Glasses, Raw Materials; Silica sand, Limestone, Soda ash , Glass Manufacturing Process, Glass Forming, Glass Structure, Glass Properties, Glass Types, Soda-lime glasses , Lead glasses , Heat-resistant or borosilicate glasses, High-purity silica glasses, Specialty glasses, Heat Treating Glasses, Annealing glass, Tmpered glass, Chemistry of Glass Manufacture, Recycling of Glass, Virtification

1. Topic 4: GLASS
Hassan Z. Harraz
hharraz2006@yahoo.com
2013- 2014

2. OUTLINE OF TOPIC 4:
 Glasses
 Raw Materials:
a) Silica sand
b) Limestone
c) Impurity
 Glass Manufacturing Process
 Glass Forming
 Glass Structure
 Glass Properties
 Glass Types:
i) Soda-lime glasses
ii) Lead glasses
iii) Heat-resistant or borosilicate glasses
iv) High-purity silica glasses
v) Specialty glasses
 Heat Treating Glasses:
a) Annealing glass
b) Tempered glass
 Chemistry of Glass Manufacture
 Recycling of Glass
 Virtification
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 2

3. Question
What is Glass?
A glass can be defined as an inorganic product which has cooled to rigid structure without
crystallization.
A state of matter as well as a type of ceramic.
 As a state of matter, the term refers to an amorphous (noncrystalline) structure of a
solid material.
 The glassy state occurs in a material when insufficient time is allowed during
cooling from the molten state for the crystalline structure to form.
 As a type of ceramic, glass is an inorganic, nonmetallic compound (or mixture of
compounds) that cools to a rigid condition without crystallizing.
 Glass ceramics have an amorphous phase and one or more crystalline
phases and are produced by a so called "controlled crystallization" in
contrast to a spontaneous crystallization
 Glass-ceramics are mostly produced in two steps:
 First, a glass is formed by a glass manufacturing process.
 The glass is cooled down and is then reheated in a second step. In this
heat treatment the glass partly crystallizes
 Two prime characteristics of glass are their optical transparency and the
relative ease with which they may be fabricated.
21 November 2015 Prof. Dr. H.Z. Harraz Presentation Glass 3

4. Ceramics Materials
Glasses Clay
Products
Refractories
Glass
Glass-ceramics
Abrasives Advance
Ceramics
Structural clay
products
Whiteware
Fireclay
Silica
Basic
Special
Sandpaper
Cutting
Polishing
Cement
Taxonomy of Ceramics
21 November 2015 Prof. Dr. H.Z. Harraz Presentation Glass 4

5. Glasses
 A glass can be defined as an inorganic product which has cooled to rigid structure without crystallization.
 Glass is hard material normally fragile and transparent common in our life.
Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so
called "controlled crystallization" in contrast to a spontaneous crystallization
Glass-ceramics are mostly produced in two steps:
 First, a glass is formed by a glass manufacturing process.
 The glass is cooled down and is then reheated in a second step. In this heat treatment the glass
partly crystallizes
Two prime characteristics of glass are their optical transparency and the relative ease with which they may
be fabricated.
Amorphous Ceramics (Glasses) Main ingredient is Silica (SiO2)
 If cooled very slowly will form crystalline structure.
 If cooled more quickly will form amorphous structure consisting of
disordered and linked chains of Silicon and Oxygen atoms.
 This accounts for its transparency as it is the crystal boundaries that
scatter the light, causing reflection.
 Glass can be tempered to increase its toughness and resistance to
cracking.

6. RAW MATERIALS
Raw Materials Approximate
Proportion (wt %)
Provides Approximate Proportion
in glass (wt %)
Soda ash (NaHCO3) 25 Soda (Na2O) 18
Limestone (CaCO3) 10 Lime (CaO) 7
Silica sand (SiO2) 65 Silica (SiO2) 75
Raw materials used in lime-soda glass
a) Silica sand
 Silica sand suitable for glass manufacture is however relatively
rare, because of the need for a high degree of chemical purity.
 The essential requirements for silica sand for glass manufacture
are that it must be even grain size - more than 90% of grains must
lie in the range 125-500µm, and its chemical composition must
meet the requirements shown in Table 4.
Maximum
Cr2O3
Maximum
Fe2O3
Minimum
SiO2Glass
0.000150.01399.7Opthalmic glass
0.00020.01099.6Tableware, crystal and borosilicate glass
0.00050.03098.8Colourless containers
--0.2597.0Coloured containers
0.00010.1099.0Clear flat glass
Table 4: Required chemical composition of silica sand for glass manufacture
Fig.1: High pure silica sand raw
materials
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 6

7. a) Silica sand
 The discolouring impurities iron and chromium occur within the non-quartz mineral fraction of the
sands.
 Iron can occur as haematite, giving the sand a red colour, or as oxy-hydroxidcs (giving a yellow or brown
colour) as well as in silicate minerals.
 Chromium occurs as the heavy mineral chromite (FeCr2O4), which is stable during glass manufacture,
and so rather than resulting in a discoloured glass, it persists as solid inclusions within the finished
product, which can cause it to be brittle. This is especially important for float glass manufacture, where
persistence of chromite grains can render useless substantial lengths of glass strip. Because of the
difficulties involved in the chemical determination of minor amounts of Cr it may be appropriate simply
to count the number of grains of chromite detected optically within a sample of known weight in order
to classify a sand as suitable for float-glass.
 Alumina is a natural impurity in glass sands, arising from the presence of feldspars, mica or clay
minerals, and varies from 0.4% to 1.2% Al2O3 High values in this compositional range are preferred
because they help to reduce melting temperatures (yet another component is added) and involve no
negative effect on glass colour or other physical properties. The occurrence of aluminium as an
impurity may also be beneficial by reducing the need to add aluminosilicates (feldspar, aplite or
nepheline syenite) for the manufacture of certain glasses.
 Great care is taken to consider the minor components of a glass, as small traces of impurities may have
a major positive or negative effect on the quality of the finished product. For example, the presence of
traces of iron may give a pale green colour (often visible when examining a pane of glass end on), and
this can be tolerated in some applications (such as container glass).
 Other minor components might have beneficial effects on the qualities of the glass produced. For
example, addition of lithium (reduces the temperature required to melt the glass, and so yields savings
in energy costs.
21 November 2015 Prof. Dr. H.Z. Harraz Presentation Glass 7

8. b) Limestone
• Limestone is required twice in glass manufacture - once to produce
sodium carbonate and secondly as an ingredient in the batch to be
melted.
• As an ingredient in batches to be melted to produce glass, limestone
purity is critical. In particular, Fe contents have to be very low, and the
amount of MgO, as in dolomite, has to be known. In some glasses MgO is
added using pure dolomite, but the amounts have to be controlled.
• Like CaO, MgO causes immiscibility in glass melts; the miscibility gap in the
system SiO2-MgO is wider than that in the system SiO2-CaO (Fig.4).
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 8

9. Impurity
 The Na2O and CaO decrease the softening point of this glass from 1600oC to 730oC
 So that soda lime glass is easier to form.
 An addition of 1 – 4% MgO is added to Soda lime glass to prevent cracks.
Magnesium can be substituted for a proportion of the calcium content by the use of
dolomite instead of limestone
 In addition of 0.5 – 1.5% Al2O3 is used to Increase the durability. Alumina is a
widespread component of glasses in addition to soda ash and silica, and helps
improve resistance to weathering.
 Boric oxide (to produce heat-resistant glasses such as 'Pyrex' and 'Vycor') and
 Lead oxide (for lead crystal tableware).
 Potassium can be substituted for some of the sodium with the use of feldspar, aplite
or nepheline syenite.
 fluorides.: used to produce Opaque glasses .
 Lithium (Li2O) is added to the glass composition: The amounts required are very
small, frequently ~1 to <4%. Lithium is added to glasses for several reasons, because
it reduces liquidus temperatures; it improves moulding properties (reduces
viscosity); it improves thermal properties ('Pyrex', ceramic hobs) and it improves
strength.
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 9

10. Glass Manufacturing Process
1. Silica sand, limestone, soda ash and cullet (recycled glass or
broken glass) are keep dry and cool in a batcher house in
silos or compartments
2. Mixing and weighting into proper proportion:
 Sand (SiO2), Quartz, or Silica sand
72%
 Flux → to lower T – e.g. Soda or
Soda Ash (NaHCO3) 17%; (1700 –
900oC)
 Stabilizing agent → to mitigate
water solubility of the glass
formed – e.g. CaO normally added
as Limestone {Lime 5%}
www.glassforever.co.uk/howisglassmade/
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 10

11. Why So Much SiO2 in Glass?
• Because SiO2 is the best glass former :
 Silica is the main component in glass products, usually comprising 50% to 75% of total chemistry.
 It naturally transforms into a glassy state upon cooling from the liquid, whereas most ceramics
crystallize upon solidification.
Other Ingredients in Glass
• Sodium oxide (Na2O), calcium oxide (CaO), aluminum oxide (Al2O3),
magnesium oxide (MgO), potassium oxide (K2O), lead oxide (PbO), and boron
oxide (B2O3)
• Functions:
 Act as flux (promoting fusion) during heating
 Increase fluidity in molten glass for processing
 Improve chemical resistance against attack by acids, basic
substances, or water
 Add color to the glass
 Alter index of refraction for optical applications
21 November 2015Prof. Dr. H.Z. Harraz Presentation Glass11

12. Glass Manufacturing Process (Cont. )
3. Send to furnaces in hoppers:
 operated by natural gas
 heat the mixture at 1300-1600oC into soften or molten state
4. Molding (or Casting ): molten glass flows to forming machine to
mold into desire shapes
5. Annealing lehrs : reheating the glass in an oven
 to ensure even cooling of glass for strengthening of the
products
6. Cooling process: Cool for 30 min to an hour for safe to handle.
7. Glass products are then decorated, inspected again and finally
packaged and shipped to our customers. Glass Furnace Cooling Systems
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 12
Process

13. Glass Forming
Flat glass – floating / rolling
Glass fibre – continuous strands and Crown
process for glass wool
1) Casting : molding
2) Pressing: pressing second mold into molten glass
3) Core-forming: clay core dipped into molten mass
4) Fusing : fusing glass rods together around a mold
5) Blowing: blowing air into a glob
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 13

14. Glass Fabrication Methods
• Pressing:
GLASS
FORMING
Adapted from Fig. 13.8, Callister, 7e. (Fig. 13.8 is adapted from C.J. Phillips, Glass: The
Miracle Maker, Pittman Publishing Ltd., London.)
Gob
Parison
mold
Pressing
operation
• Blowing:
suspended
Parison
Finishing
mold
Compressed
air
plates, dishes, cheap glasses
-mold is steel with graphite
lining
• Fiber drawing:
wind up
PARTICULATE
FORMING
CEMENTATION

15. Blow Molding
Softened
glass
Softened
glass
Pressed Glass Processing
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 15

16. Float Glass: The Process
Image from Prof. JS Colton, Ga. Institute of Technology
Modern Plate/Sheet Glass making:

17. Glass Structure
• Quartz is crystalline
SiO2:
• Basic Unit: • Glass is amorphous
• Amorphous structure
occurs by adding impurities
(Na+,Mg2+,Ca2+, Al3+)
• Impurities:
interfere with formation of crystalline
structure.
(soda glass)
Adapted from Fig. 12.11, Callister, 7e.
SiO 4 tetrahedron
4-
Si 4+
O2-
Si 4+
Na +
O2-
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 17

18. Glass Properties
 Specific volume (1/r) vs Temperature (T):
• Glasses:
 do not crystallize
 change in slope in spec. vol. curve at
glass transition temperature, Tg
-- transparent
- no crystals to scatter light
 Crystalline materials:
 crystallize at melting temp, Tm
 have abrupt change in spec. vol. at
Tm
Adapted from Fig. 13.6, Callister, 7e.
T
Specific volume
Supercooled
Liquid
solid
T m
Liquid
(disordered)
Crystalline
(i.e., ordered)
T g
Glass
(amorphous solid)
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 18

19. Glass Types
Five common types of glass:
i) Soda-lime glasses
ii) Lead glasses
iii) Borosilicate or Heat-resistant glasses
iv) High-purity Silica glasses
v) Speciality glasses
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 19

20. i) Soda-Lime-Silica Glasses
• 65% sand; 15% soda; 10% lime
• In this glass component are:
 71 – 73% SiO2
 12 – 14% Na2O
 10 – 12% CaO
• Adding sodium oxide (soda) lowers melting point
• Adding calcium oxide (lime) makes it insoluble
• Sodium and calcium ions terminate the network and soften
the glass
• The Na2O & CaO decrease the softening point of this glass from
1600oC to 730oC, So that soda lime glass is easier to form.
• An addition of 1 – 4% MgO is added to Soda lime glass to prevent
cracks.
• In addition of 0.5 – 1.5% Al2O3 is used to Increase the durability
• Soda-lime-silica glass is most commonly produced glass which
accounts for ~95% of all the glass produced in the world.
• Soda-lime-silica glass expands much when heated
 Breaks easily during heating or cooling
Uses
Soda lime glass is used for flat glass, containers, lightening
products.
It is used where chemical durability and heat resistant are
not needed
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 20

21. ii) Lead Glasses
• Lime and soda replaced with lead oxide (PbO)
• Contains lead oxide (PbO) to improve refractive index
• High refractive index- clarity sparkle
• Softer –cut and engrave
• Good electrical resistance - electronics
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 21

22. iii) Heat-resistant (or Borosilicate) Glasses
• Contains Boron oxide, known as
Pyrex.
• Boron-oxide-silica glass expands
less
 Tolerates heating or cooling
reasonably well
• Pyrex and Kimax are borosilicate
glasses
• Boron oxide replaces lime and
most of soda – low thermal
expansion coefficient
• Al2O3 - B2O3 – aluminosilicate glass
with even better heat resistance
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 22

23. iv) High-purity Silica Glasses
• Highest quality – most durable
• 3 processes – melting pure SiO2; making 96% silica and flame
hydrolysis
• Pure SiO2 – pure silica melted @ 1900 ºC under vacuum
• 96% - Vycor process – borosilicate glass heated to
grow crystalline sodium borate channels –
extracted hot HNO3 – leaving 96% pure silica after
heat reduction @ 1200 ºC
• flame hydrolysis – SiCl4 in CH4 / O flame (1500ºC,
produces high-surface silica soot thermally
sintered to pure silica at 1723 ºC)
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 23
2H2O + SiCl4 SiO2 + 4HCl
Flame

24. v) Specialty Glasses
• Coloured glass:
MnO2 – violet,
CoO – blue,
Cr2O3 - green
• Opal glass:
white opaque or translucent glassware
colour due to scattering of light from small particle
usually NaF/CaF crystals
nucleating after a cooling and reheating process
• Frosted glass:
 satiny look when exposed to HF
OHSiFSiOHF 242 24 
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 24

25. v) Speciality (Cont.)
• Coated glass:
 unique properties
 metal / metal oxides Ag+ + RA  Ag mirror
 electrically conducting with SnO2 coating (thermal SnCl4
hydrolysis)
• Photosensitive glass:–
 glass that changes colour upon exposure to light
 Phototropic:
 darkens upon exposure to light and returns to original clear
sate afterwards.
 AgCl/AgBr
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 25
Ag+ X-  Ag + X
light
dark Blue-greycolorless
Non-silicate glasses are becoming increasingly important for special optical
purposes,
 for example in the use of glasses prepared from CaF2, AlF3 and P2O5
for infrared optics or the use of fluoride glasses for optical fibres

26. Heat Treating Glass
 Annealing:
 removes internal stress caused by uneven cooling.
 Tempering:
 puts surface of glass part into compression
 suppresses growth of cracks from surface scratches.
 sequence:
further cooled
tension
compression
compression
before cooling
hot
surface cooling
hot
cooler
cooler
 Result: surface crack growth is suppressed.
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 26

27. a) Annealing Glass
 Annealing is a process of slowly cooling glass to relieve internal
stresses after it was formed.
 The process may be carried out in a temperature-controlled kiln
known as a Lehr.
 Annealing glass is critical to its durability.
 Removes internal stress caused by uneven cooling.
 Glass which has not been annealed is liable to crack or shatter
when subjected to a relatively small temperature change or
mechanical shock.
 If glass is not annealed, it will retain many of the thermal stresses
caused by quenching and significantly decrease the overall
strength of the glass.
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 27

28. b) Tempered Glass
• The tempering process consists of the following steps:
1) First the glass is washed and then heated.
2) In order to temper glass, it must reach 1100°F (the softening point for glass.)
3) The glass is then cooled with cold air. Quenching with forced cold air sets up the tension and compression
zones.
4) The tempered glass continues down the rollers to cool more and be packed for shipping. Glass to be tempered
must be cut to size before the tempering step.
• A flow chart in the next slide provides a summary of the tempering process.
Tempered Glass: The Process
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 28

29. b) Tempered Glass (Cont.)
• Tempering glass:
 Heat glass to softening point
 Cool outside of glass quickly
 Outside stiffens while inside is still
hot
 Shrinking inside compresses
outside
 Compressed outside stretches
inside
• Resists fractures because surface is
compressed
• Crumbles when cracked because inside
is tense
 Glass expands when heated
 Quenching “freezes” this expansion on the
outside
 Center cools more slowly, and contracts. Sets up
tension and compression zones.
 Tempered Glass is required for door products and
some windows installed near doors. If tempering
is done improperly then distortion can result.
 Tempered glass is stronger than annealed glass.
If annealed glass (raw float) has a strength factor
of “1”, tempered glass would be “4”.
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 29

30. What is the difference between (regular) annealed glass and tempered glass?
Annealed (regular) Glass
• Advantages:
 Cost
• Limitations:
 Breaks in sharp pieces
 Not as strong as
Tempered Glass
 Size limitations
Tempered Glass
• Advantages:
 4 times the stronger than
annealed
 Breaks into small, harmless
pieces.
 Qualifies as Safety Glazing
• Limitations:
 Must be cut to size before
tempering
 Optical distortion (roller wave,
strain pattern)
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 30

31. Examples of today’s glass products:
 Containers (jars and bottles)
 Flat glass (windows, vehicle
glazing, mirrors, etc.)
 Lighting glass (fluorescent
tubes, light bulbs, etc.)
 Tableware (drinking glasses,
bowls, lead crystal, etc.)
 Laboratory equipments (test
tubes, cylinders, measuring
flasks, etc.)
 TV tubes and screens
 Decorative glass
 Fiberglass
 Optical glass
 Vacuum flasks
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 31

32. CHEMISTRY OF GLASS MANUFACTURE
 In general terms, soda-lime-silica glass manufacture involves melting the required
raw material mix at 1600°C, which yields a very fluid melt, from which gases can
escape (especially carbon dioxide produced by the decomposition of carbonate raw
materials).
 The glass is then worked to produce the articles required at about 1000°C, followed
by annealing at 500-600°C.
 Example; the float glass process, used to produce flat panes of glass suitable for
windows, illustrates this well (Fig.3).
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 32
Fig.3: Diagram of the float glass process, showing the way a continuous ribbon of glass is drawn from the melting furnace, through
the float bath (which gives the perfect surface to the sheet) and then is annealed and allowed to cool before preparation for sale.

33. CHEMISTRY OF GLASS MANUFACTURE (Cont.)
 A glass is little more than a rapidly quenched liquid
 The term 'Glass' can be applied to many different materials, but in common
usage it refers to quenched silicate liquids, , which behaves as a solid but
retains the molecular structure of the liquid.
 The production of commercial glasses is therefore dictated by the
application of phase diagrams which allow the melting behaviour of
particular compositions to be predicted and the optimum conditions for
glass manufacture to be identified.
 The appropriate phase diagram is that for the system SiO2-CaO-Na2O (Fig.4).
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 33

34. CHEMISTRY OF GLASS MANUFACTURE (Cont.)
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 34
Fig 4: Phase relation ships for part of the system SiO2-CaO-Na2O at atmospheric pressure (weight%).
The system includes the following crystalline phases:
Name Formula Abbreviated formula
Cristobalite SiO
2
S
Tridymite SiO
2
S
Quartz SiO
2
S
Pseudowollastonite CaSiO
3
CS
Sodium silicate NaSiO
3
NS
Sodium disilicate Na
2
Si
2
O
5
NS
2
Sodium calcium silicate Na
4
CaSi
3
O
9
N
2
CS
3
Sodium calcium silicate Na
2
Ca
2
Si
3
O
9
NC
2
S
3
Sodium calcium silicate Na
2
Ca
3
Si
6
O
16
NC
3
S
6
O
 Point O is the ternary eutectic,
at 725ºC, with the composition
5.2% CaO , 21.3% Na2O and
73.5% SiO2

35.  Liquidus phase relationships within the three-component system SiO2-CaO-Na2O go well beyond those relevant for glass
manufacture.
 Consequently, Figure 4 focuses on the silica-rich corner of the triangular diagram, as this includes most glass compositions. In
this region, the silica mineral on the liquidus is cristobalite, tridymite or quartz (depending on temperature), with very steep
temperature gradients particularly towards more sodic compositions. Towards the lime apex, a field of two liquids is drawn; in
this field, liquid compositions separate out into two contrasting liquids, one silica-rich and one lime-rich.
 These two liquids are immiscible in the same way that oil and water are immiscible, and like a good mayonnaise they are
opaque to light and can be quenched to produce an opaque white solid. The other liquidus fields show shallower temperature
gradients.
 On the boundaries between them arrows are marked to show the "downhill direction". These all converge on a single point,
where the temperature at which liquid can exist is lowest, which is a ternary eutectic. The ternary eutectic composition can be
read from the compositional axes and corresponds to 5% CaO, 21% Na2O, and 74% SiO2. The minimum temperature can be
read from the contours is 725°C.
 In order to decide on the optimum blend of ingredients required to make a soda-lime-silica glass, the ternary liquidus diagram
can be used to indicate the temperature required to initiate melting. The ternary eutectic composition is therefore the one
which appears to be ideal for glass manufacture, as it will begin to melt at the lowest temperature, saving energy and
manufacturing costs. Melting is carried out at 1600°C to give enough superheat to ensure that all of the solid grains within the
raw materials dissolve within the liquid and to ensure that the viscosity of the liquid is sufficiently low that gases can escape.
Compositions which are more silica-rich have a rapidly rising liquidus temperature, and may not completely melt, leaving a
glass which contains crystals of a silica mineral or bubbles and appears frosted. It is therefore important to use this and similar
diagrams not only to design batch mixes but also to diagnose problems which arise when glasses are not correctly made.
 The sources of soda and lime are respectively sodium carbonate (soda ash) and limestone (dolomite is used if magnesium is
needed). These materials decompose on heating with the loss of carbon dioxide. Thus, in the formulation of batches consisting
primarily of silica sand, limestone and soda ash, proportions must be corrected to take into account the loss of carbon dioxide
so that they correspond to the compositions required for the finished glass. In order to carry out this correction, relative
atomic masses (atomic weights) are used to determine the proportions of CaO within CaCO3 and Na2O in Na2CO3:
 Relative atomic masses: Ca = 12 ; O = 16 ; Na = 23 ; Ca =40
 Relative molecular masses:
CaO = 56 ; Na2O = 62; CO2 = 44, CaCO3 = 100; Na2CO3 = 106
• Therefore;
100 tonnes of limestone (CaCO3) yields 56 tonnes of CaO and 44 tonnes of CO2. and
100 tonnes of soda ash (Na2CO3) yields 100 x 62/106 = 58 tonnes of soda and 42 tonnes of CO2
CHEMISTRY OF GLASS MANUFACTURE (Cont.)

36. Glass Industries
The World Glass Industry has a gross production value totaling $82.3
billion
Fig. 14
www.icem.org/events/ bled/matdocen.htm
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 36

37. Recycling of Glass
• Recycle of glass is mostly used for packaging
• Recycle process
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 37

38. Virtification
 Definition:
a new technology has been
discovered to use recycle glass for
radioactive waste management
 Process:
 melt glass together with
radioactive waste in barrels or
some other container
 glass will then bind up with
radioactive contamination into a
huge glass block
 radioactive waste is bond by the
glass and become immobilized
 keep radioactive waste from
interacting with water, stop
spreading the waste
Fig. 20
www.vitrification.com/ vitrification.htm
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 38

39. Good & Bad of Virtification
Benefit of virtication:
 Prevent radioactive waste
pollution
 Minimize the amount of glass
waste produced
 Increase the efficiency of glass
use (to stabilize hazardous
waste)
 High volume reduction of waste
 Landfill space can be saved
Volume percent of vitrified product
compared to the original waste volume
Fig. 21 www.vitrification.com/ vitrification.htm
21 November
Prof. Dr. H.Z. Harraz Presentation Glass 39