JPH0781780B2 - Oxygen gas production equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxygen gas production apparatus capable of easily producing high-purity and high-pressure oxygen gas.

[Conventional technology]

Conventionally, oxygen gas is produced by using an air separation device and separating the two by utilizing the difference in boiling points of nitrogen and oxygen. That is, in the air separation device,
Usually, as shown in JP-A-56-124880,
In order to generate the cold required for the liquefaction separation of air, it is equipped with an expansion turbine and utilizes the Joule-Thomson effect due to adiabatic expansion. However, since the expansion turbine has an extremely high rotation speed (tens of thousands of revolutions / minute), it is difficult to perform detailed follow-up operation with respect to load fluctuation (change in the amount of product oxygen gas taken out).

[Problems to be Solved by the Invention]

On the other hand, an apparatus has been developed which stores liquid oxygen in a liquid oxygen storage tank and supplies it as cold into the rectification column (Japanese Patent Publication No. 33-9870). Since this device does not use an expansion turbine, it does not have the above-mentioned drawbacks. However, it has a drawback that the cost of the product is high because the liquid oxygen produced by another cryogenic separation device has to be transported to the device. Further, in both of the above devices, the oxygen gas produced is at a relatively low pressure, so if it is intended to use it for high pressure applications, an oxygen gas booster device can be installed to increase the pressure through it. Has been done. However, in addition to the large scale of the device, the size of the device also increases the driving power. In addition, oxygen gas has a strong activity and, in a gas state, has a risk of reacting with lubricating oil of the pressure pump and exploding.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an oxygen gas production apparatus capable of supplying product oxygen gas in a pressurized state and at a relatively low cost, and in a state with less variation in purity. To do.

[Means for Solving the Problems]

In order to achieve the above object, the oxygen gas production apparatus of the present invention comprises an air compression means for compressing the air taken in from the outside, and a carbon dioxide gas and moisture in the compressed air compressed by the air compression means. Removal means for removing, first heat exchange means for cooling the compressed air that has passed through this removal means to an ultralow temperature, and liquefaction separation of the compressed air that has been cooled to an ultralow temperature by this first heat exchange means to make nitrogen a gas state. A rectification column for holding oxygen in a liquid state in the liquid state, liquid oxygen storage means for receiving and storing liquid oxygen from the outside of the device, and a cold source for liquefying compressed oxygen in the liquid oxygen storage means for compressed air. As a first introduction path leading to the inside of the rectification column as above, the liquid level of the liquid oxygen held in the rectification column is monitored, and the liquid oxygen storage means is operated in accordance with the change in the liquid oxygen level. Level that controls the supply of liquid oxygen in The discharge control means, a second introduction path for guiding the nitrogen in a gas state held in the rectification column to the first heat exchange means as a refrigerant, and the gaseous nitrogen in the second introduction path are adiabatically expanded. An expander for cooling by means of the above, an oxygen gas take-out path for guiding liquid oxygen in the rectification tower as a refrigerant to the first heat exchange means, and taking out vaporized oxygen generated by the heat exchange as product oxygen gas, The liquid oxygen discharged from the rectification tower is heated by using the stored liquid air that is provided in the oxygen gas take-out path upstream of the first heat exchange means and is sent from the bottom to the top of the rectification tower. And a liquid oxygen pressurizing pump provided in the oxygen gas outlet passage upstream of the second heat exchanging means.

Next, the present invention will be described in detail based on examples.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the figure, 9 is an air compressor, 10 is a drain separator, 11 is a Freon cooler, and 12 is a set of two adsorption cylinders, inside of which a molecular sieve (excellent adsorption ability at low temperature) is provided. They are filled and alternately perform adsorption and regeneration. That is, one suction cylinder
While the H ₂ O and CO ₂ in the air compressed by the air compressor 9 and cooled by the Freon cooler 11 are adsorbed and removed, the other adsorption column 12 regenerates the adsorbent. Reference numeral 7 is a first heat exchanger, and the compressed air from which the H ₂ O and CO ₂ have been adsorbed and removed by the adsorption column 12 is sent through the compressed air supply pipe 8. The compressed air sent into this is cooled to an ultra-low temperature by the heat exchange action of the first heat exchanger 7. Reference numeral 13 is a rectification tower, and 15 is a lower tower thereof. In the first heat exchanger 7, the condenser 17 generates compressed air that is cooled to an ultralow temperature by the cold heat generated by the expansion turbine 31 and sent through the pipe 8. Then, it is subjected to countercurrent contact with the reflux liquid flowing down and distilled to be stored as oxygen-rich liquid air 18 at the bottom portion, and only nitrogen is kept in the gaseous state at the upper portion. Reference numeral 14 is an upper tower of the rectification tower 13, in which the condenser 17 is arranged. In this condenser 17, a part of the nitrogen gas accumulated in the upper part of the lower column 15 in the rectification column 13 is fed through the pipe 24 and liquefied, and then in the liquid nitrogen reservoir 26 of the lower column 15 through the pipe 25. It is designed to be fed as a reflux liquid. The inside of the upper tower 14 is in a reduced pressure state than the inside of the lower tower 15,
Storing liquid air in the bottom of the lower column _{15 (N 2: 50~70%,} O 2: 30~
50%) 18 passes through the pipe 21, is cooled by the second heat exchanger 21a, is further adiabatically expanded by the expansion valve 20, and is fed,
The nitrogen component, which is the low boiling point component, is vaporized to store the oxygen component in the liquid state in the lower part. 19 is a liquid level gauge, and the expansion valve 20 is controlled by the amount of liquid air at the bottom of the lower tower 15.
Control the opening and closing of. Reference numeral 28 denotes a second introduction pipe for taking out the nitrogen content (purity not so high) accumulated in the upper part of the upper tower 14 as waste nitrogen gas, and guiding the waste nitrogen gas to the first heat exchanger 7 The raw material air is cooled to an ultralow temperature by cold heat, and the waste nitrogen gas that has completed the heat exchange is released into the atmosphere as shown by arrow A. In the lower part of the upper tower 14, liquid oxygen from the liquid oxygen storage tank 23 serves as a cold source for the first introduction pipe.
The internal condenser 17 is cooled together with the liquid oxygen produced in the upper tower 14 by being sent in via 23a. Liquid oxygen is externally supplied to the liquid oxygen storage tank 23 from a tank truck or the like via a pipe 27. 27a is a variable opening valve provided in the first introduction path pipe 23a, and is a level gauge 22a.
Controlled by. That is, this opening degree variable valve 27
a is that the opening is adjusted by a liquid level gauge 22a according to the liquid level of the liquid oxygen 22 accumulated at the bottom in the upper tower 14, and the liquid level of the liquid oxygen 22 is higher than a predetermined height. When it is lowered, the opening becomes large, and the flow rate of liquid oxygen from the liquid oxygen storage tank 23 is increased. Conversely, when the liquid level rises above a predetermined height, the opening is decreased and the flow rate of liquid oxygen is decreased. The liquid level of the liquid oxygen 22 is maintained at a predetermined height. 29 is the lower tower
It is a second inlet pipe for taking out the nitrogen gas accumulated in the upper part of 25 and guiding it to the first heat exchanger 7. Both the second introduction path pipe 29 and the second introduction path pipe 28 are rectification tower 13
The nitrogen gas therein can be collectively included in that it is guided to the first heat exchanger 7. Reference numeral 30 denotes the waste nitrogen gas fed into the first heat exchanger 7 by the second introduction path pipe 29.
The waste nitrogen gas taken out is sent to the expansion turbine 31 by a pipe taken out from the middle of the heat exchanger 7. This expansion turbine 31 is a well-known one, and adiabatically expands the taken-out waste nitrogen gas to generate cold heat, which is merged with the waste nitrogen gas flowing through the inside of the second introduction pipe 28 to be extremely heated. It is cooled and fed again to the first heat exchanger 7. Reference numeral 32 denotes a liquid oxygen take-out pipe, one end of which is open at a position above the bottom of the upper tower 14, and delivers the liquid oxygen staying at the bottom of the tower 14 to the liquid oxygen pressurizing pump 33. The pressurizing pump 33 pressurizes oxygen in a liquid state to a predetermined pressure. As shown in FIG. 2, a high-speed rotation motor 126 is placed on the upper part of the motor support 125 and compressed on the lower part. It is configured by attaching the portion 127 via the liquid oxygen leak prevention portion 128. More specifically, as shown in FIG. 3, a main shaft 135 is provided through the centers of the motor support 125, the liquid oxygen leak prevention unit 128 and the compression unit 127.
135 is connected to the rotary shaft 126a of the motor 126 via a coupling 136, and is connected to a bearing 137 provided inside the motor support base 125 and fixed by a bearing cover 137a and a bearing 138 provided at the tip of the compression unit 127. It is rotatably supported. 140 is a sleeve. The compression unit 127 is
Two spiral type impellers 146 are attached to the upper and lower two stages on the 135, and a casing for accommodating them is provided, and liquid oxygen is sucked from the central suction port 146a of the impeller 146 by the rotation of the main shaft 135. The ejection port 146b on the outer circumference is adapted to eject under pressure. That is, the impeller 14
By rotating 6, suction the liquid oxygen from the suction nozzle 148,
First, the impeller 146 of the first stage pressurizes, and then the pressurized fluid is pressurized by the impeller 146 of the second stage via the passage 147 to raise the liquid oxygen to a predetermined pressure. The liquid oxygen leak prevention portion 128 encloses the outer periphery of the main shaft 135 with a sleeve 150, and further, a labyrinth 151 and a labyrinth cover 152 are provided on the outer periphery of the sleeve 150, and liquid oxygen leaks from the compression portion 127, and the motor support base 125 is provided. I try not to reach inside and cause an explosion. In this respect, the motor support base 125 is airtightly divided into three parts to prevent leaked oxygen from reaching the motor side. 153 is an oxygen discharge pipe,
Even if liquid oxygen leaks from the leak prevention unit 128, the liquid oxygen is vaporized and discharged to the outside so that it does not reach the motor side. In FIG. 1, reference numeral 34 denotes an oxygen transport pipe, which is configured to deliver the liquid oxygen pressurized by the pressure pump 33 to the first heat exchanger 7 via the second heat exchanger 21a. Reference numeral 35 is a product oxygen gas extraction pipe for sending out the product oxygen gas, which has reached room temperature, from the first heat exchanger 7 to the outside of the system.

Reference numeral 36 is a back-up system line, which opens the valve 36a when the air compression system line fails, evaporates the liquid oxygen in the liquid oxygen storage tank 23 by the evaporator 37 and sends it to the pipe 35 to supply the oxygen gas. Don't be jealous. The alternate long and short dash line indicates a vacuum cold storage box. This vacuum cool box blocks heat from the outside and further improves the purification efficiency.

This apparatus produces product oxygen gas as follows. That is, air is compressed by the air compressor 9, water in the air compressed by the drain separator 10 is removed and cooled by the Freon cooler 11, and then sent to the adsorption cylinder 12 in that state to remove H _{2 in} the air. Adsorbs and removes O and CO ₂ . Then,
The compressed air from which H ₂ O and CO ₂ have been adsorbed and removed is sent to the first heat exchanger 7 to be cooled to an ultralow temperature, and in that state, the rectification column 13
Into the lower tower 15 of. Next, this input compressed air is brought into contact with the liquid nitrogen overflowing from the liquid nitrogen reservoir 26 countercurrently, and a part of it is liquefied to bring the liquid air 18 to the bottom of the lower tower 15.
Collect as. In this process, the difference between the boiling points of nitrogen and oxygen (in the standard state, the boiling point of oxygen-183 ° C, the boiling point of nitrogen nitride-1
At 96 ° C), oxygen, which is a high boiling point component in compressed air, is liquefied and nitrogen remains as a gas. Then, the nitrogen gas remaining as such gas is taken out from the second introduction path pipe 29 and fed into the first heat exchanger 7, and when it is heated up to about −140 ° C., taken out from the pipe 30 to the expansion turbine 31. Send out. In this case, the nitrogen gas sent to the expansion turbine 31 is adiabatically expanded by the expansion turbine 31 to generate cold heat, and in that state, the second introduction pipe 28 from the upper tower 14 is supplied.
The waste nitrogen gas delivered by
The heat exchanger 7 exchanges heat with the compressed air sent into the heat exchanger 7 and cools it to an ultralow temperature. On the other hand, the oxygen-rich liquid air 18 accumulated at the bottom of the lower tower 15 is
After being further cooled in the heat exchanger 21a of the expansion valve 2
It is sent in the form of a spray into the upper tower 14 through a 0-attached pipe 21. In the upper tower 14, the liquid air 18 fed in this way vaporizes the nitrogen component due to the difference in boiling point and shifts it to the upper part, liquefying oxygen and causing it to flow downward, and accumulate as liquid oxygen 22 at the bottom. The liquid oxygen take-out pipe 32 takes out the liquid oxygen 22 accumulated at the bottom, pressurizes it with the liquid oxygen pressurizing pump 33, and then heat-exchanges it with the second and first heat exchangers 21a, 7 to produce normal temperature product oxygen gas. To the take-out pipe 35 as. In this way, highly pure oxygen gas is produced.

In particular, even if the demand amount of the product oxygen gas changes, this device can promptly respond to the fluctuation of the demand while keeping the purity constant. That is, when the demand amount of the product oxygen gas rapidly increases, the retention amount of the liquid oxygen 22 in the upper tower 14 decreases, whereby the liquid level becomes lower than the predetermined height. As a result, the liquid level gauge 22a immediately detects the liquid level and the valve 27a
Increase the opening of. As a result, a large amount of liquid oxygen is supplied from the liquid oxygen storage tank 23 into the upper tower 14, and the liquid level of the liquid oxygen 22 in the upper tower 14 rises to a predetermined height. When the demand for product oxygen gas decreases,
The opposite operation is performed. In this way, by controlling the liquid level of the liquid oxygen 22 to a predetermined height at all times, the condenser 17
The amount of reflux liquid generated in step 3 becomes appropriate, and the entire device operates properly. Therefore, an appropriate amount of product oxygen gas can be delivered from the pipe 35 according to the demand amount without changing the purity.

As described above, the oxygen gas production apparatus of this embodiment can not only produce high-purity oxygen gas but also expand the turbine 31.
The rotational speed of the liquid oxygen is constantly kept constant to keep the cooling capacity constant, and the fluctuation of the required coldness based on the fluctuation of demand is controlled by the liquid level gauge 22 from the liquid oxygen supply tank 23.
It is controlled by a and the valve 27a. As a result, the amount of oxygen gas generated can be increased or decreased to smoothly respond to fluctuations in the demand amount of product oxygen gas. That is, the above-described configuration solves the disadvantage of the expansion turbine system that cannot quickly respond to demand fluctuations, and makes use of the advantage of the expansion turbine system that the product cost is low (the cost of transporting liquid oxygen is unnecessary). (Inexpensive late-night power can be used, especially by operating the expansion turbine). Moreover, in this embodiment, the product oxygen gas is delivered in a pressurized state for the purpose of smooth delivery of the product oxygen gas and the use on the consumption side. Since it is not performed, but is performed in a liquid state, the pressurization efficiency is increased, and pressurization can be performed with a small amount of power.
This eliminates the need for a conventional large-scale oxygen gas pressurization device, and has a great effect that equipment cost and power required for pressurization are both about 1/10. Besides,
In particular, oxygen has a strong activity, and in a gas state, it explodes immediately against the lubricating oil of a pressure pump.In a liquid state, such a situation can be prevented, and the seal of the pump is more liquid than a gas. It has the advantage of safety and construction that it is easier.

In each of the above embodiments, the liquid level gauge 22a is used for the variable opening valve 27a.
Although the opening degree is controlled, an opening / closing valve that opens / closes may be used instead of the opening degree variable valve 27a, and the opening / closing of the opening / closing valve may be controlled by the liquid level gauge 22a.

〔The invention's effect〕

As described above, the oxygen gas production apparatus of the present invention includes both the expander such as an expansion turbine and the liquid oxygen storage means, and the expander in which it is difficult to switch the operating speed rapidly is operated at a constant speed at all times. Keeping the cooling capacity constant, and for the fluctuation of the required cold amount based on the fluctuation of the demand for the product oxygen gas, by controlling the supply amount of liquid oxygen from the liquid oxygen storage means by the liquid level detection control means, Increase or decrease the amount of oxygen gas generated. Therefore, it becomes possible to promptly respond to the change in the demand amount of the product oxygen gas without lowering the purity. As a result, the disadvantage of the expansion turbine type in that it is not possible to quickly respond to fluctuations in demand is eliminated, and the low product cost, which is an advantage of the expansion turbine type, can be maintained. Further, since the device of the present invention pressurizes the product oxygen gas not in the gas state but in the liquid state, the pressurization efficiency is increased and the pressurization can be performed with a small amount of power. .
That is, since 1 mol of gas has a large volume of 22.4 l,
A large-scale device is required to pressurize the liquid, but since the liquid has a smaller volume than the gas, the pressurization is relatively easy. This eliminates the need for a conventional large-scale oxygen gas pressurization device, and has a great effect that equipment cost and power required for pressurization are both about 1/10. In addition, oxygen is particularly active, and in a gas state, it reacts with the lubricating oil of the pressure pump and immediately explodes,
In a liquid state, such a situation can be prevented,
As for the seal of the pump, the liquid is easier than the gas, which is a safety and construction advantage. Further, the apparatus of the present invention is provided with the second heat exchange means, and the liquid oxygen discharged from the rectification column is heated by the liquid air sent from the bottom to the upper part of the rectification column, and then the first heat exchange means. The temperature is further increased by heat exchange. Therefore, all the oxygen guided to the first heat exchange means is in a gaseous state, and has a moderate temperature. Therefore, there is no inconvenience that a part of the liquid enters the oxygen entering the first heat exchanging means, heat exchange becomes unsatisfactory, and the overall heat balance is disturbed. Moreover, since the oxygen pressurizing pump is provided on the upstream side of the second heat exchanging means, the liquid oxygen passing through the pump is introduced into the second and first heat exchanging means in a heated state. As a result, the heat exchange efficiency is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a plan view of a pressurizing pump, and FIG. 3 is a sectional view thereof. 7 ... First heat exchanger, 9 ... Air compressor, 12 ... Adsorption column, 13 ... Oxygen rectification column, 22 ... Liquid oxygen, 22a ... Level gauge, 23 ... Liquid oxygen storage tank , 23a ...... First introduction passage pipe, 27a ...... Variable opening valve, 28,29 ...... Second introduction passage pipe, 31 ...... Expansion turbine, 35 ...... Product oxygen gas extraction pipe

Claims (1)

[Claims] 1. An air compression means for compressing air taken in from the outside, a removal means for removing carbon dioxide gas and moisture in the compressed air compressed by the air compression means, and a compression through this removal means. First heat exchange means for cooling air to ultra low temperature, and rectification column for liquefying and separating compressed air cooled to ultra low temperature by this first heat exchange means to hold nitrogen in a gas state and oxygen in a liquid state And a liquid oxygen storage means for receiving and storing liquid oxygen from outside the apparatus, and a first introduction for introducing the liquid oxygen in the liquid oxygen storage means into the rectification column as a cold source for liquefying compressed air. And a liquid level detection for monitoring the liquid level of the liquid oxygen held in the rectification column and controlling the supply amount of the liquid oxygen from the liquid oxygen storage means according to the change in the liquid level of the liquid oxygen. Control means and held in the rectification column The nitrogen in the body state as a refrigerant first
Second introduction path leading to the heat exchange means, an expander for cooling gaseous nitrogen in the second introduction path by adiabatic expansion, and the first heat using the liquid oxygen in the rectification column as a refrigerant. It is provided in an oxygen gas take-out path guided to the exchange means to take out vaporized oxygen generated by heat exchange as a product oxygen gas, and in the oxygen gas take-out path upstream of the first heat exchange means. Second, in which the stored liquid air sent from the bottom to the top is used as a heat source to heat the liquid oxygen discharged from the rectification column
And a liquid oxygen pressurizing pump provided in the oxygen gas extraction passage upstream of the second heat exchange means.