Dual Temperature Control Research Articles

Heat integration and dynamic control of reactive pressure-swing distillation for separation of tetrahydrofuran/ethanol/water

In this paper, heat integration and dynamic control of reactive pressure-swing distillation (RPSD) for separating tetrahydrofuran/ethanol/water was investigated from the aspects of energy consumption, environmental protection and practical applications. By exploring the heat exchange between separating tetrahydrofuran and ethanol distillation columns, the full heat integration process (FHI) was designed. Robust control of heat and non-heat integrated processes was realized based on the dual temperature control structure. All processes were resistant to ±20% feed flow and composition disturbances. Finally, these processes were compared from three aspects: economy, environment and dynamic performance. The results show that compared with the non-heat integration process, the FHI process can reduce the total annual cost by 24.14%, the CO2 emission by 20.21% and the SO2 and NO emission by 34.38%, meanwhile, having the best dynamic performance. This study is valuable and instructive in promoting the integrated optimal and control design of the RPSD process.

Numerical simulation and printability analysis of fused deposition modeling with dual-temperature control

Numerical simulation and printability analysis of fused deposition modeling with dual-temperature control

Novel temperature-control strategy for single column side-stream extractive distillation process with intermediate-boiling entrainer

A simple, novel, and energy-saving single column side-stream extractive distillation (SSED) process was recently proposed in literature, for separating the azeotropic mixture of methanol (MeOH) and toluene (TOL) using triethylamine (Et3N) as an intermediate boiling entrainer. However, within the limited progress regarding the control of this process, composition controllers were required to maintain stringent product specifications in the face of disturbances. In view of this, our work firstly uncovers the feasibility of establishing control strategies without using composition loops. The research scope also covers the revision of thermodynamic properties in between MeOH and Et3N, re-design of the process with systematic optimization, development and evaluation of four control schemes. With thorough analyses, a dual-temperature control structure with three measurement (i.e. a side-stream temperature control loop, and a temperature difference control loop in the extractive section of the SSED column) was found to satisfactorily reject the specified feed disturbances (i.e. ±20% change in flowrate and composition). Notably, the loop adjusting the makeup flowrate to control the side stream temperature, which has not been proposed to the single column SSED process, greatly reduced the settling time under disturbances. Comparing with other control structures in literature, the one proposed in this work provides good control performances, but in a manner that is more industrially maneuverable.

Comparison of optimization methods for the design and control of reactive distillation with inter condensers

Reactive distillation (RD) is a promising alternative that can produce high-purity Silane. However, it requires a large amount of expensive refrigerant to condense it. Therefore, this work assesses the feasibility of installing intermediate condensers at stages in the RD column to reduce the utility cost. Thus, RD columns with one and two Intermediate Condensers named RD-IC and RD-2IC are studied in addition to the RD column. A Simulated Annealing Algorithm (SAA) minimizes the total annual cost (TAC) of the RD, RD-IC, and RD-2IC. In contrast, a Mixed Integer Linear Programming (MILP) problem minimizes the utility cost. The solutions of each approach are compared, and the control performance of the best alternative is studied. Dual temperature control is applied for all alternatives, and it can stabilize the process and maintain the purities of the products against throughput and composition disturbances.

Non-Interventional and High-Precision Temperature Measurement Biochips for Long-Term Monitoring the Temperature Fluctuations of Individual Cells.

Monitoring the thermal responses of individual cells to external stimuli is essential for studies of cell metabolism, organelle function, and drug screening. Fluorescent temperature probes are usually employed to measure the temperatures of individual cells; however, they have some unavoidable problems, such as, poor stability caused by their sensitivity to the chemical composition of the solution and the limitation in their measurement time due to the short fluorescence lifetime. Here, we demonstrate a stable, non-interventional, and high-precision temperature-measurement chip that can monitor the temperature fluctuations of individual cells subject to external stimuli and over a normal cell life cycle as long as several days. To improve the temperature resolution, we designed temperature sensors made of Pd–Cr thin-film thermocouples, a freestanding Si3N4 platform, and a dual-temperature control system. Our experimental results confirm the feasibility of using this cellular temperature-measurement chip to detect local temperature fluctuations of individual cells that are 0.3–1.5 K higher than the ambient temperature for HeLa cells in different proliferation cycles. In the future, we plan to integrate this chip with other single-cell technologies and apply it to research related to cellular heat-stress response.

Development of a dual temperature control system for isoprene biosynthesis in Saccharomyces cerevisiae

Development of a dual temperature control system for isoprene biosynthesis in Saccharomyces cerevisiae

MEMS-based dual temperature control measurement method for thermoelectric properties of individual nanowires

Abstract

Dynamic study in enhancing the controllability of an energy-efficient double side-stream ternary extractive distillation of acetonitrile/methanol/benzene with three azeotropes

The exploration of control strategy for the double side-stream ternary extractive distillation (denoted as DSTED) process is essential because it has a significant potential for energy-saving. However, how to effectively control the energy-efficient DSTED process is a unique and complex issue due to the additional coupled variables of double side-streams. Consequently, in this study, control schemes of the energy-efficient DSTED process for separating acetonitrile/methanol/benzene with multi-azeotrope are investigated. Firstly, a dual-temperature control strategy is proposed based on the existing single temperature control with feedforward scheme. Temperature difference control strategy is then studied to effectively reduce the offset of product purities for the disturbances of feed composition. Following that, a double-temperature difference control strategy is studied to maintain the product purities. Finally, the comparisons of product purities and energy consumption are introduced to clearly assess the stability and controllability of the different temperature control structures. Dynamic performances show that the temperature difference control structure has the best performance facing the ±10% feed disturbances.

Flash/distillation for separating 2-pentanone/4-heptanone/water azeotropic mixture based equilibrium data and process design

4-heptanone and 2-Pentanone are promising organic solvents due to their high thermal stability. Due to the lack of binary interaction parameters between 4-heptanone and 2-Pentanone, the vapour-liquid equilibrium experiment is measured for 4-heptanone and 2-Pentanone in this work. The binary interaction parameters are obtained by UNIQUAC model, Wilson model and NRTL model regression. Based on the heterogeneous characteristics of the system, two kinds of steady-state processes are designed. Based on the minimum annual cost, TAC, carbon emissions and thermodynamic efficiency of the corresponding steady-state process were calculated, and for different feeding ways were compared. In addition, the internal cycle dynamic control (basic control structure and dual temperature control structure) are explored. The anti-disturbance performance of the system is detected by introducing 5% the feed disturbance. The result shows that the dual temperature control structure has a good anti-disturbance ability in the face of feed and composition disturbance. The interaction parameters obtained by experimental regression provide a theoretical basis for the design of steady-state process. Flash/distillation technology provides guidance for industrial purification of 2-pentanone/4-heptanone.

Design and control of a novel side-stream extractive distillation column for separating methanol-toluene binary azeotrope with intermediate boiling entrainer

It is innovative and important to perform complex binary azeotrope separation via single distillation column. In the article, design and control of a novel and simple side-stream extractive distillation (SSED) column with extraction and solvent recovery function is investigated for the separation of methanol and toluene binary azeotrope with intermediate boiling triethylamine (Et3N) as solvent. The steady-state design parameters of the novel SSED column are optimized and obtained with the objective of minimal total annual cost (TAC) via conventional sequential iterative procedure. On the basis of steady-state design, four single-end temperature control structures (STCS), four dual-temperature control structures (DTCS) and four dual-composition control structures (DCCS) are developed and established successively to overcome the operation and control challenges caused by the novel scheme. To seek the robust control, the dynamic performance analysis on account of the above control structures is conducted for the SSED column, which is evaluated for feed flowrates and composition disturbances. The results show that the control performance of DCCS is significantly superior to that of STCS and DTCS while the integral squared error (ISE) and energy-consuming effect are equivalent, and can take shorter time to bring the product purities back to the original steady state in coping with specified feed disturbances.

Scalable fabrication of organic solar cells based on non-fullerene acceptors

Organic solar cells have recently experienced a substantial leap in power conversion efficiency, in part driven by formulations with new non-fullerene acceptors. This has brought the technology past the psychologically important mark of 15% efficiency for unscaled laboratory devices, and the results are stimulating another burst of research activity. Whether this will propel the technology into a viable commercial contender has yet to be determined, but to realize the potential of organic solar cells for utility scale application, fabrication using scalable processing techniques has to be demonstrated—otherwise, the passing of the 15% mark will eventually leave no more lasting impact than what the passing of the 10% mark did. Thus, addressing the scaling lag between the 15% cell efficiencies of lab-scale devices on rigid glass substrates fabricated using non-scalable techniques and the 7% efficiencies of scalably fabricated devices on flexible substrates is key. Here, we discuss the concept of scalability and give an account of the literature on non-fullerene acceptor devices fabricated with scalable methods and materials. On the basis of this, we identify three crucial focus points for overcoming the lab-to-fab challenge: (i) dual temperature control, i.e. simultaneous control of the ink and substrate temperatures during deposition, (ii) systematic in situ morphology studies of active layer inks with new, green solvent formulations during continuous deposition, and (iii) development of protocols for continuous solution processing of smooth, transparent interfacial layers with efficient charge transfer to the active layer. Combining these efforts and in general accompanying such studies with stability analyses and fabrication of large-area, scalably processed devices are believed to accelerate the relevance of organic solar cells for large-scale energy supply.

Experimental study on characteristics of a dual temperature control valve in the chilled water system of an air-conditioning unit

The excess flow of water increases the energy consumption of water pumps in the chilled water systems of air-conditioning units. This paper proposes a strategy to control the chilled water flow rate of a fan coil unit (FCU) using a control valve. A physical simulation test bench was built to verify valve control and energy-saving effects. Results showed that the control valve could effectively regulate the flow rate of chilled water, improve the temperature difference (delta-T) between supply and return water, and reduce the energy consumption of the chilled water pump. With a supply water temperature of 7 C and low (325 m3⋅h−1), medium (500 m3⋅h−1), and high (600 m3⋅h−1) FCU air velocity levels, the average delta-T values were 4.79 °C, 4.39 °C, and 4.97 °C, respectively, and the energy consumption of the chilled water pump decreased by 12.20%, 11.31%, and 10.66%, respectively. With medium air velocity and supply water temperatures of 7 °C, 8 °C, and 9 °C, the average delta-T between supply and return water was 4.39 °C, 3.56 °C, and 3.33 °C, respectively, and the energy consumption of the chilled water pump decreased by 11.31%, 5.10%, and 7.80%, respectively. These research results provide useful insights in relation to the problem of excess chilled water flow identified above.

Temperature-Controlled Solvent Vapor Annealing of Thin Block Copolymer Films.

Solvent vapor annealing is as an effective and versatile alternative to thermal annealing to equilibrate and control the assembly of polymer chains in thin films. Here, we present scientific and practical aspects of the solvent vapor annealing method, including the discussion of such factors as non-equilibrium conformational states and chain dynamics in thin films in the presence of solvent. Homopolymer and block copolymer films have been used in model studies to evaluate the robustness and the reproducibility of the solvent vapor processing, as well as to assess polymer-solvent interactions under confinement. Advantages of utilizing a well-controlled solvent vapor environment, including practically interesting regimes of weakly saturated vapor leading to poorly swollen states, are discussed. Special focus is given to dual temperature control over the set-up instrumentation and to the potential of solvo-thermal annealing. The evaluated insights into annealing dynamics derived from the studies on block copolymer films can be applied to improve the processing of thin films of crystalline and conjugated polymers as well as polymer composite in confined geometries.

Dynamic Control of Hybrid Processes with Liquid–Liquid Extraction for Propylene Glycol Methyl Ether Dehydration

Dynamic control structures are significant for liquid–liquid extraction combined with heterogeneous azeotropic distillation (LEHAD) and liquid–liquid extraction combined with extractive distillation (LEED) processes, which were proposed in our previous work for the separation of the azeotrope of propylene glycol methyl ether and water. However, there may be complications regarding the dynamic controllability of the two hybrid processes, and this work investigates the dynamic control structures. For the LEHAD process, an improved composition–temperature cascade control structure using the ratio of the reboiler duty to feed flow (QR/F) can realize effective control when feed disturbances are added. For the LEED process, the improved dual temperature control structure with QR/F was able to handle the disturbances well. Moreover, a comparison between the two hybrid processes was made according to the dynamic controllability, and the integral of the squared errors was calculated. The results show that the LEHA...

Development of the Knudsen effusion methodology for vapour pressure measurements of low volatile liquids and solids based on a quartz crystal microbalance

The principle of operation, concepts and recent developments of the Knudsen effusion methodology for the vapour pressure measurement of ionic liquids and other low volatile liquids and solids are presented. A new version of a Knudsen effusion apparatus, coupled with a quartz crystal microbalance, which is used for a reliable measurement of the mass flow from a Knudsen effusion cell, is described in detail. In the new system, designed and optimized for the vapour pressure measurement of ionic liquids, it is possible to measure the vapour pressure of small samples using very short effusion time over a wide temperature range. This apparatus allows the vapour pressure measurements using step-temperature and continuous-temperature modes that have the advantage of reducing the measurement time interval and minimize the effect of a sample degradation. A significant number of improvements on the performance and capability for the vapour pressure measurements of ionic liquids has been implemented: in situ temperature control of the vacuum chamber for a better stability of background signal; a new design of a stainless steel effusion cell to decrease the reactivity and sample decomposition; dual temperature control ensuring a positive temperature gradient between bottom and top of the cell in order to avoid the ionic liquids condensation on the effusion cell lid and significantly improved stability of the time frequency derivative at high temperatures; Installation and test of a mass flow tube, on the top of the outlet of the cell lid oven block in order to increase the mass sensitivity coefficient of QCM. The tests and benchmarking concerning the measurement of vapour pressures of ionic liquids performed with [C2mim][NTf2] indicate that the described Knudsen effusion apparatus and methodology is able to produce reproducible and reliable experimental vapour pressure data with an accuracy and quality similar than the achieved in the measurements with low volatile solids. The effect of the improvements on the performance of the Knudsen effusion apparatus was tested and evaluated by the comparison of the vapour pressure results of 1,3,5-triphenylbenzene and 1-ethyl-3-methylimidazolium with the available literature data.

Control Structures Evaluation for a Salt Extractive Distillation Pilot Plant: Application to Bio-Ethanol Dehydration

This paper addresses the challenge of evaluating control structures for a salt extractive distillation column producing absolute ethanol for use as biofuel. A sensitivity analysis aided with designing a pseudo-binary distillation pilot plant and examining the conceived process and the influence of the reflux ratio on both product purity and energy consumption. We compare three control structures for inferential tracking of the distillate composition: a dual-temperature control with an RV (reflux/boilup) structure and two single-end temperature control configurations, and their performance is measured using deterministic indicators. The result is the proposal of a pilot plant design for treating 15 kg/h of a diluted mixture with mole fraction of ethanol equal to 0.2 and assuming a column efficiency of 50%. The R/F (reflux to feed ratio) configuration is the best control structure, given that its corresponding performance indicators conduct lowest steady-state errors, less oscillating responses, and reduced settling times. For this configuration, the reflux flow rate is rationed to the feed flow rate, and the temperature is controlled manipulating the distillate flow rate. Even subject to perturbations, the energy consumption of the plant remains close to the nominal value. The three evaluated control structures consistently met international quality standards for fuel ethanol and enhanced the use of salts in ethanol dehydration.

Influence of the Location of the Internal Temperature Control Loop on the Performance of the Dual Temperature Control for Feed Temperature Disturbance

Influence of the Location of the Internal Temperature Control Loop on the Performance of the Dual Temperature Control for Feed Temperature Disturbance

Dual adaptive temperature control of magnesium reduction furnace

To propel the automation of production and save energy consumption, the dual adaptive control problem of the magnesium reduction furnace is studied in this paper. The detailed temperature control process is analysed and divided into four phases. The control process of one area of the furnace is described by a simplified single-in-single-out (SISO) discrete model with large input delay. With sufficient input/output experiment data, the optimal model structure and parameters are identified offline. The dual generalised minimised variance (GMV) controller which can cope with non-minimum phase plants with time delay is chosen in the temperature control of the magnesium reduction process. The control performance is verified by both simulations and experiments. The results show that the dual GMV controller is superior to a cautious controller or a conventional PID controller.

Dual adaptive temperature control of magnesium reduction furnace

To propel the automation of production and save energy consumption, the dual adaptive control problem of the magnesium reduction furnace is studied in this paper. The detailed temperature control process is analysed and divided into four phases. The control process of one area of the furnace is described by a simplified single-in-single-out (SISO) discrete model with large input delay. With sufficient input/output experiment data, the optimal model structure and parameters are identified offline. The dual generalised minimised variance (GMV) controller which can cope with non-minimum phase plants with time delay is chosen in the temperature control of the magnesium reduction process. The control performance is verified by both simulations and experiments. The results show that the dual GMV controller is superior to a cautious controller or a conventional PID controller.

Comparison of Two Types of Control Structures for Benzene Chlorine Reactive Distillation Systems

The “neat” operation of the two-reactant reactive distillation column has better steady-state economics, while it presents a challenge for design, optimization, and control of the process. Based on the optimal economic design, the dual-composition control structure and dual-temperature control structure are designed respectively for the benzene chlorine consecutive reactive distillation process. The effectiveness and robustness are analyzed comparably for the disturbance resistance in terms of changes of production rate and feed composition. Results show that dual-temperature control with propose selection of tray temperatures and the optimal profile of the set point can provide better transient process performance than the composition control structure.