RH vacuum refining system and method of using the same

Abstract

The present invention relates to an RH vacuum refining system, wherein the mechanical vacuum pump unit comprises a three-stage Roots pump unit and a water ring vacuum pump unit which are arranged in series on an exhaust main pipe, the first-stage Roots pump unit is connected to an RH vacuum chamber and a vacuum main valve is arranged on the exhaust main pipe between the two, the first three-stage Roots pump units each comprise at least one Roots pump, and the water ring vacuum pump unit comprises at least one water ring vacuum pump. In addition, the present invention also relates to a method for using the RH vacuum refining system. The present invention adopts a water ring vacuum pump to replace a traditional screw pump. Since the water ring vacuum pump can be directly discharged into the atmosphere and has a large exhaust capacity, when the vacuum chamber pressure drops to a set value, the third-stage Roots pump is started, which can effectively reduce the pressure difference between the air inlet and the air outlet of the Roots pump, and effectively solve the problem of heating and blocking of the Roots pump. In addition, a water ring vacuum pump is adopted to replace the screw pump, and the first three-stage Roots pumps can all adopt domestic pumps, which can significantly reduce the investment cost and maintenance cost.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking production, and in particular relates to an RH vacuum refining system and a use method thereof. Background Art

[0002] RH (Rheinstahl Hutlenwerke) refining technology was successfully developed by Rheinstahl and Hutlenwerke in Germany in 1959. RH combines vacuum refining with the circulation of molten steel, and has the advantages of short processing cycle, large production capacity, and good refining effect. It is suitable for converter steel plants with short smelting cycle and large production capacity. Due to the large amount of gas generated during the vacuum refining process of molten steel, there are currently two main types of vacuum pump systems, namely steam jet pumps and dry mechanical vacuum pumps. Among them, dry mechanical vacuum pumps mainly have two forms, namely modular and non-modular. The main problems of dry mechanical vacuum pump systems at present are high investment costs and high production failure rates. The reasons are:

[0003] (1) At present, the final pump of dry mechanical vacuum pumps is a screw pump. Due to the working conditions of the pumped gas, when the Roots pump uses a domestic pump, the screw pump needs to use an imported pump, resulting in a higher investment cost;

[0004] (2) The main reason for the high failure rate of dry mechanical vacuum pumps is that the production process of the vacuum pump system is limited by the exhaust capacity of the final screw pump: the steel liquid vacuum refining process requires the pressure in the vacuum chamber to drop rapidly from the standard atmospheric pressure (101325Pa) to about 67Pa within 4 minutes. Limited by the exhaust capacity of the final screw pump, it can only be discharged directly to the atmosphere through the third-stage air-cooled Roots pump. When the pressure in the vacuum chamber reaches the set value, the final screw pump is connected to the system in series. Although the heat and blockage of the Roots pump is alleviated by the return air cooling method during the direct discharge of the air-cooled Roots pump, the heat and blockage problem of the Roots pump is not completely solved. In fact, due to the excessive return air volume, the exhaust efficiency of the Roots pump is reduced. Summary of the invention

[0005] The present invention relates to a RH vacuum refining system and a method of using the same, which can at least solve some of the defects of the prior art.

[0006] The invention relates to an RH vacuum refining system, comprising an RH vacuum chamber and a mechanical vacuum pump unit connected to the RH vacuum chamber, wherein the mechanical vacuum pump unit comprises an exhaust main pipe and a first-stage Roots pump unit, a second-stage Roots pump unit, a third-stage Roots pump unit and a water ring vacuum pump unit arranged in series on the exhaust main pipe, wherein the first-stage Roots pump unit is connected to the RH vacuum chamber and a vacuum main valve is arranged on the exhaust main pipe between the two, the first three-stage Roots pump units each comprise a Roots pump or a plurality of Roots pumps arranged in parallel, and the water ring vacuum pump unit comprises a water ring vacuum pump or a plurality of water ring vacuum pumps arranged in parallel.

[0007] As one of the implementation modes, each Roots pump of the third-stage Roots pump unit is an air-cooled Roots pump.

[0008] As one of the embodiments, each Roots pump of the first-stage Roots pump unit is a first Roots pump, and each Roots pump of the second-stage Roots pump unit is a second Roots pump;

[0009] The first-stage Roots pump unit and the second-stage Roots pump unit are combined and arranged to form a pump group module or a plurality of pump group modules arranged in parallel, each pump group module includes an exhaust branch and a front-stage pump group and a rear-stage pump group arranged in series on the exhaust branch, the front-stage pump group includes a first Roots pump or a plurality of first Roots pumps arranged in parallel, and the rear-stage pump group includes a second Roots pump or a plurality of second Roots pumps arranged in parallel.

[0010] As one of the implementation modes, both the inlet side and the outlet side of the air extraction branch are provided with a shut-off valve.

[0011] As one of the embodiments, the mechanical vacuum pump unit also includes a first bypass pipe and a shut-off valve is provided on the first bypass pipe, the inlet end of the first bypass pipe is connected to the inlet side exhaust pipe of the first-stage Roots pump unit, and the outlet end of the first bypass pipe is connected to the outlet side exhaust pipe of the second-stage Roots pump unit.

[0012] As one of the embodiments, the mechanical vacuum pump unit also includes a second bypass pipe and a shut-off valve is provided on the second bypass pipe, the inlet end of the second bypass pipe is connected to the inlet side exhaust pipe of the third-stage Roots pump unit, and the outlet end of the second bypass pipe is connected to the outlet side exhaust pipe of the third-stage Roots pump unit.

[0013] As one of the embodiments, the mechanical vacuum pump unit further includes a dust removal unit, which is arranged between the vacuum main valve and the first-stage Roots pump unit, and includes a group of dust collectors or multiple groups of dust collectors arranged in parallel.

[0014] As one of the implementation modes, the dust collector is a bag dust collector.

[0015] The present invention also relates to a method for using the RH vacuum refining system as described above, comprising:

[0016] According to the received working instructions, the RH vacuum refining system is operated in different working modes by controlling the working state of each pump, wherein:

[0017] When the system is running in the pre-pumping working mode, the vacuum main valve is closed, the water ring vacuum pump unit is put into operation, the roots pumps of the first three-stage roots pump units are stopped and bypass pipelines are built accordingly to perform pre-pumping treatment on the air extraction main pipe after the vacuum main valve;

[0018] When the system operates in the light treatment working mode or the forced oxygen blowing decarbonization working mode, the vacuum main valve is opened, the third-stage Roots pump unit and the water ring vacuum pump unit are both put into operation, and the Roots pumps of the first-stage Roots pump unit and the second-stage Roots pump unit are stopped and bypass pipelines are built accordingly, so that the pressure in the RH vacuum chamber is reduced and maintained at a preset pressure;

[0019] When the system operates in this processing working mode, the vacuum main valve is opened, and the first three-stage Roots pump units and the water ring vacuum pump unit are put into operation to reduce the pressure in the RH vacuum chamber and maintain it at a preset pressure.

[0020] The present invention has at least the following beneficial effects:

[0021] The present invention adopts a water ring vacuum pump to replace the traditional screw pump to form a mechanical vacuum pump unit. Due to the working characteristics of the water ring vacuum pump, the water ring vacuum pump can be directly discharged into the atmosphere and has a large suction capacity. When the vacuum chamber pressure drops to the set value, the third-stage Roots pump is started, which can effectively reduce the pressure difference between the air inlet and the air outlet of the Roots pump, and effectively solve the problem of heating and blocking of the Roots pump. In addition, the water ring vacuum pump is used to replace the screw pump, and the first three-stage Roots pumps can all use domestic pumps, which can significantly reduce investment costs and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic structural diagram of an RH vacuum refining system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] like Figure 1 An embodiment of the present invention provides an RH vacuum refining system, comprising an RH vacuum chamber 1 and a mechanical vacuum pump unit connected to the RH vacuum chamber 1, wherein the mechanical vacuum pump unit comprises an exhaust pipe and a first-stage Roots pump unit, a second-stage Roots pump unit, a third-stage Roots pump unit and a water ring vacuum pump unit arranged in series on the exhaust pipe, wherein the first-stage Roots pump unit is connected to the RH vacuum chamber 1 and a vacuum main valve 10 is provided on the exhaust pipe between the two, the first three-stage Roots pump units each comprise a Roots pump or a plurality of Roots pumps arranged in parallel, and the water ring vacuum pump unit comprises a water ring vacuum pump 5 or a plurality of water ring vacuum pumps 5 arranged in parallel.

[0026] The above-mentioned RH vacuum chamber 1 is a container for the circulation reaction of molten steel, which is a conventional device in this field and will not be described in detail here.

[0027] The vacuum main valve 10 is used to control the connection or isolation between the RH vacuum chamber 1 and the mechanical vacuum pump unit, and preferably adopts an automatic valve suitable for remote control, such as a pneumatic valve.

[0028] The first-stage Roots pump unit preferably includes a plurality of Roots pumps. In the present embodiment, the Roots pumps are all defined as first Roots pumps 2. As described above, the first Roots pumps 2 of the first-stage Roots pump unit are arranged in parallel, and one or more first Roots pumps 2 can be selected to be put into the air extraction operation as needed.

[0029] The second-stage Roots pump unit preferably includes a plurality of Roots pumps. In the present embodiment, the Roots pumps are defined as second Roots pumps 3. As described above, the second Roots pumps 3 of the second-stage Roots pump unit are arranged in parallel, and one or more second Roots pumps 3 can be selected to be put into the air extraction operation as needed.

[0030] The third-stage Roots pump unit preferably includes a plurality of Roots pumps. In this embodiment, the Roots pumps are defined as the third Roots pumps 4. As described above, the third Roots pumps 4 of the third-stage Roots pump unit are arranged in parallel, and one or more third Roots pumps 4 can be selected to be put into the air extraction work as needed. Preferably, each third Roots pump 4 is an air-cooled Roots pump. During the direct exhaust process, the problem of heating and blocking of the Roots pump can be alleviated by return air cooling, thereby improving the working reliability of the third-stage Roots pump unit and the service life of each third Roots pump 4.

[0031] The water ring vacuum pump unit preferably comprises a plurality of water ring vacuum pumps 5. As mentioned above, the water ring vacuum pumps 5 of the water ring vacuum pump unit are arranged in parallel, and one or more water ring vacuum pumps 5 can be selected to be put into vacuum operation as required.

[0032] In one embodiment, the mechanical vacuum pump unit adopts a non-modular form. Specifically, a cut-off valve is provided on the exhaust branch where each first Roots pump 2 is located, and preferably, a cut-off valve is provided on the inlet side and the outlet side of the first Roots pump 2. Similarly, a cut-off valve is provided on the exhaust branch where each second Roots pump 3 is located, and preferably, a cut-off valve is provided on the inlet side and the outlet side of the second Roots pump 3; a cut-off valve is provided on the exhaust branch where each third Roots pump 4 is located, and preferably, a cut-off valve is provided on the inlet side and the outlet side of the third Roots pump 4; a cut-off valve is provided on the exhaust branch where each water ring vacuum pump 5 is located, and preferably, a cut-off valve is provided on the inlet side and the outlet side of the water ring vacuum pump 5.

[0033] In another embodiment, the mechanical vacuum pump unit is in modular form, for example, one or more first Roots pumps 2, one or more second Roots pumps 3, a third Roots pump 4 and a water ring vacuum pump 5 form a module, and the specific configuration is not described in detail here.

[0034] In this embodiment, a partially modular structure is adopted, specifically, Figure 1 The first-stage Roots pump unit and the second-stage Roots pump unit are combined and arranged to form a pump group module 7 or a plurality of pump group modules 7 arranged in parallel, each pump group module 7 includes a pump group branch and a front-stage pump group and a rear-stage pump group arranged in series on the pump group branch, the front-stage pump group includes a first Roots pump 2 or a plurality of first Roots pumps 2 arranged in parallel, and the rear-stage pump group includes a second Roots pump 3 or a plurality of second Roots pumps 3 arranged in parallel; Figure 1 In the structure shown, four first Roots pumps 2 and one second Roots pump 3 are combined into a pump module 7, and there are multiple pump modules 7, but it is not limited to this combination; in the above pump module 7, not only the first Roots pumps 2 and the second Roots pumps 3 are installed in combination accordingly, which can save installation space and improve installation efficiency, but also the Roots pumps in each pump module 7 work synchronously, and can be started and stopped by a fixed program, which can effectively reduce the difficulty of starting and stopping the mechanical vacuum pump unit. At the same time, each third Roots pump 4 and each water ring vacuum pump 5 are independently controlled, which can ensure the working stability and reliability of the mechanical vacuum pump unit.

[0035] In the above-mentioned partially modular structure, such as Figure 1A first shut-off valve 91 is provided on the pump group branch where each pump group module 7 is located, and it is further preferred that the first shut-off valve 91 is provided on both the inlet side and the outlet side of the pump group branch. A second shut-off valve 92 is provided on the air extraction branch where each third Roots pump 4 is located, and it is preferred that the second shut-off valve 92 is provided on the inlet side and the outlet side of the third Roots pump 4; a third shut-off valve 93 is provided on the air extraction branch where each water ring vacuum pump 5 is located, and it is preferred that the third shut-off valve 93 is provided on the inlet side and the outlet side of the water ring vacuum pump 5.

[0036] Further optimize the structure of the above mechanical vacuum pump unit, such as Figure 1 The mechanical vacuum pump unit further comprises a first bypass pipe 11 and a fourth shut-off valve 94 is arranged on the first bypass pipe 11. The inlet end of the first bypass pipe 11 is connected to the inlet side exhaust pipe of the first-stage Roots pump unit, and the outlet end of the first bypass pipe 11 is connected to the outlet side exhaust pipe of the second-stage Roots pump unit. Through the first bypass pipe 11, it can be selected whether the first-stage Roots pump unit and the second-stage Roots pump unit are put into operation. When the first-stage Roots pump unit and the second-stage Roots pump unit are not put into operation, the RH vacuum chamber 1 can be connected with the subsequent third-stage Roots pump unit and the water ring vacuum pump unit through the first bypass pipe 11.

[0037] Further optimize the structure of the above mechanical vacuum pump unit, such as Figure 1 The mechanical vacuum pump unit further includes a second bypass pipe 12 and a fifth shut-off valve 95 is provided on the second bypass pipe 12. The inlet end of the second bypass pipe 12 is connected to the inlet side exhaust pipe of the third-stage Roots pump unit, and the outlet end of the second bypass pipe 12 is connected to the outlet side exhaust pipe of the third-stage Roots pump unit. Through the second bypass pipe 12, it can be selected whether the third-stage Roots pump unit is put into operation. When the third-stage Roots pump unit is not put into operation, the RH vacuum chamber 1 can be connected to the subsequent water ring vacuum pump unit through the second bypass pipe 12.

[0038] Further optimize the structure of the above mechanical vacuum pump unit, such as Figure 1 The mechanical vacuum pump unit further includes a dust removal unit, which is arranged between the vacuum main valve 10 and the first-stage Roots pump unit, and includes a group of dust collectors 6 or multiple groups of dust collectors 6 arranged in parallel. The dust collector 6 is preferably a dry dust collector 6, such as a bag dust collector 6; a control valve 96 is provided on the exhaust branch where the dust collector 6 is located, and preferably a control valve 96 is provided on the inlet side and the outlet side of the dust collector 6, such as a solenoid valve.

[0039] Further refine the above structure, such as Figure 1The above-mentioned exhaust main pipe includes a first main pipe 81, a second main pipe 82, a third main pipe 83, a fourth main pipe 84 and a fifth main pipe 85, wherein:

[0040] One end of the first main pipe 81 is connected to the RH vacuum chamber 1 and the other end is sealed, the inlet end of the dust removal unit is connected to the first main pipe 81, and the outlet end of the dust removal unit is connected to the second main pipe 82 (sealed at both ends); the inlet ends of the above-mentioned pump group modules 7 are connected to the second main pipe 82, and the outlet ends of the pump group modules 7 are connected to the third main pipe 83 (sealed at both ends); the inlet end of the third-stage Roots pump unit is connected to the third main pipe 83, and the outlet end of the third-stage Roots pump unit is connected to the fourth main pipe 84 (sealed at both ends); the inlet end of the water ring vacuum pump unit is connected to the fourth main pipe 84, and the outlet end of the water ring vacuum pump unit is connected to the fifth main pipe 85, and the fifth main pipe 85 can be selected to be sealed at one end and directly discharged to the atmosphere at the other end.

[0041] Based on the structure of the above RH vacuum refining system, an embodiment of the present invention further relates to a method for using the above RH vacuum refining system, including:

[0042] According to the received working instructions, the RH vacuum refining system is made to pump gas in different working modes by controlling the working state of each pump, wherein:

[0043] (1) When the system is running in the pre-evacuation working mode, the vacuum main valve 10 is closed, the water ring vacuum pump unit is put into operation, the roots pumps of the first three-stage roots pump unit are stopped and bypass pipelines are built accordingly to perform pre-evacuation treatment on the exhaust main pipe after the vacuum main valve 10.

[0044] More specifically, the bypass pipelines constructed accordingly are the first bypass pipelines 11 and the second bypass pipelines 12; the vacuum main valve 10 is closed, the first cut-off valves 91 at the inlet and outlet sides of each pump group module 7 are closed, the second cut-off valves 92 at the inlet and outlet sides of each third Roots pump 4 are closed, and each first Roots pump 2, each second Roots pump 3 and each third Roots pump 4 are in a pump-off state;

[0045] The control valve 96 on the inlet and outlet side of each dust collector 6 is opened, the fourth shut-off valve 94 on the first bypass pipe 11 is opened, the fifth shut-off valve 95 on the second bypass pipe 12 is opened, the third shut-off valve 93 on the inlet and outlet side of each water ring vacuum pump 5 is opened, and each water ring vacuum pump 5 is in an open state.

[0046] In one embodiment, the pressure in the pipeline after the vacuum main valve 10 can be rapidly reduced to 25000 Pa through the above-mentioned pre-evacuation process.

[0047] (2) When the system operates in the light treatment working mode or the forced oxygen blowing decarbonization working mode, the vacuum main valve 10 is opened, the third-stage Roots pump unit and the water ring vacuum pump unit are both put into operation, and the Roots pumps of the first-stage Roots pump unit and the second-stage Roots pump unit are stopped and bypass pipelines are built accordingly, so that the pressure in the RH vacuum chamber 1 is reduced and maintained at a preset pressure.

[0048] More specifically, the bypass pipeline constructed accordingly includes constructing the first bypass pipeline 11 described above;

[0049] The first shut-off valve 91 on the inlet and outlet sides of each pump module 7 is closed, and each first Roots pump 2 and each second Roots pump 3 are in a pump-off state (when there is a second bypass pipeline 12, the fifth shut-off valve 95 on the second bypass pipeline 12 is closed);

[0050] The vacuum main valve 10 is opened, the control valve 96 on the inlet and outlet side of each dust collector 6 is opened, the fourth shut-off valve 94 on the first bypass pipe 11 is opened, the second shut-off valve 92 on the inlet and outlet side of each third Roots pump 4 is opened, the third shut-off valve 93 on the inlet and outlet side of each water ring vacuum pump 5 is opened, and each third Roots pump 4 and each water ring vacuum pump 5 are in the open state.

[0051] In one embodiment, in the light treatment working mode or the forced oxygen blowing decarburization working mode, the pressure in the RH vacuum chamber 1 can be rapidly reduced and maintained at about 6000Pa, such as 5500-6200Pa, through the above operation.

[0052] (3) When the system operates in this processing working mode, the vacuum main valve 10 is opened, and the first three-stage Roots pump units and the water ring vacuum pump unit are put into operation, so that the pressure in the RH vacuum chamber 1 is reduced and maintained at a preset pressure.

[0053] More specifically, the vacuum main valve 10 is opened, the control valve 96 on the inlet and outlet side of each dust collector 6 is opened, the first cut-off valve 91 on the inlet and outlet side of each pump group module 7 is opened, the second cut-off valve 92 on the inlet and outlet side of each third Roots pump 4 is opened, the third cut-off valve 93 on the inlet and outlet side of each water ring vacuum pump 5 is opened, and each first Roots pump 2, each second Roots pump 3, each third Roots pump 4 and each water ring vacuum pump 5 are all in an open state;

[0054] When there are the first bypass pipeline 11 and the second bypass pipeline 12, the fourth shut-off valve 94 on the first bypass pipeline 11 is closed, and the fifth shut-off valve 95 on the second bypass pipeline 12 is closed;

[0055] In one embodiment, in the present processing working mode, the pressure in the RH vacuum chamber 1 can be rapidly reduced and maintained at about 67Pa, for example, 60-70Pa, through the above operations.

[0056] It can be understood that the above three working modes can be gradually operated within a processing cycle. For example, before the light treatment working mode or the forced oxygen blowing decarbonization working mode, the above pre-pumping working mode is first performed. After the pre-pumping is completed, the vacuum main valve is opened. Due to the pressure equalization effect, the pressure in the pipeline will rise again, and the water ring vacuum pump will continue to pump air until the pressure in the RH vacuum chamber drops to about 25000Pa, and then the third-stage Roots pump is started.

[0057] The RH vacuum refining system and its use method provided in this embodiment use a water ring vacuum pump 5 to replace a traditional screw pump to form a mechanical vacuum pump unit. Due to the working characteristics of the water ring vacuum pump 5, the water ring vacuum pump 5 can be directly discharged into the atmosphere and has a large suction capacity. When the vacuum chamber pressure drops to a set value, the third-stage Roots pump is started, which can effectively reduce the pressure difference between the air inlet and the air outlet of the Roots pump and effectively solve the problem of heating and blocking of the Roots pump. In addition, the water ring vacuum pump 5 is used to replace the screw pump, and the first three-stage Roots pumps can all use domestic pumps, which can significantly reduce investment costs and maintenance costs.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A RH vacuum refining system, comprising a RH vacuum chamber and a mechanical vacuum pump unit connected to the RH vacuum chamber, characterized in that: The mechanical vacuum pump unit comprises an exhaust main pipe and a first-stage Roots pump unit, a second-stage Roots pump unit, a third-stage Roots pump unit and a water ring vacuum pump unit arranged in series on the exhaust main pipe, wherein the first-stage Roots pump unit is connected to the RH vacuum chamber and a vacuum main valve is arranged on the exhaust main pipe between the two, the first three-stage Roots pump units each comprise a Roots pump or a plurality of Roots pumps arranged in parallel, and the water ring vacuum pump unit comprises a water ring vacuum pump or a plurality of water ring vacuum pumps arranged in parallel; Each Roots pump of the first-stage Roots pump unit is a first Roots pump, and each Roots pump of the second-stage Roots pump unit is a second Roots pump; the first-stage Roots pump unit and the second-stage Roots pump unit are arranged in combination to form a pump group module or a plurality of pump group modules arranged in parallel, each pump group module comprises an air extraction branch and a front-stage pump group and a rear-stage pump group arranged in series on the air extraction branch, the front-stage pump group comprises a first Roots pump or a plurality of first Roots pumps arranged in parallel, and the rear-stage pump group comprises a second Roots pump or a plurality of second Roots pumps arranged in parallel; The inlet and outlet sides of the air extraction branch are both provided with cut-off valves; The mechanical vacuum pump unit further comprises a first bypass pipeline and a cut-off valve is arranged on the first bypass pipeline, the inlet end of the first bypass pipeline is connected to the inlet side exhaust pipe of the first-stage Roots pump unit, and the outlet end of the first bypass pipeline is connected to the outlet side exhaust pipe of the second-stage Roots pump unit; The mechanical vacuum pump unit also includes a second bypass pipeline and a shut-off valve is provided on the second bypass pipeline. The inlet end of the second bypass pipeline is connected to the inlet side exhaust pipe of the third-stage Roots pump unit, and the outlet end of the second bypass pipeline is connected to the outlet side exhaust pipe of the third-stage Roots pump unit.

2. The RH vacuum refining system according to claim 1, characterized in that: Each Roots pump of the third-stage Roots pump unit is an air-cooled Roots pump.

3. The RH vacuum refining system according to claim 1, characterized in that: The mechanical vacuum pump unit further includes a dust removal unit, which is arranged between the vacuum main valve and the first-stage Roots pump unit. The dust removal unit includes a group of dust collectors or multiple groups of dust collectors arranged in parallel.

4. The RH vacuum refining system according to claim 3, characterized in that: The dust collector is a bag dust collector.

5. The method for using the RH vacuum refining system according to any one of claims 1 to 4, characterized in that: include: According to the received working instructions, the RH vacuum refining system is operated in different working modes by controlling the working state of each pump, wherein: When the system is running in the pre-pumping working mode, the vacuum main valve is closed, the water ring vacuum pump unit is put into operation, the roots pumps of the first three-stage roots pump units are stopped and bypass pipelines are built accordingly to perform pre-pumping treatment on the air extraction main pipe after the vacuum main valve; When the system operates in the light treatment working mode or the forced oxygen blowing decarbonization working mode, the vacuum main valve is opened, the third-stage Roots pump unit and the water ring vacuum pump unit are both put into operation, and the Roots pumps of the first-stage Roots pump unit and the second-stage Roots pump unit are stopped and bypass pipelines are built accordingly, so that the pressure in the RH vacuum chamber is reduced and maintained at a preset pressure; When the system operates in this processing working mode, the vacuum main valve is opened, and the first three-stage Roots pump units and the water ring vacuum pump unit are put into operation to reduce the pressure in the RH vacuum chamber and maintain it at a preset pressure.

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