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A two-dimensional (2D) rotary axisymmetric model has been developed to describe the formation and development of cathode spot in vacuum arc. The model includes hydrodynamic equations and thermal conductivity equation. Parameters used in this model come from experiments and other researchers' work. The simulation results show that when the energy flux density is 1.5∼3×1012W, discharge current is 1∼6A...
Copper-chromium contact material having 30% to 60 % chromium was prepared using vacuum consumable arc melting technique. The micro-structure and performance of the contact material was investigated. The arc-melted material was solidified into a fine-grained and uniform micro-structure. The type test at a 12 kV/31.5 kA grade showed that the vacuum interrupter made of the arc-melted material switched...
A simple testing procedure has been developed in order to investigate and screen the current interruption capability of vacuum interrupter contact materials. A synthetic circuit delivering adjustable AC currents, followed by a pulsed of 21 kV peak for 2 seconds has been used. The electrical tests has been developed to reproduce the conditions close to a fault current rated at 12 kV; only the recovery...
Metal vapor has a significant influence on dielectric recovery behaviors after interrupting a high vacuum arc. The objective of this paper is to study breakdowns in copper, chromium and copper-chromium vapors employing the PIC-MCC method. A 2d model with a given DC voltage is applied to study the breakdown processes in the metal vapor after vacuum arc extinctions taking into account thermal-field...
The copper chromium composite coatings produced by the electron beam cladding in the vacuum on the cooper substrate and electrical contacts CuCr25 produced by solid-phase sintering in a hydrogen atmosphere have been investigated. The copper chromium composite coatings produced by the electron beam cladding showed higher values of breaking capacity compared with the sintered contact material.
A self-consistent space-resolved numerical model of cathode spots in vacuum arcs is developed on the basis of the COMSOL Multiphysics software. The model is applied to cathode spots on copper-chromium (CuCr) contacts of vacuum interrupters. In the limiting case of large grains, the main effect of change in cathode material from Cu to Cr is the reduction of thermal conductivity of the cathode material,...
Copper-Chromium (CuCr) based contact material is widely used for vacuum interrupter (VI) contacts and has found worldwide acceptance in medium-voltage VIs, especially for high-current interruption. Contact material with chromium content between 25 and 50 wt. % is almost exclusively used. Conventionally, copper and chromium are uniformly distributed throughout the body of the contact. In a few cases,...
The copper chromium composite coatings produced by the electron beam facing in the vacuum on the cooper substrate have been investigated. The effect of the electron beam facing on the structure and the properties of the coatings has been determined. The chromium based solid solution containing 2, 5–4, 5% at. Cu and the copper based solid solution containing 3–5% at. Cr form in process of the electron...
In this paper, a new coupling process called Fe-Cu internal electrolysis coupling with bentonite in treating chromate waste water was introduced. Iron slag, copper wire and bentonite with suitable proportion were put in an airtight jar with chromate waste water. The influence of contact time, pH, the ratio of weight of iron and copper, the dosage of bentonite and initial concentration of Cr(VI) on...
Activated Carbon is a water treatment adsorbent with a large adsorption capacity, its adsorption capacity will be able to greatly enhance after modified activated. Through the use of before and after the modification of mesoporous activated carbon powder to the heavy metals copper ion adsorption, the effects of different pH, adsorption temperature, balance time, the amount of activated carbon adsorption...
Heavy metal pollution is one of the most serious pollution problems. Microorganisms in the long-term heavy metal contaminated environments formed different mechanisms of resistances in cell structure, physiological metabolism and genetic. In this review, we discuss physiological and molecular mechanisms of microbial heavy metals tolerance and elaborate on the interaction between metal and microorganisms,...
The ferrite process has been used in the treatment of wastewater containing Nickel, Chromium, Zinc and Copper in this paper. The operation parameters of wastewater treatment were also studied. Based on the experiment, optimum condition in terms of pH and dosage of FeSO4 were obtained. The concentration of Nickel, total Chromium, Zinc and Copper were less than 1.0mg/L, 1.5mg/L, 2.0mg/L, and 0.5mg/L...
A combined process of acid-leaching, electrodepositing and ammonium jarosite precipitating was developed to recover heavy metals from electroplating sludge. About 95% of copper and nickel, 90% of chromium and 86% of iron were extracted from the sludge with 10% H2SO4 leaching. More than 99% of copper was recovered from the leaching solution with electrodepositing process. The left solution after copper...
This paper reports the high biosorptive properties of an indigenous plant for Cr(VI) biosorption. The biomass uptake capacity is found 85 mg Cr(VI)/gm of biomass in batch mode. The influence of different experimental parameters such as pH, dose of adsorbent and Cr(VI) levels (15-200 mg/l), effect of contact time etc. on biosorption was evaluated. The adsorption data fitted well to Langmuir and Freundlich...
In order to identify the content of various heavy metals, soils of the farmland surrounding the Huashan's gold tailing mine are studied. Surrounding soil samples are collected in new and old tailing mines. Flame atomic absorption spectrometry is taken to measure the content of Pb, Zn, Cd, Cr, and Cu. In addition, the method of combining the Geo-accumulation index and the potential ecological risk...
Aspergillus Niger and Pseudomonas fluorescens have the ability to absorb heavy metals during the stationary phase of growth. To improve the removal the efficiency of the oxidation ditch, we have introduced Aspergillus Niger and Pseudomonas fluorescens to the traditional Carrousel oxidation ditch process and the comparative experimental study were carried out when the Hydraulic Retention Time (HRT)...
To study the spatial distribution characteristics of 10 heavy metals(As, Hg, Mo, Cd, Cr, Zn, Cu, Mn, Pb, Ti) in the soil of Dexing area, Semi-variance function is used to quantitatively describe the structural features of the spatial distribution and map the content distribution. The analysis shows, in addition to cadmium and lead, other elements fit relatively well, which reflects a good spatial...
The concentrations of As, Cd, Ni, Cr, Zn, Cu, Hg and Pb in the sediment of Xiyi River were analyzed by flame atomic absorption spectrophotometer (AAS). The results showed the average concentration of total As, Cd, Ni, Cr, Zn, Cu, Hg and Pb in the sediment was higher than the national threshold limit. The values of pollution index and integrated pollution index showed that the pollution level was Cd>;...
The contents and characteristics of ten heavy metals in surface sediments from Yangzonghai Lake in Yunnan, China were analyzed. Ecological risk index presented by Håkanson to assess the potential ecological risk of Yangzonghai Lake was utilized. The results showed that the average concentrations of titanium(Ti), manganese(Mn), zinc(Zn), vanadium(V), chromium(Cr), copper(Cu), nickel(Ni), cobalt(Co),...
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