JPH10325672A - Method and device for forecasting operation state of air liquefying and separating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly change the flow of extraction of each product of liquefied nitrogen and liquefied oxygen in the middle of the change of availability factor. SOLUTION: In an air liquefying and separating device which circulates the nitrogen of a compressive freezer 7 using nitrogen as a refrigerant, in a rectifying tower 6 supplied with material air and separates liquefied nitrogen and liquefied air from the material air and takes them out, the total quantity y of manufactured liquefied nitrogen and liquefied oxygen after a wasteful time T corresponding to the cold flow x in the pipe line 18 of nitrogen gas supplied to the high-pressure rectifying tower 6 is estimated with the primary function using the cold flow x as a parameter. The extraction of the product is performed with the flow equal to this estimated total manufacture quantity y.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for predicting the operation state of an air liquefaction / separation apparatus for liquefying air and separating the constituents of the air into components such as nitrogen and oxygen. More particularly, the present invention relates to a configuration for changing the product extraction flow rates of liquefied nitrogen and liquefied oxygen when changing the operation rate of an air liquefaction / separation apparatus.

[0002]

2. Description of the Related Art Conventionally, in an air liquefaction / separation apparatus, a compression refrigerator using nitrogen as a refrigerant is provided in connection with a rectification tower, and liquefied nitrogen gas is injected into the rectification tower. Change the cooling flow rate, which is the flow rate of circulating nitrogen supplied to
A configuration for adjusting the operation rate is conventionally known to those skilled in the art. Here, the operating rate η is the actual production amount of liquefied nitrogen yN (units) with respect to the total rated production amount yR (units Nm ³ / h) of liquefied nitrogen and liquefied oxygen obtained by separation from the air liquefaction separation device. Nm ³ / h) and the actual liquefied oxygen production amount yO (unit Nm ³ / h).

Η = (yN + yO) / yR (1) When the operation rate η is changed, the flow rate of the cold and the flow rate of the raw material air are gradually changed with the lapse of time so as not to disturb the balance of the entire air liquefaction / separation apparatus. There is a need to. With the change of the cooling flow rate and the raw material air flow rate, the production amounts yN and yO of the products of liquefied nitrogen and liquefied oxygen change after a lapse of dead time. Therefore, it is necessary to change the product withdrawal flow rate of liquefied nitrogen and liquefied oxygen in accordance with each product production amount. If the product withdrawal flow rates of liquefied nitrogen and liquefied oxygen do not match the production volume of the product, the operation of the entire air liquefaction / separation apparatus will be out of balance, and the product purity will deteriorate. The production volume of each product of liquefied nitrogen and liquefied oxygen is
It is like an internal parameter of an air liquefaction separator and cannot be directly measured.

[0004] In the prior art, the product withdrawal flow rates of liquefied nitrogen and liquefied oxygen during the operation rate change are manually determined by the experience of a skilled operator. The operator therefore requires a high degree of skill. In addition, the operating state of the air liquefaction / separation apparatus varies for each individual operator.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for predicting the operating state of an air liquefaction / separation apparatus, which can accurately predict the operation state when the operation rate of the air liquefaction / separation apparatus is changed. And equipment.

It is another object of the present invention to stably operate the air liquefaction / separation apparatus without changing the operation balance of the whole apparatus, without deteriorating the product purity of liquefied nitrogen and liquefied oxygen. It is an object of the present invention to provide a method and an apparatus for operating an air liquefaction / separation apparatus which can be operated while maintaining the same.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a rectification tower in which a lower high-pressure rectification tower and an upper low-pressure rectification tower are formed in a vertically extending cylindrical housing via a heat transfer member. Prepared, by a compression refrigerator using nitrogen as a refrigerant, nitrogen gas was extracted from the high-pressure rectification column and led to a heat exchanger for cooling the raw material air, and after cooling the raw material air, the nitrogen gas was compressed by a compressor. The condensed liquefied nitrogen is condensed by a cold heat source, and is injected into the high-pressure rectification tower to expand it.Then, the nitrogen gas from the high-pressure rectification tower is extracted to the heat exchanger for cooling the raw material air to form a closed loop for circulation, The raw material air cooled by the air-cooling heat exchanger is supplied to the lower part of the high-pressure rectification tower, and liquefied nitrogen liquefied at the upper part of the high-pressure rectification tower is taken out. To the low pressure rectification column,
Liquefied oxygen is taken out from the lower part of the low-pressure rectification tower, nitrogen gas is discharged from the upper part of the low-pressure rectification tower, and after a dead time corresponding to the cooling flow rate x of the liquefied nitrogen supplied to the high-pressure rectification tower by the compression refrigerator. The total production amount y of liquefied nitrogen and liquefied oxygen of
This is a method for predicting the operation status of the air liquefaction / separation apparatus, wherein the prediction is performed by a predetermined linear function using the cooling flow rate x as a variable.

According to the present invention, in the air liquefaction / separation apparatus, the raw air is cooled by a raw air cooling heat exchanger to which nitrogen, which is a refrigerant of a compression refrigerator, is introduced, and is supplied to a lower part of a high-pressure rectification column. , Where it is cooled and liquefied. In the lower part of the high-pressure rectification column, a liquid mainly containing oxygen, that is, an oxygen-rich liquid is stored, and this liquid is supplied to the low-pressure rectification column, where high-purity liquefied oxygen is produced as a product. It is manufactured and stored in the lower part of the low pressure rectification column. The liquefied oxygen stored in the lower part of the rectification column is taken out as a product.

In the high-pressure rectification tower, the nitrogen gas rises, and the nitrogen gas is cooled and liquefied at the upper part of the high-pressure rectification tower via a heat transfer member separating the high-pressure rectification tower and the low-pressure rectification tower. The liquefied liquefied nitrogen is taken out as a product. Further, argon is extracted from the low-pressure rectification column.

[0010] In the air liquefaction / separation apparatus provided with the rectification tower and the compression refrigerator described above, the present inventor changed the cooling flow rate x, which is the flow rate of liquefied nitrogen supplied to the high-pressure rectification tower by the compression refrigerator. Then, it has been found that the total production amount y of liquefied nitrogen and liquefied oxygen that can be extracted as a product after the dead time T can be predicted by a linear function having the cooling flow rate x as a variable. In the present specification, the “production amount” is a volume or a weight per unit time, for example, the unit is Nm ³ / h.

Therefore, when the cold flow rate x that has been changed and set at the present time is kept constant, the total production amount y (= yN + yO) of the product after the dead time T from the present time can be calculated and predicted. This allows the extraction flow rates of liquefied nitrogen and liquefied oxygen products to be selected equal to their respective production volumes and to be changed without breaking the overall balance of the air liquefaction / separation device, thereby increasing the product purity. Can be kept. In this manner, the flow rate of the product withdrawal can be automatically changed, and the operation rate can be changed in a short time and reliably while keeping the operation of the air liquefaction / separation device stable.

Further, the present invention is characterized in that a product of the total production amount y and a predetermined constant C is calculated to predict the production amount zN of liquefied nitrogen.

According to the present invention, the production amount of liquefied nitrogen zN
Is the product (zN) of the total production amount y and a predetermined constant C.
= Y · C).

The present invention also provides a method for producing a liquefied oxygen production amount zO by subtracting the liquefied nitrogen production amount zN from the total production amount y.
Is predicted.

According to the present invention, the production amount of liquefied oxygen zO
Can be predicted by subtracting the liquefied nitrogen production amount zN from the total production amount y (zO = y−zN).

According to another concept of the present invention, the production amount zN of liquefied nitrogen is set to zN = 2 · y / 3, or the production amount zO of liquefied oxygen is obtained by calculating from zO = y / 3. It is also possible.

According to yet another aspect of the present invention, instead of predicting the total production amount y in claim 1, the total production amount y
, The production amount zN of liquefied nitrogen can be directly predicted, and similarly, the production amount zO of liquefied oxygen can be directly predicted.

The present invention also provides (a) an air liquefaction / separation apparatus, in which (a1) a lower high-pressure rectification tower and an upper low-pressure rectification tower are provided via a heat transfer member in a vertically extending cylindrical housing. A rectification tower having a tower formed therein, and (a2) a compression chiller, which uses nitrogen as a refrigerant, extracts nitrogen gas from the high-pressure rectification tower, and supplies heat for cooling the raw material air. Nitrogen gas after cooling the raw material air by introducing it to an exchanger is compressed by a compressor, condensed by a cold heat source, and the condensed liquefied nitrogen is injected into a high-pressure rectification tower to expand, and nitrogen from the high-pressure rectification tower is expanded. A compression refrigerator that forms a closed loop for extracting and circulating the gas to the heat exchanger for cooling the raw material air, and (a3) supplying the raw material air cooled by the heat exchanger for cooling the raw material air to the lower part of the high-pressure rectification column. A liquid mainly containing oxygen from the pipe line and (a4) the lower part of the high-pressure rectification column An air liquefaction / separation device having a pipe that is taken out and supplied to the low-pressure rectification tower, (a5) a pipe that discharges nitrogen gas from the upper part of the low-pressure rectification tower, and (b) a condensate of a compression refrigerator. A cold flow rate control means for controlling a cold flow rate x at which liquefied nitrogen is supplied to the high-pressure rectification tower; and (c) a dead time corresponding to the cold flow rate x of liquefied nitrogen supplied to the high-pressure rectification tower by the compression refrigerator. The total production amount y of the liquefied nitrogen and liquefied oxygen is determined in advance by using the cooling flow rate x as a variable.
An apparatus for estimating the operating state of an air liquefaction / separation apparatus, comprising an estimating means for estimating by means of a next function.

According to the operating condition predicting apparatus, as described above, it is possible to automatically change the withdrawal flow rate of each product of liquefied nitrogen and liquefied oxygen. The operating rate can be changed in a short time and reliably while maintaining stability without breaking the balance.

The present invention also provides a rectification tower having a lower high-pressure rectification tower and an upper low-pressure rectification tower formed in a vertically extending tubular housing via a heat transfer member, The nitrogen gas is extracted from the high-pressure rectification column by a compression refrigerator using nitrogen as the gas, and then guided to a heat exchanger for cooling the raw material air, and after cooling the raw material air, the nitrogen gas is compressed by the compressor and condensed by a cold heat source. Then, the condensed liquefied nitrogen is injected into the high-pressure rectification tower to expand, forming a closed loop for extracting and circulating the nitrogen gas from the high-pressure rectification tower to the heat exchanger for cooling the raw material air,
The raw material air cooled by the raw material air cooling heat exchanger is supplied to the lower part of the high-pressure rectification tower, and liquefied nitrogen liquefied at the upper part of the high-pressure rectification tower is taken out, and mainly contains oxygen from the lower part of the high-pressure rectification tower The liquid is supplied to the low-pressure rectification column, liquefied oxygen is taken out from the lower portion of the low-pressure rectification column, nitrogen gas is discharged from the upper portion of the low-pressure rectification column, and the total rated production amount yR of liquefied nitrogen and liquefied oxygen is determined. A target value ηt of the operation rate η, which is the ratio y / yR of the actual total production amount y, is set, and the total production amount y1 at the start of the change of the operation rate η and the target total production amount yt corresponding to the target operation rate ηt And the total production amount y for each predetermined control cycle W is obtained, and the cooling flow rate x of the liquefied nitrogen supplied to the high-pressure rectification column by the compression refrigerator corresponding to the total production quantity y for each control cycle W Is a linear function determined in advance with the total production amount y. Therefore, the air liquefaction and separation apparatus is characterized in that the raw air flow rate Qa is set, and the total production amount y obtained for each control cycle W is extracted after the elapse of the dead time T from each control cycle W. It is a driving method.

According to the present invention, the target operating rate ηt, which is the target value of the operating rate η, is set, and the target operating rate ηt and the target operating rate ηt are set every predetermined control cycle W from the start of the change of the current operating rate η1. Is calculated and obtained. A cold flow rate x corresponding to the total production amount y obtained for each control cycle W is calculated and calculated according to a predetermined linear function of the cold flow rate x and the total production amount y. Further, the total production amount y, that is, the raw material air flow rate Qa corresponding to the cold flow rate x is calculated and set. After a lapse of the dead time T from each start point in each control cycle W, the total production amount y predicted and obtained is extracted. As a result, the current operation rate η1 is maintained without breaking the overall balance of the air liquefaction / separation apparatus.
Automatically changes to the target operation rate ηt in a short time and reliably.

Further, the present invention is characterized in that a product of the total production amount y and a predetermined constant C is calculated to extract a production amount zN of liquefied nitrogen.

The present invention also provides a method for producing a liquefied oxygen production amount zO by subtracting the production amount of liquefied nitrogen zN from the total production amount y.
It is characterized by extracting

According to the present invention, it is possible to automatically calculate and obtain the extraction flow rate corresponding to the production amounts zN and zO of liquefied nitrogen and liquefied oxygen. This makes it possible to automate the change of the operation rate as described above.

The present invention also provides (a) an air liquefaction / separation apparatus, wherein (a1) a lower high-pressure rectification tower and an upper low-pressure rectification tower via a heat transfer member in a vertically extending cylindrical housing. A rectification tower having a tower formed therein, and (a2) a compression chiller, which uses nitrogen as a refrigerant, extracts nitrogen gas from the high-pressure rectification tower, and supplies heat for cooling the raw material air. Nitrogen gas after cooling the raw material air by introducing it to an exchanger is compressed by a compressor, condensed by a cold heat source, and the condensed liquefied nitrogen is injected into a high-pressure rectification tower to expand, and nitrogen from the high-pressure rectification tower is expanded. A compression refrigerator that forms a closed loop for extracting and circulating the gas to the heat exchanger for cooling the raw material air, and (a3) supplying the raw material air cooled by the heat exchanger for cooling the raw material air to the lower part of the high-pressure rectification column. A liquid mainly containing oxygen from the pipe line and (a4) the lower part of the high-pressure rectification column (A5) an air liquefaction / separation device having a pipe for discharging nitrogen gas from the upper part of the low-pressure rectification tower, and (b) a pipe for discharging nitrogen gas from the upper part of the low-pressure rectification tower. A flow control valve for extracting liquefied liquefied nitrogen as a product; (c) a flow control valve for extracting liquefied oxygen liquefied at the lower part of the low-pressure rectification column as a product; and (d) a condensed liquefied nitrogen of a compression refrigerator having a high pressure. A cold flow control means for controlling a cold flow x supplied to the rectification column, (e) a raw air flow control means for controlling a raw air flow Qa supplied to the raw air cooling heat exchanger, and (f) control Means for setting a target value ηt of an operation rate η, which is a ratio y / yR of an actual total production amount y to a total rated production amount yR of liquefied nitrogen and liquefied oxygen, at the time of starting the change of the operation rate η Corresponding to the total production amount y1 and the target operation rate η Standard total production amount y
t, the total amount of production y per control cycle W determined in advance, and the cooling flow rate of liquefied nitrogen supplied to the high-pressure rectification column by the compression refrigerator corresponding to the total production amount y per control cycle W x is set by a predetermined linear function with the total production amount y, and the raw material air flow rate Qa is set. After a dead time T from each control cycle W, the liquefied nitrogen flow control valve and the liquefied oxygen flow rate are set. An operation device for an air liquefaction / separation device, comprising: a control means for controlling an opening degree with a control valve to extract the total production amount y obtained for each control cycle W.

According to the present invention, the cold flow rate control means controls the cold flow rate x, and the raw material air flow rate control means controls the raw material air flow rate Qa, thereby controlling the current operating rate η1 to the target operating rate ηt. Control cycle W
The cooling flow rate x and the raw material air flow rate Qa are changed every time, and after a lapse of dead time from the start of each control cycle W, liquefied nitrogen is taken out from the liquefied nitrogen flow control valve, and liquefied oxygen is taken out from the liquefied oxygen flow control valve. Take out.

Further, in the present invention, the cold heat source includes a liquefied natural gas heat exchanger for condensing nitrogen gas compressed by compressed air with liquefied natural gas, and the control means includes a liquefied natural gas heat exchanger. A flow rate control valve for temperature control for controlling the flow rate of liquefied natural gas to be supplied, a flow rate control valve for discharge pressure control interposed between the inlet and the outlet of the compressor to control the discharge pressure of nitrogen gas, and a cold flow rate and a valve opening control means for controlling the opening of the temperature control flow control valve and the discharge pressure control flow control valve corresponding to x.

Further, according to the present invention, the valve opening control means includes a temperature detecting means for detecting a temperature of liquefied nitrogen on the outlet side of the liquefied natural gas heat exchanger, and a temperature detecting means responsive to an output of the temperature detecting means. Means for controlling the opening of the temperature control flow control valve so that the detected temperature becomes a value corresponding to the cooling flow rate x.

According to the present invention, the cold heat source of the compression refrigerator has a liquefied natural gas heat exchanger using liquefied natural gas, and the nitrogen gas compressed by the compressor is condensed.

In order to change and set the cooling flow rate x, the temperature of the liquefied nitrogen condensed in the liquefied natural gas heat exchanger is changed, and the discharge pressure of the nitrogen gas at the outlet of the compressor is changed. In order to control the temperature of liquefied nitrogen condensed in the liquefied natural gas heat exchanger, the flow rate of liquefied natural gas supplied to the liquefied natural gas heat exchanger is controlled by the opening of a temperature control flow control valve. . Regarding the opening degree of the temperature control flow control valve, the temperature of the liquefied nitrogen on the outlet side of the liquefied natural gas heat exchanger is detected by the temperature detecting means, and the temperature of the liquefied nitrogen detected by the temperature detecting means is the cold flow rate. x
, The opening of the temperature control flow control valve, that is, the flow rate of the liquefied natural gas is controlled.

In order to control the discharge pressure of the compressor,
A bypass pipe is connected between the inlet and the outlet of the compressor, and a discharge pressure control flow control valve is interposed in the bypass pipe.

[0032]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention. In the air liquefaction / separation apparatus 1, as shown in a simplified form in FIG. 2, raw air is supplied from a pipe line 2, whereby liquefied nitrogen as a product is stored in a tank 3. Oxygen is obtained in tank 4 and liquefied argon is obtained in tank 5. For the liquefaction and separation of the feed air, a line 40
Liquefied natural gas (abbreviated as LNG) at a pressure of 50 k
g / cm ² , supplied at −150 ° C., and the cold heat is used. In the air liquefaction / separation apparatus 1, cold of circulating nitrogen used as a refrigerant is used.

The air liquefaction / separation apparatus 1 basically includes a rectification column 6 and a compression refrigerator 7. The raw material air is supplied to the compressor 9 from the pipe 2 via the flow control valve 8 by, for example, 5 kg / cm ^2.
And the code box 11
Is supplied to the rectification tower 6 from the pipe 13 via the air-cooling heat exchanger 12. The removal device 10 removes CO and H ₂ contained in the raw material air.

The rectification tower 6 is connected to a lower high-pressure rectification tower 15 and an upper low-pressure rectification tower via a heat transfer member 41 made of a stainless steel plate or the like in a cylindrical housing 14 having a substantially cylindrical shape extending vertically. A tower 16 is formed and configured.

FIG. 3 is an enlarged sectional view of the rectification column 6. Referring also to FIG. 1, the raw material air from line 13 is supplied to a lower part of high-pressure rectification column 15. A plurality of baffle plates 17 are provided in the high-pressure rectification tower 15 at intervals up and down, and a gas passage bent zigzag up and down is formed. The liquefied nitrogen from the line 18 of the compression refrigerator 7 is injected into the high-pressure rectification tower 15 from the nozzle 19 at the upper part of the high-pressure rectification tower 15 and is adiabatically expanded.

A liquid containing mainly oxygen is stored in a storage section 20 below a position where the high-pressure rectification tower 15 is connected to the pipe 13. The gas mainly containing nitrogen is supplied to the high-pressure rectification column 1
5, is cooled and liquefied by the heat transfer member 41, and the liquefied nitrogen is stored in the storage unit 21. The liquefied nitrogen in the storage unit 21 is supplied to the pipeline 2 as a product.
Take out from 2. This liquefied nitrogen is stored in the above-mentioned tank 3 via the liquefied nitrogen flow control valve 23. The inside of the high-pressure rectification column 15 is, for example, 5 kg / cm ² , and the inside of the low-pressure rectification column 16 is, for example, 0.5 kg / cm ² . The liquid stored in the storage section 20 below the high-pressure rectification column 15 contains, for example, about 50% oxygen and has a temperature of about -170 ° C.

In the upper part of the high-pressure rectification column 15, below the liquefied nitrogen storage part 21, there is connected a conduit 24 for taking out and circulating nitrogen gas as a refrigerant of the compression refrigerator 7.

A pipe 25 is connected to the lower part of the high-pressure rectification tower 15, and the oxygen-rich liquid stored in the storage part 20 is supplied to the upper part of the low-pressure rectification tower 16. A plurality of baffles 26 are provided in the low-pressure rectification column 16 at intervals above and below. The liquid mainly containing oxygen from the pipe 25 flows through the low-pressure rectification column 16 through a zigzag path up and down by the action of the baffle plate 26, and is stored by the heat transfer member 41 below the low-pressure rectification column 16. The part is stored as indicated by reference numeral 27. The liquid level LO of the liquefied oxygen in the storage unit 27 is detected by the liquid level sensor 28, and the production amount of the liquefied oxygen, which is the operation status of the air liquefaction / separation apparatus 1, can be known. Near the middle position of the low pressure rectification column 16, a pipe line 29 is connected, and liquefied argon Ar is taken out.

From a substantially intermediate position of the high-pressure rectification column 15,
The gas is led to the upper part of the low-pressure rectification column 16 via the line 30 and the flow control valve 31. From the top of the low-pressure rectification column 16, nitrogen gas is discharged through a pipe 32, and the flow control valve 3
3 through the heat exchanger 12 for cooling the raw material gas,
And a part of the nitrogen gas is returned from the flow control valve 35 to the pipe 2 on the inlet side of the raw air compressor 9 via the pipe 36.

The liquefied oxygen stored in the storage part 27 at the lower part of the low-pressure rectification tower 16 is guided from the pipe 37 through the pump 38 to the tank 4 from the flow control valve 39 and stored therein.

The city gas from the pipe 41a is led to a hydrogen producing device 42 to produce hydrogen, stored in a hydrogen holder 43, and mixed into the liquefied Ar pipe 29 from a pipe 44. A mixture of Ar from the line 29 and hydrogen gas from the line 44 is supplied to the argon purifier 45 via the line 46, and oxygen contained in the gas in the line 46 is supplied to the argon purifier 45.
Removed by combustion of hydrogen from 4. Argon purifier 45
The liquefied argon from is introduced into the tank 5 from the pipe line 47 and stored therein.

In the compression refrigerator 7, nitrogen is used as a refrigerant, and the nitrogen gas extracted from the high-pressure rectification tower 15 via the pipe 24 is led to the heat exchanger 12 for cooling the raw material air to convert the raw material air. After cooling, it is led to a nitrogen cooler 50 via a pipe 49. The nitrogen gas from the nitrogen cooler 50 is
It is compressed by the low-pressure compressor 51, cooled again by the nitrogen cooler 50 via the pipe 52, and then further compressed by the high-pressure compressor 53. The nitrogen gas of, for example, 60 kg / cm ² from the high-pressure compressor 53 is led from a pipe 54 to a liquefied natural gas heat exchanger 55 to be cooled and condensed.
Liquefied nitrogen from the liquefied natural gas heat exchanger 55 is supplied to a line 56.
Is supplied to the flash bottle 57 and adiabatically expanded to liquefy the nitrogen gas. Partially unliquefied gas is removed, for example, to 25 kg / cm ² . As described above, the liquefied nitrogen from the flash bottle 57 is injected from the nozzle 19 into the high-pressure rectification tower 15 through the pipe 18 and adiabatically expanded to evaporate. Thus, the nitrogen as a refrigerant circulates in the compression refrigerator 7. Is done.

In the compression refrigerator 7, the low pressure compressor 51
Then, a bypass line 66 is connected between the inlet and the outlet. A flow control valve 67 is interposed in the bypass line 66. Between the inlet and the outlet of the high-pressure compressor 53,
The bypass line 68 is connected. This bypass line 68
, A flow control valve 69 is interposed. By controlling the degree of opening of these flow control valves 69 and 67, the pressure P1 of the nitrogen gas in the pipeline 54 can be controlled.

Nitrogen cooler 50 and liquefied natural gas heat exchanger 5
The refrigerant 5 is circulated between the refrigerant 5 and the refrigerant 5 through a pipe 60 by a fluorocarbon pump 59. Thereby, the nitrogen gas guided to each of the compressors 51 and 53 is cooled by the cold heat of the liquefied natural gas.

The liquefied natural gas from the line 40 is led to the liquefied natural gas heat exchanger 55 via the flow control valve 61. Thus, the nitrogen gas in the conduit 54 is condensed as described above, and the Freon circulated by the Freon pump 59 is condensed.

The vaporized liquefied natural gas from the liquefied natural gas heat exchanger 55 via a pipe 62 is supplied to a natural gas heater 63.
Then, it is heated by the circulating cooling water flowing through the pipe 64. The natural gas from the heater 63 is guided as city gas from the pipe 65 at, for example, 30 kg / cm ² .

FIG. 4 is a block diagram showing an electrical configuration of the embodiment of the present invention shown in FIGS. The operation rate η of the air liquefaction / separation apparatus 1 is input from input means 72 including a keyboard and the like input by an operator, and is provided to a processing circuit 73 implemented by a microcomputer or the like. The output of the liquid level sensor 28 for detecting the liquid level in the liquefied oxygen storage section 27 is also supplied to the processing circuit 73, whereby the dead time T can be measured. Further, a pressure gauge 74 is provided in the conduit 54. A thermometer 75 is provided in the conduit 56.
Further, the temperature of the chlorofluorocarbon removed from the liquefied natural gas heat exchanger 55 via the line 60 is detected by a thermometer 76.

The flow meter 7 is connected to the line 18 of the compression refrigerator 7.
7 are interposed. The flow meter 77 measures the flow rate of the liquid nitrogen flowing through the pipe 18 and thus the cold flow rate x. The change in the cold flow rate x can be performed by changing the pressure P1 in the pipe 54 and the temperature TE in the pipe 56 as described above. The processing circuit 73 controls the opening degree of the raw air flow control valve 8 and the opening degree of the flow control valve 23 which controls the flow rate of liquefied nitrogen as a product in order to change and adjust the flow rate Qa of the raw air. , And the opening of a flow control valve 39 for setting and controlling the flow rate of liquefied oxygen as a product. Further, in order to change the pressure P1 of the nitrogen gas in the pipe 54, the opening degrees of the bypass valves 67 and 69 are controlled. Further, in order to control the temperature of the liquefied nitrogen in the line 56, the processing circuit 73 controls the opening degree of the flow control valve 61 interposed in the line 40 to control the flow rate of the liquefied natural gas.

FIG. 5 is a diagram showing a pipeline 18 in the compression refrigerator 7.
FIG. 3 is a diagram showing a relationship between a cooling flow rate x, which is a flow rate of liquefied nitrogen, and a flow rate Qa of raw air to be supplied from the pipeline 2 to the raw air compressor 9. As the cold flow rate x is increased, the feed air flow rate is increased. As a result, the entire air liquefaction / separation apparatus 1 is balanced, and stable operation can be maintained.

FIG. 6 shows a cooling flow rate x, which is a flow rate of liquefied nitrogen injected into the high-pressure rectification tower 15 via the pipe 18 of the compression refrigerator 7, and a compressor for achieving the cooling flow rate x. 5
3 is a graph showing the relationship with the nitrogen gas pressure P1 in the outlet line 54 of FIG. In order to increase the cold flow x,
The pressure of the nitrogen gas in the pipe 54 is increased.

FIG. 7 is a graph showing the relationship between the cooling flow rate x in the compression refrigerator 7 and the temperature TE of the liquefied nitrogen in the pipeline 56 for achieving the cooling flow rate x. To increase the cooling flow rate x, the temperature TE of the liquefied nitrogen in the line 56 is decreased. To change the cooling flow rate x, as shown in FIG. 6, the pressure P1 of the nitrogen gas supplied from the high-pressure compressor 53 to the pipe 54 and the liquefied natural gas heat exchanger 55 to the pipe 56 as shown in FIG. It is necessary to change the temperature TE of the introduced liquefied nitrogen.

In the air liquefaction / separation apparatus 1 described with reference to FIGS. 1 to 7, according to the present inventor, as shown in FIG. The total production amount y (= yN + yO) of the liquefied oxygen withdrawal flow rate yO through the flow control valve 39 is predicted based on a predetermined linear function y = Ax + B (2) using the cooling flow rate x as a variable. I found that I could do it.

As is clear from FIG. 8, the parameters A and B of the linear function represented by the above equation 2 are 2
From the cold flow rates K1 and K2 collected at or above the point and the corresponding total production amounts ON1 and ON2, it can be obtained based on a two-way simultaneous equation.

The total production amount y corresponding to the cooling flow rate x is obtained after the dead time T. The dead time T is defined as a change in the cooling flow rate x in a state where the operation of the air liquefaction / separation apparatus 1 is in a stable state and in which the extraction flow rates of the products liquefied nitrogen and liquefied oxygen are kept constant. , The raw material air flow rate Qa corresponding to the cold flow rate x
Is the time until the stored amount of liquefied oxygen stored in the storage section 27 below the low-pressure rectification column 16 changes. The storage amount of liquefied oxygen stored in the storage unit 27, that is, the liquid level, can be detected by the liquid level sensor 28 as described above. In this way, as shown in FIG. 9A, the cooling flow rate x is greatly changed at time t11, for example, and the flow rate Qa of the raw air is changed. The stored amount of liquefied oxygen stored in the tank 27 is equal to the time t11 by the dead time T.
It changes so as to become larger at time t12 after elapse.

FIG. 10 shows a line 1 in the compression refrigerator 7.
8 which is the amount of change in the flow rate of liquid nitrogen flowing through
6 is a graph showing a relationship between x and a dead time T. As the cooling change amount Δx increases, the dead time T changes so as to increase according to a predetermined linear function.

FIG. 11 is a flowchart for explaining the basis of the operation of the present invention. In step r1 of FIG. 11, when it is necessary to change the operation rate η from the initial value η1 to the target operation rate ηt while maintaining the operation of the air liquefaction and separation apparatus 1 in a stable state, the operation proceeds to the next step r2. As shown in the figure, during the change of the operation rate from the current operation rate η1 to the target operation rate ηt, the product withdrawal flow rate of the products of liquefied nitrogen and liquefied oxygen by the flow rate control valves 23 and 39 is optimal for maintaining the stable state. It is necessary to set the product production amounts yN and yO, which are appropriate values. For this purpose, as shown in step r3, during the change of the operation rate η, the product production amount yN, yO per unit time
It is necessary to extract liquefied nitrogen and liquefied oxygen at each flow rate equal to the predicted values yN and yO. For this purpose, as shown in step r4, based on the cold flow rate x, the respective production amounts y of the products of liquefied nitrogen and liquefied oxygen at the time when the dead time T has elapsed after the setting of the cold flow rate x
N, yO must be predicted. In the present invention, the product production amounts yN and yO at the time when the dead time T has elapsed from the setting of the cooling flow rate x are predicted from the linear function as described with reference to FIG.

FIG. 12 is a flowchart for explaining the overall operation of the embodiment of the present invention shown in FIGS. When changing the operation rate η from the current operation rate η1 to the target operation rate ηt, for example, by increasing the amount, the cooling flow rate x is increased in step s1 for each predetermined control cycle W, and as shown in FIG. As described above, the raw material air flow rate Qa is increased stepwise in accordance with the cold flow rate x. After the dead time T shown in step s2, the product production amount yN of liquefied nitrogen and the product production amount yO of liquefied oxygen obtained in the rectification column 6 increase.
Accordingly, in step s4, the product production amount yN,
so that the same flow rate as yO is extracted to tanks 3 and 4
The degree of opening of the flow control valves 23 and 39 is increased.

To estimate the product production amounts yN and yO after the lapse of the dead time T after setting the cooling flow rate x and the raw material air flow rate Qa in step s1 described above, FIG.
The following operations are sequentially performed as indicated by reference numeral 78 in FIG. First, the cold flow rate x changed at the current time
Is measured by the flow meter 77. Next, the total production amount y after the dead time T is predicted from the linear function of Expression 2 as described with reference to FIG. 8 described above, using the cooling flow rate x measured by the flow meter 77.

Of the total production amount y, the production amount yN of liquefied nitrogen can be predicted based on Equation 3, where C is a predetermined constant.

YN = y · C (3) Further, of the total production amount y, the production amount of liquefied oxygen can be predicted based on Equation 4.

YO = y−yN (4) In another embodiment of the present invention, instead of predicting the above-mentioned total production amount y, using the cooling flow rate x, the above-described formulas 2, 3,
From 4, the production amounts yN and yO of liquefied nitrogen and liquefied oxygen may be directly obtained and predicted.

The cooling flow rate x in step s1 in FIG.
The increase in the raw material air flow rate Qa is based on each production cycle W calculated by calculating the current total production amount y1 and the target production amount yt, which are the input data of the input means 72 described above with reference to FIG.
Although the processing circuit 73 may automatically calculate and obtain the values x and Qa based on the total production amount y for each case, the operator may set the values x and Qa. Also, for setting the product withdrawal amount in step s4, the flow control valve 23,
Although the operation of adjusting the opening degree of the opening 39 may be automatically performed by the processing circuit 73, the operator may adjust and set the opening degree.

FIG. 13 is a graph for explaining the operation of the embodiment of the present invention. Refer to the cold flow rate x 81
As shown by, the flow rate changes stepwise at every predetermined control cycle W, and the raw air flow rate Qa also changes accordingly. The control cycle W may be, for example, three minutes.
In response to such an increase in the cold flow rate x and the raw material air flow rate Qa, the total production amount y in the rectification tower 6 continuously increases with time as indicated by reference numeral 82 in FIG. go. This total production amount y is delayed by a dead time T from the point of change of the cold flow rate x and the raw material air flow rate Qa.
The dead time T may be, for example, 9 minutes. This total production amount y can be predicted as described in connection with FIG. 8 described above. Therefore, corresponding to this total production amount y, each flow control valve 23, 3 for each of liquefied nitrogen and liquefied oxygen.
9, the dead time T for each control cycle W of the cooling flow rate x.
Just delay, set and control, extract the product. The control period W may be selected to be equal to or less than the dead time T (W ≦ T), and the control period W may be selected to be a natural number of the dead time T. However, in another embodiment of the present invention, W> T You may choose. By setting the control cycle W to a relatively short time, the total extraction flow rate F can be set to a continuous value that is approximately similar to the total production amount y.

FIG. 14 explains the operation of the processing circuit 73 shown in FIG. 4 for performing the automatic operation by increasing or decreasing the operation rate η of the air liquefaction / separation apparatus 1 shown in FIG. It is a flowchart for the. In step u1, the operator inputs data on whether the operating rate η is to be increased or decreased by the input means 72, inputs the target operating rate ηt, and further inputs the control cycle W and the dead time T. At the same time, the parameters A and B of the linear function in Equation 2 for predicting the total production amount y using the cooling flow rate x as a variable are input. Such parameters A and B are set in advance by experiments on the air liquefaction / separation apparatus 1.

The processing circuit 73 determines in step u2
The following calculation is performed as preprocessing for changing the operation rate.
(1) The cooling flow rate x of the liquefied nitrogen in the pipe line 18 for each control cycle W is determined by comparing the operating rate η1 and the target operating rate η at the current time t1.
Based on the total production amounts y1 and yt respectively corresponding to t and the cooling amount x for each of the plurality of control cycles W, assuming that the total production amount y is changed by a linear function, for example, 1 Calculated based on the following function, the nitrogen gas pressure P1 in the pipe 54 and the liquefied nitrogen temperature TE in the pipe 56 corresponding to the thus obtained cooling flow rate x for each control cycle W, (2) for each control cycle W 5 corresponding to the cold flow rate x of (1), (3) a flow rate Q1 of refluxing nitrogen from the high-pressure rectification tower 15 to the low-pressure rectification tower 16 via the pipe line 30, and (4) ) Temperature T1 to be detected by thermometer 76 for circulating Freon by pump 59
Is calculated. Further, the constant C in Equation 3 described above is calculated and obtained from experimental data. This constant C may be input from the input means 72 by the operator in step u1.

In step u3, if the control cycle W has elapsed from the initial time t1 at which the change in the operation rate η should be performed or from the start times t2, t3,... Of the change in the operation rate, the flow proceeds to the next step u4. . FIG. 13 for each control cycle W
Are performed at the times t1, t2, t3, t4, t5,... Shown in FIG. (1) Pressure gauge 74
The opening degree of the flow control valve 69 interposed in the bypass line 68 of the high-pressure compressor 53 is adjusted and controlled so that the pressure detected by the step S2 coincides with the discharge pressure P1 obtained in step u2. The opening degree of the flow control valve 67 interposed in the bypass line 66 of the compressor 51 is adjusted and controlled. (2) The temperature of the liquefied nitrogen detected by the thermometer 75 is equal to the value TE determined in the aforementioned step u2.
The opening of the liquefied natural gas flow control valve 61 interposed in the pipeline 40 is controlled so that (3) The opening of the flow control valve 8 is controlled so that the raw material air flow Qa is achieved. (4) The opening of the flow control valve 31 is set so that the reflux flow rate of the nitrogen gas becomes the value set in step u2.
(5) The temperature of Freon detected by the thermometer 76 is
The rotation speed of the motor 59 and the like are controlled so as to reach the temperature calculated and determined in step u2.

The opening of the flow control valve 31 is changed at the timing of the dead time T in step u6 described later when the operating rate η is reduced. The temperature of the liquefied nitrogen detected by the thermometer 75 is changed only once after the start of the program, that is, at the time t1 in FIG. 13, and thereafter, the opening of the flow control valve 61 is maintained.

Further, at the present time, that is, at time t1 in FIG.
.., And the liquefied nitrogen production amount yN and the liquefied oxygen production amount yO after the dead time T are calculated and predicted. This prediction is calculated based on the above 3 and 4.

In step u5, it is determined whether or not the dead time T has elapsed. If so, the flow advances to the next step u6. In this step u6, the aforementioned step u
The opening degrees of the flow control valves 23 and 39 are changed so that the extraction flow rates are equal to the liquefied nitrogen production amount yN and the liquefied oxygen production amount yO calculated and predicted in 4, respectively.
For example, in FIG. 13 described above, the cold flow rate x and the raw material air flow rate Qa are changed stepwise at time t1, and the state is maintained from time t1 to t2, and the cold flow rate x and the raw material air flow rate Qa are changed at time t2. The respective values are maintained between times t2 and t3, and similar operations are sequentially performed for each control cycle W. The opening of the flow control valves 23 and 39 is performed at time t21 when the dead time T has elapsed from time t1, and the flow control valves 23 and 3 at this time t21.
The opening degree 9 is a value that matches the liquefied nitrogen production amount yN and the liquefied oxygen production amount yO calculated using the cooling flow rate x set at the time t1 by the above-described equations 2 to 4.
Similarly, at time t22 when dead time T has elapsed from time t2
Then, based on the cold flow rate x set by changing the opening degrees of the flow control valves 23 and 39 at the time t2, the above-described equation (2) is used.
This is a value obtained by calculation using. At time t21,
t22, t23,... correspond to times t4, t
5, t6,..., But not necessarily.

When it is determined in step u7 that the operating rate η has reached the target operating rate ηt, step u8 is performed.
Ends a series of operations.

[0071]

According to the present invention of claim 1, a rectification column,
The total production amount y of liquefied nitrogen and liquefied oxygen by an air liquefaction / separation apparatus including a compression refrigerator using nitrogen as a refrigerant for cooling the raw material air supplied to the rectification column is represented by a cooling flow rate x and a linear function. Therefore, by changing the cooling flow rate x, it becomes possible to predict the total production amount y after a lapse of dead time from the time point of the change.

Further, by setting the total production amount y, the cold flow rate x corresponding to the total production amount y can be calculated and obtained.

As described above, since the total production amount y can be predicted, it is possible to automatically change the extraction flow rates of liquefied nitrogen and liquefied oxygen. In this way, the operation rate can be changed in a short time and reliably without breaking the balance of the operation while maintaining the stability of the operation of the entire air liquefaction / separation apparatus. Thus, the product purity of liquefied nitrogen and liquefied oxygen can be kept high.

According to the second aspect of the present invention, it is possible to automatically predict the production amount zN of liquefied nitrogen from the predicted total production amount y.

According to the third aspect of the present invention, the production amount zO of liquefied oxygen can be automatically predicted from the total production amount y obtained by the prediction.

According to the fourth aspect of the present invention, the total production amount y of liquefied nitrogen and liquefied oxygen at the time point when the dead time T elapses after the cooling flow rate x is changed as described above is equal to the cooling flow rate x and 1 Due to the relationship of the following function, the total production amount y
Can be realized automatically.

According to the fifth aspect of the present invention, the cold flow rate x and the raw material air flow rate Qa are set and changed stepwise from the current operating rate η1 to the target operating rate ηt for each control cycle W. Liquefied nitrogen and liquefied oxygen, which are products, can be extracted while maintaining stability without breaking the overall balance of the air liquefaction / separation unit, and thus the operation rate can be reliably changed in a short time, resulting in deterioration of product purity. Never.

According to the sixth and seventh aspects of the present invention, as described above, the liquefied nitrogen and the liquefied oxygen can be automatically extracted at flow rates respectively corresponding to the production amounts zN and zO.

According to the eighth aspect of the present invention, it has been discovered that the cooling flow rate x and the total production amount y in the air liquefaction / separation apparatus have a linear function relationship, and the operation rate η
With the lapse of time during a predetermined change period of the operation rate η within a range from the current initial value η1 to the target value ηt,
For example, assuming that the amount changes linearly, a total production amount y corresponding to the operating rate η for each predetermined control cycle W during the change period is set, and corresponding to the total production amount y for each control cycle W, The cooling flow rate x and the raw material air flow rate Qa are changed stepwise in each control cycle W. When a dead time T has elapsed from the start of each control cycle W, the total production amount y is extracted. As a result, the operation rate η can be maintained while maintaining stable operation without breaking the overall balance of the air liquefaction / separation apparatus.
Can be reliably changed in a short time from η1 to ηt.

According to the ninth aspect of the present invention, the cold heat source of the compression refrigerator has a liquefied natural gas heat exchanger acting as a condenser for condensing circulating nitrogen. The flow rate of liquefied natural gas is controlled by a temperature control flow control valve to control the temperature of liquefied nitrogen supplied from the liquefied natural gas heat exchanger, thereby utilizing the cold heat of liquefied natural gas to liquefy air. Separation can be performed, and the discharge pressure of nitrogen gas supplied from the compressor to the liquefied natural gas heat exchanger is controlled. Thus, the cooling flow rate x can be changed and set.

According to the tenth aspect of the present invention, the temperature of the liquefied nitrogen at the outlet of the liquefied natural gas heat exchanger is supplied to the liquefied natural gas heat exchanger such that the temperature corresponds to the cooling flow rate x. Control the flow rate of liquefied natural gas. Thus, the temperature of the liquefied nitrogen injected into the low-pressure rectification column can be easily controlled and adjusted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a simplified block diagram showing the operation of the air liquefaction / separation apparatus 1 shown in FIG.

FIG. 3 is an enlarged sectional view of the rectification column 6.

FIG. 4 is a block diagram showing an electrical configuration of the embodiment of the present invention shown in FIGS. 1 to 3;

FIG. 5 is a cooling flow rate x which is a flow rate of liquefied nitrogen in a pipe 18 in the compression refrigerator 7 and a flow rate Qa of raw air to be supplied from the pipe 2 to the raw air compressor 9 in correspondence thereto.
FIG.

FIG. 6 is a cooling flow rate x, which is a flow rate of liquefied nitrogen injected into the high-pressure rectification column 15 via a line 18 of the compression refrigerator 7;
It is a figure which shows the relationship with the pressure P1 of the nitrogen gas in the pipe line 54 of the outlet side of the compressor 53 for achieving the cold flow rate x.

FIG. 7 is a diagram showing a relationship between a cold flow rate x in the compression refrigerator 7 and a temperature TE of liquefied nitrogen in a pipeline 56 for achieving the cold flow rate x.

FIG. 8 is a graph showing a relationship between a cooling flow rate x and a total production amount y of liquefied nitrogen and liquefied oxygen obtained as a product.

FIG. 9 is a diagram for explaining a dead time T of the air liquefaction / separation apparatus 1.

FIG. 10 is a graph showing a relationship between a cooling change amount Δx which is a change amount of a cold flow rate x of liquefied nitrogen in a pipe line 18 in the compression refrigerator 7 and a dead time T.

FIG. 11 is a flowchart for explaining the basis of the operation of the present invention.

FIG. 12 is a flowchart for explaining the overall operation of the embodiment of the present invention shown in FIGS. 1 to 10;

FIG. 13 is a graph for explaining the operation of the embodiment of the present invention.

14 is a flowchart for explaining the operation of the processing circuit 73 shown in FIG. 4 for increasing or decreasing the operation rate of the air liquefaction / separation apparatus 1 shown in FIG. 1 and performing automatic operation. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air liquefaction separation apparatus 3, 4, 5 Tank 6 Rectification tower 7 Compression refrigerator 8 Flow control valve 9 Compressor 12 Heat exchanger for raw material air cooling 14 Cylindrical housing 15 High pressure rectification tower 16 Low pressure rectification tower 19 Nozzle 20 Storage part of liquid mainly containing oxygen 21 Liquid nitrogen storage part 23 Liquid nitrogen flow control valve 27 Liquid oxygen storage part 28 Level sensor 33, 35, 39, 61, 67, 69 Flow control valve 41 Heat transfer member 51 Low pressure compressor 53 High pressure compressor 55 Liquefied natural gas heat exchanger 59 Freon pump 66, 68 Bypass line 72 Input means 73 Processing circuit 74 Pressure gauge 75, 76 Thermometer 77 Flow meter

Claims (10)

[Claims] 1. A rectification tower having a lower high-pressure rectification tower and an upper low-pressure rectification tower formed in a vertically extending cylindrical housing via a heat transfer member is provided, and nitrogen is used as a refrigerant. Nitrogen gas is extracted from the high-pressure rectification tower by the compression refrigerator used and guided to a heat exchanger for cooling the raw material air.Then, after cooling the raw material air, the nitrogen gas is compressed by a compressor, condensed by a cold heat source, and condensed. The liquefied nitrogen is injected into the high-pressure rectification tower and expanded, forming a closed loop that circulates the nitrogen gas from the high-pressure rectification tower by extracting it to the heat exchanger for cooling the raw material air, and cooling it with the heat exchanger for cooling the raw material air The supplied raw material air is supplied to the lower part of the high-pressure rectification tower, the liquefied nitrogen liquefied at the upper part of the high-pressure rectification tower is taken out, and the liquid containing mainly oxygen is supplied to the low-pressure rectification tower from the lower part of the high-pressure rectification tower And removes liquefied oxygen from the lower part of the low pressure rectification column. The nitrogen gas is discharged from the upper part of the pressure rectification column, and the total production amount y of liquefied nitrogen and liquefied oxygen after a dead time corresponding to the cooling flow rate x of the liquefied nitrogen supplied to the high pressure rectification column by the compression refrigerator Is predicted by a predetermined linear function using the cooling flow rate x as a variable. 2. The operation of the air liquefaction / separation apparatus according to claim 1, wherein a product of the total production amount y and a predetermined constant C is calculated to predict the production amount zN of liquefied nitrogen. Method. 3. The operation prediction of the air liquefaction / separation apparatus according to claim 2, wherein the production amount zO of liquefied oxygen is predicted by subtracting the production amount zN of liquefied nitrogen from the total production amount y. Method. 4. An air liquefaction / separation apparatus comprising: (a1) a lower high-pressure rectification tower and an upper low-pressure rectification tower in a vertically extending cylindrical housing via a heat transfer member. (A2) a compression-type refrigerator, wherein the compression-type refrigerator comprises:
Using nitrogen as a refrigerant, nitrogen gas was extracted from the high-pressure rectification column and led to a heat exchanger for cooling the raw material air, and after cooling the raw material air, the nitrogen gas was compressed by a compressor, condensed by a cold heat source, and condensed. A compression refrigerator that forms a closed loop in which liquefied nitrogen is injected into a high-pressure rectification column to expand and extract nitrogen gas from the high-pressure rectification column to a heat exchanger for cooling the raw material air and circulate; A pipe for supplying the raw material air cooled by the cooling heat exchanger to the lower part of the high-pressure rectification tower; and (a4) extracting a liquid mainly containing oxygen from the lower part of the high-pressure rectification tower, (A5) an air liquefaction / separation device having a line for discharging nitrogen gas from the upper part of the low-pressure rectification column; and (b) a liquefied nitrogen condensed from the compression refrigerator to the high-pressure rectification column. A cold flow rate control means for controlling a supplied cold flow rate x; (C) The total production amount y of liquefied nitrogen and liquefied oxygen after a dead time corresponding to the chilled flow rate x of liquefied nitrogen supplied to the high-pressure rectification column by the compression refrigerator is determined in advance by using the chilled flow rate x as a variable. An apparatus for estimating an operation state of an air liquefaction / separation apparatus, comprising: an estimating unit for estimating the operating state using a linear function. 5. A rectification tower in which a lower high-pressure rectification tower and an upper low-pressure rectification tower are formed in a vertically extending cylindrical housing via a heat transfer member, and nitrogen as a refrigerant is prepared. Nitrogen gas is extracted from the high-pressure rectification tower by the compression refrigerator used and guided to a heat exchanger for cooling the raw material air.Then, after cooling the raw material air, the nitrogen gas is compressed by a compressor, condensed by a cold heat source, and condensed. The liquefied nitrogen is injected into the high-pressure rectification tower and expanded, forming a closed loop that circulates the nitrogen gas from the high-pressure rectification tower by extracting it to the heat exchanger for cooling the raw material air, and cooling it with the heat exchanger for cooling the raw material air The supplied raw material air is supplied to the lower part of the high-pressure rectification tower, the liquefied nitrogen liquefied at the upper part of the high-pressure rectification tower is taken out, and the liquid containing mainly oxygen is supplied to the low-pressure rectification tower from the lower part of the high-pressure rectification tower And removes liquefied oxygen from the lower part of the low pressure rectification column. Nitrogen gas is discharged from the upper part of the pressure rectification column, and a target value ηt of an operation rate η which is a ratio y / yR of an actual total production amount y to a total production amount yR of liquefied nitrogen and liquefied oxygen is set. A total production amount y for each predetermined control cycle W between the total production amount y1 at the start of the change in the operation rate η and the target total production amount yt corresponding to the target operation rate ηt is obtained. The cooling flow rate of liquefied nitrogen supplied to the high-pressure rectification column by the compression refrigerator corresponding to the total production amount y of x
Is set by a predetermined linear function with the total production amount y, the raw material air flow rate Qa is set, and after the lapse of the dead time T from each control period W, the total production amount determined for each control period W a method for operating an air liquefaction / separation apparatus, wherein y is extracted. 6. The method according to claim 5, wherein a product of the total production amount y and a predetermined constant C is calculated to extract a production amount zN of liquefied nitrogen. 7. The method for operating an air liquefaction / separation apparatus according to claim 6, wherein the production amount zO of liquefied oxygen is extracted by subtracting the production amount zN of liquefied nitrogen from the total production amount y. 8. An air liquefaction / separation apparatus comprising: (a1) a lower high-pressure rectification tower and an upper low-pressure rectification tower in a vertically extending tubular housing via a heat transfer member. (A2) a compression-type refrigerator, wherein the compression-type refrigerator comprises:
Using nitrogen as a refrigerant, nitrogen gas was extracted from the high-pressure rectification column and led to a heat exchanger for cooling the raw material air, and after cooling the raw material air, the nitrogen gas was compressed by a compressor, condensed by a cold heat source, and condensed. A compression refrigerator that forms a closed loop in which liquefied nitrogen is injected into a high-pressure rectification tower to expand and extract nitrogen gas from the high-pressure rectification tower into a heat exchanger for cooling the raw material air and circulate; A pipe for supplying the raw material air cooled by the cooling heat exchanger to the lower part of the high-pressure rectification tower; and (a4) extracting a liquid mainly containing oxygen from the lower part of the high-pressure rectification tower, (A5) an air liquefaction / separation device having a line for discharging nitrogen gas from the upper part of the low-pressure rectification column; and (b) liquefied nitrogen liquefied at the upper part of the high-pressure rectification column as a product. (C) at the bottom of the low pressure rectification column A flow control valve for taking out the liquefied oxygen as a product; (d) a cold flow control means for controlling a cold flow x at which the condensed liquefied nitrogen of the compression refrigerator is supplied to the high-pressure rectification column; (F) raw air flow control means for controlling the raw air flow rate Qa supplied to the air-cooling heat exchanger, and (f) control means, wherein the actual total production relative to the total rated production amount yR of liquefied nitrogen and liquefied oxygen A target value ηt of the operation rate η, which is a ratio y / yR of the quantity y, is set, and the target production rate yt corresponding to the target operation rate η between the total production amount y1 at the start of the change in the operation rate η is set. A total production amount y for each predetermined control cycle W is obtained, and a cooling flow rate x of the liquefied nitrogen supplied to the high-pressure rectification column by the compression refrigerator corresponding to the total production amount y for each control cycle W
Is set by a predetermined linear function with the total production amount y, the raw material air flow rate Qa is set, and after the dead time T from each control cycle W, the liquefied nitrogen flow control valve and the liquefied oxygen flow control are set. An operating device for an air liquefaction / separation device, comprising: a control unit that controls an opening degree of a valve and extracts the total production amount y obtained for each control cycle W. 9. The liquefied natural gas heat exchanger includes a liquefied natural gas heat exchanger that condenses nitrogen gas compressed with compressed air by the liquefied natural gas, and the control unit includes a liquefied natural gas heat exchanger. A flow control valve for temperature control that controls the flow rate of natural gas, a flow control valve for discharge pressure control that is interposed between the inlet and outlet of the compressor, and controls the discharge pressure of nitrogen gas. 9. The air liquefaction / separation apparatus according to claim 8, further comprising valve opening control means for controlling the opening of the temperature control flow control valve and the discharge pressure control flow control valve. 10. A valve opening control means, comprising: a temperature detecting means for detecting a temperature of liquefied nitrogen at an outlet side of the liquefied natural gas heat exchanger; and a temperature detecting means responsive to an output of the temperature detecting means. The operating device for an air liquefaction / separation device according to claim 9, further comprising means for controlling an opening degree of the temperature control flow control valve so that the temperature becomes a value corresponding to the cold flow rate x.