STUDY OF CHEMICAL AND PHYSICAL PROPERTIES OF PERLITE AND ITS APPLICATION IN INDIA Mueena Samar1, Dr. Shweta Saxena 2 1Assistant Professor Department of Engineering Chemistry, Vedant College of Engineering and Technology, Bundi, Rajasthan,(India) 2 Asso. Prof. Department of Engineering Chemistry, Maa Bharti Girls College, Kota, Rajasthan,(India)
ABSTRACT Perlite is not a trade name but a generic term for naturally occurring siliceous volcanic rock. The distinguishing feature which sets Perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands four to twenty times of its original volume. Perlite is amorphous volcanic glass that has relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. Perlite is an industrial mineral and a commercial product useful for its light weight after processing. Perlite is a non-renewable resource. The world reserves of Perlite are estimated at 700 million tones. In 2011, 1.7 million tons were produced, mostly by Greece (500,000 t), United States (375,000 t) and Turkey (220,000 t). However, no information for China – a leading producer was available.[1] Perlite can be substituted for all of its uses. Substitutes include: Diatomite, Expanded clay, Shale Pumice, slag, Vermiculite.[2] The chemical composition of Perlite are: 70–75% Silicon
Oxide: SiO2,12–15% Aluminum Oxide:Al2O3, 3–4% Sodium oxide: Na2O, 3–5% Potassium Oxide: K2O, 0.5-2%
Iron oxide: Fe2O3, 0.2–0.7% Magnesium oxide: MgO, 0.5–1.5% Calcium oxide CaO 3–5% loss on ignition (chemical / combined water). Perlite is used in industries, agriculture, horticultural aggregate, vermiculite, refractory material, ladle topping, building construction products, fillers, filter aid and used in hot tops and risers. This paper summarizes the study of chemical and physical properties of Perlite and its application in India.
Keyboard: Perlite, volcanic glasses, non-renewable resource, Vermiculite, refectories material, ladle topping.
I. INTRODUCTION
The name of Perlite is a derivation from ―Perl stein‖ originally given ―to certain glassy rocks with numerous concentric cracks, from the fancied resemblance of broken fragments to pearls[2] Petro graphically, Perlite can be described as a glassy, volcanic rock having a pearl- like luster and usually exhibits numerous concentric cracks that cause it to resemble an onion skin in appearance. Chemically, crude Perlite is essentially a Meta
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stable amorphous aluminum silicate. Commercially, the term ―Perlite‖ also includes the expanded product. [3] A typical Perlite sample is composed of 71 to 75 percent silicon dioxide, 12.5 to 18.0 percent alumina, 4 to 5 percent potassium oxide, 1 to 4 percent sodium and calcium oxides, and trace amounts of metal oxides. Crude Perlite ore is mined, crushed, dried in a rotary dryer, ground, screened, and shipped to expansion plants. Horizontal rotary or vertical stationary expansion furnaces are used to expand the processed Perlite ore. Perlite is amorphous volcanic glass that has relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. Perlite is an industrial mineral and a commercial product useful for its light weight after processing. Perlite is a non- renewable resource. Perlite is a versatile and sustainable mineral that is mined and processed with a negligible impact on the environment. The green community recognizes Perlite-enhanced products as a high-performance solution drawn from a natural material of nearly unlimited supply throughout the world. Perlite comes from different kinds of rocks. Perlite is a glassy volcanic rock, gray and with a pearly shine on the rocks surface. It consists mostly of silica and has water molecules trapped within it. Vermiculite comes from 19 varieties of minerals and the ores contain silica, alumina, iron oxides and magnesium oxide. The expanding properties upon heating were observed by Thomas Webb in 1824, which heated ore over a candle and watched it turn into elongate forms that resembled worms. He named it vermiculite from the Italian word for worm, vermicular. Perlite in the natural state is a dense, glassy rock formed by volcanic action, which in the raw form contains about 3 % of crystal water and has a density of about 1,050 kg/m³. When rapidly heated to high temperature (1.000 °C) the water vaporizes instantaneously and the crushed Perlite "pops" like pop corn, expanding till 20 times its original volume. The resulting snow-white granules are composed of many tiny closed air cells or bubbles. They are very light in density, fully inert and neutral. The resultant cellular structure accounts for the lightweight and excellent thermal insulation properties. Due to the sealed nature of the cells, expanded Perlite has more strength and resists penetration of water to a greater extent than open celled aggregates of the same weight. Perlite insulation an inorganic product that does not support combustion, or rot, nor does it provides a habitat for rodents. It is ideal for use under concrete slabs, in chimneys and in high-temperature applications such as pizza ovens and rocket stoves.
Fig-1
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Fig-2 Sources: Perlite come from glassy volcanic rock, gray and with a pearly shine on the rock's surface. It consists mostly of silica and has water molecules trapped within it. Manufacture: Perlite ores are heated to expand them into horticultural products. Crushed Perlite ore is rapidly heated to about 1472 to 1562 degrees Fahrenheit. The water trapped in the ore particles pops and expands, similar to popcorn, forming round glass bubbles within the particles. Perlite can expand up to 15 times its original volume. The expansion is called exfoliation, and is thought due to the sudden escape of water in the shape of steam.
Chemical properties: The chemical composition of Perlite are: 70–75% Silicon Oxide:SiO2,12–15%
Aluminium Oxide:Al2O3,3–4%Sodiumoxide:Na2O,3–5%Potashium Oxide: K2O,0.5-2% Ironoxide:Fe2O3,0.2– 0.7% Magnesium oxide:MgO,0.5–1.5% Calcium oxide CaO 3–5% loss on ignition (chemical / combined water). Table-1 Typical chemical properties of Perlite Element composition, % Chemical composition, %
Silicon Si 33,8 Silicon dioxide SiO2 72,08
Aluminium Al 7,2 Alumina Al2O3 12,92 Titanium Potassium K 3,5 TiO2 0,90 dioxide
Sodium Na 3,4 Iron oxide Fe2O3 1,50 Magnesium Iron Fe 0,6 MgO 0,63 oxide
Calcium Ca 0,6 Quick lime CaO 0,88
Magnesium Mg 0,2 Caustic soda Na2O 3,76 Potassium Mica - 0,2 K2O 4,33 oxide
Oxygen O 47,5 Bound water H2O 3,0
Characteristic property of Perlite is that if subject to rapid heating of 900 to 1.200°C it increases its volume 4 to 20 times. This happens because Perlite includes the bound water which extends during heating according to a
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well-known popcorn effect and adopts the form of a porous swollen material. The size of swollen pellets varies between 1 and 10 mm, with apparent density of 75 to 150 kg/m3. Table-2Typical Values after Expansion
Lose Weight 35 - 45 kg/m³ Density:
Tamped Weight 55 - 60 kg/m³ Density:
Color: White
Free Quartz: < 0.5 %
Mechanical 0.6 - 1.51 Resistance: kg/cm²/cm
Thermal 0.034 - 0.042 Conductivity λs = W/(m.K)
Softening point: 890 - 1100 °C
Fusion point: 1280 - 1350 °C
Specific heat: 0.20
Specific gravity: 2.2 - 2.4
Perlite is non- Fire resistance: combustible
II. PHYSICAL PROPERTIES
Perlite Rock structures are Classical rock and Moisture- max. 1 % present in Perlite. Perlite softens when it reaches temperatures of 850–900 °C (1560-1650 °F). Water trapped in the structure of the material vaporizes and escapes, and this causes the expansion of the material to 7–16 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles. Unexpanded ("raw") Perlite has bulk density around 1100 kg/m3 (1.1 g/cm3), while typical expanded Perlite has a bulk density of about 30–150 kg/m3 (0.03-0.150 g/cm3). Physical properties of Perlite that are exploited commercially include its chemistry (Si, Al); state (alkaline, inert, and hydrated); habit (amorphous, fibrous) and physical behavior (thermal insulator, low density and porosity) — as summarized below: Fig-3
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Table-3Typical physical properties of Perlite
S.No. Property Value 1 Color White/Grey 2 Brightness, % GE 70-80 3 Apparent density, kg/m3 50-300 4 Hardness index (Mohs) 5,5 5 Specific Gravity 2.2 – 2.4 6 pH 6 - 8.5 7 Water absorption, % of mass 200-600 8 Ability to absorb oils, gram of oil per gram of 50-100 Perlite 9 Melting point, C° 980 10 Burn losses (3 hours under t of 900°C), % up to 1,5 11 Humidity, % up to 1,0 12 Maximum strength, MPa up to о 6,0 13 Porosity, % 70-85 14 Portion of air, % 80-95 15 Thermal conductivity, W/mK 0,043-0,093 16 Thermal diffusivity, m2/sec 0,632-0,330
III. APPLICATION OF PERLITE
Perlite is a non-renewable resource. The world reserves of Perlite are estimated at 700 million tons In 2011, 1.7 million tons were produced, mostly by Greece (500,000 t), United States (375,000 t) and Turkey (220,000 t). However, no information for China – a leading producer – was available[1]Starting 2003, Greece was a leader in processed Perlite production; however, estimates of Perlite production from USGS Mineral Commodity Summaries 2013 indicate that US may have overtaken Greece[2]. Because of its low density and relatively low price (about US$50 per ton of unexpanded Perlite), many commercial applications for Perlite have developed. In the construction and manufacturing fields, it is used in lightweight plasters and mortars, insulation and ceiling tiles [3].In horticulture, Perlite can be used as a soil amendment or alone as a medium for hydroponics or for starting cuttings. When used as an amendment it has high permeability / low water retention and helps prevent soil compaction. [4] Perlite is an excellent filter aid. It is used extensively as an alternative to diatomaceous earth. The popularity of Perlite usage in this application is growing considerably worldwide. Perlite filters are fairly commonplace in filtering beer before it is bottled. Small quantities of Perlite are also used in foundries, cryogenic, insulation, as a lightweight aggregate in mortar(fire stop) and in ceramics as a clay additive. It is also used by the explosives industry [1]. In 2010, estimated Perlite consumption in the US was as shown in the table:
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Fraction Use[3]
53% building construction products
14% horticultural aggregate
14% fillers
8% filter aid
Other 11%
• In the ceramics and hollow glass industries by utilizing the silica, alumina and alkaline components • For production of explosives, using the structural water in the raw material which is suitable for serving as heat points • In filter manufacture, where it is used as an inert bed aggregate • In electrode manufacture, using its composition, granulation and amorphous nature • In cement production, utilizing the alumina silicate composition as an amorphous pozzolanic aggregate in Portland cement • In the Zeolite industry as a raw material for the hydrothermal process • As a mineral additive aggregate in the production of wet phosphoric acid from phosphate rock • In mineral fiber manufacture • In metallurgical operations as a covering for molten metal as thermal insulation, for prevention of oxidation and for collection of flux materials.
IV. INDUSTRIAL APPLICATIONS
Industrial applications for Perlite are the most diverse, ranging from high performance fillers for plastics to cement for petroleum, water and geothermal wells. Other applications include its use as a filter media for pharmaceuticals, food products, chemicals and water for municipal systems and swimming pools. Additional applications include its use as an abrasive in soaps, cleaners, and polishes; and a variety of foundry applications utilizing Perlite insulating properties and high heat resistance. This same heat resistant property is taken advantage of when Perlite is used in the manufacture of refractory bricks, mortars, and pipe insulation. When Perlite ore is expanded by exposure to rapid, controlled heating, it grows up to 20 times its original volume and takes on a foam-like cellular internal structure—essentially clusters of microscopic glass bubble .Over half of all the Perlite expanded in the United States annually is used to make ―formed products.‖ These products include ceiling tiles, pipe insulation, roofing board and fire-rated door cores, and are manufactured with a variety of binders. Perlite can safely be used over a wide range of temperatures. Being lightweight, non-combustible, and insulating, Perlite has been found to be useful in a wide variety of industrial applications, e.g., refractory brick, high temperature insulation, molten metal topping, cryogenic insulation, filtration, and lightweight fillers. Perlite and vermiculite are both used to improve moisture retention and aeration in soil. They are used in a similar manner, but they are not interchangeable. Perlite and vermiculite are quite different in composition and in how they improve your soil. Determining which is better for use in your garden depends on your plants and their needs.There are many uses for perlite. These uses can be broken down into three general categories:
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construction applications, horticultural applications, and industrial applications. Although perlite used in construction comprises the bulk of sales worldwide (a primary market is in ceiling tiles), most people are probably familiar with perlite as the small white rocks in high quality potting soils. While the characteristics of the perlite from American Perlite's Fish Springs deposit are suitable for almost all applications that perlite is used in, it should be particularly noted that it is probably the best in the world for cryogenic insulation and is pre-qualified for use by many of the major companies that do cyrogenic installations. It expands at a little lower temperatures than most other perlite (saving fuel costs), and expands to extremely low densities (as low as 2 pounds per cubic foot). This increases the volume produced per ton (saving costs) and provides for a better insulating value. CRYOGENIC APPLICATIONS FOR PERLITE INSULATION: Because of its unique properties, perlite insulation has found wide acceptance in the insulating of cryogenic and low temperature storage tanks, in shipping containers, cold boxes, test chambers, and in food processing.Storage temperatures of -150 F (-100 C) and below are considered cryogenic. Storage temperatures of -150 F (-100 C) and above to 40 F (4 C) are considered low temperature. Super cold or extremely cold cryogenic fluids such as hydrogen and helium are normally stored in spherical, double walled vessels with evacuated annual spaces using evacuated perlite. PROPERTIES OF PERLITE INSULATION:Perlite insulation suitable for nonevacuated cryogenic or low temperature use exhibits low thermal conductivity throughout a range of densities, however, the normal recommended density range is 3 to 4.5 lbs/ft3 (48 to 72 kg/m3). In addition to its excellent thermal properties, perlite insulation is relatively low in cost, easy to handle and install, and does not shrink, sell, warp, or slump. Perlite is noncombustible, meets fire regulations, and can lower insurance rates. Because it is an inorganic material, it is rot and vermin proof. As a result of its closed cell structure, the material does not retain moisture. TYPICAL NONEVACUATED INSTALLATION:There are many different design concepts for low temperature and cryogenic storage vessels. However, most are of double wall construction with the annulus filled with expanded perlite. Packaged or bulk perlite (pneumatic bulk trucks) may be used to insulate smaller vessels by pouring or blowing the insulation in place. Portable perlite expansion plants often are used to insulate very large storage tanks, cold boxes, ships, and other double wall vessels and pipes. In these applications perlite ore is expanded on-site and the expanded perlite insulation is conveyed pneumatically into the annulus.perlite can be manufactured to weigh from 2 lb/ft3 (32 kg/m3) to 15 lb/ft3 (240 kg/m3) making it especially suitable for use in insulation applications. Perlite is used in the manufacture of high temperature and cryogenic insulation, lightweight perlite insulating concrete, insulating board, insulating plasters, masonry wall insulation and as underfloor insulation. SERVICE TO 2000 0F (11000)C:High temperature performance of expanded perlite insulation has been well documented over a period of many years. The data in Figure 1 (not yet on web page) details the thermal conductivity for various density perlite insulations up to 1800°F (980°C). Although thermal conductivity increases appreciably above 1800°F (980°C), expanded perlite has been used at service temperatures as high as 2000°F (1100°C). HIGH TEMPERATURE APPLICATIONS:Perlite insulation is used in high temperature applications in the steel and foundry industries such as ladle topping, hot topping and risering, in topping compounds, in
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exothermic and insulating shapes, as a cushioning agent, in molding sand and in the manufacture of refractory blocks and bricks. LADLE TOPPING:In ladle topping applications, expanded or un-expanded granular ore forms of perlite are added to molten metal pouring ladles. Most often the ore form is used which reacts with slag in the ladle to allow easy removal of the slag layer. In cases where it is desirable to maintain a metal temperature in a ladle, the expanded perlite layer forms an efficient in-sulating blanket. When perlite is introduced during ladle filling, a gentle rolling motion is produced which cleanses the metal by coagulating impurities. In addition, ladle-lining life is increased by virtue of a vitreous residual coating left on the refractory by the perlite. An added advantage of perlite in this application is that no objectionable smoke or noxious fumes are produced.
Fig-4Perlite in ladle topping applications allows easy removal of slag and helps maintain the temperature of the molten metal in the ladle.
HOT TOPPING AND RISERING:Perlite is often mixed with exothermic powders and used in hot tops and risers to prevent shrinkage cavities in ingots and castings. Perlite is the most commonly used lightweight filler used for these applications because of its availability, cost and superior properties. Normal additions of perlite to insulating and exothermic compounds are in the range of 3 to 20% by weight.Formed shapes are often employed which take the form of hollow cylindrical sleeves for risers and panels for hot tops. These shapes perform essentially the same function as hot topping and risering powders and compounds. REFRACTORIES:Perlite is used in the manufacture of refractories where the average temperature does not exceed approximately 2000°F (1 100°C). Because of its excellent insulating properties, there is substantial usage of perlite in refractory castables, bricks and blocks. In higher temperature applications, perlite refractories are often used as back-up insulating layers for higher duty refractories. FOUNDRY CORE AND MOLDING SAND:Perlite is added to foundry core and molding sand mixtures as a cushioning agent to com-pensate for the expansion of crystalline silica as it goes through phase changes at tempera-tures in excess of 1000°F (540°C). Casting defects such as buckles, veining, fissuring and penetration are minimized and cleaning room costs are reduced. In addition, perlite improves permeability of core sands thus re-ducing defects attributable to poor venting
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HORTICULTURAL APPLICATIONS In horticultural applications, perlite is used throughout the world as a component of soilless growing mixes where it provides aeration and optimum moisture retention for superior plant growth. For rooting cuttings, 100% perlite is used. Studies have shown that outstanding yields are achieved with perlite hydroponic systems. Other benefits of horticultural perlite are its neutral pH and the fact that it is sterile and weed-free. In addition, its light weight makes it ideal for use in container growing. Other horticultural applications for perlite are as a carrier for fertilizer, herbicides and pesticides and for pelletizing seed. Horticultural perlite is as useful to the home gardener as it is to the commercial grower. It is used with equal success in greenhouse growing, landscaping applications and in the home in house plants. Table:4 Substitutes for Perlite
Use Substitute
Animal feed Bentonite, sepiolite, talc, vermiculite, zeolite supplement
Filler Barite, calcite, feldspar, kaolin, mica, nepheline syenite, pyrophyllite, silica, talc, wollastonite
Fire Antimony oxide, asbestos, borates, bromine, chromite, diatomite, magnesite, retardant magnesia, phosphates, pumice, vermiculite
Filter media Activated carbon/anthracite, asbestos, cellulose, diatomite, garnet, ilmenite, magnetite, pumice, silica sand
Foundry Bauxite and alumina, chromite, kaolin, olivine, pyrophyllite, silica sand, vermiculite, zircon
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Lightweight Expanded clay, pumice, vermiculite, zeolite aggregate
Soil additive Bentonite/kaolin, diatomite, gypsum, peat, vermiculite, zeolite / amendment
Thermal or Asbestos, brick clays, diatomite, foamed glass, cement, mineral wool, sound pumice, vermiculite, wollastonite, zeolite insulator
V. CONCLUSION
Because of perlite's outstanding insulating characteristics and light weight, it is widely used as loose-fill insulation in masonry construction. In this application, free-flowing perlite loose-fill masonry insulation is poured into the cavities of concrete block where it completely fills all cores, crevices, mortar areas and ear holes. In addition to providing thermal insulation, perlite enhances fire ratings, reduces noise transmission and it is rot, vermin and termite resistant. Perlite is also ideal for insulating low temperature and cryogenic vessels. When perlite is used as an aggregate in concrete, a lightweight, fire resistant, insulating concrete is produced that is ideal for roof decks and other applications. Perlite can also be used as an aggregate in Portland cement and gypsum plasters for exterior applications and for the fire protection of beams and columns. Other construction applications include under-floor insulation, chimney linings, paint texturing, gypsum boards, ceiling tiles, and roof insulation boards.
REFERENCES
[1] Perlite, USGS Mineral Commodity Summaries 2011 [2] USGS Mineral Commodity Summaries 2013 [3] Wallace P. Bolen Perlite USGS 2009 Minerals Yearbook United States Patent 4940497 [4] "Perlite". U.S. Geological Survey Mineral Commodity Summaries,: 122–123. January 2006. [5] Calciners And Dryers In Mineral Industries -- Background Information For Proposed Standards, EPA- 450/3-85-025a, U. S. Environmental Protection Agency, Research Triangle Park, NC, October 1985. [6] Perlite: US Minerals Yearbook 1989, Volume I: Metals And Minerals, U. S. Department of the Interior, Bureau of Mines, Washington, DC, pp. 765 – 767 [7] Perlite Industry Source Category Survey, EPA-450/3-80-005, U. S. Environmental Protection Agency, Research Triangle Park, NC, February 1980 [8] Emission Test Report (Perlite) : W. R. Grace And Company, Irondale, Alabama, EMB Report 83-CDR-4, U. S. Environmental Protection Agency, Research Triangle Park, NC, February 1984.
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[9] Particulate Emission Sampling And Analysis: United States Gypsum Company, East Chicago, Indiana, Environmental Instrument Systems, Inc., South Bend, IN, July 1973 [10] Air Quality Source Sampling Report #216: Greco, Inc., Perlite Mill, Socorro, New Mexico, State of New Mexico Environmental Improvement Division, Santa Fe, NM, January 1982 [11] Air Quality Source Sampling Report #198: Johns Manville Perlite Plant, No Agua, New Mexico, State of New Mexico Environmental Improvement Division, Santa Fe, NM, February 1981 [12] Stack Test Report, Perlite Process: National Gypsum Company, Roll Road, Clarence Center, New York, Buffalo Testing Laboratories, Buffalo, NY, December 1972 [13] Particulate Analyses Of Dryer And Mill Baghouse Exhaust Emissions At Silbrico Perlite Plant, No Agua, New Mexico, Kramer, Callahan & Associates, NM, February 1980 [14] Ashish Mathew, Dr. Ashish Dutt Sharma. "ADVANCED MANUFACTURING TECHNOLOGY IMPLEMENTATION IN SMALL SCALE MANUFACTURING INDUSTRIES." International Journal of Advanced Technology in Engineering and Science 3.Special Issue No. 01 (2015): 158-167.
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