阅读说明：本技术 一种炼钢用机械真空泵系统管道设计的温降修正法 (Temperature drop correction method for pipeline design of mechanical vacuum pump system for steelmaking ) 是由 吴建龙 朱浪涛 任彤 张虎 刘蒙 马正锋 张明 曹海玲 于 2020-04-24 设计创作，主要内容包括：本发明属于钢水真空精炼装设备技术领域,具体涉及一种炼钢用机械真空泵系统管道设计的温降修正法。本发明通过将机械真空泵系统管道划分为j个区段、引入真空气体绝热膨胀降温公式、初步计算获取第j段的修正前管道直径D<Sub>j</Sub>、初步选取第j段修正前管道长度L<Sub>j</Sub>、修正多级机械真空泵入口前的管道长度、修正多级机械真空泵之间的管道直径和调整管道设置七个步骤,利用真空状态下不同区段管道内气体的绝热膨胀特性,依据稳定运行需求,修正了相关区段管道长度或直径,增强了气体冷却除尘器和机械真空泵出口强冷换热器的冷却能力,降低冷却水耗量,提高机械真空泵排气效率,保持设备长期稳定安全运行。采用本发明可取消现有设备中的强冷换热器,避免漏水现象。(The invention belongs to the technical field of molten steel vacuum refining equipment, and particularly relates to a temperature drop correction method for pipeline design of a mechanical vacuum pump system for steelmaking. The method comprises the steps of dividing a pipeline of a mechanical vacuum pump system into j sections, introducing a vacuum gas adiabatic expansion cooling formula, and preliminarily calculating to obtain the diameter D of the pipeline before correction of the j section j Selecting the length L of the pipeline before the j section correction j The method comprises seven steps of correcting the length of a pipeline in front of an inlet of a multistage mechanical vacuum pump, correcting the diameter of the pipeline between the multistage mechanical vacuum pumps and adjusting the pipeline setting, and corrects the length or the diameter of the pipeline of a relevant section according to the stable operation requirement by utilizing the adiabatic expansion characteristic of gas in the pipelines of different sections in a vacuum state, so that the cooling capacity of a gas cooling dust remover and a forced cooling heat exchanger at an outlet of the mechanical vacuum pump is enhanced, the cooling water consumption is reduced, the exhaust efficiency of the mechanical vacuum pump is improved, and the long-term stable and safe operation of equipment is kept. The invention can eliminate the forced cooling heat exchanger in the prior equipment and avoid water leakage.)

1. A temperature drop correction method for the pipeline design of a mechanical vacuum pump system for steelmaking is characterized by comprising the following steps

The method comprises the following steps: dividing a mechanical vacuum pump system pipeline into j sections;

step two: introducing a vacuum gas adiabatic expansion temperature reduction formula;

step three: preliminarily calculating to obtain the corrected pipeline diameter D of the j section_j

For the vacuum pipe with j being more than or equal to 4, the diameter D of the pipeline before correction of the j section is preliminarily calculated through a vacuum gas adiabatic expansion cooling formula introduced in the step two_j；

Step four, preliminarily selecting the length L of the pipeline before the j section correction_j；

Step five: correcting the length of a pipe before the inlet of a multistage mechanical vacuum pump

Selecting the jth segment according to the fourth step to correct the length of the pipeline L_jFor the pipeline before the inlet of the multi-stage mechanical vacuum pump, i.e. j<4, correcting the pipeline length of the pipeline section;

step six: modifying pipe diameters between multiple stages of mechanical vacuum pumps

According to the corrected pipeline diameter D of the j section obtained by the preliminary calculation in the step three_jCorrecting the diameters of pipelines between the multistage mechanical vacuum pumps, namely the diameters of the pipelines of the pipeline sections with j being more than or equal to 4;

step seven: adjusting the pipe setting

And adjusting the length or the diameter of the pipeline of the relevant section of the mechanical vacuum pump system for steelmaking according to the correction results obtained in the fifth step and the sixth step.

2. The method as claimed in claim 1, wherein the step one is to divide the mechanical vacuum pump system pipeline into five sections, and the specific method for dividing the sections is as follows:

j is 1, namely a pipeline section from the outlet of the vacuum chamber (2) for storing the molten steel (1) to the inlet of the gas cooling dust remover (3);

j is 2, namely a pipeline section from the outlet of the gas cooling dust remover (3) to a vacuum main valve (4);

j is 3, namely a pipeline section from a vacuum main valve (4) to an inlet of a primary mechanical vacuum pump (5);

j is 4, namely the pipeline section from the outlet of the primary mechanical vacuum pump (5) to the inlet of the secondary mechanical vacuum pump (6)

j is 5, namely a pipeline section from the outlet of the secondary mechanical vacuum pump (6) to the inlet of the tertiary mechanical vacuum pump (7).

3. The method for correcting the temperature drop of the pipe design of the steel-making mechanical vacuum pump system according to claim 1, wherein the method comprises the following steps: the vacuum gas adiabatic expansion temperature reduction formula introduced in the second step is as follows:

wherein: gamma is the adiabatic coefficient of vacuum gas;

T_ithe corrected exhaust gas temperature of the j section pipeline, namely the target temperature after the gas which meets the stable operation of each section of equipment in the steelmaking process is subjected to adiabatic cooling, and the unit is;

T_jthe temperature of the waste gas of the j-th section of pipeline before correction, namely the temperature of the waste gas in each section of pipeline in the steelmaking process, is measured in units of;

V_ithe minimum volume of the j section of pipeline after correction, namely the minimum volume for realizing the temperature reduction of waste gas in each section of pipeline in the steelmaking process, is m³；

V_jFor correcting the theoretical volume of the j-th pipeline section before correction, the unit is m³

V_jThe solving formula of (2) is as follows:

wherein, L_jThe length of the j section of pipeline before correction is in m;

D_jfor the corrected pipe diameter, the unit is m;

substituting the formula (2) into the formula (1) to obtainThe value of (c).

4. The method for correcting the temperature drop of the pipe design of the steel-making mechanical vacuum pump system according to claim 1, wherein the method comprises the following steps: the diameter D of the pipeline before the correction of the j section in the third step_jThe following formula is adopted for preliminary calculation

Wherein D is_jCorrecting the diameter of the pipeline before the jth section, wherein the unit is m;

G_jthe unit of the air pumping quantity of a mechanical vacuum pump at the outlet of the j section of pipeline is kg/h;

P_jthe vacuum degree in the j section of pipeline is Pa;

v_jthe gas flow velocity in the j section of pipeline is in m/s;

k is a conversion coefficient.

5. The method of claim 1, wherein the fourth step is performed by initially selecting L the length of the pipeline before the j section of the pipeline is corrected_jThe method is preliminarily selected in the following range: the length range of the j-th pipeline is 10-50 m; the length range of the j-th 2-section pipeline is 5-10 m; the length range of the j-th 3-section pipeline is 20-100 m.

6. The method for correcting the temperature drop of the pipe design of the steel-making mechanical vacuum pump system according to claim 1, wherein the method comprises the following steps: the concrete method for correcting the length of the pipeline in front of the inlet of the multistage mechanical vacuum pump in the fifth step is as follows

Firstly, calculating an adiabatic coefficient gamma according to the characteristics of gases in different j sections in a vacuum state;

secondly, calculating the temperature T of the waste gas in the vacuum chamber for storing the molten steel according to field measurement or theory_j＝1；

Thirdly, according to the inlet temperature T required by the design of the gas cooling heat exchanger_i＝1Determining the corrected j-1 section of pipeline exhaust gas temperature;

fourthly, primarily selecting the corrected pipeline length L according to the j-th-1-segment pipeline design requirement_j＝1；

The fifth step, according to the following formula

The length of the corrected j-1-th pipeline is L_i＝1；

Thus, the pipe diameter L of j 2 and j 3 is calculated and corrected in sequence_i＝2、L_i＝3。

7. The method for correcting the temperature drop of the pipe design of the steel-making mechanical vacuum pump system according to claim 6, wherein the first step of calculating the adiabatic coefficient gamma according to the characteristics of the gases in the different j sections under the vacuum state comprises the following specific steps: the gas passing through the pipeline is subject to the thermal insulation coefficient gamma of the diatomic gas₂Coefficient of thermal insulation gamma with monatomic gas₁According to the percentage of 30-50 percent to 70-50 percent, the following formula is adopted

γ＝30％～50％γ₁+70％～50％γ₂

And (4) calculating.

8. The method for correcting the temperature drop of the pipe design of the steel-making mechanical vacuum pump system according to claim 1, wherein the concrete method for correcting the diameter of the pipe between the multiple stages of mechanical vacuum pumps in the sixth step is as follows:

the first step is as follows: selecting an adiabatic coefficient gamma according to the characteristics of the gases in different j sections in a vacuum state;

the second step is that: according to the outlet temperature T of the 1-stage vacuum pump when j is 4 hours_j＝4J is 4 hours, the inlet temperature T of the two-stage vacuum pump_i＝4By the following formula

Calculating the diameter D of the pipeline before correction_j＝4；

By the following formula

Calculating the corrected diameter D_i＝4；

Thus, the corrected diameter D of j ≧ 5 is sequentially calculated_i＝5、D_i＝6。

9. The method of claim 8, wherein the method comprises the following steps: the first step is to calculate the adiabatic coefficient gamma according to the characteristics of the gases in different j sections under the vacuum state by the following specific method: the gas passing through the pipeline is subject to the thermal insulation coefficient gamma of the diatomic gas₂Coefficient of thermal insulation gamma with monatomic gas₁According to the percentage of 30-50 percent to 70-50 percent, the following formula is adopted

γ＝30％～50％γ₁+70％～50％γ₂

And (4) calculating.

Technical Field

The invention belongs to the technical field of molten steel vacuum refining equipment, and particularly relates to a temperature drop correction method for pipeline design of a mechanical vacuum pump system for steelmaking.

Background

The vacuum refining process of molten steel has the main tasks of removing harmful gas in the molten steel, enabling non-metallic inclusions to float upwards and uniformize molten steel components and temperature through molten steel circulation, simultaneously adding alloy, having multiple metallurgical functions of deoxidation, decarburization, desulfurization, dephosphorization, component fine adjustment and the like, greatly improving the cleanliness of the molten steel and improving the physical and chemical properties of steel. At present, vacuum refining is widely applied to molten steel treatment process, which is an essential process method for producing high-quality steel and an important means for producing high value-added steel.

The vacuum refining process of molten steel is that under the vacuum condition, molten steel is circularly degassed in a vacuum chamber (vacuum tank or vacuum groove) to finally achieve the purpose of purifying the molten steel. The main equipment for vacuum refining is a vacuum generating device, and a steam jet vacuum pump and a mechanical vacuum pump are commonly used. Because the mechanical vacuum pump has the advantages of energy conservation and environmental protection, the mechanical vacuum pump is increasingly applied to a vacuum refining process.

For mechanical vacuum pumps, the temperature of the inlet exhaust gas directly affects their operating efficiency and safety. Within the allowable range, the exhaust amount of the mechanical vacuum pump decreases as the exhaust gas temperature increases. If the temperature of the waste gas is too high, the thermal expansion between rotors and between the rotors and the cavity of the dry mechanical vacuum pump is blocked, and even the accident of seriously damaging equipment occurs. If the waste gas temperature is too high, the working solution in the cavity of the wet mechanical vacuum pump is gasified, the exhaust efficiency is rapidly reduced, and even the fault that the working solution cannot be exhausted after being consumed in a large amount is caused. Therefore, it is important to effectively lower the exhaust gas temperature.

At present, the mechanical vacuum pump system pipeline design is performed according to fig. 2. The vacuum chamber 2, the gas cooling dust remover 3, the vacuum main valve 4, the primary mechanical vacuum pump 5, the secondary mechanical vacuum pump 6, the tertiary mechanical vacuum pump 7 and other multistage mechanical vacuum pump system equipment are connected through air extraction pipelines with different lengths and pipe diameters. As is known, the length and diameter of the evacuation line are generally determined by the gas flow velocity in the line, the flow resistance of the line, and the system equipment layout. Because the heat exchange mechanism under the flowing state of vacuum gas in the pipeline is not considered, the design of the pipeline is not fully utilized to improve the temperature reduction capability of the system. And the cooling capacity of the gas cooling dust remover 3 and the cooling capacity of the strong cooling heat exchanger arranged at the machine body outlets of the primary mechanical vacuum pump 5, the secondary mechanical vacuum pump 6 and the tertiary mechanical vacuum pump 7 are completely relied on.

Because the temperature drop capability of the vacuum pipeline is not fully considered, the existing pipeline design method has the following two defects:

(1) the problems of huge equipment structure, complex cooling water pipeline, increased cooling water consumption, increased gas flow resistance and the like are caused by blindly increasing the cooling capacity of the gas cooling dust remover 3.

(2) The strong cooling heat exchangers are arranged at the outlets of the machine bodies of the primary mechanical vacuum pump 5, the secondary mechanical vacuum pump 6 and the tertiary mechanical vacuum pump 7 blindly, so that the gas resistance of the outlet of the mechanical vacuum pump is increased, the compression ratio is increased, the air exhaust capacity is reduced, the power consumption is increased, and the serious problems that the machine body generates heat seriously and the like can be caused. Meanwhile, the problems of complicated outlets of the primary mechanical vacuum pump 5, the secondary mechanical vacuum pump 6 and the tertiary mechanical vacuum pump 7, complicated cooling water pipelines, high cooling water consumption and the like are caused. After long-time use, the strong cooling heat exchanger sealed in the outlet pipeline of the machine body has water leakage phenomenon, and a steam-water mixture is generated. When the steam-water mixture flows through the mechanical vacuum pump body, the high-speed rotating vacuum pump rotor can be seriously damaged.

Disclosure of Invention

The invention provides a temperature drop correction method for pipeline design of a mechanical vacuum pump system for steelmaking, and aims to provide a method which can control the temperature of waste gas at an inlet of a multistage mechanical vacuum pump, improve the exhaust efficiency of the mechanical vacuum pump and keep long-term stable and safe operation of system equipment; the second purpose is to provide a method which can simplify the structure of the equipment, reduce the consumption of cooling water and reduce the flow resistance of gas; the second purpose is to provide a method which can avoid the phenomenon of generating steam-water mixture after the pipeline of the mechanical vacuum pump system for steelmaking is used for a long time.

In order to achieve the purpose, the invention adopts the technical scheme that:

a temperature drop correction method for the pipeline design of a mechanical vacuum pump system for steelmaking comprises the following steps

The method comprises the following steps: dividing a mechanical vacuum pump system pipeline into j sections;

step two: introducing a vacuum gas adiabatic expansion temperature reduction formula;

step three: preliminarily calculating to obtain the corrected pipeline diameter D of the j section_j

For the vacuum pipe with j being more than or equal to 4, the diameter D of the pipeline before correction of the j section is preliminarily calculated through a vacuum gas adiabatic expansion cooling formula introduced in the step two_j；

Step four, preliminarily selecting the length L of the pipeline before the j section correction_j；

Step five: correcting the length of a pipe before the inlet of a multistage mechanical vacuum pump

Selecting the jth segment according to the fourth step to correct the length of the pipeline L_jFor the pipeline before the inlet of the multi-stage mechanical vacuum pump, i.e. j<4, correcting the pipeline length of the pipeline section;

step six: modifying pipe diameters between multiple stages of mechanical vacuum pumps

According to the corrected pipeline diameter D of the j section obtained by the preliminary calculation in the step three_jCorrecting the diameters of pipelines between the multistage mechanical vacuum pumps, namely the diameters of the pipelines of the pipeline sections with j being more than or equal to 4;

step seven: adjusting the pipe setting

And adjusting the length or the diameter of the pipeline of the relevant section of the mechanical vacuum pump system for steelmaking according to the correction results obtained in the fifth step and the sixth step.

The method comprises the following steps of firstly, dividing a mechanical vacuum pump system pipeline into five sections, wherein the specific method for dividing the sections is as follows:

j is 1, namely a pipeline section from the outlet of the vacuum chamber for storing the molten steel to the inlet of the gas cooling dust remover;

j ═ 2, the section of pipe between the outlet of the gas-cooled dust collector and the vacuum main valve;

j is 3, namely a pipeline section between a vacuum main valve and an inlet of the primary mechanical vacuum pump;

j-4, i.e. the section of the conduit from the outlet of the primary mechanical vacuum pump to the inlet of the secondary mechanical vacuum pump

j is 5, namely the pipeline section from the outlet of the secondary mechanical vacuum pump to the inlet of the tertiary mechanical vacuum pump.

The vacuum gas adiabatic expansion temperature reduction formula introduced in the second step is as follows:

wherein: gamma is the adiabatic coefficient of vacuum gas;

T_ithe corrected exhaust gas temperature of the j section pipeline, namely the target temperature after the gas which meets the stable operation of each section of equipment in the steelmaking process is subjected to adiabatic cooling, and the unit is;

T_jthe temperature of the waste gas of the j-th section of pipeline before correction, namely the temperature of the waste gas in each section of pipeline in the steelmaking process, is measured in units of;

V_ithe minimum volume of the j section of pipeline after correction, namely the minimum volume for realizing the temperature reduction of waste gas in each section of pipeline in the steelmaking process, is m³；

V_jFor correcting the theoretical volume of the j-th pipeline section before correction, the unit is m³

V_jThe solving formula of (2) is as follows:

wherein, L_jThe length of the j section of pipeline before correction is in m;

D_jfor the corrected pipe diameter, the unit is m;

substituting the formula (2) into the formula (1) to obtain

The value of (c).

The diameter D of the pipeline before the correction of the j section in the third step_jThe following formula is adopted for preliminary calculation

Wherein D is_jCorrecting the diameter of the pipeline before the jth section, wherein the unit is m;

G_jthe unit of the air pumping quantity of a mechanical vacuum pump at the outlet of the j section of pipeline is kg/h;

P_jthe vacuum degree in the j section of pipeline is Pa;

v_jthe gas flow velocity in the j section of pipeline is in m/s;

k is a conversion coefficient.

In the fourth step, the length L of the pipeline before the j section of correction is preliminarily selected_jThe method is preliminarily selected in the following range: the length range of the j-th pipeline is 10-50 m; the length range of the j-th 2-section pipeline is 5-10 m; the length range of the j-th 3-section pipeline is 20-100 m.

The concrete method for correcting the length of the pipeline in front of the inlet of the multistage mechanical vacuum pump in the fifth step is as follows

Firstly, calculating an adiabatic coefficient gamma according to the characteristics of gases in different j sections in a vacuum state;

secondly, calculating the temperature T of the waste gas in the vacuum chamber for storing the molten steel according to field measurement or theory_j＝1；

Thirdly, according to the inlet temperature T required by the design of the gas cooling heat exchanger_i＝1Determining the corrected j-1 section of pipeline exhaust gas temperature;

fourthly, primarily selecting the corrected pipeline length L according to the j-th-1-segment pipeline design requirement_j＝1；

The fifth step, according to the following formula

The length of the corrected j-1-th pipeline is L_i＝1；

Thus, the pipe diameter L of j 2 and j 3 is calculated and corrected in sequence_i＝2、L_i＝3。

The first step selects a specific method of the adiabatic coefficient gamma according to the characteristics of different j section gases in a vacuum state, and the specific method of calculating the adiabatic coefficient gamma according to the characteristics of different j section gases in the vacuum state in the first step is as follows: the gas passing through the pipeline is subject to the thermal insulation coefficient gamma of the diatomic gas₂Coefficient of thermal insulation gamma with monatomic gas₁According to the percentage of 30-50 percent to 70-50 percent, the following formula is adopted

γ＝30％～50％γ₁+70％～50％γ₂

And (4) calculating.

The concrete method for correcting the diameter of the pipeline between the multistage mechanical vacuum pumps in the sixth step is as follows:

the first step is as follows: calculating the adiabatic coefficient gamma according to the characteristics of the gases in different j sections in the vacuum state;

the second step is that: according to the outlet temperature T of the first-stage vacuum pump when j is 4 ═ h_j＝4J is 4 hours, the inlet temperature T of the two-stage vacuum pump_i＝4By the following formula

Calculating the diameter D of the pipeline before correction_j＝4；

By the following formula

Calculating the corrected diameter D_i＝4；

Thus, the corrected diameter D of j ≧ 5 is sequentially calculated_i＝5、D_i＝6。

The first step is to calculate the adiabatic coefficient gamma according to the characteristics of the gases in different j sections under the vacuum state by the following specific method: the gas passing through the pipeline is subject to the thermal insulation coefficient gamma of the diatomic gas₂Coefficient of thermal insulation gamma with monatomic gas₁According to the percentage of 30-50 percent to 70-50 percent, the following formula is adopted

γ＝30％～50％γ₁+70％～50％γ₂

Has the advantages that:

compared with the prior art, the invention has the following beneficial technical effects:

(1) the invention utilizes the adiabatic expansion characteristic of gas in different sections of pipelines in a vacuum state, and corrects the length and the diameter of each section of pipeline according to the stable operation requirement of each device in a mechanical vacuum pump system.

(2) The invention is beneficial to relieving the cooling capacity of the gas cooling dust remover and the mechanical vacuum pump outlet forced cooling heat exchanger, simplifying the equipment structure, reducing the cooling water consumption and reducing the gas flow resistance.

(3) By means of the pipeline designed by the invention, a strong cooling heat exchanger sealed in the outlet pipeline of the mechanical vacuum pump can be omitted, and the water leakage phenomenon is avoided, so that the steam-water mixture phenomenon is avoided.

(4) The invention is beneficial to controlling the temperature of the waste gas at the inlet of the multistage mechanical vacuum pump, improving the exhaust efficiency of the mechanical vacuum pump and keeping the long-term stable and safe operation of system equipment.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to clearly understand the technical solutions of the present invention and to implement the technical solutions according to the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a modified flow diagram of the present invention;

figure 2 is a schematic diagram of a mechanical vacuum pump.

In the figure: 1-molten steel; 2-a vacuum chamber; 3-gas cooling dust remover; 4-vacuum main valve; 5-primary mechanical vacuum pump; 6-a secondary mechanical vacuum pump; 7-three-stage mechanical vacuum pump.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.