Ladce has always understood thatstable clinker mineralogy and maxi-mum hydraulic reactivity is centralto the success of this strategy of

product innovation and development. Highand consistent clinker reactivity allows theadditions of granulated blast furnace slag,limestone and other extenders to be max-imised, while not compromising the finalperformance of the blended cement. Inorder to guarantee this stable clinker reac-tivity Ladce have developed a visionaryapproach to quality control together withvarious Slovak and foreign partners.

The development of this clinker miner-alogy control approach has taken placealongside an ongoing process of mod-ernising and upgrading the factory equip-ment. This has demanded a flexibleapproach to the implementation of thelong-term vision for quality, with elementsof the entire vision being introduced inconjunction with the wider modernisationof the factory.

Quarry chemistry controlLimestone and marl have been supplied tothe Ladce cement factory from the Butkovquarry for more than 100 years resulting ina complex layout with currently 15 loadingplatforms and multiple possible loadingpoints. The raw material deposit is variablewith limestone overlying marl, four differ-ent grades of limestone, and variation fromnorth to south along the loading platforms.Control of the composition of the run-of-quarry material from the Butkov quarry isthe first fundamental requirement of theLadce clinker mineralogy control vision.

No pre-homogenisation blending bed isprovided to blend the material from thequarry and installation of this equipmentremains under discussion due to the varia-tion in the composition of the raw materialthroughout the quarry. In order to stabilisethe composition of the run-of-quarry mate-rial loads must be continuously propor-

tioned directly from the loading points.The first requirement of such a continuousproportioning control system is a reliableestimate of the material composition ateach of the available loading points. Inorder to provide this Ladce has regularlysampled and tested the blast holesdrillings in the quarry for many years andhas built up a history of the compositionvariation. In addition, extensive geologicalinvestigations involving test bore holesand analysis of the core samples have beenconducted over the years. The first elementof the new vision for quality control was tocombine these twosources of informa-tion to enhance theestimates of thematerial compositionat each of the avail-able loading points.

The geologicalsurvey information isall available inCzech and Slovaklanguages and thisprompted Ladce toselect YMS fromTrnava, a Slovakgeographical infor-mation systems sup-

plier, to capture this data and incorporateit into a block model of the raw materialdeposit and reserve. This was completed inthe first months of 2002 ready for theintroduction of the continuous load propor-tioning control system in the third quarter.

UK cement industry consultant,Whitehopleman, has been working withLadce for three years and assisted in thedevelopment of the vision for clinker mineralogy control. In addition to thisassistance with the development of theconcept, Whitehopleman has also providedsoftware incorporating the necessary

51INTERNATIONAL CEMENT REVIEW / FEBRUARY 2003

ANALYSIS

Quarry toclinker

Povazská Cementáreñ a.s. Ladce supply cement into the central Europeanmarkets of Slovakia, Czech Republic, Hungary, Austria and Germany fromits factory at Ladce in the river Vah valley of western Slovakia. The company has been successful in selling all its cement production duringthe last five years despite the prevailing difficult market conditions.Central to this success has been a strategy of ongoing product innovationinvolving development of new cements targeted on specific applicationssuch chromateless, sewers and tunnels. With market conditions deteriorat-ing, particularly in Germany, this strategy will remain central to the success of the company.

Complex quarrying platforms

by Ing. Pavel Martauz, Director of Strategy & Quality, PovazskáCementáreñ a.s. Ladce & Dr Michael Clark, Whitehopleman

Batch blending at Ladce

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proportioning algorithms alongwith statistical process controltechniques. Ladce required a system that incorporated thelogic and features of the existing,manual, quarry chemistry controlregime as closely as possible,leading to the following featuresbeing built into the new com-puter based system.

Firstly, the location of everyblast-hole drilled in the quarry isentered into the system and thesoftware returns the compositionof the material at that point fromthe YMS block model of the quarry. In thisway the geological surveys and computerblock model are continuously involved inthe day-to-day control of the run-of-quarrymaterial composition. The features of theexisting quality control regime are incorpo-rated by provision of the facility to enterthe laboratory test analysis of the blast-hole drill chippings for cross-ref-erence and comparison with theanalysis returned from the YMSblock model. When all the blast-hole locations have beenentered into the system thesoftware gathers these intoblocks and provides theweighted average compositionof each block based on both theYMS model and the laboratorytests. Ladce personnel have theoption to select either estimateof the composition of the mate-rial block for use in the subse-quent proportioning of loadsfrom the quarry.

Secondly, the blasting of thedrilled blast-holes is enteredinto the system and this signalsto the software that the mater-ial from those blocks is nowavailable for loading. The sys-tem keeps a record of the com-position and location of all the blocks ofmaterial that have been blasted and arecurrently available for loading for use inthe proportioning algorithms. When all thematerial from a block has been loaded thisis also entered into the system and thesoftware removes that block from therecord of materials available for loading.

These first and second elements of thesoftware act as data management to ensurethat the proportioning algorithms advisethe quarry management of the loads to betaken from each loading based on the

materials that are actually available forloading at any time. The third element ofthe software is used at the beginning ofevery shift, or day, to determine the ratioof loads to be taken from the various load-ing points during an operating campaign.The system prompts the quarry manage-ment to nominate the first material to be

loaded by providing a list of the availableblocks for loading. Adherence to the long-term quarry development plan is encour-aged by ranking this list of the availableblocks dependent on the current deviationfrom the long-term plan on each of theloading platforms.

After nomination of the first loadingpoint the lime saturation target is enteredand the software then prompts the quarrymanagement to select the second loadingpoint to be mixed with the material fromthe first loading point. The software pro-

vides a list of the available loading pointsthat can be mixed with the first loadingpoint to meet the lime saturation target.In this way the software does not allow asecond loading point to be selected thatcannot be blended with the material fromthe first point. Again the list of the secondloading points is prioritised based on thedeviation from the long-term quarry devel-opment plan, however there is also theoption to prioritise the second loadingpoint to minimise the haulage distances tothe crusher.

After selection of the second loadingpoint the quarry management have theoption to blend the material from thesetwo points or add a third loading point tothe mix and control the silica or aluminamodulus in addition to the lime saturation.If blend is selected then the proportions ofthe materials from the first two loadingpoints to meet the lime saturation targetare provided. If a third or fourth material

is to be added to the mixthen the targets for silica or alumina modulus are entered,followed by selection of theloading points, and the proportions of material fromeach loading point are againprovided to the quarry management.

At the end of a campaign,loading materials from thevarious loading points thequarry management enter theactual number of tonnesloaded and the analysis ofthe composite run-of-quarrymaterial sent to the Ladcefactory. The software usesthese quantities and thecomposite composition toback-calculate the composi-tion at each of the loadingpoints. This provides a thirdestimate of the composition

of the material at each loading point forfurther cross-reference and comparisonwith the estimates from the YMS blockmodel and with the testing of the blast-hole drill chippings.

Raw mill feed proportioningThe quarry chemistry control is designed toensure that limestone of consistent chemi-cal composition is placed in the storagebins for subsequent delivery to the rawgrinding mills. In these raw mills the lime-stone is ground together with marl and

INTERNATIONAL CEMENT REVIEW / FEBRUARY 200352

ANALYSIS

Cement deliveries from Ladce

Quarry block model

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ANALYSIS

iron oxide corrective materialto meet the lime saturationand silica modulus targets forthe kiln feed.

Again, Whitehopleman hasprovided proportioning soft-ware to monitor and advisechanges to the individual feed-ers for each of the three rawmaterials based on the hourlysampling and testing of theraw mill product. Test resultsare read directly into the soft-ware from the X-ray fluores-cence spectrometer avoidingany possibility of operator error in theentry of the data. The software uses statis-tical process control techniques involvingthe principles of control and cusum chartsto avoid unnecessary adjustment of theraw mill feeders.

Additional complexity is required asthe Ladce factory uses batch blending toensure the homogeneity of the kiln feedand the statistical process control routinesmust consider the deviation of the batch

from the required targets rather than theindividual raw mill hourly test results.There is also the complication that electro-static precipitator dust can be added tothe batches of kiln feed raw mix at anytime during the building of the batch, andthe targets for the batch and the individual

raw mills must anticipate the impact of theaddition of this dust.

St Chromy real clinker mineralogy controlDr Stanislav Chromy from Brno in the CzechRepublic has been retained by Ladce as anadviser in the control of real clinker min-eral composition for many years. Dr Chromyis a specialist in clinker microscopy andhas developed a unique approach to clinker

mineralogy control. At Ladce this approachis based on microscopic examination of theclinker, however the approach would beequally valid with X-ray diffraction andRietveld Analysis.

Samples of clinker from the Ladce kilnare analysed under the microscope and the

quantities of alite,belite and interstitialmaterial are estimated.Significant deviationfrom the targets forthese mineral compo-nents triggers adjust-ment of the targets forkiln feed lime satura-tion and silica modulusin the Whitehoplemanraw mill feed propor-tioning software.The estimate of the realclinker phase composi-

tion, the oxide analysis determined by X-ray fluorescence and the free lime contentare also entered into the Whitehoplemansoftware. Multiple regression between thetrue mineral composition and the oxideanalysis is carried out providing coeffi-cients for the multiple relationshipbetween these dependent and independentvariables. This relationship can then beused to predict the real mineral composi-tion of clinker samples that have not beenexamined microscopically.

Dr Chromy is a strong advocate of thevisual inspection of clinker samples underthe microscope to estimate the true min-eral composition, however Ladce recognisethat this is not practical for hour-to-hourclinker quality control on shifts. Skilledpersons to make this visual analysis cannotbe provided on every shift and inevitablythere is variation between even the besttrained analysts. For this reason Ladcehave retained Kvant, a Slovak companybased in Bratislava, to develop a patternrecognition system that automatically esti-mates the clinker mineral composition ofthe samples presented to the microscope.

Achievements and future plansThe development and implementation ofthis vision for clinker mineralogy control isongoing, however at this interim stage significant improvements have beenachieved. Alite and belite content of theclinker produced on the Ladce kiln havebeen stabilised and enhanced strengthdevelopment from clinker has enabled awider range of blended cements to be produced, with an overall higher substitu-tion rate of clinker.

Many further enhancements and addi-tions to the control system are planned. DrChromy has developed methods for assess-ing the reactivity or combinability of kiln

Selection of first loading material from Ladce quarry

Loading ratio of material blends

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ANALYSIS

feed raw mix based on the mineralcomposition of the raw materials inaddition to the chemical composi-tion and fineness of grinding of thekiln feed. The four grades of lime-stone in the Butkov quarry eachhave different reactivities and thequarry chemistry control system willbe extended to take this into con-sideration and control the run-of-quarry material delivered to theLadce factory to reactivity as well aschemistry targets. This is expectedto contribute significantly to thestability of kiln operations and fur-ther enhance the clinker mineralogycontrol.

In the quarry load tracking willbe introduced to close the control loop andprovide feedback on the proportions actu-ally being taken from each of the nomi-nated loading points. This will be com-bined with a cross-the-belt analyser on therun-of-quarry material being delivered tothe factory to automate and enhance theback-calculation of the composition of thematerial at each of the loading points.

The Whitehopleman raw mill feed pro-

portioning software will be extended toincorporate Dr Chromy’s techniques for thecontrol of the reactivity and combinability.Sieve residues at 90 and 200 microns willbe entered into the system and combinedwith the chemical composition to deter-mine the overall reactivity of the raw millproduct. If significant deviation from tar-get is detected using statistical processcontrol techniques the software will advise

the operators to adjust the feedrate to the mill and the settingsof the classifier to bring the rawmix back to the reactivity target.

Finally, the Kvant pattern recog-nition software will be extendedto provide estimates of the crystalform and polymorph of the clinkerminerals. Distinguishing betweenthe α, β and Γ forms of belite,and the triclinic, monoclinic andrhombohedral forms of the alitewill further enhance the controlof the clinker hydraulic reactivityand further the long-term strat-egy to produce high qualityblended cements.This article has outlined the

Ladce vision for clinker mineralogy andhydraulic reactivity control. This vision iscontinuously evolving and Ladce expect tocontinuously refine, enhance and expandthis vision to ensure that its long-termstrategy of providing innovative blendedcements targeted on specific applicationscontinues to underwrite the future successof Povazská Cementáreñ a.s. Ladce.________________________________ ❒

Microscopic examination of clinker

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