JP2001342013A - Nitorgen gas generation method - Google Patents
Nitorgen gas generation methodInfo
- Publication number
- JP2001342013A JP2001342013A JP2001080069A JP2001080069A JP2001342013A JP 2001342013 A JP2001342013 A JP 2001342013A JP 2001080069 A JP2001080069 A JP 2001080069A JP 2001080069 A JP2001080069 A JP 2001080069A JP 2001342013 A JP2001342013 A JP 2001342013A
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- Japan
- Prior art keywords
- pressure
- nitrogen
- adsorption
- nitrogen gas
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Separation Of Gases By Adsorption (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、窒素ガス発生方法
に関し、詳しくは、分子ふるい炭素を吸着剤として空気
中の窒素を分離して高純度窒素ガスを発生させる方法に
関する。The present invention relates to a method for generating nitrogen gas, and more particularly, to a method for generating high-purity nitrogen gas by separating nitrogen in air using molecular sieve carbon as an adsorbent.
【０００２】[0002]
【従来の技術】分子ふるい炭素を吸着剤とするＰＳＡ法
（圧力変動吸着法）によって空気から窒素ガス（以下、
窒素に富むガスも単に窒素と呼ぶことがある）を分離発
生する方法が普及してきた。この分子ふるい炭素を使用
するＰＳＡ法は、典型的には、適当な圧力に加圧した原
料空気を吸着剤を充填した吸着筒に導入して筒内を所定
の圧力にする加圧工程、酸素分を吸着剤に優先的に吸着
させて吸着しにくい窒素ガスを採取する吸着工程、筒内
に残留する窒素分を他の吸着筒に送り出す減圧均圧工
程、吸着筒を大気に解放して圧力を下げることにより吸
着剤に吸着していた酸素分を脱着させて吸着剤を再生す
る減圧再生工程、他の吸着筒内から窒素分を受け入れる
加圧均圧工程の各工程を繰り返して行うことにより空気
中の窒素を分離する。2. Description of the Related Art Nitrogen gas (hereinafter, referred to as air) is produced from air by PSA method (pressure fluctuation adsorption method) using molecular sieve carbon as an adsorbent.
Separation and generation of nitrogen-rich gas (also referred to simply as nitrogen) have become widespread. In the PSA method using molecular sieve carbon, typically, a pressurizing step in which raw air pressurized to an appropriate pressure is introduced into an adsorption cylinder filled with an adsorbent to bring the inside of the cylinder to a predetermined pressure, Adsorption process to remove nitrogen gas that is difficult to adsorb by preferentially adsorbing the adsorbent to the adsorbent, depressurization equalizing process to send out the remaining nitrogen in the cylinder to other adsorption cylinders, and release the adsorption cylinder to the atmosphere to increase the pressure The pressure reduction regeneration step of desorbing the oxygen content adsorbed on the adsorbent and regenerating the adsorbent by lowering the pressure, and the pressure equalization step of receiving the nitrogen content from the other adsorption column are repeatedly performed. Separate nitrogen in air.
【０００３】この方法は、１分前後の比較的短い運転サ
イクルで圧力を変化させることができるので、吸着剤単
位重量当たりの空気処理量を大きくすることができる特
徴がある。このため、従来から行われている深冷空気分
離法に対し、装置構成を大幅に簡略化でき、設備コスト
の面でも優位にあるため、小／中規模の用途では広く採
用されている。[0003] This method is characterized in that the pressure can be changed in a relatively short operation cycle of about one minute, so that the amount of air treatment per unit weight of the adsorbent can be increased. Therefore, as compared with the conventional cryogenic air separation method, the configuration of the apparatus can be greatly simplified, and it is advantageous in terms of equipment cost. Therefore, it is widely used in small / medium scale applications.
【０００４】一方、従来のＰＳＡ法で発生させている窒
素ガスの純度は、経済的には、酸素含有率が１０００ｐ
ｐｍ程度であるとみなされ、それを満たすための様々な
方法が開発されてきた。例えば、特開昭５３−８１４９
３号公報に記載の方法では、原料ガス（空気）の送入を
最終圧力まで連続的に行い、かつ、その量を０．０４〜
０．０７Ｎｍ３／吸着剤１ｍ３とし、吸着工程を６０〜
１２０秒、均圧工程時間を１〜３秒とすることにより、
酸素含有率１０００ｐｐｍの窒素ガスを発生することが
開示されている。また、特開昭５７−１０３１３号公報
では、均圧工程時間は４〜５秒が適当であることを開示
している。On the other hand, the purity of nitrogen gas generated by the conventional PSA method is economically limited to an oxygen content of 1000 p.
pm, and various methods have been developed to meet it. For example, JP-A-53-8149
In the method described in Japanese Patent Publication No. 3 (KOKAI), the feed of the raw material gas (air) is continuously performed up to the final pressure, and the amount is set to 0.04 to
And 0.07 nm 3 / adsorbent 1 m 3, 60 to the adsorption step
By setting the equalizing step time to 120 seconds and the equalizing step time to 1 to 3 seconds,
It is disclosed that nitrogen gas having an oxygen content of 1000 ppm is generated. Further, Japanese Patent Application Laid-Open No. 57-10313 discloses that an appropriate equalizing step time is 4 to 5 seconds.
【０００５】しかし、近年では、窒素純度をより高く、
例えば酸素含有率を１００ｐｐｍ程度にする技術も開発
されるようになってきている。例えば特開平８−６７５
０６号公報に記載の方法では、均圧工程におけるガスの
流れ経路を、均圧工程時間の経過に伴って変更すること
が開示されている。詳述すると、均圧工程の前半では、
吸着工程が終了した筒の上部（製品取出し口）と、吸着
工程を開始する筒の上部とを連結して窒素分を回収し、
均圧工程の後半では、吸着筒の下部（原料ガス導入口）
同士をも連結して窒素分を回収する方法が開示されてい
る。このときの均圧工程の時間は、前半：後半が、１：
１乃至１：１．３であり、ガス移送時間は２〜６秒とし
ている。However, in recent years, nitrogen purity has been higher,
For example, a technique for reducing the oxygen content to about 100 ppm has been developed. For example, JP-A-8-675
No. 06 discloses that the gas flow path in the equalizing step is changed as the equalizing step time elapses. Specifically, in the first half of the pressure equalization process,
The upper part of the cylinder (product outlet) where the adsorption process has been completed is connected to the upper part of the cylinder where the adsorption process starts, and nitrogen is recovered.
In the latter half of the pressure equalization process, the lower part of the adsorption column (source gas inlet)
There is disclosed a method of recovering nitrogen by connecting them together. In this case, the time of the equalizing step is as follows: first half: second half, 1:
1 to 1: 1.3, and the gas transfer time is 2 to 6 seconds.
【０００６】[0006]
【発明が解決しようとする課題】しかし、上述の方法
は、ＰＳＡプロセスが複雑になってしまうために調整が
難しく、また、設備コスト等が高くなるという欠点を有
している。本発明は、このような実状を鑑みてなされた
ものであり、単純なプロセスによって電力消費を低く
し、かつ、装置コストを低くしながら、酸素含有率１０
０ｐｐｍ以下の窒素ガスを製造することができる窒素ガ
ス発生方法を提供することを目的としている。However, the above-mentioned method has a drawback that the PSA process is complicated, so that the adjustment is difficult and the equipment cost is high. The present invention has been made in view of such circumstances, and has a low oxygen consumption rate of 10 while reducing power consumption by a simple process and lowering device costs.
It is an object of the present invention to provide a nitrogen gas generation method capable of producing nitrogen gas of 0 ppm or less.
【０００７】[0007]
【課題を解決するための手段】上記目的を達成するた
め、本発明の窒素ガス発生方法は、分子ふるい炭素を吸
着剤とし、加圧、吸着、減圧均圧、減圧再生、加圧均圧
の各工程を繰り返す圧力変動吸着法によって空気から酸
素含有率が１００ｐｐｍ以下の窒素ガスを分離する方法
において、前記加圧工程における圧力上昇速度を０．１
５〜１．６ＭＰａ／ｍｉｎとし、前記均圧工程の時間を
７〜２７秒とし、さらに、前記加圧均圧工程におけるガ
ス回収率を７０〜１００％としたことを特徴としてい
る。In order to achieve the above object, a method for generating nitrogen gas according to the present invention uses a molecular sieve carbon as an adsorbent, and performs pressurization, adsorption, reduced pressure equalization, reduced pressure regeneration, and pressurized equalization. In a method of separating nitrogen gas having an oxygen content of 100 ppm or less from air by a pressure fluctuation adsorption method in which each step is repeated, the pressure increasing rate in the pressurizing step is set to 0.1.
5 to 1.6 MPa / min, the time of the pressure equalization step is 7 to 27 seconds, and the gas recovery rate in the pressure equalization step is 70 to 100%.
【０００８】[0008]
【発明の実施の形態】図１は本発明の窒素ガス発生方法
を適用したＰＳＡ装置の一形態例を示す系統図である。
この窒素ガス発生装置は、吸着剤として分子ふるい炭素
を充填した２つの吸着筒Ａ，Ｂと、原料空気を加圧する
空気圧縮機１１と、原料空気中の水分を除去するエアド
ライヤ１２と、原料空気を貯留する空気貯槽１３と、製
品窒素ガスを貯留する製品窒素貯槽１４と、吸着筒Ａ，
Ｂ工程の切換えに伴って開閉する弁１ａ，１ｂ，２ａ，
２ｂ，３ａ，３ｂ，４，５，６と、ガス流量を所定流量
に調節する流量調節弁７，８，９，１０とにより形成さ
れている。FIG. 1 is a system diagram showing one embodiment of a PSA apparatus to which the nitrogen gas generating method of the present invention is applied.
This nitrogen gas generator comprises two adsorption cylinders A and B filled with molecular sieve carbon as an adsorbent, an air compressor 11 for pressurizing the raw air, an air dryer 12 for removing moisture in the raw air, a raw air An air storage tank 13 for storing product nitrogen, a product nitrogen storage tank 14 for storing product nitrogen gas,
Valves 1a, 1b, 2a, which open and close with the switching of the B process
2b, 3a, 3b, 4, 5, 6, and flow control valves 7, 8, 9, 10 for controlling the gas flow rate to a predetermined flow rate.
【０００９】この窒素ガス発生装置は、図２に示す各工
程を繰り返すことによって空気中の窒素を分離し、含有
酸素濃度が１００ｐｐｍ以下の製品窒素ガスを発生す
る。なお、図２では、図１に示した各弁の中で開弁状態
にある弁及び関連する経路のみを図示している。This nitrogen gas generator separates nitrogen in the air by repeating the steps shown in FIG. 2 to generate a product nitrogen gas having an oxygen content of 100 ppm or less. FIG. 2 shows only the valves in the open state and the related paths among the valves shown in FIG.
【００１０】以下、吸着筒Ａを中心にして各工程を説明
する。まず、図２（Ａ）は加圧工程であって、空気圧縮
機１１で所定の圧力、例えば０．６５ＭＰａに加圧さ
れ、エアドライヤ１２で水分を除去された原料空気が、
空気貯槽１３に一旦蓄えられてから、流量調節弁７及び
入口弁１ａを通って吸着筒Ａに供給される。このとき、
吸着筒Ａの出口弁２ａ、排気弁３ａ、パージ弁４，両均
圧弁５，６は、それぞれ閉弁状態になっており、原料空
気によって吸着筒Ａが所定圧力に加圧される。一方の吸
着筒Ｂは、排気弁３ｂから筒内ガスの放出が行われてい
る。Hereinafter, each step will be described focusing on the adsorption cylinder A. First, FIG. 2 (A) is a pressurizing step, in which the raw material air which has been pressurized to a predetermined pressure, for example, 0.65 MPa by the air compressor 11 and whose moisture has been removed by the air dryer 12,
Once stored in the air storage tank 13, it is supplied to the adsorption column A through the flow control valve 7 and the inlet valve 1 a. At this time,
The outlet valve 2a, the exhaust valve 3a, the purge valve 4, and the pressure equalizing valves 5, 6 of the adsorption cylinder A are each in a closed state, and the adsorption cylinder A is pressurized to a predetermined pressure by the raw material air. In the adsorption cylinder B, the in-cylinder gas is released from the exhaust valve 3b.
【００１１】吸着筒Ａの圧力が製品窒素貯槽１４の圧力
以上になると、出口弁２ａが開いて図２（Ｂ）に示す吸
着工程に切り替わり、入口弁１ａから吸着筒Ａ内に導入
された原料空気の中の酸素を吸着剤（分子ふるい炭素）
に吸着させ、吸着剤に吸着しにくい窒素が出口弁２ａを
介して製品窒素貯槽１４に送り出される。また、この吸
着工程の適当な時期にパージ弁４が開き、窒素の一部が
流量調節弁８で所定流量に調節されて吸着筒Ｂに導入さ
れ、吸着筒Ｂのパージ操作が行われる。この吸着工程
は、通常、吸着筒Ａ内の吸着剤が酸素で飽和する直前ま
で行われる。また、前記加圧工程からこの吸着工程が終
了するまでの合計時間を、一般的に半サイクル時間と呼
んでいる。When the pressure in the adsorption cylinder A becomes equal to or higher than the pressure in the product nitrogen storage tank 14, the outlet valve 2a is opened to switch to the adsorption step shown in FIG. 2 (B), and the raw material introduced into the adsorption cylinder A from the inlet valve 1a. Adsorbent for oxygen in air (molecular sieve carbon)
The nitrogen which is hardly adsorbed by the adsorbent is sent out to the product nitrogen storage tank 14 through the outlet valve 2a. Further, at an appropriate time in the adsorption step, the purge valve 4 is opened, a part of nitrogen is adjusted to a predetermined flow rate by the flow rate control valve 8 and introduced into the adsorption cylinder B, and the purging operation of the adsorption cylinder B is performed. This adsorption step is usually performed until immediately before the adsorbent in the adsorption column A is saturated with oxygen. The total time from the pressurization step to the end of the adsorption step is generally called a half cycle time.
【００１２】吸着工程が終了すると、吸着筒Ａの入口弁
１ａ及び出口弁２ａが閉じて均圧弁５，６が開き、図２
（Ｃ）に示す均圧工程が始まる。この均圧工程では、吸
着筒Ａ内のガスが、流量調節弁９，１０で所定流量に調
節されて吸着筒Ｂに導入される。これにより、吸着工程
を終了した吸着筒Ａ内の窒素に富むガスが再生工程が終
了している吸着筒Ｂに回収される。このとき、吸着筒Ａ
は減圧均圧工程となり、吸着筒Ｂは加圧均圧工程とな
る。When the adsorption step is completed, the inlet valve 1a and the outlet valve 2a of the adsorption cylinder A are closed, and the pressure equalizing valves 5 and 6 are opened.
The pressure equalizing step shown in FIG. In this pressure equalizing step, the gas in the adsorption cylinder A is adjusted to a predetermined flow rate by the flow control valves 9 and 10 and introduced into the adsorption cylinder B. Thus, the nitrogen-rich gas in the adsorption column A that has completed the adsorption process is recovered in the adsorption column B that has completed the regeneration process. At this time, the suction tube A
Is a pressure equalization step, and the adsorption cylinder B is a pressure equalization step.
【００１３】均圧工程が終了すると、均圧弁５，６が閉
じて排気弁３ａが開き、図２（Ｄ）に示す減圧再生工程
の第１段階が始まる。この減圧再生工程の第１段階で
は、吸着筒Ａ内のガスが排気弁３ａから大気に放出さ
れ、吸着筒Ａ内が減圧される。吸着筒Ｂでは入口弁１ｂ
が開いて加圧工程が行われる。出口弁２ｂが開いて吸着
筒Ｂが吸着工程に切り替わった後、パージ弁４が開いて
図２（Ｅ）に示す減圧再生工程の第２段階に進む。この
減圧再生工程の第２段階では、吸着筒Ａの出口側から所
定量の窒素ガスを筒内に導入し、吸着剤から脱着した酸
素を窒素で筒内から追い出すことにより、吸着剤の分子
ふるい炭素を再生する。このとき、必要に応じて吸着筒
Ａ内を真空ポンプで減圧排気することもできる。このよ
うな減圧再生工程の第１段階と第２段階との合計時間
は、同じ半サイクル時間となる。When the pressure equalizing process is completed, the pressure equalizing valves 5 and 6 are closed and the exhaust valve 3a is opened, and the first stage of the pressure reducing regeneration process shown in FIG. In the first stage of this decompression regeneration step, the gas in the adsorption cylinder A is released from the exhaust valve 3a to the atmosphere, and the pressure in the adsorption cylinder A is reduced. In the suction tube B, the inlet valve 1b
Opens to perform the pressurizing step. After the outlet valve 2b is opened and the adsorption tube B is switched to the adsorption process, the purge valve 4 is opened and the process proceeds to the second stage of the reduced pressure regeneration process shown in FIG. In the second stage of the reduced pressure regeneration step, a predetermined amount of nitrogen gas is introduced into the cylinder from the outlet side of the adsorption cylinder A, and oxygen desorbed from the adsorbent is expelled from the cylinder with nitrogen to thereby remove the molecular sieve of the adsorbent. Regenerate carbon. At this time, if necessary, the inside of the adsorption cylinder A can be evacuated to a reduced pressure by a vacuum pump. The total time of the first stage and the second stage of such a reduced pressure regeneration step is the same half cycle time.
【００１４】減圧再生工程が終了すると、排気弁３ａ及
びパージ弁４が閉じて均圧弁５，６が開き、図２（Ｆ）
に示す吸着筒Ａの加圧均圧工程が始まり、吸着工程後の
減圧均圧工程となる吸着筒Ｂ内の窒素に富むガスが吸着
筒Ａに回収される。この均圧工程が終了すると、最初の
加圧工程に戻り、各工程が繰り返して行われる。When the pressure reduction regeneration step is completed, the exhaust valve 3a and the purge valve 4 are closed, and the pressure equalizing valves 5 and 6 are opened.
The pressure equalizing step of the adsorption column A shown in FIG. 4 starts, and the nitrogen-rich gas in the adsorption column B, which is the pressure equalization step after the adsorption step, is collected in the adsorption column A. When the equalizing step is completed, the process returns to the first pressurizing step, and each step is repeatedly performed.
【００１５】このようにして空気から窒素を分離して製
品窒素ガスを発生させるにあたり、前記加圧工程におけ
る圧力上昇速度、すなわち、均圧工程後の圧力と吸着工
程開始前の圧力との圧力差、つまり加圧工程における上
昇圧力を、均圧工程終了から吸着工程開始までに要した
時間、つまり加圧工程時間で割った値を、毎分０．１５
〜１．６ＭＰａ／ｍｉｎ、好ましくは０．２６〜１．２
５ＭＰａ／ｍｉｎになるように調整する。In separating nitrogen from air to generate product nitrogen gas in this manner, the rate of pressure increase in the pressurizing step, that is, the pressure difference between the pressure after the equalizing step and the pressure before the start of the adsorption step. That is, the value obtained by dividing the rising pressure in the pressurizing step by the time required from the end of the equalizing step to the start of the adsorption step, ie, the time of the pressurizing step, is 0.15 per minute.
To 1.6 MPa / min, preferably 0.26 to 1.2
Adjust so as to be 5 MPa / min.
【００１６】この圧力上昇速度が、０．１５ＭＰａ／ｍ
ｉｎ未満であると、製品窒素ガスの圧力を維持するため
に吸着筒からの窒素ガスの取り出し量を絞らざるを得
ず、窒素発生量、窒素収率共に低下してしまう。また、
圧力上昇速度が１．６ＭＰａ／ｍｉｎを超えると、吸着
筒への空気の流入速度が速くなるため、酸素濃度の上昇
が早くなり、結果として窒素収率、窒素発生量共に極端
に低下してしまうことになる。The pressure increasing rate is 0.15 MPa / m
If it is less than in, the amount of nitrogen gas taken out of the adsorption column must be reduced in order to maintain the pressure of the product nitrogen gas, and both the amount of generated nitrogen and the yield of nitrogen decrease. Also,
If the pressure rise rate exceeds 1.6 MPa / min, the flow rate of air into the adsorption column becomes faster, so that the oxygen concentration rises faster, and as a result, both the nitrogen yield and the amount of generated nitrogen decrease extremely. Will be.
【００１７】なお、一般的なＰＳＡ装置では、吸着工程
における時間を横軸に、圧力を縦軸にとった圧力変化プ
ロフィールは、多くの場合に上に凸の曲線となるが、本
発明方法では、直線的かつ徐々に圧力が上昇するように
設定することが望ましい。このとき、吸着筒への空気の
流入速度は、加圧工程の当初は筒内圧力が低いために見
かけの流速は速くなり、加圧工程の後半では筒内圧力が
高くなるので見かけの流速は遅くなる。In a general PSA device, the pressure change profile in which the time in the adsorption step is plotted on the horizontal axis and the pressure is plotted on the vertical axis is often an upwardly convex curve. It is desirable to set the pressure so as to increase linearly and gradually. At this time, the apparent flow velocity of the air flowing into the adsorption cylinder is high at the beginning of the pressurizing step because the in-cylinder pressure is low, and the apparent flow velocity is high in the second half of the pressurizing step, so the apparent flow velocity is Become slow.
【００１８】また、均圧工程の時間は、７〜２７秒、好
ましくは１０〜２０秒になるように調節する。酸素含有
率が１０００ｐｐｍ程度の純度の窒素ガスを製品とする
従来のＰＳＡ装置においては、均圧時間は１〜５秒が適
当とされている。これは、均圧工程時間が５秒を超える
と、製品窒素ガスを取り出す時間が相対的に短くなって
窒素発生量が減少するからである。The time of the pressure equalizing step is adjusted so as to be 7 to 27 seconds, preferably 10 to 20 seconds. In a conventional PSA apparatus using a nitrogen gas having a purity of about 1000 ppm in oxygen as a product, the equalizing time is appropriately set to 1 to 5 seconds. This is because, if the equalizing step time exceeds 5 seconds, the time for removing the product nitrogen gas becomes relatively short, and the amount of generated nitrogen decreases.
【００１９】しかし、均圧時間が１〜５秒という短時間
では、減圧側が急激に圧力低下することになるため、吸
着剤に吸着している酸素の脱着が促進され、加圧側に回
収されるガス中の酸素分が多くなるという欠点がある。
特に、製品吐出端である筒上部（出口弁側）が酸素で汚
染され、製品として高純度窒素ガスを発生させる場合に
は大きな影響を及ぼすことになる。すなわち、酸素含有
率１０００ｐｐｍの窒素ガスを製造する場合には問題な
いレベルであるが、本発明が対象とする酸素含有率１０
０ｐｐｍ以下の高純度窒素ガスの製造においては、この
汚染が極めて悪い影響を与える。However, if the pressure equalization time is as short as 1 to 5 seconds, the pressure on the reduced pressure side drops rapidly, so that the desorption of oxygen adsorbed on the adsorbent is promoted and collected on the pressurized side. There is a disadvantage that the oxygen content in the gas increases.
In particular, the upper part of the cylinder (outlet valve side), which is the product discharge end, is contaminated with oxygen, which has a great effect when high-purity nitrogen gas is generated as a product. In other words, this is a level that is not a problem when producing nitrogen gas having an oxygen content of 1000 ppm.
In the production of high-purity nitrogen gas of 0 ppm or less, this contamination has a very bad influence.
【００２０】このことから、本発明方法では、均圧時間
を７〜２７秒という比較的長い時間に設定することによ
り、加圧側の吸着筒、特に筒上部が酸素により汚染さえ
ることを極力防止するようにしている。このように均圧
工程時間を７〜２７秒の比較的長時間にすると、吸着筒
から製品窒素ガスが発生しない時間が長くなるが、これ
は、製品送出ラインに設ける製品窒素貯槽の容量を適切
に設定することで解決できる。但し、均圧工程時間が２
７秒を超えると、製品窒素ガスを取り出せる時間が短く
なり過ぎて製品発生量が大きく低下するため、均圧工程
で回収するガス中の酸素濃度の影響を小さくする効果が
相殺されてしまう。Therefore, in the method of the present invention, by setting the pressure equalizing time to a relatively long time of 7 to 27 seconds, the adsorption cylinder on the pressurized side, especially the upper part of the cylinder is prevented from being contaminated with oxygen as much as possible. Like that. If the pressure equalizing step time is set to a relatively long time of 7 to 27 seconds as described above, the time during which no product nitrogen gas is generated from the adsorption column becomes longer. This is because the capacity of the product nitrogen storage tank provided in the product delivery line is appropriately adjusted. It can be solved by setting to. However, the equalizing process time is 2
If the time exceeds 7 seconds, the time during which the product nitrogen gas can be taken out is too short, and the amount of product generated is greatly reduced. Therefore, the effect of reducing the effect of the oxygen concentration in the gas recovered in the pressure equalization step is offset.
【００２１】さらに、均圧工程における回収率を、７０
〜１００％、好ましくは７０〜９７％、より好ましくは
８３〜９３％に設定することにより、回収ガスによる酸
素汚染をより確実に防止することができる。ここで、回
収率（Ｋ％）は、吸着工程終了時の絶対圧力をＰｂ、減
圧再生工程終了時の絶対圧力をＰｖ、減圧均圧工程終了
時の絶対圧力をＰｅとしたときに、Ｋ＝（Ｐｅ−Ｐｖ）
÷｛（Ｐｂ―Ｐｖ）÷２｝×１００で求められた値とす
る。Further, the recovery rate in the pressure equalization step is set to 70
By setting the concentration to -100%, preferably 70-97%, more preferably 83-93%, it is possible to more reliably prevent oxygen contamination by the recovered gas. Here, the recovery rate (K%) is as follows: Pb is the absolute pressure at the end of the adsorption step, Pv is the absolute pressure at the end of the pressure reduction regeneration step, and Pe is the absolute pressure at the end of the pressure reduction equalization step. (Pe-Pv)
{(Pb−Pv)} 2} × 100.
【００２２】減圧再生工程を大気圧までとする、いわゆ
る大気圧再生の場合で、Ｐｂが０．７５ＭＰａ、Ｐｖが
０．１ＭＰａ、Ｐｅが０．３３５ＭＰａの場合は、回収
率Ｋは、（０．３３５−０．１）÷｛（０．７５−０．
１）÷２｝×１００＝７２％となる。In the case of so-called atmospheric pressure regeneration in which the pressure reduction regeneration step is performed up to atmospheric pressure, when Pb is 0.75 MPa, Pv is 0.1 MPa, and Pe is 0.335 MPa, the recovery rate K is (0. 335-0.1) ÷ ｛(0.75-0.
1) {2} × 100 = 72%
【００２３】減圧再生工程で真空ポンプを使用して吸着
筒内を減圧する、いわゆる真空再生の場合で、Ｐｂが
０．７５ＭＰａ、Ｐｅが０．２７ＭＰａの場合（Ｐｖは
０）、回収率Ｋは、（０．２７−０）÷｛（０．７５−
０）÷２｝×１００＝７２％となる。In the case of so-called vacuum regeneration in which the inside of the adsorption cylinder is depressurized using a vacuum pump in the decompression regeneration step, when Pb is 0.75 MPa and Pe is 0.27 MPa (Pv is 0), the recovery rate K is , (0.27-0) ÷ ｛(0.75-
0) {2} × 100 = 72%.
【００２４】酸素含有量１０００ｐｐｍ程度の窒素ガス
を製造する従来のＰＳＡにおいては、均圧工程における
回収率は、１００％、あるいはできるだけ１００％に近
い値が良いとされている。回収率を１００％にすると、
酸素を数十ｐｐｍ含むガスが回収されて製品吐出端が汚
染されるが、酸素含有量が１０００ｐｐｍ程度の窒素ガ
スを発生させる場合は、この数十ｐｐｍの汚染は、製品
窒素純度にほとんど影響を与えることがなく、窒素に富
むガスをできるだけ多く回収することにより、窒素発生
量の向上が期待されるからである。In a conventional PSA for producing nitrogen gas having an oxygen content of about 1000 ppm, the recovery rate in the pressure equalization step is preferably 100%, or a value as close to 100% as possible. If the recovery rate is 100%,
A gas containing tens of ppm of oxygen is collected and the product discharge end is contaminated. When nitrogen gas having an oxygen content of about 1000 ppm is generated, the tens of ppm of contamination hardly affects the product nitrogen purity. This is because an increase in the amount of generated nitrogen is expected by recovering as much nitrogen-rich gas as possible without giving it.
【００２５】一方、本発明方法においては、前述のよう
に均圧工程時間を長く設定して酸素による汚染を抑えて
いるので、回収率を１００％にしても窒素純度への悪影
響はほとんど無いが、この回収率の最大値を９７％以
下、好ましくは９３％以下に設定することにより、酸素
による汚染を確実に防止することが可能となるので、よ
り安定した状態で高純度窒素ガスを発生させることがで
きる。なお、回収率を７０％未満にすると、減圧均圧側
の吸着筒内に窒素が多く残存し、次の減圧再生工程で大
気に放出して捨てる窒素量が増大するため、窒素収率が
低下してしまう。On the other hand, in the method of the present invention, since the contamination by oxygen is suppressed by setting the pressure equalizing step time long as described above, even if the recovery rate is 100%, there is almost no adverse effect on the nitrogen purity. By setting the maximum value of the recovery rate to 97% or less, preferably 93% or less, it becomes possible to surely prevent contamination by oxygen, so that high-purity nitrogen gas is generated in a more stable state. be able to. If the recovery rate is less than 70%, a large amount of nitrogen remains in the adsorption column on the reduced pressure equalizing side, and the amount of nitrogen released to the atmosphere and discarded in the next reduced pressure regeneration step increases, so that the nitrogen yield decreases. Would.
【００２６】また、均圧工程は、上述のように、吸着筒
上部同士間及び吸着筒下部同士間でそれぞれガスの移動
を行う、いわゆる上下部同時均圧法だけに限らず、吸着
筒上部同士間でのみガスを移動させる上部均圧法を採用
することができる。The pressure equalization step is not limited to the so-called simultaneous upper and lower pressure equalization method in which gas is moved between the upper portions of the adsorption columns and between the lower portions of the adsorption columns, as described above. The upper pressure equalization method in which the gas is moved only at the pressure can be adopted.
【００２７】前記半サイクル時間は、６０〜２４０秒、
好ましくは９０〜１８０秒、さらに好ましくは１２０〜
１５０秒が適当である。この半サイクル時間を６０秒未
満に短くすると、吸着剤単位重量当たりの窒素発生量は
増大するが、時間当たりの再生工程の回数が増加するの
で、廃棄する窒素量が増大して窒素収率が低下する欠点
がある。このような窒素収率の低下は、空気圧縮機の容
量増加、すなわち、必要電力の増加をもたらすので好ま
しくない。The half cycle time is 60 to 240 seconds,
Preferably 90 to 180 seconds, more preferably 120 to 180 seconds
150 seconds is appropriate. If this half cycle time is shortened to less than 60 seconds, the amount of nitrogen generated per unit weight of the adsorbent increases, but the number of regeneration steps per hour increases. There is a disadvantage that it decreases. Such a decrease in the nitrogen yield is not preferable because it causes an increase in the capacity of the air compressor, that is, an increase in required power.
【００２８】一方、半サイクル時間が２４０秒を超える
長さになると、窒素収率は増加するが、吸着剤単位重量
当たりの窒素発生量が低下し、吸着剤必要量が多くなっ
て装置の大型化を招く欠点がある。窒素収率の増加は、
ある程度のところで頭打ちとなるので２４０秒以下が適
切である。On the other hand, when the half cycle time exceeds 240 seconds, the nitrogen yield increases, but the amount of nitrogen generated per unit weight of the adsorbent decreases, and the required amount of adsorbent increases, resulting in an increase in the size of the apparatus. There is a drawback that leads to conversion. The increase in nitrogen yield is
240 seconds or less is appropriate because it reaches a plateau at some extent.
【００２９】[0029]
【実施例】実施例１ 図１に示したＰＳＡ装置を使用して図２に示すパターン
で運転を行い、酸素含有量１０ｐｐｍの高純度窒素ガス
を発生させた。半サイクル時間は１２０秒、均圧工程時
間は１５秒、回収率は１００％、吸着圧力は０．６５Ｍ
Ｐａ（製品窒素仕様圧力は０．６ＭＰａ）とした。EXAMPLE 1 The PSA apparatus shown in FIG. 1 was used to operate according to the pattern shown in FIG. 2, and high-purity nitrogen gas having an oxygen content of 10 ppm was generated. Half cycle time is 120 seconds, pressure equalization step time is 15 seconds, recovery rate is 100%, adsorption pressure is 0.65M
Pa (product nitrogen specification pressure was 0.6 MPa).
【００３０】そして、加圧工程における圧力上昇速度
［ＭＰａ／ｍｉｎ］を表１に示すように変化させ、各速
度における窒素発生量［Ｎｍ３／ｈ／ｔ（ＭＳＣ・１
筒）］と窒素収率［％］（製品窒素量÷原料空気中の窒
素量×１００）とを求めた。結果を表１に示す。Then, the pressure increase rate [MPa / min] in the pressurizing step was changed as shown in Table 1, and the nitrogen generation amount [Nm 3 / h / t (MSC · 1) at each rate was changed.
Cylinder)] and nitrogen yield [%] (product nitrogen amount / nitrogen amount in raw air × 100). Table 1 shows the results.
【００３１】なお、半サイクル１２０秒で圧力上昇速度
が０．１ＭＰａ／ｍｉｎの場合は、吸着筒圧力の上昇が
遅いため、製品窒素仕様圧力である０．６ＭＰａを維持
するためには、製品取り出し量を絞る必要があった。In the case where the pressure rise rate is 0.1 MPa / min in a half cycle of 120 seconds, the pressure of the adsorption column is slowly increased. Therefore, in order to maintain the product nitrogen specification pressure of 0.6 MPa, the product is taken out. The amount had to be reduced.
【００３２】[0032]
【表１】 [Table 1]
【００３３】実施例２ 加圧工程における圧力上昇速度を０．２６ＭＰａ／ｍｉ
ｎに設定し、均圧工程時間を表２に示すように変化させ
た以外は、実施例１と同様にして窒素発生量と窒素収率
とを求めた。結果を表２に示す。Example 2 The pressure increasing rate in the pressing step was 0.26 MPa / mi.
n, and the amount of generated nitrogen and the yield of nitrogen were determined in the same manner as in Example 1, except that the pressure equalization step time was changed as shown in Table 2. Table 2 shows the results.
【００３４】[0034]
【表２】 [Table 2]
【００３５】実施例３ 実施例２と同様にして、均圧工程時間を表３に示すよう
に変化させ、酸素含有量１００ｐｐｍの高純度窒素ガス
を発生させた。実施例１と同様にして窒素発生量と窒素
収率とを求めた。結果を表３に示す。Example 3 In the same manner as in Example 2, the pressure equalizing step time was changed as shown in Table 3, and a high-purity nitrogen gas having an oxygen content of 100 ppm was generated. In the same manner as in Example 1, the amount of generated nitrogen and the nitrogen yield were determined. Table 3 shows the results.
【００３６】[0036]
【表３】 [Table 3]
【００３７】実施例４ 加圧工程における圧力上昇速度を０．２６ＭＰａ／ｍｉ
ｎに設定し、均圧工程における回収率を表４に示すよう
に変化させた以外は、実施例１と同様にして酸素含有量
１０ｐｐｍの高純度窒素ガスを発生させた。実施例１と
同様にして窒素発生量と窒素収率とを求めた。結果を表
４に示す。Example 4 The pressure increasing rate in the pressing step was 0.26 MPa / mi.
n, and a high-purity nitrogen gas having an oxygen content of 10 ppm was generated in the same manner as in Example 1 except that the recovery in the pressure equalization step was changed as shown in Table 4. In the same manner as in Example 1, the amount of generated nitrogen and the nitrogen yield were determined. Table 4 shows the results.
【００３８】[0038]
【表４】 [Table 4]
【００３９】実施例５ 実施例４と同様にして、均圧工程における回収率を表５
に示すように変化させ、酸素含有量１００ｐｐｍの高純
度窒素ガスを発生させた。実施例１と同様にして窒素発
生量と窒素収率とを求めた。結果を表５に示す。Example 5 In the same manner as in Example 4, the recovery rate in the pressure equalization step is shown in Table 5.
And a high-purity nitrogen gas having an oxygen content of 100 ppm was generated. In the same manner as in Example 1, the amount of generated nitrogen and the nitrogen yield were determined. Table 5 shows the results.
【００４０】[0040]
【表５】 [Table 5]
【００４１】これらの各実施例の結果から、加圧工程に
おける圧力上昇速度を０．１５〜１．６ＭＰａ／ｍｉｎ
の範囲にすることによって、また、均圧工程の時間を７
〜２７秒の範囲にすることによって、窒素発生量及び窒
素収率を低下させることなく、酸素含有量１０ｐｐｍ及
び１００ｐｐｍの高純度窒素ガスを発生できることがわ
かる。さらに、均圧工程における回収率を適度に低くす
ることにより、窒素発生量を増大できることがわかる。From the results of each of these examples, it was found that the rate of pressure increase in the pressurizing step was 0.15 to 1.6 MPa / min.
And the time for the pressure equalization step is 7
It can be seen that by setting the range to 27 seconds, high-purity nitrogen gas having an oxygen content of 10 ppm and 100 ppm can be generated without lowering the nitrogen generation amount and the nitrogen yield. Further, it can be seen that the nitrogen generation amount can be increased by appropriately reducing the recovery rate in the pressure equalization step.
【００４２】[0042]
【発明の効果】以上説明したように、本発明の窒素ガス
発生方法によれば、酸素含有量が１００ｐｐｍ以下の高
純度窒素ガスを効率よく発生させることができ、消費電
力や分子ふるい炭素の使用量も削減でき、装置価格の低
減も図れる。As described above, according to the method for generating nitrogen gas of the present invention, high-purity nitrogen gas having an oxygen content of 100 ppm or less can be efficiently generated, and power consumption and the use of molecular sieve carbon can be reduced. The amount can be reduced, and the cost of the apparatus can be reduced.
【図１】 本発明の窒素ガス発生方法を適用したＰＳＡ
装置の一形態例を示す系統図である。FIG. 1 shows a PSA to which the nitrogen gas generation method of the present invention is applied.
It is a system diagram showing an example of one form of a device.
【図２】 各工程におけるガスの流れを示す説明図であ
る。FIG. 2 is an explanatory diagram showing a gas flow in each step.
Ａ，Ｂ…吸着筒、１ａ，１ｂ…入口弁、２ａ，２ｂ…出
口弁、３ａ，３ｂ…排気弁、４…パージ弁、５，６…均
圧弁、７，８，９，１０…流量調節弁、１１…空気圧縮
機、１２…エアドライヤ、１３…空気貯槽、１４…製品
窒素貯槽A, B: adsorption cylinder, 1a, 1b: inlet valve, 2a, 2b: outlet valve, 3a, 3b: exhaust valve, 4: purge valve, 5, 6: equalizing valve, 7, 8, 9, 10: flow rate adjustment Valve, 11 ... Air compressor, 12 ... Air dryer, 13 ... Air storage tank, 14 ... Product nitrogen storage tank
───────────────────────────────────────────────────── フロントページの続き (72)発明者 渡辺 良紀 東京都港区西新橋１−16−７ 日本酸素株 式会社内 (72)発明者 川井 雅人 東京都港区西新橋１−16−７ 日本酸素株 式会社内 Ｆターム(参考） 4D012 BA04 CA06 CB16 CD07 CE03 CF01 CF03 CF05 CF10 CG01 CH05 CJ01 CJ03 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshinori Watanabe 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo Inside Nippon Sanso Corporation (72) Inventor Masato Kawai 1-16-7, Nishi-Shimbashi, Minato-ku, Tokyo Japan F-term in Oxygen Co., Ltd. (reference) 4D012 BA04 CA06 CB16 CD07 CE03 CF01 CF03 CF05 CF10 CG01 CH05 CJ01 CJ03
Claims (2)
着、減圧均圧、減圧再生、加圧均圧の各工程を繰り返す
圧力変動吸着法によって空気から酸素含有率が１００ｐ
ｐｍ以下の窒素ガスを分離する方法において、前記加圧
工程における圧力上昇速度を０．１５〜１．６ＭＰａ／
ｍｉｎとし、前記均圧工程の時間を７〜２７秒とするこ
とを特徴とする窒素ガス発生方法。1. A pressure fluctuation adsorption method in which molecular sieve carbon is used as an adsorbent and pressure, adsorption, reduced pressure equalization, reduced pressure regeneration, and pressurized equalization are repeated to obtain an oxygen content of 100 p from air.
pm or less, wherein the pressure increasing rate in the pressurizing step is 0.15 to 1.6 MPa /
min, and the time of the equalizing step is 7 to 27 seconds.
が、７０〜１００％であることを特徴とする請求項１記
載の窒素ガス発生方法。2. The nitrogen gas generation method according to claim 1, wherein the gas recovery rate in the pressure equalization step is 70 to 100%.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7670408B2 (en) | 2004-08-30 | 2010-03-02 | Kuraray Chemical Co., Ltd. | Method of separating nitrogen gas and molecular sieve carbon |
| JP2010227770A (en) * | 2009-03-26 | 2010-10-14 | Jfe Steel Corp | Method of controlling flow rate for pressure swing adsorption equipment |
| WO2013176413A1 (en) * | 2012-05-21 | 2013-11-28 | 사단법인 한국선급 | Nitrogen generation, storage, and supply system for tanker ships, and method for controlling same |
-
2001
- 2001-03-21 JP JP2001080069A patent/JP4761635B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7670408B2 (en) | 2004-08-30 | 2010-03-02 | Kuraray Chemical Co., Ltd. | Method of separating nitrogen gas and molecular sieve carbon |
| JP2010227770A (en) * | 2009-03-26 | 2010-10-14 | Jfe Steel Corp | Method of controlling flow rate for pressure swing adsorption equipment |
| WO2013176413A1 (en) * | 2012-05-21 | 2013-11-28 | 사단법인 한국선급 | Nitrogen generation, storage, and supply system for tanker ships, and method for controlling same |
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