MXPA00002129A - Electrically assisted partial oxidation of light hydrocarbons by oxygen - Google Patents

Abstract

The purpose of the process and device (1) to assist with gliding electric discharge plasma (4) the partial oxidation of hydrocarbons, accompanied by their steam reforming and/or reforming with CO2, is to produce gases rich in CO and H2 that may also have high contents of C2H4 and C2H2, without any formation of soot or coke. This mixture of products is achieved in a plasma reactor with gliding electric discharges (1) that glow in the compartment (15a) brought to a temperature lower than 1200°C and at a pressure of less than 6 bars. The discharges act directly in an oxothermic reactive medium consisting of hydrocarbons mixed with gaseous oxygen of any origin, and possibly with H2O and/or CO2. The flow of products activated by the plasma and exiting the zone (15a) comes into contact with a metal or ceramic material (19) placed in the compartment (15b) that is brought to a temperature not exceeding 1100°C. This material becomes active in thepresence of the flow of products and, as such, it contributes to the enhancement of the conversion of the products exiting the plasma compartment (15a) into the final product.

Description

ELECTRICALLY ASSISTED PARTIAL OXIDATION OF LIGHT HYDROCARBONS BY OXYGEN BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to a process for the conversion of light hydrocarbons (HCs) through the use of plasma and, in particular, through sliding electric discharges in the presence of oxygen O2 and possibly water vapor H2O added to these HCs. 2. Description of the relevant technique The production of 'syngas' from saturated light HCs is a relatively well known and very important stage, especially for a chemical evaluation of natural gases (NGs). A valuation The chemistry of NG's immense resources would be much more interesting than its total finite combustion toward direct energy recovery in furnaces, kettles or turbines. There are also situations where NGs with high HC content are released into the earth's atmosphere, even without any energy recovery; this can be illustrated by oil field flares that burn a hydrocarbon contained in gas known as "associated gas", or by different biogas emissions (a mixture mainly of methane and carbon dioxide of almost equal content) that originate from an anaerobic fermentation of organic waste. Any HC emission burned uselessly and, in special, not burned, contributes enormously to air pollution. The current process most used to produce syngas, the catalytic steam reforming process (or also "steam reformer"), 5 encounters greater difficulties. In principle, it requires only a high temperature (thermodynamic ratio) and a high pressure (kinetic ratio). However, in practice, despite the 'know-how' for the production of syngas according to this process, the control of union of the positions, pressures and temperatures is delicate, even im possible, without resorting to the use of catalysts. Consequently, in order to perform NG vapor reformation, a catalytic device is generally selected: the presence of solid material in a highly dispersed and active form (with a specific surface area of at least one hundred m2 per gram) for temperatures that can to be reached without much difficulty. 15 The classical steam reforming technology thus used requires furnaces containing several hundred fragile metal tubes (filled with a catalyst and whose length can reach several tens of meters) heated externally with NG. Thus, the large amounts of carbon dioxide that originate from the combustion are discharged to the atmosphere by these furnaces, which have a very poor thermal performance. This technology is also linked to very high pressure losses. The temperature that can be supported by the pipes also prevents the reduction of the CO2 content in the real syngas (product of obstruction that results from a lateral reaction at a temperature too low). Other difficulties are related to t --- A -, A - Contamination of the catalysts by sulfur and / or itrogen, the aging of the catalysts, the necessary excess of steam and / or the formation of hollín (which block the complete tubular system in the macroscopic scale and, in particular, the microscopic pores of the catalyst). These difficulties are mainly observed in the steam reforming of heavier HCs than methane; they are more fragile and, thus, more susceptible to coking. A literature review covering the last three decades gave very few published results regarding the conversion partially oxidant of saturated HCs assisted by oxygen and plasma. This could be due to the difficulties related to the presence of free oxygen that attacks the conventional graphite or tungsten electrodes of the traditional plasma devices. We know only one attempt to use plasma in this environment (outside our own efforts). P. CAPEZZUTO et al. ["The oxidation of methane with carbon dioxide, water vapor, and oxygen in radio-frecuency discharges at modérate pressures" (The oxidation of methane with carbon dioxide, water vapor and oxygen in radio frequency discharges at moderate pressures), 3rd I nt. Symp. On Plasma Chemistry, Limoges, 1 976, contribution G.5.1 1, 7 pp] studied a partial oxidation of methane mixed separately with CO2, either with O2 or H2O, with a molar ratio of oxidant / CH4 = 1. The 35 M HZ RF plasma reactor needed an additional flow of argon and could only work at a very low pressure of approximately 2.7 kPa. For a total incoming gas flow from 3 to 36 l (n) / min, the energy density was very high and ranged from 1 to 1 2 ; ^ - fe ^ -, - ^ ^ - ^^ ^ í ^ ^^^^^^^ & ^ í ^ six: > é¿ ^ r S - ^ - ttaÉfc-ffi kWh / m3. No industrialization was possible due to high electric power and noble gas consumption (in addition to the complicated electrical power supply and the need to work under vacuum). Due to the mechanical requirements of the implantation, the poor performance of 5 energies and the insufficient energy units of the RF plasma sources, this method is poorly adapted, from an economic point of view, for the transformation of flows of significant gas. In Orleans, since 1986, we also worked in the conversion of NGs into thermal plasma reactors. These arc plasma torches transferred or simple classics make it possible to obtain small volumes of plasma at very high temperatures (T> 1 0kK). Although these devices are potential sources of active species, they are poorly adapted notwithstanding chemical applications that require much lower temperatures (in order not to destroy hydrocarbon molecules to the extent that they become soot) and especially larger volumes, filled with plasma, in order to act tightly in the complete fluid to be processed. Plasma torch technology that is well established, for example, in the field of solid projection, was found to be both costly and very difficult to implement for chemical processes. However, we achieved improvements in the field of thermal plasmas, in the case of a methane transformation in a specifically controlled electric arc, see P. JORG ENSEN et al. , "Process of Production of Reactive Gases Rich in Hydrogen and Carbon Monoxide m an Electric Post-Arc" (Process of production of reactive gases rich in hydrogen and carbon monoxide - ^ Aa = -s. - ^ -. "1 -» - ^ * &. - in an electric arc post), BF 2 593 493 (1986) .The structure of the device, as implemented then, was not possible, unfortunately , use water vapor as reagent or work without consuming the necessary argon as the gas that forms the plasma of a first pilot arc, so we use almost the same arc of high current (20 -150 A) to study the oxidation of ethane, see K. MEGU ERN ES et al., "Oxidation of ethane C2H6 by CO2 or O2 in an electric are" (Oxidation of ethane C2H6 by CO2 or O2 in an electric arc), J. High Temp. Chem. Process, vol. (3), pp. 71-76 (1992) without much improvement in the consumption of electrical energy and argon.

BRIEF DESCRIPTION OF THE INVENTION The invention comprises a process and device for electrically assisted partial oxidation of light hydrocarbons by oxygen. The purpose of the process and device is to produce gases rich in CO and H2 that can have high contents of C2H and C2H2, without any formation of soot or coke when assisting the partial oxidation of hydrocarbons with electric discharge plasma, accompanied by its reformation of steam and / or CO2 reformation. This mixture of products is achieved in a plasma reactor with sliding electric discharges that shine in the compartment brought to a temperature lower than 1 200 ° C and at a pressure of less than 6 x 1 05 Pa. The discharges act directly in a reactive medium Exothermic consisting of hydrocarbons mixed with gaseous oxygen of any origin, and possibly with H2O and / or CO2. The flow of products activated by the plasma and leaving the area enters -a-afe »; -a-a _r i-te-a- * in contact with a metal or ceramic material placed in the compartment that is brought to a temperature not exceeding 1 100 ° C. This material becomes active in the presence of the flow of products and, as such, contributes to the intensification of the conversion of the products that leave the plasma compartment in the final product.

BRIEF DESCRIPTION OF THE DIAMETERS Other objects and advantages of the invention will become apparent upon reading the following detailed description and on the reference to the accompanying drawings, in which: FIG. 1 is a cross-sectional view of a sliding discharge reactor according to an embodiment of the invention. Fig. 2 is a schematic representation of a system used to test the hydrocarbon conversion process according to one embodiment of the invention. Although the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the drawing and detailed description for the same do not intend to limit the invention to the particular form described, but on the contrary, the intention is to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the invention. the present invention as defined by the appended claims.

The process is illustrated by the conversion of some typical mixtures of light HCs (containing mainly methane CH4 and ethane C2H6, propane C3H8 and C4H6). the two butanes C4H1 0) in a slurry reactor fitted with a post-plasma compartment filled with solid material These HC mixtures can contain any amount of nitrogen N2 and / or carbon dioxide CO2.As a consequence, the invention can be applied to any pure HC, such as, CH4, C2H6, C3H8 or C4H1 0, and to their natural or industrial mixtures, such as, NG, "associated" gas from oil wells, flare gas, pyrolitic gas, "mine gas" , biogas, etc. In the presence of oxygen and possibly water vapor (both added to the hydrocarbon feed), it is thus possible to completely or partially convert all of these NGs into "synthesis gas", also referred to as "syngas", the which is a composite mixture pr Incipiently hydrogen H2 and carbon monoxide CO. The conversion can also be carried out in order to produce a syngas containing other valuable products, such as ethylene (C2H4) and acetylene (C2H2). The process is based mainly on the exothermic reactions of the partial oxidation of methane and / or its paraffinic (saturated) equives: CH4 + 1/2 O2 = CO + 2 H2 (1) CnH2n + 2 + n / 2 O2 = n CO + (n + 1) H2 (2) Accompanied by steam endothermic reforming, such as: CH4 + H2O = CO + 3 H2 (3) CnH2n, 2 + n H2O = n CO + (2n + 1) H2 (4) and / or endothermic cracking, such as: 2 CH4 = C2H4 + 2 H2 (5) 2 CH4 = C2H2 + 3 H2 (6) as well as the simple and inverse "water displacement" (quasi-athermic reactions): Additionally, highly exothermic reactions are observed from total oxidation, such as: CH4 + 2 O2 = CO + 2 H2O (11) CnH2 + 2 + (3n + 1) / 2 O2 = n CO2 + (n + 1) H2O (12) from a deep (endothermic) pyrolysis of HCs that go to elemental carbon, such as: CH4 = C + 2 H2 (1 3) CnH2n + 2 = n C + (n + 1) H2 (1 4) and of endothermic reformation with the carbon dioxide produced during the reactions: CH4 + CO2 = 2 CO + H2 (1 5) CnH2n +2 + n CO2 = 2n CO + (n + 1) H2 (1 6) All these reactions were performed in a highly activated medium by the presence of a particular plasma produced by sliding electric discharges. The activation of the medium is reflected by the presence of quite unusual species (compared with the conventional conditions of NG conversions) that originate from the material where these discharges take place. A) Yes, it is possible to detect electrons, as well as atoms, ions and / or molecular radicals, such as, H, OH, O, O2, H \ O \ O2 +, O2", HO2, CH3, CH2, CH, C2 and many more. Most of these species can exist in their "long-lived" electronic or vibrational excited state.They are also known to be chemically extremely active.The conversion of HCs according to the endothermic reactions (3) to (9) and ( 1 3) a (1 6) would require the addition of preferably "clean" energy, detached from any external combustion that is not cost effective and highly contamnt.The best way to promote these reactions would be to perform electric arcs and / or discharges. directly in the middle to be converted, by imposing a permanent distribution of energy in the largest volume to be processed.The transfer of electrical energy to the gas medium would be achieved through the direct transfer of energy to the molecules. in the phenomenon s of excitation, ionization, dissociation and also in the Joule effect, considering the ionized medium as a gaseous conductor. The gas medium, which became conductive after the ionization (by itself due to the dielectric breakdown, in this way, a preionization) between electrodes brought to different potentials, would be considered as an electrical resistance and, at the same time, as a class of electrolyte in a gas phase: the plasma. Plasma is defined as the fourth state of matter and, consequently, can not be used, under any circumstance, as a criterion of similarity for the different previously known processes. There are many different plasmas and several ways to reach each of these plasmas. By definition, plasma is a gas medium where the particles are partially ionized. In most plasmas, the macroscopic physical quantity - the temperature - is the same for all components: that represents thermodynamic equilibrium. Such conditions are easy to obtain: all that is required is to provide a large amount of energy, as in the case of plasma torches ("plasmatrons"), where plasma is produced by an electric arc of very high current. There are also other devices capable of generating this state, such as induction or radiofrequency (RF) torches, where »• --.-. a-- -, "A, - ^ -; - ^ - the gas medium enters into resonance with an electromagnetic field of very high frequency. Such plasmas are known as thermal plasmas. It is obvious that a thermal plasma will modify the chemistry of a gas medium by destroying practically all molecules, especially those that are fragile as HCs. The fragments that remain at the end of the process, after a sudden temperature drop due to extinction without any energy recovery, originate from the phenomenon of partial recombination that produces simple molecules. Such a chemical offers very poor possibilities, requires a large amount of energy and faces problems related to high temperature, in particular, the resistance of the materials. The physicists prefer plasmas that do not comply with the conditions of total thermodynamic equilibrium. It is enough, for example, to act on free electrons. It is also possible to act on the properties of rotation or vibration of some molecules. In terms of energy, this consists of breaking the equilibrium of energy exchanges between the plasma and its surrounding environment. This state is referred to as "non-thermodynamic equilibrium". Such plasmas are sometimes referred to as "low temperature" plasmas, although the notion of tem perature can not be used more. There are several methods to generate such plasmas: micronodes, electron beams, flame fronts, etc. But generators of such plasmas that can be converted to the industrial scale are rare and serve only a very specific purpose. This is the reason why such plasmas are rarely used in chemistry.

In addition, when a plasma is established or terminated, the equilibrium breaks down. These transition stages really constitute non-equilibrium plasmas and only last a few more. A type of plasma exploits this phenomenon, the plasma of the sliding electric discharges and the arcs known as "GlidArc". Out of the numerous geometric possibilities of such a plasma generator and, in a very general way, the parameters on which the chemical can act are: pressure, temperature, gas velocity, current intensity, voltage and electric frequency. Such a number of parameters exceeds the traditional reasoning capabilities of the experts. For each application, a real know-how and inventive activity is required in order to achieve the result, whose obtaining is as effective in terms of cost as environmental condescension. The GlidArc thus allows the chemist to consider the distribution of a power supply directly in the gas mixture and, for example, to resort to catalysts. The chemical can also distribute the energy directly either as thermal energy or as chemical energy. It can also act on the flow that is still loaded with active species that leave the area of arcs or sliding discharges, in order to provoke a reaction between these species and the feed to be converted or reconverted into a post-plasma zone. We have then discovered that, with a few modifications, the GlidArc is well suited for a pure water vapor supply as the only plasma-forming medium. Water vapor overheating tests were performed with these devices at the scale of ', A- ^ c- ^ -S; _? -a laboratory and at atmospheric pressure. The improved GlidArc was fed with very wet steam at * 1 05 ° C. No deterioration of the generated plasma fed with water vapor was observed after several long experiments. Thus, the steam drains overheated at atmospheric pressure and is activated chemically by the presence of H, O, OH and other metastable species, it can be interesting for drying or for chemical transformations, see P. CZERN ICHOWSKI and A. CZERN ICHOWXKI , "Gliding electric ares to overheat water vapor" (Electric sliding arches to reheat water vapor), 9the University- 10 Industry Colloquium "The electrical techniques and the quahty of drying" (Electric techniques and drying quality), Bordeaux- Talence, 1 994, p. B1 -1 - B1 -7. It is at this stage that we think that a classical steam reforming of pure methane could be improved in the presence of arcs or electric sliding discharges, which would bring to the reactive medium both an easily controllable enthalpy and highly reactive species. These particular discharges and arcs can play, in this way, the role of a catalyst in a homogeneous phase, see A. CZERN ICHOWSKI et al. , "Procces and device using plasma to enhance non catalytic steam reforming of hydrocarbon and halogeno-organic compounds "(Process and device that uses plasma to intensify the reforming of non-catalytic vapor of hydrocarbons and halogeno-organic compounds), BF 2 724 806 (1 994) The endothermic reaction previously mentioned ( 3) Reform methane vapor requires, in order to be completed under standard conditions (298 K, 1 atm), an energy equivalent to 206 kJ per mol of CH4 transformed, or otherwise to 0.64 kWh per 1 m3 (n) of CO + 3 H2 mixture produced. Since the reaction starts just under standard conditions (the transformation rate of CH being only 0.005%), according to Thermodynamics, the reactants must be heated to higher temperatures, which not only requires to provide the enthalpy of the reaction, It also leads to heating the entire mixture. Our calculations indicated that a minimum cost, 0.933 kWh per 1 m3 (n), corresponded to the temperature of 950 K, where a initial transformation of 75% CH. However, at this stage, the molar ratio of H2 / CO is too high (4.98) for some applications of such syngas. Such a gas composition was completely inadequate for Fischer-Tropsch (FT, synthesis of synthetic hydrocarbon fuels, "syncrude") technology or technology. similar for methanol production The two processes require a syngas with an H2 / CO ratio of approximately 2, plus a low concentration of residual methane. In order to increase the conversion ratio of methane to 97%, the complete reactive mixture should be heated to 1 200 K, at the theoretical price of 0.986 kWh per 1 m3 (n) of syngas, but the excess hydrogen would remain at a level of H2 / CO = 3.04. The decomposition of pure CH in the presence of superheated steam in a GlidArc reactor actually produced large quantities (in terms of volume percentages) of H2 (up to 66%) in the dry product) and CO (up to 1 5%), while the percentages of - ^ _.-_ • * "> volume of C2H2 (max.1.1%) and C2H2 (max. -0.34%) were low, in all cases, we had proportions of H2 / CO of 4 and even up to 5.8 Additionally, the price of energy to be paid in order to produce 1 m3 / n) of such syngas was quite high and another problem arose: too much methane content remained in the product, so we had another idea: apply simultaneously H2O and O2 mixed in order to carry out at the same time, during a single operation in the sliding discharge reactor, a conversion of some light HCs by an endothermic vapor reformation (reactions 3 and 4) and a partial oxidation with oxygen (reactions 1 and 2), which would produce a significant portion of the energy required for the endothermic vapor reformation, Part of the oxygen would be consumed by the reactions (1 1) and (1 2) that would appear to be side reactions (but strongly exothermic), however, CO2 produced by these reactions could contribute to decrease the proportion of H2 / CO via the reverse reaction (10). A similar approach to such reformation of NGs is known in the industry as "Auto-thermal reformation" ("ATR" or "auto-thermal" process), but this mixed reformation is necessarily coupled with a catalytic post-treatment of the gas that exits of the partial combustion zone, see TS CH RISTENSEN e 1.1. PRI M DAHL, "I mprove syngas production using autothermal reforming" (Improvement of syngas production using autothermal reforming), Hydrocarbon Processing, vol. 73 (3), p. 39-46 (1 994). A highly sophisticated thermal burner is at the core of the ATR process, as the entire safety related to ^ -a ^ '? ^ f ^.

Operations involving the mixing of oxygen and HCs in the uncontrolled explosive limit depends on their proper operation. Our reactive system for the mixed reformation of HCs with oxygen and water vapor in the presence of sliding electric discharges also contains an inverse displacement of part of the hydrogen to CO (reaction 10). This makes it possible to obtain a syngas which has a good molar ratio of H2 / CO for a subsequent use of the syngas, for example, via an FT process. This objective was achieved and, in addition, we were surprised by the appearance of other products of the feed conversion according to reactions (5) to (9): C2H4 and C2H2 at relatively high contents. These unsaturated products can thus add something of value to this lightweight HC conversion process, assisted by sliding electric discharges. Another new idea is to divide a sliding discharge reactor into two compartments. By adding a more or less virtual separation, for example in the form of a perforated diaphragm, we create a sliding electric discharge compartment with a reinforcement of the circulation of reagents. We isolate this compartment thermally, so that the temperature of its walls and the electrodes themselves can be raised as much as possible. To this, we add another "post-plasma" compartment where the reactions generated in the plasma zone can be completed and where the products generated in the plasma zone can be modified eventually. The two compartments (or zones) of the reactor communicate through a relatively large orifice, or preferably a perforated plate, or even a porous material, allowing reactants and active species produced in the plasma zone to penetrate into the zone post-plasma. Finally, another new idea is to partially fill the post-plasma zone with a solid material that leaves the role of a contact in which we promote reactive exchanges between the species generated in the plasma zone. The solid material does not need to be known as a catalyst. It can become one by contact with the species that originates from the plasma zone.

PLASMA DEVICE Several types of slip discharge reactors can be used. One illustrated in Fig. 1 is a laboratory scale device used to illustrate the invention. Naturally, this is just a non-limiting example for the development of a future industrial scale reactor. The sliding discharge reactor / 1 / uses six electrodes 121 in profiled stainless steel sheet 2 mm thick (only two of the six electrodes arranged symmetrically around the flow axis of the fluid to be processed are shown in Fig. 1) . Each of the electrodes has a length of 8 cm and a width of 25 mm. The electrodes delimit a nozzle-shaped volume 121, where sliding electric discharges / 4 / can develop. This reactor contains a simple nozzle 151 with a diameter of 4 mm, which blows the premixed fluid / 6 / to be converted in space 171 between the arranged electrodes so that the fluid flows along the central part of these exposed electrodes to the downloads. A more complete "double nozzle" can also be used (but not shown in this Fig. 1); It consists of two concentric pipes through which the hydrocarbon feed arrives, possibly mixed with water vapor, and oxygen or air enriched with oxygen, or even atmospheric air, the three being possibly mixed with water vapor. In this case, the reagents are mixed in such a new "double nozzle" or even out of it, just near the electrodes. Several nozzles can be arranged in the same reactor. The roots / 8 / of the discharges that blow and preionize the gas at the point / 9 /, where the distance between the electrodes is the shortest, slide on these electrodes and disappear at the point / 1 0 / near the end of the electrodes, to reappear once more at the starting point. The process is sequential and the useful life of a discharge / 4 / observes ranges from 1 to 20 ms depending on the linear velocity of the fluid in zones 171, / 9 /, 121 and / 1 0 /, between electrodes 121. Given the moderate temperature (<; 1200 ° C) of the electrodes and a very short contact time of the discharge supply with the electrodes, even in uncooled steel, we did not observe any deterioration that could prevent the dislodging of these limited current discharges. The sliding discharges / 4 / have variable characteristics from the point / 9 /, where they are initiated in their extinction / 1 / with, in particular, energy dissipation that increases with time. The tubular reactor is enclosed by two covers. One of them / 1 1 / supports electrodes that are electrically isolated with high voltage connections / 1 2 /. The other / 1 3 / encloses the reactor on the other side and comprises a product outlet tube / 22 /. The complete structure is hermetic; supports both a partial vacuum of 7 kPa and a _-- &---; t? _? 6? .g -r_8S _--- overpressure of 6x105 Pa. A ceramic or perforated metal plate / 14 / separates a plas-fea zone / 1 5a / and a post-plasma zone / 1 5b / partially filled with solid material. The two zones are housed within the same IM reactor. Plate / 14 / fvace possible to run products from 5 the plasma treatment to the post-plasma zone / 1 5b /. The reactor (external diameter of 85 mm and height of 88 cm) is externally insulated by a ceramic / 16 /. We pack the internal walls of the post-plasma reactor area with a ceramic tube / 1 / with an internal diameter of 55 mm. The plasma zone is isolated by a felt heat resistant / 1 8 /. The total free volume (in terms of fluid) inside the reactor is 1.9 dm3. The volume of the solid material / 1 9 / inserted in the post-plasma zone / 1 5b / (in most cases we use Ni metal bars with a total mass of 1.5 kg) is 1 70 cm3, which corresponds to a geometric surface of 1 670 cm2. The proportion between the volumes of solid material inserted in the post-plasma zone and the empty volume of this zone is only 1 to 6.5, while the proportion between the volumes of the plasma zone / 15a / and those of the post-plasma zone is 1 to 2.4. No part of the reactor is cooled in a forced manner. The incoming fluids 16 / are mixed away from the mouthpiece of injection / 5 /, on the nozzle alone, or even near the nozzle. They can be preheated together or separately with a temperature controlled heating furnace / 20 /. This last method would be even preferable for an industrial reactor, in order to prevent the early combustion of O2 + HC during preheating. Two holes in the cover / 13 / provide the connection to a pressure gauge / 21 a / and the ^ - > . ,,. insertion of a thermocouple wire / 21 b /. The conversion products leave the reactor through a / 22 / tube. With a more rapid injection (> 10m / s) and almost punctual fluid between the electrodes 121, we already cause a recirculation phenomenon / 23 / of the reactants in the sliding dischazone / 1 5a /. In order to reinforce this recirculation, we also added this separation plate / 14 /, thus dividing the reactor into two parts: an electric dischaplasma compartment / 1 5a / and a post-plasma compartment / 1 5b /. The perforated plate provides the flow of reactive (partially consumed) and active species of "long life", resulting from the excitation of the gases by the sliding discha. In the post-plasma zone, the conversion is susceptible in this way, if it is completed in the presence of solid material and in an environment where the temperature is much lower than that of the walls and electrodes of the plasma zone. / 1 5a /. The fluid, once it is in this post-plasma zone, can not re-enter the plasma zone. The luminous area of the sliding electric discha, as well as part of the wall of the zone, can be observed through a glass / 24 / with a diameter of 1 5 mm, in order to verify the proper operation of the reactor and determine the temperature in the compartment / 1 5a /. Very important information can be derived from the plasma emission spectrum. The conversion of NGs is usually sufficient with a simple run through the simple reactor. Otherwise, the products partially converted to a reactor can be reprocessed in several reactors thus described and sequentially arranged (not shown).

The presence of the perforated dT sron / 14 / cre-i ina plate and post-plasma reactive zone / 1 5b /, where the highly active and metaestable species (thus having catalytic properties) can be deactivated in other molecules , directly in the gaseous phase or indirectly in the surface of the solid material / 1 9 / inserted in the zone. This makes it possible to reform HCs that originate from violent reactions in the plasma zone. It is also possible to further advance the conversion of the reagents. Physics provides us with information about atomic and molecular species, such as, H *, OH *, O2 *, CO2 *, H2 *, H3 * (and many others), which have a long enough life to cover long distances in gas flows, even at atmospheric pressure or a higher pressure. This phenomenon is very important for the conversion of HCs known for their fragility. In fact, the action of a non-thermal (or non-equilibrium) plasma makes it possible to completely avoid the formation of coke from the hydrocarbon feed. Long operating times of the reactor thus constructed and a perfect transparency of the virdio (all in the presence of HCs as fragile as propane and butanes), constitute the best evidence of "soft" transformations that can be carried out in such reactor, with said compartment post -plasma. The reactor is fed with controlled volumes (by means of mass flow meters) of gas taken in gas cylinders (or other sources) and / or water vapor originating from a steam generator. The reactor can also be fed with water through the use of a metering pump. The constant flow of such liquid, controlled by a - ?. ^. The valve and a flow meter are evaporated in this way in the furnace / 20 /, to be then injected into the reactor, being previously mixed or not with another process fluid. Chemical analyzes are done by using classical gas chromatography methods in a gas phase. We use three chromatographs, each dedicated to individual dry gases: CO, CO2, O2, N2 and CH4 for the first, only H2 for the second and all HCs for the third. The flow of water vapor in the products is calculated from material balances or quantified by trapping a known volume of the exit gas. The sliding discharges inside the reactor are fed by a special high voltage system that provides both preionization of the medium and then the transfer of electrical energy to the plasma. The electric power of the reactor used varies between 0. 1 5 and 0.56 kW under 0. 1 2 or 0.25A for a fluid flow rate to be treated from 1.3 to 2.6 m3 (n) / h; The supply of energy in relation to food is 0.1 0 to 0.34 kWh / m3 (n). However, nothing prevents the use of higher energy, flow rates and / or energy supplies for industrial applications.

RESULTS EXPERIM ENTALES The reform of a NG will be better understood with the help of the Fig. 2. The reactor used is that which is illustrated in Fig. 1 . Fig. 2 is a schematic representation of the global team. In this figure, the IM reactor is powered by a special high voltage electric generator / 25 /. This reactor is operated directly with, as a plasma-forming gas, an NG taken from the city system / 26 / or from a pressurized cylinder / 27 / containing 1 a simulated NG, mix! oxygen / 28 / o air enriched with oxygen / 28 / or even atmospheric air / 28 / and possibly water vapor (or liquid water) / 29 /. The gas flows are controlled by mass meters / 30 / The incoming gas mixture (dry) can be sampled by chromatographic analysis with a / 31 / derivation. The flow of water vapor is also known following the calibration of the measuring pump of the device / 29 /. A thermocouple / 32 / makes it possible to measure the temperature of the fluid at the inlet of the injection nozzle, while an optical pyrometer / 33 / and a thermocouple / 21 b / indicate the temperatures in the two compartments / 1 5a / y / 15b / of the reactor. A pressure indicator / 21 a / provides the pressure inside the reactor at all times. The products leaving the reactor are cooled in an air heat exchanger / 35 /. On the outlet of the exchanger, the gases are directed to a reversal valve / 36 /, which is used to redirect them to either the analysis / 37 / or the evacuation tube / 38a /. During our tests, we sampled and weighed the water leaving the reactor, by condensation / 39 / and absorption / 40 /. We also sampled the dry gas product for chromatographic analyzes. To that end, we first send the wet gas to the exit / 38a / and then, once we consider that the reactor is operating at the desired level (stable in most cases), we invert the valve / 36) and send the product that goes to the analysis / 37 /. The water is deposited in the cooled flask / 39 / and in an absorbent material / 40 /. Valve / 41 / which is previously closed and valves / 42a / and / 42b / open, dry gas flows through a bulb or balloon / 43 /, then through a gas meter / 44 / and leaves of the experimental device through a pipe / 38b / located near the evacuation tube. The temperature of the gas leaving the meter / 44 / is measured with a thermometer / 45 /. In each test, we also measure the atmospheric pressure with a barometer, in order to readjust our volume balances to their normal marked conditions ("n"). Numerous feasibility tests of the NG reforming process were carried out in the new reactor with the "post-plasma" compartment. We present only the 7 most significant series of tests in the form of tables. The composition (in% vol) of the NG originating from the city's distribution system changed from one week to the next: CH4 from 90.7 to 98.8; C2H6 from? .9 to 6.9; C3H8 from 0.2 to 1 .9; C4H10 from 0.1 to 0.5 (mixture of n-and isobutane); this gas contained very little nitrogen and CO2. We also carefully analyze these NGs during each test, in order to establish an accurate material balance. Table 1 and Table 2 respectively summarize four and six examples of the partial oxidation of NG with pure oxygen without the addition of water vapor. Table 3 summarizes seven examples of partial oxidation of NG with pure oxygen and added water vapor, in the presence of a solid metal body inserted in the post-plasma zone of the reactor. Another body, this time ceramic, was then placed in this area and the results of four tests with pure oxygen and water vapor added are presented in Table 4. Table 5 summarizes seven new examples of partial oxidation of NG with enriched air with oxygen and added water value, in the presence of the same metal body in the post-plasma zone. Table 6 summarizes seven examples of partial oxidation of NG with atmospheric air in a "shortened" reactor filled (or not) with different bodies (metal or ceramic) in the post-plasma zone. Finally, Table 7 presents the results of 4 pairs of common tests with and without discharges in the plasma zone. In these tables, we indicate some of the operational parameters of the test and the results obtained. The same abbreviations are used: • O2 / HC and H2O / HC - the volume ratios between these components in the mixture (reactants) that enter the reactor. • SE - specific energy injected into the plasma (actual electrical energy of the discharges in relation to the normal flow rate per hour of all incoming reagents). • Temp. - the temperature (° C) in the post-plasma zone (marked "post zone") or the temperature of the walls in the plasma zone (marked "zone pl"); this last temperature may not be correlated with a "temperature" under which partial oxidation takes place in the area covered by our electric discharges. • H2 / CO - the molar or volume ratio of two gases in the product leaving the reactor. • SG / HC - the relative amount of syngas (H2 + CO) produced from an incoming HC volume unit (other gases are not considered). • EC - the amount of electrical energy (in kWh) consumed to produce 1 m3 (n) of syngas (other products such as acetylene or ethylene are - - - --V * ^ -5 * - * "%, * ^ -;.} .. considered" free "), this value indicates a real energy cost (in electricity directly injected in the sliding discharge) of the process in the laboratory scale • Conv C - the overall proportion (in%) of carbon conversion initially contained in the NG (in "organic" form in saturated HCs) in any other "mineral" form (CO and CO2) ) or "organic" unsaturated (acetylene or ethylene), at this point, it is convenient to note the absence of coke, soot, tar or other ionic pyrol compound in our products (within the 0.5% limit expressed in the mass of converted carbon), which helps us to establish our gas composition balances • Conv O2 - the overall proportion (in%) of the conversion of oxygen element added to the hydrocarbon feed in any other form (CO, CO2 and H2O) • Selectivities - the relative proportions (in%) of carbon or hydro conversion rógeno initially present in the NG and transformed into another useful product or parasite.

Accordingly, Table 1 summarizes the four tests 20 to 23 of partial oxidation of an NG with oxygen without added water vapor. Whenever the term "add-on" is used, we emphasize the external origin of this reagent, which appears in any form (but in a smaller amount) as a product of additional oxidation reactions (11) and (12). The NG (with a composition of volume of 97.3% of CH4, 1.4% of C2H6, 0.3% of C3H8 and 0. 1% of C H1 0) is mixed with pure oxygen of according to a constant O2 / HC ^ ratio of 0.48, and then injected into the reactor without pre-heating. The flow velocity of the mixture (1.3 m3 (n) / h), the pressure in the reactor (1.5x1 05 Pa) and the power supply arrangements are kept constant. p ^ pf- as, it is heated prog- resively and the output products are shown when the thermocouple installed in the post-plasma zone indicates the temperatures listed in column 2 of the table at that time, we also measure the electrical energies dissipated in the the plasma zone. They are not strictly constant due to the evolution of the temperatures of all the elements of the plasma zone, but the specific energy IS varies little1 0.29 ± 0 03 kWh / m3 (n).

Table 1 The results of this series of tests inform us that it is preferable to convert a NG when the post-plasma zone reaches a temperature of at least 480 ° C since, for lower temperatures, all the performance indicators of the process are less good. Thus, when going from 1 30 ° C to 480 ° C, we approach the desired H2 / CO ratio ~ 2. We obtain almost 6 times more syngas of a unit volume of HCs, and this at an energy price over 7 times better. These enormous improvements are also visible from other figures: the (absolute) conversion of carbon increases 1.8 times, and this more towards the desired product (the selectivity towards CO goes from 46% to 83%) that the molecule does not desired (the selectivity to CO2 ranges from 44% to 1 5%). By increasing the temperature in the post-plasma zone, we also retain much more H2 elemental hydrogen by decreasing (from 68% to 30%) the relative selectivity of water vapor formation. We can also observe that an increase in temperature in the post-plasma zone of more than 480 ° C does not lead to an improvement of the process. It should also be noted that the temperature of all solid elements present in the plasma zone easily exceed 900 ° C for all these tests. Table 2 summarizes the six tests 27a to 30 and 67 to 68 of partial oxidation of an NG with oxygen without added water vapor. The "light" NG (with a volume composition of 96.6% of CH, 2.6% of C2H6, 0.6% of C3H8 and 0.2% of C4H 1 0 for tests 27a to 30, and 98.8% of CH4, 0.9% of C2H6, 0.2% of C3H8 and 0.1% of C4H1 0 for tests 67 and 68) is mixed with pure oxygen in variable O2 / HC ratios = 0.49 to 0.65, and then injected into the reactor without preheating. For a constant pressure of 1.5x105 Pa (except exp 68 for 2.0x105 Pa), the flow velocity of the incoming mixture (1.3 to 1.6 m3 (n) / h) and the power supply settings are quasi-constants. This time, the complete reactor is closer to its thermal plateau and we observed Se values that were almost constant at a level intentionally maintained low: 0. 1 5 ± 0.03 kWh / m3 (n). At this level of Se, we add very little "~ - ^^^" a - ^ - j - * energy to the partial combustion "of the NG; Instead, we "electrify" it.

Table 2 > f ' The results of this series of tests inform us that it is preferable to convert an NG when the O2 / HC ratio reaches a value close to 0.65. at this level, we obtain very good results of total conversion (1 00%) of carbon and oxygen under 1 .5x1 05 Pa, we approach the desired proportion of H2 / CO, we produce 2.6 m3 of syngas per 1 m3 of HC, very low power unit price ED of 0. 1 1 kWh per 1 m3 (n) of syngas. These performances are also visible from the selectivities of carbon conversion. Interestingly, these figures evolve towards the desired product (the selectivity towards CO is 89%) than towards the parasite CO2. Another surprising point is that, by increasing the proportion of O2 / HC, we produce much more H2 elemental hydrogen and the selectivity of water vapor formation decreased from 33% to 1 3%. g ¿g * -__--- -? jfcti = -. .

A pressure increase of 1.5x1 05 to 2.0x1 05 Pa is beneficial for the amount of syngas produced from one unit volume of HCs. This is also visible in the figures pertaining to the carbon conversion ratio, as well as in the selectivities towards CO and unwanted products. We also perform other tests under a pressure approaching 6x1 05 Pa. We currently consider this limit as the maximum value with which our team will work in a stable and problem free manner. Additionally, we are considering developing a partial oxidation of HCs under relatively low pressures for specific applications, such as the chemical conversion of petroleum-associated gas (otherwise burned by flares at quasi-atmospheric pressures), biogas produced in digesters of low pressure, hydrocarbon permeate resulting from membrane separation, etc. In this way, our relatively low pressure process makes it possible to avoid "hungry" energy compressors and installations with higher technological requirements due to the classic high-pressure technology of the catalytic auto-thermal process. Table 3 summarizes the seven tests 38b to 44 of partial oxidation of an NG with oxygen and water vapor added. The question was whether we could convert an NG with a little less oxygen by replacing it with water vapor, while maintaining a relatively low energy price (EC) for syngas with a composition similar to the H2 / ratio. CO = 2 The target NG selected was slightly heavier: 91.6% of CH4, 6.2% of C2H6, 1.7% of C3H8 and 0.5% of C4H1 0. It was mixed with pure oxygen and water (injected in the form of the above liquid). of being evaporated in the furnace) in variable (molar) proportions: O2 / HC = 0.25 to 0.64, H2O / HC = 0.58 or 1.0. A slight preheating was used (between 1 1 5 and 1 50 ° C) exclusively to evaporate the water. For a constant pressure of 1.5x1 05 Pa, the flow velocity of the mixture (1.7 to 2.0 m3 (n) / h) and the electrical supply settings were almost constant. The reactor is close to its thermal plateau and we observe almost constant SE values at a level of 0.24 ± 0.02 kWh / m3 (n).

Table 3 The results of this series of tests show that it is possible to obtain a mixture very close to the ideal mixture of H2 / CO = 2, by oxidizing the hydrocarbon feed with a deficit of O3 / HC = 0.33 (this is equivalent to a Molar of O2 / C = 0.31), provided that this missing oxidizing agent is replaced by water vapor. Another advantage ? --- -% -TJ ~ that could justify using water vapor together with oxygen is that a relatively high amount of ethylene and acetylene can be created in the syngas (see exp. When comparing the exp. 38b with 39, we observed that a limited addition of H2O makes it possible to decrease EC; In this way we demonstrate that it is possible to add a well proportioned H2O in order to achieve a particular objective. It should be noted that the overall limited conversion ratio in some of the experiments presented here (and in the tables that follow), it can be brought to 1 00% by injecting more energy and / or by reducing the flow of NGs entering the reactor (this is equivalent to increasing S E). We should also add that when analyzing the conversion ratios of each HC individually, we observe that the heavier HCs react more easily. For example, for a conversion rate of global carbon equal to 32.6% in the exp. 44, butanes and propane are completely converted, ethane is converted to 96.6%, while methane conversion is limited to 1 9.2%. Consequently, our partial oxidation process assisted by sliding discharges could be applied regardless of the HC content of an NG (or other hydrocarbon mixture) to be converted. Table 4 summarizes the four tests 46 to 49 of partial oxidation of an NG with oxygen and water vapor added in the presence of another inert material in the post-plasma compartment. In fact, instead of metal bars present in the area during the tests summarized in Tables 1 to 3, we fill this area with large pieces of 'chamotte'. The question was: is the mixed conversion of O2 + H2O of a NG sensitive to the nature of the solid fttft >; ducic_ in the post-plasft zone | 2 The "heavy" NG had the following cc | f position: 90.7% of CH4, 6.9% of C2H6, 1.9% of C3H8 and 0.5% of CH1 0 (consequently , very close to the composition of the NG tested during tests 38b to 44). It was mixed with pure oxygen and water in variable (molar) projections: O2 / HC = 0.22 to 0.58, H2O / HC = 0.72 to 1.22. A slight preheating 8150 ° C) was used exclusively to evaporate the water. For a constant pressure of 1.5x1 05 Pa, the flow velocity of the mixture (1.6 to 2.1 m3 (n) / h) and the electrical supply settings were almost constant. He The reactor was more or less in its thermal mefseta and SE values were almost constant at a level of 0.24 ± 0.04 kWh / m3 (n).

Table 4 The results of this series of tests show that it is possible to obtain a mixture very close to the ideal mixture of H2 / CO = 2, by oxidizing the hydrocarbon feed with a deficit of O2 / HC = 0.22 (this is equivalent to a molar ratio of O2 / C = 0.20), provided that this -% - &- • .- * missing oxidizing agent be replaced by water vapor. We can now create a greater amount of ethylene and acetylene in the syngas (see exp 49). The comparison of two series of tests presented in Tables 3 and 4 indicates the possibility of closely controlling the contents of ethylene and acetylene in the syngas, by acting on the nature of the solid material placed in contact with the gas flow resulting from the electro- treatment in the plasma area of sliding electric discharges. The relatively high energy price EC is not surprising since it does not take into account these two more intense energy products of the process (refer again to the definition of CE). Table 5 summarizes the seven tests 51 to 57 of partial oxidation of an NG with air enriched with oxygen and eventually mixed with water vapor. The questions of whether we could convert a NG with such enriched air (for example, of membrane origin and in this way much less expensive and more readily available than pure oxygen of cryogenic origin) and if we could obtain a syngas at a reasonable price of energy, while also having an H2 / CO ratio of approximately 2. The target NG selected was quite heavy: 91.2% of CH4, 6.5% of C2H6, 1.7% of C3H8 and 0.5% of C4H1 0 It was mixed with enriched air containing 43% oxygen and eventually with water in variable (molar) proportions: O2 / HC = 0.73 to 0.94, H2O / HC = 0 to 0.28. A slight preheating (between 170 and 1 80 ° C) was used exclusively to evaporate the water in exp. 56 and 57. The pressure varied from 1.6x1 05 to 1 .9x1 05 Pa for incoming mixture flow rates between 1.9 and 2.6 m3 (n) / h. The reactor was close * _. ! _, of its thermal plateau and SE almost constant at a level of 0.22 ± 0.04 kWh / m3 (n).

Table 5 The results of this series of tests show that it is possible to obtain a mixture very close to the ideal mixture of H2 / CO = 2 (exp 56 and 57), by partially oxidizing the hydrocarbon feed with enriched air (43% O2) by adding a small amount of water vapor. We obtain very good proportions of syngas / HC volume, a sufficient carbon conversion ratio and very reasonable selectivities towards all valuable products. The energy cost EC is also approximately twice that of the tests performed with pure oxygen, but it continues at a very low level of approximately 0.24 kWh / m3 (n). We note that the addition of water vapor in exp. 56 and 57 generates well the reaction (10) of "water displacement" (lower selectivity towards H2O, greater selectivity towards CO2) and also a blockage of the pyrolysis of HCs in ethylene and acetylene. Despite the presence of a strong nitrogen ballast (between 28 and 38% vol in the incoming stream), we are able to maintain, thanks to the energy and the active species present in the plasma zone, a reactive environment which promotes the development of reactions for the partial oxidation of HCs. This is seen at the level of temperatures that are still quite high in the two reactor zones. A ballast (up to 40% in volume) of carbon dioxide, CO2, present in some NGs that we also tested does not prevent the smooth conversion of HCs into syngas. Such ballast can be compared to inert nitrogen ballast, although a fraction of CO2 can actively escape through the reactions (1 5) and (1 6), on the conversion of the original HC carbon into CO, which increases the content of this valuable product. We also observed that the CO2 present in the mixture to be converted plays a positive role in preventing the formation of soot by the following reaction: C + CO, = 2 CO (1 7) Another series of tests was carried out with atmospheric air mixed with a light NG. This complete mixture was subjected to the action of sliding electric discharges in another "shortened" reactor (30 cm of total length) with little thermal insulation. All the other details of the equipment were equal, except that the reactor only had a large hole to separate the plasma zone from the post-p ^ -a zone. Some results of these seven tests are presented in Table 6.

Table 6 This time, under a pressure of 1.1 x1 05 and with significant energy losses preventing the reactor from increasing its temperature (especially in the plasma zone), which would have made it possible to ensure a sufficient thermal energy formation of the reactions (1 1), (1 2), (1) and (2), and would cause an "inflammation" of the reactor, we did not obtain very good results. However, this series of tests shows us the feasibility of a partial oxidation of HCs with atmospheric air. This oxidation can be performed even with a very strong oxygen deficit (O2 / C = 0.23), but it is only possible in the presence of sliding electric discharges, otherwise the purely auto-thermal process would stop very quickly (here the inertia of the reactor is _, -% -.-v ---- - quite small) We must point out the strong influence of the material introduced in the post-plasma zone on the chemical composition of the products. In this way, we can obtain more or less unsaturated hydrocarbons, almost block the production of hydrogen in large pieces of copper metal, regulate the proportion of H2 / CO, etc. When comparing Tables 1 to 6, we observed that it is possible to partially oxidize and pyrolyze a light or heavy NG, with or without the addition of water vapor, within a wide range of proportions of O2 / HC and H2O / HC, in the presence of a ceramic or metal material initially non-catalytic in the post-plasma zone, in order to obtain a more or less syngas accompanied by ethylene and acetylene without (or almost) soot. A free choice of the solid material placed in contact with the post-plasma flow and the free choice of its temperature gives us ample possibilities to direct the composition of the product that comes out in accordance to the requirements, depending on the composition of the hydrocarbon feed, the availability of oxygen, etc. In addition, by injecting more or less electrical energy directly into the discharges (see SE values), we can convert more or less HCs into syngas. For example, we can obtain a natural gas that is seeded only with hydrogen and carbon monoxide, in order to provide their improved combustion in piston engines (in this case, unconverted oxygen does not present a problem) or for their transportation via a traditional gas pipeline to a civilized location, where the CO and / or H2 would be extracted for a nobler use.

We could also convert the complete hydrocarbon feed and iAs &;,. '.. _. - __ * »- --a ---- t & . ,. - * - - * - --- j¿_ - then send it to a synthesis of FT of syncrude. Everything indicates that a combination of the automatic process with electrical discharges provides a new opening to more interesting products (presence of ethylene and acetylene), obtained from ¡É. feeds of light or heavy HCs, partially oxidized by oxygen or by air enriched with O2, or even by atmospheric air, all under a low pressure of less than 6x 1 05 Pa. In this way, we have arrived at the very important questions of if really our sliding electric discharge is the one that produces such smooth production of syngas and that would pacaría if we completely cut the electrical supply of these discharges, causing their complete disappearance once the reactor reached its stable operation condition. The points included in Table 7 answer these basic questions. fifteen Table 7 The tests without discharges carried out in the "long" and very well insulated reactor follow those carried out with discharges, without modifying any of the adjustments. In this way, the exp. 26 performed at a pressure of 1.7x1 05 Pa, exp. 34 to 1 .6x1 05 Pa, exp. 45 to 1 .3x1 05 Pa and exp. 50 to 1 .5x1 05 Pa, respectively 26, 21, 44 or 9 m were made after the preceding experiments. It should be added that this reactor is quite solid and cools very slowly. We observed a partial oxidation process for a long time after the electric discharges were cut, but, in this case, all the indicators of the quality of the conversion of NG in syngas are lower than those in the presence of discharges. The pair 33/34 indicates that the temperature in the The "plasma" zone (but without asthma in exp.34) did not decrease much since the relatively high proportion of O2 / HC = generates enough oxidation energy to compensate for the thermal losses of the zone. This is not the case during exp. 45 the temperature drops rapidly (in less than 2 min) below ^ the threshold of our pyrometric measurements (600 ° C). However, the temperature in the post-plasma zone increases progressively, reaches a maximum (at which point we sample the product for the analysis) and finally falls very quickly to a threshold below which the conversion stops. However, at the beginning, the temperature of the solids introduced in the post-plasma zone (Ni or chamotte) increases due to the lateral reactions (1 1) and (1 2) which are highly exothermic (the selectivities towards CO2 and H2O increase for all pairs). Despite this increase in temperature, the conversion of oxygen becomes static or even decreases. Without the electric discharges to assist the conversion, we find, despite a huge surplus of fuels, a very high content of elemental oxygen which, if not separated, would exhaust the catalysts of an FT process for which the syngas is produced. However, everything indicates that it is actually the presence of sliding electric discharges in the electrodes immersed in a very rich mixture of fuel / oxidant in the plasma zone which provide the smooth execution of the process, objective of this application. Additionally, the still active flow of intermediate products leaving the plasma zone undergoes a post-plasma conversion in the presence of a non-catalytic solid (chamotte) or a metal (Ni) known for its catalytic properties, provided that it is highly dispersed Given the ridiculous surface of the metal (less than 1,700 cm2 by 1.5 kg), only one conclusion can be drawn: the inert or quasi-inert material introduced into the post-plasma zone plays the role of a catalyst only in the presence of a flow of products that come out of the plasma. Without this constant flow of plasma, this material deactivates itself very quickly and even begins to play a reverse role of the desired reaction. Our preferred material would be N i, although other solid materials could be even more advantageous. The volume of the reactor zone that houses the Ni bars is 660 cm3. Under the conditions of exp. 33/34, this volume, which comprises a (geometrical) surface of Ni of 1670 cm2, is covered by a product flow of approximately 6.6 m3 / h (at the pressure and temperature of the zone). This gives a space velocity of approximately 1.000 h "1.

DI SCUSI ÓN The comparison of our results, as provided in Tables 1 to 7, with the results obtained from the documentation, indicates the superiority of the device described above, compared with a classic O2 / HC burner used in an auto-process. -thermal. For reference, we will select the details published by Haldor Tapsoe (Denmark) in the article by CH RISTENSEN and PRI M DAHL mentioned above. Although the information is incomplete, we are able to establish a few material balances of the j ^ -strial process using only the chemical energy of more or less exothermic reactions (11), (12), (1) and (2). Because we have no information regarding the composition of the treated NG, we compare it with pure methane. Table 8 summarizes the data (marked HT) obtained from said article. Another comparison is made with relatively complete data published in November 1995 by S C. NIRULA in "Synthesis Gas, Report No. 148A" (Synthesis Gas, Report No. 148A), SRI International, Menlo Park, California. The data and balances (recalculated by us) are also included in Table 8 under the SRI sign.

Table 8 We must first note that these are thermo-catalytic processes under high pressure exposed to a relatively oxygen-rich flame (theoretically, we should stop at O2 / HC ~ 0.5) at more than 2000 ° C, the HCs are preferentially consumed in CO2 and H2O of according to reactions 811) and (12), instead of (1) and (2), leaving large quantities without consuming HCs (mainly chemically stronger methane). sgfl- It is only in the presence of a large mass of brittle catalyst that the total conversion of HCs is completed according to the endothermic reforming reactions (3), (4), (1 5) and (1 6), in a catalytic bed exposed to very high temperatures (1 1 00 to 1400 ° C). This catalyst and its support should thus exhibit a very high strength and very good stability under these severe conditions. CH RI STENSEN and PRI MDAHL do not mention any proportion of O2 / C less than 0.54 or any proportion of H2O / C less than 0.58 in any industrial example or pilot test. On the contrary, they emphasize the need to add at least these amounts of oxygen and water vapor to ensure the proper operation of your burner, which also requires a special recirculation. However, it can reduce these proportions to 0.22 and zero, respectively, since we had another adjustment device: the very active energy of electric discharges added to the highly substoichiometric flame. The N I RU LA report provides some information regarding the volume of the industrial reactor (94 m3) and the incoming gas flows (200, 000 m3 (n) / h). From gas analyzes at the reactor outlet, we were able to calculate the reactor's space velocity, which operates under 68x1 05 Pa and at a very high exit temperature of 1 350 ° C. This speed is approximately 310 h "1, which does not compare in any way with ours, which even brought to the total volume of the reactor, is 3500 h-1. We demonstrate for the first time the viability of a new process for the conversion of NGs assisted by sliding discharges in the presence of oxygen or air enriched with oxygen, or even atmospheric air, with an eventual addition of water vapor.This process is illustrated in Tables 1 to 7 by the conversion of different NGs into a new one. reactor from which the plasma compartment (zone) (with all electrodes) is brought to a temperature not exceeding 1200 ° C. Another post-plasma compartment (zone) communicates directly with the plasma compartment through a separation perforated (or even if n separation) This post-plasma zone, at a temperature of less than 1100 ° C, can be partially filled with a solid ceramic or metal material which, in contact with a flow of products from treatment derived from the plasma hydrocarbon feed, it becomes active and contributes to the total or quasi-total conversion of HCs into syngas, with a cogeneration of more or less ethylene and acetylene. In the presence of oxygen and possibly added water vapor, we are able, in this way, to convert all HCs, such as CH, C2H6, C3H8 and / or CH10 into synthesis gas and also, partially, into other products valuable: C2H4 and C2H2. This is done without using any conventional catalyst. A wide range of relative proportions can be used between two oxidizing agents (O2 and H2O) and the HCs. Our examples are given by O2 / HC values between 0.22 and 0.94, and H2O / HC between 0 and 1.22, but it is clear that we could still increase these two limits as desired from zero to infinity, since our Sliding discharges can be generated both in pure oxygen and in pure water vapor. Thus, all H2O / O2 / NG mixtures can be converted into the reactors described herein. Depending on the needs, : > ", we can obtain a synthesis gas with a H2 / CO ratio that approaches 2 for the synthesis of a synthetic oil, or methanol, or a synthesis gas very rich in hydrogen for the synthesis of ammonia, or still a gas very rich in CO for syntheses called "oxo". These examples are intended to be illustrative and not limiting. It should be noted that the total or quasi-total absence of binders, coke or other annoying products during the conversion of heavy HCs, such as butanes that were present in non-negligible amounts during some tests. On the contrary, the increasing fragility of the increasing heavy HCs is a "plus" for our process in terms of the energy cost for the production of syngas and also of other valuable unsaturated products. This is a strong point of our process compared to the traditional processes that are faced with the problem of coke and tar deposits, especially in the presence of HCs heavier than methane. Finally, it is appropriate to note the presence of non-negligible amounts (but with adjustable contents) of unsaturated hydrocarbons C2H4 and C2H2 in our plasma-assisted conversion products with sliding discharge. They have an added value as a final commercial product or as a raw material for other organic syntheses. Mixed with synthesis gas, the construction of hydrocarbon chains is also promoted during the FT synthesis (information derived from recent scientific work conducted by Professor A. LAPI DUS of the Organic Chemistry Institute, Moscow). In this way, they are simultaneously formed with CO and H2 during the conversion of hydrocarbons into the sliding discharges, these unsaturated ones can contribute to the direct implementation of an improved FT synthesis of liquid hydrocarbons. On a more technical level, it should be noted that the reactor and its assembly operate with surprising smoothness. 'without deterioration of the electrodes, electrode holders, perforated diaphragm, or reactor walls, or the post-plasma zone, all undergoing the action of input reagents and output products. We should add that we never changed the Ni bars in the post-plasma zone; they experienced conditions severe temperatures (from 20 to 990 ° C) and pressure (1 x1 05 to 6x1 05 Pa), they "found" heavy or light HCs, all kinds of proportions of O2 / HC and H2O / HC, worked covered with a layer of soot during some tests with very low O2 / HC and proportions of H2O / HC, were then exposed with a pure air or oxygen plasma, or pure CO2. It is clear that its activity does not depend on pre-treatment. They become active as long as they are exposed to the residual flow of species derived from the plasma zone.

CONCLUSION 20 Our experiments have demonstrated the feasibility of a new process for the production of gases rich in hydrogen and carbon monoxide, also containing significant amounts of C2H and C2H2. The process consists of producing these gases through sliding electric discharges that flash directly into the NGs mixed with steam and / or pure oxygen, or air enriched with oxygen, or i * - _- $ .- «- áa-.s - a. - > - > even atmospheric air, and this under almost any proportion. This causes the partial oxidation and / or cracking of these HCs while avoiding the drawbacks of the existing processes. The reagents, partially converted into a sliding discharge compartment, penetrate into another post-plasma compartment which is eventually separated from the direct reaction zone by a perforated diaphragm. There, in the presence of still active species produced in the discharges and transported by the gas leaving the plasma zone, the gases undergo an additional conversion at a lower temperature than that present in the direct reaction zone. In this way, the process establishes the partial oxidation and cracking of HCs in the active presence of water vapor and / or elemental oxygen, without requiring the intervention of any other reagent or catalyst, as well as without the formation of soot, coke. or pitch, which would obstruct the proper operation of the reaactor. The evidence clearly demonstrates the ease of partial oxidation, combined with vapor reformation initiated by the addition of water vapor in the hydrocarbon feed, or by water vapor created spontaneously by over-oxidation side reactions. This partial oxidation and steam reforming are also accompanied by the reformation with carbon dioxide present in the NG, or created by the over-oxidation side reactions. This partial oxidation of gaseous HCs is also accompanied by a non-catalytic cracking of hydrocarbons. The process also makes it possible to directly transfer electrical power under high voltage and relatively low current in a medium se * .-- - *; -: .rt '^ sA exothermic reagent. These electrical conditions, combined with a high velocity of the plasma forming medium in the discharge zone, cause a strong disturbance of the electrical balance and also of the thermodynamic one. The material injected in this non-equilibrium plasma zone of the sliding discharge device thus reacts in a non-thermal manner. No difficulties were encountered during the experiments, and it is easy to extrapolate for large volumes. Despite a reactor that is not optimized and another that is poorly thermally insulated, regardless of the fact that the reagents ran only once through the plasma compartment of electric discharges, followed by a simple run in the post-plasma zone, a large portion (or even 1 00%) of the initial molecules of HCs and oxygen can be converted into synthesis gas and unsaturated hydrocarbons. This conversion is greatly improved by the quasi-point injection of reagents in the discharge area with a nozzle (single or double) and, eventually, by a perforated diaphragm placed opposite the nozzle, in order to reinforce the recirculation of the reagents in this direct reaction zone.

Consequently, the process can provide some of the following benefits: • the transformation of hydrocarbons into value-added products (H2, CO, unsaturated hydrocarbons), • the only reagent required is water and / or O2, • the absence of any conventional catalyst, • very compact equipment, which can be installed in restricted areas (for example, on offshore oil platforms for the conversion of associated gases), • the method does not depend on the chemical composition of the hydrocarbon mixture to be converted, • the sliding discharges do not have thermal inertia, consequently, they respond immediately to the control signals, • with the exception of the use of atmospheric or enriched air and the conversion of NGs initially rich in CO2, the resulting products, after the condensation of water vapor, contain very little CO2 and no other strange ballast that can increase its volume, which makes e easier conversion and / or recycling operations.

Although the present invention has been described with reference to particular embodiments, it will be understood that the modalities are illustrative and that the scope of the invention is not limited thereto. Any variation, modification, addition and improvements to the modalities described are possible. These variations, modifications, additions and improvements may fall within the scope of the invention as detailed within the following claims.

Claims (8)

REIVI NDICATIONS

1 . A process for the conversion of hydrocarbons comprising, such as methane CH4, ethane C2H6, propane C3H8 and butanes C4H1 0, by partial oxidation with elemental oxygen O2 or by simultaneous reformation with O2 and water vapor H2O, characterized by the fact that a (or several) hydrocarbon (s) mixed with water vapor and / or oxygen, is exposed to a sliding electric discharge plasma in a sliding electric arc, in order to generate and maintain chemical reactions of partial or total conversion of such mixture into a synthesis gas, the latter being a mixture of hydrogen H2 and carbon monoxide CO; this synthesis gas can be accompanied by unsaturated hydrocarbons, such as, ethylene C2H and / or acetylene C2H2, produced by the same conversion process.

2. The process according to claim 1, characterized in that one (or several) of such hydrocarbon (s) to be converted, referred to as the feed, enter contact with electric discharges, provided that said feed is mixed with gaseous oxygen with a volume ratio of O2 / feed at least equal to 0.22, knowing that said mixture can also contain any proportion of water vapor H2O and / or nitrogen N2 and / or CO2 carbon dioxide, and that the mixture containing the feed and oxygen, possibly with H2O and / or N2 and / or CO2, is of natural origin or derived from an industrial activity, or intentionally prepared before its introduction in the reactor »- -dj_jj = a ^ s ^^^^ -iiÉ -___ j electrical discharge, or intentionally prepared in the reactor by itself by the separate introduction of preheated gases.

3. The process according to claims 1 and 2, characterized in that the elemental oxygen O2 pure or contained in the air enriched with oxygen, or even in atmospheric air, is partially or totally converted into carbon monoxide. CO, when reacting with one (or several) hydrocarbon (s) in contact with electrical discharges, with or without the presence of water vapor and / or carbon dioxide.

4. The process according to claims 1 to 3, characterized in that the conversion is carried out in the presence of a metal or ceramic body / 1 9 / l brought to a temperature not exceeding 1 1 00 ° C and placed in contact with a flow of products resulting from the partial conversion by plasma of electric discharge, knowing that such body becomes active, in relation to the process of conversion of the feed into synthesis gas, only in the presence of said flow of products that leave the zone of electrical discharge and that, without said flow, the body deactivates by itself in relation to the process.

5. The process according to claims 1 to 4, characterized in that the conversion is achieved at a pressure ranging from 7 kPa to 6x1 05 Pa, and that the temperature of the conversion, defined as the temperature Any solid element placed in contact with electric shock is less than 1 200 ° C.

6. The process according to claims 1 to 5, characterized in that the conversion products contain H2 and CO, possibly accompanied by ethylene and / or acetylene, the relative H2 / CO contents, expressed in mol, being included. / mol or volume / volume, between 0.46 and 3.05. The process according to claims 1 to 6, characterized in that the conversion is achieved without the hydrocarbon feed being decomposed into soot, coke or pitch, in relative amounts exceeding 0.05%, expressed as mass of carbon converted during the process. 8. A device (1) for the implementation of the process of claims 1 to 7, comprising: a structure for producing the sliding electric discharge plasma (4); said structure comprising a plasma compartment (15a) and a post-plasma compartment (15b); a nozzle (5) in the plasma compartment (15a) for introducing premixed fluid (6) to be converted or reactants; a diaphragm or similar separation device that is constructed and mounted between the plasma compartment and post-plasma compartment, where the plasma compartment (15a) communicates with the post-plasma compartment (15b) without discharges, so that the reagents in the plasma compartment (15a) are reinforced and recirculated and at the same time, to allow gas to flow between the plasma compartment (15a) and the post-plasma compartment (15b), where the chemical species contained in the products of the contact between reagents and discharges contribute, in the presence of a metal or ceramic body (19), to the conversion of the products leaving the plasma compartment (15a).? - \ -