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This paper deals with the investigation of nonsteadystate discharge regimes in the plasmatron as applied to air--hydrocarbon mixtures. The electrode system is based on the design of a classical high-current arc plasmatron. Compared with a thermal plasmatron mode, the averaged discharge current in the described device has been decreased to about 0.2 A. Then, the discharge regime can be interpreted as a kind of glow discharge with the random transitions from glow to sparks. Two types of transitions have been observed: completed and noncompleted transitions. Completed transition is accompanied by the appearance of a high-conductivity spark channel, and for noncompleted transition, a low-conductivity diffuse channel arises. The discharge features have been investigated for plasmatrons with a long-length and with a short-length anode nozzle. The principal features of the nonsteady-state discharge behavior are the same for both designs. However, for the long nozzle, the discharge phenomena mainly proceed inside the anode cavity and for the short nozzle outside the cavity. Use of different designs of the plasmatron anode cavity offers to extend an area of plasmatron applications. Index Terms--Combustion stabilization, glow-to-spark transition, hydrocarbon partial oxidation, plasma torches.

This paper presents thermodynamic and kinetic modeling of plasma-aided bituminous coal gasification. Distributions of concentrations, temperatures, and velocities of the gasification products along the gasifier are calculated. Carbon gasification degree, specific power consumptions, and heat engineering characteristics of synthesis gas at the outlet of the gasifier are determined at plasma air/steam and oxygen/steam gasification of Powder River Basin bituminous coal. Numerical simulation showed that the plasma oxygen/steam gasification of coal is a more preferable process in comparison with the plasma air/steam coal gasification. On the numerical experiments, a plasma vortex fuel reformer is designed. Index Terms--Coal, kinetic simulation, plasma-aided gasification, thermodynamic modeling, vortex fuel reformer.

The authors report the results of design and experimental investigation of a high flow and high concentration NOx production system based on a radio frequency (RF) plasma torch for a variety of applications. Unique gas dynamics of the first stage avoids plasma disturbance by feeding quenching gas and enables NO oxidation into NO2 with a total NOx yield over 6% by mass. The developed system is tunable for NOx concentration, scalable for higher flow, applicable for various technological processes, flexible for using different plasma gases and quenching media, including gases, liquids, and solids. [ABSTRACT FROM AUTHOR]

This article reports results of the design and experimental investigation of a high-flow and high-concentration NOx production system based on a radio-frequency plasma torch for a variety of applications. The system includes a commercial APT-100 plasma torch with plume power from 25 to 35 kW, a double-stage quenching reactor with “fast” first stage and “slow” second stage, measuring unit, and auxiliary systems. The first stage allows quenching by any gas, such as air, air-based blends, and the products of recirculation. [ABSTRACT FROM AUTHOR]

Oxidant selection is the highest priority for advanced coal gasification-process development. This paper presents comparative analysis of the Powder River Basin bituminous-coal gasification processes for entrained-flow plasma gasifier. Several oxidants, which might be employed for perspective commercial applications, have been chosen, including air, steam/carbon-dioxide blend, carbon dioxide, steam, steam/air, steam/oxygen, and oxygen. Synthesis gas composition, carbon gasification degree, specific power consumptions, and power efficiency for these processes were determined. The influence of the selected oxidant composition on the gasification-process main characteristics have been investigated. Index Terms--Coal, modeling, oxidant, plasma gasification.

The major advantages of a new plasma-assisted fuel reformation system are its cost effectiveness and technical efficiency. Applied Plasma Technologies has proposed its new highly efficient hybrid-type plasma-assisted system for organic fuel combustion and gasification. The system operates as a multimode multipurpose reactor in a wide range of plasma feedstock gases and turndown ratios. This system also has convenient and simultaneous feeding of several reagents in the reaction zone such as liquid fuels, coal, steam, and air. A special methodology has been developed for such a system in terms of heat balance evaluation and optimization. This methodology considers all existing and possible energy streams, which could influence the system's efficiency. The developed hybrid-type plasma system could be suitable for combustion applications, mobile and autonomous small- to mid-size liquid fuel and coal gasification modules, hydrogen-rich gas generators, waste-processing facilities, and plasma chemical reactors. Index Terms--Coal, combustion, liquid fuel, plasma, reformation, waste processing.

The mathematical model of a direct-current arc at atmospheric pressure and low currents has been proposed. This paper presents the results of 2-D simulations for an air arc within the plasmatron channel, as well as the anode, composite cathode, and external regions. The model does not employ any adjustable parameter and therefore enables direct comparison with the experiments. The model predictions were compared with the experimental data of a plasma igniter and indicated good agreement. Index Terms--Air arc, conjugate problem, thermal plasma.

The major advantages of plasma treatment systems are cost effectiveness and technical efficiency. A new efficient electrodeless 1-MW hybrid plasma torch for waste disposal and coal gasification is proposed. This product merges several solutions such as the known inductive-type plasma torch, innovative reverse-vortex (RV) reactor and the recently developed nonequilibrium plasma pilot and plasma chemical reactor. With the use of the computational-fluid-dynamics-computational method, preliminary 3-D calculations of heat exchange in a 1-MW plasma generator operating with direct vortex and RV have been conducted at the air flow rate of 100 g/s. For the investigated mode and designed parameters, reduction of the total wall heat transfer for the reverse scheme is about 65 kW, which corresponds to an increase of the plasma generator efficiency by approximately 6.5%. This new hybrid plasma torch operates as a multimode, high power plasma system with a wide range of plasma feedstock gases and turn down ratio, and offers convenient and simultaneous feeding of several additional reagents into the discharge zone. Index Terms--Coal, modeling, plasma, waste processing.

This paper deals with the investigation of a new regime in a plasma ignition and flame control system as applied to air-hydrocarbon mixtures. The system is based on the design of a classical high-current arc plasmatron. Compared with a thermal plasmatron mode, the average discharge current in the described device has been decreased to about 0.1 A. Although average power dissipated in the discharge does not exceed 200 W and average gas temperature at the plasmatron exit for typical regimes of the discharge operation in air is less than 500 K, the device demonstrates reliable ignition and flame stabilization in a wide range of equivalence ratios. Physical mechanism of ignition is associated with the nonsteady-state properties of discharge. At a low current level, the discharge burns in a kind of glow mode, and because of the glow-to-spark transitions, the high-current nanosecond pulses are superimposed on the glow plasma background. Then, the spark discharge initiates the combustion process, which is efficiently sustained in the glow plasma. Index Terms--Combustion stabilization, glow-to-spark transition, ignition, plasma torches.

This paper deals with investigations of gas discharge in a recently developed plasma pilot for ignition and flame control. The characteristic features of this discharge burning mode are extremely low current (about 0.1 A) and low average power (less than 100 W). However, ignition and flame stabilization in a wide range of equivalence ratios for air-hydrocarbon mixtures are demonstrated. The physical mechanism of ignition is associated with the nonsteady-state properties of discharge. At the low current level, discharge burns in a kind of glow mode, and because of the glow-to-spark transition, the high-current nanosecond pulses are superimposed on the glow plasma background. Then spark discharge initiates combustion process, which is efficiently sustained in the glow plasma. Index Terms--Combustion stabilization, glow-to-spark transition, plasma pilot, plasma torches.