reused as a refining agent. A dust hopper for storing the collected dust in the dust collector, a means for transporting the dust stored in the dust hopper to a pressure tank for injection after removing lumped dust, and the transportation. A pressure tank for storing the dust that has come in and a blowing device that blows the dust stored in the pressure tank for the injection into the hot metal alone or together with other refining agent. An apparatus for recycling hot metal pretreatment dust, characterized in that 5. A trap or a classifying device or a crushing device for excluding lumpy dust is provided in the middle of a means for transporting the dust stored in the dust hopper to a pressure tank for injection. Recycling device for hot metal pretreatment dust described. 6. The reprocessing of hot metal pretreatment dust according to claim 4, further comprising a crushing device for lumpy dust provided in the vicinity of an outlet of a dust hopper for storing the dust collected by the dry dust collector. Utilization device.