• Korean Journal of Materials Research
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• v.19 no.4
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• pp.212-219
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• 2009

A study on the dry beneficiation of sericite occurring in the Daehyun Mine of the Republic of Korea region as performed by applying selective grinding and air classification techniques. Quartz and sericite occurred in the raw ore as major components. The results of liberation using a ball mill and an impact mill showed that the contents of $R_2O$ were increased while $SiO_2$ was decreased in proportion to decreasing particle size. According to the XRD, XRF analysis and the EDS of SEM analysis, the ball mill gave a better grade product in $R_2O$ content than the impact mill when the particle size was the same. When the raw ore was ground by the impact mill with arotor speed 57.6 m/sec and then followed by 15,000rpm classification using an air classifier, the chemical composition of the over flowed product was 49.65wt% $SiO_2$, 32.15wt% $Al_2O_3$, 0.13wt% $Fe_2O_3$, 10.37wt% $K_2O$, and 0.14wt% $Na_2O$. This result indicates that the $R_2O$ contents were increased by 49.5% compared to that of the raw ore. From these results described above, it is suggested that hard mineral such as Quartz little ground by selective grinding using impact mill whereas soft mineral such as sericite easily ground to small size. As a result of that hard minerals can be easily removed from the finely ground sericite by air classification and the $R_2O$ grade of thus obtained concentrate was improved to higher than 10wt% which can be used for ceramics raw materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.20-25
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• 2021

The cement clinker, the main raw material of cement, is manufactured using limestone as the main material. Depending on the quality of limestone, the use of subsidiary materials changes, and has a great influence on the production of cement clinkers. In this study, the effect of CaO content of limestone, a cement clinker material, on Raw Mill grinding and sintering of cement clinker was investigated. The grinding time of the union materials changed in the content of limestone CaO was measured to identify the grinding properties. The raw material combination was cleaned within a range of 1,350-1,500℃. The sintering performance of cement clinker by Burnability index calculation was identified. The lower the grade of limestone, the lower the grinding quality of the raw material combination. The lower the CaO content of limestone, the greater the variation in F-CaO for sintering temperature. The lower the class of limestone, the higher B. I. value was calculated, indicating the lower cement clinker sintering. In addition, the mineral analysis results of cement clinker showed that if the F-CaO value was low due to the increase in sintering temperature, the Belite content decreased and the Alite content increased. In the case of Alite, the ratio of R-type decreased and that of M-type increased as the content of limestone CaO increased.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.1
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• pp.69-74
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• 2014

An OrthoMTA compacter is made by machining a Ni-Ti alloy wire using tapered helix creep-feed grinding machines. This aim of this study is to find the optimal dressing conditions to sharpen the corner of a cubic boron nitride (CBN) wheel. On the basis of the results of various experiments, it is verified that the most important factors in dressing are the dressing depth and feeding method, whereas the feed rate has less importance for producing a smaller corner R value. The study also finds the optimum dressing depth to reduce the dressing time, a feeding speed and method to stabilize the machining, and the mesh grade for the CBN wheel to make the groove of the compacter deeper.

• Resources Recycling
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• v.32 no.2
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• pp.3-11
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• 2023

The aim of this study was to develop a physical treatment method for obtaining iron concentrate with a grade higher than 60% from slag generated in the Waelz Kiln (WK) process. The size of the WK slag used in this work was several millimeters, with T-Fe and ZnO contents of 40.24% and 1.03%, respectively. The slag samples were pulverized in a laboratory rod mill for various grinding times, followed by a magnetic separation test under a low magnetic intensity of 0.05 T initially. The results showed that the highest iron grade was obtained from samples with a grinding time of 10 min. Additionally, for a grinding time of 20 min, the highest grade and recovery ratios were achieved at a magnetic intensity of 0.8 T. Based on these findings, the optimal physical treatment process proposed in this study resulted in iron concentrates with a grade of 61.34% and an enrichment ratio of 1.52.

• Korean journal of food and cookery science
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• v.27 no.1
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• pp.85-99
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• 2011

Grinding is an indispensible step in preparation of espresso coffee. The purpose of this study was to evaluate physicochemical and sensory characteristics of espresso according to the grinding grades of coffee beans. Specifically, physicochemical characteristics according to the grinding grades of coffee beans were tested based on foam index, persistence of foam, total solids, concentration, extraction yield, pH, viscosity, total soluble solid content and density. With regard to sensory characteristics, QDA were carried out by 10 trained panels. Persistence of foam, total solids, concentration, extraction, pH and viscosity in physicochemical test showed significant differences among the three categories of the samples. In other words, the finer the size of particles was, the higher value was, at the p=0.001 value. Meanwhile, the value of foam index and total soluble solid content to the grinding grades was the highest in 'fine', at the p=0.001 value. Tiger-skin effect in crema, an important attribute for excellent espresso coffee, was perceived by all of the panels in 'fine'. Also, intensity of flavor was perceived as to the strongest in 'fine'. Moreover, 'fine' had the sweetness to balance the acids and bitters. In conclusion, according to the grinding grades, it was identified that there were differences in the physicochemical and sensory characteristics. Furthermore, when the size of particles was 'fine', it brought to the most positive result.

• Journal of the Korean Ceramic Society
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• v.13 no.4
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• pp.20-24
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• 1976

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.129-138
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• 2008

The characteristics of beneficiating kaolin mineral by liberation (selective grinding) and air classification have been investigated, comparing the grinding rates of ball mill and impact mill. The ore was ground using a ball mill and a impact mill to evaluate the grindability of the two grinding methods based on the constant production amount of fine particles in size less than 325 mesh. Then, the fine product was further separated into two fractions using an air-classifier and each fraction was chemically analyzed to compare the beneficiation efficiency of the two grinding methods. The chemical grade of kaolin mineral decreased as increasing the grinding rate of both the mills. particularly in the case of ball mill because of overgrinding impurities such as quartz and feldspar. In the case of the ball milling, the fine fraction less than 325 mesh was air-classified at a cutting point of $43\;{\mu}m$. The production rate of the air-classified concentrate was found to be 66.2 wt%, removing 5.3% of $Fe_2O_3$ and 34.6% of CaO. Under the same conditions mentioned above with the impact mill, the production rate of the air-classified concentrate was 64.4 wt%, removing 34.2% of $Fe_2O_3$, 67.6% of CaO and 25.0% of $TiO_2$. Therefore, our results indicate that impact mill is superior to ball mill in terms of impurity removal.

• Journal of Ocean Engineering and Technology
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• v.22 no.2
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• pp.58-64
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• 2008

Large-scale tests of welded tubular K-joint sunder balanced in-plane bending braces were carried out to observe the fatigue behavior of the API 2W Gr.60 steel plate produced by POSCO. Toe grinding and weld profiling were used to improve the fatigue life of a tubular K-joint. The effects of the steel grade and chord wall thickness on the fatigue life were also investigated. The present results were compared with the UK DEn design curve.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.124-130
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• 1995

연삭작업에 있어서 요구되는 가공능률과 가공정밀도를 얻기 위해서는 적절한 결합도를 갖는 연삭숫돌을 선택하 는 것이 중요한 요건이 된다. 본 연구에서는 결합도를 평가하기 위한 일정한 기준을 설정할 목적으로 AE계측 시스템을 이용하여 대월식결합도시험방법에 따라 연삭숫돌표면의 일부를 파괴시켰을 때 발생되는 AE신호를 검출 하고 연삭숫돌의 파괴량과 AE 신호특성과의 관계 및 AE를 이용한 결합도평가의 가능성을 검토하였다.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.661-666
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• 2009

Froth flotation has been carried out in order to produce roasting-molybdenite concentrate from molybdenite ore in the Shin-yeomi mine. In our study, roasting-molybdenite (Mo 0.43%) from Shin-yeomi mine was recovered by varying the conditions of regrinding time, dosage of collector and alkalinity. Liberation and flotation efficiency more were effective at regrinding time of six minutes than at single grinding. Mo recovery curves increased considerably as dosage of kerosene increased, whereas Mo grade curves decreased gradually. The separation efficiency of molybdenite was effective when the dosage of collector (kerosene) was adjusted to 300 g/t. The molybdenite concentrate was agglomerated in the range of pH 5-7 and its separation efficiency increased to pH 9-10. The concentrate of 49.5% Mo grade ($MoS_2$, 82.6%) with 81.5% recovery from Shin-yeomi molybdenite ores was obtained under conditions of 20% pulp concentration, 300 g/t kerosene 325 g/t frother (AF65), 2.5 kg/t depressant ($Na_2SiO_3$), pH 9-10 and four cleaning times. In the future, a trial run that can separate up to 50% Mo grade from Shin-yeomi molybdenite ores will be performed.