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Determination of Rare Earth Elements Content in Hard Coal Type 31.1

Determination of Rare Earth Elements Content in Hard Coal Type 31.1 The aim of the article is to present the results of laboratory analyses determining the content of rare earth ele- ments (REE) in hard coal type 31.1. Coal was extracted directly from the mining excavation located in the Upper Silesian Coal Basin. Mass spectrometry tests with ionization in inductively coupled plasma (ICP-MS), were aimed at the quantitative analysis of the share of REE in coal, taking into account the economic aspects of recovery of these elements. Fine ground hard coal samples and ashes obtained after coal burning were assessed for the rare earth elements concentration. Results of the rare earth elements concentration (lanthanum and cerium) in hard coal are similar in the values obtained in previous tests. The current analyses present higher concentration of europium or neodymium. The article also contains the concept of possible future research work, consisting in the recovery of rare earth elements using, among others, a classifying hydrocyclone. Key words: mining industry, processing of hard coal, rare earth elements (REE) INTRODUCTION LITERATURE REVIEW Rare earths elements are of strategic economic im- Despite the name these elements are not rare, but their portance, in the aspect of a development of state-of-the- high dispersion is a problem. That is why, in many cases art technologies. The demand for REE increases every their recovery is not economically justified. REE is a group year with a development of new technologies. of 17 elements, which due to their specific physical and Currently conducted fragmentary tests on the content of chemical properties are used in many branches of indus- rare earths elements in Polish hard coal, showed the con- try. The examples of their use are given below [1, 4, 7]: tent of valuable metals in coal. A full range of the carbon − scandium (Sc) – aviation industry, construction of chain for hard coal is divided into the following types due planes and radiotherapy, to physical and chemical properties, and hence technolog- − lanthanum (La) – optical products, hybrid vehicles, ical usability: − yttrium (Y) – ceramics, metal alloys, − type 31 – cannel coal, − cerium (Ce) –metallurgy, dye for china, analytic chem- − type 32 – gas-cannel coal, istry, − type 33 – gas coal, − praseodymium (Pr) – dye for glass and stones, − type 34 – gas-coking coal, − neodymium (Nd) – laser technology, magnetic materi- − type 35 – ortho- coking coal, als, − type 36 – meta- coking coal, − samarium (Sm) – cinematography, nuclear technol- − type 37 – semi- coking coal, ogy, − type 38 –loan coal, − europium (Eu) – nuclear engineering, − type 41 – anthracite coal, − gadolinium (Gd) – alloys admixture, microwave tech- − type 42 – anthracite, nology , − type 43 – meta-anthracite [12, 22]. − promethium (Pm) – source of Beta radiation, Analyses at all the stages of the carbon chain starting from − terbium (Tb) –lasers, diodes, the youngest coal of type 31 are required to determine − dysprosium (Dy) – petrochemical industry, the REE concentration in hard coal. In connection with the − holmium (Ho) – nuclear technology, electronics, above, the KOMAG Institute of Mining Technology has un- − erbium (Er) – optical amplifiers, dertaken research and development work consisting in − thulium (Tm) – magnetic materials, assessing the rare earth elements abundance in hard coal, − ytterbium (Yb) – micro-electronics, starting from hard coal type 31.1. − lutetium (Lu) –manufacture of ferrites. R. BARON – Determination of Rare Earth Elements Content … 241 China, USA, Russia, India and Australia have the REE de- coal from the Upper Silesian Industrial District has a high posits, whose exploitation is economically justified [11, cerium content (2.05-108.0 ppm) compared to the global 13, 14, 16]. Global REE production remains at around 139 average content (23.0 ppm). A significant content of lan- thousand Mg and is largely dominated by China, which thanum (1.5-33.6 ppm) and scandium (1.5-20.5 ppm) was has 23% of the world resources and covers 93% of the found in the coal from the Lublin Coal Basin [3, 12]. world demand for rare earth elements [3, 4, 12]. The current tests confirm the presence of rare earth ele- Poland does not have deposits of rare earth elements, ments in hard coal (Table 1). thus the following natural raw materials, secondary and Laboratory analyses of power plant wastes from the com- waste materials are potential sources of these elements bustion of hard coal show a significant content of rare [4, 19]: earth elements, exceeding the concentration of these el- − hard coal, ements in coal even by several times. A relatively high ac- cumulation of cerium (39.0-186.0 ppm) or lanthanum − post-mining wastes, (16.0-86.0 ppm) was determined [10]. − ashes and slags from power plants, Due to big hard coal resources and lack of rare earth ele- − sand and gravel deposits, ments deposits in Poland, research work was undertaken − scraped electronic equipment. to determine the sources and possibilities of REE recovery RARE EARTH ELEMENTS IN THE POLISH HARD COAL from hard coal. The taken coal samples will also be used Content of REE in hard coal is a result of presence of such to determine the concentration of rare earth elements in minerals like kaolinite, biotite, hornblende and muscovite. ashes obtained in the combustion process in accordance with the compulsory standard. At the moment, the recov- According to the fragmentary tests of Polish hard coal from the Upper Silesian Coal Basin and the Lublin Coal Ba- ery economic aspect of these elements from hard coal is sin, it was proved that this raw material is a carrier of rare difficult to predict [3, 12]. earths elements. According to the conducted tests, the Table 1 Content of rare earth elements in hard coal in the selected mines in Poland Source: [3]. 242 Management Systems in Production Engineering 2020, Volume 28, Issue 4 TESTING MATERIALS AND METHODS Hard coal type 31.1 (cannel coal), from a mine located in the Upper Silesian Coal Basin was the subject of labora- tory analysis aimed at determining the concentration of rare earth elements. This type of coal, used for a combus- tion in industrial and domestic furnaces, is the first link of the carbon chain. In Poland coal seams of this type are de- posited at relatively low depths, about 300 m. It has a high content of volatile matter and lack or poor sintering abil- ity. Characteristics of material Coal samples for testing were taken directly from the ge- Fig. 2 Laboratory crusher ologically recognized seam, possibly from the lowest min- ing level, to determine the REE abundance in the newly Apart from the coal testing the ash, obtained after its opened deposit. The weight of the taken sample was combustion, was also analysed. about 50 kg. A preparation of the representative sample of ash con- Coal samples were taken manually from randomly se- sisted in crushing separated lumps of coal in a laboratory lected locations along the entire length of the longwall crusher, then milling it in a ring mill (Fig. 3). A preparation panel to provide a representative sample characterizing of the fine granulation material results from the standards the entire seam. Coal samples were taken from two seams for a sample combustion, to obtain hard coal ashes. being exploited in the mine. Characteristics of the seams, from which the samples were taken: − Sample 1: coal type 31.1 (cannel coal), seam 301 in the part “Podłęże S”, thickness – 2.2 – 2.7 m, depth of min- ing operations – from 288 to 335 m, date of taking the sample – 01.04.2019. − Sample 2: coal type 31.1 (cannel coal), seam 212 in the part “Wschód”, thickness – 2.9 – 4.2 m, depth of min- ing operations – from 540 to 712 m, date of taking the sample – 01.04.2019 [25]. Preparation of samples for laboratory tests A preparation of coal for testing consisted in selecting the Fig. 3 Cylindrical – roller mill representative sample of 0.5 kg from the 50 kg seam sam- ple (Fig. 1), using a sample divider (in the case of coal Then 10 crucibles were prepared and filled with 2 g of lumps larger than the gap of the divider it was necessary finely ground coal in each one, weighted on a laboratory to crush them first). scale. They were placed in the PM-6/1100A (Fig. 4) labor- atory chamber furnace to obtain about 1-2 g of ash after burning. The coal was burnt in the laboratory furnace, ac- cording to the Standard PN-ISO 1171:2002 [26]. Fig. 1 Selected sample The obtained coal sample of 0.5 kg was then crushed in a laboratory crusher (Fig. 2), to obtain grains below 2 mm in Fig. 4 Laboratory furnace PM-6/1100A size. R. BARON – Determination of Rare Earth Elements Content … 243 RESULTS AND DISSCUSION tent was obtained for cerium (27.2 ppm), while the con- The next part of the article presents the results of the centration of yttrium and europium for both seam sam- analyses determining the REE concentration, included in ples were very similar. the first stage of the task, consisting in the recovery of In Table 4, the REE contents (> 5 ppm) for ashes obtained rare earth elements from hard coal. after burning the hard coal samples, are given. Tested coal had a low ash content (Table 2). Table 4 Content of the selected REE in the hard coal ashes samples Table 2 Mass distribution of hard coal ashes REE content [ppm] Content Hard coal Material weight Ashes weight of ash samples origin [g] [g] [%] Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu Sample1 – 20.0654 1.1268 5.61 Seam 301 Sample 2 – 20.0380 2.1724 10.84 Seam 212 15.4 15.6 28.7 25.1 16.5 <5.0 8.0 <5.0 <5.0 <5.0 <5.0 <5.0 Such a preparation of hard coal and ash samples, after hard coal combustion, enabled to conduct laboratory analyses determining the content of rare earth elements in the tested samples. 31.3 32.3 27.8 21.3 33.6 8.1 9.7 11.8 11.5 10.4 8.2 <5.0 Obtained results Source: [9]. Laboratory tests to determine the REE content in the tested material were carried out in the Laboratory of Ma- In the tested ashes, the highest content of REE was ob- terial Engineering and Environment at the KOMAG Insti- tained for neodymium (33.6 ppm) and slightly lower for tute of Mining Technology. The obtained samples were yttrium (32.3 ppm) and scandium (31.3 ppm). analysed in relation to the dry matter content, where the Table 5 compares the REE content in hard coal samples wet mineralization process was carried out by a micro- with the REE content in ashes resulting from the combus- wave mineralizer. The obtained water solution was ana- tion of coal samples. lysed for the REE content by mass spectrometry with in- ductively coupled plasma (ICP-MS). Table 5 In Table 3, the content of the selected REE in the tested Comparison of REE content in hard coal and hard coal ashes hard coal samples is given. In the other analyzed REEs, the REE content [ppm] obtained concentration was below 5 ppm. Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu Table 3 Content of the selected REE in the hard coal type 31.1 samples REE content [ppm] <5.0 17.912.9 27.214.4 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.5 Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu 15.4 15.628.7 25.116.5 <5.0 8.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 17.9 12.9 27.2 14.4 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.5 <5.0 17.5<5.0 9.6 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.4 <5.0 17.5 <5.0 9.6 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.4 31.3 32.327.8 21.333.6 8.1 9.7 11.8 11.5 10.4 8.2 <5.0 Source: [9]. Source: [9]. Five rare earth elements were determined in the analysed Comparing the REE contents, determined in hard coal and hard coal ashes, an increase in concentration of specific hard coal samples (> 5 ppm) for sample 1 (seam 301) and elements and other valuable elements after the thermal 3 elements for sample 2 (seam 212). The highest REE con- processing is noticeable. Ashes have higher content of several elements. And so, for example: in the sample 2 the Sample 2 – Sample1 – Hard coal Seam 212 Seam 301 samples origin Sample: Sample 2 – Sample1 – Hard coal Sample 2 Sample 2 Sample 1 Sample 1 W-Coal Seam 212 Seam 301 samples origin (P) (W) (P) (W) P-Ash 244 Management Systems in Production Engineering 2020, Volume 28, Issue 4 neodymium content in coal < 5 ppm and in ash 33.6 ppm; elements (from the selected material with prospective in sample 2, the lanthanum content in coal < 5 ppm, and sufficient REE content) in the gravitational beneficiation in ash 27.8 ppm; in sample 1 lanthanum content in coal process. The obtained material will be a commercial prod- 12.9 ppm, and in ash 28.7 ppm. As a result of the hard coal uct, prepared for the recovery of valuable rare earth ele- combustion process, the presence of: scandium, praseo- ments in further chemical processes. dymium, samarium, gadolinium, dysprosium, erbium and Due to the fine-grain characteristics of the material (it is ytterbium was found. necessary to obtain a small granulation < 1 mm to release A hard coal thermal transformation increased in the REE REE), the concept of increasing concentration of these el- concentration significantly and it increased the number of ements assumes the use of a classifying hydrocyclone. the elements which were not determined previously. A hydrocyclone (Fig. 5) is a high-performance device that uses the centrifugal force in a liquid medium to separate Verification of results the mixture into two components effectively. Comparing the results of the REE content in hard coal with the literature reports (Table 6), some similarities in the re- sults, obtained for each element are noticeable. Table 6 Comparison of the REE content results in hard coal with the literature reports REE content based REE content based on the on the tests current test results [ppm] REE [ppm] obtained from the literature Sample 1 Sample 2 [ppm] Yttrium (Y) not determined 17.5 17.9 Fig. 5 Model of hydrocyclone Lanthanum (La) 1.06 – 14.58 12.9 <5 Cerium (Ce) 2.53 – 108.0 27.2 9.6 This device allows a classification of very fine material, Neodymium (Nd) 1.37 – 12.93 14.4 <5 Europium (Eu) 0.09 – 0.58 5.5 5.4 with a clear cut limit into the desired grain grades. The hy- Source: [3, 9]. drocyclone (Fig. 6) consists of: a cylindrical part (1), giving the mixture a swirl motion; a conical part (2), where a sep- Referring to the results of the tests obtained from the lit- aration occurs due to different grain sizes; an inlet nozzle erature (Table 1), it should be noted that they do not spec- (3), introducing the mixture, an overflow nozzle (4), re- ify any characteristics of the tested coal (e.g. coal type, el- ceiving fine grains and an outflow nozzle (5), collecting ement determination method). Thus, the following com- coarse grains [5, 8, 18, 24]. parison is indicative, taking into account the selected rare earths elements (Sc, Y, La, Ce, Nd, Eu), which were deter- mined as a part of current research work and laboratory analyses. The obtained REE content is within the limits of the value of previous tests for lanthanum and cerium. The current analyses confirm a higher concentration of europium or neodymium. Apart from the issues related to the generality of the re- sults so far, similar values confirm the correctness of the adopted cognitive method, determining the content of rare earth elements. CONCEPT OF RARE EARTH ELEMENTS RECOVERY In connection with the problems of rare earth elements dispersion, the recovery process is complex and requires a number of different processing methods. The initial en- richment process takes an advantage of a gravitational method, using devices such as a jig, a spiral separator, a cone concentrator, a concentration table or a hydrocy- clone. The obtained concentrate undergoes further pro- cesses, such as: flotation, leaching, magnetic-electrostatic separation or the use of concentrated acid solution and extraction with concentrated sodium hydroxide [4, 6, 15, 17, 20, 21, 23]. The final stage of the work aimed at recovering or obtain- Fig. 6 Schematic diagram of hydrocyclone ing the feed with a significant concentration of rare earth R. BARON – Determination of Rare Earth Elements Content … 245 In prototype installations of rare earth elements recovery, [3] Całus-Moszko J., Białecka B.: „Analiza możliwości pozyska- nia pierwiastków ziem rzadkich z węgla kamiennego i po- the hydrocyclone is a device included in the system of the piołów lotnych z elektrowni”. Gospodarka Surowcami Mi- processing machines. In the British concept for the REE re- neralnymi – Tom 29, z. 1. Instytut Gospodarki Surowcami covery from hard coal ashes, the hydrocyclone enriches Mineralnymi i Energią PAN, Kraków, 2013. the suspension based on different grain sizes, from which [4] Całus-Moszko J., Białecka B.: „Potencjał i zasoby metali the organic concentrate in the turbulent mixer and the ziem rzadkich w świecie oraz w Polsce„ Prace Naukowe magnetic concentrate in the magnetic drum were sepa- GIG. Górnictwo i Środowisko – Kwartalnik, Tom 4, pp. 61- rated previously. The results show a dozen or so percent- 72. Główny Instytut Górnictwa, Katowice, 2012. age increase in the REE content in the hydrocyclone over- [5] Collins A.R.: „Classification of Multi-Component Feeds in a Hydrocyclone”. A thesis submitted for the degree of Doc- flow [2]. tor of Philosophy at The University of Queensland, Austra- In addition, the selected material will be used to improve lia, 2016. the functional characteristics of the hydrocyclone, in or- [6] Case M., Fox R., Baek D., Chien W. „Extraction of Rare der to improve the efficiency of its operation through Earth Elements from Chloride Media with Tetrabutyl Digly- computer simulation of the flow, and then to manufac- colamide in 1-Octanol Modified Carbon Dioxide”, Metals 9 ture the testing prototype. (4), 429, 2019. [7] Charalampides G., Vatalis K. I., Apostoplos B., Ploutarch- CONCLUSIONS Nikolas B. „Rare Earth Elements: Industrial Applications The article presents the results of tests and analyses of and Economic Dependency of Europium e”, Procedia Eco- rare earth elements content in the Polish hard coal, start- nomics and Finance 24, pp. 126-135, 2015. ing from the first stage of the carbon chain, namely coal [8] Dubey R.K., Climent E., Banerjee C., Majumder A.K.: “Per- formance monitoring of a hydrocyclone based on under- type 31. flow discharge angle”. International Journal of Mineral As a part of the undertaken research work, a cooperation Processing – Volume 154, pp. 42-52, France, 2016. with the mine representatives was established and the [9] Grynkiewicz-Bylina B., Wundersee M., i inni. „Identyfikacja following tasks were completed: potencjalnych źródeł pierwiastków ziem rzadkich na pod- − a plan of testing and taking the samples of the as- stawie badań próbek węgla energetycznego i koksowego sumed type of hard coal, oraz odpadów z procesu flotacji węgla, popiołów i kruszyw − a methodology for a determination of rare earth ele- naturalnych – weryfikacja procedury badawczej”, E/DLS- ments content using mass spectrometry with induc- 24820/OR1. ITG KOMAG, Gliwice, 2019 (not published). [10] Hordyńska M.: „Popioły elektrowniane w procesach stabi- tively coupled plasma ionization (ICP-MS) was devel- lizacji odpadów niebezpiecznych”. Praca doktorska. Wydz. oped, Inżynieria Materiałowa i Metalurgii, Politechnika Śląska, − samples were prepared and the contents of rare earth Katowice, 2003. elements were determined in hard coal of type 31 and [11] Jaireth, S., Hoatson, D. M., & Miezitis, Y. „Geological set- also in ash from this coal, ting and resources of the major rare-earth-element depo- − an analysis of the results. sits in Australia”. Ore Geology Reviews, 62, pp. 72-128, Hard coal of type 31 and ash resulting from the combus- tion of this coal show the presence of rare earth elements. [12] Jarosiński A.: „Możliwości pozyskania metali ziem rzadkich w Polsce”, Zeszyty Naukowe – Tom 92, pp. 75-88. Instytut The obtained test results confirm a higher concentration Gospodarki Surowcami Mineralnymi i Energią PAN, Kra- of valuable elements in hard coal ash than in hard coal. ków, 2016. At this stage of technology advance, it is difficult to talk [13] Kanazawa Y., Kamitani M. „Rare Earth Minerals and Reso- about a possibility of recovering the REE from the coal of urces in the World”, Journal of Alloys and Compounds 408- type 31 on the industrial scale. This is due to a low con- 412(19), pp. 1339-1343, 2006. centration level of these elements in this type of coal and [14] Kathryn M. Goodenough K. M.,Wall F., Merriman D. „The a high energy consumption for separation processes. The Rare Earth Elements: Demand, Global Resources,and Chal- research work has a cognitive character and it seems rea- lenges for Resourcing Future Generations”, Natural Reso- sonable to conduct this type of research work and analysis urces Research volume 27, pp. 201-216, 2018. for other types of hard coal. [15] Lai Q. T., Thriveni T., Chilakala R., Hong Ha Thi Vu, Ji W. A., Jeongyun K. Leaching „Characteristics of Low Concentra- Hard coal, showing an economic justification for the REE tion Rare Earth Elements in Korean (Samcheok) CFBC Bot- recovery, can be a raw material for tests aimed at a recov- tom Ash Samples”, Sustainability 11(9), 2019. ery of these elements using a classifying hydrocyclone. [16] Mariano, A. N., & Mariano, A. „Rare earth mining and exploration in North America”, Elements, 8(5), pp. 369- REFERENCES 376, 2012. [1] Balaram V. „Rare earth elements: A review of applications, [17] Meisam Peiravi M., Ackah L., Guru R., Mohanty M., Liu J., occurrence, exploration, analysis, recycling, and environ- Xu B., Zhu X., Chen L., „Chemical extraction of rare earth mental impact”, Geoscience Frontiers, Volume 10, Issue 4, elements from coal Ash”, Minerals and Metallurgical Pro- pp. 1285-1303, 2019. cessing 34(4), pp. 170-177, 2017. [2] Blissett R.S., Smalley N., Rowson N.A.: „An investigation [18] Nowak Z.: „Hydrocyklony w przeróbce mechanicznej kopa- into six coal fly ashes from United Kingdom and Poland to lin”, Wydawnictwo Śląsk, Katowice, 1970. evaluate rare earth element content”. Fuel – the science [19] Paulo A.: „Pierwiastki ziem rzadkich pod koniec XX wieku”, and technology of Fuel and Energy – Volume 119, pp. 236- Przegląd Geologiczny – Tom 47, pp. 34-41. Państwowy In- 239, United Kingdom, 2013. stytut Geologiczny, Warszawa, 1999. 246 Management Systems in Production Engineering 2020, Volume 28, Issue 4 [20] Peelman S., Sun Z. H. I., Sietsma J., Yang Y. „Hydrometal- [23] Vossenkaul, D., Birich, A., Müller, N., Stoltz, N., Friedrich, lurgical Extraction of Rare Earth Elements from Low Grade B. „Hydrometallurgical processing of eudialyte bearing Mine Tailings”, Rare Metal Technology pp. 17-29, 2016. concentrates to recover rare earth elements via low-tem- [21] Quinn J. E., Soldenhoff K. H., Stevens G. W., Lengkeek N. A. perature dry digestion to prevent the silica gel formation”, „Solvent extraction of rare earth elements using phospho- Journal of Sustainable Metallurgy, 3, pp. 1-11, 2016. nic/phosphinic acid mixtures”, Hydrometallurgy, Volume [24] Yuan Hsu Ch., Jhih Wu S., Ming Wu R.: “Particles Separa- 157, pp. 298-305, 2015. tion and Tracks in a Hydrocyclone”. Tamkang Journal of [22] Sobolewski A., Micorek T., Winnicka G., Heilpern S.: „Pro- Science and Engineering – Volume 14, Pages 65-70, Tam- pozycja polskiej klasyfikacji węgli koksowych”, Przegląd kang University, Taiwan, 2011. Górniczy – Miesięcznik Stowarzyszenia Inżynierów i Tech- [25] Materiały otrzymane od TAURON Wydobycie S.A. ników Górnictwa, Katowice, 2016. [26] PN-ISO 1171:2002 – Solid mineral fuels – determination of ash content. Rafał BARON ORCID ID: 0000-0002-7141-8960 KOMAG Institute of Mining Technology Division of Preparation Systems Pszczyńska 37, 44-101 Gliwice, Poland e-mail: rbaron@komag.eu http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Management Systems in Production Engineering de Gruyter

Determination of Rare Earth Elements Content in Hard Coal Type 31.1

Management Systems in Production Engineering , Volume 28 (4): 7 – Dec 1, 2020

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de Gruyter
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© 2020 Rafał Baron, published by Sciendo
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2450-5781
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10.2478/mspe-2020-0034
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Abstract

The aim of the article is to present the results of laboratory analyses determining the content of rare earth ele- ments (REE) in hard coal type 31.1. Coal was extracted directly from the mining excavation located in the Upper Silesian Coal Basin. Mass spectrometry tests with ionization in inductively coupled plasma (ICP-MS), were aimed at the quantitative analysis of the share of REE in coal, taking into account the economic aspects of recovery of these elements. Fine ground hard coal samples and ashes obtained after coal burning were assessed for the rare earth elements concentration. Results of the rare earth elements concentration (lanthanum and cerium) in hard coal are similar in the values obtained in previous tests. The current analyses present higher concentration of europium or neodymium. The article also contains the concept of possible future research work, consisting in the recovery of rare earth elements using, among others, a classifying hydrocyclone. Key words: mining industry, processing of hard coal, rare earth elements (REE) INTRODUCTION LITERATURE REVIEW Rare earths elements are of strategic economic im- Despite the name these elements are not rare, but their portance, in the aspect of a development of state-of-the- high dispersion is a problem. That is why, in many cases art technologies. The demand for REE increases every their recovery is not economically justified. REE is a group year with a development of new technologies. of 17 elements, which due to their specific physical and Currently conducted fragmentary tests on the content of chemical properties are used in many branches of indus- rare earths elements in Polish hard coal, showed the con- try. The examples of their use are given below [1, 4, 7]: tent of valuable metals in coal. A full range of the carbon − scandium (Sc) – aviation industry, construction of chain for hard coal is divided into the following types due planes and radiotherapy, to physical and chemical properties, and hence technolog- − lanthanum (La) – optical products, hybrid vehicles, ical usability: − yttrium (Y) – ceramics, metal alloys, − type 31 – cannel coal, − cerium (Ce) –metallurgy, dye for china, analytic chem- − type 32 – gas-cannel coal, istry, − type 33 – gas coal, − praseodymium (Pr) – dye for glass and stones, − type 34 – gas-coking coal, − neodymium (Nd) – laser technology, magnetic materi- − type 35 – ortho- coking coal, als, − type 36 – meta- coking coal, − samarium (Sm) – cinematography, nuclear technol- − type 37 – semi- coking coal, ogy, − type 38 –loan coal, − europium (Eu) – nuclear engineering, − type 41 – anthracite coal, − gadolinium (Gd) – alloys admixture, microwave tech- − type 42 – anthracite, nology , − type 43 – meta-anthracite [12, 22]. − promethium (Pm) – source of Beta radiation, Analyses at all the stages of the carbon chain starting from − terbium (Tb) –lasers, diodes, the youngest coal of type 31 are required to determine − dysprosium (Dy) – petrochemical industry, the REE concentration in hard coal. In connection with the − holmium (Ho) – nuclear technology, electronics, above, the KOMAG Institute of Mining Technology has un- − erbium (Er) – optical amplifiers, dertaken research and development work consisting in − thulium (Tm) – magnetic materials, assessing the rare earth elements abundance in hard coal, − ytterbium (Yb) – micro-electronics, starting from hard coal type 31.1. − lutetium (Lu) –manufacture of ferrites. R. BARON – Determination of Rare Earth Elements Content … 241 China, USA, Russia, India and Australia have the REE de- coal from the Upper Silesian Industrial District has a high posits, whose exploitation is economically justified [11, cerium content (2.05-108.0 ppm) compared to the global 13, 14, 16]. Global REE production remains at around 139 average content (23.0 ppm). A significant content of lan- thousand Mg and is largely dominated by China, which thanum (1.5-33.6 ppm) and scandium (1.5-20.5 ppm) was has 23% of the world resources and covers 93% of the found in the coal from the Lublin Coal Basin [3, 12]. world demand for rare earth elements [3, 4, 12]. The current tests confirm the presence of rare earth ele- Poland does not have deposits of rare earth elements, ments in hard coal (Table 1). thus the following natural raw materials, secondary and Laboratory analyses of power plant wastes from the com- waste materials are potential sources of these elements bustion of hard coal show a significant content of rare [4, 19]: earth elements, exceeding the concentration of these el- − hard coal, ements in coal even by several times. A relatively high ac- cumulation of cerium (39.0-186.0 ppm) or lanthanum − post-mining wastes, (16.0-86.0 ppm) was determined [10]. − ashes and slags from power plants, Due to big hard coal resources and lack of rare earth ele- − sand and gravel deposits, ments deposits in Poland, research work was undertaken − scraped electronic equipment. to determine the sources and possibilities of REE recovery RARE EARTH ELEMENTS IN THE POLISH HARD COAL from hard coal. The taken coal samples will also be used Content of REE in hard coal is a result of presence of such to determine the concentration of rare earth elements in minerals like kaolinite, biotite, hornblende and muscovite. ashes obtained in the combustion process in accordance with the compulsory standard. At the moment, the recov- According to the fragmentary tests of Polish hard coal from the Upper Silesian Coal Basin and the Lublin Coal Ba- ery economic aspect of these elements from hard coal is sin, it was proved that this raw material is a carrier of rare difficult to predict [3, 12]. earths elements. According to the conducted tests, the Table 1 Content of rare earth elements in hard coal in the selected mines in Poland Source: [3]. 242 Management Systems in Production Engineering 2020, Volume 28, Issue 4 TESTING MATERIALS AND METHODS Hard coal type 31.1 (cannel coal), from a mine located in the Upper Silesian Coal Basin was the subject of labora- tory analysis aimed at determining the concentration of rare earth elements. This type of coal, used for a combus- tion in industrial and domestic furnaces, is the first link of the carbon chain. In Poland coal seams of this type are de- posited at relatively low depths, about 300 m. It has a high content of volatile matter and lack or poor sintering abil- ity. Characteristics of material Coal samples for testing were taken directly from the ge- Fig. 2 Laboratory crusher ologically recognized seam, possibly from the lowest min- ing level, to determine the REE abundance in the newly Apart from the coal testing the ash, obtained after its opened deposit. The weight of the taken sample was combustion, was also analysed. about 50 kg. A preparation of the representative sample of ash con- Coal samples were taken manually from randomly se- sisted in crushing separated lumps of coal in a laboratory lected locations along the entire length of the longwall crusher, then milling it in a ring mill (Fig. 3). A preparation panel to provide a representative sample characterizing of the fine granulation material results from the standards the entire seam. Coal samples were taken from two seams for a sample combustion, to obtain hard coal ashes. being exploited in the mine. Characteristics of the seams, from which the samples were taken: − Sample 1: coal type 31.1 (cannel coal), seam 301 in the part “Podłęże S”, thickness – 2.2 – 2.7 m, depth of min- ing operations – from 288 to 335 m, date of taking the sample – 01.04.2019. − Sample 2: coal type 31.1 (cannel coal), seam 212 in the part “Wschód”, thickness – 2.9 – 4.2 m, depth of min- ing operations – from 540 to 712 m, date of taking the sample – 01.04.2019 [25]. Preparation of samples for laboratory tests A preparation of coal for testing consisted in selecting the Fig. 3 Cylindrical – roller mill representative sample of 0.5 kg from the 50 kg seam sam- ple (Fig. 1), using a sample divider (in the case of coal Then 10 crucibles were prepared and filled with 2 g of lumps larger than the gap of the divider it was necessary finely ground coal in each one, weighted on a laboratory to crush them first). scale. They were placed in the PM-6/1100A (Fig. 4) labor- atory chamber furnace to obtain about 1-2 g of ash after burning. The coal was burnt in the laboratory furnace, ac- cording to the Standard PN-ISO 1171:2002 [26]. Fig. 1 Selected sample The obtained coal sample of 0.5 kg was then crushed in a laboratory crusher (Fig. 2), to obtain grains below 2 mm in Fig. 4 Laboratory furnace PM-6/1100A size. R. BARON – Determination of Rare Earth Elements Content … 243 RESULTS AND DISSCUSION tent was obtained for cerium (27.2 ppm), while the con- The next part of the article presents the results of the centration of yttrium and europium for both seam sam- analyses determining the REE concentration, included in ples were very similar. the first stage of the task, consisting in the recovery of In Table 4, the REE contents (> 5 ppm) for ashes obtained rare earth elements from hard coal. after burning the hard coal samples, are given. Tested coal had a low ash content (Table 2). Table 4 Content of the selected REE in the hard coal ashes samples Table 2 Mass distribution of hard coal ashes REE content [ppm] Content Hard coal Material weight Ashes weight of ash samples origin [g] [g] [%] Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu Sample1 – 20.0654 1.1268 5.61 Seam 301 Sample 2 – 20.0380 2.1724 10.84 Seam 212 15.4 15.6 28.7 25.1 16.5 <5.0 8.0 <5.0 <5.0 <5.0 <5.0 <5.0 Such a preparation of hard coal and ash samples, after hard coal combustion, enabled to conduct laboratory analyses determining the content of rare earth elements in the tested samples. 31.3 32.3 27.8 21.3 33.6 8.1 9.7 11.8 11.5 10.4 8.2 <5.0 Obtained results Source: [9]. Laboratory tests to determine the REE content in the tested material were carried out in the Laboratory of Ma- In the tested ashes, the highest content of REE was ob- terial Engineering and Environment at the KOMAG Insti- tained for neodymium (33.6 ppm) and slightly lower for tute of Mining Technology. The obtained samples were yttrium (32.3 ppm) and scandium (31.3 ppm). analysed in relation to the dry matter content, where the Table 5 compares the REE content in hard coal samples wet mineralization process was carried out by a micro- with the REE content in ashes resulting from the combus- wave mineralizer. The obtained water solution was ana- tion of coal samples. lysed for the REE content by mass spectrometry with in- ductively coupled plasma (ICP-MS). Table 5 In Table 3, the content of the selected REE in the tested Comparison of REE content in hard coal and hard coal ashes hard coal samples is given. In the other analyzed REEs, the REE content [ppm] obtained concentration was below 5 ppm. Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu Table 3 Content of the selected REE in the hard coal type 31.1 samples REE content [ppm] <5.0 17.912.9 27.214.4 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.5 Sc Y La Ce Nd Pr Sm Gd Dy Er Yb Eu 15.4 15.628.7 25.116.5 <5.0 8.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 17.9 12.9 27.2 14.4 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.5 <5.0 17.5<5.0 9.6 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.4 <5.0 17.5 <5.0 9.6 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 5.4 31.3 32.327.8 21.333.6 8.1 9.7 11.8 11.5 10.4 8.2 <5.0 Source: [9]. Source: [9]. Five rare earth elements were determined in the analysed Comparing the REE contents, determined in hard coal and hard coal ashes, an increase in concentration of specific hard coal samples (> 5 ppm) for sample 1 (seam 301) and elements and other valuable elements after the thermal 3 elements for sample 2 (seam 212). The highest REE con- processing is noticeable. Ashes have higher content of several elements. And so, for example: in the sample 2 the Sample 2 – Sample1 – Hard coal Seam 212 Seam 301 samples origin Sample: Sample 2 – Sample1 – Hard coal Sample 2 Sample 2 Sample 1 Sample 1 W-Coal Seam 212 Seam 301 samples origin (P) (W) (P) (W) P-Ash 244 Management Systems in Production Engineering 2020, Volume 28, Issue 4 neodymium content in coal < 5 ppm and in ash 33.6 ppm; elements (from the selected material with prospective in sample 2, the lanthanum content in coal < 5 ppm, and sufficient REE content) in the gravitational beneficiation in ash 27.8 ppm; in sample 1 lanthanum content in coal process. The obtained material will be a commercial prod- 12.9 ppm, and in ash 28.7 ppm. As a result of the hard coal uct, prepared for the recovery of valuable rare earth ele- combustion process, the presence of: scandium, praseo- ments in further chemical processes. dymium, samarium, gadolinium, dysprosium, erbium and Due to the fine-grain characteristics of the material (it is ytterbium was found. necessary to obtain a small granulation < 1 mm to release A hard coal thermal transformation increased in the REE REE), the concept of increasing concentration of these el- concentration significantly and it increased the number of ements assumes the use of a classifying hydrocyclone. the elements which were not determined previously. A hydrocyclone (Fig. 5) is a high-performance device that uses the centrifugal force in a liquid medium to separate Verification of results the mixture into two components effectively. Comparing the results of the REE content in hard coal with the literature reports (Table 6), some similarities in the re- sults, obtained for each element are noticeable. Table 6 Comparison of the REE content results in hard coal with the literature reports REE content based REE content based on the on the tests current test results [ppm] REE [ppm] obtained from the literature Sample 1 Sample 2 [ppm] Yttrium (Y) not determined 17.5 17.9 Fig. 5 Model of hydrocyclone Lanthanum (La) 1.06 – 14.58 12.9 <5 Cerium (Ce) 2.53 – 108.0 27.2 9.6 This device allows a classification of very fine material, Neodymium (Nd) 1.37 – 12.93 14.4 <5 Europium (Eu) 0.09 – 0.58 5.5 5.4 with a clear cut limit into the desired grain grades. The hy- Source: [3, 9]. drocyclone (Fig. 6) consists of: a cylindrical part (1), giving the mixture a swirl motion; a conical part (2), where a sep- Referring to the results of the tests obtained from the lit- aration occurs due to different grain sizes; an inlet nozzle erature (Table 1), it should be noted that they do not spec- (3), introducing the mixture, an overflow nozzle (4), re- ify any characteristics of the tested coal (e.g. coal type, el- ceiving fine grains and an outflow nozzle (5), collecting ement determination method). Thus, the following com- coarse grains [5, 8, 18, 24]. parison is indicative, taking into account the selected rare earths elements (Sc, Y, La, Ce, Nd, Eu), which were deter- mined as a part of current research work and laboratory analyses. The obtained REE content is within the limits of the value of previous tests for lanthanum and cerium. The current analyses confirm a higher concentration of europium or neodymium. Apart from the issues related to the generality of the re- sults so far, similar values confirm the correctness of the adopted cognitive method, determining the content of rare earth elements. CONCEPT OF RARE EARTH ELEMENTS RECOVERY In connection with the problems of rare earth elements dispersion, the recovery process is complex and requires a number of different processing methods. The initial en- richment process takes an advantage of a gravitational method, using devices such as a jig, a spiral separator, a cone concentrator, a concentration table or a hydrocy- clone. The obtained concentrate undergoes further pro- cesses, such as: flotation, leaching, magnetic-electrostatic separation or the use of concentrated acid solution and extraction with concentrated sodium hydroxide [4, 6, 15, 17, 20, 21, 23]. The final stage of the work aimed at recovering or obtain- Fig. 6 Schematic diagram of hydrocyclone ing the feed with a significant concentration of rare earth R. BARON – Determination of Rare Earth Elements Content … 245 In prototype installations of rare earth elements recovery, [3] Całus-Moszko J., Białecka B.: „Analiza możliwości pozyska- nia pierwiastków ziem rzadkich z węgla kamiennego i po- the hydrocyclone is a device included in the system of the piołów lotnych z elektrowni”. Gospodarka Surowcami Mi- processing machines. In the British concept for the REE re- neralnymi – Tom 29, z. 1. Instytut Gospodarki Surowcami covery from hard coal ashes, the hydrocyclone enriches Mineralnymi i Energią PAN, Kraków, 2013. the suspension based on different grain sizes, from which [4] Całus-Moszko J., Białecka B.: „Potencjał i zasoby metali the organic concentrate in the turbulent mixer and the ziem rzadkich w świecie oraz w Polsce„ Prace Naukowe magnetic concentrate in the magnetic drum were sepa- GIG. Górnictwo i Środowisko – Kwartalnik, Tom 4, pp. 61- rated previously. The results show a dozen or so percent- 72. Główny Instytut Górnictwa, Katowice, 2012. age increase in the REE content in the hydrocyclone over- [5] Collins A.R.: „Classification of Multi-Component Feeds in a Hydrocyclone”. A thesis submitted for the degree of Doc- flow [2]. tor of Philosophy at The University of Queensland, Austra- In addition, the selected material will be used to improve lia, 2016. the functional characteristics of the hydrocyclone, in or- [6] Case M., Fox R., Baek D., Chien W. „Extraction of Rare der to improve the efficiency of its operation through Earth Elements from Chloride Media with Tetrabutyl Digly- computer simulation of the flow, and then to manufac- colamide in 1-Octanol Modified Carbon Dioxide”, Metals 9 ture the testing prototype. (4), 429, 2019. [7] Charalampides G., Vatalis K. I., Apostoplos B., Ploutarch- CONCLUSIONS Nikolas B. „Rare Earth Elements: Industrial Applications The article presents the results of tests and analyses of and Economic Dependency of Europium e”, Procedia Eco- rare earth elements content in the Polish hard coal, start- nomics and Finance 24, pp. 126-135, 2015. ing from the first stage of the carbon chain, namely coal [8] Dubey R.K., Climent E., Banerjee C., Majumder A.K.: “Per- formance monitoring of a hydrocyclone based on under- type 31. flow discharge angle”. International Journal of Mineral As a part of the undertaken research work, a cooperation Processing – Volume 154, pp. 42-52, France, 2016. with the mine representatives was established and the [9] Grynkiewicz-Bylina B., Wundersee M., i inni. „Identyfikacja following tasks were completed: potencjalnych źródeł pierwiastków ziem rzadkich na pod- − a plan of testing and taking the samples of the as- stawie badań próbek węgla energetycznego i koksowego sumed type of hard coal, oraz odpadów z procesu flotacji węgla, popiołów i kruszyw − a methodology for a determination of rare earth ele- naturalnych – weryfikacja procedury badawczej”, E/DLS- ments content using mass spectrometry with induc- 24820/OR1. ITG KOMAG, Gliwice, 2019 (not published). [10] Hordyńska M.: „Popioły elektrowniane w procesach stabi- tively coupled plasma ionization (ICP-MS) was devel- lizacji odpadów niebezpiecznych”. Praca doktorska. Wydz. oped, Inżynieria Materiałowa i Metalurgii, Politechnika Śląska, − samples were prepared and the contents of rare earth Katowice, 2003. elements were determined in hard coal of type 31 and [11] Jaireth, S., Hoatson, D. M., & Miezitis, Y. „Geological set- also in ash from this coal, ting and resources of the major rare-earth-element depo- − an analysis of the results. sits in Australia”. Ore Geology Reviews, 62, pp. 72-128, Hard coal of type 31 and ash resulting from the combus- tion of this coal show the presence of rare earth elements. [12] Jarosiński A.: „Możliwości pozyskania metali ziem rzadkich w Polsce”, Zeszyty Naukowe – Tom 92, pp. 75-88. Instytut The obtained test results confirm a higher concentration Gospodarki Surowcami Mineralnymi i Energią PAN, Kra- of valuable elements in hard coal ash than in hard coal. ków, 2016. At this stage of technology advance, it is difficult to talk [13] Kanazawa Y., Kamitani M. „Rare Earth Minerals and Reso- about a possibility of recovering the REE from the coal of urces in the World”, Journal of Alloys and Compounds 408- type 31 on the industrial scale. This is due to a low con- 412(19), pp. 1339-1343, 2006. centration level of these elements in this type of coal and [14] Kathryn M. Goodenough K. M.,Wall F., Merriman D. „The a high energy consumption for separation processes. The Rare Earth Elements: Demand, Global Resources,and Chal- research work has a cognitive character and it seems rea- lenges for Resourcing Future Generations”, Natural Reso- sonable to conduct this type of research work and analysis urces Research volume 27, pp. 201-216, 2018. for other types of hard coal. [15] Lai Q. T., Thriveni T., Chilakala R., Hong Ha Thi Vu, Ji W. A., Jeongyun K. Leaching „Characteristics of Low Concentra- Hard coal, showing an economic justification for the REE tion Rare Earth Elements in Korean (Samcheok) CFBC Bot- recovery, can be a raw material for tests aimed at a recov- tom Ash Samples”, Sustainability 11(9), 2019. ery of these elements using a classifying hydrocyclone. [16] Mariano, A. N., & Mariano, A. „Rare earth mining and exploration in North America”, Elements, 8(5), pp. 369- REFERENCES 376, 2012. [1] Balaram V. „Rare earth elements: A review of applications, [17] Meisam Peiravi M., Ackah L., Guru R., Mohanty M., Liu J., occurrence, exploration, analysis, recycling, and environ- Xu B., Zhu X., Chen L., „Chemical extraction of rare earth mental impact”, Geoscience Frontiers, Volume 10, Issue 4, elements from coal Ash”, Minerals and Metallurgical Pro- pp. 1285-1303, 2019. cessing 34(4), pp. 170-177, 2017. 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W., Lengkeek N. A. perature dry digestion to prevent the silica gel formation”, „Solvent extraction of rare earth elements using phospho- Journal of Sustainable Metallurgy, 3, pp. 1-11, 2016. nic/phosphinic acid mixtures”, Hydrometallurgy, Volume [24] Yuan Hsu Ch., Jhih Wu S., Ming Wu R.: “Particles Separa- 157, pp. 298-305, 2015. tion and Tracks in a Hydrocyclone”. Tamkang Journal of [22] Sobolewski A., Micorek T., Winnicka G., Heilpern S.: „Pro- Science and Engineering – Volume 14, Pages 65-70, Tam- pozycja polskiej klasyfikacji węgli koksowych”, Przegląd kang University, Taiwan, 2011. Górniczy – Miesięcznik Stowarzyszenia Inżynierów i Tech- [25] Materiały otrzymane od TAURON Wydobycie S.A. ników Górnictwa, Katowice, 2016. [26] PN-ISO 1171:2002 – Solid mineral fuels – determination of ash content. Rafał BARON ORCID ID: 0000-0002-7141-8960 KOMAG Institute of Mining Technology Division of Preparation Systems Pszczyńska 37, 44-101 Gliwice, Poland e-mail: rbaron@komag.eu

Journal

Management Systems in Production Engineeringde Gruyter

Published: Dec 1, 2020

Keywords: mining industry; processing of hard coal; rare earth elements (REE)

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