Showing papers on "Contactor published in 2020"

Hollow Fiber Membrane Contactors for Post-Combustion Carbon Capture: A Review of Modeling Approaches

Abstract: Hollow fiber membrane contactors (HFMCs) can effectively separate CO2 from post-combustion flue gas by providing a high contact surface area between the flue gas and a liquid solvent. Accurate models of carbon capture HFMCs are necessary to understand the underlying transport processes and optimize HFMC designs. There are various methods for modeling HFMCs in 1D, 2D, or 3D. These methods include (but are not limited to): resistance-in-series, solution-diffusion, pore flow, Happel's free surface model, and porous media modeling. This review paper discusses the state-of-the-art methods for modeling carbon capture HFMCs in 1D, 2D, and 3D. State-of-the-art 1D, 2D, and 3D carbon capture HFMC models are then compared in depth, based on their underlying assumptions. Numerical methods are also discussed, along with modeling to scale up HFMCs from the lab scale to the commercial scale.

Mass transfer performance and correlation for CO2 absorption into aqueous 3-diethylaminopropylamine solution in a hollow fiber membrane contactor

Abstract: 3-Diethylaminopropylamine (DEAPA), a diamine with high reaction rate and large absorption capacity, was investigated in this work to evaluate its CO2 absorption mass transfer performance in a hollow fiber membrane contactor in terms of the CO2 absorption flux (JCO2). A series of experiments were conducted at various operation conditions and the effects of several influential parameters on JCO2 were examined and discussed in detail, including the liquid flow rate, the inlet gas flow rate, amine concentration, feed liquid temperature, CO2 partial pressure, lean CO2 loading, and membrane contactor height. Experimental results indicated that lean CO2 loading and membrane contactor height have negative effect on the total mass transfer performance since the value of JCO2 decreases with the increase of these two factors, while the other five parameters exhibit positive effect and their increase lead to the increase of JCO2 values. In addition, a numerical correlation was established to predict the overall gas phase mass transfer coefficient and the CO2 absorption flux, and the average absolute deviation (AAD) is 6.84%.

Intelligent Three Tie Contactor Switch Unit-Based Fault Detection and Isolation in DC Microgrids

Abstract: Faults in dc microgrids require quicker interruption than those in traditional ac power systems. This is due to the reduced stiffness of dc microgrids being powered by low inertia distributed energy resources interfaced through power electronic converters. For a high impedance fault, the limited magnitude of the fault current poses additional challenges in detection and identification of fault location in the system, with difficulty in distinguishing the fault condition from the normal operating condition. This article proposes a new cost-effective protection system for fast identification, selective isolation of short circuit and high impedance faults, and system restoration in such dc microgrids. It is achieved through proper coordination of source converters with intelligent three tie contactor switch units (ICU) and there are no solid-state circuit breakers in action. The high impedance faults are identified through multi resolution analysis of the locally measured current signals with discrete wavelet transform and K -nearest neighbor-based classifier at each source converter and contactor. The selectivity is achieved through adaptive resistance time curves set by the programmable relay units installed at each ICU node in the system.

Electric Power Consumption and Current Efficiency of Electrochemical and Electrobiological Rotating Disk Contactors Removing Nutrients from Wastewater Generated in Soil-Less Plant Cultivation Systems

Abstract: The study was conducted in a one-stage rotating electrobiological disk contactor (REBDC) and a rotating electrochemical disk contactor (RECDC). Synthetic wastewater with characteristics similar to the wastewater from soil-less cultivation of tomatoes was used in the experiment. Current efficiency (CE) values, that express the denitrification performance of bio- and electrochemical reactors, were higher in the electrobiological contactor than in the electrochemical one. Combining biological processes with electrochemical processes in the electrobiological contactor resulted in almost 20% higher current efficiency in the contactor operated at a density of 0.63 A/m2 and hydraulic retention time (HRT) = 4 h. The study showed that, in both the electrochemical and the electrobiological contactor, current density increase and hydraulic retention time extension increased electric power consumption (E) during phosphorus compounds removal and simultaneously lowered current efficiency.

Optimization and Control of a Z-Source, Ultrafast Mechanically Switched, High-Efficiency DC Circuit Breaker

Abstract: A novel design of the Z-source circuit breaker topology is presented to minimize on -state losses of the protection device. An ultrafast mechanical switch is proposed to commutate the fault current and improve the controllability of the circuit breaker. Replacing the power thyristor in the Z-source circuit breaker and integrating an advanced control scheme reduces energy losses with a low-resistance mechanical contactor. The proposed design facilitates bidirectional current flow, enhances control capability for distributed energy resources, and improves ride-through capabilities during load transients. Z-source circuit breakers utilize an impedance network to create a forced current zero crossing in the event of a fault, allowing the inline thyristor to isolate the fault from the source through reverse bias. However, full load current flows through the thyristor, resulting in high loss and heat generation. The concept is validated, and a proper control scheme is developed for this circuit breaker through an analytical estimation model of the system dynamics during a fault. Simulation and modeling are performed in power systems computer aided design (PSCAD) and piecewise linear electrical circuit simulation (PLECS). Finally, an experimental laboratory prototype is tested to validate the analytical and simulation models and certify the control logic.

Electrical Performance Degradation Model and Residual Electrical Life Prediction for AC Contactor

Abstract: The electrical performance of ac contactor degrades under electric load stress, and the degradation data contains the information concerning the residual electrical life (REL). This article proposes an online reliability evaluation method that relates contact erosion loss (CEL) to electric load stress, performance degradation process, and electrical life prediction. First, the degradation variable of normal distribution is constructed by segmenting accumulation of CEL, and a degradation model based on Wiener process is established. With the knowledge of the first accumulation of CEL beyond failure threshold, the probability density function (PDF) of REL for ac contactor is presented, and the point estimation value and an interval estimation value of REL are calculated. Second, a simulation electrical life test is conducted using Monte Carlo method, and results show that the electrical performance degradation model and the prediction method of REL raised in this article are effective. Finally, CELs weighed in the electrical life test are applied in the prediction process of REL of ac contactor and the prediction error is proven acceptable in practical application. Compared with the neural network-based methods, the proposed method provides an intuitive and simple mathematical model with clear physical interpretations.

Removal of nickel from water using rotating packed bed contactor: Parametric studies and mode of operations

Abstract: Performance of rotating packed bed (RPB) contactor in the removal of nickel from water was investigated from two aspects: i) effect of operating parameters, and ii) effect of mode of operation. The results showed that the performance of RPB was highly governed by the rotational speed and activated carbon dosage. The increase in centrifugal force generated by the RPB from 200 rpm – 875 rpm was found to displace the activated carbon to the outer side of the RPB, which reduced the liquid flow path length and contact time between the packed bed and nickel solution and this reduced the removal efficiency. Nevertheless, a further increase in rotational speed from 875 rpm to 1200 rpm improved the removal efficiency as the enhancement in mass transfer process had outperformed the effect given by reduced path length. Higher activated carbon dosage also improved RPB performance by providing higher number of adsorption sites, as well as improving the packing density of the packed bed which minimized the reduced path length effect. The study also revealed that the mode of operation for a RPB contactor has crucial impact on the nickel adsorption. The removal efficiency was found to follow the sequence of multiple cycle mode operation > batch mode operation > continuous mode operation, as a result of better contact time and consistent contact between the solution and the packed bed.

Application of Taguchi method for the optimization of Fe2+ removal from contaminated synthetic groundwater using a rotating packed bed contactor

Abstract: Malaysia contains elevated levels of iron in shallow groundwater in the range of 3-7 mg Fe/L compared to USEPA safe limit of 0.3 mg Fe/L. Air Kelantan Sdn Bhd in Malaysia uses “River Bank Filtration” (RBF) technology to harvest hyporheic water. RBF treatment removes turbidity of the river water through river bed acting as a filter, but is unable to remove the Fe from the harvested water. This work proposes a technology to reduce Fe concentration in the extracted water using granular activated carbon in a laboratory scale rotating packed bed contactor (RPBC). Taguchi method was used for optimizing operating conditions for adsorption of Fe onto activated carbon in RPBC system. Taguchi optimisation results showed that a removal efficiency of 87% Fe from a 50 mg Fe/L concentration could be achieved by RPBC at initial pH of 6.5, feed rate of 40 L/h, rotating speed of 1600 rpm and packing density of 357 kg/m3.

Energy-Efficient Eco-Friendly Zero-Holding-Energy Magnetic Contactor for Industrial and Vehicular Applications

Abstract: This paper reports an energy-efficient permanent magnet (PM) zero-holding-energy magnetic contactor (ZMC) that consumes no energy while maintaining an open or closed state. Conventional solenoid magnetic contactor (MC) technology has several critical drawbacks, including high continuous energy consumption, continuous vibration, and low reliability. The proposed ZMC substantially reduces energy consumption and heat generation, produces no vibration, and provides increased reliability. Traditional MC analysis typically requires computationally expensive finite element analysis (FEA). To reduce the analysis costs, a recently proposed fast and accurate nonlinear transient path energy method (NT-PEM) is utilized to significantly reduce analysis time and costs. Analysis accuracy was verified experimentally using a fabricated ZMC prototype. The economic and environmental benefits of the proposed ZMC confirm its significant potential as an energy-efficient eco-friendly alternative to traditional MC technology. ZMC is particularly promising for vehicular micro-grids due to the prolongation of the lifetime of batteries owing to reduced energy consumption.

Neural Network-Based Co-Simulation Technology for Intelligent Contactors

Abstract: A simulation method of an intelligent contactor is presented by using a neural network to fit the proven relationship among the flux linkage, the electrical current, and the moving core displacement of a contactor in this article. First, the neural network algorithm is trained by the operational data of a contactor driven by a basic training circuit to solve the coil current. Then, a dynamic simulation program of the contactor model is constructed via combining the algorithm and dynamic differential equations. On this basis, by means of the co-simulation technology, the point-by-point closed-loop simulation between the control module and the contactor model is carried out. Accordingly, the co-simulation of an intelligent contactor based on a neural network is completed. The simulation method can avoid the complex finite-element modeling of a contactor and realize the model extraction of an arbitrary contactor. The extracted model can be combined with a drive circuit and any control strategy to perform the co-simulation, which is convenient for the flexible design of hardware control circuits and software control strategies of various intelligent contactors.

Switching Behavior of a Gas-Filled Model DC-Contactor Under Different Conditions

Abstract: The switching behavior of gas-filled contactors was investigated using a model switch High-speed imaging and spectroscopy provided information regarding the characteristics of the arc plasma The impact of external magnetic fields, fill gas, fill pressure, and current amplitude was investigated The most important factor, influencing the switching behavior for currents below 100 A, is provided by external magnetic fields, which increase arc voltage and arc instability considerably The observed changes of the side-on profiles of the characteristic emission lines indicate changes in particle densities and arc temperature

Research on the Influence of Vibrations on the Dynamic Characteristics of AC Contactors Based on Energy Analysis

Abstract: Aimed at the influence of the vibration environment on the performance degradation of AC contactors, the purpose of this study is to investigate the failure mechanism of AC contactors under vibration conditions. During the closing process of AC contactors, the impact energy of the iron core may change due to the vibration stress, which may have an uncertain effect on the parameters of the dynamic response characteristics of the contact, and affect the working performance and service life of AC contactors. In this paper, a double-E AC contactor is selected as the research object. Based on the calculation of the transient magnetic field of the electromagnetic mechanism, an energy distribution model of the AC contactor is established. Based on this, considering the influence of vibrations and the input electrical energy under different closing phase angles, the energy model of the iron core collision under simple harmonic oscillation is investigated. The steady-state vibration energy at different frequencies and accelerations is calculated, and its influence on the dynamic response parameters of the AC contactor is analyzed. Finally, the simulation model is verified by experimental data. The results show that the energy analysis model can effectively reflect and explain the uncertainty of the dynamic characteristics of AC contactors under vibrations, from the perspective of the mechanism.

Larger contactor area increases low-frequency vibratory sensitivity in hairy skin.

Abstract: Background In research, assessing vibratory cutaneous sensitivity is an important research branch to quantify various diseases or to develop devices for pattern recognition. The measured vibration perception thresholds (VPTs), however, are subjective and usually result in a large data variability. This might induce difficulties to detect differences, for example, when comparing different anatomical locations. Hence, a higher ability to detect changes is desirable. Another feature of VPTs is spatial summation, but in the literature it is controversially discussed whether or not this phenomenon is also present in the lower frequency range. For these reasons, the present study aimed to investigate whether an enlarged matrix contactor area (measured at the hairy skin) induces improvements in subjective sensitivity using high and low frequencies, and whether a large contactor area is better able to identify changes of VPTs than a small contactor area of a single contactor. For each frequency, we hypothesized an increased sensitivity for the matrix compared to the single contactor. We also hypothesized that changes can be better-detected between the anatomical locations when using the matrix than the single contactor. Methods Twenty healthy and young participants voluntarily took part in this study. Three anatomical locations at the torso were measured at the middle aspect of the lower back, middle lateral aspect of the upper arm, and the region just below the armpit. At each location, two frequencies (30, 200 Hz) and two contactor conditions (single contactor: 0.48 cm2 , contactor matrix: 9 × 0.48 cm2 = 4.32 cm2) were tested in a randomized order. Results Supporting our hypothesis, we found that improved cutaneous sensitivity after increasing the contactor size occurs not only at high, but also at low frequencies at all anatomical locations. Large contactor sizes resulted in higher sensitivity and in a superior ability to detect changes. The superior behavior of the matrix to exhibit a lower variability could not always be proven. This work may be relevant for future studies aiming to identify changes of VPTs in various patient groups, for example.

CO2 Capture From Air in a Radial Flow Contactor: Batch or Continuous Operation?

Abstract: The capture of CO2 from the atmosphere via Direct Air Capture using solid supported-amine sorbents is an important option to reduce the atmospheric concentration of CO2. It addresses CO2 emissions from dispersed sources and delivers a location independent sustainable carbon source. This study evaluates the possibility for a continuous adsorption process for direct air capture in a radial flow contactor, using both batch and continuous mode of operation. Gas and solids flow were varied to determine hydrodynamic feasible operating conditions. The operation modes are compared by their capture efficiencies in the optimal adsorption time range of 0.5 t_sto^B and 1.5 t_sto^B. A 15-25% lower capture efficiency is found for a continuous process compared to a batch process in the relevant range for direct air capture. This decline in gas-solid contact efficiency is more pronounced at longer adsorption time and higher superficial gas velocity. Overall, a batch process is preferred over a continuous process in the majority of operating conditions.

Optimal design and control of a new permanent magnet AC contactor with forced breaking mechanism

Abstract: This study addresses the design of a new type of permanent magnet contactor, which uses forced breaking to overcome failure conditions. A multi-objective optimisation method based on the genetic algorithm is used to design the contactor considering the effects of average closing time, average breaking time, impact energy, Joule heat and contactor volume. Four prototypes have been fabricated according to the optimised parameters. A control circuit is developed to increase breaking reliability. The circuit is designed as two separate modules: a normal working module and a protection module. The former is used during the normal contactor operation and the latter is used for forced breaking protection. Breaking failures are detected by comparing the time delay between the breaking control voltage and the auxiliary contact voltage. A durability experiment has been conducted to verify the protection function of the proposed PM contactor. Experimental results show that the normal working module fails to break the contactor in the last testing cycle. However, under the actuation of the protection mechanism, the contactor is forced to break and the power circuit can be successfully switched off.

Experimental study of gas dehydration via PDMS/CaCO3 NP-coated PVC hollow fiber membrane contactor

Abstract: In this study, diethylene glycol (DEG) as an absorbent was used for gas dehydration. For this purpose, hollow fiber membrane contactor was fabricated from polyvinyl chloride. The effect of surface modification with polydimethylsiloxane in the presence of calcium carbonate nanoparticles, relative humidity percentage of inlet air, variation in the gas and liquid flow rates in a dehydration process were investigated. The surface modification of the membranes increased the contact angle from 64° to 101° and a liquid entry pressure of as high as 7 bar was achieved. Moreover, increasing the gas flow rate led to a significant enhancement in absorption performance. Conversely, it was observed that the liquid flow rate had marginal effect on the mass transfer efficiency and flux i.e. RM+L/RM+G = 0.001–0.01. This revealed that the mass transfer resistance was not controlled by the liquid phase. Although higher fluxes were observed for the unmodified membrane contactor, the membrane modified with polydimethylsiloxane and calcium carbonate nanoparticles (i.e. M0.5-1) was more effective compared to the neat membrane (M0) in a 35-day long-term performance test i.e. ηM0.5-1 ≈ 0.12 versus ηM0 = 1.0. The results show that the applied technique for fabricating the hollow fiber membrane contactor can be a promising technique in gas conditioning.

Puffer type gas circuit breaker

Abstract: To prevent interfering with operation of an insulated nozzle, make it less likely to be damaged, prevent high-temperature, high-pressure gas from flowing around the insulating nozzle, and prevent a backflow of an arc-extinguishing gas around a main contactor of a stationary side main contactor or a drive side main contactorSOLUTION: A puffer type gas circuit breaker includes: an insulating nozzle 1, installed on a driving-side main contactor 4, for causing an arc-extinguishing gas to flow when a stationary-side arc contactor 5 and a driving-side arc contactor 6 separate from each other and extinguishing arc discharge by blowing the arc-extinguishing gas between the fixed side arc contactor 5 and the driving side arc contactor 6; and a guide 2 for installing a stationary-side main contactor 3 and the stationary-side arc contactor 5 at a position facing the driving-side main contactor 4 and the driving-side arc contactor 6 The insulating nozzle 1 includes a thin-walled part 10 that contacts the guide when it is openSELECTED DRAWING: Figure 1

High-voltage DC contactor

Abstract: The invention provides a high-voltage DC contactor. The high-voltage DC contactor comprises two main contacts, contact bridges and a transmission part and also comprises a sealing cavity, wherein the two contacts are respectively and electrically connected with two connection points in a main circuit and are isolated with each other, the contact bridges are respectively contacted with or separated from the two main contacts to achieve conduction or disconnection of the two main contacts, the transmission part is used for driving the contact bridges to be respectively contacted with or separated from the two main contacts, the sealing cavity is filled with inertia gas, and the two main contacts and the contact bridges are all arranged in the sealing cavity. The ceramic sealing cavity is filled with a certain pressure of nitrogen-hydrogen hybrid inertia gas, the hybrid inertia gas can have a good cooling effect on arc particles so that an arc can be extinguished rapidly, and an experiment shows that the arc is extinguished within 0.5 millisecond.