Training material cement process (NXPowerLite)

ISO Team Training CEMENT PROCESS Hon Chong flow chart Raw material preparation Raw meal preparation Clinker producing Cement grinding Coprocessing Coprocessing at HN Plant Rice husk Rubber wastes Liquid wastes Hazardous wastes

ISO Team Training

04-Sept-2007

CEMENT PROCESS

1 Hon Chong flow chart

2 Raw material preparation

3 Raw meal preparation

4 Clinker producing

5 Cement grinding

6 Co-processing

CONTENT

Hon Chong Flow chart

Cement Production Diagram

Production of Cement by the Dry Process

Raw Materials Storage and Preblending Corrective Materials Crushing Plant (s)

Quarry

Feed Bins Sampling Station

Coal

Coal Mill Cooler Dedusting

Rotary Kiln

Cyclone Preheater

Raw Meal

Homogenizing and Storage Silo

W ater

Conditioning Tower

Electrostatic Precipitator

Silo

Mineral Components Clinker Cooler

Air-to-Air Cooler

Cement Production Process _ Steps

 Mining of limestone

 drilling or blasting

 crushing of limestone

 pre homogenization

 grinding of raw material

 homogenization of raw meal

 coal grinding, co-processing

 cement grinding

 cement storage, packing, and dispatching

Raw material extraction

Raw material preparation

Raw meal preparation

Clinker production

Raw Material Preparation-Crusher

CRUSHER Type: Impact crusher

Size reduction: 1.2 m to 0.1/ 0.05m

Using impact forces do the size reduction

of raw materials from the quarry

It is easier to transport smaller material, and spread it along the pre-blending stockpile.

Raw Material Preparation-General

Reduction ratios:

3:1 to 7:1 by compression

To 50:1 by impact and combination of 2-3 stages

The type of crushers depends on:

The work index of the material Abrasiveness

Stickiness Throughput, tons per hour etc.

Size of feed Power consumption Reduction Ratios needed

RMP_ Crusher type application

The pre-blending efficiency is a function

of the number of layers: the higher the number of layers the better the pre- blending effect.

Pre-blending will be sufficient with material reclaim in thin slices from the front

Pre-blending will be insufficient when material is reclaimed in lateral slices

RMP_ Pre-blending

 Mixing LS and Clay/sand for reducing impact

of sticky clay

 Sand is silica corrective material

 Mixing process controlled by PGNAA, and weighing system of sand, clay, and limestone

 Process control parameters are ratio of clay to limestone, percentage of sand, stockpile volume

 Quality control parameters: LSF and SR of stockpiles

 Other quality factors for controlling: MgO,

RMP_ key concerns

 Wet and sticky materials in raining season

 PGNAA operation and maintenance

 Quarry master and mixing muck-piles at quarry

 Accuracy of weigh feeders

 Limestone size control for OPC LS mixing in cement

 Cement quality impact of MgO, P205

 Kiln process impact of SO3

Raw Meal Preparation- Function

Purposes of raw grinding systems

 Producing a raw meal fineness (particle size and distribution) adequate for

the production of the required clinker quality

 Provide the proper proportioning of the components in the correct ratios

Raw Meal Preparation- Fineness

Factors affect fineness

 Feed material grindability

Raw Meal Preparation- VRM and grinding process

Raw Meal Preparation- VRM and grinding process

Drying

 Drying heat source: the hot gas from the kiln or hot gas generator

 Fine material is lifted up, exposed to and flash-dried by the hot gas

stream

 The drying process occurs mainly in a short distance from the

nozzle ring area to raw mill outlet

Drying is necessary to guarantee proper:

Raw Meal Preparation- VRM and grinding process

Grinding

 Feed material consisting of fresh feed plus return from

separator is fed onto the center of the grinding table

 There it is centrifuged and ground by compression of rollers

when passing below the rollers.

Raw Meal Preparation- VRM and grinding process

2.Fine separation

 The rest of the material arrives to the to

the rotor cage separator where fine separation takes place

 The coarse material is returned to the

grinding table through the separator grits cone

 The fine product with the gas/air

Raw Meal Preparation- Quality aspects

Feed material components:

1 LS/Clay provides majority of CaO, SiO2 affect LSF, SR

2 Laterite provides majority of Fe2O3, Al2O3 affect AR

3 High grade limestone provides majority of CaO affect LSF

Quality control factors:

LSF: 99-100, SR: 2.4-2.5, AR: 1.4-1.5

Process control:

% weigh feeder, separator speed, mill outlet temperature

Raw Meal Preparation- Blending Silo

It is the last step in the line of the raw mix preparation processes

with the aim to reduce the residual variations in composition The inverted cone (central cone) features:

 Equipped with a large inverted cone covering most of the center of the

bottom area

 The remaining annulus is divided into sectors that are covered by open air

slides Each sector is equipped with its own outlet

 Raw meal is aerated by air supply to the individual sectors at a low rate

and a low pressure This air leaves the silo together with the activated raw meal.

 Aeration is switched systematically by means of solenoid valves sector by

sector.

 Height / diameter ratio: up to 2.5:1

 Spec power cons system: 0.1-0.2 kWh/t

Clinker Manufacturing- Basis reaction sequence

alite + belite

+ melt (1450°C)

reactants + products

+ intermediate products

(450 - 1300°C)

Raw mixture

(20°C)

cooled clinker

Sequence of Reactions Occurring in a Rotary Kiln

Heating (°C)

20 - 100 Evaporation of H2O

100 - 300 Loss of physically adsorbed water

400 - 900 Removal of structural H2O (H2O and OH groups)

from clay minerals

>500 Structural changes in silicate minerals

decomposes into free lime

and carbon dioxide.

CaCO3 → CaO + CO2

Basis Reactions-Calcination

While calcination is taking place, the argillaceous components are

breaking down, making Al2O3, Fe2O3 and SiO2 available

Argillaceous Components

At elevated temperatures of the process, lime will react readily with

silica to form C 2 S

belite

Lime & Silica Reaction

At elevated temperatures of the process lime will also react readily with aluminum and Iron to form a number of intermediate products The resulting synthetic minerals

C3A and C4AF are key components not only

in cement but as precursors to the liquid phase of the

sintering process

C 3 A

Lime, Aluminum & Iron

C2S will continue to form as long

as silica can come into contactwith lime

This is an endothermic reaction

Solid reactions are verydependant on particle size For that reason, typical kiln feedfineness is R90 µm = 15 %

C2S formation

Upon completion of C2S formation at approximately 1250 °C, the Calcium salts of Aluminum and Iron reach apoint where they become a LIQUID.

In the heart of the BZ, 20 – 30 %

of the clinker will be a liquid

Liquid Phase

C2S, Free Lime → C3S

In that liquid, the C2S reacts

with the residual lime to form

C3S This is an exothermic

reaction

In the heart of the BZ

20 – 30 % of the clinker will be

45-65%

10-25%

Uncombined lime 0.75-1.5%

Cooling

Once the formation of the C3S

is complete

there is no further value in

prolonging the process at this

elevated temperature

This final process is called

cooling, not just to reduce the

temperature, but to freeze the crystal growth and to convert the liquid phase back to a solid for easier transport

At this point, C3A and C4AF

The objective now

aluminat e

ferrite

What Makes Good Clinker?

Influences of Major and Minor Phases on Cement

Properties

 C3S - early strengths, setting

 C2S - late stage strengths, durability

 C3A - initial set, early heat evolution

 C4AF - color

 CaOfree (free lime) - setting time, early strengths

 alkali / sulfates - early strengths

Free Lime in Clinker

 Uncombined CaO is produced in clinker by:

 excessively high LSF (above 100)

- not possible to combine all CaO that is available

 under-burning

- kiln not hot enough to combine all CaO

 The less likely reasons are decomposition of alite, oversize limestone grains and possible heterogeneous kiln feed

 Favorable range 0.75 - 1.5 %

 < 0.75 % is the result of over-burning

- excessive amount of fuel

Clinker manufacturing process

Preheater cyclones

Design features of preheater

cyclones

 Low pressure drop by using

the new cyclone design

 Good separation efficiency,

particularly in the top and the bottom stage.

 Cyclone inlet velocities are

designed in the range of 10 to

15 m/s

 all stages are equipped with:

Dip Tubes

 About 2/3 of the total heat consumed or about 2000 kJ/kg are required for calcination process

CaCO3 + heat > CaO + CO2

 Heat introduced a part of the fuel, i.e up to 65% into calciner

 The combustion air (tertiary air) is from the cooler

 The rotary kiln operates at significantly lower specific thermal load and gas flow

Rotary Kiln Hon Chong

Rotary Kiln_ Features

 Important mechanical features are:

1 Riding ring fixation

2 Roller station / alignment

3 Seals at inlet and outlet

4 Kiln drive

5 Kiln girth gear

With modern precalciner technology, outputs exceeding 10’000 t/d per kiln are

possible with diameters still below the 6.5 m

 The rotary kiln has to satisfy three types of requirements:

1 Combustion: a combustion chamber for burning fuel.

2 Process: as a reactor for the clinker burning process (retention time) as a

material conveyor (® slope, speed).

3 Mechanical: stability of shape, carrying load, thermal flexibility, tightness

Kiln control parameters and variables

 Control parameters and variables

Kiln control parameters & variables_ Diagram

Kiln operation_ some problems

Clinker Cooler- Main functions

Clinker coolers have predominantly three tasks to fulfil:

1 Recuperate as much heat as possible from the hot clinker by heating up the air used

Clinker Cooler Operation Controls

Grate speed

Clinker bed presented by under grate pressure of the second chamber is controlled by grate speed For example, high under grate pressure indicates high clinker bed, grate speed should be increased to reduce the bed to target hight

Airflow

Each cooling fan is equipped with a piezometer sensor which will recognize an increase or decrease of the airflow and cause the cooling fan damper to close or open or the fan motor speed

to decrease or increase During normal conditions the cooling fans operate at about 2/3

to 3/4 of their capacity.

Hood draft

Clinker Cooler Operation Controls - Diagram

Clinker Cooler Operation- represent problems

Electrostatic precipitator Operating principle:

 Gas velocity is about 1 m/s.

 Normally the spacing of the discharge and collecting electrodes varies between 125 and 200 mm

 The voltage applied is 35 to 110 kV negative DC according to spacing, gas and dust conditions.

 The highest voltage occurs near the discharge electrodes As the voltage is raised, electrical breakdown of the gas close to the electrode surface takes place This breakdown is called "corona ”

 The corona produces large numbers of gas ions, the positive ions move to the discharge electrodes while the negative ions migrate towards the collecting plates.

 Dust particles are charged either by bombardment by the ions moving under the influence of the electrical field, or by ion diffusion, both types of charging taking place simultaneously.

 The particle size determines which type of charging is predominant, ion diffusion being the prevailing

mechanism for particle sizes below 1 micron.

 The negatively charged particles migrate towards the collecting plate to which they adhere while being electrically discharged These particles build up a layer of dust on the plate surface which is then dislodged by rapping

 The dislodged particles fall by gravity to the bottom of the precipitator, into a hopper from where the dust is extracted by either mechanical conveyor (drag chain or screw conveyor) or pneumatic type system.

Dedusting – EP Operating Principle

thu

Dedusting – Dust resistance

Dust resistance in function of gas temperature and dust sources

Dedusting- Bag House

Dedusting- Bag House purging system

Cleaning systems / pulse jet cleaning

Cleaning the bags involves three stages:

1 The normal filtration gas flow is interrupted by a

barrier to allow purging air to flow in the opposite

direction.

2 The purging air injected into the bag expands it to

its original circular section and removes the dust

cake which falls down into the dust bunker.

3 The purging air then flows outward through the

filter medium in the direction opposite to that of

the raw gas flow.

Cement Grinding

Cement Grinding_ Role of Gypsum

Cement Grinding_ Occurrence of cement hydration

Cement Grinding_ Hydration of calcium silicates

2Ca3SiO5 + 6H2O ⇒ Ca3Si2O7 • 3H2O + 3Ca(OH)2

or in cement nomenclature:

2C3S + 6H ⇒ C3S2H3 + 3CH

Hydrated OPC contains about

50 - 60% of C-S-H and 20 - 25% of CH

Belite: Dicalcium silicate, β -C2S

2Ca2SiO4 + 4H2O ⇒ Ca3Si2O7 • 3H2O + Ca(OH)2

or in cement nomenclature:

Cement Grinding_ Hydration of Aluminate

C-S-H phases, type I

C-S-H phases, type II

C-S-H phases, type III

Ettringite

Portlandite, Ca(OH) 2

Monosulfate

Mineral components

 Lower water requirement and/or improved consistency

(exception pozzolans)

 delay in setting

 lower heat of hydration

 lower early and higher long term strength

 lower permeability

 improved resistance to sulphate & other chemical attacks

 lower sensitivity for AAR

General effects

Effect of composite cements on concrete

Effect of main mineral components on

Cement Grinding_ V ertical R oller M ill ( VRM )

Cement Mill_ Airflow inside of Vertical Roller Mill

Cement Grinding_ Operation control

fresh air Clinker Gypsum

[mbar]

[min -1 ]

Adjustment parameter

[min -1 ]

Basic Prerequisites for Optimum VRM Performance

Reliable airflow control

Accurate feeders

Air tight feeding gate

Fast feed control

Well functioning metal detector

Normal VRM Roller Operation

Vertical roller mill

Feed size:

f (Roller Ø )

Stable Material bed

Feed size OK

No Vibrations

Max Particle size in feed: 5-8 % of roller diameter

For a roller of 1m diameter: Max feed size 50-80 mm

Abnormal VRM Roller Operation / too much feed

Vertical roller mill Too High Feedrate

Vibrations

Abnormal VRM Roller Operation / too low feed

Vertical roller mill

Feed size:

f (Roller Ø )

Too Low Feedrate

Modification of setpoints and impact on Process

Impact on Setpoint Fineness Drying Vibration Pressure drop Production

Airflow HIGH HIGH MEDIUM MEDIUM MEDIUM

Roller press. LOW NO HIGH NO LOW

Sep Speed HIGH NO LOW LOW MEDIUM

Water inject. NO HIGH HIGH LOW MEDIUM

Cement Grinding_ Quality aspects

 Ensures to achieve the required chemical and physical properties

 The product mix and cement quality targets set by marketing and

manufacturing

 Typical quality indicators for the finished product are:

 Compressive strength at different ages

 Fineness (blaine, sieve residues, particle size distributation)

 SO3 for gypsum dosage

 Cement temperature for dehydration of gypsum

 Selected elements or components for mineral component dosage (e.g CaCO3 for limestone dosage)

They can also contribute to keeping our manufacturing costs low

Coprocessing_ Solid handling system

Co-processing_ Liquid Handling System