Investigation of breakage behavior of different mineralogical and morphological characteristic pumices

The objective of this study is to analyze dry grinding behavior of four different pumices in terms of Bond grindability value, selection and breakage parameters values. For this purpose, firstly, Bond grindability test were made for four pumices. Then, eight different mono-size fractions for each of pumices were carried out between 1.7 and 0.106 mm formed by a \({\surd 2}\) sieve series, and ground batch wise in a laboratory ball mill for determination of breakage parameters. Finally, S _i and B _i,j equations were determined from the size distributions at different grinding times, and the model parameters (S _i , a _T , α, γ, β and \({\phi_{j}}\)) were compared for four different pumice samples.     

Application of artificial neural network method to predict the breakage properties of PGE bearing chromite ore

In the present investigation, systematic grinding experiments were conducted in a laboratory ball mill to determine the breakage properties of low-grade PGE bearing chromite ore. The population balance modeling technique was used to study the breakage parameters such as primary breakage distribution (B_{i, j}) and the specific rates of breakage (S_i). The breakage and selection function values were determined for six feed sizes. The results stated that the breakage follows the first-order grinding kinetics for all the feed sizes. It was observed that the coarser feed sizes exhibit higher selection function values than the finer feed size. Further, an artificial neural network was used to predict breakage characteristics of low-grade PGE bearing chromite ore. The predicted results obtained from the neural network modeling were close to the experimental results with a correlation of determination R² = 0.99 for both product size and selection function.     

The kinetics and efficiency of batch ball grinding with cemented tungsten carbide balls

Cemented tungsten carbide balls (hereafter abbreviated as WC balls) are commonly applied in grinding of wasted tool steel for reuse owing to their extraordinary surface hardness (89.5 HRA) and high density (14.5 –14.9 g/cm³). In this study, grinding tests were conducted with WC balls on quartz ore to estimate comminution kinetics. Compared with steel balls, they provided high breakage rates, lower energy-specific breakage rates, and finer breakage distributions due to their high density. Simulations were conducted using an energy-based population balance model. The simulated results demonstrated that WC balls had higher throughput for coarse particles and lower energy efficiency for fine particles. Subsequently, a preliminary criterion for ball selection was established and indicated that WC balls could be substituted for steel balls to certain particle size ranges.     

Characterization of the Grinding Behavior of Binary Mixtures of Clinker and Colemanite

The purpose of this study is to determine the grindability and kinetic behavior of clinker and colemanite in cement production when they are ground separately and together. Bond and Hardgrove grindability methods were employed to determine grindability properties clinker and colemanite by varying proportions. Bond work index (BWI) values of clinker and colemanite are 18.89 kWh/t and 12.33 kWh/t, respectively. BWI value of mixture decreases by added colemanite and the experimental BWI values of mixtures were lower than those of calculated, considering their proportions. Hardgrove grindability index (HGI) values of clinker and colemanite are 51.81 and 99.62, and Blaine fineness values are 920 cm²/g and 2430 cm²/g, respectively. As colemanite addition increases HGI and Blaine fineness values also increase. Experimental Blaine fineness values are greater than calculated values meaning that during intergrinding different ingredients do not show the same behavior as in the case of separate grinding. These findings explain that clinker particles have an abrasion effect thus an extra grinding effect on colemanite particles. The specific rates of breakage were determined through kinetic experiments to understand the grinding mechanisms of colemanite, clinker and their mixtures. The model parameters of S_i, a_T, and α were established in kinetic experiments.     

Influence of interstitial filling on breakage kinetics of gypsum in ball mill

Gypsum is an industrial material used in many applications such as building and chemical industry, fertilizer manufacture, medicine and dentistry. In these industries, there is need for finely ground gypsum. Energy consumption is very high in grinding processes. Therefore, the effects on breakage kinetics of powder filling and ball filling were investigated on gypsum samples taken from the Denizli-Honaz region (Turkey), for batch grinding conditions based on a kinetic model. For this purpose, firstly, eight different mono-size fractions between 1.7 mm and 0.106 mm formed by a √2 sieve series were obtained. Then, S_i and B_i,j equations were determined from the size distributions at different grinding times, and the model parameters (S_i, a_T, α, γ and ?_j) were compared for five different proportions of powder filling (5%, 7.5%, 10%, 15% and 20%), and three different proportions of ball filling (25%, 35% and 45%). Finally, model parameters are discussed for each test.From the result of tests, obtained of the effect of ball filling and powder filling on the grinding, it was found our results differed from those of other investigators.     

The effects of ball filling and ball diameter on kinetic breakage parameters of barite powder

The absolute fineness of the ball diameter and the ball charge grading are important factors for the optimal operation of a ball mill. Therefore, the effects on breakage kinetics of the ball diameter and the fractional ball filling were investigated on the barite powder at batch grinding conditions based on a kinetic model. For this purpose, firstly, six different mono-size fractions were carried out between 0.850 and 0.106 mm formed by a 2 sieve series. Then, S_i and B_i,j equations were determined from the size distributions at different grinding times, and the model parameters were compared for three different ball filling and three different ball diameter. The results of tests, the effect of ball filling and ball diameter on the grinding were found to be different than other investigators regarding some results.     

Experimental investigation of the impact breakage characteristics between grinding media and iron ore particle in ball mills

The particle breakage of the ball mill is an extremely complicated breakage process. It is difficult to quantify and describe the particle breakage behavior. In this study, a drop-ball experimental setup was developed to demonstrate the impact process of grinding media on ore particles. The quantitative analysis of the effects of particle size, impact energy, and the number of impacts on particle breakage behavior was performed separately. The results show that the breakage probability model and product size distribution model used can be excellent to predict the particle breakage behavior for the single-particle impact experiments. The breakage probability of particles is highly sensitive to impact energy and particle size, exponentially increasing with the increase of impact energy. In addition, the application of the t_n-t₁₀ relationship provides a convenient means to characterize and predict the particle size distribution. In multi-layer particle impact experiments, the captured thickness of ore particles is approximately 2 layers during the crushing process. The broken mass of iron ore particles is proportional to the number of concessive impacts at different impact energies. This paper provides theoretical and methodological support for the evaluation and optimization of particle breakage in ball mills.     

Impact of grinding aids on dry grinding performance,bulk properties and surface energy

In dry fine grinding processes the relevance of particle-particle interactions rises with increasing product fineness. These particle-particle interactions reduce the grinding efficiency and complicate the process control. The adsorption of grinding aid molecules on the product particle surface is a common measure to handle these effects. To ensure an efficient grinding aid application, the impacts of additives on particle and bulk properties, which influence the micro-processes inside the mill, need to be understood. Within this study the effects of several grinding aids on dry fine grinding of limestone in a laboratory vibration mill were investigated. Unlike in many other scientific works, the impacts of grinding aids were analyzed on different levels simultaneously: Grinding success and agglomerate size distributions were evaluated by wet and dry particle size measurements, respectively. Additionally, material coating on the grinding media, powder flowabilities and particle specific surface energies were measured. It was shown that all of the investigated grinding aids influence the grinding efficiency. However, the formation of agglomerates is not necessarily linked to the product fineness. Furthermore, a strong impact of certain grinding aids on the flowability of the product powder was determined. Thereby, the bulk flow behavior also determines the grinding result as it affects the stress mechanism inside the mill. Moreover, a direct relation between surface energy and powder flowability as well as agglomeration behavior could be demonstrated.     

Effect of grinding aids on the kinetics of fine grinding energy consumed of calcite powders by a stirred ball mill

An experimental investigation was carried out on the ultra-fine grinding of inorganic powders using a stirred ball mill. The power consumed in the grinding process was measured, and the comminution coefficient, K, in the grinding kinetics equation was examined, based on an analysis of the relationship between the experimental specific surface area and the particle-size distribution of ground products. The effect of grinding aids on the comminution coefficient, K, was also investigated. It was demonstrated that the grinding rate for calcite could be improved by the addition of grinding aids. When using grinding aids, K improved by 16.0% and 34.2% for 60 wt% and 70 wt% slurry concentrations, respectively. Thus grinding aids are very effective in the submicron range grinding process.     

Investigation of the breakage parameters of gypsum as dependent on interstitial filling in a laboratory ball mill

Gypsum is an industrial material used in many applications such as building and chemical industry, fertilizer manufacture, medicine and dentistry. In these industries, there is need for finely ground gypsum. Energy consumption is very high in grinding processes. Therefore, the effects on breakage kinetics of powder filling and ball filling were investigated on gypsum samples taken from the Denizli-Honaz region (Turkey), for batch grinding conditions based on a kinetic model. For this purpose, firstly, eight different mono-size fractions between 1.7 and 0.106 mm formed by a \({\surd 2}\) sieve series were obtained. Then, S _i and B _i,j equations were determined from the size distributions at different grinding times, and the model parameters (S _i , a _T , α, γ and \({\phi_{j}}\)) were compared for four different proportions of powder filling (5, 7.5, 10 and 15%), and three different proportions of ball filling (25, 35 and 45%). Finally, model parameters are discussed for each test. From the result of tests, obtained of the effect of ball filling and powder filling on the grinding, it was found our results differed from those of other investigators.     

Analysis of ball mill grinding operation using mill power specific kinetic parameters

With a view to developing a sound basis for the design and scale-up of ball mills, a large amount of data available in the literature were analyzed for variation of the two key mill performance parameters: power specific values of the ‘absolute breakage rate of the coarsest size fraction’, S^*, and ‘absolute rate of production of fines’, F^*, with some of the important operating and design variables such as the mill speed, ball load, particle load, ball diameter and mill diameter. In general, values of both the mill performance parameters were found to vary significantly with the mill operating conditions. The nature and relative magnitude of variation for the two parameters also differed significantly. Moreover, the effect of any particular variable on the S^* and F^* values was found to be significantly different for different sets of operating conditions. It has been emphasized that, as the purpose of grinding is to produce fine particles, the mill design and scale-up work should be based mainly on the F^* parameters. Moreover, it is not correct to regard the S^* values to be independent of the mill design and operating variables as a general rule, especially for a fine analysis of the performance of the grinding systems.     

Practical strategy to produce ultrafine ceramic glaze: Introducing a polycarboxylate grinding aid to the grinding process

In this work, a polycarboxylate comb-like polymer was used as grinding aid for ceramic slurry, and the effect of addition of this grinding aid on ceramic process property was highlighted. The grinding efficiency of the polycarboxylate grinding aid (PG) in terms of the particle size distribution and specific surface of unit volume of the ceramic slurry being ground were investigated. Consequently, the PG that was synthesized via free radical polymerization under the condition of an APEG/AA/MA molar ratio of 0.3:1:1, an initiator dosage of 5 wt%, and a reaction time of 6 h at 90 °C, provided better grinding efficiency than those of the triethanolamine and other commercial grinding aids. Specifically, with a dosage of 0.21% and 2 h of grinding, the d₉₇ and d₅₀ of ceramic slurry decreased from 13.956 μm and 2.043 µm to 3.739 µm and 0.561 µm, respectively. The cumulative distribution, frequency distribution and SEM results exhibited a uniform particle size distribution for ceramic ground with PG-C. Furthermore, the sintering experiment indicated that a lower processing temperature was capable of producing ultrafine ceramic. These improvements indicated the potential application of the PG as an efficiency ceramic grinding aid, which further facilitating the preparation of uniform ultrafine slurry by a sand mill.     

Grindability of Quartz in Stirred Media Mill

Nowadays, ultrafine grinding in the submicron particle size range is becoming an increasingly conventional process. One of the mostly used ultrafine grinding ways is the size reduction in the so called stirred media mill. This article deals with the experimental investigation of wet grinding of quartz in a stirred media mill. The applicability of the introduced operating Rittinger index and the lower limit size of Rittinger law are studied. Furthermore, the effect of solid concentration of suspension, ball filling ratio, circumferential speed of the stirrer, and size of grinding media on the fineness (median particle size and specific surface area) was examined. Additionally, a relative grindability calculated from the operating Rittinger index is introduced in order to compare the efficiency of stirred media milling. It was found that the grinding conditions greatly affect the applicability of Rittinger's law and its lower limit size.     

Studying the effect of different operation parameters on the grinding energy efficiency in laboratory stirred mill

In this study, considering different operational parameters for stirred media mill, change in specific energy was compared to the change in R_x values, i.e. the cumulative weight of the material undersized to a specific sieve. R values, namely R₃₈, R₇₅, R₁₀₆, were measured before and after grinding in stirred mill. The change in R_x (ΔR_x, %) values were calculated and they were used to evaluate the certain unit of effectual energy (Ecb). This abovementioned calculation is performed by proportioning the Specific Energy (SE) to ΔR_x values. The effectual part of SE is considered to be the ratio of the energy needed only for size reduction in grinding and it should be related to the ΔR_x. The relative Ecb ratios of different grinding conditions give the relative specific energy efficiency ratio (SEe). The relative specific energy efficiency ratio is inversely proportional to specific grinding parameters and ground product particle sizes. The relative specific energy efficiency can be considered as the relative amount of energy for various grinding conditions. The variation between relative energy amount and the previously specified particle size provides a realistic comparison of different grinding parameters. The abovementioned variation could be employed to understand the resistance particle size which is a new concept to describe the particle size at which the maximum effectual SE is directly used. In the context of this study, it was aimed to figure out the interrelation between specific energy efficiency and PSD variation along with the resistance particle size.     

Effect of grinding conditions on mechanochemical grafting of poly(1-vinyl-2-pyrrolidone) onto quartz particles

Grinding of quartz in an aqueous solution of 1-vinyl-2-pyrrolidone (VP) in a stirred media mill results in grafting of poly(1-vinyl-2-pyrrolidone) (PVP) onto the quartz particles as proven by FTIR-spectroscopy. The grinding kinetics, the particle size of the final product and the amount of PVP grafted onto the silica particles depend on grinding conditions like VP and quartz concentration, pH and size of grinding media. The grinding kinetics becomes slower in the presence of VP due to the damping effect of the forming PVP chains. The final particle size, however, is almost independent on VP concentration. The amount of PVP grafted onto the silica particles ground for 12 h increases with growing VP concentration because the amount of adsorbed VP and the polymerization rate increase with growing VP concentration.The primary particle size and the kinetics of particle breakage do not depend on the pH-value of the dispersing medium, whereas the degree of agglomeration of the particles decreases with increasing pH-value of the medium. Under alkaline conditions, however, less PVP is grafted onto the quartz particles than under neutral or strong acidic conditions. The reasons for these effects are pH-dependent interactions between the grafted PVP chains and the surface hydroxyl groups on the quartz particles. If the quartz concentration in the suspension decreases the grinding kinetics becomes much faster because the specific energy input increases with decreasing particle concentration if the other process parameters are kept constant. For a very low quartz concentration (1 wt.%), however, after 7 h of grinding the particle size measured by dynamic light scattering starts to increase with grinding time. SEM investigations reveal that grinding of 1 wt.% quartz in aqueous VP solution for longer than 7 h results in the formation of plate-like particles.     

Analysis of grinding aid performance effects on dry fine milling of calcite

The control mechanism in the production of fine particles is important in dry grinding processes, which are popular in the grinding of some minerals. The behavior of the fine particles with each other and with the mill environment is complex and needs to be investigated in detail (on a micro-scale) in every application. One of the parameters controlling the fine particles in a mill is the use of the correct amount and type of grinding aid. Mechanisms of action must be understood well to develop grinding aids and fully utilize their positive effects. As a general explanation, with the use of grinding aids, the production tonnage can be increased at the desired product fineness, as well as achieving a finer product at the same production tonnage. However, it is necessary to know other mechanisms and effects to increase efficiency and correct use. The influence of grinding aids on the dry fine grinding of calcite using several analysis methods was revealed in the present study. Within the context, the results were assessed considering grinding performance (particle size distribution and size reduction ratio), product quality (color properties), flowability, adsorption properties (FTIR), and agglomeration behavior (SEM). Moreover, the tested effect of each grinding aid was discussed for each analysis, and the collected results were combined around a summary core diagram.     

助磨剂组分对缓凝剂作用效果的影响及其机理探究

分别掺加3种常用助磨剂组分三乙醇胺(TEA)、丙三醇(PG)和多聚磷酸钠(STPP)进行水泥粉磨试验,控制出磨水泥的比表面积在(375±5)m2/kg范围内,测试了各水泥试样的凝结时间和粒径分布等基本性能。选用常用缓凝剂组分葡萄糖酸钠(PN),探究了3种助磨剂组分对缓凝剂作用效果的影响,通过水化热分析、X射线衍射(XRD)分析和缓凝剂分子吸附量分析揭示了助磨剂组分对缓凝剂作用效果的影响机理。结果表明:TEA和PG对缓凝剂的作用效果存在明显的负面作用,而STPP显著改善了缓凝剂的作用效果;一方面,助磨剂通过自身的早强(或缓凝)作用影响缓凝剂的作用效果,另一方面,助磨剂组分也会影响缓凝剂分子的吸附量进而改变缓凝剂的作用效果。     

Effects of Mill Speed on Kinetic Breakage Parameters of Four Different Particulate Pumices

In this study, the effect of mill speed was investigated on different particulate pumice samples at batch grinding conditions based on a kinetic model. For this purpose, S _i and B _i,j equations were determined from the size distributions at different grinding times, and the model parameters (S _i , a _T , α, γ, and φ _j ) were compared for three different mill speed (fraction of mill critical speed; 65%, 75%, and 85%).

The effect of fraction of mill critical speed (φ_c) on the grinding for model parameter a _T found to be different for four different pumices. Additionally, in this study it was found that optimum grinding occurs at φ_c = 85% for all pumice samples, in contrast to the 75% of critical speed of the ball mill.     

Predicting breakage behavior and particle size of bronze and cast iron machining chips pulverized by jet milling

It has been proposed that the breakage behavior of particulate materials can be described by two material parameters f_mat and W_min. f_mat describes the resistance of the material to fracture in impact pulverization and W_min characterizes the specific energy which a particle can absorb without fracture. It is shown in this study that this concept can be used to quantify breakage behavior of bronze and cast iron chips in jet milling process and also to predict particle size of the jet milled product. Different tin bronze and cast iron chips with varying initial size were pulverized in a target plate jet mill with different velocity. f_mat was found to be in the range of 0.06–0.09 and 0.18–0.25 for bronze and cast iron alloys, respectively. For the cast iron alloys f_mat increased with increasing content of carbon and silicon. Similarly, for the bronze alloys, f_mat increased with increasing tin content. An equation was developed to predict mean particle size of the jet milled chips as a function of the kinetic energy, initial chip size and material parameters. The experimental results of various alloys confirmed that the mean particle size after single and multiple impacts were accurately predicted.     

Stabilization of Local Anesthetics in Liposomes

Abstract

The first-order hydrolysis rate constants of local anesthetic drugs have been measured in aqueous buffer solution, k_B, and in liposomes, k_obs, at pH 12.2 and 30°C. Also, the fraction of drug associated with the lipid phase, f_L, and the partition coefficient between the aqueous and lipid phase, Kg, were determined. The stability of benzocaine was measured in several liposome compositions, and as a function of benzocaine concentration, phospholipid concentration, and ionic strength of the medium. Values of the rate constant in the lipid phase, k_L, were estimated from a simple kinetic model and predictions of the relative contributions of k_L and k_B to k_obc were made. Different methods of liposome preparation, and the stabilities of local anesthetics in liposomal and micellar systems were compared.