CN102834159B - Cyclic adsorption control method and controller - Google Patents
Cyclic adsorption control method and controller Download PDFInfo
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- CN102834159B CN102834159B CN201080013425.6A CN201080013425A CN102834159B CN 102834159 B CN102834159 B CN 102834159B CN 201080013425 A CN201080013425 A CN 201080013425A CN 102834159 B CN102834159 B CN 102834159B
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- 239000003463 adsorbent Substances 0.000 claims abstract description 462
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- 239000000047 product Substances 0.000 claims description 238
- 238000004519 manufacturing process Methods 0.000 claims description 101
- UGFAIRIUMAVXCW-UHFFFAOYSA-N carbon monoxide Chemical group [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 51
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 51
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 49
- 239000003795 chemical substances by application Substances 0.000 claims description 40
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- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 32
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- 229910052739 hydrogen Inorganic materials 0.000 claims description 27
- 229910052757 nitrogen Inorganic materials 0.000 claims description 27
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Abstract
The present invention provides method and the control system controlling adsorbent bed unit, wherein measures the adsorbent bed impurity concentration in the adsorbent bed of adsorbent bed unit.Adsorbent bed concentration is controlled, so that adsorbent bed concentration is maintained at target affinity bed concentration by controlling feed cycle time adsorbent bed adsorbing contaminant during this period.Measure target affinity bed concentration so that impurity in products concentration is maintained at impurity in products concentration target value.The method and control system can include responding impurity in products concentration level and associated target value to determine the Supervised Control level of target affinity bed concentration and major control level based on the Error Calculation feed cycle time recorded between target affinity bed concentration.Proportional plus integral control can be used for this type of purposes.
Description
Invention field
The present invention relates to control thus produce the method for the absorbing unit (absorption unit) of product stream containing one or more adsorbent beds with one or more impurity in absorption feed stream and realize the controller of this method.More particularly, the present invention relates to such method and controller, the wherein impurity concentration in sampling adsorbent bed, and control the feed cycle time of adsorbent bed adsorbing contaminant, so that the concentration recorded in this is close to guaranteeing to produce the desired value of product stream with specific purity level.
Background of invention
Kinds of processes uses and can be easier to adsorb one or more impurity contained by feed stream and surpass the adsorbent of other impurity in feed stream, has the product stream of the impurity concentration lower than feed stream with generation.Adsorbent is included in adsorbent bed, can use one or more adsorbent bed in this type of technique.Such as, this type of technique can be used for purifying the hydrogeneous stream from reformer.In this case, there is water vapour, carbon dioxide, carbon monoxide, other hydrocarbon and nitrogen in feed stream.Hydrogen is the component less easily adsorbed, and therefore constitutes product stream.Impurity or component water vapour, carbon dioxide etc. are to be easier to the impurity of absorption and remove to produce product stream from feed stream by absorption.Adsorbent is positioned at adsorbent bed, and it can be made up of the container with one or more adsorbent layer.In the case of hydrogeneous stream, can be adsorbent bed provide the aluminium oxide first floor with absorption water vapour, active carbon layer with absorbing carbon dioxide and heavy hydrocarbon and final zeolite adsorbent layer with sorbing carbon monoxide and nitrogen.
In any absorbing process, all can arrive adsorbent be fully loaded with impurity and when adsorbent bed must regenerate.Therefore, absorbing process uses adsorbent bed during this period of such cycle online and adsorbing contaminant or component and off-line regenerating subsequently.Absorbing process can be distinguished by the cycle used, such as, and pressure-variable adsorption, temp.-changing adsorption and Vacuum Pressure Swing Adsorption.In the example about production hydrogen product stream given above, the cycle used is pressure-variable adsorption (pressure
Swing adsorption).
In pressure-variable adsorption, two or more contain absorbent containers of adsorbent bed and use with different phase cycles so that while a bed adsorbing contaminant, regenerate another or other bed.The pressure-variable adsorption cycle can have such as lower unit: absorption, wherein supplies product；Reduced pressure by one or more equalization step；Being followed by this provides purging gas with step of desorbing absorbed component from this to another；Discharge step, wherein opens this arrival end to discharge the component of absorption；It is followed by the purge step of another purging gas provided with desorbing component further from the adsorbent of this adsorbent bed.It is followed by one or more equalization step, wherein by the supercharging again of adsorbent bed part, with product pressure increase step again, wherein by adsorbent bed supercharging the most again and can recover to work online.Each adsorbent bed, through all unit in this cycle, carries product the most continuously.In temp.-change adsorptive process, by adsorbent bed being heated to high temperature to reduce adsorbent capacity and thus to make impurity desorbing carry out reproducing adsorbent bed with steam.After heating, before recovering to work online, cool down this adsorbent bed.In Vacuum Pressure Swing Adsorption, adsorbent bed the most at least partly regenerates.Such as, the adsorbent using easy adsorption of nitrogen, carbon dioxide and water vapour in this cycle manufactures oxygen.This method may utilize Single adsorbent bed, therefore by product withdraw to surge tank so that product can be manufactured continuously.Multiple adsorbent bed can also be used in this approach to manufacture product with the speed higher than single adsorbent bed.
In any such absorbing process, adsorbent bed is connected to has the flow control network (flow control network) of valve so that this carries out the various steps of specific period.Valve in the flow control network of the absorbing unit that control carries out above-mentioned technique or other technique makes each adsorbent bed produce and regenerate to open and close through predetermined period.But, as known in the art, the charging of adsorbent bed by such as the interference of flow, concentration and variations in temperature etc so that product stream does not meets product specification or in other words, there is the highest impurity in products concentration.The major way controlling product purity is known which are the feed cycle time that each adsorbent bed of regulation spends in adsorption step.If the impurity in products concentration in product stream is the highest, then shorten the feed cycle time.On the other hand, if impurity in products concentration is less than desired value, then extends and feed cycle time to improve Product yields again.As usual, operator monitors impurity in products concentration, the most manually regulation feed cycle time.This can pass through feedback control system automatization.But, in both cases, all there is delay in the product purity change after interference, or in other words, the purity change after interference occurs is the most instant.Therefore, in the case of manually or automatically controlling, select to take the desired value of control action so that product never surmounts product specification.Its result is the actual time met needed for product specification that is shorter than the average feed cycle time, and therefore the productivity ratio of product is less than the original level obtained.Use feedforward control system, wherein on-line measurement feed composition and flow velocity.The subject matter of this system is, it is necessary to using the impact on product purity of this kind of change in model evaluation charging, this is imperfect, and therefore conservative selection desired value is so that productivity ratio is relatively low.
United States Patent (USP) No. 4,693,730 provide a kind of control systems, wherein sense the feature of effluent from the adsorbent bed that decompression occurs, and the feature then responding to sensing takes corrective action.Such as, the feature of sensing can be the impurity content in effluent, and corrective action can be to change the feed cycle time.In the control system imagined in that patent, effluent concentration is compared with desired value.After reaching desired value, if product gas impurity content is not at desirable value, then use the Error Calculation fresh target value between reality and desirable value.But, this effluent concentration does not occur immediately to change when interference, and therefore, selected desired value is conservative desired value.
United States Patent (USP) No. 7,025,801 disclose the control method of psa unit, wherein monitor the flow velocity of feed stream and when the flow velocity tending to order about product purity and deviateing its specification improves, reduce cycle time, and vice versa.It addition, also measure the purity of product stream.When product purity brings up to more than product specification, reducing cycle time, vice versa.When in the case of flow velocity does not improves, the impurity concentration in feed stream improves and when indicating this event from the data of controller, regulating cycle time and may other step in this pressure-variable adsorption cycle.Therefore, the method for this patent contemplates feedback and the feedforward with disadvantages mentioned above.
As discussed, the present invention provides advantages such as controlling the control method of absorbing unit and system, wherein sensing adsorbent bed itself is interior rather than impurity concentration in feed stream, product stream or effluent stream.When being disturbed in change ratio charging, effluent or the product of this impurity concentration faster.Therefore, it is possible to select unlike desired value conservative in the prior art, to realize longer cycle time and more high production rate.
Summary of the invention
One aspect of the present invention provides the method controlling adsorbent bed unit.According to this method, in the adsorbent bed of adsorbent bed unit, measure the adsorbent bed concentration (adsorbent of impurity
Bed concentration of an impurity).This adsorbent bed is adsorbing contaminant from the feed stream sending into adsorbent bed, thus produces the production concentration (product containing the no more than impurity of target product concentration
Concentration of the impurity) product stream.This adsorbent bed unit is according to following periodic duty, during this period feed stream is sent into adsorbent bed, thereafter through the adsorbent in the desorption and regeneration adsorbent bed of impurity, and this cycle includes that feed stream is introduced adsorbent bed by the feed cycle time during this period, and adsorbing contaminant also produces product stream.
So that adsorbent bed concentration tends to the target affinity agent bed concentration of the close level making production concentration be maintained at no more than target product concentration, the production concentration in product stream is controlled by the feed cycle time used in controlling adsorbent bed unit.In this respect, the feed cycle time is controlled so that the feed cycle time improves with adsorbent bed concentration and reduces and reduce with adsorbent bed concentration and improve.
In product stream this impurity production concentration response interference and change before, in adsorbent bed, in the position measurement adsorbent bed concentration that its adsorbent bed concentration changes, so that control adsorbent bed concentration is so that adsorbent bed concentration is maintained at target affinity agent bed concentration, the production concentration of product stream this impurity interior also can be made to be maintained at the level of no more than target product concentration.
In one embodiment of the invention, this adsorbent bed can be constructed to adsorb at least two impurity.Therefore, above-mentioned impurity is a kind of impurity in described at least two impurity, and production concentration is a production concentration at least two production concentration, and target product concentration is a target product concentration at least two target product concentration.Measure described at least two production concentration and adsorbent bed concentration, and by Continuous plus, the control parameter setting the feed cycle time in adsorbent bed cell controller is controlled the feed cycle time, and this control parameter is inputted adsorbent bed cell controller.This adsorbent bed cell controller is designed to the valve controlling to be connected in the flow control network of adsorbent bed, in order to during the feed cycle time, feed stream is sent into adsorbent bed.
Calculate this control parameter in such an implementation, with adsorbent bed concentration when by this control parameter input adsorbent bed cell controller close to target affinity agent bed concentration.By calculating described at least two impurity respective potential target adsorbent bed concentration, to produce the product stream of the described at least two production concentration of the level with the most described at least two target product concentration, determine target affinity agent bed concentration.Utilize the minima of potential target adsorbent bed concentration as target affinity agent bed concentration so that all described at least two impurity in products concentration are also all controlled to less than described at least two target product impurity concentration by the control of adsorbent bed concentration.
In another specific embodiments of the present invention, this impurity is the first impurity, and adsorbent bed concentration is the first adsorbent bed concentration, and production concentration is the first production concentration and target product concentration is first object production concentration.This adsorbent bed is configured to the absorption the first impurity in the ground floor of this adsorbent bed and the second impurity and the 3rd impurity in the second layer of adjacent ground floor this adsorbent bed swimming setting on the first layer.It is the first adsorbent bed concentration (the of the first impurity in this ground floor by controlling the adsorbent bed concentration that controls of feed cycle time
First adsorbent bed concentration of the first impurity within the first layer) so that the first adsorbent bed concentration tends to close to first object adsorbent bed concentration.Measure the first impurity in products concentration in product stream and the second impurity in products concentration of the second impurity, in ground floor, measure the first adsorbent bed concentration and measure the second adsorbent bed concentration of the 3rd impurity in the second layer in its another selected location, so that the instruction impurity level before the second impurity breaks through to ground floor of measuring of the 3rd impurity concentration changes.
In such other embodiment, control the feed cycle time by Continuous plus by setting the control parameter of feed cycle time in adsorbent bed cell controller.This control parameter is inputted adsorbent bed cell controller.This adsorbent bed cell controller controls the valve being connected in the flow control network of adsorbent bed, in order in feed cycle time course, feed stream is sent into adsorbent bed.Calculate this control parameter with the first adsorbent bed concentration when by this control parameter input adsorbent bed cell controller close to first object adsorbent bed concentration.Additionally, by calculating the potential first object adsorbent bed concentration of the first impurity, the second impurity and the 3rd impurity, to produce the product stream of the second production concentration of the second impurity of the first impurity in products and the no more than second target product concentration with no more than first object production concentration, determine first object adsorbent bed concentration, and the second adsorbent bed concentration is not more than selected second target affinity bed concentration to prevent the 3rd impurity from breaking through to ground floor.Followed by the minima of potential target adsorbent bed concentration as target affinity agent bed concentration, so that the first production concentration, the second production concentration and the second adsorbent bed concentration are also controlled to being respectively smaller than target the first impurity in products concentration, target the second impurity in products concentration and target the second impurity concentration by the control of the first adsorbent bed concentration.
The invention described above the two specific embodiments any one in, can have include monitoring controller with calculate potential target adsorbent bed concentration Supervised Control level level (supervisory
Level of control) and include that master controller is to calculate the major control level level (primary controlling parameter
Level of control) product purity controller in Continuous plus control parameter.This product purity controller runs continuously with controller frequency, and monitoring controller and master controller are individually pi controller.
In a still further aspect thereof, it is provided that the control system of adsorbent bed unit.In this control system, sample tap (portal) is positioned at the adsorbent bed of adsorbent bed unit, to sample the adsorbent bed concentration of the impurity in adsorbent bed.This adsorbent bed in feed cycle time course from the feed stream sending into adsorbent bed adsorbing contaminant, thus produce the product stream containing the no more than production concentration of the impurity of target product concentration.Gas analysis apparatus is conscientiously connected with sample tap and is configured to generate and the concentration dependent data of adsorbent bed.Product purity controller responds this data, it is configured to the control parameter of feed cycle time used in calculating will set adsorbent bed unit, with by this control state modulator adsorbent bed concentration with close to target affinity agent bed concentration, it makes the production concentration of this impurity be maintained at the level of no more than target product concentration.Calculate this control parameter so that the feed cycle time improves with adsorbent bed concentration and reduces, and reduce with adsorbent bed concentration and improve.This sample tap is positioned at, the production concentration response interference of this impurity in product stream and the adsorbent bed concentration in adsorbent bed changes before changing position, so that controlling adsorbent bed concentration to be maintained at the level of no more than target product concentration with the production concentration of this impurity in also making product stream close to target affinity agent bed concentration.
Adsorbent bed cell controller responds the control parameter calculated by product purity controller.This adsorbent bed cell controller controls the valve in the stream of this adsorbent bed unit so that feed stream is sent into adsorbent bed according to following periodic duty in feed cycle time course by this adsorbent bed unit during this period, thereafter through the adsorbent in the desorption and regeneration adsorbent bed of impurity.
In the specific embodiments of this control system, construct this adsorbent bed to adsorb at least two impurity.Therefore, above-mentioned impurity is the only a kind of impurity in described at least two impurity, and production concentration is a production concentration at least two production concentration and target product concentration is a target product concentration at least two target product concentration.Additionally, this gas analysis apparatus is to position to produce and a gas analysis apparatus in multiple gas analysis apparatuss of the described at least two production concentration in product stream and the concentration dependent data of adsorbent bed.
Product purity controller runs continuously with controller frequency and controls parameter to calculate and include Supervised Control level and major control level.Supervised Control level is configured to be calculated target affinity agent bed concentration by the minima of the potential target adsorbent bed concentration calculated at least two monitoring controller.These data that the response of described at least two monitoring controller is relevant to described at least two production concentration, and it is configured to the product stream calculating potential target adsorbent bed concentration to produce the described at least two production concentration with the most described at least two target product concentration.Major control level have respond with adsorbent bed concentration and with the master controller of the concentration dependent a part of data of target affinity agent bed calculated by Supervised Control level.This master controller is configured to be calculated this control parameter by adsorbent bed concentration and target affinity agent bed concentration.
In another specific embodiments of the present invention, this impurity is the first impurity, and adsorbent bed concentration is the first adsorbent bed concentration, and production concentration is the first production concentration and target product concentration is first object production concentration.Construct this adsorbent bed to adsorb the first impurity in the ground floor of this adsorbent bed and the second impurity and at adjacent ground floor the 3rd impurity in the second layer of this adsorbent bed of this ground floor upstream setting.Therefore, adsorbent bed concentration be in ground floor the first adsorbent bed concentration of the first impurity so that the first adsorbent bed concentration tends to close to first object adsorbent bed concentration, produce the product stream of the second production concentration of second impurity also with the no more than second target product concentration, and in the second layer, the second adsorbent bed concentration of the 3rd impurity is not more than selected second target affinity bed concentration to prevent the 3rd impurity from breaking through to ground floor.
This sample tap is the first sample tap, and the second sample tap is positioned at the certain position second adsorbent bed concentration with the 3rd impurity of the sampling second layer of this adsorbent bed.This gas analysis apparatus is to position a gas analysis apparatus in the multiple gas analysis apparatuss to produce the data relevant to the first production concentration, the second production concentration, the first adsorbent bed concentration and the second absorbent concentration.
Product purity controller runs and has Supervised Control level and major control level continuously with controller frequency.Supervised Control level is configured to be calculated first object adsorbent bed concentration by the minima of the potential first object adsorbent bed concentration calculated in response with the monitoring controller of the first production concentration, the second production concentration and the concentration dependent data of the second adsorbent bed.This monitoring controller is configured to calculate potential first object adsorbent bed concentration and is not more than first object production concentration and the first impurity in products concentration of the second product aimed concn and the product stream of the second impurity in products concentration respectively to produce to have, and the second adsorbent bed concentration is not more than the second target affinity agent bed concentration.Major control level has master controller, and its response and the first adsorbent bed concentration and a part of data concentration dependent with the first object adsorbent bed calculated in Supervised Control level also are configured to be calculated this control parameter by the first adsorbent bed concentration and first object adsorbent bed concentration.
Include supervision and major control level to control in any embodiment of the present invention of the second adsorbent bed impurity content of first and second impurity in products and the 3rd impurity and in its any aspect, each ratio and integral controller have proportional element and integral element.Each proportional element and each integral element have tuning factor.Each monitoring controller is by calculating potential first object adsorbent bed concentration plus proportional element and integral element in the potential first object adsorbent bed concentration calculated before.Each ratio and integral element have error term.First production concentration, the second production concentration, the first adsorbent bed concentration and the second adsorbent bed concentration are measured the most continuously and are converted into denary logarithm value, by them averagely to produce average log value.In first monitoring controller relevant to the first impurity, the average log value by deducting the first production concentration from the denary logarithm of first object production concentration calculates error term.Calculate the error term in the second monitoring controller relevant to the second impurity by the average log value deducting the second production concentration from the denary logarithm of the second target product concentration, calculate the error term in the 3rd monitoring controller relevant to the 3rd impurity with the average log value by deducting the second adsorbent bed concentration from the denary logarithm of the second target affinity agent bed concentration.Average log value by deducting the first adsorbent bed concentration from the denary logarithm of first object adsorbent bed concentration calculates error term in the host controller.
It addition, proportional element may be included in the difference between the error calculated in the current running of monitoring controller and master controller and the error calculated in running before monitoring controller and master controller.The controller frequency cycle may be set to the current total cycle time equal to adsorbent bed unit.Furthermore, it is possible to further determine that integral element by error current being multiplied by current total cycle time.
The method and control system are utilized within the environment that this cycle is the pressure-variable adsorption cycle and adsorbent bed is one of multiple adsorbent bed.Feed stream can be hydrogeneous stream and product stream can be hydrogen product stream.In this case, the first impurity is carbon monoxide, and the second impurity is nitrogen and the 3rd impurity is carbon dioxide.In order to adsorb this type of impurity, ground floor contains zeolite adsorbents and is immediately adjacent to the outlet of adsorbent bed.The second layer contains acticarbon with absorbing carbon dioxide.
Accompanying drawing is sketched
Although description is to be expressly noted that the defending party to the application is considered as claims of theme of its invention and terminates, it is believed that the present invention be may be better understood during connection with figures, wherein:
Fig. 1 is the schematic diagram of the control system of the method for implementing the present invention, its with for by steam methane reforming facility generate transform stream (shifted
Stream) the connected diagram of the psa unit of hydrogen manufacturing；
Fig. 2 is the schematic diagram of psa unit used in Fig. 2；
Fig. 3 is the schematic diagram of a preferred embodiment of control system and method for the present invention used in Fig. 1；And
Fig. 4 is the control logic chart of the control system shown in Fig. 3 and method；
Fig. 5 is the diagram of the carbon monoxide product concentration of the pressure swing adsorption system shown in Fig. 2 that response interference controls in prior art manner；
Fig. 6 is the diagram of the carbon monoxide product concentration responding the pressure swing adsorption system shown in Fig. 2 that interference controls in the present invention in the way of elaboration；
Fig. 7 is the diagram that the adsorption system according to the present invention shown in Fig. 2 controls, and it shows the response of this adsorption system target product concentration to reseting carbon monoxide.
Describe in detail
With reference to Fig. 1, display facility 1, such as facility of reforming, it has steam methane reformer 10, produce and mainly contain the feed stream 12 of hydrogen and impurity, this impurity include about 5% and about 25 volume % carbon dioxide, less than about .5 volume % water vapour, less than about 3 volume % methane, less than about 1 volume % carbon monoxide, be less than about 1 volume % nitrogen and the heavy hydrocarbon of less concentration.Feed stream 12 is introduced psa unit 14 and with adsorbing contaminant and thus produces the hydrogen product stream 16 containing above-mentioned impurity with the amount less than product specification tolerable injury level.Point out, the discussion of following facility 1 is not intended to limit the purposes of the present invention, i.e. present disclosure applies equally to the control of other type of absorbing unit, this unit is intended to adsorb other type of impurity and run according to other type of adsorption cycle (such as containing Vacuum Pressure Swing Adsorption and the temp.-changing adsorption of single or multiple adsorbent bed).
Steam methane reformer 10 is to hydrocarbon stream 18, and such as, natural gas imposes steam methane reforming.In steam methane reformer 10, from hydrocarbon stream 18 remove sulfur species (species) and add superheated steam with produce reaction logistics, then be introduced into be positioned at steam methane reformer 10 burning radiation heat exchange segment (fired,
Radiant heat exchange section) in the reformer tubes filling up catalyst in.Hydrocarbon produces hydrogen and carbon monoxide with steam reaction, and it reacts further in water-gas shift and produces feed stream 12.Flue gas from the radiant section of steam methane reformer is used for producing superheated steam in the convection section (being discharged from flue gas stream 16) of steam methane reformer 10.
Feed stream 12 is introduced the absorbing unit 14 with six adsorbent beds 22,24,26,28,30 and 32 according to pressure-variable adsorption periodic duty discussed below.There is provided absorbing unit controller 34 with the control signal that substantially indicated by arrow 36 of generation for absorbing unit 14 further, thus control the valve including in the flow control network of adsorbent bed 22 to 32, and thus adsorbent bed 22 to 32 is imposed the pressure-variable adsorption cycle.Each adsorbent bed 22 to 32 is online successively to be arranged with the impurity in absorption feed stream 12, and therefore produces hydrogen product stream 16.It addition, regenerate impurity that each adsorbent bed adsorbed before desorbing and thus produce tail gas stream 38.Tail gas stream 38 burner in the radiant section lighting steam methane reformer 10 again, it is possible to be sent to the fuel header in facility 1.
The purity of product stream 16 is controlled by product purity controller 40 that is constructed according to the invention and that run.Product purity controller 40 with calculating feed cycle time the most each adsorbent bed 22 to 32 online (on-line) with Supervised Control level 42 and major control level 44 and adsorbs the impurity in feed stream 12 or directly affects other control parameter of feed cycle time.As discussed in more detail below, Supervised Control level 42 calculates the target affinity agent bed concentration of carbon monoxide to be realized in adsorbent bed 32 based on the target product impurity concentration of nitrogen and carbon monoxide in product stream 16 and the target impurity concentration of carbon dioxide in adsorbent bed 32.These above-mentioned desired values input the most as shown in arrow 46 Supervised Control level.Arrow 46 represents described three different target values, i.e. carbon monoxide target product impurity concentration 158, nitrogen target product impurity concentration 166 and carbon dioxide target affinity agent bed impurity concentration 172, and they are inputted three independent controls being incorporated in Supervised Control level 42.These desired values are compared with the actual measured value of the adsorbent bed impurity concentration of carbon dioxide in carbon monoxide in product stream 16 the most as shown in arrow 48 and the actual measured value of nitrogen and adsorbent bed 32 as shown in arrow 50.The data the most as shown in arrow 52 input Supervised Control level 42 relevant to each actual concentrations level.As discussed, arrow 48 is made up of the data relevant to carbon monoxide product impurity concentration 48a and nitrogen impurity in products concentration 48b the most discussed below.Supervised Control level 42 calculates the target affinity bed concentration of carbonomonoxide concentration subsequently, and the gas concentration lwevel that its nitrogen making product stream 16 and carbonomonoxide concentration are not more than in the aimed concn of each of which and adsorbent bed 32 is not more than its target affinity agent bed concentration.The most as discussed below, shown Supervised Control level 42 and major control level 44 are according to proportional plus integral control logic operation.As discussed, can other type of control logic used according to the invention.
Subsequently by the target affinity bed concentration input as shown in arrow 54 major control level 44 of the carbon monoxide in adsorbent bed 32.By this desired value of carbonomonoxide concentration in adsorbent bed 32 and actual measured value (it also serves as input signal 56 and inputs major control level 44), calculate the bed cycle time making the carbonomonoxide concentration in adsorbent bed 32 close to the target carbonomonoxide concentration calculated by Supervised Control level.Due to this target affinity bed concentration impurity in products based on nitrogen and carbon monoxide concentration, the adsorbent bed impurity concentration of carbon dioxide and their associated target value, the control of carbonomonoxide concentration can control the gas concentration lwevel in product stream 16 in nitrogen and the impurity content of carbon monoxide and adsorbent bed 32.
The feed cycle time calculated introduces adsorbent bed cell controller 34 consequently as input signal 58, controls other adsorbent bed 22 to 30 each the most in the same manner.The most as shown in fig. 1, for following purpose, it is also possible to using total bed cycle time 60 as input signal 62 and 64 input Supervised Control level 42 and major control level 44.As the data of total bed transmission cycle time 60 can include indicating total cycle time (adsorbent bed start its adsorbing contaminant work online and off-line (off-line) and regenerate) data and indicate this cycle to complete.Additionally, although Supervised Control level 42, major control level 44 and absorbing unit controller 34 show as discrete unit, but they can be all in individual unit, or absorbing unit control 34 is the independent control provided by the manufacturer of adsorbent bed unit 14, and Supervised Control level 42 and major control level 44 can be able to programme in the independent controls of this type of purposes.
With reference to Fig. 2, still it is limited to purpose to illustrate rather than, provides the explanation of the operation of flow control network about adsorbent bed unit 14 briefly described above.For being prone to explain, do not show that valve and adsorbent bed unit control the conventional electrical connection between 34.Assume that all valves in following discussion are all to cut out, open in the moment in pressure-variable adsorption cycle unless expressly stated.In this respect, this cycle is whole has 12 stages, and the most in two stages, adsorbent bed is online and produces, in the later stage in the two stage, online adsorbent bed by the supercharging again of another adsorbent bed to recover online.After the two stage, make adsorbent bed offline and be referred to as, by standing three continuous print, the equalization step (equalization that reduces pressure
Down step) pressure equalization step regenerate, wherein reduce the pressure in adsorbent bed and by void space gas supply to other adsorbent bed with forward part these beds of supercharging again worked online in recovery.Being followed by purging gas and provide step, wherein purging gas is discharged into another adsorbent bed carrying out purge step to remove absorbed component from this adsorbent bed from adsorbent bed.Purging gas provides step followed by discharge step, wherein by arrival end, adsorbent bed is decompressed to atmospheric pressure so that absorbed component desorbing is thus supplied as the tail gas of tail gas stream 38, it is followed by purge step, wherein to this adsorbent bed port of export supply purge gas so that the further desorbing of absorbed component and through entrance discharge, in order to continue supply tail gas.Hereafter it is that three continuous print are referred to as supercharging equalization step (equalization
Up step) equalization step, wherein the pressure in bed improve, be followed by product pressure increase step again, wherein make adsorbent bed recover to operating pressure and in the next stage recover work online.
Specifically, in the first stage in this cycle, adsorbent bed 22 is in the first adsorption step and is supplied with feed stream 12 to produce product stream 16.Meanwhile, adsorbent bed 24 carries out the 3rd supercharging equalization step by adsorbent bed 30, and wherein gas is discharged in adsorbent bed 24 and thus carries out the 3rd and the equalization step that finally reduces pressure by adsorbent bed 30.3rd adsorbent bed 26 carries out the first supercharging equalization step by adsorbent bed 32, and the equalization gas of the adsorbent bed 32 wherein carrying out its first decompression equalization step is discharged in adsorbent bed 26.Adsorbent bed 28 carries out discharge and discharges the impurity of desorbing to form tail gas stream 38.For such purpose, valve 70,86,108,114,118,124 and 128 is set in open position.In the second stage in this cycle, adsorbent bed 22 carries out the second adsorption step and also by product gas supply to adsorbent bed 24, and a part of product that the latter produces with adsorbent bed 22 carries out product booster step.Adsorbent bed 26 carries out the second equalization step by the adsorbent bed 32 carrying out the second decompression equalization step.Adsorbent bed 28 provides the adsorbent bed 30 in step to carry out purge step by being in purging gas.Open position stayed by valve 70,128,86,108,114 and 118, and valve 98,100 and 116 is set in open position and valve 124 is reset at closed position.
In the phase III in this cycle, the adsorbent bed 24 of supercharging the most again supplies product with the form of product stream 16 now.Adsorbent bed 22 regenerates now by standing the first decompression equalization step, and wherein it supplies equalization gas to the adsorbent bed 28 being in the first supercharging equalization step.Adsorbent bed 26 carries out the 3rd supercharging equalization step, and wherein it receives gas from the adsorbent bed 32 being thus in the 3rd decompression equalization step.Adsorbent bed 30 is in discharge step.For such purpose, valve 72,88,104,110,120,126 and 130 is set in open position.Valve 70,128,86,108,114,118,98,100 and 116 is refitted in closed position.In the fourth stage in this cycle, adsorbent 22 carries out the second decompression equalization step and equalization gas is sent to carry out the adsorbent bed 28 of the second supercharging equalization step, and adsorbent bed 24 manufactures product and product booster gas is sent to adsorbent bed 26 simultaneously.Adsorbent bed 30 provides the adsorbent bed 32 of step to receive purging gas in purge step and from being in purging gas.Open position stayed by valve 72,88,104,110,120 and 130 and valve 100,102 and 118 is set in open position.Valve 126 is refitted in closed position.
In the 5th stage in this cycle, adsorbent bed 26 manufactures product gas, therefore the most online generation product stream 16 now.In this stage, adsorbent bed 22 by adsorbent bed 28 by provide to the adsorbent bed 28 carrying out the 3rd supercharging equalization step equalization gas carry out the 3rd decompression equalization step.Nowadays the adsorbent bed 24 of off-line by providing equalization gas to start regeneration to carry out the first equalization step to the adsorbent bed 30 carrying out the first supercharging equalization step.Adsorbent bed 32 is in the discharge stage, and it supplies tail gas to tail gas stream 38.For such purpose, valve 74,90,106,116,122 and 132 is set in open position and valve 72,88,104,110,120,130,100,102 and 118 is reset at closed position.In the 6th stage in this cycle, adsorbent bed 22 is in purging gas and provides step, and it is by the adsorbent bed 32 being now arranged in purge step.Adsorbent bed 24 carries out the second decompression equalization step by equalization gas is sent to carry out the adsorbent bed 30 of the second supercharging equalization step.Some products are sent to adsorbent bed 28 as product booster gas by adsorbent bed 24.Valve 74,90,106,122 and 132 stays open, and valve 92,102 and 120 is set in open position and valve 116 sets to closed position.
In the 7th stage in this cycle, adsorbent bed 28 produces product and adsorbent bed 24 off-line now.Adsorbent bed 22 carries out discharge (blow down) step.During this period, adsorbent bed 24 by providing equalization gas to carry out the 3rd decompression equalization step to the adsorbent bed 30 carrying out the 3rd supercharging equalization step.Adsorbent bed 26 and 32 carries out first and equalizes to bed, and the adsorbent bed 26 wherein carrying out the first decompression equalization step supplies equalization gas to the adsorbent bed 32 carrying out the first supercharging equalization step.Valve 76,80,108,114,118,124 and 134 is set in open position.Valve 74,90,106,122,132,92,102 and 120 returns to closed position.In the 8th stage in this cycle, adsorbent bed 28 continues manufacture product and provide product booster to adsorbent bed 30.Adsorbent bed 22 is in purge step now by receiving purging gas from the adsorbent bed 24 being thus in purging gas offer step, adsorbent bed 26 and 32 carries out second and equalizes to bed, wherein adsorbent bed 26 carries out the second decompression equalization step, and it supplies equalization gas to the adsorbent bed 32 carrying out the second supercharging equalization step.Open position stayed by valve 76,80,108,104,124 and 134, and valve 92,94 and 122 is set in open position, and valve 118 resets to closed position.
In the 9th stage in this cycle, make adsorbent bed 30 online and make adsorbent bed 28 off-line to regenerate.Adsorbent bed 22 carries out the first supercharging equalization step by receiving equalization gas from the adsorbent bed 28 carrying out the first decompression equalization step.During this period, adsorbent bed 24 is in discharge step, and adsorbent bed 26 carries out the 3rd decompression equalization step by providing equalization gas to the adsorbent bed 32 being in the 3rd supercharging equalization step.Valve 77,82,104,110,120,126 and 136 is set in open position.In the tenth stage in this cycle, adsorbent bed 30 provides product booster to adsorbent bed 32.Adsorbent bed 22 carries out the second supercharging equalization step by receiving high pressure equalization gas from the adsorbent bed 28 carrying out the second decompression equalization step.In identical process, adsorbent bed 26 provides in step at purging gas to supply purging gas to the adsorbent bed 24 being in purge step.Open position stayed by valve 77,82,104,126 and 136, and valve 94,96 and 124 is set in open position, and closes valve closing 120.
In the 11st stage in this cycle, adsorbent bed 32 is made now to recover to work online provide product stream 16 and make adsorbent bed 30 off-line to regenerate.During this period, adsorbent bed 22 is in the 3rd supercharging equalization step by receiving equalization gas from the adsorbent bed 28 carrying out the 3rd decompression equalization step.Adsorbent bed 24 carries out the first supercharging equalization step and receives equalization gas from the adsorbent bed 30 being in the first decompression equalization step.Adsorbent bed 26 is in discharge step.Valve 78,84,106,116,122 and 138 is set in open position, and valve 77,82,104,126,136,94,96 and 124 is reset at closed position.In the tenth two-stage in this cycle, adsorbent bed 22 receives product booster gas from adsorbent bed 32 to recover to work online.Adsorbent bed 24 carries out the second supercharging equalization step by receiving equalization gas from the adsorbent bed 30 being in the second decompression equalization step.Adsorbent bed 26 is in purge step and reception is in the purging gas that purge gas body provides adsorbent bed 28 output of step.For such purpose, 78,84,106,116 and 138 stay open position, and valve 96 and 98 is set in open position, and closes valve closing 122.After the tenth two-stage terminated, this cycle returns to first stage repeated as described above.
Although the most substantially discussing product purity controller and adsorbent bed unit 14 and controlling, being discussed in greater detail about product purity controller 40 is given below.Referring specifically to Fig. 3, product purity controller 40 is preferably capable of with programming in logic processed with the programmable logic controller (PLC) representing Supervised Control level 42 and major control level 42 and the specific controller in this class hierarchy being discussed herein below.Such as, product purity controller 40 can be to utilize programmable software, such as available from Rockwell Automation Inc. of 1201 South Second
The RSLOGIX of Street, Milwaukee, WI 53204-2496 USATM
The ALLEN-BRADLEY of 500 softwares®Controller.Other similar control device, above-mentioned this being only used for can be used to illustrate.
In the application being specifically exemplified by of the present invention, adsorbent bed 32 and other adsorbent bed 22 to 30 are with having entrance 142 and the container 140 of outlet 144.It is contained within three adsorbent layers, i.e. zeolite layer 146, active carbon layer 148 and optional alumina layer 150 at adsorbent bed 32.The conversion air-flow 12 introduced is introduced into alumina layer 150 with adsorbed moisture, subsequently enters active carbon layer 148 with absorbing carbon dioxide and heavy hydrocarbon, such as methane.Hereafter carbon monoxide and N2 adsorption are in zeolite layer.It is important to note that, it is necessary to control the operation of adsorbent bed unit so that carbon dioxide never breaks through active carbon layer 148 to zeolite layer 146.Its reason is, carbon dioxide adsorbs by force in zeolite beds so that the extremely difficult regeneration of adsorbent bed 32.Another important control Consideration is, if the level that carbon monoxide requires higher than product specification, this product stream does not has any practical use.Finally, nitrogen tends to be enriched in zeolite beds 146 towards adsorbent bed outlet 144.Due to all these Considerations, control adsorbent bed unit 14 so that carbon dioxide never breaks through to zeolite layer 146, and control the feed cycle time so that carbonomonoxide concentration in product stream 16 never rises to more than the level listed in product specification.The control of carbon monoxide product concentration also controls nitrogen production concentration.As described below, gas concentration lwevel and carbonomonoxide concentration in sensing active carbon layer 148 and zeolite layer 146 as adsorbent bed concentration and compare with desired value, as it have been found that, the change of this type of adsorbent bed concentration changes faster appearance than downstream, therefore, it can make this control more fast so that feed cycle time average is long as far as possible so that the maximum production of product stream.
Supervised Control level 42 uses three separate controllers, i.e. carbon monoxide monitoring controller 152, nitrogen monitoring controller 154 and carbon dioxide monitoring controller 156.In the illustrated embodiment, these controllers are based on ratio and integration control logic operation and therefore there is ratio and integral error item, and they can be the function of error and error intergal.But, in the illustrated embodiment, use the velocity form of this control, therefore proportional is the error current recorded in the current running of this controller and the function of the difference between first error recorded in running before this controller.The integral term of velocity form is the function of error current.
These controllers each calculate the target affinity agent bed concentration of carbonomonoxide concentration to be obtained in zeolite beds, it makes the carbon monoxide in product stream 16 and nitrogen concentration each be held equal to and the target product impurity concentration that is less than in product stream 16 and target affinity agent bed concentration, for the carbon dioxide in active-carbon bed 148, prevent carbon dioxide breakthrough in zeolite layer 148.
First turning to carbon monoxide monitoring controller, this controller runs according to following equation:
MV1i = MV1i-1 + Kc1 * (ε1i- ε1i-1)
+ Kc1/τI1 * Δt * ε1i
Wherein:
MV1iThe potential CO target affinity agent bed concentration of=current period
MV1i-1=final cycle (at same time simultaneously
Last cycle) potential CO target affinity agent bed concentration
Kc1 The CO ratio of profit increase of=bed inner looping
ε1i The error of the current period of CO in=bed
ε1i-1 The error of final cycle while CO in=bed
τI1 The resetting time of=CO bed inner looping
Δ t=total cycle time
During each run of product purity controller 40, by the potential CO target affinity agent bed concentration value MV1 that will record in the previous running of product purity controlleri-1Plus ratio and the integral element of this control, calculate MVli.By calculating the error ε 1 of current periodi, the target product impurity concentration by the input signal in being set as carbon monoxide monitoring controller 152 as shown in arrow 158 deducts the impurity in products concentration of carbon monoxide, measures proportional element Kc1
* (ε1i- ε1i-1).By sampling the impurity concentration in product stream 16 by the gas analysis apparatus 160 of the product collector 162 being connected to adsorbent bed unit 14, and carbon monoxide monitoring controller 152 will be sent to as represented by arrows 48 with this concentration dependent data, measure concentration.As discussed, arrow 48a is actual represents the several steps controlling logic, and data reduction wherein becomes denary logarithm form, maintains Continuous Observation meansigma methods (running average) and this meansigma methods is introduced carbon monoxide monitoring controller 152.The error ε 1 recorded in the same manner in the previous running of product purity controller 40 is deducted from error currenti-1, and this difference is multiplied by this area the tuning factor K being referred to as " ratio of profit increase (gain) "c1(it records in the running of product purity controller 40 in the same manner).By error current is multiplied by Kc1/τI1Business and Δ t(its be the current period time recorded by adsorbent bed cell controller 34, it is as shown in arrow 62, especially as shown in arrow 62a input controller) product, measure integral element.Item " τI1" be resetting time and be another tuning factor recorded in a known way in the running of product purity controller 40.
Nitrogen monitoring controller 154 runs according to following equation:
MV2i = MV2i-1 + Kc2 * (ε2i- ε2i-1)
+ Kc2/τI2 * Δt * ε2i
Wherein:
MV2iThe potential CO target affinity agent bed concentration of=current period
MV2i-1The potential CO target affinity agent bed concentration of=final cycle simultaneously
Kc2The ratio of profit increase of=N2 product loop
ε2iThe error of the current period of=N2 product
ε2i-1The error of final cycle while=N2 product
τI2The resetting time of=N2 product loop
Δ t=total cycle time
Nitrogen monitoring controller 154 calculates in the way of identical with carbon monoxide monitoring controller 152.But, for this quasi-controller, by the Nitrogen in Products impurity concentration from the product stream 16 recorded by gas analysis apparatus 168 deducts target nitrogen impurity in products concentration (it is the input signal shown in arrow 166), evaluated error " ε ".The data being converted into the representative mean concentration of denary logarithm form are inputted nitrogen monitoring controller 154 as shown in arrow 48b.Independently measure and tuning factor " K is setc2”。
Carbon dioxide monitoring controller runs according to following equation:
MV3i = MV3i-1 + Kc3 * (ε3i- ε3i-1)
+ Kc3/τI3 * Δt * ε3i
Wherein:
MV3iThe potential CO target affinity agent bed concentration of=current period
MV3i-1The potential CO target affinity agent bed concentration of=final cycle simultaneously
Kc3The ratio of profit increase of=CO product loop
ε3iThe error of the current period of=CO product
ε3i-1The error of final cycle while=CO product
τI3The resetting time of=CO product loop
Δ t=total cycle time
Carbon dioxide monitoring controller 156 calculates in the way of identical with carbon monoxide monitoring controller 152.But, for this quasi-controller, adsorbent bed concentration by the carbon dioxide from the active carbon layer 148 recorded by gas analysis apparatus 172 deducts target CO 2 impurity concentration (it is the input signal shown in arrow 170), evaluated error " ε ", the data of its representative average value measured that will be converted into denary logarithm form are as shown in arrow 50 to be transferred in carbon dioxide monitoring controller 156.Gas analysis apparatus 172 by by be positioned at the half length less than active carbon layer 148 position and be preferably placed at this length about 1/3 the gas port (gas that formed of pipeline
Portal) 174 sampling gas concentration lwevel, in order to sensed concentration change before the downstream change that such as interface occurs between zeolite layer 146 and active carbon layer 148.Independently measure and tuning factor " K is setc3" and " τI3", cycle time is the input signal as shown in arrow 62b.
The MV1 of carbon monoxide monitoring controller 152, nitrogen monitoring controller 154 and carbon dioxide monitoring controller such as output each of which shown in arrow 176,178 and 180i、MV2iAnd MV3iValue, introduces these values subsequently in comparing these three value as shown in square frame 182 and determining the logic of minima, and introduces master controller 44 as input signal 184.Master controller 44 runs according to following equation:
MV4i = MV4i-1 + Kc4 * (ε4i- ε4i-1)
+ Kc4/τI4 * Δt * ε4i
Wherein:
MV4iThe combined feed cycle time of=current period
MV4i-1The combined feed cycle time of=final cycle simultaneously
Kc4The ratio of profit increase of=CO bed inner looping
ε4iThe error of=current period
ε4i-1The error of=final cycle simultaneously
τI4The resetting time of=CO bed inner looping
Δ t=total cycle time
Master controller 44 with the controller class in Supervised Control level 42 as mode run, simply its output feed cycle time.By adding on feed cycle time of recording in running before product purity controller 40, there is tuning factor " Kc4" proportional and there is tuning factor " τI4" integral term (both of which the most independently measures and applies) measure this output signal MV4i, and combined feed is delivered to adsorbent bed controller 36 as input signal 64 cycle time.Error term is the adsorbent bed concentration of carbon monoxide and the difference inputted as indicated by arrow 184 between the target affinity agent bed concentration of this controller or the minima that records in Supervised Control level 42.Measure this adsorbent bed concentration by being connected to the sample tap 186 of gas analysis apparatus 188, its produce input master controller 44 in this concentration dependent data.Sample tap 186 is positioned at zeolite layer 146 compared with outlet 144 closer to the position of entrance 142, and in the first half of this layer and preferably before this layer in 1/3.Output signal feed cycle time MV4iInput adsorbent bed cell controller 34 as shown by arrow 190.
With reference to Fig. 4, the programmed logic of display product purity controller 40.Product purity controller 40 runs with the controller frequency equal to the total cycle time of adsorbent bed unit 14 (that is, the total time from the time point making the online also adsorbing contaminant of adsorbent bed 22 to regeneration and recovers online the most again).During this period, as shown in logic step 200, from above-mentioned gas analyzer or from the Supervised Control recording this type of reading and data acquisition program, read carbon dioxide and current adsorbent bed the concentration (" CO in carbon-coating of carbon monoxide in the currency (" N2 in product " and " CO in product ") of the production concentration of nitrogen and carbon monoxide in product stream 16 and activated carbon and zeolite layer 148 and 1462" and " CO in screen layers (sieve layer) ").Each value is converted into as shown in logic step 202 denary logarithm value (" LOG10 ").The Continuous Observation meansigma methods of the LOG10 value of conversion is maintained as shown in logic step 204.At the end of the complete cycle of the adsorbent bed in this adsorbent bed unit, send end cycle order from the adsorbent bed cell controller 36 possibly together with the cycle time " Δ t " utilized by controller as shown in logic step 206 to this programmable logic controller (PLC), and from the error in previous cycle and as shown in logic step 208, calculated the error of each variable by record by mean value calculation error current.It is to be noted, that send end cycle order and cycle time as shown in the label 60 in Fig. 1.In this respect, if using single controller, it can program in a known way with by correlation "ON" and "Off" and supervision and the major control function being sent to this program cycle time.If additionally, absorbing unit controller 34 is independent unit, then can connect single timer for such purpose on controller 34, if or can obtain, the related data from this independent unit can be sent to product purity controller 40.The value calculated is used subsequently to calculate the potential target adsorbent bed concentration of carbon monoxide, i.e. MV1 as shown in the logic step 210,212 and 214 of simulation monitoring controller 170,158 and 156i、MV2iAnd MV3i.Comparative result also finds minima, and be inputted the logic step 216 containing the calculating implemented by master controller 44 as shown in 182.As shown in logic step 216, record from the error in previous cycle and calculates error by deducting this minimum target carbonomonoxide concentration in the average LOG10 value of carbon monoxide impurities concentration in the zeolite beds the most calculated in logic step 204.Fall into a trap at logic step 218 subsequently and add material cycle time and subsequently by output signal MV4iAdsorbent bed cell controller 34 is introduced as the feed cycle time.As indicated by the arrow 220, the execution of program returns to logic step 200, and product purity controller performs above-mentioned steps.It is readily apparent that the controller frequency cycle is overlapped with the total cycle time of the adsorbent bed unit 14 controlled by adsorbent bed cell controller 36.
In the favourable example run of the present invention, the adsorbent bed unit of type described herein runs according to prior art and the present invention.Dry basis and by volume, incoming mixture contains: 75.6% hydrogen；15.6% carbon dioxide；3.4% carbon monoxide；4.8% methane and 0.7% nitrogen.In the control method of prior art, proportion of utilization integration control logic is based only upon the product purity regulation feed cycle time.Following table summarizes these results:
Table
| The control of prior art | The control of the present invention | |
| Cycle time | 540 | 606 |
| First bed | Zeolite | Zeolite |
| The amount of adsorbent in first bed | 2150 lb/ton/sky hydrogen | 2000 lb/ton/sky hydrogen |
| Second bed | Activated carbon | Activated carbon |
| The amount of adsorbent in second bed | 1775 lb/ton/sky hydrogen | 1700 lb/ton/sky hydrogen |
| 3rd bed | Aluminium oxide | Aluminium oxide |
| The amount of adsorbent in 3rd bed | 300 lb/ton/sky hydrogen | 275 lb/ton/sky hydrogen |
| High pressure (psig) | 250 | 250 |
| Low pressure (psig) | 6 | 6 |
| Charging rate (Ft3/hr (ntp) | 689 | 692 |
| Hydrogen purity | 99.999% | 99.9985% |
| Hydrogen retrieval rate | 80.8% | 84.6% |
| Total bed size factor | 4200 lb/ton/sky hydrogen | 4000 |
| Temperature | 311 K | 311 K |
| Bed diameter | 2.16 inch | 2.16 inch |
| Bed length | 20 feet | 20 feet |
It is clear that the control method of the invention described above makes cycle time longer and improves hydrogen retrieval rate from this table.The reduction of bed size factor shows to produce more hydrogen under the adsorbent of specified rate.
With reference to Fig. 5, control Fig. 2's in prior art manner and have the adsorbent bed unit 14 of the feature shown in upper table, i.e. passing ratio integration control is run and feedback control based on the carbonomonoxide concentration in product stream 16.By the carbonomonoxide concentration in feed stream 12 is caused interference from 4.5% raising to 5.5%.Feed stream mixture is made up of 74% hydrogen, 16% carbon dioxide, 5% methane, 4.5% carbon monoxide and 0.5% nitrogen before interference and is made up of 73% hydrogen, 16% carbon dioxide, 5% methane, 5.5% carbon monoxide and 0.5% nitrogen after interference.Product purity fluctuation from this figure it is clear that between 3 ppm and 4 ppm is persistently more than 20 hours.Referring additionally to Fig. 6, control Fig. 2's according to prior art as mentioned above and there is the adsorbent bed unit 14 of the feature shown in upper table.By the carbonomonoxide concentration in feed stream 12 is caused interference from 4.5% raising to 5.5%.Feed stream mixture is made up of 74% hydrogen, 16% carbon dioxide, 5% methane, 4.5% carbon monoxide and 0.5% nitrogen before interference and is made up of 73% hydrogen, 16% carbon dioxide, 5% methane, 5.5% carbon monoxide and 0.5% nitrogen after interference.Do not observe the notable fluctuation of the product purity recorded.
With reference to Fig. 7, illustrate the response above-mentioned control system when the first object production concentration of carbon monoxide 158 is down to 1 ppm carbon monoxide from 7.5 ppm.From this figure it is clear that in 10 hours, in product stream 16, the first production concentration of carbon monoxide follows desired value with minimum deviation.For controlling response, the first object adsorbent bed concentration 158 recorded by Supervised Control level 42 is reduced, and after 10 hours, in the ground floor 146 of adsorbent bed 32, the first adsorbent bed concentration of carbon monoxide starts to follow desired value.If the first production concentration of the carbon monoxide recorded is higher than desired value, then the feed cycle time produced by major control calculating initially reduces.At the first production concentration of carbon monoxide close to after first object production concentration, the feed cycle time improves to realize higher hydrogen product recoveries.
Although the present invention has been described as the control of the psa unit being used in connection with hydrogen manufacturing, but the present invention has the bigger suitability.Such as, present disclosure applies equally to control to comprise the adsorbent bed unit of one or more adsorbent bed, wherein use single two or more impurity of adsorbent.In this case, in major control level, in adsorbent bed, sample only single critical impurities concentration sample two or more impurity in Supervised Control level in product stream.Product purity controller as described above has the controller frequency set by the cycle time of psa unit 14.Therefore, the meansigma methods of LOG10 purity level is used in this computation.This has been observed that favorably, because the peak value measuring impurity does not interferes with the control of psa unit 14.It has been said that one embodiment of the invention can be constructed, wherein control system is run with higher frequency or nearly singular integral mode.This control has a problem in that, it is impossible to continuously adjusts the feed cycle time and must program this unit to abandon based in charging or the unrelated results of operating transient condition of analysis itself.The advantage using the data of LOG10 form is, this control all can run with same response under high and low impurity level.If impurity level purifies in arrowband anticipated in purposes at such as air, then, in simplified system, such LOG10 can not be used to convert.
As described above, Supervised Control level 42 and major control level 42 velocity form based on proportional plus integral control are run.One embodiment of the invention can be run with position form, and therefore proportional simply uses error current and integral term to use the integration of error.Under another is extreme, this control can be that only ratio controls.This latter two probability embodiment the most as exemplified is desirable.Another probability, although embodiment the most as exemplified is desirable, but does not use total cycle time " Δ t ".Other embodiments of the present invention can use ratio, integration and difference quotient to control.It addition, those skilled in the art will recognize that, each monitoring controller 152,154 and 170 and master controller 44 can be each based on other control theory, as fuzzy logic is run.Model Predictive Control is the another type of control theory that can be used in conjunction with.In this control program, the adsorbent bed impurity composition of the impurity in products concentration of nitrogen and carbon monoxide and carbon monoxide and carbon dioxide.Additionally, it is possible to optionally measure feed stream, temperature and composition.By all current of these variablees and value and the history value input prediction model of feed cycle time before.Whatever will be based on this product compositions of these values for this forecast model.The Part II iterative computation of optimization this computer program of program is minimum with the subtractive of required product purity with the product purity that will record to the necessary amendment of feed cycle time.Once calculate the optimal trajectory of following feed cycle time, select in time closest to the feed cycle time value of current feed cycle time and as the current feed cycle time.
It should be mentioned that another be characterized by, although product purity controller 40 calculates the feed cycle time, i.e. adsorbent bed is carried out the time adsorbed, and absorbing unit controller 34 responds this result and improves the feed cycle time of each bed in complete cycle, and final result is that total cycle time improves.Will be consequently realised that, product purity controller 40 or any other type of control system as described above can be run by the calculating of cycle time itself.Additionally, program some adsorbent bed cell controller to respond capacity coefficient.Although the definition of capacity coefficient becomes with manufacturer, but capacity coefficient is generally equal to the product of design current velocity of time design cycle and feed stream divided by the product of feed stream flow rate currency with the period time value used by control unit.Owing to this adsorbent bed cell controller has the necessary instrument of measurement flow rate, design current velocity and cycle time represent the operating rate of adsorbent bed unit 14 design and operation, control formula given above or another type of system can be inputted, and this controller can measure capacity coefficient to input this adsorption control units, rather than the feed cycle time.Therefore, can be exactly, any embodiment of the present invention can substantially be said to be calculate the regulation control parameter of feed cycle time and this type of to control parameter can be feed cycle time itself, total cycle time or capacity coefficient, described capacity coefficient is also the function of cycle time and therefore feed cycle time.
Although discussing the present invention with reference to preferred embodiment, but many amendments and the omission that those skilled in the art will recognize that can be made in the case of without departing substantially from the spirit and scope of the present invention as described in the appended claims.
Claims (15)
1. the method controlling adsorbent bed unit, including:
The adsorbent bed concentration of the impurity in the adsorbent bed of measurement adsorbent bed unit, this adsorbent bed adsorbs this impurity from the feed stream sending into adsorbent bed, thus produces the product stream containing the no more than production concentration of this impurity of target product concentration；
This adsorbent bed unit is according to periodic duty, feed stream is sent into adsorbent bed and thereafter by the adsorbent in this adsorbent bed of desorption and regeneration of this impurity during this cycle, and this cycle includes the feed cycle time, feed stream is introduced this adsorbent bed by this feed cycle time course, adsorbs this impurity and produce this product stream；
By the feed cycle time used in calculating adsorbent bed unit so that adsorbent bed concentration tends to the target affinity agent bed concentration of the close level making production concentration be maintained at no more than target product concentration and the feed cycle time in the use cycle after being computed, control the production concentration in this product stream, calculate this feed cycle time so that the feed cycle time improves with adsorbent bed concentration and reduces and reduce with adsorbent bed concentration and improve；With
In this product stream this impurity production concentration response interference and change before, in adsorbent bed, in the position measurement adsorbent bed concentration that its adsorbent bed concentration changes, make to control adsorbent bed concentration so that adsorbent bed concentration is maintained at target affinity agent bed concentration and the production concentration of product stream this impurity interior also can be made to be maintained at the level of no more than target product concentration
Wherein:
Construct this adsorbent bed to adsorb at least two impurity；
This impurity is a kind of impurity in described at least two impurity, and production concentration is a production concentration at least two production concentration and target product concentration is a target product concentration at least two target product concentration；
Measure described at least two production concentration and adsorbent bed concentration；
The feed cycle time is controlled by setting the control parameter of feed cycle time in adsorbent bed cell controller by Continuous plus；
This control parameter is inputted adsorbent bed cell controller, and it controls the valve being connected in the flow control network of adsorbent bed, in order in feed cycle time course, feed stream is sent into adsorbent bed；
Calculate this control parameter with adsorbent bed concentration when by this control parameter input adsorbent bed cell controller close to target affinity agent bed concentration；
By calculating described at least two impurity respective potential target adsorbent bed concentration to produce the product stream of the described at least two production concentration of the level with the most described at least two target product concentration, determine target affinity agent bed concentration, and utilize the minima of potential target adsorbent bed concentration as target affinity agent bed concentration so that all described at least two impurity in products concentration are also all controlled to less than described at least two target product impurity concentration by the control of adsorbent bed concentration.
2. the process of claim 1 wherein:
This impurity is the first impurity, and adsorbent bed concentration is the first adsorbent bed concentration, and production concentration is the first production concentration and target product concentration is first object production concentration；
Construct this adsorbent bed to adsorb the first impurity in the ground floor of this adsorbent bed and the second impurity and the 3rd impurity in the second layer of adjacent ground floor this adsorbent bed swimming setting on the first layer；
By control the adsorbent bed concentration that controls of feed cycle time be in ground floor the first adsorbent bed concentration of the first impurity so that the first adsorbent bed concentration tends to close to first object adsorbent bed concentration；
Measure the first impurity in products concentration in product stream and the second impurity in products concentration of the second impurity, in ground floor, measure the first adsorbent bed concentration, and measure the second adsorbent bed concentration of the 3rd impurity in the second layer in its another selected location so that the instruction impurity content before the second impurity breaks through to ground floor of measuring of the 3rd impurity concentration changes；
The feed cycle time is controlled by setting the control parameter of feed cycle time in adsorbent bed cell controller by Continuous plus；
This control parameter is inputted adsorbent bed cell controller, and this adsorbent bed cell controller controls the valve being connected in the flow control network of adsorbent bed, in order in feed cycle time course, feed stream is sent into adsorbent bed；
Calculate this control parameter with the first adsorbent bed concentration when by this control parameter input adsorbent bed cell controller close to first object adsorbent bed concentration；And
By calculating the first impurity, the potential first object adsorbent bed concentration of the second impurity and the 3rd impurity is to produce the product stream of the second production concentration of the second impurity of the first impurity in products and the no more than second target product concentration with no more than first object production concentration, determine first object adsorbent bed concentration, and second adsorbent bed concentration be not more than selected second target affinity bed concentration to prevent the 3rd impurity from breaking through to ground floor, with by utilizing the minima of potential target adsorbent bed concentration as target affinity agent bed concentration so that the control of the first adsorbent bed concentration is also by the first production concentration, second production concentration and the second adsorbent bed concentration control to being respectively smaller than target the first impurity in products concentration, target the second impurity in products concentration and target the second impurity concentration.
3. the process of claim 1 wherein:
Have include monitoring controller with calculate potential target adsorbent bed concentration Supervised Control level and include master controller with calculate control parameter major control level product purity controller in Continuous plus control parameter；
This product purity controller runs continuously with controller frequency；And
Monitoring controller and master controller are individually pi controller.
4. the method for claim 2, wherein:
Have include monitoring controller with calculate potential target adsorbent bed concentration Supervised Control level and include master controller with calculate control parameter major control level product purity controller in Continuous plus control parameter；
This product purity controller runs continuously with controller frequency；And
Monitoring controller and master controller are the pi controllers each with proportional element, integral element, and each proportional element and each integral element have tuning factor；
Each monitoring controller is by calculating potential first object adsorbent bed concentration by the potential first object adsorbent bed concentration calculated before plus proportional element and integral element；
Each ratio and integral element have error term；
First production concentration, the second production concentration, the first adsorbent bed concentration and the second adsorbent bed concentration are measured the most continuously and are converted into denary logarithm value, by them averagely to produce average log value；
Error term: the average log value by deducting the first production concentration from the denary logarithm of first object production concentration calculates in the first monitoring controller relevant to the first impurity；In second monitoring controller relevant to the second impurity, the average log value by deducting the second production concentration from the denary logarithm of the second target product concentration calculates, and is calculated by the average log value deducting the second adsorbent bed concentration from the denary logarithm of the second target affinity agent bed concentration with in the 3rd monitoring controller relevant to the 3rd impurity；And
Average log value by deducting the first adsorbent bed concentration from the denary logarithm of first object adsorbent bed concentration calculates error term in the host controller.
5. the method for claim 4, the difference between error and the error calculated in running before product purity controller that wherein proportional element calculates in being included in the current running of product purity controller.
6. the method for claim 4, its middle controller frequency cycle is equal to the current total cycle time of adsorbent bed unit.
7. claim 4 or the method for claim 5, wherein further determines that integral element by error current is multiplied by current total cycle time.
8. the method for claim 7, wherein:
This cycle is the pressure-variable adsorption cycle；
This adsorbent bed is one of multiple adsorbent bed；
Feed stream is hydrogeneous stream and product stream is hydrogen product stream；
First impurity is carbon monoxide；
Second impurity is nitrogen；
3rd impurity is carbon dioxide；
Ground floor contains zeolite adsorbents and is immediately adjacent to the outlet of adsorbent bed；And
The second layer contains acticarbon.
9. the control system of adsorbent bed unit, it comprises:
Sample tap, it is positioned at the adsorbent bed adsorbent bed concentration with the impurity of sampling adsorbent bed of adsorbent bed unit, this adsorbent bed in feed cycle time course from the feed stream sending into adsorbent bed adsorbing contaminant, thus produce the product stream containing the no more than production concentration of the impurity of target product concentration；
Gas analysis apparatus, it is conscientiously connected with this sample tap and is configured to generate and the concentration dependent data of adsorbent bed；
Product purity controller, its respond this data being configured to calculate the control parameter that will set the feed cycle time used in adsorbent bed unit with by this adsorbent bed concentration of this control state modulator with close to target affinity agent bed concentration, the production concentration of this impurity is maintained at the level of no more than target product concentration by this, calculates this control parameter so that the feed cycle time improves with adsorbent bed concentration and reduces and reduce with adsorbent bed concentration and improve；
This sample tap be located at the production concentration response interference of this impurity in product stream and change before the position that changes of adsorbent bed concentration in adsorbent bed so that controlling adsorbent bed concentration to be maintained at the level of no more than target product concentration with the production concentration of this impurity in also making product stream close to target affinity agent bed concentration；With
Adsorbent bed cell controller, it responds the valve in the control parameter calculated by product purity controller the stream controlling this adsorbent bed unit so that this adsorbent bed unit is according to periodic duty, feed stream was sent into during this cycle adsorbent bed and thereafter by the adsorbent in the desorption and regeneration adsorbent bed of impurity in feed cycle time course
Wherein:
This adsorbent bed is configured to adsorb at least two impurity；
This impurity is a kind of impurity in described at least two impurity, and this production concentration is a production concentration at least two production concentration, and target product concentration is a target product concentration at least two target product concentration；
This gas analysis apparatus is to be located to produce and a gas analysis apparatus in multiple gas analysis apparatuss of the described at least two production concentration in product stream and the concentration dependent data of adsorbent bed；
Product purity controller runs continuously with controller frequency and controls parameter to calculate and include Supervised Control level and major control level；
This Supervised Control level is configured to be calculated target affinity agent bed concentration by the minima of the potential target adsorbent bed concentration calculated at least two monitoring controller, these data that the response of described at least two monitoring controller is relevant to described at least two production concentration, and it is configured to the product stream calculating potential target adsorbent bed concentration to produce the described at least two production concentration with the most described at least two target product concentration；And
This major control level have respond with adsorbent bed concentration and with the master controller of the concentration dependent a part of data of target affinity agent bed calculated by Supervised Control level, and be configured to be calculated this control parameter by adsorbent bed concentration and target affinity agent bed concentration.
10. the control system of claim 9, wherein:
This impurity is the first impurity, and this adsorbent bed concentration is the first adsorbent bed concentration, and this production concentration is the first production concentration and this target product concentration is first object production concentration；
This adsorbent bed is configured to absorption the first impurity and the second impurity and the 3rd impurity in adjacent ground floor the second layer of this adsorbent bed that arranges in this ground floor upstream in the ground floor of this adsorbent bed；
This adsorbent bed concentration be in ground floor the first adsorbent bed concentration of the first impurity so that the first adsorbent bed concentration tends to close to first object adsorbent bed concentration, produce the product stream of the second production concentration of second impurity also with the no more than second target product concentration, and in the second layer, the second adsorbent bed concentration of the 3rd impurity is not more than selected second target affinity bed concentration to prevent the 3rd impurity from breaking through to ground floor；
This sample tap is the first sample tap, and the second sample tap is positioned at the certain position second adsorbent bed concentration with the 3rd impurity of the sampling second layer of this adsorbent bed；
This gas analysis apparatus is to position a gas analysis apparatus in the multiple gas analysis apparatuss to produce the data relevant to the first production concentration, the second production concentration, the first adsorbent bed concentration and the second absorbent concentration；
Product purity controller runs and has Supervised Control level and major control level continuously with controller frequency；
This Supervised Control level is configured to be calculated first object adsorbent bed concentration by the minima of the potential first object adsorbent bed concentration calculated in monitoring controller, the response of this monitoring controller and the first production concentration, second production concentration and the concentration dependent data of the second adsorbent bed, and be configured to calculate potential first object adsorbent bed concentration and be not more than first object production concentration and the first impurity in products concentration of the second product aimed concn and the product stream of the second impurity in products concentration respectively to produce to have, and second adsorbent bed concentration be not more than the second target affinity agent bed concentration；And
This major control level has master controller, its response and the first adsorbent bed concentration and with the concentration dependent a part of data of first object adsorbent bed calculated in this Supervised Control level, and be configured to be calculated this control parameter by the first adsorbent bed concentration and first object adsorbent bed concentration.
The control system of 11. claim 10, wherein:
This monitoring controller and this master controller are the pi controllers with proportional element, integral element, and each proportional element and each integral element have tuning factor；
Each monitoring controller is configured to by calculating potential first object adsorbent bed concentration in the potential first object adsorbent bed concentration calculated before plus proportional element and integral element；
Each ratio and integral element have error term；
The running of each comfortable product purity controller of the first production concentration, the second production concentration, the first adsorbent bed concentration and the second adsorbent bed concentration is measured continuously and is converted into denary logarithm value, by them averagely to produce average log value；
Error term: the average log value by deducting the first production concentration from the denary logarithm of first object production concentration calculates in the first monitoring controller relevant to the first impurity；In second monitoring controller relevant to the second impurity, the average log value by deducting the second production concentration from the denary logarithm of the second target product concentration calculates, and is calculated by the average log value deducting the second adsorbent bed concentration from the denary logarithm of the second target affinity agent bed concentration with in the 3rd monitoring controller relevant to the 3rd impurity；And
Average log value by deducting the first adsorbent bed concentration from the denary logarithm of first object adsorbent bed concentration calculates error term in the host controller.
The control system of 12. claim 11, the difference between error and the error calculated in running before monitoring controller and master controller that wherein this proportional element calculates in being included in the current running of monitoring controller and master controller.
The control system of 13. claim 11, wherein this controller frequency is equal to the current total cycle time of adsorbent bed unit.
14. claim 11 or the control system of claim 12, wherein further determine that this integral element by error current is multiplied by current total cycle time.
The control system of 15. claim 14, wherein:
This cycle is the pressure-variable adsorption cycle；
This adsorbent bed is one of multiple adsorbent bed；
This feed stream is hydrogeneous stream and this product stream is hydrogen product stream；
This first impurity is carbon monoxide；
This second impurity is nitrogen；
3rd impurity is carbon dioxide；
This ground floor contains zeolite adsorbents and is immediately adjacent to the outlet of adsorbent bed；And
This second layer contains acticarbon.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12/410,523 | 2009-03-25 | ||
| US12/410523 | 2009-03-25 | ||
| US12/410,523 US8016914B2 (en) | 2009-03-25 | 2009-03-25 | Adsorption control method and controller |
| PCT/US2010/027089 WO2010111049A1 (en) | 2009-03-25 | 2010-03-12 | Cyclic adsorption control method and controller |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102834159A CN102834159A (en) | 2012-12-19 |
| CN102834159B true CN102834159B (en) | 2016-11-30 |
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|---|---|---|---|---|
| US3703068A (en) * | 1971-03-26 | 1972-11-21 | Union Carbide Corp | Control system for selective adsorption process |
| US4127395A (en) * | 1976-10-18 | 1978-11-28 | Pall Corporation | Adsorbent fractionator with fail-safe automatic cycle control and process |
| WO2004058630A3 (en) * | 2002-12-24 | 2005-01-27 | Praxair Technology Inc | Process and apparatus for hydrogen purification |
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3703068A (en) * | 1971-03-26 | 1972-11-21 | Union Carbide Corp | Control system for selective adsorption process |
| US4127395A (en) * | 1976-10-18 | 1978-11-28 | Pall Corporation | Adsorbent fractionator with fail-safe automatic cycle control and process |
| WO2004058630A3 (en) * | 2002-12-24 | 2005-01-27 | Praxair Technology Inc | Process and apparatus for hydrogen purification |
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