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EP-4736576-A1 - DYNAMIC MIXER FOR OHMIC HEATING SYSTEM

EP4736576A1EP 4736576 A1EP4736576 A1EP 4736576A1EP-4736576-A1

Abstract

An apparatus for the continuous ohmic thermal treatment of a fluid product includes a conduit defining a longitudinal flow path for the product to be treated extending between an inlet and an outlet. The conduit includes a first and a second heating chamber that are disposed longitudinally along an axis and arranged in sequence, with each heating chamber including a first electrode and a second electrode, separated by an electrical insulating member. The first electrode is located near the inlet or the outlet of the conduit, and the second electrode is located in an intermediate zone of the conduit. A first and a second rotor extend into the first chamber and the second chamber, respectively, and are rotatable about the longitudinal axis. A support system is configured to support in the radial direction the first and second rotors at the intermediate zone of the conduit.

Inventors

  • Demicheli, Luigi

Assignees

  • John Bean Technologies S.p.A.

Dates

Publication Date
20260506
Application Date
20240627

Claims (20)

  1. 1. An apparatus for the continuous thermal treatment of a fluid product by resistive heating, comprising: a conduit defining a longitudinal flow path for the product to be treated extending between an inlet and an outlet, the conduit comprising at least a first and a second heating chamber that are disposed longitudinally along an axis and arranged in sequence, each heating chamber comprising a first electrode and a second electrode, separated by an electrical insulating member, wherein the first electrode is located near the inlet or the outlet of the conduit, and the second electrode is located in an intermediate zone of the conduit; a first and a second rotor extending into the first chamber and the second chamber, respectively, and rotatable about the longitudinal axis; and a support system configured to support in the radial direction the first and second rotors at the intermediate zone of said conduit.
  2. 2. The apparatus according to claim 1, wherein the support system is configured so that the first and second rotors are radially supported by the fluid product which flows between a first and a second distal end portions of the first and second rotors and the second electrode.
  3. 3. The apparatus according to claim 1 or 2, wherein said first and second rotors comprise a central elongated body extending along the longitudinal axis and a plurality of projections extending radially from the central body.
  4. 4. The apparatus according to claim 3, wherein the support system comprises the second electrode shaped as an annular body having an inner surface which the projections face.
  5. 5. The apparatus according to claim 4, wherein the distance separating the projections and the inner surface of the annular body is from between 0.1-0.3 millimeters, through which the fluid product passes.
  6. 6. The apparatus according to claim 3, wherein the projections have a radial height extending from the body that is less than the inner radius of the electrical insulating member of the first and the second chambers so as to leave a space for the passage of the product.
  7. 7. The apparatus of claim 6, wherein space between the projections and the inner radius of the electrical insulating member is from between 0.5-10 millimeters.
  8. 8. The apparatus of claim 6, wherein space between the projections and the inner radius of the electrical insulating member is from between 0.5-5 millimeters.
  9. 9. The apparatus according to any one claims 1-8, wherein the first electrode is a negative electrode.
  10. 10. The apparatus according to any one of claims 1-9, wherein the second electrode is a positive electrode.
  11. 11. The apparatus according to claim 10, wherein the second electrode is connected to a square-wave current power source.
  12. 12. The apparatus according to any one of claims 1-11, wherein the first electrode and the second electrode are subjected to an electric current of a potential difference of at least 700V with a frequency of at least 16kHz.
  13. 13. The apparatus according to claim 12, wherein the voltage of the electric current applied to the pair of electrodes ranges between 700V and 5100V, and the frequency of the electric current ranges between 16 and 50kHz.
  14. 14. The apparatus according to any one of claims 1-13, wherein the first and second rotors are coupled to handling and support devices adapted to rotate the first and second rotors independently of one another.
  15. 15. The apparatus according to claim 14, wherein the handling and support devices comprise a first motor coupled to an initial portion of the first rotor, and a second motor coupled to an initial portion of the second rotor.
  16. 16. The apparatus according to claim 3, wherein the projections of the first and second rotors are spaced apart along the length of the central body.
  17. 17. The apparatus according to claim 16, wherein the proj ections of the first and second rotors define gaps extending along the length of the central body, the gaps extending around the entire circumference of the central body.
  18. 18. The apparatus according to any one of claims 1-17, wherein the second electrode is common to the first and the second chambers, wherein, with respect to the direction of flow of the product, the first chamber ends with the second electrode and the second chamber starts with the second electrode.
  19. 19. The apparatus according any one of claims 1-17, wherein the second electrode of the first chamber is distinct from the second electrode of the second chamber, and one or more connecting members are interposed between the two second electrodes.
  20. 20. The apparatus according to any one of claims 1-19, wherein the first and second rotors are composed of dielectric material.

Description

DYNAMIC MIXER FOR OHMIC HEATING SYSTEM CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of US Utility Application No. 18/344,751, filed June 29, 2023, the entire contents of which are incorporated herein by reference. BACKGROUND [0002] The present disclosure relates to apparatuses for thermal treatments of products, in particular foodstuffs. In particular, these are ohmic heating or resistive heating treatments. Ohmic heating treatments are a thermal process whereby heat is generated within the foodstuff. The heat generation is caused by the passage of an electric current generated by a voltage differential through the foodstuff. The ohmic heating treatments can be used to heat, pasteurize, sterilize, or otherwise heat treat food and non-food products. [0003] Ohmic heat treatments are an alternative process to traditional pasteurization methods. Conventional pasteurization processes are based on the transfer of heat to the food or not-food products by convection. In a conventional pasteurization process, the external parts of foodstuffs are exposed more to the heating action than the internal parts. In order to adequately rid the product from pathogens, high temperature heat sources must be used, which could damage the product by causing changes in the chemical, physical, and organoleptic characteristics of the treated foodstuff. [0004] On the other hand, in ohmic heating the heat source is generated from inside the foodstuff, and the heat propagates outwardly. This helps to ensure that all the food particles are thermally treated. [0005] Depending on the result to be achieved and the foodstuff to be treated, ohmic heating involves heating to a specific temperature and maintaining it for an appropriate period of time. The process must ensure that the treatment temperature is homogeneous within the product and maintained for the time necessary within a well-defined temperature range. [0006] Ohmic treatment uses the electrical conductivity of the product to be treated. In particular, it involves passing a certain electrical current through the product, which, by the effect of the electrical resistance of the product, generates heat and consequently raises the temperature product. [0007] Ohmic apparatuses generally involve a continuous operation in which the product to be treated flows inside a conduit in dielectric material, at the ends of which two electrodes are located that have a negative pole, and centrally in the conduit an electrode is located that has a positive pole. [0008] In its flow through the apparatus, the product passes through the first negative pole, then the positive pole, and before exiting it passes through the second negative pole. The potential difference generated by the electrodes may have a value ranging between about 700 and 5100 V and a frequency ranging between about 16 and 25 KHz. This potential difference generates a current which is inversely proportional to the electrical resistance of the product, and which results in the generation of heat. [0009] Ohmic processing temperatures can generally range between about 1° C and 150° C. The dwelling time of the food product in the ohmic apparatus is a function of the product that is treated and the process temperature. [0010] To help ensure the maximum homogeneity of heating of the product, an ohmic apparatuses may include, within the conduit, a rotor extending along its entire length from the first to the second negative pole. The function of the rotor is to mix the product that is being processed. [0011] In one prior form, the one end of the rotor is supported and mechanically connected to a rotating source, and the opposite end is cantilevered free. [0012] Also, the rotor generally has a plurality of projections along its outer surface that contact the inner surface of the conduit. Also, the projections extend continuously along the length of the rotor so that there are no gaps along the length of the projections. This rotor construction can create the undesired effect of spreading and adhering the product being treated to the inner surface of the conduit. [0013] Therefore, with known rotors, particularly when the product being treated has a high density and/or viscosity, a layer of product can be created on the inner surface of the conduit that advances at a slower rate along the conduit than the advancement rate of the product away from said inner surface. This can result in an undesirable increase in dwelling time and temperature of the product. Furthermore, the laminar motion of the product in the proximity of the walls can cause changes in the electrical resistance of the product that adversely affect the homogeneity of the treatment temperature. [0014] In addition, the fact that the rotor extends along the entire length of the conduit, is cantilever-mounted, and is supported only at the end corresponding to the handling device has the drawback that it may not be possible to reach a high en