5th World Congress on Industrial Process Tomography

The foundation of Industrial Process Tomography (IPT) is to conduct several measurements around the periphery of a multiphase process, and use these measurements to unravel the cross sectional distribution of the process components in time and space. This information is used in the design and optimisation of industrial processes and process equipment, and also to improve accuracy of multiphase system measurements in general.

There has been tremendous development within measurement science and technology over the past couple of decades. New sensor technologies and compact versatile signal recovery electronics are continuously expanding the limits of what can be measured and with what accuracy this can be done. Miniaturisation of sensors and the use of nano-technology push these limits further. Also, thanks to powerful and cost-effective computer systems, sophisticated measurement algorithms previously only accessible in advanced laboratories are now available for in situ on-line measurement systems. The process industries increasingly require more process related information, motivated by key issues such as improved process control, process utilization and process yields, ultimately brought forward by cost effectiveness, quality assurance, environmental and safety demands.

Industrial tomography methods have taken advantage of the general progress in measurement science, and aim at providing more information, both quantitatively and qualitatively, on multiphase systems and their dynamics. In many cases, the traditional approach for such systems has been to carry out one local or bulk measurement and assume this is representative for the whole system. In some cases, this is sufficient. However, there are many complex systems where the component distribution varies continuously and often unpredictably in space and time.

IPT has several similarities to medical tomography: Several sensors or detectors are used to provide multiple measurement data at the boundary process which can be used to reconstruct the cross-sectional component distribution. Unlike medical systems, many IPT technologies are fast in order to also unravel the dynamics of the processes. Some IPT systems provide several thousand data sets or images per second.

A large number of IPT measurement principles have been, and are still being, developed: electrical methods, such as the measurement of capacitance, inductance and resistance, optical and radiation-based methods ranging from infrared, microwave, X-rays, gamma-rays and even neutrons, magnetic resonance, ultrasound and acoustic methods to mention a few. The sensor technology for a specific application is primarily selected to achieve sensitivity to a physical property which is different for the components of the process, e.g. density, or electrical permittivity. For the measurement or imaging of more than two components, multi-modality systems are often employed, either by measuring with one principle at several wavelengths or energies, or by combining several independent sensor principles. IPT is inherently interdisciplinary, so that R&D requires skills in process engineering (chemical, combustion, pharmaceutical, etc), physics and electronic engineering for the sensor system, and mathematics and computer science for data processing algorithms.

The output of an IPT imaging system need not be an image: it is just as often merely a few parameters describing the component distribution in the process. Actually, the complexity of an IPT system depends very much on the application: full imaging systems are most often encountered in the development of multiphase processes or the equipment for these, whereas in situ on-line process measurement systems frequently use a limited number of sensors and only a few parameters as output. In some chemical processes, the degree of component mixing is important; in others, it is the other way around and the degree of separation is the issue.