CEE Oct-Dec 2002

- TECHNOLOGY UPGRADATION PROCESS & OPERATION AN AID TO GRINDING Dr . Lunfi·u nco So lf if i, /)a vide Padomlll and Amw Bra\'0 ofMpei ·~iJ.I Th is article is a summary of the use of add itives in the production of cemen t. focuss ing on th e mechan ism o f act ion used by grind ing aids (GA). A disti nction will be made between pure GA and G!\ - performance enhancers. that act on the mec hani ca l characterist ics of th e cement. Fi nal ly. the bene fi ts of util is ing cement additives are cons idered, together w ith a brief outli ne on their industrial and economic evaluation. In modern grinding it is essential that the grind ing uid improve not on l) the mill production capacity but also the quality o f the finished cement. I n the case o f gr in di ng of' bknded cements (pozzo lonic cemen ts, slag cemems or lly ash cements). grinding aids are no more sul'lic ient and it is advisab le to opt for a tai lor-made cement addi ti ve. the so-ca ll ed performa nce enhancers. ('our/c.\\' · lntemaliono/ Cement Rc1•ielt'. Sep. 2002, 1)1191-93, /:'-mail' mfoa CemNet .co.uk ll'eh: ('emNet. co. uk AN AID TO PRODUCTION W Zinuner. I ;)R !ndustriclechnik GmhH Fo r many years, air cannons have proven themselves in low temperature app l ica t ion (fo r example. silo activation) as well as in high-temperatu re appl ica tions. Tocla:. they are v i r tu al ly indipen~ahk as reliable production aids. !\ ir cannons reduce the risk of p roduct io n mal funct io ns and minim ise. or even elimi nate. the need fo r manual c leani ng. Furthermore. th ey notably decrease the wear to hea t-res i stant k i In refractory, whereas other clean ing methods are much more abrasive. In low-temperature applications, ai r cannons are used o n silos fo r addi ti ves and for loading silos. The increasing use o f' secondary ra w material s orten leads to new deposi t formations. Therefore there are many di ffe rent appli cati ons availab le ror air cannons. T he sound wave causes material parti cles in the vicinity of' the blow outl et to oscillate, (an effect, based on th e resul ts or th e so- ca ll ed acousti c-horn in hi gh-ca pacity boilers) : th e pneumati c pu lse performs the mechanical cleaning, usua ll y car ri ed out by stokl: rs. and I or high-pressure hydraul ic systems. As production aids. air cannons ge nera ll y req uire a ve ry high avail ubility. I !ere, malfunctionscan lead to considerable stra i ns on product ion. or even stoppages in production. f- or this reason. the sys tems sho ul d have a reliable. simple and clea r design. Furthermore. relevun1 mai ntenance pa rts shou ld be easi ly access ible '' ithout havi ng to disman tle the air cannon vessels. T he air can nons <tre pneumatica ll y cont roll ed via solenoid valves. For many ye~1rs. the va lves have been housed in protective cases. made out or sheet stee l. An essential operational feature or the air can nons arc i ts blow nov.les . They gather or di sperse the air impulse stream depending on the probkm area. Simpk pipes. 3 1 which are used as blowi ng elements tend to produce a dot-matrix output. and arc therefore not an integral part of the operation. Isobar ic swo rd nozzles have prove n themselves especially su ita b le fo r l ow- tempe r atu re applica ti ons . They allo\\ even st ubbo rn mate rial , SLi ch as used foundry sand, to be removed easily from rectangular bunkers. The positi oning o f the nozzles and thei r eiTect ive range depends upon whether the depos its have mai nly nn amorphous or crysta lli ne structure. T he li fetime or t he nozzles depends upon their' arious exposures to temperature. chemical substances (such as chlorides and sulphides) and corrosive agents. O rten. nozzles arc rep laced during planned system shutdowns. l'oday there arc ot her ulternativcs avai lab le to the classica l high– tempera ture noz7lcs (ul tra-high– alloyed ma tainl) or VSR-lJIIL nonlc system. !\ ir cannons alone are on I ~ a pan of' an overall cleani ng ~~stem. I I ighly effective and stable no.ales optimise the overall cleaning. while innovative control techniques he lp to m inimise air consumption. I n conjunction \\ ith robust. durable. simple and highl y el'fectivc air cannon uni ts the cost of such production aids can be kl.!pt lo\\'. Therefo re, th is inc reases the ciTcc tivencss or the ai r cannon S) stem and provides a positive impulse f'or product ion. as well as. the quality or the product. ( 'our/cs.\ ·: World ( 'ement Sefl. 10U2. Pp I03 - I fr. t.'ncJIIin• 11u ]<J. Fax: +.f./(0) I 151- -1891.)2 t.'-nwil · IIIClll<a li'OI'Idcemcnt cum l 'RL: ll 'll 'll'. li'Orldcement.coJ/1