Control system for selective adsorption process

Claim 2

In a substantially adiabatic pressure swing adsorption process for continuously separating feed gas mixture in at least three adsorbent beds by the repeating cycle steps of sequentially contacting said feed gas mixture with each bed at first higher pressure for selective adsorption of at least one component and discharge of a one component depleted product gas, Desorption of depressurization of the bed to second lower pressure and at least partial repressurization of the desorbed bed with said product gas followed by recontact of said desorbed bed with said feed gas mixture, an improved control method comprising the steps of: a. sensing the adsorption rate of a first adsorbent bed during the selective adsorption step; b. simultaneously and continuously diverting a portion of said product gas discharged from said first adsorbent bed for return to said process with at least part thereof continuously introduced during the entire adsorption step as repressurizing gas for another adsorbent bed, and discharging the undiverted product gas from said process; c. converting the relative adsorption rate sensing of a into a transmittable signal; and d. controlling the diverted gas return flow rate by means of the transmitted relative adsorption rate signal of c such that the ratio of said relative adsorption rate to the diverted gas return flow rate is constant.

Claim 3

A process according to claim 1 in which the feed gas mixture flow rate is sensed as step a.

Claim 4

A process according to claim 1 in which the product gas flow rate is sensed as step a.

Claim 5

A process according to claim 1 in which the gas composition is sensed in the first adsorbent bed as step a.

Claim 6

A process according to claim 1 in which the feed gas temperature is sensed as step a.

Claim 7

A process according to claim 1 in which the feed gas pressure is sensed as step a.

Claim 8

In a pressure swing adsorption process for continuously separating feed gas mixture in at least three adsorbent beds by the repeating cycle steps of sequentially contacting said feed gas mixture with each bed at first higher pressure for selective adsorption of at least one component and discharge of one-component-depleted product gas, desorption by depressurization of the bed to second lower pressure and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture, an improved control method comprising the steps of: a. sensing the relative adsorption rate connected with a first adsorbent bed during the selective adsorption step; b. simultaneously and continuously diverting a portion of said product gas discharged from said first adsorbent bed for return to said process with at least part thereof as repressurizing gas for another adsorbent bed, and discharging the undiverted product gas from said process; c. converting the relative adsorption rate sensing of a into a transmittable signal; d. controlling the diverted gas return flow rate to the process by the transmitted relative adsorption rate signal c such that the ratio of said relative adsorption rate to the diverted gas return flow rate is constant; e. sensing the product gas repressurization rate as controlled in step (d) during repressurization of the desorbed first bed; f. converting the product gas repressurization gas pressure sensing of (e) into a transmittable signal when it rises to a predetermined value; and g. employing the product gas repressurization signal to simultaneously: (1) terminate repressurization of said first bed and return the first bed to said selective adsorption step, and (2) initiate cycle changes in the other adsorbent beds.

Claim 9

In a pressure swing adsorption process for continuously separating feed gas mixture in at least three adsorbent beds by the repeating cycle steps of sequentially contacting said feed gas mixture with each bed at first higher pressure for selective adsorption of at least one component and discharge of one-component-depleted product gas, desorption by depressurization of the bed to second lower pressure and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture, an improved control method comprising the steps of: a. sensing the relative adsorption rate connected with a first adsorbent bed during the selective adsorption step; b. simultaneously and continuously diverting a portion of said product gas discharged from said first adsorbent bed for return to said process with at least part thereof as repressurizing gas for another adsorbent bed, and discharging the undiverted product gas from said process; c. converting the relative adsorption rate sensing of a into a transmittable signal; d. controlling the diverted gas return flow rate to the process by the transmitted relative adsorption rate signal c such that the ratio of said relative adsorption rate to the diverted gas return flow rate is constant; e. sensing the product gas repressurization rate as controlled in step (d) during repressurization of the desorbed first bed; f. converting the product gas repressurization gas pressure sensing of (e) into a transmittable signal when it rises to a predetermined value; and g. employing the product gas repressurization signal to simultaneously: (1) terminate repressurization of said first bed and return the first bed to said selective adsorption step, and (2) initiate cycle changes in the other adsorbent beds.

Claim 10

A process according to claim 7 in which all of the diverted product gas from step b is returned to the process as repressurization gas for the desorbed bed.

Claim 11

A process according to claim 7 in which a first part of the diverted product gas from step b is returned to the process as purge gas for a depressurized bed at said second lower pressure, and the remaining part of the diverted product gas is returned to the process as repressurization gas for a purged and desorbed bed.

Claim 12

In a pressure swing adsorption process for continuously separating feed gas mixture in four adsorbent beds having void space between adjacent adsorbent particles by the repeating cycle steps of sequentially contacting said feed gas mixture at first higher pressure with a first bed for selective adsorption of at least one component and discharge of one-component depleted product gas, pressure equalization to second intermediate pressure with a second previously desorbed bed initially at lower pressure by flowing void space gas thereto, cocurrent depressurization to third lower-than-intermediate pressure by flowing additional void space gas from said first bed through a third bed as purge gas, countercurrent depressurization to a lowest pressure for partial desorption and partial removal of said one component, countercurrent purging by cocurrent depressurization gas from a fourth bed at said lowest pressure for desorption and removal of the remaining one component, and countercurrent repressurization of the desorbed first bed to a higher pressure by introduction of void space gas from said second adsorbent bed and product gas from a third adsorbent bed such that the last part of repressurization is performed with only said product gas, followed by recontact of said feed gas mixture with the fourth, second and third beds successively following the first bed in the adsorption and succeeding cycle step sequence, an improved control method comprising the steps of: a. sensing the feed gas load rate to the first adsorbent bed during the selective adsorption step; b. simultaneously and continuously diverting a portion of said product gas discharged from said first adsorbent bed at about said first higher pressure for return to said process as the product repressurization gas for another desorbed bed, and discharging the undiverted product gas from said process; c. converting the feed gas load rate sensing of a into a transmittable signal; d. controlling the diverted gas return flow rate to the process by the transmitted feed gas load rate signal (c) such that the ratio of said feed gas load rate to the diverted gas return flow rate is constant; e. sensing the product gas pressure during repressurization of the desorbed first bed as controlled in step (d); f. converting the product repressurization gas sensing of (e) into a transmittable signal when it rises to predetermined value; and g. employing the product gas repressurization signal to simultaneously: (1) terminate repressurization of said first bed and return the first bed to said selective adsorption step, (2) terminate the cocurrent depressurization step in said second bed and initiate the countercurrent depressurization step, (3) terminate the selective adsorption step in said third bed and initiate the pressure equalization step, and (4) terminate the countercurrent purging step in said fourth bed and initiate the countercurrent repressurization step.

Claim 13

In a pressure swing adsorption process for continuously separating feed gas mixture in four adsorbent beds having void space between adjacent adsorbent particles by the repeating cycle steps of sequentially contacting said feed gas mixture at first higher pressure with a first bed for selective adsorption of at least one component and discharge of one-component depleted product gas, pressure equalization to second intermediate pressure with a second previously desorbed bed initially at lower pressure by flowing void space gas thereto, cocurrent depressurization to third lower-than-intermediate pressure by flowing additional void space gas from said first bed through a third bed as purge gas, countercurrent depressurization to a lowest pressure for partial desorption and partial removal of said one component, countercurrent purging by cocurrent depressurization gas from a fourth bed at said lowest pressure for desorption and removal of the remaining one component, and countercurrent repressurization of the desorbed first bed to a higher pressure by introduction of void space gas from said second adsorbent bed and product gas from a third adsorbent bed such that the last part of repressurization is performed with only said product gas, followed by recontact of said feed gas mixture with the fourth, second and third beds successively following the first bed in the adsorption and succeeding cycle step sequence, an improved control method comprising the steps of: a. sensing the feed gas load rate to the first adsorbent bed during the selective adsorption step; b. simultaneously and continuously diverting a portion of said product gas discharged from said first adsorbent bed at about said first higher pressure for return to said process as the product repressurization gas for another desorbed bed, and discharging the undiverted product gas from said process; c. converting the feed gas load rate sensing of a into a transmittable signal; d. controlling the diverted gas return flow rate to the process by the transmitted feed gas load rate signal (c) such that the ratio of said feed gas load rate to the diverted gas return flow rate is constant; e. sensing the product gas pressure during repressurization of the desorbed first bed as controlled in step (d); f. converting the product repressurization gas sensing of (e) into a transmittable signal when it rises to predetermined value; and g. employing the product gas repressurization signal to simultaneously: (1) terminate repressurization of said first bed and return the first bed to said selective adsorption step, (2) terminate the cocurrent depressurization step in said second bed and initiate the countercurrent depressurization step, (3) terminate the selective adsorption step in said third bed and initiate the pressure equalization step, and (4) terminate the countercurrent purging step in said fourth bed and initiate the countercurrent repressurization step.

Claim 14

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure under substantially adiabatic conditions employing at least three adsorbent beds with interconnecting conduits and associating valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas following by recontact with said feed mixture comprising: (a) means for sensing the relative adsorption rate in each of the adsorption beds when contacted with said feed gas mixture; b. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and continuously returning during the entire adsorption step at least part of the diverted product gas to a desorbed bed for repressurization thereof; c. flow control means in product gas diverting conduit means b; and d. means foR transmitting signals from said relative adsorption rate sensing means a to said flow control means c for adjustment of diverted product gas flow to maintain a predetermined constant ratio of relative adsorption rate to diverted product gas returned flow rate.

Claim 15

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure under substantially adiabatic conditions employing at least three adsorbent beds with interconnecting conduits and associating valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas following by recontact with said feed mixture comprising: (a) means for sensing the relative adsorption rate in each of the adsorption beds when contacted with said feed gas mixture; b. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and continuously returning during the entire adsorption step at least part of the diverted product gas to a desorbed bed for repressurization thereof; c. flow control means in product gas diverting conduit means b; and d. means foR transmitting signals from said relative adsorption rate sensing means a to said flow control means c for adjustment of diverted product gas flow to maintain a predetermined constant ratio of relative adsorption rate to diverted product gas returned flow rate.

Claim 16

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure comprising: a. at least three adsorbent beds with interconnecting conduits and associated valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one-component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture; b. means for sensing the relative adsorption rate in each of the adsorption beds when contacted with said feed gas mixture; c. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and returning at least part of the diverted product gas portion to a desorbed adsorption bed for repressurization thereof; d. flow control means in product gas diverting conduit c; e. means for transmitting signals from said relative adsorption rate sensing means b to said flow control means d for adjustment to maintain a predetermined constant ratio of relative adsorption rate to the diverted product gas return flow rate; f means for sensing the product gas repressurization pressure between flow control means d and said one end of the adsorbent beds; g. cycle flow sequencing means associated with said interconnecting conduits and valving a for initiating the step changes among the adsorbent beds; and h. means for transmitting signals from the product gas repressurization pressure sensing means f to cycle flow sequencing means g when the repressurization gas rises to a predetermined value to simultaneously: (1) terminate repressurization of each bed and return same to the adsorption step; and (2) initiate step changes in the other beds.

Claim 17

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure comprising: a. at least three adsorbent beds with interconnecting conduits and associated valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one-component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture; b. means for sensing the relative adsorption rate in each of the adsorption beds when contacted with said feed gas mixture; c. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and returning at least part of the diverted product gas portion to a desorbed adsorption bed for repressurization thereof; d. flow control means in product gas diverting conduit c; e. means for transmitting signals from said relative adsorption rate sensing means b to said flow control means d for adjustment to maintain a predetermined constant ratio of relative adsorption rate to the diverted product gas return flow rate; f means for sensing the product gas repressurization pressure between flow control means d and said one end of the adsorbent beds; g. cycle flow sequencing means associated with said interconnecting conduits and valving a for initiating the step changes among the adsorbent beds; and h. means for transmitting signals from the product gas repressurization pressure sensing means f to cycle flow sequencing means g when the repressurization gas rises to a predetermined value to simultaneously: (1) terminate repressurization of each bed and return same to the adsorption step; and (2) initiate step changes in the other beds.

Claim 18

Apparatus according to claim 12 in which the product gas repressurization pressure sensing means f comprises a cell adapted to sense the pressure difference between the repressurization gas and the feed gas mixture, and generate a signal when said pressure drops to a predetermined value.

Claim 19

Apparatus according to claim 12 in which said flow control means d comprises a flow restrictor, means for sensing the differential pressure across the flow restrictor, a flow regulator downstream of said flow restrictor, means for converting said differential pressure into a signal, and means for transmitting the signal to said flow regulator for adjustment thereof.

Claim 20

Apparatus according to claim 12 in which the relative adsorption rate sensing means b comprises an orifice and means for sensing the differential pressure across the orifice, and the signal transmitting means e includes a linear converter.

Claim 21

Apparatus according to claim 12 in which said flow control means d comprises a first orifice, means for sensing the diverted product gas differential pressure across the first orifice, means for converting said differential pressure into a signal, a flow ratio controller adapted to generate a signal representative of the variation from a predetermined ratio of relative adsorption rate to diverted gas return flow rate, means for transmitting the diverted product gas differential pressure signal to said flow ratio controller; and in which the relative adsorption rate sensing means b comprises a second orifice, means for sensing the differential pressure across the second orifice, and means for converting said differential pressure into a signal being transmitted to said flow ratio controller by means e; a regulator iN said product gas diverting conduit c downstream of said first orifice, and means for transmitting said signal for said flow ratio controller to said regulator for flow adjustment responsive to variation from the predetermined flow rate ratio.

Claim 22

Apparatus according to claim 12 in which said flow control means d comprises an adjustable valve, the signal transmitting means e provides adjustment thereof, and a regulator is provided in product gas diverting conduit c. downstream of said adjustable valve to maintain a constant pre-determined pressure in said conduit c between said adjustable valve and said regulator.

Claim 23

Apparatus according to claim 12 in which the product gas repressurization pressure sensing means f comprises a cell adapted to sense the pressure difference between the repressurization gas and the product gas, and generate a signal when said pressure difference drops to a predetermined value.

Claim 24

Apparatus according to claim 14 in which said flow restrictor is the variable type, said flow control means d also comprises a purge gas conduit joined at one end of said product gas diverting conduit c between the variable flow restrictor and said flow regulator and joined at the other end to said adsorption beds for intermittent sequential flow of a first part of the diverted product gas thereto for purging, flow control means in said purge gas conduit for maintaining the purge gas flow rate constant during the intermittent flow periods, and a signal modifier in the signal transmitting means to said variable flow restrictor adding a constant incremental value to the signal being representative of the total purge gas flow averaged over the entire cycle time for said adsorption beds.

Claim 25

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure comprising: a at least three adsorbent beds with interconnecting conduits and associated valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one-component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture; b. means for sensing the mass transfer adsorption front in each of the adsorption beds when contacted with said feed gas mixture, and means for transmitting signals from said sensing; c. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and returning at least part of the diverted product gas portion to a desorbed adsorption bed for repressurization thereof; d. flow control means in product gas diverting conduit c; e. means for sensing the product gas repressurization pressure between flow control means d and said one end of the adsorption beds, and means for transmitting signals from said sensing; f. means for comprising the transmitted signals from the mass transfer adsorption front b and from the product gas repressurization pressure e, and generating a comparison signal; g. means for transmitting said comparison signal from f to said flow control means d for adjustment to maintain a predetermined constant ratio of relative adsorption rate to the diverted product gas return flow rate; h. cycle flow sequencing means associated with said interconnecting conduits and valving a for initiating the step changes among the adsorbent beds; and i. means for transmitting signals from the mass transfer adsorption front sensing means b to cycle flow sequencing means h when the gas purity reaches a predeter-mined value to simultaneously: (1) terminate repressurization of each bed and return same to the adsorption step, and (2) initiate step changes in the other beds.

Claim 26

Apparatus for continuously separating feed gas mixture by selective adsorption of at least one component at higher pressure and desorption at lower pressure comprising: a at least three adsorbent beds with interconnecting conduits and associated valving for consecutive introduction of said feed gas mixture to one end of each bed as the adsorption step at first higher pressure with discharge of one-component depleted product gas from the bed''s other end, depressurization to second lower pressure for desorption and at least partial repressurization of the desorbed bed by said product gas followed by recontact with said feed gas mixture; b. means for sensing the mass transfer adsorption front in each of the adsorption beds when contacted with said feed gas mixture, and means for transmitting signals from said sensing; c. conduit means for simultaneously diverting a portion of the product gas discharged from each adsorption bed when contacted with said feed gas mixture and returning at least part of the diverted product gas portion to a desorbed adsorption bed for repressurization thereof; d. flow control means in product gas diverting conduit c; e. means for sensing the product gas repressurization pressure between flow control means d and said one end of the adsorption beds, and means for transmitting signals from said sensing; f. means for comprising the transmitted signals from the mass transfer adsorption front b and from the product gas repressurization pressure e, and generating a comparison signal; g. means for transmitting said comparison signal from f to said flow control means d for adjustment to maintain a predetermined constant ratio of relative adsorption rate to the diverted product gas return flow rate; h. cycle flow sequencing means associated with said interconnecting conduits and valving a for initiating the step changes among the adsorbent beds; and i. means for transmitting signals from the mass transfer adsorption front sensing means b to cycle flow sequencing means h when the gas purity reaches a predeter-mined value to simultaneously: (1) terminate repressurization of each bed and return same to the adsorption step, and (2) initiate step changes in the other beds.