Hydrogen and elemental carbon production from natural gas and other hydrocarbons

A method for thermal conversion of carbon dioxide and methane in a thermodynamically stable high temperature gaseous stream to carbon monoxide and diatomic hydrogen, comprising the following steps:

• introducing a stream of plasma arc gas between the electrodes of a plasma torch including at least one pair of electrodes positioned at the inlet end of an axial reactor chamber, the stream of plasma arc gas being introduced at a selected plasma gas flow while the electrodes are subjected to a selected plasma input power level to produce a plasma within the reactor chamber and extending toward its outlet end;
• thoroughly mixing an incoming reactant stream into the plasma by injecting at least methane into the reactor chamber at or adjacent to its inlet end at a selected injection angle and at a selected reactant input rate to progressively effect heat transfer between the plasma and the resulting gaseous stream as it flows axially toward the outlet end of the reactor chamber;
• the length of the reactor chamber being sufficient to effect heating of the gaseous stream to a selected equilibrium temperature at which an intermediate product stream comprising unsaturated hydrocarbons is available as a thermodynamically unstable reaction product within the gaseous stream at a location adjacent to the outlet end of the reactor chamber;
• directing the intermediate product stream through a converging section of a coaxial convergent-divergent nozzle positioned in the outlet end of the reactor chamber to rapidly cool the gaseous stream by converting thermal energy to kinetic energy as a result of adiabatic and isentropic expansion as it flows axially through the nozzle, the nozzle having a converging section and a diverging section respectively leading to and from a restrictive open throat;
• directing the intermediate product stream through the diverging section of the nozzle, thereby creating a recirculation of the intermediate product stream which results in a local reheating of the intermediate product stream as the intermediate product stream flows axially through the diverging section of the nozzle, wherein the reheating is sufficient to decompose the unsaturated hydrocarbons in the intermediate product stream to an end product comprising at least one of diatomic hydrogen and elemental carbon;
• and
• cooling the gaseous stream exiting the nozzle by reducing its velocity while removing heat energy at a rate sufficient to prevent increases in its kinetic temperature.

A method of converting one or more hydrocarbon reactants to an end product in the form of a diatomic hydrogen gas or ultrafine solid particles, comprising:

• introducing a hydrocarbon reactant stream at one end of an axial reactor;
• first heating the hydrocarbon reactant stream as the hydrocarbon reactant stream flows axially toward an outlet end of the axial reactor, wherein the axial reactor has a length and a temperature and is operated under conditions sufficient to effect heating of the hydrocarbon reactant stream to a selected reaction temperature at which at least diatomic hydrogen is available as an intermediate product stream at a location adjacent the outlet end of the axial reactor;
• expanding the intermediate product stream by directing the intermediate product stream first through a convergent nozzle arranged at the outlet end of the axial reactor and second through a means for rapid gas expansion, thereby retaining the desired intermediate product stream;
• second heating the intermediate product stream as the intermediate product stream flows axially through the means for rapid gas expansion sufficient to decompose a hydrocarbon in the intermediate product stream to a diatomic hydrogen and elemental carbon end product;
• cooling at least some of the diatomic hydrogen by heat exchange with some of the hydrocarbon reactant stream;
• supplying the diatomic hydrogen to a fuel cell;
• and
• preheating at least some of the hydrocarbon reactant stream by heat exchange with waste heat effluent from the fuel cell.

A method of converting one or more hydrocarbon reactants to an end product in the form of a diatomic hydrogen gas or ultrafine solid particles, comprising:

• introducing a hydrocarbon reactant stream at one end of an axial reactor;
• first heating the hydrocarbon reactant stream as the hydrocarbon reactant stream flows axially toward an outlet end of the axial reactor, wherein the axial reactor has a length and a temperature and is operated under conditions sufficient to effect heating of the hydrocarbon reactant stream to a selected reaction temperature at which at least diatomic hydrogen is available as an intermediate product stream at a location adjacent the outlet end of the axial reactor;
• expanding the intermediate product stream by directing the intermediate product stream first through a convergent nozzle arranged at the outlet end of the axial reactor and second through a means for rapid gas expansion, thereby retaining the desired intermediate product stream;
• second heating the intermediate product stream as the intermediate product stream flows axially through the means for rapid gas expansion sufficient to decompose a hydrocarbon in the intermediate product stream to a diatomic hydrogen and elemental carbon end product;
• cooling at least some of the diatomic hydrogen by heat exchange with some of the hydrocarbon reactant stream;
• and
• supplying the diatomic hydrogen to an internal combustion engine.

A method of converting one or more hydrocarbon reactants to an end product in the form of a diatomic hydrogen gas or ultrafine solid particles, comprising:

• introducing a hydrocarbon reactant stream at one end of an axial reactor;
• first heating the hydrocarbon reactant stream as the hydrocarbon reactant stream flows axially toward an outlet end of the axial reactor, wherein the axial reactor has a length and a temperature and is operated under conditions sufficient to effect heating of the hydrocarbon reactant stream to a selected reaction temperature at which at least diatomic hydrogen is available as an intermediate product stream at a location adjacent the outlet end of the axial reactor;
• expanding the intermediate product stream by directing the intermediate product stream first through a convergent nozzle arranged at the outlet end of the axial reactor and second through a means for rapid gas expansion, thereby retaining the desired intermediate product stream;
• second heating the intermediate product stream as the intermediate product stream flows axially through the means for rapid gas expansion sufficient to decompose a hydrocarbon in the intermediate product stream to a diatomic hydrogen and elemental carbon end product;
• cooling at least some of the diatomic hydrogen by heat exchange with some of the hydrocarbon reactant stream;
• supplying the diatomic hydrogen to an internal combustion engine;
• and
• preheating at least some of the hydrocarbon reactant stream by heat exchange with waste heat effluent from the internal combustion engine.