Energy applicators adapted to dielectric heating

2 An energy applicator, of the type comprising a waveguide and lateral chimney members, for dielectric heating of any compound, at microwave frequencies or high frequencies, under static or dynamic conditions, at relative power density higher than that of the usual applicators, without risk of electric arcs or “discharge”, regardless of the dielectric constants of the said compound, characterized in that the said applicator is provided with at least one chimney member of geometry adapted to form a resonant cavity around the waveguide, for treatment of the product under consideration,

3 An applicator according to claim 1 or 2, characterized in that this cavity is formed on each side of the waveguide.

4 An applicator according to claim 1 or 2, characterized in that this cavity is formed around the waveguide by one or more chimney members.

5 An applicator according to claim 4, characterized in that the chimney member or chimney members is or are placed on each side of the waveguide, around the resonant cavity.

6 An applicator according to any one of claims 1 to 5, characterized in that the shape of the said cavity formed around the waveguide is chosen from among:

• the symmetric shapes,
• the shapes composed of at least a conical base, a spherical shape or a shape of ellipsoidal volume, the broadest portion opening into the waveguide.

7 An applicator according to any one of claims 4 to 6, characterized in that it contains a plurality of chimney members of identical geometry.

8 An applicator according to any one of claims 4 to 7, characterized in that the chimney members are composed of two main portions:

• an upper portion, which must be as close as possible to the reactor in order to prevent waves from leaking out, and a lower portion whose shape flares toward the waveguide to prevent electric arcs.

9 An applicator according to claim 8, characterized in that the upper portion of the chimney members must be as close as possible to the reactor in order to prevent leakage of waves, and it can have cylindrical shapes with circular, rectangular or square cross section.

10 An applicator according to claim 9, characterized in that the chimney members have a geometry composed of different successive shapes.

11 An applicator according to claim 9 or 10, characterized in that the upper portion of the chimney members has a cylindrical shape with circular cross section, in order to conform best to the shape of the reactor and to avoid the presence of edges, which favor electric arcs. The height of this portion of the chimney member is determined so as to exclude any leakage of waves.

12 An applicator according to claim 9 or 10, characterized in that the lower portion of these chimney members, or in other words that close to the waveguide, is of flared shape.

13 An applicator according to claim 12, characterized in that the said shape is chosen from among the conical and/or spherical shapes having variable angles relative to the vertical, and from the pyramidal shapes having square or rectangular bases.

14 An applicator according to claim 12 or 13, characterized in that the base diameter of these flared shapes must not exceed the width of the waveguide, and then the height and apex angle of the flared portion are fixed as a function of the power used.

15 Applicators according to any one of claims 1 to 14, characterized in that there are used single-mode microwave applicators at 2450 MHz, and in that the recommended waveguide width for remaining in TE 0.1 mode (transverse electric) ranges between approximately 70 and 100 mm, the TE 0.1 fundamental mode of excitation permitting the wave to propagate along a single arc.

16 Applicators according to any one of claims 1 to 15, characterized in that there are used applicators operating at other microwave frequencies and at high frequencies.

17 Applicators according to any one of claims 1 to 16, characterized in that the chimney members comprise an upper standard cylindrical portion and a lower conical portion at the waveguide.

19 Applicators according to any one of claims 1 to 18, characterized in that a resonant microwave system is created by means of a localized-field or a diffuse-field applicator.

20 An applicator according to claim 19, characterized in that it creates a “single-mode” system (localized field), which is formed from single-mode cavities resonating at the emission frequency along a beam in the direction of the guide.

21 An applicator according to claim 19, characterized in that it creates a “multimode” system (diffuse field).

22 An applicator according to any one of claims 4 to 21, characterized in that the length of each chimney member is determined so as to exclude any leakage of waves and to comply with the safety measures relating to personnel and telecommunications.

23 Chimney members for energy applicators for dielectric heating of any compound at microwave frequencies or high frequencies, under static or dynamic conditions, with high power density, without risk of electric arcs or “discharge”, regardless of the dielectric constants of the said compound, characterized in that the said chimney members are such as described in any one of claims 1 to 22.

24 Use of the applicators or chimney members according to any one of claims 1 to 22 or 23 for application of microwave or high-frequency electromagnetic waves for heating applications on compounds that absorb the radiation weakly and on compounds having high dielectric constants (∈′>5 and ∈″>0.5).

25 Applications according to claim 24 for performing heat treatments on compounds that absorb electromagnetic waves weakly or on polar or polarized compounds.

26 Applications according to claim 24 or 25 for the treatment of fatty acid esters (unsaturated or otherwise), of hydrocarbons (unsaturated or otherwise), of aromatic compounds and of derivatives of the latter, and of products that absorb electromagnetic waves, to increase the production capacity of a given system (fatty and non-fatty alcohols, carboxylic acids, amines, etc.), and for all reactions of “lipochemistry”, with in particular a very strong interest for the case of products that absorb electromagnetic waves weakly, such as for isomerization of fatty acids or of esters of monounsaturated or polyunsaturated fatty acids, or of waxes, and in particular of castor oil.

27 Applications according to any one of claims 24 to 26, characterized in that there are achieved all the heating applications involving a single reactant or a mixture of reactants in variable proportions, such as esterification, transesterification, epoxidation, sulfatization, phosphatization, amidification, polymerization and polycondensation reactions as well as decolorization, deodorization and the systems for elimination of volatile compounds.

28 Applications according to any one of claims 24 to 28 for synthesis of polymers of unsaturated fatty acids, of esters of unsaturated fatty acids, of unsaturated hydrocarbons or of derivatives of such products by means of dielectric heating with microwaves.