JPH08311533A - Method for removing dust in exhaust line of vacuum degasifier and device therefor - Google Patents

Abstract

PURPOSE: To continuously and surely remove a large amt. of dust in an exhaust gas in the vacuum exhaust line of vacuum degasification even in the process of degasification, to conduct a stabilized vacuum degasifying operation, to conduct a latest heating and refining tachnique, etc., and to use even a vacuum pump. CONSTITUTION: The dust generated in the vacuum degasifier under vacuum or reduced pressure in the front or rear of the pressure-reducing multistage booster 21 and/or ejector 22 and/or in the front and rear of a vacuum pump device 31 is collected by a reticular filter 34. The collected dust is washed with water by a washing water spraying device 35 in the process of vacuum degasification or while the degasification is suspended from the filter 34, and the washing water and dust are discharged into a sealed tank 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum degassing equipment exhaust system for a vacuum degassing equipment (ejector, vacuum pump, etc.) of a vacuum degassing equipment used for refining molten metal and for preventing dust from adhering to the inner wall of an exhaust duct. The present invention relates to a dust removing method and an apparatus therefor, and particularly, the dust in the exhaust gas of a recent vacuum degassing treatment facility in which the dust in the exhaust gas flowing in the duct tends to increase (temperature rising refining, etc.), The present invention relates to an effective method and apparatus for continuous discharge.

[0002]

2. Description of the Related Art Generally, molten steel obtained in a converter for refining molten pig iron from a blast furnace or an electric furnace for melting raw materials is
Since it is contaminated by gas components such as oxygen, nitrogen, hydrogen, etc., while transferring the molten steel to the ladle and transferring it to the mold,
The molten steel in the ladle is subjected to secondary refining such as degassing (outside furnace refining). This degassing process is a method of degassing by sucking molten steel in a ladle into a vacuum tank and exposing it to a vacuum, and usually a reflux type RH vacuum degassing process is adopted.

FIG. 3 shows an example of a conventional vacuum degassing equipment consisting of an existing RH vacuum degassing device and a vacuum exhaust system. In the RH vacuum degassing device 1, a ladle 2 is moved up and down. 2 dip tubes 3
The ladle is immersed in the molten steel in the ladle, and the molten steel is sucked into the vacuum degassing tank 4 by vacuum, and at the same time, the ladle 2 is raised according to the degree of vacuum in the vacuum tank. Then, a reflux gas such as Ar gas is blown into or below the ascending pipe, the molten steel is sucked up into the vacuum tank by the principle of the air lift pump, and the descending pipe lowers it into the ladle, thereby making the molten steel into the vacuum degassing tank 4. Ladle 2
It is refluxed between.

At the upper part of the vacuum degassing tank 4, there are provided a ferroalloy feeding device 5 for adjusting components, an ITV 6 for monitoring, a top lance for blowing oxygen or the like for decarburization, an exhaust port 7, etc. The port 7 communicates with a vacuum exhaust mechanism via a horizontal exhaust duct 8, a gas cooler 9, a shutoff valve box 10, and a vertical exhaust duct 11.

The vacuum evacuation mechanism comprises, in order from the upstream side, a multistage pressure reducing booster 21 in which steam ejectors are arranged in multiple stages, a plurality of steam ejectors 22, and a condenser 23 respectively installed on the downstream side thereof. . In addition, the start ejector 22 _-0 is installed between the No. 1 condenser 23 _-1 and the after condenser -23 _-4.
Is provided, the clean gas in the after-condenser -23 _-4 are exposed to the atmosphere through the drain separator 24.
The bottom of each condenser 23 and drain separator 24 is a sealing tank (water collection pit, hot well pit) 2
It communicates with 5.

In such vacuum degassing equipment,
Part of the dust contained in the exhaust gas from the vacuum degassing tank 4 is collected by the dry gas cooler 9 and the shutoff valve box 10, but the residual dust in the exhaust gas that is not collected here is evacuated by a vacuum exhaust mechanism. And then adheres to the inner walls of each ejector and duct of the vacuum generator, causing a problem such as deterioration in function.

Conventionally, various methods for removing dust in vacuum degassing equipment have been developed. Vacuum degassing device 1, dry gas cooler 9, shut-off valve box 10
Regarding the exhaust port / exhaust duct between the exhaust port and the exhaust port, exhaust port dust removal methods or exhaust ducts described in JP-A-1-279708, JP-A-6-207789, JP-A-6-220522 and the like. There is a method to prevent internal dust adhesion. On the other hand, dry gas cooler 9
The following methods and devices have been proposed as dust prevention and dust removal methods in the vacuum exhaust mechanism located on the downstream side of the shutoff valve box 10.

No. 63-50865 gazette A washing water nozzle is arranged near the lower part of each ejector nozzle of the multistage booster 21 for decompression shown in FIG. 3, and during the non-degas treatment, this washing water nozzle causes the inside of the multistage booster to be increased. The dust accumulated on the surface of the condenser is washed away, and a plurality of water film spray nozzles are arranged on the inlet side and the outlet side of the condenser 23. During degassing, a water film is formed on the cross section of the condenser by the water film spray nozzle. The water film blocks the dust.

JP, 6-158188, A Inert gas supply circuit is connected to the steam flow supply circuit to the nozzle which injects steam in the multistage booster 21 for pressure reduction of FIG. 3 and / or the ejector 22, and operation stop of an exhaust system is carried out. When the system returns to atmospheric pressure, the inert gas is supplied to the ejector nozzle immediately after the supply of driving steam is stopped.
The nozzle is pre-compressed to prevent backflow, and after a few seconds, inert gas is supplied from another location to recompress to prevent dust from backflow exhaust gas from adhering to the inner wall of the ejector nozzle. .

[0010]

However, the above-mentioned method of removing the residual dust in the exhaust gas in the conventional vacuum exhaust system has the following problems.

(1) The dust collection in the exhaust gas is insufficient, and the function and performance of the vacuum generator cannot be maintained. That is,
In recent vacuum degassing processes (such as decarburization refining in a vacuum degassing tank and molten steel temperature rising refining) that perform long-term operation under reduced pressure and perform sophisticated refining, the amount of dust has increased remarkably. In the spray water film of, the dust passes through and the effect is halved. Further, these spray water films are installed in a duct with a lot of dust, and the fact is that the spray nozzle is clogged and its function is not fully exerted. Although the conventional method of supplying an inert gas into the ejector nozzle can prevent the ejector nozzle from being clogged, it does not collect dust, so the dust that increases in the vacuum exhaust mechanism is removed. You cannot do it.

(2) In the prior art, since the dust removal in the vacuum exhaust system is not sufficient, when a vacuum pump is adopted as the vacuum generator, this vacuum pump cannot be operated stably and maintained for a long life. . Recently, it has been increasing to adopt a vacuum pump that is inexpensive in equipment investment and running cost, instead of a plurality of stages of ejectors installed on the downstream side of the vacuum generator. It is essential to reduce the amount of dust in exhaust gas.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to reliably collect and remove a large amount of dust in exhaust gas in a vacuum exhaust system, and also to provide a vacuum. Vacuum degassing equipment exhaust that can continuously collect and remove even during degassing, enables stable vacuum degassing operation, implements the latest temperature-up refining technology, etc. and adopts a vacuum pump. It is intended to provide a method and a device for removing dusts.

[0014]

The present invention relates to a method for removing dust in exhaust gas of a vacuum exhaust system connected to a vacuum degassing tank, and a front part of a decompression booster and / or an ejector of the vacuum exhaust system. Or the rear, and /
Or in the front part of the vacuum pump device, the dust in the exhaust gas generated by the vacuum degassing process under vacuum or reduced pressure is collected by a mesh filter, the collected dust, during the vacuum degassing process, Alternatively, by washing with water during the non-degassing process, it is removed from the mesh filter,
It is characterized in that cleaning water and dust are discharged to the sealing tank.

A device for carrying out such a dust removing method is a device for removing dust in exhaust gas of a vacuum exhaust system connected to a vacuum degassing tank, and covers a channel of an exhaust duct of the vacuum exhaust system, A mesh filter that can collect dust in the exhaust gas, a cleaning water spray device that sprays cleaning water on the exhaust gas downstream side of this mesh filter to wash away dust adhering to the mesh filter, and cleaning water and dust. And a dust collection and drainage device for discharging the

The mesh filter may be made of rust-prevented metal or synthetic resin, but is made of stainless steel because it does not cause rust and its surface is smooth and dust can be easily washed off. Is preferred. In addition, the mesh roughness of the mesh filter is preferably about # 20 to # 80 mesh (preferably # 40 to # 80 mesh) from the viewpoint of washing off adhered dust and collecting dust.

In the cleaning water supply pipe of the cleaning water spray device,
A water supply valve will be installed, and a drain valve will be installed in the drainage pipe of the dust collector / drainage device if necessary. By operating this water supply valve or drain valve, dust cleaning discharge is continuously performed during vacuum degassing under reduced pressure (including vacuum), or
Every time the refining process is completed, the dust cleaning and discharging are performed in batch mode under atmospheric pressure. Further, the refining treatment system is used to remotely operate the water supply valve or the drain valve so that dust cleaning and discharging are appropriately performed according to the amount of dust. A seal pot or hot well pit of a condenser, which is an existing facility, can be used for the seal tank to which the lower end of the drainage pipe is connected.

[0018]

With the above structure, the dust in the exhaust gas is captured by the mesh filter during the vacuum degassing process under reduced pressure (including vacuum), and then the vacuum degassing process or the non-degassing process is performed. The washing water is sprayed from the washing water spraying device onto the outer surface of the mesh filter, and the dust adhering to the mesh filter is washed off. The wash water and dust after washing and removal are discharged to a sealing tank such as a condenser water collecting pit by a dust collecting and draining device.

The exhaust system dust removing device equipped with the mesh filter and the washing water spray device is most efficiently installed at the front of the condenser of the vacuum exhaust mechanism, the rear of the ejector, or the front of the vacuum pump. . That is,
The dust collector function of the vacuum degassing equipment is
Since the gas cooler / shut-off valve box is dry type and the depressurizing multi-stage booster / condenser / ejector is wet type, the dust flowing through this part is 100% humidity in the part located on the downstream side of the depressurizing multi-stage booster.
The dust in the state is very easy to attach to the inner wall of the duct or the vacuum generator.If you pass a mesh filter with a large surface area in this state, the dust easily attaches to the filter and most of the dust is removed. Can be collected.

Further, after the dust is washed, the mesh filter is wet and the dust is easily attached. Therefore, even dry dust in the front part of the multistage booster for depressurization easily adheres, and even if an exhaust system dust removing device is installed here, it is effective.

The dust adhering to the mesh filter is wet from the surface of the mesh filter and is slippery, and the dust itself is in a state of 100% humidity except for a part thereof. By spraying the cleaning water, the dust attached from the inner surface of the primary side can be easily cleaned and removed. As a result, a new mesh state is established, and dust can be attached again. By forming the mesh filter from stainless steel, corrosion and rust do not occur and the surface is slippery, so that dust adhering to the filter can be easily washed and removed.

By providing a water supply valve on the supply pipe of the cleaning water spraying device and discharging the cleaning water and dust to the sealing tank, it is possible to continuously remove the cleaning water with the cleaning water even during vacuum degassing under reduced pressure including vacuum. If necessary, it can be removed even at the timing of returning to atmospheric pressure, and various uses can be performed.

If the height of the water column is 10.5 m (1 atm is 10.3 m) or more, the drainage outlets for washing water and dust are
Needless to say, by setting the diameter of the drain pipe larger than the diameter of the water supply pipe, only the cleaning water and dust settle in the seal tank through the drain pipe. Therefore, when the exhaust system dust removing device can be installed at a position where this height can be taken, the drain valve on the drain side is unnecessary. The vacuum exhaust gas system of the vacuum degassing treatment facility is generally located at a height of 12 to 15 m, and a condenser water collecting pit (seal pot or hot well pot) or the like is arranged at the bottom of the system so that the dust concentration High drainage need only be poured into this pit. No special water treatment equipment is required.

When the exhaust system dust removing device equipped with the mesh filter and the washing water spray device is installed in the front portion of the condenser, the dust collecting and draining apparatus can use the dust collecting and draining apparatus of the condenser.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an illustrated embodiment. This is an example applied in the case of subjecting molten steel from a converter to RH vacuum degassing treatment. Fig. 1 shows an example of the RH vacuum degassing treatment equipment according to the present invention, and Fig. 2 shows dust collection according to the present invention. An example of a collecting device is shown.

As shown in FIG. 1, in the embodiment of the present invention, a vacuum pump is used in a part of the vacuum evacuation mechanism on the downstream side of the vacuum generator, and the conventional start ejector _22-0. Steam Ejector 22 _-2 / No.3 Steam Ejector 22 _-3 / No.3 Condenser 23 _-3 /
Eliminating the after-condenser -23 _-4 are the provided vacuum pump device 31 of the vacuum pump 30 has a plurality of parallel arrangement instead. Other configurations are the same as the conventional one. The dust collecting function is dry in the vacuum degassing tank 4, the gas cooler 9, and the shutoff valve box 10, and wet in the multistage booster 21 for depressurization, the condenser 23, and the ejector 22.

In such a vacuum exhaust mechanism, a dust collecting device 32 is newly installed between the No. 2 condenser 23 _-2 and the vacuum pump device 31. This dust collecting device 32
As shown in FIG. 2, is a mesh-shaped container that is mainly installed in the dust collection container 33 so as to cover the dust collection container 33 inserted in the middle of the exhaust duct 26 and the inlet of the exhaust duct 26 on the upstream side. It is composed of a filter 34, a cleaning water spray device 35 for cleaning the dust attached to the filter 34, and a dust collecting and draining device 36 for discharging cleaning water and the like.

The mesh filter 34 is used in the exhaust duct 26.
The filter is a filter for collecting dust in the exhaust gas flowing therein, and the center axis of the filter is located on the center axis of the exhaust duct 26 and the dust contacts the filter for efficient collection of the dust. It has a cylindrical shape (or a rectangular parallelepiped) to maximize the area. The material of the mesh filter 34 is made of stainless steel, and the mesh roughness is # 20 mesh (line diameter g = 760 μm) to # 8.
It is set to 0 mesh (g = 200 μm) (FIG. 2B).
reference).

Further, such a mesh filter 34
Is attached to the inner surface of the dust collecting container 33 so as to be replaceable so that it can be replaced periodically after a certain period of use. The shape of the filter is not limited to the above-described shape, and a flat filter may be installed, and the collection efficiency may be further increased by installing a plurality of stages. Furthermore, in order to reduce the cost, it is also possible to use the elements of the commercially available Y-strainers that are commonly used.

The cleaning water spray device 35 comprises a cleaning water supply pipe 40, an electric water supply valve 41 which is opened and closed by remote control, and a nozzle header 42 having a large number of nozzles 42a.

A low pressure (0.98 MPa [10 kgf / c) is supplied to the cleaning water supply pipe 40 by a pump from a tank (not shown).
m ² ] or less) of washing water is supplied. Nozzle header 4
No. 2 is arranged in the dust container 33 in order to spray and wash the mesh filter 34 from the secondary side (exhaust gas downstream side).
The nozzle 42a of the nozzle header 42 is directed toward the outer surface and the tip surface of the mesh filter 34. In this embodiment, sprinkling and washing can be performed from all directions of the upper part, the lower part, the side part and the tip part of the mesh filter 34.

The dust collection and drainage device 36 comprises a drainage pipe 50 connecting the lower part of the dust collection container 33 and the seal tank 25, and an electric drainage valve 51 which is provided as needed and which is opened and closed by remote control. In this embodiment, since the lower outlet of the dust collecting container 33 is located at a water column height of 13 m (atmospheric pressure: water column 10.3 m), the electric drain valve 51 is not provided. The diameter of the drainage pipe 50 was 1.5 times the diameter of the wash water supply pipe 40. Sealing tank 25
The existing water collection pit to which the dust collection and drainage device of the condenser 23 is connected is used for the.

In the above structure, the electric water supply valve 41 (or the electric drain valve 51) is operated by the controller of the refining treatment system to continuously wash and remove dust during vacuum degassing treatment, or to remove dust. Dust is washed and removed appropriately according to the amount of adhesion.

It is also possible to carry out dust cleaning and removal in batches every time one refining process is completed. The cleaning water and dust after cleaning settle down the drainage pipe 50 by a water column at atmospheric pressure or higher, and are continuously discharged to the seal tank 25.

The above is an example in which the dust collecting device 32 is installed in the front part of the vacuum pump device 31 on the upstream side of the exhaust gas.
As shown in FIG. 1, No. 1 condenser 23 _-1 , No. 2 condenser 23 _-2 , or multistage booster 21 for pressure reduction
(In this case, the collected dust is in a dry state). In this case, the mesh filter 3 in the duct
4 and the nozzle header 42 of the cleaning water spray device 35 may be arranged. Also, No. 1 condenser 23 _-1 , No. 2
In the case of the condenser 23 _-2 , the existing dust collection and drainage device can be used below the condenser without providing the dust collection and drainage device 36. It should be noted that the above may be arranged alone and used, or some of them may be used in combination. The most effective one is the front part of the vacuum pump device 31 and No. 1
It was the front of the condenser 23 _-1 .

In the vacuum degassing equipment shown in FIG.
Dust is collected and discharged under the configuration and conditions of the dust collector and dust collector shown in Table 1.

[0037]

[Table 1]

FIG. 4 is a graph showing the particle size distribution of the dust collected by the condenser 23. From this graph, the dust to be collected in the vicinity of the front part of the multi-stage booster 21, the condenser 23, and the vacuum pump device 31 is characterized by having a large particle size but a large amount, and this dust is present in each ejector duct inner wall pump It adheres to the blades and the like and deteriorates the function.

Such a particle size (0.1 μm to 30 μm:
Filter 3 for dust with median value = 8.5 μm
No. 4 mesh with # 20 to # 80 mesh (760 μm to 20
0 μm) and the stainless steel make the filter surface slippery, and if washing water is poured, dust D attached to the filter wire
Can be washed away (see FIG. 2 (b)). Further, the mesh renewed by washing away the dust D is damp, and it becomes very easy to attach dust having a humidity of 100% and dry dust, and the dust can be reliably collected.

Although the embodiment in which the vacuum pump is used as a part of the vacuum generator has been described above, the present invention can be applied to the case where the conventional general vacuum generator has a plurality of ejectors on the downstream side. Needless to say. Further, the vacuum degassing treatment of molten steel from the converter has been described above, but it goes without saying that the present invention can be applied to the vacuum degassing treatment of molten steel and other molten metals from an electric furnace or the like.

[0041]

Industrial Applicability The present invention collects dust in exhaust gas with a mesh filter in front of a vacuum generator such as an ejector in a vacuum exhaust system of a vacuum degassing facility,
Since the collected dust is washed away by water washing during the vacuum degassing process or the non-degassing process, and the wash water and the dust are discharged to the sealing tank, the following effects are obtained.

(1) A large amount of dust in the vacuum exhaust system of the vacuum degassing equipment can be reliably and sufficiently collected and removed, and the dust adheres to the ejector of the vacuum generating device, the inner wall of the duct, the pump blade, or the like. Functions of vacuum generator
It is possible to prevent the performance from deteriorating and to perform stable vacuum degassing operation.

(2) Even if the amount of dust at the time of refining increases, it is possible to deal with it, and the latest refining technology, such as decarburization refining in a vacuum degassing tank and molten steel temperature rising refining, becomes possible.

(3) It is unnecessary to perform the conventional work of cleaning dust accumulated on the inner wall of the exhaust duct and the vacuum generating device by human power at the time of stoppage, or it is significantly reduced, and the cost can be reduced.

(4) A vacuum pump can be adopted as the vacuum generator, and the equipment investment and running cost can be reduced.

(5) By the above, the cost of secondary refining (vacuum degassing refining) can be significantly reduced.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram showing an example of a vacuum degassing treatment facility according to the present invention.

FIG. 2A is a partial sectional view showing an example of the dust collecting apparatus according to the present invention, and FIG. 2B is an enlarged view of the mesh filter.

FIG. 3 is an overall schematic view showing a conventional vacuum degassing treatment facility.

FIG. 4 is a graph showing a particle size distribution of dust collected in a condenser unit in a vacuum exhaust mechanism of vacuum degassing equipment.

[Explanation of symbols]

 D ... Dust 1 ... RH vacuum degassing device 2 ... Ladle 3 ... Immersion pipe 4 ... Vacuum degassing tank 7 ... Exhaust port 8 ... Horizontal exhaust duct 9 ... Gas cooler 10 ... Shutoff valve box 11 ... Vertical exhaust duct 21 ... For decompression Multi-stage booster 22 ... Steam ejector 23 ... Condenser 24 ... Drain separator 25 ... Seal tank 26 ... Exhaust duct 30 ... Vacuum pump 31 ... Vacuum pump device 32 ... Dust collection device 33 ... Dust collection container 34 ... Reticulated filter 35 ... Wash water Spray device 36 ... Dust collection and drainage device 40 ... Wash water supply pipe 41 ... Electric water supply valve 42 ... Nozzle header 50 ... Drain pipe 51 ... Electric drain valve

Claims (2)

[Claims] 1. A method for removing dust in exhaust gas of a vacuum exhaust system connected to a vacuum degassing tank, the front or rear portion of a decompression booster and / or an ejector of the vacuum exhaust system, and / or a vacuum pump. Dust in the exhaust gas generated by vacuum degassing under vacuum or reduced pressure is collected by a mesh filter in the front part of the device, and the collected dust is vacuum degassed or not degassed. By washing with water during gas treatment,
A method for removing dust from a vacuum degassing device exhaust system, characterized in that cleaning water and dust are removed from the mesh filter and discharged to a sealing tank. 2. An apparatus for removing dust in exhaust gas of a vacuum exhaust system, which is connected to a vacuum degassing tank, can cover a flow path of an exhaust duct of the vacuum exhaust system and collect dust in the exhaust gas. A mesh filter, a cleaning water spray device that sprays cleaning water on the exhaust gas downstream side of this mesh filter to wash away dust adhering to the mesh filter, and a dust collection and drainage device that discharges cleaning water and dust to a sealing tank. And a vacuum degassing device, an exhaust system dust removing device.