JP2967421B2 - Method and apparatus for controlling argon sampling by air liquefaction separation - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the collection of argon by air liquefaction separation, and more specifically, to oxygen, nitrogen, argon, etc. by cryogenic separation using air as a raw material. Control method of argon sampling by air liquefaction and separation which can increase or decrease the production amount and change the operation mode efficiently and in a short time, and obtain the optimal production amount Related to the device.

[Conventional technology]

Conventionally, when producing oxygen and crude argon or oxygen and nitrogen and crude argon, it is known that control of the amount of oxygen production is extremely important in order to efficiently collect crude argon.

Therefore, conventionally, while controlling the amount of oxygen to be collected so that the purity of the oxygen is constant, crude argon is
A method of controlling the production amount so that the oxygen concentration in the crude argon becomes equal to or lower than a specified value is often used.

JP-A-64-90982 discloses a method in which the nitrogen concentration in a gas introduced into a crude argon column is analyzed in real time, and the flow rate of each part is controlled in accordance with the result.

[Problems to be solved by the invention]

However, the former method is effective when a large amount of nitrogen is taken out as an expansion turbine fluid or as a liquid product from the lower tower (high-pressure column) of the double rectification column, but is effective when the amount of nitrogen is small. However, there is a disadvantage that the nitrogen concentration in the crude argon increases due to an increase in the production amount of oxygen and / or crude argon.

In the latter method, the operation line of the upper column (low-pressure column) of the double rectification column is fixed by controlling the reflux amount of liquefied nitrogen supplied from the lower column, but argon is collected in high yield. In such devices, the measures against the fact that the crude argon production is also affected by slight changes in the oxygen production are insufficient.
Further, this method requires an analyzer for nitrogen gas in the gas introduced into the crude argon column.

FIG. 4 shows that the amount of reflux liquid supplied from the lower tower to the upper tower is relatively large, and the oxygen concentration in the exhaust gas discharged from the upper tower and the oxygen concentration in the crude argon under an operating condition where the oxygen production is high, Similarly, the relationship with the nitrogen concentration in the crude argon is shown. The solid lines show the respective concentrations with respect to the crude argon production at a certain oxygen production, and the broken lines (',', ') show the oxygen concentration respectively. The graph shows the oxygen concentration in the exhaust gas, the oxygen concentration in the crude argon, and the nitrogen concentration in the crude argon when the production amount increases. That is, under such conditions, the nitrogen concentration in crude argon is affected by the production of oxygen and crude argon, and the change appears in the oxygen concentration in exhaust gas.

The limit value of the oxygen concentration in the exhaust gas depends on the amount of nitrogen derived from the lower tower and supplied to the upper tower or the amount of liquefied nitrogen for reflux introduced from the outside into the upper tower,
When the amount of nitrogen derived from the lower tower and introduced into the upper tower is small, monitoring the oxygen concentration in the exhaust gas becomes more important.

In addition, if the amount of product collected increases or decreases due to fluctuations in product demand, the flow rate of each part must be adjusted accordingly, and the flow rate must be fine-tuned by the change in purity due to the flow rate change. It takes a long time to obtain an operation state, or operation is performed at the expense of yield.

For example, when increasing or decreasing the amount of oxygen gas collected,
When the changed amount of oxygen gas is input to the controller, the amount of raw material air, the amount of turbine fluid, the amount of nitrogen collected, and the flow rates of other parts are set to amounts corresponding to the changed amount of oxygen. Is controlled to reach the set value according to the time constant of Then, after reaching the set value, the deviation of the purity or heat balance of the product is corrected by a feedback method. Therefore, there is a possibility that the correction must be repeated many times based on the product purity and the heat balance deviation occurring after the correction, and it takes a long time to shift to the specified operation state.

The present invention has been made in view of the above circumstances, and product oxygen is collected so that its concentration is maintained at or above a specified value, and crude argon is obtained when the oxygen concentration in the crude argon becomes equal to or less than a specified value. Air liquefaction separation that can control the production amount so as to prevent the nitrogen concentration in the gas introduced from the upper tower into the crude argon tower from exceeding a specified value and obtain argon in high yield. It is an object of the present invention to provide a method and a device for controlling the collection of argon by the method.

[Means for Solving the Problems] In order to achieve the above object, a method for controlling the collection of argon by air liquefaction separation according to the present invention comprises compressing raw air,
Purification, cooling, introduction into a rectification column, separation of oxygen, nitrogen, crude argon, exhaust gas, etc. by liquefaction and separation In the method of controlling argon sampling by air liquefaction, the current operation based on the flow rate of each part of the device Recognize the pattern, infer the optimal operation pattern based on the previous operation command, the latest operation command, operating conditions such as the capability of the equipment constituting the device, and the measured value of the oxygen concentration in the exhaust gas. The crude argon collection amount and / or the product oxygen amount are calculated in accordance with the operation pattern and the oxygen concentration, and the optimum flow rates of the respective parts of the apparatus other than the above are calculated and controlled based on the inference and the calculated value. And

Further, the control device for collecting argon by air liquefaction separation of the present invention is an air liquefaction separation device which liquefies and separates compressed, purified and cooled raw material air to derive oxygen, nitrogen, exhaust gas and the like. Measuring means for measuring the oxygen concentration, recognizes the current operation pattern based on the flow rate of each part of the device, the optimal operation pattern based on the operation command and the operating conditions such as the capabilities of each device constituting the device and the measurement value by the measuring means , And calculate the flow rate of each part such as the amount of crude argon, the amount of product oxygen, the amount of product nitrogen, the amount of reflux liquid, the flow rate of the expansion turbine, etc., which are the optimal material balances, and control the flow rate of each part based on the calculated value. Control means.

〔Example〕

Hereinafter, the present invention will be described in more detail based on an example of the air liquefaction / separation apparatus shown in FIG.

The air liquefaction / separation apparatus 1 includes a double rectification column 5 for rectifying raw material air A cooled to near a liquefaction point via a compressor 2, a purification facility 3, and a main heat exchanger 4, and a double rectification column 5 An upper column 5a is connected to an argon column 6, a main condensing evaporator 7 disposed at the bottom of the upper column 5a, and an expansion turbine 8 using a nitrogen gas as a working fluid to be separated above the lower column 5b. .

As is well known, the air liquefaction / separation apparatus 1 performs liquefaction rectification and separation using air as a raw material, and as products, oxygen gas GO at the lower part of the upper tower, nitrogen gas GN at the top of the upper tower, liquefied oxygen LO at the bottom of the upper tower, and main condensate. The liquefied nitrogen LN liquefied in the evaporator 7 and the crude argon AR at the upper part of the argon tower are produced, respectively, and the exhaust gas W is discharged from the upper part of the upper tower, and the nitrogen gas N is discharged from the upper part of the lower tower via the expansion turbine 8. Have been.

In the present invention, the air liquefaction / separation apparatus 1 thus configured
In order to maintain the optimal operating condition according to product demand,
Various controllers, measuring instruments, analyzers, etc. are arranged in each part, and the measurement controllers are operated based on the information obtained from these devices and each predetermined set value to control the flow rate of each part. And control means 9 for controlling.
As the control means 9, a control computer and / or an expert system are used. In the figure, d indicates data input / output.

First, a measurement controller 30 including a flow meter 30a for measuring the flow rate of the raw material air A and a guide vane 30b is provided in the pipeline 10 for supplying the raw material air A. This measurement controller 30
The control unit 9 outputs the opening degree of the guide vanes 30b together with the flow rate of the raw material air A to the control means 9, and controls the supply amount of the raw material air A by opening and closing the guide vanes 30b according to an instruction from the control means 9. The value calculated according to the GO production is the set value. The same can be done by providing an automatic valve in the pipeline instead of the guide vane.

The product oxygen gas GO
A measurement controller 31 including a flow meter 31a for measuring the GO flow rate and an automatic valve 31b is provided. The measurement controller 31 outputs the opening degree of the automatic valve 31b together with the flow rate of the product oxygen gas GO to the control means 9, and the automatic valve 31b is instructed by the control means 9.
To open and close to control the output of product oxygen gas GO.
The value calculated according to the demand amount of the product oxygen gas GO becomes the set value, and the oxygen purity is finely adjusted to maintain the specified value. In connection with this product oxygen gas measurement controller 31, the product oxygen gas
An analyzer 31c for measuring the purity of GO is provided, and outputs the purity to the control means 9.

The product nitrogen gas GN
A measurement controller 32 including a flow meter 32a for measuring the flow rate of GN and an automatic valve 32b is provided. The measurement controller 32 outputs the opening degree of the automatic valve 32b together with the flow rate of the product nitrogen gas GN to the control means 9, and in accordance with an instruction from the control means 9, the automatic valve 32b
To open and close to control the output of product nitrogen gas GN.
The value calculated according to the supply amount of the raw material air A is the set value.

The conduit 13 for leading the crude argon AR has a measurement controller 33 including a flow meter 33a for measuring the flow rate of the crude argon AR and an automatic valve 33b and an analyzer for measuring the oxygen concentration in the crude argon.
33c is provided. The measurement controller 33 outputs the opening of the automatic valve 33b together with the flow rate of the crude argon AR to the control means 9, and controls the output of the crude argon AR by opening and closing the automatic valve 33b according to an instruction from the control means 9. The raw material air A
The value calculated according to the supply amount of the crude argon AR is set to a set value, and the production amount of the crude argon AR is maximized while satisfying the condition that the oxygen concentration in the crude argon obtained from the analyzer 33c is equal to or less than a specified value. Is fine-tuned.

A line 14 for deriving the liquefied oxygen LO has a measurement controller including a flow meter 34a for measuring the flow rate of the liquefied oxygen LO and an automatic valve 34b.
34 are provided. The measurement controller 34 controls the liquefied oxygen LO
The opening degree of the automatic valve 34b is output to the control means 9 together with the flow rate of
The automatic valve 34b is opened and closed in accordance with an instruction from the control means 9 to control the output of liquefied oxygen LO, and is controlled so as to maintain a preset value or a balance in cold weather.

A measurement controller including a flow meter 35a for measuring the flow rate of the liquefied nitrogen LN and an automatic valve 35b is provided in a conduit 15 for leading the liquefied nitrogen LN.
35 are provided. This measurement controller 35 is a liquefied nitrogen LN
The opening degree of the automatic valve 35b is output to the control means 9 together with the flow rate of
The automatic valve 35b is opened and closed by a command from the control means 9 to control the production amount of liquefied nitrogen LN, and is controlled so as to maintain a preset value, or the balance and purity on cold, and It is controlled in relation to the flow rate of the expansion turbine fluid so that the purity of the reflux liquefied nitrogen in the column 5b can be maintained.

A pipe 16 for introducing nitrogen gas N into the expansion turbine 8 includes:
A measurement controller 36 including a flow meter 36a for measuring the flow rate of the nitrogen gas N and an automatic valve 36b is provided. The measurement controller 36 outputs the opening degree of the automatic valve 36b together with the flow rate of the nitrogen gas N to the control means 9, and opens and closes the automatic valve 36b according to an instruction from the control means 9 to control the amount of fluid introduced into the expansion turbine. The value calculated from the amount of the raw material air is set as a set value and is controlled. The value is adjusted by a value set in relation to the balance in the cold and the flow rate of the liquefied liquefied nitrogen according to the operation purpose.

The pipe 17 for introducing the reflux liquid into the upper tower 5a is provided with a measurement controller 37 comprising a flow meter 37a for measuring the flow rate of liquefied nitrogen in the pipe 17 and an automatic valve 37b. This measurement controller
37 outputs the opening degree of the automatic valve 37b together with the flow rate of the liquefied nitrogen to the control means 9, and in accordance with an instruction from the control means 9, the automatic valve 37b.
The amount of the reflux liquid is controlled by opening and closing b, and the value calculated from the amount of the raw material air becomes a set value and is controlled.

A pipe for introducing liquefied air at the bottom of the lower tower 5b into the upper tower 5a
An automatic valve 38b for controlling the flow rate of the liquefied air is provided at 18, and a liquid level gauge 38c for measuring the liquid level at the bottom is provided at the bottom of the lower tower. This automatic valve 38b and liquid level gauge 38
The measurement controller 38 comprising a controls the opening of the automatic valve 38b in accordance with the liquid level of the liquefied air at the bottom of the lower tower, and controls the liquid level at the bottom of the lower tower to be constant.

A line 19 for introducing the liquefied air at the bottom of the lower tower into the condenser 6a of the crude argon column 6 is provided with a measurement controller 39 including a flow meter 39a for measuring the flow rate of the liquefied air and an automatic valve 39b. ing. The measurement controller 39 outputs the opening degree of the automatic valve 39b together with the flow rate of the liquefied air introduced into the condenser 6a to the control means 9, and opens and closes the automatic valve 39b according to an instruction from the control means 9 to open and close the liquefied air amount. The value calculated from the amount of raw material air becomes a set value and is controlled.

An analyzer 40 for measuring the oxygen concentration in the exhaust gas is provided in the pipeline 20 for discharging the exhaust gas W from the upper tower upper part,
The control means 9 controls the concentration of oxygen contained in the exhaust gas in the pipe 20.
Output to Further, the pipe 20 is provided with a measurement controller 41 including a flow meter 41a for controlling the flow rate of the exhaust gas and an automatic valve 41b.

The control means 9 includes, for example, a distributed control device 9a.
The inference calculation means 9b composed of an AI station (expert system). As described above, each measurement controller is based on information obtained from each device and an appropriate flow rate set value in each predetermined operation pattern. Is operated to control the flow rate of each part. That is, the air liquefaction / separation apparatus 1 captures the change in the oxygen concentration in the exhaust gas W by taking advantage of the characteristic that the change in the material balance appears in the change in the oxygen concentration in the exhaust gas W. Whether the change is due to a change in the heat balance or not is adjusted based on the recognition of the operation pattern based on the flow rate, the concentration, and the like of each section so that the optimum operation state is obtained.

Further, the oxygen concentration in the exhaust gas W changes due to fluctuations in the production amount of the oxygen gas GO and the crude argon AR, and the nitrogen concentration in the crude argon AR increases when the oxygen concentration falls below a specified value. Oxygen gas GO so that the oxygen concentration in W does not fall below the lower limit determined by the operation mode.
And control the production of crude argon AR.

Further, the flow rate of each section and a preset optimal setting value in each operation pattern are compared to recognize the current operation pattern, and a lower limit value of the oxygen concentration in the exhaust gas W is set, and, for example, a product By changing the oxygen gas flow rate due to the change in oxygen gas demand, set the flow rate of each part corresponding to the increase or decrease of oxygen production, change the opening of each automatic valve, and fine-tune this according to the output of each analyzer Then, the device is promptly shifted to the optimal operation state.

For example, when the control of the air liquefaction / separation apparatus is performed by the emmispart system configured as described above, and the amount of oxygen gas to be collected is increased or decreased, the changed amount of oxygen gas to be collected is input to the controller. The current operation pattern and the previous operation command are recognized from the density. Next, the optimum flow rate of each section is calculated based on the appropriate flow rate set value of each section predetermined according to the product sampling amount according to the current operation command, and the flow rate of each section is controlled based on the calculated value.
Prior to this, it is inferred whether or not the operation according to the previous command can be continued or changed after the shift to the operation according to the new command. This inference is based on priority items, such as product purity, the amount of each product to be ensured in each operation mode, and the securing of heat balance, etc., based on the reduction limit of the raw air compressor and the demand information of the liquefied gas product. (Information on the storage amount in the storage tank), and further, an optimal operation pattern is selected from information such as the previous operation command, and a time constant until operation transition is set according to the change amount. For example, if oxygen gas reduction is commanded and the previous command was liquefied nitrogen sampling operation, the nitrogen gas amount and air compressor reduction limit to be secured when the raw material air amount was reduced according to the oxygen gas sampling amount Infer the amount of liquefied nitrogen and the flow rate of each part.
As a result, the flow rate of each part is controlled so as to reach a value set by each time constant. Then, after reaching the set value, the deviation of the product purity or the heat balance that occurs is inferred from the current operation pattern as to which part should be corrected and how much, and control is performed based on the result. For example, in the operation without sampling the liquid product, the turbine fluid amount set value is finely adjusted in relation to the flow rate of each part so that the flow rate or the valve opening of the system for heat balance adjustment falls within a predetermined range.

In addition, the amount of crude argon collected in the air liquefaction separator for collecting argon greatly changes due to subtle changes in the amount of reflux liquid introduced into the upper tower and the amount of oxygen collected. Therefore, the argon operation requires control according to the amount of the reflux liquid to the upper column, that is, control of the flow rate of each part, and delicate adjustment of the oxygen collection amount is required. Here, the optimal ratio of liquefied air and liquefied nitrogen introduced from the lower tower to the upper tower can be easily determined by calculation, but the management index for the amount of oxygen and crude argon collected is derived from the upper tower. The oxygen concentration in the exhaust gas to be discharged, which is increased by reducing the amount of oxygen and crude argon collected, and is decreased by increasing the amount of collected oxygen and crude argon.

Therefore, the adjustment of the amount of oxygen and crude argon collected is the second
It can be performed by the procedure shown in the figure. That is, step 10
When the change in the oxygen concentration in the exhaust gas is detected in step 1, the current operation pattern is first recognized from the flow rates of the respective parts as described above, and the lower limit value of the oxygen concentration in the exhaust gas is determined according to the pattern (step 102). . The oxygen concentration in the exhaust gas is compared with the lower limit (step 103). If the oxygen concentration is lower than the lower limit, the crude argon collection amount is reduced, and / or
Alternatively, the amount of product oxygen collected is reduced (step 104). If the oxygen concentration is higher than the lower limit, the crude argon collection amount is increased and / or the product oxygen collection amount is increased (step 105). If only the control of each step described above maintains the predetermined product oxygen concentration and the crude argon concentration, and the respective product sampling amounts are maintained according to the operation command, the control of the crude argon sampling system in the control system of the present invention is sufficient. It is.

However, in the control of the above-described steps, a slight error occurs due to the indication of the flow meter, the flow rate setting of each part corresponding to various operation patterns, and the like. Therefore, it is desirable to finely adjust the production amounts of oxygen and crude argon.

In this case, the adjustment of the amount of oxygen and crude argon collected is
This can be performed according to the procedure shown in FIG. That is, similarly to the above, when the change in the oxygen concentration in the exhaust gas is detected in step 101, first, as described above, the current operation pattern is recognized from the flow rate of each part and the like, and the lower limit of the oxygen concentration in the exhaust gas according to the pattern is determined. A value is obtained (step 102). The oxygen concentration in the exhaust gas is compared with the lower limit value (step 103). If the oxygen concentration is lower than the lower limit value, the oxygen collection amount is reduced after passing through a counter (step 106) in which the upper limit of the number of passages is set. Control of the direction is performed (step 107). In the control in step 107, adjustment is performed for a half amount of the previous adjustment amount, and the process returns to step 103. This step 10
In the loop of 3, 106, 107, the number of times of control is counted by the counter, and if the number of times of control exceeds the set number of times, no further control is performed (step 108).

If the oxygen concentration is higher than the lower limit in step 103, in step 109, the oxygen gas purity is compared with the lower limit of the purity required for the product. When the purity is equal to the lower limit and the oxygen concentration in the crude argon is at the upper limit (step 110), even if the oxygen concentration in the exhaust gas is high, the setting is not changed in this loop (step 110). 108).

In step 109, if the oxygen gas purity is higher than the lower limit, the oxygen concentration in the crude argon is compared with the upper limit (step 111). Return to step 103.
When the oxygen concentration in the crude argon is lower than the upper limit in step 111, the amount of crude argon is slightly increased (step 113), and the process returns to step 103.

If appropriate control cannot be performed in this loop, the flow rate of another part is further reviewed to perform optimal control.

By controlling the flow rate of each part in this manner, various products can be efficiently collected, and the operation mode can be switched in a short time. In particular, in the air liquefaction separator that collects argon, the crude argon AR
Crude argon AR can be produced at a high yield without increasing the nitrogen concentration in the air, and the yield of other oxygen and nitrogen can also be improved, greatly improving the production efficiency of air liquefaction and separation equipment. be able to.

The flow of the gas and liquid in each part of the apparatus is the same as that of a general air liquefaction / separation apparatus, and a detailed description thereof will be omitted. Further, the configuration of the air liquefaction / separation apparatus is not limited to the above-described embodiment, and the present invention can be applied to a device equipped with various types of conventionally used capacity improvement equipment, and is described in the embodiment. It is not limited to those that produce all products together.

〔The invention's effect〕

As described above, the control method and apparatus of the air liquefaction / separation apparatus of the present invention can be applied to the gas / liquid flow rate of each part of the apparatus, the oxygen concentration in the exhaust gas from the rectification column, or the crude argon and the product oxygen collected therefrom. Recognizing the current operation pattern based on the oxygen concentration inside, and controlling the flow rate of each part based on this, each product can be produced in the optimal operation state in each operation pattern, and crude argon In addition, the yield of each product can be improved. In particular, the operation mode can be quickly shifted due to fluctuations in product demand, and it is possible to obtain the maximum yield while keeping the nitrogen concentration in the crude argon below a specified value.

[Brief description of the drawings]

FIG. 1 is a system diagram of an air liquefaction / separation apparatus showing one embodiment of the present invention, FIGS. 2 and 3 are flowcharts showing an example of control, and FIG. 4 is oxygen concentration in exhaust gas with respect to the amount of crude argon collected. FIG. 3 is a diagram showing a relationship between oxygen concentration in crude argon and nitrogen concentration in crude argon. DESCRIPTION OF SYMBOLS 1 ... Air liquefaction separation apparatus, 2 ... Compressor, 3 ... Purification equipment, 4 ... Main heat exchanger, 5 ... Double rectification column, 6 ... Argon column, 7 ... Main condensing evaporator, 8 ... Expansion turbine, 9 ...
... Control means, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41 ... Measurement controller, 40 ... Analyzer, A ... Raw material air, AR ... Crude argon, GO …… Oxygen gas, GN… Nitrogen gas, LO …… Liquid oxygen, LN …… Liquid nitrogen, W …… Exhaust gas

Claims (7)

(57) [Claims] 1. A raw material air is compressed, purified, cooled, introduced into a rectification column, and subjected to liquefaction rectification to separate oxygen, nitrogen, crude argon,
In the control method of argon sampling by air liquefaction separation to separate into exhaust gas, etc., the current operation pattern is recognized based on the flow rate of each part of the device, and the previous operation command and the latest operation command and the capability of the equipment constituting the device are recognized. Based on the operating conditions and the measured value of the oxygen concentration in the exhaust gas, an optimal operation pattern is inferred, and a crude argon collection amount and / or a product oxygen amount are calculated in accordance with the operation pattern and the oxygen concentration, A method for controlling the collection of argon by air liquefaction and separation, wherein an optimum flow rate of each part of the apparatus other than the above is calculated and controlled based on the inference and the calculated value. 2. The measured values are, in addition to the measured oxygen concentration in the exhaust gas, the measured oxygen concentration in the sampled crude argon and the measured oxygen concentration in the product oxygen. The method for controlling argon collection by air liquefaction separation according to claim 1, wherein the amount of crude argon and / or the amount of oxygen collected are calculated and controlled accordingly. 3. The method according to claim 1, wherein the calculation of the optimum flow rate of each section is performed based on a predetermined predetermined priority, and the control of the flow rate of each section is performed based on a predetermined time constant. 3. The method for controlling argon collection by air liquefaction separation according to claim 1 or 2. 4. The method according to claim 1, wherein the control is performed by a control computer or an expert system. 5. An air liquefaction and separation apparatus for liquefying and separating compressed, purified and cooled raw material air to derive oxygen, nitrogen, exhaust gas and the like. Recognize the current operation pattern based on the flow rate, infer the optimal operation pattern based on the operation conditions such as the operation command and the performance of the equipment components and the measurement values by the measuring means, and obtain an optimal material balance. Control means for calculating a flow rate of each part such as a crude argon amount, a product oxygen amount, a product nitrogen amount, a reflux liquid amount, and an expansion turbine flow rate, and controlling the flow rate of each part based on the calculated value. Control device for argon sampling by air liquefaction separation. 6. The measuring means further comprises an oxygen concentration measuring means in the crude argon sampled and an oxygen concentration measuring means in the product oxygen in addition to the oxygen concentration measuring means in the exhaust gas. 6. The control device for collecting argon by air liquefaction separation according to claim 5, wherein the amount of crude argon and / or product oxygen collected is controlled in accordance with the oxygen concentrations measured by the three measuring means. 7. The control apparatus according to claim 5, wherein said control is performed by a control computer and / or an expert system.