Carbon Stripper Research Articles

High Temperature Characteristics of a Carbon Strip Sliding against Copper with Electrical Current

Abstract High temperature and arc discharge are two important phenomena that occur in the electrical sliding processes. The extensive adhesive wear, due to high temperature, and arc erosive wear are two mechanisms that potentially cause severe wear of copper-carbon strips with electrical current. Herein, we describe a series of experiments done to better understand the high-temperature characteristics of a carbon strip rubbing against copper with electrical current passing from one to the other. During the experiments, the temperature of the copper-carbon strips was recorded and the wear volumes of carbon strips were measured. The results show that the carbon strip wear volumes are larger when electrical currents pass through the strips. To study how the temperature affects the wear of carbon strips, several wear tests were conducted at an elevated temperature both with and without electrical currents. The results show that adhesive wear is the main mechanism to cause severe wear of carbon strips.

Graphitization of amorphous carbon by swift heavy ion impacts: Molecular dynamics simulation

Stable C-C bonds existing in several sp hybridizations place carbon thin films of different structural compositions among the materials most tolerant to radiation damage, for applications in extreme environments. One of such applications, solid state electron stripper foils for heavy-ion accelerators, requires the understanding of the structural changes induced by high-energy ion irradiation. Tolerance of carbon structure to radiation damage, thermal effects and stress waves due to swift heavy ion impacts defines the lifetime and operational efficiency of the foils. In this work, we analyze the consequences of a single swift heavy ion impact on two different amorphous carbon structures by means of molecular dynamic simulations. The structures are constructed by using two different recipes to exclude the correlation of the evolution of sp2-to-sp3 hybridization with the initial condition. Both initial structures contain approximately 60% of sp2-bonded carbon atoms, however, with different degree of clustering of atoms with sp3 hybridization. We simulate the swift heavy ion impact employing an instantaneous inelastic thermal spike model. The analysis of changes in density, bonding content and the number and size of carbon primitive rings reveals graphitization of the material within the ion track, with higher degree of disorder in the core and more order in the outer shell. Simulated track dimensions are comparable to those observed in small angle x-ray scattering measurements of evaporation-deposited amorphous carbon stripper foils irradiated by 1.14 GeV U ions.

EXPERIMENTAL INVESTIGATIONS OF REINFORCED CONCRETE STRUCTURES OF HYDRAULIC STRUCTURES WITH BLOCK SEAMS, ENHANCED BY THE EXTERNAL REINFORCEMENT SYSTEM

A method of strengthening reinforced concrete structures by external reinforcement systems based on carbon fiber is widely used. Significant experience is accumulated in industrial and civil construction; there is also a certain experience of strengthening reinforced concrete structures of hydraulic structures. It was necessary to conduct experimental studies to justify technical solutions for strengthening the reinforced concrete structures of hydraulic structures. A characteristic feature of reinforced concrete structures of hydraulic structures is the mandatory availability of inter-block construction joints, which are caused by the need to build massive hydraulic structures with tiers and blocks with interruptions in concreting. Previously studies of reinforced concrete structures strengthened by composite materials were conducted without taking into account the block structure. The results of experimental studies of reinforced concrete beam structures of hydraulic structures reinforced with carbon strips having horizontal and vertical inter-block building seams are presented in the article. Experimental studies of a series of reinforced concrete beam-type models made of concrete of class B15 with longitudinal reinforcement from two bars. Their diameter is 10 mm and class is A500C (percentage of reinforcement 0.39%). The used concrete class is B25 with longitudinal reinforcement of three bars of diameter 12 mm and class A500C (percentage of reinforcement 0.84%). Their inter-block construction joints is before their strengthening and after reinforcement by longitudinal and transverse carbon composite tapes. In this case, a special type of cracking was recorded, in which cracks propagate along vertical and horizontal inter-block building seams. Due to the strengthening of reinforced concrete structures with carbon composite strips, the strength of the structures has increased, on average, by 1.78 times.

Tribological properties of pure carbon strip affected by dynamic contact force during current-carrying sliding

Abstract Contact force between pantograph and contact wire presents periodic variation with the running of trains. In this paper, the effects of dynamic contact force on friction coefficient and wear rate of pure carbon strip were studied on a pin-on-disk test rig with coupling and decoupling tests. Coupling results showed that the best tribological properties were obtained at 80 km/h. Decoupling results suggested that the increasing amplitude resulted in the production and extension of cracks and severe arc erosion; the increasing frequency contributed to the formation of the oxide film at low arc rate phases. This paper studied the detailed electrical wear behaviors of pure carbon strip and the related mechanism. The results may provide some practical guidance for railway operation.

Characteristics of the Sliding Electric Contact of Pantograph/Contact Wire Systems in Electric Railways

The sliding electric contact of pantograph/contact wire systems plays a significant part in the current collection stability and operation life of pantograph/contact wire systems. This paper addresses the evolutionary process of sliding electric contact of pantograph/contact wire systems by analyzing three key characteristics including contact resistance, temperature distribution and microstructure. The influence of electric current on contact resistance was interpreted. Furthermore, the evolution of the spatial temperature distribution of the carbon strip was obtained in the zigzag movement, while the dominant role of electric effect in temperature rise was demonstrated. In the end, the wear morphology differences under pure friction and current-carrying conditions were analyzed. The formation of radial cracks was illustrated and its influenced on the wear process was discussed.

A pantograph arcing model for electrified railways with different speeds

Pantograph arcing is an unavoidable phenomenon in electrified railways, which not only causes damage to the carbon strip and the catenary contact line but also results in voltage surge and electromagnetic interference. In recent years, there are more cases of pantograph arcing due to the increase in speed of trains. Therefore, it is essential to understand the basic electrical characteristics of pantograph arcing at different running speeds of trains. In this work, a pantograph arcing model was proposed, which considers the effects of the speed of a train on the arc-dissipated power. An overall electrical model, concerning the traction power system and the traction drive system, was further established. The results indicated that the running speed of trains significantly influenced the arcing voltage, duration of arcing, and the zero-crossing time. A qualitative relation between the average power of the arc and the speed of the train was also presented. Finally, field tests were carried out, and comparisons between the field testing data and the calculated results were made, which validate the accuracy of the developed model.

Electron cyclotron resonance plasma reactor for production of carbon stripper foil

A graphite antenna for the production of carbon-containing hydrogen plasmas is being developed to prepare impurity-free charge exchange foils for high-energy synchrotrons. Microwave power at 2.45 GHz frequency drives a coaxial structure antenna with a 12-mm-diameter central graphite cylinder and a tapered surrounding cylinder serving as the ground electrode. The antenna was placed in a linear magnetic field to investigate how it performs under an electron cyclotron resonance (ECR) condition. A clear resonance phenomenon was observed in plasma luminosity, microwave power absorption, and microwave power reflection when the induction current used to produce a linear magnetic field was changed. The antenna realized the best microwave coupling to the plasma with the ECR zone formed 5 mm from the end of the center electrode. The antenna realized stable operation for more than 5 h with 100 W input microwave power and with operating hydrogen pressure from 0.5 to 50 Pa.

Research on the delamination wear properties of the pure carbon strip at the high-sliding speed with electric current

PurposeThis paper aims to investigate the delamination wear properties of a carbon strip in a carbon strip rubbing against a copper wire at the high-sliding speed (380 km/h) with or without electrical current.Design/methodology/approachThe friction and wear properties of a carbon strip in a carbon strip rubbing against a copper wire are tested on the high-speed wear tester whose speed can reach up to 400 km/h. The test data have been collected by the high-speed data collector. The worn surfaces of the carbon strip are observed by the scanning electron microscope.FindingsIt was found that there was a significant increase of the delamination wear with the decrease of the normal load when the electric current is applied. The size of the flake-like peeling also increases with the decrease of normal load. The delamination wear extends gradually from the edge of the erosion pits to the surrounding area with the decrease of the normal load. However, the delamination wear never appears in the absence of electric current. It is proposed that the decreased normal load and the big electrical current are the major causes of the delamination wear of the carbon strip.Originality valueThe experimental test at high-sliding speed of 380 km/h was performed for the first time, and the major cause of the delamination was discovered in this paper.

Estimation of dose delivered to accelerator devices from stripping of 18.5 MeV/n 238U ions using the FLUKA code

In Korea, a heavy ion accelerator facility (RAON) has been designed for production of rare isotopes. The 90° bending section of this accelerator includes a 1.3-μm-carbon stripper followed by two dipole magnets and other devices. An incident beam is 18.5 MeV/n 238U33+,34+ ions passing through the carbon stripper at the beginning of the section. The two dipoles are tuned to transport 238U ions with specific charge states of 77+, 78+, 79+, 80+ and 81+. Then other ions will be deflected at the bends and cause beam losses. These beam losses are a concern to the devices of transport/beam line. The absorbed dose in devices and prompt dose in the tunnel were calculated using the FLUKA code in order to estimate radiation damage of such devices located at the 90° bending section and for the radiation protection. A novel method to transport multi-charged 238U ions beam was applied in the FLUKA code by using charge distribution of 238U ions after the stripper obtained from LISE++ code. The calculated results showed that the absorbed dose in the devices is influenced by the geometrical arrangement. The maximum dose was observed at the coils of first, second, fourth and fifth quadruples placed after first dipole magnet. The integrated doses for 30 years of operation with 9.5 pμA 238U ions were about 2 MGy for those quadrupoles. In conclusion, the protection of devices particularly, quadruples would be necessary to reduce the damage to devices. Moreover, results showed that the prompt radiation penetrated within the first 60 - 120 cm of concrete.

Computational fluid dynamics simulations of a binary particle bed in a riser-based carbon stripper for chemical looping combustion

Chemical-looping combustion (CLC) is a next generation combustion technology that shows great promise as a solution for the need of high-efficiency low-cost carbon capture from fossil fueled power plants. In this paper, numerical simulations are conducted of a binary particle bed associated with a coal-direct CLC system consisting of coal (represented by plastic beads) and oxygen carrier particles and validated against an experimental riser-based carbon stripper. The detailed particle dynamics and solid-gas and solid-solid interactions are investigated using the Lagrangian particle-tracking approach known as the discrete element method coupled with the computational fluid dynamics solution for the flow field. The simulation results of the fluidization behavior and the separation ratio of the particles are in excellent agreement with the experiment. A credible simulation of a binary particle bed is of particular importance for understanding the details of the fluidization behavior; the baseline simulation established in this work can be used as a tool for designing and optimizing the performance of such systems.

Tribology Behaviors of Carbon Strip/Copper Contact Wire of Pantograph/Centenary System Under Electric Current

The service life of pantograph/catenary system is determined by the wear performance of contact couple materials. The contact properties of pantograph/catenary system directly affect the stable operation and steady current-receiving of the electrical locomotives. A series of tests were carried out to study the tribology behavior of carbon strips and copper contact line with a high-speed friction and wear tester. The friction and wear behavior of carbon strips/copper contact line are significant affected by normal load, electric currents and sliding speed. By observing the different worn microscope of carbon strips, it can be found that the abrasive wear, adhesive wear and arc ablation are mainly wear mechanisms, accompanied by material transferring.

Chemical looping combustion of hard coal and torrefied biomass in a 1 MWth pilot plant

Chemical looping combustion (CLC) is an emerging CO2 capture technology utilizing two interconnected circulating fluidized beds (CFB). An oxygen carrier is oxidized in the air reactor and reduced in the fuel reactor. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal or biomass, is gasified in the fuel reactor, and the products from gasification are oxidized by the oxygen carrier. This work presents results of 110h autothermal and partial autothermal CLC operation with ilmenite and iron ore as oxygen carriers. Hard coal and a fuel blend of hard coal and torrefied biomass were used as fuels. The results show that the oxygen demand of the fuel reactor required for a complete conversion of unconverted gases was in the range of 27%. At the same time, the carbon capture efficiency was low in the present configuration of the 1 MWth pilot. This means that unconverted char left the fuel reactor and burned in the air reactor. The reason for this is that no carbon stripper unit was used during these investigations. Some possible modifications like an oxygen carrier with oxygen uncoupling, a lower fuel feeding point or a secondary fluidization of the fuel reactor could significantly enhance the carbon capture efficiency.

An experimental study on absorption/stripping CO 2 using mono-ethanol amine hollow fiber membrane contactor

Abstract The present article focuses on making asymmetric porous hollow fiber membranes of polysulfone (PSF) through alternating phases of process using ethanol (2 wt.%) as a non-soluble additive in polymer solution. An aqueous solution of 1-methyl-2-pyrrolidone (NMP) was used as the splitter fluid to prevent the formation of internal dense crust and water was used as an external coagulant. The surface porosity, the pore size and the effective porosity of membrane were examined through characteristic tests. The structure of membrane was studied by scanning electron microscopy (SEM). The performance of the produced membranes was examined to absorb and excrete carbon dioxide in a gas–liquid contactor membrane through the solution of mono-ethanolamine (MEA). The results of gas absorption and stripping test showed that the liquid phase is enhanced by increasing the flow rate. Membranes produced by ethanol indicated that the absorption and excretion of carbon dioxide hollow fiber membrane made of PSF were more than other membranes. The highest absorption of carbon dioxide (3.9 × 10 −3 mol/m 2 /s) and stripping (2.00 × 10 −4 mol/m 2 /s) could be obtained at the liquid flow rate of 300 and 200 ml/min, respectively.

Beryllium and boron decoration form planar tetracoordinate carbon strips at the edge of BCN nanoribbons result in energy gap opposite variation and third-order nonlinear optical response improvement

Planar tetracoordinate carbon (ptC) with intriguing planar bond structure has triggered great attentions. In this work, B/Be-terminated decoration form armchair hybridized boron nitride and graphene nanoribbons with ptC structure (ptC-aBCNNRs) are investigated theoretically for third-order nonlinear optical (NLO) response by employing time-dependent density functional theory combined with sum-over-states method. Our calculations reveal Be and B decorated on ptC-aBCNNRs would result in opposite variation of energy gaps, and strongly enhance the NLO response in different third-order NLO processes. The strong third-order NLO response predicted for ptC-aBCNNRs is originated from the charge redistribution induced by ptC structure and hexagonal-BN ribbon insertion.

An integrated fuel reactor coupled with an annular carbon stripper for coal-fired chemical looping combustion

An integrated fuel reactor (FR) coupled with an annular carbon stripper (CS) was proposed for coal-fired chemical looping combustion. The FR was designed as two independent bubbling fluidized beds that efficiently used the reactor's space and made the particle residence time longer and more uniform. An annular CS was integrated into the FR, which aimed to separate char from the oxygen carrier and decrease the system complexity. A coal-fired CLC system consisting of an integrated fuel reactor and an air reactor for fast fluidization was designed. A cold-flow model of the 30-kWth coal-fired CLC system was built and operated. Plastic beads were used to simulate char particles, and the oxygen carrier was ilmenite. Continuous and stable operation of the cold model was achieved, and the solid circulation rate was easily controlled. The plastic bead was found to be separated efficiently from the oxygen carrier using the annular CS and then concentrated in the FR. The separation efficiency in the CS was increased by decreasing the solid flow rate or by increasing the gas velocity in the annular zone of the CS. The separation efficiency decreased when coupling the annular CS into the CLC system due to the more severe non-uniformity structure of gas-solid two-phase flow in the CS of system. The carbon capture efficiency of the coal-fired CLC system was calculated and predicted, and the integrated FR with annular CS was concluded to greatly enhance the carbon capture efficiency of the coal-fired CLC system.

Friction and Wear Behaviors with Electric Current of Carbon Strip /Copper Contact Wire for Pantograph /Centenary System

The service life of pantograph/catenary system directly affects the stable operation and steady current-receiving of the electrical locomotives. A series of tests were carried out to study the friction and wear behavior of carbon strips and copper contact line using a high speed line-on-block tester. The friction and wear behavior of carbon strips/copper contact line are significant affected by normal load, electric currents and sliding speed. By comparing the different worn microscope of carbon strips, it can be found that the abrasive wear, adhesive wear and arc ablation are mainly wear mechanisms.

Evaluation of hybrid joints strengthened by carbon plates connecting new steel frames with existing concrete slabs

This paper introduces hybrid joints strengthened by carbon plates for connecting new steel frames onto concrete slabs, enabling rapid and effortless assembly of frames relative to traditional wall frame construction; this study proved that the use of carbon strips was efficient in strengthening the joint. The nonlinear structural response of the proposed joints with carbon strips, which can transfer moments through the interconnected components, was evaluated experimentally and numerically based on identified parameters that influence the structural behavior of retrofitted frames. The parameters are also capable of evaluating failure modes of the extended structure with vertical additions by identifying the structural behavior of the joints with carbon strips. This study performed numerical analysis based on delamination growth predictions using cohesive finite elements, in an attempt to engender better practice for cost effective analytical investigations, and demonstrated a good correlation with test data obtained from extensive experimental investigations.

Comparative investigation into the friction and wear behaviours of a Cu–Ag contact wire/carbon strip and a pure copper contact wire/carbon strip at high speeds

Several experimental tests are conducted on a high-speed block-on-ring tester to study friction and wear behaviours of a Cu–Ag contact wire and a pure copper contact wire rubbing against a carbon strip with electric current. The test parameters are set as follows: electric current 0–250A, sliding speed 110–170km/h and normal load 50–130N. The friction coefficient, wear volume and arc discharge energy are analyzed. The experimental results show that the friction coefficient of the carbon strip/Cu–Ag alloy contact wire is larger than that of the carbon strip/pure copper contact wire, and that the wear rate of the carbon strip which rubbed against the Cu–Ag alloy contact wire is larger than that of the carbon strip which rubbed against the pure copper contact wire. Discussion is presented to explain the friction and wear behaviours.

Validation of an HS-MS method for direct determination and classification of ignitable liquids

Fire debris analysis is a key step in fire investigation. Most of the analytical methods used for the analysis of ignitable liquid residues in fire debris require pre-concentration of the ignitable liquid residues prior to the chromatographic analysis. The standard method, ASTM E1412, involves a passive headspace concentration with activated charcoal strips to isolate the ignitable liquid residues from fire debris followed by a desorption procedure from the carbon strip with carbon disulfide.In this study a non-separative analytical method based on HS-MS eNose (headspace mass spectrometry electronic nose) in combination with chemometric tools, including hierarchical cluster analysis and linear discriminant analysis, has been used to detect and classify ignitable liquid residues in fire debris into the classes defined by the ASTM E1618 standard method. This method allows a direct analysis of fire debris in 10min and avoids the use of solvent and sorbents.The method was validated by analyzing a set of burned samples by GC–MS according to the standard methods ASTM E1412 and ASTM E1618. The results obtained on using the method proposed in this study were comparable to those obtained with the reference method. The correct classification rates for assigning ignitable liquid residues into ASTM E1618 classes were in the range of 90% for both methods. In comparison to the standard methods HS-MS does have specific advantages. Apart from the speed of the analysis and the fact that the sample does not require sample pre-concentration, this technique is also safer and ecofriendly since it does not use any solvents or produce any residues.

Annular Carbon Stripper for Chemical-Looping Combustion of Coal

The carbon stripper (CS), which is a fluidization bed aimed at separating char particles from oxygen carriers during coal-fired chemical looping combustion (CLC), is vital for achieving high carbon capture efficiency of a CLC system. An effectively designed CS could transport most char particles back to the fuel reactor and simultaneously allow most oxygen carriers to reach the air reactor. An annular carbon stripper was designed, and a cold model apparatus was built for operation and optimization. The CS consists of an annular fluidized bed and a center riser. The riser was inserted into the annular fluidized bed, and the fluidized bed was divided into the annular zone and the cylindrical zone. Plastic beads were used to simulate char particles, and ilmenite was used as the oxygen carrier. The effect of operational parameters (solid feeding rate and gas velocities) and particle properties (average size of plastic beads and mass concentration of plastic beads) on the separation efficiencies of plastic bea...