project poc

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IN THE NAME OF ALLAH ALMIGHTY, THE MOST MERCIFUL,
THE MOST BENEVOLENT, THE CREATOR OF ALL THE
WORLDS THE PRESERVER
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PROJECT TITLE
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Submitted To
Engr. Dr. Ayub Elahi
Submitted By
MUHAMMAD BIN ANWAR
42 TALHA AKBAR BUTT
08 FARHAN SAJID
38 RANA WASEEM SAEED
01 MUHAMMAD RIZWAN
TAHIR 34

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INTRODUCTION

• Definition Cement is a crystalline compound of
  calcium silicates and other calcium compounds
  having hydraulic properties (Macfadyen, 2006).

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Manufacture of Portland cement

• Cement is made primarily from a calcareous
  material, such as limestone or chalk, and from
  alumina and silica found as clay or shale. Marl,
  a mixture of calcareous and argillaceous
  materials, is also used.
• The process of manufacturing of cement consists
  essentially of grinding the raw materials, mixing
  them intimately in certain propositions and
  burning in a large rotary kiln at a temperature
  of up to about 1450 0 C when the material
  sinters and partially fuses into the balls known
  as clinker. The clinker is cooled and ground to a
  fine powder, with some gypsum added, and the
  resulting product is the commercial Portland
  cement so widely used throughout the world.
• The mixing and grinding of the raw materials can
  be done either in water or in a dry condition
  hence the name wet and dry processes. The
  actual methods of manufacture of cement depend
  also on the hardness of materials used and on
  their moisture content.

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Manufacture of Portland cement

• Raw materials
• Preparation of materials
• Burning
• Final processing
• Quality control

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RAW MATERIALS

• The fundamental chemical compounds to produce
  cement clinker are
• Lime (CaO)
• Silica (SiO2)
• Alumina (Al2O3)
• Iron Oxide (Fe2O3)

Raw materials used in the production of clinker
cement
Fly ash by-product of burning finely grounded
coal either for industrial application or in the
production of electricity
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Raw materials

• Limestone (calcium carbonate) is a common source
  of calcium oxide.
• Iron-bearing aluminosilicates are the most
  common source of silica.
• Aluminum and iron oxides act as fluxing agents
  i.e. lower fusion temperature of part of the raw
  mix to a practical firing temperature

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Preparation of Materials

• Crush the materials and store them
• Blend the materials and grind them
• Store them and do final blending
• Blending assure constant composition and
  predictable properties.
• Wet, dry, processes.
• Burn the materials
• Grind, blend, and store the materials

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WET PROCESS

• When chalk is used, it is finely broken up and
  dispersed in water in a wash mill this is a
  circular pit with revolving radial arms carrying
  rakes which break up the lumps of solid matter.
• The clay is also broken up and mixed with water,
  usually in a similar wash mill. The two mixtures
  are now pumped so as to mix in predetermined
  proportions and pass through a series of
  screens. The resulting cement slurry flows into
  storage tanks.
• When limestone is used, it has to be blasted,
  then crushed, usually in two progressively
  smaller crushers, and then fed into a ball mill
  with the clay dispersed in water. There the
  comminution of the limestone (to the fineness of
  flour) is completed, and the resultant slurry is
  pumped into storage tanks.

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• Raw materials are homogenized by crushing,
  grinding and blending so that approximately 80
  of the raw material pass a No.200 sieve.
• The mix will be turned into form of slurry by
  adding 30 - 40 of water.
• It is then heated to about 2750 0 F(1510ºC) in
  horizontal revolving kilns (76-153m) length and
  3.6-4.8m in diameter.
• The slurry, in its movement down the kiln,
  encounters a progressively higher temperature.
• At first the water is driven off and CO2 is
  liberated further on, the dry material undergoes
  a series of chemical reactions until finally, in
  the hottest part of the kiln, some 20 to 30
  percent of the material becomes liquid, and lime,
  silica and alumina recombine.
• The mass then fuses into balls, 3 to 25 mm (1/8
  to 1 in.) in diameter, known as clinker.
• The clinker is then cooled and stored, after
  that its finish grinding is done and It is stored
  in silos.

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CEMENT CLINKERS
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• Natural gas, petroluem or coal are used for
  burning. High fuel requirement may make it
  uneconomical compared to dry process.
• Wet process is obsolete.

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DRY PROCESS

• Raw materials are homogenized by crushing,
  grinding and blending so that approximately 80
  of the raw material pass a No.200 sieve.
• The raw materials are crushed and fed in the
  correct proportions into a grinding mill, where
  they are dried and reduced in size to a fine
  powder. The dry powder called the raw meal is
  then pumped to a blending silo, and final
  adjustment is now made in the proportions of the
  materials required for the manufacture of cement.
• In the dry process, the raw meal, which has a
  moisture content of about 0.2 percent, is passed
  through a pre-heater, usually of a suspension
  type that means that the raw meal particles are
  suspended in the rising gases. Here, the raw meal
  is heated to about 800 0 C before fed into the
  kiln.
• Mixture is fed into kiln burned in a dry state.

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• This process provides considerable savings in
  fuel consumption and water usage but the process
  is dustier compared to wet process that is more
  efficient than grinding.
• It is then heated to about 2750ºF (1510ºC) in
  horizontal revolving kilns (76-153m length and
  3.6-4.8m in diameter.
• In the kiln, water from the raw material is
  driven off and limestone is decomposed into lime
  and Carbon Dioxide.
• limestone lime Carbon
  Dioxide
• In the burning zone, portion of the kiln, silica
  and alumina from the clay undergo solid state
  chemical reaction with lime to produce calcium
  aluminate.
• silica alumina lime
  calcium aluminate

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Burning process

• Sintering (become a coherent mass with no
  melting)
• Fusion (complete melting)
• Clinkering only about ¼ of the charge is in the
  liquid state
• Kiln
• Long steel cylinder pipe
• Lined with refractory brick
• Inclined a few degrees
• Rotated at 60 to 200 rev/h
• Typically 6 m (20 ft) in diameter and 180 m (600
  ft) long
• Time in the kiln from 2 h (wet process) to 1 h
  (dry process) or even (20 min) modern heat
  exchangers
• Four processes take place in the kiln
• Evaporation 240 to 450 C

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• Calcination 600 to 1100 C
• Clay decomposes (600 C)
• Limestone decomposes (700 C) CO2 driven off
• Formation of initial compounds (1000 C)
• Initial formation of C2S (1200 C), formation of
  calcium aluminates and Ferrites
• Formation of melt (flux compounds melt) (1350 C)
• Clinkering charge temperature is 1400 to 1600
  C
• Formation of C3S
• Cooling
• Rate of cooling significantly affects the
  reactivity of the final cement. Clinkers should
  be cooled quickly to get high quality cement.
• Clinkers

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• The rotation and shape of kiln allow the blend
  to flow down the kiln, submitting it to gradually
  increasing temperature.
• As the material moves through hotter regions in
  the kiln, calcium silicates are formed.
• These products, that are black or greenish black
  in color are in the form of small pellets, called
  cement clinkers.
• Cement clinkers are hard, irregular and ball
  shaped particles about 18mm in diameter.
• On exit from kiln, regardless of the type of
  process, the clinker is cooled, the heat being
  used to preheat the combustion air.

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• The cool clinker, which is characteristically
  black, glistering, and hard, is interground with
  gypsum in order to prevent fresh setting of
  cement.
• The grinding is done in ball mill consisting of
  several compartments with progressively smaller
  steel balls, sometimes preceded by passing
  through a roll press.
• In most plants a closed-circuit grinding system
  is used the cement discharged by the mill is
  passed through a separator, fine particles being
  moved to the storage silo by an air current,
  while the coarser particles are passed through
  the mill once again.
• The performance of a ball mill can be improved
  by pre-grinding the clinker in a horizontal
  impact crusher.

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• The cement clinkers are cooled to about 150ºF
  (51ºC) and stored in clinker silos.
• When needed, clinker are mixed with 2-5 gypsum
  to retard the setting time of cement when it is
  mixed with water.
• Then, it is grounded to a fine powder and then
  the cement is stored in storage bins or cement
  silos or bagged.
• Once the cement has been satisfactorily ground,
  when it have as many as 1.1 1012 particles per
  kg (5 1011 per lb), it is ready for transport
  in bulk.

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• Less commonly, the cement is packed in bags or
  drums.
• However, some types of cement, such as white,
  hydrophobic, expansive, regulated-set, oil-well,
  and high alumina, are always packed in bags or
  drums.
• A standard bag in the United Kingdom contains 50
  kg (110 lb) of cement a US sack weighs 94 lb
  (42.6 kg) other bag sizes are also used. Bags of
  25 kg are becoming popular.
• Cement bags should be stored on pallets in a
  dry place.

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COMPARISON OF WET AND DRY PROCESS

• Except when the raw materials necessitate the
  use of the wet process, the dry process is used
  now a days in order to minimize the energy
  required for burning.
• Typically, the burning process represents 40 to
  60 percent of the production cost, while the
  extraction of the raw materials for the
  manufacture of cement represents only 10 percent
  of the total cost of cement.

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KILN
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Oxides composition of cement
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CEMENT SILOS
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THE CEMENT MANUFACTURING PROCESS
quarry
1. BLASTING The raw materials that are used to
manufacture cement (mainly limestone and clay)
are blasted from the quarry.
2. TRANSPORT The raw materials are loaded into
a dumper.
3. CRUSHING AND TRANSPORTATION The raw
materials, after crushing, are transported to the
plant by conveyor. The plant stores the materials
before they are homogenized.
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THE CEMENT MANUFACTURING PROCESS
Raw grinding and burning
1. RAW GRINDING The raw materials are very
finely ground in order to produce the raw mix.
2. BURNING The raw mix is preheated before it
goes into the kiln, which is heated by a flame
that can be as hot as 2000 C. The raw mix burns
at 1500 C producing clinker which, when it
leaves the kiln, is rapidly cooled with air fans.
So, the raw mix is burnt to produce clinker the
basic material needed to make cement.
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THE CEMENT MANUFACTURING PROCESS
Grinding, storage, packing, dispatch
dispatch
1.GRINDING The clinker and the gypsum are very
finely ground giving a pure cement. Other
secondary additives and cementitious materials
can also be added to make a blended cement.
2. STORAGE, PACKING, DISPATCH The cement is
stored in silos before being dispatched either in
bulk or in bags to its final destination.
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• In addition to the main processes, there are
  also processes of manufacture of cement, of which
  one, using gypsum instead of lime.
• Gypsum, clay and coke with sand and iron oxide
  are burnt in a rotary kiln, the end products
  being Portland cement and sulfur dioxide which is
  further converted into sulfuric acid.
• In areas where only a small production is
  required or whole investment capital is limited,
  a vertical kiln of the Gottlieb type can be used.
  This fires nodules of raw meal and fine coal
  powder combined, and produces agglomerated
  clinker which is then broken up. A single kiln,
  10 m (33 feet) high, produces up to 300 tonnes of
  cement a day.
• China uses several thousand of such kilns.