Cement, Energy and Environment July-Sep 2002

. SEEKfNG PERFECTION (Orrie Fenn (Operations DirecL01) , !'PC, Dr Tony Lange (MD) , OPTIN &.Johan Claw·en (General Manager) Dwaalboom cement plant) In 1999, Pretoria Portland Cement (PPC) introduced a new generation kiln cooler controller at its Dwaalboom cement plant. This controller differs from the well– established, rule-based controllers in that it is based primarily on Model Based Predictive Control technology. The controller provides optimal kiln/cooler control , improving not only the kil n' s thermodynamic behaviour but clinker quality as well. The control philosophy employed is novel and has been patented. The controller has been operating successfully for more than two years contributing signifcantly to clinker qual ity and production improvements. It was designed and installed in a co llaborati ve effort between PPC and local experts in the field of control, MES and automation soluti ons. The strategy was that PPC's cement knowledge, together with externally available control and automat ion knowledge wo uld faci litate the development of a truly new and innovative ki ln cooler ·controller. Courtesy :InTernational Cement Review, Aug. 2002 Pp 63- 68. E-mail: il?(o@CemNet co. uk Web site: CemNet. co. uk POSJMETRIC FEEDERS Pennsylvania Crusher Corporation [E-mail bchase@penncrusher.com Web: penncrusher. com} The company originally made its reputation based on the crushers and breakers they ' ve built since 1905. ··we produce more types and sizes of crushers and breakers than any other firm in the world'' sa id Chase, "but the company now offers the unique Posimetric feede r, a break-through 1n feeding technology that's been proven on the job. In fact , it's rapidly supplanting mo st older feeder technologies within the US and overseas. The principle ofthe Posimetric feeder by using a small Plexiglas model which was open at both ends, and running a pi ston throu gh it freely. "But fill this empty tube with a dry bulk so lid, and it 's then impossible to force piston through the tube. The material locks itself firmly agai nst the tube wall s, and that demonstrates the principle of operation that makes it so unique .... material bridging! In fact, if the material did not bridge, the feeder cold not feed ." When the hollow tube was filled with material , the piston, in fact, would not budge. Courtesy: Cement Americas July/Aug. 2002, P II, Fax. 312726-4 107/312- 726-2574 E-mail. primediabusiness.com Web: 111\JIJV.Cementamricas.com QUALITY AND STANDARD WHAT IS DELAYED ETTRINGITE FORMATION AND HOW IT CAN BE PREVENTED'? Kshemendra Nath P., RMC Readymix india Ltd. The damage to concrete caused due to de layed ettringite (calcium sulphoalumi nate hydrate) formation (DEF) is ass uming immense significance the world over. Damage in conjunction with ettring ite format ion in hardened concrete was first identified in heat– treated pre-cast concrete e lement, which during use had being exposed to open-air weathering with frequent wetting. A characteri stic feature of this type of damage is the conspicuous formation of ettringite in voids, cracks and the contact zone between the aggregates and the hardened cement paste without any external sulphate attack having taken place. Delayed ettringite formation is caused by the heat-induced decomposition of ettringite formed during initial hydration of cement in concrete. With rise in temperature there is drop in the thermodynamics stab ility of ettringite and it transforms into mono-sulfates. The the oriti ca l temperature for this transformation ranges between 70°C and 90°C. The ettr ingite decomposes at this temperature to form metastable monosul fates and sulfates. With subsequent cooling and in presence of water, this metastable compound reverts back to from expansive ettringite. Delayed ettringite fo rmation can cause product cracking to suddenly start appearing many years after manufacture. Courtesy : Materbuilder. Apr.-May 02. PI !. Fax: 8529259 Email: dicomnet@vsnl.com Web: wwH•.masterbuilderindia. com ONLINE MANAGEMENT Victor Lant, Analyser Systems (ASYS). USA The development of new and cost savi ng quarry raw material management procedures driven by the availabi lity of reliabl e and accu rate re al time e leme nt al composition information, has been made possible by the use ofso called prompt gamma neutron activation analysis (PGNAA) online analysers. The economic benefits derived from PGNAA are expected to lead to more widespread use of these belt mounted process control sensors, as well as better materi als management strategies.