KR20000031296A - Method of preparing nitrogen by pressure swing absorption and device therefor - Google Patents

Abstract

PURPOSE: A method of preparing nitrogen by pressure-change absorption and a device therefor are provided which separates gaseous nitrogen from air and produces the nitrogen by employing pressure swing absorption method. CONSTITUTION: The method comprises steps of: (i) absorption process; (ii) atmospheric desorption process(I); (iii) washing desorption process; (iv) uniform-pressure process; (v) condensing-pressure process; and (vi) atmospheric desorption process(II). In the absorption process, raw material air is compressed at an air compressor(1) and then gone through a filter(2), and it is moisture-eliminated and cooled down at an air drier(3) and then introduced to an absorption tower(20), where oxygen, carbon dioxide and moisture is absorbed, and non-absorbed product nitrogen component is stored at a product tank. In the atmospheric desorption process(I), the absorbed oxygen, carbon dioxide and moisture are emitted through a muffler(4) by opening an automatic valve(17). In the washing desorption process, product nitrogen component is stored at the product tank through the absorption process by continuously opening automatic valves(6 and 10) at the absorption tower(20), while an absorption tower(21) opens a hand valve(28) and an automatic valve(18) at the product storing tank and washes inside of the top with washing gas. In the uniform-pressure process, the pressure of the absorption tower(20) and the absorption tower(21) become same by closing the automatic valves(6), (17), (18) and (10) and opening a uniform automatic valve(9). In the condensing-pressure process, the nitrogen gas in the product tank compresses inside of the absorption tower by closing the automatic valve(9) and opening the automatic valve(18), so the oxygen on top of the absorption tower is moved downward. In the atmospheric desorption process(II), the absorbed oxygen, carbon dioxide and moisture are emitted through the muffler(4) by opening the automatic valve(17).

Description

Pressure swing adsorption nitrogen production method and device

The present invention relates to a pressure swing adsorption nitrogen production method and apparatus for separating and producing gaseous nitrogen from the air by pressure swing adsorption.

In the conventional method of preparing nitrogen by pressure swing adsorption (PSA), the activated alumina is filled at the bottom of the adsorption tower and the carbon molecular sieve (CMS) is adsorbed at the top to remove moisture from the air. Development of a nitrogen production method and apparatus for continuously repeating the adsorption and desorption of adsorbents by selectively adsorbing and removing oxygen, carbon dioxide, and water in the air using two adsorption towers, recovering nitrogen and reducing the pressure to atmospheric pressure It has been rapidly spreading for a long time.

In particular, Japanese Patent Publication No. H5-32087 sends part of the product nitrogen separated in the adsorption process into the tower, which is an atmospheric pressure desorption process, through an orifice, and is used as a cleaning gas. Also, in the pressure equalization process, the oxygen content in the lower part of the adsorption tower on the supply side is transferred to the upper part of the adsorption tower on the side of the adsorption tower on the side of the absorption tower. This change causes the instability of the nitrogen concentration gradient to be difficult to keep the product purity constant, resulting in a drop in product recovery.

In addition, in Korean Patent Publication No. 95-703396, product nitrogen, which is separated in the adsorption process and stored in the balance tank, is sent to the tower, which is a desorption process, through a check valve, which is used as a cleaning gas. Causes deterioration. And even in the equalization process, the adsorption tower on the supply side and the adsorption tower on the receiving side are released to the atmosphere at the same time as the equalization pressure, there is a problem that the nitrogen recovery rate is lowered.

An object of the present invention is to recover the concentration of nitrogen in the air by using a two-stage adsorption tower filled with carbon alumina to selectively adsorb the active alumina, the upper portion of the adsorption column to solve the above problems, In the adsorption process, the carbon molecular sieve filled in the adsorption column selectively adsorbs oxygen and collects the concentrated nitrogen exhausted in the product tank and recovers it to the product tank. After the regeneration and adsorption process, the residual nitrogen component in the upper part is connected to the tower where the desorption process is completed to recover the residual nitrogen component to provide a pressure change adsorption nitrogen production method and apparatus to improve the purity and recovery rate of the product.

The pressure swing adsorption nitrogen production method of the present invention is subjected to a pressure storing process and a pressure supplying side and a pressure supplying side to pressurize a product nitrogen to a tower which has been subjected to an atmospheric pressure desorption process and a pressure equalizing process, which does not introduce product nitrogen gas into an adsorption tower during atmospheric pressure desorption. It has a pressure equalization process connecting to the upper side of the adsorption tower.

The apparatus for producing pressure swing adsorption nitrogen according to the present invention uses nitrogen in the air by using two adsorption towers filled with activated alumina in the lower part of the adsorption column and carbon molecules for selectively adsorbing oxygen in the upper part to remove moisture in the air. Concentrate and recover.

1 is a process flow diagram showing a nitrogen production method and apparatus of the present invention.

<Description of Symbols in Drawings>

1: air compressor 2: filter

3: air dryer 4: silencer

5: Product tank 6,16: Automatic air supply valve

7,17: Automatic exhaust gas valve 8,18: Automatic cleaning gas supply valve

9: Equal pressure automatic valve 10,19: Production discharge automatic valve

20, 21: adsorption column 28: cleaning gas supply manual valve

The present invention will be described in detail with reference to the accompanying drawings.

1 is a process flow diagram showing a nitrogen production method and apparatus of the present invention.

The apparatus of the present invention provides an air compressor (1) for supplying raw air, a filter (2) for removing impurities in the supplied air, a refrigeration air dryer (3) for dehumidifying and cooling the air, and product cleaning gas. Air supply automatic valves 6 and 16 for supplying raw air to the silencer 4, product tank 5, adsorption tower 20 and 21, and an exhaust gas automatic valve for exhausting exhaust gas from the adsorption tower ( 7) and (17), automatic cleaning gas supply valves (8) and (18), manual valves (28), pressure equalizing automatic valves (9) and product nitrogen production discharge automatic valves (10), which send cleaning gas from the product tank to the adsorption tower. And (19).

Nitrogen production method of the present invention consists of the following steps.

Nitrogen production method of the present invention consists of an adsorption process, atmospheric desorption process, cleaning desorption process, pressure equalization process, pressure storage process and atmospheric pressure desorption process.

In the adsorption process, raw air compressed at a predetermined pressure in the air compressor (1) is dehumidified and cooled in the air dryer (3) via the filter (2), and introduced into the adsorption tower (20) via the automatic valve (6) to provide oxygen and carbonic acid. Gas and moisture are adsorbed, but the product nitrogen component is not adsorbed is made to be stored in the product tank via an automatic valve (10).

The atmospheric desorption process is performed by releasing oxygen, carbon dioxide, moisture, etc. adsorbed in the adsorption tower 21 to the atmosphere through the silencer 4 by opening the automatic valve 17.

The cleaning desorption process continuously opens the automatic valves 6 and 10 of the adsorption tower 20 to perform the adsorption process to store the product nitrogen components in the product storage tank, while the adsorption tower 21 is a manual valve of the product storage tank. (28) and the automatic valve 18 are opened to clean the inside of the tower with the product cleaning gas, and the air is discharged through the automatic valve 17 and the silencer (4).

The pressure equalizing step is to close the automatic valves (6), (17), (18) and (10), and open the equalizing pressure automatic valve (9) so that the pressure of the adsorption step 20, where the adsorption step is completed, is the normal pressure desorption step and the cleaning desorption step. The pressure is moved to the adsorption tower 21, and at this time, the nitrogen component remaining in the upper part of the adsorption tower 20 is recovered from the adsorption tower 21 and pressure equalization is performed.

In the pressure storing process, the automatic valve 9 is closed and the automatic valve 18 is opened to accumulate nitrogen gas in the product tank in the column of the adsorption tower 21. Therefore, the oxygen component of the upper part of the adsorption tower is moved as low as possible before entering the adsorption process in the tower. It can be made by improving the purity and product recovery rate of the product.

The atmospheric desorption process is performed by releasing oxygen, carbon dioxide, moisture, etc. adsorbed in the adsorption tower 20 to the atmosphere through the silencer 4 by opening the automatic valve 7.

In the nitrogen production method of the present invention, product nitrogen can be continuously produced by repeatedly performing adsorption, desorption, equalization, and accumulating by alternating adsorption towers 20 and 21 in the same process as described above.

In the nitrogen production method of the present invention, the carbon molecular sieve filled in the adsorption tower in the adsorption process selectively absorbs oxygen and collects the concentrated nitrogen exhausted in the product tank and recovers the product, and the adsorption tower saturated with oxygen is first subjected to atmospheric pressure desorption to atmospheric pressure. Then, it is washed with product nitrogen and regenerated.

In addition, the residual nitrogen component of the upper part after the adsorption process is connected to the tower after the desorption process to recover the residual nitrogen component to improve the purity and recovery rate of the product.

Example

Production of nitrogen from air using the nitrogen production apparatus of the present invention shown in Figure 1 was carried out according to the nitrogen production method of the present invention.

In order to remove moisture in the air, the bottom of the air dryer and the adsorption tower was filled with activated alumina, and the upper part was filled with carbon molecular sieve. The inner diameters of the adsorption towers 20 and 21 were 84.9 mm and the height 2,600 mm.

The adsorbent filling amount per tower was 1.7 kg of alumina and 8.7 kg of carbon molecular sieve.

Using the above experimental device, the raw material air pressure was 6 to 7 kg / cm ² G, the flow rate was 66.0 ℓ / min, and the operating cycle time was 120 seconds. It produced and obtained 34% recovery.

Under the same conditions as above, the product nitrogen purity was maintained at 99.9%, and the yield was 25.5% to produce 13.0 L / min of product nitrogen.

Comparative example

The same equipment as in Example was used to clean the inside of the column with product nitrogen gas in the atmospheric desorption process, and the pressure storing step was omitted to separate nitrogen from the air in the same process as in Example. As a result, the product nitrogen recovery was 32% when the product nitrogen purity was 99.9%, and the product nitrogen recovery was 23% when the product nitrogen purity was 99.99%.

In the nitrogen production method and apparatus of the present invention, an automatic valve is installed between the tower and the product nitrogen tank, which is an atmospheric pressure desorption process, so that the product nitrogen cleaning gas is not discharged to the atmosphere during atmospheric pressure desorption, thereby improving the product recovery rate and introducing an optimal cleaning gas. In this way, the product nitrogen purity can be kept constant.

In addition, since the nitrogen component of the upper part of the adsorption tower connected to the upper part of the adsorption tower of the supply side and the upper side of the adsorption tower of the supply side is moved to the upper part of the adsorption tower of the receiving side, the flow of gas inside the tower does not change, and the upper part of the adsorption tower By accumulating the product with nitrogen, it facilitates the material movement between the product nitrogen and the oxygen component remaining in the tower to the maximum, and moves the oxygen component of the upper part of the adsorption column to the lower part as possible before entering the adsorption process, thereby improving the purity and product recovery rate of the product. can do.

Claims (2)

It consists of adsorption process, atmospheric desorption process, cleaning desorption process, pressure equalizing process, accumulating process and atmospheric pressure desorption process, wherein the adsorption process is carried out through the filter (2) where the raw air compressed at a predetermined pressure in the air compressor (1) is passed through the filter (2). The product nitrogen (3) is dehumidified and cooled and introduced into the adsorption tower (20) through the automatic valve (6) to adsorb oxygen, carbon dioxide, and water, and the non-adsorbed product nitrogen components through the automatic valve (10). The atmospheric pressure desorption process is performed by releasing oxygen, carbon dioxide, and moisture adsorbed in the adsorption tower 21 into the air through the silencer 4 by opening the automatic valve 17. The cleaning desorption process is performed by the adsorption tower. The automatic valves (6) and (10) of (20) are continuously opened to perform the adsorption process to store the product nitrogen components in the product tank, while the adsorption tower 21 is a manual valve 28 and an automatic valve (in the product tank). 18) Open and wash the inside of the tower with product cleaning gas. The air is discharged through the automatic valve 17 and the silencer 4, and the equalizing process is performed by closing the automatic valves 6, 17, 18 and 10, and opening the equalizing automatic valve 9. The pressure of the adsorption tower 20 after the adsorption process is moved to the adsorption tower 21 where the atmospheric pressure desorption process and the cleaning desorption process are completed. At this time, the nitrogen component remaining in the upper portion of the adsorption tower 20 is recovered from the adsorption tower 21. The pressure accumulating process closes the automatic valve 9 and opens the automatic valve 18 to accumulate the nitrogen gas in the product tank in the column of the adsorption tower 21 so that the oxygen in the upper part of the adsorption tower before entering the adsorption process in the tower. It is made by moving the components to the lower side as possible, the atmospheric pressure desorption process is the pressure that is released through the silencer (4) by opening the automatic valve (7) of oxygen, carbon dioxide, water, etc. adsorbed in the adsorption tower (20) tower Variable adsorption nitrogen production method. The method of claim 1, Nitrogen production method for continuously producing the product nitrogen by repeatedly performing the adsorption, desorption, equalization, accumulator alternately adsorption tower (20) and (21) in the same process as described above.