Method for transforming nitrogen protection device of blast furnace top gear box

Abstract

The invention relates to a transformation method of a blast furnace top gear box nitrogen protection device. The transformation method comprises the following steps: 1) removing instruments which are not used after production on a nitrogen pipeline; and (2) the adjusting valve group on the nitrogen main pipe entering the top of the gear box is detached, a main pipe current-limiting orifice plate is arranged on the nitrogen main pipe, the nitrogen main pipe is connected with the top of the gear box through a plurality of nitrogen branch pipes, and branch pipe current-limiting orifice plates are arranged on the nitrogen branch pipes. According to the invention, the problems of various and complicated field temporary detection instruments and tedious installation of various accessories in pipeline construction of a gearbox protection nitrogen device are solved. The flow limiting orifice plate is used for replacing a regulating valve to limit flow or reduce pressure, and plays an important role in safe operation of the whole process device.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, and in particular to a method for modifying a nitrogen protection device of a blast furnace top gear box. Background Art

[0002] With the advancement of large-scale blast furnace ironmaking technology and equipment, the advantages of large-scale blast furnaces have become more and more apparent. At present, large-scale blast furnaces generally use bell-less charging. Among all bell-less equipment, the transmission gearbox is the key equipment. Blast furnaces have adopted bell-less top distributors for decades, and have developed a variety of transmission structure forms. For example, the traditional Luxembourg PW company distributor is often called "water-cooled gearbox" or "airtight box" in China. The common feature of distributors is that they all have a rotating simple structure, that is, a certain gap is reserved between the joint of the rotating cylinder and the distributor shell.

[0003] Since the inner cavity of the blast furnace is a high-temperature, high-pressure dust environment, and the pressure instability often occurs in the furnace, the blast furnace dust and gas can easily penetrate into the inner cavity of the distributor through these gaps. Therefore, it is very necessary to introduce nitrogen with a pressure higher than the pressure in the blast furnace into the distributor shell for sealing. In this case, the introduction of nitrogen has two functions: one is to prevent the internal gas of the furnace from entering the gearbox working equipment, thereby causing damage to the working equipment; on the other hand, nitrogen is used to cool its working equipment. At present, there are many on-site detection instruments installed on the nitrogen pipeline. These instruments lose their specific working significance after the equipment works normally. At the same time, the installation of these instruments is only for the construction of some pipelines, so they do not have long-term significance.

[0004] There are a large number of regulating valves in the protective nitrogen pipeline. The setting of these regulating valves increases the power load of the system on the one hand, and increases the unsafe factors of equipment operation on the other hand. In some cases, the flow rate of the nitrogen pipeline is only required to be limited to a certain specified range and does not need to be adjusted. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for modifying a nitrogen protection device of a blast furnace top gear box, so as to reduce the on-site construction amount of the nitrogen pipeline and the amount of protective nitrogen of the water-cooled gear box.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for modifying a nitrogen protection device of a blast furnace top gearbox, comprising:

[0008] 1) Remove the instruments on the nitrogen pipeline that are no longer used after production;

[0009] 2) Remove the regulating valve group on the nitrogen main pipe at the top of the gearbox, set a main pipe flow limiting orifice plate on the nitrogen main pipe, the nitrogen main pipe is connected to the top of the gearbox through multiple nitrogen branch pipes, and each nitrogen branch pipe is provided with a branch pipe flow limiting orifice plate;

[0010] The apertures on the main flow limiting orifice plate and the branch flow limiting orifice plate are calculated according to formula ①:

[0011]

[0012] Where:

[0013] d k -Aperture of the flow limiting orifice; unit: mm;

[0014] ρ-nitrogen density; unit: kg / m 3 ;

[0015] ΔP-pressure difference before and after the flow limiting orifice; unit: MPa;

[0016] G-nitrogen flow rate; unit: t / h;

[0017] G is calculated according to formula ②:

[0018]

[0019] Where:

[0020] N-molecular weight of nitrogen per mole, unit: g / mol;

[0021] m-nitrogen molar volume, unit: L / mol;

[0022] P1-nitrogen pressure after the limiting orifice, unit: kPa;

[0023] P0-nitrogen pressure before the limiting orifice, unit: kPa;

[0024] T1-nitrogen temperature after the limiting orifice, unit: °C;

[0025] T0-nitrogen temperature before the limiting orifice, unit: °C;

[0026] q m -Mass flow rate of nitrogen through the orifice plate, unit: m 3 / min;

[0027] q m Calculate according to formula ③

[0028]

[0029] Where:

[0030] P2=P0, unit: kPa;

[0031] A2- cross-sectional area of ​​the pipe after diameter reduction, unit: m 2 ;

[0032] A3- Pipe cross-sectional area before diameter reduction, unit: m 2 ;

[0033] Cc-contraction coefficient, Cc=A3 / A2;

[0034] Cv-velocity coefficient, that is, the ratio of the flow velocity at the front and rear sections;

[0035] β - ideal gas adiabatic index.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention solves the problems of numerous and complicated temporary detection instruments on site and cumbersome installation of various accessories in pipeline construction in the gear box protection nitrogen device.

[0038] 2. Using a flow limiting orifice instead of a regulating valve to limit flow or reduce pressure plays an important role in the safe operation of the entire process unit.

[0039] 3. The modification of the nitrogen pipeline in the present invention effectively reduces the amount of nitrogen used in the system.

[0040] 4. The present invention can not only reduce the work intensity of construction personnel and improve work efficiency, but also reduce the construction difficulty and create conditions for reducing the project cost, which will greatly reduce the total project investment and operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of the existing blast furnace top gearbox nitrogen protection device.

[0042] Figure 2 It is a schematic structural diagram of the nitrogen protection device for the blast furnace top gear box of the present invention.

[0043] In the figure: nitrogen main pipe 1, main pipe flow limiting orifice plate 2, nitrogen branch pipe 3, branch pipe flow limiting orifice plate 4. DETAILED DESCRIPTION

[0044] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means more than two.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0047] A method for modifying a nitrogen protection device of a blast furnace top gearbox, comprising:

[0048] 1) Remove the instruments on the nitrogen pipeline that are no longer used after production;

[0049] 2) Remove the regulating valve group on the nitrogen main pipe 1 at the top of the gearbox, set a main pipe flow limiting orifice plate 2 on the nitrogen main pipe 1, and connect the nitrogen main pipe 1 to the top of the gearbox through multiple nitrogen branch pipes 3, and each nitrogen branch pipe 3 is provided with a branch pipe flow limiting orifice plate 4; (see attached Figure 2 ).

[0050] The apertures on the main flow limiting orifice plate 2 and the branch flow limiting orifice plate 4 are calculated according to formula ①:

[0051]

[0052] Where:

[0053] d k -Aperture of the flow limiting orifice; unit: mm;

[0054] ρ-nitrogen density; unit: kg / m 3 ;

[0055] ΔP-pressure difference before and after the flow limiting orifice; unit: MPa;

[0056] G-nitrogen flow rate; unit: t / h;

[0057] G is calculated according to formula ②:

[0058]

[0059] Where:

[0060] N-molecular weight of nitrogen per mole, unit: g / mol;

[0061] m-nitrogen molar volume, unit: L / mol;

[0062] P1-nitrogen pressure after the limiting orifice, unit: kPa;

[0063] P0-nitrogen pressure before the limiting orifice, unit: kPa;

[0064] T1-nitrogen temperature after the limiting orifice, unit: °C;

[0065] T0-nitrogen temperature before the limiting orifice, unit: °C;

[0066] q m -Mass flow rate of nitrogen through the orifice plate, unit: m 3 / min;

[0067] q m Calculate according to formula ③

[0068]

[0069] Where:

[0070] P2=P0, unit: kPa;

[0071] A2- cross-sectional area of ​​the pipe after diameter reduction, unit: m 2 ;

[0072] A3- Pipe cross-sectional area before diameter reduction, unit: m 2 ;

[0073] Cc-contraction coefficient, Cc=A3 / A2;

[0074] Cv-velocity coefficient, that is, the ratio of the flow velocity at the front and rear sections;

[0075] β - ideal gas adiabatic index.

[0076] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. In addition, the various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0077] In order to make the purpose, technical scheme and technical effect of the present invention clearer, the technical scheme in the embodiment of the present invention is now clearly and completely described. However, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. In combination with 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.

[0078] Example

[0079] Based on the terminal nitrogen consumption of 2.7m 3 / h,ρ[nitrogen density]=1.25×10 -3 kg / m 3 ,ΔP[pressure difference before and after the orifice plate]=0.6-0.1=0.5MPa,N[nitrogen molar molecular weight]=14g / mol;m[nitrogen molar volume]=22.4L / mol calculation.

[0080] First, assume that the diameter is The pipe wall thickness is 4 mm and the inner diameter is 65 mm, then A3 [pipe cross-sectional area] = 3.318 × 10 -3 m 2 , before the diameter change is Pipe, wall thickness is 4mm, A2 [pipe cross-sectional area] = 7.854 × 10 -3 m 2 , Cc [contraction coefficient] = 0.4225, Cv [velocity coefficient] = 8.997, P1 [nitrogen pressure before the orifice] = 60 kPa, P2 [nitrogen pressure after the orifice] = 50 kPa, β [ideal gas adiabatic index] = 1.4.

[0081] According to formula ③

[0082]

[0083] Substitute the calculated result into formula ②

[0084]

[0085] Substitute the calculated result into formula ①

[0086]

[0087] Comparing the calculated value of 66.285 with the assumed value of 65mm pipe inner diameter, the error is within 3%. pipeline.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and basic spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for modifying a nitrogen protection device for a blast furnace top gearbox, characterized in that: include: 1) Remove the instruments on the nitrogen pipeline that are no longer used after production; 2) Remove the regulating valve group on the nitrogen main pipe at the top of the gearbox, set a main pipe flow limiting orifice plate on the nitrogen main pipe, the nitrogen main pipe is connected to the top of the gearbox through multiple nitrogen branch pipes, and each nitrogen branch pipe is provided with a branch pipe flow limiting orifice plate; The apertures on the main flow limiting orifice plate and the branch flow limiting orifice plate are calculated according to formula ①: Where: d k -Aperture of the flow limiting orifice; unit: mm; ρ-nitrogen density; unit: kg / m 3 ; ΔP-pressure difference before and after the flow limiting orifice; unit: MPa; G-nitrogen flow rate; unit: t / h; G is calculated according to formula ②: Where: N-molecular weight of nitrogen per mole, unit: g / mol; m-nitrogen molar volume, unit: L / mol; P1-nitrogen pressure after the limiting orifice, unit: kPa; P0-nitrogen pressure before the limiting orifice, unit: kPa; T1-nitrogen temperature after the limiting orifice, unit: °C; T0-nitrogen temperature before the limiting orifice, unit: °C; q m -Mass flow rate of nitrogen through the orifice plate, unit: m 3 / min; q m Calculate according to formula ③ Where: P2=P0, unit: kPa; A2- cross-sectional area of ​​the pipe after diameter reduction, unit: m 2 ; A3- Pipe cross-sectional area before diameter reduction, unit: m 2 ; Cc-contraction coefficient, Cc=A3 / A2; Cv-velocity coefficient, that is, the ratio of the flow velocity at the front and rear sections; β - ideal gas adiabatic index.

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