Grinding Aid Research Articles

Pan-milling to prepare ultrafine high-density polyethylene powder with sodium chloride serving as grinding aid

In this article, our self-designed pan mill equipment was used to pulverize high-density polyethylene (HDPE) to prepare its powder product. This pan mill based on three-dimensional shear forces shows much better pulverization effects on ductile polymer materials when compared with conventional pulverizing equipment based on impact force, and it can mill original HDPE pellets (particle size: 3–4 mm) into fine powder (particle size: 75 μm) at ambient temperature. To further improve the pulverization efficiency to obtain ultrafine HDPE powder, sodium chloride (NaCl), serving as a grinding aid, was comilled with HDPE. Taking the advantages of the cutting and isolating effects of NaCl crystals, HDPE can be pulverized into ultrafine powder with the particle size below 10 μm. Another advantage of NaCl as a grinding aid lies in an easy removal process through water wash, thus conveniently separating from hydrophobic HDPE powder. This technology provides a novel and efficient method to prepare the ultrafine powder of those polymers with high ductility and low melt point, and shows a promise in future commercial application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Parameters Influencing on Mechanochemical Synthesis of Lanthanoid Ferrites

Reactive grinding using a planetary ball-mill has been applied to the mechanochemical synthesis of lanthanoid ferrites, LnFeO3 (Ln: La, Pr, Sm, Gd, Dy, Yb). Colloidal lanthanoid hydroxides, Ln(OH)3, have first been formed from their oxides in organic liquids under grinding. The hydroxides not only promote the size reduction of the other reactant Fe2O3 in acting as the grinding aid but react with Fe2O3 to form hydroxide-complexes. The hydroxide complexes can be converted to LnFeO3 by the following stress-induced dehydration-condensation reaction. The reactivity strongly depends on the free energy change of hydroxide formation (delta GR) for the lanthadoid oxides and an electrostatic parameter of lanthanoid ions (Z/r), where Z is the ionic charge number and r the ionic radius. Although the delta GR values for all Ln2O3 are negative, the high Z/r value disturbs the formation of hydroxide-complexes. The adequate combination of the starting materials and the influence of the grinding stress have been discussed.

Preparation of Li[Ni 1/3Co 1/3Mn 1/3]O 2 powders for cathode material in secondary battery by solid-state method

Employing Li 2CO 3, NiO, Co 3O 4, and MnCO 3 powders as starting materials, Li[Ni 1/3Co 1/3Mn 1/3] O 2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the synthesis process. After successive heat treatments at 650 and 950 °C, the prepared powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy, and transmission electron microscopy. The powders prepared by adding salt (NaCl) as grinding aid exhibit a clear R ▪ m layer structure. The powders by other grinding aids like heptane show some impurity peaks in the XRD pattern. The former powders show a uniform particle size distribution of less than 1 μm average size while the latter shows a wide distribution ranging from 1 to 10 μm. Energy dispersive X-ray (EDX) analysiss show that the ratio of Ni, Co, and Mn content in the powder is approximately 1/3, 1/3, and 1/3, respecively. The EDX data indicate no incorporation of sodium or chlorine into the powders. Charge-discharge tests gave an initial discharge capacity of 160 mAh·g −1 for the powders with NaCl addition while 70 mAh·g −1 for the powders with heptane.

Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill — Examination of grinding kinetics of using grinding aids

Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill — Examination of grinding kinetics of using grinding aids

Production of mechanically activated rock flour fertilizer by high intensive ultrafine grinding

This paper provides a first assessment of the use of mechanical activation to enhance the availability (i.e., leachability) of potassium from K-feldspar containing materials for soil improvement and agricultural purposes. A planetary mono mill was used to achieve high intensive dry grinding of both a K-feldspar concentrate and a nepheline syenite concentrate that served as a reference material. The K-feldspar concentrate was also milled in a pilot-scale HiCOM 15 nutating mill. The mill products were characterised with respect to their size distributions, specific surface areas and their relative degree of structural disordering as calculated from X-ray diffraction analysis. The enhanced solubility of the products in terms of potassium was determined directly through a three-step cascade leaching test. The results show that high intensive dry grinding could be used to increase the release of potassium from K-feldspar containing materials by more than an order of magnitude. When subjected to planetary milling, less than 10 min of milling was required to make the K-feldspar mineral more reactive than the intrinsically more soluble nepheline. The enhanced reactivity of the mill products is predominantly a function of their specific surface areas, but a significant part of the observed increase in reactivity must be attributed to structural disordering. The use of water as a grinding aid makes it possible to produce very reactive structurally disordered products with high specific surface areas.

An Investigation on the Effective Use of Fly Ash-Fine Grinding of Limestone with Fly Ash as a Grinding Aid-

In this study, the role of fly ash as a grinding aid to facilitate fine grinding of limestone for improved flowability was examined by carrying out batch grinding test for varying feed amount and grinding time, while maintaining the limestone to fly ash ratio at 5: 1. As a result, it was found that fly ash was an effective grinding aid for the fine grinding of limestone, and the optimum feed amount of limestone and fly ash to the grinding mill increased with increase of grinding time.

Improved grindability and gold liberation by microwave pretreatment of a free-milling gold ore

The gravity concentration of gold is very efficient if the metal is fully liberated and the particle size of the gold is relatively coarse. Liberation is usually achieved by comminution, but due to the association of the gold with the other minerals in the ore, overgrinding occurs in conventional comminution circuits and slime generation leads to inefficient recovery. The liberation of minerals can be improved by adding grinding aids, which modify the mechanical properties of the ore and allow breakage at lower stress levels. In this research, microwave pretreatment was used to augment the grinding of a free-milling gold ore containing quartz, silicates and iron oxides. Under microwave irradiation, selective heating of the different mineral components resulted in thermal stresses that caused cracking. These intergranular and transgranular fractures were confirmed by scanning electron microscopy. After microwave processing, the grindability of the ore was improved and the crushing strength and the Bond Work Index were reduced by 31˙2% and 18˙5%, respectively. In addition to the enhanced grindability, gold was released from the matrix of the host minerals at a coarser size, resulting in a significant increase in free gold recovery by gravity concentration. For a gold ore with a head grade of 6˙4 gt−1, the gold recovery improved from about 28% to 40% after microwave pretreatment.

Monolayer capacity and specific surface area of cement pastes determined from benzene adsorption isotherms

Hydrated cement pastes, prepared from Portland cements with different degrees of dispersity obtained by adding small quantities of triethanol amine and ethylene glycol as a grinding aids were investigated. The adsorption isotherms of benzene vapor on the pastes were interpreted by means of the Brunauer - Emmet - Teller (BET), N - layer Brunauer - Emmet -Teller (N - BET) and Huttig equations. The monolayer capacity and specific surface areas of the pastes after 28 days of hydration were determined. By comparison of the results obtained using different equations, the most suitable equation could be selected and used to determine the monolayer capacity and specific surface area. The influence of the dispersity of the cement on the specific surface area of the cement gel in the pastes could also be analyzed from the obtained results. The investigations were in accordance with the results of the physical mechanical properties of cement plasters.

The effect of a grinding aid on comminution of fine limestone particle beds with single compressive load

Defined particle bed arrangements are an appropriate and useful tool for studying the substantial comminution behaviour of a particle collective. Two fractions of the material limestone were comminuted batch-wise by high pressure in a die press under defined conditions for eliminating the wall effects of the confinements. The particle interactions were modified by using the additive caproic acid and by varying the lateral confinements. The influence of feed size, additive amount and confinement on the specific surface growth and the energy absorption was investigated. It could be proved that a decrease of internal friction due to the additive exerts a small effect on the comminution process, whereas the material transport out of the stressing zone is decisive. For higher amounts of the additive, a decrease of the energy absorption in the fully confined particle bed with a concurrent decrease of the specific surface growth could be shown. On the contrary, there is a very high increase of the energy absorption in the partially open particle bed arrangement according to a high mass transport and specific surface growth. The inhomogeneous densification was observed in a half-cut configuration with a CCD camera. Superpositioning the pictures from tests with vertical and horizontal layers enables to study the reached densities in a grid pattern.

Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill

An experimental investigation on grinding mechanism for calcite used in a stirred ball mill was carried out. The slurry concentration and the amount of grinding aids were chosen as main experimental factors of the grinding process. The effect of grinding aids on particle size distribution and grinding efficiency, defined as the increases of specific surface area per the specific grinding energy, was investigated. It was demonstrated that the grinding rate for calcite could be improved by addition of grinding aids. The grinding energy efficiency by adding a specific grinding aids was improved approximately 45.2% in comparison with and without grinding aids (n=700rpm, J=0.7, dB= 1.0 mm, Cs=60wt%).

Talc grinding in an opposed air jet mill: start-up, product quality and production rate optimization

We present a study of talc grinding in an Alpine 100 AFG opposed air jet mill with an inline laser granulometer. The conditions for steady state operation have been determined from continuous grinding experiments and show that overloading occurs above a critical value of feed rate classifier resulting in unstable product size distribution. For each rotation speed of the classifier, there is an optimum feed rate, which gives the finest product, thus fixing a maximum reduction ratio. A linear relation exists between this ratio and the rotation speed of the classifier. The use of liquid grinding aids have been studied and showed they can result in an increase in the production rate but can also lead to a coarser product.

Estimation of mechanochemical dechlorination rate of poly(vinyl chlorde).

Poly(vinyl chloride) (PVC) was ground in air with CaO in the presence of quartz powder as a grinding aid by a small-scale planetary ball mill to investigate the relation of the dechlorination rate of PVC with the impact energy of the balls calculated from a computer simulation based on the Discrete Element Method under various conditions. Mechanochemical dechlorination proceeds as the grinding progresses and is improved with an increase in both the mill speed and the amount of balls introduced into the mill. The same trend can be seen in the relation between the specific normal impact energy of the balls and the rotational speed. The relationship between the observed dechlorination rate and the computed normal impact energy of the balls is linear, with a correlation coefficient of 0.965. This relationship can be used to estimate the dechlorination rate of PVC in a large-scale planetary ball mill.

アルミナの超微粉砕における液体添加物の助剤効果とアルミナ粉体の挙動

The effect of liquid additives of grinding aid on the ultrafine grinding of alumina was studied by using a vibration rod mill. Liquid additives studied were five alcohols and two glycols with different alkyl groups. Experiments were carried out by batch operation, and the changes in specific surface area of products with grinding were measured by BET adsorption method. The behavior of alumina powder during grinding was also investigated by monitoring the temprature change of the grinding vessel. The results showed that alcohols and glycols had a significant effect on the ultrafine grinding of alumina as a grinding aid. The maximum specific surface area of alumina obtained with an additive was found to increase proportionally with the amount of additive. The thermal analysis of ground products suggested that three molecular layer of the additive molecules existed on the product surface when the specific surface area reached the maximum value. It was found that the monitoring of the temperature change of grinding vessel would be useful in understanding the grinding status.

Room Temperature Extraction of Co and Li from Ground Lithium-ion Secondary Battery Scrap.

Lithium-ion secondary battery scrap, which contains LiCoO2, graphite and PVDF (poly vinyliden fluorine), was subjected to dry grinding using a planetary mill with and without quartz powder as a grinding aid, following its room temperature leaching using 1N HCl solution. The scrap material becomes amorphous state as grinding time and the quartz additive ratio increase. Accordingly, Co and Li in the scrap can be easily extracted from the ground product, and the former yield reaches about 90 mass% at 4-hour grinding with 50 wt% additive. Only about 2 mass% of F in PVDF in the scrap can be extracted under the same grinding condition.

Laboratory-produced high-volume fly ash blended cements: physical properties and compressive strength of mortars

This paper describes the production of laboratory-produced high-volume fly ash blended cements. The effect of grinding of the Portland cement clinker, fly ash, and gypsum with or without a superplasticizer on the physical properties of the cements, and the compressive strength of the mortars made with the resulting blended cements, is discussed. The use of ground fly ash compared with unground fly ash resulted in a substantial increase in the compressive strength of the mortars; the improvement in the strength seems to increase with an increase in the fineness of the fly ash. This was particularly significant for the coarser fly ash. The superplasticizer interground with the clinker seems to act as a grinding aid in the production of Portland cement.

Determination of grinding aids in portland cement by pyrolysis gas chromatography-mass spectrometry

The pyrolysis of Portland cement followed by gas chromatography/mass spectrometry is described for the determination of chemical additives interground with cement clinkers known as grinding aids. This technique, coupled with in situ derivitization using BSTFA-TMCS reagent, has been found to be readily applicable for detecting phenol, along with five glycol and alkanolamine-type compounds in cement. The recovery rate was found to be highly dependent upon the grinding process and the binding capacity of the various additives. Using a relatively short grinding process conducted at ambient temperature, most of the additives tested can be recovered at greater than 85% of their originally added concentration. However, in the case of a longer, more intense grinding procedure conducted at 105°C, only phenol had recovery rates greater than 50%. The formation of salts or stable complexes between the grindings aids and cations at the freshly fractured cement surfaces, is proposed as the major cause of the variable recovery rates for the various grinding aid compounds.

Novel pyrolysis-gas chromatography/mass spectrometric techniques for the characterization of chemical additives in portland cement and concrete

The application of pyrolysis gas chromatography mass spectrometry (py-GC/MS) has been improved for the determination of chemical additives that are either interground with cement clinker during the manufacture of Portland cement or admixed with a mixture of cement, sand, and stone, and water for the production of concrete. This technique has been found to be readily applicable for phenol-based cement grinding aids and naphthalene sulfonate formaldehyde condensate (NSFC)-based concrete admixtures. Furthermore, pyrolytic decomposition of a nitrite-based corrosion inhibitor incorporated into a concrete mixture was found to produce abundant dinitrogen oxide (N 2O), a unique indicator of the nitrite additive. Volatile methyl esters of fatty and rosin acid-based air entraining agents can be formed from the pyrolysis of powdered concrete treated with methanolic tetramethylammonium hydroxide (TMAH). Overall, the py-GC/MS analysis of cement and concrete has the potential to be far more specific and less tedious than the common extraction-spectroscopic based methods currently used. In-situ pyrolytic reactions can further expand the capability of py-GC/MS by volatilizing otherwise thermally stable or strongly adsorbed additives in cement and concrete.

Investigation of Portland slag cement activated by waterglass

The relatively poor reactivity of Indian BF slags results in lower strength of slag cement in comparison to OPC. In this investigation, a dosage of waterglass as an activator has been optimised. Percentage substitution of slag, concentration of waterglass, and their effects on properties of activated PSC have been studied. Up to 60% slag substitution and use of 1% waterglass as activator have yielded the best results. The activator has also acted as a grinding aid. Long-term storage of activated slag cement has been found to be detrimental.

Dry grinding of chitosan powder by a planetary ball mill

Dry grinding of chitosan powder was carried out using a planetary ball mill for its applications to drug carriers. Eighty grams of zirconium oxide balls of 1-5 mm diameter and 1-4 g of 100% deacetylated chitosan were loaded into a 45 ml agate pot and then ground at 440-723 r.p.m. The particle size was analyzed by a laser scattering diffraction method. When surface grinding was induced by lower rotation speeds and smaller beads, except for I mm balls, the chitosan powder was ground at a lower rate, but to a smaller size. The median diameter of the powder ground without any additives was minimized to 5.0 μm at 440 r.p.m. rotation speed using 2 mm balls. Further, various additives were tested to find an effective material as a grinding aid. Hydrophobic compounds, including fatty acids with a long acyl chain and cholesterol, and hydrophilic polyethylene glycol 4000 were effective to reduce the particle size. Lauryl compounds with the same number of carbons exhibited almost the same size reducing effect as a grinding aid, regardless of polar head groups, consisting of carboxylic acid, alcohol or amine. The optimal content was 10-20% in the case of lauric acid. Fatty acids with a longer acyl chain were more effective as a grinding aid. Among the additives studied, stearic acid was most effective and reduced the median diameter to 1.8 μm.

Mechano-Chemical Interactions in the Use of Polyacrylic Acid as a Grinding Aid in Fine Grinding in Stirred Media Mills

ABSTRACT Mechano-chemical interactions have been studied by using polyacrylic acid as a grinding aid for fine grinding in stirred media mills. The polymer additive was found to enhance grinding efficiency by up to 100%. Optimum operating conditions and mechanisms involved with the additive effects are discussed. It was also found that polymer conformation and polymer molecular weight change during stirred milling. Extension of the polymeric species and fragmentation of the high molecular weight polymer molecules resulting from grinding treatment may be beneficial.