JPS621434A - Dehumidification/heat recovery method of gas separation apparatus - Google Patents

Abstract

PURPOSE:To reduce power cost, in a pressure swing method, by interposing a dehumidifying part and a heat exchange part in a flow passage, which supplies a gaseous mixture to an adsorbing tower, from the upstream side and performing dehumidification and cooling in an adsorbing process while reversely flowing adsorbed gas in a regeneration process. CONSTITUTION:Air compressed by a compressor 32 is passed through a dehumidifying tower 37 and subsequently cooled by a plate fin heat exchanger 41 and further cooled by a cooling tower 43 and again cooled by a heat exchanger 47 to enter a N2-adsorbing tower 50 to adsorb N2 while a product O2 is collected. The N2-adsorbing tower 50' in a regeneration process is reduced in pressure by a vacuum pump 55 and desorbed N2 reaches a cooling tower 43' through a heat exchanger 47' to recover cold heat and reversely flows through a dehumidifying tower 37' while dry N2 is flowed to regenerate the humidifying tower 37' and moisture is discharged out of the system along with N2 from the vacuum pump 55.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas separation device using a pressure swing method.
This relates to a method for regenerating the dehumidifying agent and recovering the cold energy used in the adsorption process in the adsorbent regeneration process.0 [Prior Art] One of the methods of separating mixed gases One method is the pressure swing method. This is a method in which gases are separated using an adsorbent that adsorbs specific gases, and the adsorbed gases are desorbed by changing the pressure (swing). Various adsorbents are available, and various mixed gases are separated.

A separation method in which air is separated into N2 and O2 using an adsorbent that selectively adsorbs N2 has the advantage that the equipment is small and simple, and requires almost no maintenance as it can be operated unmanned. For this reason, 02 production volume is 10 to 3,00ONtr? -〇2/)
In recent years, the number of uses for small and medium-sized oxygen production equipment has been increasing, and replacement of cases where liquid oxygen produced in cryogenic separation equipment is transported and used is progressing.

Let me give an overview of the typical devices.

The apparatus consists of an air compressor, two or more N2 adsorption towers, and possibly a vacuum poise. In this device, when compressed air is sent to one column, the N
N2 in the air is adsorbed and removed by the 2 adsorbent, and the remaining high pressure 02 flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed N2 is released under reduced pressure conditions (sometimes a part of product 02 is flowed in a countercurrent, or a vacuum pump is used to forcefully release N2).
(There are also methods for removing the .). This is repeated alternately to continuously separate 02 and N2. A typical N2 adsorbent packed in the adsorption tower mentioned above is a 60-70% Ca exchanger of Na-A type zeolite, which was put into practical use by Union Carbide. The co-adsorption of 02 under air conditions is estimated to be less than 10 times the amount of N2 adsorption.

02 due to this adsorption. As mentioned above, N2 separation equipment is advantageous in small and medium-sized areas, but it takes 0.75 to produce IN-02.
The power consumption is larger than the 0.45 Kwh of 02, which is manufactured by large-capacity cryogenic separation method. Also, there is little merit of scale for increasing equipment capacity (3,0
0ON7! ' It is said that it cannot compete with the cryogenic separation method in the range of Os+/h or higher.

Therefore, various methods of improving these drawbacks can be considered, but when describing methods of improvement in connection with the present invention, the following problems usually occur.

First, in order to reduce power consumption, it is possible to lower the blowing pressure and perform the adsorption operation at low pressure, but since the amount of pN2 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 may be possible to perform the adsorption operation under low temperature conditions, but in this case, although the amount of N2 adsorption increases, the adsorption/desorption rate will decrease significantly, so the length of the column remains the same. The concentration of product 02 at room temperature is actually lower than that at room temperature.

Furthermore, as the temperature decreases, the amount of 02 co-adsorbed during N2 adsorption increases, so the power consumption rate gradually increases.

Therefore, the present inventors have already conducted intensive research and experiments on a high-performance separation method for 02°N2 under low-temperature, low-pressure adsorption conditions that improves the above-mentioned drawbacks.
In particular, Ca2/3-
If a Na/3-A type adsorbent is inserted and a Na-X type adsorbent is filled in the rear high 02 concentration area and a N2 adsorption tower is used, the amount of N2 adsorption will increase under low temperature and low pressure adsorption conditions. We discovered that it is possible to maintain the N2 adsorption rate within a practical range, and that the decrease in N2 adsorption selectivity is small.

The method will be explained below with reference to FIG.

1.05 to 3 at compressor 2 through inlet side line 1
The air pressurized to m enters the dehumidification tower 4 from the flow path 3 and becomes extremely clean pressurized air.

The valve 5 installed downstream of the channel element is open,
Clean pressurized air enters adsorption tower 8 through channel 6 and valve 7 which is open. The pressurized air that has entered the adsorption tower 8 has N2 adsorbed and removed by the N2 adsorbent 9, and the 02 concentration increases as it goes toward the rear. The pressurized air is then recovered as product 02 through the product 02 tank 13 inserted between the open valves 10.11.12 and 11.12. On the other hand, a part of the product 02 is depressurized by the pressure reducing valve 15 located in the middle of the flow path 14, and enters the adsorption tower through the open valve 10', and enters the adsorption tower 8' through the open valve 16' and the flow path 17'.
It is powered by a vacuum pump 18 connected through the air.

For this reason, part of the product 02 flows in the adsorption tower 8' in the opposite direction to the air flow under negative pressure, and the N2 adsorbed on the adsorbent 9' in the adsorption tower 8' is easily separated from the adsorbent 9'. will be played in a short time. When the N2 adsorbent 9 of the adsorption tower 8 is saturated and, on the other hand, N2 is separated from the N2 adsorbent q of the adsorption tower 8' and regeneration is completed, the inlet air flow path 6 is switched to 6' and the method described so far is performed. By performing these steps alternately, product 02 can be collected continuously. Note that a heat exchanger 19 is provided between the clean pressurized air line 3' at the inlet and the gas line 17 whose main component is separated N2, allowing heat exchange.

There is also a heat exchanger 22 between the product 02 line 21 and the flow path 3'.
Heat exchange is possible. Also, a compression type refrigeration system [20] is installed in the flow path 3'.

Very efficiently, adsorption towers 8 and 'o-8' are cooled and set to low temperature conditions. In addition, when switching the adsorption tower, it is necessary to not only simply switch from flow path 6 to 6' (or vice versa), but also to prevent inlet air from blowing away due to pressure increase immediately after switching, and to prevent air from remaining at the rear of the adsorption tower. To minimize the release of pressurized air from the front and outside of the system.

First, the valves 10, 15, and 10' are fully opened, and a portion of the remaining 02 at the rear of the adsorption tower 8 immediately after adsorption is transferred to the adsorption tower 8' immediately after regeneration. At this time, the pressure of the adsorption tower 8 is Pt]s (atm
) The pressure of the adsorption tower 8' is 1 pt (atm). After this, the pressure of the adsorption tower 8' is equalized by opening the valves 10' and 11' to equalize the pressure of the product 02 tank 13 and the adsorption tower at approximately P o + P I (atm). Full,
Light. Pressure P2 (a
tm) is the dead capacity of the adsorption towers 8 and 8' (the volume of the space not occupied by the adsorbent in the adsorption tower) is V + (L), and the product 02
Assuming that the capacity of the tank is vl (1) and the pressure of product 02 tank 13 before pressure equalization is approximately equal to Po (atm),
The pressure becomes equalized, and the pt (atm
) to Po(atm) in operations above 9, pt(atm), ""(atm),
Pz(atm).

Since the pressure is gradually increased to Po (atm), it prevents air from blowing through when the pressure increases, and reduces the residual 0.2. Measures can be taken to minimize the release of high-pressure air outside the system.

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.

Table 1: Adsorption device specifications Under the operating conditions shown in Table 1, 02 and N2 were completely separated from air.

In addition, in the process shown in FIG.
4. Valve 15. It is not necessarily necessary to flow countercurrently under reduced pressure through the column in the regeneration step in the order of valve 10'.

Note that it is desirable to equalize the inter-column pressure at the end of the adsorption step (and regeneration step) for at least 6 seconds or more.

=Problems to be Solved by the Invention] However, the pressure swing method shown in FIG. 3 has the drawbacks listed below, and has the disadvantage of increasing equipment costs and power costs.

That is, (1) Since the dehumidification tower 4 is installed independently, the equipment cost increases accordingly. As 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, while the pressure swing method requires the addition of a vacuum pump (this In some cases, the adsorption pressure is low, so atmospheric pressure regeneration is insufficient), and the power consumption for this is additional.

(2) The cold heat recovery heat exchanger 19 between the inlet air and the desorption N2 performs gas-gas heat exchange, so it is expensive and requires a considerable amount of space.

(2) If the dew point at the outlet of the dehumidification tower 4 rises for some reason, and the concentration in the adsorption process (or the surface temperature of the heat exchanger) falls below 0°C, the heat exchanger 19, 22. Compression refrigerator20. Pulp 5゜6, 6', 7. Water freezes at 7', making normal operation impossible. It is also quite difficult to remove.

■Valve 5, 6. ．． 6', 7.7'1.1□e,
167, 1o, '1. o';11.11', 12.15
is in the low temperature range.

It is necessary to consider cold storage, etc.

To separate the air into N2 and 02, use the above-mentioned more N2
02 adsorbent may be used without using an adsorbent.

The pressure swing method is also used to separate CO in exhaust gas and to separate and recover Kr and Xe from radioactive off-gas.

Although there are many points to be considered in the future regarding the type of adsorbent used in these cases, temperature and pressure conditions, etc., many adsorbents that are efficient in the low temperature range have been developed. However, the cost of power to cool the mixed gas is high, and it is thought that there are no devices in actual operation.

[Means for solving problems]

The method of the present invention is used in a device that separates mixed gas using a pressure swing method, and a dehumidification section and a heat exchange section are interposed from the upstream side of the flow path that supplies mixed gas to an adsorption tower. In the process, the mixed gas is dehumidified and cooled, and then a specific gas is adsorbed by the adsorbent packed in the adsorption tower.In the regeneration process, the adsorbed gas is passed through the mixed gas flow path. Let it flow back through.

The cold energy of the adsorbed gas is recovered in the heat exchange section.

This is a method of regenerating the dehumidifying section with heated adsorbed gas.

[Effect]

Depending on the type of adsorbent, cooling the mixed gas may be desirable for gas separation.

In the method of the present invention, in the adsorption step, the mixed gas is first dehumidified in the dehumidification section, cooled in the heat exchange section, and then supplied to the adsorption tower. The gas adsorbed in the adsorption tower is desorbed, flows back through the mixed gas flow path, and is recovered via the heat exchange section and dehumidification section, but the adsorbed gas is sufficiently cooled and the gas desorbed in the regeneration process is recovered. The cold energy is recovered by a heat exchanger. Therefore, the gas temperature rises, and since the adsorbed gas is dry and has little moisture, when passing through the dehumidifying section, the moisture adsorbed by the dehumidifying agent is removed and the dehumidifying agent is regenerated.

Furthermore, the ice that has formed in the flow path is sublimated and removed by the flow of the dry adsorbed gas.

〔Example〕

The method of the present invention will be explained in detail below with reference to Examples.

Example 1 In order to demonstrate the effectiveness of the present invention, 02. N2 separation was attempted.

The details of the implementation will be explained below based on FIG.

Through the filter 30 and the artificial flow path 31, the compressor 32
50 Nrr? /h of air is pressurized to 1.05 to 3 atm, and the flow path 33. Passed through aftercool 234 to 30℃
cooled until After this, the pulp 35 enters a dehumidification tower 37 through a channel 36. The dehumidifying tower 37 is filled with approximately 25 kg of silica gel as a dehumidifying agent 38, and has a dew point of -70.
Moisture is removed up to ℃.

A plate fin heat exchanger 41 is installed between the flow path 39 and the product O2 line 4°, and the temperature of the product 02 is raised from -15°C to 30°C by the plate fin heat exchanger 41. At this time, the air dehumidified in the dehumidification tower 37 is cooled from 30° C. to 25° C. in a plate-fin heat exchanger 41 and passes through a flow path 42.

The cold storage material 4 enters the cold storage base 43 which is a cold storage material type heat exchanger.
4, and at the outlet of the cold storage base 43, the temperature drops to 110
Cooled to ℃.

In this embodiment, the cold storage material 44 has a thickness of 0.6 and a width of 16y+.
Uses am aluminum corrugated plate.

One tower Todoroki filled with 50kli'. The air cooled to -10°C flows from the refrigerator 45 through the flow path 46.
℃ is further cooled in the heat exchanger 47 through which Freon flows, reaching the coldest temperature of approximately -15℃.N
2 adsorption tower 50. N2 in the air is adsorbed and removed by the N2 adsorbent 49, and the O2 concentration increases. Product 02 with a 02 concentration of 93% is passed through the flow path 52 through the opened valve 51 to 110
Nm'02/h was collected.

On the other hand, the N2 adsorption tower 50' which is in the regeneration process has a valve 35'.
, 51', 53, and 54 are closed, and when the valve 53' is opened, the pressure is reduced through the flow path 56 by the vacuum pump 55, and N2 is released from the N2 adsorbent 49' in a direction countercurrent to that during adsorption. ing. The separated N2 enters the cold storage base 43' through the flow path 48' and the heat exchanger 47', and its cold heat is recovered by the cold storage material 44', and the temperature rises to about 25° C. in the flow path 39'. After that, dry N2 flows through the dehumidifying tower 37' in a countercurrent direction to that during adsorption under reduced pressure conditions, so water leaves the dehumidifying agent 38' and goes along with the N2 to the channel 36', the valve 53', and the channel 56. It is discharged from the vacuum pump 55 to the outside of the system through the vacuum pump 55.

In this example, the adsorption step was carried out for 75 seconds.

The regeneration steps were alternately switched from 60 to 240 seconds.

In addition, just before switching the tower, close the valves 35°35' and 5.
1, 51', and 53.53' are closed and only the valve 54 is opened to remove the remaining 0 concentrated at the rear of the N2 adsorption tower 50 during the adsorption process.
2 was transferred to the N2 adsorption tower 50' under reduced pressure conditions to equalize the pressure between the two towers. This is extremely effective in improving the 02 recovery rate and slowing down the rise and fall of pressure to suppress disturbances within the column. (If this step is omitted, the recovery rate of 02 will drastically decrease from around 70% to about 40%.) In addition, N2 adsorption tower 50.50', heat exchanger 47.47'
, cold storage base 43.43', plate fin heat exchanger 41.
41' is 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 2 Adsorption device specifications 02.0 from air under the operating conditions shown in Table 2. Nzi separated friends.

The conventional example shown in Figure 3 and Table 1, and the conventional example shown in Figure 1 and Table 2.
Table 3 summarizes the comparison of the experimental results with one example of the invention shown in the table.

(The conventional dehumidification process was based on a pressure swing method with an adsorption pressure of 1.2 atm and a regeneration pressure of 0.05 atm.) Table 3 Comparison of the conventional example and an embodiment of the present invention (Operating conditions °°
°Adsorption 1 force"・'°""・Regeneration pressure Q, 2at"・Switching time °° seconds・) Inter-column pressure equalization time 10 seconds, adsorption temperature -15
℃ Example 2 As shown in Figure 2, in Example 1, the dehumidification tower 37.37
', plate fin heat exchanger 41.41', cold storage base 43
．． 43', heat exchanger 47, 47', N2 adsorption tower 50
, 50' are flow paths 39.39', 42.42', 48.4
8', but in this example, N2
A dehumidifying agent 38 is introduced into the adsorption tower 50 or 50' from the inlet air side.
．． 38', an air-product 02 heat exchanger 41.41', a cold storage agent 44.44', and a coldest cold heat exchanger 47.47'. In addition.

In FIG. 2 illustrating Example 2, Example 1 (FIG. 1)
The same parts are given the same numbers. The action and function remain the same.

By simplifying the equipment, equipment costs for towers and tanks can be reduced by 10%.
% reduced. In addition, since the intrusion heat was reduced by approximately 15%, the refrigerator 45
．． The coldest heat exchanger 47°47' and the cold insulation material 57 were also saved proportionately.

Example 3 In Example 2, N2 adsorption tower 5 was used instead of Na-X.
Ca as N2 adsorbent 49°49' in front of 0.50'
In Examples 1 and 2, 93% of 110 Ni-02/h was produced by filling 2/3-Na 1/3-A with Na-X [N2 adsorbent 49.49 'l
Whereas 2.5 TON was charged per column, 2. IT
Savings (approximately 15%) were achieved in ON filling. Note that the recovery rate remains almost unchanged.

〔Effect of the invention〕

According to the method of the present invention, the required power unit and equipment cost are lower than that of conventional gas separation equipment, and a method for dehumidifying and recovering cold heat is proposed for an equipment for separating component gases from a mixed gas, which is very useful industrially. It is something to do.

[Brief explanation of the drawing]

Figure 1 is an illustrative diagram of an apparatus used to implement Example 1 of the dehumidification/cold heat recovery method for a gas separation device that embodies the method of the present invention, and Figure 2 is an illustration of the apparatus used to implement Example 2 of the present invention. FIG. 2 is an illustration of the apparatus used to carry out the conventional separation method. 37, 37'... Dehumidification tower, 41, 41'... Heat exchanger. 43.43'...Insoukaba Saki cold storage tower arrow, 49.49'
6...Adsorbent, 50.50'...Adsorption tower.

Claims (1)

[Claims] A mixed gas at room temperature or lower is flowed into an adsorption tower at a pressure higher than atmospheric pressure, a specific gas in the mixed gas is selectively adsorbed by the adsorbent packed in the adsorption tower, and unadsorbed gas is left in the adsorption tower. In a gas separation device that regenerates the adsorbent by reducing the pressure inside the adsorption tower and releasing the gas adsorbed by the adsorbent, a dehumidification section, a heat An exchange section is provided to dehumidify and cool the mixed gas in the adsorption step, and bring the mixed gas into contact with the adsorbent, and in the regeneration step, the adsorbed gas is passed through the mixed gas flow path. 1. A dehumidification/cold heat recovery method for a gas separation device, which comprises causing the adsorbed gas to flow backwards, recovering the cold heat of the adsorbed gas in a heat exchange section, and regenerating the dehumidification section with the heated adsorbed gas.