Bypass Reactor Research Articles

Kinetics and reactor modeling of a Pd-Ag/Al2O3 catalyst during selective hydrogenation of ethyne

The selective hydrogenation of ethyne is one process to remove traces of ethyne from steam cracker cuts during the production of ethene. Even though Pd-Ag/Al2O3 catalysts are predominantly used in industrial C2-tail end-selective hydrogenation reactors, a detailed kinetic study with this catalyst type has not yet been published in the open literature. For this reason, kinetic measurements were carried out on a Pd-Ag/Al2O3 catalyst in an integral fixed bed reactor at different process conditions for the selective hydrogenation of ethyne. The results of these measurements were fitted on different kinetic models ranging from a classical Hougen–Watson, Langmuir–Hinshelwood and Rideal–Eley approach up to simple power law equations. The kinetic model with the best fit was found by statistical and thermodynamical evaluations of all models and their respective kinetic parameters. This model is based on a Langmuir–Hinshelwood reaction mechanism involving two different active sites for the hydrogenation of ethyne and ethene. The kinetic measurements were not dependent on mass and heat transfer as demonstrated by using the criteria from Mears and the Weisz–Prater as well as for the Damkoehler numbers in 3rd and 4th order. Finally the performance of a bypass reactor, running in parallel to an industrial C2-tail end-selective hydrogenation reactor, was successfully calculated with a reactor model.

Verification of a Design Technique of an SFCL System With a Copper Bypass Reactor

This paper presents a study on design technique of superconducting fault current limiters (SFCLs) with a bypass reactor. The SFCL system consists of a non-inductive superconducting coil and a copper coil as a bypass reactor. Since typical resistive SFCL impedance is too high to adopt the existing grid protection scheme, a bypass reactor is required to adjust the impedance. The superconducting coil is a current-driven passive element; hence, connecting a bypass reactor in parallel affects the current sharing between the superconducting coil and the copper reactor. We proposed a design technique to estimate the generated impedance considering the current sharing. The technique is based on a SPICE simulation and thermal finite element analysis (FEA). By comparing to the test result with two kinds of bypass reactors, it is confirmed that the proposed method can simulate all currents and voltages properly. As a result, a case study was conducted on the design of the SFCL system, rated on 13.2 kV/2.5 kA was being considered as a new distribution grid in Korean metropolitan areas.

이종초전도 코일을 이용한 하이브리드형 한류기의 제작 및 단락실험

Hybrid fault current limiters (FCL) have been researched at Yonsei University. The hybrid FCL has advantages such as having a rapid response to a sudden fault situation and a fast recovery time from a quench. It consists of an asymmetric HTS coil, a switching module, and a bypass reactor. The asymmetric HTS coil is wound with two different types of HTS wires in an opposite direction so that it has nearly zero inductance at the superconducting state. When the quench occurs at the fault state, a strong magnetic field is generated from the asymmetric coil because of different quench characteristics of two HTS wires, and then a repulsive force is induced in the switching module. The force opens the switch and the fault current is pushed into the bypass reactor. In this research, we analyzed the cause of the repulsive force and confirmed, experimentally and computationally, that the magnitude of a repulsive force is varied by changing the gap distance between the asymmetric coil and the switching module. By using the FEM simulation, we calculated the repulsive force with respect to the gap distance and verified that the effect of the gap distance. Then, short circuit test was carried out to confirm the correct operation of the fast switch.

Characteristic Comparison of the Superconducting Fault Current Limiter With Various Bypass Reactors

A resistive superconducting fault current limiter (SFCL) has two drawbacks-relatively higher impedance and longer recovery time than the requirement of the electric power system. A parallel-connected bypass reactor (BPR) can be a solution to both problems. As a stage of proof-of-concept, an SFCL comprised of an YBCO S/N switch and a Bi2223-BPR had been presented in the former paper. Although the previous one has shorter recovery time, the generated impedance after a fault was too low to satisfy the requirement of the power system. To apply the SFCL into the power system, the SFCL has proper impedance during the fault. Therefore, we proposed bypass reactors to achieve higher impedance than the previous one in this paper. The SFCLs with a bypass reactor were fabricated and short-circuit test with the SFCLs were conducted. The test results were compared in point of current limiting characteristics and recovery. This research would be applied to a conceptual design of BPR.

A Study on the Non-Inductive Coils for Hybrid Fault Current Limiter Using Experiment and Numerical Analysis

A Hybrid fault current limiter (FCL) proposed by our group previously is composed of a superconducting coil, a fast switch and a bypass reactor. The superconducting coil wound with two kinds of HTS wire has zero impedance when normal current flows in the coil. However, different quench characteristics of the HTS wire generate magnetic flux in the coil when fault current flows in the coil. As a result, the fast switch was opened by the repulsive force applied to the aluminum plate above the coil. In previous studies, our group verified operating characteristics and feasibility of the fast switch. In this paper, comparison of pancake type and solenoid type non-inductive coil wound with two kinds of the HTS wire was performed by using short-circuit test and finite element method. From these results, short-circuit characteristic of a coil can be acquired and magnitude of the repulsive force and magnetic field can be analysed.

Protection of semiconductor converters for controlled bypass reactors

Possible ways of protecting thyristor converters in systems for magnetizing 110 – 500 kV controlled bypass reactors during switching and automatic reclosing are examined based on experience with the development of equipment, line tests, and mathematical modelling.

Novel Bridge-Type FCL Based on Self-Turnoff Devices for Three-Phase Power Systems

In this paper, a novel bridge-type fault current limiter (FCL) based on self-turnoff devices for three-phase power systems is proposed. Compared with the SCR-based bridge type FCL, the new one is smaller in size, better in dynamic performance, and simpler in control method and control circuitry. The novel FCL is composed of a rectifier bridge-a dc-limiting reactor and one/three bypass reactor/reactors-for a single-phase/three-phase structure. The increasing speed of the fault current just after the occurrence of a fault is limited by a dc-limiting reactor, whose inductance is designed according to the response speed of the control circuit. The bypass reactors are designed in terms of the requirements of the coordination of protective relays. The source currents during limiting events are sinusoidal and do not have any harmful effects on the overall protection schemes, impedance relays, and conventional current and voltage transformers. The topologies of the proposed FCL for three-phase four-wire and three-phase three-wire power systems are investigated, respectively, in detail. Parameter design and optimization are presented. The fault and fault-mode judgment method is described briefly. Simulations and experimental results prove the feasibility of the new FCL.

Design and Manufacture of a Superconducting Fault Current Limiter With Bypass Reactor by Employing Two Different Types of HTS Wires

A resistive superconducting fault current limiter (SFCL) using Bi2223 wire and YBCO coated conductor has been developed. The SFCL has two coils; one is a bifilarly wound coil wound using coated conductor, and the other is typical inductive coil using Bi2223 wire. The bifilar coil plays the role of switching when a fault occurs, while it has a very small impedance in the normal operation. On the other hand, the inductive coil using Bi2223 wire has a very small resistance but a large inductance. The two coils were connected in parallel. Current flows mainly through the bifilar coil during normal operation. A partial fault current flows through Bi2223 coil because the resistance of the coated conductor bifilar coil rises. Two types of FCL were manufactured and tested; a conventional bifilar one, which has only one coil using a coated conductor, and the proposed one, which has two coils. The proposed one has a faster recovery than the conventional one.