Plasma reformer

The plasma decomposition process is applicable to any hydrocarbon fuel, from methane to heavy hydrocarbons. Similar to oxidative plasma reforming, plasma decomposition processes fall into two major categories thermal and nonthermal plasma systems. 

Novel reforming techniques such as supercritical reforming, plasma-assisted reforming, and cool flame POX have also attracted attention for syngas production for fuel cell applications. 

Product of reforming Plasma w/o catalyst, vol % Plasma with catalyst, vol %... 

In a cascade process, one incident electron (e ) collides with a neutral atom ((S)) to produce a second electron and an ion ( ). Now there are two electrons and one ion. These two electrons collide with another neutral atom to produce four electrons and three ions. This process continues rapidly and — after about 20 successive sets of collisions — there are millions of electrons and ions. (The mean free path between collisions is very small at atmospheric pressures.) A typical atmospheric-pressure plasma will contain 10 each of electrons and ions per milliliter. Some ions and electrons are lost by recombination to reform neutral atoms, with emission of light. 

Other methods iaclude hydrogen reduction of TiCl to TiCl and TiCl2 reduction above the melting poiat of titanium metal with sodium, which presents a container problem plasma reduction, ia which titanium is collected as a powder, and ionized and vaporized titanium combine with chlorine gas to reform TiCl2 on cool-down and aluminum reduction, which reduces TiCl to lower chlorides (19,20). 

Direct thermal decomposition of methane was carried out, using a thermal plasma system which is an environmentally favorable process. For comparison, thermodynamic equilibrium compositions were calculated by software program for the steam reforming and thermal decomposition. In case of thermal decomposition, high purity of the hydrogen and solidified carbon can be achieved without any contaminant. 

Simplified schematics of a thermal plasma reformer for the production of synthesis gas from hydrocarbons. 1 = Anode, 2 = cathode, 3 = discharge, and 4 = insulator. 

Several types of nonthermal plasma systems have been reported in the literature for reforming of hydrocarbons to hydrogen-rich gas ... 

Simplified schematics of a gliding arc-type plasma reformer. 1 = Electrodes, 2 = discharges, 3 = vessel with insulation, and 4 = electrode connectors. 

The plasma reformer efficiency reached 12.3% and 26% in gasoline auto thermal and steam reforming regimes, respectively. The typical composition of the effluent gas from the reformer operating in steam reforming mode was (vol%) H2—28.7, CO—15, C02—3, and CH4—40. 

The objective of plasma-assisted decomposition of hydrocarbons is to produce hydrogen and carbon in an oxidant-free environment (as opposed to plasma-assisted POx and steam reforming that produce hydrogen and C02), according to the following generic reaction ... 

Schematics of thermal plasma reformer for decomposition of methane to hydrogen and carbon. 1 = Thermal plasma reactor, 2 = graphite electrodes, and 3 = hydrogen-carbon separation unit (cyclone).

Bromberg, L. et al., Plasma reforming of methane, Energy Fuels, 12,11,1998. 

Seguichi, H. and Mori, Y., Steam plasma reforming using microwave discharge, Thin Solid Films, 435, 44,2003. 

However, an alternative pathway that bypasses clathrin-mediated endocytosis and EEs appears to be available as well. This model of endocytosis known as kiss and run or its variant kiss and stay have attracted increasing interest in recent years [74] (Fig. 9-9B). Kiss and run has been directly demonstrated with dense-core granules in neuroendocrine cells [84, 85], and this model would explain some observations that are not readily accommodated by the classical pathway. The kiss and run model proposes that neurotransmitters are released by a transient fusion pore, rather than by a complete fusion with integration of the synaptic vesicle components into the plasma membrane. Synaptic membrane proteins never lose their association and the vesicle reforms when the pore closes. As a result, the empty vesicle can be refilled and reused without going through clathrin-mediated endocytosis and sorting in the EEs. 

Since pyrolysis converts waste into CO, CH4, and H2, the product gases can be processed in an atmospheric pressure non-equilibrium plasma reformer to improve the energy-recovery potential of the product gas. Energy-recovery options include heat and chemical energy recovery. 

Novel Processing Schemes Various separators have been proposed to separate the hydrogen-rich fuel in the reformate for cell use or to remove harmful species. At present, the separators are expensive, brittle, require large pressure differential, and are attacked by some hydrocarbons. There is a need to develop thinner, lower pressure drop, low cost membranes that can withstand separation from their support structure under changing thermal loads. Plasma reactors offer independence of reaction chemistry and optimum operating conditions that can be maintained over a wide range of feed rates and H2 composition. These processors have no catalyst and are compact. However, they are preliminary and have only been tested at a laboratory scale. 

The steam reformer is a serpentine channel with a channel width of 1000 fim and depth of 230 fim (Figure 15). Four reformers were fabricated per single 100 mm silicon wafer polished on both sides. In the procedure employed to fabricate the reactors, plasma enhanced chemical vapor deposition (PECVD) was used to deposit silicon nitride, an etch stop for a silicon wet etch later in the process, on both sides of the wafer. Next, the desired pattern was transferred to the back of the wafer using photolithography, and the silicon nitride was plasma etched. Potassium hydroxide was then used to etch the exposed silicon to the desired depth. Copper, approximately 33 nm thick, which was used as the reforming catalyst, was then deposited by sputter deposition. The reactor inlet was made by etching a 1 mm hole into the end... 

T0696 Science Applications International Corporation, Plasma Hearth Process T0698 Scientific Ecology Group (SEG), Steam Reforming—Synthetica Technologies Detoxifier (STD)... 

---