CN115449601A - Method for controlling vacuum degree by variable frequency speed regulation of RH refining furnace mechanical pump - Google Patents
Method for controlling vacuum degree by variable frequency speed regulation of RH refining furnace mechanical pump Download PDFInfo
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- CN115449601A CN115449601A CN202211048759.8A CN202211048759A CN115449601A CN 115449601 A CN115449601 A CN 115449601A CN 202211048759 A CN202211048759 A CN 202211048759A CN 115449601 A CN115449601 A CN 115449601A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
Abstract
The invention relates to a method for controlling vacuum degree by frequency conversion speed regulation of a mechanical pump of an RH refining furnace, which sends a corresponding current signal to a frequency converter of the mechanical pump according to a set value of a vacuum pressure control curve, and adjusts the output frequency of the frequency converter, thereby controlling the rotating speed of a motor and achieving the purpose of controlling the pressure of a vacuum system; and then according to the actual pressure measured by the vacuum chamber in the production process, feeding back a current signal to a frequency converter of the mechanical pump through the functional block, adjusting the frequency of the frequency converter, realizing automatic output regulation and keeping the vacuum pressure within a specified range. The method has accurate control precision and small vacuum degree fluctuation range, reduces the waste of steam energy, improves the automation level of the TH-TB furnace, reduces cost, improves efficiency and improves productivity.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy automation, in particular to a method for controlling vacuum degree by frequency conversion and speed regulation of a mechanical pump of an RH refining furnace.
Background
RH-TB external refining is a very important link in steelmaking production, and many high value-added products can be cast in a casting machine only after being treated by an RH-TB furnace. It has the functions of removing C, H and N, regulating temperature and components, etc. in vacuum state. With the progress of industrial technology, users have higher and higher requirements on the quality of steel products, and RH-TB has become an indispensable refining means for producing high value-added products. The RH-TB furnace has the advantages of short treatment period, large production capacity, good refining effect and the like, so the RH-TB furnace is widely applied to steel mills.
In the RH furnace, the degree of vacuum is maintained at 0.2kpa or less during the production to perform deep decarburization of molten steel. The early stage of the treatment is when the carbon-oxygen reaction is the most severe, molten steel is splashed greatly, the hot top cover is easy to form serious slagging, the more steel slag is formed, the more the treatment effect is influenced, and the cleaning difficulty is higher. Therefore, the vacuum degree is controlled by vacuum pressure in the early stage, and the traditional pressure control mode is to fill waste gas into the system through a regulating valve, automatically realize the operations of opening and closing the valve according to pressure set values in different time periods, and maintain the vacuum degree within a set horizontal range. The method has the defects of inaccurate control precision, large vacuum degree fluctuation range, waste of steam energy, frequent adjustment, large damage to the regulating valve and troublesome maintenance.
Pressure control is generally divided into three phases:
the first stage is the opening of the main valve for 2min, the molten steel enters the circulating treatment state from the static state, the splashing is most intense, the vacuum pressure is controlled within the range of 30-45 kpa, and the pressure in the stage is set to be 35kpa.
The second stage is the 2 nd min-3 rd min of the treatment, and the pressure is controlled within the range of 20kpa-30kpa by adopting a progressive process, and the pressure set value of the stage is 25kpa.
The third stage is from 3min to 4min of the treatment, the pressure requirement of this stage is controlled in the range of 10kpa to 20kpa, and the set value is 15kpa.
Disclosure of Invention
The invention provides a method for controlling vacuum degree by frequency conversion speed regulation of a mechanical pump of an RH refining furnace, which is characterized in that according to a set value of a vacuum pressure control curve, a corresponding current signal is sent to a frequency converter of the mechanical pump, and the output frequency of the frequency converter is adjusted, so that the rotating speed of a motor is controlled, and the purpose of controlling the pressure of a vacuum system is achieved; then according to the actual pressure measured by the vacuum chamber in the production process, a current signal is fed back to the frequency converter of the mechanical pump through the functional block, the frequency of the frequency converter is adjusted, automatic output adjustment is realized, and the vacuum pressure is maintained within a specified range. The method has the advantages of accurate control precision, small vacuum degree fluctuation range, reduced waste of steam energy, improved automation level of the TH-TB furnace, reduced cost, improved efficiency and improved productivity.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for controlling vacuum degree by variable frequency speed regulation of a mechanical pump of an RH refining furnace comprises the following steps:
1) Setting an automatic control program I, and sending a corresponding current signal to a frequency converter of the mechanical pump by the program according to a set value of a vacuum pressure control curve; procedure i was set as follows:
when the vacuum degree is required to be adjusted to be less than 20kPa and less than or equal to 10kPa, controlling the current input into the frequency converter of the mechanical pump to be 19 +/-0.1 mA;
when the vacuum degree is required to be adjusted to be less than 30kPa and less than or equal to 20kPa, controlling the current input into the frequency converter of the mechanical pump to be 17.5 +/-0.1 mA;
when the vacuum degree is required to be adjusted to be less than 45kPa and less than or equal to 30kPa, controlling the current input into the frequency converter of the mechanical pump to be 16 +/-0.1 mA;
2) The frequency converter adjusts the output frequency, thereby controlling the rotating speed of the motor and achieving the purpose of controlling the pressure of the vacuum system;
3) An automatic control program II is set, the program II feeds back current signals to a frequency converter of the mechanical pump through a functional block according to the actual pressure measured by the vacuum chamber in the production process, the frequency of the frequency converter is adjusted, automatic output adjustment is realized, and the vacuum pressure is maintained within a specified range, and the program II is set as follows:
when the difference between the measured value of the vacuum pressure and the set value is less than-20 kPa, the current input into the frequency converter of the mechanical pump is increased by-2 mA per second;
when the difference between the measured value of vacuum pressure less than or equal to-20 kPa and the set value is less than-10 kPa, the current input into the frequency converter of the mechanical pump is increased by-1.5 mA per second;
when the difference between the measured value of vacuum pressure is less than or equal to minus 10kPa and the set value is less than minus 5kPa, the current input into the frequency converter of the mechanical pump is increased by minus 1mA per second;
when the difference between the measured value of the vacuum pressure and the set value is less than 0kPa and less than or equal to-5 kPa, the current input into the frequency converter of the mechanical pump is increased by-0.5 mA per second;
when the difference between the measured value of the vacuum pressure and the set value is less than or equal to 0kPa and less than 5kPa, the current input into the frequency converter of the mechanical pump is increased by 0.5mA per second;
when the difference between the measured value of the vacuum pressure which is less than or equal to 5kPa and the set value is less than 10kPa, the current input into the frequency converter of the mechanical pump is increased by 1mA per second;
when the difference between the measured value of the vacuum pressure is less than or equal to 10kPa and the set value is less than 20kPa, the current input into the frequency converter of the mechanical pump is increased by 1.5mA per second;
when the difference between the measured value of the vacuum pressure and the set value is more than or equal to 20kPa, the current input into the frequency converter of the mechanical pump is increased by 2mA per second.
The program I is set as follows:
when the vacuum degree is required to be adjusted to be less than 20kPa and is less than or equal to 10kPa, controlling the current input into the frequency converter of the mechanical pump to be 19mA;
when the vacuum degree is required to be adjusted to be less than 30kPa and less than or equal to 20kPa, controlling the current input into the frequency converter of the mechanical pump to be 17.5mA;
when the vacuum degree is required to be adjusted to be less than 45kPa and less than or equal to 30kPa, the current input into the frequency converter of the mechanical pump is controlled to be 16mA.
The mechanical pump is a motor model YPT 355M1-4.
Two mechanical pump working modes are adopted.
The working mode that two mechanical pumps work and one is used is adopted.
The volume of the vacuum chamber is 20-30 cubic meters.
The RH refining furnace vacuum pumping system adopts a combined mode of a vapor pump and a mechanical pump, and within 0-4 min of pressure control, the combined mode of the vacuum pump is as follows: only two mechanical pumps are started in the first three minutes, one steam pump is started in the third minute, the mechanical pump is stopped in the fourth minute, and the rest steam pumps are started.
Compared with the prior art, the invention has the beneficial effects that:
the invention relates to a method for controlling the vacuum degree of a RH refining furnace mechanical pump by frequency conversion speed regulation, which sends a corresponding current signal to a frequency converter of the mechanical pump according to a set value of a vacuum pressure control curve, and adjusts the output frequency of the frequency converter, thereby controlling the rotating speed of a motor and achieving the purpose of controlling the pressure of a vacuum system; and then according to the actual pressure measured by the vacuum chamber in the production process, feeding back a current signal to a frequency converter of the mechanical pump through the functional block, adjusting the frequency of the frequency converter, realizing automatic output regulation and keeping the vacuum pressure within a specified range. The method has the advantages of accurate control precision, small vacuum degree fluctuation range, reduced waste of steam energy, improved TH-TB furnace automation level, reduced cost, improved efficiency and improved productivity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example (b): a vacuum pumping system of an RH-TB furnace of a steel-making main factory of a certain iron and steel company adopts a combined mode of a steam pump and a mechanical pump, the mechanical pump adopts three 220kw variable-frequency asynchronous motors (YPT 355M 1-4) to drive a pump body to rotate to pump the system, and the three motors are in a working mode of two working and one standby. During production, the rotating speed of the motor can be controlled by adjusting the frequency of the frequency converter of the motor of the mechanical pump, so that the vacuum pressure is controlled.
The normal working frequency of the two mechanical pumps of the RH-TB furnace is 45Hz, the two mechanical pumps work under the frequency, the two mechanical pumps are started simultaneously, the vacuum degree can be pumped to 18 kPa-20kPa, and when a combined mode of the two mechanical pumps and a steam pump is started, the vacuum degree can be pumped to 10 kPa-12 kPa. The requirement of minimum 15kPa at the later stage of pressure control is met.
Within 0 min-4 min of pressure control, the combined mode of the vacuum pump is as follows: only two mechanical pumps are started in the first three minutes, one steam pump is started in the third minute, the mechanical pump is stopped in the fourth minute, and the rest steam pumps are started.
When the pressure is controlled in the first stage, the two mechanical pumps work, the target vacuum degree is in the range of 30kPa-45kPa, and the current input into the frequency converter is set to be 16mA.
When the actual vacuum measurement pressure exceeds 30-45 kPa, an automatic adjustment control system is put into operation, and the program finely adjusts the parameters of the frequency converter according to the actual pressure. For example, when the actual pressure measurement value is 49kPa, the output current is increased by 0.5mA per second and readjusted according to the actual pressure feedback value.
When the pressure is controlled in the second stage, the two mechanical pumps work, the target vacuum degree is in the range of 20kPa-30kPa, and the current input into the frequency converter is set to be 17.5mA. When the actual vacuum measurement pressure exceeds 20-30 kPa, an automatic adjustment control system is put into operation, and the program finely adjusts the parameters of the frequency converter according to the actual pressure. For example, when the actual pressure measurement is 14kPa, the output current is reduced by-1 mA per second and readjusted according to the actual pressure feedback value.
And in the third stage of pressure control, two mechanical pumps and one steam pump work, the target vacuum degree is in the range of 10-20 kPa, and the current input into the frequency converter is set to be 19mA. When the actual vacuum measurement pressure exceeds 10-20 kPa, an automatic adjustment control system is put into use, and the program finely adjusts the parameters of the frequency converter according to the actual pressure. For example, when the actual pressure measurement value is 26kPa, the output current is increased by 1mA per second, and the adjustment is performed again according to the actual pressure feedback value.
When the treatment time reaches 4min, the residual steam pumps are started in sequence according to the vacuum pressure.
Claims (6)
1. A method for controlling vacuum degree by variable frequency speed regulation of a mechanical pump of an RH refining furnace is characterized by comprising the following steps:
1) Setting an automatic control program I, and sending a corresponding current signal to a frequency converter of the mechanical pump by the program according to a set value of a vacuum pressure control curve; procedure i was set as follows:
when the vacuum degree is required to be adjusted to be less than 20kPa and less than or equal to 10kPa, controlling the current input into the frequency converter of the mechanical pump to be 19 +/-0.1 mA;
when the vacuum degree is required to be adjusted to be less than 30kPa and less than or equal to 20kPa, controlling the current input into the frequency converter of the mechanical pump to be 17.5 +/-0.1 mA;
when the vacuum degree is required to be adjusted to be less than 45kPa and less than or equal to 30kPa, controlling the current input into the frequency converter of the mechanical pump to be 16 +/-0.1 mA;
2) The frequency converter adjusts the output frequency, thereby controlling the rotating speed of the motor and achieving the purpose of controlling the pressure of the vacuum system;
3) An automatic control program II is set, the program II feeds back current signals to a frequency converter of the mechanical pump through a functional block according to the actual pressure measured by the vacuum chamber in the production process, the frequency of the frequency converter is adjusted, automatic output adjustment is realized, and the vacuum pressure is maintained within a specified range, and the program II is set as follows:
when the difference between the measured value of the vacuum pressure and the set value is less than-20 kPa, the current input into the frequency converter of the mechanical pump is increased by-2 mA per second;
when the difference between the measured value of vacuum pressure less than or equal to-20 kPa and the set value is less than-10 kPa, the current input into the frequency converter of the mechanical pump is increased by-1.5 mA per second;
when the difference between the measured value of the vacuum pressure and the set value is less than-5 kPa and is less than-10 kPa, the current input into the frequency converter of the mechanical pump is increased by-1 mA per second;
when the difference between the measured value of the vacuum pressure and the set value is less than 0kPa and less than or equal to-5 kPa, the current input into the frequency converter of the mechanical pump is increased by-0.5 mA per second;
when the difference between the measured value of the vacuum pressure and the set value is less than or equal to 0kPa and less than 5kPa, the current input into the frequency converter of the mechanical pump is increased by 0.5mA per second;
when the difference between the measured value of the vacuum pressure is less than or equal to 5kPa and the set value is less than 10kPa, the current input into the frequency converter of the mechanical pump is increased by 1mA per second;
when the difference between the measured value of the vacuum pressure which is less than or equal to 10kPa and the set value is less than 20kPa, the current input into the frequency converter of the mechanical pump is increased by 1.5mA per second;
when the difference between the measured value of the vacuum pressure and the set value is more than or equal to 20kPa, the current input into the frequency converter of the mechanical pump is increased by 2mA per second.
2. The method for controlling the vacuum degree of an RH refining furnace mechanical pump through variable frequency speed regulation according to claim 1, wherein the program I is set as follows:
when the vacuum degree is required to be adjusted to be less than 20kPa and less than or equal to 10kPa, controlling the current input into the frequency converter of the mechanical pump to be 19mA;
when the vacuum degree is required to be adjusted to be less than 30kPa and is less than or equal to 20kPa, controlling the current input into the frequency converter of the mechanical pump to be 17.5mA;
when the vacuum degree is required to be adjusted to be less than 45kPa and is less than or equal to 30kPa, the current input into the frequency converter of the mechanical pump is controlled to be 16mA.
3. The method for controlling the vacuum degree of a RH refining furnace by variable frequency speed regulation of a mechanical pump according to claim 1, wherein the mechanical pump motor is a 220kw variable frequency asynchronous motor.
4. The method for controlling the vacuum degree of an RH refining furnace according to claim 1, wherein a two-in-one and one-out operation mode of two mechanical pumps is adopted.
5. The method for controlling the vacuum degree of an RH refining furnace mechanical pump through variable frequency speed regulation according to claim 1, wherein the volume of the vacuum chamber is 20-30 cubic meters.
6. The method for controlling the vacuum degree of the RH refining furnace through variable frequency speed regulation according to any one of claims 1 to 4, wherein a combined mode of a vapor pump and a mechanical pump is adopted in a vacuumizing system of the RH refining furnace, and the combined mode of vacuum pumps is that within 0-4 min of pressure control: only two mechanical pumps are started in the first three minutes, one steam pump is started in the third minute, the mechanical pumps are stopped in the fourth minute, and the rest steam pumps are started.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211048759.8A CN115449601A (en) | 2022-08-30 | 2022-08-30 | Method for controlling vacuum degree by variable frequency speed regulation of RH refining furnace mechanical pump |
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| CN202211048759.8A CN115449601A (en) | 2022-08-30 | 2022-08-30 | Method for controlling vacuum degree by variable frequency speed regulation of RH refining furnace mechanical pump |
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Citations (5)
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| CN102586723A (en) * | 2012-03-09 | 2012-07-18 | 江苏丰东热技术股份有限公司 | Method and device for automatically controlling vacuum pressure of ion chemical heat treatment furnace |
| CN105736326A (en) * | 2014-06-18 | 2016-07-06 | 宝钢工程技术集团有限公司 | Vacuumizing process equipment |
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| CN108823357A (en) * | 2018-07-09 | 2018-11-16 | 上海宽量节能投资有限公司 | A kind of degassing system and its degassing method based on flexible mechanical vacuum pump group |
| CN111878374A (en) * | 2020-07-14 | 2020-11-03 | 中国重型机械研究院股份公司 | Control method of mechanical vacuum pump system based on RH refining process |
-
2022
- 2022-08-30 CN CN202211048759.8A patent/CN115449601A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102586723A (en) * | 2012-03-09 | 2012-07-18 | 江苏丰东热技术股份有限公司 | Method and device for automatically controlling vacuum pressure of ion chemical heat treatment furnace |
| CN105736326A (en) * | 2014-06-18 | 2016-07-06 | 宝钢工程技术集团有限公司 | Vacuumizing process equipment |
| CN108180144A (en) * | 2018-01-03 | 2018-06-19 | 上海宽量节能投资有限公司 | A kind of mechanical pump group composing method and its mechanical pump system for liquid steel degassing is united |
| CN108823357A (en) * | 2018-07-09 | 2018-11-16 | 上海宽量节能投资有限公司 | A kind of degassing system and its degassing method based on flexible mechanical vacuum pump group |
| CN111878374A (en) * | 2020-07-14 | 2020-11-03 | 中国重型机械研究院股份公司 | Control method of mechanical vacuum pump system based on RH refining process |
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