Browsing by Subject "Separation (Technology)"
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item Analysis and optimization of heat integrated distillation sequences(Texas Tech University, 1985-05) Shankar, HariharanThis work proposes a heuristic-evolutionary method to optimize heat-integrated distillation sequences. The key to this method is the use of a quantitative measure which evaluates the Overall Difficulty of Separation for a separation problem (ODOS). ODOS is defined as ODOS=(Q/dt)/F where Q is the condenser duty in the column, dt is the temperature difference between the condenser and reboiler and F is a factor, proposed by Nadgir and Liu (1983), which reflects the balance between the top and bottom products. F is defined as F = Min (V/L, L/V) where V and L are respectively the amounts of the top and bottom products. The ODOS, developed in this work, not only enabled selection of a good upper bound for the cost of the 'optimal' sequence, but allowed prediction of a band of 'good' sequences for the problems considered in this work. This quantitative measure was also successful in eliminating the non-competitive sequences from further consideration. The selection of a band of sequences enables the designer to choose the sequence for actual implementation from objectives other than economics, like ease of control, plant layout, etc. The method involves no intermediate evaluation of the candidate sequences, unlike traditional evolutionary methods. This work has also confirmed the decomposition principle of Sophos et al (1981, 1982), which stated that the separation sequencing problem should be tackled first and then heat integration should be attempted for the 'good' sequences identified. This method was tested by calculating the costs for each sequence with and without integration for seven of the nine examples considered in this work. For the other two examples, as well as for the first seven examples, values reported in the literature were used to assess this method. This method has also been compared with the standard heuristic methods in the literature. This method compares very favorably with the literature methods in terms of locating a good initial sequence, identifying competitive sequences, eliminating non-competitive sequences and providing a quantitative measure for the competitiveness of a sequence.Item Axial illumination based optical detection in Micro LC(Texas Tech University, 1995-12) Abbas, Ahmad AbdullaNot availableItem Design and control of a heat-integrated distillation train(Texas Tech University, 1985-08) Bryan, Kent ENot availableItem The effect of uni-axial stretching on microporous phase separation membrane structure and performance(2006) Morehouse, Jason Andrew; Lloyd, Douglas R., 1948-Item Effects of structural variation within polyether and calix[4]arene ligands and matrix variation on metal ion complexation(Texas Tech University, 2002-05) Chun, SangkiNot availableItem Evaluation of X-ray imaging to investigate hydraulic performance of vapor-liquid contactors(2001) Schmit, Carolyn Elizabeth; Bonnecaze, R. T. (Roger T.); Eldridge, Robert BruceItem Microsecond electrophoresis(2006) Plenert, Matthew Lee; Shear, Jason B.Spectroscopy is a powerful tool for the investigation of chemical phenomena, but often is hindered in the analysis of species in chemical mixtures—in which chemical interferences can convolute the attainable spectroscopic information. Separation techniques such as liquid chromatography and capillary electrophoresis provide a means of deconvoluting such information but typically are performed over timescales much longer than the life span of highly unstable compounds. This dissertation describes the development of the world’s fastest separation technique, microsecond electrophoresis, and application of this technique to the study of transient species. Chapter 1 provides a discussion of issues involved in the performance of high speed electrophoretic separations. Chapter 2 describes development of multiphoton excited (MPE) optical injection and detection strategies which allow transient species to be analyzed using electrophoresis over low micron separation distances. Chapter 3 presents a method by which separation capillaries are modified such that electric field strengths exceeding 0.1 MV/cm can be used to perform separations (resulting in a ~ 100-fold reduction in analysis time over previous high speed separation techniques). Chapter 4 presents further instrumental developments which allow differently-charged species to be detected at different locations within the separation channel (allowing “infinite resolution’ microsecond separations to be performed). Chapter 5 details work towards application of low-timescale electrophoretic separations to the study of folding protein and peptide species.Item Planar liquid-membrane mass transfer.(Texas Tech University, 1975-12) Cheaney, Richard StevenNot availableItem Process model based control of distillation columns(Texas Tech University, 1988-12) Sinha, RupakNot availableItem Superfractionator process control(Texas Tech University, 1998-08) Hurowitz, Scott EdwardAn in-depth study is conducted regarding product composition control of superfractionators with an emphasis on control configuration selection. A propylenepropane (C3) splitter is chosen as a representative column by which to investigate superfractionator process control issues. An ethylene-ethane (C2) splitter is also investigated for comparative purposes. Detailed steady state and dynamic simulations of a C3 and C2 splitter are developed and benchmarked against industrial C3 and C2 splitter process data. These simulations are used to investigate single-ended and dual Proportional-Integral (PI) composition control. For C3 splitter single-ended PI composition control, the (L, V) configuration provides the best control performance. For C3 splitter dual PI composition control, the (L, B) and (L, V/B)configurations provide the best control performance. The (L, V) and (L, V/B) configurations are determined as optimal for dual PI composition control of the C2 splitter. The control benefits provided by the use of decoupling techniques and feedforward compensation for dual PI composition control are also investigated. An evaluation of the control benefits realized by feedforward compensation indicate that, when a material balance (product) stream is used to control composition, feedforward compensation will provide a significant improvement in composition control performance. Dynamic Matrix Control (DMC), a model-based control algorithm, is applied to the C3 and C2 splitters, and its performance is compared to that obtained by PI control. Dynamic Matrix Control generally provides control performance that is equal to or better than that obtained by PI control for unconstrained, 2x2 distillation composition control, provided that the process is adequately modeled by the DMC controller. A technique is developed for predicting closed-loop product variabilities based on a signal processing analysis of feed composition data, from which usefiil information can be extracted and used to predict closed-loop product variabilities. This technique is applied to a C3 splitter for demonstrative purposes and is shown to accurately predict the product variabilities that result from feed composition disturbances.Item Transient Behavior of Mass Transfer Through Liquid Membranes(Texas Tech University, 1977-08) Shen, Sidney YihNot Available.Item Vacuum distillation control(Texas Tech University, 1998-12) Anderson, John JosephA detailed study of vacuum distillation column control implementations was performed with special emphasis placed on control configuration selection. Two vacuum separations were studied; toluene from xylene and ethylbenzene from styrene. Rigorous, dynamic simulations were developed for these two systems that incorporated varying tray-to-tray pressure drops and coupled, dynamic material and energy balances for each tray of the column. These columns were benchmarked against published data. For single-ended composition control, manipulating the reflux flowrate provided the best control of the overhead impurity for setpoint changes as well as for feed composition disturbance rejection. Bottom impurity control was best handled by ratioing the vapor boilup rate and the bottoms flowrate (boilup ratio, V/B). For dual-ended control, the [L,V] and [L,V/B] configurations provided better control of both product streams when the column has a reflux ratios near 1. In addition, the [L/D,V] and [L,V] configurations both provide good product impurity control especially when the bottom product stream is more valuable. These two configurations also performed best as the column's reflux ratio increased. Advanced control techniques such as decoupling and feedforward compensation were studied and decoupling was found to improved control performance on both product streams. Feedforward compensation improved configurations were ratio control was implemented (reflux ratio or boilup ratio) or when the process has slow dynamics. In addition, Dynamic Matrix Control (DMC) was applied to both the xylene/toluene columns and the styrene/ethylbenzene column. A [2x2] DMC controller was compared with decentralized PI controllers on several control configurations. For setpoint tracking, DMC improved control responses by decoupling control action on both ends of the column. For unmeasured feed composition disturbances, DMC did not have the control performance of PI as DMC lacked feedforward compensation for disturbances. In addition, DMC considered both product compositions as having equal importance. Finally, the minimum move suppression factors allowed by the DMC package were used which limited DMC performance for unmeasured disturbances. DMC does provide benefits on the styrene/ethylbenzene column by allowing the styrene composition to have a higher control priority. As a result, DMC performed comparably to PI for feed disturbances.