Cement, Energy and Environment July-Sep 2002

specific energy per ton of product to break the agglomerates in case of liquid injection. In the case of continuous mixers, also to be taken int o consideration is the ax ial dispersion effect, the possibil ity to vary the residence time, the hourly production related to the residence time, the degree of loading and the actual loadi ng. On the basis of the principle and the parameters of mixing, this article describes the mixers most frequently in use in the chemical, building, pharmaceutical, plastics, ceramics, food, environmental etc. industries to mix granul ar so lids between them and in certain cases, also so lid s with liquids or so lid s with gas . The list is nor exhaustive, as there are many variants as well as a multitude of possible uses: • Blending and Homogenising • Humidification: distribution of • • • • • • • liquids in solid masses Agglomeration: enlargement of the cross-selection of the powder particles introduced De-agglomeration: break ing apart of the agglo1:nerates Fluidisation: distribution of gas in the solid mass Sus pens ion: distribution of solids in liquids Coating: formation of a layer on the outer surface of the granules Drying: heating to remove the liquid part of the mixture Coo li ng: reduction of the materials temperature during mixing. By und e rsta nding the phenomenon of segregation and throu gh the desc ription of the worki ng principle of each type of mixer it wi ll be possible to interpret the choice criteria. Cuurresy : PoiVder handling processing. Vol. 1-1. No. /., Jan-Mar 02, Pp. 30-39 Fax: +49 5323 969 796 l~mai 1: 1/p(t'j lrans/er.:h-online.cum II 'eh: H'll'\1'./ranstech-on/ine. com SELECTED CASE STUDIES ON THE SILO QUAKING PROBLEM C. Wensrich, Australia Th is paper examines the quaking phenomenon from the perspective of f ive sepa rate in dustrial in stallations whe re quaking caused a s ign ificant problem. In each separate study the details of the installation are outl ined and the distinct issues surrounding the quaking problem at each site are described. ·What is clear from these st udi es is that quaking can occur in a variety of different systems and a sing le so lution to the problem is far from apparent. In some cases the problem can be addressed by a change in the procedures by which the install ~tion operated, however in some ci rcumstances no so lution is apparent. These case stud ies highlight the need for a better understanding of the phenomenon and its mechanisms. Although, seeming like very simple systems, the fiow ofgranular material s from silos can often be observed to di splay large, se lf ind uced, dynamic pul sations that are known as quakes. These quakes usually take the form of distin ct events that occur very rapidly (of the order of milli- seconds). With several seconds (possibly ·minutes) between each distinct quake. Courresy : Bulk Solids Handling, Vol. 22 (2002) No. 2, Mar.-Apt. 02, P I08, fi1x: +49 5323 969796 Email: llp@lranstech-unline. com Web: wwwlranstech-online.com T\VO DECADES DYNAMICS OF BELT CONVEYOR SYSTEMS G. Lodew[jks, The Netherlands The quest for a use ful design tool that incorporates the effect of dynamics of conveyor belts on the design of a conveyor system sta1ted halfway the 1950s . It was however not until halfway 1980s that the first useful design tool became available. In the earl y days of using dynamics of bel t conveyor systems the attent ion was focussed on analys is of both the stmts and the stops of long overland, high tonnage/li ft/ speed conveyors. With the sign ifi cant improvement of drive technol ogy over the last twenty years, however, it is now possible to start and (operationa lly) stop <l be lt conveyor in a very smooth manner. For analysis of these non– stationary conditions the application of belt conveyor dynamics is no longer required prov id ed tha t sufficiently long start ing and stoppi ng times are used. Therefore. the attention shifted to the analysis of emergenc y stops and th e determination of'what if scenarios. It is <1n i!Ius ion to assume tha t theoretical ana lys is g ives all the answers. A practical verification of the resu lts is of utmost importance to ensure that the assumptions made in the theoretical analysis were right and the advice given to the client correct. This paper gives an overview of th e work done on the ma th ematical descrip ti on of dynamics of belt conveyor systems till date and briefiy discusses the most impo1 ant variables that effect be lt conveyor dynam ics. It wi ll fu rther g ive some practical recommendations ai1d examples of the app lication of be lt conveyor dynamics in the design process of conveyor· sys tem s, the practical verifi cation of the resu lts and the lessons learned. Finally , it wi ll highlight the latest developments in the field and provide answers to frequentl y asked quest ions. Courresy. Bulk Solids llaiUI!ing, Vol. 22 (2002) No. 2. Mar. -Api.02, {' 12-1. Fax: +-19 5323 96 9796 Emai 1: llp(GJ !ransrech-online.com IVeb: Wll'lli.lranslech-unline.co111 FREE FLO\VING PRODlJCTI\TfY uave Laing, Mole Master, USA In general , almost a ll types of bulk storage vessels can suffer from bridged, arched, ratholecl, lumpy or :-