Alexander Fridman, Alexander GutsolYoung I Cho, Chiranjeev Kalra

Conversion of Hydrocarbons into Syn-Gas Stimulated by Non-thermal

Atmospheric Pressure Plasma

• Plasma Catalysis Vs. Plasma Processing• Methane Conversion to Hydrogen• Gliding Arc in Tornado• Experiments and Modeling• Plasma Catalytic Conversion of Hydrocarbons

as Hydrogen Production Technology

Plasma-Chemical Hydrogen Production from Water

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moleVEv,

n, %

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CO2 = CO + ½ O2 – 2.9 eVH2O = H2+ ½ O2 – 2.6 eV

CO2 = CO + ½ O2 – 2.9 eV

CO+H2O = H2+ CO2 + 0.3 eV

Non-Equilibrium PlasmaCO2dissociation Gas Separation Unit

Catalytic “Shift” Unit

CO2 , CO, O2

O2

CO

CO2

CO2

CO2

H2O

H2

Two Step Plasma Cycle for Hydrogen Production

Plasma Catalysis Vs. Thermo-Catalytic Partial Oxidation

Thermo-Catalytic Conversion:•High Temperature Requirements (>1100K)•Large Specific Size of Reactor•Special Materials Requirements and Reactor Design•Sulfur from Natural Gas Causes Catalyst Poisoning •Low Conversion at Moderate Equivalence Ratios (3.0-3.5)

Catalysis TemperatureCH4 + 1/2 (O2 + 3.76 N2) CO + 2 H2 + 1.88 N2 + 36 kJ/mol

Plasma-Catalysis:•Low Temperature Operation (~750K)•Large Specific Productivity•Lower Temperature Requirements•No Sensitivity to sulfur or other impurities•Possibility to Operate at High Equivalence (3.5-4.5)

Plasma As CatalystPlasma Catalytic Hydrogen Production

from Natural Gas

Plasma PO optimal parameters:

CH4+0.5O2 = CO + 2 H2optimal equivalence ratio = 3.3,

[O2]/ [CH4]=0.6

Preheating temperature = Internal, 750KConversion = 92%Electric energy cost :

experimental = 0.06 kWh/m3

modeling EQ = 0.11 kWh/m3

modeling NE = 0.07 kWh/m3

Output Syn-Gas energy = 3.00 kWh/m3

power for 100,000 barrel/day of Liquid Fuel:experimental = 4.5 MWmodeling EQ = 8.2 MWmodeling NE= 5.2 MW

Oscilloscope & data acquisition

Temperature controller

GLIDING ARC REACTOR

Quartzheater

mixing chamber

Flowcontrollers

gas chromatography

gas sampling

resistor box

powersupply

Thermal Plasma

Non-Thermal Plasma

Corona Discharge

Aurora

X-ray view of the sun

ICP Torch

TORNADO

Gliding Arc

Which Plasma to Choose?

Gliding Arc as Transitional Non-Equilibrium Plasma:

THERMAL PLASMA

NON-THERMAL PLASMA

MAJOR CHALLENGES :

• Power Density & Productivity.

• Selectivity.•Very High Plasma power and density.

•High Gas temperature.

•No selective chemical process can be achieved.

•Low gas temperature and very high electron temperature.

•Low Power Density

•Chemical Selectivity can be achieved.“Gliding Arc in Tornado”

Fast Equilibrium to Non-Equilibrium Transition

•Arc starts in a narrow gap between diverging electrodes in a gas flow.

•Current increases very fast and the voltage on the arc drops.

•Gas flow forces the arc to move along the diverging electrodes and elongate. The growing arc demands more power to sustain itself.

•Arc cools down and becomes Non-Equilibrium to sustain itself with less power.

“GLIDING ARC in Flat Geometry”“GLIDING ARC in Flat Geometry”“GLIDING ARC in Flat Geometry”

“GLIDING ARC in Flat Geometry”“GLIDING ARC in Flat Geometry”“GLIDING ARC in Flat Geometry”

Initial Breakdown

Extinction

Elongation

Fast Equilibrium to Non-Equilibrium Transition

Point of DevelopedGliding Arc when Maximum Energy is Transferred

Gas inlet

Reactor

Point of Gliding Arc Ignition

Point of Total Extinction

R

DC Power Supply

Vo

J

l

Electrical scheme of the DC Gliding Arc.

Pmax

Pmax

PmaxP*

P*

P*

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400

600

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1000

0.00 0.10 0.20 0.30 0.40Current (A)

Pow

er (W

)

R = 25 kOhmR = 50 kOhmR = 100 kOhm

R = 50 kOhm

R = 100 kOhm

R = 25 kOhm

R = 25 kOhm

R = 50 kOhm

R = 100 kOhm

Non-Equilibrium Gliding Arc

Reverse Vortex Flow (Tornado) Stabilization of Gliding Arc

Methane

Air Air

ReverseVortex flow

CircumferentialVelocity component

NozzleFor reverseVortex flow

Syn-Gas out

ReverseVortex flow

Axial velocitycomponent

Syn-Gas out

Gas Burner with Reverse Vortex Flow, “Tornado” Stabilization of Flame

ε ∼ 0.5 ε ∼ 1.1 ε ∼ 1.8

“THE GLIDING ARC IN TORNADO”“THE GLIDING ARC IN TORNADO”“THE GLIDING ARC IN TORNADO”

Schematic Diagram for GAT reactor.

•Gliding Arc in Tornado works in a Reverse Vortex Flow setup.

•A circular and spiral electrode is placed in the plane of the flow act as diverging High Voltage DC Electrodes.

•The flow conditions and the characteristics of the power supply determine the shape of the spiral electrode.

Gliding Arc in Tornado Flow

Anode

High Voltage

DC

Discharge Zone

Spiral Electrode

Tangential Gas inlet

Cylindrical Volume

Ground

Axial Inlet

Ring Electrode

Gliding Arc “Tornado”From the Spiral to the Ring

Gliding of Arc on Spiral Electrodes in Reverse Vortex Flow

The arc ignites as an equilibrium discharge and elongates on the

Spiral Electrode

“It Can Melt a Metal Rod But You Can Touch It”

EXPERIMENTAL SETUP

Oscilloscope & data acquisition

Gas Chromatography

resistorbox

powersupply

Flow Controllers

Gliding Arc

Reactor

Heat Exchanger

Gas Sampling

THE EXPERIMENTAL SETUP

FIRED AT EQUIVALENCE

RATIO 4.

Plasma Catalytic Methane Partial Oxidation

Syn-gas Burner

Plasma-Catalytic Reactor

The entire process includes three main stages:1.) Electric discharge stage 2.) Mixing of air and post discharge methane.3.) Post discharge regime .

The neutral species chemistry was described by the GRI-MECH 2.11 kinetic scheme including 65 species and 200 reactions. In the post discharge region the gas mixture is allowed to react within a certain residence time, with small heat losses.

The syn-gas production is characterized by two stages: 1.) The short combustion zone.2.) The longer zone, which can be called as the reforming zone

At the first stage the concentrations of O and OH radicals are relatively large, and it is characterized by very fast chemistry.

At the second stage, much slower chemistry takes place. Water and CO2 are consumed, yielding hydrogen and CO, the corresponding reaction are endothermic ones, causing the observable temperature decrease.

Chemical Kinetics Simulation

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2.8 3.2 3.6 4 4.4 4.8Equivalence Ratio

Con

vers

ion

Deg

ree

Simulation Vs Experiments The conversion degree: α = ([H2] + [CO]) / 3[CH4]

Modeling results With plasma

Experimental results with plasma

Modeling results without plasmaExperimental results without plasma

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2.8 3.2 3.6 4 4.4 4.8Equivalence Ratio

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tric

Ene

rgy

Cos

t

(KW

hr/m

^3 o

f syn

gas)

Modeling results

Experimental results

Simulation Vs Experiments Electric Energy Cost = Wel(KW-hr)/ meter cube of

Syn-Gas (Output Syn-Gas Energy = 3.00 kWh/m3)

Simulation Vs Experiments Methane Energy Cost = [CH4] (KW-hr) per

meter-cube of Syn-Gas

Modeling results with Plasma

Experimental results with plasma

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2.8 3.2 3.6 4 4.4 4.8Equivalence Ratio

Met

hane

Ene

rgy

cost

K

W-h

r/m^3

of w

yn g

as

Modeling results without plasmaExperimental results without plasma

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2.8 3.2 3.6 4 4.4 4.8Equivalence Ratio

Ener

gy C

ost

(K

Whr

/m^3

of s

ynga

s)

Simulation Vs Experiments Total Energy Cost = (Electric Energy Cost +

Methane Energy Cost) per meter Cube of Syn-Gas

Modeling results With plasma

Experimental results with plasma

Modeling results without plasmaExperimental results without plasma

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2.8 3.2 3.6 4 4.4 4.8Equivalence Ratio

Effic

ienc

y

Theoretical maximum ef f ic iency can be 0.84.

Modeling results With plasma

Experimental results with plasma

Modeling results without plasmaExperimental results without plasma

Simulation Vs ExperimentsEfficiency = KW-hr of Syn-Gas Produced / Total

Energy Input in KW-hr

•Only 2.0% of Total Energy Consumption Required for Plasma Power

•Electric Energy Cost 0.06 kWh/m3 of syn-gas (energy from syn-gas = 3.0 KW-hr/m3).

•92% conversion at Equivalence ratio of 3.3.

•Internal Heat Recuperation (Preheating) at 750 K.

•No soot Deposition.

•Large Specific Production rates due to low residence times.

•Effective for Higher Hydrocarbon conversion to Syn-Gas.

•Not Sensitive to Sulfur and Other Impurities.

Plasma Catalysis Highlights:

Best Regards, Chiranjeev Kalra from the city of

brotherly love