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EP-4396548-B1 - DEVICE FOR DETERMINING THE TEMPERATURE OF A MIXTURE IN A ROTARY MIXER

EP4396548B1EP 4396548 B1EP4396548 B1EP 4396548B1EP-4396548-B1

Inventors

  • EITZEN, THEODOR
  • ADAM, PATRICK

Dates

Publication Date
20260513
Application Date
20210831

Claims (14)

  1. A rotary mixer (2), comprising: a device (1) for determining a temperature of a mixed material (13) in said rotary mixer (2); a stationary housing (3); a mixing container (10) that can be moved on a circular path (14) into different rotational positions about a main axis of rotation (16), the mixing container having a mixied material receptacle (9) with a bottom (7) and a side wall (8), wherein the mixed material receptacle (9) is in form of a solid of revolution with an axis of symmetry (11) arranged obliquely to a plane (15) of the circular path (14) and orthogonally to the bottom (7); and wherein the mixing container (10) is rotably mounted about the axis of symmetry (11) and wherein the mixing container (10) in an idle state (R) has no mixed material (13) and in an operating state (A) the mixing container (10) filled with mixed material (13) rotates on the circular path (14) characterized in that a non-contact measuring radiation detector (4) is arranged in a stationary manner on the housing (3) and is directed towards the circular path (14).
  2. The rotary mixer (2) according to claim 1, characterized in that the radiation detector (4) has a radiation sensor (5) on which incident radiation is focused, and the extent of the maximum area detected by the radiation detector (4) as a measuring spot (18) on the mixed material (13) is proportionally dependent on the distance between the radiation detector (4) and the mixed material (13).
  3. The rotary mixer (2) according to one of the preceding claims, characterized in that the measuring spot (18) in the idle state (R) is completely in the upper half of the surface of the bottom (7) within the mixed material receptacle (9) and in the operating state (A) at least part of the mixed material (13) is completely introduced into the beam path (17) of the radiation detector (4) in one or more rotational positions.
  4. The rotary mixer (2) according to claim 3, characterized in that the measuring spot (18) is circular and has a diameter that is not larger than the radius of the bottom (7) of the mixed material receptacle (9).
  5. The rotary mixer (2) according to one of the preceding claims, characterized in that the radiation detector (4) is connected to a data processing unit.
  6. The rotary mixer (2) according to one of the preceding claims, characterized in that the radiation detector (4) is part of a pyrometer (6).
  7. The rotary mixer (2) according to one of the preceding claims, characterized in that the data processing unit is set up to record the data units received by the radiation detector (4), to calculate individual temperature values from the data units and to determine the respective maximum of the individual temperature values in predetermined time periods.
  8. The rotary mixer (2) according to claim 7, characterized in that the data processing unit is configured to calculate the individual temperature values by specifying the emissivity of the mixed material (13).
  9. The rotary mixer (2) according to one of the preceding claims, characterized in that the mixing container (10) has a closable lid (19), in which a germanium disk (20) is installed, which is positioned in at least one rotational position of the mixing container (10) in the beam path (17) of the radiation detector (4) and is so designed that it has no influence on the measurement using the radiation detector (4).
  10. The rotary mixer (2) according to one of the preceding claims, characterized in that the mixed material (13) and the radiation detector (4) are arranged in a space which can be sealed in such a way that a uniform negative pressure compared to normal pressure can be generated therein, to which the mixed material (13) and the radiation detector (4) are equally exposed.
  11. Method for determining temperature using a rotary mixer (2) according to one of claims 1 to 10, characterized by the following steps: i) filling the mixing container (10) with the mixed material (13) and positioning the mixed material (13) in the beam path (17) of the radiation detector (4) with subsequent determination of the temperature of the mixed material (13) at rest as T 0 using the data processing unit; ii) transferring the rotary mixer (2) into the operating state (A) with a speed of rotation of the mixing container (10) on the circular path (14) of more than a predetermined number of revolutions per minute (rpm); iii) selective measurements of the mixed material temperature at regular time intervals; iv) determination of the maximum measured mixed material temperature after a predetermined number of revolutions.
  12. Method according to claim 11, characterized by the following additional step: v) Repeated determination of the maximum measured mixed material temperature after a predetermined number of revolutions.
  13. Method according to claim 11 or 12, characterized by the recording of the specific temperature maxima as a graph.
  14. Method according to one of claims 11 to 13, characterized in that the value of the time interval between the point measurements specified in milliseconds is not greater than the quotient of the radius of the bottom (12) of the mixed material receptacle (9) and a 60,000th of the speed (rpm) multiplied by the circumference of the circular path (14).

Description

The present invention relates to a device for determining the temperature of the mixture in a rotary mixer. Determining the temperature of a mixture allows conclusions to be drawn about its condition and thus also whether the desired thoroughness of mixing has been achieved or whether further mixing is necessary. Furthermore, continuously recording the mixture temperature during the mixing process is suitable as an in-process control and can quickly identify undesirable deviations during mixing, as well as segregation processes caused by overmixing. The literature on the state of the art mainly describes measurement techniques that require direct contact between a sensor and the mixture. DE 1 257 113 A The invention discloses a mixer for fine-grained, powdery, liquid, or pasty materials, comprising an upright, cylindrical, sealable mixing container and concentrically arranged, high-speed rotating mixing tools. Among other things, it aims to determine the continuously rising actual temperature of the mixture during the mixing process in a particularly simple and suitable manner. It is proposed to design a deflector for the mixture as a body tapering in cross-section in the direction of rotation of the mixing tools, with supply lines for liquids and/or gases and a thermometer. In a practical embodiment, a thermometer sensor is arranged in the deflector, protruding from the deflector near its lower end on the side facing the container wall. The sensor extends obliquely downwards and at an acute angle to the container wall. The sensor projects forwards from the deflector in such a direction that the rotating and upwardly forced mixture strikes the tip of the sensor practically perpendicularly. This prevents the mixture from settling in dead zones of the sensor and thus forming a heat-insulating layer on the sensor surface, which would make a largely delay-free and accurate thermometer reading impossible. The measuring lead of the remote thermometer is routed through the cavity of the deflector. The DE 10 113 451 A1 Disclosing a bearing housing for a stirring shaft, to which a stirring disc is preferably attached, with a lance which is connected at one end to the bearing housing and at the other end of which a temperature sensor is arranged, with a supply line for the temperature sensor which is at least partially The cable runs through the bearing housing and extends, at least partially, through the lance to the temperature sensor. Preferably, the lance is provided with a predetermined breaking point. Here, too, the problem arises that part of the temperature measuring device, in this case the lance, is located in the mixing vessel and is therefore exposed to the risk of excessive mechanical forces. The DE 10 2008 041 104 A1 The invention first discloses a mixing device consisting at least partially of an electrically conductive, preferably metallic, material. A heating device, comprising at least one coil excitable by an alternating electric field, is arranged such that eddy currents are generated in the electrically conductive material of the mixing container by the change in the magnetic field resulting from the altered current flow. This allows the mixing container and the material to be mixed to be heated quickly, as the eddy currents heat the mixing container. In a preferred embodiment, at least one scraper device is provided inside the container near the container wall and/or the container bottom. This scraper device is movable relative to the container wall. In the simplest case, the scraper device is static, so that the necessary relative movement is generated solely by rotating the container. The temperature of the material to be mixed can then be controlled according to the... DE 10 2008 041 104 A1 The temperature can be detected by a temperature sensor integrated into the scraper device, as this is in direct contact with the mixture. Alternatively, the mixture temperature can also be determined using a separate, product-contacting or non-contact temperature sensor placed in the mixing chamber. In either case, the temperature sensor is located within the mixing vessel. Another rotary mixer with a moving pyrometric temperature sensor is from the US5951164 A known. A disadvantage of the current state of the art is that all temperature sensors are currently positioned inside the mixing vessel. At high rotational speeds, such as those that can occur in rotary mixers, these temperature sensors are subjected to high centrifugal forces, and the electronic connection or wiring can lead to high maintenance costs or the frequent replacement of the sensors. Furthermore, measurement inaccuracies can arise if it is not possible to generate a material flow along the sensor, as baked-on material can act as thermal insulation. A non-contact sensor, where the sensor is nevertheless positioned inside the mixing vessel, would absolutely have to be positioned in such a way as to prevent contamination by the mixture. Th