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GLIDARC-ASSISTED REFORMING OF GASOLINE AND DIESEL OILS INTO SYNTHESIS GAS

Albin Czernichowski (1), Mieczyslaw Czernichowski (2), and Piotr Czernichowski (3)

(1) University of Orleans, Department of Physics,

rue de Chartres, 45067 Orleans cedex 02, France, albin.czernichowski@univ-orleans.fr (2) Etudes Chimiques et Physiques (ECP) , 22 rue Denis Papin, 45240 La Ferté Saint Aubin,

France, echph@wanadoo.fr, phone/fax +33 238 631 590, www.glidarc-tech.com (3) presently with WESCO, Conroe, TX 77301-3284, USA

ABSTRACT

Various commercial diesel oils (including logistic ones that contain up to 4% of Sulfur) and a gasoline are converted into synthesis gas using GlidArc-assisted Partial Oxidation reactors and atmospheric air. We produce up to 6.9 m3(n)/h of Nitrogen-diluted syngas containing up to 21% of H2 and up to 21% of CO. It corresponds to 8.4 kW of electric power when such syngas is converted in an ideal Fuel Cell (FC). Power requirement for GlidArc assistance of such non-catalytic reforming is below 2% of the FC output. 1. INTRODUCTION

Fuel Cells (FC) use pure Hydrogen extracted from the Synthesis Gas (CO+H2) or even directly the syngas in the case of specific Solid Oxide (SO) or Molten Carbonate (MC) cells. It appears that for commercial FCs the syngas will be produced massively via fossil or bio-derived carbonaceous matter reforming. However almost all reforming technologies are based on catalytic processes so that the feeds containing Sulfur, Chlorine, Metals and other contaminants must be first deeply cleaned in order to avoid the reformer's catalyst poisoning.

We run our reforming process in a presence of high-voltage and low-current discharges (called GlidArc) that assist the partial oxidation (POX) of various primary carbonaceous feedstocks into the syngas without their prior cleaning. Electric power consumption of our reformer is generally less than 2 % of a typical FC electric power output range so that a recycling of such a small portion of the electric power produced in a FC is, in our opinion, an acceptable compromise alowing an impementation of such a specific plasma-assisted technology into the FC chain. Very active and also very simple GlidArc discharges play there a role of an igniter and the homogeneous phase catalyst; they also stabilize and activate a supplementary post-plasma reaction zone of our reformer. For the sake of simplicity and economics, our unique oxidant source is the atmospheric air.

This contribution presents first some of our tests with pure cyclohexane, heptane, and toluene as the components of commercial gasolines and diesel oils. More results are then done in the second part on very successfull reforming of one gasoline and various diesel oils (French, Canadian, and Texan) as well as some out-off-spec samples containing up to 4 % of Sulfur). Due to the complex composition (long hydrocarbon chains and cycles) and the Sulfur content, diesel oils represent probably the hardest fuels to reform. They are however one of the most available fuels through a very dense distribution chain. The ability to reform "dirty" diesels (and similar feeds like naphtas and jet fuels) for use in the FC is critical for industrial and military operations in many parts of the world where only off-spec feedstock is available.

Our results on other carbonaceous feedstocks processing using various GlidArc reactors are presented separately in this Conference, see biogas upgrading [1], as well as POX reforming of natural gas [2], propane(LPG) [3], or rapeseed oil [4].

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2. EXPERIMENTAL 2.1. GlidArc-assisted reformers

The GlidArc-assisted reformers for various carbonaceous feeds into syngas conversion, a part of our Gas-to-Liquid (clean diesel and gasoline) advanced technology [5], have proved to be also excellent reformers for other fuels. Our here-presented test work has been based on small reactors, similar to those described in [6]. The reformer is shown schematically on the Fig. 1. SG Fig. 1. Schematic view of the GlidArc-assisted reformer.

The reactor contains three or six knife-shaped electrodes. The electrodes delimit a volume filled with gliding discharges. A feed + air premix is blown into that space through a simple tube and flows along the diverging electrodes. The plasma space (chamber) is thermally isolated in order to limit heat loses. Two flanges close the tubular reactor. The upper one supports the electrodes isolated electrically with high voltage connections. The other flange closes the reactor's bottom and comprises a product (SG) output tube. The entire structure is tight; it can support higher pressures but for the present runs we only worked at atmospheric pressure.

The gliding discharges ionize the gas mix. Given the moderate temperature of the electrodes (not cooled) and a very short contact time (some ms) of the discharge roots with the electrodes, we do not observe any deterioration (even at a high Sulfur presence) that may prevent the gliding of these current-limited (< 0.3 A) discharges.

The plasma chamber communicates with a post-plasma zone filled with packing. It makes it possible to transfer the products of partial reforming in plasma into the post-plasma zone. The whole reactor is externally insulated by a ceramic felt. In addition we thermally insulate the inner walls of the post-plasma zone of the reactor with a ceramic tube and a felt in order to keep it as hot as possible.

The total inside volume the reactor is 1 L (in our earlier experiments we also used a 2-L reactor). No part of the reactor is cooled in a forced manner. Two extra holes in the bottom flange provide for the insertion of two thermocouples measuring the post-plasma zone temperatures at 13 cm and 6 cm above the lower flange.

Almost punctual injection of the premixed feed + air between the electrodes provokes a phenomenon of re-circulation of the reactants in the plasma zone. The flow of partially converted reactants containing long-living active radicals (and other catalytic species resulting from the gas excitation by gliding electric discharges) enters the post-plasma zone where the conversion is completed in the presence of packing where all excited species deactivate. The luminous zone of the gliding electric discharges is observed through a window in order to verify the operation of the plasma chamber. A 10-kV power supply provides both ionization of the premix and then a transfer of electric energy into the discharges. The 3- or 6-phase supply is composed of commercial neon-light transformers. The time-averaged electric power

Gliding discharges

feed

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is measured at the mains using a 3-phase kWh-meter and a chronometer. The averaged net GlidArc power during our runs could be as high as 0.8 kW.

A syngas sample crosses a white mineral wool in order to check if soot is present. Other sample is analyzed on-line using a 2-channels micro gas chromatograph (CP-2003) dedicated to H2, N2, O2, CH4, CO for one channel, and CO2 as well as some light HCs (C2H4, C2H6, C2H2, and C3H8+C3H6) for the second one. The gas analysis takes only 255s. 2.2. Preliminary tests As the feeds we took three pure liquid HCs: Cyclohexane, Heptane, and Toluene. The reactor was fed by controlled flows of compressed air and HCs. Both flows were simply mixed together before their injection into the reactor. Some input/output data for these completely non-sooting experiments are presented in Tab. 1.

Table 1. Some input/output data of our preliminary tests

Feed C6H12 C7H16 C7H8 Flow rate input air L(n)/min 42 35 47 HC cm3/min 14 15 12 O/C atomic ratio @ input 1.0 0.9 1.2 Electric power injected kW 0.33 0.37 0.33 Output gas conc. (vol.%) CH4 3.1 6.7 1.0 C2H6 0.0 0.2 0.0 C2H4 0.2 1.8 0.0 CO2 2.1 2.3 3.0 CO 21 18 23 H2 21 18 15 N2 52 53 58 Output gas flow rate in m3(n)/h Total 3.8 3.2 3.8 Syngas 1.6 1.1 1.4 kWh spent to produce 1 m3(n) of H2+CO 0.20 0.33 0.24 Output power* from syngas kW 5.3 4.0 4.7 kW produced* per kW injected 19 11 20

* An ideal chemical-into-electric conversion of a FC is supposed; it takes into account the

Lower Heating Value (LHV) of the produced H2+CO mixture.

All feeds were totally reformed. We got a good energetic efficiency (defined in the bottom of the Tab. 1): always more than 10 times of chemical enthalpy contained in the syngas with respect to the electric energy injected into the GlidArc. We had no problem to reform such a cyclic compound as Toluene that is very fragile. No soot was observed even in this case at a sufficient O/C ratio. 2.3. Tests with Gasoline 95

Almost the same experimental set-up was used. The output tube got a supplementary connector that allows easy access to the lower part of reactor in order to check on soot presence in the reactor without its disassembling. Gasoline was tested in long runs. The feed and feeding systems are characterized as follows:

Commercial unleaded French Gasoline 95 containing: Aromatics 26.7%, Olefins 15.2%, Saturated 58.1% and no Oxygenates. Density of 0.728 g/cc. Our mass balances indicate that the H/C atomic ratio of this gasoline is equal to 2.05 ± 0.01. The gasoline was sucked from a calibrated cylinder to a gear pump at a controlled speed and then crossed a

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rotameter and entered a "T" connector for air/gasoline mixing. The gasoline flow rates were kept constant (rotameter indication) ranging from 21.0 to 22.4 mL/min, according to our needs. These values were measured frequently from the gasoline level in the cylinder, and time. Continuous run times for the Gasoline were 6 h 31 min and 2 h 52 min. Table 2 shows some parameters of one run. For soot presence checking we have installed a quartz filter at the stream of the produced syngas. Then, after a certain time, the filter was removed for inspection. No soot has been found.

Table 2. Results of completely non-sooting reforming of Gasoline 95.

Flow rate input air L(n)/min 77 HC mL/min 22 O/C atomic ratio @ input mol/mol 1.2 Electric power injected kWe 0.44 Output gas conc. (vol.%) CH4 2.4 C2H6 none C2H4 none CO2 3.0 CO 21 H2 19 N2 55 Output gas flow rate in m3(n)/h Total 6.6 H2+CO 2.6 kWhe spent to produce 1 m3(n) of H2+CO 0.17 Output power from syngas kWe 8.4 kWhe produced per L of HC injected 6.3 kWe produced per kWe injected 19

We are totally converting all injected Gasoline obtaining an energetic efficiency of

19 kWe that can be produced in an ideal FC from 1 kWe power injected to the GlidArc assisted processor. Again, no soot was observed for the Gasoline reforming at a sufficient O/C ratio. We took care to not operate our reactor, even in a short period of time, at a deficit of air in order to avoid any controversy, when dismantling the reactor after its cooling under pure Nitrogen stream, for the soot inspection. 2.4. Tests with Diesel Oil (DO)

Almost the same experimental set-up was used. A shorter reactor has a total free volume (in terms of fluid) of about 1.1 L. As previously, no part of the new reactor is cooled in a forced manner. The entire structure of the reactor is tight; it can support a higher pressure but for the presented tests we worked at the absolute pressures not exceeding 0.13 MPa.

A commercial road Canadian DO was tested in a Canadian laboratory using ECP's GlidArc reformer. The oil density was 0.846 g/mL and the Sulfur content at about 300-ppm level. Our mass balances indicate that the H/C atomic ratio of this oil is equal to 1.82 ± 0.02. The DO stream was mixed with air in a simple "T" connector (1/4") and the mixture just crossed a short 3/8" heated pipe (150 W). A slightly preheated mixture entered then (through a single opening) the plasma zone between the electrodes.

The lower flange of the reactor holds a thermocouple and a product output tube. This tube got some supplementary connectors that allow us: to send a part of the products for the moisture analysis and then to transfer it into a 3-channels micro-GC, to inject (optionally) a tap water for the syngas cooling, and to send all (or only a part) of the syngas through a ceramic filter for soot detection. A couple of preparative series of tests and then 3 main series

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of DO reforming runs were performed totalizing almost 11 hours of runs. The reactor was never dismantled; it was always easy to start. We always decided ourselves when a test stop should be so the stoppage was never caused by any problem coming from the set-up side. We fully analyzed 30 syngas samples. Table 3 shows some results of this DO reforming.

Table 3. Result of completely non-sooting Diesel Oil reforming.

Air flow rate in L(n)/min 91 Diesel Oil flow rate in mL/min 20 O/C atomic ratio 1.4 Electric power injected (kWe) 0.28 Total gas flow output in m3(n)/h 6.9 H2+CO output in m3(n)/h 2.2 kWhe spent per 1 m3(n) of produced H2+CO 0.12 Calc. power from Syngas (kWe) 7.4 Calc. kWhe per 1 L of spent DO 6.1 kWe produced per kWe injected 26 Output gas conc. in vol.% (dry) CH4 1.5

C2H6 none C2H4 0.04 CO2 3.3 CO 19 H2 14 N2 62

During these preliminary tests on such Sulfur-polluted DO we have detected some H2S

in the syngas. A simple way to remove it from the syngas can be, for example, a ZnO cartridge. We found therefore that our technology does not require any clean feed and that our non-catalytic GlidArc-assisted reformer can accept some Sulfur-contaminated feeds. 2.5. Tests with heavy logistic Diesel Oils

Based on that we have performed a testing of some highly S-charged DO. Such fuels are widely spread over the world and therefore considered, for example, as logistic fuels for a local production of the electric energy on the battlefields. Our tests [presented orally as "Reforming of high-Sulfur diesel oil into synthesis gas in a plasma-assisted reactor", 3rd Department of Defense Conference on "Logistic Fuel Reforming", Panama City Beach, Florida, August 27-28, 2002] confirm that such dirty (up to 4% of S) and quite heavy fuel (end-point of distillation at 600°C) can be converted totally at no soot appearance and no harm to our compact reactor and electrodes (we worked several hours) at a 5-10 kW level of an ideal FC output. 3. CONCLUSION

This contribution presents some of our tests on gasoline 95 and various diesel oils (including high-Sulfur containing ones) as well as some pure HC compounds: Heptane, Cyclohexane, and Toluene. These feeds were completely converted into syngas in our GlidArc-assisted reformer at atmospheric pressure and at low electric power assistance. No structural modifications of the whole converter or its parts are observed. As detailed and general conclusions we note: • Soot is not produced if a sufficient O/C atomic ratio (and consequently some H2O and

CO2 products) is accepted as compromise.

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• Up to 4% of Sulfur content in the feeds is not harmful for our reactor and process so that the GlidArc assisted technology opens the way for much simpler integrated reformer/SOFC (or /MCFC) units without prior removal of sulfur or other additives. This greatly expands the market potential to include military logistic fuels and/or other highly sulfur-polluted fuels.

• The flow rates of produced Hydrogen and Carbon Monoxide can be kept constant by fine-controlling the flow rates of entering HC feed and air. The syngas output can also match an actual need by regulating the rates of fuel and air.

• The temperature profile of the reactor is self-controlled by the process and by the GlidArc assistance. Frequent start-ups or quite drastic changes of syngas output can be done in a fraction of minute so that an integrated power-generation system can be much easier developed.

• Here presented 1-L (and not yet optimized reformer) already produces up to 2.6 m3(n)/h of pure syngas (N2 and other components not accounted). It can generate an amount of syngas corresponding to 8.4 kW of electric power (when syngas is fully converted in an ideal SOFC or MCFC). Further ECP's developments are in progress including systems to generate the syngas equivalent to 30 m3(n)/h of pure H2+CO mix corresponding to the LHV power of 100 kW.

• Electric power consumption assisting our reforming is less than 2% of the LHV power of produced syngas stream. Such a low power recycling level (or an import from outside) is, in our opinion, a worthy compromise. Instead of using a delicate catalyst that asks for a very clean fuel we dedicate an almost negligible part of produced syngas power to support electrically a non-catalytic reforming of almost any dirty fuel.

• No water or steam circuits, heaters, etc. are necessary. The process starts with compressed air (of any quality), a fuel, and the GlidArc. No special vaporizer/fuel injector unit is needed. The syngas appears after a short warm-up. If the reformer is kept hot than the full operation of our reformer can be achieved in about 1 min.

These steps of ECP's project guarantees the development of a compact and reliable fuel

processor fed by various HC feeds. It can be used on-board of a vehicle or on-site for syngas or Hydrogen production for various applications.

* * * Some qualitative tests indicate that crude petroleum oils, heavy bitumen, and

petroleum wastes can also be directly converted in our reformers… Large multiple-electrode ("GlidArc Multicluster", ECP's pending patent [7]) reformers are under development for a large-scale syngas production from almost any gaseous or liquid carbonaceous feed. Moreover, we are developing a new GlidArc-III device for extra-heavy hydrocarbon feeds processing, including coal, petroleum coke, etc. REFERENCES 1 A. Czernichowski, M. Czernichowski, K. Wesolowska, Glidarc-assisted production of

synthesis gas from biogas, this Conference. 2 A. Czernichowski, M. Czernichowski, P. Czernichowski, Glidarc-assisted production of

synthesis gas from natural gas, this Conference. 3 A. Czernichowski, M. Czernichowski, P. Czernichowski, Glidarc-assisted reforming of

propane into synthesis gas, this Conference. 4 A. Czernichowski, M. Czernichowski, Glidarc-assisted production of synthesis gas from

rapeseed oil, this Conference. 5 M. Czernichowski, A. Czernichowski, French patent 2824755.

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6 A. Czernichowski, GlidArc assisted preparation of the synthesis gas from natural and waste hydrocarbons gases, Oil & Gas Science and Technology - Revue de l'IFP, 56(2), 181-198 (2001).

7 A. Czernichowski, M. Czernichowski, pending patent.