Changming Du

Non-Thermal Plasmas for VOCs Abatement

Volatile organic compounds (VOCs) are some of the most common air pollutants emitted from commercial and industrial processes; VOCs may also reduce indoor air quality. Increased environmental awareness, however, has resulted in stringent regulations controlling VOCs emission and has motivated researchers to develop various kinds of treatment. Non-thermal plasma (NTP) processes are regarded as promising methods for VOCs abatement. This paper reviews the state of the art and achievements of NTP for VOCs abatement and includes a description of several reactor configurations based on different discharge principles. Of particular interest are NTP-catalytic systems, characterized by higher energy efficiencies and lower byproduct production than the NTP-alone systems. Physical–chemical effects of NTP-catalytic systems occurring during plasma catalytic processes are discussed. The NTP decomposition mechanisms for toluene, naphthalene and trichloroethylene are discussed in detail. Influences of various processing parameters are summarized, and comments are given based on removal efficiencies and operational costs.

Enhanced hydrogen production by methanol decomposition using a novel rotating gliding arc discharge plasma

Hydrogen production from methanol decomposition was performed in a novel direct current (DC) rotating gliding arc (RGA) plasma reactor. The effects of various important parameters (feed flow rate, applied voltage, CH3OH concentration, operating current, preheating temperature, and water addition) on the reaction performance of the plasma methanol decomposition were investigated. The results showed that increasing the applied voltage and the operating current remarkably enhanced the CH3OH conversion in contrast to the effects of increasing feed flow rate, CH3OH concentration, and water addition. The selectivities of gas products (primarily H2 and CO) appeared to be positively correlated with the specific energy input. A comparison of the methanol decomposition processes using different non-thermal plasmas (e.g., dielectric barrier discharge and corona discharge) clearly showed that the RGA plasma provided a significantly higher CH3OH conversion (28.6–95.6%) and a relatively high energy yield of H2 (8.5–32.0 g kW−1 h−1) while maintaining a processing capacity that was several orders of magnitude higher than the other plasmas. A mathematical model was established to predict the CH3OH conversion and energy yield of H2. The model sensitivity analysis indicated that the CH3OH concentration was the most influential parameter, whereas the water addition was the least important parameter for the reaction performance.

Decontamination of Bacteria by Gas-Liquid Gliding Arc Discharge: Application to \(Escherichia~coli\)

This paper investigated the bacterial inactivation/sterilization effects of a gas-liquid gliding arc discharge reactor, which created plasma at atmospheric pressure and ambient temperature. Bacteria Escherichia coli were subjected to plasma treatment and the survivability was examined. With the bacteria suspension circulated at defined flow rate, the E. coli cells were almost killed in <;3 min. The inactivation efficiency with circulation was much higher than that with no circulation, and it could even reach a reduction of 7 logarithm units in the number of viable bacteria within 30 s after 1-min treatment. Flow rates of the suspension caused slightly impact on the bacteria inactivation to a certain extent. Observations of scanning electron microscopy images helped to draw a conclusion that gas-liquid gliding arc discharge plasma acts under various mechanisms driven essentially by oxidation and electric effect. The results demonstrate that gas-liquid gliding arc discharge allows a rapid and complete inactivation of E. coli bacteria in the water, which shows the great industrial interest of gliding arc discharge technique for decontamination.

Qualitation and Quantitation on Microplasma Jet for Bacteria Inactivation

In this work, a self-made microplasma jet system was used to conduct the qualitation and quantitation of inactivation with Escherichia coli as the target bacteria. The logarithmic concentration and the size of antimicrobial rings served as the evaluation parameters, respectively. The effect of various parameters on inactivation effect was studied. The results showed that the majority of bacteria had been inactivated in 30 s. The inactivation effect enhanced and then weakened with the increase of air flow rate, and receded as the extension of treatment distance. The effect with different carrier gases showed as follows: oxygen > air > nitrogen > argon. Meanwhile, the effect of different components of microplasma was studied in the optimum conditions (The flow rate was 5 L/min; inactivation distance was 2 cm). The results showed that electrically neutral active species was the main factor of inactivation rather than heating effect, ultraviolet radiation and charged particles. Finally the experiments of thallus change proved that microplasma jet had etching effect on cell membrane. It also found that microplasma could degrade organic material like protein. Furthermore, the images of scanning electron microscope (SEM) revealed the change of cell morphology step by step in the whole process of inactivation.

Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H2, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper temperature and H2 concentration was indispensable for the synthesis of VG sheets. Rich defects of VG were formed with a high ID/IG ratio (1.29), consistent with the dense edges structure observed in electron microscopy. Additionally, the morphologies, crystalline degree, and wettability of nanostructure carbon induced by PECVD and ICP separately were comparatively analyzed. The present work demonstrated the potential of our PECVD recipe to synthesize VG from abundant natural waste oil, which paved the way to upgrade the low-value hydrocarbons into advanced carbon material.

Hydrodynamics of Plasma Fluidized Bed

This chapter systematically reviews the hydrodynamics of plasma fluidized bed and its progress. Firstly, the hydrodynamics of plasma spouted bed is introduced from the aspects of minimum spouted velocity, spoutable height, pressure drop and particle attrition, and the relevant formulas are given. Finally, the hydrodynamics of plasma fluidized bed was analyzed.

Heat Transfer and Mass Transfer in the Plasma Fluidized Bed

This chapter introduces the heat transfer and mass transfer of plasma fluidized bed from three aspects: temperature distribution, heat transfer, circulation and mass transfer in the plasma fluidized bed. In terms of heat transfer, the effects of gas ionization effects, radiation effects and evaporation effects are introduced in detail, and the specific calculation formulas are given. In addition, this chapter summarizes the conditions and parameters of many studies and practical applications, which provide references for future research and application.

Scientific and Industrial Application of Plasma Fluidized Bed

This chapter introduces the application of plasma fluidized bed in detail, including the following four fields: metallurgy process, coal gasification and pyrolysis, environmental protection and materials. The metallurgy process includes: metallurgy extraction, synthetic of calcium carbide, alloy granulation, etc. In the field of gasification/pyrolysis of coal, including gasification/pyrolysis of coal for acetylene, pyrolysis/gasification of coal to syngas, biomass pyrolysis/gasification, gasification/pyrolysis of biomass for syngas, gasification/pyrolysis of biomass for bio–oil, gasification of solid waste cracking of heavy hydrocarbon and reformation of biogas. In terms of environmental protection, there are applications of abatement of VOCs, control of NOx, sterilization of food, plasma modified catalyst for water purification and solid waste treatment. In the field of materials, there are applications of surface activation and functionalization, plasma enhanced chemical vapor deposition (PECVD) and synthesis of nanoparticles. The application of plasma fluidized bed has been widely used, and it has a wide application prospect.

Applicative Ability and Environmental Risk

This chapter analyses the application and environmental risks of plasma fluidized bed. Firstly, energy analysis and economic analysis are mentioned. Plasma fluidized bed has more advantages than traditional processes. Secondly, the application ability and environmental risk are mentioned. The problem of plasma fluidized bed has not been reported in the relevant literature. Therefore, further research and discovery are needed in this area. Finally, the prospect of future application of plasma fluidized bed is presented in this chapter, and several existing problems are proposed, which need further development and improvement.

Influencing Factors on Understanding Plasma Fluidized Bed

There is a comprehensive introduction about the influencing factors of plasma fluidized bed treatment effect in this chapter, which includes: the resident time, input power, gas flow rate, carrier gas composition, the design of the distributor, gas pressure, temperature, particle size and density, solid mass flow rate. All kinds of influencing factors are analyzed in detail, and the relevant precautions when using plasma fluidized bed are presented.