SULFUR

• Sulfur is the basic raw material for manufacture of sulfuric acid,

which is considered the barometer of India’s industrial process
Pertinent properties
Atomic wt.: 32.07
It exists as rhombic crystals and as monoclinic crystals
M.P -119oC, B.P – 444.6oC.
It is insoluble in water, but soluble in organic solvents and liquid
ammonia.
It exists in the form of rock, lump, molten, ground powder
CONSUMPTION PATTERN
• 80-90% of sulfur are converted to these oxidized form
• Sulfur dioxide (SO2), sulfur trioxide (SO3),
• sulfuric acid (H2SO4) and oleum (H2SO4 +SO3 )
End uses of elemental sulfur are:
• sulfuric acid manufacture (85-90%)
• Production of (SO2,SO3,CS2,P2S5)
• Rubber vulcanization agents
• Gunpowder, sulfur dyes
• Putties, sulfur concrete
• Paper manufacture
• India is practically devoid of deposits of elemental sulfur
Important deposits of pyrites are those of
• Amjhore in Rohtas district of Bihar,
• Saladipur in sikar district of Rajasthan
• The only deposits of sulfur are found in the puga valley of Kashmir.
• But due to terrain conditions, these deposits have not acquired due
economic importance
• Alternative sources of recovering sulfur:
1. Recovery of sulfur from petroleum refineries
2. Production of H2SO4 from zinc & copper smelters
3. Production of H2SO4 from pyrites
Madras refinery ltd is the only plant from which elemental sulfur is
recovered during the refining of crude petroleum
CLASSIFICATION OF PROCESS
1. Elemental sulfur mining from salt domes
2. Hydrogen sulfide conversion from natural or industrial gas
(oxidation-reduction of H2S)
3. Iron pyrites from Amjhore in Bihar state.
Elemental sulfur Mining (Frasch process)
Quantitative requirements: Basis: 1 ton of sulfur, water 6 tons (160oc)
Process Description:
Wells drilled into free sulfur-bearing salt domes. Treated hot water is
pumped into deposit melt sulfur.
Water moves upward and outward to bleeder wells an outer periphery of
area when its aerated and discharged
• Molten sulfur sinks to bottom of casing and is jet pumped with
composed air to sump-separation units and shipment or storage.
• Filtration is used to remove carbonaceous and mineral matter
Major Engineering problems:
1. Heat transfer in melting and shipping operations
2. Finding suitable sources of treated water
3. Corrosion
Oxidation –reduction of H2S (chemical Rxn)
2H2S + 3O2 2SO2 + 2H2O ∆Ho= - 247.89 Kcal
4H2S + 2SO2 Al O 2 3 S6 + 4H2O ∆Ho= - 42.24 Kcal
Raw materials: H2S from natural gas and petroleum refinery streams
recovered by scrubbing with ethanol amines and high temperature
stripping.
Quantitative requirements: Basis: 1 metric ton of sulfur
H2S– 1.2 tons, Air- 1,700 Nm3
Process description:
H2S and air bound in rxn. The product SO2 oxidizes H2S by reaction in a
two stage.
catalytic converter with intercooling and condensing.
Final waste gas is scrubbed with molten sulfur.
Major Engineering Problems
➢Two stage reactor design from exothermic SO2 oxidation of H2S
➢70-80% conversion in first stage at 300-400oC operation in second
reactor to obtain favorable equilibrium.
➢Heat exchange for molten sulfur handling
➢Corrosion
➢Final cleanup of stock gases
Elemental surface from pyrites (Finnish process)
Thermal dissociation :
FeS2 ½ S2 (g) + FeS (l)
General combustion reaction
C + H + S + O2 SO2, H2S, CO, HCO2, H2O
Sulfur recovery from gases-hot stage
2COS + CS2 + SO2 S6 + 3CO2
Sulfur recovery from gases-cold stage
4H2S + 2SO2 4H2O + S6
Roasting of Fes (pyrolite) for so2 recovery
2FeS + 3 ½ O2 Fe2O3 + 2SO2
Quantitative Requirements
• Basis: 1 ton of elemental surface
MATERIALS QUANTITY
Pyrites ore 4.4 tons
Lime stone 0.65 tons
Fuel oil 0.76 tons
Water 25 tons
Electricity 1.800 KWH

Co-products :
SO2 from Fes roasting = 1.2 tons
Fe2O3 from FeS roasting = 2.8 tons
Electricity = 3,200 kWH
PROCESS DESCRIPTION
• Pyrites ore is dried in a rotary kiln flue gases and ground to 200mesh.
• It is dispersed with hot combustion gases from oil burners at the top of a
vertical circular shaft furnace (5.5mm dia x 10m Height)
• Heat of dissociation and fusion is transferred to the FeS2 as it moves
downward in the suspension
• At the bottom of the vertical shaft the gases change 90oC and more
horizontally.
• The liquid droplets of Fes are caught in the molten horizontal batch and any
silica gangue is trapped and fluxed with time, floating on top of the molten Fes
matter.
• The liquid Fes is tapped periodically and granulated in water to produce 4mm
grains for further roasting operations.
• Hot gases at 1300 oC move through a high pressure heat recovery boiler
section (70 atm), cooling to 300oC
Contd..
• Dust is next separated by electrostatic precipitation
• The first step is combined sulfur recovery is done in a high
temperature catalytic reactor where carbon compounds with S are
eliminated
• The reaction gases, still containing so2 and H2s are cooled to 150oC by
passing through a low pressure heat recovery boiler. (4.5 atm)
• This is followed by “cold stage” catalytic reaction where aluminium
oxide catalyzes the H2S + SO2 reaction to produce S6 vapour
• After catalysis, sulfur gas is condensed on molten sulfur droplets in a
spray condenser
• The heat of fusion is recovered via low-pressure steam boiler
(0.7atm).The exit gases are next washed with water in another tower to
further recover entrained and uncondensed sulfur
• The sulfur usually contains arsenic which attacks the vanadium or
platinum catalyst in the SO2 SO3 contact process for H2SO4
• It can be removed by contacting molten sulfur with milk of lime in a
continuous autoclave
• Sulfur as SO2 for sulfuric acid can be obtained by roasting the
granulated FeS from the smelting furnace
• Fluidized roasting at 1000oC produces SO2 gas which is cooled in
waste heat boiler, cleaned by cyclones and electrostatic precipitation
• The hot cinders of iron oxide, suitable for blast furnace sinter cake,
are cooled on conveyors and shipped to steel plants
Major Engineering problems
1. Pyrites ore beneficiation : Indian ore has 5-7% SiO2 and requires
extra limestone
2. Grinding: Particle size range of 200 mesh
3. Substituting of coal for fuel oil
4. Gaseous reactions in the smelting furnace: combustion of fuel
without excess air to avoid unbalance of the HS-SO ratio
5. Two stage catalytic reaction design and combined with carbon to be
removed to increase efficiency from 85-92%
6. Heat recovery and generation of electricity
Economics:
Elemental surface deposits and supply
SULFURIC ACID
Pertinent properties:
Mol.wt – 98.08 oC, M.pt – 10.5 oC, B.pt – 340 oC
Completely miscible with H2o with large heat of solution. SO3 soluble in
H2SO4 to give varying percentage of oleum.
Grades of acid:
62.2% (Fertilizer grade),
95,98, 100% H2SO4
20%, 40% and 65% oleum
20% free SO3
Classification of process
Contact process – yields 98% H2SO4
Chamber process – yields 80% H2SO4
CONTACT PROCESS
• Reaction:
S + O2 SO2 ∆H = - 70.9 kcal
SO2 + ½ O2 SO3 ∆H = -23.0 kcal
• Raw materials
SO2 is obtained from the following sources
1. Sulfur source: combustion yields very pure so2 which requires only
filtration and drying
2. Pyrite source:
Iron pyrites containing 40-45 % S are roasted and purified by dust removal,
cooling, scrubbing, filtering and drying by acid
Scrubbing to remove dust, moisture and catalyst poisons (As,cl,F)
Contd..
• Smelter sources: SO2 obtained by roasting non-ferrous sulfide ores such as
zinc, lead and copper given same treatment as pyrites gas
• Waste H2SO4: FeSO4 from iron steel pickle liquors and H2SO4 from
petroleum refinery operations are roasted to recover SO2
• H2s sources: H2S is recovered by scrubbing various fuel and Refinery gases
with ethanolamine followed by hot stripping
• Catalyst: Vanadium pentoxide is mostly used. Platinum catalyst suffer easy
poisoning, fragility, rapid heat deactivation, high initial investment
Advantages of V2O5 catalyst:
➢Relatively immune to poison
➢Low initial investment and only 5% replacement /year
➢Requires only 10kg of catalyst mass containing 7-8% V205/daily ton of 100%
acid
Disadvantages:

❑ Must use dilute so2 input 7-10% as catalyst is less active and requires high O2 & SO2 to give economic conversion

❑ Larger convertors and high initial investment are necessary

Quantitative requirements:

Basis 1 ton of 100% H2SO4

SO2 – 0.67 ton, Au – 1,450 to 200 Nm3

Process description:

Au-SO2 gas containing 7-10% so2 and 11-14% o2 is pretreated by convertor gas and sent to first stage reactor of steel

construction.

This is the high temp (500-600oc) stage, contains 30% of total catalyst and converts about 80% of so 2.The convertor product is

cooled by heat exchanger at 300oc and fed to a second stage where total yield is increased to 97% by operating at 400-500oc

for favorable equilibrium.

• High yield product gases are cooled to 150oC by water and air heat exchangers
and absorbed in oleum fed at a rate to allow not over a 1% rise in acid strength
• Final scrubbing is done with a lower strength(97%). Oleum conc up to 40% can be
made by tower absorption. Higher strength oleum up to 5% is prepared by
distilling 20% oleum
Major Engineering Problems:
1. Design of multistage catalytic convertor for a highly exothermic reaction . Some
may contain 3 to 4 stages
2. Optimization of space velocity in catalyst chamber pumping cost vs fixed
charges of reactor
3. Corrosion problems: Increase in pressure increase compression cost and
corrosion problems
4. Removal of heat of absorption of SO3 in acid
HYDROCHLORIC ACID
• Hydrochloric acid is listed as title III hazardous air pollutant.
• Hydrochloric acid used in production of alumina and titanium dioxide,
chlorine dioxide synthesis , hydrogen production, activation of
petroleum wells, metal cleaning operation such as steel pickling
• It is most preferred acid for catalyzing organic process such as
carbohydrate reaction promoted by hydrochloric acid, analogous to
these in the digestive tracts of mammals
Hydrochloric acid can be produced by following processes
1. Synthesis from elements: H2 + Cl2→ 2HCl
2. Reaction of metallic chlorides with sulfuric acid:
NaCl + H2SO4 → NaHSO4 + HCl
NaCl +NaHSO4 Na2SO4 + HCl
2NaCl + H2SO4 Na2SO4 + 2HCl
As a byproduct of chlorination such as for the production of
dichloromethane, trichloroethylene, perchloroethylene or vinyl chloride
C2H4 + Cl2 C2H4Cl
C2H4Cl2 C2H3Cl + HCl
By thermal decomposition of the hydrated heavy metal chlorides from spent
pickle liquor in metal treatment
2FeCl3 + 6H2O Fe2O3 + 3H2O + 6HCl
From incineration of chlorinated organic waste
C4H6Cl2 + 5O2 4CO2 + 2H2O + 2HCl
CEMENT
• Cement is a generic name for powdered material which initially have plastic
flow when mixed with water or other liquid but form a solid structure in
several hours with varying degree of strength and bonding properties which
continue to improve with age
• Portland cement is the basis for a number of cement products. It is defined
as finely ground calcium aluminates and silicates of various compositions
which hydrate when mixed with water to form a rigid continuous structure
with good compressive strength
• Constituents of cement are
• Portland: 2Cao.sio2 (c2s), 3Cao.sio2 (C3s), 3Cao.Al2o3 (C3A), 4cao.Al2o3
Fe2o3 (C4AF) and Mgo
• High Alumina: 3Cao.Al2o3 (c3A), 2cao.sio2 (c2s) and 2Cao.Al2o3.sio2 (c2As)
• Hydraulic hydrated lime: Ca(oH)2, 2Cao.sio2 and 3Cao.Al2o3
Types of Portland cement
• Varying the % of constituents changes the rate of setting heat
evolution and strength characteristics
• Type I regular: 40-60% C3s, 10-30% C2s and 7-13% C3A. Hardens to
full strength in 8 days
• Type II Modified : Higher c2s/c3s to resist sulfate attack
• Type III High energy strength: Attains strength of type II in only 3
days, high heat rates. Useless in massive structure. Higher C3s and
c3A% with finer grinding to increase hydratum rate
• Type IV Low Heat : Designed for massive structure lurk, low C3s and
C3A which are largest contributors to heat of hydration
• Type V Surface resistant: Good for sea water contact C3A < 4%
Other types of cement
High alumina:
❖Manufacture by fusing limestone and bauxite
❖Rapid rate of strength development to high values but with high values but with high heat
rate liberation, superior resistance to sea and sulfate waters
Pozzolona:
• Mixture of volcanic ash, burnt clay or shade in 2-4 packets with hydrated lime
• Mixed with Portland cement as a cheap extender
Hydraulic lime:
❑Used only for brick mortar composition
❑Low price & strength
Magnesium chloride:
✓Lightly calcined Mgo mixed with Mgcl2 forms
✓Excellent high-strength, spark proof
✓Water resistant flooring
✓High bonding strength to wood fibers so useful in forming indoor construction material with
only fair resistance to water
Relative compressive strength characteristics
• Cement when mixed with other ingredients such as sand and gravel is
used for structural purposes under compressive loading since it has very
poor tensible strength
• High Alumina: 3Cao.Al2o3 (c3A), 2cao.sio2 (c2s) and 2Cao.Al2o3.sio2
(c2As)
• Hydraulic hydrated lime: Ca(oH)2, 2Cao.sio2 and 3Cao.Al2o3
TYPES 1 DAY 3 DAYS 28 DAYS
Portland Type I 37 120 340
Portland Type II 28 83 260
Portland Type III 103 240 440
Portland Type IV 20 49 177
Portland Type V 28 88 214
Hydrated lime - 14 30
Aluminous 280 480 690
Contd..
• India ranks as the fourth largest producer of cement in the world after
china, Japan & USA
• The first bag of cement was picked in the year 1914 at Porbundar. A
mere 945 mts was produced in that year throughout India compared to
the production of 48.75M tons in the year 1990-91
• Cement factories are in M.P, TN, A.P, Rajasthan, Gujarat, Bihar and
Karnataka. Location of cement factory near limestones resources has its
own advantages
• Different varieties of cements produced in India are Portland,
Pozzolana, Portland blast furnace slag, Special high strength cement, low
heat cement, oil well cement, coloured cement and white cement
Contd..
Cement rock beneficiation:
Most of the locally available limestone has to high a silica and iron content for
direct use in cement manufacture.
These undesirable constituents can be removed by ore dressing or
beneficiation methods which are based on fluid mechanics and adsorption
Quantitative requirements:
Basis: 1 ton of low-grade limestone
Water -3 tons, Reagents 50-200 grams and Electricity – 2.5 KwH
Process Description:
The operators are grinding, classification, flotation and thickening.Rock is
wet-ground,fed to a hydro separator where the overflow goes directly to the
final thickener, being of satisfactory composition. If not, it is subjected to
floatation separation which must be floated to remove Silica, mica and talc
Contd…
Major Engineering problems:
Choice of flotation agents, old type is oleic acid 200gm/ton, New types
of detergents have better selectivity and lower consumption, Grinding
which includes optimizing particle size range with power input
Portland Cement Process
Basis: 1 ton of type I content
MATERIAL QUANTITY

Clay 0.1-0.3 tons

Lime stone 1.2 -1.3 tons
Gypsum 0.03 – 0.05 tons
Coal 0.25 – 0.40 tons
Water 3 tons
Electricity 80 KWH
Contd..
• Chemical reactions:
Caco3 Cao + Co2
Cao + Al2o3 + sio2 Mixture of C3s, C2s, C3A
Process description:
Cement grade limestone + clay + sand + Iron containing materials + gypsum
and coal are ground together. Grinding may be a wet or dry process. Dry
process predominates because of savings in heat and accurate control possible.
The sequence may include rough crushing followed by gyratory and hammer
mills then drying and fine grinding in tube mills followed by air separation
and pneumatic blending. The cement compounds (c2s, c3s, c3A). The hot
clinker (3-10mm size) is dropped to a rotary cooler which preheats
combustion air for the kiln. The product from tube milling the clinker is a
powder of which 90% passes 200 mesh .It is bagged or stored and shipped
Rough crushing Gyratory Hammer mills Drying

Air separator Fine grinding

Pneumatic blending

Rotatory Kiln Decarbonator and

fired to form
Contd..
Major Engineering Problems:
Types of Grinding : Wet or dry grinding may be used with dry grinding
being used in most new plants
80% of the total power is consumed for crushing, grinding and blending
operations.
Kiln design:
✓Calcining involves decomposition of Caco3 to Cao and firing at 1400-
1500oc to promote compound formation.
✓Heat is required for water evaporation, oxidizing organic materials,
partial volatilization of sulfates, chlorates and alkalies.
✓Wet process requires 90-170m length kiln with 2.5-6m diameter.
✓Dry process includes 50m length with 2.5-m diameter and speed of 2-1/2
rpm
Cont..
Heat economy:
❖Minimizing fuel consumption is an economic balance between fuel cost and
addition of waste heat boiler and air preheater
❖Theoretical heat required is 430 Kcal/kg of Portland cement
❖Wet grinding releases 1300-1800 kcal/kg of cement
❖Dry grinding releases 700-1000 Kcal/kg of cement
Quality control
Product performance is quite sensitive to rock composition, particle size and
degree of calcining. Instrumentation and automatic control of the calcining
kiln has improved the cement quality
Economics of cement industry
High grade and beneficiated circuit rock will have to be supplemented by
blending with burnt clays and blast furnace slag to conseive native
limestone.The sludge from fertilizer industry is used for the manufacture of
cement
PROBLEMS
▪ Shortage of capital
▪ Power shortage
▪ Locatorial problems
Western & southern produces 71%, consumes 57%
East & North produces 29% , consumes 43%
▪ Shortage of coal
▪ Non-availability of Railway wagons
▪ Defective method of transport
▪ Negligible share in world trade
▪ Technological obsolescence
▪ Mini cement plant
▪ Research includes flyash blending, cement from paddy husk
LIME
• Quick lime: Cao
• M.pt 2570oc, Density 3.32 g/cc, soluble in water and acid
• Hydrated or slaked lime Ca(oH)2 , density = 2.2 gm/u, slightly soluble in water
and decomposition to Cao at 580oc
• Commercial lime is not 100% Cao or Ca(oH)2 but mixtures with Mgo and or
Mg(oH)2
• Quick lime: high calcium (>90% cao), low magnesium (5-25%mg),dolomite (25-
40%Mgo)
• Hydraulic lime and slaked lime : Ca(oH)2 plus Mgo-Mg(oH)2 in varying
percentage
• Lime is used s a basic flux in the manufacture of steel. Sio2 is a common impurity
in iron ore which cannot be melted unless it combines with another substance first
to convert it to a more fluid lava called slag
• Sio2 is a lewis acid and reacts with Lewis base lime.The molten silicate slag is less
dense than the molten iron and collects at the top of the reactor, where it can be
drawn off.Over 100 lbs of lime must be used to manufacture a ton of steel
Contd..
• Cao + Sio2 Casio3
• The uses of lime in chemical industries are numerous over 150 chemicals
are made with this basic material. Five other raw materials are salt, coal,
sulfuric acid and water
• Classification of process: calcining limestone to yield quick lime,
Hydration of quicklime
• Quicklime process: Caco3 Cao + Co2
• Basis: limestone 1.87 tons, coal 0.3 ton
• Process description:
Lime stone is quarried or mixed and put on conveyors feeding the mill
crushing unit. Lime stone of several sizes is produced. Jaw or gyratory
crushes are used for hard rock. Hammer or roll mill used for soft rock
The size depends on type of calcines as follows:
Vertical shaft 10-20 cm, Moving bed 1-10cm, Rotary kiln 0.5-5cm and
Fulidized bed 0.5-0.05cm
Contd…
✓Vertical shaft or Rotary kilns are usually specified
✓A vertical shaft kiln is 3-8mts in dia and 10-25m height lined with refractory brick
and covered with sheet steel outside for strength and prevention of gas leakage
✓Operation is of two types:
✓Unmixed coal is fixed in separate combustion chamber and flue gases supply heat
of decomposition
✓Mixed coal is mixed with limestone lump, simplifies kiln design but coal ash is
added to product.
✓Feed is from top of furnace where combustion gas preheats the stone it gradually
slides down the shaft into the calcining zone. This section of the shaft kilns
operates at 100-1100oc (Caco3 decomposes at 898oc)
✓The lime dump moves to the cooling section where heat exchanger occurs
between the secondary air and hot lime particles.
✓After further cooling in a conveyor, the lime is either packaged as lump lime or
crushed and screened to yield pulverized lime containers are jute bags with inner
seal lining of polyethylene to prevent moisture contact.
Hydrated Lime Process
Cao + H2o Ca(oH)2
1 ton of Ca(oH)2 require quicklime 0.787 ton, water 0.242 ton
Process description:
Quick lime lump crushed to 2cm or less is added along with water or
steam to a vertical cylindrical pug mill containing 18-24 extended
horizontal arms. Product from complete rxn is light, dry slaked lime
which is classified by screen or air seperators to remove any over buried
lime that did not hydrate. The finely divided product is packaged in bags
for shipping. Steam under pressure is used to more rapidly convert Mgo
where dolomite lime is used. The product is known as hydraulic lime
Contd..
Major Engineering Problems:
➢Large production rates of Quality product
➢Degree of calcining is controlled
➢Produce porous solid structure
➢Over buried lime require high temperature resistance time to produce unreacted
Mgo-cao for refractory sals.
➢Beneficiated limestone slurry or precipitated calcium carbonate sludges as from
caustizing ammonium sulfate, paper and sugar plants can only be handles with
rotary kilns. For smaller capacity vertical kilns are used
Heat transfer operations:
Optimization of Particle size, residence time, gas temperature, velocity profile
and heat economy in kilns
Economics of lime industry:
Lime production is very dependent on the steel industry which in turn fluctuates
directly with automobile and housing demand. Lime being an energy intensive
chemical because of the high temperature required
Glass industries
❑Glass may be defined physically, a rigid, undercooled liquid having no
definite melting point and a sufficiently high viscosity to prevent
crystallization and chemically as the union of non-volatile inorganic
oxides resulting from the decomposition and fusion of alkali and
alkaline earth compounds, sand and other glass contituents ending in a
product with random atomic structure
❑Glass has many uses because of its transperancy high resistance to
chemical attack, effectiveness as an electrical insulator and ability to
contain a vaccum.
❑Glass is a brittle material and exhibits greater compressive strength
than tensile strength. 800 different glass compositions are produced.
Contd..
History
➢Glass is discovered when cooking a meal in a vessel upon a mass of tuna at
the sea-shore. The union of the sand and alkali caught the man’s attention
and led to subsequent efforts at imitation
➢As early as 6000 or 5000 B.C Egyptians were making jewels of glass.
Window glass was made by A.D 290.
➢Glasswares started by 1608.
➢In 1914, the Fourcault process for drawing a sheet of glass continuously was
developed in Belgium.
➢Types of glass and glasswares are Flat glass, Pressed and Blown glass and
Glass containers
COMPOSITION
Lime, silica, soda fors 90% of all glasses. There have been minor changes in
major ingredients and major changes in minor ingredients.
Lime ,soda,sand are major ingredients
 Contd…
CLASSIFICATION
Commercial glasses fall into several classes
Fused silica:
• Made by the high temp pyrolites of silicon tetrachloride or by fusion of Quartz or pure
sand.
• Also or fused as Quartz glass and is characterized by low expansion and a high softening
point which have high thermal resistance and permit to be used beyond temperature range
of other glasses.
• Transparent to ultra violet radiation
Alkali silica:
• Sand & soda melted together simply called sodium silicate.
• Composition ranging from Na2osio2 to Na2o.4sio2. Equilibrium btwn in the two
components determine the behavior of complicated system.
• Silicate of soda ash also known as water glass
• It is usd as an adhesive for paper manufacture
• Used as detergents and soap builders
 Contd…
Soda-lime glass:
❑It is used for containers of all kinds, flat glass, automobile and other
windows, tumblers and tableware
❑Composition lies Sio2 (70-74%), Cao (8 to 13%), Na2o (13 to 18%)
❑Difficult to melt, chemically resistant, better colour
❑Selerium is used as a decolorizer of raw materials
Lead glass:
• By stabilizing leas oxide for calcium oxide in the glass melt, lead glass is
obtained
• High index of refraction and dispersion for optical work
• When lead content is 92% (RI=2.2)
• The brilliance of good “cut glass” is due to its lead bearing composition
• Because of its high electrical resistance, its used for construction of electric
light bulbs, neon-sign tubing and radiations.
Contd..
Special glasses
❑Colored and coated, opal, translucent, safety, optical, photometric glasses,
glass ceramics and special glasses.
❑Varying compositions depending upon the final products
Glass Fibers
• Resistant to weather conditions
• Low in silica about 85%
• Low in alkali
Raw materials:
Soda ash, salt cake & lime stone are required to flux this silica.In addition lead
oxide, pearl ash (potassium carbonate) salt peter, borax, boric acid, arsenic
trioxide, field space, fluoroscope together with great variety of metallic oxides,
carbonates and other reuired for coloured glass. In furnishing operations,
abrasives and hydro fluoric acid are consumed
Contd…
Sand for glass manufacture should be pure quartz.
• Should not exceed 0.45% Iron for tableware or 0.015% for optical glass
• Iron affects the color of most glass adversely
Field spares have formula R2o.Al2o3.6sio2 where R2o corresponds to Na2o or
K2o or mixture of these two
• It is a source of aluminate.
• Cheap, pure & fabric
• Composed of glass forming oxides
Burax for lower expansion value & high refractive index for optical ware. Salt
cake is to remove troublesome scum from tank furnaces. Carbon is used to
reduce sulfates to sulfites. Arsenic trioxide added to remove bubbles. Nitrates
of Na or K used to oxidise iron and make it less notification in the finished
glass. Cullet is crushed glass from imperfect articles, time and other waste glass.
It facilitates melting & utilizes waste material. 10 to 80% is added
Refractory blocks
To serve for severe conditions,

• sintered zirum, alumina, mullite, mullite-alumina, electrocast zirconia-alumina-silica,

chronic alumina are typical for glass tanks
• The reactions
Na2CO3 + aSiO2 Na2O.SiO2 + CO2
CaCO3 + bSiO2 CaO.bSiO2 + CO2
Na2SO4 + cSiO2 Na2OaSiO2 + SO2 + CO
The last rxn may be take place by following
Na2SO4 + C Na2SO3 + CO
2Na2SO4 +C 2Na2SO3 + CO2
Na2SO3 + cSiO2 Na2O.cSiO2 + SO2
Typical manufacturing sequences
1. Transportation of raw materials to the plant
2. Sizing of some raw materials
3. Storage of raw materials
4. Conveying, weighing and mixing raw materials and feeding them into
the glass furnace
5. Burning of the fuel to serve temperature needed for glass formation
6. Reactions in the furnace to form glass
7. Saving of heat by regeneration or recuperation
8. Shaping of glass products
9. Annealing of glass products
10. Finishing of glass products
Melting
Pot furnaces with capacity of 2tons or less are used for the small production of
special glasses
✓Employed for optical and art glass by the casting process
✓Made of clay or platinium
✓It is very difficult to melt glass in the vessels without contaminating the
product or partly melting the container itself, except when platinium is used
Tank furnaces
Batch materials are changed into one end of a large “tank” built of refractory
blocks
• Capacity is 1350 tons
• The glass forms a pool in the hearth of the furnace, across which the flames
play alternately from oneside and the other. The fined glass is worked out of
the opposite end of the tank
• The wall may gets corrode under the action of the hot glass
Shaping or Forming
• Glass may be shaped by either machine or hand molding machine molding should
be completed in a very few seconds. Relatively short time the glass changes from a
viscous liquid to a clear solid
• Design problem should solve the flow of heat, stability of metals and clearance of
bearings
• Machine shaped glasses are window glass, plate glass, float glass, bottles, light,
bulbs and tubing
• Window glass is made by Fourcault process, where the melted glass is drawn
vertically from the kiln through “debiteuse” by means of drawing machine
• The debit use consist of a refractory boat with seat in the center through which the
glass flows continuously upward when the boat is partly submerged. A metal bait
lowered into the glass through the slot at the same line
• The glass is drawn upward in ribbon form as faster, it flows up through slot and its
surface is chilled by adjacent water coils.
• The ribbon still travelling vertically and pass through a 7.5m long annealing
chimney or then it is cut into sheets of desired size and sent for grading or cutting
Annealing
To reduce strain, it is necessary to anneal all glass objects.
It involves two operations
1. Holding a mass of glass above a certain critical terms long enough to reduce
internal strain by plastic flow to less than a predetermined maximum

2. Cooling the mass to room temperature slowly enough to hold the strain below
the maximum
This is a heating chamber in which rate of cooling is controlled
Establish the relationship between stress & strain to meet the mechanical or thermal
stress of glass
Finishing:
This includes cleaning, grinding, polishing, cutting, sand blasting, enameling,
grading and gaging