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- 1. WELCOME TO LECTURE ON PROCESS FORNONPROCESS ENGINEERS K.P.Pradeep kumar
- 3. Cement is asubstance (often a ceramic) that by a chemical reaction binds particulates aggregates into a cohesive structure. ( hydraulic binder). The quality of raw material is the main point in maintaining of quality of cement. The mineral compounds containing the main components of cement: lime, silica, alumina and iron oxide are used in cement manufacturing process. Therefore it is usually necessary to select a measured mixture of a high lime component with a component which is lower in lime, containing however more silica, alumina and iron oxide (clay component). The purpose of calculating the composition of the raw mix is to determine the quantitative proportions of the raw components, in order to give the clinker the desired chemical and mineralogical composition What is cement ?
- 5. In 1824, JosephAspdin, a British stone mason, obtained a patent for a cement he produced in his kitchen. The inventor heated a mixture of finely ground limestone and clay in his kitchen stove and ground the mixture into a powder create a hydraulic cement-one that hardens with the addition of water.Aspdin named the product portland cement because it resembled a stone quarried on the Isle of Portland off the British Coast. With this invention, Aspdin laid the foundation for today's portland cement industry History of Cement Manufacture of cement has a history, which traces back to millennia. The Romans who were prolific builders used burnt calcareous (calcium bearing) rocks along with pozzolanic materials in an era Before Christ. The structures built by them, like the Pantheon, are still there for us to see proving the goodness of cementitious materials as input material for construction. The Roman called it as Opus cementum and pozzalana as Pozzolui. Post industrialization and as infrastructure development started globally, demands for cement have been growing steadily both quantitatively & qualitatively.
- 6. Background Although the useof cements (both hydraulic and non-hydraulic) goes back many thousands of years (to ancient Egyptian times at least), the first occurrence of portland cement" came about in the 19th century. In 1824, Joseph Aspdin, a Leeds mason took out a patent on a hydraulic cement that he coined "Portland" cement (1824) He named the cement because it produced a concrete that resembled the color of the natural limestone Quarried on the Isle of Portland, a peninsula in the English Channel Since then, the name "portland cement" has stuck and is written in all lower case because it is now recognized as a trade name for a type of material and not a specific reference to Portland, England.
- 7. few years later,in 1845, Isaac Johnson made the first modern Portland Cement by firing a mixture of chalk and clay at much higher temperatures, similar to those used today. At these temperatures (1400C-1500C), clinkering occurs and minerals form which are very reactive and more strongly cementitious. While Johnson used the same materials to make Portland cement as we use now, three important developments in the manufacturing process lead to modern Portland cement: - Development of rotary kilns - Addition of gypsum to control setting - Use of ball mills to grind clinker and raw materials Rotary kilns gradually replaced the original vertical shaft kilns used for making lime from the 1890s. Rotary kilns heat the clinker mainly by radiative heat transfer and this is more efficient at higher temperatures, enabling higher burning temperatures to be achieved. Also, because the clinker is constantly moving within the kiln, a fairly uniform clinkering temperature is achieved in the hottest part of the kiln, the burning zone.
- 9. Raw materials requiredto make cement • Lime stone ( calcareous material , Calcium carbonate) • Shale , low grade lime stone , clay ( argillaceous materials, Silica) • Aluminous mateial ( clay, bauxite or Laterite) • Ferrous material, haematite ( iron ore , ferric oxide )
- 10. Cement quality –type of cement Clinker quality Fuel chemistry Raw mix design OPC, PPC, WC, OWC, SRC,SC Ordinary portland cement, Pozalona portland cement White cement, Oil well cement, Sulfate resistant cement, Slag cement Other cements for special application Gpsum&fly ash or Other additive quality
- 11. quality Factors influencing thecement quality 1. Mechanical handling of clinker 2. Chemical and mineralogical composition of raw mix 3. Chemical and mineralogical composition of clinker 4. Burning process & cooling process 5. Chemical composition of fuels (ash) 6. Circulation phenomena (volatiles)
- 12. Mining crushing preblending Raw meal preparation Raw meal blending Pyro process Clinkercooling Cement grinding Packing& despatch Process steps Dust collection& pollution control Quality control
- 13. Process flow diagramin general
- 15. Mining • Core drilling(bore) holes to explore the mines • Drill holes for blast • Blasting • Excavation and haulage • Transportation to crusher • Size reduction for process requirements
- 16. Mining Quarry planning • Ensure- that the required quality & quantity on daily / monthly/ yearly is available to the plant • Minimise – total operating and capital costs • Optimise - raw feed quality • Fulfil – all the safety and legislative requirement • Maximise – return on capital employed • Achieve - peak quarring / plant efficiency
- 17. overburden Good quality limestone Moderate quality Poor quality overburden Good quality lime stone Moderate quality Poor quality selfish mining – short term benefits Efficient mining –for well blended – long term benefits Well developed mine Long term benefits Bench = 10 M
- 18. Picture of awell developed mine All benches are used effectively to improve the mine blend and increase the reserve for long term business
- 19. Mining on hill& under ground mining is challenge to the mining engineer
- 20. Geology and locationof boreholes
- 22.
- 23. Before blasting drillholes are drilled
- 24. The released energyof the explosive is converted into various other forms of energy • heat • seismic energy ( stress waves) • new surface energy ( rock fragmentation) • concussion and noise ( airblast) Explosion • kinetic energy of spoil ( throw) rock displacement
- 25.
- 26. Material breakage involvedin crushing process Impact Attrition shearing compression Crushing process Size reduction stages Primary n = 5 secondary n = 8 Tertiary n = 6
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- 30.
- 31. Crushing Crushing is aprocess which does size reduction Crushers are chosen depending upon the material characteristics such as hardness ,abrasiveness, feed input size, moisture content etc The commonly used crushers are hammer crushers, Impact crushers, roll crushers, gyratory crushers, jaw crushers. Size reduction depends upon the grinding system to be adopted ie., ball mill or vertical mill Size reduction ratio Max feed size ( linear edge dimension) Maximum feed size of crushed product =--------------------------------------------------- ( linear edge dimension)
- 32.
- 33. Stress type-1 Between twosolid Surfaces( compression, Shearing) Stress type-2 at solid Surface( impact) Stress type-3 Not at a solid Surface , but by action of The surrounding medium (shear stress) Stress type-4 Non mechanical introduction Of energy ( thermal shock, explosive shattering & electro hydraulic)
- 34. crushers Jaw crushers Gyratory crushers conecrushers roll crushers impact crushers Hammer crushers
- 35. MMD crusher (Rollcrusher) It can crush lime stone with high % of moisture
- 36. Selection of crushersfor different product size
- 37.
- 38. Preblending Variation is adevil in any process
- 39. Types of stacking Chevronmethod Window method Axial stacking Strata method Single cone shell stacking double cone shell stacking
- 40. Storage system Circular storage Linearstacker & storage Front acting machine Side acting machine
- 41. Advantage and disadvantagesof circular and linear piles Circular pile Advantages • space saving and hence low capital cost • end cone problem is avoided • un interrupted operation Disadvantages • pile correction is not possible and it depends on mines operation with less variation Linear pile Advantages • it occupies more space • while shunting the operation has interruption • end cone problem Disadvantages • Pile correction is possible if quality varies
- 42. Chevcon method (at Ariyalur) Chevcon - was developed for a circular stockpile arrangement. the stacker boom slews back and forth over the curved stockpile ridge maintaining a constant pile length. With each individual movement, the end of one movement or the start of the next movement is advanced by the dimension ∆L. In that way many layers - similar to the Chevron mode - are superimposed and the stockpile grows continuously in one direction. Chevcon configuration refers on to circular stock piles and relates to Chevron when it is applied to a circle. In this cofiguration the chevcon layers are inclined as in the side of a cone , each layer runs from the full height of the stock pile to the ground
- 43. Well blended slicewithout end cone End cone problems Linear stock pile Blending ratio = S in / S out More variation, high std Less variation, low std
- 44. X (t) Quantity(t) X (t) Reclaiming Slicestransversely Stacking in Equal layers Material quantity Per layer = t Material quantity Per slice = q Variations in the raw material composition homogenised in the blending bed ∆τ ∆τ ∆Q ∆Q ∆Q ∆Q ∆τ ∆τ ∆τ
- 45. Assessment of blendingmethod S in S out Blending ratio = S in S out Blending efficiency n n = number of layers n = V*(S*3600) / d d = volume discharged cum/hr S = cross sectional area, sq m V = travelling speed of the stacker η
- 46. Homogenising systems 3.1 Variabilitvand standard deviation The normally accepted method of measuring variability is in the form of a term called standard deviation. The standard deviation of a property can be calculated by taking a number of measurements on the property (such as LSF, SR etc.), and applying the following formula:- Where X is the measured variable (e.g. LSF) X is the variable mean (or average) N is the number of measurements or observations Table 1 illustrates a worked example using actual kiln feed LSF data:- Blending ratio = Std in/ Std out , = 1 for an ideal blending system. σ = Σ ( X - X ) 2 N - 1
- 47. Main parameters forraw mix design Lime saturation factor = CaO / (2.8 SiO2+1.65Al2O3 + 0.65 Fe2O3) ( LSF) Silica modulus = SiO2 / ( Al2O3+Fe2O3) Alumina modulus = Al2O3 / Fe2O3 AlM Here we have apply the formula (as per British Standard) CaO-0.7SO3 (2.8*SiO2 + 1.2* Al2O3 + 0.65*Fe2O3) (SIM) LSF =
- 48. Lime saturation factoron clinker basis If MgO is below 2 % LSF = 100( CaO – free CaO+0.75 MgO) (2.85 SiO2) + ( 1.18 Al2O3) +(0.65 Fe2O3) If MgO is above 2 % LSF = 100( CaO – free CaO+1.5 MgO) (2.85 SiO2) + ( 1.18 Al2O3) +(0.65 Fe2O3) 95 –harder to burn, tendency to high free lime & C3S clinker , high early strength high fuel consumption < 95 , easy to burn , excess coating , excess liquid phase , possible brick infiltration reduced cement strength , low free lime acceptable standard deviation = 1.2
- 49.
- 50. Raw mills Ball mill Rollerpress & Ball mill Vertical roller mill Horizontal roller mill
- 51. Grinding media forball mills
- 52.
- 53.
- 54. qopEffective interval q >>> qop; balls hit each other, not grinding material At critical speed qmax q <<< qop ; The ball waves through the material = 42.3/ D effectiveCritical speed cascading cataracting Ball mill grinding
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- 57.
- 58. Influence of millspeed on Trajectory of balls
- 59. Ball millsOpen circuitClosed circuit separator product product Coarse return Vertical mills are closed circuit mills with built in separators separator Circulation factor =1 Circulation factor = 2 to 2.5 Vertical mill
- 60.
- 62. Vertical mill operation( over view)
- 63. Separator Residue = 12– 18 % on 90 µ = 1.5 – 2.5 % on 212 µ An efficient separator is one which operates with no fines in coarse return ( rejects) and no coarse in product fines
- 64. Air drag Gravitational force Centrifugalforce Stationary vanes Rotary cage Function of separator
- 66. Centrifugal force GravitationforceAirdragforce Separation space Stationaryvanes Guide vanes rotor
- 67.
- 68. Advantages of verticalmills • Energy consumption is less compared to ball mills • Flexiblity in operation as all forces can be controlled • Drying capcity is better than ball mills • Noise level (noise pollution) is much less than ball mills • Particle size distribution better than ball mills
- 69.
- 70. Roller press compressed &Caked material Compression zone
- 71. In homogeneous homogeneous Kilnfeed uniformity index (KFUI) KFUI= n ( C3S actual - C3S target )2 n i - n C3S actual = the calculated C3S of one instantaneous daily sample of kiln raw mix feed C3S Target = the C3S target established for the mill product n = number of samples ( calculation of average C3S is done monthly) Target for KFUI is < 10 ( an instantaneous sample is one made up of 5 consecutive increments taken at short intervals)
- 72. Preblending Variation is adevil in any process
- 73. Blending silo The efficientblending silo does efficient blending with minimum energy The variation in chemistry at the silo outlet is to be at the minimum possible , Standard deviation of LSF < 1 Standard deviation of CaO < 0.2 Standard deviation of Silica ratio < 0.1 Standard deviation of A/F < 0.01
- 74. Flow properties ofpowders : • Importance of measuring flow properties • Various problems in powder handling and storage Arching Channeling Segregation
- 75.
- 76.
- 77.
- 78. Controlled flow inverted cone blendingSiloCapacity = 18000 t 18 M 40 MAdvantages • low inventory • low capital cost Disdvantages • can not be operated on low stock as raw mill operation directly affect silo effciency and hence the quality and production. • as the buffer stock is only for 1 day the incoming raw meal std must be < 1 for LSF and Silical modulus < 0.1
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- 80.
- 81.
- 82.
- 83. Pyro process • Wetprocess • Semi dry process • Semi wet process • Dry process ( wet milling and slurry is fed into the kiln ) (dry milling , water sprinkled to make nodulation, nodules are fed into the kiln) (wet milling , dried in vacuum drier, caked dried , powedered and fed into kiln (dry milling , dry meal is fed into kiln) • VSK process Vertical shaft kiln ( First process invented in cement process )
- 84.
- 85. Wet process Semiwet process Semi wet process Semi dry process
- 86. Long dry process kiln Drykiln , suspension preheater kiln Dry kiln , suspension preheater kiln With pre calciner
- 87. Kiln = 4500tpd 4.35 M * 67 M % filling = 9 – 11 % Material retention time =18 mts calciner
- 88. Clinker manufacture • Calcite– CaCO3 • Dolomite – CaMg(CO3)2 • Quartz – SiO2 • Clay minerals • Micas • Feldspars • Aluminum oxide • Pyrite • Iron oxide • Gypsum / anhydrite • Alite,C3S • Belite,C2S • Aluminate,C3A • Ferrite,C4AF • Free lime(un wanted) • Periclase(un wanted) • Alkali sulfates(unwanted) Mineral phases in raw meal Mineral phases in clinker Temperature Pressure Time
- 89. Alite CaO Belite Liquid CaCO3 Beta quartz Gamma quartz C3A Calcining zoneTransition zone Burning zone cooling zone 1400 1200 1000 800 600 400 200 1450 OC Deg C Pre heating zone C12A7 C2(A, F) C4AF Clinkering process
- 90. Refractories The function ofthe refractories are • to protect the shell from the heat • to insulate to reduce heat losses • to withstand thermal stresses • to with stand thermo-chemical stresses • to withstand thermo-mechanical stresses
- 91. Kiln refractory lining Refractoriesare lined inside the kiln shell and preheater cyclones to the metal from heat as well as to insulate to conserve heat.The bricks used are low alumina , high alumina bricks, magchrome bricks and spinel bricks. Mag chrome bricks are banned due to health hazard.Chromium is poisenous.For severe conditions special bricks like zirconia based , are used. 1400-1500 deg C 1200 -1250 deg C 1000-1100 deg C 1100-1200 degc Gas temperature Refractory brick
- 92. Always to beremembered If coal is mixed it is burnt If flame is wrong everything goes wrong whatever you may do with chemistry or higher heat input through calciner or kiln. The burning zone needs heat and it can be only obtained from well shaped radiant flame.i.e., short, snappy and convergent flame .
- 93.
- 94. Flame of anefficient burner
- 95. 7 8 9 Burnerpositioning We do positioning of the burner for centering the flame.The positions 1,2,3, 4 and 7are close to the refractory and they are away from the charge. Positions9 and 8 are close to charge . Only 5 is close to charge and refractory and this is best as the flame in this gives the best thermal distribution to do effective burning. Position 8 & 9 is very close to charge if coal is trapped it has serious negative impact.Position 1,4 & 7 is very close to refractory and it can burn the refractory. 4 5 6 1 2 3
- 96. Heat exchange inkiln is • mainly radiation of heat from flame to refractory wall and to charge • conduction of heat from refractory and to charge • convection of heat within the charge ( particle to particle contact) radiation conduction convection Heat flows from hotter body to colder body Gases flow from high pressure area to low pressure area
- 97. 1800 deg c 1300deg C 1400 deg C 1500 deg C 1600 deg c 1700 deg c radiation conduction convection
- 98. Lower rpm ,high % filling , less active Layer , high free lime, high radiation losses high rpm , low % filling , more active Layer , low free lime and low radiation losses Influence of revolutions / minute on kiln operation Optimum % filling = 9 – 11 with raw meal retention time of 20 -25 minutes unfavorable favorable Passive layer active layer
- 99. Different flames Normal flame Flamewith low Secondary air temp Distorted nozzle Flame –poor hood geometry Or distorted nozzle Flame at the center Flame downward Flame upward
- 100. Flame length Long flame,unstable coating, High back end temp Low shell temperature Short intense divergent flame Good for burning Low back end temperature Poor refractory life, high Shell temperature Convergent flame Good for burning Good for refractory Stable coating Low shell temperature
- 101. The Ideal Flame hot! short ! stable ! T"long" flame "short" flame Complete combustion: - CO = 0 - SO2, NOX ↓ Homogeneous: - no temperature peaks - no local CO on the clinker bed Longer flame increase the back end temperature resulting in Heat loss at kiln exit and hot meal clogging
- 102. Burning zone, Flame-profile •Low momentum burner • High momentum burner rings12m (~3xD) burning zone Rotaflam ~16 m Flame !☺! rings ~23 m Flame 17m (~4xD) burning zone ! ! Burner Operation
- 103.
- 104. Satellite cooler rotary cooler gratecooler Recuperation zone Cooling zone static grate direct aeration chamber aerationchamber aeration Grate cooler With stationary inlet Walking floor pyrofloor Cross bar cooler Im provem ent in technology Rotary disc cooler MMD cross bar IKN Poly track Pyro floor ? Pyro step
- 105. Cooler ( heatrecuperator)
- 106. Heat transfer by radiation andconvectionHeat moves to clinker edge by conduction Air flows over clinker cooling surface How cooling is accomplished 800 O C 100 O C
- 107. • Convection -Surface to Air • Conduction - Inside to Surface • Heat transfer is driven by temperature difference • Takes place at the clinker surface • To maximize it: – Increase the air/material contact time with: • Deeper bed ( ⇒ more power) • Slower air flow (⇒ larger cooler) Heat transfer in clinker
- 108.
- 109. Old conventional grateplates create sand blasting effect or fluidization This creates poor heat exchange Modern cooler plates flow resistance branch off the air , creates less fluidization , better heat exchange Cross flow Counter current Mechanical flow regulator
- 110. Temperature Bedthickness clinker air Fixed bed Fluidized bed Airin Air out Clinker Air in Air out Clinker Temperature Bedthickness clinker air More efficient recovery with fixed bed Air flow requirement Has reduced from 4 kg air/ kg.cl to 2.2 kgair / kg cl Heat exchange between clinker and air
- 111. 1. The hotterthe inlet temperature the hotter the clinker outlet temperature. 2. The hotter the cooling air temperature the hotter the clinker outlet temperature. 3. The longer the air/material contact time the cooler the clinker outlet temperature. General truths ( all coolers) 4. Quicker the clinker cooling ( quenching) the smaller the crystals, results in micro cracks of the minerals, improves the soundness of the clinker ( when MgO % exceeds 1.5 %)
- 112. C4AF C3S C2S Mgo CaO C3A Pictoral representation ofclinker micrograph
- 113. • Microscopic A mixtureof different mineral phases Particle size ≈ 0 – 100 µm • Macroscopic A gray, granulated, rocky material Grain size ≈ 0 – 50 mm What is portland cement clinker
- 114. Uniform nodule Sizes Ratheruniform-sized nodules are ingeneral an advantage regarding burning efforts and uniform degree of burning.
- 115. Quickly cooled clinkersare favourable for the early strength potential; no alite is lost. The fine crystalline liquid phase prevents aluminate from an early hydration. The influence of aluminate on the setting time is limited in quickly cooled clinker.
- 116. Influence of coolingon clinker phases Fast cooling Well distributed small crystals Slow cooling Larger crystals
- 117. C3S Clinker when itis quenched in cooler it creates micro cracks which needs less energy for comminution during grinding. C3S Clinker cooling C2S
- 118. Fuels used incement industry • Solid fuels ( coal , pet coke, lignite, anthracite ) • Liquid fuels ( furnace oil) • Gas fuels ( natural gas) • Alternate fuels ( shredded tyres,waste wood chemical waste, animal meal)
- 119. Solid fuel preparation Fuellumps are crushed to suitable size depending on the grinding system and Hard groove index of fuel. The residue depends on the volatile matter
- 120. Fuel preparation (solid) Fuel properties crushing Design of firingsystem Selection of Grinding system drying storage fineness
- 121. Coal grinding Inert grinding O2% < 12 % ( preheater gases& Hot air generators) Non inert grinding O2 % > 12 % ( cooler air) Coal grinding is designed also on the basis of explosion index ( safety index) , residue , HGI Ball mill circuit Vertical mill circuit Non-inert operation
- 122. mills with inertoperation mills with non inert operation Using cooler gases for drying the coal is non inert operation as it contains > 20 % O2
- 123. The acceptable feedsize is 2 % of the roller diameter Built in separator Grinding table Grinding roller Vertical mill for coal grinding
- 124. For pet coke andanthracite For bituminous coal The residue on 90 microns is 50 % of the volatiles as a thumb rule Residue vs volatiles
- 125. Relationship between coaltypes,composition and grinding fineness Petcoke < 10 < 1.0 4%< + 0.09 mm 0 %< + 0.2 mm Normally the residue on 90 mic is 50 of the % volatiles.
- 126. Cement grinding Clinker +Gpsum + Pozalonic Material ( Fly ash , Slag) OPC , Clinker = 92 – 97 %, Gypsum = 3 – 7 % PPC , Clinker = 60 – 70 %, Gypsum = 3-7 % , Fly ash = 25 -30 % Slag cement, clinker = 50 – 60 %, Gypsum = 3 – 7 % , Slag= 45 – 55 %
- 127. Cement grinding Ball mill Rollerpress Horizontal mill Vertical roller mill
- 128. Roller press •Pressure appliedto material varies from 3,000 a 4,000 kg/cm2. They are over dimensioned in order to operate at lower pressures (2500). •Requires a subsequent de- lump, in order to separate the resulting paste, except in the case the roller press feeds a ball mill. •Pressure application angle should be around 6°. •Press consumes 20 to 25 kWh/ton of cement. •Circulation factors range from 6 to 10. •Requires great maintenance. •Wear out elements expected lifetime: 10,000 hours
- 129. Horizontal roller mill •Rotatesat hypercritical speed (1.2 times critical speed), having no feed. •Pressure on material ranging from 700 to 1,000 kg/cm2. •Pressure application angle: 15 to 20°. •Circulation factors: 3 a 8. •Requires great maintenance. •Consumes 25 to 30 kWh/ton of cement. •Expected lifetime: 10,000 hrs. Roller and ball mills hybrid. Being the most recent one, its utilization is not widespread.
- 130. Tubular mill (ballmill) •Rotates at 0.7-0.8 of critical speed. •Lacks pressure system. •Lacks application angles. •Consume 35 to 40 kWh/ton. •Circulation factors: 1 to 3. •Requires little maintenance. •Expected lifetime measured in years. It is the most widely used for cement milling. Its drying capacity is proportional to D2, so in cement the L/D proportion is 3. In raw meal milling L/D is 1.5, if humidity is not greater than 3%, a single chamber mill is recommended. In case the material has humidity greater than 7%, it is necessary to incorporate a flash dryer or change to a vertical mill. The % of material in suspension will determine which type of mill should be used.
- 131. Cement mill cooling Thesetting properties depend the water molecules of Gypsum CaSO4.2H2O If water is dehydrated ( at 125 deg C) it results in false set If it is partially dehydrated, CaSO4.1/2 H2O, called Hemihydate it contributes to initial strength. Hence cement temperature is to be maitained > 100 deg c and < 125 deg C
- 132. Ettringite 3 CaO.Al2O3 +3 CaSO4 +26 H2O 3 CaO .Al2O3.3 CaSO4.32H2O
- 133. Vertical mill (rollermill) •Pressure on material:300 to 500 kg/cm2. •Application angle: 12°. The width of the material layer is proportional to this angle and to the rollers diameter. •Consumes 25 to 35 kWh/ton of cement. •Circulation factors: 3 to 5. •Requires great maintenance. •Wear out elements expected lifetime: 15,000 hrs. •Recommended in cases where humidity is greater than 7%, taking into consideration that abrasive content must remain low. This is why it is commonly used in raw meal milling. It works better than a ball mill on plastic materials (clay).
- 134.
- 135. Dust collecting equipments ESP Electrostatic precipitators Bag filters scrubbers cyclone
- 136.
- 137. Operational Resistivity in aCement Plant
- 138. Applying ESP Technologyin a Cement Plant • Control Critical – Collection Efficiency Effected by • Dust Characteristics – Particle size ( migration velocity) – Resistivity – Composition – Stickiness • Gas Conditions – Humidity – Temperature – Composition – Flow rate – Upstream Gas Conditioning Sensitive (i.e. cooling tower) – Most Importantly Upstream Process Equipment Sensitive
- 139. Dust resistivity characteristicsas a function of moisture content Micromist Water spray
- 140. Principles of thefunction of ESP Collecting plate Charged dust particles Dust removal Dust layer Gas molecules and ions Corona generation Discharge electrodes H2O SO2 O2 N2 Gas flow T/R set
- 141. Gravitational force Air drag Migrationvelocity corona Negative electrode Positive electrodeForces acting on dust particle Positive electrode
- 142. Migration velocity andcollection efficiency η ω = q Ep ( 4 π µ r) = 1 – exp ( - W.A / Q) ω = migration velocity Ep = strength of field in which particles are collected , volts/ meter µ = Viscosity of gas Pa-s r = radius of the particle- µ m η = fractional collectional efficiency A = collection surface of the particles Q = gas volumetric flow rate W = drift velocity
- 143. PulseClean Gas/dust distribution Clean gasoutlet Raw gas with dust inlet Dust drop out Collected dust Dust up flow between bags Cake formation
- 144.
- 148. No dampers: Only possibleto do on-line cleaning. Maintenance: On-line not possible. Example A One dirty gas chamber. One clean gas chamber. With inlet and outlet dampers: Possible to do on and of-line cleaning. Maintenance: On-line possible when separate hoppers Multiple dirty gas chambers. Multiple clean gas chambers. Example B Fabric Filter Optional Arrangements
- 149.
- 150. Cement quality tests •Compressive strength (mortar) • Modulus of rupture ( bending strength) • Fineness( blaine or Particle size distribution) • Expansion ( Le Chatelier & Auto clave) ( soundness) • Setting time
- 151. Influencing parameters on Cementstrength
- 152. 1 3 728 90 days Strength MPa C3S C2S C3A C4AF 60 0 20 30 40 50
- 153. = f (C3S) 28 7 3 1 MPa70 60 50 40 30 20 10 40 45 50 55 60 65 % C3S
- 154. = f (Wk) 28 7 3 1 0 MPa70 60 50 40 30 20 10 0 0.5 1.0 % Wk A 1% increase in LOI result in decrease in strength 1 day by 25 % 2 8days by 3 % and 90 days by 2 %
- 155. Compressive strength –influencing parameters Compressive strength 1 d 3 d 7 d 28 d Influencing Normal range 5 – 15 20 – 35 30 - 45 45 - 60 Parameters OPC C3S 45 – 65 % + + + + C3A 6 – 12 % + + + + Ks 0.2 – 1.5 % + + +/0/- - SO3 2 – 4 % +/0/- +/0/- +/0/- +/0/- Blaine 280 – 300 + + + + m2/kg Wk 0 - 0.3% - - - -
- 156. Quantitative rules ofthumb C3S : 1 – 28 d : + 0.5 Mpa / % Ks ; 1 d : + 4 Mpa / % : 3 d : + 4 Mpa / % : 7 d : - 2 Mpa / % : 28 d : - 10 Mpa / % (SO3) tot : 1 - 28 d : - 5 Mpa / % from optimum Blaine : 1 d : + 0.04 Mpa / (m2/ kg) 3- 28 d : + 0.08 Mpa / (m2/ kg)
- 157. One day strengthis contributed mainly by C3A , Soluble alkalies, and C3S 3 day is contributed mainly by C3S 7 days strength is contributed by mainly C3S 28 days strength is mainly contributed by C2S Apart from the above cement strength is enhanced by higher fineness of cement Less C3S crystal size achieved by rapid burning and quenching the clinker in cooler Higher fineness of rawmeal also reduces the crystal size of clinker minerals , ie ., C3S & C2S which enhances the hydraulic reactivity Cement strength – influencing parameters
- 158. Wk , prehydrationof clinker Prehydration of clinker minerals can occur 1. As a result of incorrect internal water cooling in cement mill 2. when storing too hot cement in a silo 3. When clinker and especially cement is exposed to humidity Please note: If clinker has more soluble alkalis and sulfates it is highly hygroscopic especially when pet coke is fired. In cement silos they form Syngenite , K2SO4.2 CaSO4. H2O which forms lumps and block the cement silos. Hence venting is must to evacuate moisture and silo cleaning. cements having soluble alkalis and sulfates preferably packed in paper bags to avoid depletion of strength.
- 159. Thumb rule formulaefor prediction of strength FLS predicted the formula for cement ground to 300 kgs/ m2 With 4 % gypsum strength, d28 = 52 - 10.( Ks) + 0.15.(C3S) The content of soluble alkalis Ks is dependent on the total alkali content and SO3 content in clinker. As per Knofel it is F 28 = (3*C3S)+ (2*C2S) + C3A – C4AF N / mm2 Strength prediction for 3 d = 97 + 35.8 Ma + 38.1K2SO4 + 28.7 Ms – 1.3 C3S Kg/ cm2 7 d = 300 + 13.4 Ms + 2.8 C2S + 56.1 Ma – 15.4 K2SO4 + 15.5 Na2O 28 d = 490 – 55.3 K2SO4 + 1.3 C3S (or) = 490 – 86 K2O + 2 C3S – 26 Na2O
- 160. Influence of finenesson cement strength For cements with the same specific surface the increase of the uniformity factor results in increase of strength of all ages. 1. The specific surface , the percentage of fractions 3- 32 mm and the uniformity factor n really influences the development of cement strength. The influence of 3 - 32 mm fraction and the uniformity factor is higher in cement with higher in specific surface ( > 3400 cm2/ g) 2. The fractions with particle size less than 3 mm contributes only to early strength while the fraction with particle size more than 24 mm influences strength development significantly. 3. While the fractions 3 – 16 mm and 16 – 32 mm seems to be more significant factor for specific surface 3500 – 4000 cm2/ g) . This is relevant only if the granulometric distribution is continuous and steep. 4. The optimistic granulometric distribution of a cement is a continuous and steep ( with high uniformity factor) distribution with a high (65 %) content in 3 – 32 mm fraction and specifically in 16 - 24 mm fraction and low content of fine particles ( < 3 mm , 10 % ) and specific surface of 2500 – 3000 cm2/ g according to Blaine.( high efficiency separator and grinding media distribution plays significantly here)
- 161. Properties of cementminerals Characteristics C3S C2S C3A C4AF Setting quick slow rapid nil Hydration rapid slow rapid nil 3 days heat 1.1 cal / g 0.4 cal / g 2 cal / g nil liberation Early strength high upto low upto not much nil Contribution 14 days 14 days beyond one day Late strength less later high later nil nil contribution Resistance to moderate high poor high Chemical attack Drying shrinkage nil low nil nil
- 162. Problems and solutions 1.Grinding problems a) False set lower cement mill temperature add less gypsum add part anhydrite b) reduced strength high mill temperature less water cooling correct water cooling 2. Silo storage a) False set short storage time cooling of cement < 70 deg c b) reduced strength increase gypsum dehydration in mill c) lump formation and add less gypsum, use partly silo blockage (syngenite anhydrate , decrease K2O content formation, K2SO4.2CaSO4.H2O to avoid the formation of Syngenite Problems solutions
- 163. 3 ) Bagstorage a. reduced strength short storage time b. lump formation add TEA during grinding (tri ethanal amine) add hydrophobic agents c. crust formation plastic coated bags d. abnormal setting plastic covering pallets
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- 167. Customer is theking. He is a better business man than you. Tomorrow’s market is competitive with quality/ price ratio. Customer creates the customers. Bon’t brand the quality alone , brand your service too.
- 168. Hope you hada fruitful training
- 169. Wish you allthe best – Pradeep kumar
- 170. Thank you foryour kind attention