KR100305694B1 - Apparatus for controlling concentration of acids separated from circulation tanks in pickling line - Google Patents

Abstract

PURPOSE: An apparatus for controlling a concentration of acids separated from circulation tanks in a pickling line is provided which prevents deterioration of surface quality of products due to the change of a surface material by removing scale which is a compound of a black and hard iron film and oxygen, thereby producing products of high quality. CONSTITUTION: The apparatus for controlling a concentration of acids separated from circulation tanks in a pickling line is characterized in that first and second circulation tanks(18,19) are installed so that acids passing through nitric acid, hydrofluoric acid and reproduction flow rate meters(2,3,4) are supplied into the first and second circulation tanks(18,19) through respective nitric acid, hydrofluoric acid and reproduction supplying valves(5,6,7,8,9,10), waste acid tanks are installed so that waste acids are discharged into the waste acid tanks through respective waste acid discharging valves(13,14), counters(42,43,44) are connected to separation integrators(27¯32) so that the countered signals together with control signals of input amount setters(21¯26) of each acids are integrated in the respective separation integrators(27¯32) before being outputted after flow rate sensing signals by the flow rate meters(2,3,4) are countered in each of counters(42,43,44), valve separators(35¯37) are connected to valve outputters(39¯41) so that integrating control signals of each of the respective acids are impressed to the valve outputters(39¯41) through the valve separators(35¯37), and the acid supply valves(5,6,7,8,9,10) are connected so that the acid supply valves(5,6,7,8,9,10) of the first and second circulation tanks(18,19) are controlled by selective open/close control signals by the valve outputters(39¯41) of each of the acids.

Description

Acid concentration control device for circulation tank separation in pickling facility

The present invention is to reduce the surface quality of the product due to the change of the surface material by removing the scale, which is a compound of iron (Fe) and oxygen of the black and hard film generated during the continuous annealing process after hot-rolling the slab subjected to steelmaking and playing process We propose a separate acid concentration control device for the circulation tank of a pickling plant that can produce high quality products by preventing the

The thickness of the scale layer depends on the working conditions such as the atmosphere gas of the furnace, the oxygen content and the passage time of the furnace. In general, the higher the temperature, the larger the scale production.

In order to change the surface of the material by removing the deterioration of the surface quality of the product to produce a quality product is oxygen The compounds of the strip surface by a chemical reaction with the mixed acid (H ₃ (nitrate) + HF (hydrofluoric acid)), That is, remove the scale.

The chemical reaction at this time is as follows.

In the acid concentration control of the circulating tank (HF + H ₃ ), which is the core of pickling equipment designed to remove scale layer, HNO ₃ (nitric acid) solution has no direct scale solubility and Fe ₂ O ₃ is HF (fluoric acid) solution. Because it is not dissolved in the divalent Fe is reduced to trivalent Fe to act to dissolve the Cr ₂ O ₃ layer.

In addition, HF is a FeO, Or ₂ O _3, which is a nitric acid and mixed in Hydrogen generated a strong toxicity as a mediator of the nitrate scale releasability is good and is formed geumseok and contact with FeF ₃ because dissolve the oxide layer remains on the base steel surface A good pickling effect is obtained by removing.

The pickling operation should be set up to meet the appropriate standards for the concentration, temperature and iron content of the pickling solution depending on the type of acid and the type of steel. If this is not met, it will cause surface defects due to pickling defects. Get mad.

In addition, when the iron content is more than ≒ 50g / ℓ, it causes the coagulation phenomenon of waste acid and the property treatment through acid recovery, so that the acid concentration and iron concentration can be equalized in each circulation tank in the linkage type, which is the acid concentration control method of the conventional pickling equipment. This can lead to surface defects due to poor pickling and the inability to treat waste acid in the acid recovery plant.

As shown in FIG. 1, the peristaltic system, which is a conventional circulation acid concentration method, is injected into the detected amount of the nitric acid flow meter 2 by adjusting the nitrate valve 8 to adjust the nitric acid flow rate of the second circulation tank 19. Is adjusted to the detected amount of the hydrofluoric acid flowmeter 3 by adjusting the hydrofluoric acid valve 9.

The regeneration is controlled by the regeneration valve 10, and the regeneration is input to the detected amount of the regeneration flowmeter 4, and the strip pickling pump 12 is supplied to the strip pickling tank 1, and the pickling strip 1 is pickled. One mixed acid is again circulated through the acid drain line 11 to the second circulation tank 19.

The mixed acid in which the strip is pickled is transferred to the first circulation tank 18 through the peristaltic valve 15 of the second circulation tank by the level control of the second circulation tank 19, and the strip pickling is performed in the same manner as the second circulation tank. The mixed acid which is supplied from the tank pump 12 to the strip pickling tank and pickled the strip in the pickling tank is recirculated back to the first circulation tank 18 through the acid drain line 11 and the waste acid discharge valve by the level control of the first circulation tank. Through (16), the general acid and metal concentration control standards for stainless pickling equipment in Table 1 below are controlled according to this standard.

Concentration Guan Li Performance The first circulation 2nd circulation HNO3 180 ± 20g / ℓ 160 ± 20g / ℓ 190 ± 20g / ℓ HF 30 ± 5g / ℓ 25 ± 5g / ℓ 35 ± 5g / ℓ HNO3 30 ± 5g / ℓ 45 ± 10g / ℓ 30 ± 5g / ℓ

In such a first circulation tank and a second circulation tank-type acid concentration control method, the acid concentration decreases and the metal (iron) concentration increases in the first circulation tank, and the acid concentration increases and the metal concentration decreases in the second circulation tank. There is a problem that the evil cycle continues.

An object of the present invention is to equalize the acid concentration and metal concentration management of each circulation tank in a pickling facility having first and second circulation tanks, thereby preventing surface quality defects on the produced product due to poor acid concentration and increasing the metal concentration. It is to provide a separate acid concentration control device for the circulation tank of the pickling plant to prevent the acid condensation and reduce the acid consumption.

The present invention is characterized in that the acid concentrations of the first and second circulation tanks are equalized in the acid concentration management of the most essential circulation tank of the pickling plant designed to remove the scale of the strip surface by chemical reaction using mixed acid. The present invention provides a control device capable of increasing the effect of reducing acid consumption and acid recovery by maintaining acid concentrations and metal concentrations in each circulation tank separately by separately managing the acid concentrations of the first circulation tank and the second circulation tank.

1 is a block diagram of a conventional peristaltic acid concentration control device.

2 is a block diagram of the circulation tank separated acid concentration control apparatus according to the present invention.

3 is a flow chart of a flow separation integration control step for explaining the operation of the present invention.

4 is a time chart for explaining the present invention.

<Description of the symbols for the main parts of the drawings>

1: strip pickling bath 2: nitrate flowmeter

3: hydrofluoric acid flow meter 4: regeneration flow meter

5: 1st circulation tank nitric acid supply valve 6: 1st circulation tank hydrofluoric acid supply valve

7: 1st circulation tank regeneration supply valve 8: 2nd circulation tank nitric acid supply valve

9: second circulation tank hydrofluoric acid supply valve 10: second circulation tank reproduction valve

11: drain line 12: pump

13: 1st circulation tank discharge valve 14: 2nd circulation tank discharge valve

15: 2nd circulation tank peristaltic valve 16: 1st circulation tank peristaltic discharge valve

17: acid concentration control device 18: first circulation tank level gauge

19: second circulation tank level gauge

Hereinafter, with reference to the accompanying drawings will be described the present invention.

The present invention is a circulating tank separated acid concentration control device of the pickling facility for managing the acid concentration and metal concentration management of the stainless annealing pickling plant and the general pickling plant pickling equipment for each circulation tank.

The first circulation tank 18 of FIG. 2 has a nitric acid supply valve 5 for controlling the nitric acid flow rate, a hydrofluoric acid supply valve 6 for controlling the hydrofluoric acid flow rate, a regeneration supply valve 7 for controlling the regeneration flow rate, and waste acid control. The waste acid discharge valve 13 is installed for the purpose of managing the acid concentration and the metal concentration of the first circulation tank.

The second circulation tank 19 has a nitric acid supply valve 8 for controlling the nitric acid flow rate, a hydrofluoric acid supply valve 9 for controlling the hydrofluoric acid flow rate, a regeneration supply valve 10 for controlling the regeneration flow rate, and waste acid discharge controlling the waste acid. The valve 14 is provided for the purpose of acid concentration and metal concentration management of the second circulation tank.

In addition, the nitric acid flowmeter 2, the hydrofluoric acid flowmeter 3, and the regeneration flowmeter 4 which detect the flow volume of each acid are provided as a means for measuring the flow volume of each circulation tank 18,19.

In the first and second circulation tanks 18 and 19, acids through nitric acid, hydrofluoric acid, and reflow flowmeters 2, 3, and 4 are respectively applied to nitric acid, hydrofluoric acid, and reproducing supply valves (5.6.7), (8, 9, 10) is installed to be supplied through the waste acid storage tank is installed so that the waste acid is discharged through each of the waste acid discharge valves (13), (14).

The flow rate detection signals by the flow meters (2, 3, 4) are integrated in each of the totalizers (42, 43, 44), and then separately separated together with the control signals of the input amount setters 21-26 of each acid. The devices 27-32 are integrated and connected to output.

Integration control signals of the respective mountains are connected to the valve output unit 39-41 via the valve separator 35-37.

The acid supply valves (5.6.7), (8, 9, 10) of the first and second circulation tanks (18, 19) are controlled by an optional open / close control signal by the valve outputs of the respective mountains. It is connected to form an acid concentration control device separate from the circulation tank of the pickling facility.

Such a description of the nitric acid input method in the present invention will be described with reference to the time chart of FIG. 4.

The amount set in the first nitric acid input setter 21 and the amount set in the second nitric acid input setter 22 are separated by the first nitric acid separate accumulator 27 and the second nitric acid separate accumulator 27 and the second nitric acid separator. After processing the setting value in the integrator 28 and recognizing the setting value of the input time setting unit 33 and initializing the nitrate accumulator 42, the first nitrate accumulator 45 and the second nitrate accumulator 46, It is provided to the nitric acid valve separator 35 and the input time command unit 34 automatically calculates the input time.

Accordingly, the nitric acid valve separator 35 recognizes the set value of the valve closing time setting unit 38, and the nitric acid valve output unit 39 selects the first nitric acid valve 5 and the second nitric acid by the selection of the nitric acid valve separator 35. Open and close valve (8).

When the first nitric acid valve 5 is opened by the selection of the nitric acid valve separator 35, the nitric acid separation accumulators 27 and 28 adjust the flow rate detected by the nitric acid flow meter 2 to the first nitric acid accumulator 45. Integration begins at 42.

At this time, the first nitric acid totalizer 45 feeds the accumulated amount back to the first nitric acid separator 27 so that the first nitric acid separator 27 continuously compares the integrated amount with the first nitric acid input setter 21.

If the set amount and the input amount are the same, the first nitric acid separator 21 and the integrated amount are compared.

If the set amount is equal to the input amount, the first nitric acid separator 27 continuously compares the integrated amount with the first nitric acid input amount setter 21.

If the set amount and the input amount are the same, the first nitric acid separator 27 instructs the nitric acid valve separator 35 to close the first nitric acid valve 5 regardless of the valve input time set value 38.

If the set amount is larger than the input amount, the nitric acid valve separator 35 closes the first nitric acid valve 5 after processing the valve input time set value 38.

Accordingly, the nitric acid splitting accumulators 27 and 28 stop the integration of the first nitric acid accumulator 45 and initialize the nitric acid accumulator 42 and the first nitric acid accumulator 45 maintains the current integrated value.

When the second nitric acid valve 8 is opened by selection of the nitric acid valve separator 35, the nitric acid separation accumulators 27 and 28 initialize the flow rate detected by the nitric acid flowmeter 2 to the second nitric acid accumulator 46. Integration is started through the nitric acid totalizer 42.

In this case, like the first nitric acid totalizer 45, the second nitric acid totalizer 46 feeds back the accumulated amount to the second nitric acid separator 28, so that the second nitric acid separator 28 continuously sets the second nitric acid input amount setter. (22) and accumulated amount are compared.

If the set amount and the input amount are the same, the second nitric acid separator 28 commands the nitric acid valve separator 35 to close the second nitric acid valve 5 regardless of the valve input time set value 38.

If the set amount is larger than the input amount, the nitrate valve separator 35 closes the second nitrate valve 8 after processing the set value 38 when the valve is turned on.

Accordingly, the nitric acid splitting accumulators 27 and 28 stop the integration of the second nitric acid accumulator 46 and initialize the nitric acid accumulator 42 and the second nitric acid accumulator 46 maintains the current integrated value.

In this way, the nitric acid separating accumulators 27 and 28 manage the first nitric acid accumulator 45 and the second nitric acid accumulator 46 for the time commanded by the input time command unit 34, and also the nitric acid separators 27 and 28. Always compares the integrated amount with the nitric acid input amount setting unit (21, 22), and if the set amount and the input amount are the same, the first nitric acid is controlled by controlling the nitric acid valve separator (35) regardless of the time commanded by the input time command unit (34). The valve 5 and the second nitric acid valve 8 are controlled.

In addition, the nitric acid separation accumulators 27 and 28 open / close the first nitric acid valve 5 and the second nitric acid valve 8 while recognizing values of the input time command part 34 and the valve input time setting part 38. By closing, the integrated values of the first and second nitric acid accumulators 45 and 46 are maintained and increased, and the amount of nitric acid required by the nitric acid amount input setters 21 and 22 is added to each circulation tank.

The regeneration input method includes a first regeneration input amount setter 25, a second regeneration input amount selector 26, a first regeneration separate accumulator 31, a second regenerator totalizer 32, and a regeneration valve separator ( 37, the regeneration valve output unit 41, the reproduction totalizer 44, the first reproduction totalizer 49, the second reproduction totalizer 50, the reproduction flow meter 4, the first reproduction valve 7, the second reproduction valve (10) is controlled in the same manner as the nitric acid input method, and the hydrofluoric acid input method also includes a first hydrofluoric acid input amount setter 23, a second hydrofluoric acid input amount setter 24, and a first hydrofluoric acid separate accumulator 29 ), The second hydrofluoric acid totalizer 30, the hydrofluoric acid valve separator 36, the hydrofluoric acid valve output unit 40, the hydrofluoric acid totalizer 43, the first hydrofluoric acid totalizer 47, the second hydrofluoric acid totalizer 48, the hydrofluoric acid flow meter (3), the first hydrofluoric acid valve 6 and the second hydrofluoric acid valve 9 are introduced into each mixing tank in the same manner as the nitric acid injection method.

The input time setting unit 33 manages the input time of nitric acid, hydrofluoric acid, and regeneration, and when the input time is completed, the nitric acid separate accumulators 27 and 28, the hydrofluoric acid separate accumulators 29 and 30, and the regeneration separate accumulator ( 31, 32), input time commander 34 and all totalizers (45, 46, 47, 48, 49, 50) are initialized and commanded to separate totalizers (27, 28, 29, 30, 31, 32). Control again in this way.

Figure 3 is a flow chart illustrating the acid input and selection process for each cycle of the apparatus of the present invention, the acid can be manually added to the first circulation tank and the second circulation tank when the manual injection of the acid is selected as referred to here In this case, when the first nitric acid valve 5 and the second nitric acid valve 8 are open at the same time, the flow rate detected by the nitric acid flowmeter 2 is controlled by the nitric acid accumulator 42 to control the nitric acid separation accumulators 27 and 28. By (ⓓ) the first nitrate totalizer 45, the second nitrate totalizer 46 is bisected and integrated, it is possible to know the amount of integration put into each circulation tank.

Reproduction and hydrofluoric acid are also integrated in the above manner and the amount can be easily identified.

In addition, the waste acid discharge valves 13 and 14 of each circulation tank are sent to the waste acid storage tank by the amount of acid input by the level control of each circulation tank, and acid input and discharge are performed without mutual interference, so that the separate acid concentration control of the circulation tank of the pickling facility is performed. And level control is performed.

In addition, in the case of automatic input after selecting manual / automatic input in FIG. 3, when the acid input amount of each circulation tank is set, nitric acid and regeneration are introduced into the first circulation tank, and hydrofluoric acid is introduced into the second circulation tank.

When nitric acid is introduced into the first circulation tank, hydrofluoric acid is never added, and when hydrofluoric acid is introduced into the first circulation tank, nitric acid is never input.

This is not related to the level control of each circulation tank and the chemical reaction of nitric acid and hydrofluoric acid, and reproduction is an exception.

As described above, the circulating acid separation control device of the pickling plant of the present invention prevents surface quality defects on the produced product due to acid and metal concentration inequality in the conventional interlocking acid control method and also prevents waste acid aggregation. By doing so, it is possible to prevent the problem of property disposal through acid recovery and to increase the effect of reducing acid consumption and recovery.

Claims (1)

In the first and second circulation tanks 18 and 19, acids through nitric acid, hydrofluoric acid, and reflow flowmeters 2, 3, and 4 are respectively applied to nitric acid, hydrofluoric acid, and reproducing supply valves (5.6.7), (8, 9, 10) and installed in the waste acid storage tank so that the waste acid is discharged through each of the waste acid discharge valves 13 and 14, and the flow rate detection signals by the flow meters 2, 3 and 4 are respectively After the integrated process in the totalizer 42, 43, 44 of the integrated with the control signal of the input amount setter (21-26) of each acid is integrated in each separate accumulator (27-32) and connected to each other, The integration control signals of the mountains are connected to the valve outputs 39-41 via the valve separators 35-37, and the first, the open and close control signals by the valve outputs of the respective mountains. 2. A circulation tank separate acid concentration control device for a pickling plant, characterized in that the acid supply valves (5.6.7) and (8, 9, 10) of the circulation tanks (18, 19) are controlled and connected.

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