JPS6155035B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically controlling the amount of oxygen product in an air separation device that extracts argon as well as oxygen and nitrogen through liquefaction and cryogenic separation of air.

Conventionally, the operation of air separation equipment that collects argon is more difficult than that of general air separation equipment that collects oxygen and nitrogen, which does not collect argon.
It required a professional driver with many years of driving experience. However, in recent years, due to the shortage of these specialized operators and the demand for labor-saving operation of air separation equipment, there has been a strong demand from various quarters for automation of the product output of air separation equipment.

Automation of the amount of product oxygen generated in general oxygen and nitrogen extraction air separation equipment that does not collect argon has been done until now by using a control method that keeps the temperature difference between the upper columns of the rectification column constant and a method that maintains the oxygen purity at a specified value. Several ideas have been devised, including a computer control system that uses a computer to track the amount generated, and some of them have been put into practical use. However, air separation equipment that extracts argon at the same time as oxygen and nitrogen is difficult to operate, and an optimal control method for the amount of product oxygen generated has not been put into practical use.

A problem in the operation of air separation equipment for extracting argon is the normal operation of the crude argon column. The operation of the crude argon column is closely related to the operation with the main rectification column, including the differential pressure of the crude argon column, the oxygen concentration of the liquid air blown from the lower column to the upper column of the main rectification column, and the product oxygen. It varies greatly depending on etc.

Furthermore, in air separation equipment, an absorber filled with gel is installed in the liquid air line to prevent the concentration of acetylene and hydrocarbons in the air in liquid oxygen. The operation of the crude argon column fluctuates greatly due to changes in switching.

In this way, air separation equipment that collects argon has several variable factors to stabilize the crude argon column, and it is difficult to accurately and easily understand these factors, so until now Optimal automatic control of the amount of product oxygen generated in the air separation equipment that collects argon is not performed.

An object of the present invention is to perform automatic control using an optimal computer of the amount of product oxygen in an argon sampling air separation device, which has been difficult to control automatically until now.

The main point of the present invention is that, in order to stabilize the operation of the crude argon column, a liquid air blowing stage of the upper column of the main rectification column;
A thermometer is installed between the feed stage to the crude argon column, and the temperature difference between the saturation temperature of this stage and the oxygen saturation temperature of the liquid oxygen reservoir of the main condenser is used to determine the temperature for stable operation of the crude argon column. A limit value is established, and the amount of product oxygen or raw material air is calculated and controlled according to the oxygen purity within the range of this limit value.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, after dust removal, the raw material air passes through the conduit 1 and the capacity control valve 2, and is transferred to the raw material air compressor 3 at approximately 5 kg/kg.
The pressure is increased to cm ² G. The compressed air is led from conduit 4 to main heat exchanger 7 through conduit 6 after moisture and carbon dioxide are removed from the air by adsorption device 5 . Most of the air, which has been cooled to the saturation temperature by exchanging heat with the return gas in the main heat exchanger 7, is blown into the lower column 10 of the main rectification column 9 through the conduit 8, where it is rectified into nitrogen. and is separated into liquid air with a purity of approximately 40% _O2 . The remaining part of the air cooled by the main heat exchanger 7 is extracted from the middle of the main heat exchanger 7 and guided to the expander 12 through the conduit 11, where the pressure is about 0.3 Kg/cm ² G. It performs external work by adiabatically expanding to a maximum temperature, lowering its temperature to almost the saturation temperature and compensating for the total cooling loss of the device. Expansion machine 12
The air leaving the main rectification column 9 is transferred to the upper column 1 from the conduit 13.
4 It is blown into the middle part and subjected to rectification and separation.

On the other hand, the nitrogen that has been rectified and separated in the lower column 10 becomes a liquid from the upper part of the lower column 10 and passes through the conduit 15 and the expansion valve 1.
6. Through the conduit 17, the pressure is reduced to about 0.2 Kg/cm ² G, and the resultant is supplied to the upper part of the upper column 14 of the main rectification column 9 as a reflux liquid. The remaining liquid air with a purity of about 40% O ₂ stored in the lower part of the lower column 10 is supercooled by nitrogen gas from the upper part of the upper column 14 through a conduit 18 and a supercooler 19, and is then passed through a conduit 20 through a supercooler 19. Branched in two directions. One of them is an expansion valve 22 from a conduit 21,
The reflux liquid is supplied to the middle part of the upper column 14 through the conduit 23, and the other liquid is supplied from the conduit 24 to the expansion valve 25.
The pressure is reduced to approximately 0.3 Kg/cm ² G, the temperature is lowered to the saturation temperature, and the crude argon is introduced into the condenser of the crude argon column 27. Here, the liquid air is in the crude argon column 27
It exchanges heat with the crude argon gas with a purity of about 95% that has been rectified and separated in
It is blown into the middle part of the tank and subjected to rectification and separation.

Air, liquid nitrogen, liquid air, etc. blown into the upper column 14 of the main rectification column 9 are separated into the upper column 14 of the main rectification column 9.
Nitrogen is separated in the upper part of 4, and oxygen is separated in the lower part.

Nitrogen is directly supplied from the upper part of the upper column 14 in a gaseous state through a conduit 29 through a subcooler 19 to a conduit 30.
It is guided to the main heat exchanger 7, and by exchanging heat with air, the temperature is recovered to approximately room temperature, and then taken out of the apparatus.

The oxygen that has been rectified and separated in the upper column 14 is stored as a liquid in the lower main condenser 32, and a part of the gaseous oxygen that has been reevaporated with nitrogen gas in the lower column 10 is transferred to the conduit 3.
3 and guided to the main heat exchanger 7, where the temperature is recovered to normal temperature by exchanging heat with air, and then passed through a flow control valve 35 from a conduit 34 and supplied to the end of use from a conduit 36.

Argon is led in gaseous form to the lower part of the crude argon column 27 through a conduit 37 from an argon-rich feed gas outlet (hereinafter referred to as feed stage) at the bottom of the upper column 14 of the main rectification column 9, and is purified in the crude argon column 27. about
It is rectified and separated into 95% crude argon, and taken out from the upper part as a gas or liquid through a conduit 38.

Generally, in an air separation device that does not collect argon, the oxygen purity is input into the computer 40 from the oxygen purity meter 39 attached to the product oxygen outlet conduit 33 taken out from the main condenser 32, and the purity is adjusted to the specified value. Methods such as controlling the amount of product oxygen using the flow rate controller 41 via the regulating valve 35, or controlling the amount of product oxygen via the volume regulating valve 2 using the air flow regulator 42 are being put into practical use. In the separation device, depending on the operating state of the crude argon column 27, controlling the oxygen purity alone may not be successful, and stabilizing the operation of the crude argon column 27 is an absolute requirement.

In order to stabilize the crude argon column 27, it is necessary to prevent the concentration of nitrogen gas in the feed stage of the upper column 14 of the main rectification column 9 to the crude argon column 27 from exceeding a specified value.

As a solution to this problem, the present invention provides a temperature sensing end 43 between the liquid air blowing stage and the feed stage of the upper column 14.
A temperature detection end 44 is installed to measure the saturation temperature of oxygen in the main condenser 32, and a temperature difference meter 45 is installed to measure the temperature difference between the temperature detection ends 43 and 44.
When the temperature difference exceeds a certain limit value, the crude argon column 27
Since a large amount of nitrogen enters the feed gas to the feed gas, making the operation of the crude argon column 27 unstable, the amount of oxygen in the product or the raw material will be reduced depending on the concentration of the oxygen purity meter 39 within the specified temperature difference limit. It is designed to adjust the amount of air, and during the operation process, the oxygen purity is much better than the specified value, and the oxygen purity meter 39
Even if the instruction indicates that the amount of oxygen can be increased, if the value of the temperature difference meter 45 exceeds the limit value, priority is given to controlling the temperature difference and the amount of air or product oxygen is increased. The crude argon column 2
This is to stabilize the operation of the 7.

Controlling the amount of product oxygen using only the temperature difference meter 45 has been conventionally done, and has been put into practical use in air separation equipment that does not collect argon, but these are measures to keep the purity of product oxygen constant. , is not suitable for stable operation of the crude argon column 27 and optimum oxygen purity control during argon extraction.

In the argon sampling operation, even if the purity of oxygen exceeds the specified value due to the load condition of the crude argon column 27, temporary fluctuations in the amount of reflux liquid when the adsorber is cut off, etc., the crude argon column 27 The feed stage to the reactor may become rich in nitrogen, and conversely, even if the feed stage is devoid of nitrogen, the oxygen purity may fall below the specified value. In such a case, in the method of the present invention, a limit value is set with the temperature difference gauge 45 to prevent nitrogen from entering the feed stage to the crude argon column 27, so that the operation of the crude argon column 27 will not fail. , it is possible to optimally control the amount of oxygen in the product.

Since the present invention is as described above, it is possible to optimally automatically control the amount of product oxygen generated in an air separation device for extracting argon, which has conventionally been difficult to operate and required many years of experience, resulting in labor savings and This eliminates the shortage of experienced personnel and eliminates losses caused by driving errors.

[Brief explanation of the drawing]

The drawing is a system diagram showing an example of an automatic control method for an air separation device for collecting argon according to the present invention. 2... Capacity control valve, 3... Air compressor, 5...
Adsorption device, 7... Main heat exchanger, 9... Main rectification column,
10...lower tower, 12...expansion machine, 14...upper tower,
16, 22, 25... Expansion valve, 19... Supercooler, 27... Crude argon column, 32... Main condenser,
35...Flow control valve, 39...Oxygen purity meter, 40
...Electronic computer, 41, 42...Flow rate controller, 4
3, 44... Temperature detection end, 45... Temperature difference meter.

Claims (1)

[Claims] 1 In an air separation device that collects argon,
The temperature difference between the saturation temperature between the liquid air blowing stage of the upper column of the main rectification column and the feed stage to the crude argon column and the saturation temperature of oxygen in the main condenser of the main rectification column is detected. A limit value for stable operation of the crude argon column is set, and the amount of product oxygen or feed air is adjusted to constantly control the temperature difference within the limit value, and the oxygen purity meter is controlled within the limit value of the temperature difference. 1. A method for controlling an air separation device for collecting argon, the method comprising controlling the amount of product oxygen or the amount of raw material air according to the oxygen concentration of the argon.