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Zircon (ZrSiO4) is found usually as a constituent in heavy mineral sand assemblages which ...

Zircon (ZrSiO4) is found usually as a constituent in heavy mineral sand assemblages which
include ilmenite, rutile, leucoxene, monazite and garnet in varying proportions. Investigations are
carried out on the zircons recovered as a non magnetic and non conducting heavy mineral from the
entire process for effective utilization. Recovered zircons are used for making zircon bricks and are
fired at different temperatures in an industrial tunnel kiln. Physical, chemical and thermo-mechanical
properties are evaluated. Mineralogical properties are correlated with the thermo-mechanical
properties. The developed bricks are compared with the standards for their suitability in industrial
applications.

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30120140505007 30120140505007 Document Transcript

  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 73 RECOVERY OF ZIRCONS OF SOUTH EASTERN COAST OF INDIA: THEIR POTENTIAL AS REFRACTORIES AND CERAMICS 1 Sunita Routray, 2 L.N. Padhi, 3 Tanusree Bera 1,3 C V Raman College of Engineering, Bhubaneswar 2 DISIR, Rajgangpur ABSTRACT Zircon (ZrSiO4) is found usually as a constituent in heavy mineral sand assemblages which include ilmenite, rutile, leucoxene, monazite and garnet in varying proportions. Investigations are carried out on the zircons recovered as a non magnetic and non conducting heavy mineral from the entire process for effective utilization. Recovered zircons are used for making zircon bricks and are fired at different temperatures in an industrial tunnel kiln. Physical, chemical and thermo-mechanical properties are evaluated. Mineralogical properties are correlated with the thermo-mechanical properties. The developed bricks are compared with the standards for their suitability in industrial applications. Keywords: Beach sand, Dune sand, Zircon, Beneficiation, Brick, Refractories. 1. INTRODUCTION Beach placer deposits of India essentially consist of ilmenite, rutile, garnet, zircon, monazite, sillimanite and quartz. The heavy mineral deposits at Southeastern coast of India, in the states of Orissa, Andhra Pradesh have a significant concentration of heavy minerals. Owing to high demand of zircon, the exploitation of the sand deposits and recovery of zircon from beach and dune sands is a priority at present. The reserves of zircon in Indian beach sands contain 21.14 million metric tons out of which Andhra Pradesh and Orissa contribute 4.43 and 1.33 million metric tons respectively. Hence, it has attracted the wide attention of scientists, engineers and users to exploit zircons from alluvial deposits and in depth characterizations for end use. [1] Zircon is used in industry in a wide range of applications, as zircon sand directly from the mine; as a milled product in the form of zircon flour (95 % micronized to <45µm used in the manufacturing of frit) and opacifier grade (100% micronized to <6 µm, used in ceramic glazes for titles and sanitary wares). The most important market for zircon is as an opacifier for ceramic titles and sanitary ware. INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 74 Zircon finds its application in ceramics (54%) and refractory industries (14%), which account for 68% of zircon’s total world consumption of 1.2 million tonnes. The rest (32%) is consumed in foundry, TV glass, zirconia chemicals and other applications. [2] Zircon sand and fines are widely used for making refractory bricks with the addition of magnesia or alumina in glass industries due to high resistance to batch carryover attack and sulphate attack in regenerators or tank furnaces. Zircon alumina is the most sought after refractories for glass casting. Also these refractories find applications in cement industries due to superior thermal and thermo-mechanical properties. Zircon alone is a potential mineral for casting refractory in iron and steel industries for superior resistance to abrasion, erosion, high volume stability and thermal spalling. The superior performance of zircon sand for nozzle filling is not new to steel industries. Heating the zircon sand to 1700° C, dissociation into zirconia and silica occurs, represented by the following reaction. [3] ZrSiO4 = ZrO2 + SiO2 On addition of alumina, the liberated SiO2 reacts with Al2O3 to form mullite (3 Al2O3.2SiO2), releasing ZrO2. Thus, the mullite-zirconia composites can be developed by reaction sintering of zircon and alumina in the temperature range 1400-1600° C. The reaction is represented as 2ZrSiO4 + 3Al2O3 = 3Al2O3.2SiO2 + 2ZrO2 In this paper, an attempt is made for recovery of zircon from beach and dune sands of Konark–Ramchandi (Lat.17o 49’-22o 34’N and Long.81o 29’-87o 29’E), Puri District, Orissa. The recovered zircon is then used for making refractory bricks with different compositions for value addition. The developed bricks are compared with the standards for its suitability in industrial application. 2. MATERIALS AND METHODS 2.1. Raw material Samples were collected along the beach and dunes of Konark- Ramachandi beach using auger sampler up to 4 -6 feet depth. Bulk sample was prepared for beneficiation studies to recover zircon. Zircon flour and opacifier were prepared separately for making bricks. Dextrine (AR grade) was used for binding purpose. 2.2. Beneficiation studies The bulk sample was subjected to a laboratory model, Humphrey’s spiral concentrator, supplied by M/s. Humphreys Mineral Industries, Inc., Denver, USA with 17½” pitch used to recover total heavy minerals (98% THM). The concentrate was then subjected to Wet High Intensity Magnetic Separator (WHIMS) to recover magnetic heavies and non-magnetic heavies separately. The non magnetic fraction contains mostly sillimanite, zircon, rutile, quartz etc. The non magnetic fraction was subjected to flotation cell to separate sillimanite from zircon, rutile and quartz. The rutile-zircon-quartz sample obtained from flotation was further subjected to High Tension Separator (HTS) to separate conducting fraction rutile from zircon and quartz. The non conducting fraction of HTS was subjected to gravity table to recover zircon concentrate. All spiral, magnetic, HTS and flotation products were subjected to sink and float tests to assess the quality of the products. Initially sink float tests were carried out with bromoform (2.89 sp.gr) to assess the total heavy minerals content. Methylene iodide (3.3 sp.gr) was used to assess the sillimanite content in the total heavy minerals.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 75 Recovered zircon was used for making zircon refractory bricks along with other raw materials such as sillimanite sand, tabular alumina and dextrine. The composition of the prepared refractory bricks is given in Table 1. Prepared bricks were fired at different temperatures in an industrial tunnel kiln. Physical, chemical and thermo-mechanical properties of the bricks were evaluated. Mineralogical properties of the bricks were correlated with the thermo-mechanical properties. Table.1: Compositions of the prepared refractory bricks RAW MATERIALS COMPOSITION 1 COMPOSITION 2 COMPOSITION 3 Zircon sand 60 % 10 % 30 % Zircon flour 30 % 30 % - Zircon opacifier 10 % 10 % - Sillimanite sand - 50 % - Tabular alumina (8- 14 mesh) - - 20 % Tabular alumina ( 14- 28 mesh) - - 5 % Tabular alumina (28- 48mesh) - - 5 % Tabular alumina (48- 60 mesh) - - 10 % Tabular alumina (325 mesh) - - 30 % Dextrin 2.5P 2.5P 2.5P Moisture content 1.1 1.1 1.3 2.3. Development of brick Different size fractions were taken according to compositions and mixed in a laboratory counter current mixer for homogeneity with the addition of green binder (dextrin) and water for about 20 minutes. The mixtures were formulated into brick shape in high capacity hydraulic press with a specific pressure of 1800kg/cm2 . Sufficient care was taken during pressing to avoid cracks and lamination All the bricks were dried in an industrial drier at a temperature of 100-120°C for 24 hours to drive out moisture which may lead to explosion during firing. After drying all the bricks were checked for physical defects and loaded in top bench of the kiln car giving equidistance gap for ensuring uniform firing. All the bricks of different compositions were fired at a peak temperature of 1580°C for 6 hours in industrial tunnel kilns with a predetermined scheduled firing rate. The typical photographs of these fired bricks are shown in Fig 1.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 76 Fig 1: Typical bricks of different compositions [Composition 1 (a and b), Composition 2 (c and d), Composition 3 (e and f)] 2.3a. Evaluation of mixer Sieve analysis and moisture content were determined according to BIS standard. 2.3b Evaluation of green brick Green size, weight and bulk density were determined according to BIS standard. 2.3c Evaluation of bricks after firing at 1580°C Physical properties such as apparent porosity, bulk density, cold crushing strength and modulus of rupture were determined according to BIS standard. Thermo- mechanical properties such as refractories under load was determined according to BIS standard. Hot modulus of rupture test was carried out in Pereco test kiln USA assisted with Netzsch 522 Germany bending test apparatus following ASTM C 583 standard. Spalling test was carried out following DIN 51068 standard. Phase analysis was done in X-ray diffractometer supplied by Philips using copper target and nickel filter. Micro structural analysis was done under reflected light in a Leitz universal microscope with image analyzer. 3. RESULTS AND DISSCUSSION 3 a. Beneficiation studies Beneficiation studies was carried out on beach sand by using spirals, WHIMS, flotation, HTS, and gravity separation for recovery of zircon. The results are given in Table 2. The data given in Table 2a indicates the recovery of total heavy minerals (THM) using spirals. Data show that 98% grade THM could be recovered from a feed sample containing 16.7 % THM. The results of WHIMS on spiral concentrate (THM) given in Table 2b indicate that 98.9 % purity of magnetic heavy minerals and 95% grade of non magnetic heavy minerals could be recovered from WHIMS at 1.4 T magnetic intensity.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 77 The non magnetic fraction mostly contains sillimanite, zircon and rutile with other associated minerals. The sillimanite mineral has been separated by flotation process and the results are given in Table 2c. The flotation concentrate contain 98.7% grade sillimanite. The tailings contain 85.9% THM, where mostly zircon and rutile are present. Results of HTS on separation of rutile from flotation tailing are given in Table 2d, which shows rutile concentrate is recovered as a conducting fraction in HTS with 98% grade. Zircon concentrate with 98% grade and 86% recovery could be achieved from the flotation tailings using gravity separator (Table 2e). The flow sheet with material balance on recovery of zircon is shown in Fig 2. It can clearly be seen from this Figure that zircon concentrate contain 98 % grade with could be achieved from a feed contain 0.16% zircon concentration in the beach sand. This quality of zircon can be used for refractory applications. Fig 2: Flow Sheet with Material balance on Recovery of Zircon for Konark-Ramachandi beach Sand
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 78 Fig 3: XRD Diffractogram of Zircon Brick Showing Zircon and Baddeleyite Fig 4: XRD Diffractogram of Zircon Sillimanite Showing Zircon, Baddeleyite and Sillimanite
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 79 Fig 5: XRD Diffractogram of Zircon alumina Showing corundum, Mullite, Baddeleyite and Zircon Fig 6: X150 Photomicrograph of Fig 7: X150 Photomicrograph of Alumina Zircon Brick Zircon Brick
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 80 Fig 8: X150 Photomicrograph of Zircon Sillimanite Brick Table 2: Results of beneficiation studies a. Spiral concentration Details Wt, % Wt. dist, % THM, % THM dist.,% THM Rec., % Concentrate Tailings 16.7 83.3 16.7 83.3 98.0 0.4 16.4 0.3 98.0 2.0 Total 100.0 100.0 16.7 100.0 b. Results of WHIMS on spiral concentrate (Table 2.a) Details Wt, % Wt. dist, % THM, % THM dist.,% THM Rec., % Magnetic Non magnetic 76.0 24.0 12.7 4.0 98.9 95 12.6 3.8 75.2 22.8 Total 100.0 16.7 16.4 16.4 98.0 c. Results of flotation studies on non magnetic fraction (Table 2.b) Details Wt, % Wt. dist, % THM, % THM dist.,% THM Rec., % Concentrate Tailings 82.5 17.5 3.3 0.7 98.0 85.9 3.2 0.6 19.4 3.6 Total 100.0 4.0 3.8 3.8 23.0 d. Results of HTS on separation of rutile from flotation tailing (Table 2.c) Details Wt, % Wt. dist, % THM, % THM dist.,% THM Rec., % Conducting Non conducting 18.6 81.4 0.13 0.57 98.0 82.5 0.13 0.47 0.8 2.8 Total 100.0 0.7 0.6 0.6 3.6 e. Results of gravity table on recovery of zircon from non conducting fraction (Table 2.d) Details Wt, % Wt. dist, % THM, % THM dist.,% THM Rec., % Concentrate Tailings 24.6 75.4 0.14 0.43 98.0 76.7 0.14 0.33 0.8 2.0 Total 100.0 0.57 0.47 0.47 2.8
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 81 Table 3: Physical, chemical and thermo-mechanical properties of fired bricks Properties analyzed Composition 1 Composition 2 Composition 3 Standard Zircon brick Green size, mm 300x150x60.05 300x150x69.5 300x150x67.5 Green weight, Kg 10.45 9.97 10.01 - Green B.D. , gm/cc 3.83 3.18 3.29 - Apparent porosity, % 17.3 17.0 14.9 17.6 Bulk density, gm/cc 3.73 3.08 3.28 3.74 Apparent specific gravity 4.6 3.76 3.91 4.61 Cold crushing strength, kg/cm2 1023.5 680.5 903.5 1040 Modulus of rupture, kg/cm2 235.5 126.5 142.5 225 Hot modulus of rupture at 1400 ºC, kg/cm2 41.5 48.5 50.0 40 Spalling(Air quenching), Cycles 25+ 25+ 25+ 25+ Refractoriness under load ta, ºC 1680 1670 1640 1680 CA (wt %) Al2O3 1.2 30.6 70.1 1 ZrO2 64.7 32.4 19.2 65.1 SiO2 33.6 34.1 10.1 33.3 XRD analysis Major- Zircon Major- Zircon Major- Zircon, Corundum Minor- Baddeleyite Medium- Sillimanite Medium- Baddeleyite Minor- Baddeleyite Minor - Mullite 3. EVALUATION OF BRICK 3a. Zircon brick Zircon brick shows excellent physical and thermo-mechanical properties which are comparable to standard products [4] . The brick has lower apparent porosity, high cold crushing strength and high refractoriness under load. Phase analysis X-ray diffractogram shows zircon as the primary phase with baddeleyite as the secondary phase. Photomicrograph shows partial dissociation of zircon in the matrix and dissociation of coarser zircon grain in the boundary. 3b. Zircon Alumina The brick has low apparent porosity, high cold crushing strength and excellent thermo- mechanical properties. The physical and thermo-mechanical properties shows it is comparable to zircon alumina bricks available from reputed manufacturers and expected to give good performance in glass and cement industries.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 73-82 © IAEME 82 Phase analysis X-ray diffractogram shows alumina and zircon as the principal phases along with mullite and baddeleyite as the minor phase. Microscopic studies under reflected light reveal al dissociation of zircon grained leading to precipitation of baddeleyite and mullite reinforcing the matrix and making the microstructure compacted. 3c. Zircon Sillimanite brick The brick shows excellent physical properties and thermo-mechanical properties. This developed brick has the potential to replace zircon nozzle in tundish os iron and steel industries and expected to give better performance as paving blocks, separator in glass industries and may be a potential candidate for use in glass crucible. Phase analysis X-ray diffractogram shows zircon and Sillimanite as the main phase along with mullite and baddeleyite. Microscopic examination reveals Sillimanite and zircon both get dissociated leading to formation of mullite and baddeleyite. The glassy phases are found in the intergranular spaces. CONCLUSIONS Following inferences can be made from this work • The feed sample contains 16.7 % THM out of which zircon is 0.16 %. • After spiral concentration studies, the concentrate contains 98% THM. • Zircon concentrate obtained at the end of process, contains 98 % grade with 86% recovery. • The zircon brick made out of this zircon is comparable to standard zircon brick in every respect. • Zircon alumina brick made out of beneficiated zircon can be used as expandables, AZS and silica separator in glass industries and can be used in the transition zone of cement kiln. • Developed zircon sillimanite has the potential to replace zircon brick in glass and iron and steel industries. ACKNOWLEDGEMENTS Authors are thankful to Chairman of C V Raman group of Institutions, Bhubaneswar, Orissa, India for providing support to carry out the research work. REFERENCES 1. Indian Minerals year book, 80, [1], (2008). 2. V.G.K. Murtty Ch, Upadhyaya and S. Asokan, “Recovery of zircon from Sattankulam deposit in India- problems and prospects,” The 6th International Heavy Minerals Conference “Back to Basics” The Southern African Institute of Mining and Metallurgy, 69-74 (2007). 3. G. Banerjee, “Beach sand minerals: A new material resource for glass and ceramics,” Bulletin of Materials Science, 21, [4], August, 349-354(1998). 4. Website -http://www.associatedceramicsltd.com/. 5. Mohammed Yunus, Dr. J. Fazlur Rahman and S.Ferozkhan, “Evaluation of Machinability Characteristics of Industrial Ceramic Coatings using Genetic Programming Based Approach”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 2, Issue 2, 2011, pp. 127 - 138, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.