Catalytic combustion burner made of porous material, with optimised operating performance and bottle equipped with such a burner

Abstract

A catalytic combustion burner made of porous material and a bottle equipped with such a burner have an optimized operating performance, which enables the burner to withstand and not be extinguished when it is subjected to strong air currents such as air conditioning.

Claims

1. Catalytic combustion burner made of porous material, comprising: an end piece comprising: a lower part of outside diameter ϕ.sub.1 and delimiting a first cavity of diameter ϕ.sub.2, said first cavity extending along a main axis and being adapted to receive a wick that is capable of soaking the end piece with a combustible composition, and an upper part having a peripheral side wall comprising an inner face of essentially frustoconical shape and delimiting a second cavity of depth P, an outer face, an upper face of circular shape and a base, said inner face having a lower end of diameter ϕ.sub.3 greater than ϕ.sub.2 and an upper end of diameter ϕ.sub.4 greater than ϕ.sub.3, the upper end of said side wall communicating with the atmosphere and said lower end of said base communicating with said first cavity, the lower end of said inner face terminating with structure defining a counterbore of diameter ϕ.sub.3, communicating with said second cavity, the lower end of said inner face terminating with structure defining a counterbore of diameter ϕ.sub.3, communicating with said second cavity, at least a part of said outer face of said peripheral side wall is doped with a catalyst, a sleeve arranged in the extension of said lower part of the end piece and delimiting a third cavity extending said first cavity of said lower part, and an insert arranged in said second cavity of the end piece and having a surface in contact with said base of the end piece, wherein said porous material is obtained from a composition comprising, as a percentage of the total weight of said composition, between 0.5 and 1% of silicon carbide as a heat-conducting compound, between 30% and 70% of at least one refractory compound, between 2% and 30% of at least one binder, and between 5% and 40% of at least one pore-forming agent, and in that all of said circular-shaped upper face is doped with said catalyst.

2. Burner according to claim 1, in which at least a part of said inner face of said peripheral side wall is doped with said catalyst.

3. Burner according to claim 1, in which the depth P of said second cavity is between 2 and 8 mm.

4. Burner according to claim 3, in which the depth P of said second cavity is between 6 and 7.5 mm.

5. Burner according to claim 4, in which the depth P of said second cavity is 7 mm.

6. Burner according to claim 1, in which each said refractory compound is chosen from the group constituted of alumina, silica, mullite, zirconia and cordierite, and mixtures thereof.

7. Burner according to claim 1, in which said binder is a mineral compound which allows sintering at a temperature of less than or equal to 1100° C.

8. Burner according to claim 7, in which said mineral compound is a glass.

9. Burner according to claim 8, in which said glass is a borosilicate glass.

10. Burner according to claim 1, in which the pore-forming agent is polymethyl methacrylate (PMMA), which is present in a proportion of from 18% to 30% by weight relative to the total weight of said composition.

11. Burner according to claim 1, according to which said porous material is obtained from a composition comprising, as a percentage of the total weight of said composition, about 1% of silicon carbide, between 60% and 70% of mullite, between 5% and 15% of glass, and between 18% and 30% of PMMA.

12. Burner according to claim 11, in which said sleeve has a length of between 10 and 20 mm.

13. Burner according to claim 12, in which said sleeve has a length of 14 mm.

14. Catalytic combustion bottle, which is suitable for containing a combustible liquid and for receiving on its neck a catalytic combustion burner receiving a wick which is soaking in said liquid, wherein said bottle is equipped with a burner as defined according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 represents schematically a cross section of a first example of a burner that may be used in the context of an embodiment of the present invention;

(2) FIG. 2 is a schematic front view of a bottle equipped with one of the combustion burners represented in FIG. 1, on the one hand, and in FIGS. 5 and 6, on the other hand;

(3) FIGS. 3 and 4 represent, respectively, a view in side perspective and a top view of an insert that may be used in the burner according to an embodiment of the invention;

(4) FIG. 5 represents schematically a cross section of a second example of a burner that may be used in the context of the present invention;

(5) FIG. 6 is a perspective view of the burner illustrated in FIG. 5;

(6) FIGS. 7 to 18 are IR thermographs produced to show the impact of air conditioning on a burner according to an embodiment of the invention, on the one hand, and on a control burner not having any catalyst on the circular zone;

(7) FIG. 19 illustrates the protocol for measuring by infrared camera the impact of air conditioning on the temperature of the burner during functioning.

(8) The technical characteristics common to these two figures are each designated by the same reference numeral in the figures concerned.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) FIGS. 1, 5 and 6 show two examples of burners 10 that may be used in the context of the present invention. These two examples of burner 10 each comprise, on the one hand, an end piece 1 with a lower part 1a and an upper part 1b, and, on the other hand, a sleeve 7 arranged in the extension of the lower part 1a of the end piece 1.

(10) As more particularly regards the end piece 1, it comprises: the lower part 1a of outside diameter ϕ.sub.1 and delimiting a first cavity 2 of diameter ϕ.sub.2, this first cavity 2, which extends along a main axis 3, being adapted to receive a wick that is capable of soaking the end piece 1 with a combustible composition, and an upper part 1b having a peripheral side wall 5 comprising an inner face of essentially frustoconical shape and delimiting a second cavity 6 of depth P, an outer face of essentially cylindrical shape (but frustoconical at its base) and of diameter ϕ.sub.5, an upper face and a base communicating with the first cavity.

(11) The inner face has a lower end 61 of diameter ϕ.sub.3 greater than ϕ.sub.2 and an upper end 62 of diameter ϕ.sub.4 greater than ϕ.sub.3, the upper end 62 of the side wall communicating with the atmosphere and the lower end 61 being connected to the base 5d. The first 2 and second 6 cavities communicate together.

(12) As more particularly regards the sleeve (also known as the barrel) 7, it is arranged in the extension of the lower part 1a of the end piece 1. It delimits a third cavity 2′ extending the first cavity 2 of the lower part. This sleeve is constituted of the same porous material as the end piece.

(13) FIGS. 5 and 6 schematically show, respectively, a schematic cross section and a view in perspective of a second burner example, which differs from the first burner example in that, in the second burner example, the lower end 61 of the inner face terminates with a counterbore 18 of diameter ϕ.sub.3, communicating with the cavity 2. In the first burner example represented in FIG. 1 (without counterbore), the inner face is entirely frustoconical between its two ends 61 and 62.

(14) The two burner examples (represented in FIGS. 1, 5 and 6) each comprise an insert 8 arranged in the second cavity 6 of the end piece 1 and having a surface 8a in contact with the base of the end piece.

(15) In addition, at least a part of their outer face is doped with a catalyst, for example based on a metal belonging to groups 9 or 10 of the Periodic Table of the Elements (according to the terminology recommended by the IUPAC).

(16) When the first burner example does not comprise any catalyst on its face, it is used as control in the tests of behavior with respect to air conditioning (designated hereinbelow by the reference 1C).

(17) When the first burner example does not comprise any catalyst doping its face, it is used as first burner example according to an embodiment of the invention in the tests of behavior with respect to air conditioning (designated hereinbelow by the reference 1).

(18) The second burner example comprises a catalyst doping its face, and is used as second burner example according to an embodiment of the invention in the tests of behavior with respect to air conditioning (designated hereinbelow by the reference 2).

(19) In order to test the catalytic functioning in the presence of air conditioning of the burners represented in FIGS. 1, 5 and 6, these burners were placed in a catalytic combustion bottle 20, represented in FIG. 2.

(20) Such a bottle 20 contains during functioning a combustible liquid 30. The burner 10 (either the burner according to an embodiment of the invention as represented in FIG. 5, or the prior art burner represented in FIG. 1, each equipped with an insert as represented in FIG. 3) is installed in the neck 50 of the bottle (for example with the aid of a metallic seat placed in the neck 50). A wick 40 is received inside the cavities 2 and 2′ of the burner 10, this catalytic combustion wick 40 receiving a wick (40) which is soaking in the liquid 30. The bottle 20 may be a bottle of any shape having a neck 50 into which is fitted the burner 10. The combustible liquid 30 is usually an alcohol, for example isopropyl alcohol, or any other suitable combustible liquid that is compatible with the legislation in force in this field. In particular, this combustible must be such that its vaporization and its catalytic combustion do not give off any unpleasant odor. The combustible liquid 30 may also comprise a fragranced material and/or an active material. The wick 40 is any known wick, for example a wick made of cotton, or a wick made of mineral material, for example made of mineral fibers.

(21) During functioning, the combustible liquid 30 in the bottle 20 rises in the wick 40 by capillary action and penetrates the pores of the porous material of the burner, which, when it has been preheated, ensures its catalytic combustion.

(22) The examples that follow illustrate embodiments of the invention, in connection with the figures, without, however, limiting the scope thereof

(23) In these examples, unless otherwise indicated, all the percentages and parts are expressed as mass percentages.

EXAMPLES

(24) Compounds Included in the Composition of the Porous Materials Used:

(25) heat-conducting compound: silicon carbide, refractory compound: mullite, binder: glass, pore-forming agent: polymethyl methacrylate (PMMA).
Compositions of the Porous Material:

(26) The burners used in the examples are made by dry pressing from compositions C1 and C2 below indicated in Table 1. For each of these compositions, the porosity of the ceramic structure and the median diameter of the interconnections have been indicated in Table 1.

(27) TABLE-US-00001 TABLE 1 Interconnection Mullite SiC Glass PMMA Porosity diameter Composition (%) (%) (%) (%) (%) (μm) C1 64 5 10 21 58% to 9 60% at 975° C. C2 66.5 1 11.5 21 60.2% at 9.5 1050° C. C3 67 0.5 11.5 21 58.9 —
Catalysts

(28) The catalyst used (whether on parts 5a, 5b or 5c of the burner) is a metal belonging to groups 9 or 10 of the Periodic Table of the Elements.

(29) Burners Used:

(30) As Comparative Example:

(31) Burner 1C (represented in FIG. 1), the outer face of which is doped with a catalyst impregnating it, the burner 1C being constituted of a porous material obtained from composition C1.

(32) As Examples According to Embodiments of the Invention:

(33) burner 1 (also represented in FIG. 1 and comprising the insert represented in FIGS. 3 and 4) identical to burner 1C, except for its face which is doped with the same catalyst as that of the outer face, burner 1 also being constituted of a porous material obtained from composition C1. burner 2 (represented in FIGS. 5 and 6 and comprising the insert represented in FIGS. 3 and 4), the outer face and the upper face of which are doped with the same catalyst which impregnates them, burner 2 being constituted of a porous material obtained from composition C2. burner 3 (represented in FIGS. 5 and 6 and comprising the insert represented in FIGS. 3 and 4), the outer face and the upper face of which are doped with the same catalyst which impregnates them, burner 3 being constituted of a porous material obtained from composition C3.

(34) During functioning, when the burner is equipped with a catalyst in its circular peripheral part, the part of the combustible liquid which reaches this part undergoes catalytic combustion thereat, which keeps this part at a high temperature. Bottle used: the one shown in FIG. 2 for burners 1C, 1 and 2. Wick used: cotton wick (for burner 3, two different wicks were tested). Combustible liquid used: isopropyl alcohol.
Tests and Measurements

(35) 1) Porosity (%) and Diameter D of the Interconnections

(36) The open porosity of the porous material constituting the burner is measured by mercury intrusion into the material of a Micromeritics Autopore IV 9510 brand porosimeter. This measurement is taken at a maximum pressure of 414 MPa approximately, which corresponds to a minimum detectable pore size of about 0.0035 μm.

(37) Method and Operating Protocol:

(38) The measurement of the porosity by mercury intrusion is based on the principle of penetration of an unreactive liquid into a porous material, by immersing the material in the liquid and increasing the pressure isostatically. Mercury, which does not react with the majority of materials, is furthermore an ideal liquid due to the high value of its contact angle, it does not wet the majority of materials.

(39) From this measurement, the pore size is determined in terms of the diameter D in μm (interconnection diameter), then penetrated, which is inversely proportional to the applied pressure, P, according to an embodiment of the Washburn equation:

(40) $D=\frac{-4\gamma \cos \Theta }{P}$
with: γ: surface tension of mercury, γ=0.00485 N/cm (485 dynes/cm). θ: contact angle of mercury, θ=140°

(41) 2) Operating Characteristics of the Burners 10 Installed on the Bottle 20 in the Presence of an Air Conditioner at 18° C. With Ventilation

(42) The test protocol is represented in FIG. 19. It consists globally in measuring, by infrared (IR) thermograph using an IR thermal camera, the temperature on each of the burners tested, placed at a reasonable distance from an air conditioner (the power of which is 800 W in the context of the tests performed). These measurements are compared, for each burner tested (control 1C and according to embodiments of the invention 1 and 2), with measurements taken without ventilation.

(43) The thermographs produced are detailed below: Burner 1C: without air conditioning: FIGS. 7 and 8; with air conditioning: FIG. 9 (measurement taken on the side opposite the air conditioning) and FIG. 10 (measurement taken on the side facing the air conditioning); Burner 1: without air conditioning: FIGS. 11 and 12; with air conditioning: FIG. 13 (measurement taken on the side opposite the air conditioning) and FIG. 14 (measurement taken on the side facing the air conditioning); Burner 2: without air conditioning: FIGS. 15 and 16; with air conditioning: FIG. 17 (measurement taken on the side opposite the air conditioning) and FIG. 18 (measurement taken on the side facing the air conditioning).

(44) When the measurement is taken on the side of the burner that is opposite the flow of air coming from the air conditioner, the air flow has little impact on the temperature measured on this side of the burner, as shown by comparison of FIGS. 7 and 9 (burner 1C), FIGS. 11 and 13 (burner 1 according to an embodiment of the invention), and FIGS. 15 and 17 (burner 1 according to an embodiment of the invention). This temperature decreases very little for burners 1 and 2 according to an embodiment of the invention, and slightly more for the control burner 1.

(45) This is not likewise the case when the measurement is taken on the side of the burner facing the air conditioner: burners 1 and 2 according to an embodiment of the invention show better resistance than the control burner 1C, as shown by comparison of FIGS. 7 and 10 (drastic drop for the control burner), that of FIGS. 11 and 14, and finally that of FIGS. 15 and 18. It is considered that when the temperature measured at a given place on the catalyst is below 300° C., the catalyst has a high likelihood of extinguishing rapidly.

(46) The temperatures measured are collated in Table 2 below:

(47) TABLE-US-00002 TABLE 2 Temperature measurement with Temperature measurement air conditioner without air conditioning Side facing Side Top Side opposite the the air Face 5b Face 5c Centre air conditioner conditioner Burner 535° C. 460° C. 283° C. 413° C. 157° C. 1 C. Burner 1 559° C. 521° C. 313° C. 443° C. 327° C. Burner 2 553° C. 537° C. 339° C. 486° C. 379° C. Burner 3 546° C. 559° C. 347° C. 483° C. 404° C. (test wick 1) Burner 3 556° C. 532° C. 336° C. 523° C. 411° C. (test wick 2)

(48) These tests show that the presence of a catalyst on the circular zone of the burner makes it possible to maintain the temperature of the burner when it is subjected to a strong air current such as, for example, that emitted by a portable air conditioner, both for an SiC content of 1% and for an SiC content of 0.5%. This catalyst allows thermal conduction of the heat to the burner zone, which, when subjected to an air current, does not ultimately become unprimed.