MX2008005637A - Pressure swing adsorption process for oxygen production - Google Patents

Abstract

The present invention generally relates to large capacity (e.g., greater than 350 tons/day O2) vacuum pressure adsorption (VPSA) systems and processes that employ a single train including four beds (42, 44, 46, 48) , at least one feed compressor (36, 38) feeding two beds simultaneously at any given instant in time, and a single vacuum pump (52) . The compressor (s) and the vacuum pump can be utilized 100%of the time. Use of product quality gas for purging is avoided, with about 10-20%improvement in O2productivity and 5-10%reduction in capital cost expected.

Description

ADSORPTION PROCESS OF PRESSURE OSCILLATION FOR OXYGEN PRODUCTION Field of the Invention The present invention generally relates to high capacity vacuum pressure adsorption (VPSA) systems (e.g., more than 350 tonnes / day of O2) and to processes utilizing a single train that includes four beds, at least one feed compressor that feeds two beds simultaneously at any given time, and a single vacuum pump. The compressor and the vacuum pump can be used 100% of the time. The use of product quality gas for purging is avoided, with approximately 10-20% improvement in O2 productivity and 5-10% reduction in expected capital cost. BACKGROUND OF THE INVENTION The production of oxygen from air currently uses the technology of vacuum pressure swing adsorption systems (VPSA) or pressure swing adsorption (PSA, for its acronym in English). These systems often have a capacity of < 200 tons per day of O2. Currently, there is renewed interest in extending the capacity of small scale PSA or PSA systems (<200 tons per O2 day) for large scale oxygen production (approximately 350 tons per day or more of O2) to from the air. In the application of the VPSA or PSA processes, the energy input required to achieve the O2 separation of the feed mixture (eg, air), is provided as mechanical work through the feed compressor and the feed pump. empty. The cost of this work is a significant component of the total operating costs of the VPSA or PSA process. In addition, VPSA or PSA technology is currently economically competitive with cryogenic distillation only for small scale application. For PSA or VPSA processes to have a competitive cost with cryogenic distillation for large-scale applications, improved cycles are required to operate the PSA or VPSA processes.

Two bed vacuum pressure oscillation adsorption (VPSA) processes for the production of oxygen from air are US Pat. No. 5,518,526 to Baksh et al. and U.S. Patent No. 6,010,555 to Smolarek et al. described, US Pat. Nos. 5,518,526 and 6,010,555 use the VPSA processes with the simultaneous stages of compensation and evacuation followed by the simultaneous steps of pressurization of feed and product. Figure 1 shows the VPSA cycle for the production of oxygen from the air described in Smolarek et al., US Patent No. 6,010,555, US Patent Nos. 5,518,526 and 6,010,555 are for small-scale oxygen production (< 200 tons per day, (TPD, for its silgas in English)). The adsorption and desorption pressures in U.S. Patent Nos. 5,518,526 and 6,010,555 are characterized by a low pressure ratio and relatively high desorption pressure values. The significant reduction in equipment and operating costs can be observed using the small scale VPSA processes (<200 TPD O2) of US Patent Nos. 5,518,526 and 6,010,555. In applications where large-scale oxygen production is desirable (eg, 350 tons per O2 day), four-bed VPSA processes are used. A VPSA process is described by Smolarek et al., US Patent No. 5,656,068. The bed VPSA processes described in U.S. Patent No. 5,656,068 as two pairs of 2-bed systems, referred to as a 2x2 cycle / system. Each pair of beds is operated 180 ° out of phase and the two pairs of beds are operated out of phase by one half of a half cycle. Two compressors (one Roots or positive displacement and one Centrifugal) and two vacuum pumps (one Roots or positive displacement and one centrifuge), are described in the VPSA process of U.S. Patent No. 5,656,068. One of the two compressors is periodically in idle or discharge mode. Four-bed VPSA systems that operate as two pairs of adsorption beds to produce approximately 100 tons per day of oxygen are described in Doong, US Patent No. 5,997,612 to Doong. The VPSA process includes two pairs of beds, an intermediate storage tank (to collect the parallel depressurization gas), a gas blower and a pair of vacuum pumps. The system described in Doong (Patent North American No. 5,997,612) includes three pumps with respect to the four pumps described in US Patent No. 5,656,068. In addition, the system shown in Doong (US Patent No. 5,997,612) is for small-scale oxygen production (<200 tons per day) instead of large-scale O2 production using the dual-feed VPSA process. Smolarek et al. (US Patent No. 5,656,068). Thus, it would be desirable to provide four highly productive and cost efficient bed VPSA processes and systems with the capacity for large-scale oxygen production (eg,> 350 tonnes / day of O2). Brief Description of the Invention The present invention generally relates to four bed VPSA systems and processes with dual feed input for large scale oxygen production (eg,> 350 tonnes / day of O2). The systems of the present invention include the implementation of three pumps (e.g., two compressors and one vacuum pump) in place of four pumps (e.g., two compressors and two vacuum pumps) as described in U.S. Patent No. 5,656,068. The present invention also contemplates the use of single four-bed VPSA cycles that include the use of 100% of the compressors and the vacuum pump while at the same time allowing two beds to simultaneously receive the feed gas. On the other hand, at any time during the VPSA cycle of four beds, two beds receive the power simultaneously while the other two beds are in the regeneration / reflow mode. The processes and systems provided in accordance with the present invention include multiple advantages. For example, and while not being construed as limiting, the systems and processes of the present invention may include: (1) the steps of making the continuous feed and the product; (2) a minimum of one compressor and one vacuum pump; (3) 100% utilization of the compressors and the vacuum pump; (4) smaller storage tanks of product / buffer in relation to the prior art processes due to the steps of elaboration of the continuous feed and the product; (5) the option to use the same or different compressors (eg, centrifugal and Roots) to compress the input power for the VPSA process; (6) the purge gas coming from the other bed which is undergoing the parallel depressurization stage, and this purge gas goes directly to another bed which undergoes the purge stage without the use of any additional storage tank; (7) the purge step between the evacuation stages in the VPSA cycle (ie, the VPSA cycle has an evacuation step before and after the purge step to allow use of the empty space gas to purge the another bed directly (without the need for an additional storage tank) or to avoid the use of product quality gas for purging); (8) use of absorbers with high intrinsic adsorption rates and with an optimum particle size to increase the total transfer rate, high recovery of O2 product, and a low bed size factor (BSF, for its acronym in English ) in surface adsorbents of the rapid cycle in the VPSA process, and / or (9) all stages of the VPSA process of four fully-integrated beds so that none of the beds have any inactive stage. Therefore, it is expected that the systems of the present invention provide approximately 10-20% improvement in O2 productivity / recovery and 5-10% reduction in capital cost while oxygen is produced on a large scale basis (> 350 tons / day) using a single train, a pump less, a lower bed size factor, and thus avoid the use of product quality gas for purging. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and the advantages thereof, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: Figure 1 illustrates the VPSA cycle for the production of oxygen from air, described in Smolarek et al., US Patent No. 6,010,555; Figure 2 illustrates a schematic diagram of a four-bed process using two compressors to supply the total power to a dual process of input power VPSA according to the present invention; Figure 3 shows a column cycle for the dual VPSA process of four feed input beds of Figure 2; Figure 4 illustrates a four-bed VPSA process using two compressors to supply the total power to a dual VPSA input feed process according to an alternative embodiment of the present invention; Figure 5 shows a column cycle for the dual VPSA process of four feed inlet beds of Figure 4; Figure 6 shows an alternate schematic diagram of a four-bed VPSA process using two compressors to supply the total power for a dual VPSA input feed process according to the present invention; Figure 7 shows a column cycle for the dual VPSA process of four feed inlet beds of Figure 6; Figure 8 illustrates an alternative column cycle for the dual VPSA process of four feed inlet beds of Figure 6 in which the cycle uses two stages of product pressurization and a compensation stage; and Fig. 9 shows another alternative column cycle for the dual VPSA process of four feed input beds of Fig. 6 in which the cycle uses eight stages instead of twelve stages. Detailed Description of the Invention As discussed above, the present invention relates to the processes and vacuum pressure swing adsorption apparatus (VPSA) for large-scale oxygen production (preferably> 350 tons / day). The present invention includes systems and processes in which twelve-step VPSA cycles are performed using four adsorption beds, at least one feed compressor (preferably two, eg, a centrifugal and a positive displacement compressor such as Roots). ), and a single vacuum pump. At any time, two of the beds are simultaneously in the feed mode while the other two beds are in the regeneration / reflow mode. The feed to these two beds can be supplied from separate compressors or from a single compressor. The gas generated during a parallel depressurization stage can be sent as a purge gas to another bed without the use of any additional storage tank. At any time, only one bed is in the evacuation stage, thereby allowing the use of only one vacuum pump that results in the saving of capital and operating costs. The evacuation step is carried out before and after the purge stage. This mode of operation allows for flexibility in the VPSA cycle to allow the use of the empty space gas, obtained during the parallel depressurization of another bed, to purge the bed directly (without using an additional storage tank) or to avoid using the product quality gas for purging. In addition, the VPSA process steps of four beds provided in accordance with the present invention are fully integrated so that none of the beds have any inactive stage, ie 100% utilization of the compressor and the vacuum pump in the VPSA cycle. While not being construed as a limitation, the systems of the present invention may include some or all of the following advantageous features. For example, the present invention includes the application of a four-bed single-train VPSA process instead of two two-bed VPSA process trains for large-scale O2 production. Therefore, a lower capital cost and improved process performance can be expected, for example, a higher recovery of O2, relative to the parallel trains of the two-bed VPSA processes. further, it is expected that the systems of the present invention have less distribution of airborne concentration of impurities (for example N2) as a result of the new VPSA cycles of four beds. This is due to the expectation that less purge gas will be required during the bed regeneration in relation to the prior art methods.1 The continuous steps of feeding and evacuating the product in the cycle allow a 100% utilization of the compressor /bomb of void. The present invention also provides the application of dual power input at any time during the VPSA cycle. On the other hand, the incorporation of a counter-current blow stage in the VPSA cycle can allow a portion of the waste (obtained during bed regeneration) to be diverted to the vacuum pump instead of having the waste through the vacuum pump as in the North American Patents. 5,656,068 and 6,010,555. The present invention also includes a cleaner gas used for refluxing. For example, the lower purity gas O2 is used for purging and the higher purity gas of O2 is used for pressurization of the product, that is, the product gas of increasing purity is used for purging, raising the compensation and for the pressurization of the product in the VPSA cycle of the present invention, thereby resulting in more defined areas of O2 concentration or better bed regeneration before bringing the bed in line for the production of O2. A further advantage of the present invention is expected due to a higher pressure gradient driving force for vacuum gas recovery during bed-to-bed compensation and to the unique multi-stage configurations in the VPSA cycle one cycle in relation to the prior art systems. In addition, there may be less feed blowing through or during feed pressurization because the bed compensated! begins the adsorption pressure during the overlap of the compensation and pressurization stage of the VPSA cycle. In the present invention, all the purge gas can come from the empty space gas recovered from another bed which is undergoing the parallel depressurization step. In addition, this purge gas can be used directly for the other bed undergoing the purge stage without the use of any additional storage tank (as in for example US Patent No. 5,997,612). The purge stage is between the evacuation stages in the VPSA cycle. More specifically, the VPSA cycle has evacuation stages before and after the purge step to allow the use of the empty space gas to purge the other bed directly or to avoid the use of product quality gas for purging as in US Patents Nos. 5,656,068 and 6,010,555. The systems of the present invention also provide the option of using the same or different compressors (eg, centrifugal and Roots or positive displacement) to compress the input power for the VPSA process and for 100% utilization, ie , no compressor without load through the VPSA cycle. As a result of the present invention, approximately 10-20% productivity improvement or recovery of O2 and approximately 5-10% reduction of capital cost is expected due to large-scale oxygen production (>; 350 tons / day) using a single train, one pump less, a lower bed size factor (BSF), and avoiding the use of product quality gas for purging. The present invention will now be described with reference to the four-bed VPSA process shown in Figure 2, the four-bed VPSA cycle shown in Figure 3, and the valve switching logic according to the indications of Figure 1. The four-bed VPSA system (30) shown in Figure 2 includes four adsorbent beds (42, 44, 46, 48), 24 on / off valves (some or all may or may not have flow control), two power compressors 36, 38, a vacuum compressor 52, muffler / power inlet filter 34 for power 32, muffler / post-chiller power discharge (40), vacuum discharge muffler 54, and piping and configurations associated Referring to Figures 2 and 3 and Table 1, one embodiment of the present invention is illustrated with respect to a VPSA cycle. In Figure 1, it will be appreciated that "C" represents the valves in the closed position while "O" represents the valves in the fully open or partially open position, depending on whether the valve is a flow control or ignition valve / off to manipulate the desired flow. It will be appreciated by those skilled in the art that the flow control valves will be utilized during the pressurization of the product (e.g., stage 3 in Figure 3). Table 1: Valve start sequence for a VPSA oxygen process of four beds of twelve stages.

AD: Adsorption / product production: PG: Purge received ED: Compensation decrease UE: Increase of PPG compensation: Provide purge gas PP: PPP product pressurization: Provide FP product pressurization gas: Pressurization BD power: Purge EV : Evacuation Stage No. 1 At the beginning of stage 1, the pressure in the bed 42 (B1) is at the adsorption pressure. The valve 1 is open to allow gas to be supplied to the bottom of the bed 42 and the valve 21 is open to allow the product 50 to exit the upper part of the bed 42. The feed gas is supplied to the bed 1 of the compressor 38 (C1). The valve 11 is open to allow evacuation of the bed 44 (B2) through the compressor 52 (C3) to the vacuum discharge silencer 54 for the waste 56. The valve 13 is opened to allow the bed 46 (B3) to be discharge to the atmosphere. Valve 8 opens to allow gas supply to the bottom of the bed 48 (B4) and the valve 24 opens to allow the product 50 to exit the upper part of the bed 48. The feed gas is supplied to the bed 48 of the compressor 36 (C2). Step No. 2 At the beginning of step 2, valve 1 closes and valve 2 opens to allow supply of gas from compressor 36 (C2) to bottom of bed 42. Valve 21 remains open to allow Product production continues from bed 42. Valve 11 closes and valve 3 opens to stop evacuation of bed 44 and to allow compressor feed gas 38 (C1) to enter bottom of bed 44. Also, the valves 18 and 20 are opened to allow the compensation gas to flow from the bed 48 in the upper part of the bed 44. The valve 13 is closed and the valve 14 is opened to begin the evacuation of the bed 46 (B3) . Step No. 3 At the beginning of stage 3, valves 2 and 21 remain open to allow product production 50 to continue from bed 42. Valve 3 remains open and allows compressor feed gas 38 to continue to enter. to the bottom of the bed 44. The valve 22 opens to allow product pressurization gas to enter the top of the bed 44. The valve 20 remains open and the valve 19 is opened to allow the purge gas to flow from bed 48 to bed 46. Valve 14 remains open to continue evacuation of bed 46. Valve 18 closes. Step No. 4 At the beginning of step 4, valves 2 and 21 remain open to allow production of the product to continue from bed 42. Valves 3 and 22 remain open and production of the product begins in bed 44. The valve 14 remains open to continue with the evacuation of the bed 46.

Valve 16 opens to allow bed 48 to discharge to atmosphere. Step No. 5 At the beginning of step 5, the valves 17 and 19 are opened to allow the compensation gas to flow from the bed 42 to the top of the bed 46. The valve 3 is closed and the valve 4 is opened to allow the gas supply from the compressor 36 (C2) to the bottom of the bed 44. The valve 22 remains open to allow product production to continue from the bed 44. The valve 13 is closed and the valve 5 is opened to stop the evacuation of the bed 46 and to allow the compressor feed gas 38 (Cl) to be incorporated into the lower part of the bed 46. The valve 16 is closed and the valve 15 is opened to begin the evacuation of the bed 48. Stage No At the beginning of step 6, the valve 17 remains open and the valve 20 opens to allow the purge gas to flow from the bed 42 to the bed 48. The valves 4 and 22 remain open to allow the production of the product. continue from the bed 44. Valve 5 remains open and allows compressor feed gas 38 (C1) to continue to enter the bottom of bed 46. Valve 23 is opened to allow product pressurization gas to enter top of the bed 46. The valve 15 remains open to continue with the evacuation of the bed 48 while receiving the purge gas. The valve 19 closes. Stage No. 7 At the beginning of stage 7, the valve 9 opens to allow the bed 42 to discharge to the atmosphere. Valves 4 and 22 remain open to allow production of the product to continue from bed 44. Valves 5 and 23 remain open and production of the product begins in bed 46. Valve 15 remains open to continue evacuation of the bed 48. Stage No. 8 At the beginning of stage 8, valve 9 closes and valve 10 opens to begin evacuation of bed 42. Valves 18 and 20 are opened to allow compensation gas to flow from the bed 44 at the top of the bed 48. The valve 5 closes and the valve 6 opens to allow the compressor feed gas 36 (C2) to go to the bottom of the bed 46. The valve 23 remains open to allow production of the product continues from the bed 46. The valve 15 is closed and the valve 7 is opened to stop the evacuation of the bed 48 and to allow the feed gas of the compressor 38 (C1) to enter the lower part of the bed 48. Stage No. 9 At the beginning of stage 9, the valve 10 remains open to continue with the evacuation of the bed 42 while receiving the purge gas. Valve 18 remains open and valve 17 opens to allow purge gas to flow from bed 44 to bed 42. Valves 6 and 23 remain open to allow product production to continue from bed 46. Valve 7 it remains open and allows the compressor feed gas 38 (C1) to continue to enter the bottom of the bed 48. The valve 24 opens to allow product pressurization gas to enter the top of the bed 48. The valve 20 closes. Step No. 10 At the beginning of step 10, the valve 10 remains open to continue with the evacuation of the bed 42. The valve 12 opens to allow the bed 44 to discharge to the atmosphere. Valves 6 and 23 remain open to allow product production to continue from bed 46. Valves 7 and 24 remain open and production of the product begins in bed 48. Stage No. 11 At the beginning of stage 11, valve 10 closes and valve 1 opens to stop evacuation of bed 42 and to allow the compressor feed gas 38 (C1) enters the bottom of the bed 42. The valve 12 closes and the valve 11 opens to begin evacuation of the bed 44. The valves 17 and Í9 are opened to allow the gas from compensation flows from the bed 46 to the top of the bed 42. The valve 7 closes and the valve 8 opens to allow the compressor feed gas 36 (C2) to go to the bottom of the bed 48. The valves 24 it remains open to allow the production of the product to continue from the bed 48. Stage No. 12 At the beginning of the step 12, the valve 1 remains open and allows the feed gas of the compressor 38 (C1) to continue its entry to the lower bed 42. L The valve 21 is opened to allow the pressurizing gas of the product to enter the upper part of the bed 42. The valve 11 remains open to continue with the evacuation of the bed 44 while receiving the purge gas. Valve 19 remains open and valve 18 opens to allow purge gas to flow from bed 46 to bed 44. Valves 8 and 24 remain open to allow product production to continue from bed 48. Valve 17 closes. The modality described above uses two compressors to supply the feed gas to the VPSA vessels. In a preferred embodiment, a Roots compressor 38 (C1 or compressor 1) and a centrifugal compressor 36 (C2 or compressor 2) will supply the total feed flow to an integrated four-bed VPSA process. In addition, in the preferred mode of operation for large scale O2 production, the radial beds are used in the VPSA process. Additional details of radial bed adsorbents are given by Ackley et al., US Patent No. 6,506,234 B1. Referring to the stages of the bed 42 (B1) in Figure 3, if two different compressors are used (eg, Roots and centrifugal), then in the preferred operating mode, the Roots compressor is used in steps 1, 11, and 12, while the centrifugal compressor is used in stages 2, 3 and 4. Referring to Figures 2 and 3, during stage 1 of the VPSA cycle, a total feed portion (dual VPSA feed process) is it supplies via the compressor Roots to the bed 42 (B1) while the centrifugal compressor supplies the other portion of total supply to the bed 48 (B4). It is also observed that at any time, two beds receive the feed gas simultaneously and a continuous product exists through the VPSA cycle. Table 2 gives an example of the operating and performance conditions of the VPSA process using a selective nitrogen adsorbent in the beds. In the table, the symbols have the following meaning: TPD = ton (2000 Ib) per day of oxygen, kPa = Pa 1000 = unit of S.l. for the pressure (1.0 atmospheres = kPa 101.323), s = unit of time in seconds. In addition, the selective nitrogen balance adsorbent "'in Figure 2 is highly exchanged Li-x (> 95% Li), as described by Chao et al., U.S. Patent Nos. 5,413,625 and 4,859,217, which are incorporated herein by reference to a constant degree with Although the highly exchanged LiX adsorbent is described in these patents, it is anticipated that adsorbent or adsorbent mixture layers could be used and preferably used (eg, when there is moisture in the air) in each bed of the process of VPSA without departing from the scope of this invention Representative examples of various adsorbents for use in this invention include but are not limited to those described in U.S. Patent Nos. 6,027,548 and 6,790,260 B2, which are incorporated herein by reference to a constant degree with it See also, US Patents Nos. 6,743,745 B2; 6,506,234 B1; 6,500,234; 6,471,748 B1; and 6,780,806. The adsorbent could be a mixture of adsorbents or an adsorbent with layers. Preferably, the same adsorbent, if it is a single adsorbent, adsorbent mixture or adsorbent layer, is the same in all four beds. Table 2: Example of large-scale O2 production (> 350 TPD) (Figures 2-3, operating conditions and performance). Each of the four beds contains Li-x zeolite for the removal of N2. The results shown below were obtained from experiments a VPSA simulation and pilot installation using dry air containing 0.934% Ar, 78.12% N2 and 20.95% O2. Adsorbent in each bed: Li-X Feed composition (N2 / O2 / Ar): 78. 12% / 20.95% O2 / 0.934% High pressure: 160 kPa Low pressure: 30 kPa Total power: 2.85X106 NCFH O2 quantity produced: 3.58X105 NCFH (355 TPD O2) Oxygen purity: 90% Total oxygen recovery: 60 % Bed Size Factor: 350 Ib / O2 TPD Temperature: 300K The VPSA process discussed above focuses on the production of O2 from air using a four-bed VPSA process and system. In the alternative embodiments of the present invention, less than four (e.g., three beds) or more than four beds could be used. In such embodiments, it is necessary to develop appropriate VPSA cycles of three beds or VPSA cycles of more than four beds to incorporate the aforementioned characteristics of the present invention. In addition, additional storage tanks may or may not be required in such alternative embodiments to incorporate the features of the invention depending on whether three or more than four beds are used in the VPSA cycles. On the other hand, each bed could alternatively include one or more layers of adsorbents, or a mixture of adsorbents. Several kinds of adsorbents could also be used in the VPSA process for the production of O2 from air. Details of preferred convenient adsorbents and layers of adsorbents are described in U.S. Patent Nos. 5,413,625; 4,859,217; 6,027,548; and 6,790,260 B2. In other modes of operation, other adsorbents could be used in the aforementioned VPSA processes of the present invention. For example, 5A, 13X ,? CaX, and mixed cation zeolites could be used as the selective adsorbent of N2 in the VPSA process. In the preferred and alternative mode of operation, a section of the pre-purifier is placed at the rising end of each zeolite bed to remove water and carbon dioxide from the feed air. For example and as long as it is not interpreted as a limitation, an alumina or silica layer is preferably placed upwardly from each of the adsorbent beds to remove water and carbon dioxide from the feed air before passing to the selective adsorbent of N2 in the VPSA process. The selected adsorbent configuration (eg, radial, axial, structured, etc.) and the choice and arrangement of the adsorbents will be determined based on the size of the feed flow, type of power source, and operating conditions of the VPSA process. . In an alternative operation mode for example, the axial beds can be used in the VPSA process. It is preferred that all beds have the same configuration. In yet another alternative operation mode, a compressor (instead of two compressors) could be used to supply the full power to the dual VPSA input process (e.g., the VPSA processes illustrated in the figures). In a certain mode of operation, the highest adsorption pressure is in the range of 100 kPa to about 2000 kPa, and the lowest desorption pressure is in the range of 20 kPa to about 100 kPa. In addition, optimization between the achievement of high O2 recovery and low energy consumption in the VPSA process will determine the optimal adsorption and desorption pressures for a given adsorbent. The average purity of the oxygen product is expected to be in the range of 85 percent oxygen to about 95 percent oxygen; which corresponds to an expected recovery of O2 of approximately 55-75%. It is expected that the lowest O2 recovery corresponds to the highest purity of O2, and vice versa. In the alternative operation mode, other processes and cycles could be used. For example, Figure 4 shows an alternate schematic diagram of a four-bed system 60 and of the process using two compressors 36, 38 to supply the total power 32 to the dual process of input power VPSA and two compressors 52, 53 to evacuate waste 56 of the VPSA process. In the preferred mode of operation only one vacuum blower 52 (preferably, a Roots type blower) is used to evacuate the waste. In this alternative mode, a first vacuum blower 52 is used to evacuate waste (preferably a Roots type blower) followed by a second vacuum blower 53 (preferably a centrifugal type blower). Figure 5 shows the column cycle for the dual VPSA process of four feed inlet beds of Figure 4. In this alternative mode, an additional purge gas, obtained from another bed in the adsorption stage (e.g. the bed 42 (B1) undergoing AD4 in Figure 5 while simultaneously supplying the purge gas to another bed), is used in the VPSA process. In addition, the low compensation stage in this alternative mode overlaps with a countercurrent evacuation to accelerate the depressurization of the bed.

Also, during the supply of the purge stage (for example, bed 42 (B1) in stage 6 of figure 5), the bed is simultaneously undergoing countercurrent evacuation. Referring to Figures 4 and 5 and Table 3, an alternative embodiment of the present invention is illustrated with respect to a complete VPSA cycle. In table 3, AD represents adsorption / product production, ED: low compensation, PPG: provide purge gas, PPP: Provide product pressurization gas, BD: Purge, PG: Receive purge, UE: compensation high (UE equals EQUP), PP: product pressurization, FP: Feed pressurization, RC: Roots compressor, CC: Centrifugal compressor, RV: Vacuum cleaner Roots, CV: Centrifugal vacuum cleaner, EV: Evacuation. As discussed above with reference to table 1, it will be appreciated that in figure 3, the "C" represents the valves in the closed position while "O" represents the valves in the open or partially open position, depending on whether the valve It is an on / off valve or flow control to manipulate the desired flow. It will also be appreciated by those skilled in the art that flow control valves will be used during product pressurization (e.g., step 3 in Figure 5).

Table 3: Valve start sequence for the VPSA oxygen process of four twelve-stage beds.

The adsorbents, mixtures and suitable layers of such adsorbents are discussed above. Figure 6 shows another alternate schematic diagram of a four-bed system 70 and of the process according to the present invention using two compressors 36, 38 to supply the full power to the dual input power VPSA process. Figure 7 shows a column cycle for the dual VPSA process of four feed inlet beds of Figure 6. In the preferred mode of operation (Figures 2 and 3) described above, eight waste valves are used to allow a purge stage (bypassing the vacuum blower) followed by the evacuation stages using the vacuum blower. In the alternative operation mode shown in Figures 6 and 7, only four waste valves are required. Therefore, all the waste gas is evacuated through the vacuum blower. In the preferred mode shown in Figures 2 and 3, the compensation does not overlap with the evacuation as in the alternative mode illustrated in Figures 6 and 7. In addition, the purge is provided from the parallel depressurization gas in the embodiment shown in Figures 2 and 3 while the purge is provided from the bed during production in the embodiment shown in Figures 6 and 7. In addition, there is an evacuation step after the purge step in the preferred embodiment shown in Figures 2 and 3 as long as there is no evacuation step following the purge in the alternative embodiment described in Figures 6 and 7. The cycles of Additional alternative columns for the dual VPSA process of four feed inlet beds of Figure 6 are shown in Figures 8 and 9. Particularly, the cycle shown in Figure 8 uses two stages of product pressurization and a compensation stage. and the cycle shown in Figure 9 uses eight stages instead of twelve stages. The column cycle "illustrated for the dual VPSA processes of four feed input beds shown in Figures 2, 4 and 6 and the associated column cycles are arranged in the order of the most preferred (Figures 2-3) to the less preferred ones (Figures 6 and 9) In addition, for the VPSA process of Figure 6 and for the associated column cycles (Figures 7-9), the column cycles are arranged in the order of the most preferred at least preferred; that is, the cycle in Figure 7 is preferred over the cycle shown in Figure 8, and the cycle shown in Figure 8 is preferred over the cycle shown in Figure 9. This is because it is expected that the recovery of O2 of VPSA and productivity of O2 are less using the cycle shown in Figure 8 than using the cycle illustrated in Figure 7 and recovery of O2 is expected to be less than using the cycle represented in Figure 9 in relation to cycle use shown in Figure 8. It is expected that the column cycles for the dual VPSA process of four feed inlet beds of Figure 6 illustrated in Figures 7-9 will vary in bed size factor and consumption. of energy, the cycle represented in Figure 7 is more efficient than that shown in Figure 8 and the cycle in Figure 8 is more efficient than that shown in Figure 9. It is expected that the consumption of BSF and energy will be higher for figure 9, smaller for figure 8 e even smaller for Figure 7 for the schematic diagram in Figure 6 because the efficiencies for the cycles shown are expected to decrease with the increase in the numbers in the figure. In the VPSA processes and systems discussed above, it is contemplated to use air as the feed gas to recover oxygen in a large-scale base. Because oxygen can be produced on a large scale (> 350 tons / day) using a single train, one pump less (that is, one less than using 2 power pumps and 2 vacuum pumps), a lower factor of bed size, and avoiding the use of product quality gas for purging, it is expected that there will be approximately 10-20% productivity improvement / O2 recovery and 5-10% reduction of capital cost. It is expected that the systems and processes of the present invention will also be useful for feed currents other than air such as rare gas (e.g. He, Ar, Ne, Kr) containing feed streams or feed streams containing H2 such as those obtained from reacts of steam methane reformation or partial oxidation of hydrocarbons, etc. for example and while not being construed as limitation, it is expected that a H2 containing the synthesis gas feed mixture, generated from the steam methane reformation, would be suitable for use in accordance with the present invention. In such a mode, hydrogen could be recovered. It is anticipated that the process and the system could be completely adapted in an easy manner for the desired production of the product or co-product. For example, co-production of O2 and N2 or H2 and CO could be easily achieved from the air supply and the H2-containing feed, respectively. Those skilled in the art will recognize that appropriate modifications to the adsorbent, pre-purifier and operating conditions of the process will be selected based on the intended application. The systems and processes discussed above have contemplated the use of VPSA processes to produce oxygen from air. In the alternative embodiments of the invention, pressure swing adsorption (PSA) could be used, where the operating pressures are above the ambient pressure, thus a vacuum pump may not be necessary. In still other modalities, more than one vacuum pump can be desired.

It should be appreciated by those skilled in the art that the specific embodiments described above can be readily used as a basis for modifying or designing other structures to accomplish the same purposes of the present invention. It should also be observed by those skilled in the art that such equivalent constructions do not deviate from the spirit and scope of the invention in accordance with the provisions of the appended claims.

Claims (19)

1. An adsorption process of the vacuum pressure oscillation (VPSA) for separating a gas from the power source containing at least one more strongly absorbable component and at least one gas component of the less strongly absorbable product, comprising: continuously feeding a feed source gas to the ends of the feed inlet of each of the two adsorbent beds, each bed contains at least one adsorbent that preferentially absorbs the most strongly absorbable component, and the elimination of at least one gas component of absorbable product more strongly from the outlet ends of the adsorbent beds, the production in staged cycles in which two beds are simultaneously in a feed mode and the other two beds are in a regeneration / reflow mode, where at any time during the process, only one bed is in an evacuation stage.

2. The vacuum pressure swing adsorption process of claim 1, wherein the VPSA process contains four beds in a single train.

3. The vacuum pressure swing adsorption process of claim 2, wherein the stepped cycles comprise a twelve stage cycle.

4. The vacuum pressure swing adsorption process of claim 3, wherein the evacuation step is performed before and after a purge step.

5. The vacuum pressure swing adsorption process of claim 4, wherein the vacuum space gas obtained during the parallel depressurization of a bed other than the bed undergoing evacuation is suitable for use as a purge gas. .

6. The vacuum pressure swing adsorption process of claim 1, wherein at least one more strongly absorbable component comprises nitrogen.

7. The vacuum pressure swing adsorption process of claim 1, wherein at least one gas component of absorbable product less strongly comprises oxygen.

8. The vacuum pressure swing adsorption process of claim 7, wherein the oxygen has an average purity of about 85-95% oxygen.

9. The vacuum pressure swing adsorption process of claim 7, wherein the oxygen corresponds to an oxygen recovery of about 55-75%.

10. The vacuum pressure swing adsorption process of claim 7, wherein each adsorption bed contains a N2-selective adsorbent.

11. The vacuum pressure swing adsorption process of claim 10, wherein the adsorbent comprises at least one of: Li-x zeolite, 5A, 13X, CaX, and mixed cation zeolites.

12. The vacuum pressure swing adsorption process of claim 11, wherein the adsorbent comprises a LiX adsorbent.

13. The vacuum pressure swing adsorption process of claim 1, wherein at least one gas component of absorbable product less strongly comprises hydrogen. The vacuum pressure swing adsorption process of claim 1, wherein a higher adsorption pressure is from about 100 kPa to about 2000 kPa, and the lowest desorption pressure is from about 20 kPa to about 100. kPa. 15. The vacuum pressure swing adsorption process of claim 1, wherein the process can produce at least 200 tonnes / day of O2. 16. The vacuum pressure swing adsorption process of claim 15, wherein the process can produce at least 350 tonnes / day of O2. 17. A vacuum pressure swing adsorption process of claim 1, wherein the process is a twelve stage cycle in a four bed system. 18. A vacuum pressure swing adsorption process of claim 1, where the process is a cycle of twelve stages in a four-bed system. 19. A vacuum pressure oscillation adsorption system for separating a gas from the power source containing at least one more strongly absorbable component and at least one product gas component to be less strongly bsorbable, the system It comprises: four adsorption beds in a single train configured such that a gas from the power source can be continuously fed to the feed inlet ends of two of the adsorption beds; at least one power compressor configured to supply the gas from the power source to the adsorption beds; and a vacuum pump.