glass industry 2

7/21/2019 Glass Industry 2

http://slidepdf.com/reader/full/glass-industry-2 1/37

Glass Industry

Dat

Lunas,

Orillan,

Sardan



DEFINITION

•

PHYSICALLY:• A rigid, undercooled liquid having no definite melting point and a s

high viscosity (greater than 10^12 Pa s) to prevent crystallization

• CHEMICALLY:

• The union of the nonvolatile inorganic oxides resulting from thedecomposition and fusion of alkali and alkaline earth compounds,

other glass constituents, ending in a product with a random atomi

• A completely vitrified product, or a product with a relativelyamount of non-vitreous material in suspension



DEFINITION

Sand – 70%

Soda ash – 15%

Limestone – 10%



BRIEF HISTORYb.c.

•

6000-5000 Egyptians were making fake jewels of glass, often of fine workmanshmarked beauty

a.d.

• 290 Window glass was mentioned as early as this year

• 12th century hand-blown glass cylinder invented by a monk

• 15th century use of window glass became general; Venice previously monopolizeindustry

• 16th century Start of glass manufacture in Germany and England

• 1688 Plate glass appeared as rolled product in France

• 1914 Fourcault process for drawing a sheet of glass continuously was devBelgium

• 1967 Pilkington perfected the float glass process using concepts patentedand 1905



CLASSES OF GLASS

1. Fused silica/ Vitreous silica:

• Made by the high temperature pyrolysis of silicontetrachloride or by fusion of quartz or pure sand.

• Characterized by low expansion and a high softeningpoint which impart high thermal resistance and permitit to be used beyond the temperature ranges of otherglasses.

• Also transparent to ultraviolet radiation.



CLASSES OF GLASS

2. Alkali silicates :

• The only two-component glasses of commercialimportance.

• Sand and soda ash are simply melted together,producing sodium silicates, having a range of composition from Na2O·SiO2 to Na2O·4SiO2.

• Uses include adhesives (in the form of silicate of

soda solution aka water (soluble) glass),fireproofing, and higher alkaline varieties forlaundering as detergents and soap builders.



CLASSES OF GLASS

3. Soda-lime glass :

• Also called soda-lime-silica glass

• Constitutes 95% of all glass manufactured

• Used for containers of all kinds, flat glass, automobile,and other windows, tumblers, and tableware.

• Composition ranges:

a) SiO2, 70 to 74%b) CaO, 8 to 13%

c) Na2O, 13 to 18%

• Melt at relatively low temperatures, sufficientlyviscous that they do not devitrify and yet are not tooviscous to be workable at reasonable temperatures.



CLASSES OF GLASS

4. Lead glass:

• By substituting lead oxide for calcium oxide in the glassmelt. Lead glass is obtained.

• These glasses are of very great importance in opticalwork because of their high index of refraction anddispersion.

• The brilliance of good "cut glass" is due to its lead-

bearing composition

• Large quantities are used also for the construction of electric light bulbs, neon-sign tubing, and radiotronsbecause of the high electrical resistance of this glass.

• Also suitable for shielding from nuclear radiation



CLASSES OF GLASS

5. Borosilicate glass:

• Borosilicate glass usually contains about 10 to 20%B2O3, 80 to 87% silica, and less than 10% Na2O.

• Has a low expansion coefficient, superior resistance toshock, excellent chemical stability, and high electricalresistance.

• The laboratory glassware made from this glass is sold

under the tradename Pyrex.• Uses: lab ware, high tension insulators and washers,

pipelines, telescope lenses



CLASSES OF GLASS

6. Special glasses:

• Include colored and coated, opal, translucent, safety,optical, photochromic glasses, and glass ceramics.

• All have varying compositions according to the desiredfinal product.

7. Glass fibers:

• Produced from special glass compositions that areresistant to weather conditions.

• The very large surface area of the fibers makes themvulnerable to attack by moisture in the air.

• Low In silica, about 55%, and low in alkali.



RAW MATERIALS

1. Sand• should be almost pure quartz; iron content should not exceed 0.45

tableware or 0.015% for optical glass, as iron affects the color of madversely.

2. Soda (Na2O)

• principally supplied by dense soda ash (Na2CO3)

• other sources are sodium bicarbonate, salt cake, and sodium nitralatter is useful in oxidizing iron and in accelerating the melting.

• The important sources of lime (CaO)are limestone and burnt lime dolomite (CaCO3 ·MgCO3)the latter introducing MgO into the batc



RAW MATERIALS

3. Feldspar• Have the general formula R2O.Al2O3.6SiO2, R2O represents Na2O or K2

mixture of these two.

• Have many advantages over other material as a source of Al2O3 since thcheap, pure, and fusible and are composed entirely of glass-forming oxi

• Also supply Na2O or K2O and SiO2. The alumina content lowers the methe glass and retards devitrification

4. Borax• Supplies glass with both Na2O and boric oxide.

• A high index borate glass has a lower dispersion value and a higher refrathan any glass previously known and is valuable as an optical glass

• Lowers the expansion coefficient, has high fluxing powers, increases chedurability



RAW MATERIALS

5. Salt cake• Said to remove troublesome scum from tank furnaces

6. Cullet• Crushed glass from imperfect articles, trim, and other waste glass, facilit

and utilizes waste material• May be as low as 10% of the charge or as high as 80%

7. Refractory block•

developed especially because of the severe conditions encountered in gproduction• Furnace operating temperatures are limited mainly by silica-brick crown

cheap for use in the industry• Sintered zircon, alumina, mullite, mullite-alumina, and electrocast zircon

of these for glass tanks



MANUFACTURING PROCESS

Glass manufacture consists mainly of the following steps:1. MELTING;

2. SHAPING AND FORMING;

3. ANNEALING;

4. FINISHING.



MELTING

• MELTING:

Based on the type of the glass suitable glass manufacture materials are selecmaterials are reduced in size by crushing and grinding. Raw materials are now smelting in furnace.

POT FURNACE.

TANK FURNACE.

Pot furnace:

• With an approximate capacity of 2 t or less, are used for the small production oglasses or where it is essential to protect the melting batch from the products o

• For optical glass and art glass through casting process

• The pots are crucibles made of selected clay or platinum.



MELTING

• TANK FURNACE:

Molten glass is obtained by melting the raw materials in 1350-14capacity regenerative tank furnace and can be used in continuous proDuring melting of raw materials various reactions occur at various tem

Chemical reactions :

Na2CO3 + aSiO2 Na2O.aSiO2 + CO2

CaCO3 + bSiO2 CaO.bSiO2 + CO2

Na2SO4 + cSiO2 + C Na2O.cSiO2 + SO2 + CO



SHAPING AND FORMING

Glass may be shaped by either machine or hand molding. The outstanding factor to

in machine molding is that the design of the glass machine should be such that the completed in very few seconds. During this relatively short time the glass changes frliquid to a clear solid. The design problems to be solved, such as flow of heat, stabiland clearance of bearings, are very complicated.

• Fourcault process window glass

• Colburn process window glass

•

Continuous automatic process plate glass• Pilkington process float glass

• Glass blowing bottles, light bulbs, tubing



SHAPING AND FORMING

1. WINDOW GLASS• was made by an extremely arduous hand process that involved gathering a gob

the end of a blowpipe and blowing it into a cylinder until its ends are cut off, thsplit, heated into an oven, and finally flattened

FOURCAULT PROCESS:

• A drawing chamber is filled with glass from the melting tank.

• The glass is drawn vertically from the kiln through a so-called “debiteuse” by m

drawing machine.Debiteuse: consists of a refractory boat with a slot in the center through which thcontinuously upward when the boat is partly submerged.

• A metal bait lowered into the glass through the slot at the same time the debitlowered starts the drawing as the glass starts flowing.

• The glass is continuously drawn upward in ribbon form as fast as it flows up thr



SHAPING AND FORMING

2. PLATE GLASS

• (1922-1924) Ford Motor Co. and PPG Industries independently decontinuous process for rough rolled glass in a continuous ribbon.

• The glass is melted in large continuous furnaces holding 1000 or m

• The raw materials are fed into one end of the furnace, and the mea temperature as high as 1595 C passes through the refining zone

opposite end in an unbroken flow.• From the wide refractory outlet, the molten glass passes between

cooled forming rolls which give it a plastic ribbon configuration, wdrawn down over a series of smaller water cooled rolls running as higher surface speed than the forming rolls.



SHAPING AND FORMING

2. PLATE GLASS

• The stretching effect of the different speeds and the shrinking of tit cools flatten the ribbon as it enters the annealing lehr.

• After annealing, the ribbon may be cut into sheets for grinding andor it progress automatically for 50 to 100 m, undergoing annealingpolishing, and inspection before it passes through cutting machinereduced to salable plates.

• Grinding and polishing removes about 0.8 mm of glass from each s

• About 30 years later this system was substantially modified by theand polishing of both sides of the continuous ribbon simultaneous



SHAPING AND FORMING

3. FLOAT GLASS

• Developed by Pilkington Brothers in England.

• The float process employs the tank furnace melting system in which ramaterials are fed into one end of the furnace and the molten glass pathrough the refining zone Into a narrow canal that connects the furnacbath. Rate of flow is precisely controlled by automatically raising or lo

gate that spans the canal.• The molten glass is conducted onto and along the surface of a pool of

in a non-oxidizing atmosphere under closely controlled conditions of twhich produces a glass with both sides fiat and parallel.



SHAPING AND FORMING

3. FLOAT GLASS

• In 1975 PPG Industries improved the process by having the stream of glass from the melting furnace be of the desired width (usually 4 m) aonto the molten bath. This minimizes the effects of flow from a thick umass to the sheet which introduces optical distortion.

• The glass is cooled while still on the molten tin until its surfaces are ha

to enter the lehr without the lehr rollers spoiling the bottom surface.• 50,000 m2/day of float, thicknesses 3-19 mm and widths of 3-3.5m



Raw

Batch

HEAT ZONEFIRE

POLISHING

ZONE

COOLING ZONE

Controlled

atmosphere

FURNACE HEAT BATH ANNEALING

LEHR

Heat Heat Heat

Molten glass

HEATER



SHAPING AND FORMING

4. WIRED AND PATTERNED GLASS

• Molten glass flows over the lip of the furnace and passes bemetal rolls on which a pattern has been engraved or machinforming and imprinting the pattern on the glass in a single o

• This variety of glass diffuses light and ensures a certain amoprivacy.

• Used in rooms, doors, and shower enclosures

• Can be reinforced with wire during the initial forming for spsafety needs e.g. for windows near fire escapes



SHAPING AND FORMING

5. BLOWN GLASS

• Previously depended solely upon human lungs to form and molten glass until modern demands for blown glass have redevelopment of more rapid and cheaper methods of produc

• Bottle-making is a casting operation that uses air pressure thollow.

A. suction-feed type

B. gob-feed type



SHAPING AND FORMING

5. BLOWN GLASS

A. Suction-feed type

• Glass contained in a shallow revolving tank is drawn up into moldsthen the mold swings away from the surface of the glass, opens, aaway, leaving the parison sustained by the neck

• The bottle mold, in position, receives a blast of compressed air cau

glass to flow into the mold.• 60 units per minute



SHAPING AND FORMING

5. BLOWN GLASS

B. Gob-feed type

• The molten glass flows from the furnace through a trough at the loan orifice.

• The glass drops through the orifice and is cut into a gob of the exasize by mechanical shears, then is delivered through a funnel into

mold, which starts the formation of the bottle in an inverted posit• A neck pin rises into place, and another plunger drops from the to

whereupon compressed air in the “settle blow” forces the glass intfinished form of the neck.



SHAPING AND FORMING

5. BLOWN GLASS

B. Gob-feed type

• The mold is closed on top bottom of the bottle, the neck pin is retair is injected in the “counter blow” through the newly formed necthe inner cavity.

• The parison mold opens, and the parison is inverted as it passes to

station, so that the partly formed bottle is then upright. The blow around the parison, which is reheated for a brief interval. Air is thefor the final blow, simultaneously shaping the inner and outer surfbottle. The blow mold swings away, and the bottle moves on the le



SHAPING AND FORMING

6. GLASS TUBING

DANNER PROCESS:

• The molten glass flows onto the top end of a revolving, hollow clay rodabout 30°

• Air is blown through it and the glass on the rod slowly flows toward thend where it is pulled off to form a tube.

• A pair of belts grip the tubing and draw it at a uniform speed. The diamwall thickness are controlled by the temperature, speed of drawing, aof air that is blown through the rod.

• Tubing does not require annealing.



ANNEALING

• To reduce strain, it is necessary to anneal all glass objects, whether they are

machine- or hand-molding methods.

• Briefly, annealing involves two operations.

1. holding a mass of glass above a certain critical temperature long enouinternal strain by plastic flow to less than a predetermined maximum

2. cooling the mass to room temperature slowly enough to hold the stramaximum.

• The lehr, or annealing oven, is nothing more than a carefully designed heatewhich the rate of cooling can be controlled so as to meet the foregoing requ

• The establishment of a quantitative relationship between stress and birefricaused by the stress has enabled glass technologists to design glass to meetconditions of mechanical and thermal stress.



FINISHING

All types of annealed glass must undergo certain finishing operatio

are simple and important. These include:• Cleaning,

• Grinding,

• Polishing,

• Cutting,

• Sandblasting,

• Grading etc.

Although these are not required for every glass objemore is almost necessary.

CHEMICAL ENGINEERS IN GLASS



CHEMICAL ENGINEERS IN GLASS

INDUSTRIES• Quality Control Officer

• Process Engineer

• Process Control Engineer

• Process Safety Engineer/Professional

• Head-Sales & Marketing

GLASS MANUFACTURING IN THE



GLASS MANUFACTURING IN THE

PHILIPPINES• Philtech Glass Industries Corporation

• AGC Flat Glass Philippines, Inc.

• Pacific Glass Corporation

• Asahi Glass Philippines, Inc.

glass industry 2

Documents