Frédéric Fabry

Plasma processing: a step towards the production of new grades of carbon black

Abstract More than 99% of the carbon black is presently produced by incomplete combustion processes; the by far dominant one is the ‘furnace process’ developed 60 years ago. This paper presents a new route in which the cracking operation is carried out in the absence of oxygen thanks to an external electric energy supply given by a plasma arc.

Carbon black processing by thermal plasma. Analysis of the particle formation mechanism

Abstract An original plasma process for carbon black and hydrogen synthesis is presented. A pilot scale ( 100 kW ) reactor is developed to obtain new carbon black grades from hydrocarbon cracking. Even if three populations of particles are observed, the plasma carbon black is mainly characterised by spherical nanoparticles with a high degree of turbostratic organisation. A particle formation mechanism is proposed on the basis of a multiscale analysis of the plasma reactor accounting for: heat and mass balance, RTD measurement and internal flow modelling and particle characterisation by TEM. The mechanism is characterised by two steps: first, a low temperature particle growth and second, a high temperature annealing. As a result, particle structure is strongly related to internal mixing phenomena.

Fullerene production in a 3-phase AC plasma process

We present in this paper a new original process for fullerenes production consisting of treating carbon powders through a 3-phase thermal plasma. The main difference with the classical arc process is that the input carbon rate, not limited to the electrodes erosion, can be independently controlled. As expected, the experiments carried out using ten different industrial carbon grades have shown a high sensitivity depending on the carbon precursor. These results have confirmed that the new process is a very promising route for producing bulk quantities of fullerenes. Before optimization, 3.5% of extractable fullerenes were obtained at atmospheric pressure with acetylene black.

Influence of the Electromagnetic Forces on Momentum and Heat Transfer in a 3-Phase ac Plasma Reactor

A new 3-phase ac plasma reactor has been developed within the framework of research on hydrocarbon cracking for the production of carbon black and hydrogen.(1,2)One of the main characteristics of the system is related to the 3-phase, 50 Hz ac current plasma generator which induces a very particular arc motion affecting the heat and mass transfer inside the reactor. In a first step, the general flow inside the reactor in the absence of hydrocarbon injection has been studied. A simplified approach to characterize the heat and mass transfer inside the reactor is presented in this paper. The arc zone analysis is carried out simultaneously by a theoretical analysis of the electromagnetic forces and by an ultrahigh-speed cine-camera analysis. The flow in the reactor is modeled with a CFD commercial code. Results are compared with experimental temperature measurements.

Production of Carbon Nanotubes and Other Nanostructures Via Continuous 3‐Phase AC Plasma Processing

Abstract The highly flexible plasma system allows the independent flow control of plasma gas, carbonaceous feedstock and metal catalyst. Further important control parameters include current intensity and product quenching rate yielding in an excellent control of the thermal history of the carbon products. Temperature profiles measured along the reactive flow of carbon particles are presented, mapping time–temperature relations for typical operating conditions. In addition, the principle product families are presented. From the characteristics observed and NT product analysis, it is concluded that the AC plasma technology shows a significant potential for the continuous production of bulk quantities of carbon‐based nanotubes of controlled properties and novel tube‐like nanostructures.

Unsteady state analysis of free-burning arcs in a 3-Phase AC plasma torch: comparison between parallel and coplanar electrode configurations

An MHD model with parallel electrode configuration was developed to determine the influence of the electrode configuration on 3-Phase arc discharge behavior. The results obtained with this model were compared to previous results obtained with coplanar graphite electrode configuration. Results show a different arc behavior in both cases. In a parallel electrode configuration, the arcs are not confined within the inter-electrode gap as in coplanar electrode configuration. These results were compared to the arc behavior observed with a high-speed video-camera in a nitrogen atmosphere with a high correlation. The influence of frequency and current was also investigated. By adjusting the electrode configuration, the arc elongation and the dissipated power could be controlled. According to the application, such as plasma-assisted combustion, plasma gasification, plasma spray or for different plasma gases, the electrode configuration could play a key role to improve the discharge or operation. This study gives us a better understanding of 3-Phase AC arc plasma discharge.

Quality and performance of carbon blacks from plasma process

Abstract Plasma carbon black, a new material? For several years already, the Plasma process for carbon black production has been promoted and considered as a threat to the furnace black production. After a brief introduction to the fundamental differences between a partial combustion process and plasma process, plasma blacks have been compared with partial combustion blacks. The plasma blacks have not been optimised but are more a selection of materials based on feedstock and operating conditions. Physico-chemical properties as well as SEM and high resolution TEM micrographs illustrate differences and similarities. Surface heterogeneity of those carbon blacks has been characterised by static gas adsorption. This way the more graphitic nature of the selection of plasma blacks could be demonstrated, explaining the specific behaviour of those blacks in rubber compounds. The specificity of the carbon blacks investigated is not only in the production technique, namely plasma torch, but also in the variety of t...

A Comparison Between MHD Modeling and Experimental Results in a 3-Phase AC Arc Plasma Torch: Influence of the Electrode Tip Geometry

Arc behavior in 3-Phase AC plasma technology remains poorly explored. This system noticeably differs from the classical DC plasma torches and aims to overcome certain limitations, such as efficiency, equipment cost and reliability. A MHD model of a 3-Phase AC plasma torch was recently developed at Mines-ParisTech. The model does not include the electrodes in the computational domain. In parallel, experiments were conducted using a high-speed video camera shooting 100,000 frames per second. In this paper, the comparison between MHD modeling and experimental results shows that the arc behavior is in line with the results from the MHD model. Particularly, the strong influences of both the electrode jets and Lorentz forces on the arc motion are confirmed. However, some differences between experimental and numerical electrical waveforms are observed and particularly in the current–voltage phase shift. A new model was then developed by integrating the electrodes into the computational domain and adjusting the electrode tip geometry. With this simulation, we were able to reproduce the phase shift, power and voltage values with a good accuracy showing the strong influence of electrode tip geometry on the 3-Phase arc plasma discharge.

Continuous production of Fullerenes and other carbon nanomaterials on a semi-industrial scale using plasma technology

A new production method is presented allowing the production of bulk quantities of fullerenes and other carbon nanomaterials using a 3‐phase thermal plasma (260 kW). The main characteristics of this method lie in the independent control of the carbon throughput by injection of a solid carbon feedstock, and the immediate extraction of the synthesised product from the reactor, allowing production on a continuous basis. The currently investigated plasma facility is of an intermediate scale between lab‐size and an industrial pilot plant, ready for further up scaling to an industrial size. The influence of a large number of different carbon precursors, plasma gases and operating conditions on the fullerene yield has been studied. At this state, quantities of up to 1 kg of carbon can be processed per hour with further scope for increase, leading to production rates for this type of materials not achievable with any other technology at present.

Tailor-made carbon nanomaterials for bulk applications via high-intensity arc plasma

Abstract Different families of carbon nanostructures produced by a continuous plasma process are presented. Due to the flexibility of this original technology, properties of classical carbon black products can be adjusted more freely during synthesis and an even wider range of parameters is accessible. Novel products with distinctive characteristics are observed when treating nanostructured material in the high‐temperature plasma. Evaluation of the application properties of selected materials indicates in certain cases an excellent performance. Plasma‐synthesised or plasma‐treated carbon nanomaterials have an important potential to improve the performance of carbon‐black‐containing materials.