1

A MINI PROJECT ON

A STUDY OF HAMMER MILL DESIGN

In partial fulfillment of the requirements for the award of BACHELOR OF TECHNOLOGY

IN MECHANICAL ENGINEERING

Submitted by

N.BALAMURALI 08691A0303 S.HEMANTH KUMAR 08691A0308 S.MASTHAN 08691A0316 D.WILSON EMMANUEL 08691A0333

Under the guidance of

INTERNAL GUIDE J. CHANDRASHEKAR, Mr. Vamsi Krishna, M.E Production Manager Assistant Professor Coke oven Plant Dept. Mechanical Engineering LANCO Ltd.

DEPARTMENT OF MECHANICAL ENGINEERING

MADANAPALLE INSTITUTE OF TECHNOLOGY& SCIENCE

(AFFILIATED TO JNTU, ANANTAPUR)

P.B.No.14, Angallu, Madanapalle-517 325

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HAMMER MILL

PROJECT REPORT In partial fulfillment of the requirements for the award of

BACHELOR OF TECHNOLOGY IN

MECHANICAL ENGINEERING Submitted by

N.BALAMURALI 08691A0303 S.HEMANTH KUMAR 08691A0308 S.MASTHAN 08691A0316 D.WILSON EMMANUEL 08691A0333

Under the esteemed guidance of

Mr. Vamsi Krishna, M.E

Assistant Professor

DEPARTMENT OF MECHANICAL ENGINEERING

MADANAPALLE INSTITUTE OF TECHNOLOGY& SCIENCE

(AFFILIATED TO JNTU, ANANTAPUR)

P.B.No.14, Angallu, Madanapalle-517 325

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BONAFIDE CERTIFICATE This is to certify that the Project Report entitled “HAMMER MILL” is a benefited work done

N.BALAMURALI 08691A0303 S.HEMANTH KUMAR 08691A0308 S.MASTHAN 08691A0316 D.WILSON EMMANUEL 08691A0333 under the guidance and supervision, in partial fulfillment of the requirement for

the award of the degree of BACHELOR OF TECHNOLOGY in

Mechanical Engineering in Madanapalle Institute of Technology & Science,

Jawaharlal Nehru Technology University, during the academic year 2010. It is

also certified that any part of this project work was not submitted earlier to any

other University

Sri C.YUVARAJ Mr. Vamsi Krishna, M.E

Professor & Head of the Department, Assistant professor,

Mechanical department. Mechanical department.

Submitted for the University examination held on:

Examiner

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DECLARATION

We,

N.BALAMURALI 08691A0303 S.HEMANTH KUMAR 08691A0308 S.MASTHAN 08691A0316 D.WILSON EMMANUEL 08691A0333

Hereby declare that the Project Report entitled “HAMMER MILL’’ Done by us under

the guidance of Sri C.YUVARAJ Professor & head of the dept is submitted in partial

fulfillment of the requirements for the award of the degree of Bachelor of Technology in

Mechanical Engineering.

DATE: PROJECT ASSOCIATES

PLACE: Madanapalle

N.BALAMURALI

S.HEMANTH KUMAR

S.MASTHAN

D.WILSON EMMANUEL

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ABSTRACT

The study of project deals with the hammer mills employing a high speed rotating disc, to

which an ‘n’ number of hammer bars are fixed and swung outwards by centrifugal forces.

Material is fed in, either at the top or at the Centre, and it is thrown out centrifugally and crushed

between the hammer bars or against breaker plates fixed around the periphery of the cylindrical

casing.

For high production of crushed coal it is better to use the hammer mills having higher

contact surface of hammer. Hence, it is easy to produce the high rate of crushing coal with in less

time.

The purpose of the crushing is to produce the coal having size of less than 3mm (<3mm)

and the moisture content is 10-12% .The type of hammer mill used is a Reversible swing

hammer with open Bottom.

The project involves the changing of hammer head, which gives the better crushing of

coal. Therefore by changing the design of the Hammer head ,the following result is obtained

Aspects Before Design After Design

Crushing efficiency(<3mm) 81-84% 88-91%

Life time of Hammer head 10 Months 12 Months

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ACKNOWLEDGEMENT

We are greatly indebted to Sri Mr.M.Vamsi Krishna, M.E., Assistant Professor

Department of Mechanical Engineering, for his inspiring guidance, whole hearted support,

cooperation, encouragement, and readiness to spare his valuable time. His dynamic approach has

generated inspiration and confidence in us to carry out this investigation.

We are grateful to Dr.C.YUVARAJ, Professor & Head, Department of Mechanical

Engineering whose scholastic supervision this assignment has been successfully completed. We

acknowledge his unstinted help, many useful suggestions, constant encouragement and inspiring

guidance.

We extend our sincere thanks to our Principal Dr.K.Sreenivasa Reddy, for his moral

support.

We thank our faculty of the Mechanical Department for their constructive suggestion and

help whenever sought for.

Our sincere gratitude to our parents for their affection and continuous encouragement

without which we could not completed this work.

We also express our thanks to all those who have helped us either directly or indirectly in

completing this Project Work.

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LIST OF TABLES

Page No. Table 4.1 Lubrication chart for Hammer mill 23 Table 4.2 Lists of Essentials Spare Parts 24 Table 4.3 Application data of old hammer 30 Table 4.4 Application data of new hammer 31 Table 4.5 Product details of stepped taper Crusher Hammer 32 Table 4.6 Product details of taper Crusher Hammers 33

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LIST OF FIGURES

Page No. Fig 1.1 Anthracite coal 4 Fig 1.2 Raw coke 5 Fig 1.3 Plant Layout 8 Fig 1.4 Pictorial view of ovens 10 Fig 1.5 Pictorial view of pushing unit 10 Fig 1.6 Quenching unit 11 Fig 2.1 Crushing Process 12 Fig 3.1 Hammer mill 18 Fig 3.2 Screen degin 19 Fig 3.3 Arrangement of hammers 21 Fig 4.1 Hammer heads type-1 26 Fig 4.2 Hammer heads type-2 27

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CONTENTS S.No. Page. No. ABSTRACT i ACKNOWLEDGEMENT ii LIST OF TABLES iii LIST OF FIGURES iv

CHAPTER 1

1. Introduction to industry 1-11 1.1 Configuration &capacity of COP 1 1.2 Operation, process control and coke quality 2

1.2.1 Coal blend used 3 1.2.2 Coke quality 3 1.2.3 Different factors of coke availability 4

1.3 Introduction to coal 4 1.3.1 Composition 4 1.3.2 Coal content 5

1.4 Introduction to coke 5 1.4.1 Uses 6 1.4.2 Coke contents 6

1.5 Coal to coke conversion 6 1.5.1 Coal 6 1.5.2 Coke 6 1.5.3 Process involved in conversion of coal to coke 7 1.5.3.1 Heaps 7 1.5.3.2 Blending unit 7 1.5.3.3 Crushing unit 9 1.5.3.4 Stamping unit 9 1.5.3.5 Coke oven 9 1.5.3.6 Pushing unit 10 1.5.3.7 Quenching unit 10 1.5.3.8 Cutting unit 11

CHAPTER 2

2. Introduction to Hammer Mill 12-14 2.1 Hammer mill 12

2.1.1 Hammer mill features 12 2.2 Types of Hammer mill 13

2.2.1Super hammer mill 13 2.2.2 Grinder Hammer mill 13 2.2.3 Pilot Hammer mill 14 2.2.4 The Precious Hammer mill 14

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CHAPTER 3

3. Introduction to Grinder Hammer Mill 15-21

3.1. Description 15 3.2. Installation 16

3.2.1. Feed material 16 3.3. Operational introduction 16 3.4. Hammer mill design 17

3.4.1. Feeder design 18 3.4.2. Screen design 18

3.5. Hammer design of hammer mill 19 3.5.1. Calculations 20

3.6. Replacing wearing items 21

CHAPTER-4

4. Lubrication & maintenance of bearings 22-34 4.1. Hammer description 25 4.2. ISO 9001-2000 32

4.2.1. ISO certified for crusher hammer 32 4.2.2. ISO certified crusher parts Foundry crusher hammer Features 32 4.2.3. ISO certified crusher parts Foundry crusher

hammer Applications 32 4.3 Advantages 33

4.3.1 Crushing Action 34 4.3.2 Specification 34

4.4 Material used for preparation of hammer head 34 4.4.1 Cast iron 34 4.4.1.1 Composition 34 4.4.2 Hammer head material 34 4.4.2.1 Composition 34

CHAPTER-5

Theoretical Result & Conclusion 35 References 36

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Chapter - 1

1.Introduction to industry

Lanco Industries Limited is engaged in manufacturing of the ductile iron pipes

manufactured through a spinning process from 1999, with a capacity of 1,00,000TPY. To meet

the pipe plant requirement of hot metal Lanco operates a mini blast furnace with a capacity of

1,65,000TPY.

Previously, Lanco use to import coke from Japan and China to meet the requirement of

the mini blast furnace but then due to the steep rise in the coke prices in the international market

it was very difficult to maintain the cost of hat metal produced.

Thus it was decided to install a coke manufacturing facility to meet the in-house coke

requirements. The company was attracted by the low cost of the non-recovery type of coke ovens

with its easy compliance with the pollution control norms without any major investments. Now

the company operates a coke oven plant with a set of 68 ovens based on the Dasgupta

Technology. The plant was commissioned in May 2005 and is producing to the rated capacity of

1,25,000 Tons/year.

1.1 Configuration and capacity of Lanco's Coke Oven Plant

Lanco's plant at Srikalahasthi, AP consists of two batteries with 34 ovens each with a

level coal charge capacity of 14 tones and coking cycle of 48 Hours. The plant is producing to

the rated capacity of 1, 25,000 TPY

Each battery is connected to an independent stack. The flue gas will be tapped to the

waste heat recovery boilers just before the stack for steam generation for the 12MW captive

power plant. A comprehensive coal handling and blending plant with a coal tower of 200 MT

capacity, a quenching tower with wet quenching and a coke cutting and screening plant service

both the coke oven batteries. The plant is equipped with a coal charging car, hot coke quenching

car and a leveler cum pusher car.

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Four different types of coals can be blended together to get the desired coal properties in

charging coal. The blend is set considering high coke yield and the optimum coke quality. The

low sulphur content in the coal blend ensures the same in the coke also which makes it suitable

to be used for a mini blast furnace and also ensures low sulphur oxide emissions through the

stack exhaust. Complete combustion of the flue gases in the waste heat tunnels is maintained by

maintaining the draft and adequate supply of air in tunnels ensures no exhaust of carbon

monoxide and the presence of over 6% of oxygen in the stack exhaust. Particulate emission

through the stacks is also very less as all the combustible particulates are completely burnt in

waste heat tunnels. Thus the plant is operating satisfactorily under the operational regime that

can meet the norms of environmental legislation.

The combination of low capital cost and the low operational costs per ton of coke

produced and the excellent coke quality helps the company to maintain the cost of hot metal

under control.

Now the company is about to commission a 12MW captive power plant to meet the

power requirements of the total complex at Srikalahasthi comprising of a spun pipe plant, a mini

blast furnace, a coke oven plant and a cement plant based on the waste heat recovery of the coke

oven plant. This will also help to reduce further the cost of the ton of coke produced by about

Rs.2000/-. There are plans to increase the plant capacity by 50% with the proposed installation of

additional 34 ovens.

Now the company is setting up a stamp charging facility from SSIT, China which will

increase the throughput of the plant and allow the usage of more inferior coals in the blend for

the same quality of coke produced presently and in turn will lower the cost of coke produced.

1.2 Operation, Process Control and Coke Quality

At present the plant is operated by top charging. The coal is charged by gravity through

the charging ports in the hot oven chamber after the pushing of previous cycle coke bed with the

help of coal charging car. The charging car discharges the predetermined quantities of coal from

the four canisters in the sequence to facilitate uniform leveling and achieve optimum bulk

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density inside the oven. The coal is than leveled to a flat profile inside the oven with the help of a

leveler which ensures optimum coking of the total coal charge within a cycle of 48 hrs. This also

restricts the burning losses to the maximum of 2%

1.2.1 Coal Blend Used

The blending of different types of coals is heart of the coke oven plant as the coke quality

primarily depends on the qualities of the blended coal. Lanco procures coal keeping in view the

desired quality of the blended coal. A typical blend is developed with the with the quality as

mentioned below:

Moisture : 7%

Volatile matter : 22-23%

Ash : 8-9%

Fixed carbon : 68-69%

Phosphorous : 0.04%

Silica : 0.5%

CSN : 6-7

BD : 0.77

Size (below 3mm) : 85%

Reflectance : 1.15

1.2.2 Coke Quality:

Due to the high coking temperatures (1200-1250°c), the coking cycle time and the draft regime in the coke oven process the quality of the coke produced in the plant is very good compared to the coke produced in the conventional byproduct type coke ovens using the same quality coal blend. The usage of this coke in the Lanco's mini blast furnace has resulted in lower coke rates, higher productivity and better quality of hot metal than those achieved in the same furnace using good quality Japanese and Chinese Cokes.

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1.2.3 Different Fractions of Coke Available

Lanco's coke oven plant is equipped with a comprehensive coke cutting and screening plant which can give different sizes of coke as per requirement of the customers. The sizes can be made available are as mentioned below:

Foundry coke : +70mm

BF coke : +20-60mm

Nut coke : +10-25mm

Pearl coke : +8-15mm

Coke breeze : +0-8mm

1.3 Introduction to Coal

Fig 1.1 Anthracite coal

1.3.1 Composition

Primary : Carbon

Secondary : Sulfur

Hydrogen

Oxygen

Nitrogen

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Coal is a combustible black or brownish-black sedimentary rock normally occurring in rock

strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite

coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and

pressure. Coal is composed primarily of carbon along with variable quantities of other elements,

chiefly hydrogen, with smaller quantities of sulfur, oxygen and nitrogen.

1.3.2 Coal content;

Moisture : 7%

Volatile matter : 22-23%

Ash : 8-9%

Fixed carbon : 68-69%

1.4 Introduction to Coke

Coke is the solid carbonaceous material derived from destructive distillation of low-ash,

low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be

formed naturally, the commonly used form is man-made.

Fig 1.2 Raw coke

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1.4.1 Uses

Coke is used as a fuel and as a reducing agent in meltingiron ore in a blast furnace. It is

there to reduce the iron oxide (hematite) in order to collect iron.

Since smoke-producing constituents are driven off during the coking of coal, coke

forms a desirable fuel for stoves and furnaces in which conditions are not suitable for the

complete burning of bituminous coal itself. Coke may be burned with little or no smoke

under combustion conditions, while bituminous coal would produce much smoke.

1.4.2 Coke content

Moisture : 8% Volatile matter : 22-23% Ash : 8-9% Fixed carbon : 83-86%

1.5 Coal to Coke Conversion

1.5.1 Coal

Coal is solid and usually black in color but sometimes brown. It is formed by carbon-rich

material that occurs in stratified sedimentary deposits. It is one of the most important fossil fuels,

it is found in many parts of the world. Coal is formed by heat and pressure over millions of years

on vegetation deposited in ancient shallow swamps. It varies in density, porosity, hardness, and

reflectivity. The major types are Lignite, Sub bituminous, Bituminous, and Anthracite. Coal has

long been used as fuel, for power generation, for the production of coke, and as a source of

various compounds used in synthesizing dyes, solvents, and drugs. The search for alternative

energy sources has periodically revived interest in the conversion of coal into liquid fuels;

technologies for coal liquefaction have been known since early in the 20th century. For the

production of coke, Cole is mainly imported from Australia.

1.5.2 Coke

Solid residue remaining after certain types of coals are heated to a high temperature out

of contact with air until substantially all components that easily vaporize have been driven off.

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The residue is chiefly carbon, with minor amounts of hydrogen, nitrogen, sulphur, and

oxygen. Also present in coke is the mineral matter in the original coal, chemically altered and

decomposed. The gradual exhaustion of timber in England had led first to prohibitions on cutting

of wood for charcoal and eventually to the introduction of coke. Thereafter the iron industry

expanded rapidly and Britain became the world's greatest iron producer. The crucible process

(1740) resulted in the first reliable steel made by a melting process. Oven coke (about 1.5–4 in.,

or 40–100 mm, in size) is used in blast furnaces to make iron. Smaller quantities of coke are used

in other metallurgical processes, such as the manufacture of certain alloys. Large, strong coke,

known as foundry coke, is used in melting. Smaller sizes of coke (0.6–1.2 in., or 15–30 mm) are

used to heat buildings.

1.5.3 Process involved in conversion of Coal to Coke is as follows

1.5.3.1 Heaps

Coal is imported from different parts of the world mainly from Australia. This Coal is imparted

by means of ships and from there by trains and trucks to the industries. It is dumped in the form

of HEAPS (small hill). Heaps covered with the help of covers in order to avoid the wash away of

minerals due to rain or wind or other natural calamities. Different types of Coals are dumped in

different places. Coal is dumped in the form of heaps in order to preserve their properties. In case

of rainy season, small paths are made through heaps in order to let the water go out. These Heaps

are made with the help of prolongers, JCB and tippers

1.5.3.2 Blending Unit

Blending is nothing but mixing. Different type’s coals are carried from the heaps and are spread

in the form of a thin layer one over the other. During this time, a little amount of mixing is done.

Tractors which consist of blending rollers are made to run over the coal which is spread in the

form of layers. These blending rollers which are connected to the tractors are fixed with some

angle of inclination. Due to this, the blending of coal is done up to 99%. This Coal is carried out

with the trucks and is dumped into the bunkers. The bunkers consist of vibrators which makes

the bunker to vibrate. Due to this vibration, the mixture of coal is spread over the conveyor belts.

These belts are made up of rubber. These belts carry the coal to the crushers from the blending

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Fig 1.3 Plant Layout

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unit. In between, some water is sprinkled over the coal in order to maintain 9 to 10% of moisture

in the coal and any impurities like plastic covers, wood etc. are removed manually.

.

1.5.3.3 Crushing Unit

The following step after blending is crushing. The coal is carried out with the help of

belts to the crushing unit. A big magnetic block is fixed at the entrance of the crushing unit. This

magnet separates the iron particles present in the coal. This coal is dropped into the bunkers

present over the crushers. A reversible belt conveyer is present which helps to drop the coal in

both the bunkers. The coal is crushed in to a size of -0.3 to 0.5% with the help of hammers

present in the crushing unit. This finely crushed powder is again sent to the big bunkers present

in the stamping unit with the help of belts over a very long distance at a very big height. Here

again with the help of reversible conveyer belts, the powder is filled into the bunkers.

1.5.3.4 Stamping Unit

Stamping unit consists of two bunkers which is used to store the powdered coal. The

upper part of the stamping unit is movable and the bed is constant. Sensors are fixed on the bed

which is used to show the position where the stamping has to be done. This unit is

preprogrammed and then constructed to work automatically with the help of the sensors. It

consists of 2 hydraulic pressers whose pressures are (150 bars). Stamping car is placed in front

of the stamping unit and a plate or sheet of length (1100 meters) is inserted into the bed. The coal

is spread over the bed like a layer and stamping is done. This process is repeated for three layers.

The coal is pressed and made into a form of a cake. This cake is carried out with the help of

stamping car and is inserted into the oven.

1.5.3.5 Coke Oven

Ovens are constructed with the bricks made of Aluminum, Silica and Lime. These bricks

are very strong in nature and can withstand high temperatures i.e. (12000 c).

The Picture of oven is as shown below

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Fig 1.4 pictorial view of ovens

These ovens consist of two iron doors, one in the front side and the other in the rear side. The Cake is fed into the oven from the front and it is pushed to the rear side for quenching. Two holes are provided for both the doors for the inlet of Oxygen into the oven which helps for combustion. The cake when kept in the oven takes 8hrs to convert into coke. The same temperature is maintained in the oven all through. 1.5.3.6 Pushing Unit

Pushing is done after the coke get ready. Here pushing car is used in this process. It consists of a ram which is used to push the hot red coke from the front end to the rear end. The pushing unit is as shown below.

Fig1.5 Pictorial view of pushing unit

The coke is directly pushed from the oven into the Quenching car which is placed in the rear side of the oven. 1.5.3.7 Quenching Unit

Quenching means rapid cooling, it is done as by immersion in oil or water, of a metal object from the high temperature at which it is shaped.

Quenching is usually done to maintain mechanical properties that would be lost with slow

cooling. It is commonly applied to steel objects, to which it gives hardness. The quenching media

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and the type of agitation during quenching are selected to obtain specified physical properties

with minimum internal stresses and distortions. Oil is the mildest medium, and salt brine has the

strongest quenching effect. In special cases, steel is cooled and held for some time in a molten

salt bath, which is kept at a temperature either just above or just below the temperature where

martensitic begins to form. These two heat treatments, called mass tempering and ash tempering,

both result in even less distortion of the metal. Copper objects hardened by hammering or other

deformation at ordinary temperatures can be restored to malleability by heating and quenching.

Fig 1.6 Quenching unit

1.5.3.8 Cutting Unit

After quenching, the coke is pushed into a funnel like bunker which is below the

ground level and from there the pieces of coke is carried to the cutting with the help of belts. The

size of the coke when taken out from the oven will not be uniform. So as per the requirement of

the purchasers, the coke is cut into the required size with the help of the cutters. After the cutting

is completed, the coke with size smaller than required is separated and again dumped in the form

of heaps. From there it is sent to the industries with the help of tippers.

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Chapter - 2

2.Introduction to Hammer Mill

2.1 Hammer Mill

The hammer mill is an impact mill employing a high speed rotating disc, to which are fixed a number of hammer bars which are swung outwards by centrifugal force. Material is fed in, either at the top or at the Centre, and it is thrown out centrifugally and crushed by being beaten between the hammer bars, or against breaker plates fixed around the periphery of the cylindrical casing.

Fig 2.1 Crushing Process

The hammer mill crushes by the collisions between high-speed hammer and material, and the hammer crusher features in its simple structure, high reduction ration, high efficiency, etc. The PC hammer crush (hammer mill) was developed for both dry and wet crushing of brittle, medium-hard materials for the mining, cement, coal, metallurgic, construction material, road building, and petroleum & chemical industries.

2.1.1 Hammer Mill Features

Ø Material is reduced by impact from free-swinging bar hammers.

Ø Finished Product size controlled by grates or screen sizes.

Ø Materials can be reduced to granular powder at high rate.

Ø Heavy-duty cast-iron or carbon steel construction.

Ø Right-hand or left-hand machine available.

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Ø Easy access for maintenance and screen/grate change.

Ø High and constant capacity

Ø High availability

Ø Long life time

Ø High reduction ratio

Ø Broad range of application

Ø Easy replacement of wear and spare parts

2.2 The Types of Hammer Mill

ü Super Hammer Mill ü Grinder-hammer Mill ü Pilot Hammer Mill ü The Precious Hammer Mills

2.2.1 Super hammer Mill

Mill Powder Tech Co. offers super hammer mills that are pulverizes with easily changeable fineness by change of screen from 100 meshes [150 micron] to 10 mm. The super hammer mills come with or without cyclone & dust collector system. The company also supplies super hammer mills placed on arm pads without foundation. The super hammer mills are useful for different chemicals, minerals, pigments, coal, agricultural products like gram, maize, rice husk, saw dust, Ayurveda herbs etc.

2.2.2 Grinder-hammer Mill

Hard case engineering works Mill Powder Tech Co., Ltd. Manufactures grinder-hammer mills useful for reducing the particle sizes of grinding. The company is a provider of feed milling plants and equipment and fodder processing machines. The hammer mills are also suitable as swinging hammers type. The company supplies different types of hammer mills such as full screen hammer mills having largest possible screen area and both directions rotation and lower end models for standard broiler feed formulation on 8mm dia hole screen and material and hole diameter of screen features. The hammer mills from the company are available with salient features like

Ø Best possible power to output ratio. Ø Vibration free operation Ø Long life. Ø Easy change of screen & hammers.

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2.2.3 Pilot Hammer Mill

Size reduction equipment designed to achieve perfection in pulverizing and minimize

power consumption, labor and maintenance. The materials to be ground enter the crushing

chamber from feed hopper by gravity or through an auto feeder. The beaters inside the drum

accelerate the material to a very high speed to the toothed liner placed at the upper half of the

crushing chamber. The material is pulverized by impact and shearing is continuously sucked by a

centrifugal blower through screens placed at the bottom periphery of the crushing chamber and is

conveyed through a pipe into the cyclone dust collector for bagging. Excess air is filtered

through a cotton balloon. Particle size can be varied using screens with different whole size.

2.2.4 The Precious Hammer Mills

The precious hammer mills produced by Mill Powder Tech Co., Ltd. are the durable

utility grinders that are capable of drudging most free-flowing materials. The precious hammer

mill is projected for fine smashing of soft up till medium hard, non-harsh and non-adhesive

materials, such as bituminous coal, limestone etc. Materials that have been grind with the

precious hammer mills include: charcoal, chemicals, clay, coal, and limestone. The salient

features of the precious hammer mill are, Basic arrangement with the closed milling path is used

especially for crushing limestone for sintering purpose and for grinding similar types of material.

Fineness of the outlet product thus obtained is of 3 mm with grate slots of 10 mm.

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3.Chapter - 3

Introduction to Grinder-Hammer Mills

3.1 Description

With uniform feed across the width of the rotor, material gets crushed between the high

speed, swinging arms and tips and the grinding walls to the desired fineness. The direction of

rotation is reversible to take care of uniform wear on tips and grinding wall. The either direction

of rotation of rotor can achieve by the motor starter.

The hammer mill consists of lower housing bolted to detachable upper housing with

grinding walls (grinding glib) on either side or rotor with swinging hammer arms and tips.

The housing consists of welded fabricated structure with replaceable liners on both sides

of upper and lower housing. On the side of lower housing 2 Nos. of hanger’s are provided for

upper housing.

The upper housing is in two pieces, separated through center line. The upper protection

is connected to feed chute through inclined flange. Fabricated grinding wall bracket carries high

wear resistant alloy steel liners (grinding, glib).bolted through liner’s nib bolts. Grinding wall

can be adjusted at top as well as at the bottom through threaded spindle.

Rotor consists of forged steel shaft with rotor discs mounted by parallel key. The arms

are suspended freely on the rotor disc by mans of rotor pin. For smooth running, the arm and tips

which are placed two or three or four in rows between the discs should be of same weight. The

tips of same weight per row are marked. The rotor shaft runs in large spherical roller bearing in

study housing, sealed by lubricant filled with grease.

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3.2 Installation

For assembly the hammer mill can be split into three pieces

Ø Upper Housing split- up in 2 halves with grinding wall, side liners

Ø Rotor with hammer arms and tips along with bearing blocks and pulley

Ø Lower housing with bearing supporting platform and hinged bracket (for open /close the

upper housing )

First place, the lower house on foundation structure and anchored after proper leveling. In

case of RCC foundation place hammer mill on prepared bed. Screw jacks may be used to lift and

lower the hammer mill during leveling. Check by the sprit level and finally grout the foundation

bolts. Maintain the opening in foundation bed.

Secondary rotor with bearing blocks to be assembled. After perfect leveling of rotor

assembly; the bearing blocks are to be dowelled and bolted. Now assemble both halves of upper

housing with lower housing through hinge pins and bolting. But ensure that the hammers on

hammer arms do not touch grinding wall or side walls during rotation of hammers

3.2.1 Feed Material

Hard coal and lignite in coal processing plants, coking coal for the iron and steel industry,

limestone and gypsum rock or other related soft to medium-hard minerals as well as various

types of salts

3.3. Operational Instruction

Ø All bolts of hammer mill and drive are to be checked and tightened if loose.

Ø The adjustment is important for product size control. It consists of 2 types of gap

adjustments.

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First the upper gap adjustment can be done by the movement of hinge pin. The hinge pin

supports the grinding jib bracket on sliding blocks on either side of the machine. The position of

sliding blocks on guide way under normal operation is at the Centre of guide way, which is set

our works. By screwing in the grinding wall position itself close to rotor tips, opposite takes

place when screwing out. The gap can be inspecting by inspection windows in upper housing.

The bottom adjustment is by means of threaded spindle and nut. The spindle is mounted

through steady nut which is housed in hinge housing. Equal movement of spindle can achieve by

rotate both nut simultaneously through chain sprocket or individually for initial adjustment. After

maintain desired gap between rotor tips and grinding wall fix up the spindle position by lock nut.

When the rotor comes to full speed, adjust the grinding wall slowly and carefully till a

scarping noise is just start due to tip touching the wall. But the spindle are to be retracted till

require gap. The gap can be check through inspection windows in lower housing.

Product fines are achieved with the grind wall close to the running hammer tips at the

bottom and wider at the top. Before starting the mill ensure that mill is free from any foreign

material or feed material. Feeding can start when the rotor has reached its full speed and is

running smoothly. The fee should be take place across the full width of the rotor. The feed

material should be free from tramp iron or uncrushable material. Hammer mill should run

smoothly without vibration and noise. In case of any sudden noise, it indicates presence of a

large size of foreign material or tramp iron. DO NOT continue to run with this noise as it will

damage the mill. Hammer mill is to be brought to rest and cleaned. In case the mill is to be re-

examined after completely stopping. Damaged parts are to be changed immediately

3.4 Hammer Mill Design

A delivery device is used to introduce the material to be ground into the path of the

hammers. A rotor comprised of a series of machined disks mounted on the horizontal shaft

performs this task. - Free-swinging hammer that is suspended from rods running parallel to the

shaft and through the rotor disks. The hammer carries out the function of smashing the

ingredients in order to reduce their particle size. - a perforated screen and either gravity- or air-

assisted removal of ground product. Acts to screen the particle size of the hammer mill to ensure

particles meet a specified maximum mesh size.

28

Fig 3.1 Hammer mill

3.4.1 Feeder Design

Materials are introduced into the paths of the hammers by a variable speed vein feeder.

This type of feeder can have its motor slaved by a programmable controller to the main drive

motor of the hammer mill. The operational speed of the feeder is controlled to maintain optimum

amperage loading of the main motor.

3.4.2 Screen Design

The amount of open area in hammer mills screen determines the particle size and

grinding efficiency. The screen must be designed to maintain its integrity and provide the

greatest amount of open area. Screen openings (holes) that are aligned in a 60-degree staggered

pattern optimize open area while maintaining screen strength. This method will result in a 40

percent open area using 3.2 mm (1/8 inch) holes aligned on 4.8 mm (3/16 inch) centres.

29

Fig 3.2 Screen degin

Feed producers need to pay particular attention to the ratio of open screen area to

horsepower. Recommended ratio for grains would be 55 cm2 (~ 8-9 inches square) per

horsepower (Bliss, 1990). Not enough open area per horsepower results in the generation of heat.

When the heat generated exceeds 44C to 46C (120-125F), capacity may be decreased as much as

50 percent.

The removal of sized material from hammer mill is a critical design feature. Proper output of

material affects not only the efficiency of operation, but also particle size. When the correct ratio

of screen area to horsepower is used and proper distance between hammers and screen face is

maintained, most of the correctly sized particles will exit the screen in a timely manner.

Anderson (1994) stated the particles that do not pass through the screen holes become part of a

fluidized bed of material swept along the face of the screen by the high-speed rotation of the

hammers. As these particles rub against the screen and each other their size is continually

reduced by attrition. This excessive size reduction is counterproductive. Energy is wasted in the

production of heat, throughput is restricted, and particles become too small.

3.5 Hammer Design

Hammer is used inside the hammer mill to impact smash ingredients up into smaller

particles, making it more suitable for uniform mixing and usage in feed. Hammer is available in

a huge range of configurations, shapes, facings and materials. Hammer is available as single

holed or with two holes, with two holes allowing the hammer to be used twice as the wear is

30

done to one end of the hammer; the hammers can be rotated and used a second time. The hole

fits onto a rod inside the hammer mill and swings to hit the material.

The hammer design of hammer mill is determined by operating parameters such as rotor

speed, motor horsepower, and open area in the screen. Optimal hammer design and placement

will provide maximum contact with the feed ingredient. Hammer mill in which the rotor speed is

approximately 1,800 rpm, should be using hammers which are around 25cm (~ 10 inches) long,

6.35cm (~2.5 inches) wide, and 6.4mm (0.25 inches) thick. For a rotor speed of about 3,600 rpm,

hammers should be 15 to 20 cm (~ 6-8 inches long, 5 cm (~ 2 inches) wide, and 6.4 mm (0.25

inches) thick.

The number of hammers used for hammer mill of 1,800 rpm, should be 1 for every 2.5 to

3.5 horsepower, and for 3,600 rpm, one for every 1 to 2 horsepower. Hammers should be

balanced and arranged on the rods so that they do not trail one another. The distance between

hammer and screen should be 12 to 14 mm (~ 1/2 inch) for size reduction of cereal grains.

The velocity or tip speed of the hammers is critical for proper size reduction. Tip speed is

the speed of the hammer at its tip or edge furthest away from the rotor, and is calculated by

multiplying the rotational speed of the drive source (shaft rpm) by the circumference of the

hammer tip arc. See the following formula:

3.5.1 Calculations

Feed per minute= (π D×RPM) ÷12 in V ft.

D=Diameter in inches

RPM=Revolutions per minute

π =3.14

31

Fig 3.3 Arrangement of hammers

A common range of tip speeds seen in hammer mill is commonly in the range between

5,000 and 7,000 m/min (~ 16,000 and 23,000 feet per minute). When the tip speeds exceed

23,000 feet per minute, careful consideration must be given to the design of the hammer mills,

the materials used in its construction, and the fabrication of all the components. Simply changing

the rotational speed of the drive source is not a recommended method of increasing hammer

speed in excess of 23,000 feet per minute. Impact is the primary force used in hammer mills.

Anything which increases the chance of a collision between a hammer and a target;

increases the magnitude of the collision; or improves material take-away provides an advantage

in particle size reduction. The magnitude of the collisions can be escalated by increasing the

speed of the hammers.

3.6 Replacing wearing items

• Upper housing

• Takeout the bolts of joining the feed chute and upper housing

• Takeout Bolts of two halves of upper housing and joining of upper and lower housing.

Also detach the felt sealing ring from upper housing.

• Now these two halves of upper housing can be tilted by means of hinge bracket. During

replacing the parts these halves are to be supported by probes. In this position the

grinding glib plates and liners can be replaced.

32

Chapter - 4

4. Lubrication & Maintenance of Bearings

Refer drawing for bearing assembly and strictly follows the instruction as per lubrication

schedule. This is to be strictly followed. Bearing blocks are filled with grease at our works to last

for nearly 4 weeks. However, check grease before commissioning the hammer mill. In case the

machine was idle for a long time back the bearing for any rust formation and take necessary

action to remove it. Labyrinth alloys are to be full of grease all the time. While greasing, it is

necessary to rotate the shaft so that grease gets filled up all over the periphery.

Very six months labyrinth alloys are to be washed from old grease and filled with fresh

grease. To do thus, open the covers and clean with petrol or kerosene.

Every two years of operation the bearings blocks are to be dismantled. All parts and

bearings thoroughly cleaned and checked. Reassemble with fresh grease. Too much grease heats

up the bearing while running. During initial period check the quantity by opening the covers. Do

not wipe-off grease from nipple after greasing cycle is over. Wipe grease nipple clean before

greasing. Depending upon local condition the greasing schedule may have to be revised in

consultation with service engineer’s from bearing manufacturer.

The upper hinge point of grinding wall brackets is to be cleaned and greased every 12

months.

33

Table 4.1 Lubrication chart for Hammer mill

Lubrication

points

Types of

lubrication

Frequency

of

lubrication

Lubricant

properties

Lubricant

making

First

filling

Qty.

during

running

HP

Indian

oil

Bearing

blocks on

rotor shaft

with

labyrinth

points

Manual

grease gun

200 hrs.

Lithium

based

bearing

grease

violet

1450

Grms

250 Grms

Liti

on-

3

Servo-

gem-3

Bearing

blocks on

counter shaft

with

labyrinth

points

-Do-

-Do-

-Do-

-Do-

800 Grms

200 Grms

-

Do-

-Do-

Upper sliding

block of

grinding gib

Manual

brush

Every 4

weeks

-D0-

-Do-

As

required

As

required

-

Do-

-Do-

3 k k

34

s.no Description quantity

1 Hammer 60

2 Hammer arm 60

3 Grinding Gib (straight) 4

4 Grinding Gib (curve) 12

5 Rotor pin 1 set

6 Spring dowel sleeve 60

7 Spring dowel sleeve 60

8 Spring dowel bush 60

9 Rotor shaft 1

10 End disc no.1 (Free brg.side) 1

11 Middle disc 14

12 Spring clip 24

13 End disc no .2 (fixed brg side) 1

14 Lock nut 4

15 Lock washer 4

16 Felt seal 4

17 Brg block assembly.(Fix + Free) Without bing 1+1

18 Brg block assembly .(fix + free) Witho earing 1+1

19 Spherical roller bearing with adopter 2

Sleeve

20 Spherical roller bearing with adopter Sleeve 2

21 Liners for housing 1 seet

22 Vee belt (matched set ) 8

23 Nib bolt M 16 * 60 Lg. with nylock 240

Nut and plain washer

24 Nib bolt M 30 * 100 Lg. with plain washer, 64

Hex lock nut & hex nut

25 Motor pulley 375 PCD, 8-SPC with taper 1

Lock bush

Table 4.2 Lists Of Essentials Spare Parts

35

4.1 Hammers description

Conventional bar hammers also become less efficient and effective as they wear, since

the initially-square edges become rounded. This reduced effectiveness also increases the

tendency of the hammers to lay back, thus further reducing efficiency. The hammers must

therefore be replaced more frequently than is desirable, in order to maintain optimum efficiency

and effectiveness.

In the invention, fewer hammers are employed these hammers are uniquely configured in

order to provide optimum performance both initially and throughout their useful life.

Two primary embodiments are described herein, although many other variations are

possible within the scope of the invention. In each embodiment, multiple impact points are

provided by tips at different radii from the axis of rotation of the hammer mill, and the tips

preferably are at substantially the same radius from the axis of rotation of the hammer about the

hammer support shaft, so that efficiency is maintained even as the hammers lay back, as will be

explained later herein. The multiple impact points produce a more effective result, by partially

sizing the debris on initial impact, before more precise final sizing in the grinding chamber.

Angled surfaces on the hammer tips provide more effective shearing and tearing action than with

conventional bar hammers. Wear patterns are such that grinding efficiency as the hammers wears

down is maintained throughout the life of the replaceable tips.

Preferably, but not essentially, the hammers weigh substantially more than conventional

hammers, to provide a higher energy impact, and to reduce the tendency of the hammers to lay

back.

Additional features of the invention will be described or will become apparent in the

course of the following detailed description.

Hammer mill generally has three more or less circular steel disks 32. A shaft mounted

on bearings of the frame of a grinder (not shown), extends through the center of disks. During

the operation of the grinder, shaft is rotated at approximately 1100R.p.m. more or less, by a

36

motor (not shown). A positive engagement between shaft and disks results in those disks rotating

together at that same angular speed.

The hammer mill may be built to carry any desired number of hammers. Several examples are

illustrated, namely the versions in fig-6. Hammers are generally arranged in pairs. Each pair of

hammers is mounted in tandem on the hammer mill, although it should be clear that a mill could

be constructed with only a single hammer at each location, or with three or more hammers at

each location, depending on the desired width of the mill.

Fig-4.1 Hammer heads type-1

Hammer mill shown in fig-6 has four 60 hammers arranged around the shaft. Each

periphery contains 12 hammers in 5 series depending on the number of hammer support shafts or

hammers in the assembly.

37

Fig 4.2Hammer heads type-2

Two types of hammers are described as examples of the invention. The first type is shown

in fig 4.1and fig 4.2. Both types preferably but not necessarily use the same shank member.

Shank member has a central bore through which passes one of the hammer support shafts.

Although it is convenient from a manufacturing cost viewpoint to use the same shank for

each type of hammer, it is not essential that the shanks be identical nor that there is a separate

shank member at all. The hammers could be constructed with different shanks, or in one piece if

desired, and with or without replaceable wear components. The invention is not intended to be

limited to embodiments having a common shank, even though that may be preferable.

The shank, as seen best in fig 4.1and fig 4.2.has a tongue for engaging the remaining

portion of each hammer, as will be subsequently described. The side opposite the one side has a

well with corrugated walls for accepting molten lead. This permits the weight of shank members

to be maintained to within 1 gram of each other by using molten lead, that tolerance being

important for maintaining optimum hammer mill balance.

Hammers in the present invention preferably weigh in the range 8to 9 kilograms in

comparison with a prior art bar hammer weighing typically

about7kgs. Lighter hammers embodying the features of the invention could be used, and are

contemplated as being within the scope of the invention, although the results may not be as

38

impressive. Approximately 80 percent of the mass of the hammer is outside the radius of the

hammer support shaft, and the center of gravity of the overall hammer is on the center lines

shown in fig 4.2

The second type of hammer preferably uses the same shank member as the first type of

hammer, although as mentioned above, it could instead be produced as one piece. However, the

tip portion does not have replaceable tips as in the first type of hammer, but instead has three

integral "claws", split in the middle to provide six integral tips.. The shape of the claws and tips

is designed to rip into tree stumps and the like, the rake angle of approximately 15 degrees at the

tips produced combined shearing and tearing action for greater efficiency. The tips of this type of

hammer are configured to withstand heavier use than the tips of the first type, are capable of

tearing through a broader range of materials, and are not as subject to breakage when

encountering contamination such as rocks, steel, etc.

39

40

Material to be crushed : Coal Bulk density : 1.1 T/Cu.m . Moisture content of feed material : 10 – 12% (upto 20% during rainy season ) Feed size : 0 – 100 mm (0 to 50 mm with occasionally

Coming upto 100 mm max.) Product size : - 3 mm (81 -84% ) Capacity (throughput) : 75 TPH TECHNICAL DATA TYPE : Reversible swing hammer with open

Bottom Size : 1212/12 Rotor diameter : 1200 mm Rotor width : 1200 mm No. of Hammers : 60 Speed : 40 M/Sec.(645 RPM) Approx. @ 960 RPM

60 M/sec (965 RPM) Approx. @ 1440 RPM Drive : Through ‘V’ belt & Gear coupling Motor recommended : 160 KW (215 HP)/ 1485 RPM with A.C.

Variable frequency drive for soft start and Variable speed.

V- belt : 106 SC06300 (spec) matched set for 8 nos. Motor pulley : 375 mm PCD -8 groove SPC with taper lock

Bush no. 5050

Machine pulley : 560 mm PCD- 8 groove SPC with taper lock Bush no.5050

Fly wheel : 570 dia with taper lock bush no.5050

Gear coupling : 105-HI-Cliff

Gross weight : 12.0 tones (approx.)

Table 4.3 Application data of old hammer

41

Material to be crushed : Coal Bulk density : 1.1 T/Cu.m . Moisture content of feed material : 10 – 12% (up to 20% during rainy season )

Feed size : 0 – 100 mm (0 to 50 mm with occasionally Coming up to 100 mm max.)

Product size : - 3 mm (88 -92% ) Capacity (throughput) : 75 TPH TECHNICAL DATA TYPE : Reversible swing hammer with open

Bottom Size : 1212/12 Rotor diameter : 1200 mm Rotor width : 1200 mm No. of Hammers : 60 Speed : 40 M/Sec.(645 RPM) Approx. @ 960 RPM

60 M/sec (965 RPM) Approx. @ 1440 RPM

Drive : Through ‘V’ belt & Gear coupling Motor recommended : 160 KW (215 HP)/ 1485 RPM with A.C.

Variable frequency drive for soft start and Variable speed.

Vee belt : 106 SC06300 (spec) matched set for 8 nos. Motor pulley : 375 mm PCD -8 groove SPC with taper lock

Bush no. 5050

Machine pulley : 560 mm PCD- 8 groove SPC with taper lock Bush no.5050

Fly wheel : 570 dia with taper lock bush no.5050

Gear coupling : 105-HI-Cliff

Gross weight : 12.0 tones (approx.)

Table 4.4 Application data of new hammer

42

4.2 ISO9001-2000 4.2.1 ISO Certificated for Crusher Hammer:

Crusher hammers are highly wear-resistant parts. DSMAC manufactures this type of crusher hammers with external refining and pressure casting technologies. Manganese steel is purer and the matrix is more compact. This crusher hammers have a service life longer than those made of common steel and is safer to use.

4.2.2 ISO Certificated Crusher Parts Foundry Crusher Hammer Feature

• Crusher hammers casted the Tungsten Titanium alloy in the high-manganese steel substrate, It may resist the severe grinding abrasion.

• Crusher hammers service life has been enhanced by 50% compared to the ordinary steel! • Compared to the similar products, crusher hammers have the advantage strong wear

resistance and low price. 4.2.3 ISO Certificated Crusher Parts Foundry Crusher Hammer Application

Ø 1. DSMAC manufactures this type of Crusher Hammers with external refining and pressure casting technologies.

Ø Crusher hammers aim at the crushing of limestone with abnormal content of SiO2. Ø Crusher Hammers can be used in hard condition of serious abrasion.

Standard: ISO9001: 2008 Machine Type Crusher Deformation Temperature Casting Molding Techniques Pressure Casting Model Number Crusher Spare Parts Material High Nickel Cast Iron Model NO Wear Resistant Parts high nickel hammers Molding Style Stepped tapered bar Life time 10 Months Trademark DSMAC Crushing capacity More Technology Advantage Tungsten Titanium Alloy Application Hammer Crusher, Limestone Crusher etc.

Table 4.5 Product details of stepped taper Crusher Hammer

43

Standard: ISO9001: 2008

Machine Type Crusher

Deformation Temperature Casting

Molding Techniques Pressure Casting

Model Number Crusher Spare Parts

Material High Manganese Steel

Model NO Wear Resistant Parts high manganese hammers

Molding Style Taper

Life time 12 Months

Trademark DSMAC

Crushing capacity More

Technology Advantage Tungsten Titanium Alloy

Application Hammer Crusher, Limestone Crusher etc.

Table 4.6 Product details of taper Crusher Hammers

4.3 Advantages

Ø High and constant capacity

Ø Low space requirement

Ø High machine availability

Ø Long lifetime

Ø Easy replacement of wear and spare parts through hydraulic opening device

Ø Broad range of applications

Ø High reduction ratio

In case one side of the beater heads is worn, the rotor direction can be reversed by

switching the motor accordingly. This will increase the service Life of the beater heads and

reduces downtimes during maintenance procedures.

44

4.3.1 Crushing Action – Adjusting the grinding wall to the crushing radius (gap width), the rotor Diameter, the rotor speed (m/s), and the perfect combination of these Variables are major factors in determining the reduction ratio and productize – The grinding wall is fitted with grinding ledges and a replaceable grate in The lower section to reduce oversized grain 4.3.2 Specification – Feed size: up to 300 mm (12 in) – Product size: up to <1 mm depending on type and size of feed material – Reduction ratio: 1: 30 – Installed power: up to 1800 kW (2414 hp) 4.4 Material used for preparation of hammer head 4.4.1 Cast iron

Cast irons are basically the alloys of iron and carbon in which the carbon varies between 2.0 to 6.67%.For commercial applications the cast iron contain carbon in the range of 2.3 to 3.75% with other elements. Various types of cast irons are available in market, but mostly we prefer white cast iron because of more hardness and wear resistance.

4.4.1.1 Composition Carbon - 2.3 to 3.0% Silicon - 0.5 to 1.3% Sulpher – 0.06 to 0.1% Phosphorous -0.1 to 0.2% Nickel - 3 to 5% Chromium – 1 to 3% 4.4.2 Hammer Head Material Steel is an alloy of iron and carbon in which the carbon content is in between 0.008 - 2%. In order to increase the hardness manganese is added to steel alloy which is called as manganese steel. 4.4.2.1 Composition Carbon – 1.2 to 1.8% Manganese - 10 to14% Compare to manganese steel, cast iron is having more carbon content. So brittleness is more in cast iron. Here we require low brittle and high hardness material in order to sustain high rubbing action. Finally we prefer manganese steel for the preparation of hammer head.

45

Chapter – 5

Theoretical Results and Conclusions

Theoretical Result 1. Contact area of the hammer head is increased. 2. Material of hammer head is change(cast iron to manganese steel) Therefore, the following result is obtained

Aspects Before design After Design Crushing efficiency(<3mm) 81-84% 88-91% Life time of Hammer head 10 Months 12 Months

Conclusion

The main aim is to convert the coal into coke, because the ash content in the coal is more compared to coke. To improve the quality of coke, the complete combustion of coal is required.

In order to get complete combustion of coal, the size of coal is decreased by using Hammers. The main conclusion of this project is increasing of crushing efficiency and also got the good quality of coke. The life of hammer head is also increased due to the change of material (Cast iron to Manganese steel).

46

References

[1]D.D.Barkan, Dynamics of base and foundation, McGraw-Hill. [2]V.Kolousek et al., building structure under dynamic effects (in Czech), SVTL, Bratislava.1967. [3]A. Major, Dynamics in civil engineering. Academician kiado, Budapest, 1980. [4]D.Makovicka et al.., calculation of building structures loaded by dynamic effects of machines (in Czech), commentary to CSN 73 0032, Vydavatelstvi UNM, praha, 1980. [5] Power plant engineering by P.K. NAG [6]Material science by Kodigiri [7] Power plant engineering by Aurora