Carbon Stripper Research Articles

Gold leaf electrochemical flow cell for determination of iodide in nuclear emergency tablets

This work introduces an innovative gold-leaf flow cell for electrochemical detection in flow injection (FI) analysis. The flow cell incorporates a hammered custom gold leaf electrochemical sensor. Hammered gold leaves consist of pure gold and are readily available in Thailand at affordable prices (approximately $0.085 for a sheet measuring 40 mm × 40 mm). Four sensing devices can be made from a single sheet of this gold leaf, resulting in a production cost of approximately $0.19 per sensor. Each electrochemical sensor has the gold leaf as the working electrode, together with a printed carbon strip, and a printed silver/silver chloride strip as the counter and reference electrodes, respectively. Initial investigations using cyclic voltammetry of a standard 1000 μmol L⁻1 iodide solution in 60 mmol L⁻1 phosphate buffer (PB) solution at pH 5, demonstrated performance comparable to that of a commercial screen-printed gold electrode. The hammered gold leaf electrode was then installed in a commercial flow cell as part of an FI system. A sample or standard iodide solution (100 μL) is injected into the first carrier stream of phosphate buffer (PB) solution, which then merges to mix with the second stream of the same buffer solution before flowing into the flow cell for amperometric detection of iodide. The optimized operating conditions include a fixed potential of +0.39 V (vs Ag/AgCl), and a total flow rate of 3 mL min⁻1. A linear calibration is obtained in the concentration range of 1 to 1000 μmol L⁻1 I− with a typical equation of μA = (0.00299 ± 0.00004) × (μmol L−1 I−) + (0.021 ± 0.020), and R2 = 0.9994. Analysis of iodide using this gold leaf-FI system is rapid with sample throughput of 86 samples h⁻1 and %RSD of a sample of 100 μmol L⁻1 I⁻ of 1.2 (n = 29). The limit of detection, (calculated as 2.78 × SD of regression line/slope), is 27 μmol L⁻1 I−. This method was successfully applied to determine iodide in nuclear emergency tablets.

Parametric evaluation of clean syngas production from pine forest residue by chemical looping gasification at the 20 kWth scale

In the framework of the EU H2020 CLARA project, jet biofuel production via Fischer-Tropsch synthesis is intended from syngas generated by Biomass Chemical Looping Gasification (BCLG). BCLG is based on the lattice oxygen transference between a solid oxygen carrier and the biofuel to energetically support the biomass gasification. This process produces low tar and nitrogen-free syngas under autothermal conditions, and at the same time includes an intrinsic separation of carbon compounds from nitrogen in air, avoiding future carbon capture costs. This work evaluates the syngas production from pine forest residue (PFR) through the BCLG process with ilmenite as the oxygen carrier. The effects of several key operating variables, including temperature, oxygen-to-biomass ratio and mean residence time of solids, on the performance of the BCLG process were analyzed at 20 kWth scale. The syngas yield depended on the oxygen-to-biomass ratio and improved with the char conversion in the fuel reactor. Temperature and mean residence time of solids in the fuel reactor were identified as the primary factors affecting char conversion. A dedicated study was performed to assess the impact of the biomass size on char conversion, as well as the relevance of a carbon stripper unit on the improvement on char gasification due to its role either as a secondary gasifier or as a char-oxygen carrier separator. Higher char conversion values were achieved with the lowest biomass particle size (1–2 mm vs. pellets 6 mm Ø) due to lower restrictions to gas diffusion inside the particles. The carbon stripper may act as a secondary gasifier, thus improving the char conversion, but it was not able to take away the unconverted char particles from ilmenite in any case due to it was designed for powdered fuels. Besides, the generation of light hydrocarbons was hardly affected by any operating variables. The tar content remained below 4.5 g/kg dry biomass. The ilmenite showed a good performance during the continuous operation without signs of defluidization.

Evaluation of CLC as a BECCS technology from tests on woody biomass in an auto-thermal 150-kW pilot unit

In this work, woody biomass is converted by chemical looping combustion (CLC) in the auto-thermally operated 150-kW pilot unit at SINTEF Energy Research in Norway, using ilmenite as an oxygen carrier. The pilot unit consists of two inter-connected circulating fluidized bed reactors, being the air and fuel reactor, respectively. The unit is simplified compared to many other lab and pilot units by not having a carbon stripper. The aim of the present study is to evaluate the main performance parameters when operating a relatively large CLC unit in auto-thermal mode, using a cheap natural mineral, ilmenite, as oxygen carrier. Another aspect with the tests is to verify if the omission of a carbon stripper can provide high enough capture efficiencies for solid fuels as biomass, with a large share of volatiles and a char remnant with high reactivity. As a comparison, tests with petcoke were performed, to assess the effect when using a fuel with a low share of volatiles and slow char conversion. The results imply that CO2 capture efficiencies can be well above 95 % in a larger industrial unit operating on biomass, even without a carbon stripper, but that a carbon stripper is definitely needed for fuels with less volatiles and low char reactivity.

Full-Range fatigue behavior of NSM CFRP-to-Concrete bonded joints

The interfacial bond characteristics and failure mechanism of near-surface mounted (NSM) fiber reinforced polymer (FRP) composites in concrete under fatigue loading are less understood compared to their bond behavior under static loading. In this paper, degradation of the local bond strength of FRP-to-concrete bonded joints subjected to direct pull-out fatigue loading is presented for both carbon FRP (CFRP) rods and strips under different fatigue load ranges, i.e., 10–50%, 10–60%, and 10–70%, of the corresponding static load-carrying capacity. The interfacial debonding between FRP and adhesive was observed during fatigue cycles for CFRP rod specimens to different extents. Specimens using CFRP rods with sand-coated and spirally wound surface treatment presented a higher local bond strength and a slower degradation rate, as compared to the ones using CFRP rods with roughened or sand-coated treatment. Using epoxy adhesives with higher strengths benefitted the fatigue bond performance of the tested specimens in terms of local bond strength and stable behavior. Higher fatigue load ranges substantially accelerated the local bond degradation resulting in a much shorter fatigue life of the bonded joints.

Effect and behaviors of ambient humidity on the wear of metal-impregnated carbon strip in pantograph-catenary system

The causes of abnormal wear in contact strip of pantograph have been extensively investigated. Initially, based on field data analysis, the wear rate of strip was found to be strongly correlated with ambient humidity. Subsequently, a series tests of the strip was conducted, and the micromorphology was preformed post-tests, which indicated the evolution law of wear rate under different ambient humidity conditions. Finally, through grey relational analysis, it was observed that the degree of correlation between different influencing factors and wear rate at low humidity was greater than that at high humidity. Based on the findings of the aforementioned study, it is concluded that the abnormal wear of strip is caused by a decrease in ambient humidity.

Experimental research on the non-uniform wear of the carbon strip of the metro pantograph

The present study simulated the actual contact conditions between the catenary and pantograph of a metro line using high-speed ring block current that carried friction and wear testers, from which the uneven wear of the pantograph carbon strip under different working conditions was studied. The results show that the arc power, friction coefficient, and wear amount will change correspondingly with increasing current and normal load. Additionally, all carbon strips showed non-uniform wear after the test, and the edge erosion and wear depth of the carbon strip perpendicular to the moving direction were higher than those in the middle part. The ablation of the back end of the carbon strip running with the catenary was higher than that of the front end.

Wear rate and profile prediction of Cu-impregnated carbon strip for high-speed pantograph

The wear status of pantograph carbon strips has a crucial impact on the receiving quality of high-speed trains, and accurate wear rate prediction is essential for timely maintenance and replacement. In this study, the wear mechanism of Cu-impregnated carbon strip is analyzed through micro-analysis, and an improved method for calculating wear rate is proposed by enhancing the original Holm-Archard adhesive wear model. The proposed approach considers the collecting current of the pantograph, burning arc, and contact loss rate of the pantograph, thereby improving the accuracy of wear rate calculation. Moreover, the study validates the relationship between contact resistance and contact force by comparing the model's results with experimental data. Furthermore, the wear profile of MCS is predicted and calculated by considering the wear position of the zigzag catenary on the sliding plate, which provides a more comprehensive analysis of the wear behavior of MCS. To validate the proposed model, actual wear and operation data of an eight-unit high-speed train's pantograph are employed, and the results indicate an average absolute error of 0.19 mm at the deepest wear depth (−16 mm–16 mm) of MCS, which demonstrates the feasibility and effectiveness of the proposed model.

Failure analysis of the pure carbon strip affected by dynamic contact force during current-carrying sliding

The pure carbon strip is widely used in high-speed Electro Mechanical Units (EMUs) transit. Dynamic contact between the pantograph and the catenary produces internal cracks in the pure carbon strip, which results in the break of the pantograph and interruption of power transmission. The tribological properties and failure mechanism of the pure carbon strip is studied in this paper. The current-carrying tribology experiments were carried out on a flexible loading test rig. It is found that the dynamic contact in pantograph/catenary system produces regular influence on arc discharge and current transmission. The cracks and arc erosion are the most important failure mechanisms subjected to the periodic vertical contact force. The carbon fibers in the strip became orderly arranged honeycomb-structures after oxidation and sublimation. These honeycomb-structures distributed nearby the pores and induced the initiation and propagation of cracks. Therefore, preparing high-strength carbon fibers and eliminating the combination gap between the carbon fibers and the carbon matrix are recommended to prevent the failure of pure carbon strip. Results in this paper are expected to provide data support for the failure analysis and manufacturing technology to the pure carbon strip, as well as providing theoretical supports to the locomotives in service.

Effect of counterpart materials on tribological behaviors of copper impregnated carbon/carbon composite under electric current condition

Copper impregnated carbon/carbon composite (Cu-C/C composite) was fabricated for novel sliding collector material by weaving carbon fiber, heat treatment and Cu alloy impregnation. The effects of counterpart materials (Fe ball and Cu ball) on friction and wear behaviors were investigated and compared with the result of carbon contact strip used in high-speed railway. Morphology, chemical composition, phase and structure of wear surface and tribolayer were characterized to clarify tribological mechanisms. The results show that friction coefficient follows the order: Cu-C/C composite/Cu ball > carbon contact strip/Fe ball > Cu-C/C composite/Fe ball > carbon contact strip/Cu ball. The carbon crystalline of wear surface appears preferred orientation along the sliding orientation, which is benefit for boundary lubrication. When the counterpart material is Fe ball, Cu-C/C composite is superior to pure carbon strip in mechanical strength, electrical conductivity, wear resistance and friction performance.

Experimental investigation and structural optimization prediction of a novel carbon stripper for solid-fuel chemical looping combustion

The addition of carbon stripper (CS) can effectively improve the carbon conversion efficiency in the fuel reactor of solid-fuel chemical looping combustion system. An independent CS system is constructed, and the feasibility of the system is verified through feasibility tests and reference work condition tests. The effects of important conditions on the separation performance of CS are also explored based on the experimental platform. It is found that increasing the main gas velocity and cross-flow velocity in the air reactor can effectively improve the directional separation efficiency of binary particles. On the other hand, based on the Computational Fluid Dynamics platform, the important structural factors, including baffle angle, deflector angle and deflector length of the CS, are studied for the directional separation mechanism of binary particles. The results show that a CS structure with the baffle length of 140 mm, the baffle angle of 110°, the deflector length of 40 mm, and the deflector angle of 60° exhibits good directional separation performance. In this case, the separation efficiency of quartz sand is close to 100%, and that of polyvinyl chloride (PVC) particles can reach a high value of 93.7%, demonstrating the high separation efficiency and promising application prospects of this novel CS.

Tribological behaviors of copper modified carbon/carbon composites for pantograph strip under electric current conditions

Copper fiber reinforced carbon/carbon composite (C/C-Cuf) and copper alloy impregnating carbon/carbon (C/C-Cu) composite as promising materials of pantograph strip were fabricated and investigated for tribological behaviors and relevant mechanisms, comparing results with pure carbon strip currently used in high-speed railway. C/C-Cuf composite and C/C-Cu composite have more advantage than the pure carbon strip in terms of electric conductivity and mechanical performances. During current-carrying friction tests, C/C-Cu composite has the lowest arc discharge energy and smoothest worn surface. It is attributed that suitable heat treatment decreases the interlaminar defects (Covalent cross-bonds and sp3 structure) of amorphous carbon, and the tribolayer with grapheme-like structure is formed through the processes of rehybridization, rearrangement and reorganization on the worn surface of C/C-Cu composite.

Assessment of the chemical looping gasification of wheat straw pellets at the 20 kWth scale

In this work, the Biomass Chemical Looping Gasification (BCLG) process was evaluated for syngas production at the 20 kWth scale using wheat straw pellets as the fuel feedstock and ilmenite as the oxygen carrier. The effect of different operational variables –namely the fuel reactor temperature, the mean residence time of solids in the fuel reactor, the oxygen-to-biomass ratio (controlled by the oxygen fed into the air reactor) and the gas velocity in the carbon stripper– on the process performance and the syngas yield was analyzed. Interestingly, smooth operation of the CLG unit was observed and no agglomeration issues detected. In addition, char produced during devolatilization still retained its initial pellet shape and unconverted char pellets were elutriated from the fuel reactor mixed with the finer oxygen carrier particles. Both steady-state and transition periods were evaluated to have a complete overview of the process. Transition periods were characterized by a different oxygen transfer rate in the air and fuel reactors. Steady state was reached when the oxygen transference rate was the same in both reactors. In this sense, the oxygen transference rate in the fuel reactor was the main factor affecting the syngas yield and the cold gas efficiency. Also, the temperature and mean residence time of solids in the fuel reactor showed a considerable effect on the char conversion and, consequently, on the syngas yield. However, operating conditions hardly affected the production of light hydrocarbons (CH4 and C2-C3) and tar, which were maintained roughly constant throughout the experimental campaign.

Experimental research on the mechanism of the delamination extension of the carbon strip with heavy electrical current at the speed of 360 km/h

Delamination wear leads to a surge in the wear loss of the carbon strip. It also has a significant influence on the physicochemical properties of the contact pairs in the pantograph-catenary system (over 250 km/h). In this paper, the pure carbon/copper-alloy friction pair was chosen as the research object to study the wear evolution mechanisms and the law of delamination wear extension of the carbon strip, using a ring-on -block wear tester with a design speed of 400 km/h. And the arc discharge energy was calculated to investigate the quantitative relationship between the delamination wear and the arc discharge in the process of the test. The experimental results show that the frictional coefficient increases gradually with the experiment. The frictional coefficient with electric current is much bigger than that without electric current under the same test conditions. Under the intense arcing (when the average single arc discharge energy e > 76J), the delamination wear initially appears on one edge of the strip and gradually extends to the middle of the strip when sliding time t exceeds a certain value, which results in the increase of the wear of the strip and the further enhancement of the arc discharge. The result also indicates that delamination wear and its extension are occurred by the cumulative effect of the heat caused by the long-time strong arc discharge.

Tubular metal–organic framework membranes enabling exceptional atmospheric water harvesting by fast air permeation

Atmospheric water harvesting (AWH) with monolithic metal–organic frameworks (MOFs) represents an industrially favorable solution to freshwater scarcity, while its water productivity is rather poor due to the limited water adsorption–desorption cycling capacity of MOFs. Herein, versatile tubular MOF membranes (TMMs) with well-aligned lamellar microstructures and containing helical porous carbon strips (PCSs) are presented. Such unique shapes and microstructures of TMMs allow the airflow to rapidly pass through TMM walls, resulting in their highly efficient surface exposure to air and dramatically accelerated atmospheric water adsorption. PCSs embedded within TMMs enable to deliver localized electrical heating (LEH) to achieve rapid and sufficient heating of the entire TMMs, endowing TMMs with highly efficient water desorption capacity. These merits synergistically impart TMMs with fast and well-controlled water adsorption–desorption cycling capabilities, enabling the TMM-based AWH devices to deliver 6.2, 3.2 and 8.6 LH2O kgTMM-1 day−1 of record-high water productivity at 20 %, 35 % and 60 % relative humidity and 25 °C, respectively. The TMM with fast air permeation and sufficient LEH capacity thus demonstrate a novel design of industry-favorable AWH sorbent towards exceptional water productivity, paving a bright avenue towards the real-world water production at scales with sorption-based AWH.

Preparation of different carbon stripper foils and application in beam diagnostics

The production of carbon stripper foils that are mounted at different locations of the heavy-ion accelerator is an important task of the target laboratory, and the process for the preparation of carbon foils is constantly improved. Recently, we tested additional heat treatment of the carbon stripping foils following our standard procedure to reduce stress in the foils, since the performance and the durability of these stripping foils is a crucial factor for effective operation. We investigated the properties of foils produced some time ago and of foils freshly produced with the standard procedure, and foils treated thermally after the standard procedure. For the beam diagnostic department at GSI radiation resistant target materials for transverse ion beam profile measurement is an ongoing research topic. In that framework, the feasibility of Optical Transition Radiation (OTR) generation due to ion beam interaction with metal target for beam profile determination has been investigated. Here, carbon stripper foils are applied to enhance the OTR signal. The differently prepared foils were applied in many different experiments of the beam diagnostic department. We describe the performance of the foils during irradiation and compare the features of foils before and after irradiation.

Installation and commissioning of the stripping foil system in the new CERN PS booster 160 MeV H− injection region

During Long Shutdown 2 (LS2) at CERN, the new Linac4 (L4) accelerator was connected to the PS Booster (PSB) to inject 160 MeV H− beam into the 4 superposed PSB rings. In order to achieve this, a completely new H− charge-exchange injection chicane system, with 200 µg/cm2 carbon stripping foil units, to convert the negative hydrogen ions into protons, by stripping off the electrons, has been installed. Beam commissioning of this system started in December 2020 and different types of foils have been used for this purpose. In parallel, stripping efficiency measurements, of different foil types, continued to take place with the stripping foil test stand in the L4 Transfer Line. This paper briefly recalls the final design, and installation of, the main components in the PSB injection region, before reporting on the important results obtained during measurements and commissioning with beam.

Study on Current-Carrying Tribological Characteristics of C-Cu Sliding Electric Contacts under Different Water Content

Previous studies have often observed that moisture can promote the lubricity and wear resistance of carbon-metal contact pairs in purely mechanical conditions. However, the damage to pantograph carbon strips was found to be aggravated in rainfall conditions, leading to a much lower service life than anticipated. This suggests a novel influence mechanism of water on carbon-copper (C-Cu) contacts during current-carrying friction. In this paper, the influence mechanism of water on the current-carrying friction characteristics of carbon-copper contacts, including friction coefficient, wear loss, electrical contact resistance, and arc discharge characteristics, was studied under different current levels by controlling the water content of carbon sliders. The results show that the variation trend of current-carrying tribological parameters of C-Cu contacts with water content at 60–100 A is significantly different from that at 20–40 A, which is mainly the result of the competition of lubrication, cooling, and obstruction of current transmission by moisture. The abnormal wear of carbon sliders in the water environment occurs when the current is greater than 60 A, and the main reason for the abnormal wear is the intensification of discharge erosion. In addition, micro-crack propagation under high water content is an important factor in the deterioration of carbon strip properties.

Pressurised Chemical Looping Combustion (PCLC): Air Reactor design

Bioenergy combustion with Carbon Capture and Storage (BECCS) is a key technology to achieve carbon negative emissions power generation. This can be achieved by coupling the biofuels combustion with CO2 capture and storage (CCS). The lowest cost for CCS corresponds at the moment to the Chemical Looping Combustion (CLC) process. This can use biofuels which can be gaseous (biomethane, biogas or syngas etc.), liquid (biodiesel, bioethanol, biobutanol and pyrolysis oils etc.) or solids (wood dust, charcoal dust, wood chips, wood pellets etc.) While plant design with gaseous and liquid biofuels would be simpler, plants using solid biofuels and based on two couple fluidisd beds would need the use of a third reactor named carbon stripper. In the specific case if we plan to couple a CLC plant with a turbo expander (to achieve the high efficiencies of a combined cycle power plant) we have to work with pressurized reactors. However, there are some technical barriers to the coupling of a chemical looping combustor with a turbo expander, such as: the operation of the combustor in pressurised conditions; the inventory balance among reactors; elutriated particles reaching the turbo expander. This explaind why there is no commercial plant at the moment capable to do this. The aim of this paper is to present a model for the dimensioning of an air reactor to be coupled to a turbo expander of the power of about 12 MWe. Based on this, the air mass flow can be obtained and the geometric parameters can be calculated, to have an air velocity which is needed to achieve the fast fluidization regime and to ensure a high conversion rate as well as particles and heat exchage among air and fuel reactor.

Electrical capturing system for train supplying and involving parameters

Electric trains are powered by a current distribution device which depends on several parameters. The research works presented in this paper are located upstream of two types of important applications in the railway field: the electrical supply of trains involving the sliding or stationary pantograph/catenary contact and the famous problem of shunting of trains involving the wheel/rail rolling contact. These cannot be assumed without energy loss. In the case of train navigation, electric current can be transmitted by spots established between sources and the carbon strip. The quality of the pantograph/catenary contact obeys very strict specifications to ensure its maintenance, for permanent current connection. However mechanical aging of the contact and/or infrastructures, alteration of electrical contacts due to electrical arcing, the wear of collection strips during sliding, aging of the materials, are limiting effect for current flow. In this paper we will explicitly describe all the elements necessary to supply trains with electric current.

The State of Deformation and Stiffness Analysis of RC Beams Strengthened by Means of CFRP Strips at Different Load Levels

This work presented some selected results of laboratory tests and FEM analysis study of simple supported RC beams strengthened using carbon strips. The beams were examined to establish the effectiveness of this method of strengthening in terms of increasing their load-carrying capacity as well as flexural stiffness at different preloading states. A set of beams was divided into five groups, which differ in the level of the load applied before application of the composite strips on their bottom surfaces. Laboratory tests were supplemented with numerical analyses based on the finite-element method (FEM) using Abaqus software. The created numerical models were validated, and good agreement of the experimental results with the results obtained in the numerical analyses was observed. The deformation state existing in the main reinforcing bars, in concrete as well as in the strengthening composite strip, and its influence on the failure mechanism of the beams were analyzed. In the stiffness analysis, it was assumed that the stiffness of a beam strengthened with composite material after the elastic range (concrete and reinforcement steel) can be represented by the relation between the stiffness of the noncracked section B and beam curvature κ. The curvature–bending moment diagram as well as bending moment–stiffness diagram were prepared on the basis of laboratory and numerical results. Based on the results, it can be stated that the preload on the beam before strengthening affects the levels of deformation and the utilization rates of the composite material as well as reinforcing bars. The curvature and stiffness of the beams depend on the load level at which the CFRP strip strengthening is realized. The results of the analysis of preloaded beams before strengthening indicate that totally relieving them prior to strip application turns out to be the most beneficial solution.