JPH0378126B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an O _{2 production method using an N 2 adsorbent that selectively adsorbs N 2 from a} mixed gas mainly composed of O 2 and N 2 such _as air. The feature is that the cold heat possessed by N ₂ during the regeneration process is recovered by contacting with a cold storage material, and then the heated N ₂ is brought into contact with a dehumidifying adsorbent to regenerate the dehumidifying adsorbent as well. and O ₂
The present invention relates to a method for dehumidifying and recovering cold heat from manufacturing equipment. [Prior art] O ₂ and N ₂ adsorption separation method from air using N ₂ adsorbent has the advantage that the equipment is small and simple and requires almost no maintenance, which is close to _unmanned operation. In recent years, the use of small and medium-sized equipment with a production capacity of 10 to 3000Nm ³ -O ₂ /h has been increasing, and alternatives to cases in which liquid oxygen produced in cryogenic separation equipment is transported and used are progressing. . To give an overview of a typical device, the device consists of an air compressor, two or more N ₂ adsorption towers, and in some cases a vacuum pump. In this device, when compressed air is sent to one tower, the N ₂ in the air is adsorbed and removed by the N ₂ adsorbent filled, and the remaining high-pressure O ₂ flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed N ₂ is released under reduced pressure conditions (sometimes a part of the product O ₂ is flowed in a countercurrent, or a vacuum pump is used to powerfully remove N ₂ ) for regeneration. This is repeated alternately to continuously separate O ₂ and N ₂ . Typical N ₂ adsorbents packed in the adsorption towers mentioned above are:
Na−, which was put into practical use by Union Carbide
It is a 60-70% Ca exchanger of type A zeolite, and contains O ₂ ,
It selectively adsorbs N ₂ from a two-component mixed gas, and the co-adsorption _of O ₂ under air conditions _is
Estimated to be less than 10% of adsorption. As mentioned above, this adsorption-based O ₂ and N ₂ separation device is advantageous in small and medium-sized areas, but it is difficult to produce 1Nm ³ of O ₂ .
It requires 0.75 to 1Kwh, which is higher than the 0.45Kwh of O ₂ produced by large-capacity cryogenic separation.
Furthermore, it is said that there is little merit of scale for increasing the capacity of the equipment, and that it cannot compete with the cryogenic separation method in the region of 3000 Nm ³ -O ₂ /h or more. Therefore, various methods for improving these drawbacks are conceivable, but when describing the improvement methods in relation to the present invention, the following obstacles usually appear. First, to reduce power consumption, it is possible to lower the blowing pressure and perform adsorption operation at low pressure, but since the amount of _N2 adsorption decreases almost in proportion to the pressure,
The capacity of the device increases significantly. Next, in order to increase the amount of adsorption, it is possible to perform the adsorption operation under low temperature conditions, but in this case, although the amount of N ₂ adsorbed increases, the adsorption/desorption rate will decrease significantly, so it is possible to On the contrary, the product O ₂ concentration will be lower than at room temperature. Furthermore, as the temperature decreases, the amount of O ₂ co-adsorbed during N ₂ adsorption increases, so the power consumption rate gradually increases. [Prior application invention] Therefore, the present inventors have already developed a zeolite-based adsorption method in the process of conducting intensive research and experiments on a high-performance O ₂ and N ₂ separation method under low temperature and low pressure adsorption conditions that improves the above-mentioned drawbacks. Ca2 _/ 3-Na1 _/ 3 _- A, rear high o ₂
The Na adsorption tower filled with Na-X in the concentration range increases the amount of N ₂ adsorption under low temperature and low pressure adsorption conditions, and can maintain the N ₂ adsorption rate within a practical range.
and found that the decrease in N ₂ adsorption selectivity was small,
An invention based on this has already been published in Japanese Patent Application No. 58-54626.
The patent applications were filed as Japanese Patent Application No. 58-232348 and Japanese Patent Application No. 58-204408. An embodiment of the invention disclosed in Japanese Patent Application No. 58-54626 will be described below with reference to FIG. 1.05 to 3 ata in compressor 2 through inlet side line 1
The pressurized air enters the dehumidification tower 4 through the flow path 3 and becomes extremely clean pressurized air. The valve 5 installed downstream of the flow path 3' is open, and clean pressurized air enters the adsorption tower 8 through the flow path 6 and the open valve 7. The pressurized air that entered the adsorption tower 8
N ₂ is adsorbed and removed by the N ₂ adsorbent 9, and the O ₂ concentration increases as it moves toward the rear. After this, the pressurized air is supplied to the valves 10, 11, 12 and 11 in the open state.
The product O 2 is recovered as product O ₂ through the product O ₂ tank 13 inserted between 12 and 12 . On the other hand, a part of the product O ₂ is depressurized by the pressure reducing valve 15 located in the middle of the flow path 14, and enters the adsorption tower 8' through the open valve 10', and the adsorption tower 8' passes through the open valve 16 and the flow path 17.
The pressure is reduced by a vacuum pump 18 connected through the adsorption tower 8', so that part of the product O ₂ flows in the opposite direction to the air flow in the adsorption tower 8' under negative pressure, and the adsorbent 9' in the adsorption tower 8' The N ₂ adsorbed on the adsorbent 9' is easily released and the adsorbent 9' is regenerated in a short time. The N ₂ adsorbent 9 of the adsorption tower 8 is saturated, while the N 2 adsorbent 9 of the adsorption tower 8' is saturated.
When N ₂ is released from the N ₂ adsorbent 9' and regeneration is completed,
By switching the inlet air flow path 6 to 6' and performing the methods described so far alternately, product O ₂ can be continuously recovered. In addition, the clean pressurized air line 3' at the inlet
A heat exchanger 19 is installed between the gas line 17 and the gas line 17 whose main component is separated _N2 .
There is also a heat exchanger 22 between the _O2 line 21 and the flow path 3'.
heat exchange is possible. Furthermore, since a compression refrigerator 20 is installed in the flow path 3', the adsorption towers 8 and 8' are extremely efficiently cooled and set to a low-temperature condition. When switching the adsorption tower, it is important not only to simply switch from flow path 6 to 6' (or vice versa), but also to prevent the inlet air from blowing through due to pressure increase immediately after switching, and to In order to minimize the release of the O ₂ remaining at the rear and the pressurized air at the front to the outside of the system, first, the valves 10, 15, and 10' are fully opened to remove the O ₂ remaining at the rear of the adsorption tower 8 immediately after adsorption. A portion is transferred to the adsorption tower 8' immediately after regeneration. At this time, the pressure of adsorption tower 8 is P ₀ (ata), and the pressure of adsorption tower 8' is P ₁ (ata)
Then, the pressure after pressure equalization will be approximately P ₀ +P ₁ /2 (ata). After this, the adsorption tower 8', which has reached approximately P ₀ + P ₁ /2 (ata), opens the valves 10 and 11' to equalize the pressure of the product O ₂ tank 13 and the adsorption tower, and then the adsorption tower 8' is exposed to even higher pressure O2. Fill with ₂ . The pressure P ₂ (ata) when the pressure is equalized with the product O ₂ tank 13 is the dead capacity of the adsorption towers 8 and 8' (volume of the space not occupied by adsorbent in the adsorption tower).
V ₁ (l), the capacity of the product O ₂ tank is V ₂ (l),
Assuming that the pressure in the product O ₂ tank 13 before pressure equalization is approximately equal to P ₀ (ata), the equalization pressure P ₂ (ata) is
Roughly P ₂ = P ₀ + P ₁ /2V ₁ +P ₀ V ₂ /V ₁ +V ₂ , and from P ₁ (ata) when simply switching towers
Compared to _the rapid increase in pressure to _{P 0} (ata), _{the above} operation reduces _the
) Since the pressure is gradually increased, it is possible to prevent air from blowing through when the pressure is increased, and to minimize the release of residual O ₂ and high-pressure air to the outside of the system during the desorption process. Air separation was carried out using the air separation apparatus shown in FIG. 3 using the above operating method. The operating specifications of the device are shown in Table 1.

[Problem that the invention seeks to solve]

However, the pressure swing method shown in FIG. 3 has the following drawbacks, which leads to increased equipment costs and power costs. Since the dehumidification tower 4 is installed independently, the equipment cost increases accordingly. For the dehumidification tower 4, either the temperature swing method or the pressure swing method can be considered depending on the regeneration method, but the temperature swing method requires power consumption for the heater and the replenishment of adsorbent, and the pressure swing method If so, a vacuum pump will be required (in this case, the adsorption pressure is low, so atmospheric pressure regeneration is insufficient) and power consumption will be added. Heat exchanger 19 for cold heat recovery between inlet air and desorption _N2
Since it is a gas-gas heat exchanger, it is expensive and requires a considerable amount of space. If the above outlet dew point rises for some reason, the temperature of the adsorption process (or the surface temperature of the heat exchanger)
When the temperature drops below 0℃, the heat exchanger 19, 22 refrigerator 2
0. Moisture freezes on the valves 5, 6, 6', 7, and 7', making normal operation impossible. It is also quite difficult to remove. Valve 5, 6, 6', 7, 7', 16, 16',
10, 10', 11, 11', 12, and 15 are in the low-temperature range, so it is necessary to consider cold storage, etc. [Means for Solving the Problems] In order to solve these various problems in pressure swing type O ₂ production under low temperature and low pressure conditions, the present inventors have
As we proceeded with process considerations, we decided to use a cold storage material to recover the cold energy of desorbed _N2 during the regeneration process.
The dehumidifying adsorbent is regenerated by the contact between the desorbed _N2 and the dehumidifying adsorbent, and in the adsorption process, the moisture in the inlet air can be removed by the dehumidifying adsorbent, and the coolant can be used for cooling. I discovered that. This eliminates the need for an independent dehumidifier and inlet air-desorption _N2 gas-gas heat exchanger, solving the above problems and significantly reducing equipment costs and dehumidifying power. . That is, the present invention provides a synthetic zeolite-based adsorbent, particularly an N ₂ adsorption tower filled with sodium phaujasite, a mineral name represented by Na- In at least two N ₂ adsorption towers filled with Nitrogen contained in the gas is selectively adsorbed, and high-purity oxygen or oxygen-enriched gas flows out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen does not have to recirculate the product to 0.08 ata or more and 0.5 ata or less. O ₂ characterized by being depressurized and regenerated
In the manufacturing method, from the inlet air side, connect an adsorbent for dehumidification, a cold storage material, an air-cold heat heat exchanger for cold heat supply, and a zeolite-based _N2 adsorbent in order,
In the adsorption process, successive dehumidification using an adsorbent for dehumidification from the inlet air side, cooling by contact between the cold storage material and air, replenishment of cold heat deficiency, and zeolite-based N ₂ adsorption under the above adsorption pressure conditions O 2 is produced by adsorption and removal of N ₂ from the air using a regeneration agent, and in the regeneration process, O ₂ is produced by adsorption and removal of N 2 from the air.
After desorbing N ₂ , the cold heat of N ₂ is first brought into contact with a cold storage material and recovered, and then the heated N ₂ is brought into contact with a dehumidifying adsorbent to regenerate the dehumidifying adsorbent. It is characterized by the fact that it eliminates the conventional independent dehumidification equipment and cold recovery using gas-gas heat exchange, and reduces dehumidification power costs and equipment costs _. This project proposes a cold heat recovery method. [Example] Hereinafter, the method of the present invention will be explained in detail with reference to Examples. (1) First Example In order to demonstrate the effectiveness of the present invention, O ₂ and N ₂ were separated from air using a sodium phaujasite-based N ₂ adsorbent such as Na-X using the air separation device shown in Figure 1. I tried. The details of the implementation will be explained below based on FIG. Compressor 3 through filter 30 inlet channel 31
2, approximately 750Nm ³ /h of air is pressurized to 1.05 to 3ata, passes through the flow path 33 and aftercooler 34, and is
Cooled to ℃. Valve 35 flow path 3 opened after this
It enters the dehumidification tower 37 through 6. The dehumidifying tower 37 is filled with about 25 kg of silica gel as a moisture adsorbing adsorbent 38, and moisture is removed to a dew point of -70°C. After that, a product O2 line 40 and a plate fin heat exchanger 41 are installed in the flow path 39, and the product _O2 line 40 and plate fin heat exchanger 41 are installed.
_O2 temperature is from -15℃ with plate fin heat exchanger 41
The temperature rises to 30℃. At that time, the air dehumidified in the dehumidification tower 37 is cooled from 30°C to 25°C by the plate fin heat exchanger 41, enters the cold storage tower 43 through the flow path 42, and is lowered in temperature while contacting the cold storage material 44, At the outlet, it is cooled down to -10℃. In this example, the cold storage material 44 has a thickness of 0.6 mm and a width of 16 mm.
A corrugated aluminum plate with a diameter of 50 mm was used, and 50 kg was packed per tower. The air cooled to -10℃ is transferred to the refrigerator 45
The -22°C freon flowing through the flow path 46 is further cooled by the heat exchanger 47, reaching the coldest temperature of approximately -15°C, and Na is released as an O ₂ adsorbent 49 through the flow path 48.
-The N ₂ adsorption tower 50 is filled with approximately 2.5 TON of X. N ₂ in the air is adsorbed and removed by the N ₂ adsorbent 49 and the O ₂ concentration increases, and the O 2 concentration increases through the outlet flow path 40, the plate fin heat exchanger 41, and the opened valve 51 to the flow path 52.
110 Nm ³ −O ₂ /h of product O ₂ with an O ₂ concentration of 93% is collected from the sample. On the other hand, the N ₂ adsorption tower 50' in the regeneration process is depressurized through the channel 56 by the vacuum pump 55 with the valves 35', 51', 53, and 54 closed and the valve ₅₃ ' opened. From 49' N ₂
is separated in the countercurrent direction from that during adsorption. left
_N2 passes through the flow path 48' and the heat exchanger 47' to the cold storage tower 4.
3', the cold energy is recovered by the cold storage material 44', and the temperature rises to about 25°C in the flow path 39'. After that, the dehumidifying tower 37' is dried with N ₂ under reduced pressure in a countercurrent to that during adsorption.
flows, water is separated from the adsorbent 38' and N ₂
At the same time, it is discharged from the vacuum pump 55 to the outside of the system through the flow path 36', the valve 53', and the flow path 56. In this example, the adsorption step was alternately switched between 75 seconds and the regeneration step between 60 and 240 seconds. In addition, just before switching the tower, valves 35, 3
Close valve 5', 51, 51', 53, 53'.
4 was opened and the residual O ₂ concentrated behind the N ₂ adsorption tower 50 during the adsorption step was transferred to the N ₂ adsorption tower 50' under reduced pressure conditions to equalize the pressure between the two towers. This is extremely effective in improving the O ₂ recovery rate and slowing down the rise and fall of pressure to suppress disturbances within the column. (If this step is omitted, the O ₂ recovery rate will drastically decrease from around 70% to _about 40%.)
7', cold storage tower 43, 43', plate fin heat exchanger 4
1 and 41' are entirely surrounded by a cold insulating material 57. Air separation was carried out using the air separation apparatus shown in FIG. 1 using the above operating method. The operating specifications of the device are shown in Table 2.

【table】

[Table] O ₂ and N ₂ were separated from air under the operating conditions shown in Table 2. Table 3 summarizes the comparison of experimental results between the conventional example shown in FIG. 2 and Table 1 and the embodiment of the present invention shown in FIG. 1 and Table 2. (The conventional dehumidification process was based on a pressure swing method with an adsorption pressure of 1.2ata and a regeneration pressure of 0.05ata.)

【table】

〔Effect of the invention〕

As explained in detail above, the present invention requires less power consumption and equipment costs than conventional O ₂ production equipment, and produces O ₂ from a mixed gas that is very useful industrially.
This paper proposes a method for dehumidifying and recovering cold heat from manufacturing equipment.

[Brief explanation of drawings]

FIG. 1 is an illustrative diagram of an air separation device used to carry out the first embodiment of the dehumidification/cold heat recovery method for _{an O 2 production} device of the present invention, and FIG. FIG. 3 is an illustration of an air separation device used to carry out the second embodiment of the wet/cold heat recovery method. FIG. 3 is an illustration of an air separation device used to carry out the conventional separation method. 37, 37'... Dehumidification tower, 38, 38'... Adsorbent for moisture adsorption, 41, 41'... Plate fin heat exchanger, 43, 43'... Cold storage tower, 44, 44'...
Cold storage material, 49,49'... _N2 adsorbent, 50,5
0'... _N2 adsorption tower.

Claims (1)

[Claims] 1 At least two adsorption towers filled with zeolite-based _N2 adsorbent are charged with a gas mixture mainly consisting of oxygen and nitrogen at a pressure of 3 ata above atmospheric pressure at a temperature below room temperature.
The nitrogen contained in the mixed gas is then selectively adsorbed by flowing into an adsorption tower, and high-purity oxygen or oxygen-enriched gas is flowed out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is heated to 0.08 ata or more. In the O ₂ manufacturing method, which regenerates by reducing the pressure without recirculating the product to 0.5 ata or less, from the inlet air side, the dehumidifying adsorbent, the cold storage material, the air for cold heat supply, and the heat exchange of cold heat and Connect zeolite _N2 adsorbent in order,
In the adsorption process, sequential dehumidification is performed from the inlet air side using an adsorbent for dehumidification, cooling by contact between the cold storage material and air, replenishment of cold heat deficiency, and zeolite-based N ₂ adsorption under the above adsorption pressure conditions. Oxygen is produced by adsorption and removal of _N2 from the air using a regeneration agent, and in the regeneration process, oxygen is removed in the countercurrent direction under the above reduced pressure conditions.
N ₂ is desorbed, first the cold heat of N ₂ is brought into contact with a cold storage material and recovered, and then the heated N ₂ is brought into contact with a dehumidifying adsorbent to regenerate the dehumidifying adsorbent. A method for dehumidification and cold recovery for O ₂ production equipment, characterized by: