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Traditional industrial nitrogen fixation (NF) process uses the Haber-Bosch process which requires high temperature and high pressure, causing high energy consumption and serious pollution. Gliding arc plasma (GAP) combines the advantages of thermal plasma and cold plasma, which can efficiently produce active species and improve energy efficiency obviously. It has great application potential in the field of NF, and has received extensive attention in recent years. However, the research on NF via GAP is relatively fragmented at present. It is necessary to summarize the specific content. The research progress of NF via GAP at home and abroad in past 10 years is reviewed in this paper, mainly including GAP discharge mechanism, reactor design, process parameters and NF reaction mechanism. GAP discharge has B-G mode with breakdown following gliding discharge and A-G mode with continuous steady discharge. A-G mode discharge helps to improve nitrogen fixation efficiency. With the continuous development of GAP discharge technology, the electrode structure in GAP reactor has evolved from the traditional 2D blade structure to a variety of 3D cylindrical structures. Based on process optimization, GAP facilitates the vibrational excitation of N2 molecules, thereby promoting the splitting and transformation of N2 molecules. In the last, the research on NF through GAP is prospected. [ABSTRACT FROM AUTHOR]

Objective The characteristics of molten slag produced by hot plasma melting of oil-based drill cuttings were investigated. Methods The orthogonal experiment was designed with treatment power, treatment distance and treatment time as factors. XRD, XRF, SEM, heavy metal leaching and other means were used to identify the changes of oil-based drilling cuttings before and after melting and the effect of harmless treatment of oil-based drilling cuttings. Results (1) The input power has a significant effect on the thermal plasma melting behavior of oil-based drilling cuttings. When the power is greater than 13 kW, oil- based drilling cuttings turn into spherical glass slag. When the power is 22 kW, the surface smoothness of the slag decreases. (2) The orthogonal test finds that the input power has the greatest influence on the mass fraction of the slag glassy phase, and the thermal plasma treatment distance has the greatest effect on the acid dissolution rate of the slag. When the melting temperature is above 1 300 C, the glassy phase mass fraction of the slag can reach more than 90%. (3) Thermal plasma can completely remove the organic matter in the oil-based drill cuttings. The contents of Cd, Ni, Zn and Pb in the slag are reduced to less than 0. 200 mg/L, 1.000 mg/L. 0.027 mg/L and 0, 100 mg/L. meeting the requirements of relevant policies and regulations about resource utilization. Conclusions Thermal plasma can be used to melt oil-based drill cuttings into glassy slag and seal heavy metals in the glass plase to reduce the leaching rate of heavy metals to meet the needs of harmless. The research results can provide a certain reference for the industrial application of thermal plasma melting technology of oil-based drilling cuttings. [ABSTRACT FROM AUTHOR]

Production of hydrogen from methane in traditional way is accompanied by a mass of carbon dioxide emission. Pyrolysis of methane via plasma for the production of hydrogen and carbon materials could avoid the carbon dioxide emission and provide a way for the high added-value utilized of methane. Therefore, this paper reviews and analyzes domestic and foreign main research progresses on the production of hydrogen and carbon materials by methane pyrolysis using plasma in recent years by means of literature investigation. And the following research results were obtained. First, thermal and cold plasma are the mainly used in the methane pyrolysis. The active species in cold plasma are the high-energy free electrons, the active species in thermal plasma are the high-energy free electrons and heavy particles. Second, the ways to produce cold plasma mainly include corona discharge, dielectric barrier discharge, gliding arc and the power need for generation cold plasma is low. The ways to produce thermal plasma mainly include direct current arc discharge, direct current-radio frequency discharge and the power need for generation thermal plasma is high. Third, the methane conversion and the hydrogen productive rate are related to the plasma gas, the molar ratio between methane and plasma gas, the gas discharge power, the configuration of electrode and the structure of reaction chamber. Fourth, the morphology of carbon materials from methane pyrolysis by plasma differs significantly. The form of carbon materials cloud be carbon black, carbon nanotube, carbon graphene nanosheet and so on, different morphology could be obtained by adjusting the operational condition and configuration of electrode. In conclusion, methane pyrolysis by plasma can reduce the emission of greenhouse gas, moreover, provide a new way for the high added-value utilization of methane. In the future, increasing the energy efficiency for hydrogen production and the selectivity for production of carbon materials are the development direction of methane pyrolysis by plasma. [ABSTRACT FROM AUTHOR]

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