Microwave processing of vermiculite

Vermiculite is a clay mineral that is generally used for a wide range of applications such as in agricultural, horticultural and construction industries. This is due to its various properties which include high porosity, lightweight, thermo-insulating, non-toxic and good absorption capacity when exfoliated. The objective of this research was to critically evaluate the fundamental interaction of electromagnetic waves with vermiculite from different source locations and to understand the mechanism of exfoliation in an applied microwave field. When vermiculite minerals are placed under the influence of high electric fields, they expand due to the rapid heating of their interlayer water, which subsequently builds up pressure that pushes apart the silicate structure. The degree of exfoliation is directly related to the intensity of the applied electric field. The principal areas covered in this thesis include: a detailed review of the fundamentals of microwave processing and issues surrounding scale up; a critical literature review of vermiculite mineralogy, and previous methods of vermiculite processing and their limitations; understanding the interaction of microwave energy with vermiculite by carrying out mineralogical and dielectric characterisation; microwave exfoliation tests of vermiculite minerals from different source locations and a comparative energy and life cycle analysis of microwave and conventional exfoliation of vermiculite. A detailed review of the literature revealed that conventional exfoliation of vermiculite by gas or oil fuelled furnaces has significant limitations such as emissions of greenhouse gases, high-energy requirements (greater than 1 GJ/t), health and safety issues and poor process control. All work reported so far on microwave exfoliation of vermiculite has been limited to laboratory scale using domestic microwave ovens (2.45 GHz, power below 1200 W) and the route to scale up the process to industrial capacity has not given due consideration. Mineralogical characterisation of vermiculite from different geographical locations (Australia, Brazil, China and South Africa) revealed that only the sample from Brazil is a pure form of vermiculite while the other samples are predominantly hydrobiotite. All the samples have varying degrees of hydration with the Brazilian sample having the highest total water content. The presence of water in any form in a material influences its dielectric response and ultimately the microwave absorbing properties. The dielectric characterisation carried out on the different vermiculite samples shows that the vermiculite mineral structure is effectively transparent to microwave energy, but it is possible to selectively heat microwave absorber, which is the interlayer water in the vermiculite structure. The continuous microwave exfoliation tests carried out at both pilot scale at 53-126 kg/h and the scaled up system at 300-860 kg/h demonstrated that microwave energy can be used for the industrial exfoliation of vermiculite at high throughputs and is able to produce products below the specified product bulk densities standard required by The Vermiculite Association (TVA). The degree of vermiculite exfoliation depends on factors such as power density, feedstock throughput, energy input, interlayer water content, particle size of the feedstock, and vermiculite mineralogy. The highest degree of exfoliation was recorded for the Brazilian sample, which also had the highest water content. Life cycle analysis (LCA) frameworks by the International Organisation for Standardisation (The ISO 14040: principles and framework and ISO 14044: Requirements and guidelines) and British standards institution (PAS2050) were used to carry out comparative life cycle analysis of vermiculite exfoliation using microwave heating and conventional (industrial and Torbed) heating systems. The results showed that the microwave system potentially can give an energy saving of about 80 % and 75 % over industrial and Torbed Exfoliators respectively, and a carbon footprint saving potential of about 66 % and 65 %. It can be concluded that the reduced dust emission and noise from the microwave system would improve the working conditions, health and safety. Furthermore, the methodology discussed in this project can be used to understand the fundamental of microwave interaction with perlite and expanded clay, which are minerals with similar physical and chemical compositions as vermiculite

Understanding our celestial neighbors: an indian perspective in planetary sciences and exploration

The planetary exploration program of the Indian Space Research Organization is described. The important results obtained from the two successful missions, Mars orbiter Mission (2014) and the earlier Chandrayaan-1 mission (2008-9) to moon are summarized. High-resolution maps of Valles Marineris enabled several surface, aqueous and atmospheric features to be delineated and the highly elliptical orbit of MOM enabled imaging of the surface of the farther side of Deimos as well as study of Mars exospheric constituents. The results from Chandrayaan-1 mission changed many lunar concepts e.g. from dry, passive and inactive to moon to wet, tectonically and volcanically active moon. Some recent results based on the space borne and laboratory based study of Titan, Pluto, Comets and meteorites coming from Mars and Vesta are summarized. The future planetary exploration plans, such as Chandrayaan-2 and second Mars mission are briefly mentioned

In-Soil Measuring of Sugar Beet Yield Using UWB Radar Sensor System

Yield mapping is a basic entity of the Precision Farming concept and provides crucial information about the success of cultivation. Several approaches to site-specific yield recording during the sugar beet harvest are known. Most of them are based on the weighing of sugar beets together with soil tare. Another real-time yield mapping approach with the option of plant population counting is based on estimating the mass of individual sugar beets on the basis of their maximal diameter. The main goal of the research was to develop and evaluate a yield recording procedure based on radar technology, which will provide non-invasive in-soil detection and identification of single sugar beets in order to enable the counting of individual sugar beets and determining of the single sugar beet root mass. Further goals were to enhance the radar technology for other applications in the agriculture, as a general goal, and to define applicability restrictions of practical utilisation of the system for the sugar beet and similar crops. The research activities have been divided into laboratory and field experiments. The results of the laboratory experiments have provided valuable information about the measuring system’s behaviour, which enabled the successful field measurements. The used method allowed the identification and detection of 90% to 96% of sugar beets under test in the various field conditions, with correlation coefficients between real sugar beet positions and detected positions of about 99%, and average positioning error from 1,1 to 3,6 cm. The correlation coefficients between single sugar beet root masses and recorded reflected energy amounts were for the majority of tests over 70%, and the best results have been on the level close to 90%. This project was a joint venture of the Institute for Agricultural Engineering from Bonn and the Technical University of Ilmenau.Teilflächenspezifische Ertragsmessung von Zuckerrüben im Boden mittels UWB Radarsensorsystem Die Ertragskartierung ist ein wesentlicher Bestandteil des Konzeptes „Precision Farming“. Die Erntemasse von Kulturpflanzen ist für den Landwirt eine elementare Information über den Erfolg pflanzbaulicher Maßnahmen. Es sind mehrere Verfahren zur Ertragsermittlung von Zuckerrüben während der Ernte mit dem Bezug auf Teilflächen bekannt. Ein sensorischer Ansatz besteht in der Pflanzenzählung und Ermittlung der Masse der einzelnen Zuckerrüben über den maximalen Durchmesser. Das Hauptziel dieser Forschungsarbeiten war die Entwicklung und Bewertung eines berührungslosen Ertragserfassungssystems für Zuckerrüben, das teilflächenbasiert eine Zählung und Massebestimmung der Einzelrüben ermöglicht. Die weiteren Ziele bestanden in der Weiterentwicklung der Radartechnologie für andere Einsatzgebiete der Landwirtschaft und in der Bestimmung der Anwendbarkeitsgrenzen des Systems für Zuckerrüben und ähnliche Wurzelfrüchte. Die Forschungsaktivitäten fanden im Labor und unter Feldbedingungen auf Versuchsparzellen eines typischen Zuckerrübenstandortes statt. Die Ergebnisse unter Laborbedingungen lieferten wertvolle Informationen, die erfolgreiche Feldmessungen ermöglicht haben. Die angewendete Methode hat in unterschiedlichen Messbedingungen eine 90% bis 96% erfolgreiche Zuckerrübenidentifikation ermöglicht, mit Korrelationskoeffizienten zwischen tatsächlichen und detektierten Zuckerrübenpositionen von um 99% und einem durchschnittlichen Positionierungsfehler von 1,1 bis 3,6 cm. Die Korrelationskoeffizienten zwischen der Einzelrübenmasse und der gemessenen reflektierten Energiemenge lagen im Bereich von über 70% und die besten Ergebnisse erreichten Werte von 90%. Das Projekt wurde in der Zusammenarbeit des Instituts für Landtechnik Bonn und des Instituts für Kommunikations- und Messtechnik der Technischen Universität Ilmenau durchgeführt