Experimental Study On Preparation Of Carbon Black By Magnetically Rotating Arc Plasma

Carbon black,as a chemical basic raw material is widely applied to rubber,ink,coating,plastic,electronic components and many other industrial fields.Compared with the traditional process,the production of carbon black by plasma method has the advantages of high carbon yield,high energy efficiency and a large reduction of emissions.Furthermore,the rate of heat transfer and chemical reaction increases remarkably due to the characteristics of high temperature,high chemical activity and optional inert,oxidizing or reducing atmosphere in plasma.In this paper,carbon nanomaterials are prepared by pyrolysis of various hydrocarbons using magnetically rotating arc thermal plasma.The effects of temperature and feedstocks on the morphology and structure of carbon black particles are investigated,in order to find out the evolution law and microscopic physical properties of plasma carbon black particle aggregates.Contents and results as follows:A plasma reactor for carbon black is designed which employs argon as plasma gas and methane,ethylene and acetylene as feedstocks.The relationship between experimental parameters(reaction temperature,raw material flow rate)and the device should be established before research.So the radial temperature distribution of reactor is measured by B-type platinum-rhodium thermocouple.Meanwhile,the temperature and flow field are simulated by computational fluid dynamics(CFD).The experimental and numerical simulation results exhibit the flow heat transfer characteristics of the magnetic rotating arc plasma generator and the reactor.Carbon black particles are obtained by plasma pyrolysis of hydrocarbons at atmospheric pressure.The transmission electron microscopy(TEIM)and image postprocessing are applied to characterize the fractal dimension,particle size distribution and average particle size.Results show that all products are spherical carbon particles at lower reaction temperature(1500K).As the temperature increases,the primary particle size decreases,the fractal dimension becomes larger,and the morphology becomes more complex.Additionally,the graphene flakes are obtained by the pyrolysis of methane and ethylene at higher reaction temperature(2500K).Preliminary analysis indicates that the process of nucleation,surface growth and collisions of primary particles are affected by the reaction temperature and hydrocarbons species,which determines morphology of final products.High-resolution transmission electron microscopy,Raman spectroscopy and X-ray diffraction analysis were used to characterize the nanoscopic morphology and structural properties of the primary particles of carbon black.The results show that the microcrystal structure of the primary particles of the three pyrolysis products change significan tly with the increase of temperature,and the primary particles develop from multi-nuclear disordered structure to ordered structure.Raman spectral peak fitting and XRD analysis indicate that an increase in temperature leads to a corresponding increase in the degree of graphitization of the three materials.At the same temperature,the internal structure of the primary particles of different raw materials is different.The acetylene primary particles have more on-order ordered onion structures.The primary particles formed by methane and ethylene are mostly composed of disordered short carbon layers.The degree of graphitization of different raw materials is more complicated,which means that changing the raw materials will also cause the change of the microcrystalline structure inside the primary particles,thus affecting the physical and chemical properties of the carbon black particles.