The plasma-driven gas-phase thermal decomposition of methane yielding hydrogen and solid-phase carbon has been suggested as an environmentally friendly alternative to conventional
methods of producing hydrogen from natural gas. The advantage of the process is that hydrogen
is obtained directly from methane without producing CO2 as a byproduct. The process was
experimentally examined using a modified version of a dc plasma reactor originally developed
for the conversion of methane to acetylene. Carbon yields of 30%, a factor of 6 increase, with a
corresponding decrease in acetylene yield were obtained by simply increasing the residence or
reaction time. A detailed kinetic model that includes the reaction mechanisms resulting in the
formation of acetylene and heavier hydrocarbons through benzene is described. A model for
solid carbon nucleation and growth is included. The model is compared to experimental results
and is used to examine process optimization.
This report describes the experimental demonstration of a process for the direct thermal conversion of methane to acetylene. The process utilizes a thermal plasma heat source to dissociate methane. The dissociation products react to form a mixture of acetylene and hydrogen. The use of a supersonic expansion of the hot gas is investigated as a method of rapidly cooling (quenching) the product stream to prevent further reaction or thermal decomposition of the acetylene which can lower the overall efficiency of the process.
The development of inert gas atomization (IGA) as a primary production route for Nd - Fe - B type magnets has not been commercially successful due to a cooling rate which is much lower than the maximum achievable in melt-spinning (MS). It is further complicated by the fact that powder particles of a range of sizes are produced which solidify at different rates and form significantly different microstructures. The role of the cooling rate is analysed in a general way by processing the same alloy composition by IGA and MS. MS allows a much broader but controlled range of cooling rates to be studied than is possible in IGA. General MS concepts of underquenching and overquenching are applied to IGA to indicate the state of the microstructure. Although the bulk of the IGA powder was formed in an underquenched condition, energy products approaching those obtainable in optimally quenched MS ribbons could be achieved in the finest size fraction () of powder. Changes in susceptibility show the general trend of improvement in hard magnetic property with decreasing scale of the microstructure. Quenchability diagrams show that TiC additions to the base alloy increase the quenchability and may allow future IGA alloys to be produced in an overquenched condition.
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