Transcript Glasses
FACULTY OF ENGINEERING TECHNOLOGY &RESEARCH , AFWA-ISROLI , BARDOLI. Chemical Process Industries - 1 Prepared By SR. NO STUDENTS NAME PEN Glass industries Introduction Structure manufacturing processes uses 1 PATEL KRUPESH 130840105035 2 PATEL PRATIK 130840105037 3 PATEL PRIYANSHI 130840105038 4 PATEL RINAL 130840105039 5 RANKA YASH 130840105045 Guided by 6 ROHIT KETAN 130840105046 Prof. K.D.Desai. Introduction What is glasses? Glasses – melting & solidification processing Glass is one of three basic types of ceramics. Glass is distinguished by its amorphous (noncrystalline) structure. Structure : Network formers Molecules that link up with each other to form long chains and networks. Hot glass cools, chains unable to organize into a pattern. Solidification has short-range order only.Amorphous structure occurs by adding impurities (Na+,Mg2+,Ca2+, Al3+). Impurities: interfere with formation of crystalline structure Structure Raw Materials 1. Glass forming oxides: usually the dominant constituent , B2O3, P2O5, etSiO2c. 2. Fluxes: reduce melting temperatures Na2O, PbO, K2O, Li2O, etc. 3. Property modifiers: added to tailor chemical durability, expansion, viscosity, etc. CaO, Al2O3, etc. 4. Colorants: oxides with 3d, 4f electron structures; minor additives (<1 wt%) 5. Fining agents: minor additives (<1 wt%) to help promote bubble removal As-, Sb-oxides, KNO3, NaNO3, NaCl, fluorides, sulfates Glassmaking • The ingredients for glass are mixed, and along with a proportion of cullet (broken glass), are added to a bath furnace, where they are heated to about 1500°C and fused together. • Molten glass is fed as ‘gobs’ to an automatic bottle or jar making machine. A hot gob is first made into a parison or blank shape (by either pressing or blowing), which is then blown to the final bottle or jar shape. Surface coatings (sc) may be applied while hot. • The bottles or jars pass into a Lehar (an annealing oven), where they are first reheated to soften the glass to remove stresses, and then cooled gradually to prevent stresses developing. • The bottles or jars are inspected and tested to meet quality standards. Bottles not passing the quality checks are broken and returned to the furnace as cullet. Cullet reduces the amount of energy required to melt the glass ingredients. • Bottles passing inspection and testing are packed for dispatch to where they will be filled, capped, and labeled. Shaping Processes in Glassmaking Shaping processes to fabricate these products can be grouped into three categories: 1. Discrete processes for piece ware (bottles, jars, plates, light bulbs) 2. Continuous processes for making flat glass (sheet and plate glass) and tubing (laboratory ware, fluorescent lights) 3. Fiber-making processes to produce fibers (for insulation and fiber optics) Shaping of Piece Ware Ancient methods of hand-working glass included glass blowing. Handicraft methods are still used today for making glassware items of high value in small quantities. However, most modern glass shaping processes are highly mechanized technologies for producing discrete pieces in high quantities. Piece Ware Shaping Processes 1. Spinning – similar to centrifugal casting of metals 2. Pressing – for mass production of flat products such as dishes, bake ware, and TV tube faceplates 3. Press-and-blow – for production of wide-mouth containers such as jars 4. Blow-and-blow - for production of smaller-mouth containers such as beverage bottles and incandescent light bulbs 5. Casting – for large items such as large astronomical lenses that must cool very slowly to avoid cracking. Spinning of funnel-shaped glass parts such as back sections of cathode ray tubes for TVs and computer monitors: (1) gob of glass dropped into mold; and (2) rotation of mold to cause spreading of molten glass on mold surface Pressing of flat glass pieces: (1) glass gob is fed into mold from furnace; (2) pressing into shape by plunger; and (3) plunger is retracted and finished product is removed (symbols v and F indicate motion (velocity) and applied force) 1. A gob of hot glass drops into the blank (parison) mould. 2. The mould is sealed shut by a ‘base’ part and a plunger pushes the glass into the mould (made from iron). 3. The glass is shaped into a ‘blank’ and also pushed into the neck finish by the plunger. This part of a jar or bottle is finished to its final shape at this stage. 4. The blank shape (parison) is removed, rotated 180°, and transferred to the blow (finishing) mould. 5. This mould is in two halves, made from fine-grain cast iron, and is highly polished. 6. Air is blown into the hot parison to expand it tightly against the mould walls. 7. The mould opens, the bottle is removed, annealed in the lehr, inspected and tested, and shipped for filling. 1. A gob of hot glass drops into the blank (parison) mould. 2. The end is sealed and a puff of air pushes glass into the neck (finish). 3. A puff of air from below pushes glass into the mould and shapes it into a ‘blank’ or parison, a thick-walled bottle looking vaguely like the final bottle shape. 4. The blank shape (parison) is removed, rotated 180°, and transferred to the blow (finishing) mould. 5. This mould is in two halves, made from fine-grain cast iron, and is highly polished. 6. Air is blown into the hot parison to expand it tightly against the mould walls. 7. The mould opens, the bottle is removed, annealed in the lehr, inspected and tested, and shipped for filling. Casting If molten glass is sufficiently fluid, it can be poured into a mold. Relatively massive objects, such as astronomical lenses and mirrors, are made by this method. After cooling and solidifying, the piece must be finished by lapping and polishing. Casting of glass is not often used except for special jobs. Smaller lenses are usually made by pressing. Shaping of Flat and Tubular Glass Processes for producing flat glass such as sheet and plate glass: Rolling of Flat Plate Starting glass from melting furnace is squeezed through opposing rolls whose gap determines sheet thickness, followed by grinding and polishing for parallelism and smoothness Float Process Molten glass flows onto the surface of a molten tin bath, where it spreads evenly across the surface, achieving a uniform thickness and smoothness - no grinding or polishing is needed. Danner Process Molten glass flows around a rotating hollow mandrel through which air is blown while the glass is drawn. Forming of Glass Fibers Glass fiber products can be divided into two categories, with different production methods for each: 1. Fibrous glass for thermal insulation, acoustical insulation, and air filtration, in which the fibers are in a random, wool-like condition. Centrifugal spraying 2. Long continuous filaments suitable for fiber reinforced plastics, yarns, fabrics, and fiber optics. Drawing Heat Treatment Annealing of Glass Heating to elevated temperature and holding for a time to eliminate stresses and temperature gradients; then slow cooling to suppress stress formation, followed by more rapid cooling to room temperature. Annealing temperatures are around 500°C. Tempering of Glass Heating to a temperature somewhat above annealing temperature into the plastic range, followed by quenching of surfaces, usually by air jets. When the surfaces cool, they contract and harden while interior is still plastic. As the internal glass cools, it contracts, putting the hard surfaces in compression. Tempered glass is more resistant to scratching and breaking due to compressive stresses on its surfaces. Uses Glass is used in following non-exhaustive list of products: packaging (jars for food, bottles for drinks, flacon for cosmetics and pharmaceuticals) Table ware housing & buildings Interior design & furniture Appliances & electronics medical technology, biotechnology, life science engineering. Optical glass radiation protection from X-ray & gamma-rays, Fiber optic cables. Renewable energy All of this made possible by the count less properties of the glass substance. THANK YOU 19