Development and Optimization of Modular Hybrid Plasma Reactor

INL developed a bench–scale, modular hybrid plasma system for gas-phase nanomaterials synthesis. The system was optimized for WO{sub 3} nanoparticle production and scale-model projection to a 300 kW pilot system. During the course of technology development, many modifications were made to the system to resolve technical issues that surfaced and also to improve performance. All project tasks were completed except two optimization subtasks. Researchers were unable to complete these two subtasks, a four-hour and an eight-hour continuous powder production run at 1 lb/hr powder-feeding rate, due to major technical issues developed with the reactor system. The 4-hour run was attempted twice, and on both occasions, the run was terminated prematurely. The termination was due to (1) heavy material condensation on the modular electrodes, which led to system operational instability, and (2) pressure buildup in the reactor due to powder clogging of the exhaust gas and product transfer line. The modular electrode for the plasma system was significantly redesigned to address the material condensation problem on the electrodes. However, the cause for product powder clogging of the exhaust gas and product transfer line led to a pressure build up in the reactor that was undetected. Fabrication of the redesigned modular electrodes and additional components was completed near the end of the project life. However, insufficient resource was available to perform tests to evaluate the performance of the new modifications. More development work would be needed to resolve these problems prior to scaling. The technology demonstrated a surprising capability of synthesizing a single phase of meta-stable #2;{delta}- Al{sub 2}O{sub 3} from pure #2;{alpha}-phase large Al{sub 2}O{sub 3} powder. The formation of {delta}#2;-Al{sub 2}O{sub 3} was surprising because this phase is meta-stable and only formed between 973–1073 K, and {delta}#2;-Al{sub 2}O{sub 3} is very difficult to synthesize as a single phase. Besides the specific temperature window to form this phase, this meta-stable phase may have been stabilized by nanoparticle size formed in a high-temperature plasma process. This technology may possess the capability to produce unusual meta-stable nanophase materials that would otherwise be difficult to produce by conventional methods. A 300 kW INL modular hybrid plasma pilot-scale model reactor was projected using the experimental data from PPG Industries’ 300 kW hot-wall plasma reactor. The projected size of the INL 300 kW pilot model reactor would be about 15% that of the PPG 300 kW hot-wall plasma reactor. Including the safety-net factor, the projected INL pilot-reactor size would be 25-30% of the PPG 300 kW hot-wall plasma pilot reactor. Due to the modularity of the INL plasma reactor and the energy-cascading effect from the upstream plasma to the downstream plasma, the energy utilization is more efficient in material processing. It is envisioned that the material throughput range for the INL pilot reactor would be comparable to the PPG 300 kW pilot reactor, but energy consumption would be lower. The INL hybrid plasma technology is rather close to being optimized for scaling to a pilot system. More near-term development work is still needed to complete the process optimization before pilot scaling