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The Global market for Float glass in 2004 was approximately 38 million tonnes, representing a value of around 18 billion US Dollars. Of this tonnage, around 70% is consumed in windows for buildings, 10% in glazing products for automotive applications and 20% used in furniture and other interior applications.
Europe, China and North America together account for 75% of global demand for glass. Just 4 companies : Pilkington, Saint-Gobian, Asahi and Guardian produce 61% of the world�s float glass.
Globally, glass demand is growing at nearly 4% per annum. In 2004, the industry was running at around 90% capacity utilisation.
China, Russia, India and the Middle East have been identified as the top four priority areas for growth in the glass industry.
Out of the global supply of 38 million tons, China supplies around 13 million tons, adopting the foreign technology. The number of Float glass units in China reached 130 in 2005.
On an average, 1 ton of Float glass is 125 sq. meter. Taking 4 mm as the standard, 1 cubic meter weighs approximately 2,000 kgs.
A float glass project from Europe is highly capital intensive, typically costing around Rs. 500 � 800 crores, according to size and location. Once operational, it is designed to run continuously 365 days per year, throughout its compaign life of between 10 � 15 years. Float lines are normally capable of several campaigns, following major repairs/ upgrade programmes, costing Rs. 150 � 250 crores from Europe.
The float glass is not labour-intensive. Energy and raw material costs are significant in the total cost of production. Distribution costs are around 10% of total costs. In most cases, transport costs are uneconomical for float glass to travel long distances by land. Typically, 300 kms would be seen as the normal, while upto 1,000 kms are the economic limits. It is possible for float glass to be transported longer distances by sea, provided additional road transportation is not required at both the ends.
Global market for Float glass � (2004) �
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In
million tons
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Percentage
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Per
capita consumption
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China
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13
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34%
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Europe
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9
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24%
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|
|
|
North
America
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6
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15%
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15
kgs
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|
South
East Asia
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3
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8%
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|
11
kgs
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|
West
Asia
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2
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5%
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Rest
of the World
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� 4 kgs
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Former
Soviet Union
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2
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5%
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|
|
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Japan
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1
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3%
|
|
|
|
South
America
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1
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3%
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|
|
|
Africa
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0.7
|
2%
|
|
|
|
Oceania
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0.3
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1%
|
|
|
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World
Total
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38
million tons
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100%
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|
|
|
|
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The world glass market is expected to reach 42 million tones by 2006. To satisfy growth rate of 4% per annum between 2000 & 2010, the industry will need to add more than 100 new float lines worldwide.
Glass manufacture -Glass is obtained by the fusion of several inorganic substances. The fused mass is cooled to ambient temperature at a rate fast enough to prevent crystallization i.e., the molecules cannot arrange themselves into a crystalline pattern.
Silica sand, soda ash, dolomite / limestone represent together 99% of all rawmaterials used in the production of glass, excluding recycled glass (cullet). Sodium sulphate forms the balance 1%, excluding bubble removers and colouring agents.
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Float glass composition
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Sand
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51 %
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Soda Ash
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16 %
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Dolomite
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13 %
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Limestone
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� 4 %
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Sodium Sulphate
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� 1 %
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Recycled glass
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15 %
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Total
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100%
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Cost- components of glass manufacture �
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Rawmaterials
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20 %
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Energy
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20 %
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Labour
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15 %
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Overheeds
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17 %
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Depreciation
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13 %
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Transport
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10 %
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Others
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� 5 %
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Total Cost
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100 %
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Methods of manufacture �
There are 3 main flat glass manufacturing methods for producing the basic glass, from which all processed glass products are made �
1. Float glass �� Over 85 % of the world�s flat glass is made by the
float process. This is the way all the world�s high quality, optically clear
glass is made.
2. Sheet glass -� Approximately 8% of the world�s flat glass is made by
the sheet process.� This process is
pre-dated and is gradually being replaced by float.
3. Rolled glass -� The rolling process makes patterned, figured and wired glass products.� Semi-molten glass is squeezed between metal rollers to produce a ribbon, which controlled the thickness and surface pattern.
The Float process �
At the heart of the world�s glass industry is the float glass process � invented by Sir Alastair Pilkington in 1952 � which manufactures clear, tinted and coated glass for buildings and vehicles. The process, originally able to make only 6 mm thick glass, now makes it as thin as 0.4 mm and as thick as 25 mm.
Molten glass, at approximately 1,0000 C, is poured continuously from a furnace into a shallow bath of molten tin. The floats on the tin, spreads out and forms a level surface. Thickness is controlled by the speed at which solidifying glass ribbon is drawn off from the bath. After annealing (controlled cooling), the glass emerges as a �fire� polished product with virtually parallel surfaces.
A float plant, which operates non- stop between 10 � 15 years, makes around 6,000 kilometres of glass a year in thicknesses of 0.4 to 25 mm and in widths upto 3 metres.
Globally, around 320 float glass plants are in operation.
There are 3 main forms of modification to the basic manufacturing processes �
A) Modification to the basic manufacturing processes �
1. Tinted glass �� Extra ingredients are added to
the rawmaterials of glass at the melting stage to produce tinted products.� Cobalt and nickel tint glass grey;ferrous
oxide tints glass blue, while ferric iron generates a yellow tint-both together
tint glass green.
Tinted glass is
used in buildings and�� vehicles to
control heat and light transmission.
2.
Coated
glass � Glass can be coated
on-line in the float process as the ribbon of glass is being formed in the float glass bath. This surface coating gives modified properties to the glass.
3. Wired glass �� Wired glass is made by the
rolling processes.� In one such process,
steel wire mesh is sandwiched between two separate ribbons of glass in a
semi-molten state and passed through a pair of consolidating rollers which may
also impress a required pattern.� Its
uses include fire resistance and safety glazing.
B) Semi � finished processing �
The following types of processing are high volume and predominantly performed by glass manufacturers-
1. Off � line coating �� Off-line processes use a vacuum coating
technology called sputtering, mainly to produce suncool glasses.
2. Laminating �� Plies of glass are bonded or laminated
together with a layer of polymer film in between.� By using heat and pressure, air bubbles are eliminated from the
laminate, so that it appears optically as a single sheet of glass.� Mechanically, it is more robust.� If the laminate is fractured, the broken
glass fragments are held together and are less likely to cause injury.
Laminated glass is
used in safety and security applications.
3. Silvering �� Float glass is made into mirrors in a
process which deposits a thin film of high purity silver on one surface of the
glass.� A further thin film is then
deposited to protect the silver from oxidation.� Finally, a ceramic paint is applied.
C) Down-stream processing �
The following types of processing are performed by glass manufacturers and also by other companies
1. Heat treatment �� Toughened glass, or tempered glass as it is
also known, is produced when float glass is heated to around 6500,
then quenched with air jets so that the surfaces are cooled quickly, and the
inside core more slowly.� At room
temperature, the core continues to cool.�
The surface goes into compression and the core goes into tension.� When the glass breaks the core releases
tensile energy resulting in the formation of small, safer glass particles.� Toughened glass is used in safety glazing in
building.
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2. Shaping � Glass can be bent
into shape for some building applications.�
Between 5000C & 6000 C, the viscosity of glass
falls by a factor of 10,000 as it transforms from a brittle solid to a plastic
substance.� The science of glass bending
is to use this plastic phase to shapes that are free from wrinkles and other
optical defects.� Sag-bending is the
most widely used process.� The glass is
heated to the plastic phase and allowed to sag under its own weight to the
required shape.
3. Surface working � Fine surface textures can be applied using sand
blasting and acid etching.
At more than 13 million tonnes per year, china produces over 34% of the global output of flat glass. At the end of 2005, 130 float lines were believed to be in operation, although only 14 of these floats are of a western style design. Nevertheless, the quality and the output of Chinese float is increasing quickly. In terms of consumption and output, the market has been growing faster than 10% per annum, a trend which looks set to continue.
Approximately 5% of Chinese flat glass demand is imported, mainly specialized products that are not yet produced in china, while around 10% of the Domestic float glass output is exported, mainly standard grazing products into Asia.
China offers Float glass plants from 150 tons per day to 900 tons per day with a furnace campaign of 5 to 10 years. The cost of the plant ranges from USD 12 million to 35 million, while the total cost of the project comes to USD 20 million to USD 60 million. The most popular capacity is 600 tons per day all over the world, in which the plant cost is USD 24 � 27 million and the total project cost is USD � 40 � 45 million.
The cost of producing Float glass is USD 140 per ton in China, which is lowest in the world. The Ex-factory price of a standard 4mm clear glass in China is USD 312 per ton, whereas the same is USD 375 for 4mm tinted glass.
The retail prices of glass in India range from USD 700 per ton for clear glass to USD 1,000 per ton for tinted glass.
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Main technical
data for a 350 Tons/day Float Glass Plant from china �
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1
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Melting capacity
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-
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350 tons per day
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2
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Drawing capacity
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-
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350 tons per day
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3.
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Finished product capacity
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-
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260 tons per day
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4.
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Product variety
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Clear float glass and Tinted
float glass
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5.
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Quality
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-
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In
compliance with JIS R 3202 � 1996
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6.
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Gross width of the glass
ribbon
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-
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3500 mm
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7.
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Net width of the glass
ribbon
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-
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Maximum 3210 mm
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8
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Size of the finished product
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-
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Maximum 3210 x 2250 mm
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9
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Thickness if the glass
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-
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3 ~ 12 mm
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10.
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Working System
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-
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Continuous production with 8 hours per shift, 3 shifts per day and 365 days per year.
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11.
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Effective time of operation of the machine
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-
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97%
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12.
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Yield (Percentage of finished products)
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-
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76%
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13.
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Designed Furnace compaign before major over - hauling
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-
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5 to 10 years
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14.
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Consumption data
- Silica sand
- Soda ash
- Lime stone
- Feld spar
- Dolomite
- Salt cake
- Coal powder
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-
-
-
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-
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-
-
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Per annum
73,000 tons
20,000 tons
6,800 tons
5,000 tons
18,000 tons
1,600 tons
150 tons
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15
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Natural gas consumption for furnace
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-
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82,000 Nm3/day
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16
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Protective gas (N2+H2
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-
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~1500 Nm3/hour
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17.
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Water consumption
Fresh water for process and domestic
Circulating water
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-
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1,600 m3 per day
600 m3/day
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18.
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Installed power of the factory
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11 mw
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19.
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Power Consumption
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1.86 x 107 kwh/year
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20.
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Manpower(operators)
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-
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187
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21.
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Occupied area of the factory site
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150,000 m2(15 hectares)
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22.
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Total building area
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450,000 m2(4.5 hectares)
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23.
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Cullet ratio in the batch for re-use
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-
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20 - 25%
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Process description �
When float glass technology was developed, it gave revolutionary technical capabilities for glass manufacturing. For the first time it was possible to produce high quality flat glass in huge quantities without post polishing.
Glass is an ecologically most important working material. Its rawmaterials are pure nature. Main component of the batch is quartz sand with a share of approximately 60%, which is available to an almost unlimited extent. Limestone and dolomite with a share of about 20% are stabilizers in the glass. Soda ash and sulphate with a 20% share are helping to improve melting.
In the process, all kinds of rawmaterials are received in the factory and stored in the silo. Then, they are automatically weighed by electronic weighing system before being mixed. The mixed batch is conveyed to the feeding bin of the melting furnace. It is fed into the melting furnace by skew blanket feeders.
The batch is melt into molten glass under high temperature in the furnace. For the purpose of homogenization, the molten glass is stirred by a pair of horizontal stirrer at the neck before it flows into the working of the furnace. The homogenized and refined molten glass flows from the working end through a canal and a special canal block into the tin bath.
In the tin bath, the molten glass forms into a stream of definite geometry, which is spreaded, attenuated or thickened, cooled and formed into a glass ribbon of required thickness. In order to protect the molten tin in the tin bath from oxidization, the protective gas (H2 + N2) of required purity is continuously conducted into the tin bath. The formed glass ribbon then leaves the tin bath via the lift-out rollers and enters into an annealing lehr, where the temperature is automatically controlled according to the fixed annealing temperature curve. The glass ribbon after annealing moves on the roller conveyor for scoring, snapping, accelerating and edge trimming. Finally, the glass sheets are conveyed to taking-off and stacking area. The sheets are taken off from the conveyor and stacked on rack manually. The full stacked rack will be sent into finished product storehouse by overhead crane and fork lift.
All the process parameters are controlled by Intelligent batching controllers, PLC, Level meter controls, Differential pressure transmitters and Signelling systems. Monitors are installed at the melting zone of the furnace to show the flame and batch pile.
Cullet (glass waste) after the drop door will be crushed and returned to the cullet hopper at the charging end of the furnace for re-use. The system is controlled by Computer automatically.
It is important to note that on the liquid tin, the lighter glass melt is spreading out to a flat ribbon with exact parallel surfaces. The principle is very simple but the effect is enormous. Absolutely plane glass not achievable by any other former known process is achieved by the floating process.
Goodrich offers Float glass technology from china to the Indian entrepreneurs. The plant is highly cost-effective and the process is economical, enabling a quick pay-back period of 3 years.
For more details, please contact -
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GoodRich MAGMA Industrial Technologies Limited | |
No. 704, 4th 'A' Cross, HRBR Layout 1st Block, | Kalyan Nagar, Bangalore - 560 043, | | Karnataka, India. | | Ph: 0091 - 80 - 41138200 | Email: [email protected] / | [email protected] | Website: www.goodrichmagma.com / | www.goodrichsugar.com | | |
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