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Working Party on Mechanics of Particulate Solids

Technical Projects



The correct structural design of storage silos for granular solids depends on the lateral and vertical stresses that are exerted by the stored solids on the silo walls. Standard structural design specifications are reported in international design codes as Eurocode EN 1991-4:2006 [1] and in related national standards. The estimate of the load that acts on a vertical silo wall is usually performed by applying the Janssen method of differential slices [2], which requires the evaluation of the horizontal to vertical stress ratio or the lateral pressure ratio, K. An experimental device for the measurement of the horizontal to vertical stress ratio had been purposely built and tested for fine and cohesive solids [3].
Experimental campaigns in the project were dedicated:
1) to find out a reproducible procedure able to provide representative measures of the ratio of vertical to horizontal stresses which free flowing and cohesive materials;
2) to determine the principal sources of error in the experimental campaign;
3) to find out any possible improvement in the design of the cell.

[1]  Eurocode 1. DD ENV 1991-4 (1996).
[2]  Janssen, H.A. Zeitschr. d. Vereines deutscher Ingenieure, 39, 1045-1049 (1895).
      As reported by Sperl, M., Granular Matter 8, 59-65 (2006).
[3]  Barletta, D. and Poletto M. Granular Matter 15, 487–497 (2013).

Contact: M. Poletto (U Salerno, IT)


The increased use of biomass materials in industries is causing more and more handling problems, many of them associated to bottlenecks. Nowadays, there is still a lack of knowledge in the flow properties of biomass materials. The irregular shape and the elastic, fibrous, flaky, and stringy nature that present, is responsible of the completely different behaviour to those commonly found in the process industry; characterization methods are being urgently demanded. WP members are working on the study of biomass flow during the last 5 years. The initiative started in 2011 with a demonstration project called Bio4Flow, involving 4 countries. It was funded by Processum Biorefinery Initiative AB. The activities continued aiming at creating a European network on biomass handling related activities. Related projects in progress are an ITN-Marie Curie proposal titled “Efficient, reliable and safe BIOmass HAndling, Pretreatment and Processing for a sustainable EU Bio-based economy” (BIOHAPPBY) and a COST Action titled “Towards the Security of Supply of Biomass and Solid Waste Feedstock - Efficiency and Safety for the Bioeconomy (EFFSAF)”. Partners from countries such as Spain, Italy, Sweden, United Kingdom, France, Germany, Portugal, Denmark, Poland, Serbia, Turkey, Israel and Australia, are participating in these initiatives. Furthermore, the debate on biomass handling problems is also pursued in forums such as the 7th International Conference for Conveying and Handling of Particulate Solids – ChoPS, September 2012, in Friedrichshafen (Germany) (roundtable discussion) or the 2nd International Symposium on Handling and Hazards, July 2014, in Madrid (Spain) organized by WP members. A significant number of industrial consultancy projects related to biomass handling issues have been already carried out. The experience gained is also being used to train specialists in this field. The PhD thesis titled ‘The effect of pellets physical properties on handling of pelleted biomass fuels in practical use’ is being written up by M Abdulmumini. This research has been funded by PTDF, Nigeria and has been undertaken in collaboration with Forever Fuels Ltd.

Contacts: Diego Barletta (U Salerno, IT), Sylvia Larsson (SLU, SE), Robert Berry (U Greenwich, UK), Álvaro Ramírez-Gómez (UPM Madrid, SP)



Prior investigations by the Working Party encountered considerable scatter in the results of wall friction tests obtained by various experienced bodies testing bulk materials on contact surfaces that were carefully selected to have common properties. An initial series of tests will be conducted by UK participants and a preliminary examination made of the reports and test results to review the suitability of the process, procedure and presentation of results.

Contact: L. Bates (Ajax Equipment, Bolton, UK)



The WPMPS workshop endeavors to increase the acceptance of DEM-codes for simulation of bulk solids behavior. This requires the codes to be validated, which in turn needs carefully selected problems with a good experimental database for test runs. As an initial step a workshop shall produce a framework for engagement between academic researchers, professional software companies and potential industrial beneficiaries of DEM numerical simulations and identify areas that need significant further development both in terms of computational methodologies as well as the experimental validation procedures. It is hoped that in the longer term, the group of researchers brought together for the event will form the nucleus of a wider project formation aimed at setting the European/International standards of "best practice" in DEM Simulation software development and implementation in a broad range of industry sectors. Projects developed in this direction were PARDEM - PARticle Systems: Training on DEM Simulation for Industrial and Scientific Applications, an EU Funded Framework 7, Marie Curie Initial Training Network (2009-2013), and T-MAPPP - Training in Multiscale Analysis (MA) of multiPhase Particulate Processes and systems (PPP) also an Initial Training Network funded by FP7 Marie Curie Actions ITN (2014-2018).

Contacts: S. Luding (TU Delft, NL), J. Ooi (U Edinburgh, UK) and U. Tuzun (U Surrey, UK)



Much information is available on the properties of bulk material, but broad industrial experience indicates that there is often inadequate appreciation of the characteristics that are relevant to the satisfactory performance of solids handling equipment in the formation of a contract between the purchaser and supplier. The British Materials Handling Board has undertaken to remedy the deficiency by preparing a 'Guide to the Specification of Bulk Solids for Storage and Handling Applications'. The Working Party endorsed this initiative and looks to co-operate with a view to attaining European acceptance of the document as a working tool for agreeing the requirements between user and supplier of the value of relevant physical properties of bulk materials that are to be used in any solids storage and/or handling project. This Guide is in preparation for draft circulation.

Contact: L. Bates (Ajax Equipment, Bolton, UK)



Since 1969 the characterization of bulk solids has been the focus of the work of the "Working Party on the Mechanics of Particulate Solids" of the European Federation of Chemical Engineers. Led by John Williams and Jan Novosad the WPMPS developed the first international standard on the measurement of the flow properties of bulk solids during the 1970's and 80's. After its publication in 1989 this "Standard Shear Testing Technique for Particulate Solids Using the Jenike Shear Cell" or SSTT became the common worldwide basis for silo design. Globalization has made us feel that anything documented in internationally accessible standards must be usable for everybody. However, the knowledge about proper shear testing spreads only slowly through the educated world. It is my believe that one reason for this unsatisfactory state remains the language barrier. Therefore, after the German translation published in 2005, now a Czech edition of the SSTT has been prepared.

Contact: J. Zegzulka (U Ostrava, CZ)


© DECHEMA e.V. last update March 10, 2015