JP3596292B2

JP3596292B2 - Nitrogen enrichment equipment

Info

Publication number: JP3596292B2
Application number: JP19531798A
Authority: JP
Inventors: 直己高田; 行男池田; 真二目伯; 喜博楠木
Original assignee: Ube Industries Ltd
Current assignee: Ube Corp
Priority date: 1998-07-10
Filing date: 1998-07-10
Publication date: 2004-12-02
Anticipated expiration: 2018-07-10
Also published as: JP2000024442A

Description

【０００１】
【発明の属する技術分野】
本発明は、中空糸分離膜を用いて空気から、窒素富化空気を製造する装置に関し、詳しくは、運転休止後の運転再開時に、所定の特性のガスを製造し始めるまでの時間を短縮することを目的にした窒素富化装置に関するものである。
【０００２】
【従来の技術】
窒素富化空気は、包装、保存等の食品加工分野、穀類の防かび、防虫、果物・野菜の保存等の食糧分野、配管やタンクのパ−ジ、防爆等の化学・燃料分野をはじめ、電子工業分野、薬品分野、金属分野等々において広く利用されている。近年、中空糸膜及びその製造技術、分離膜モジュ−ル製造技術等分離膜技術の進展に伴い、分離膜を用いて空気から窒素富化空気或いは酸素富化空気を製造する方法が、例えば特開昭５６−９１８０２号公報、特開昭５７−８２１０５号公報、特開平２−２５２６０９号公報等において種々提案されている。
【０００３】
窒素富化装置は、冷凍除湿機や分離膜モジュールを用いて通常あらかじめ乾燥されている原料空気が供給されており、原料空気は、分離膜モジュールの非透過側に供給され、酸素などの透過速度の大きいガスは膜を透過し、透過側から回収あるいは除去され、窒素の富化された空気は非透過側から回収される。窒素富化装置は、周期的にあるいは間欠的に運転されるのが通常である。
【０００４】
しかしながら、一般に、高分子材料を分離膜材料とする窒素富化装置では、運転をある期間休止し再稼動する場合、始動後すぐには所定の分離性能は得られず、また、所定の分離膜性能に回復するまでの時間が長いため無駄な運転を強いられるという問題が発生している。
【０００５】
【発明が解決しようとする課題】
本発明は、窒素富化装置において、運転休止時に起こる分離膜モジュールの一時的な性能低下を防止し、運転を再始動したときの膜の性能回復までの時間を短縮する方法とその装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者らは、分離膜モジュールの空気の分離性能が低下する原因を種々検討し、それが運転休止期間中にモジュール内に進入する大気中の汚染物質や水分の影響であることを見出し、本発明を創生するに至った。
【０００７】
即ち、本発明は、空気供給口、透過側排出口および非透過側排出口を有する窒素富化装置であり、圧縮乾燥空気を、中空糸膜の束からなる分離膜モジュールを内蔵する窒素富化装置の中空糸の内側へ供給し、該空気中の酸素を該中空糸膜の外側へ選択的に透過させて、内側に非透過の窒素富化空気を生成させる窒素富化装置において、空気供給口、透過側排出口および非透過側排出口のそれぞれに、運転休止中外気と遮断する手段を設けたことを特徴とする窒素富化装置に関するものである。
【０００８】
本発明の上記運転休止中の外気と遮断する手段としては、バルブ、逆止弁が好ましい。
【０００９】
また、本発明は、空気供給口、透過側排出口および非透過側排出口を有する窒素富化装置であり、圧縮乾燥空気を、中空糸膜の束からなる分離膜モジュールを内蔵する窒素富化装置の中空糸の内側へ供給し、該空気中の酸素を該中空糸膜の外側へ選択的に透過させて、内側に非透過の窒素富化空気を生成させる窒素富化装置において、運転休止中、分離膜モジュールの内部に外気が進入しないように空気供給口、透過側排出口および非透過側排出口を遮断しておくことを特徴とする分離膜の性能維持方法に関するものである。
【００１０】
【発明の実施の形態】
本発明の窒素富化装置について、図面を参照にして詳細に説明する。
【００１１】
図１は、窒素富化空気の製造法を表わす概略図である。また、図２は、窒素富化装置の一例を示す断面図である。水分を含有する原料空気は加圧機（コンプレッサ）１に供給されて、タンク２に貯蔵される。タンク２に貯蔵された加圧空気は、分離膜モジュールあるいは冷凍除湿機などの脱湿装置３を通過し、エアフィルタ４（必要に応じてミストセパレータ）を経て、減圧弁５で圧力調整され、本発明の遮断手段６を通過後、分離膜モジュール７の一方の中空糸膜の内側、即ち中空（孔）に入り、中空糸中を流動して通過する間に、酸素または水分が中空糸膜の外側に透過して、モジュールの透過側出口から本発明の遮断手段９を通過して装置外部に出てくる。一方、中空糸の内部を通過し、非透過の窒素富化空気は、中空糸のもう一方の出口から本発明の遮断手段８を通過し流量調整弁１０を経て装置外部に出てくる。
【００１２】
窒素富化装置は、図２に示すように、少なくとも乾燥された空気を供給するための供給口２１と、非透過の窒素富化空気を回収・排出させるための排出口２２及び中空糸膜を透過した酸素富化空気を回収するための排出口２３を備えた容器２０に、酸素を選択的に透過する中空糸膜２４の束からなる分離膜モジュ−ルが内蔵されているものが使用され、容器の供給口、排出口にそれぞれ遮断手段６，８、９を設けたもので構成される。中空糸膜２４はその両端の中空（孔）が塞がらない様に両端をエポキシ樹脂の如き樹脂で一体的に固着されている。
【００１３】
装置を運転しているときは、遮断手段は、開いた状態であり、運転休止の時は、遮断手段は閉じた状態となり、モジュールの内に外気は入らない状態となるようにする。
【００１４】
外気との遮断手段としては、バルブ、逆止弁、ブリーザバルブなど遮断機能を有するものなら何でも良いが、窒素富化の機能を低減させないために極力通気抵抗の小さいものが好ましい。
【００１５】
遮断手段として、逆止弁など、ガスがくればガスの圧力で遮断板が開き、ガスが停止すれば、重力で遮断板が閉じる形式のものを用いれば、運転停止、再開ごとに遮断手段を開閉する作業を行なう必要がない。
【００１６】
なお、本発明は、窒素富化装置について述べたものであるが、膜の透過側に注目すれば、酸素発生装置であり、発明の内容は、酸素発生装置にも適用できる。
【００１７】
【実施例】
実施例１
図１の工程に従って、膜厚１００μｍ、外径５００μｍ及び長さ４５０ｍｍの芳香族ポリイミドの非対称性中空糸膜を束ねた中空糸モジュールからなる直径４０ｍｍ、長さ５００ｍｍの分離膜モジュールを使い、遮断手段６，８，９としてガスの供給が止まると遮断する機能を有する逆止弁を使用して、以下の操作を行なった。
【００１８】
最初に、モジュールに入る原料空気の圧力を７ｋｇ／ｃｍ^２Ｇ、温度を２５℃にし、窒素富化空気流量が１５ＮＬ／ｍｉｎになるように調整し、２４時間運転を行なった。その後、運転を停止した。運転を停止しているときの大気の温度は２５〜３１℃、湿度は６０〜７０％であった。運転を停止してから２４時間後に、再び前記と同じ条件で運転を開始した（この運転を停止後１回目の運転とする）。２４時間の運転と２４時間の停止を繰り返し、膜の非透過側から出てくる空気の酸素濃度を測定した。酸素濃度計は、図１の非透過側の流量調整弁１０の直後に設けた。運転再開時の酸素濃度の経時変化を表１に示す。酸素濃度は、運転開始直後から、ほぼ運転終了時に近い濃度４．９％を示した。
【００１９】
【表１】

【００２０】
比較例１
実施例１のモジュールへの入り口および２つの出口につながった逆止弁を取り外し、遮断手段を有しない状態で、実施例１と同じ条件で、運転と停止を繰り返し、膜の非透過側から出てくる空気の酸素濃度を測定した。運転再開時の経時変化を表２に示す。運転再開直後は、酸素濃度は５．４〜６．０％を示し、およそ、５〜６時間を要して安定値４．９％に到達した。実施例１と比較例１のそれぞれの測定結果の平均値をグラフにしたものを図３に示す。本発明により運転再開時の定常運転に達するまでの時間が大幅に短縮されることがわかる。
【００２１】
【表２】

【００２２】
【発明の効果】
窒素富化装置において空気の供給口および排出口のそれぞれに外気がモジュール内部に進入する遮蔽手段を設けることにより、運転休止時に起こる分離膜モジュールの一時的な性能低下を防止し、運転再始動したときの膜の性能回復までの時間を節約することができる。
【図面の簡単な説明】
【図１】本発明の窒素富化装置の説明のための窒素富化空気の製造工程
【図２】本発明の遮断手段を有する窒素富化装置
【図３】運転休止中に外気との遮断を行なう場合と行なわない場合の運転再開時の非透過側出口酸素濃度の経時変化を示す図
【符号の説明】
１；加圧機（コンプレッサ）
２；タンク
３；脱湿装置
４；エアフィルタ（及びミストセパレータ）
５；減圧弁
６；モジュール入り口への遮断手段
７；モジュール
８；非透過側出口の遮断手段
９；透過側出口の遮断手段
１０；流量調節弁
２０；モジュール容器
２１；モジュール入り口
２２；モジュール非透過側出口
２３；モジュール透過側出口
２４；中空糸膜[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for producing nitrogen-enriched air from air using a hollow fiber separation membrane, and more specifically, to reduce the time required to start producing gas having a predetermined characteristic when the operation is resumed after the operation is stopped. The present invention relates to a nitrogen enrichment apparatus for the purpose.
[0002]
[Prior art]
Nitrogen-enriched air is used in the food processing field such as packaging and preservation, the food field such as fungicide and insect control of cereals, the preservation of fruits and vegetables, the purging of pipes and tanks, and the chemical and fuel fields such as explosion protection. It is widely used in the fields of electronics industry, medicine, metal, and the like. In recent years, with the development of separation membrane technology such as a hollow fiber membrane and its production technology, and a production technology of a separation membrane module, a method for producing nitrogen-enriched air or oxygen-enriched air from air using a separation membrane has been developed. Various proposals have been made in JP-A-56-91802, JP-A-57-82105, JP-A-2-252609, and the like.
[0003]
The nitrogen enrichment apparatus is supplied with raw air which is usually dried in advance using a refrigeration dehumidifier or a separation membrane module, and the raw air is supplied to the non-permeate side of the separation membrane module, and the permeation rate of oxygen and the like is increased. Larger gases permeate the membrane and are collected or removed from the permeate side, and nitrogen-enriched air is collected from the non-permeate side. The nitrogen enrichment unit is usually operated periodically or intermittently.
[0004]
However, in general, in a nitrogen enrichment apparatus using a polymer material as a separation membrane material, when the operation is stopped for a certain period and restarted, a predetermined separation performance cannot be obtained immediately after starting, and a predetermined separation membrane is not obtained. Since the time until the performance is restored is long, there is a problem that useless driving is forced.
[0005]
[Problems to be solved by the invention]
The present invention provides a method and an apparatus for preventing a temporary decrease in performance of a separation membrane module caused during a suspension of operation in a nitrogen enrichment apparatus, and shortening a time until the performance of the membrane is recovered when the operation is restarted. The purpose is to do.
[0006]
[Means for Solving the Problems]
The present inventors have studied various causes of the decrease in the air separation performance of the separation membrane module, and found that it is the effect of atmospheric contaminants and moisture entering the module during the shutdown period, This led to the creation of the present invention.
[0007]
That is, the present invention is a nitrogen enrichment apparatus having an air supply port, a permeate side discharge port, and a non-permeate side discharge port. In a nitrogen-enriching apparatus, which supplies air inside the hollow fiber of the apparatus and selectively permeates oxygen in the air to the outside of the hollow fiber membrane to generate nitrogen-enriched air impermeable inside, The present invention relates to a nitrogen-enriching apparatus characterized in that a means for shutting off outside air during operation suspension is provided at each of the mouth, the permeate-side outlet and the non-permeate-side outlet.
[0008]
As a means for shutting off the outside air during the operation stoppage of the present invention, a valve and a check valve are preferable.
[0009]
The present invention is also a nitrogen-enriching apparatus having an air supply port, a permeate-side outlet, and a non-permeate-side outlet. The nitrogen-enriched apparatus includes a separation membrane module including a bundle of hollow fiber membranes. In a nitrogen-enrichment device that supplies inside the hollow fiber of the device and selectively permeates oxygen in the air to the outside of the hollow-fiber membrane to generate non-permeated nitrogen-enriched air inside, The present invention relates to a method for maintaining performance of a separation membrane, wherein an air supply port, a permeation side discharge port, and a non-permeation side discharge port are shut off so that outside air does not enter the inside of the separation membrane module.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The nitrogen enrichment apparatus of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a schematic diagram illustrating a method for producing nitrogen-enriched air. FIG. 2 is a sectional view showing an example of the nitrogen enrichment device. The raw material air containing water is supplied to a pressurizing machine (compressor) 1 and stored in a tank 2. The pressurized air stored in the tank 2 passes through a dehumidifier 3 such as a separation membrane module or a refrigeration dehumidifier, passes through an air filter 4 (if necessary, a mist separator), and is pressure-adjusted by a pressure reducing valve 5, After passing through the blocking means 6 of the present invention, oxygen or moisture is introduced into the inside of one hollow fiber membrane of the separation membrane module 7, that is, into the hollow (hole), and flows and passes through the hollow fiber. And exits the apparatus through the blocking means 9 of the present invention from the transmission side outlet of the module. On the other hand, the non-permeated nitrogen-enriched air passing through the inside of the hollow fiber passes through the shut-off means 8 of the present invention from the other outlet of the hollow fiber, and comes out of the apparatus through the flow control valve 10.
[0012]
As shown in FIG. 2, the nitrogen-enriching device includes a supply port 21 for supplying at least dried air, an outlet 22 for collecting and discharging non-permeated nitrogen-enriched air, and a hollow fiber membrane. A container 20 having a discharge port 23 for collecting the permeated oxygen-enriched air and having a built-in separation membrane module composed of a bundle of hollow fiber membranes 24 selectively permeable to oxygen is used. , And the supply port and the discharge port of the container are provided with

blocking means

6, 8, and 9, respectively. Both ends of the hollow fiber membrane 24 are integrally fixed with a resin such as an epoxy resin so that the hollows (holes) at both ends are not closed.
[0013]
When the apparatus is operating, the shut-off means is in an open state, and when the operation is stopped, the shut-off means is in a closed state so that no outside air enters the module.
[0014]
As the means for shutting off the outside air, any means having a shutoff function such as a valve, a check valve or a breather valve may be used. However, a means having as low a ventilation resistance as possible is preferable so as not to reduce the function of enriching nitrogen.
[0015]
If a shut-off means such as a check valve is used, the shut-off plate opens with the pressure of the gas if gas comes, and if the gas stops, the shut-off plate closes by gravity. There is no need to open and close.
[0016]
Although the present invention has been described with respect to a nitrogen enrichment apparatus, if attention is paid to the permeation side of the membrane, it is an oxygen generator, and the content of the invention can be applied to an oxygen generator.
[0017]
【Example】
Example 1
According to the process shown in FIG. 1, using a separation membrane module having a diameter of 40 mm and a length of 500 mm, which is a hollow fiber module obtained by bundling aromatic polyimide asymmetric hollow fiber membranes having a thickness of 100 μm, an outer diameter of 500 μm and a length of 450 mm, The following operations were performed using check valves having a function of shutting off when the supply of gas was stopped as 6, 8, and 9.
[0018]
First, the pressure of the raw material air entering the module was adjusted to 7 kg / cm ² G, the temperature was adjusted to 25 ° C., the flow rate of the nitrogen-enriched air was adjusted to 15 NL / min, and the module was operated for 24 hours. Thereafter, the operation was stopped. When the operation was stopped, the temperature of the atmosphere was 25 to 31 ° C and the humidity was 60 to 70%. Twenty-four hours after the operation was stopped, the operation was started again under the same conditions as above (this operation is referred to as the first operation after the stop). The operation for 24 hours and the stop for 24 hours were repeated, and the oxygen concentration of the air emerging from the non-permeate side of the membrane was measured. The oxygen concentration meter was provided immediately after the flow control valve 10 on the non-permeate side in FIG. Table 1 shows changes over time in the oxygen concentration when the operation is restarted. The oxygen concentration showed a concentration of 4.9% immediately after the start of the operation and almost at the end of the operation.
[0019]
[Table 1]

[0020]
Comparative Example 1
The check valve connected to the entrance and the two exits to the module of Example 1 was removed, and the operation and the stop were repeated under the same conditions as in Example 1 without the shut-off means, and the membrane exited from the non-permeate side of the membrane. The oxygen concentration of the incoming air was measured. Table 2 shows changes over time when the operation is restarted. Immediately after restarting the operation, the oxygen concentration showed 5.4 to 6.0%, and reached the stable value of 4.9% in about 5 to 6 hours. FIG. 3 is a graph showing the average values of the respective measurement results of Example 1 and Comparative Example 1. It can be seen that the time required to reach steady operation at the time of restart of operation is greatly reduced by the present invention.
[0021]
[Table 2]

[0022]
【The invention's effect】
In the nitrogen enrichment apparatus, by providing a shielding means for the outside air to enter the inside of the module at each of the supply port and the discharge port of the air, it is possible to prevent a temporary decrease in performance of the separation membrane module which occurs at the time of suspension of operation and restart the operation. The time until the performance recovery of the membrane can be saved.
[Brief description of the drawings]
FIG. 1 shows a process for producing nitrogen-enriched air for explaining the nitrogen-enriched apparatus of the present invention. FIG. 2 shows a nitrogen-enriched apparatus having shut-off means of the present invention. Showing the change over time in the oxygen concentration at the non-permeate side outlet when the operation is restarted with and without [Description of Signs]
1: Pressing machine (compressor)
2; tank 3; dehumidifier 4; air filter (and mist separator)
5; pressure reducing valve 6; shut-off means 7 to module inlet; module 8; shut-off means 9 for non-permeate outlet; shut-off means 10 for permeate outlet; flow control valve 20; module container 21; module inlet 22; Side outlet 23; module transmission side outlet 24; hollow fiber membrane

Claims

A nitrogen-enriching apparatus having an air supply port, a permeate-side outlet, and a non-permeate-side outlet, and compresses dry air into the inside of a hollow fiber of a nitrogen-enrichment apparatus incorporating a separation membrane module comprising a bundle of hollow fiber membranes. In a nitrogen-enriching apparatus that selectively permeates oxygen in the air to the outside of the hollow fiber membrane to generate non-permeated nitrogen-enriched air inside the hollow fiber membrane. By shutting off the air supply port, the permeate-side discharge port and the non-permeate-side discharge port with a blocking means directly connected to the supply port and the discharge port so that outside air does not enter the inside, the predetermined concentration can be obtained when the operation is resumed. A method for shortening the time until nitrogen-enriched air is obtained .

2. The method according to claim 1, wherein the separation membrane is an asymmetric hollow fiber membrane made of an aromatic polyimide, the time required until a predetermined concentration of nitrogen-enriched air is obtained when the operation is restarted.