Compositional and Structural Deficiencies Causing Failure of Local Fire Assaying Crucibles in Ghana

2020 ◽  
Vol 51 ◽  
pp. 57-70
Author(s):  
Yongdan Hou ◽  
Lemuel Gbologah ◽  
Derrick Boateng Asante ◽  
Parpah Senanu Kwawukume
Keyword(s):  
Field Investigation ◽  
Silica Content ◽  
High Alumina ◽  
High Porosity ◽  
Quartz Content ◽  
Structural Investigations ◽  
Mullite Phase ◽  
Free Silica ◽  
Basic Flux ◽  
Stable Performance

Locally produced crucibles in Ghana experience dimensional failures during fire assaying of ores, therefore, even with a higher cost, imported crucibles are still the most preferred choice by laboratories in Ghana because of the stable performance of up to three cycles. Assay crucibles of locally manufactured, imported and theoretically composed were sampled and analysed via reverse engineering to identify factors that are attributed to the failure during use. Field investigation and compositional, physical and structural investigations were carried out using XRD, water boiling and SEM-EDS analyses, respectively. The results indicated that failure of the local crucible can be attributed to low mullite phase in both content and planes, which could ease the crack development and enhance the thermal stability of the crucible; non converted quartz into cristobalite, which stabilises the volume expansion coefficient during the fire assaying cycles; excess quartz content and absence of alumina content weakened the corrosion resistance against attack from the basic flux of litharge; and high porosity, allowed penetration of molten charge into the structure of crucible, leading to the dissolution of free silica content into the charge and causing structural failure. To overcome such deficiencies, higher firing temperature (~1240 °C), extra soaking time, and blending of high alumina contained clay/minerals were suggested.

Engineering Geological and Petrological Characterization of Paleoweathered Rock in The K1/j2 Contact Zone in the Ordos Basin, China

2021 ◽  
Author(s):  
Tingen Zhu ◽  
wenping Li ◽  
Qiqing Wang ◽  
Yanbo Hu
Keyword(s):  
Mechanical Properties ◽  
Bulk Density ◽  
Contact Zone ◽  
Mutual Influence ◽  
Experimental Testing ◽  
Ordos Basin ◽  
Field Investigation ◽  
High Porosity ◽  
Quartz Content ◽  
Geological Processes

Abstract Various geological processes (mineral composition, structure, tectonics and weathering, etc.) affect the physical-mechanical properties of rock. Petrological and engineering geological characteristics of paleoweathered rock (PWR) from the K1/J2 contact zone are described in detail via field investigation and experimental testing. This PWR exhibits mainly sandy grains and mud structures, layered and massive strata, and calcareous and argillaceous cements; fissures are developed and often filled with argillaceous and detrital materials; 9 minerals and 7 oxides are present, and quartz is present in each sample. Long-term weathering results in a consistent bulk density and high porosity due to the transformation of primary minerals into secondary clay minerals, forming PWR that undergoes argillization in water. The axial point load strength (PLS) is the largest among the tested PLSs, followed by the diametral PLS, and the irregular PLS. The uniaxial compressive strength (UCS) varies widely, but the results are reliable. The mineralogical, physical and mechanical properties of the PWR are compared to predict one parameter from another and study their mutual influence. The PLS and UCS of the PWR are negatively correlated with the elastic mineral group (EMG) content, weathering alteration indexes, water content, and total porosity and positively correlated with the quartz content, brittle mineral group (BMG) content, bulk density, real density, and longitudinal wave velocity. The UCS and the PLS, axial (diametral) PLS and irregular PLS are positively correlated. These results provide a theoretical basis for physical and mechanical property prediction of PWR masses and rapid estimation of UCS in engineering.

scholarly journals Evaluation of Occupational Exposure to Silica Dust in Mining Workers in Eastern Iran

2019 ◽  
Vol 12 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Farideh Golbabaei ◽  
Abdollah Gholami ◽  
Gholamheidar Teimori-Boghsani ◽  
Mehdi Yaseri ◽  
Mojtaba Kianmehr
Keyword(s):  
Occupational Safety ◽  
Cross Sectional Study ◽  
Silica Content ◽  
Crystalline Silica ◽  
Respirable Dust ◽  
Breathing Zone ◽  
Mining Operations ◽  
Cross Sectional ◽  
Silica Dust ◽  
Free Silica

Background and Objective: Silica dust is present in almost all mining operations and can cause various health problems such as silicosis in workers. The present study aimed to determine the total and respirable dust levels and the crystalline silica content of the soil in the breathing zone of workers in Iranian mines. Methods: This cross-sectional study was carried out in 2016-2017 on six Iranian silica mines. Dust sampling was performed according to the National Institute of Occupational Safety and Health (NIOSH) method No. 0600. The samples were collected from the respiratory zone of workers at 114 stations in different units of the mines. The silica content was measured using the standard NIOSH method No. 7601. The crystalline silica content in bulk samples collected from the soil was determined by using the X-Ray Diffraction (XRD) spectroscopy method. Results: The highest concentration of crystalline silica dust was 2.81±0.49 mg/m3 and was observed in the air of crushing unit of mine no. 6, and the lowest was 0.08±0.208 mg/m3 and was measured in the management/administration unit of mine no.1. The mean silica content in the solid surface of the mines was 91%. The total and respirable dust levels in all units of the mines except management/administration were higher than the permissible limit. The free silica content of all collected samples was substantially higher than the permissible limits, and in some cases, it was as much as 100 times above the standard level, which reflects the extremely high risk of working in these mines. Conclusion: Exposure of workers with crystalline silica dust in all units was higher than the standard recommended limits. It is imperative to adopt immediate measures based on technical, managerial, and personal protection solutions to reduce the exposure of workers to silica.

scholarly journals Life cycle assessment of crushed glass abrasive manufacturing from recycled glass

2021 ◽  
Vol 880 (1) ◽  
pp. 012054
Author(s):  
I Zulkarnain ◽  
L S Lai ◽  
M I Syakir ◽  
A A Rahman ◽  
S Yusuff ◽  
...  
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Raw Materials ◽  
Silica Content ◽  
Motivation Factors ◽  
Recycled Glass ◽  
Free Silica ◽  
Disability Adjusted Life ◽  
Carbon Emissions Reduction ◽  
Development Goals

Abstract Sustainable Development Goals (SDGs) are the key motivation factors to determine the characteristics of green abrasives, contributing to carbon emissions reduction, reduce waste generation and build up a recycling-based sustainable blasting industry. Such aim can be evaluated through life cycle assessment as a structured basis for evaluating the performance of environmental impacts and benefits of green abrasives application in blasting industry. Crushed glass is one of zero free silica content abrasives from recycled glass, and it is widely used due to inert and safe characteristics. Database of life cycle inventory (LCI) are obtained through literature review. Production of 1 ton/year of crushed glass abrasives has been modelled at gate-to-gate boundary where the human health appears as the major impact potentials (0.71 DALY, disability-adjusted life year) at the production stage. The selection of 100% recycled glass as the raw materials in the supply chain has led to insignificant impact potentials of resources scarcity and ecosystem damages per unit production of 1 ton of crushed glass at USD 4.79 and 0.06 species. year, respectively.

scholarly journals Determination of Free Silica Content on the Deck Glass

1958 ◽  
Vol 74 (846) ◽  
pp. 1001-1005
Author(s):  
Yoshikazu HAGIWARA ◽  
Tadaharu NAKAMURA
Keyword(s):  
Silica Content ◽  
Free Silica

Optimizing Performance of ZnO Nanorod and Activated Carbon as a Composite Anode for Lithium-Ion Batteries

2020 ◽  
Vol 1000 ◽  
pp. 31-40
Author(s):  
Bambang Priyono ◽  
Ananta Riezky Bachtiar ◽  
Hugo Abraham ◽  
Mohammad Ridho Nugraha ◽  
Faizah ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Electrochemical Impedance ◽  
Zno Nanorods ◽  
Specific Capacity ◽  
Lithium Ion ◽  
High Porosity ◽  
Composite Anode ◽  
X Ray Diffraction ◽  
Stable Performance

To obtain the high specific capacity anode for Lithium-ion battery with stable performance is conducted by synthesizing a composite anode of ZnO-nanorods (ZnO-NR) and as a matrix is the activated carbon (AC). In this study, ZnO-NR synthesized a process that uses basic materials hexamethylenetetramine (HMTA) and zinc oxide. Activated carbon has been activated because it has high porosity and good electrical conductivity properties. Variable used is the percentage of ZnO-NR, which is 30wt%, 40wt%, and 50wt%. Characterization of the samples was examined using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Brunauer–Emmett–Teller (BET). The battery performance of the samples was obtained by Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), and Charge-Discharge (CD) testing after being assembled into coin cell batteries. This study discusses the effect of adding activated carbon to ZnO NR composites. The results showed that the ZnO-NR30/AC has the highest specific capacity of 270.9 mAh g-1. According to Brunner-Emmet-Teller (BET) test, the largest surface area was 631.685 m2 g-1. Electrochemical performance is the best obtained by ZnO-NR30/AC.

Localization of silica in Equisetum arvense (horsetail)

1992 ◽  
Vol 50 (1) ◽  
pp. 856-857
Author(s):  
Barbara A. Reine
Keyword(s):  
Vascular Plants ◽  
Silica Content ◽  
Hydrated Silica ◽  
Rice Hulls ◽  
Reproductive Structures ◽  
Free Silica ◽  
Silicon Carbide Whiskers ◽  
Temperature Regimes ◽  
Significant Public Health ◽  
Substantial Extent

Silica is deposited as amorphous silica gel in the shoots (as well as in leaves, roots and reproductive structures) of many vascular plants such as grasses and cereals (notably rice and oat), hemp, pea, nettle, palms, sedges, and horsetails. Of this group, the horsetails, grasses and sedges, exhibit an especially pronounced capacity to take up large amounts of silicon as silicic acid from the soil and polymerize it as hydrated silica in various tissue locations and sometimes specialized cells (3). The application of this naturally produced silica and other minerals to technology, has stimulated a renewed and refocused interest in biomineralization (2). Historically, the silica-impregnated shoots of horsetails (Equiserum) were used by pioneer settlers for scouring dirty dishes and as a substitute for sandpaper. Today, rice hulls, whose silica content can exceed 20 wt.%, are pyrolyzed commercially to produce silicon carbide whiskers and platelets for use in composites. Rice hulls are also used as fuel in co-generation plants in rice-growing regions of the country but if combustion takes place in certain oxygen concentration and temperature regimes, crystalline “free silica” forms to a substantial extent and. if discharged as respirable dust, may present a significant public health risk.

scholarly journals Numerical Analysis of Ground Motion Effects in the Loess Regions of Western China

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Tuo Chen ◽  
Wei Ma ◽  
Jianzhou Wang
Keyword(s):  
Numerical Analysis ◽  
Ground Motion ◽  
Soil Structure ◽  
Seismic Vulnerability ◽  
Field Investigation ◽  
Western China ◽  
Triaxial Tests ◽  
High Porosity ◽  
Special Soil

Loess is widely distributed in the western part of China and its area comprises 6.6% of Chinese territory. Because of the characteristics of high porosity, low strength, and weak cementation, the loess is characterized by high seismic vulnerability which has been observed and confirmed by many researchers at home and abroad. The postquake field investigation and the laboratory study have shown that the ground motion effects, including the amplification effects and slope effects, were obvious in loess sites. Moreover, the causes of landslides, seismic subsidence, and liquefaction were mainly attributed to this special soil structure and properties. In this paper, based on the data of shear wave velocity of typical loess in Lanzhou region, combining the results of dynamic triaxial tests, the numerical analysis of ground motion effects in the loess regions is analyzed. The results reveal how the ground motion effects are checked and demonstrated the important role of numerical simulations while studying the characteristics of ground motions.

scholarly journals Characteristics of calcined palm oil pastes for biosilica extraction as a function of calcination temperatures

2021 ◽  
Vol 19 (1) ◽  
pp. 23-34
Author(s):  
N. A. S. Abdul Samat ◽  
U. Z. Kamarul Jaman ◽  
S. Saree ◽  
D. S. A. Mahmod ◽  
J. C. H. Lai
Keyword(s):  
Weight Loss ◽  
Palm Oil ◽  
Palm Kernel ◽  
Silica Content ◽  
High Porosity ◽  
Color Analysis ◽  
Palm Kernel Shell ◽  
Calcination Temperatures ◽  
Empty Fruit Bunches ◽  
Bet Analysis

Palm oil production in Malaysia has increased over the years. As the consequence of high production of palm oil, surplus quantities of palm oil biomass wastes such as empty fruit bunches (EFB), palm kernel shell (PKS), and oil palm decanter cake (DC) are generated. Generally, these wastes are used as fuel to generate steam for boilers, which end up as ash. As several agricultural wastes are well-known to be rich in silica content, this study aims to investigate the bio-silica content of EFB, PKS and DC and their characteristics when calcined at various calcination temperatures from 400°C to 800°C. Several analyses were conducted such as weight loss, color, BET, SEM and FTIR. The results have shown that all samples favorably exhibited silica at higher temperatures, i.e., 800°C. Color analysis depicted that combustible elements were mostly removed at 800°C, leaving non-combusted silica in the waste ash. Weight loss analysis presented that EFB achieved the highest weight loss at 99.05%, followed by PKS at 95.65% and DC at 83.95%. This led to a relatively high amount or purity of silica in the sample. BET analysis showed highest surface area, 20.087m2/g (PKS) and the lowest is 9.492m2/g (DC) at 800°C which verified the high porosity of samples for further absorption applications. The presence of silica was also significantly observed in 800°C FTIR spectra for all waste samples. Overall, it is concluded that EFB, PKS, and DC are highly potential wastes to contribute to the production of bio-silica, which thus can be an option to overcome waste disposal issues in palm oil industries.

scholarly journals THE INFLUENCE OF SEDIMENTATION AND POST-SEDIMENTATION TRANSFORMATIONS ON THE RESERVOIR PROPERTIES OF THE ROCKS

2019 ◽  
pp. 14-19
Author(s):  
V. Khomyn ◽  
M. Maniuk ◽  
O. Maniuk ◽  
A. Popluiko ◽  
N. Khovanets
Keyword(s):  
Oil And Gas ◽  
Scientific Evidence ◽  
Gas Content ◽  
High Porosity ◽  
Reservoir Properties ◽  
Quartz Content ◽  
Positive Correlation ◽  
Median Diameter ◽  
Porosity And Permeability ◽  
Cover Thickness

The topicality of the research is proved by the scientific evidence of the peculiarities of the sedimentation and post-sedimentation transformations of the rocks in relation to their possible oil and gas content. The productive sediments of the deposits of the interior of the Precarpathian Depression were thoroughly and lithologically researched. The objective implied the study and recognition of the reservoir properties within primary (sedimentation) and secondary (post-sedimentation) factors. The primary ones are as follows: granulity (grains median diameter), sorting, and rock maturity. Consequently, a positive correlation between the grains median diameter and rock porosity has been determined; the very coefficient equals 0.56. Evidently, unlike the well-sorted sandstones, the badly graded ones are marked by poor porosity and permeability. The positive correlation between porosity and clastic quartz content is revealed: should the latter increase, the former will go up as well. Apparently, more mature sandstones are characterized by dramatically high porosity; this factor positively affects the reservoir properties of the rocks. After studying the secondary transformations of the sandy rocks, we have determined that the diagenesis stage is defined by the change of mineral composition. This alteration is mainly caused by organic material decomposition and the appearance of reducing environment. Considering the cover thickness, we have graded the transformations of the fragments of the sandy-aleuritic rocks of the depression. The pattern of the catagenetic changes at various depths has been introduced. In the end, we have inferred that the increasing depth starts influencing the three types of the structures, i.e. incorporating, reclaiming and microstilolite rather gradually. In addition, the declining importance of the conformal structures has been identified. The stress pattern of the catagenetically transformed solid rocks promotes the microfracture within the late catagenesis zones; this factor predetermines the development of decompression zones at the depths exceeding 4 km characterised by good reservoir properties.

scholarly journals Assessment of Occupational Dust and Silica Exposure in Indian Stone Mining and Crushing Unit- A Case Study

2017 ◽  
Vol 12 (3) ◽  
pp. 661-669
Author(s):  
Anand Deshmukh ◽  
Nikhil Pradip ◽  
Sarang Dhatrak ◽  
Subroto Nandi
Keyword(s):  
Personal Exposure ◽  
Mining Area ◽  
Silica Content ◽  
Vital Role ◽  
Dust Exposure ◽  
Silica Exposure ◽  
Free Silica ◽  
Limit Value ◽  
Exposure Limit ◽  
Precautionary Measures

Stone crushing industry plays a vital role in the economy and urban development of fast developing countries like India. Stone mines and crushers in India are located around major cities and roughly employ around 5,00,000 peoples throughout the country. However this employment generating industry also happens to be one of the most dust generating activity and also a precursor to the respiratory disease, silicosis. This study was undertaken with an objective to estimate the personal exposure of the workers to silica laden dust in this industry sector. Personal dust sampling (n=11) and (n=6) was carried out in stone crushing and stone mining (quarry)areas respectively over a period of three consecutive days in selected units in a suburban area of Nalgonda district of Telangana state in India. The respirable dust exposure and free silica content was then estimated. It was observed that three (3) samples of crusher helper from the Crushing Unit had exposures exceeding the Permissible Limit Value (PLV) of Indian Factories Act1948. Two (2) Heavy Earth Moving Machineries (HEMM) operators from stone mining area were observed to have exceeded the Permissible Maximum Exposure Limit (PMEL) prescribed by the Indian Mines Act 1952 and subsequent rules their under. The remaining samples of HEMM operators from mining area and of the crusher helper from the crusher plant were observed to be within the prescribed limits of respective guidelines prescribed by the Indian statutory agencies. Two different acts were considered, because of the fact that stone mining is regulated by the Indian mining act and under the overall control of Directorate of Mines and Safety (DGMS), Government of India. On the other hand Crusher plant comes under the ambit of Model Factory Rule 120 under section 87 of Indian Factories Act 1948 under the overall control of Directorate General Factory Service and Labour Institute (DGFASLI) Government of India. Post the study it could be concluded that, stone crushers are dustier as compared to stone mining area. Workers in stone mining and crushing units of study area are indeed exposed to high levels of respirable and silica laden dust. It was observed that safety and precautionary measures towards dust and silica exposure are not implemented necessitating to be taken by unit operators.

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