Company profile

Jaypee group is the 3rd largest cement producer in the country. The groups

cement facilities are located in the Satna Cluster (U.P), which has one of the

highest cement production growth rates in India.

The group produces special blend of Portland Pozzolana Cement under the brand

name ‘Jaypee Cement’ (PPC). Its Cement Division currently operates modern,

computerized process control cement plants with an aggregate capacity of 22.80

MnTPA*. The company is in the midst of capacity expansion of its cement

business in Northern, Southern, Central, Eastern and Western parts of the

country and is slated to be 37.55 MnTPA BY FY12 (EXPECTED) WITH CAPTIVE THERMAL

POWER PLANTS.

Keeping pace with the advancements in the IT industry, all the 140 cement

dumps are networked using TDM/TDMA VSATs along with a dedicated hub to

provide 24/7 connectivity between the plants and all the 120 points of cement

distribution in order to ensure “track – the – truck” initiative and provide

seamless integration. This initiative is the first of its kind in the cement industry in

India.

In the near future, the group plans to expand its cement capacities via acquisition

and greenfield additions to maximize economies of scale and build on vision to

focus on large size plants from inception.The Group is committed towards the

safety and health of employees and the public. Our motto is '  Work For Safe, 

Healthy, Clean & Green Environment '.

Content Company profile

Introduction

Cement

Type of cement

Brief layout of cement plant

Cement manufacturing process

Thermal power plant

INTRODUCTION

CEMENT-:

In the most general sense of the word, a cement is a binder, a substance that sets

and hardens independently, and can bind other materials together. The volcanic

ash and pulverized brick additives that were added to the burnt lime to obtain a

hydraulic binder were later referred to as cement.

The most important use of cement is the production of mortar and concrete—the

bonding of natural or artificial aggregates to form a strong building material that

is durable in the face of normal environmental effects.

Concrete should not be confused with cement because the term cement refers

only to the anhydrous powder substance (ground clinker) used to bind the

aggregate materials of concrete. Upon the addition of water and/or additives the

cement mixture is referred to as concrete, especially if aggregates have been

added.

Cement

TYPES OF MODERN CEMENT

Portland cement

Cement is made by heating limestone (calcium carbonate), with small quantities

of other materials (such as clay) to 1450 °C in a kiln, in a process known

as calcination, whereby a molecule of carbon dioxide is liberated from the calcium

carbonate to form calcium oxide, or quicklime, which is then blended with the

other materials that have been included in the mix . The resulting hard substance,

called 'clinker', is then ground with a small amount of gypsum into a powder to

make 'Ordinary Portland Cement', the most commonly used type of cement

(often referred to as OPC).

Portland cement is a basic ingredient of concrete, mortar and most non-

speciality grout. The most common use for Portland cement is in the production

of concrete. Concrete is a composite material consisting

of aggregate (gravel and sand), cement, and water. As a construction material,

concrete can be cast in almost any shape desired, and once hardened, can

become a structural (load bearing) element. Portland cement may be gray or

white.

Portland cement blends

These are often available as inter-ground mixtures from cement manufacturers,

but similar formulations are often also mixed from the ground components at the

concrete mixing plant.[7]

Portland blastfurnace cement contains up to 70 % ground granulated blast

furnace slag, with the rest Portland clinker and a little gypsum. All compositions

produce high ultimate strength, but as slag content is increased, early strength is

reduced, while sulfate resistance increases and heat evolution diminishes. Used

as an economic alternative to Portland sulfate-resisting and low-heat cements.[8]

Portland flyash cement contains up to 30 % fly ash. The fly ash is pozzolanic, so

that ultimate strength is maintained. Because fly ash addition allows a lower

concrete water content, early strength can also be maintained. Where good

quality cheap fly ash is available, this can be an economic alternative to ordinary

Portland cement.[9]

Portland pozzolan cement includes fly ash cement, since fly ash is a pozzolan, but

also includes cements made from other natural or artificial pozzolans. In countries

where volcanic ashes are available (e.g. Italy, Chile, Mexico, the Philippines) these

cements are often the most common form in use.

Portland silica fume cement. Addition of silica fume can yield exceptionally high

strengths, and cements containing 5-20 % silica fume are occasionally produced.

However, silica fume is more usually added to Portland cement at the concrete

mixer.[10]

Masonry cements are used for preparing bricklaying mortars and stuccos, and

must not be used in concrete. They are usually complex proprietary formulations

containing Portland clinker and a number of other ingredients that may include

limestone, hydrated lime, air entrainers, retarders, waterproofers and coloring

agents. They are formulated to yield workable mortars that allow rapid and

consistent masonry work. Subtle variations of Masonry cement in the US are

Plastic Cements and Stucco Cements. These are designed to produce controlled

bond with masonry blocks.

Expansive cements contain, in addition to Portland clinker, expansive clinkers

(usually sulfoaluminate clinkers), and are designed to offset the effects of drying

shrinkage that is normally encountered with hydraulic cements. This allows large

floor slabs (up to 60 m square) to be prepared without contraction joints.

White blended cements may be made using white clinker and white

supplementary materials such as high-purity metakaolin.

Colored cements are used for decorative purposes. In some standards, the

addition of pigments to produce "colored Portland cement" is allowed. In other

standards (e.g. ASTM), pigments are not allowed constituents of Portland cement,

and colored cements are sold as "blended hydraulic cements".

Very finely ground cements are made from mixtures of cement with sand or with

slag or other pozzolan type minerals that are extremely finely ground together.

Such cements can have the same physical characteristics as normal cement but

with 50% less cement particularly due to their increased surface area for the

chemical reaction. Even with intensive grinding they can use up to 50% less

energy to fabricate than ordinary Portland cements.[11]

LAYOUT OF THE CEMENT PLANT

Cement Manufacturing Process

Mining

The cement manufacturing process starts from the mining of limestone,

which is the main raw material for making cement. Limestone is excavated

from open cast mines after drilling and blasting and loaded on to dumpers

which transport the material and unload into hoppers of the limestone

crushers.

Crushing Stacking & Reclaiming of Limestone

The LS Crushers crush the limestone to minus 80 mm size and discharge

the material onto a belt conveyor which takes it to the stacker via the Bulk

material analyser. The material is stacked in longitudinal stockpiles.

Limestone is extracted transversely from the stockpiles by the reclaimers

and conveyed to the Raw Mill hoppers for grinding of raw meal.

Crushing Stacking & Reclaiming of Coal

The process of making cement clinker requires heat. Coal is used as the

fuel for providing heat. Raw Coal received from the collieries is stored in a

coal yard. Raw Coal is dropped on a belt conveyor from a hopper and is

taken to and crushed in a crusher. Crushed coal discharged from the Coal

Crusher is stored in a longitudinal stockpile from where it is reclaimed by a

reclaimer and taken to the coal mill hoppers for grinding of fine coal.

Raw Meal Drying/Grinding & Homogenisation

Reclaimed limestone along with some laterite stored in their respective

hoppers is fed to the Raw Mill for fine grinding. The hot gasses coming

from the clinkerisation section are used in the raw mill for drying and

transport of the ground raw meal to the Electrostatic Precipitator / Bag

House, where it is collected and then stored and homogenised in the

concrete silo. Raw Meal extracted from the silo (now called Kiln feed) is

fed to the top of the Preheater for Pyroprocessing.

Clinkerisation

Cement Clinker is made by pyroprocessing of Kiln feed in the preheater

and the rotary kiln. Fine coal is fired as fuel to provide the necessary heat

in the kiln and the Precalciner located at the bottom of the 5/6 stage

preheater. Hot clinker discharged from the Kiln drops on the grate cooler

and gets cooled. The cooler discharges the clinker onto the pan / bucket

conveyor and it is transported to the clinker stockpiles / silos. The clinker

is taken from the stockpile / silo to the ball mill hoppers for cement

grinding.

Cement Grinding & Storage

Clinker and Gypsum (for OPC) and also Pozzolana (for PPC) are extracted

from their respective hoppers and fed to the Cement Mills. These Ball

Mills grind the feed to a fine powder and the Mill discharge is fed to an

elevator, which takes the material to a separator, which separates fine

product and the coarse. The latter is sent to the mill inlet for regrinding

and the fine product is stored in concrete silos.

Packing

Cement extracted from silos is conveyed to the automatic electronic

packers where it is packed in 50 Kgs. Polythene bags and dispatched in

trucks.

Electrical Power

For total power requirement of 90 MW (Jaypee Rewa Plant and Jaypee

Bela Plant), we have

CPP 1 - 25.0 MW

CPP 2 - 25.0 MW

CPP 3 - 37.0 MW

CEMENT MILL

Conveyor

A conveyor belt (or belt conveyor) consists of two or morepulleys, with a

continuous loop of material - the conveyor belt - that rotates about them. One or

both of the pulleys are powered, moving the belt and the material on the belt

forward. The powered pulley is called the drive pulley while the unpowered pulley

is called the idler. There are two main industrial classes of belt conveyors; Those

in general material handling such as those moving boxes along inside a factory

and bulk material handling such as those used to transport industrial and

agricultural materials, such as grain, coal, ores, etc. generally in outdoor locations.

Generally companies providing general material handling type belt conveyors do

not provide the conveyors for bulk material handling. In addition there are a

number of commercial applications of belt conveyors such as those in grocery

stores.

The belt consists of one or more layers of material they can be made out

of rubber. Many belts in general material handling have two layers. An under

layer of material to provide linear strength and shape called a carcass and an over

layer called the cover. The carcass is often a cotton or plastic web or mesh. The

cover is often various rubber or plastic compounds specified by use of the belt.

Covers can be made from more exotic materials for unusual applications such as

silicone for heat or gum rubber when traction is essential.

Material flowing over the belt may be weighed in transit using a beltweigher.

Belts with regularly spaced partitions, known as elevator   belts, are used for

transporting loose materials up steep inclines. Belt Conveyors are used in self-

unloading bulk freighters and in live bottom trucks. Conveyor technology is also

used in conveyor transport such as moving sidewalks or escalators, as well as on

many manufacturing assembly lines. Stores often have conveyor belts at

the check-out counter to move shopping items. Ski areas also use conveyor belts

to transport skiers up the hill.

A wide variety of related conveying machines are available, different as regards

principle of operation, means and direction of conveyance, including screw

conveyors, vibrating conveyors, pneumatic conveyors, the moving floor system,

which uses reciprocating slats to move cargo, and roller conveyor system, which

uses a series of powered rollers to convey boxes or pallets.

TYPE OF CONVEYOR

1. APRON (PAN) CONVEYOR

2. BELT CONVEYOR

3. SCREW CONVEYOR

4. AIR SLIDE

5. BUCKET ELEVETOR

Apron Conveyors

With our expertise in the domain, we offer precision engineered apron

conveyor, a metallic belt conveyor. The metal aprons with or without

side walls are fixed on two strands of chains running around end

sprockets. The conveyors find application for handling heavy, hot,

abrasive material. It is also used for continuous duty in hostile working

atmosphere. The MOC used for manufacturing the conveyor is to suit

the duty condition. The range is available in various configuration and

profile as required.

Our range is widely used in steel plant, fertilizer industries, collieries,

cement plants, heavy chemical plants, mines, wood handling, aggregate

handling, quarries and many others.

WEIGH FEEDER

The series of Weigh Feeders developed at Mil Mech are designed

according to the users need. The weigh feeders provide accurate

and dependable performance combining the simplicity and

cleanliness of a vibratory conveyor with robust weighing

capabilities. With only one mobile part, these weigh feeders are

compact in design and occupies too little space as compared to

other heavy duty weigh feeders, but with equal productivity.

The Mil Mech Weigh Feeders are simple in-line weighing conveyor

designed to feed products by weight.

In order to achieve the desired setting qualities in the finished product, a

quantity (2-8%, but typically 5%) of calcium sulfate (usually gypsum or anhydrite)

is added to the clinker and the mixture is finely ground to form the finished

cement powder. This is achieved in a cement mill. The grinding process is

controlled to obtain a powder with a broad particle size range, in which typically

15% by mass consists of particles below 5 μm diameter, and 5% of particles above

45 μm. The measure of fineness usually used is the "specific surface area", which

is the total particle surface area of a unit mass of cement. The rate of initial

reaction (up to 24 hours) of the cement on addition of water is directly

proportional to the specific surface area. Typical values are 320–380 m2·kg−1 for

general purpose cements, and 450–650 m2·kg−1 for "rapid hardening" cements.

The cement is conveyed by belt or powder pump to a silo for storage. Cement

plants normally have sufficient silo space for 1–20 weeks production, depending

upon local demand cycles. The cement is delivered to end-users either in bags or

as bulk powder blown from a pressure vehicle into the customer's silo. In

industrial countries, 80% or more of cement is delivered in bulk.

Ball mill

A typical type of fine grinder is the ball mill. A slightly inclined or

horizontal rotating cylinder is partially filled with balls,

usually stone or metal, which grinds material to the necessary

fineness by friction and impact with the tumbling balls. The feed is

at one end of the cylinder and the discharge is at the other. Ball

mills are commonly used in the manufacture of Portland cement.

These industrial ball mills are mainly big machines. Small versions

of ball mills can be found in laboratories where they are used for

grinding sample material for quality assurance.

Specification of BALL MILL -3

TYPE-TWO CHAMBER BALL MILL

SIZE-

1. DIAMETRE- 4.8 METRE

2. LENGTH- 14 METRE

SPEED- 14.8 rpm

CAPASITY- 150 TPH

PRINCIPLES OF GRINDING

SPEED OF MILL

Experimental work conducted in our laboratory and supplemented by

our pictures in slow motion definitely indicates that the action inside

the Mill drum is not a haphazard stirring and throwing of the charge.

There is a specific operating speed for most efficient grinding. At a

certain point, controlled by the Mill speed, the load nearest the wall of

the cylinder breaks free and it is so quickly followed by other sections in

the top curves as to form a cascading, sliding stream containing several

layers of balls separated by material of varying thickness. The top layers

in the stream travel at a faster speed than the lower layers thus causing

a grinding action between them. There is also some action caused by

the gyration of individual balls or pebbles and secondary movements

having the nature of rubbing or rolling contacts occur inside the main

contact line.

It is important to fix the point where the charge, as it is carried upward,

breaks away from the periphery of the Mill. We call this the “break

point”, or “angle of break” because we measure it in degrees. It is

measured up the periphery of the Mill from the horizontal.

There are four factors affecting the angle of break:

1. Speed of Mill

2. Amount of grinding media

3. Amount of material

4. In wet grinding, the consistency or viscosity

As this section deals entirely with speeds, we will confine our discussion

to this item and cover the other factors in their respective categories.

While, in the old days, operating speeds were determined by trial and

error, we have been able to establish practical operating speeds

through correlation with the critical speed, which is the speed at which

the grinding media, without material, begin to centrifuge. Therefore, to

determine the critical speed for any given size Mill, we use the

following formula: 54.19 divided by the square root of the radius in

feet.

The smaller the Mill the faster in RPM it must run to attain critical

speed. Our 4.5” diameter Specimen Jar has a critical speed of 125 RPM,

and our size #00 90” diameter Ball Mill 28 RPM.

For most grinding and dispersing problems, we strive to attain the

cascading, sliding action described earlier, and to accomplish this we

have found that the most desirable angle of break ranges from 50 to 60

degrees from the horizontal.

The lower range is recommended for most wet grinding operations like

paints and soft dry materials, and the higher break point (which

provides a more severe grinding action) for most dry materials and wet

grinding such hard products as enamel frit and glaze.

It is also known that the grinding action in a larger Mill is more severe

than in the smaller sizes and, consequently, we are of the opinion that

the angle of break should be lower for the larger Mills than for the

smaller.

The rule of speed applies regardless of the type of grinding media.

A Pebble Mill the same size as a Ball Mill is expected to run at a slightly

faster speed. This is due to the smaller inside diameter of the Pebble

Mill with its lining, which is lacking in the Ball Mill.

In the production of bronze and aluminum powders, the Mills are run

almost a critical speed so that the balls are drooped to give the same

effect as a hammer blow. Without this action the product grinds finely

but no flaking of any consequence can be obtained and aluminum or

bronze powders are only effective as coatings when they are used in

flake form.

TYPE OF GRINDING

WET GRINDING

The void volume between the grinding media, with the mill half

charged, represents approximately 20% of the total volume of the mill

– and with a one-third charge of grinding media 13 ½%.

Fastest grinding occurs where there is just sufficient material in a batch

to fill all voids and slightly cover the grinding media. This equals

approximately 25% of the total volume with a half ball charge and 18%

with a one-third ball charge. The material should never be allowed to

drop below the surface of the grinding media, because when this

happens, excessive wear occurs to the Mill and grinding media and

contaminates the material itself. The largest size batches should not

exceed 60% of total Mill volume which corresponds with our catalog

rating.

There are occasions where additional thinning of the batch after

grinding may be done to increase the yield of the Mill. For example: A

Paul O. Abbé #3-C lined Pebble Mill has a volume of 450 gallons. A

minimum 25% material charge for this Mill would be 112 gallons and

the maximum 60% charge 270 gallons. After grinding, if the Mill were

loaded to the extreme top with thinner, the yield produced would be

315 gallons, or 70% of the total volume of the Mill.

We find that the most general batch size is about 30% for products that

are hard to grind like enamel frit and glazes and 40 t0 45% for products

like the average high grade paint and enamel. Larger batches are run

where a good mix rather than a grind is involved or where grinding time

is not a particularly important factor. A general rule in determining the

grinding efficiency for different size batches is to figure that a 40%

batch takes twice as long as the 25% and the 60% batch four times as

long when a 50% charge of grinding media is used. This is particularly

applicable to high grade dispersions. When grinding material such as

enamel frit, it is unlikely that the extreme upper limit in batch size will

ever grind.

It is a practical plan to establish the batch size consistent with the

allowable running time. For example: Assuming that a 25% batch takes

9 hours, this would be too long for an 8 hour shift. Therefore, it is

usually advisable to increase the batch size and continue running the

Mill to the next working day. Assuming again that 40% batch takes 9

hours, then a slight cutback should make it possible to turn out a batch

within an 8 hour working day. It is therefore; always wise to do a little

experimenting with the batch size to try to develop a system that will

work out best under your particular grinding conditions. The one

principal rule to remember is that the grinding media must be covered

with material.

CONSISTENCY OR VISCOSITY OF MATERIAL – The most important

element in wet grinding is the consistency, or viscosity, of the batch.

Low viscosity materials permit the grinding media to move with

excessive speed and this combined with the thin protective film around

the media, may cause abnormal wear, contamination and heat build-

up. If the low viscosities cannot be avoided then it is imperative that

small grinding media be used.

With high viscosities free movement of the grinding media is impeded.

This can cause a carrying over and “throw” of the media resulting in

inefficiencies and contamination.

Based on accepted milling techniques, we have found the following

consistencies measured at milling temperature usually work out best:

For flint pebbles and porcelain balls 75 to 90 Kreb Units, 600 to 1100

centipoises

For high density balls 90 to 100 Krebs Units, 1100 to 2100 centipoises

For steel balls 90 to 115 Krebs Units, 1100 to 2400 centipoises

These viscosities are based on using 1 to 1 ½” flint pebbles – 1 to 1 ½”

porcelain balls – ½ to ¾” steel balls. The smaller sizes for the lower

viscosities and the larger sizes for the higher viscosities.

Some producers of high density media have been recommending a

higher viscosity range than the figures we have indicated. In effect, this

merely increases the thickness of the film surrounding the media

thereby providing more cushion against impact. We find this desirable

where a shearing action is only required to obtain results. However,

impact is one of the most important advantages of Ball Mill and Pebble

Mill operations, consequently, excessive restriction of media

movement should be avoided for highest operating efficiency. This

same rule also applies where other types of media are used.

Our viscosity readings were made on a Stormer Impeller type

Viscometer. We have found this accurate on both high and low shear

materials, as well as on products of a thixotropic nature, whether

acqueous or non-acqueous mixtures.

WETTING AGENTS -- The use of wetting agents has greatly increased

the capacity of Ball Mills and Pebble Mills without altering the viscosity

during the grind. A typical example is the case of one operator who,

prior to the use of wetting agents, could load no more than 50% solids

to retain a suitable working viscosity. By adding the proper wetting

agent he was able to increase his solids content to 85%.

It has generally been found that, combined with the increased

production, the grinding operation can be performed in a much faster

time because the wetting agents aid in breaking down the surface

tensions of the aggregated particles and the finished product has

greater stability.

DILUTION BEFORE DISCHARGE – Where the product being ground has

a heavy consistency which makes it difficult to discharge, it is

sometimes advisable to add sufficient additional liquid to thin down the

batch. If the mill is equipped with a discharge valve, the liquid is best

added to the batch through the valve. The reason for suggesting this is

that there is likely to be some unground material packed between the

flanges of the manhole frame and cover. To prevent dropping this

material into a finished batch, try to avoid disturbing the cover until the

ground material has been removed.

If there is any surging of the liquid as it is being loaded into the mill, the

brass vent plug on the head of the mill, the brass vent plug on the head

of the mill should first be removed. BE SURE TO REPLACE PLUG BEFORE

RE-STARTING THE MILL. If the mill is not equipped with a discharge

valve, extra liquids must be added through the manhole opening.

The mill should be run form 10 to 15 minutes with the added thinner.

The mill can be comple tely full after the additional thinner is added. In

some cases, the minimum 25% grinding charge of semi-paste material

is being ground first and additional liquid to fill the remaining 45% of

total volume of the mill is added later to make the finished mix. Where

still further thinning is desired, this can only be accomplished by

unloading the batch of material and adding the extra thinner in mixing

tanks.

Another method is to discharge part of the grinding slurry, mix thinner

into the remainder in the mill, discharge this material into the receiver

holding the first portion, and finally mix the entire batch with a portable

mixer. A variation of this is to be discharge as much of the grinding

slurry as possible, and then make the thinner serve the twofold

purpose of washing the mill out and finally thinning the entire batch.

COATINGS COMPRISING PAINT, INK AND SIMILAR MATERIALS– While

we recognize that actual grinding, i.e. – size reduction of some

pigments is not required, the action of Ball and Pebble Mills embodies a

combination of impact, shear and attrition. Therefore, it is the

utilization of all these forces that insures the best performance of these

Mills.

Most desirable applications for Ball and Pebble Mills are on pigments

requiring further reduction -- Non-uniform pigments that must be

made uniform in the finished product, -- Agglomerated pigments

resulting from storage and handling -- Manufactured agglomerates

such as carbon beads – Raw materials lacking complete compatibility --

Grinding inexpensive coarse extender pigments in the batch giving

more hiding power to expensive pigments, -- Where uniformity and

stability of the finished product are essential and must be constant,

batch after batch.

On the other hand, simple dispersions can be quickly and easily

accomplished in a consistent, productive fashion without the need for

elaborate controls or supervision.

One of the most successful techniques employed in the dispersion of

pigment in vehicle and solvent is known as low solids grinding. Utilizing

this procedure offers two distinct advantages:

1. Dispersion is accomplished in a fraction of the time formerly

required. Typical results include a white architectural enamel 8 +

grind in one hour with flint pebbles. Light green trim enamel 6 +

grind in one hour with steel balls. Yellow enamel to 7 grind in 2 ½

hours with steel balls.

2. A greater pigment quantity can be dispersed in a mill batch than

the ultimate formula requires. The remainder of the formula, i.e.:

vehic le and solvent, is then added when the dispersion is

complete. Many instances are known where mills have yielded

two to four times the actual batch loading in finished product.

Excellent papers covering this subject have been presented to the

Federation of Societies for Paint Technology.

The first article presented by Frederick K. Daniel describes the “Flow

Point” method of determining the optimum relationship of pigment –

binder and solvents.

A second article also presented in October 1950 by R.B. Shurtz gives

further data on the “Flow Point” method with tables and graphs

showing results on many combinations. If this method of determining

pigment concentration or percentage of vehicular solids is used, the

danger of seeding or pigment shock is decreased. However, to reduce

this danger further it is frequently advantageous to step load the

balance of the vehicle solids and solvent with the temperature as close

as possible to the mill temperature.

A third paper presented by Frederick K. Daniel in October 1956

discusses the effect on seeding by the solvents utilized in the mill base

and let-down phase.

While the use of all forces comprising the action of ball and pebble mills

is beneficial on most pigmented products, there are a few pigments on

which it is desirable to avoid direct impact and attrition and rely mostly

on shear.

For example, one of these is toluidine red. Excessive grinding through

impact can destroy the pigment structure thereby reducing its hiding

power. To avoid excessive grinding by impact the consistency should be

heavier than for normal operation and the size batch should be

sufficient to induce spreading of the grinding media in order to prevent

direct contact and merely induce a shearing action.

Other operating suggestions of value include the following:

Most operators prefer to first charge the liquids and follow this with

the pigment. They find they get faster initial wetting and there is less

danger of pigment balls forming

Step loading is more advantageous than tightly packing a bulky pigment

to try and get it all in the Mill in one loading. Pigment manufacturers

report that excessive packing can cause reaggregation of pigment

particles.

Most operators prefer to first charge the liquids and follow this with

the pigment. They find they get faster initial wetting and there is less

danger of pigment balls forming Step loading is more advantageous

than tightly packing a bulky pigment to try and get it all in the Mill in

one loading. Pigment manufacturers report that excessive packing can

cause reaggregation of pigment particles.

Wetting or dispersing agents have a definite place in formulating

techniques. There are many types on the market and the manufactures

of these should be consulted in determining their application.

DRY GRINDING

Whenever there is a choice between grinding a product wet or grinding

it dry, wet grinding will generally prove better. However, in many cases,

it is impractical to grind wet due to the nature of the process or

product.

The void volume between the grinding media, with the mill half

charged, represents approximately 20% of the total volume of the mill-

and with a one-third charge of grinding media 13 1/3%.

We usually try to limit the size of the batch to 25% of the total Mill

volume which is sufficient to fill all voids and slightly cover the grind ing

media. Any larger batches cause the pebbles to spread out through the

mass of solids so they cannot make effective contact with each other,

because of the layers of material between them. This greatly reduces

the grinding efficiency of the mill and, in some cases, makes it

impossible to attain the desired results. The only occasion for larger

batches than 25% of total volume, is on products requiring a good mix

rather than a grinding action or on products that are soft and easy to

grind and the grind ing media do not necessarily have to make close

contact with each other.

The feed material should preferably be about 8 mesh or smaller,

although many operators start with much larger pieces. Having the feed

material as fine as possible enable the use of smaller sizes of grinding

media, which are always best for fine Uniform grinding and dispersions.

For hard material, it is especially advantageous to start with a fairly fine

product.

Clogging of material in the Mill makes further operation harmful. This is

generally caused by moisture of fat, as in oily seeds. Possible remedies

include:

1. Taking the material out and thoroughly drying it.

2. Adding a dry filler to absorb the excessive moisture while the

batch is being ground.

3. Adding a few pieces of steel angle, bar, or chain which can slide

along the Mill surface and scrape off any materials starting to

pack.

4. If the material is packing due to particle size alone, grinding

should be stopped prior to this point. The material should then be

screened and tailings returned to the mill.

GRINDING MEDIA

In the grinding mill numbers of solid metel ball are use for

grinding the raw material.these are called grinding media.

QUANTITY OF GRINDING MEDIA

For the most efficient results, the Mill should be at least half filled with

grinding media. Some operators prefer to go a little beyond the halfway

mark to compensate for wear. There is no objection to this and we have

been suggesting a limit of about 5 percent.

In steel ball grinding, many operators, especially in the paint industry,

are satisfied to run with a smaller ball charge ranging as low as one-

third the volume of the Mill. They find the smaller charge gives them

the required grind within allowable limits of grinding time and the extra

space gives them more loading room.

There is no objection to this practice when the grinding cycle falls

within the desired working limits. Where speed of grind is of utmost

importance, larger ball charges ranging up to the recommended 50%

for other types of grinding media are advisable. The logic in this system

is best illustrated as follows:

5/8” steel balls are one of the most popular sizes, and there are 36 of

these per pound. In a 54” x 60” Steel Ball Mill, for example, the

difference between the weight of a one-third and one-half ball charge is

3,970 pounds, or 103,220 balls. The ½” steel ball is another very

popular size and, as there 53 of these per pound, the difference would

amount to 200,410 balls. It s therefore, reasonable to expect (and

experience has proven this to be true) that any addition above the

minimum limits prescribed can only result in increased grinding

efficiency. This improvement is usually related to the surface area of

the media involved.

It is not true that a one-half ball charge consumes proportionately more

power than a one-third ball charge. The difference in weight between

the tow charges is about 50% but the center of gravity of the larger is

nearer the center of rotation of the Mill. Consequently, the power

required to turn the larger charge only runs between 15 and 20% more.

The grinding efficiency of the one-half charge is considerably greater

than for the one-third and, therefore it ca be expected that power

consumption per gallon output will actually be less than with the

smaller charge.

Grinding media should be periodically checked. Reduction in the

quantity and size of the grinding media will result in poor grinding. We

suggest a maximum schedule of once every six months, but any

established procedure should be decided by individual experience. In

some cases, where abrasive materials are involved, once a month is not

too often and, in a few cases, even shorter intervals are indicated.

A simple method for checking is to have a rod cut indication the

distance from the top of the grinding media to the underside of the

manhole opening and use this for checking the depth of the charge.

When grinding enamel frit, wear to the porcelain balls is quite excessive

because to the abrasive nature of the frit. Consequently, many

operators have been able to closely determine the ball wear per batch

and, when a batch of frit is loaded for grinding, a quantity of new balls

is added equaling the weight lost during the previous grind. However,

even with this system, we still advise an occasional check with the

measuring rod because there is no positive guarantee that all balls will

wear the same.

We also advocate dumping the charge once a year, or as often as

experience indicates, and removing any grinding media found to be

excessively worn or damaged.

1. Special note: No matter how good the metal ball might be, care

must be exercised in the operation of the Mill if excessive wear

with its resultant contamination is to be avoided. (See other

sections in this chapter; also sections on Cleaning and

Discharging.)

The following general rules should be carefully adhered to regardless of

the type media used.

1. There should be enough material in the batch to cover the

grinding media.

2. Grinding time must be watched carefully to avoid excessive

grinding.

3. Excessive buildup of heat should be avoided. In paint grinding, this

may lower the operating viscosity beyond the critical point. A

reduction in Mill speed may help to avoid overheating, but it is

more desirable to circulate a cooling medium around the cylinder.

If the Mill is not jacketed, a water spray can be used with

satisfaction.

4. The smallest grinding media should be employed. These not only

reduce the danger of overheating but, as is well known, the

smaller grinding media provide faster and better results.

5. When using extenders, their abrasive nature may cause excessive

wear. To avoid this, some operators are able to hold out the

extenders until the grinding is almost completed and then add

them for the final operation.

SIZE OF GRINDING MEDIA

Probably the most common cause for faulty operation and complaints

has been due to the size of grinding media. It is strongly recommended

that the smallest feasible grinding media be used in all cases. The

optimum size of media should not change with Mill size. If the

laboratory Pebble or small Ball successfully grinds a sample batch in a

lab Mill, the same size grinding media will do the best job in a

production Mill whether the Mill is one foot or eight feet in diameter.

Small grinding media are recommended because:

1. They provide many more grinding contacts per revolution than

larger media. This results in much quicker grinding action.

2. They provide smaller voids, limiting the size of particles or

agglomerates which can exist there.

3. They do not create excessive energy which cannot be utilized.

Oversized grinding media frequently develop more grinding

energy than is needed for the job. This excess merely builds up

heat and wears down the media and lining, introducing

contamination in the batch. Using an extremely large grinding

media is somewhat like using a sledgehammer to drive in a carpet

tack.

The chief disadvantage of the smallest size grinding media is that

discharging takes somewhat longer due to increased surface tension in

the smaller voids. Almost invariably, however, the reduced grinding

time realized by smaller media more that offsets this disadvantage.

Slight air pressure may be used to assist in more rapid discharge.

Using extremely small media, with their greater surface area for the

material to adhere to, may yield a smaller initial batch. Subsequent

batches will be of normal size, however.

When steel balls are used, the optimum sizes we have usually been

recommending have been ½ and 5/8”. However, many operators are

now using media as small as ¼” in production mills and find these

extremely advantageous where exceptionally fine grinds are required.

Generally, the viscosities must be slightly lower for the small size balls

than we would recommend for the more popular ½ and 5/8” sizes.

CEMENT MILL DRIVE & LUBRICATION SYSTEM

Technical Data

The gearbox comprises two co-axial planetary stages arranged one

behind the other. Both stages are straight-toothed planetary gears with

fixed ring gear and rotating planet carrier.

The drive is achieved through the sun pinion. The rotating planet

carrier is, at the same time, also the output drive shaft of the first stage.

The planetary gears are supported on planetary gear axles in the planet

carrier. All bearings in the first stage are plain bearings. The fist stage is

provided with its own housing which is bolted to the second stage.

The second stage is a straight-toothed planetary gear with fixed ring

gear and rotating planet carrier. The drive is achieved through the sun

pinion, which is driven by the planet carrier of the first stage via a

toothed coupling. The rotating planet carrier is, at the same time, also

the output drive shaft of the first stage. The planetary gears are

supported on planetary gear axles in the planet carrier. All bearings in

the second stage are slide bearings.

Gearing

The spur teeth of the sun pinion and the planet wheels are case-

hardened and grinded. The toothed flanks of the sun pinions have both

profile and longitudinal corrections to fully compensate for

deformations occuring under load. This method guarantees optimum

tooth flank contact and very long life. The inner gear rings are heat

treated.

Gear Unit Types

Make- MAAG

Drive- General Drive

Power-4650 kw

R.P.M-14.8 rpm

Additional Components

Auxiliary Drive

During maintenance of the ball mill different jobs need to be

performed, such as cooling down, level out, clean and position the mill.

The auxiliary drive facilitates these operations by providing: interval mill

turning, smooth start, position hold with brakes, automatic auxiliary

drive disengagement at main motor start-up and level out function.

FLSmidth MAAG Gear is able to provide all the necessary turning

functions for your maintenance operations. Personal safety, an

essential requirement for your staff, is given top priority.

Coupling ZCF

The ZCF toothed coupling installed between the mill and the gearbox is

a unique FLSmidth MAAG Gear design combining a high degree of

freedom (alignement) with efficient torque transmission. Thermal

expansions and mechanical deflections resulting from operating

conditions are safely absorbed by the ZCF coupling, and only the torque

is transmitted to the gearbox through a torsion shaft. Upon request a

water injection system can be installed. During gearbox maintenance

the ZCF coupling remains in place.

Coupling ZEXF

The gearbox to motor coupling ZEXF is a toothed coupling specially

designed by FLSmidth MAAG Gear. The coupling has a limited axial

displacement and therefore requires an axial bearing on either the

motor or gearbox side. The easy disassembly of the coupling spool

piece allows the first planetary stage to be displaced towards the motor

side for maintenance purposes, allowing the main motor to remain in

place during maintenance works. With this coupling the gearbox is

electrically insulated from the motor.

Lubrication System

The gearbox is lubricated by a closed circuit oil system which is ideally

located beneath the mill drive motor. The design of the lubricant

system is standardised thus it is applicable for several gear types. This

ensures an easy handling, optimal insertion and lower costs. Also the

components of the lubrication system as instrumentation, filter and

cooling/heating system are consistent. The oil system is monitored with

digital indication on site. Top priority is given to guarantee operational

reliability.

General bearing lubrication specification-:

Lubricating oil-: ISo VG-46

Oil flow-:12.0 lpm

Oil pressure-:0.2 bar

Air classifier {separator}

An air classifier is an industrial machine which sorts materials by a

combination of size, shape, and density. It works by injecting the

material stream to be sorted into a chamber which contains a column

of rising air. Inside the separation chamber, air drag on the objects

supplies an upward force which counteracts the force of gravity and

lifts the material to be sorted up into the air. Due to the dependence of

air drag on object size and shape, the objects in the moving air column

are sorted vertically and can be separated in this manner.

Air classifiers are commonly employed in industrial processes where a

large volume of mixed materials with differing physical characteristics

need to be sorted quickly and efficiently. One such example is

in recycling centers, where various types of metal, paper,

and plastics arrive mixed together and need to be sorted before further

processing can take place.

Types of dust collectors

Five principal types of industrial dust collectors are:

Inertial separators

Fabric filters

Wet scrubbers

Electrostatic precipitators

Unit collectors

Inertial separators

Inertial separators separate dust from gas streams using a combination of forces,

such as centrifugal, gravitational, and inertial. These forces move the dust to an

area where the forces exerted by the gas stream are minimal. The separated dust

is moved by gravity into a hopper, where it is temporarily stored.The three

primary types of inertial separators are:

Settling chambers

Baffle chambers

Centrifugal collectors

Neither settling chambers nor baffle chambers are commonly used in the minerals

processing industry. However, their principles of operation are often incorporated

into the design of more efficient dust collectors.

Settling chamber

A settling chamber consists of a large box installed in the ductwork. The sudden

expansion of size at the chamber reduces the speed of the dust-filled airstream

and heavier particles settle out.

Settling chambers are simple in design and can be manufactured from almost any

material. However, they are seldom used as primary dust collectors because of

their large space requirements and low efficiency. A practical use is as precleaners

for more efficient collectors.

Baffle chamber

Baffle chambers use a fixed baffle plate that causes the conveying gas stream to

make a sudden change of direction. Large-diameter particles do not follow the gas

stream but continue into a dead air space and settle. Baffle chambers are used as

precleaners

CYCLONE

Centrifugal collectors

Centrifugal collectors use cyclonic action to separate dust particles from the gas

stream. In a typical cyclone, the dust gas stream enters at an angle and is spun

rapidly. The centrifugal force created by the circular flow throws the dust particles

toward the wall of the cyclone. After striking the wall, these particles fall into a

hopper located undern eath

.

The most common types of centrifugal, or inertial, collectors in use today are:

Single-cyclone separators

They create a dual vortex to separate coarse from fine dust. The main vortex

spirals downward and carries most of the coarser dust particles. The inner vortex,

created near the bottom of the cyclone spirals upward and carries finer dust

particles,.

Multiple-cyclone separators

Also known as multiclones®, consist of a number of small-diameter cyclones,

operating in parallel and having a common gas inlet and outlet, as shown in the

figure. Multiclones® operate on the same principle as cyclones—creating a main

downward vortex and an ascending inner vortex

.

Multiclones® are more efficient than single cyclones because they are longer and

smaller in diameter. The longer length provides longer residence time while the

smaller diameter creates greater centrifugal force. These two factors result in

better separation of dust particulates. The pressure drop of multiclone® collectors

is higher than that of single-cyclone separators.

Babcock & Wilcox is the original manufacturer and trademark holder of

Multiclone® dust collectors and replacement parts formerly offered by Western

Precipitation. Multiclone® dust collectors are found in all types of power and

industrial applications, including pulp and paper plants, cement plants, steel mills,

petroleum coke plants, metallurgical plants, saw mills and other kinds of facilities

that process dust.

Secondary Air Flow Separators

This type of cyclone uses a secondary air flow, injected into the cyclone to

accomplish several things. The secondary air flow increases the speed of the

cyclonic action making the separator more efficient; it intercepts the particulate

before it reaches the interior walls of the unit; and it forces the separated

particulate toward the collection area. The secondary air flow protects the

separator from particulate abrasion and allows the separator to be installed

horizontally because gravity is not depended upon to move the separated

particulate downward.

BAG FILTER & BAGHOUSE

Fabric filters

Commonly known as baghouses, fabric collectors use filtration to separate dust

particulates from dusty gases. They are one of the most efficient and cost

effective types of dust collectors available and can achieve a collection efficiency

of more than 99% for very fine particulates.

Dust-laden gases enter the baghouse and pass through fabric bags that act as

filters. The bags can be of woven or felted cotton, synthetic, or glass-fiber

material in either a tube or envelope shape.

The high efficiency of these collectors is due to the dust cake formed on the

surfaces of the bags. The fabric primarily provides a surface on which dust

particulates collect through the following four mechanisms:

Inertial collection - Dust particles strike the fibers placed perpendicular to the

gas-flow direction instead of changing direction with the gas stream.

Interception - Particles that do not cross the fluid streamlines come in contact

with fibers because of the fiber size.

Brownian movement - Submicrometre particles are diffused, increasing the

probability of contact between the particles and collecting surfaces.

Electrostatic forces - The presence of an electrostatic charge on the particles

and the filter can increase dust capture.

A combination of these mechanisms results in formation of the dust cake on the

filter, which eventually increases the resistance to gas flow. The filter must be

cleaned periodically.

Types of baghouses

As classified by cleaning method, three common types of baghouses are:

Mechanical shaker

In mechanical-shaker baghouses, tubular filter bags are fastened onto a cell plate

at the bottom of the baghouse and suspended from horizontal beams at the top.

Dirty gas enters the bottom of the baghouse and passes through the filter, and

the dust collects on the inside surface of the bags.

Cleaning a mechanical-shaker baghouse is accomplished by shaking the top

horizontal bar from which the bags are suspended. Vibration produced by a

motor-driven shaft and cam creates waves in the bags to shake off the dust cake.

Shaker baghouses range in size from small, handshaker devices to large,

compartmentalized units. They can operate intermittently or continuously.

Intermittent units can be used when processes operate on a batch basis-when a

batch is completed, the baghouse can be cleaned. Continuous processes use

compartmentalized baghouses; when one compartment is being cleaned, the

airflow can be diverted to other compartments.

In shaker baghouses, there must be no positive pressure inside the bags during

the shake cycle. Pressures as low as 0.02 in. wg can interfere with cleaning.

The air to cloth ratio for shaker baghouses is relatively low, hence the space

requirements are quite high. However, because of the simplicity of design, they

are popular in the minerals processing industry.

Reverse air

In reverse-air baghouses, the bags are fastened onto a cell plate at the bottom of

the baghouse and suspended from an adjustable hanger frame at the top. Dirty

gas flow normally enters the baghouse and passes through the bag from the

inside, and the dust collects on the inside of the bags.

Reverse-air baghouses are compartmentalized to allow continuous operation.

Before a cleaning cycle begins, filtration is stopped in the compartment to be

cleaned. Bags are cleaned by injecting clean air into the dust collector in a reverse

direction, which pressurizes the compartment. The pressure makes the bags

collapse partially, causing the dust cake to crack and fall into the hopper below. At

the end of the cleaning cycle, reverse airflow is discontinued, and the

compartment is returned to the main stream.

The flow of the dirty gas helps maintain the shape of the bag. However, to

prevent total collapse and fabric chafing during the cleaning cycle, rigid rings are

sewn into the bags at intervals.

Space requirements for a reverse-air baghouse are comparable to those

of a shaker baghouse; however, maintenance needs are somewhat

greater.

Electrostatic precipitators (ESP)

Electrostatic precipitators use electrostatic forces to separate dust particles from

exhaust gases. A number of high-voltage, direct-current discharge electrodes are

placed between grounded collecting electrodes. The contaminated gases flow

through the passage formed by the discharge and collecting electrodes.

Electrostatic precipitators operate on the same principle as home "Ionic" air

purifiers.

The airborne particles receive a negative charge as they pass through the ionized

field between the electrodes. These charged particles are then attracted to a

grounded or positively charged electrode and adhere to it.

The collected material on the electrodes is removed by rapping or vibrating the

collecting electrodes either continuously or at a predetermined interval. Cleaning

a precipitator can usually be done without interrupting the airflow.

The four main components of all electrostatic precipitators are-

Power supply unit, to provide high-voltage DC power

Ionizing section, to impart a charge to particulates in the gas stream

A means of removing the collected particulates

A housing to enclose the precipitator zone

The following factors affect the efficiency of electrostatic precipitators:

Larger collection-surface areas and lower gas-flow rates increase efficiency

because of the increased time available for electrical activity to treat the dust

particles.

An increase in the dust-particle migration velocity to the collecting electrodes

increases efficiency. The migration velocity can be increased by-

Decreasing the gas viscosity

Increasing the gas temperature

Increasing the voltage field

Enexco is a pioneer in silo feeding, storage and extraction systems for

flat bottom as well as inverted cone silos. Enexco has to its credit the

expertise in designing and supplying various types of silos for indian as

well as overseas clients. We offer clients a wide range of machine that

meet the requirements of cement, flyash, opc & slag processing the

range offered by us include silo storage plants, mixers, solid flow

meters and others. Our process expertise also allow us to offer these in

other customized specifications as desired by the clients.

Enexco offers complete equipment required for the silo system

including open and closed airslide, manual & pneumatic cut off gate,

dosing valves, parallel distributors, adaptor box, bin weighing and

aeration system, solid flow feeders, control panels, piping etc.

Types of silos-

Rcc silos and steel silos

Inverted cone, normal cone and flat bottom silos

Continuous blending silo

Clinker silo with dustless extraction gates

Single compartments, ring and multi compartment silos for

storage of cement / flyash / ground slag

Advantages of storage silos-

High extraction efficiency (guarantee emptiness 99% in case of

inverted cone)

Low

References-