Cement Process Ashgrove

8/6/2019 Cement Process Ashgrove

1/38

Cement Manufacturing Process

!What is Cement?

" History

" Overview of the Cement

Manufacturing Process! Brief Overview of Kiln Operations

! Why Burn Wastes?

Reference Website: www.ashgrove.com
http://www.ashgrove.com/http://www.ashgrove.com/


2/38

" A hydraulic cement made by finelypulverizing the clinker produced by

calcining to incipient fusion a mixture of

argillaceous and calcareous materials

" Portland cement is the fine gray powder that

is the active ingredient in concrete

Portland Cement


3/38

Concrete

"

One Shovel Powder...Portland Cement" Two Shovels SandMineral Aggregate

" Three Shovels Rock.Mineral Aggregate

" Add water & mix

" Binds & sets to a solid mass


4/38

Concrete

"

Mixture of ingredients into a paste & triggersa chemical reaction hydration

" Reaction forms a gel which coats & fills

spaces between the stone/sand;" Hardens into a solid mass that get stronger &

stronger


5/38

Concrete

"

The worlds most widely used buildingmaterial

" Global production is 5 billion cubic yards

per year (using approximately 1.25 billiontons of cement)


6/38

Portland Cement

" Limestone + Shale/Clay + Heat = Clinker +

CKD + Exit Gas

"

Material Temperatures Exceed 27000

F" Pulverized Clinker + Gypsum = Portland

Cement

! Cement is powder so fine that one poundcontains

150 billion grains


7/38

" Basic Chemical Components of Portland Cement:

- Calcium (Ca)

- Silicon (Si)

- Aluminum (Al)- Iron (Fe)

" Typical Raw Materials:

- Limestone (CaCO3)

- Sand (SiO2)

- Shale, Clay (SiO2,Al2O3,Fe2O3)

- Iron Ore/Mill Scale (Fe2O3)

Portland Cement (contd)


8/38

" Calcareous Component

(providing Lime CaO)

- limestone

- marly limestone

- chalk

- coral limestone

- marble

- lime-sand

- shell deposits

- lime sludge

"

Argillaceous Component(SiO2, Al2O3, and Fe2O3)

- clay

- shale- calcareous marl

- marl

- marly clay- tuff, ash

- phyllite, slate

- glass



9/38


! Clinker Chemistry

- Tricalcium silicate (3CaO.SiO2), (50-70%)

- Dicalcium silicate (2CaO.SiO2), (15-30%)

- Tricalcium aluminate (3CaO.Al2O3), (5-10%)

- Tetracalcium aluminoferrite

(4CaO.Al2O3.Fe2O3), (5-15%)


10/38


Tricalcium Silicate Tricalcium Aluminate

CaO

SiO2

CaO CaO

CaO

Al2O3

CaO Cao


11/38

Energy/Capital Intensive Industry

! Requires 80 separate & continuous operations

1990 - 6th the nation for energy usage

! 18,700,000 tons of coal burned in the U.S.(value

of$748,000,000)

! 1,398,400,000 kW of power used(value of

$700,000,000)! A one million ton plant requires approximately

$175 million in capital


12/38

Types of Cement Processes

" Wet Process

" Dry Process 74% of cement produced

" Preheater/Precalciner Process


13/38

Evolution of the Cement Process

! Wet process easiest to control chemistry & betterfor moist raw materials

! Wet process high fuel requirements fuel needed

to evaporate 30+%slurry water! Dry process kilns less fuel requirements

! Preheater/precalciners further enhance fuel

efficiency & allow for high production rates


14/38

gas flow

2,000F 3,200FF ( gas temperatures( gas temperatures F ))

x The kiln is a continuous stream process vessel in

which feed and fuel are held in dynamic balancex 5 distinct process functions are performed in the kiln:

xDry

xPreheatxCalcine

xSinter

xCool

1900F 550F

material flow


15/38

Preheater Precalciner Kiln

There are still five jobs to be done

Drying

Preheating

CalciningSintering

Cooling

Dry Process Preheater/Precalciner System

60%

Fuel Split

40%


16/38


17/38


18/38


19/38

kiln feedkiln feed

pumppump

limestone

shale

shale

30%30%70%70%

32% water32% water

slurry millslurry mill

Kiln Feed PreparationKiln Feed Preparation

basinsbasins

xx

Proportioning of feed stock.Proportioning of feed stock.

xx Size reduction to < 125.Size reduction to < 125.

xx Control of moisture.Control of moisture.

xx Blending to reduce standard deviation.Blending to reduce standard deviation.

xx Uniform delivery rate of feed to the Kiln.Uniform delivery rate of feed to the Kiln.


20/38

Figure 4 : Vertical Roller Mill

Product

Hot Gas from

Pre-heaterHot Gas

Generator

CLAY

LIME

IRON

FLY

A

SH

Rejects

Water Spray

Fresh Feed

Mill Fan

Recirculation

KilnFeed

ProportioningDrying

Grinding


21/38


22/38


23/38

cement mill

clinker

gypsum

gypsum

5%5%95%95%

additive

up toup to

15%15% Separator

Fines

Finish

Grinding System

Rejects

Clinker, gypsum, and optional additives are weighedClinker, gypsum, and optional additives are weighed

to proper proportions and ground in the cement mills.to proper proportions and ground in the cement mills.

Additives may include: Fly-ash, Limestone..Additives may include: Fly-ash, Limestone..


24/38

Cement Kilnthe Largest Moving Equipment in anyManufacturing Operation

Cement Kilnthe Largest Moving Equipment in anyManufacturing Operation

And the Hottest


25/38

gas flow

2,000F 3,200FF ( gas temperatures( gas temperatures F )) 1900F550F

material flow

Critical Parameters: Fuel, Feed, Kiln Speed, Gas Flow

Kiln Temperatures


26/38

Cement Kilns

" High temperature" Long residence time

" Natural alkaline environment

" CKD is only by-product of the process" Thermal stability


27/38

Kiln Process Control

" Critical Parameters: Fuel, Feed, Kiln Speed,Gas Flow

" Kiln Temperatures Burning Zone

" Kiln Stability" Chemistry

" Instrumentation


28/38

Wet Kiln Process Material and

Gas Temperatures

Wet Kiln Process Material andWet Kiln Process Material and

Gas TemperaturesGas Temperatures

D P P h t /P l i S t


29/38

Preheater Precalciner Kiln

Dry Process Preheater/Precalciner System

60%

Fuel Split

40%


30/38

Dry Kiln Process Material and

Gas Temperatures

Dry Kiln Process Material andDry Kiln Process Material and

Gas TemperaturesGas Temperatures


31/38

T.D.F.

A typical wet kiln burns about 400# of fuel to make a ton

of clinker (5.0 mmBtu/ton of clinker)Fuels can be any combustible hydrocarbon such as:

x coal, coke, natural gas, used motor oil, wood, tires,

cellulose others.

Coal&

Pet Coke


32/38

Why Burn Wastes?

A cement kiln is a proven technology for

recycling by beneficial REUSE of solid and

hazardous wastes

The benefits are:

- energy recovery

- material recovery- economics

- environmental preservation


33/38

Federal & State Established Priorities forIndustrial Waste Disposal

! Reduction at the source

" Recycling

" Energy recovery

"

Incineration" Stabilization

" Landfill


34/38

Benefits of a Recycling Program

Allows for reuse of waste materials

" Conserves virgin fuels & raw materials

" Regulated stringently for environmental

protection


35/38

Waste Recycling Process

"

Waste fuels are destroyed, releasing heat,water and carbon dioxide

" Solid materials are physically andchemically combined in the clinker product


36/38

Cement Kilns Excellent Environment forDestroying & Recycling Wastes

A Cement Kiln Provides:

! 3,000oF + Flame

! Long retention times of gasses and materials

! Stability of a large dependable industrial

process

! Many inherent safeguards


37/38

A Cement Kiln Is A Proven Technology ForBeneficial REUSE of Otherwise Waste Materials

The Benefits are:! Energy Recovery

!

Material Recovery


38/38

Recycling Programs

Energy Replacement for Coal/Coke! Liquid fuels! Solid fuels

Material Replacement for Raw Materials (Limestone,Shale and Sand)! Solids/sludge slightly contaminated with metals

! Solids/sludge slightly contaminated withorganics

Documents

Cement Process Ashgrove