An alternative solution to the grinding equation in cumulative size distribution form

An alternative analytical exact solution for the discrete-size kinetic equation of grinding in cumulative-fraction-passing mode was formulated as a matrix equation and tested successfully for predicting the transient evolution of the cumulative particle-size distribution and also for back-calculating the selection and breakage function parameters. The compact matrix form of the equation makes it computationally simple, and easy to extend the treatment to continuous mills. The solution should be particularly useful for parameter estimation purposes as it is expected to reduce the variability of the estimates because of the monotonic nature of the cumulative size distributions

Tinkal Cevheri Kolloidal Atıklarının Flokülasyon Özellikleri

Çalışmanın kapsamı: 1.İki farklı kilden oluşan süspansiyonların kimyasal dengeye ulaştıkları andaki flokülasyon davranışlarının incelenmesi. 2. Saf simektit veya dolomit mineralinin farklı hidrodinamik koşullardaki polimer etkileşimlerinin incelenmesi 3.Kil süspansiyonlarının farklı katyonlar (Ca2+ ve Mg2+) ile koşullandırılmasından ve mineral yüzeylerinin polimer adsorpsiyonları için hazırlanmasından sonra flokülasyon davranışları incelenmesi ve en uygun koşullandırmanın belirlenmesi ile hidrodinamik koşulları değiştirerek flokülasyon performansının yükseltilmesi. 4.Farklı polimer çiftlerinin (Dual-flokülant etkisi) tatbiki ile süspansiyondaki değişim gözlenecektir. 5.Bor konsantre tesislerinin atıklarından alınacak atık su numunelerinin yüzey yanıt yöntemini kullanarak optimum dozaj, optimum hidrodinamik koşul, optimum su geri kazanımı, optimum bulanıklık ve katı–sıvı ayırımı değerlerinin belirlenmesi

CAKE FILTRATION-RATE EQUATIONS - A REVIEW OF CLASSICAL AND MODERN APPROACHES

Fundamental concepts of cake filtration - cake compressibility, liquid drag-pressure drop relationships, average porosity, and external mass balance - are presented. Two distinct approaches to the formulation of cake filtration rate, the classical and the modern theories, are critically reviewed. The definition of average specific cake resistance is re-examined. The equivalent specific cake resistance for a compressible cake is shown to be the harmonic mean of local specific cake resistances. Weaknesses of the classical theory in data analysis are pointed out. Recognition of the cake-filter medium interface by the modern theory as the rate-controlling part of the filtration system is stressed

Grinding kinetics of steady-state feeds in locked-cycle dry ball milling

The size-discrete breakage rate and distribution parameters of the grinding kinetic model are mostly determined in laboratory batch mills using single-size feeds. However, there is evidence in the literature that particle size distribution in the mill affects the breakage parameters. Previous work studying this effect was mostly conducted with feeds whose size distributions were not closely representative of those normally dealt with in industrial mills. This study was undertaken with the main purpose of investigating the effect of particle size distribution on the breakage parameters of quartz and calcite minerals in dry ball milling using steady-state feeds obtained from Bond's locked-cycle tests. Different closing screen sizes were used in the locked-cycle work to produce different feed size distributions that would resemble feeds to industrial closed-circuit ball mills. Experimental results have shown that the breakage rate parameter of the top size interval increases as the feed size distribution in the mill becomes finer. There is some evidence implying grinding-environment dependency of the non-normalizable breakage distribution parameters. The cumulative-basis one-parameter linear population balance model gives a simple and reliable representation of the kinetics of closed-circuit dry ball milling

An industrial comparative study of cement clinker grinding systems regarding the specific energy consumption and cement properties

This paper is concerned with a comparative analysis of modern cement grinding systems, namely, combined grinding (Comflex (R)), high-pressure roll mill (HPRM) grinding, and horizontal roller mill (Horomill (R)) grinding. Cement production trials were run with these grinding systems in the same cement plant by using the same clinker/gypsum feed to produce cements of almost identical chemical compositions and similar Blaine fineness values of about 3600 cm(2)/g. The grinding systems were compared in terms of specific energy consumption and mortar properties of the produced cements. The specific energy consumption and the cement setting times increased in the order of combined grinding, HPRM grinding, and horizontal roller mill grinding. No significant difference was detectable among the water demands of the cements from the three grinding systems. The HPRM cement was superior in strength development, particularly at early ages

FEN BİLİMLERİ ENSTİTÜSÜ/LİSANSÜSTÜ TEZ PROJESİ

KİMYASAL ÖN KOŞULLANDIRMANIN PARÇACIĞIN ÇATLAMA ŞEKLİ VE MİNERAL SERBESTLEŞMESİNE ETKİS

Characterization of clay rock samples of a borax ore in relation to their problematical flocculation behavior

Beneficiation process in the Kirka Borax Concentrator in Turkey generates a tailings effluent containing 3-10% solids that are composed mainly of colloidal particles of clay-rock-type gangue minerals and some unrecoverable borax fines. These colloidal particles form very stable aqueous suspensions in the tailings, hindering solid/liquid separation and clean water recovery. This leads to difficulties in the sustainable and environmentally acceptable operation of the concentrator. Flocculation studies on these colloidal suspensions had shown that the particles of the gangue minerals presented significant resistance to destabilization and remained in suspension forming high-turbidity supernatants in settling tests. For this reason, this study was undertaken to characterize the nature of such gangue particles with the intention of understanding the reason for their extreme colloidal stability and poor performance in polyethylene oxide (PEO)-induced flocculation tests. Particle size and zeta potential measurements elucidated the suspension stability with d(80) <= 5 mu m and zeta-potential <= -70.1 mV. XRF and XRD studies showed that the problematical particles were rich in Mg-minerals (dolomite and trioctahedral smectite). A plausible explanation of the insufficient destabilization might be that the surface Mg ions have very high hydration energy and hold the water molecules very tightly by blocking the surface for the polymer adsorption and particle-particle interaction. FTIR spectra indicated the lack of isolated hydroxyl groups on the particle surfaces. Due to this vital drawback, the polymer chains could not be adsorbed through hydrogen bonding mechanism and this highly turbid suspension could not be flocculated

Filtration testing of a ceramic capillary filter produced from a high-silica glaze

A laboratory procedure for the production of a ceramic capillary filter from a high-silica glaze was described and its filtration response was tested in dead-end and periodic vacuum filtration modes with suspensions containing micron and sub-micron clay particles obtained from a ceramic factory wastewater stream. The same glaze raw material ground to two different levels of fineness was used for the production of the porous ceramic substrate and its surface coating. The coating particulate sol was deposited onto the substrate by the filtration technique. The filter substrate and the coating were sintered at relatively lower temperatures (950-980degreesC) than conventional ceramic sintering. The filter indicated a non-clogging behavior in both of the filtration modes, and proved a potential for filtering large volumes of dilute clay slurries by periodic filtration operations

Assessment of grinding additives for promoting chromite liberation

Liberation of the valuable minerals of an ore from its gangue is a prerequisite for the economic recovery of the valuable minerals to concentrates. Mineral liberation is achieved by reducing the size of ore particles in various crushing and grinding devices. The fineness to which the ore must be ground, so as to yield sufficient degrees of liberation, increases if the valuable minerals with small grain sizes are disseminated throughout the gangue. Intensive fine grinding, however, increases energy costs and can lead to the loss of very fine untreatable particles into the tailings. Therefore, research should be oriented toward developing methods to foster breakage through the mineral grain boundaries to accomplish liberation at relatively coarser grinds. The purpose of this study is to determine if the pretreatment of the samples of a chromite ore with aqueous solutions of some salt and surfactant additives could improve the liberation by promoting preferential fracturing at the grain boundaries between the chromite and silicate minerals in the ore. For this purpose, untreated and pretreated samples of - 9.53 + 6.35 mm size fraction of the ore were broken in a drop-weight tester, and the liberation spectra and the mass distribution of the resultant progenies were measured and compared. Optical and scanning electron microscope images and spectroscopic tools were used to find evidence for grain-boundary fracturing in the breakage progeny fragments. Results support the promoting effect of hydrolysis on grain-boundary fracturing. Aqueous salt and surfactant species enhance grain-boundary fracturing by forming surface complexes and dislocating aluminum atoms at the grain boundaries. Grain-boundary fracturing yields exposed chromite surfaces and enriched chromite content in the coarse progeny particles. The grain-boundary weakening is associated with slight hardness variation along the boundary