Our research in this area investigates powder modelling, flow properties and the development of a toolkit to predict air-induced segregation.

If any of these projects are of interest to you, please contact us for more details

Predicting storage vessel requirements for discharge of extreme shape materials

The feedstocks used for the renewable energy industry are difficult to handle because of their irregular particle shape and size. The erratic flow of these particles during processing results in equipment down-time and waste.

Equipment providers/designers to the bioenergy industry are facing problems putting values to the mechanical properties of the material to characterise them. Methods of flowability measurement which work well with ordinary powder and granular particles totally break down, when applied to fibrous, irregular shaped biomass materials.

This project utilises a recently developed characterisation test to measure the tensile strength of fibrous bulk solids. This failure property has been combined with a new failure criterion to determine the critical outlet dimension for reliable gravity flow of fibrous materials. This potential design technique has been evaluated against actual silo discharge tests for a range of extreme shape biomass materials. It is anticipated that this will enhance reliable flow and eradicate poor handling and flow problems at power stations, energy from waste plants and bio-refineries.

Development of a 'toolkit' for controlling flow properties of engineered food powders (2014)

This project is designed to build upon the success of a recent project which has produced an instrument to measure the flowability of food powder ingredients, intermediates and products, (powder flow tester) so that the ability to measure flowability is extended into the practical understanding of how to control flowability of these powders in a cost-effective way with minimal effect on other performance properties.

The key deliverable will be a 'toolkit' to assist those people involved in formulating powder blends to select and apply flow-property-modifying ingredients to engineered powder blends, to deliver the optimum balance of fast development, low production cost, minimum addition level and minimum effect on other aspects of powder performance with consequent reductions in wastage of food materials. 

The concept of the toolkit is to give the user not just a body of science or a model, but a complete, integrated system of characterisation test(s), models, science and user guidance necessary to take a blend which has problematic flow properties, and turn it into one with acceptable flow properties quickly and economically with minimum compromise of its performance in other respects. 

The project is sponsored by the Department of Environment Food and Rural Affairs through the Advanced Food Manufacturing LINK programme for collaborative research, in conjunction with five industrial partners.

Improvement of constitutive physical CFD models for powder modelling (2014)

This project is designed to attempt to use CFD (computerised fluid dynamics) code in connection with the most advanced powder mechanics continuum constitutive models, to develop a system capable of giving realistic predictions of the flow of powder in actual handling equipment which is not currently possible.

Many raw, intermediate and finished materials are handled as powders, in the mining, minerals, chemicals, petro-chem, food, chemicals and pharmaceuticals industries; many billions of pounds worth in the UK alone.

In spite of massive differences in scale (milligrammes in pharmaceuticals to thousands of tonnes in minerals) many of the problems and challenges are the same, and the underlying physics are the same across the scales. In spite of the common use of powders, and many hundreds of references in the area over the last twenty years, making an accurate prediction of the flow of powders in a 'packed bed' through equipment such as hoppers, silos, feeders, coolers, strippers etc. using a computerised fluid dynamics approach remains elusive.

Improved discharge equipment performance for coals with poor handling characteristics (2014)

Some coals handled at UK steelworks and power stations exhibit flow characteristics that adversely impact upon their efficient transport and storage. In many cases this is because the equipment used has not been designed appropriately, giving rise to unreliable flow, variable discharge rates and undesirable flow stoppages. However, it is rarely economically justifiable to redesign and rebuild existing equipment. Consequently, Wolfson researchers are developing cost-effective alternatives to solve these problems, concentrating on the use of inserts and on the design and production of a discharge control device to help improve discharge regularity and repeatability for different materials

Low feed rate dosing of cohesive powders into processes (2013)

Conventional approaches to the discharge of cohesive powders invariably utilise physical agitators that pass through the powder on a cyclic path. Whilst this serves to disrupt the flow channel above the screw feeder (and thus prevent complete flow stoppages), it also introduces work into the static regions of material that can be found around and ahead of the flow channel. For some types of powders this approach can introduce the potential for electro-static charging (depending upon the electro-static work function for the powder/agitator) or contribute to particle attrition (especially for blends comprised of rod like particles).

It is therefore desirable to establish more accurately predictions of stress conditions in small scale handling equipment and model the implications of stress reduction upon geometrical requirements for reliable and consistent operation. A protocol for design options relating to the controlled metering of cohesive powders will be of considerable benefit to equipment designers and formulation developers.

This project was funded by EU Framework 7, Marie Curie Initial Training Network (ITN Powtech)

Modelling of dosator filling and discharge

This project builds upon investigation already undertaken by The Wolfson Centre on existing dosator equipment. Wolfson Researchers are working on a "toolkit" consisting of an improved model and a suite of powder characterisation techniques. Together, these will enable engineers and powder formulators to make predictions of the likely performance of any powder in a given machine. The toolkit will further allow evaluation of the likely improvements to be had from different formulations or engineering changes. Supplementary benefits include an improved understanding of what it is that makes powders easy or difficult to fill accurately using dosators, an indication of the effects of environmental conditions and a general improvement in process understanding. The Wolfson research team will gain a deep insight into this key technology in secondary manufacturing, with the potential to transmit this understanding to scientists and technologists in industry.

Engineering the green state of powder products (2012)

Constructed of a group of 17 researchers studying in six universities, the aim of this project was to address the problems associated with net shape forming powder compacts. The part taken by the Wolfson Centre was to investigate the effect of powder/granulate flowability on blend segregation during powder handling.

Development of a toolkit to predict the intensity and scale of air-induced segregation in powder handling and for flow compaction processes (2011)

It happens that some pharmaceutical powders tend to segregate whilst being handled on site, but by that stage if modifications to the powder or the handling equipment are needed they are often not economical. Instead manufacturers will opt to routinely discard those parts of the batch which are found to be afflicted. This project developed a model to predict segregation problems ahead of time and therefore avoid such measures.

Improving the adhesion of particulate ingredients to food products (2011)

This EU Framework six funded project focused on the defining characteristics that contribute towards the formation of bond strength between food-coating particles and base food products. As part of the project a novel laboratory scale impact tester to evaluate the adhesion strength of flavourings on food substrates.

Start up and running loads exerted by bulk materials on belt feeders – a comparison between experimental results and predictive techniques (2011)

This project was led by Professor M Bradley, assisted by Corin Holmes

This thesis reviewed the academic literature in the area of predicting loads exerted by bulk solid materials across the outlet of storage vessels, and, thereby, on to belt feeders, while also undertaking an experimental study, using an instrumented test rig to measure the loads acting on the feeder for three different bulk solid materials. A comparison of the experimental results with those predicted from the models identified in the literature review was also conducted.

Direct on-line measurement of wall friction of coal as an indicator of handleability (2009)

This project adapted a technique for the measurement of plate abrasion into a measurement of friction as the bulk solid is conveyed on a belt underneath the plate. The objective was to use continuous on-line measurement of wall friction (wall adhesion) to predict flow problems e.g. material build in transfer chutes and bunkers. This instrument was developed from lab to industrial scale and was subsequently trialled successfully on coal transfer belts at power stations and steel works.

Handling characteristics of biomass/coal mixes for co-firing: measurement techniques and establishing benchmarks (2008)

This project dates back to 2003, when power generators were co-firing biomass with coal to meeting UK Government emissions targets. The project investigated the flow problems that were likely to be encountered when handling coal-biomass mix instead of coal. This project led to the production of:

  • Large scale shear testers for characterising the flow properties of coarse biomass pellets and
  • The Best Practice Guide for Handling of Biomass Fuels and Coal-Biomass mixes, available at the Wolfson Centre.

Effect of flow channel profiles on repeatability of discharge rates from dispensing heads used for flow control of particulate materials in bulk (2006)

The project was prompted by several programmes of work undertaken for industry by the author with the aim of improving discharge efficiency, in terms of repeatability and consistency, of vessels of varying sizes and operational characteristics. A test rig was designed and constructed in order to facilitate a detailed assessment of the variability of discharge rates, which, in turn, indicated the problem areas existing which compromise accurate metering of materials.

The measurement of cohesive arches in silos using the technique of laser ranging (2003)

The aim was to measure the shape of the flow obstructions that formed over the outlet of the silo, to enable more appropriate design equations to be formulated than were in existence at the time. A pilot scale plane-flow silo with variable hopper geometry was constructed, along with a computer controlled laser ranging device to measure the arches that formed. Results and subsequent comparisons were recorded.

Investigations into the segregation of heaps of particulate materials with particular reference to the effects of particle size (1999)

The object of the project was to provide an improved understanding of the significance of principle variables that determine the propensity that a particulate solid bulk material will segregate. The most important outcome of the work was to develop a technique to predict the profile of segregation produced in a conical heap formed under identical conditions to that produced in a plane-flow vessel.