CN-122006410-A - Follow-up control method for multi-tower feeding pressure swing adsorption system

CN122006410ACN 122006410 ACN122006410 ACN 122006410ACN-122006410-A

Abstract

The invention discloses a follow-up control method of a multi-tower feeding pressure swing adsorption system, and belongs to the technical field of pressure swing adsorption. The follow-up control method of the multi-tower feeding pressure swing adsorption system comprises the steps of sequentially carrying out n process steps in each sub-period, wherein one designated step positioned in the P step is a time adjustable step, the operation duration of the designated step is tx seconds, and the sub-period time is calculated and assigned to tx when the designated step is operated to the last 1 seconds of the P-1 step, so that the operation time of the sub-period is adjusted. According to the invention, the feeding amount and the operation sub-period of the adsorption tower are accurately calculated in all the feeding sub-periods, and the variable duration step is arranged at the tail end of the sub-period, so that when the sub-period time is calculated, not only are the flow of other sub-periods comprehensively considered, but also the full-time space information of the flow in the operation sub-period is fully considered, and the timeliness and the accuracy of adjustment are obviously improved.

Inventors

BU LINGBING
ZHENG JIANCHUAN
GUO LI
ZHANG HONGYU
ZHANG JIE
WU YI
LIU XIAOJUN
WANG JUNJIAN
AI LIJIANG
HUANG PINGLIANG
ZENG QIANG

Assignees

西南化工研究设计院有限公司

Dates

Publication Date: 20260512
Application Date: 20260304

Claims (10)

1. A follow-up control method of a multi-tower feeding pressure swing adsorption system is characterized in that at any running time, the number of adsorption towers in a feeding adsorption state is m, m is an integer which is more than or equal to 1, each sub-period comprises n sequentially carried out process steps, wherein one designated step positioned in the P step is a time adjustable step, the running time is tx seconds, and the sub-period time is calculated and assigned to tx when the multi-tower feeding pressure swing adsorption system runs to the last 1 seconds of the P-1 step, so that the running time of the sub-period is adjusted; tx is calculated according to formula (1): Formula (1) In the formula (1), k 1 is a flow adjustment coefficient, the value range is 0.5-1.5, F 0 is the design flow, unit Nm 3 /h, T 0 is the design part-cycle time, in seconds, F -1 is the average flow rate of the previous minute period, unit Nm 3 /h, T -1 is the previous minute cycle time, in seconds, F -2 is the average flow rate of the first half cycle, unit Nm 3 /h, T -2 is the first half cycle time, in seconds, F -m+1 is the average flow rate of the previous (m-1) minute period, unit Nm 3 /h, T -m+1 is the previous (m-1) minute cycle time, in seconds, F 1 is the average flow rate of the operation sub-period, namely the average flow rate from the P-th step of the previous sub-period to the P-1 st step of the operation sub-period at the moment of calculating, the unit Nm 3 /h, T 1 is the time in seconds of running step 1 of the minute period, T 2 is the time in seconds of step 2 of the run sub-cycle, T p-1 is the time of the P-1 step of the operation sub-period, unit seconds, T p+1 is the time of the p+1 step of the operation part period, unit seconds, T n is the time in seconds of running the nth step of the sub-cycle.
2. The method for controlling the servo of a multi-column feed pressure swing adsorption system according to claim 1, wherein tx is calculated as the formula (2) when m=1: formula (2); The definition of k 1 、F 0 、F 1 、T 0 、t 1 、t 2 、t p-1 、t p+1 、t n in equation (2) is the same as that of equation (1).
3. The method according to claim 1 or 2, wherein a feedback coefficient k 2 dynamically adjusted based on the product gas quality is increased based on the effect of the product gas quality on the split cycle time for correcting tx; The initial value of the feedback coefficient k 2 is 0 seconds, and tx is calculated according to the formula (3): Formula (3) k 1 、F 0 、F 1 、F -1 、F -2 、F -m+1 、T 0 、T -1 、T -2 、T -m+1 、t 1 、t 2 、t p-1 、t p+1 、t n 、m In equation (3) is defined as in equation (1), The feedback coefficient k 2 is updated in each operation sub-period, and the value of the feedback coefficient k 2 is the sum of the k 2 value of the last sub-period and the adjustment value calculated according to the current product gas quality deviation.
4. The method according to claim 3, wherein in the formula (3), if the non-adsorption phase is used as the product gas, the feedback coefficient k 2 is dynamically adjusted according to the deviation between the product gas quality and the design value: When the product gas quality exceeds the upper threshold of the design value, k 2 is calculated to be 1 second, namely k 2 is increased by 1 second on the basis of the upper sub-period to serve as k 2 of the operation sub-period; When the product gas quality is below the lower threshold of the design value, k 2 is calculated to be-3 seconds, i.e. k 2 is reduced by 3 seconds on an up-part-cycle basis, as k 2 for the run part-cycle.
5. The method according to claim 3, wherein if the non-adsorption phase is used as the product gas, when the purity of the target product component is significantly affected by the content of a certain key impurity component and there is a coupling relationship between the two components for controlling the product quality, the feedback coefficient k p corresponding to the purity of the target product and the feedback coefficient k i corresponding to the impurity content are respectively set, and the smaller value of the two components is used as the calculated value of the feedback coefficient of the system, namely k 2 ＝min{k p ,k i .
6. The method of claim 5, wherein the product is H 2 , the corresponding feedback coefficients k H2 and k CO are calculated based on the on-line analysis results of H 2 and CO in the product gas, respectively, and the smaller value of the two is taken as the calculated value of the feedback coefficient of the product gas quality, namely k 2 =min{k H2 ,k CO .
7. The method for controlling a multi-column feed pressure swing adsorption system according to claim 6, wherein the hydrogen feedback coefficient k H2 is determined as follows: (1) If the product hydrogen purity is not detected to meet the design requirement, k H2 = is set 3 Seconds; (2) The purity of the hydrogen in the product is at the design lower limit edge, and k H2 = is set 1 Second; (3) The purity of the hydrogen in the product is superior to the design requirement, and the hydrogen is further judged by combining the change trend A Offset of deflection -H2 , wherein A Offset of deflection -H2 =the sampling value of the up-division period H 2 -the sampling value of the present-division period H 2 : (31) If A Offset of deflection -H2 < 0.02%, K H2 = +1 seconds; (32) If a Offset of deflection -H2 > +0.02%, k H2 =is set 1 Second; (33) If a Offset of deflection -H2 is less than or equal to 0.02%, k H2 =0 seconds is set; (34) If the purity of the product hydrogen is significantly better than the design value, k H2 = +2 seconds is set.
8. The method for servo control of a multi-column feed pressure swing adsorption system of claim 6, wherein the CO feedback coefficient k CO is determined as follows: (1) The CO content is far lower than the design upper limit, and k CO = +2 seconds is set; (2) The CO content is within the safe range, setting k CO =0 seconds; (3) The CO content is close to the exceeding threshold value, and is judged by combining the change trend A Offset of deflection -CO that A Offset of deflection -CO =the up-sub-period CO sampling value-the present sub-period CO sampling value: (31) Only when a Offset of deflection -CO < -0.5ppm, k CO =is set 2 Seconds; (32) If the CO content is high, but the CO content is in a descending or stable trend, setting k CO = 0 seconds; (4) If the CO content has reached or exceeded the design upper limit, k CO = 3 Seconds.
9. The method according to claim 3, wherein in the formula (3), if the adsorption phase is used as the product gas, the feedback coefficient k 2 is dynamically adjusted according to the deviation between the product gas quality and the design value: If the product gas quality is too high and exceeds the upper limit threshold of the design value, the calculated value of k 2 is-1 second, namely k 2 is reduced by 1 second on the basis of the upper sub-period to be used as k 2 of the operation sub-period; If the product gas quality is too low and is lower than the lower threshold of the design value, the calculated value of k 2 is 3 seconds, namely k 2 is increased by 3 seconds on the basis of the upper sub-period as k 2 of the operation sub-period.
10. A multi-column feed pressure swing adsorption system servo control method according to claim 3 wherein feed gas composition feed-forward modifications are introduced based on feed gas composition changes, and the modified tx is calculated according to equation (4): Formula (4) In the formula (4), Y 0 is the designed adsorption phase content, and the unit mol/mol; y -1 is the average content of the adsorption phase in the previous cycle, and the unit mol/mol; Y -2 is the average flow rate of the first half period, and the unit mol/mol; y -m+1 is the average content of the adsorption phase in the previous (m-1) part cycle, and the unit mol/mol; Y 1 is the average content of the adsorption phase in the operation sub-period calculation time (namely the flow calculation time from the P-th step of the previous period to the P-1 th step of the operation sub-period), and the unit mol/mol; k 1 、F 0 、F 1 、F -1 、F -2 、F -m+1 、T 0 、T -1 、T -2 、T -m+1 、t 1 、t 2 、t p-1 、t p+1 、t n 、m And k 2 is as defined in equation (3).

Description

Follow-up control method for multi-tower feeding pressure swing adsorption system Technical Field The invention belongs to the technical field of pressure swing adsorption, and particularly relates to a follow-up control method of a multi-tower feeding pressure swing adsorption system. Background Pressure swing adsorption (PressureSwingAdsorption, PSA) technology has been one of the important processes in the field of gas separation and purification over many years since the first industrial application in the sixty of the twentieth century. The technology realizes the efficient separation of target gas based on the difference of selective adsorption of different components in the mixed gas by the adsorbent under the condition of pressure change. With the technical progress, the scale of the PSA device is continuously enlarged, the operation pressure is gradually increased, and the role of the PSA device is gradually changed from an auxiliary link in the production flow to a key process unit, so that the PSA device is widely applied to a plurality of fields such as hydrogen purification, air separation oxygen production, carbon dioxide capture, natural gas purification and the like. In the continuous popularization and deepening of the PSA technology, the optimization of the process flow and the control system is increasingly emphasized, and particularly, certain progress is made in the aspects of improving the auxiliary flow and controlling the stability. However, in the actual operation process, key parameters such as flow, composition, pressure and temperature of the raw material gas often fluctuate, and the purity and yield of the product gas are directly affected. In order to ensure stable product indexes and realize optimal recovery rate, how to automatically adjust the adsorption time in real time according to the change of raw material conditions becomes a core challenge in the automatic control of the PSA device. The current common control method is generally used for adjusting the adsorption time only based on the raw material gas flow of the previous single sub-period, and a control model is simpler. The method is difficult to accurately reflect the comprehensive influence of the dynamic change of the flow of each tower on the adsorption process under the working condition of parallel or sequential feeding of multiple towers, and the flow accumulation effect and the hysteresis characteristic between sub-periods in the operation process cannot be effectively described. Therefore, when the existing control strategy is used for coping with the fluctuation of the actual working condition, the accuracy of the adsorption time adjustment is often insufficient, and the stable operation and the energy efficiency optimization of the PSA device under the variable load condition are restricted. Therefore, the adsorption time self-adaptive regulation and control method and system suitable for the multi-tower pressure swing adsorption process have the characteristics of dynamically responding to the change of the raw gas parameters and fusing the multi-cycle flow characteristics and the multi-tower cooperative regulation and control mechanism, so that the problems of inaccurate adsorption time adjustment and weak working condition adaptability caused by the simplification of a control model in the prior art are solved, and the technical problems to be solved by the person in the art are solved. Disclosure of Invention The invention aims to provide a follow-up control method of a multi-tower feeding pressure swing adsorption system, which adjusts the time of operating sub-periods through flow data of a plurality of sub-periods and flow data of the operating sub-periods, and corrects the sub-period time according to the mass of product gas and the relative adsorption content of raw gas, thereby realizing dynamic adjustment of the sub-period time along with the change of the mass of raw gas, the composition and the mass of the product gas and achieving the accurate control of the pressure swing adsorption system. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The invention discloses a follow-up control method of a multi-tower feeding pressure swing adsorption system, which is characterized in that the time sequence characteristics of the method are defined by the following parameters that the number of adsorption towers in a feeding adsorption state is m (an integer with m being more than or equal to 1) at any running time, each sub-period of each adsorption tower comprises n sequentially carried out process steps, wherein one designated step in the P step is a time adjustable step, the running time is tx seconds, and the sub-period time is calculated and assigned to tx when the adsorption tower runs to the last 1s of the P-1 step, so that the running time of the sub-period is adjusted. Tx is calculated according to formula (1): Formula (1) In the formula (1),