JPS6125619A - Pressure swing system gas separation utilizing cold heat - Google Patents

Abstract

PURPOSE:To lower power consumption of a vacuum pump in pressure swing adsorbing process, by utilizing cold heat of an adjoining detaching gas. CONSTITUTION:Air is introduced to pretreating towers 6, 6' through an air compressor 1, a flow passage 2, an air cooler 3 and a flow passage 4 and processed by adsorbents 7, 7'. The adsorbed H2O and CO2 are removed by a vacuum pump 12, and the adsorbent repeats regeneration and adsorption. Then, air entered a flow passage 9 is cooled through heat exchangers 13, 14, and further cooled by a heate exchanger 29 with LNG cold heat 30 and enters adsorbing towers 18, 18'. There, N2 is adsorbed, and O2 of high purity is put out to outside of the system. Adsorbing towers 18, 18' are regenerated alternately by a vacuum pump 26, and the entrance of the vacuum pump is cooled by a heat exchanger 28 with LNG cold heat.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a gas separation method using an adsorbent.
In particular, it relates to improvements in pressure swing gas separation methods.

(Prior art) As a conventional example, N! Na4 type zeolite is used as the adsorbent, and the adsorption pressure is 1 to 3 ata.

The production of 03 from air under operating conditions of 0.05 to 0.5 ata as desorption pressure and 10 to -50°C as adsorption temperature will be described with reference to FIG.

In Figure 2, 1 is an air compressor, with a maximum of 5 at
The air pressurized near a passes through a flow path 2, is cooled to around 30° C. by an air cooler 3, and enters a pretreatment tower 6 through a flow path 4 and an open valve 5. Pretreatment tower (adsorption tower) 6 and 6
' Dehumidifying silica gel is placed in the front half of the building, and zero is placed in the back half.
It is filled with Ma-'X adsorbents 7 and 7' for removing 0g, and the dew point -
Clean air with a temperature of 70°C or lower and a concentration of 2 PPm or lower flows through. In the adsorption tower 6', no(lube S/, a/
is closed and valve 10' is open, flow path 11,
130 adsorbed on the adsorbent 7' through the vacuum pump 12
, co! is removed and the adsorption capacity is regenerated.

The operation mode of the pressure swing method is to repeat this method alternately, and the N3 adsorption at the rear of the flow path 9 is also performed using the same method.

The air cooled through the heat exchanger 15 and the heat exchanger 14 at the rear of the flow path 9 is cooled to the lowest temperature by the refrigerator 15, and then reaches the adsorption tower 18 through the flow path 16 and the valve 17 in an open state. a in the adsorption tower 18, N used as an N3 adsorbent
From the pulp 20 in the open state, high-purity air with N snow removed from the air flows into the flow path 21, where the cold heat is recovered by the inlet air in the heat exchanger 13, and the flow is carried out. It is carried out of the system from route 22.

On the other hand, for the adsorption tower 18', the valve 17'.

20' is closed and the pulp 23' is opened and the flow path 2
4, communicates with the heat exchanger 14, flow path 25, and vacuum pump 26.

For this reason, when the pressure is reduced, the 9N adsorbed by the Na-x used as the N3 adsorbent is recovered from the inlet air by the heat exchanger 14, and then removed from the system by the vacuum pump 26.

By repeating this operation alternately for the adsorption towers 18 and 18', the product 03 can be continuously extracted from the air.

Note that the part surrounded by a broken line here is a cold box 27 for keeping the adsorption tower at a low temperature.

This method is popular because it is easy to maintain and easy to operate. The electrical energy required to manufacture 03 of ``I MEll'' is α4 to α6 k'qh, and the breakdown is K as shown in Table 1, and the power of the vacuum pump and refrigerator is large.

Table 1 (Adsorption pressure 1.2 ata, regeneration pressure 0.2
ata, adsorption temperature -15°C) Other examples of pressure swing type gas separation using low temperature conditions and vacuum regeneration are shown in Table 2.

Table 2 It is also known to lower the gas temperature at the inlet of the compressor in order to reduce the power consumption of the compressor. It has not been adopted.

(Problems to be Solved by the Invention) The present invention seeks to provide a method that can overcome the disadvantage of high power consumption of vacuum pumps of the prior art in the pressure swing method that uses both low-temperature adsorption and vacuum regeneration. be.

(Means for Solving the Problems) The present invention utilizes a pressure swing gas separation method in which cold heat from a cold source adjacent to the separation system is transferred through a flow of ultra-dry gas with a dew point of -70°C or less that is free from freezing. This cools the inlet of the vacuum pump, significantly reducing power consumption. That is, the present invention is a pressure swing type gas adsorption separation method in which adsorption is performed under pressurized conditions above atmospheric pressure and regeneration is performed under reduced pressure conditions below atmospheric pressure. One part is used to cool the adsorption tower, and if there is excess cold energy, the other part is used to cool the desorption gas at the vacuum pump inlet to reduce the power consumption required for separation.
The gist of this paper is a pressure swing type gas separation method.

Hereinafter, examples of the present invention will be given and further detailed description will be given.

Example 1 As an example of the present invention, Ha-'' type zeolite was used as the 4 adsorbent, and the adsorption pressure was 1.2 ata.

0 from air by operating at desorption pressure α2ata and adsorption temperature -15℃! 0sJll by utilizing the cold during evaporation of adjacent LNG when manufacturing! FIG. 1 shows an embodiment in which the N2 removal vacuum pump of the production equipment is cooled and the inlet air is cooled to -15°C.

In FIG. 1, the same reference numerals as those in the inner cylinder 1 correspond to the same part names.

In Fig. 1, a heat exchanger 28 with LNGN cold cold 5o is installed in the flow path 25 to cool the inlet of the vacuum pump from the conventional 25°C to -160°C. A heat exchanger 29 is installed, and the refrigerator 15 shown in FIG. 2 is omitted.

Power consumption (kwh) during manufacturing of conventional I Nm”08
Table 5 shows the power consumption (kwh) and power breakdown (ch) for each unit, the power consumption (kwh) for each unit, and the power consumption (kwh) for each unit.

Table 3 Example 2 Using Na-A type zeolite containing 14 Fe(ll) as the 02 adsorbent, oxygen-enriched air was removed from air at an adsorption pressure of 2 ata, a regeneration pressure of α2 ata, and an adsorption tower at -30°C. Separation was performed.

In this case 0. N from behind the adsorption tower! Or N, enriched air flows down at high pressure and zero enriched air is obtained from the vacuum pump side.

In the absence of an adjacent LNG cold source, 0.35 kWh was required to obtain 1N-01 enriched air (0! concentration 85%).

However, by using an LNG cold heat source to cool the inlet of the vacuum pump and cooling the tower, it was possible to reduce the power consumption to α24 kWh to obtain 1Nm of zero-enriched air (0!concentration: 85chi). .

The breakdown of power consumption is shown in Table 4.

Table 4 Example 5 Na-A type zeolite Fi, C02N, which is often used as a zeolite adsorbent! In the adsorption of CO from a two-component system, the adsorption pressure is 1 to 5 ata, and the desorption pressure is CL05 to α.
5 ata, adsorption temperature 10-! Shows high CO selective adsorption at 50°C.

Here, we attempted to recover CO from a mixed gas consisting of 70% Co and 50% Nm at an adsorption pressure of 2 ata, a desorption pressure of 0.2 ata, and an adsorption temperature of 5°C.

As a result, CO concentrated to a concentration of 99 or more could be recovered from the vacuum pump side.

At this time, the power consumption required to produce CO of I Nm is α
It was 15 kWh.

However, by using the adjacent IJG cold source to cool the vacuum pump inlet and also cooling the adsorption tower, the IN
The power consumption required to produce m” of CO is α105 kWh.
This could be reduced to

Example 4 The IJa-x type zeolite shown in Example 1 was used as the N2 adsorbent, and the operation was performed at an adsorption pressure of 1.2 ata, a desorption pressure of 0.2 ata, and an adsorption temperature of -15°C.
□Concentration q s, a % (residual gas Ar) of 02
In a plant that produces 1100 ON"-0 spirits/h, an adjacent liquid 0!concentration q 9. b
% liquid 0! 1. to this plant. OQ ONm"-
o! The liquid acid was vaporized by heat exchange with the inlet air of this plant at a flow rate of 1500 lm/h, and the following good results were obtained.

■ 0 liquids! By using this plant in combination, we can obtain 02 with a high purity of about 98%, and at the same time use the latent heat of vaporization of the liquid 02 to cool the inlet air, making a cooling refrigerator unnecessary.

■ The cold generated by Liquid 02 is nearly 10 times the cold heat required by this plant, so the excess cold heat can be used to simplify heat exchange in this plant and detach the vacuum pump inlet N! By cooling the air and dehumidifying the inlet air (moisture condensation), we were able to downsize the pretreatment equipment.

Example 5 The Fe(l[)-containing Na-A zeolite shown in Example 2 was used as the 02 adsorbent, and the adsorption pressure was 2 a.
ta, desorption pressure (L 2 ata, adsorption temperature -30°C
Operate with N! N with a concentration of 99 t (residual gas 0 t)! 10
Liquid N adjacent to the pressure swing type N1 production equipment that produces at 0 Nm" -0,/h, liquid N with a Ntm degree of 99, 9% from the holder is transferred to this plant at a pressure of 100 Nm
The liquid N2 was vaporized by heat exchange with the inlet air of the plant at 160 Nm3/h, and the following good results were obtained.

■ By using liquid N in combination with this plant? Since high-purity N of about 95q6 is obtained and at the same time the latent heat of vaporization of liquid N is used to cool the inlet air, a refrigerator for cooling is no longer required.

■ The cold generated by liquid N2 is nearly twice the cold heat required for this plant, so the excess cold heat can be used to simplify heat exchange in this plant and remove the vacuum pump inlet N! By cooling the air and dehumidifying the inlet air (moisture condensation), we were able to downsize the pretreatment equipment.

[Brief explanation of drawings]

FIG. 1 shows a flow of an embodiment of the present invention, and FIG. 2 shows a conventional method 70-. Sub-agents 1) Meifuku agent Hikaru Hagiwara -

Claims (2)

[Claims] (1) In a pressure swing type gas adsorption separation method in which adsorption is performed under pressurized conditions above atmospheric pressure and regeneration is performed under reduced pressure conditions below atmospheric pressure, one of the cold energies of an adjacent plant that generates cold heat is This pressure swing type gas separation is characterized in that one part is used to cool the adsorption tower, and if there is excess cold energy, the other part is used to cool the desorbed gas at the inlet of the vacuum pump, reducing the power consumption required for separation. Method. (2) The method according to claim 1, wherein the cold heat from an adjacent plant that generates cold heat is the heat of evaporation of a liquefied product gas that is the same as the gas obtained by the pressure swing type gas separation device.