PIN MILLS

BY:- PRATHAMESH KUDALKAR 13FET1011

MONTICA SAWANT 13FET1007

A PIN MILL

SIZE REDUCTION

Raw materials often occur in sizes that are too large to be used and, therefore, they must be reduced in size.

Size reduction of solids is termed as grinding or cutting. Grinding usually refers to reducing solids to fine particles while cutting involves reducing solids to macroscopic particles.

Grinding involves reducing the size of solid materials by mechanical action, dividing them into smaller particles.

It is an energy intensive process, therefore the selection of right grinder is important.

TYPES OF MILLS

The different types of mills used in fine grinding are as

follows:

The Hammer Mill

High Impact Turbo Mill

Pin Mill

The Vibrating Mill

Stirred Media Mill

Fluid Energy Mill

Here after, we will concentrate on Pin Mills.

PIN MILL

Pin Mills are type of Disc Grinders.

Also known as Centrifugal Impact Mills (CIM)

Pin mills are a type of high-speed-impact mills consisting

of a feed inlet, a set of two disks with concentric rings of

pins and a product outlet.

Particle size of as low as 2 µm can be achieved with the

use of finest quality Pin Mills.

Pin mills are capable of very fine grinding without the

need for screens and provide a uniform product size.

PRINCIPLE Pin mill employs shearing and impact forces to produce fine

particles

The grinding action within the Pin Mill is achieved by

impacting the product particles with a series of hardened steel

pins.

The product enters through the eye of the machine and then

passes through rows of pins rotating at high speed between

stationary pins.

The product particles are shattered into fragments as they

progress towards the outlet, progressive becoming smaller in

size as they approach the periphery(this is because the

distance between the pins decreases as we move radially

outwards)

The machine’s grinding action can be controlled by altering the

feed rate to the machine and the speed of the rotor.

WORKING

Pin Mill consists of two round disks parallel to each other.

Material is fed continuously in the gap between the rotating disks.

Depending on the type of the machine, one or both disks can rotate.

In cases where both disks rotate, the second disk rotates in counter

direction.

Feeding of the product is usually done by means of a chute, shifting

the product in the hole center of one of the two disks.

To reduce the temperature increase, air is blasted during grinding or

in construction to avoid oxidation, cooled inert gas is used; Blast of

inert gas helps prevent accumulation of particles in between the pins

and on the disks

WORKING

•The disk has several metallic pins, placed symmetrically

and concentrically on the disk surfaces.

WORKING The centrifugal force causes the particles to accelerate

outward toward the disc edges and pass through the pins

on the discs.

The exiting particles impact a stationary outer ring (called

an impact wall or liner) typically consisting of stator pins

or a smooth or corrugated wall, which further reduces the

particles.

Sieve of the required particle size is placed on the lower

part of the mill. It acts as a barrier mechanism to ensure

no particle having size more than specified is found in

the output.

Thus, ground particles are obtained as output.

TYPES OF PIN MILLS

Vertical Pin Mill Configuration Horizontal Pin Mill Configuration

SPECIFICATIONS When one disc rotates , the size of the

ground particles is 50-5 micro meter . If

both the discs counter rotate , the particle

size may be reduced to 2 micro meter.

Pin mills may grind 0.05-6 tons/hr.

Depending on the product end size of

particles and capacity , the energy

consumption may vary from 3 to more than

100 kW.

The specific energy consumption is10-

100kWh/ton at peripheral velocities 100-

200m/s

Usually the peripheral velocity of the pin

grinder is 80-160m/s

The diameter of the disc is upto 1m.

The fineness of final product depends on

distribution of pins, the circumferential

speed of the rotors, the feed rate, and the

physical properties of the material.

Tips for specifying a Pin Mill

Specify right number and arrangement of pins

Appropriate pin arrangement (typically in rows) for your pin mill discs helps produce the final particle size distribution of choice and controls narrowness of that distribution to meet your product requirements

Specify high quality parts

Any internal mill surface in contact with the material during grinding is subject to wear, and in a pin mill this includes the pins, the wear plate (that is, the disc surface on which the pins are mounted), the rotor, and the impact wall at the disc periphery. These parts can also be subject to corrosion if your pin mill handles a corrosive material.

Order wear parts to keep on hand

ADVANTAGES AND DISADVANTAGES

ADVANTAGES DISADVANTAGES

•Very fine grinding at relatively

reasonable energy consumption

•Little floor space required

•Low maintenance

•Gravity or pneumatic feed

•Dry or wet grinding

•Easy cleaning ensures higher

hygiene standards

•Noiseless operation

•Various internal components are

available to custom-design the Pin

Mill to the process

•Low Capacity

•High wear

•Narrow range of size

reduction

•Internal cooling may be

required(heat damages

products like cocoa)

APPLICATIONS

Spices Foodstuff Biotech & Pharma Chemical

Germ Salt Spaghetti Pill Ore Iron oxide

Curry Rice Red bean Collagen Rosin Talcum powder

Clove Oats Black bean Chitosan Sulfur Washing powder

Garlic MSG Green bean Medicine Shellac Chemical materials

Fagara Sugar Pearl barley Agar ager Ceramic Calcium carbonate

Crocus Xylitol Banana chip Monascus Dyestuff

Mustard Barley Healthy food Antibiotics Pigment

Starch Dry vegetable Yeast powder Gypsum

Wheat Glutinous rice Chinese herbs Feldspar

Soybean Polysaccharide Pesticides

REFERENCES

Handbook of Food Preservation, Second Edition- Edited

by Shafiur Rahman

Handbook of Food Processing Equipment, Gustavo V.

Barbosa-Canovas, Washington State University

Unit Operations in Food Processing : By R.L.Earle &

M.D.Earle

Dry processing technology - A Review, Mineral Industry

Research Organisation, Warren Spring Laboratory

Brochures of miscellaneous Pin mill manufacturers.

THANK YOU!