Angel Zabchev, Romeo Alexandrov

ABSTRACT. The AZUR apparatus is intended to control the insulating resistance in mine networks with an isolated star centre. The indication of the measured insulating resistance is realised by a pointer meter with a reversed nonlinear scale, which makes it difficult to read. The methodology for the development of an analogue converter is considered here, which linearises the non-linear characteristic current-resistance and, together with a light indicator, the device allows for more accurate and easy reading. An analysis of the error and the measurement range is made.
Keywords: insulating resistance control, mine power networks, measuring analogue converter.

DOI: 10.5281/zenodo.7007092
https://doi.org/10.58903/c16182124

MEASURING THE INSULATING RESISTANCE IN NETWORKS WITH ISOLATED STAR CENTRE CONTROLLED BY AN AZUR DEVICE

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Danail Terziyski, Dimitar Kaykov

ABSTRACT. Modern mining practices rely to a great extent on the application of numerical methods for establishing design alternatives, leading to significant economic benefits. In the current article mine haul road design and construction are treated as two interconnected problems – 1) selection of a suitable optimisation for haul road design and selection of an optimal pit design solution; 2) selection of a suitable technology for haul road construction. Based on previous research, the main factors which determine haul road design feasibility have been identified. They are used for the purpose of establishing the key performance parameters which define the optimality of a haul road design solution. An optimisation problem is defined, which relies on different design solutions and the alternatives for a feasible ultimate pit design. Solutions of this optimisation problem are expected to maximise the mine’s long-term profit. Furthermore, statistical parameters were obtained providing insight into affirming why a certain design solution is more dominant to others in a more robust way.
Key words: haul road design, haul road construction, open-pit mining

DOI: 10.5281/zenodo.7007086
DOI: https://doi.org/10.58903/c16182123

HAUL ROAD DESIGN OPTIMISATION APPROACH FOLLOWING TECHNOLOGICAL CONSTRAINTS IN OPEN-PIT MINING

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Veneta Stefanova, Petar Petrov

ABSTRACT. Sustainable land application in post-mining areas is an essential ecological issue, connected with disturbed areas, pollution of heavy metals, etc. The current research studies opportunities for phytoremediation of lands disturbed by copper mining. Environmental state and soil conditions are examined. Analyses show that soils are weakly acidic, with a low concentration of total nitrogen, a very high concentration of K2O and P2O5, and arsenic above permissible values. The research determines phytostabilisation as a more reliable method for phytoremediation of disturbed lands in this case. The appropriate species for phytostabilisation have been studied. Based on the analysis of data, climate, and soil conditions, it is determined that tree species of four genera show the best ability for phytoremediation in this type of terrain: Populus, Betula, Acer, Salix. Afforestation schemes and possible methods for biomass treatment are proposed.
Keywords: copper mining, reclamation, phytoremediation, phytostabilisation

DOI: 10.5281/zenodo.7007076
DOI: https://doi.org/10.58903/c16182122

PHYTOREMEDIATION OF POST-MINING DISTURBED LAND

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Siilegmaa Sereenen, Oyuntugs Magsar, Terry O’Neill

ABSTRACT. Energy independence is one of the most important issues for almost every country and the world. Mongolia strives to have various types of energy sources and reduce energy dependence. Energy dependence always influences economic dependence of any country. Utilising its own country’s resources is optimal to reduce energy dependence. In recent years, the Mongolian Government has been encouraging unconventional oil and gas exploration and foreign investment and implementing supporting policies, such as coal bed (seam) methane. As a result of these activities, unconventional oil and gas investment and exploration have been intensified in the last few years in Mongolia, especially during pandemics. There are 32 oil and gas blocks in Mongolia and coal bed methane exploration and foreign investments have been invested in eight blocks. In 2022, some foreign investment companies are going to introduce proven reserves of coal bed methane to the Mongolian Government and Parliament. Therefore, we have to model the positive and negative impacts of coal bed methane on the Mongolian economy and find methods to increase the positive sides. Unfortunately, there is no experience in any situation for unconventional oil and gas exploration, extraction, and field development. Because of it, we have cooperated with Australian scientists and experts and completed some studies for making a model of the impact of coal seam methane on the Mongolian economy. For today’s condition, the Mongolian Government or Mongolian private companies can’t process coal bed methane activities because of lack of capital expenses and experience. To raise the positive impacts of coal bed methane, foreign investment is of course very important. There are some main purposes to model the impact of coal seam methane on the Mongolian economy.
Key words: cost, price, payment, profit, tax.

DOI: 10.5281/zenodo.7007066
DOI: https://doi.org/10.58903/c16182121

MODELLING THE IMPACT OF COAL SEAM METHANE ON THE MONGOLIAN ECONOMY

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Vessela Petrova

ABSTRACT. Circular economy is a key instrument for reducing climate change and transition to green economy. The industrial symbiosis is a circular business model – a concept, discussed as a platform for exchange of materials among business companies in order to achieve sustainability and reduce waste. “Shared use” of wastes as raw-materials results in multiple benefits – economic (reduction of cost to produce raw materials), environmental (reduction of generated waste, reduction of CO2 emissions, opportunities for applying the green policies), as well as social benefits (creating “green” job positons, support to local communities). A discussion is presented in the paper on industrial symbiosis as an important opportunity for developing a circular economy by the established business model. A survey among thirteen (13) companies from the mineral raw-material sector has been performed and it has proved that companies are aware of the concept, even more – to a certain extent, companies perform the concept in their day-to-day activities. The paper has marked the need of actually mapped networks, which will model a sustainable industrial symbiosis.
Key words: industrial symbiosis, circular economy, mineral raw-material industry

DOI: 10.5281/zenodo.7007062
DOI: https://doi.org/10.58903/c16182120

INDUSTRIAL SYMBIOSIS IN RAW-MATERIAL SECTOR AS AN OVERARCHING SOLUTION IN CIRCULAR ECONOMY

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Cyril T. O’Connor, Kirsten C. Corin

ABSTRACT. It has been shown that the partial molar excess Gibbs energy (G̅ex) can be used as an indicator of hydrophobicity and hence contributes to explaining the behaviour of collectors in the recovery of minerals by flotation. This is because hydrophobicity of a mineral particle on which a collector is adsorbed is related to the fact that the alkyl chain associated with the collector behaves in the same way as any hydrocarbon would in a non-ideal mixture with water. Such mixtures are quantified thermodynamically by determining the activity coefficient of the hydrocarbon moiety of the collector and hence its G̅ex in the mixture. The present paper is aimed at extending the above concepts in two different ways. Firstly, an investigation is made of the relationship between G̅ex and contact angle and/or recovery for systems such as ionic liquids and aminothiophenols. Secondly, on the basis of the observation that increases in G̅ex are indicative of increases in the hydrophobicity of the mineral particle-collector aggregate, a study was undertaken to examine, respectively, the effects of the presence of electrolytes or alcohols in the system, of pH and changing concentrations of the collector, on G̅ex of the collector alkyl group and hence its hydrophobicity. In the first instance, the relationship between G̅ex and contact angle and recovery is sustained. With respect to the latter, the absence of any correlation between G̅ex and recoveries supported the proposition that the major effect of electrolytes and added alcohols is rather on particle – bubble attachment. Similarly, it is also indicated that since the change in G̅ex is minimal when collector concentration or pulp temperature is increased these changes do not significantly affect the hydrophobicity of the collector-mineral particle and hence also the recovery in a microflotation.
Key words: hydrophobicity, partial molar excess Gibbs energy, reagents, flotation.

DOI: 10.5281/zenodo.7007051
DOI: https://doi.org/10.58903/c16182119

ON USING EXCESS GIBBS ENERGY AS AN INDICATOR OF HYDROPHOBICITY IN THE FLOTATION PROCESS

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Nikolaos Koukoulis, Georgios N. Anastassakis

ABSTRACT. The current paper deals with the re-processing of mineralised mine waste from magnesite processing operations aiming at the recovery of the value. Two cases of mineralised waste were examined. First, waste derived from the removal of “fine” before hand-sorting, with particle size of -40 mm; this waste is usually stockpiled, comprises mostly of relatively coarse particles and is of relatively high-grade in magnesite. The separation methods applied were sorting, sink-float tests and magnetic separation. In general, the results from the application of physical separation methods were satisfactory. Commercial concentrates were obtained from sorting with MgCO3-grade ranging between 94 and 97% MgCO3 and yield about 46%; in case of mixing concentrate with middling, yield rises to 58-64% while grade slightly drops to 91-94%. Equally satisfactory were the results from sink-float separation at sp.gr. 2.88 (grade 95%, yield 45%) but questions arise from the small sp.gr. difference of magnesite and gangues. Finally, the less satisfactory results obtained from magnetic separation (grade around 80-85%, yield 33-65%) may be due to inefficient particles liberation and higher magnetic field is maybe required. Second, mineralised waste consisting of fine particles from size reduction operations were tested. These fines were processed with selective magnetic coating as well as co-agglomeration / magnetic separation techniques. In general, the results of physicochemical processing of fines were very encouraging both on single minerals and their artificial mixtures. In case of magnetic coating, the effect of pH, collector concentration and kerosene dose was studied first on single minerals. Optimum results were obtained for pH=9, dodecylamine solution 4.5×10-5 M and kerosene 2.5 L/t. Tests on artificial mineral mixtures at optimum conditions and magnetic separation at 0.8 A resulted in non-magnetic product with MgCO3-grade higher than 99%. The parameters examined in co-agglomeration / magnetic separation tests were the same as with magnetic coating. Best conditions for co-agglomeration on single minerals were pH=8, dodecylamine 2 kg/t, kerosene 4 L/t. Tests on mineral mixture reveals that the MgCO3-grade increases with dodecylamine but the yield drops.
Key words: magnesite, serpentine, waste, hydrophobic agglomeration.

DOI: 10.5281/zenodo.7007041
DOI: https://doi.org/10.58903/c16182118

REPROCESSING OF MAGNESITE BENEFICIATION-WASTE TO RECOVER MINERAL VALUE AND MINIMISE ENVIRONMENTAL FOOTPRINT

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12. Hoang D. H., Ebert D., Robert Möckel R., Rudolph M., 2021. Impact of sodium hexametaphosphate on the flotation of ultrafine magnesite from dolomite-rich desliming tailings, Minerals, 2021, 11(5), 499. https://doi.org/10.3390/min11050499

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Gospodinka Gicheva, Alexander Chanachev, Sergei A. Kulinich

ABSTRACT. Nowadays, mining industry is striving to be regarded as a modern and highly-technological field with no negative connotation to its name. The human factor is constantly increasing in significance, making mining industry more people oriented, and more and more efforts are being made to bring modern technologies into service and help create safer work environment. Utilising new types of biosensors provides remote health monitoring of workers in mining industry, thus enabling the real time monitoring of vitals of a person, permitting timely medical care and preventing long-term negative exposures. In this regard, the use of flexible, lightweight and wearable biosensors is seen as very convenient and patient-friendly in work environment without interfering with the daily activities. In this study we present a non-enzymatic glucose sensors based on ZnO nanoparticles prepared by a laser ablation in liquid method.
Key words: ZnO nanoparticles, laser ablation, biosensors, glucose

DOI: 10.5281/zenodo.7007033
DOI: https://doi.org/10.58903/c16182117

BRINGING SPACE TECHNOLOGY TO MINING – BIOSENSORS FOR HEALTH MONITORING IN REAL TIME AS A MODERN MANAGEMENT PRACTICE

1. Bandodkar A. J, Jeang W. .J, Ghaffari R., Rogers J. A., 2019. Wearable sensors for biochemical sweat analysis, Annual Review of Analytical Chemistry, 12, 1–22. DOI: 10.1146/annurev-anchem-061318-114910

2. Bhalla N., Jolly P., Formisano N., Estrela P., 2016. Introduction to biosensors, Essays in Biochemistry, 60(1): 1–8. doi: 10.1042/EBC20150001

3. Choi J., Ghaffari R., Baker L. B., Rogers J. A., 2018. Skin-interfaced systems for sweat collection and analytics, Science Advances 16; 4(2), eaar3921 DOI: 10.1126/sciadv.aar3921

4. Currano L. J., Sage F. C., Hagedon M., Hamilton M, L., Patrone J., Gerasopoulos K., 2018. Wearable sensor system for detection of lactate in sweat, Scientific Reports 8, 15890. https://doi.org/10.1038/s41598-018-33565-x

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8. Kondo T., Sato Y., Kinoshita M., Shankar P., Mintcheva N. N., Honda M., Iwamori S., Kulinich S. A., 2017. Room temperature ethanol sensor based on ZnO prepared via laser ablation in water, Japanese Journal of Applied Physics. 56 (8), 080304. DOI 10.7567/JJAP.56.080304

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17. Yang X., Cheng H., 2020. Recent developments of flexible and stretchable electrochemical biosensors, Micromachines, 11, 243. DOI: 10.3390/mi11030243

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Plamen Georgiev, Marina Nicolova, Maria Filipa Ivanova, Irena Spasova, Stoyan Groudev

ABSTRACT. The study aimed to determine the effect of the acid mine drainages` flow rate on the iron adsorption by ion-exchange resin LEWATIT MonoPlus TP 207 in a fixed-bed column and to evaluate which widely used models describe that process better. The ferrous iron was preliminary chemically oxidised by H2O2 and Na2CO3 addition and increased pH to 3.50 combined with the solution purging with air. After assembling fixed-bed columns, their bed volume (BV) was determined. The treated mining solution was delivered to fixed-bed columns by a peristaltic pump at 2.0, 3.0, and 4.0 BV flow rates. The iron adsorption efficiency on the LEWATIT resin was studied depending on the applied flow rate and the volume being treated. The experimental data obtained were modelled using the Bohart-Adams, Thomas, Yoon-Nelson, and Clark models. The results showed that at constant experimental conditions (temperature, ferric iron concentration, and pH), the applied flow rate had a significant effect on the parameters which are important from a practical (efficiency of iron removal, (Y); equilibrium iron and equilibrium copper contents of the resin, (qeq)) and a theoretical point of view (rate constants (kBA, kTh, kYN, r); time of breakthrough (τ)). The Yoon-Nelson and Clark models were the models that best fitted the experimental results.
Keywords: iron, LEWATIT, adsorption, a fixed bed column

DOI: 10.5281/zenodo.7007024
DOI: https://doi.org/10.58903/c16182116

STUDY ON THE FERRIC IRON ADSORPTION FROM ACID MINE DRAINAGE ON LEWATIT RESIN IN A FIXED BED COLUMN

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8. Georgiev P., Nicolova M., Ivanova M.-F., Spasova I., Groudev S., 2021. Studies on the ferric iron sorption from acid mine drainage of LEWATIT resin as a step of metal conversion to a value-added product, Sustainable Extraction and Processing of Raw Materials Journal, 2, 36-42. DOI: 10.5281/zenodo.5594863

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Nicolae Daniel Fîță, Sorin Mihai Radu, Roland Iosif Moraru, Mila Ilieva Obretenova

ABSTRACT. Until recently, the European Union’s energy policy was against coal for pollution reasons, but with the start of the military war between Russia and Ukraine, coal has become one of the energy resources to reconsider. The lack or depletion of oil and natural gas from Russia has made the coal resource the most important source and means to provide energy security. Because there are many coal-fired power stations in Romania (hard coal and lignite), its extraction and recovery becomes a real problem of national security, because it produces electricity, which is vital to Romanian society. The need to analyse the mining subsector, which generates critical mining infrastructure, comes in the context in which the possible occurrence of cases of non-energy supply, or unexpected price increases, generates major issues of national interest, with European and OTAN implications. The aim of the paper is to structure and analyzse the mining subsector within the National Energy Sector in the context of stability and increasing national energy security. The authors consider that the approach of the mining subsector is a strictly national security issue because the lack of coal can cause damage to the power sector and the national economy, which are partly dependent on the mining subsector.
Key words: coal, mining subsector, national energy sector, energy security

DOI: 10.5281/zenodo.7007013
DOI: https://doi.org/10.58903/c16182115

STRUCTURE AND ANALYSIS OF THE MINING SUBSECTOR FROM THE NATIONAL ENERGY SECTOR IN THE CONTEXT OF STABILITY AND INCREASE OF ROMANIAN ENERGY SECURITY

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5. Fîță N. D., Radu, S.M., Păculescu, D. 2021b, Ensuring, controlling and stability of energy security in the context of increasing industrial and national security – Academic Compendium, Universitas Publishing House, Petroşani, ISBN 978-973-741-743-5,

6. Fîță N. D., Radu S. M., Păsculescu D., Gregory E., 2021c, The approach of national critical energy infrastructures correlated with societal resilience and sustainability, in: Sustainability management and managerial sustainability between classical and modern paradigms, ed. D. E. Ranf, O. M. C. Bucovetchi, D. Badea, Publishing house of the Academy of Land Forces “Nicolae Bălcescu” Sibiu, Romania, ISBN 978-973-153-419, 37 – 58.

Naci Duru

ABSTRACT. Increasing complexity of ore deposits requires operations to be continuously improving their cost competitiveness. Mathematical modelling and process simulation techniques are useful tools to understand the process, define bottlenecks and increase process efficiencies. This paper presents a crushing and grinding circuit of a chromite ore gravity separation plant’ simulation model results and actual plant operating data. Throughout the study, jaw crusher, ball and rod mill summary equipment characteristics, breakage and selection functions employed, comparison of particle size distribution curves of site process streams to model results are presented. Simulation work is completed by using METSIM® software. The paper also showcases ease of flow diagram and process data presentation by the utilisation of the adequate simulation approach.
Key words: crushing-grinding circuit, chromite ore, process simulation, breakage, selection function

DOI: 10.5281/zenodo.7007007
DOI: https://doi.org/10.58903/c16182114

COMPARISON OF SIMULATION MODEL AND PLANT DATA OF A CRUSHING – GRINDING CIRCUIT

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Alexander Brodt

ABSTRACT. A method for direct liquefaction of coal is presented. After separating the coal from waste rock gravitationally in an aqueous salt solution, drying and grinding, the purified separated coal is mixed with a paste-forming reagent. The paste is ground until a colloidal particle size and hydrogenated for 2 hours at temperature of 405°C and 11 MPa hydrogen pressure. Artificial oil was obtained with over 95 % yield with respect to the initial amount of purified coal when the contact of excavated coal with air was avoided. Based on findings, a technology is proposed for underground coal liquefaction with significantly reduced energy consumption of the process, removed environmental hazards and higher efficiency with respect to existing technologies.
Key words: coal liquefaction, synthetic oil, underground

DOI: 10.5281/zenodo.7006988
DOI: https://doi.org/10.58903/c16182113

CONVERTING COAL MINING INTO UNDERGROUND PRODUCTION OF ARTIFICIAL OIL

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Diana-Maria Banu, Ana-Maria Obreja, Ioana-Carmen Popescu*, Sorin O. Mihai

ABSTRACT. Anthropogenic radioactive pollution of the environment resulting from the research and exploitation of uranium resources is a topical issue for the scientific community because it represents a threat to people’s health conditions and has a highly negative impact on the environment. The sources of radioactive pollution are due to the presence of low-level radioactive tailings and poor ore dumps resulting from the exploration and exploitation of uranium ore deposits. Uranium under the action of environmental factors can reach the groundwater, the river network, and the food chain, respectively. The contaminated food and water may cause diseases and even cancer. An important role in the pollution spreading is played by geological phenomena, the most important being landslides. Thus arises the need for geological risk management. The present study aims to implement a geological risk management system through methods of assessment, monitoring, and prediction of geological risk for a chosen uranium site. The waste rock and water samples analysis pointed out the radioactive contamination risk. The simulated scenarios in the area exposed to subsidence phenomena showed the activity of increasing the concentration of radioactive waste in the hydrographic system’s groundwater in the studied site, in a time interval of 4120 days (11.29 years): it rapidly increased in the first 1000 days (from 0.0 to 0.0033), after which it decreased in intensity until day 2500 (from 0.0033 to 0.0048), and it is supposed to stagnate after day 2500 until day 4120 when the simulation ended. The results emphasised the radioactive contamination spreading risk in the case when the subsidence phenomenon takes place.
Keywords: geological risk, uranium mining site, landslides, monitoring of geological parameters

DOI: 10.5281/zenodo.7006978
DOI: https://doi.org/10.58903/c16182112

GEOLOGICAL RISK MANAGEMENT PROCESS AND ITS PARTICULARITIES FOR A URANIUM SITE – CASE STUDY

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8. Van Westen C. J., 2004. Geo-information tools for landslide risk assessment: an overview of recent developments, Landslides: Evaluation and Stabilisation, Taylor & Francis Group, Balkema, London, p.39-57 DOI: 10.1201/b16816-6

9. Zajzon N., Szentpéteri K., Szakáll S., Kristály F., 2015. The origin of the Avram Iancu U–Ni–Co–Bi–As mineralisation, Băiţa (Bihor) metallogenic district, Bihor Mts., Romania. International Journal of Earth Sciences, 104(7), 1865–1887. doi:10.1007/s00531-015-1175-1

10. INCDMRR – Project concerning geological risk management application on a zone nearby a former uranium ore exploitation site (CEEX-MENER 723/2006) – 2006-2009 (in Romanian).

Velichka Arahangelova, Alexandre Loukanov

ABSTRACT. The copper is the second largest strategic raw material. Since there is a huge gap between copper production and consumption, a green and eco-sustainable recycling technology is necessary that is able to process the copper from secondary sources of waste and scraps. Here we demonstrate the photo-oxidising properties of pyrrolic nitrogen-dominated carbon nanodots as eco-friendly and powerful oxidase-mimicking nanozyme for leaching of copper from metal scrap under irradiation with either ultraviolet or natural sun light (average intensity of 59 000 lux). The ultra-small nanoparticles with diameter < 5 nm were prepared by 600 W microwave-assisted pyrolysis, which might be considered as energy efficient synthetic method. The developed strategy enables to dissolve Cu metal at neutral pH range (between 5.1 – 8.3) and it might break the pH limitation for recycling of copper in the conventional chemical methods, where toxic and corrosive substances are used. The obtained yield was about 5 %, which is still not satisfactory for practical application in recycle technology. Nevertheless, according to our knowledge there is not any other reported photosensitizer nanozyme, which is capable to induce oxidation and dissolving of copper under natural light irradiation of neutral leaching solution.
Key words: oxidase-mimicking nanozyme, carbon nanodots, copper leaching

DOI: 10.5281/zenodo.7006966
DOI: https://doi.org/10.58903/c16182111

CARBON NANODOTS AS LIGHT-ACTIVATED OXIDASE NANOZYME FOR ECO-FRIENDLY LEACHING OF COPPER FROM SCRAP

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15. Zhang J., Wu S., Lu X., Wu P., Liu J., 2019. Manganese as a catalytic mediator for photo-oxidation and breaking the pH limitation of nanozymes. Nano Lett., 19, 3214–3220. https://doi.org/10.1021/acs.nanolett.9b00725

16. Zhang R., Yan X., Fan K., 2021, Nanozymes inspired by natural enzymes, Accounts of Materials Research, 2, 534–547. https://doi.org/10.1021/accountsmr.1c00074

Todor Angelov

ABSTRACT. A composite flotation tailings sample from historic Medet tailings dam was characterised to understand occurrences of copper and hydraulic properties of the material and to determine if there is an economic benefit of its reprocessing using hydrometallurgical processes. Conventional ICP-OES multi-element scan and carbon and sulphur determination by Leco were followed by sequential copper assay and mineralogical analysis using the Tescan Integrated Mineral Analyser (TIMA) to identify the elemental composition, acid soluble copper and mineral abundance and liberation. The tailings sample contained 0.105% Cu, 0.41 % S and 0.05% C. The analysis of the gangue minerals showed that the bulk of the material is made up of plagioclase feldspar with moderate amounts of K-feldspars and small amounts of mica, chlorite and clay minerals. Copper minerals cuprite and chalcopyrite with minor amounts of covellite and bornite were observed in the mineralogical analysis of the sample by TIMA. Based on the sequential copper assays, it was estimated that approximately 59.8% of copper contained in the sample reports as acid soluble copper. To understand the flow behaviour in the material the main hydraulic properties like hydraulic conductivity and moisture retention capacity were determined.
Key words: tailings, copper, minerals, hydraulic properties

DOI: 10.5281/zenodo.7006957
DOI: https://doi.org/10.58903/c16182110

Todor Angelov
MINERALOGICAL AND HYDRAULIC CHARACTERISATION OF HISTORIC FLOTATION TAILINGS

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