WO2012110734A1

WO2012110734A1 - Method and device for separating simple chemical entities from chemically complex bodies or mixtures of simple bodies

Info

Publication number: WO2012110734A1
Application number: PCT/FR2012/050312
Authority: WO
Inventors: Thibaud EMIN; Jean-Marc VINSON; Pascal Andre
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives; Universite Blaise Pascal - Clermont Ii
Priority date: 2011-02-14
Filing date: 2012-02-13
Publication date: 2012-08-23
Also published as: FR2971433A1

Abstract

The invention relates to a method for separating simple chemical entities, which may or may not be charged, from chemically complex bodies or from mixtures of simple bodies, consisting in subjecting the chemically complex body or bodies or the mixture of simple bodies to the action of a plasma torch and, subsequently, subjecting the resulting plasma to the action of a magnetic field in which the field lines are essentially oriented perpendicularly to the direction of the plasma jet.

Description

PROCESS AND DEVICE FOR THE SEPARATION OF SIMPLE CHEMICAL ENTITIES FROM CHEMICALLY COMPLEX BODIES OR MIXTURES OF SIMPLE BODIES.

FIELD OF THE INVENTION

The invention belongs to the field of gas separation, and in general, of simple chemical entities, for the eventual subsequent synthesis of gases.

It is more particularly in the field of the genesis of H ₂ hydrogen gas, molecule increasingly sought after, especially as a fuel, and generally in the field of organic chemistry. The invention is not limited to the production of hydrogen alone.

PRIOR STATE OF THE ART

Various technologies are now well known and controlled to ensure the separation of complex chemical bodies and in particular to produce hydrogen.

Among these, there is electrolysis, including water for the production of hydrogen. Although this technology is now largely controlled, it has a disadvantage unacceptable, namely a low energy efficiency. In addition, the electrolysis allows to ensure the separation of two bodies, respectively at the anode and the cathode. A variant of electrolysis concerns so-called "high temperature" electrolysis, which has the advantage of an energy efficiency higher than the conventional low temperature electrolysis. However, this technology is not currently controlled industrially, mainly due to leakage at the electrodes related to the differential expansion between the insulators and the electrodes. Another separation technology consists in the implementation of porous membranes. If qualitatively, it leads to a satisfactory separation, on the other hand, the implemented processes are slow, inefficient, and have a low energy efficiency. Moreover, the membrane is traditionally dedicated to a single product.

Finally, and with regard to hydrogen production, methane cracking is known, which today is one of the main sources of production. In addition to industrial difficulties, this technology is relatively polluting and also low in energy efficiency.

In summary, there is currently no process for simultaneously ensuring a qualitative separation of complex bodies or single-element mixtures of simple elements with optimized energy efficiency and under satisfactory industrial conditions.

This is the object of the present invention.

SUMMARY OF THE INVENTION The invention firstly relates to a method for carrying out the separation of simple chemical entities, charged or uncharged, from chemically complex bodies or from mixtures of simple bodies. This method involves injecting the one or more chemically complex bodies or the mixture of single bodies into a plasma torch, and subjecting the plasma to the action of a magnetic field, the field lines of which are generally perpendicular to the direction of the plasma. plasma jet.

The method according to the invention makes it possible to operate at atmospheric pressure or at higher pressures. In doing so, the plasma torch induces, because of its energy supply resulting from the heat it generates, typically between 4000 and 25000 ° C., the effective separation of the entities constituting the mixture of simple bodies or the complex body, typically atoms or ions, and the magnetic field at the output of the torch acts on the charged species by application of the Lorentz forces, inducing their offset with respect to the direction of the plasma jet, thus likely to allow the reception of the different entities in places different.

In addition, we also observe the separation of uncharged species, and therefore not subject to the Lorentz force due to differences in viscosity between charged species (ions, electrons) and uncharged (molecules, neutral atoms), generating friction that will induce such a separation.

According to various embodiments of the invention:

the distance separating the two electrodes generating the plasma within the plasma torch can be adjustable;

one of said electrodes has a cone-shaped zone inverted with respect to the direction of propagation of the fluids;

the length of the plasma jet can be adjustable.

In addition, and according to another advantageous characteristic of the invention, it may be envisaged to mount several of the separation devices of the invention in series, so as to optimize the degree of separation of the simple bodies that are intended to obtain and hence optimize the purity that can result. Thus, at least one of the entities resulting from the separation by thermal plasma at a first stage, is recovered at the output of said first stage, and reintroduced into a new plasma torch of a second stage, with the same characteristics. or different characteristics from the first floor.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the invention can be realized and the advantages which result therefrom will emerge more clearly from the following exemplary embodiments, given as an indication and not a limitation to the accompanying figures. Figure 1 is a schematic representation of the general operating principle of the separation device according to the invention.

FIG. 2 is a figure similar to FIG. 1, the device implementing a multi-electrode plasma torch.

FIG. 3 illustrates the series connection of two devices according to FIG. 1 or 2. FIG. 4 is a synopsis of the forces applied on the plasma jet, in accordance with the invention.

FIG. 5 is a graph symbolizing the variation of the partial and total dynamic viscosity of a water plasma as a function of temperature.

FIG. 6 is a graph representing the volume emission coefficient of the O, H and Ar chemical species at a height of 20 mm above the plasma torch and subjected to a radial magnetic field of the order of 40 milliTesla.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows a device implementing the operating principle of the method of the invention.

Basically, it consists of a plasma torch (1), in this case consisting of two electrodes (1a) and (1b), electrically insulated from each other, in particular by a piece (10). made of an insulating material.

Between the two electrodes is formed a chamber (11), within which leads by pipes to generate a vortex (12), the mixture of either simple bodies or complex bodies that are desired to separate.

More precisely, and according to an advantageous characteristic of the invention, this mixture opens into the chamber (11) in the form of vapor, this vaporization occurring at a vaporizer (2), integrating for example a heat exchanger (13). adapted to raise the temperature within the vaporizer (2), and thus induce the phase change of the mixture to be separated. The characteristics of the plasma, and in particular its temperature, are regulated by the electrical supply of the electrodes, and more particularly by the voltage at their terminals. In direct current, the operating point of the plasma torch is chosen so as to have a stable operation of the torch, resulting from a compromise between the load line of the power supply and the voltage-voltage characteristic curve. current of the electric arc which depends essentially on the physical properties of the plasma which composes it.

In alternating current, one can choose a two-phase operation, an electrode successively playing the role of cathode and anode, or a multi-electrode operation is chosen in the case of a multi-phase operation. The voltage variation will generate variations in the characteristics of the arc (arc voltage, arc length, current density) which will in turn cause a change in the characteristics of the plasma (temperature, chemical composition mainly)

To obtain the same quality of plasma for a given pressure, either stabilize current and then play on the voltage, or regulate voltage and then play on the current.

Between the electrodes is thus generated an electric arc, which will transform, in known manner, the gas flowing at this level by transforming it into plasma.

The characteristics of this plasma are likely to result from the distance separating the two electrodes, since both of these depend on the intensity and the voltage of the electric arc. According to a particular embodiment of the invention, it is possible to envisage the implementation of a plurality of one of the types of electrodes, as illustrated in FIG. 2. Within this figure, the plasma comprises not one, but three anodes (lb), distributed substantially symmetrically with respect to the plasma diffusion direction.

The implementation of multiple electrodes makes it possible to generate electric arcs of different quality from that of a simple arc, namely, arc voltage, current density, length, which will also play on the "hook" of the arc and therefore the wear of the cathode. However, they produce plasma quality useful for separation.

Thus, combined with a multi-phase AC voltage, electrical arcs can be generated rotating within the plasma torch, making it possible to better control the rotation frequency of the anode spot and the cathode spot, that is to say to say respective points of attachment of the electric arc on the anode and on the cathode, and therefore corollary, to limit or slow down the wear of the corresponding parts of the torch.

According to an essential characteristic of the invention, the separation device integrates a magnetic field generator (4), the active field lines being those that are oriented substantially perpendicular to the direction of propagation of the plasma. In the example described, this magnetic field generator consists of a coil supplied with direct current or alternating current by wires (8a) and (8b).

However, one could conceive that this magnetic field generator consists of a permanent magnet correctly oriented, and for example circular, since it generates a radial magnetic field with respect to the direction of the plasma jet.

In the case of the implementation of a magnetic field generator constituted by a coil, as illustrated in FIGS. 1 to 3, it may be envisaged to adjust the intensity of the magnetic field generated by varying the intensity electrical current flowing through said coil. In addition, the electric current supplying said coil may be of variable nature, and the intensity of said current may be controlled or harmonized with that supplying the electrodes of the plasma torch, with the aim of optimizing the separation of the species contained in plasma, or to more precisely select this or that entity or species.

For the same purpose, the shape of the electrical signals can also be selected. In fact, and by a combination of these different characteristics related to the electric signals supplying the plasma torch and the coil generating a magnetic field, it is possible to generate a plasma whose physical characteristics predetermine the intensity of the magnetic field useful for the good separation of chemical species from a mixture of simple bodies or a complex body.

If the power injected into the torch decreases, the temperature decreases, the concentration of ionized species also decreases. Thus, according to the Lorentz law, in order to obtain the same force, it is therefore necessary to increase the intensity of the magnetic field to apply a sufficient force to guarantee a separation at the same place.

According to an advantageous characteristic of the invention, the internal geometry of the torch (la) has a frustoconical shape inverted with respect to the direction of displacement of the fluid to be separated, or said in an equivalent manner, according to the jet direction of the plasma, that is, the base of the truncated cone is located immediately near the chamber (11), and the opposite end of smaller diameter is located near the exit of the plasma torch. This particular conformation makes it possible to ensure the passage of the maximum gas in the plasma, to stabilize the electric arc ensuring a good electrical stability, and if condensation appears, to avoid extinguishing the arc. In addition, this particular zone of the cone-shaped electrode (5) is provided with a heat exchanger, typically consisting of a pipe (3) wound at the periphery of the partition defining it, and in which circulates a coolant, including water.

This heat exchanger (3) first allows the part in question to withstand the very high temperature generated by the plasma. In addition, it is intended to recover a portion of the energy generated by the plasma torch and to route it for example at a steam generator (not shown) able to actuate a turbine and thus to generate the electricity, or at the level of the heat exchanger (13) formed in the vaporizer (2), for, as already indicated, increase the temperature of the mixture to be separated, and in particular induce its vaporization.

Some other components of the plasma torch can also be provided with such heat exchangers. This is for example the case of the electrode or electrodes (lb) provided with such an exchanger (14).

The operation of the device will be described below. Due to the action of the thermal plasma torch on the mixture of simple bodies or on the complex body introduced into the chamber (1 1), different entities will be created and then separated, and in this case:

atomic entities, therefore not loaded on the one hand, and

charged entities besides electrons.

Thus, if water vapor is introduced into the chamber (11), it will be generated mainly at the optimum operating temperature, and typically at 6000 K oxygen and hydrogen atoms, as well as species H ⁺ , 0 ⁺ , as well as electrons. This results for example from an emission spectroscopy analysis, the electron density can also be deduced from the broadening of a specific line of hydrogen (Η _β ). At the output of the plasma torch, the plasma jet can reach a speed of several hundred m / s. This speed is adjustable by the size of the gas outlet hole and the flow of steam entering the chamber (11) of the plasma torch.

In the presence of a magnetic field, charged species are subject to Lorentz forces.

Due to the predominance of the radial component of the magnetic field generated by the magnetic field generator (8), the Lorentz forces tend to drive the charged entities in a circular configuration with respect to the axis of the plasma jet.

FIG. 4 shows a synoptic of the forces applied to the plasma jet. The latter has been symbolized by a vertical cylinder, the flow being directed upwards in said figure. In addition to the Lorentz forces, it is also necessary to take into account the partial dynamic viscosity coefficient μ; relating to each of the species involved. These have been symbolized on the graph of Figure 5.

Returning to Figure 4, the external force is mainly due to the Lorentz forces. The viscosity of monoatomic hydrogen is three times lower than that of oxygen at 6000 K. The least viscous entity will therefore remain in the center and the more viscous at the edges.

In other words, as a function of the distance r with respect to the axis of the plasma jet and for a given temperature, the species whose partial dynamic viscosity is less are able to progress further. In addition, in the context of the present invention, where precisely one seeks to separate the species resulting from pyrolysis by plasma, one can play slightly on the length of the plasma jet with the diameter of the exit hole of the torch to optimize the separation effect.

In fact, the less viscous species move faster and the more viscous species move less quickly; in doing so, we find the less viscous species rather in the center and the more viscous species on the periphery. To improve this type of separation, it is possible to play with the length of the plasma flame.

The aim of the invention is to play on this more or less important separation, in the end being able to recover the species independently of one another in the purest possible way and, correlatively, to be able to generate, because of the recombination phenomena observed between the thus separated species, including hydrogen, which may recombine to form stable molecules of hydrogen H _2.

FIG. 6 shows a separation test using the device of the invention. In this particular example, a radial magnetic field of about 40 milli Tesla is used with an argon mixing plasma and water vapor.

At r = -10 mm (from the axis of the plasma jet), a high emissivity of the mono-atomic hydrogen H is observed. Comparing with the theoretical calculation, a hydrogen concentration of about 80% is obtained (percentage molar). This demonstrates the effectiveness of the separation resulting from the device of the invention.

After separation, then separate entities are collected for the purposes sought. For this purpose, there is thus diagrammatically represented in FIG. 1 a recovery member of the species (6), having in the example described two different recovery zones (9) connected to the organ (6) through pipelines. (15). Each of these two zones (9) integrates a heat exchanger (16), at which the energy resulting from the exothermic recombination of the temporarily stored species is recovered.

The heat, and therefore the energy thus recovered by the heat exchanger (16) is once again likely to generate the genesis of steam, suitable for supplying turbines and thus generate electricity.

FIG. 3 shows the series connection of two devices of FIG. 1. Thus, it can be observed that the gas generated at the level of the lower stage is reintroduced at the level of the chamber (11) of the upper stage, area where it undergoes again the action of the thermal plasma torch. In doing so, one can refine the separation of the constituent species, and thus optimize the degree of purity.

We understand the whole point of the device of the invention.

First of all, it is worth emphasizing the facilitated and industrializable synthesis of chemical entities, especially hydrogen. The various components of such a device being further cooled, they are likely to withstand for economically viable durations to the heat inherent in the implementation of plasma technology.

In addition and above all, because of the recovery of energy by the various heat exchangers which are provided with a number of components of the device of the invention, the energy balance resulting from the production, for example hydrogen, is very largely optimized compared to what allowed the devices of the prior art, whether it is electrolysis, membranes or cracking.

Claims

A method for effecting the separation of single charged or uncharged chemical entities from chemically complex bodies or from simple body mixtures, which comprises subjecting the one or more chemically complex bodies or the mixing simple bodies with the action of a plasma torch, then subjecting the resulting plasma to the action of a magnetic field, whose field lines are oriented generally perpendicular to the direction of the plasma jet.

2. Process for carrying out the separation of chemical entities according to claim 1, characterized in that it is carried out at atmospheric pressure or at higher pressures.

3. Process for carrying out the separation of chemical entities according to one of claims 1 and 2, characterized in that the heat resulting from the plasma generated by the plasma torch is partly recovered by the implementation of heat exchangers. .

A device for performing the separation of simple charged or uncharged chemical entities from chemically complex bodies or from simple body mixtures, comprising:

A thermal plasma torch (1) defining a chamber (11) within which are conveyed the chemically complex bodies or the mixture of simple bodies to be separated,

means (4, 8) capable of generating a magnetic field, the field lines of which are oriented generally perpendicular to the direction of diffusion of the plasma.

5. Device for performing the separation of chemical entities according to claim 4, characterized in that it comprises downstream of the plasma torch means adapted to receive the different entities resulting from the separation by plasma. Device for performing the separation of chemical entities according to one of claims 4 and 5, characterized in that the internal geometry of the plasma torch has a cone-shaped zone inverted with respect to the direction of diffusion of the plasma.

Apparatus for carrying out the separation of simple charged or uncharged chemical entities from chemically complex bodies or from simple body mixtures, characterized in that it consists of at least two devices according to any one of Claims 4 to 6 connected in series.