The use of arrays of different types of sensors and the interpretation of signals derived from them provides a change in philosophy compared to traditional methods of particle characterisation and analysis. This change is necessary if measurements are to be made on line, in real process using sensor hardware that is inherently low cost, low maintenance and fault tolerant. This first report describes the objectives and deliverables of the overall programme of work, their significance, reviews the status and research development of new sensing methods that could be applied to flowing particulate systems.
In the review (Part I) attention is focused on concepts and technologies that might be used to enable measurement of the size and shape of particulates on-line in dilute and concentrated mixtures using multiple sensor arrays. The use of synergistic information from multiple sources in order to assist in the overall understanding of a phenomenon is deemed to be of considerable importance. However the application of such data fusion methods may rely upon the availability of a specific ‘model’ that describes the phenomena that are being investigated. Such a model is not always readily available, in which case more abstract methodologies based on multivariate statistical/chemometric analysis may be required.
The viability of using multiple sensors to gain more data (and hence more knowledge) about a particulate system is sensible, but the practical application is so system-specific that it is often not possible to make meaningful comments of a generalised nature. It is demonstrated that the two key factors include: translating the information that the user requires (or believes that they require) into a measurable parameter; and, defining the hierarchy of the measurements and/or analysis system so that it is sufficiently adaptable to tolerate loss of input from one or more sensor(s) or to allow new sensors inputs to be incorporated. Some examples are given relating to the use of microelectrical resistance tomography applied to gas/paste mixtures.
Experimental measurements to establish the operational reliability of different sensing strategies to achieve the above goals are reported here (Part II). It is concluded that a system of continuous measurement using 4 multi-segment ultrasound sensors and an array of current/voltage electrodes can be utilised. For example, in the case of size measurement the electrical measurement system, current injection and voltage detection (from independent electrodes) will be made and interpreted using a hierarchy of models including combinations of direct parametric interpretation and particle timing information. The next stage is fabrication of such a sensor system. Useful contact has been made with several IFPRI members regarding the use of such a system.