NL8601664A - METHOD FOR INCREASING THE CONTENT OF AT LEAST A DESIRED COMPONENT OF GAS CONTAINING MULTIPLE COMPONENTS; INSTALLATION FOR CARRYING OUT SUCH A METHOD AND AIR ENRICHED WITH OXYGEN USING THE METHOD - Google Patents

Description

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865042 / Ba / Jb

Title: A method for increasing the content of at least one desired component of a multi-component gas; installation for carrying out such a method and air enriched with oxygen using the method.

The invention relates to a method of increasing the content of at least one desired component of a multi-component gas using pressure swing adsorption.

Such a method is known from the

U.S. Patent 3,237,377. This patent discloses a method in which an air stream is introduced into an adsorbent-containing bed at relatively high pressure and nitrogen, moisture and CO2 are adsorbed by the adsorbent. The product leaving the adsorption zone therefore has an increased oxygen content. Following adsorption, a desorption step is performed at relatively low pressure to release and vent the gases selectively adsorbed by the adsorbent. The steps of adsorption and desorption are performed in relatively rapid succession and the flow direction through the bed during adsorption and desorption is opposite.

During the adsorption of gaseous substances to solid adsorbents, latent heat of adsorption is released. This heat of adsorption leads to an increase in temperature of the adsorbent and the non-adsorbed gas.

The heat released in the adsorption step is transported by the flow of the non-adsorbed gas in the direction of the adsorbent bed end where the oxygen-enriched gas is vented. During the subsequent desorption, heat is extracted from the bed and since in that case the 8601 δ δ "4 -2- *» · if k gas flow direction is opposite to the direction applied during the adsorption, the temperature will in that case bed end (ie the end of the bed that lies on the side where the gas supply was made in the adsorption step) lower than where the gas was supplied in the desorption step. By continuing to perform adsorption and desorption As a result of this, the temperature of the adsorbent on the product discharge side becomes increasingly higher and on the supply side of the untreated gas increasingly lower, so that a relatively large temperature gradient is established along the length of the bed.

Since the desorption properties of the adsorbent deteriorate at a lower temperature, this results in the situation that the adsorbed components on the feed side of the bed are poorly desorbed during continued operation of the device. On the other hand, due to the high temperature at the product discharge side of the bed, the adsorption properties of the adsorbent deteriorate. Both of these conditions therefore decrease the effectiveness of the adsorption bed over time.

By supplying warm untreated gas and cold regeneration gas, respectively, the temperature gradient caused by the adsorption -25 desorption can be partially reduced and even reversed. However, temperature equalization is not possible since the zones located at the inlet and outlet openings are strongly affected, while the more inward zones of the adsorbent bed are hardly affected.

The object of the present invention is to provide a solution to this problem in which strong temperature gradients over the adsorption bed no longer occur and in which the effectiveness thereof does not change substantially during longer use of the bed.

To this end, the method according to the invention is characterized in that one or more adsorbers are fitted, each comprising several chambers, wherein adjacent chambers are in heat exchange contact with each other and the gas flow in each of the chambers is adjusted such that the temperature gradients which form in adjacent chambers are opposite.

By ensuring that in an adsorber the temperature gradients formed in the adjoining chambers are always opposite to each other and by promoting the heat exchange by the nature of the contact between the chambers, the process according to the invention is achieved that a very high degree of temperature uniformity is achieved over the adsorbent beds present in the chambers, which leads to constant effectiveness.

In particular, in the method according to the invention, a plurality of heat exchange contact adsorbers are interconnected in such a manner that the temperature gradients 20 forming in adjacent adsorbers are opposite. This measure ensures that any gradients occurring at the boundaries of the adsorbers can be prevented as much as possible by connecting several adsorbers. One can think here of placing several adsorbers with the side walls in heat exchange contact against each other.

Advantageously, in the method according to the invention it is ensured that in adjoining chambers in which the same stage or different stages of the pressure-swing adsorption process, which are both carried out in the adsorption direction or both in the desorption direction, the gas flows in counterflow while direct current is applied, of the same or different stages, one is in the adsorption direction and the other is in the desorption direction. This measure can be considered to flow in the longitudinal direction of the different chambers of the gas to be treated S60 1 66 4 ί »-4-, thus, if the adsorption step is carried out in two adjacent chambers, the gas flow in both chambers should be opposite; whereas if adsorption takes place in one chamber and desorption in the other chamber, the direction of flow of the gas in that case must be rectified.

The present invention further relates to an installation for increasing the content of at least one desired constituent of a multi-constituent gas comprising one or more adsorbers by pressure swing adsorption.

This installation is characterized according to the invention in that each of the adsorbers belonging to the installation comprises chambers separated by heat-conducting partition walls and means for adjusting the gas flow in each of the chambers as desired.

In a special embodiment of the installation according to the invention it holds that each of the chambers of an adsorption device belonging to the installation is divided into two halves by a heat-conducting partition which are connected to each other through an opening in said partition at one of the chamber ends.

By including a bulkhead in each of the chambers, whereby the chamber is divided into two halves, the chamber is folded in half lengthwise and it is achieved that the high temperature side and the low temperature side of the same chamber are brought together, thereby also creating an important temperature equalization possibility. is.

In the installation according to the invention it is expedient for each of the chambers to be provided with an adsorber with one or more valves for adjusting the gas flow.

In particular, in the installation according to the invention, each of the chambers of an adsorber and if several adsorbers are present, all adsorbers are connected to one central rotary valve 8 60 1 6 6 4 -5-. By using one central valve to control all gas movements, it is achieved that a significant saving in installation costs is achieved. obtained in connection with the simplified control for a single valve in comparison with the control and optional actuation required when using a system containing a large number of valves.

Such a central rotary valve can for instance be formed by a housing provided with a gas supply opening 10 in which two apertured parts sealingly adjoin each other, whereby openings of the two parts for forming connections can coincide by movement of the two parts relative to each other.

In that case, at least one of the two parts will comprise connecting elements for connecting openings of that part together. By operating the above-described central valve, it can be achieved that an adsorption process and a desorption process take place alternately in each of the chambers filled with adsorbent, while in addition, as usual, in order to increase the pressure in one chamber, an excess gas quantity available in another chamber is available. of sufficiently high pressure is applied.

Of course, it is necessary, both when using valves cooperating with each of the chambers and when using one central rotary valve, that the valve movement be carried out according to a specific program.

To this end, a control unit is provided with particular advantage for the programmed operation of the valve or valves associated with the device. In that case, of course, the valves must be of a type that can be operated remotely. Such valves are generally known.

For safety reasons it will be ensured that the parts of the installation that come into contact with the gas to be treated are made of metals which do not show a tendency to spark. For the β SO 166 4-6 case of oxygen enrichment of air, copper and copper alloys can be mentioned.

In the valve or valves that form part of the installation, a coating of one of the surfaces with a suitable synthetic material, for example glass fiber-reinforced polytetrafluoroethylene, will be chosen to reduce the friction of sealing surfaces adjoining each other. The other surface can then be made from one of the aforementioned metals.

When a central flat valve is used, an elastomer layer will advantageously be applied between the plastic coating on one of the surfaces and that surface. This measure improves the sealing of the surfaces.

The invention will now be elucidated with the aid of the drawing, in which:

Figure 1 is a schematic representation of an installation according to the invention.

Figure 2 shows a perspective view of an adsorption device according to the invention with four chambers 20.

Figure 3 shows a schematic representation of an adsorption device according to the invention, in which the adsorption step is carried out in part of the chambers and desorption takes place in another part of the chambers.

Figure 4 represents an embodiment of a device according to the invention in which each of the chambers is divided into two parts by means of a partition.

Figure 5 shows a graph of the course of the pressure over time in an adsorption chamber.

In Figure 1, reference numeral 1 denotes an adsorber according to the invention, 2 denoting the chambers filled with adsorbent.

This adsorbent may consist of a material known for these purposes; for the enrichment of oxygen with air 8601664 -7-, zeolite-type molecular sieves are advantageously used to which nitrogen, water vapor and carbon dioxide can be selectively adsorbed. Numeral 3 schematically indicates the adsorbent bed 5, with screen plates 4 separating the adsorbent from the gas supply and discharge spaces. 5 and 6 denote the feed gas supply and product discharge, respectively.

As can be seen from the arrows, in adjoining chambers 2 the flow directions are opposite, resulting in opposite temperature gradients.

Figure 2 shows on a somewhat enlarged scale how in an adsorber four chambers are connected to each other, whereby adjoining chambers are ensured by suitable selection of the compounds in opposite flow. The connection between the various chambers is formed by heat-conducting intermediate partitions 7, whereby the chambers can be connected to each other by permanent joining techniques such as welding, gluing and the like, but of course also a detachable construction is possible.

Figure 3 shows the situation in which gas to be treated is supplied and distributed over three chambers. The product discharge takes place via 9; A portion 11 of the product discharge is taken off and supplied as flushing gas to the remaining chambers which are regenerated in this way. In said regeneration, desorption of the gases adsorbed on the adsorbent therefore takes place. The gas mixture released during regeneration is discharged via 8. The gas flow in adjoining chambers is rectified in this case.

In Figure 4, four chambers 12, 13, 14 and 15 are indicated, each chamber being divided into two parts by an intermediate wall 16. At the end of each chamber, the partition wall has an opening so that the gas from one chamber half can enter the second chamber half.

§601664 -8- * 'w t "

In this example, chambers 12, 13 and 14 are in use for an adsorption step or a pressure reduction step that proceeds in the same flow direction as the adsorption step. Chamber 15 is regenerated.

Figure 4 represents the process status as shown in table A in step 1 (said table will be discussed in more detail below). Chamber 12 in Figure 4 is in the adsorption step with pressing air (PV) and (PVH); chamber 13 supplies product (P) and supplies gas 10 for the pressure equalization (OVH). Chamber 14 releases gas for flushing (OOS) and chamber 15 is flushed under vacuum (USA). Since the steps (OVH) (OVL) and (OOS) run in the same direction as the desorption, the adjoining chamber parts of chambers 12, 13 and 14 are in countercurrent while between the right chamber half of 14 and the left chamber half of 15 DC occurs.

Table A shows the process progression for an adsorbent system consisting of four adsorption chambers, the process steps carried out in the various 20 chambers being indicated as a function of time. At time 0 seconds, in adsorption chamber 1, the press equalization at elevated pressure takes place using excess air of sufficient pressure from adsorption chamber 2 while at the same time feeding air is compressed. After three seconds a sufficiently high pressure is reached and the product discharge can start. This product discharge continues until 10 seconds after the start of the cycle, after which an annealing equalization takes place in which the air released thereby is supplied to adsorption chamber 4 as indicated by an arrow in the table. At time 16 seconds, air of sufficient pressure is still present to perform a low pressure pressure equalization for adsorption chamber 3 as indicated by the arrow. This press equalization has ended at time 20 seconds, after which 35 is annealed with rinsing. The air released thereby is supplied to adsorption chamber 2, which at that moment is at a sufficiently low absolute pressure at 3§01664-9. This purge annealing continues until time 26 seconds, at which time the system is placed under a greatly reduced pressure so that the desorption of adsorbed gases can be accomplished. This pressure drop continues until time 30 seconds after which the vacuum flushing starts. During vacuum purging, relatively high pressure gas is supplied to chamber 1; the capacity of the vacuum pump is sufficiently high to ensure a good desorption of 10 adsorbed components. The vacuum flushing continues until time 36 seconds after which the pressure in adsorption chamber 1 is gradually increased again by supplying gas of sufficiently high pressure from adsorption chamber 3 '. At time 40 seconds, the pressure in adsorption chamber 1 is again approximately atmospheric, after which the above-described cycle for adsorption chamber 1 can again take place in the order described above. The table also shows the pressure / time processes for the three other adsorption chambers; the table speaks for itself.

It is clear from the table that in order to increase the pressure in one of the compartments, a gas quantity of sufficiently high pressure, which is superfluous in connection with the desired pressure drop in another compartment, is used. In this way a considerable saving in pumping costs is realized.

The pressure / time history of adsorption chambers 1, 2, 3 and 4 described above with reference to Table A is again graphed in Figure 5 by adsorption chamber 1. In this graph, steps 30 from time 0 to 26 in the adsorption light and steps from time 26 to 40 in the desorption direction are performed.

It should also be noted that the design of the chambers 2 of the adsorbent system is extremely simple since the zeolite type molecular sieve filling allows support of the walls during the vacuum portion of each cycle so that the wall construction of the chambers can be particularly light which leads to significant savings of 860 1 664 \ -10.

By carrying out the method according to the invention, for example, an oxygen enrichment of air can be obtained, as indicated in table 5 below.

constituent_food air_product O2 20.95 vol. % 80-96 vol. % N2 78.08 vol. % supplement

Argon. 0.93 vol. % 3.5-4.5 vol. % 10 CO2 0.03 vol. % free H20 saturated or less free

Hydrocarbons traces free

In the above example, the application of the method for enriching air with oxygen has been assumed. However, the process can be used with equal success for enriching one or more components of another multi-constituent gas as long as there is an affinity difference between the desired component or components and the other components.

S601664

Claims (9)

Method for increasing the content of at least one desired constituent of a multi-constituent gas using pressure swing adsorption, characterized in that one or more adsorbers (1) are used. each comprising multiple chambers (2) with adjacent chambers (2) in heat exchange contact with each other and the gas flow in each of the chambers (2) being adjusted so that the adjacent chambers (2) are due to adsorption and desorption, heat-forming temperature gradients are opposite. Method according to claim 1, characterized in that a plurality of adsorbers (1) are connected to each other in heat exchange contact in such a way that the temperature gradients that form in adjacent adsorbers (1) are opposite. Method according to claim 1, characterized in that in adjoining chambers (2) in which the same stage or different stages of the pressure swing adsorption process, which are both carried out in the adsorption direction or both in the desorption direction, the gas flows are countercurrent while direct current is applied if one of the same or different stages is carried out in the adsorption direction and the other in the desorption direction. Installation for increasing by pressure swing adsorption the content of at least one desired 860 1 664 τ-12 component of a multicomponent gas comprising one or more adsorbers (1), characterized in that each of the adsorbers belonging to the installation ( 1) comprises chambers (2) separated by heat-conducting partitions (7) and provided by means of adjusting the gas flow in each of the chambers as desired. Installation according to claim 4, characterized in that each of the chambers of an adsorber belonging to the installation is divided into two halves (2,2 ") by a heat-conducting baffle (16), which pass through an opening in said baffle at one of the chamber ends. are in communication with each other. Installation according to claim 4 or 5, characterized in that each of the chambers (2) of an adsorber (1) with one or more valves 20 is provided for adjusting the gas flow. Installation according to claim 4 or 5, characterized in that each of the chambers (2) of an adsorber (1) and optionally all adsorbers (1) are connected to one central rotary valve. Installation according to claim 6 or 7, characterized in that a control unit is provided for the programmed operation of the valve or 30 valves associated with the device. 8601684 V, -13- Air enriched with oxygen, characterized in that this air is obtained using the method according to one or more of claims 1 to 4 and 5 using an adsorbent in the form of zeolite-type molecular sieves. 860 1 66 4