Driving Innovation in Product Design and Manufacturing Using 3D Printing
3.1 State of the Art Limestone Level Sensors
Limestone level is an important measuring parameter in the industrial lime production domain. Generally, the level is the measure of the height of a substance contained in a tank with respect to a point taken as reference. It is a linear measure, typically expressed in percentage or in millimeters and can be continuous or with point values: The continuous sensors measure the level inside a specific interval and determine the exact quantity of substance in a determined volume, while the point level sensors indicate only if the substance is on or under the measurement point. In the lime production industry, this is tricky business. Bulk stones, dust, high temperatures and other factors, prevent many electronic devices currently on the market from being reliable. Obstacles include:
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Capacitive level sensors, principally developed to provide point value signals, only indicate whether the substance is above or below the sensing point. Generally, they detect levels that are excessively high or low. They have always shown installation and mechanical strength limitation of the probes due to immersion modality in the material. Radioactive level devices, such as Gamma Ray types, are regulated by safety and environmental legislation. The accuracy in measuring levels can be compromised and the readings can be confused when layers of dust or foam become substantial or when measuring turbulent surfaces. Electromagnetic level sensors are critical from the point of view of the accuracy and reliability of measurement. Calibration must be done precisely according to the material to be measured. It is unsuitable to have dirty applications or processes where magnetite may be produced. Ultrasonic level sensors are used when the level cannot make contact with the material under level detection. However, the measurement is not accurate in cases where the material is powder or the surroundings have critical noise, temperature and pressure.
In processes such as twin or more than two shafts kilns in which the lime production processes occur, it is clear that the above technologies have many defects and limitations. It is not possible to use traditional tools, which are not able to resist the working conditions of the calcination process and cannot carry out accurate, precise and continuous measurements. Therefore, there is a need to provide an optimized, simple, practical and efficient sensor, which solves the technical problems described above, plus carries out accurate level measurements for application specific to limestone baking regenerative kilns.
Traditional shaft level indicators are composed of a drum of 500 mm diameter, on which is wound a steel rope that supports a 50 kg counterweight, operated by:
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An electric motor, capable of moving the counterweight along the lime kiln preheating zone in order to select the desired work area( approx. 5 meter height)- The ABSOLUTE LEVEL.
IIC Journal of Innovation- 45-