Professor Haroun Mahgerefteh
Our research in instrumentation is mainly concerned with the design and development of novel techniques for applications in environmental pollution monitoring and particle technology. The work is highly industrially oriented thus enjoying close links with industry, having resulted in several awards and prizes. Students with interest in experimental work and theoretical modelling are welcome to apply to carry out research work in any one of the following areas.
Particulate emission monitor
Sulphur is a natural constituent of diesel fuel and contributes to the emission of particulates- the visible part of which appears as smoke. Despite the fact that the human respiratory system acts as a highly efficient filter for coarse particles, recent studies have shown the smallest particles (<3 microns) are capable of penetrating deep into the lungs, where their physical presence can increase airway resistance and susceptibility to infection and in severe cases leads to fibrosis of the lung and eventual death from cancer related causes. At present time, there is no satisfactory method of monitoring such particles on an on-line basis. We are at present working on a new device based on a coaxial capacitance technique which has demonstrated considerable promise for this purpose. It works on the basis of relating the dielectric constant of the exhaust stream to the concentration of the particulates present within it. We are at present working on improving sensitivity as well as investigating the effects of temperature and humidity on the system's response.
On-line settling velocity transducer for waster water applications
The separation of solid/liquid suspensions by gravity sedimentation is a common process in several industries ranging from mineral processing to environmental pollution mitigation operations. Of particular current interest is the on-line monitoring and characterisation of waste water treatment plant. This is in the light of the fact that the estimated investment required in order to meet the recent EC Urban Waste Water Directive is of the order £107 billion. Accordingly, the measurement of settling or sedimentation kinetics is of primary importance since this governs the handling characteristics of such dispersions, and hence provides information on the optimal design specification of the appropriate sedimentation equipment.
At present time no satisfactory technique is available for this purpose.
The instrumentation team at UCL have recently developed a novel vibrating reed technique which is capable of on-line monitoring of settling velocities and sedimentation profiles in a variety of systems including liquid/solid and liquid/liquid dispersions. As well as in waste water treatment monitoring, the method has potential applications in a variety of other industries including paints, ceramics, dairy products and pharmaceuticals. Work at present involves development of multiple reeds in parallel with theoretical/empirical modelling of sedimentation kinetics of polydispere systems (both dilute and concentrated).
Vibro-spring Particle Size Distribution Analyser
Approximately 30% of the chemicals produced in the world are in the form of powder and nearly all aspects of the technology relating to their manufacture, handling or application require a knowledge of the particle size. The instrumentation team at UCL have recently invented a particle size distribution analyser, based on a resonating spring, which is capable of sizing particles in the range 20 to 3000 micrometers. The unit has been successfully evaluated against a range of powders with different shapes and flow characteristics. Pre-production prototypes constructed through joint funding from industry and DTI are being installed at some of largest multinational companies in the world.
Our next challenge is to extend the technology for on-line operation thus allowing the immediate adjustment of the particle size if and when required.
Thermogravimetry analysis (TGA) involves the continuos monitoring of the mass of a substance as a function of temperature. This method of sample characterisation has found applications in almost all areas of chemistry and its allied fields. However a common problem associated with conventional techniques available for this purpose is that they are either expensive or non-robust. The majority suffer from the effects of temperature gradients set up within the test sample during the heating cycle. These may in turn produce markedly different results even using the same technique.
We have recently designed and developed a novel instrument for TGA which overcomes most of the above problems. Basically the technique works by relating the resonant frequency of a reed to the mass of the test sample mounted at its free end. As measurements are obtained with the sample in a fluidised state, the complications associated with no-uniform temperature gradients are all together removed. We have tested the unit up to a maximum temperature of 500 oC. A typical mass resolution for 0.5 g sample is better than 1.5%.
For example, a thermogravimetric unit has recently been developed which is capable of accurately measuring the decomposition rate of substances in a fluidised state at temperatures
as high as 1200 oC.