JPS6379714A - Production of high purity nitrogen - Google Patents

Abstract

PURPOSE:To constantly produce high purity nitrogen from air at a low cost by picking three vessels with molecular sieve carbon having specified performance as an adsorbent and by alternately using two of the three vessels as adsorption vessels and the remaining one as a vacuum desorption vessel. CONSTITUTION:Molecular sieve carbon adsorbing oxygen in >=3 volume ratio of oxygen to nitrogen for 120sec adsorption time and requiring >=0.4min<-1> space velocity to separate product nitrogen having 0.01vol% concn. of residual oxygen from air under prescribed pressure swing adsorption conditions is used as an adsorbent. Three vessels are packed with the adsorbent, two of the three vessels are arranged in series and used as adsorption vessels and the remaining one is used as a vacuum desorption vessel. After adsorption and desorption operations are carried out for a certain time, the internal pressure of the desorption vessel in which desorption has been finished is made equal to that of the adsorption vessels the desorption vessel is connected to the rear side vessel of the two adsorption vessels and the front side vessel is changed over to a vacuum desorption vessel. Thus, nitrogen of >=99.99vol% purity is obtd. with air as starting material.

Description

DETAILED DESCRIPTION OF THE INVENTION Examples 1 to 3 35 parts of coal tar was added as a binder to 100 parts of finely ground coconut shell charcoal, and after granulation, carbonization was carried out at 900°C.

This carbonized carbon was immersed in a dilute hydrochloric acid solution, thoroughly washed with water, and dried. Furthermore, 5 parts of creosote distilled from 140 to 260°C was impregnated, heat treated at 700°C for 30 minutes, and then cooled to room temperature in nitrogen gas to prepare MSC.

The oxygen equilibrium adsorption amount of the obtained MSC at 25°C and 1 atm is 7.6.
c c/g, the adsorption capacity ratio of oxygen and nitrogen at an adsorption time of 120 seconds is 4.27, and the maximum space velocity at a residual oxygen concentration of 0.01% by volume in the product nitrogen obtained in the predetermined pressure swing adsorption condition range is It was 1.04m1n”.
This MSC is filled into the three-tank pressure casing adsorption device of the present invention system, and the oxygen concentration in the product nitrogen is 0.0 under the lower condition.
The space velocity and feed air basic unit for one volume were determined. The results are shown in Table-1.

Adsorption/desorption tank (per tank) capacity 1. Ol Adsorption pressure 3~61-G Desorption pressure 1QQTorr Adsorption time
120-240 seconds removal time Desorption 60
Pressurizing operation for ~120 seconds Between adsorption/desorption species (3 tanks) and between adsorption/desorption tank and product tank (3 tanks) Supply air temperature 20°C Table-1 Example 2 λ0 6.0 240 120
99.99 0.94 3.8 Example 3 2.0
3.0 120 60 99.99 0
．． 46 5.2 Adsorption pressure is □ K9/ci 3 from G
．． When the space velocity decreases to 0 Kp/, a G, the space velocity decreases greatly and the air consumption rate increases, but the pressure difference becomes a ratio greater than that, so the energy required for compression decreases. However, even in this case, an increase in the adsorption/desorption tank capacity and energy related to pressure reduction is unavoidable.

Comparative Example 1 In Comparative Example 1, the MSC of Example 1 was used, and the normal 2
The space velocity and air consumption rate were determined using a tank type pressure swing adsorption device under the following conditions.

Adsorption/desorption tank capacity (capacity per tank ff1) 2.07 Adsorption pressure
6 Lord-G Desorption pressure IQQTorr Adsorption and desorption time
Pressure equalization operation for 60 seconds each Adsorption/desorption calibration and desorption/desorption product calibration Supply air temperature 20°C The results show that when the oxygen concentration in the product is 0.01% by volume, the space velocity is 1.02mff1 and the air consumption rate is 6.1. It shows a value that is not practical.

Comparative Example 2 Equilibrium adsorption amount of oxygen at 25°C and 1 atm 6. Using a commercially available MSC that exhibits an oxygen/nitrogen adsorption ratio of 2.8 at an ICC/g adsorption time of 120 seconds, a test was conducted under predetermined pressure swing adsorption conditions, but within this condition range, the residual oxygen concentration in the product nitrogen The lowest value was 0.04% by volume.

Tokutsubo Bunbun f1k Kurai 1; Hzν Shunhachi Nahe LI
<JTanren' ((Oda Ko Eacho 1Kunio Ogawa, Director General of the Patent Office, Patent Application No. 1987-225099 λ Name of Invention High Purity Nitrogen Production Process 1 Amended Person Kuraray Chemical Co., Ltd. Kuraray Chemical Co., Ltd., 1-4-14 Shibata-cho, Kita-ku, Osaka, Representative Director Kentabe Toyoshima Co., Ltd. Subject of amendment 7, Contents of amendment (υ Page 2, line 13 of the specification) Molecular sieve charcoal of the present invention”
It has been corrected to read, "Molecular sieve charcoal of the present invention."

■ On page 5 of the specification, line 19, ``Has the ability to combine'' is corrected to ``Has a specific ability.''

■ On page 10 of the specification, line 8, "defoamed" is corrected to "dehumidified".

(4) On page 12 of the specification, line 6, “the concept of polishing” was changed to “
"The concept of breakthrough," he corrected.

I am corrected.

Claims (1)

[Claims] 1. The adsorption capacity ratio of oxygen to nitrogen is 3.0 or more at an adsorption time of 120 seconds, and the residual oxygen concentration in the product nitrogen from air is 0.01% by volume within a predetermined pressure swing adsorption condition range. Molecular sieve charcoal with a space velocity of 0.4 min^-^1 or more is used as an adsorbent, and two of the three tanks filled with the adsorbent are placed in series as adsorption tanks under reduced pressure. One tank is used for desorption, and after performing adsorption and desorption operations for a certain period of time, the tank that has completed desorption is pressure-equalized with the other two adsorption tanks, and then the two tanks arranged in series are used as adsorption tanks. By connecting the adsorption tank next to the rear tank and switching the front tank to a vacuum desorption tank and circulating it in a merry-go-round style, nitrogen with a purity of 99.99% by volume or higher can be separated using air as a raw material. A method for producing high-purity nitrogen using a pressure swing adsorption method. 2. When equalizing the pressure, connect the two adsorption tanks in series and equalize the pressure after desorption, then cut off the adsorption tanks,
The method for producing high-purity nitrogen according to claim 1, wherein the obtained high-purity nitrogen product tank, the tank in which desorption has been completed, and the rear adsorption tank are connected in series to re-equalize the pressure. 3. Maximum pressure during adsorption is 2.5-10kg/cm^2,
The method for producing high-purity nitrogen according to claims 1 and 2, wherein the maximum degree of vacuum during desorption is within the range of 50 to 150 Torr.