Evaluation and Optimization of Electrode Configuration of Multi-Channel Corona Discharge Plasma for Dye-Containing Wastewater Treatment

A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment,the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density,and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration.The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance(d/s) was 0.5.Reactive Brilliant Blue(RBB) wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5,which was consistent with the result obtained in the discharge characteristics experiments.In addition,the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration.RBB degradation processes were analyzed by GC-MS and IC,and the possible mechanism for RBB decoloration was also discussed.     

电子束辐照处理水溶液中的活性染料

印染废水是我国工业废水的主要品种之一,如何有效处理印染废水是当今一个重要的研究课题。本文选择两种活性染料为处理对象,研究其在电子束辐照下的降解和脱色。通过染料水溶液受到辐照前后的紫外可见光谱的分析,以及化学需氧量、吸光度和溶液pH值的变化,研究其辐射降解脱色特性。同时研究了过氧化氢对染料辐射降解的协同作用。结果显示利用辐射技术处理印染废水具有相当好的应用前景。     

Degradation of tiamulin by a packed bed dielectric barrier plasma combined with TiO2 catalyst

Recently, a plasma catalyst was employed to efficiently degrade antibiotic residues in the environment. In this study, the plasma generated in a packed bed dielectric barrier reactor combined with TiO2 catalyst is used to degrade the antibiotic tiamulin (TIA) loaded on the surface of simulated soil particles. The effects of applied voltage, composition of the working gas, gas flow rate and presence or absence of catalyst on the degradation effect were studied. It was found that plasma and catalyst can produce a synergistic effect under optimal conditions (applied voltage 25 kV, oxygen ratio 1%, gas flow rate 0.6 l min−1, treatment time 5 min). The degradation efficiency of the plasma combined with catalyst can reach 78.6%, which is 18.4% higher than that of plasma without catalyst. When the applied voltage is 30 kV, the gas flow rate is 1 l min−1, the oxygen ratio is 1% and the plasma combined with TiO2 catalyst treats the sample for 5 min the degradation efficiency of TIA reached 97%. It can be concluded that a higher applied voltage and longer processing times not only lead to more degradation but also result in a lower energy efficiency. Decreasing the oxygen ratio and gas flow rate could improve the degradation efficiency. The relative distribution and identity of the major TIA degradation product generated was determined by high-performance liquid chromatography–mass spectrometry analysis. The mechanism of TIA removal by plasma and TiO2 catalyst was analyzed, and the possible degradation path is discussed.     

Study on purification technology of polyacrylamide wastewater by non-thermal plasma

In this work, non-thermal plasma has been applied to treat polyacrylamide (PAM) wastewater. We have investigated the influence of the rule of PAM wastewater initial pH, solution concentration and discharge time, discharge voltage on chemical oxygen demand (COD) degradation rate. At the same time, the effect of pH and discharge time on the viscosity removal rate of PAM solution was also studied. Then, the effect of pH on the viscosity removal rate of 1.0 gl ⁻¹ PAM solution was studied separately. Through orthogonal test, the factors affecting the COD degradation rate of PAM wastewater were determined as follows: discharge time>discharge voltage>solution concentration>wastewater initial pH. The COD highest removal rate of PAM wastewater reached 85.74%, when the optimal conditions are as follows: discharge voltage 40 kV, discharge time 5 h, solution concentration 1.0 gl ⁻¹, pH 1.5. This research provides some basic data and new theoretical basis for PAM wastewater purification.     

A novel double dielectric barrier discharge reactor with high field emission and secondary electron emission for toluene abatement

Dielectric barrier discharge (DBD) has been extensively investigated in the fields of environment and energy, whereas its practical implementation is still limited due to its unsatisfactory energy efficiency. In order to improve the energy efficiency of DBD, a novel double dielectric barrier discharge (NDDBD) reactor with high field emission and secondary electron emission was developed and compared with traditional DDBD (TDDBD) configuration. Firstly, the discharge characteristics of the two DDBD reactors were analyzed. Compared to TDDBD, the NDDBD reactor exhibited much stronger discharge intensity, higher transferred charge, dissipated power and gas temperature due to the effective utilization of cathode field emission and secondary electron emission. Subsequently, toluene abatement performance of the two reactors was evaluated. The toluene decomposition efficiency and mineralization rate of NDDBD were much higher than that of TDDBD, which were 86.44%–100% versus 28.17%–80.48% and 17.16%–43.42% versus 7.17%–16.44% at 2.17–15.12 W and 1.24–4.90 W respectively. NDDBD also exhibited higher energy yield than TDDBD, whereas the overall energy constant ${k}_{{\rm{overall}}}$ of the two reactors were similar. Finally, plausible toluene decomposition pathway in TDDBD and NDDBD was suggested based on organic intermediates that generated from toluene degradation. The finding of this study is expected to provide reference for the design and optimization of DBD reactor for volatile organic compounds control and other applications.     

Effect of Water Vapor on Toluene Removal in Catalysis-DBD Plasma Reactors

The experiment was carried out in a cylindrical dielectric barrier discharge(DBD)reactor assisted with a catalyst to decompose toluene under different humidity.In order to explore the synergistic effect on removing toluene in the catalysis-DBD reactor,this paper investigated the decomposition efficiency and the energy consumption in the catalysis-DBD and the non-catalyst DBD reactors under different humidity.The results showed that the catalysis-DBD reactor had a better performance than the non-catalysis one at the humidity ratio of 0.4%,and the removal efficiency of toluene could reach 88.6% in the catalysis-DBD reactor,while it was only 59.9% in the non-catalytic reactor.However,there was no significant difference in the removal efficiency of toluene between the two reactors when the humidities were 1.2% and 2.4%.Additionally,the degradation products were also analyzed in order to gain a better understanding of the mechanism of decomposing toluene in a catalysis-DBD reactor.     

Improvement of molten core–concrete interaction model in debris spreading analysis module with consideration of concrete degradation by heat

Understanding the situation inside of the reactors at TEPCO's Fukushima Daiichi Nuclear Power Plant and planning of the methods for debris removal are important for decommissioning the reactors. A debris spreading analysis (DSA) module in the severe accident analysis code SAMPSON has been improved and verified to analyze composite phenomena of molten core (debris) spreading on a reactor containment floor and concrete erosion to the inside of the floor by molten core–concrete interaction (MCCI). The primary models in the DSA module were three-dimensional natural convection with simultaneous spreading, melting and solidification in an open space. In addition to these, the analysis capability has been improved to treat phenomena in a closed space, such as debris eroding laterally under concrete floors at the bottom of the sump pit which is done by an advanced method for boundary processing. A buffer cell for flow analysis, which is defined by a different array variable, is arranged in the same coordinates of the concrete cell (structure cell). Mass, momentum, and the advection term of energy between the debris melt cells and the buffer cells are solved. At the same instant, the heat transfer is calculated between the debris melt cells and the structure cells coexisting side by side with the buffer cells. In this study, technical knowledge regarding changes in physical properties due to thermal degradation of concrete was considered for the prediction of erosion rate, and the DSA module with the models noted above was verified by comparison with erosion data of the core–concrete interaction tests in the OECD/MCCI program. The calculated erosion depth, width, and erosion rate under the concrete floor showed good agreement with the test data and the analysis capability of the module was confirmed.     

Effect of low-temperature plasma on the degradation of omethoate residue and quality of apple and spinach

Dielectric barrier corona discharge was developed to generate low-temperature plasma(LTP) to treat apple and spinach samples contaminated with omethoate. Experimental results showed that,after 20 min exposure, the degradation rate of omethoate residue in apple and spinach was(94.55± 0.01)% and(95.55 ± 0.01)%, respectively. When the treatment time was shorter than 20 min,the contents of moisture, vitamin C and beta-carotene were not affected by LTP. Exploration of related mechanisms suggested that LTP might destroy unsaturated double bonds of omethoate and produce phosphate ion, eventually leading to omethoate destruction. It is concluded that appropriate dosage of LTP can effectively degrade omethoate residue in fruits and vegetables without affecting their quality.     

Degradation of antibiotic contaminants from water by gas–liquid underwater discharge plasma

Antibiotic contamination adversely affects human health and ecological balance.In this study,gasliquid underwater discharge plasma was employed to simultaneously degrade three antibiotics,sulfadiazine(SDZ),tetracycline(TC),and norfloxacin(NOR),to address the growing problem of antibiotic contaminants in water.The effects of various parameters on the antibiotic degradation efficiency were evaluated,including the discharge gas type and flow rate,the initial concentration and pH of the solution,and...     

Discoloration of Congo Red by Rod-Plate Dielectric Barrier Discharge Processes at Atmospheric Pressure

A dielectric barrier discharge (DBD) reactor with a rod-plate electrode configuration was used for the oxidative decomposition of Congo red dye in an aqueous solution.Plasma was generated in the gas space above the water interface under atmospheric pressure.Discharge characteristics were analyzed by voltage-current waveforms.Effects of applied voltage,initial conductivity,and initial concentration were also analyzed.Congo red discoloration increased with increased applied voltage and decreased conductivity.The initial conductivity significantly influenced the Congo red discoloration.Under the same conditions,the highest discoloration rate was obtained at 25 mg/L.The presence of ferrous ions in the solutions had a substantial positive effect on Fenton dye degradation and flocculation.At an applied voltage of 20 kV,about 100％of dye was degraded after 4 min of Fe2+/DBD treatment.Results showed that adding a certain dosage of hydrogen peroxide to the wastewater could enhance the discoloration rate.Possible pathways of Congo red discoloration by DBD plasma were proposed based on GC/MS,FTIR,and UV-vis spectroscopy analyses.     

核反应堆初次装料过程中堆芯中子计数率监测装置的研制

为实现核反应堆首次装料及换料过程中的安全控制,研制了核反应堆初次装料监测装置,完成了装置相关机械结构、电气结构设计和制造工作,装置主要包括3 He正比计数管探头组件、脉冲计数装置等.其中,探头组件采用新型结构,机械结构采用马笼头结构防水接头、防水屏蔽套筒和承重核测多芯屏蔽电缆组合的形式,探头组件电路结构采用快电荷灵敏前...     

The degradation of oxadiazon by non-thermal plasma with a dielectric barrier configuration

To explore the feasibility of a degradation approach by non-thermal plasma and the corresponding degradation pathways,studies on the oxadiazon removal in synthetic wastewater by a dielectric barrier discharge plasma reactor were investigated.The loss of the nitro group,dechlorination and ring cleavage is mainly involved in the non-thermal plasma degradation pathways of oxadiazon in a solution based on the OES and LC-MS analysis.Detection of EC25 and the production of the chlorine ion and nitrate ion further demonstrate the feasibility and validity of the approach.The conditions with a proper applied voltage,solution flow rate,oxygen flow rate,and solution pH contribute to the plasma degradation processes with a degradation ratio of over 94％.     

Novel electrode structure in a DBD reactor applied to the degradation of phenol in aqueous solution

Phenol degradation experimental results are presented in a similar wastewater aqueous solution using a non-thermal plasma reactor in a coaxial dielectric barrier discharge. The novelty of the work is that one of the electrodes of the reactor has the shape of a hollow screw which shows an enhanced efficiency compared with a traditional smooth structure. The experimentation was carried out with gas mixtures of 90% Ar–10% O_2, 80% Ar–20% O_2 and 0% Ar–100% O_2. After one hour of treatment the removal efficiency was 76%, 92%, and 97%, respectively, assessed with a gas chromatographic mass spectrometry technique. For both reactors used, the ozone concentration was measured. The screw electrode required less energy, for all gas mixtures, than the smooth electrode, to maintain the same ozone concentration. On the other hand, it was also observed that in both electrodes the electrical conductivity of the solution changed slightly from~0.0115 S m~(-1) up to ~0.0430 S m~(-1) after one hour of treatment. The advantages of using the hollow screw electrode structure compared with the smooth electrode were:(1) lower typical power consumption,(2) the generation of a uniform plasma throughout the reactor benefiting the phenol degradation,(3) a relatively lower temperature of the aqueous solution during the process, and(4) the plasma generation length is larger.     

Degradation of phenol using a combination of granular activated carbon adsorption and bipolar pulse dielectric barrier discharge plasma regeneration

A combined method of granular activated carbon (GAC) adsorption and bipolar pulse dielectric barrier discharge (DBD) plasma regeneration was employed to degrade phenol in water. After being saturated with phenol, the GAC was filled into the DBD reactor driven by bipolar pulse power for regeneration under various operating parameters. The results showed that different peak voltages, air flow rates, and GAC content can affect phenol decomposition and its major degradation intermediates, such as catechol, hydroquinone, and benzoquinone. The higher voltage and air support were conducive to the removal of phenol, and the proper water moisture of the GAC was 20％. The amount of H2O2 on the GAC was quantitatively determined, and its laws of production were similar to phenol elimination. Under the optimized conditions, the elimination of phenol on the GAC was confirmed by Fourier transform infrared spectroscopy,and the total removal of organic carbons achieved 50.4％. Also, a possible degradation mechanism was proposed based on the HPLC analysis. Meanwhile, the regeneration efficiency of the GAC was improved with the discharge treatment time, which attained 88.5％ after 100 min of DBD processing.     

Power control of CANDLE reactor by coolant flow rate

CANDLE reactors do not require control rods for burn-up control. Such reactors can achieve the excellent features of previously-considered CANDLE reactors such as constant power shape and reactivity feedback coefficients during the entire operation period at the rated power level. By eliminating control rod use for power level control, the CANDLE reactor can be operated in a load-following mode and its utility will expand dramatically.By numerical calculations, power control by coolant flow rate was studied for the sodium-cooled metallic fuel large CANDLE reactor. The effect of thermal expansion of the core support structure shows considerable contribution toward achieving negative reactivity feedback to improve the power controllability. We employ HT-9 and SUS316 for core support structures. Since the maximum cladding temperature reaches its design constraint, power level cannot be decreased less than its lower limit, which is 66% for HT-9 and 57% for SUS316.     

The structure optimization of gas-phase surface discharge and its application for dye degradation

A gas-phase surface discharge (GSD) was employed to optimize the discharge reactor structure and investigate the dye degradation. A dye mixture of methylene blue, acid orange and methyl orange was used as a model pollutant. The results indicated that the reactor structure of the GSD system with the ratio of tube inner surface area and volume of 2.48, screw pitch between a high-voltage electrode of 9.7 mm, high-voltage electrode wire diameter of 0.8 mm, dielectric tube thickness of 2.0 mm and tube inner diameter of 16.13 mm presented a better ozone (O3) generation efficiency. Furthermore, a larger screw pitch and smaller wire diameter enhanced the O3 generation. After the dye mixture degradation by the optimized GSD system, 73.21％ and 50.74％ of the chemical oxygen demand (COD) and total organic carbon removal rate were achieved within 20 min, respectively,and the biochemical oxygen demand (BOD) and biodegradability (BOD/COD) improved.     

Prototype of highly efficient liquid electrode pulsating corona plasma reactor for degradation of organics in water

Prototype of atmospheric pressure non-thermal corona plasma reactor, developed for degradation of organics in water, operates at significantly higher frequency than other reactors for that purpose, and without sparks. Its construction provides the umbrella shaped, sustained pulsating corona discharge, with defined discharge oscillations on a given pulse frequency above the water surface. Dye degradation rate decreases with the decrease of discharge current density. Plasmaformed H_2O_2 is consumed in dye degradation. The energy yield of dye degradation is 2.45 g k Wh~(-1) for 50 ppm solution, which is higher than in other publications for comparable experimental conditions.     

Safety and environmental aspects of organic coolants for fusion facilities

Organic coolants, such as OS-84, offer unique advantages for fusion reactor applications. These advantages are with respect to both reactor operation and safety. The key operational advantage is a coolant that can provide high temperature (350–400°C) at modest pressure (2–4 MPa). These temperatures are needed for conditioning the plasma-facing components and, in reactors, for achieving high thermodynamic conversion efficiencies (>40%). The key safety advantage of organic coolants is the low vapor pressure, which significantly reduces the containment pressurization transient (relative to water) following a loss of coolant event. Also, from an occupational dose viewpoint, organic coolants significantly reduce corrosion and erosion inside the cooling system and consequently reduce the quantity of activation products deposited in cooling system equipment. On the negative side, organic coolants undergo both pyrolytic and radiolytic decomposition, and are flammable. While the decomposition rate can be minimized by coolant system design (by reducing coolant inventories exposed to neutron flux and to high temperatures), decomposition products are formed and these degrade the coolant properties. Both heavy compounds and light gases are produced from the decomposition process, and both must be removed to maintain adequate coolant properties. As these hydrocarbons may become tritiated by permeation, or activated through impurities, their disposal could create an environmental concern. Because of this potential waste disposal problem, consideration has been given to the recycling of both the light and heavy products, thereby reducing the quantity of waste to be disposed. Preliminary assessments made for various fusion reactor designs, including ITER, suggest that it is feasible to use organic coolants for several applications. These applications range from first wall and blanket coolant (the most demanding with respect to decomposition), to shield and vacuum vessel cooling, to an intermediate cooling loop removing heat from a liquid metal loop and transferring it to a steam generator or heat exchanger.     

Criticality analysis of pulse core and laser module coupled small reactor with low enriched uranium

Nuclear-pumped laser can directly convert nuclear energy to optical energy. A coupled reactor which consists of two pulse cores with highly enriched metallic uranium and a subcritical thermal laser module with highly enriched metallic uranium is one of the reactors for nuclear-pumped laser. In this paper, criticality analysis of a coupled reactor which consists of pulse cores with 20% enriched metallic uranium and a subcritical thermal laser module with 20% enriched metallic uranium was performed by Monte Carlo calculation. The result of criticality analysis showed the following three points. First, a coupled reactor with 20% enriched metallic uranium can achieve criticality. Second, using eight pulse cores in axial direction is effective to achieve flattened axial power distribution in the laser module. Third, less than 20% of the energy released from fissions in the whole coupled reactor has the possibility to be converted to optical energy for a coupled reactor with 100% enriched uranium, and less than 7% for a coupled reactor with 20% enriched uranium.     

Research on resonance parameters matching based on partitioned operation method of atmospheric pressure plasma reactor array

Matching optimization of resonant parameters among the high power inverters, low power transformers and plasma reactors have significant effects on the performance and output of the reactor array when applying the partitioned operation method. In this paper, the Matlab/ Simulink electrical model was established based on the method of partitioned operation. The matching relation between resonant parameters is analyzed on the basis of experimental result. As a consequence, transformer leakage inductance and working frequency are the important parameters influencing the operational efficiency of system, leakage inductance of transformer should be adjusted based on the equivalent capacitance of plasma reactor to realize the matching optimization of resonant parameters.