Patent Application
20170022430
The present invention relates to a process for the elimination of heavy metals, and more particularly mercury, that are present in a liquid or gaseous feedstock.
Mercury is a metallic contaminant that is found in gaseous or liquid hydrocarbons produced in many regions of the world, such as the Niger Delta, South America or North Africa.
The elimination of mercury from hydrocarbon cuts is desirable in an industrial context for several reasons:
Industrially, the elimination of heavy metals, in particular mercury, from the liquid or gaseous hydrocarbon cuts is carried out by circulating them through beds of capture material. By capture material is meant in the present invention any type of solid in bulk or supported form containing within it or on its surface an active element capable of reacting irreversibly with an impurity such as mercury contained in the feedstock to be purified. The elimination of mercury from the liquid or gaseous hydrocarbon-containing cuts is generally carried out by circulating said feedstock to be treated through beds of capture materials containing an active phase capable of reacting with the mercury. It is in particular known to a person skilled in the art that mercury capture can be carried out easily by reacting the latter with an active phase based on sulphur or a sulphur-containing compound, in particular metallic sulphides, the mercury then forming with the sulphur the chemical species HgS called cinnabar or metacinnabarite. These different chemical reactions are generally implemented in a process by using contact of the feedstock to be treated with a capture material that is either bulk in which in particular particles of the active phase can be bonded together via binders, or supported in which the active phase is dispersed within or on the surface of a porous solid support.
However, it is not possible to carry out such a purification operation directly on crude oil cuts or gas condensates for several reasons. The first is that the porosity of these capture materials would very quickly become clogged by the heavy compounds present in said feedstock, which would be deposited on the surface of the materials. Moreover, these crude oil cuts or gas condensates contain mercury in different forms. In fact, unlike the gas phases, they contain not only elemental mercury but also mercury in complexed or ionic and organic form. Now, these complexed or ionic and organic compounds of mercury are called refractory, as they are stable under normal operating conditions and are not reactive with the capture materials of heavy metals. It therefore appears to be necessary to convert the refractory mercury compounds to elemental mercury.
Numerous means have been developed in order to convert the refractory forms of mercury to elemental mercury (also called mercury in atomic form Hg0). For example, U.S. Pat. No. 4,911,825 discloses a process for the transformation of the refractive species of mercury from the feedstock to elemental mercury in the presence of a catalyst and under high hydrogen pressure and at a high temperature.
U.S. Pat. No. 5,384,040 discloses a process for the elimination of the mercury from a hydrocarbon-containing feedstock comprising a stage of transformation of the mercury contained in the compounds of the feedstock to elemental mercury, the transformation stage being carried out between 120 and 400° C. and under pressure of 0.1 to 6.0 MPa. Preferably, the transformation stage is carried out in the presence of a catalyst comprising at least one metal M selected from the group formed by iron, nickel, cobalt, molybdenum, tungsten and palladium. Alternatively, the transformation stage can be carried out in the absence of a catalyst.
In the latter case, the temperature must be set at 180° C. as a minimum. In fact, in the article by Masatoshi Yamada et al. entitled “Mercury removal from natural gas condensate” in the journal Studies in Surface Science and Catalysis, volume 92, pages 433-436, 1995, it is shown that the conversion of diethyl mercury starts at 180° C. and reaches 100% conversion at 240° C. At the same time, it is shown that it is possible to reduce the transformation temperature in the presence of a catalyst. In fact, the conversion of the refractory species of mercury starts at 130° C. and reaches over 90% from 200° C. However, the problem with the use of a catalyst, apart from its cost, is that there is a tendency to promote the cracking of molecules and therefore the formation of coke. Furthermore, in the case of highly clogging feedstocks such as crude oil, a very rapid de-activation of the porous catalyst is noted, due to the deposition of heavy compounds such as asphaltenes, within the pores of said catalyst. Such a process is thus more suitable for the treatment of hydrocarbons originating from a first fractionation.
The Applicant discovered, surprisingly, that it is possible to eliminate heavy metals, and more particularly mercury, contained in a gaseous or liquid feedstock, and more particularly a crude oil feedstock, by carrying out upstream of the main fractionation unit, a stage of heating said feedstock at a target temperature and during a residence time sufficient to allow the transformation of the refractory spaces containing heavy metals, present in different forms, to metals in the atomic (or elemental) form, even in the absence of a catalyst or hydrogen, and by carrying out upstream of the main fractionation unit, a stage of capture of the heavy metals, and more particularly mercury. In fact, although the crude oil feedstocks comprise a very great diversity of molecules, bringing said feedstock up to a temperature during a sufficient residence time upstream of the main fractionation unit makes it possible to convert the majority of the refractory compounds to metallic compounds (also called elemental compounds) that can be captured by a single capture material.
The present invention relates to a process for the elimination of mercury contained in a heavy hydrocarbon-containing feedstock upstream of a main fractionation unit, in which process:
a) the non-elemental mercury contained in the compounds of said feedstock is transformed to elemental mercury, said stage being carried out in a conversion unit at a target temperature during a fixed residence time and adapted to said target temperature so that at least 90% by weight of non-elemental mercury contained in the compounds of said feedstock are converted to elemental mercury, said stage of transformation being carried out in the absence of hydrogen and in the absence of a catalyst, it being understood that:
Preferably, in stage b) a separation of the feedstock obtained in stage a) is carried out in a separation unit that consists of producing only a liquid effluent and a gaseous effluent comprising elemental mercury.
In an embodiment according to the invention, the process comprises a stage d) in which the liquid effluent obtained in stage b) is fractionated in a main fractionation unit.
Advantageously, the reduction in the total content by weight of mercury of said feedstock taken before stage a) and after stage c) is at least 90%.
According to the invention, stages a) and b) are carried out separately or simultaneously.
In an embodiment according to the invention, the separation unit of stage b) is a distillation column.
In another embodiment according to the invention, the separation unit of stage b) is a stripping column.
Advantageously, in the stripping column a carrier gas circulates in counter-current with said hydrocarbon-containing feedstock, said carrier gas at least partially originating from a liquid or gaseous fraction of the main fractionation unit.
Preferably, when the carrier gas at least partially originates from a liquid fraction of the main fractionation unit, said liquid fraction is transformed to a gaseous fraction by means of a heat exchanger.
Preferably, the at least partially de-mercurized effluent obtained in stage c) is fractionated in a main fractionation unit.
Advantageously, said hydrocarbon-containing feedstock comprises between 1 and 10 mg of mercury per kg of feedstock, preferentially 1 to 1200 μg/kg, more preferentially 10 to 500 μg/kg.
Preferably, during stage c), said feedstock is brought into contact with a bulk or supported mercury capture material comprising a phase containing at least one metallic sulphide based on a metal M selected from the group constituted by copper, chromium, manganese, iron, cobalt and nickel.
Alternatively, during stage c), said feedstock is brought into contact with a bulk or supported capture material comprising a phase containing at least sulphur in elemental form.
Advantageously, the heavy hydrocarbon-containing feedstock is a crude oil feedstock.
For better understanding of the invention, the description given hereinafter by way of an example application relates to a process for the elimination of heavy metals, and more particularly mercury, in a heavy hydrocarbon-containing feedstock, and more particularly of crude oil. Of course, the process according to the invention can be used for the elimination of other heavy metals, such as arsenic, lead, vanadium and cadmium, contained in a heavy hydrocarbon-containing feedstock.
By heavy hydrocarbon-containing feedstock is meant, within the meaning of the present invention, a feedstock having a density at 15° C. greater than 750 kg/m3, composed essentially of hydrocarbons, but also containing other chemical compounds which, apart from the carbon and hydrogen atoms, have heteroatoms, such as oxygen, nitrogen, sulphur and heavy metals such as mercury, arsenic, lead, vanadium or cadmium. More particularly, said hydrocarbon-containing feedstock comprises between 1 and 10 mg of mercury per kg of feedstock, preferentially 1 to 1200 μg/kg, more preferentially 10 to 500 μg/kg.
By non-elemental mercury is meant any form of mercury other than in the elemental (or atomic) form, i.e. in the organic molecular form, and/or in the ionic form, and/or in complexed forms.
The description of
A heavy hydrocarbon-containing feedstock, and more particularly a crude oil feedstock, is sent via the pipe 100 into a desalting unit 1000, consisting generally of washing with water. The main function of this stage is to eliminate the majority of the soluble inorganic species contained in the feedstock. The desalted feedstock is then sent via the pipe 101 into a pre-heating unit 2000. The purpose of this stage of pre-heating the desalted feedstock is to bring said feedstock to a temperature close to the temperature of the bottom of the fractionation unit 3000 situated downstream. The pre-heating temperature is generally comprised between 200 and 400° C., and depends on the number of distillation columns used in the main fractionation unit 3000. The pre-heated feedstock is then sent via the pipe 104 to the main fractionation unit 3000.
The main fractionation unit 3000 can comprise one or more distillation columns (in
At the outlet of the main fractionation unit 3000, the top effluent of the main fractionation unit generally contains hydrocarbon-containing compounds of which 90% of said compounds have a boiling point less than 200° C. at atmospheric pressure (1.01325×105 Pa). The top effluent is sent via the pipe 400 to a secondary fractionation unit 7000 comprising one or more fractionation columns, allowing the production of different hydrocarbon cuts. Generally, at the outlet of the secondary fractionation unit 7000 various hydrocarbon-containing compounds can be distinguished, such as:
The hydrocarbon-containing cuts evacuated via the pipes 401, 402 and 403 are generally each treated by a unit for the capture of heavy metals, and more particularly the capture of mercury in elemental form. As shown in
Furthermore, in this process layout, different types of capture material must be used in order to treat, on the one hand, the gaseous flows, for example evacuated through the pipe 401, and on the other hand the liquid flows, for example evacuated through the pipe 403, but also the flows that may contain hydrogen, such as certain fuel gases, requiring specifically adapted capture materials.
The Applicant discovered, surprisingly, that it is possible to eliminate the mercury contained in the compounds of a hydrocarbon-containing feedstock, and more particularly in a crude oil feedstock, upstream of a main fractionation unit, by carrying out a stage of transformation of the non-elemental mercury contained in the compounds of said feedstock to elemental mercury, and by carrying out a stage of capturing the elemental mercury upstream of the main fractionation unit of said feedstock, by means of a heat treatment of said feedstock at a target temperature and during a residence time sufficient to allow the transformation of non-elemental mercury contained in the compounds of said feedstock to elemental mercury, without the use of any catalytic or hydrogen treatment. The process according to the invention only requires a single unit for the capture of elemental mercury and therefore a single capture material.
In fact, although the crude oil feedstocks comprise a very great diversity of hydrocarbon-containing molecules, bringing said feedstock up to a temperature during a sufficient residence time upstream of the main fractionation unit makes it possible to convert the non-elemental mercury contained in the compounds of said feedstock to elemental mercury, it then being possible to capture the latter with a single capture material.
The process according to the invention comprises at least:
a) the transformation of the non-elemental mercury contained in the compounds of a hydrocarbon-containing feedstock, and more particularly in a crude oil feedstock, to elemental mercury;
b) the separation of said feedstock into a liquid effluent comprising a hydrocarbon-containing feedstock with a low mercury content, and a gaseous effluent comprising the most volatile compounds and mercury in elemental form;
c) capture of the mercury in elemental form contained in the gaseous effluent obtained in stage b) in a unit for the capture of mercury comprising a capture material.
According to the invention, stages a) and b) can be carried out separately or simultaneously.
According to the invention, the separation stage can be carried out by means of a separation unit selected from a stripping column with a carrier gas (c.f.
With reference to
When the conversion unit 900 comprises a drum, said drum advantageously comprises a double wall covering the drum in which a heat transfer fluid circulates in order to maintain the temperature of said feedstock at the target temperature up to the separation unit 5000, and/or advantageously comprises a resistive heater inserted directly inside said drum.
When the conversion unit 900 comprises a pipe or a set of pipes, the pipe or set of pipes advantageously comprise a double jacket in which a heat transfer fluid circulates in order to maintain the temperature of said feedstock at the target temperature up to the separation unit 5000.
Stage a) of transformation (or conversion) of the non-elemental mercury contained in the compounds of the heavy hydrocarbon-containing feedstock to elemental mercury is essential according to the invention. In fact, regardless of the nature and/or the origin of the heavy hydrocarbon-containing feedstock, the latter can comprise heavy metals, and in particular mercury, in different forms. For example, mercury may be found in the form of elemental or atomic mercury (also called Hg0) and/or in the organic molecular form, and/or in the ionic form, for example in the form of Hg2+ and complexes thereof.
According to the invention, the transformation of the non-elemental mercury contained in the compounds of the hydrocarbon-containing feedstock to elemental mercury is carried out via a conversion unit 900. Implementation of this stage consists of transforming the non-elemental mercury contained in the compounds of the heavy hydrocarbon-containing feedstock to elemental mercury.
Therefore, according to the invention, the process for the transformation of the non-elemental mercury contained in the compounds of said feedstock to elemental mercury comprises passing said feedstock, at a temperature determined by a person skilled in the art, into a conversion unit 900 during a residence time fixed so that at least 90% by weight, preferably at least 95% by weight, and even more preferentially at least 99% by weight of the non-elemental mercury contained in the compounds of said feedstock are converted to elemental mercury, even in the absence of a catalyst.
Therefore, depending on the temperature of the feedstock, the residence time necessary in order to carry out the transformation of the non-elemental mercury contained in the compounds of said feedstock to elemental mercury corresponds to the following equation (1):
in which:
Cs corresponds to the concentration of mercury (apart from elemental mercury) contained in the compounds of said feedstock at the inlet of the conversion unit 900 (in mol·L−1);
Co corresponds to the concentration of mercury (apart from elemental mercury) contained in the compounds of said feedstock at the outlet of the conversion unit 900 (in mol·L−1);
t corresponds to the residence time (in seconds);
k0 corresponds to the constant of the rate of transformation of non-elemental mercury to elemental mercury (in seconds−1);
Ea corresponds to the activation energy of the reaction for the transformation of non-elemental mercury to elemental mercury (in J·mol−1);
R corresponds to the ideal gas constant (R=8.314 J·K−1·mol−1);
T corresponds to the temperature of the feedstock (in K).
In the embodiment for which stages a) and b) are carried out separately, i.e. the transformation of mercury to elemental mercury is carried out upstream of the separation unit 5000, the concentration Cs corresponds to the mercury concentration (apart from elemental mercury) measured in the line 102 at the inlet of the separation unit 5000, and the concentration Co corresponds to the mercury concentration (apart from elemental mercury) measured in the line 101.
In the embodiment for which stages a) and b) are carried out simultaneously, i.e. the transformation of mercury to elemental mercury is carried out both during the transport of said feedstock to the separation unit 5000 and during the stage of separation of said feedstock in the separation unit 5000, the concentration Cs corresponds to the mercury concentration (apart from elemental mercury) measured in the line 203, and the concentration Co corresponds to the mercury concentration (apart from elemental mercury) measured in the line 101.
Furthermore, according to the invention, the total volume V of the conversion unit 900 is defined such that the ratio V/Q, with Q corresponding to the volume flow of the feedstock to be treated, is equal to the residence time “t” associated with the targeted temperature of the feedstock “T”.
Thus, in the embodiment for which stages a) and b) are carried out separately, i.e. when the transformation of mercury to elemental mercury is carried out upstream of the separation unit 5000, the volume V of the conversion unit 900 corresponds to the volume of the heating unit 2000, such as a drum, and optionally to the pipe or the set of pipes intended for the transport of the feedstock to the separation unit 5000.
In the embodiment for which stages a) and b) are carried out simultaneously, i.e. when the transformation of mercury to elemental mercury is carried out both during the transport of said feedstock to the separation unit 5000 and during the stage of separation of said feedstock in the separation unit 5000, the volume V of the conversion unit 900 corresponds to the volume of the heating unit 2000, such as a drum, and optionally to the volume of the pipe or the set of pipes intended for the transport of the feedstock to the separation unit 5000, as well as to the volume of the separation unit 5000, in which unit the transformation of the non-elemental mercury contained in the compounds of the heavy hydrocarbon-containing feedstock to elemental mercury is also carried out.
With reference to
Advantageously, during the transformation stage, and according to any one of the embodiments according to the invention (i.e. stages a) and b) being carried out separately or not):
Even more preferably:
According to the invention, the stage of transformation of the non-elemental mercury contained in the feedstock to elemental mercury is carried out at a pressure comprised between 0.1 and 12 MPa, preferably between 0.1 and 6 MPa.
Thus it is possible to transform the non-elemental mercury contained in the compounds of said feedstock to elemental mercury, starting from 150° C., by adjusting the residence time of the feedstock in the conversion unit 900. Furthermore, the absence of a catalyst simplifies the implementation of the process and makes it possible to avoid the occurrence of clogging of the capture materials of heavy metals during the stage of bringing into contact said feedstock containing heavy compounds, likely to agglomerate or precipitate, with a mercury capture material.
According to the invention, a stage of separation of the feedstock is carried out in a separation unit 5000, in order to produce a liquid effluent 103 and a gaseous effluent 203 comprising elemental mercury. The separation stage can be carried out by stripping (c.f.
According to the embodiment shown in
The separation unit 5000 can comprise internals intended to promote exchanges between the liquid and vapour phases, such as plates or packing.
At the outlet of this separation stage, a liquid effluent 103 comprising a hydrocarbon-containing feedstock with reduced volatile fractions and mercury, and a gaseous effluent 203 are obtained.
Advantageously, the carrier gas used in the separation unit 5000 is a gas that is present at the operating site and the composition thereof is selected so as to not impact on the operation of the installations situated downstream. For example, the carrier gas is a cut of the hydrocarbon-containing compounds originating from the main fractionation unit 3000, and more particularly is a cut of the hydrocarbon-containing compounds of which 90% by weight of the compounds have a boiling point less than 200° C. at atmospheric pressure (1.01325×105 Pa).
The gaseous effluent recovered via the pipe 203, comprising the mercury in elemental form, is then sent to a, preferably single, unit for the capture of mercury 6000 comprising at least one capture material. The unit for the capture of mercury 6000 can be presented for example in the form of a fixed bed comprising a capture material containing an active phase suitable for reacting with the elemental mercury in order to immobilize it in the bed so as to produce a de-mercurized gaseous effluent which is introduced via the pipe 204 to the main fractionation unit 3000. Examples of effective capture materials are described in the patents FR 2764214, FR 2980722, or also FR 2992233.
The unit for the capture of mercury 6000 can also comprise means for adjusting the pressure and the temperature (not shown in the figures) in order to be adapted to the chosen method for the elimination of mercury.
Thus, unlike the state of the art shown in
The liquid effluent recovered at the bottom of the separation unit 5000 is then sent via the pipe 103 to the main fractionation unit 3000. According to the invention, by main fractionation unit 3000 is meant a unit for the fractionation of the feedstock by atmospheric distillation (such as described previously in the section describing the prior art). The main fractionation unit 3000 can comprise one or more distillation columns (in
In the embodiment as shown in
Optionally, the effluent originating from the pressurization means 4000 is conveyed via the pipe 201 into a heat exchanger 2001. This stage is necessary when the effluent passing through the pipe 200 is in liquid form as it makes it possible to convert said effluent to gaseous form. Therefore, regardless of the nature of the effluent recovered via the pipe 200, the effluent passing through the pipe 202 is in gaseous form and is sent to the separation unit 5000 as a carrier gas (stripping gas).
In the separation unit 5000, the bringing into contact of the feedstock originating from the pipe 102 and the carrier gas originating from the pipe 202 makes it possible to recover, at the bottom of the separation unit 5000 via the pipe 103, a feedstock the most volatile fractions of which are reduced, and to recover at the top of the separation unit 5000 via the pipe 203, a gaseous stripping effluent mainly comprising the carrier gas, a light hydrocarbon fraction originating from the feedstock 102, more particularly light hydrocarbons from methane to octane, as well as mercury in elemental form in the gaseous state and optionally H2S, entrained in the separation unit 5000 by the carrier gas.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.
The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 15/57.034, filed Jul. 24, 2016 are incorporated by reference herein.
The example below is based on the process according to the invention as shown in
After passing through a desalting unit 1000, the feedstock is sent to a conversion unit 900 in order to convert the non-elemental mercury contained in the compounds of said feedstock to elemental mercury. During this stage, the feedstock is heated to a target temperature of 180° C. (set by the operator) and during a fixed residence time adapted to the target temperature in order to allow the total conversion of the non-elemental mercury contained in said feedstock to elemental mercury.
Within the context of the present example, two tests were carried out by varying the residence time of the feedstock in the conversion unit 900. A first test was carried out by heating the feedstock to a target temperature of 180° C. for a residence time (contact time) of 60 minutes, and a second test was carried out by heating the feedstock to 180° C. for a residence time of 20 minutes (c.f. Table 1 below).
The separation unit 5000 is in the form of a liquid gas contactor, making it possible to carry out stripping said feedstock upstream of the main fractionation unit 3000. The flow of feedstock sent to the separation unit 5000 via the pipe 102 is 244 t/h of crude at a temperature of 380° C. and at a pressure of 1.5 MPa. The total flow of mercury contained in the feedstock is 45.5 g/h.
The feedstock sent via the pipe 102 is introduced at the top of the separation unit 5000. A carrier gas is introduced via the pipe 202 at the bottom of the separation unit 5000. The carrier gas will travel through the separation unit 5000 by rising to the top of the separation unit, carrying with it the most volatile compounds including the elemental mercury. The mainly liquid feedstock circulates in counter-current with the carrier gas. As a result, a gaseous stripping effluent is recovered at the top of the separation unit at the level of the pipe 203 at 371° C., 0.7 MPa and 101 t/h. The gaseous stripping effluent comprises mercury in elemental form.
The de-mercurized liquid feedstock is itself recovered below the separation unit 5000 via the pipe 103 at 1.4 MPa, 371° C. and 167 t/h and is conveyed to the main fractionation unit 3000. The main fractionation unit 3000 is here in the form of a distillation column with 34 theoretical plates operating at a pressure of between 0.43 MPa at the bottom and 0.39 MPa at the top for temperatures of 339 and 168° C. respectively.
A liquid effluent is extracted at the level of the liquid clearance of the top plate of the main fractionation unit 3000 via the pipe 200 that is pressurized by means of a pump 4000. The result is a liquid effluent passing through the pipe 201 at 1.5 MPa and 169° C. The liquid effluent is re-heated to 350° C. by a heat exchanger 2001 via the gaseous stripping effluent circulating in the pipe 203. The result is a gaseous effluent passing through the pipe 202 at 350° C. and 1.49 MPa.
The gaseous stripping effluent recovered at the top of the separation column 5000 via the pipe 203 (comprising mercury in elemental form) is sent to a unit for the treatment of mercury 6000 comprising a mercury capture material based on CuS deposited on alumina, suitable for the capture of mercury in elemental form. The result is a de-mercurized flow circulating in the pipe 204 at 0.6 MPa and 150° C. and which is redirected to the main fractionation unit 3000.
For the two tests carried out, the contents of total mercury and elemental mercury in the pipes 101, 102, 103, 203 and 204 are determined in μg/L.
Liquid samples are taken for the pipes 101, 102 and 103, then analysed using a specific PE-1000® device from Nippon Instruments Corporation (NIC) for mercury analyses. In order to determine the elemental mercury content, the effluent for analysis is analyzed in the PE-1000® at the same time and stripped of nitrogen so as to eliminate the elemental mercury. By analysing the mercury content of the sample after stripping and subtracting it from the mercury content of the sample before stripping, the quantity of elemental mercury initially present in the effluents is calculated.
In the pipes 203 and 204, the effluent is gaseous. The mercury is measured with a SP3D® device (NIC) adapted for gas analysis.
The mercury content measured in the pipe 203 is identical to that of the elemental mercury content in the pipe 102. It is therefore only elemental mercury.
The mercury contents measured show that in order to be able to transform the non-elemental mercury contained in the compounds of the feedstock to elemental mercury, the contact time at a target temperature must be sufficient. If this is not the case or if the flow is not heated, decomposition of the refractory species comprising the mercury in the feedstock is not total and a part of the mercury is recovered at the bottom of the separation device. Consequently, the different units situated downstream in a refinery layout are therefore potentially polluted with mercury and it will be necessary to add as many capture materials as there are outlet flows, leading to a significant overspend in terms of investment and operating costs.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15/57.034 | Jul 2015 | FR | national |
