共查询到20条相似文献,搜索用时 31 毫秒
1.
A model predictive control strategy for a simulated moving bed (SMB) chromatographic process is proposed. For this, the average purities over one switching period of target components in extract and raffinate ports are selected as output variables, while the flow rates in Sections 2 and 3 of the SMB unit are chosen as the input variables. With this arrangement a linear input-output prediction model is identified through subspace identification and used for dynamic control. The realization of this concept is discussed and the implementation on a virtual eight column SMB unit is assessed, in the case of the separation of enantiomers behaving according to the binary bi-Langmuir adsorption isotherm. The identified prediction model is proven to be in good agreement with the first principles model used to simulate the actual SMB process. For typical control objectives encountered in real operation, i.e., disturbance rejection or set-point tracking, it is shown that the proposed controller demonstrates satisfactory control performances in minimizing off-spec products. 相似文献
2.
The simulated moving bed (SMB) process, after more than 40 years of successful operation in the petro-chemical industry, has
emerged as one of the most important separation processes in the pharmaceutical, fine chemical, and biotechnology fields.
However, optimal operation and automatic control of the SMB process is still challenging because of its complex dynamics caused
by periodic port switching and inherent nonlinearity. In this research, a novel advanced control technique for the SMB process
has been proposed. In the proposed technique, regulation of both extract and raffinate purities measured at the terminal time
of each switching period is performed by a nonlinear repetitive controller which utilizes the past period data as feedback
information. The repetitive controller was designed on the basis of a fundamental nonlinear model of the SMB process. Through
application to a numerical SMB process, it was found that the proposed control technique performs quite satisfactorily against
model error as well as set point and disturbance changes. 相似文献
3.
M. Fütterer 《化学工程与技术》2008,31(12):1816-1823
Simulated moving bed (SMB) chromatography is an increasingly used separation technology. Several chromatographic columns are interconnected to form a ring. Cyclically, the feedings and drains are changed to allow a continuous separation. This process is very sensitive to parameter variation and disturbances. For this reason, an adaptive controller is suggested. The proposed controller is based on a simplified model and automatically adjusts the volumetric flow rates and switching time in order to achieve the desired purities. Simulation results are presented to give a first impression of the capabilities of this new control concept. 相似文献
4.
Karsten-Ulrich Klatt 《化学,工程师,技术》1999,71(6):555-566
Modeling and Efficient Computational Simulation of Simulated Moving Bed Chromatographic Separation Processes . Chromatographic separation processes provide a powerful tool for the separation of mixtures in which the components have different adsorption affinities, especially when high purities are required. In this area, simulated moving bed (SMB) technology is becoming an important technique for large-scale continuous chromatographic separation processes since it provides the advantages of a continuous countercurrent operation while avoiding the technical problem of a true moving bed. Because of the complex dynamics of the process, the choice of the optimal operation parameters and the control of the process in order to keep the product specifications at any time is not straightforward. For this challenging task, a reliable dynamic model of the process is necessary which is accurate enough as well as efficient enough in order to permit its online use for model based control. The purpose of this contribution is to review the state of the art in dynamic modeling of SMB chromatographic separation processes, highlighting new trends and results in the design of computationally effective simulation models suitable for online applications. 相似文献
5.
This paper presents a multi-level optimization strategy to obtain optimum operating conditions (four flow-rates and cycle
time) of nonlinear simulated moving bed chromatography. The multi-level optimization procedure (MLOP) approaches systematically
from initialization to optimization with two objective functions (productivity and desorbent consumption), employing the standing
wave analysis, the true moving bed (TMB) model and the simulated moving bed (SMB) model. The procedure is constructed on a
non-worse solution property advancing level by level and its solution does not mean a global optimum. That is, the lower desorbent
consumption under the higher productivity is successively obtained on the basis of the SMB model, as the two SMB-model optimizations
are repeated by using a standard SQP (successive quadratic programming) algorithm. This approach takes advantage of the TMB
model as well as surmounts shortcomings of the TMB model in the general case of any nonlinear adsorption isotherm using the
SMB model. The MLOP is evaluated on two nonlinear SMB cases characterized by i) quasi-linear/non-equilibrium and ii) nonlinear/nonequilibrium
model. For the two cases, the MLOP yields a satisfactory solution for high productivity and low desorbent consumption within
required purities. 相似文献
6.
M. Fütterer 《化学工程与技术》2009,32(10):1535-1541
The simulated moving bed process is increasingly used for the separation of binary mixtures. To ensure proper operation, the volumetric flow rates and the time interval must be exactly adjusted. This study presents a general method for determining the control variables for a dispersion‐free SMB process. For noncompetitive Langmuir isotherms, explicit equations are derived for the case of complete separation. The proposed method allows both a good estimation of the time trajectories of the concentrations at the drains and the design of new applications for optimization and control of SMB plants. 相似文献
7.
Hyeon‐Hui Lee Kyung‐Min Kim Chang‐Ha Lee 《American Institute of Chemical Engineers》2011,57(8):2036-2053
A “FeedCol” strategy was developed to improve separation performance in simulated moving bed (SMB) processes. In the FeedCol operation, a short chromatographic column was simply added to the SMB unit and feed was supplied by a pulse input through the column to the SMB process. Because the feed was made in the shape of partially separated chromatographic peaks through the column, the purities in the raffinate and extract products were improved efficiently in the SMB process. All the performance parameters for a binary mixture with low selectivity (α = 1.1) were better for the FeedCol operation than for the conventional SMB operation (2‐2‐2‐2). Because the feed injection through the feed column was synchronized with the SMB process during the switching period, two new operating variables were introduced: injection length and injection time. Their effects on the suggested strategy were evaluated in terms of performance parameters through a detailed simulation study. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
8.
In this work a new approach to the control of simulated moving bed (SMB) chromatographic separation processes is presented. This approach is based on the combination of the wave theory and Multi-Model Predictive Control (MMPC). The wave theory provides the theoretical framework in which the control law is formulated whereas receding-horizon MPC is used for determining the appropriate controller parameters. As SMB plants are distributed parameter systems (DPS) with nonlinearity arising from the expression of the adsorption isotherms, classical numerical methods for the solution of DPS are computationally demanding for MPC purposes. Reduced-order models are therefore derived using the proper orthogonal decomposition (POD) technique. To ensure stability, the POD model is updated on-line, resulting in MMPC. 相似文献
9.
10.
Mariana A. Moreira Alexandre F. P. Ferreira João C. Santos José M. Loureiro Alírio E. Rodrigues 《化学工程与技术》2014,37(9):1483-1492
A new hybrid process for the production of o‐ and p‐xylene is proposed to replace the traditional plant of aromatics in refineries. The proposed process comprises a simulated moving bed (SMB) unit and two crystallizers. The SMB technology as the first unit of the suggested process is applied for the separation of xylene isomers and was investigated by simulation of an industrial size unit, using experimentally measured adsorption equilibrium data on MIL‐53(Al)‐shaped material. The separation of p‐xylene from o‐xylene with m‐xylene as desorbent is the key characteristic of this method. An industrial‐scale SMB unit could provide extract and raffinate streams with very high purities. 相似文献
11.
12.
Hariprasad J. Subramani Anjushri S. Kurup 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2006,120(3):169-179
Continuous chromatographic separation processes like simulated moving bed (SMB) systems have been employed in petrochemicals, sugar, and more recently, in pharmaceutical industries by virtue of their superior separation efficiency. Miniaturization of chromatography-based analytical techniques (e.g., high performance liquid chromatography, micro-HPLC or μHPLC) has already been successfully demonstrated in the last few years owing to the rapid development in MEMS technology. With such a rapid progress in technology, it is definitely possible to realize the miniaturization of a powerful continuous chromatographic process such as SMB. Micro-SMB (μSMB) systems could not only inherit the merits of μHPLC, but also provide efficient separation of compounds such as isomers and enantiomers that are otherwise very difficult to isolate. In this paper, new simulations of the performance of a μSMB system for the separation of a mixture of phenol and o-cresol, using a robust numerical algorithm developed that mimics the dynamic operation of the μSMB system, are presented. A systematic parametric sensitivity analysis that addresses the effects of various process parameters on the performance of the μSMB system is also presented. High purities and yields of both phenol and o-cresol is achieved in the μSMB by judicious choice of process parameters. 相似文献
13.
《分离科学与技术》2012,47(2):223-252
Abstract A new simulated moving bed (SMB) operation technique is introduced, the outlet streams swing (OSS), based on the dynamic collection of fronts from the equivalent true moving bed (TMB). This new assumption improves the product outlet purities, when compared with the classic operating mode, as a consequence of an increased separation between collection fronts and the contaminating ones. The strategy is dynamic and discontinuous, a collection front expansion is performed in zone 1 and/or 4, obtained by the violation of the classic respective design constraints during a first step and contraction during the second step using at least the classic design operating parameter for zones 1 and 4. Another non‐conventional technique, the MultiFeed (MF) SMB operation, is simulated and analyzed here as a solo technique as well as a powerful modelling technique for the particular case of inner sections Varicol® (only the zones 2 and 3 have variable number of columns). 相似文献
14.
In the simulation of cyclic processes, such as simulated moving bed (SMB), the system should be equilibrated to reach a cyclic steady state (CSS) before evaluating the process performance. However, the conventional method of successive substitution is quite time-consuming. In this work, a continuous predicting method (CPM) is developed for fast determination of CSS in SMB. In CPM, the direct prediction of state variable at CSS and solving model equation are conducted alternately until CSS is reached. In order to give a guideline for the selection of the acceleration factor, CPM is applied on SMB process for enantioseparation of 1,1′-bi-2-naphtol racemate and with the optimized acceleration factor, 59% of computation time saved compared with successive substitution. In addition, this method is further successfully used in a sugar separation process. Given its efficiency and simplicity, this method could provide a useful tool for SMB simulations. 相似文献
15.
M. Fütterer 《化学工程与技术》2010,33(1):21-34
Simulated moving bed (SMB) chromatography is an established separation technology, where chromatographic columns are interconnected to a ring. The feeding and drains are switched over cyclically, such that a continuous separation becomes possible. For a faultless operation, the volumetric flow rates and switching time must be carefully adjusted. Therefore, it is desirable to calculate these values in dependence of the model parameters exactly. In this contribution, a new method is introduced to compute operating points for dispersion‐free SMB plants and to predict the associated time trajectories of the concentrations at the drains in cyclic steady state for user‐specified purities and degree of robustness. Simulation results are presented to show the potential of this new method. 相似文献
16.
Junghui Chen Kai-Ting Hsieh Lester Lik Teck Chan 《Chemical engineering science》2010,65(10):2990-3000
The simulated moving bed (SMB) is a continuous chromatography process for separation of chemical mixtures. It has been used in large-scale industrial production of cheap specialty products like sugar separation, as well as small-scale production of high value products like enantiomer separation in the pharmaceutical industry. Physical models can be employed in control of SMB processes, but it can be difficult to obtain accurate physical parameters. Empirical models do away with the need to obtain parameters, but without physical representation, they may not be suitable for control applications. In this research paper, wave propagation is linked with the empirical model to enhance the physical constraint on designing SMB. However, there is an interaction between the zonal wave velocities and process outputs; thus, control strategies based on the partial least squares (PLS) are proposed in this work. PLS decoupling of the system to achieve pairs of SISO (single input single output) in the subspace is useful because the conventional SISO can be directly applied to the control design. The use of wave propagation allows the application of the constraints in Zones II and III based on the shifting of the wave fronts. Two modes of control are proposed: cycle to cycle and within cycle. The performance of these control strategies is assessed by implementation on a virtual eight-column SMB unit for set-point tracking and disturbance rejection. 相似文献
17.
The optimization, monitoring and control of simulated moving bed (SMB) units require the use of a process model and the estimation of the model parameters. A systematic numerical procedure for determining parameters of SMB models from batch experiments is presented and evaluated. The unknown parameters are estimated by minimizing a cost function measuring the difference between experimental and simulated concentration profiles. In contrast with previous studies, parameter identifiability is studied and errors on the estimated parameters are calculated. A sensitivity analysis is used to design the experiments and to compare the identifiability of different chromatographic models. Then, the influence of local minima is evaluated by applying the numerical procedure on fictitious measurements generated from a model with known parameters. 相似文献
18.
A rate model, which considers axial dispersion, external mass transfer, intraparticle diffusion and nonlinear isotherms, and ports periodic switching is adopted to simulate the simulated moving bed (SMB) process. The effects of flow rate in Sections 2 and 3 and switching time on the operating performance parameters: purity, recovery, productivity and dcsorbent consumption are studied. A simulation approach is applied to simulate the operation and performance of the SMB. The model predicts the performance of the transient and cyclic steady state behavior to a reasonably good extent, and provides guidance operation condition of the SMB process. 相似文献
19.
模拟移动床技术在中药有效成分分离中的应用 总被引:5,自引:1,他引:4
模拟移动床色谱(simulatedmovingbedchromatography)或简称模拟移动床(SMB)是连续色谱的一种,是模拟移动床技术和色谱技术的结合,是以模拟移动床的运转方式来实现色谱的连续分离。该文主要从模拟移动床的发展、结构、原理及其特点、难点和该项技术在中药有效成分分离中的应用等几个方面做一介绍。引用文献20篇。 相似文献
20.
《分离科学与技术》2012,47(2):246-253
Simulated moving bed (SMB) technology has attracted more and more attention in recent decades. The simulated moving bed (SMB) technology on optimal utilization of naphtha resource was studied in this paper. A simulated moving bed equipped with 16 columns was used to separate normal paraffins from naphtha. The effects of temperature (T), switching time (ts), extract oil flow rate (LAD), feed flow rate (LF), and desorbent flow rate (LD) on the separation performance were investigated, and the desorbent recycle process was simulated by Aspen Plus. The results showed that the optimal conditions for simulated moving bed were operation temperature (T) of 170°C, switching time (ts) of 900 s, extract oil flow rate (LAD) of 10 mL/min, feed flow rate (LF) of 5 mL/min, and desorbent flow rate (LD) of 20 mL/min. Through the SMB and the desorbent recycle system, the purity of the de-solvent extract oil (DEO) reached 98% and the purity of the de-solvent raffinate oil (DRO) reached 92%, which were the high-quality feed for the ethylene cracking process and the catalytic reforming process, respectively. 相似文献