Naphthalene destruction performance from tar model compound using a gliding arc plasma reformer

Recycling of various wastes such as sewage sludge requires an energy conversion process like thermal pyrolysis/gasification. During the process, tar and syngas are produced, but the tar brings trouble in pipelines and creates operating problems for the facility. In this study, to investigate naphthalene destruction in a gliding arc plasma reformer, parametric experiments were achieved in the variables that can affect the destruction efficiency. And through the parametric studies, the optimal operating conditions and the results were taken. For the parametric studies, steam input amount (steam/carbon ratio), input discharged power SEI (specific energy input), total feed gas amount, input naphthalene concentration, and electrode length were selected for experiments. Optimal conditions were 2.5 of S/C ratio, 1 kWh/m³ of SEI, 18.4 L/min of total gas amount, 1% of input naphthalene concentration, and 95 mm of electrode length. The corresponding maximum destruction efficiency of naphthalene was 79%, and energy efficiency showed 47 g/kWh.     

H2 production by ethanol decomposition with a gliding arc discharge plasma reactor

A gliding arc discharge (GRD) reactor was used to decompose ethanol into primarily H₂ and CO with small amounts of CH₄, C₂H₂, C₂H₄, and C₂H₆. The ethanol concentration, electrode gap, input voltage and Ar flow rate all affected the conversion of ethanol with results ranging from 40.7% to 58.0%. Interestingly, for all experimental conditions the S_H2/S_CO selectivity ratio was quite stable at around 1.03. The mechanism for the decomposition of ethanol is also described.     

Surface modification of multiwalled carbon nanotubes via gliding arc plasma for the reinforcement of polypropylene

To increase the applicability of multiwalled carbon nanotubes (MWCNTs), functional groups were generated on the generally inert surface of MWCNTs using gliding arc (GA) plasma. MWCNTs were modified using plasma polymerization with styrene (St) as monomer. The surface compositional and structural changes that occur on MWCNTs were investigated using FT‐IR, Raman spectroscopy, BET surface area, and elemental analysis. Dispersion of the treated MWCNTs in different solvents was evaluated. Transmission electron microscopy images showed that the plasma‐treated MWCNTs had a better dispersion than the untreated ones in nonpolar solvents. Subsequently, MWCNTs‐reinforced polypropylene (PP) composites were prepared by internal batch mixing with the addition of 1.0 wt % MWCNTs. The morphology of MWCNTs/PP nanocomposites was studied through scanning electron microscopy. Observations of SEM images showed that the plasma‐treated MWCNTs had a better dispersion than the untreated MWCNTs either on the composite fracture surfaces or inside the PP matrix. Moreover, the mechanical tests showed that the tensile strength and elongation at break were improved with the addition of polystyrene‐grafted MWCNTs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

On a possible mechanism of the methane steam reforming in a gliding arc reactor

This work is dedicated to the study of methane steam reforming (SR) using a rotating discharge reactor. The process efficiency is described in terms of methane conversion, SR selectivity, energy input and hydrogen production cost. The experiments clearly demonstrated the ability of glidarc to accelerate chemical reactions at low temperatures and with very low energetic costs. A good approximation model describing the chemical processes on the basis of classical thermodynamics is also proposed. The analysis gives information on reactor design in order to improve its chemical performances.     

旋转滑动弧降解垃圾气化焦油组分中的萘

采用新型磁场和气流协同驱动旋转滑动弧等离子体,选取萘作为垃圾气化焦油模拟组分,在氮气气氛下开展了焦油裂解初步实验研究。重点考察了进样浓度、进气流量和预热温度对萘裂解效果及气体产物的影响;此外,采用气相色谱质谱联用仪（GC/MS）对液体副产物进行了表征。结果表明,当进气流量恒定时,随着进样浓度的提高,萘的降解率先升后降,在萘浓度为6mg/L时降解率达到最大值88.3%;随着进气流量从2L/min增加到12L/min,萘的降解率持续下降,由92.1%降至82.5%;提高预热温度可促进萘的降解。实验产生的主要气体产物为H₂和C₂H₂,其选择性与萘的降解率变化趋势基本一致,最高分别为44.0%和13.7%;液体副产物主要有苯乙炔、茚、苊烯等,其GC/MS峰面积比萘低2~3个数量级;在此基础上,对滑动弧反应区域中萘的降解路径及机理进行了初步探讨与分析。     

Flame versus air atmospheric gliding arc plasma treatment of polypropylene-based automotive bumpers: Physicochemical characterization and investigation of coating properties

In this research, the polypropylene (PP) sheets used for automotive bumper surface were treated using two methods: air atmospheric gliding arc plasma and flame modifications. Atomic force microscopy was applied to study the morphology of surfaces before and after treatment processes. While calculating the surface free energy (SFE), contact angle of the surfaces was measured, and the chemical composition of the PP surface was analyzed using X-ray photoelectron spectroscopy. Surface modifications by gliding arc plasma increased the ratio of the oxygen and nitrogen atoms on the surface by 100%, indicating that polar chemical functionalities form on the surface. The surface morphology was highly affected by gliding arc plasma treatments, which triggered an impact on roughness and etching. It was also found that the SFE was drastically increased by certain modifications. Noticeable improvement was also observed in wettability by the gliding arc plasma technique. In the next stage, polyurethane paints were coated on the treated and untreated PP surfaces. Then, we examined the flame and gliding arc plasma treatments' effect on coating properties of PP bumper, adhesion analysis, water immersion resistance, and sulfuric acid resistance. Finally, high-pressure carwash test and gloss analysis were conducted on the treated and untreated coated sheets, respectively.     

直流电弧等离子体甲烷二氧化碳重整反应

采用一种简单结构的直流电弧反应器,在无催化剂存在的条件下,高效率地实现了毫秒级甲烷二氧化碳的重整反应,产物选择性好,并且在反应过程中几乎没有积炭生成。在恒定输入功率(170W)的条件下考察了气体总流量和二氧化碳/甲烷摩尔比对反应结果的影响。提高反应气体的输入能量密度可以提高甲烷和二氧化碳的转化率,并且能够有效地抑制副产物的生成。当二氧化碳/甲烷摩尔比为1时,二氧化碳转化率为89.8%,甲烷转化率为96.3%,氢气和一氧化碳的选择性分别为99.6%和99.3%。二氧化碳过量可显著促进甲烷的转化以及同时获得合成气的高选择性。采用比能耗对该过程的能量利用效率进行了分析,以期指导反应条件优化以提高过程的能量利用效率。     

大功率旋转弧氢等离子体裂解丙烷制乙炔

通过合理的简化计算,建立了物料与能量衡算模型,优选工艺条件,并进行了MW级旋转弧氢等离子体裂解丙烷制乙炔的实验研究,考察了碳氢比与氢气比焓对裂解反应的影响。实验中输入功率的最大值为794.2 kW,实验结果表明:在实验范围内,丙烷的转化率维持在99.8%以上,裂解气中乙炔的最高含量达到了12.65%;碳氢比增加时,乙炔收率和比能耗均存在最佳点;氢气比焓增加时,乙炔收率存在最佳点,而比能耗则逐渐增加;实验中得到的最高乙炔收率为85.4%,最低比能耗为8.85 kW·h·(kg C₂H₂)^-1。实验结果验证了物料与能量衡算模型可以用于指导工艺条件的优选。     

Hydrogen enrichment of fuels using a novel miniaturised chemical looping steam reformer

Experiments were conducted on the Fe₃O₄/FeO metal oxide system under pure methane and pure steam environments in a thermogravimetric analyser (TGA) and a prototype-miniaturised micro-reactor. Experimental results show that during a typical fuel oxidation step the concentration of methane in the product gas stream gradually decreases while Fe₃O₄ is being reduced to FeO. However, on or about a fractional conversion of 60% the slope of the CH₄ plot sharply increases due to catalytic effects of FeO on methane decomposition. Similarly, the H₂ plot associated with steam reforming step picks up rapidly and reaches a maximum of 98% at a fractional conversion of 30%. The conversion times of steam and fuel in the micro-reactor were generally shorter than conversion times obtained in the TGA system. The experimental results provided two vital pieces of information: (i) the chemical looping steam reforming cycle is technically viable, and (ii) the performance of the process at micro-scales needs to be further understood before high throughput miniaturised reformers could be designed and built.     

Computational analysis of the reacting flow in a microstructured reformer using a multiscale approach

A multiscale methodology is presented to analyze the transport and reaction processes in the catalyst coating of a microstructured reformer and to elucidate the effect of catalyst morphology on transport limitations and the reformer performance. This analysis includes three‐dimensional simulations of methane steam reforming at both reactor level (macroscale) and catalyst microstructure level (microscale). Hypothetical catalyst microstructures are generated using an in‐house particle packing code. Based on the generated structures, the effective transport properties of the porous catalyst and the average reaction rates in the microstructure are determined to be applied in the pseudohomogeneous model used in the macroscale simulation. Parametric study is done to demonstrate the significant effect of the catalyst intraparticle and interparticle porosity as well as the particle size on the reaction effectiveness factor and methane conversion. This study shows that an optimal catalyst coating has a decreasing porosity along the reformer length based on the difference in the degree of diffusion limitation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2263–2274, 2014     

Plasma assisted nitrogen oxide production from air: Using pulsed powered gliding arc reactor for a containerized plant

The production of NO_x from air and air + O₂ is investigated in a pulsed powered milli‐scale gliding arc (GA) reactor, aiming at a containerized process for fertilizer production. Influence of feed mixture, flow rate, temperature, and Ar and O₂ content are investigated at varying specific energy input. The findings are correlated with high‐speed imaging of the GA dynamics. An O₂ content of 40–48% was optimum, with an enhancement of 11% in NO_x production. Addition of Ar and preheating of the feed resulted in lower NO_x production. Lower flow rates produced higher NO_x concentrations due to longer residence time in the GA. The volume covered by GA depends strongly on the gas flow rate, emphasizing that the gas flow rate has a major impact on the GA dynamics and the reaction kinetics. For 0.5 L/min, 1.4 vol % of NO_x concentration was realized, which is promising for a containerized process plant to produce fertilizer in remote locations. © 2017 American Institute of Chemical Engineers AIChE J, 64: 526–537, 2018     

Synthesis of ultrafine silicon carbide nanoparticles using nonthermal arc plasma at atmospheric pressure

It remains a significant challenge for the scalable production of ultrafine silicon carbide (SiC) nanoparticles with sizes smaller than 10 nm. In this work, a novel process based on atmospheric nonthermal arc plasma was proposed for the continuous synthesis of ultrafine SiC nanoparticles. This low-cost and scalable technique allows preparation of SiC nanoparticles with small size (5–9 nm) and narrow size distribution via hexamethyldisilane (HMDS) decomposition in an argon/hydrogen plasma environment. The as-synthesized products were carbon-rich β-SiC nanoparticles with plentiful functional groups on the surface. The addition of hydrogen in plasma gas can tune the product characteristics, such as decreasing particle size, improving crystallinity, and reducing carbon and oxygen contents. Moreover, the as-prepared β-SiC nanoparticles had a high band gap (around 2.5 eV), and their photoluminescence peak showed an obvious blueshift relative to that of bulk β-SiC, which was mainly attributed to the quantum confinement effect induced by their ultrafine size. According to the spectral information of arc plasma, the formation of SiC nanoparticles in the plasma was discussed.     

直流电弧等离子体喷射法高速制备高质量纳米金刚石膜研究

利用直流电弧等离子体喷射法沉积装置在底径Ф65mm高5mm的Mo球面衬底上成功制备出纳米金刚石薄膜,文章研究了在稳定电弧状态下碳氢比对金刚石膜形貌的影响.通过扫描电子显微镜、原子力显微镜及Raman光谱对样品的晶粒尺寸及质量进行了表征. 研究结果表明: 在稳定电弧状态下,通过提高碳氢比可以在Mo球面衬底上的表面高速沉积出高质量的纳米金刚石薄膜, 晶粒尺寸大约为4～80nm,平均粒径27.4nm.     

Transformation of polymers in a stream of low-temperature arc discharge plasma

Spraying of polymer materials in a low-temperature plasma stream is a very efficient way of depositing polymer coatings on large surfaces. The deposition of powdered polymers by an arc discharge plasma flow and spraying from the bulk have been compared. The properties of powdered polymers do not change considerably during transportation by the stream because of the short residence of the particles in the plasma. When spraying from the bulk, polymers are transported in the form of melt droplets (polyethylene, polycarbonate) or in gaseous phase (polytetrafluoroethylene); autohesion of the droplets or secondary polymerization occurs, respectively, on the substrate surface. This process offers high-quality thin films and coatings whose structure depends significantly on the characteristics of the substrate as well as on the structure of the source polymer. Obtained polymer coatings contain nitrogen and oxygen entrapped from the atmosphere as well as (on the glass surface) the products of glass etching. This fact enables one to vary widely the properties of the coatings. Furthermore, the problem of obtaining combined protective coatings in which polymer melt fills the pores between metal particles can be solved successfully in a united technological cycle including plasma spraying of the polymer and the metal. © 1995 John Wiley & Sons, Inc.     

Enhanced ablation of small anodes in a carbon nanotube arc plasma

The ablation rate of a graphite anode is investigated as a function of anode diameter for a carbon nanotube arc plasma. It is found that anomalously high ablation occurs for small anode diameters. This result is explained by the formation of a positive anode sheath. The increased ablation rate due to this positive anode sheath could imply greater production rate for carbon nanotubes.     

Production of synthesis gas from methane using compression ignition reformer

A new form for a partial oxidation compression ignition reformer, which is different from existing methods of reformation, is suggested to which the concept of super-adiabatic combustion is applied. In addition, experiments are conducted on variables such as the oxygen/methane ratio, the total flow rate, the intake preheating temperature, and the oxygen enrichment ratio, all of which affect the production of hydrogen, in order to understand the optimal features of the movement of the reformer. Results showed that the concentration of hydrogen and carbon monoxide was 20.84% and 13.36%, respectively, under the optimal standard conditions of an oxygen/methane ratio of 0.26, a total flow rate of 106.5 L/min, and an intake preheating temperature of 355 oC. Under the same conditions, the concentration of hydrogen decreased to 20.31% when the oxygen enrichment ratio was 55.6%, while that of carbon monoxide increased to 20.85% when the oxygen enrichment ratio was 50.33%.     

Thermal treatment of municipal solid waste incinerator fly ash using DC double arc argon plasma

In this study, glassy slag was produced by melting fly ash samples without any additives in a thermal plasma reactor, the core of which was a DC double anode plasma torch. After vitrification, there was an obvious change in the microstructural and the mineralogical characterization, an excellent resistance against leaching of heavy metal ions and a significant decomposition rate (99.95%) of PCDD/Fs in TEQ in the produced slag. These results indicate that the thermal plasma vitrification is an alternative technology with high efficiency and energy to dispose MSWI fly ash.     

Operating characteristics and energy distribution in a nitrogen transferred arc plasma

The electrical characteristics of a nitrogen transferred arc plasma were measured in a closed chamber, which simulated a plasma furnace. The total arc voltage depended strongly on the arc length and much less on current and plasma gas volumetric flow rate, with a voltage gradient of about 12 V/cm. The various mechanisms accounting for the transfer of the energy in the arc to the system were identified and measured. The two major components of the energy distribution were by electron transfer to the anode (whether water-cooled solid copper or molten metal) and by radiation from the plasma column. The significance of these measurements for the design and optimization of plasma furnaces is discussed.