JPH01138106A - Production of nitrogen - Google Patents

Abstract

PURPOSE:To decrease the power unit and quantity of adsorbent for the production of nitrogen, by introducing air into plural adsorption columns filled with Ca-X type zeolite and performing the adsorption and desorption of N2 under specific condition. CONSTITUTION:Ca-X type zeolite is filled in plural N2-adsorption columns as an N2 adsorbent. A mixed gas composed mainly of N2 and O2, e.g., air, is introduced into the plural adsorption columns and the N2 gas is adsorbed under an adsorption pressure of 1-3atm. at an adsorption temperature of +25--30 deg.C. The adsorbed N2 is desorbed under a desorption pressure of 0.05-0.5atm.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for adsorption and separation of N2 from a mixed gas of Nz and 02 such as air, and is used to prevent explosions in chemical plants and power plants, and to maintain catalyst activity. , N1 for oil and fat oxidation prevention during food manufacturing, N1 as inert gas in semiconductor manufacturing process, raw material for ammonia synthesis:')Ns, carburizing furnace,
This invention relates to a method for producing nitrogen, which is used in large quantities and widely in nitriding furnaces and N2 as an atmospheric gas for surface treatment of steel materials.

[Conventional technology]

The N2 adsorption separation method from air using a N2 adsorbent has the advantage that the equipment is small and simple, and almost unmanned operation requires almost no maintenance.N: Manufacture! 10-3.
In recent years, its use as a medium-sized and small-sized device with a speed change of OOONm'' -N,/h has been increasing, and replacement is progressing in cases where liquid nitrogen produced in a cryogenic separation device is transported and used.

N! related to the present invention! A method for producing N2 using an adsorbent has been proposed by Mr. Miwa et al. of Higashishikki in Japanese Patent Applications 152893 and 152894. and three or more N2 adsorption towers, and in some cases a vacuum pump. In this device, when compressed air is sent to one tower, it is filled with N! N2 in the air is adsorbed by the adsorbent and the remaining high pressure is 0! flows out to the rear of the adsorption tower. On the other hand, in other towers, the adsorbed N2 is released under self-flow depressurization conditions to reduce the O2 remaining in the adsorption tower and increase the N2 concentration in the tower.

A part of the product N sampled after this is passed through the column in a countercurrent direction to further N! Increase concentration. Next, the pressure inside the column was reduced to 150 Torr using a vacuum pump to recover N2 and N! Regenerate the adsorbent. This process is repeated alternately to continuously produce N2.

Several units are already in operation in Japan, although they are small and have a capacity of less than 100 Nm” -N=/h.

The typical N and adsorbent used in the above adsorption tower was Na-A, which was put into practical use by Union Carbide.
type zeolite (:(10±12)NalO*At 03
・(1,85±CL5)SiO2・(0~6)H2O]
It is a 60-80% Ca exchanger of N, , o, 2
It selectively adsorbs N from the component mixed gas, and the co-adsorption of 02 under air conditions is estimated to be 10% or less of the adsorption of N2.

It was stated that the Nt production equipment by this adsorption is advantageous in small and medium-sized areas, but in order to produce Nt of I Nm'' (175 to I
Nt requires KWh and is produced by large-capacity cryogenic separation method.
Power consumption is large compared to α30Kwh.

In addition, there is little merit of scale for increasing equipment capacity.
It is said that it cannot compete with the cryogenic separation method in the region of 300 Nm''-N,/h or more.

[Problem that the invention seeks to solve]

The above-mentioned conventional methods have the above-mentioned problems, and the following methods can generally be considered as solutions to these problems, but each method poses very different problems.

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 N adsorption decreases approximately in proportion to the pressure, the capacity of the device increases significantly and Product N! The concentration also decreases dramatically. 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 adsorbed increases, the rate of adsorption and desorption will decrease significantly, so the product N! The concentration was actually lower than it was at room temperature. Also, as the temperature decreases, 0! during N2 adsorption! Because the amount of co-adsorption increases, the power consumption rate increases and the product N! A decrease in concentration occurs.

[Means for solving problems]

Therefore, in the process of conducting intensive research and actual testing on a high-performance N2 #Ol separation method under low temperature and low pressure adsorption conditions that improves the above drawbacks, the present inventor developed a method using the chemical formula Ca4s (AtO
x) Ca-X type zeolite, represented by sa(Siot)lon, increases the amount of N adsorption under low temperature and low pressure adsorption conditions, and can maintain the N adsorption rate within a practical range. :We have completed the present invention by discovering that the decrease in adsorption selectivity is small.

That is, the present invention provides at least two or more adsorption towers filled with Ca-X type zeolite as N and adsorbent, and N such as air.
A mixed gas containing 2*0 gas as the main component was introduced, and N2 was adsorbed under operating conditions of an adsorption pressure of 1 to 3 atm and an adsorption temperature of 25°C to -30°C, and then a desorption pressure of 0.05 to α5 atm.
This is a nitrogen production method characterized by desorbing N2 under operating conditions of m.

In a preferred embodiment of the present invention, chemical formula C'143 (A
Ca-X type zeolite (ITi) represented by tOx ) sa (S i Ol ) tos 5102
/ AtO, = 1.1 to 1.6) in at least two or more adsorption towers filled with adsorption towers, at a temperature below room temperature, a mixed gas containing N2 and 02 as main components at a pressure above atmospheric pressure and below 3 atm. A column under pressurized conditions in which N2 contained in the mixed gas is selectively adsorbed by flowing into an adsorption column and N2 is adsorbed by flowing the oxygen-enriched gas out from the outlet of the adsorption column; 05 atm or more Q, N2 remaining in the N2 adsorption tower is connected at the rear of the adsorption tower with a column under reduced pressure conditions that is regenerated by desorbing and recovering N under reduced pressure conditions of 5 atm or less.
After the regeneration is completed, the Nz of the adsorption tower is transferred to a tower under reduced pressure conditions.
After improving the rlk degree, the collected N2 is passed through an adsorption tower countercurrently to N! After increasing the linear purity, the adsorption tower was heated to 0.
High purity N by reducing the pressure to 05 atm or more and α5 atm or less
, as well as regenerating the N2 adsorbent.

〔Example〕

The method of the present invention will be explained in detail below using examples.

In order to demonstrate the effectiveness of the present invention, the adsorption separation of N from air was performed using Ca4s (AtOz) using the nitrogen production method shown in Figure 1.
An attempt was made with Ca-X type zeolite having the chemical formula ss(SiOz)xos.

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

1.05 to 3 at compressor 2 through inlet side line 1
The air pressurized to
a, 4b, and becomes extremely clean pressurized air. After the cold heat is recovered between the clean air and the recovered oxygen-enriched air in a cooled state in the heat exchanger 5 installed downstream of the flow path 3b, heat is exchanged through the pulp 6a in the closed state 1. Vessel 7
leading to.

In the heat exchanger 7, cold heat is recovered between the air and the desorbed N2 in the cooled state, and then the air reaches the coldest temperature in the Freon 1 evaporator 9, which is directly connected to the Freon refrigerator 8, and enters the adsorption tower 10a. .

The pressurized air that has entered the adsorption tower 10a is converted into N2 by the N2 adsorbent 11a.
Follow Z as it gets sucked in and goes backwards○! concentration increases. This oxygen-enriched air flows through the open valve 12a and the flow path 13.
is released outside the system through

At this time, the other N, the adsorption tower 1ob, is the product N, as described later.
! After the recovery is completed, the adsorbent 11b is regenerated and transferred to the adsorption tower 10b.
is in the most depressurized state. Here, valves 6a, 6b, 1
2a, 12b, 14a.

When 14b, 15a, and 15b are closed and the pulp 12c is opened, the pressure in the adsorption tower 10a decreases through the channel 16, and the pressure in the adsorption tower 10b increases to equalize the pressure. The 02 remaining in the adsorption tower 1oaK moves to the adsorption tower 10b as the pressure decreases,
NZ is released from the adsorbent 11a, and the N2 concentration in the adsorption tower increases. The pressure at this time is P]! ,, the end pressure of the adsorption process is 9 people, the end pressure of the regeneration process is PD Tosult・Pz
The HaPulp 12a is opened and the remaining 0.0% in the adsorption tower 1°a is passed through the channel 13. is released outside the system. If PIe<:1, the pulp 15a is opened and the product N is passed through the channel 17! 1 tank 1
NZ is introduced from 8 to the adsorption tower 10a to set 8=1. Pulp 15a for adsorption tower 10a.

12a is opened and the product N2 tank 18 passes through the flow path 17 to the adsorption tower 10I! When product N is passed through L, the remaining a
◯ in t: is also discharged from the flow path 13 to the outside of the system.

After this, the valve 14a is opened, and the pulp 6a, 12a, 12c is
, 15a are closed and the adsorption tower 10a is brought to a reduced pressure condition by the vacuum pump 19, and high purity N is recovered in the product N2 tank 18. Note that the adsorption towers 1°a and 10b are covered with a cold storage 20 in order to be cooled to -15°C using a Freon refrigerator.

After this, the same operation is performed for the adsorption tower 10b, and when one tower is in the horse adsorption process, the other tower performs product N2 purge and reduced pressure N1 recovery, and by performing this alternately, it is possible to continuously and NZ can be recovered with high purity.

When referring to the use of cold energy, inlet air and oxygen-enriched air, inlet air and desorption N! 90% of cold and heat due to heat exchange between
% is recovered, so the Freon refrigerator 8 can be extremely small.

N2 was produced using the N2 adsorption apparatus shown in FIG. 1 using the above operating method. The operating specifications of the device are shown in Table 1.

Table 1 ○t*Ni was separated from air under the operating conditions shown in Table 1. The results at this time are summarized in FIGS. 2 to 10. As shown in Fig. 2 below, pressure swing type N from air using Ca-X type zeolite, 60 to 70% Ca exchanger (hereinafter Ca % -Na!) of conventional Na-A type zeolite for adsorption separation.
The main improvements to N2 production by A-A) will be explained.

Figure 2 is a diagram showing the relationship between adsorption temperature and product NzD degrees, where the horizontal axis is adsorption temperature (°C) and the vertical axis is product N! Concentration (Vol1
%). Ca-X and Ca%-Na as adsorbents
5A-A, adsorption pressure 1.2 atm regeneration pressure α
It is set to 1 ATM. In addition, in FIG. 2 and FIG. 10, the circle mark represents Ca-X, and the four marks represent Ca%-Na%-A.

The purge rate R (6
) Product N2 was sampled at a rate of 55 Nm''/h with a time of 80 seconds and a purge rate of 50%.

As seen in FIG. 2, Ca%-Na5A-A reaches its maximum value at 25°C, but the N concentration remains at 96%.

In Ca-X, at 25℃, it is about 94% and Ca%-Na%-
99.5 at -15°C, whereas it is rather lower than A.
%, shows a nearly constant value up to -50°C, and decreases below -40°C.

Figure 3 is a diagram showing the relationship between adsorption pressure, product N, and concentration.
The horizontal axis is the adsorption pressure (atm), and the vertical axis is the product N2 concentration (
701%). Adsorbents include Ca-X, Ca
%-Na%-A is used, and the adsorption temperature is -15°C for Ca-X and 25°C for Ca%-Na%-A. Other regeneration pressure, half cycle time,
The purge rate is the same as the conditions shown in FIG. Regarding the adsorption pressure, the N3 concentration is almost saturated at about Satm in both cases.

FIG. 4 is a diagram showing the relationship between adsorption pressure and product N2 recovery rate, and the operating conditions are exactly the same as in FIG. 3. Product N: Recovery rate R (%) As the bonding pressure increases, the recovery rate of Product N2 decreases somewhat.

As can be seen from FIGS. 3 and 4, it can be seen that the production of N at an adsorption pressure of more than S.sub.atm is not effective.

Figure 5 shows desorption pressure (regeneration pressure) (atm) and product N.
It is a diagram showing the relationship with z6 degrees (701%), and for Ca-X = 15°C, for Ca%-NaE-A, it is 2
The adsorption concentration is set at 5°C. Adsorption pressure 1.2a
The influence of desorption pressure was investigated by fixing the pressure at tm. Other conditions are the same as those shown in FIG.

As the desorption pressure decreases, product N! The concentration increases significantly. However, desorption at α05 atm or less is not economical because it involves a significant increase in vacuum pump power.

FIG. 6 is a diagram showing the relationship between desorption pressure (at, m 2 ) and product N2 recovery rate (conversion), and the adsorbent and operating conditions are exactly the same as in FIG. 5. As the desorption pressure decreases, the product N2 recovery rate increases significantly.

FIG. 7 is a diagram showing the relationship between purge rate (%) and product N2 concentration (Vo1%), where the horizontal axis represents purge rate (%) and the vertical axis represents product N concentration (701%).

For adsorbent Ca-X, adsorption concentration -15℃, Ca%-
For Na3A-A, the adsorption temperature was 25°C and the adsorption pressure was 1.
The operating conditions were set to 2 atm, desorption pressure α2 atm, and half cycle time 80 sec.

As you can see in Figure 7, increasing the purge rate significantly increases N! It can be seen that the concentration increases.

Figure 8 is a diagram showing the relationship between purge rate and product N2 recovery rate.
) is shown. Naturally, as the purge rate increases, the recovery rate decreases, so a purge rate of around 50% is the product NI.
(It seems to be optimal if both the product N8 recovery rate and the product N8 recovery rate are considered together.

Figure 9 shows product N! This is a diagram showing the relationship between the concentration and the power consumption unit representing the power consumption required to produce 1% m'' of N. The horizontal axis is the product N, /a degrees (701%), and the vertical axis is the power consumption. Represents the unit (KWh/Nm"-rTz').

The operating conditions are the same as in FIG. As the product's 'h t'
Even at 9.5%, Q, 2 KWh/Nm”-N Snow and Cryogenic Separator CL 25 KWh/Nm”-N
2. Conventional PS A-N, (Ca9A-Na5A
-A used, 25℃) 0.6KWh / Nm” -N
It is a device with extremely low power consumption.

Figure 10 shows product N! This is a diagram showing the relationship between the concentration and the ability to produce N2 per hour with the ITON adsorbent. The horizontal axis is the product N and the concentration (701%), and the vertical axis is the hourly N2 production amount ( Nm3- N2/T ON/h
). Both the adsorbent and operating conditions are the same as in FIG. 9.

! ! ! Product N! As the concentration decreases, the amount of N2 produced increases significantly. Furthermore, it can be seen that the production amount of N is approximately three times that of the conventional psA-N.

〔Effect of the invention〕

As explained in detail above, the conventional PSA-N.

It can be seen that the present invention is also superior to the deep cooling method, which is often used in large-volume tNz production. That is, the present invention proposes a method for separating nitrogen from a mixed gas that requires less power consumption and less adsorbent than conventional adsorbent methods and is very useful industrially.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a nitrogen production apparatus that is an embodiment of the present invention, Fig. 2 is a relation diagram between adsorption temperature and product N2 concentration, Fig. 3 is a relation diagram between adsorption pressure and product Nz 11 degrees, Figure 4 shows the relationship between adsorption pressure and product N2 recovery rate, Figure 5 shows the relationship between desorption pressure and product N2 concentration, Figure 6 shows the relationship between desorption pressure and product N2 concentration, and Figure 6 shows the relationship between desorption pressure and product N2 concentration.
Figure 7 shows the relationship between the recovery rate and the purge rate and product Hz.
Figure 8 is a diagram of the relationship between purge rate and product N2 recovery rate, Figure 9 is a diagram of the relationship between product N, concentration change, and power consumption, and Figure 10 is a diagram of the relationship between product N2 concentration and N2 It is a relationship diagram with manufacturing capacity.

Claims (1)

[Claims] N_2, O_2 such as air is added to at least two or more adsorption towers filled with Ca-X type zeolite as an N_2 adsorbent.
A mixed gas consisting mainly of
A method for producing nitrogen, which comprises adsorbing N_2 under operating conditions of an adsorption temperature of 25°C to -30°C, and then desorbing N_2 under operating conditions of a desorption pressure of 0.05 to 0.5 atm.