Very important Notes for Purchasing Managers in cement Factory

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Very important Notes for Purchasing Managers in cement Factory

these Notes , I collected them and I wrote them in 320 page manual in around 11 years working as purchasing Officer in 3 different cement plants.

if you need any advise about purchasing any part or system in Cement plant please email me and I will help you for Fees less than 150 USD email : Purchasing@cementequipment.org

 

1 Purchasing in the Raw Milling section 

2 Purchasing in the Preheater section 

3 Purchasing in the kiln section 

4 Purchasing in the cooler section 

5 Purchasing in the kiln &cooler Filters section 

6 Purchasing in the kiln BYPASS section 

7 Purchasing in the Gas analyzing

8 Purchasing in the kiln coal mill section 

9 Purchasing in the cement grinding section 

 

10 Purchasing in the Weighing Dosing

these Notes , I collected them and I wrote them in 320 page manual in around 11 years working as purchasing Officer in 3 different cement plants.

if you need any advise about purchasing any part or system in Cement plant please email me and I will help you for Fees less than 150 USD email : Purchasing@cementequipment.org

Raw milling Best Practice / Recommendation Specifications Alternatives Operating target Not advisable Comments
CHOICE OF MILL SYSTEM Vertical Mill with cyclone and fan with VFD Vertical Mill with cyclone and fan with VFD 2 compartments closed circuit tube mills with drying chambers (if moisture < 7-8%) or
Tube mills in combination with heated hammer crushers.
High efficiency separator or
Roller Press with Ball Mill
Tube mills without drying chamber, or without external drying.
Autogenous Mills (only in case of specific applications).
Roll Press in circuit with V or VSK separator and/or dynamic separator.
Pregrinding circuit with two- compartments ball mill.
Air Swept mill Central discharge mill
Modification of existing grinding shop Closed circuit mill
High efficiency separator
Closed circuit mill
High efficiency separator
Roll Press in circuit with V or VSK separator and/or dynamic separator.
Pregrinding with two- compartments ball mill circuit. Modification of 1st generation separator
Addition of external drying drum
New Equipment Ball Mill with drying chamber
Mill Circuit Closed circuit Partial feed to the separator Open circuit
Ball mill speed 75% critical speed 75 % critical speed <73% or >78% critical speed
Ventilation ball mill Air velocity above ball charge=1,5 to 2,2 m/s
inside the trunion: 22-25 m/s inside partition:8-14 m/s
0,6 – 0,8 Nm3/kg raw mix hood < 5m/s
drop out box < 2m/s VFD fan
Air velocity above ball charge=1,5 to 2,2 m/s
VFD fan
Mill L/D ratio 1,5 < L/D < 3,2
First compartment length = 35 45% of mill total length
Raw milling Best Practice / Recommendation Specifications Alternatives Operating target Not advisable Comments
Ball mill Liners Moderate lifting liners for first compartment, classifying liners for second compartment Classifying liners in second compartment Duo lift Ripple liners Without classifying liners keep a maximum of 3 – 4 ball sizes
Intermediate Partition wall Central opening adapted to the filling degree. Slots placed concentricly. – 8 to 12 mm slot for central partition.
– open area > 50 % by central opening
Diaphragms with material flow control Slots placed radially.
Outlet partition wall Central opening adapted to the filling degree. Slots placed concentricly. Partition wall slot size + 2mm  (max slot = 0,5 min ball size) Slots placed radially.
Ball charge Volume Loading:
– for minimum kWh/t: 26-28% in C1 and 28-30% in C2
– for max output: 32-34% in C1 and 34-36% in C2
Separator Third Generation High Efficiency Dust load < 1kg/m3 Qf/Qa < 2.5 1st or 2nd generation separators
Control Fresh feed control to assure constant feed to the separator. Mill controled by LUCIE. Weighing rejects (belt weigher), measuring elevator power, mill presure loss, mill outlet temperature and electronic ear. Control mill fresh feed using only one parameter (only rejects flowrate or only elevator power , for example) Fresh feed control can be done by different ways, using different instruments or signals (rejects flowrate, elevator power, eletr. Ear, mill kW). It is recommended to use them in conjunction.
Feed Feed size 95%< 50 mm d80 feed < 20mm, Precrushing, screening, external drying The finer, the better
Drying compartment Moisture inlet C1 < 1.5% Specific drying capacity
<300kg/m3
Raw milling Best Practice / Recommendation Specifications Alternatives Operating target Not advisable Comments
Equipment VRM
Vertical Roller Mill Recirculation of gas to the mill. Metal detector and extractor in the feeding line (after reject’s return)
Gas flow measurement after cyclone or filter
Water injection system Central mill feed.
HE Separator
Material External Recirculation System >30% Fresh Feed Capacity                            Fan
with VFD
Bed depth sensor
Metal detector and extractor in the feeding line (after reject’s return)
Bed depth sensor
Water injection max 25 kg/t Material External Recirculation System >30% Fresh Feed Capacity
Fan with VFD
Water injection facilities in the mill housing Gas speeds:
Nozzle ring >30 m/s Mill Body: 5 – 7 m/s
Separator: 3 – 5 m/s
Dust Load:   600 g/m3 at mill outlet
Feed device with triple flap gate or rotary air lock valve, heated if wet or sticky raw materials.
Fan max speed typical 700 rpm and >80% efficiency
Control Constant mill exit T° Constant mill gas flow Mill feed a to mill deltaP
Preheater Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Cyclones 5 Stage Preheater – low moisture < 5% raw materials Low pressure drop
Bottom of cyclone
> 50° height
No horizonatal inlet ; no horizontal surface 4 Stage Preheater – high moisture >5% raw materials For a 5 stage PH, 4.5 to 5.5 kPa (including kiln) See priority study Preheater
Dip Tube Length relative to cyclone inlet height Top (stage 1): 100% Stage 2/3: 75%min Stage 4/5 : 50%min Top (stage 1): 100% Hurrivanes – depending on geometry Number in % of inlet height
Splash box Lafarge design cleaning devices. At least 55° to 80° between meal pipe and
splash box
2 m   from flap, pipe without elbow
60° for kiln feed to splash box.
>60o below C3 Splash plates See priority study Preheater
Pendulum flap External knife bearing
Precalciner Vessel + Hot core preferred Residence time > 6 sec for petcoke, Low-Nox Residence time > 6 sec Riser Duct plus hot core Very specific to fuel and plant conditions
Tertiary air duct Downward split design for in-line calciner Damper control
Duct velocity 20 to 30 m/s
Process
Gas duct velocity at meal entrance Mini 12 m/s top stage  with 17 m/s bottom (intermediate proportional)
Can install restriction as alternative
Riser velocity 16 m/s minimum
Preheater Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Cyclones Top cyclone efficiency > 95% Top cyclone efficiency > 95%
Meal curtain Considered if high volatile cycles expected
Most common on N-1 stage on kiln side
Lateral Consider a splitter
Kiln inlet box No dead zone
Smooth design (entrance in the middle)
No turbulances 45°- 50° slope of inlet
Downcomer Cooling by water sprays Minimum evaporation: 4 sec (for target at 185°C)
No bleed air is recommended, except for start up
Water design target able to provide 185 °C. Take care about moisture in gas to coal mill take off above water injection
ID fan preheater VFD drive
Fresh air intake before the fan (fan protection)
Fan Typical Max speed 990 rpm and efficiency >80%. Design margin 5% volume and 1 kPa pressure
number of fans 3
ID fan, raw mill fan & baghouse fan
Only 2 fans
Secondary Fuel
usage
Burner preferred for Calciner
Kiln Best Practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Burner type and position Lafarge Burner MAS burner in case of regular solid fuel and alternative fuel ; Position in center line of kiln and aligned on kiln axis (only if kiln is stable and burner having sufficient impulse) See Lafarge Burner Design Spreadsheet
Fuel speed Solid Fuel: 25 – 35 m/s in burner ; >25m/s in conveying line Solid Fuel: 25 – 35 m/s in burner ; >25m/s in conveying line Alternative Fuel: 25 – 40 m/s in burner ; >25m/s in conveying line
Total primary air <12% with coal / petcoke < 15% primary air (as low as
possible when firing alternative fuels)
Liquid (main fuel) > 25 cSt
Swirl Design:   0,15
Impulse Design: >2,2 Final design criteria to be
worked out.
Retaining rings 0,6 to 1 m from nosering as single ring, triangulkar shape Double flat bar Maggoteaux system
Kiln slope 3 – 3,5 % 4%
L/D >10,5 for preca (> 15 is required when designing for alternaitve fuels)
> 15 for preheater
Tertiary air From kiln hood
Take off velocity 5-6 m/s throat and tertiary air and 25 m/s in the duct
From kiln hood
Take off velocity 5-6 m/s throat and tertiary air and 25 m/s in the duct
Settling chamber Heat shield IKN not proven
Shell cooling fans 12 to 18 m/s at shell Supplied Fan should be below kiln so that air flow comes up on both sides.
Kiln Best Practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Process
Thermal load < 5 MW/m²   (kiln cross section) < 5 MW/m² < 6.5 MW/m² Limit for refractory.
Some wet and big kilns can overpass the limit
Kiln hood velocity <   6 m/s
Kiln load <4,5 t/d/m³
Production 24 m/s hearth velocity pc kiln <28 m/s
Clinker bypass With > 0,025% of Cl input (related to clinker) consider a bypass
Clinker storage For off specification clinker, 8 hour separate storage considered
Cooler Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Equipment Selection Cross Bar or Walking Floor
Design
Cross Bar or Walking Floor
Design
Grate load < 45 t/m² d < 45 t/m² d
Variable speed fans All on 1st grate Variable speed on all on 1st grate fans.   2nd grate fans can be with variable inlet vanes
dampers
Fan dampers (inlet radial) Flap max speed typical 1500 rpm, Efficiency > 80%. Normally 20-
30% pressure reserve.
Fix inlet rows 5 to 8 (1.5 – 2.5 m)
Max 15 degree angle Refractory Horseshoe Air Cannons
Crusher Roller crusher intermediate or at the end Hammer Crusher Hammer crusher can be the first choice if no need for very effective cooling
Grate slope 3° maximum
Evacuation hoppers Simple gate and sensor level Double gate mechanically activated
Process
Air flow design Not < 2,1 Nm3/kg > 2.1 Nm³/kg ck
> 1.7 Nm³/m²/s on first fans, 2 Nm³/m²/s for KIDS
First fans pressure > 10 kPa (100 mbar) for KIDS
Optimal bed depth Lowest stroke permitted with 20% reserve on fans
(6-8 st/min for properly designed cooler)
Air velocity above clinker 5 to 7 m/s
Clinker transport design Min. 1,5 x nominal capacity steel conveyor Min. 1,5 x nominal capacity steel conveyor
Process guidelines – Cooler  – Page 1 / 1                                                                                                                                                  06/10/2005 – 10:59
Kiln filter Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Equipment Selection Low Pressure Pulse Jet Bag Filter ( 2,5 bars) Low Pressure Pulse Jet (LPPJ) Bag Filter ( 2,5 bars) High Pressure Pulse Jet (HPPJ) Bag Filter (6bar/100psi), Electrostatic precipitator Max dP< allowed by fan capacity at end of bag life. Limit cleaning cycles to obtain target bag life. Off line cleaning is not acceptable due to the potential damage to the bags. BH sizing must maintain operating pressure drop within the limits of the ID fan and the pulse jet filter ability to clean bag on line.
Equipment Sizing Gross Air to clothe ratio: 1m/min average
1.3 m/min max (upset cond)
Gross Air to clothe ratio: 1m/min average
1.3 m/min max (upset cond)
Bag quality Fabric with PTFE membrane and fiberglass structure.
Known suppliers: Gore, BHA, Tetratec                           working at 180°C- 230°C max
Design temperature 230°C Peak temperature 260°C P84 bags of suitable construction. Adequate temperature control to prevent teflon and SGT evaporation and bag damage. working at 180°C- 230°C max Other bag materials that  are not proven.
If using P84 verify the risk of hydrolysis.
Bag quality and workmanship are critical. Bag to cage fit is critical.
Airflow Distribution Scale model to ensure good airflow distribution and correct fan sizing before purchase
Compressed Air Supply Air coolers can be acceptable for LPPJ. Use air dryers (dessicant) for HPPJ (-30deg C due point). Prevent moisture condensation in the bag during the compressed air pulse. No oil in cleaning air.
Exhaust Fan VFD VFD Fan Typical Max speed 990 rpm and efficiency >80%. Design margin 15% volume
False Air Direct < 30% Preheater Gases Compound < 50% Preheater Gases
Kiln filter Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
COOLER FILTER
Equipment Selection Air to air heat exchanger to get 130°C at exit Air to air heat exchanger to get 130°C at exit Common baghouse for RM/kiln and cooler
ESP when all cooler gas used for raw materials drying
Exhaust system capacity to handle normal operation and to provide sufficient capacity for push conditions for the full length of the bag life. Gas flow in BH hopper must not cause abrasion of filter bags due ro high velocities.
Exhaust gas flow from the cooler straight entry and oriented downwards through heat exchanger Gas velocity at heat exchanger’s  inlet in normal conditions: <10 m/s Water injection in the exhaust pipe
Cooling fan are VFD speed
Exhaust Fan VFD VFD Fan Typical Max speed 990 rpm and efficiency >80%. Design Margin 15% volume
System Sizing Design upset conditions 450 C exhaust gas temp.           Design flow 1.7 nm3/kg clinker Design upset conditions 450 C exhaust gas temp.           Design flow 1.7 nm3/kg clinker
Kiln By-pass system Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Dedusting Bag filters (240°C) ESP Wet scrubber may be a solution when cement Cl is a
limitation
Dust transport As short as possible Mechanical Air transport if Cl < 10%
Storage As small as possible, with mechanical extraction Direct dust addition to cooler filter or heat exchanger intermediate storage Addition to cooler only if clinker storage does not promote segregation (quality –
dust separation in pile)
Process
Location take-off On top of the smoke box, on the kiln side
Distant from C3 discharge to avoid dust mixing
Level of chlorine in dust Dilution with kiln feed if > 10% Cl Cl control using cyclone system with bypass (Taiheyo)
Quenching Air quenching as close as possible to the take out, either directly to 200°C or at least to 400°C Air to air cooler as second cooling step to minimize the gas quantity
Exhaust air To cooler fans to avoid SO2/Dioxins Raw mill or main stack if SO2 is acceptable, dioxins still a threat. Detached plume also a potential issue if organics in raw mix Separate stack
Dust management Cement (limiting factor forCl as allowed by local standard) Clinker (limiting factor for Cl) Dust Washing with heavy metal recovery, for low limit of Cl in cement Dust wasting
Target level of chlorine in kiln back-end mat 1,00% Higher concentration acceptable if possible for build- ups
Process guidelines – Kiln By-pass system – Page 1 / 1                                                                                                                                                     06/10/2005 – 10:59
Gas analyser Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Kiln inlet
Kiln inlet
Probe Probe long enough to enter the kiln,  retractable, motorised
Dry probe required Water cooled jacket Same probe for all gases
Back flush (clean, dry air)
Oil cooled In-situ
CO Mandatory Type: IR
Scale: 0-20000 ppm
NOx Mandatory Type IR
No NO2 converter needed
Scale: 0-20000 ppm
O2 Mandatory Type: Paramagnetic
0-10%
SO2 Required if Total SO3 input >
1.2% on clinker basis or S/A ratio > 1.2
Type UV
Quartz cells 0-20000ppm
IR (on separated line)
Gas treatment Heated line (>180°C)
2 cooler dryer 1 for SO2 and 1 for other gases
For other gases H2O2 injection
Suspension preheater kiln – no PC
Exit of preheater tower Mandatory   for O2 and CO
Exit of Precalciner
Precalciner
Probe Probe at Bottom cyclone exit retractable,
Dry probe required Water cooled jacket Same probe for all gases
Back flush (clean, dry air)
Gas analyser Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
CO Mandatory Type: IR
Scale: 0-20000 ppm
NOx Mandatory Type IR
No NO2 converter needed Scale: 0-20000 ppm
O2 Mandatory Type: Paramagnetic
0-10%
Gas treatment Heated line (>180°C)
2 cooler dryer 1 for SO2 and 1 for other gases
For other gases H2O2 injection 3 other in line O2 last
CEM (stack)
Location Follow local regulation
Dust Scattered light system
O2 In-situ system (Zircon)
0-10%
H2O Optical in-situ system IR
0-10%
CO Optical in-situ system IR
0-2000 mg/Nm3
Extractive with heated probe
and line (>180°C) + FTIR
NOx SO2
HCl
COV
Optical in-situ system-UV
0-2000 mg/Nm3
Extractive with heated probe
and line (>180°C) + FTIR
Optical in-situ system-UV
0-500 mg/Nm3
Extractive with heated probe
and line (>180°C) + FTIR
Optical in-situ system-IR
0-100mg/Nm3
Extractive with heated probe
and line (>180°C) + FTIR
Extractive FID
0-200mg/Nm3
CO Protection with ESP
Precalciner Kiln Use precalciner exit CO with preheater exit CO as back up
Suspension  preheater kiln Use kiln exit CO with preheater exit CO as back up
Coal Mill Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Equipment Selection Vertical mill Vertical mill Ball mill ,
Ring roller mills Pendulum mills
Central discharge mills “deep bowl” mills Ball mills are better suited for very hard fuels and certain cokes.   Also need to consider turndown ratios if AF is significant – need VFD or something appropriate.
Process Gas Hot gas from pre heater with de dusting Hot gas from pre heater with de dusting Direct or semi direct firing
Sensors CO analysers:
– Raw Coal Bin
– Mill Filter Exit
– Each Pulverised Fuel Bin
O2 analysers:
– Preheater Exit
– Before Mill
– Mill Filter Exit
Temperature sensors
–   Raw coal hopper/silo
– Before mill
– After mill
– Hot gas duct
– Filter bottom
– Coal dust after filter
– PF silo bottom ( In banks of four around cone)
– Differential temperature across filter
Differential temperature across separator for ball mill
Load Cells
– Raw Coal Bin
– Pulverised Coal Bins
Pressure indication
– Before mill
– After mill
– Mill differential pressure
– Filter differential pressure
Dust monitor
– Coal bag filter main stack
Coal Mill Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Fire suppression system Bulk system C02 2Kg/m3 of volume of the system coal mill, filter, silos and ducts and enough for 2 complete discharges (X3 for remote locations) Bottle CO2 systems can be considered if local conditions or regulations do not allow bulk or if delivery time is excessive.
Safety for mill   and feeding system See Safety Equipment in Model Plant See Safety Equipment in Model Plant Study fuel – need to have temperature limit at mill inlet and mill outlet appropriate for fuel.   Favor high gas volume so it can be run cooler.   High volatile O2<12%.   Moderate volatile 21% O2 is OK if temperature < 70C
Pet coke grinding Install a dynamic 3rd generation   separator According to Combustion BP the fineness should be less   0.1
% rejects on 200µ
Open circuit See Combustion manual for fineness vs. volatile
Cement Grinding Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Equipment
Equipment Selection Vertical Mill Vertical Mill Roller Press
Pregrinding circuit with two- compartment ball mill circuit.CKP with 2 compartment mill,
Ball mill
Ring roller mills, central discharge mills
Ball Mill Circuit Closed circuit mill with separate filter for mill ventilation and separator
Ball mill Single compartment with lifting and classifying liners* 2,8 < L / D <3,2
* 27% <Length first Compartment< 35% mill effective length.
1st comp: 8 – 10 kWh/t
Ball mill speed 75% of the critical speed 75% of the critical speed <73% Critical speed >78%
Separator 3rd generation high efficiency separators,
de dusting by filters
Basket variable tip speed 10 to 30 m/s,
radial process air velocity    3 to 5 m/s,
Static separator for pregrinding circuits,
fines to separator
1st generation separators, De dusting by cyclones
By-pass 5 to 10 %
Imperfection < 0.30
Acuity <= 15 µm Rosin Rammler specification value  to be provided
Ventilation ball mill Air velocity above ball charge:1.4 – 2.2 m/s
Inside the trunion: < 22m/s Inside partition:<12m/s VFD fan
>1.5% moisture at mill inlet(Pozzolanic materials should be dried before feeding) Static separators for separation of mill dust to final product for open circuit mills and mills with old dynamic separators
Cement Grinding Best practice /
Recommendation
Specifications Alternatives Operating target Not advisable Comments
Ventilation separator Separator Qf/Qa:1.8 kg/m³, VFD fan for HES,
The circulating load 200%
Separator Qf/Qa:1.8 kg/m³, VFD fan for HES,
The circulating load 200%
Separator Qf/Qa range:     1.8-
2.5 kg/m3(200% C.L), Cement temp 90-110 deg ,
VFD for fan
Final product load<0,8 kg/m3
Ball mill internals Reverse step liners for first compartment, classifying liners for second compartment Reverse step liners in first compartment with lifting ht range: 70-75mm. Classifying liners in second compartment Duo lift Ripple liners
Intermediate Partition wall central opening adapted to the filling degree
*Material transport capacity 500t/m2/h
* 6 to 8 mm slot
* Central screen open area 60
%  minimum
*Provision of Flow control gates to regulate material flow
Single plate,                         slots on reverse side of diaphragm liners
Outlet partition wall central opening adapted to the filling degree
*Material transport capacity 500t/m2/h
Intermediate partition wall slot size+2mm,
Ball charge Nominal ball charge loading 28-30% for both compartments,
(installed power on 32%  filling)
>32% ball charge Higher filling causes higher specific energy, problems for cooling. Ball charge with pregrinder needs to be modified
Process
Control Pre requisites for Lucie – Fresh feed variation through weighing of separator rejects, feed accuracy with in +/- 1%, electronic ear to detect filling of first compartment. Belt weigher for rejects Elevator power
Feed Feed size passing on 100% <30mm,
95% < 25mm
Precrushing, drying of wet additives
Temperature control Cement temp range: 90-110 deg C Cement cooler Water injection from partition wall if required
Weighing Dosing Best Practice / Recommendation Specifications Alternatives Operating target Not advisable Comments
Pulverised Coal
Equipment Selection Small bins close to the burning point <50 m
on cells for calibration Schenck Coriolis,
Variation < 0,5 % (short term)
Small bins close to the burning point <50 m
on cells for calibration Schenck Coriolis,
Variation < 0,5 % (short term)
Pfister New systems of Pfister and Coriolis > 50 m Old Pfister > 40 m.   Actual limit is back pressure.   Long distance means more backpressure but can be compensated for by proper design.   Schenk Star feeder with high pressure transport line not recommended (low tolerance).
Schenk Coriolis + Bremer Screw + FK pump for long distance is very good.
Velocity Minimum number of elbows velocity >= 25 m/s Minimum number of elbows velocity >= 25 m/s
Solid concentration 4-6 kg/nm3 4-6 kg/nm3 > 7 kg/nm3
Raw meal
Equipment Schenk Coriolis Pfister Weigh Feeder Both still recommend level bin ahead of scale to minimize silo flushes. Using airlift pressure to calculate flow can be sufficiently accurate.
Effective weighing Variation < 0,5 % (short term) Variation < 0,5 % (short term) Accuracy < 0,5 % (short term)
Transport Elevator Elevator Air-lift

 

 

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