MXPA97001724A - Improved procedure of oscillating adsorption devacio-pres - Google Patents

Abstract

The present invention relates to an oscillating vacuum-pressure adsorption process (AOVP) is carried out using a ten-step processing sequence that serves to improve the productive capacity thereof for the separation of air and other desirable applications.

Description

IMPROVED PROCEDURE OF OSCILLATING VACUUM-PRESSURE ADSORPTION BACKGROUND OF THE INVENTION Field of the Invention: This invention relates to oscillating pressure adsorption operations. More particularly, it relates to an improved vacuum-pressure oscillating adsorption process.

Description of the Prior Art: Methods and systems of pressure swing adsorption (AOP) are well known in the art, since they achieve the desirable separation of the components of a feed gas mixture. During the practice of the AOP process, a feed gas mixture, containing a more readily adsorbable component and a less easily adsorbable component, is passed through an adsorbent bed containing the adsorbent material capable of selectively adsorbing the more easily adsorbable at a higher adsorption pressure. The bed is then depressurized at a lower desorption pressure, for the desorption of the more easily adsorbable component and its removal from the bed before the introduction of additional quantities of the feed gas mixture thereto, such as adsorption-desorption operations. - Cyclic re-pressurization, are contained in an AOP system that contains one or more adsorbent beds. In conventional AOP practice, multiple bed systems, each bed in the system using the sequence of the AOP procedure, are commonly employed on a cyclic basis, interrelated to carry out said sequence on the other beds of the system. In highly advantageous variations of the AOP process, each adsorbent bed, during the desorption portion of the total AOP cycle, is depressurized at a lower desorption pressure at the subatmospheric scale, i.e., under vacuum. Said process is referred to as a vacuum-pressure oscillation adsorption process (AOVP). Despite advances in the AOP / AOVP technique, there is a need in the art for further improvements to provide more efficient oscillating pressure adsorption processes, for the production of a concentrated gas, such as oxygen, from a mixture of gas, such as air, said processes use the adsorbent in a more efficient manner (lower bed size factor), and require less energy than other processes, which use the previous technology, to produce high purity gas from mixtures of gases. As indicated above, the AOP process is based on the differential adsorption of selectively adsorbable gases and non-preferentially adsorbable gases, of mixtures thereof, on conventional adsorption bed materials, such as zeolites. In the known method, the adsorption bed unit, or the first unit of said bed of a unit system of two or three beds, each of which may contain a lower bed layer to remove water and carbon dioxide and An upper or downstream layer of bed to adsorb the selectively adsorbable gas from a supply of gas mixture passing through it, is pressurized to a high pressure value to cause the selective removal of water and carbon dioxide and the selective adsorption of a gas, while the pressurized gas, non-selectively adsorbable, is unaffected and passes through a receiving unit, which may be the second bed unit of the system. In this case, the second bed unit is pressurized by the non-adsorbed gas, preparing to enter the stream in the next cycle. The next bed unit, ie a third bed unit or the first bed unit of a two-bed system, is cleaned by backflow or counterflow, by passing a medium pressure waste gas supply or a component lacking purged gas from an equalization tank or from the bed unit that is being depressurized after producing the concentrated, non-adsorbed gas. This cleans the bed unit for subsequent repressurization and concentrated gas production. After a period, the second bed unit is brought to sequential use, the first bed unit is evacuated and the second bed unit is repressurized.

Although many modifications and variations of the AOP and AOVP processing cycle have been studied and applied to commercial procedures, such as for the production of oxygen from air, such systems are generally less efficient and more expensive for high oxygen production. purity, especially for large plants, when compared to the alternative method that uses cryogenic distillation. Therefore, it is an object of this invention to provide a highly efficient AOP process, to produce large volumes of high purity oxygen from air with a lower energy requirement. The original AOP procedure was developed by Skarstrom, patent of E. U.A. 2,944,627, and consists of a cycle that includes four basic steps: (1) adsorption, (2) depressurization, (3) purging, and (4) repressurization. Numerous variations of the Skarstrom cycle have been developed. One of these systems is described in the patent of E.U.A. 3,430,418 from Wagner, where at least four beds are required to continuously produce the product. The extra cost and complexity of providing four beds instead of a smaller number generally makes the Wagner system economically impracticable. In the patent of E. U.A. No. 3,636,679, Batta discloses a system wherein compressed air and product oxygen (obtained from another bed going through the equalizing-dropping step) are simultaneously supplied at the opposite ends of the same adsorbent bed. Another method to achieve more savings in the cost of equipment using a two-bed system is described by McCombs in the U.A.A patent. 3, 738.087, wherein an increment pressure adsorption step is used with feed air introduced into a partially repressurized adsorbent bed. following the work of McCombs, Eteve and others, the patent of E. U.A. 5,223,004 described an AOP process using the following steps: (1) pressurization of the countercurrent product, starting from the low cycle pressure level to an intermediate pressure level, (2) a parallel feed pressurization starting from the intermediate level of pressure. pressure up to the adsorption pressure without bleeding, (3) a production step, where, in parallel, air is admitted and oxygen is bled, (4) a step where oxygen is bled by partial depressurization, in parallel, where the air intake is interrupted, and (5) a desorption step depressurizing downstream to the low pressure level of the cycle. In the literature you can find many more variations of the original AOP cycle. For example, the patent of E. U.A. 4, 194,891, 4, 194,892 and 5, 122, 164 describe AOP cycles using short cycle times, where adsorbents of smaller particle size are used to reduce the diffuse resistance; Doshi et al., In the patent of E. U.A. 4, 340,398 discloses an AOP process utilizing three or more beds, wherein the gas-free component is transferred to a tank prior to bed generation, and then used for repressurization. In addition, a method of modifying a two-bed AOP process incorporating tank equalization is described in the U.S.A. patent. 3,788,036 and 3, 142, 547, wherein the conserved gas is used as the purge gas for another bed. More recently, Tagawa et al., In the patent of E. U.A. 4,781, 735, describes an AOP process using three adsorbent beds to produce oxygen, with improved oxygen recovery achieved by connecting the feed end of one bed to the feed end of another bed (bottom-bottom equalization), and for all the time or part of the equalization time, the upper-upper bed equalization is carried out simultaneously with the background-background equalization. In addition, the patent of E. U.A. 5, 328, 503, Kumar et al., Discloses an AOP process that uses an initial depressurization step to provide a purge gas, followed by an optional bed-bed pressure equalization step. According to this patent, at least two adsorbent beds are employed, and a combination of product and a feed gas is used to repressurize the adsorbent beds. Suh and Wankat (AlChE J., Vol 35, p.523, 1989) describe the use of parallel-counter-current depressurization steps in AOP procedures. They describe that for the production of oxygen from air, the addition of a parallel depressurization step is not beneficial. Liow and Kenny (A lCh E J., Vol 36, p.53, 1990) describe a "filling cycle" for the production of oxygen from air via computer simulation. They describe that a step of product repressurization against current (with respect to the feeding direction), is beneficial when included in the cycle to produce an oxygen enriched product. In the patent application of E.U.A. from Baksh et al., series No. 08 / 319,692, there is described an improved method of AOP for separating a first gas, such as oxygen gas, from gas mixtures containing said first gas and one or more other gases, including gases which they are preferentially more adsorbable. This involves novel steps of simultaneous equalization and evacuation, followed by simultaneous feeding and repressurization of product gas from AOP beds. This results in a faster and more efficient total cycle with 100% utilization of a vacuum or a pressure reduction blower, and a reduction in energy use of approximately 15%. The main aspect of the Baksh and others procedure involves overlapping the various steps of the AOP cycle to reduce the total cycle time and thus improve productivity. The other important parameters include the selection of operating conditions (high pressure, low pressure, pressure at the end of the equalization-fall step, and the amount of high purity product used in the pressurization step of the product), the times distributed for each step, the order in which each step of the cycle is executed, and the use of equalization-drop gas to provide the gas required for reflux and increase of equalization. The only step in the cycle is the step of simultaneously evacuating the bed undergoing the equalization increment step, while the other bed undergoes the equalization-fall step. The time distributed for this step must be chosen, so that at the end of this step, the starting bed has been purged and also partially pressurized. The next step in the cycle is the simultaneous feeding and pressurization of the product at opposite ends of said bed, followed by pressurization of feed to the desired adsorption pressure. Other key aspects of the invention are as follows: (a) the product gas required in the simultaneous feed and pressurization step of the product, usually comes from the product tank, or from another bed in the production step; and (b) the parallel depressurization or pressure equalization-drop gas, either to the downstream end of the other bed or to a second storage tank. In the latter case, no bed-bed communication is required, which helps greater flexibility in controlling the AOP procedure. Despite such desirable advances in the art, AOP / AOVP procedures remain less efficient and more expensive, especially for the production of high purity oxygen in large plants, than desired, particularly compared to the alternative cryogenic distillation. Therefore, there is a need in the art for further improvements to facilitate the use of highly desirable AOP / AOVP technology in large-scale commercial plants. It is particularly desirable to obtain improvements that allow the adsorbent to be used in a more efficient manner, i.e., to achieve a lower bed size factor. An improved AOP / AOVP process could desirably achieve an improved capacity, compared to the prior art processes, for the production of high purity oxygen from feed air. Therefore, it is an object of the invention to provide an AOVP process having an improved efficiency for the production of the less selectively adsorbed component, v. gr. , oxygen from a feed gas, v. gr. , air. It is another object of the invention to provide a method for increasing oxygen production from an AOVP air feed system. With these and other objects in mind, the invention will now be described in detail, the novel aspects thereof being particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE INVENTION The invention employs a sequence of adsorption-desorption processing, repressorization of AOVP that includes an oxygen purge step at a low desorption pressure, an overlap and pressure equalization step, and a step to make oxygen from the product. adsorption, constant pressure, resulting in a desirable improvement in the capacity of an AOVP system.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A illustrates the steps of a double adsorption column cycle according to one embodiment of the present invention in a bed A of the two-bed system; and Figure 1B illustrates said steps in the bed B thereof; Figure 2 is a flow diagram for the double bed cycle of Figure 1; Figure 3 is a time / pressure graph illustrating the evolution of pressure in a bed during the different steps of a complete cycle; Figure 4 is a flow diagram for a double bed cycle that has no bed-to-bed communication, according to another embodiment of the invention; Figure 5A illustrates the steps in the system cycle illustrated in Figure 4, in bed A of a two-bed system; Figure 5B illustrates said steps in the bed B thereof; Figures 6 and 7 illustrate the flow diagram and the column cycle for a single-bed process according to another embodiment of the invention; Figure 8A illustrates the steps of a normal adsorption column cycle, of the prior art, in bed A of a two-bed system, for comparison purposes, and Figure 8B illustrates said steps in bed B thereof; Figure 9 is a processing cycle diagram for the operation of a two-bed AOVP system, according to the invention; Figure 10A is a flow diagram of the process, illustrating the integration of the processing aspects of the invention in the Baksh et al. Procedure, as shown in Figure 9 in bed A of a two-bed system; and Figure 10B illustrates said steps in the bed B thereof.

DETAILED DESCRIPTION OF THE INVENTION The Baksh et al procedure incorporates a novel sequence of operation steps in the AOP cycle, where discharge times for rotating machines (eg, compressors and vacuum pumps) are minimized, product recovery is improved, the bed size factor (FTL) is comparable or less than the AOP cycles of the prior art, and the energy consumption is less than 5-20% than the AOP cycles known in the art. The operation steps of the AOP cycle of the present are as follows: (I) Simultaneous introduction of a mixture of feed gas (v, gr., Air) and a gas product that is being concentrated (e.g. , oxygen) at the opposite ends of the bed for partial repressurization at an intermediate pressure level. In this step, the gas product usually comes from the product tank, or from another bed in the production step. (Ha) Feed pressurization (parallel) from the intermediate pressure level to the adsorption pressure, in the first part of step 2. (llb) Adsorption and total product production, the second part of step 2. (lll) Depressurization parallel, where the gas is transferred directly or indirectly, that is, through an equalization tank to another bed that is being pressurized and evacuated, simultaneously. In the indirect mode, the parallel depressurization gas goes to a second storage tank. In this case, no bed-bed communication is required. (IV) Evacuation or depressurization for the waste (countercurrent), while the other bed suffers the feeding and pressurization of the product, simultaneously, for a two-bed AOP procedure. (V) Evacuation or depressurization, additional, for waste.

This step is the same as the previous step for the first bed. Nevertheless, the passage of the other bed suffers the adsorption and total production of the product (see Figure 1). (VI) Simultaneous pressurization (countercurrent) and evacuation, where the reflux gas is supplied by another bed undergoing parallel depressurization (step 3) or the second storage tank that was used to capture the parallel depressurization gas. The above steps are shown schematically in Figures 1 A and 1 B of the drawings, for a two-bed AOP procedure. Five points should be observed with respect to this cycle: (a) a bed-bed equalization step is superimposed on the purge step, where the bed that undergoes the increase in equalization, is also evacuated simultaneously, (b) all the reflux gas necessary to purge the bed during regeneration, it is supplied by the gas-free component obtained from another bed during the parallel depressurization step (equalization-fall), (c) an overlap of the product pressurization steps and Feeding, followed by only pressurization of feed to the adsorption pressure, is used to achieve a product of higher flow rate, (d) a reduction in the total cycle time due to the overlap of individual steps, results in a lower bed size factor (FTL), and (e) there is no discharge time for the vacuum pump (see Figure 1), that is, the vacuum pump is used 100%. In the Baksh and others processing cycle, the equalization-drop gas provides all the necessary gas for another bed that is simultaneously suffering the increase of equalization and evacuation. In this way, this step overlaps the equalization step with the puga step, thereby modifying the conventional purge step and equalization step, used in the prior art AOP cycles. In addition, all the reflux gas necessary to push the nitrogen out of the bed in front of the wave is provided by the other bed that goes through the equalization-fall step. In this mode of operation, lower purity gas is used for the combined purge and equalization increment steps. The next step in the cycle (product pressurization, in a countercurrent fashion) uses high purity gas product, usually from the product tank to pressurize the column at the product end, while the feed gas is simultaneously fed into the product. the other end of the bed. The overlap of the individual steps results in faster AOP cycles with a high oxygen production regime (lower FTL). In addition, since this cycle does not use a conventional purge step, none of the gas product consumed for the purge of the adsorbent bed. Also, during the evacuation and simultaneous equalization increase, the bed pressure at the end of the step must be greater than the pressure of the previous step (evacuation step). In this way, both the flow velocity of the inlet gas and the time distributed for this step must be carefully selected, so that at the end of this step, the bed has been purged and substantially pressurized. In this way, the Baksh and others procedure involves overlapping the various steps in the AOP cycle to reduce the total cycle time and thus improve productivity, the choice of operating conditions (high pressure, low pressure, pressure at the end of the equalization-fall step, and the amount of high purity product used in step 1 of Figure 1 A), the times distributed for each step, the order in which each step of the cycle is executed, and the Use of equalization-drop gas to provide the gas required for reflux and the equalization increase. The only step in the cycle is step 11 (see Figure 1A), where the bed undergoing the equalization-fall step is open for the other bed, which is simultaneously being pressurized and evacuated. The time distributed for this step must be chosen, so that at the end of this step, the second bed has been purged and partially pressurized. The next step in the cycle is the pressurization and feeding of the product, simultaneously, at the opposite ends of the second bed, followed by pressurization of feed to the adsorption pressure step HA, Figure 3. To practice the procedure of Baksh and others for the product 02, the following steps are carried out: (I) The intermediate pressure level, where both the feed and the product are introduced, at the opposite ends of the bed for partial pressurization, is selected from 0.5-1. .2 atm (1.0 atm. = 1.033 kg / cm2), and preferably at about 0.9 atm. , while the high level pressure is selected from between 1.2-2.0 atm. , and preferably at about 1.42 atm. The low level pressure is selected from 0.30-0.45 atm. , and preferably about 0.35 atm.

(II) The pressure during the production step can be increased from the intermediate pressure level of approximately 0.9 atm. (the pressure at the end of the product and feed passage, simultaneous) to the adsorption pressure of approximately 1 .42 atm. Alternatively, feed pressurization without bleeding occurs after simultaneous pressurization of the product and feed to reach the adsorption pressure, then a control valve is opened to produce the product. In this last step, the pressure during the production step is a constant pressure. (I I I) The feed inlet is terminated, and the column is depressurized in parallel to recover the component lacking gas and the light component that was co-adsorbed in the adsorbent. The pressure during this step is reduced from the adsorption pressure of approximately 1.42 atm. , down to approximately 1 .10 atm. The gas collected in this step is therefore referred to as "gas-free component." This gas can be stored in a second storage vessel (equalization tank) or can be fed to the product end of another bed undergoing the steps In the last case, at the end of this step, the bed has been purged and partially pressurized, in this way, the time distributed for this step is crucial, since some of the component lacks gas it is used as a reflux gas to move the nitrogen (heavy component) to the front of the wave outside the bed via the feed end, while the component lacking the remaining gas is used for the partial pressurization of the product. this step increases from approximately 0.35 atm to approximately 0.60 atm. (IV) and (V) The desorption phase by depressurization is reduced in parallel to the level d and low pressure of approximately 0.35 atm. (VI) The first part of the pressurization takes place, while this bed continues to undergo evacuation. The gas required for this step is obtained from another bed undergoing the equalization-fall step, or from a second tank that was used to store the component lacking gas obtained from another bed during the equalization-fall step. During this step, the pressure in the bed receiving the component lacking gas increases by approximately 0.35 atm. at approximately 0.60 atm. The basic aspects of the Baksh et al procedure can be illustrated by describing the operation of a two-bed AOP process, shown in Figure 1A and Figure 1B of the drawings. However, it should be understood that one, or more than two beds, and other operating conditions (eg, other pressure scales) may be employed in accordance with the procedure of Baksh et al. Figure 2 is a schematic diagram of a two-bed AOP process consisting of two adsorption beds A and B of Figures 1 A and 1 B, a compressor (s) or feed blower (s) 1 1, vacuum pump (s) 13, a product storage tank 18 and interconnected lines and valves. Figure 3 shows the pressure evolution during the execution of the various steps of the cycle, the cycle starting after step 6 in Figure 1. Referring to Figures 1 A, 1 B, 2 and 3, the AOP procedure for a complete cycle is described. The AOP procedure of Figure 2 consists of two beds (A &B) filled with adsorbents, each having an inlet valve 33 or 35, and an outlet valve 34 or 36. The feed inlet valves 33 and 35 are connected to an air supply conduit 10 through a blower or compressor machine 1 1; while the exhaust outlet valves 34 and 36 are connected to a vacuum exhaust duct 12 incorporating a vacuum pump 13. The bed outlet ducts 14 and 15 communicate with the valves 5 and 6 to a production duct 16 through a control valve 17 that is connected to a product storage tank 18. Valves 10A and 12A allow the two beds to communicate, if a gas purge step is included in the cycle. For example, when valve 12A is open, it allows a portion of the gas product from bed A to supply a purge stream to bed B. Similarly, when the valve 10A is open, it allows a portion of the gas product from the bed B to supply the purge gas to the bed A. The outlet ducts 14 and 15 are connected to each other by means of the valves 2 and 4. All valves in the diagram are electronically operated by means of a computer system and logic program. The conduit 19 is connected to the product storage tank, and supplies gas product, via the valves 8 and 9, for the pressurization of the product of the beds A and B, respectively. Referring to Figures 1A, 1 B and 2, the O2 procedure of AOVP for a two-bed system will now be described to illustrate the opening and closing of the valves for each step of the cycle. All valves are closed except those indicated in each step. In this example, the cycle time is approximately 60 seconds and the pressure varies from a low of 0.35 atm. and a high of 2.0 atm. Step I: The feed (air) through line 10, and product (oxygen), from tank 18, are simultaneously introduced on opposite sides of the bed. In the case of bed A, valves 33 and 9 are open to allow the feed and gas product to enter the bed, respectively. During this time, the valve 36 is open and the other bed B is undergoing evacuation. Step I I: In the feed pressurization and in the step to make the total product, the valves 33 and 5 are open and the bed A undergoes an additional feed pressurization. The logic program of the control valve 17 dictates when this valve will be opened to allow the gas product to enter the product tank 18 from bed A. For example, if a constant pressure is required during the steps to make the product, then only the control valve 17 is opened when the bed A reaches a predetermined level of pressure to allow the product to enter the product tank 18. During the feed pressurization and the step to make the product (step 2) for bed A, bed B is undergoing evacuation via valve 36. Step III: Parallel depressurization. In one version of this invention, valve 33 is closed and valve 4 is open to recover the gas-free component from bed A and direct it to bed B to partially pressurize bed B (equalization increment for bed B), and as a reflux gas to push the nitrogen in front of the wave in the bed B towards its feed end. During this time, the valve 36 continues to open, thus the bed B suffers the increase of equalization and evacuation, simultaneously. Another version of this invention collects the component devoid of equalization-dropping gas into a separate storage tank for supply to bed B. In the latter case, no bed-bed communication is necessary. Step IV: The valve 34 is now open to evacuate the bed A, against the current, and the valves 35 and 8 are open so that the bed B undergoes the feeding and pressurization of the product, simultaneously, from the opposite ends. Step V: Valve 34 continues open and bed A undergoes another evacuation, while valves 35 and 6 open for bed B to be pressurized with feed to the adsorption pressure. The control valve 17 logically determines when the gas product of the bed B enters the product tank 18. VI: The valve 35 is closed, and the bed B undergoes depressurization via the valve 2 connecting the bed A or a second tank of storage, which in turn provides increased pressure purge to bed A. During this time, valve 34 continues in the open position, allowing the A bed to simultaneously undergo equalization and evacuation. Based on the cycle described above, with respect to Figures 1A, 1B and 2, several modifications can be made to alter one or more of the steps without deviating from the application or the general sanctions of these steps. For example, step IV of depressurization against current can be preceded by opening to the air until the pressure in the bed falls to 1.0 atm., Then the evacuation begins. The two-bed process of Figure 2 using the steps of Figures 1A and 1B can produce comparable oxygen purity and recovery with a lower bed size and lower energy consumption, compared to the normal procedure depicted in FIGS. Figures 8A and 8B. Also, in this procedure, the vacuum pump is continuously used by one or the other bed during each step of the cycle. The reduction in bed size and the reduction in energy achieved are on the scale of approximately 5 to 20%. Figures 4, 5A and 5B show an alternative system for operating a two-bed AOP process using a product storage container 18 and an equalization tank 20. Execution of the various steps, including opening and closing the valves, is similar to the description given above for Figure 2. However, the use of two storage containers allows greater flexibility in the procedure. For example, the individual steps in the cycle shown in Figures 5A and 5B do not have to occupy fixed periods. In this way, you can easily use physical variables, such as pressure and composition, to determine the time distributed for each step, thus adjusting the procedure for changes in temperature, pressure and demand of variable product. Since no bed-bed gas transfer is required, then it is possible to operate each bed independently, and consider the procedure as a collection of single-bed units. However, for a dimension and distribution of compressor (s) and vacuum pump (s), some synchronization of the total cycle of each bed with the cycles of the other beds is necessary. While the apparatus employed in the Baksh and other processes preferably makes use of adsorbent beds, cylindrical, with hollow dish heads in the top and bottom, and a gas flow in the axial direction, other combinations For example, radial beds can be used to achieve a reduction in pressure losses with a concomitant reduction in energy consumption. In addition, beds can be used in layers with different adsorbents packed in various positions in the bed. For example, activated alumina can be placed at the feed end of the bed to remove water and carbon dioxide from the feed stream, and Li-X Zeolite can be placed on top of the activated alumina to perform the separation of the alumina. air to a product enriched with oxygen. The two-bed system and the procedure of Figures 4 and 5A provide improvements comparable with those provided by the system and procedure of Figures 1 A and 1 B, 2 and 3, but with a slight improvement in the recovery speed of the product. Figures 6 and 7 of the drawings illustrate the use of a single bed process using a product tank 18 and an equalization tank 20. To have high machine utilization, the procedure of Figure 6 shows a single compressor / blower 1 1 used to perform the pressurization and evacuation steps illustrated in Figure 7. Referring to Figures 6 and 7, the steps in the cycle are briefly described. Assuming that the cycle begins with simultaneous feeding and pressurization of the product (see Figures 6 and 7), valves 9, 10 and 33 are open and the other valves are closed. Valve 17 is a differential pressure check valve that only opens when the pressure, in the adsorbent vessel C, it becomes larger than the pressure in the product tank 18. After a certain time, the valve 9 closes, and starts the step 2. During step 2, the feed pressurization continues via the valves 10 and 33, the differential check valve 17 opens and the gas product enters the product storage tank 18. At the end of step 2, the valve 33 closes, and the valve 36 opens to discharge the compressor 1 1 . During this time, the bed undergoes parallel depressurization with the valve 4 in the open position to collect the gas-free component in the equalization tank 20. Note that the check valve 17 will be in the closed position during the parallel depressurization step ( step III), since the pressure of the adsorbent bed C will fall below that of the product tank 18. During the execution of step III, the valves 9, 10 and 33 are in the closed positions. At the end of step 11 l, valves 12 and 34 are in the open positions, while valves 4, 9, 10, 17 33 and 36 are closed. During this step (step IV), the gas in the adsorbent vessel C exits via valve 34 and enters through the compressor inlet. The next step (step V), illustrated in Figure 7, is just a continuation of step IV (evacuation step). The final step (step VI) is executed with valves 12 and 34 still in the open positions. During this step, the valve 4 is open, and the gas from the equalization tank 20 supplies the reflux gas to desorb the adsorbed gas and partially pressurizes the fact C. Although only one example of an individual bed process is described, easily obtain other modifications of the individual bed process, without deviating from the basic aspects of the invention. Figure 8A and Figure 8B illustrate a conventional AOP process using a prior art cycle with a cycle time about 10 to 20% longer than that of the present invention. In this figure, the symbols have the following meanings: AD = adsorption and total product production, PG = purge, EQ = equalization and EV = evacuation. It should be noted that the conventional cycle of the prior art consumes more energy than the cycle of this invention. The procedure of Baksh et al. (Figure 1A and Figure 1B) provides a significant reduction in energy consumption (more than 15%) with respect to the prior art cycle (Figures 8A and 8B) using the same adsorbent. One advantage of the process cycle of Baksh et al. (Figure 1A and Figure 1B) with respect to the normal equalization cycle (Figure 8A and Figure 8B) is that it allows a 100% utilization of the vacuum pump. Although the cycle of the procedure of Baksh et al has been described in relation to O2 procedures of AOVP, where particular modalities of said procedure have been shown, other modalities are contemplated along with the modification of the described aspects, being within the scope of the claims. For example, the cycle thereof is not restricted to transatmospheric vacuum-pressure oscillation adsorption cycles (AOVP), and superatmospheric or subatmospheric pressure swing adsorption cycles may also be used. Thus, the terms "pressurized P" high pressure "," pressure mediap "depressurizationp etc. are used in the present and in the claims as relative terms to include both negative and positive pressures Thus, a gas under a small vacuum pressure it is "pressurized" or a "high pressure" in relation to the gas under a higher vacuum or negative pressure.Also, the novel cycle can be used in other mixing separations, eg, separation of N2 / CH4 from the gas of landfill, and other gas mixtures eg, hydrogen-containing feeds as the non-preferentially absorbed product component and various impurities as selectively adsorbable components.These include light hydrocarbons, CO, CO2, N H3, H2S, argon and water. The hydrogen-rich feed gas, which contains at least one of these adsorbable components, includes: malodorous gas catalytic reformer, methanol synthesis loop purge, dissociated ammonia and demethanizer top gas, steam reformed hydrocarbons, purge gas of ammonia synthesis loop, electrolytic hydrogen and mercury cell hydrogen. The procedure of Baksh et al. Is also useful for separating any or all of the aforementioned adsorbable components from gas mixtures wherein the primary constituent is nitrogen or helium. It will be apparent to those skilled in the art that the Baksh et al. Procedure provides a desirable vacuum-pressure swing adsorption method to produce a concentrated gas from mixtures, which involves the steps of simultaneous equalization and evacuation of the gas. adsorption bed in one step, followed by the simultaneous product and feed repressurization of the adsorption bed in another step, resulting in a faster and more efficient total procedure, where the vacuum blower is used all the time and the Energy consumption is reduced by approximately 15%. The process of the invention of Baksh et al. Can be conducted at pressure levels that are superatmospheric, transatmospheric or subatmospheric, and applied to gas separation in general, using AOP procedure systems. In the further improvement described and claimed herein, the following additional steps are incorporated into the processing sequence, as shown in Figure 1A and Figure 1B, with respect to the Baksh et al procedure: (1) use one step purge; (2) use the overlap feeding and pressure equalization steps; (3) use a step to make a product of constant pressure. The present invention also optimizes the charging time for the feed compressors, and increases the average suction pressure for the vacuum pump used to achieve a subatmospheric desorption pressure. The production of the AOVP facility is improved at an equivalent energy consumption as shown by the Table below. (1) Use of the Purge Step: the introduction of a purge gas product to the Baksh and others processing sequence is based on the desire to improve the capacity of the plant without adding to the capital cost of the AOVP facility of gas separation. The product purge step allows the operation of the AOVP cycle at a high subatmospheric desorption pressure that may otherwise be possible, while maintaining bed size requirements and maximizing oxygen recovery. For this purpose, the purge oxygen gas is introduced into the top or end of the product of the adsorbent bed, while the evacuation or regeneration for the removal of the nitrogen component more selectively adsorbed from the feed air, continues at a pressure of lower desorption, constant. The oxygen purge rate is controlled to keep the desorption pressure constant or lower, slightly increasing, that is, the bed pressure remains essentially at said lower, subatmospheric desorption pressure. The incorporation of said purge step makes it possible to lengthen the process cycle time without producing deep vacuum-pressure levels. This additional cycle time results in a higher, higher, more optimal adsorption pressure, without increasing the flow velocity of the feed air, which could increase the effects of mass transfer resistance and increase the pressure drop of the adsorbent bed. This latter effect could result in an undesirable reduction in the performance of the AOVP system. The purge step also contributes to an increase in the average suction pressure for the vacuum pump, increasing the lower desorption pressure. This aspect improves the wear capacity of the vacuum system without increasing the capital invention, or increasing the vacuum flow velocity and associated pressure drop of the adsorbed bed. The use of purge gas also reduces the pressurization requirement of the product. By adding oxygen, as a purge gas, supplied directly from the bed that produces the oxygen product, the pressurization flow of the product can be reduced by an equivalent amount. This allows a reduction in the oxygen stream tank requirements to be realized, resulting in an oxygen product supply pressure. This reduction in tank size of oxygen streams results in a minor capitalization for the entire process. This reduced requirement for the product pressurization gas, which tolerates a higher pressure at the start of the product pressurization step, allows the pressure equalization steps to be extended to the essentially complete equalization of the adsorbent beds. Said complete pressure equalization results in an improved oxygen recovery. (2) Utilization of Overlapping Pressure Equalization: The improved processing cycle of the present invention also incorporates the use of a pressure equalization step that overlaps in the feed passage. This details cutting the equalization step of the Baksh procedure and others and initiating a power recharge when the pressure equalization step is completed. This aspect increases the fraction of the charge time of the feed compressor, while allowing the complete equalization of the adsorbent beds, with an associated improvement in the recovery of the product. This improvement, as with the introduction of purge gas discussed above, allows the introduction of more feed air to the adsorbent bed, per processing cycle, without increasing the feed air flow velocity (surface gas flow velocity in the adsorbent bed during the feed air passage). This aspect of the invention also results in a lower mass transfer resistance and a bed pressure drop for a given air charge rate, while obtaining the improved utilization benefit of the adsorbent, and the feed air compressor. and the supply air pipe system. The addition of the overlap equalization step also affects the operation of the vacuum pump. In this way, the suction of the vacuum pump is initiated to the pressure equalization-drop adsorbent bed during the overlap step. This results in a vacuum pump evacuating an adsorbent bed with much higher pressure during this step. Said high suction pressure results in an increased waste stream during this step, further contributing to the increase in average suction pressure associated with the processing cycle of the invention. This results in an increase in the waste removal capacity of the system, without the addition of additional vacuum equipment and pressure drop of the associated adsorbent bed. (3) Use of the Step to make a Constant Pressure Product: The processing cycle of the invention is also operated with a constant pressure product supply step, which details a continuation of a rising pressure feeding step up to the maximum stop, that is, higher adsorption pressure, before the hydrogen product is produced. Once the maximum upper pressure is reached, the product supply step is started, and controlled constant to that pressure regulating the flow rate of the product. This is presented to maximize the production of the adsorption system by increasing the recovery of oxygen therefrom. This increase in recovery is obtained as a result of an increase in the average feed pressure of the adsorption system. The effect of the same is an increase in the productive capacity of 2-3%, with a corresponding reduction in the size of the bed and compressor requirement, only a slight increase in energy consumption per unit. The invention allows an increase in the use of the equipment for the entire installation, including adsorbent bed, feed and vacuum equipment, the increased use of the feed air equipment comes directly from the increase in the load fraction time associated with the overlap / equalization step. The improved utilization of vacuum equipment comes from the average, high suction pressure of the waste gas pressure profile, which results from a combination of purge and overlap steps. The use of the adsorbent bed is improved by processing more feed and waste gas due to the increased fraction of air loading time, and the high pressure of waste suction, together with a possible shorter cycle time. The efficiency of the process is not sacrificed, since this improvement in the quality of the gas flow has been made without increasing the gas flow velocities, and associated losses. The second improvement comes from the use of manufacturing the product at constant pressure, which optimizes, in addition, the use of the adsorbent bed. This aspect increases the oxygen recovery of the cycle by increasing the average pressure of the feed air. The invention will now be described with reference to the processing cycle diagram of Figure 9 and the flow diagrams, companions, of the procedure of Figure 10A and Figure 10B. In this illustrative embodiment, a two-bed AOVP system is used, bed A and bed B, each suffering the indicated processing sequence on a cyclic basis, one bed being depressurized for regeneration, and the other bed being Pressurized and used for the selective adsorption of nitrogen from the additional quantities of air and the recovery of the oxygen product. The following description of the ten cited steps of the procedure sequence in Bed A will be shown to correspond to Bed B, on an appropriate cyclic basis, as described. In step 1, and in the product overlap / pressurization feed adsorption step, the simultaneous introduction of the feed gas, v. gr. , air, and the gas product, v.gr. , oxygen, from the feed ends and product of an adsorbent bed for partial repressurization at an intermediate level of pressure. This step is also employed as step I in the procedure described by Baksh et al. In a particular illustrative embodiment, summarized in the following table, the pressure of the adsorbent bed is increased from 0.913 kg / cm2 absolute to 1.19 kg / cm2absolute, with a step time of three seconds. The pressurization gas product is taken from a product production tank, e.g. , oxygen. In step 2, a feed gas is added, e.g. , air, from the increasing pressure feed adsorption passage, to the feed end of the adsorbent bed for the parallel pressurization of the intermediate pressure level towards the desired upper adsorption pressure. No oxygen gas was added or removed from the product end, generally the upper part of the adsorbent bed. This corresponds to step 1 of the procedure described by Baksh et al. In the illustrative embodiment, the pressure is increased from 1.19 kg / cm2 absolute to 1.54 kg / cm2 absolute, during this second step of seven seconds said pressure reached is at or near the desired upper adsorption pressure. In step 3, the constant pressure product manufacture / feed adsorption, where a feed gas, v. gr. , air, is introduced to the feed end, typically the bottom, of the adsorbent bed, while the gas product, v. gr. , oxygen, is removed from the product end of the adsorbent bed. The pressure remains relatively constant, at said 1 .54 kg / cm 2 absolute, during this ten-second step in the illustrative example. The oxygen product is passed to an oxygen production tank, as well as to the other bed in the two-bed system, or another bed in the system, if the system has more than two beds, to be used as a gas. purge in them. The purity of the oxygen product remains relatively constant during this step of product manufacture, due to the oxygen repressurization gas added, as provided in step 8 below, which introduces high purity oxygen to the product end of the adsorbent bed before the step to make oxygen. This serves to remove any part of oxygen purity at the start of the step. This step is terminated before the frontal adsorption of the nitrogen, actually breaking through the product end of the adsorbent bed. This step is similar to step l lb of the Baksh et al procedure, with the added aspect of using a portion of the gas product to provide a purge gas for another bed. In step 4, equalization-pressure drop, the adsorbent bed is simultaneously depressurized from its product end, the gas removed being transferred, directly or indirectly (ie, through a separate equalization tank) to another bed in the adsorption system, which is pressurized and evacuated simultaneously, as in step 9 below. No gas passes from the feed end of the adsorbent bed during this step. The pressure of the adsorbent bed is reduced from 1.54 kg / cm absolute to 1.26 kg / cm2 absolute, during the two second period of this step. The concentration of the oxygen removed from the adsorbent bed starts at the desired purity of the product, ie, 90%, and falls to a lower purity, e.g. , 80-90%, oxygen, at the end of the step since the frontal adsorption of selectively adsorbed nitrogen is broken through the product end of the adsorbent bed. The feed air compressor is ventilated during this step, which corresponds to step III of the Baksh et al. Procedure. In step 5, drop pressure evacuation and overlap pressure fall-over, waste nitrogen, the more selectively adsorbed component, is desorbed and removed from the end of the adsorbent bed, i.e., by counter-current depressurization, using a vacuum pump, while the adsorption vessel and the adsorbent bed, therein, are simultaneously depressurized from their product end by the equalization-pressure drop, their parallel depressurization, with the passage of the gas withdrawn from the end of the product of the same, going to the end of product of the other bed in the system of two beds, which undergoes repressurization from a lower pressure. The pressure in the adsorbent bed, in this way, drops from 1.12 kg / cm2 absolute to 0.913 kg / cm2absolute, during a period of two seconds. The concentration of oxygen at the product end of the adsorbent bed starts at said 80-90% purity and continues until it drops to about 70%. This is a novel step not included in the procedure of Baksh and others. In steps 6 and 7, drop pressure evacuation, the adsorbent bed is depressurized in countercurrent, by evacuating the gas from the feed end of the adsorbent bed, while the other bed of a two-bed system undergoes feeding and product pressurization, simultaneous. In these steps, corresponding to step IV of the Baksh et al. Procedure, the pressure drops from 0.913 kg / cm2absolute to a lower, subatmospheric (vacuum) desorption pressure of 0.28 kg / cm2absolute, over the course of a seventeen-year period seconds. No gas flows in or out of the product end of the bed during steps 6 and 7. The purity of the waste gas falls rapidly over the course of the duration of these steps, at a minimum oxygen concentration of 5-10% in said waste. In step 8, oxygen purge, the vacuum pump continues to remove the waste gas from the feed end of the adsorbent bed, while purge gas, oxygen, is added to the product end of the adsorbent bed. The pressure is kept constant during this three-second step, that is, at the level of the subatmospheric, low desorption pressure, of 0.28 kg / cm2absolute, by the flow of purge gas, oxygen, which is controlled to be equal to Waste disposal flow. The oxygen concentration of the waste stream is absolutely constant or slightly increases above the minimum level of 5-10%. This is a novel step not included in the procedure of Baksh and others. In step 9, rising pressure evacuation and overlapping pressure equalization, the vacuum pump continues to remove waste gas from the feed end of the adsorbent bed, while pressure equalizing oxygen gas is introduced to the end of the bed product. adsorbent. The operation of the power blower is interrupted during this step, said power blower being ventilated during this period. The pressure of the adsorbent bed increases during this step as a result of the oxygen equalization flow, which is greater than the evacuation flow. The bed pressure increases from 0.28 kg / cm2absolute to 0.42 kg / cm2absolute, during this two-second step. The oxygen concentration of the waste stream begins to rise slightly at the end of this step, which corresponds to step VI of the Baksh et al procedure, while an oxygen displaced frontally from the product end of the adsorbent bed in the direction of the feed end of the bed, begins to break through the feed end of the adsorbent bed . The feed blower is ventilated during this step. In step 10, which uses the pressure feed with overlap pressure equalization, the charge of the feed blower is resumed, and this step begins the period of pressurization-adsorption of feed air of the total processing cycle. The feed air is passed to the feed end of the adsorbent bed by the feed compressor. The adsorbent bed is simultaneously pressurized from the product end of the adsorbent bed, by passing, thereto, the equalization of pressure supplied from another bed, ie the second bed B of the illustrated two-bed system, which undergoes depressurization . The pressure of the adsorbent bed increases rapidly, during this two-second step from 0.63 kg / cm2absolute to 0.913 kg / cm2absolute. The Table, which is presented below, not only shows the actual times of passage, for each of the steps described and previously employed in the desirable embodiments of the invention, but also shows the average pressures at the beginning and at the end, for each processing step, summarizing the information provided above.

TABLE Description of the Product Pressurization Cycle with Purge and Equalization n Trasl ape Pressure Time Pressure Step Description Final Initial Step Step # 1 0.913 1 .19 Increasing pressure feed with pressurization of the overlap product Step # 2 1. 1 9 1 .54 Increasing pressure feed Step # 3 10 1 .54 1 .54 Constant pressure feed with product manufacture Step # 4 2 1 .54 1 .26 Fall Pressure Equalization Step # 5 2 1 .12 0.913 Fall Pressure Evacuation with Overlap Equalization Steps # 6 and # 7 17 0.913 0.28 Drop pressure evacuation Step # 8 3 0.28 0.28 Constant pressure evacuation with oxygen purge Step # 9 2 0.28 0.42 Increasing Pressure Evacuation with Overlap Equalization Step # 10 2 0.63 0.913 Increasing Pressure Feed with Overlap Equalization The improved procedure of the invention incorporates, as necessary aspects, steps 5 and 10 related to overlap matching, and Steps 3 and 8 related to the oxygen purge, in the procedure of Baksh et al. From the foregoing description, it will be seen that, in the preferred embodiments of the invention, the processing cycle of the invention specifically includes steps 2 and 7, directed only to the increasing pressure adsorption steps, and steps 3 and 8. directed to the constant pressure / adsorption product manufacturing steps. It will be understood that various changes and modifications may be made with respect to the processing cycle of the invention, described herein, without departing from the spirit of the invention as set forth in the appended claims. In this way, since the invention is particularly desirable with respect to the separation and recovery of oxygen from the feed air, it can also be used for other gas separation applications, such as those referred to above. It will also be understood by those skilled in the art, that the process conditions described with respect to the particular embodiments of the invention, e.g. , pressure operating conditions, are provided for illustrative purposes only, and are not intended to limit or restrict the scope of the invention as set forth in the appended claims. Also, the process of the invention can be carried out in adsorbent beds containing any commercially available, desired absorbent material, such as adsorbents of 13X zeolitic or advanced molecular sieves, such as adsorbents of lithium (LiX) or mixed cation exchanged zeolites. capable of selectively adsorbing a more easily adsorbable component of a feed gas, e.g. , nitrogen, from the feed air, with the recovery of less easily adsorbable component from the adsorbent bed, v. gr. , oxygen of the air supply. It should be noted that the manufacture of constant pressure / adsorption product, ie step 3 described above, can be omitted from the processing cycle of the invention, although it is employed in preferred embodiments for the reasons indicated above. In the case where a separate step 3 is not employed, the gas product is recovered from the bed, as in steps (Ha) and (llb) of the Baksh et al. Procedure. The omission of said step 3 would result in a lower production of the AOVP system, with a corresponding reduction in the energy consumption of the unit. It should also be noted that the processing cycle of the invention can be operated at a higher desorption pressure than indicated above. Such modalities could reduce the productive capacity of the system, with a corresponding reduction in the energy consumption of the unit. The invention represents a further, desirable advance in the AOVP technique. To achieve the objects of the invention set forth above, this allows that AOVP processing is advantageously employed at an improved productive capacity. The method of the invention is particularly desirable in the production of AOVP oxygen in the commercially significant production scale of 30-125 TPD, thus enabling AOVP systems to more effectively satisfy the growing desire and need for AOVP processing in business operations, practices.

Claims (1)

1. CLAIMS 1 .- In a vacuum-pressure oscillating adsorption process for the separation of a less easily adsorbable component of a feed gas mixture containing said component, and a more easily adsorbable component, in an adsorption system having two or more adsorbent beds containing adsorbent material capable of selectively adsorbing the more easily adsorbable component of said feed gas mixture, said process is carried out in an adsorbent bed lacquer, on a cyclic basis, and comprises the following steps: (a) Introduce a mixture of feed gas to a feed bed of the adsorbent bed, while a gas product is simultaneously added to a product end of the bed, the bed being pressurized, in this way, of an increasing, intermediate, lower pressure , towards an intermediate pressure; (b) Passing the feed gas mixture to the feed end of the bed, to increase the bed pressure of the intermediate pressure to a higher adsorption pressure, with the recovery of the less easily adsorbable component from the product end of the bed during or at the end of said increase in bed pressure; (c) Depressurize, in parallel, the bed of the adsorption pressure, higher, towards an intermediate, fall pressure, with the passage of gas from the product end of the bed to be used as a pressure equalization gas in another bed in the system; (d) Depressurizing, in countercurrent, the bed, with the evacuation of a gas component more readily adsorbable from its feed end, thereby reducing the bed pressure of the intermediate pressure, falling to the lower, subatmospheric desorption pressure; and (e) Downloading additional quantities of gas from the feed end of the bed, while simultaneously introducing a less readily adsorbable component to the product end of the bed, the bed pressure increasing from said subatmospheric, lower desorption pressure to the pressure Increasing intermediate, the improvement comprising: (1) After step (c) and before step (d), depressurize, countercurrent, the bed, with the gas discharge from its feed end, while, simultaneously and in parallel the bed is depressurized with the passage of gas from its end of product to be used as pressurization gas in a bed in the system undergoing repressurization, the bed pressure decreasing from the intermediate pressure of fall to a drop pressure , lower, intermediate; and (2) After step (d) and before step (e), discharge the waste gas from the more easily adsorbable component from the feed end of the bed, while simultaneously introducing a less readily adsorbable component such as a gas of purge towards the product end of the bed, the pressure of the bed remaining essentially at said lower, subatmospheric desorption pressure, by which the productive capacity of the adsorption system is increased and the efficiency of the total process is improved. 2 - The method of claim 1, wherein the feed gas mixture is air, the less easily adsorbable component is oxygen, and the more easily adsorbable component is nitrogen. 3. The process of claim 1, including, in step (b), introducing the feed gas mixture to the feed end of the adsorbent bed at the higher adsorption pressure, while the less easily adsorbable component is withdrawn from the product end of the adsorbent bed. 4. - The process of claim 3 and including the passage of a portion of the less readily adsorbable component removed from the product end of the adsorbent bed of said higher adsorption pressure directly to the product end of another bed in the adsorption system as a gas of purge for it. 5. - The procedure of claim 4, where the feed gas mixture is air, the less easily adsorbable component is oxygen, and the more easily adsorbable component is nitrogen. 6 - The method of claim 1, wherein the adsorption system comprises two adsorbent beds. 7. - The procedure of claim 4, wherein the adsorption system comprises two adsorbent beds. 8. The process of claim 5, wherein the adsorption system comprises two adsorbent beds, the upper adsorption pressure being about 1.54 kg / cm 2 absolute, and the lower desorption pressure is about 0.28 kg / cm 2 absolute. 9. The method of claim 8, wherein said increasing, intermediate, upper pressure is about 1.19 kg / cm2absolute, said intermediate pressure is about 0.913 kg / cm absolute, and said increase in intermediate pressure, lower is of approximately 0.42 kg / cm absolute. 10. The method of claim 9, wherein the upper intermediate pressure drop is about 1.26 kg / cm2absolute, and the intermediate, lower pressure drop is about 0.913 kg / cm2absolute. The method of claim 1, wherein said adsorbent material comprises a zeolitic molecular sieve. 12. The method of claim 1, wherein said zeolitic molecular sieve is capable of selectively adsorbing nitrogen from the feed air as the more selectively adsorbable component thereof, the feed gas mixture being air.