JP2967422B2 - Air liquefaction separation device and control method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling an air liquefaction / separation apparatus. More specifically, the present invention relates to a method in which products such as oxygen and nitrogen are converted to gas and / or gas by cryogenic separation using air as a raw material. In a device that produces liquid,
The present invention relates to a method for controlling an air liquefaction / separation apparatus capable of efficiently increasing / decreasing a production amount, changing an operation mode and the like in a short time and obtaining an optimal production amount.

[Conventional technology]

2. Description of the Related Art Conventionally, a distributed control device (DCS) has been widely used as a means for controlling a flow rate or the like of each part of an air liquefaction / separation device to a predetermined value according to a product output.

In the control using the conventional DCS, when the product output target amount increases or decreases due to demand fluctuation, for example, when the oxygen gas collection amount is increased or decreased, when the changed oxygen gas collection amount is input to the DCS, the raw material air The amount, turbine fluid amount, nitrogen sampling amount, and other flow rates of each part are set to predetermined values corresponding to the changed oxygen amount, and the valves of each part are controlled to reach the set values according to a predetermined time constant. After further reaching the set value, the deviation of the purity or heat balance of the product is corrected in a feedback manner.

[Problems to be solved by the invention]

However, in the control method in which only the product sampling amount is changed as described above, the operation can be changed automatically, but the operation mode is extremely limited, and the product purity and the heat balance that are changed after the correction are changed. There is a possibility that the correction must be repeated many times based on the above, and it may take a long time to obtain the optimum operation state or may have to perform the operation at the expense of the yield.

Therefore, when changing the operation mode, the current operation state is grasped, the conditions such as the limit of reduction of the apparatus and the necessity of liquid production are considered, and the operation after the change is optimized while satisfying the change target. It is desirable to set the operating conditions as described above, and to perform a detailed judgment such as shifting the operation in the shortest time and perform an operation based on this. However, at present, these judgments and operations largely depend on the skill of a skilled operator, and the shortage of successors has become a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and air liquefaction separation that can improve the operation accuracy by automating parts that need to be determined based on the experience of the conventional operator and can efficiently change the operation mode. It is an object to provide an apparatus and a control method thereof.

[Means for solving the problem]

In order to achieve the above-mentioned object, an air liquefaction / separation apparatus of the present invention is an air liquefaction / separation apparatus that liquefies and separates compressed, purified, and cooled raw material air to derive product gas such as oxygen and nitrogen, product liquefied gas, and exhaust gas. In the liquefaction / separation apparatus, (a) means for measuring the flow rate of each part such as an air amount, a product amount, a turbine amount, a reflux liquid amount, and / or their purity and a liquid level for detecting a real-time operation state of the device; Means for detecting and measuring the amount of stored gas and / or the amount of stored liquid in a product storage tank attached to the air liquefaction separation device and / or a product storage tank supplied with a product from the air liquefaction separation device; and (b) the measurement means. Calculating means for recognizing the operating state of the apparatus from the information from the apparatus and inferring the optimal operating conditions and the operation transition operation method in the shortest time based on the operating command; and (c) instructing the control of each unit based on the above calculation results. It is characterized by and a control unit for controlling the operation specifications of the flow rate, etc. of the various units by a signal from the control means and the control means that.

Further, the control method of the air liquefaction / separation apparatus of the present invention comprises compressing, purifying and cooling the raw material air, introducing the compressed air into a rectification column, and separating product gas such as oxygen and nitrogen, product liquefied gas and exhaust gas by liquefaction rectification. In the control method of the air liquefaction / separation device to be derived, the flow rate of each part such as the raw air, product gas, product liquefaction gas, and exhaust gas and the product storage tank attached to the air liquefaction / separation device and / or the product The current operation pattern is recognized based on the operation parameters such as the gas storage amount and / or liquid storage amount of the product storage tank to be supplied, and the previous operation command and the latest operation command and the operation capability of the equipment constituting the device It is characterized in that an optimal operation pattern is inferred from operating conditions such as the above, and the operation parameters of each part such as an optimum product sampling amount, a recirculation liquid amount, and an expansion turbine flow rate are calculated and controlled based on the inference.

〔Example〕

Hereinafter, the present invention will be described in more detail based on one embodiment shown in the drawings.

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.
The control means 9 uses a control computer and / or an expert system. In the figure, d indicates data (information) 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 flow rate can be controlled by providing an automatic valve in the pipeline instead of the guide vane 30b.

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 41 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 in accordance with an instruction from the control means 9, the automatic valve 31b
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.

When the liquefied crude argon tank (LAT ₁ ) 50 a is provided as an accessory to the air liquefaction / separation apparatus 1 and / or the liquefied crude argon tank (LAT ₂ ) 50 b to which the liquefied crude argon is supplied from the apparatus is provided. If provided,
Means for detecting and measuring the amount of crude argon AR in these storage tanks 50A and 50b, such as a liquid level gauge and a pressure gauge, are provided, and the data obtained by the measuring means is also transmitted to the control means 9, and the respective data and It can be configured to control each part of the device in association with it.

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.

Similarly to the liquefied crude argon, a liquefied oxygen tank (LOT ₁ ) 51 a
And / or liquefied oxygen LO from the device
If a liquefied oxygen tank (LOT ₂ ) 51b is provided, a means for detecting and measuring the amount of liquefied oxygen LO in these storage tanks 51a and 51b, such as a liquid level gauge and a pressure gauge, is provided.
The data obtained by the measuring means is also transmitted to the control means 9,
The apparatus may be configured to control each unit of the apparatus in association with each of the data.

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.

In the case of the liquefied nitrogen LN as well, a liquefied nitrogen tank (LNT ₁ ) 52 a is provided as an accessory to the air liquefaction separation device 1 and / or a liquefied nitrogen tank (LNT ₂₎ receiving the supply of the liquefied nitrogen LN from the device. ) If 52b is provided,
Means for detecting and measuring the amount of liquefied nitrogen LN in these storage tanks 52a and 52b, such as a liquid level gauge and a pressure gauge, are provided, and data obtained by the measuring means is also transmitted to the control means 9, and the respective data and It can be configured to control each part of the device in association with it.

Similar control can be performed not only for liquid products but also for gas products. In each of the above-mentioned product tanks, the tank attached to the apparatus means a tank connected to the apparatus by piping, and the tank to which the product is supplied may receive the supply of the product by a lorry or the like. It means a tank, which includes products supplied from a plurality of air liquefaction / separation devices in addition to products supplied only from the device.

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 consisting of a controls the opening degree of the automatic valve 38 according to the liquid level of the liquefied air at the lower tower bottom, and is controlled so that the liquid level at the lower tower bottom is 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 comprises a distributed control device 9a and an inference calculation means 9b composed of an AI station (expert system). The decentralized control device 9a supplies various input information such as flow rate, concentration, pressure, temperature, and product sampling target value obtained from the various devices described above to the inference means 9b, and also outputs various information from the inference calculation means 9b. Each of the controllers is operated based on the set value of the flow rate. The inference calculation means 9b recognizes the current operation pattern based on various information received from the distributed control device 9a, and also executes the last operation command and the latest operation command and the operation conditions such as the operation capability of the equipment constituting the device. From the optimum operating pattern, and based on the inference, calculate and control the operating parameters of each part such as the optimum product sampling amount, reflux liquid amount, and expansion turbine flow rate.
That is, the distributed control device 9a is configured to provide data necessary for inference by the inference calculation means 9b to the inference calculation means 9b, and to control each unit based on data received from the inference calculation means 9b.

Here, the operation of the inference calculating means 9b when the operation mode is changed will be described. First, the inference calculation means 9b recognizes the current operation pattern by comparing operation specifications such as the flow rate of each unit received from the distributed control device 9a with the optimal flow rate in each preset operation pattern, and recognizes a new operation pattern. After the shift to the operation according to the command, it is inferred whether the operation according to the previous command can be continued or should be changed. This inference is based on priorities such as product oxygen purity and production,
Based on this, based on securing the optimal material balance and heat balance, such as the amount of raw material air and the amount of each product to be secured in each operation mode, the reduction limit of the raw material air compressor, the demand for liquefied gas products, An optimum operation pattern is selected from information such as a previous operation command, and a time constant up to operation transition is set according to a change amount.

For example, if oxygen gas reduction is commanded and the previous command was a liquefied nitrogen sampling operation, the nitrogen gas amount or air compressor reduction limit to be secured when the reduced air amount was reduced according to the oxygen gas sampling amount Infer the flow rate of each part, such as the amount of liquefied nitrogen and recirculated liquid, the flow rate of the expansion turbine, etc. 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 demand information of the liquefied gas product is not limited to the storage tank attached to the air liquefaction separation device, but may include other plural storage tanks, for example, liquid storage in a large number of storage tanks at liquefied gas supply bases installed in various places. By taking the amount information online, it is possible to set the sampling amount of the liquid product including the demand information based on the fluctuation of the liquid holding amount.

By controlling the operation parameters such as the flow rate of each part in this manner, various products can be efficiently collected, and the switching to the optimum operation state can be performed in a short time. In addition to changing the operation mode during operation of the apparatus, it is also possible to control parameters such as the flow rate of each part at the time of starting the apparatus in the same manner, thereby shortening the start-up time and reducing the production efficiency of the air liquefaction / separation apparatus. It can be greatly improved.

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

It goes without saying that the operating parameters can be controlled not only for the flow rate, concentration (purity) and liquid level but also for temperature and pressure.

〔The invention's effect〕

As described above, the air liquefaction separation device and the control method of the present invention recognize the current operation pattern based on the gas-liquid flow rate, purity, storage amount, etc. of each part of the device including the product storage tank. Since the optimum operation parameters of each section are inferred, calculated and controlled based on the respective operations, each product can be produced in an optimum operation state in each operation pattern, and the yield of each product can be improved. In particular, the operating mode can be quickly changed due to fluctuations in product demand and changes in the amount of product in the storage tank, and complex operating conditions can be set on behalf of the operator's skill level. It can respond to such social demands.

[Brief description of the drawings]

FIG. 1 is a system diagram of an air liquefaction / separation apparatus showing one embodiment of the present invention. 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, 9a ... distributed control device, 9b ... inference calculation means, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41 ... measurement controller, 40 ... analysis A, raw air, AR: crude argon, GO: oxygen gas, GN: nitrogen gas, LO: liquefied oxygen, LN: liquefied nitrogen, W: exhaust gas

Claims (3)

(57) [Claims] 1. An air liquefaction apparatus for liquefying and separating compressed, purified and cooled raw material air to derive a product gas such as oxygen and nitrogen, a product liquefied gas and an exhaust gas. Means for measuring the flow rate of each part such as air quantity, product quantity, turbine quantity, recirculation liquid quantity and / or their purity and liquid level for detecting the condition, and a product storage tank and / or attached to the air liquefaction / separation apparatus Or means for detecting and measuring the amount of gas stored and / or the amount of liquid stored in the product storage tank to which the product is supplied from the air liquefaction / separation apparatus; and (b) recognizing the operation state of the apparatus based on information from the measuring means; (C) control means for instructing the optimal operation conditions and the operation transition operation method in the shortest time based on the operation command; (c) control means for instructing control of each section based on the calculation result; Cryogenic air separation apparatus characterized by comprising: a controller for controlling the operation specifications of the flow rate, etc. of each part, the. 2. The apparatus according to claim 1, wherein said measuring means is a measuring controller for a raw air flow rate, a measuring controller for a product oxygen gas flow rate, a measuring controller for a product nitrogen gas flow rate, a measuring controller for a liquefied oxygen flow rate, and a measuring control for a liquefied nitrogen flow rate. Device, measurement controller for expansion turbine fluid flow,
Measuring controller for the amount of liquefied nitrogen for the reflux liquid in the upper tower, measuring controller for the liquefied air flow introduced into the upper tower, measuring controller for the liquid level at the bottom of the lower tower, measuring instrument for oxygen concentration in exhaust gas, and product gas purity analyzer The air liquefaction / separation apparatus according to claim 1, wherein: 3. A raw material air is compressed, purified, cooled and introduced into a rectification column, and product gas such as oxygen and nitrogen is obtained by liquefied rectification separation.
In the method for controlling an air liquefaction / separation device for deriving product liquefied gas and exhaust gas, the method includes controlling the flow rate of each part of the raw material air, product gas, product liquefied gas, exhaust gas, etc., and a product storage tank attached to the air liquefaction / separation device and / or the air. Recognize the current operation pattern based on the operation specifications such as the gas storage amount and / or liquid storage amount of the product storage tank that receives product supply from the liquefaction / separation device, and recognizes the previous operation command and the latest operation command and device. The optimum operation pattern is inferred from the operation conditions such as the operation capability of the constituent devices, and the optimum product sampling amount,
A method for controlling an air liquefaction / separation apparatus, comprising calculating and controlling operating parameters of each part such as a recirculating liquid amount and an expansion turbine flow rate.