Internship Report by Ali

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nternship Report

Project: Silo Losses

Syed Ali Hassan.

09/08/2012

nstitute of chemical engineering and

technology, University of Punjab.



In the name of Allah who is the most beneficial and merciful.

Praise is to God, the cherisher and sustainer of the worlds, the most

gracious, most merciful. Master of the day of

Judgment thee we worship.

And

thine aid we seek.

Show us the straightway,

the way of those on whom thou

Hast bestowed thy grace, those whose

(Portion) is not wrath, and who go not astray

(So be it).



Dedication

I want to dedicate this project to following personalities:

HOLY PROPHET (PBUH)

My Parents

Sir Aamir mehmood (T/L N.N)

All the crew of Nestle Nutrition

Ahmad Nawaz (Plant Manager N.N)



Acknowledgement.

By the Grace of Almighty Allah, the most Merciful, the most Beneficial, I'm today submitting my

internship report. I have the pearls of my eyes to admire the blessings of the compassionate

omnipotent, the Merciful and the beneficent Allah who is the entire source of knowledge and wisdom.

Due to his bounteous blessings, I become able to contribute this comprehensive assignment

toward the deep ocean of knowledge. Heart is warm with love and thoughts have turned to the city of

knowledge – The Holy Prophet (P.B.U.H) His saying “Learn from to Cradle to Grave” inspired the

strong desire in me to undertake this course of valuable studies.

It would obviously be injustice not to mention the name of the people involved to make this

assignment possible and helped their utmost to make me understand the overall operation of the

company as of their best knowledge.

Despite of the most hectic schedule,

All SPO’s and Operators

Engr. Aamir mehmood (Team Leader N.N.)

Mr. Ahmad Nawaz( Plant Manager N.N.)

helped me so much. I'm really grateful to them for clarifying my concepts and making me learn from

their experience. Whatever I learnt from them will definitely help me in my upcoming study and theprofessional life ahead.



Executive Summary

The following report gives a detailed overview of the process and the equipment

used at Nestle Nutrition department at Nestle Pakistan’s SKP Factory. This shows my work on

evaluation of root cause of silo losses, the variation in losses on daily basis and the steps that should

be taken to minimize these losses. The report has been prepared by Syed Ali Hassan, for the

consideration of all team leaders especially Mr. Aamir mehmood and the Plant Manager, Mr. Ahmad

Nawaz.



Table of contents

1. About Nestle:………………………………………………………………...…9

2. Nestle Pakistan. ...................................................................................... 10

2.1 Sheikhupura site: .............................................................................. 10

2.2 Quailty Management Scheme (QMS): .............................................. 11

3.Plan of internship:………………………………………………………………..13

3.1 Introduction: …………………………………………………………….14

3.2 Duration: ...................................................................................... 15

3.3 Nestle Nutrition: ................................. Error! Bookmark not defined.

4. Training programme………………………………………………………… 16

4.1 Operations and processes ...................................................... 16

4.1.1 Removal of water…………………………………… .. .16

4.1.2 Evaporation…………………………………………… 16

4.1.3 Process…………………………………………………....17

4.1.4 Evaporator design ……………………………………....18

4.1.5 Type of evaporators…………………………………. ….18

4.1.6 Thermocompressor……………………………......... ….21

4.1.7 Evaporation efficiency………………………… ….….…21

4.1.8 Air and Gasses in milk…………………………… .........22

4.1.9 Deaeration of milk …………………………… ....24

4.1.10 Egron ………………………………………………. …..25

4.1.11 Stages of milk drying at egron………………… ……....25

4.1.12 Energy requirements ……………………… ….. ….....26

4.1.13 Agglomeration……………………………………….....…26

4.1.14 Factors effecting agglomeration………………………...27

4.1.15 Fluidized bed……………………………………………...28

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5 Project:Silo losses ................................................................................... 29

Losses at S.T.D. ........................................................................... 30

. Losses at evap ....................................Error! Bookmark not defined.

Losses at egron ...................................Error! Bookmark not defined.

Suggestions ........................................Error! Bookmark not defined.

6 Recommendations ............................Error! Bookmark not defined.

8 S.W.O.T. analysis………………………………………………………………….

9. Conclusions……………………………………………………………………

10. References…………………………………………………………………………

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1.

About Nestle

:

Nestlé, ever since it was first established, has been committed to achieve and sustain its position as

the world's leading Food and Beverages Company, and leaders in health and wellness.

The company’s journey began in 1867, when Henri Nestlé developed a baby formula that saved a

child's life. It has been a 140 years since then, and the company has expanded around the globe.

They have also developed a range of products designed to suit every taste, need and cultural

preference. Their distinctive seal is recognised everywhere as a guarantee of quality and

healthfulness. Nutrition, quality and convenience thus remain keystone features of their products.

Nestle believes that their responsibility does not solely lie in perfecting the products developed at

R&D centres spread across four continents, but the role their products play in making lives better -

both for the consumers and the communities in the countries they serve.

Along with old favourites such as KITKAT chocolates and NESCAFÉ, the company keeps introducing

new, exciting options worldwide. Understanding that people in every country have different tastes and

needs is one of the factors of Nestles colossal success.



2. Nestle Pakistan.

Nestlé has been serving Pakistani consumers since 1988, when the parent company, the

Switzerland-based Nestlé SA, first acquired a share in Milkpak Ltd. Sheikhupura. Today Nestle has

manufacturing sites in Sheikhupura, Kabirwala, Islamabad and Karachi.

In line with the parent company's global philosophy, Nestle Pakistan is proud of their commitment to

excellence in product safety, quality, and value. From spreading awareness about nutrition and

wellness to digging wells in the Thar Desert and succouring earthquake victims, the company is

committed to serving our country and its people.

The consumer's voice is key to Nestlé Pakistan's vision and working. Whether the consumer lives in

the remotest village or the metropolis of Karachi, the consumer services team stands ready to listen

to the concerns and provide answers about the products and guidance on matters of health and

wellness.

2.1Sheikhupura site:

Milkpak set up reception centres with cooling facilities where farmers and dodhies (small-time milk

merchants) could bring their merchandise. It was a simple, but costly solution as importing the

stainless steel chilled containers required was prohibitively expensive.

By 1988, the company purchased 120 tons of milk a day from 26,000 farmers. After acquiring a

share in Milkpak Ltd in 1988, Nestlé immediately began investing in milk cooling tanks. Between 1988

and 1992, 100 milk storage tanks were installed. 1992 onwards, with full support from the Nestlé



headquarters in Switzerland, reorganisation of the milk collection operation and the provision of

agricultural technical assistance became top priorities.



2.2Quality Management Scheme (QMS):

Quality is the foundation of Nestlé Pakistan, as the company considers itself the

standard bearers of the company’s founder Henri Nestlé’s care for safety and quality.

The motto of Good Food, Good Life is taken very seriously here. At every step, from

collecting raw materials from rural farmers to distributing finished goods in city supermarkets, the

employees are trained and retrained to understand their role in ensuring that consumers enjoy food

and beverage items of the highest quality. The Nestlé name on a product is a promise to consumers

that it is safe to consume. It complies with all relevant laws and regulations and meets high standards

of quality. In addition, constant improvement and tightening of existing regulations is often seen.

Quality wins consumer trust and preference.

The management takes the lead, sets the objectives and demonstrates its commitment

towards quality. All Nestlé functions across their Value Chain are fully responsible to follow

mandatory norms and instructions for maintaining agreed quality standards. We follow the stringent

international standards of the World Health Organization’s Codex Aliment Arius on food production.

All factory laboratories operate according to Good Laboratory Practices guidelines. The Sheikhupura

and Kabirwala laboratories have long enjoyed an 'Excellent' rating in the worldwide proficiency tests

conducted by Nestlé SA (Switzerland), and attest to the world-class quality of our factories.



Nestlé` Pakistan focuses on facts and results and strive for a zero defect and

excellence in everything they do. They have adopted a “no waste attitude” and constantly look for

competitiveness and opportunities for Continuous Improvement of the quality standards delivered to

the consumer. A solid quality management system must rely on a strong and fully empowered quality

function. Nestle enforces a full compliance with the mandatory standards and principles of their

Quality Management System, which includes Food Safety, Regulatory and Quality requirements in

every step of our Value Chain. The Nestlé Quality Management System builds on the existing Nestlé

Quality System and adds a strong management component to it. Each plant is given a set of

standards to follow. The QMS for the chilled dairy section can be seen in Appendix A.

Plan of my internship program.

3.1Introduction to N.N.:

NESTLÉ, a company with a long standing heritage and legacy of quality food products

and 135 years of experience, has grown into a trustworthy company that the citizens of Pakistan rely

on. It caters to a number of food categories and markets them successfully. A major portfolio of their

products in Pakistan comes from the Nutrition Section at the Sheikhupura factory. The major products

of nestle nutrition are….

Lactogen 1

Lactogen 2

Lactogen 3



cerelac

Duration

The training period at N.N. was commenced on 2/07/2012 ang d came to an end on

09/08/2012. It was a very nice passed that passed with the cooperative staff of N.N.



Operations and processes

4.1.1Removal of water

Concentration of a milk means removal of a solvent i.e. water. Concentration is

distinguished from drying in that the final product – the concentrate – is still liquid. There are several

reasons for concentrating food liquids, e.g. to

• reduce the cost of drying

• induce crystallization

• reduce costs for storage and transportation

• reduce water activity in order to increase microbiological and chemical stability

• recover by-products from waste streams

Concentration of a liquid by evaporation under vacuum was introduced in 1913. The

process was based on a British patent by E.C. Howard which covered a steam-heated double-

bottomed vacuum pan with condenser and air pump.

4.1.2EvaporationAt N.N evaporation is used for concentration of milk. It is also used as a preliminary

step to drying. Milk from the silo has total from10.5-11.5% intended for milk powder are normally

concentrated from an initial solids content of 9 – 13%. These are increased up to 50-55% in Multiple

Effect Evaporator. After that it is pumped to egron. For evaporating water from milk energy is

required. This energy is provided by steam. Milk to be evaporated is normally heat sensitive and can

be destroyed by adding heat. To reduce this heat impact, evaporation takes place under vacuum. At

the same time the evaporator is designed for the shortest possible residence time. Product will be of

good quality provided that the evaporator is designed for low temperature

and short holding time.



Vapour

Steam

Milk

4.1.3Process

Water is evaporated by means of indirect heating. Product and heating medium (steam)

are kept separate from one another by means of a sheet of special steel. The milk is basically in the tubes

and steam is outside the tubes. The heat released during the condensing of the steam is transferred to

the product via the partition

The extent of concentration process that can be forced is determined by product

properties such as viscosity and heat stability. Heat treatment is often an integral process step of an

evaporator in order to achieve specific properties in the finished powder. To minimize the thermaimpact on the products from the heat applied, evaporation takes place in a vacuum at temperatures of

55 – 70 °C.



4.1.4Evaporator design

It takes a large amount of energy to boil off water from the solution. This energy is supplied as

steam. To reduce the amount of steam needed, the evaporation station is normally designed as a

multiple-effect evaporator. Two or more units operate at progressively at lower pressures and thuswith

progressively lower boiling points. In such an arrangement the vapours produced in the previous

effect are used as heating medium in the following effect. The result is that the amount of steam

needed is approximately equal to the total amount of water evaporated divided by the number of

effects. The evap at N.N. has four effects however evaporators with up to seven effects are now used

in the dairy industry. Typical consumptions per kg evaporated water for falling film tubular evaporators

with thermal recompression in the dairy industry

2-effect 0,32 kg steam





4.1.5Types of evaporators: Various types of evaporators used in Dairy Industry are :-

Natural Circulation Evaporator

Forced Circulation Evaporator

Climbing Film evaporator

Falling Film Evaporator

Agitated-film evaporator

Plate evaporator

The evaporator used at N.N.is Falling Film Evaporator. The key to success with

falling-film evaporators is to obtain uniform distribution of the product over the heating surfaces.

Vertically arranged tubes are used for the most part, where the product flows

downwards on the inner surface of the tubes and the heating steam

condenses on the outer surface of the tubes. The electrically powered



compressor or fan is used to recompress the vapour leaving the first effect, it is called Thrmo Heat

Compressor (THC) in order to fulfill the requirement of pressure on the heating side. Although

evaporator plants generally work on the same principle, they differ in the details of their design.

THC

Milk

Pasteurizer Separator

Steam Condenser

Condensate

Vapor



In falling film evaporators there is a uniform distribution of the milk over the heating

surface. This is achieved by using a specially shaped nozzle that distributes the product over a

spreader plate The product is slightly superheated by the DSI station and therefore expands as soonas it leaves the nozzle. Part of the water is vaporized immediately, and the vapour forces the product

outwards against the insides of the tube. After that some of the concentrated milk leaves the tube

side from the bottom due suction of pump, some enters the shell side of that effect, there is a

separator which separates the milk from the vapours by centrifugal action. The vapours rise in the

shell side while concentrate is sucked by the pump of first effect.

In this way vapours from the product in the first effect can then be used as the heating

medium in the second, which operates at a higher vacuum (lower temperature). It is also possible to

connect several evaporators in series to improve steam economy. This makes the evaporator more

expensive and more complicated to run. It involves a higher temperature in the first effect and thetotal volume of product in the system increases with the number of

effects.



Flow sheet of Evap at NN



4.1.6 Thermocompressor

The vapour evolved from the product can be compressed and used as a heating

medium. This improves the thermal efficiency of the evaporator. Therefore a thermocompressor is

installed at the evap of NN. Part of the vapour from the vapour separator is supplied

to the thermocompressor, to which high-pressure steam (5 –7 ) is connected. The compressor uses

the high steam pressure to increase the kinetic energy, and the steam is ejected at high speed

through the nozzle. The ejector effect mixes the steam and the vapour from the product and

compresses the mixture to a higher pressure. It basically optimizes the thermal efficiency. The milk is

pumped from a balance tank to the pasteurizer, where the milk is pasteurized and the temperature is

adjusted to the boiling temperature in the first effect. The milk continues to the first effect of the

evaporator, which is under a vacuum corresponding to a boiling temperature. The water evaporates

and the milk is concentrated as the thin film of milk passes the two plate passages.

The concentrate is separated from the vapour in the cyclone separator and

pumped to the second effect. In this effect the vacuum is higher, corresponding

to a temperature which is lower. After further evaporation in the second effect, the concentrate is

separated from the vapour in the cyclone and is pumped to the fourth effect instead of third. This is

because the milk is evaporated in the third effect at the end in order to get the product at highertemperature as the temperature of outlet of third effect is higher than the temperature of outlet of

fourth effect

4.1.7 Evaporation efficiency

The evaporator installed at NN has four effects. By using 1kg of steam we canevaporate 4kg of steam from the milk and 1kg condensate will be produced. In this way thermal

efficiency is optimized



4.1.8 Air and gases in milkMilk always contains greater or lesser amounts of air and gases. The volume of air

in milk is determined by the air content of the cow’s bloodstream. The oxygen (O2) content is low

being chemically bound to the hemoglobin in the blood, while the carbon dioxide (CO2) content is high

because the blood carries large volumes of CO2 from the cells to the lungs. The total volume of air in

milk in the udder can be some 4.5 – 6 %, of which O2 constitutes about 0.1%, N2 (nitrogen) about 1%

and CO2 3.5 – 4.9%. Milk is exposed to air in several ways during milking. Atmospheric oxygendissolves in the milk, while CO2 is released from it. Part of the air does not dissolve in the milk but

remains in a finely dispersed form, often adhering to the fat. After milking and collection in a churn or

cooling tank, the milk may contain 5.5 – 7.0% air by volume with 6% as an average figure. The

equilibrium that prevails between those three states of aggregation is determined by temperature and

atmospheric pressure. When the temperature rises, during paste ration for instance, dissolved air

goes from solution to dispersion. It is the dispersed air that causes problems in milk treatment.

Air in milk occurs in three states:

1. Dispersed

2. Dissolved

3. Chemically bound



4.1.9 Deaeration in the milk treatment lineAir must be removed from the milk. It is removed by vacuum system of the

evaporator. As the milk enters the cyclone separator the vapours are separated and move up. Some

of them are sucked by thermo compressor and rest of them move through second third and fourth

effect. Here they are condensed in the condenser while the gasses which are relieved by the milk and

some from the vapours are sucked by the vacuum pumps.

4.1.10 Egron

Concentrated milk from the Evap is pumped by high pressure pump to the balane

tank from which it is sent to egron for spray.

Drying priciple:

Spray drying is a thermodynamic process where a solution is transformed into a

dried form by spraying it into a hot drying medium.

Why we dry a product?

o It is one of the oldest method for food conservation and preservation.

o Drying reduces water activity, thus avoids food degradation due microbial growth, chemical

and enzymatic reactions.

o Drying allows compensation for the seasonal effects of consumption and production.

o Drying reduces weight per unit volume, hence convenience of transport and storage of the dry

product.



4.1.11 Stages of drying milk at egron

The drying proceeds until the desired moisture content of the particles is obtained, and

the product is recovered from the air.

Spray drying involves:

1. Atomization.

2. Contact of hot air with droplet.

3. Evaporation of water contents.

4. Recovery of dried product.

4.1.12 Energy requirments

Heat is transferred from hot medium to the droplet and water is removed from it to the drying

medium.

Evaporation of water is taking place, water is being removed as the droplet is moving down

until it is dried.



4.1.13 Agglomeration

The joining together of small particles to form a large particle is called agglomeration.

Advantages:

a. Less tendency for the fine formation.

b. Improved flow ability of the powder.

c. Produces powder with constant specific density and hardness.

d. Improves dissolution of powder



4.1.14 Factors Affecting Agglomeration Efficiency

The nozzle should have sharp edges running with no blockages

The temperature before agglomeratiom should be around 30°C

4.1.15 Fluid Bed (Drier and Cooler)

The purpose of fluidized bed is to achieve the specific

moisture level by drying the moisture from a layer ofpartially dried powder particles leaving the spray dryer

followed by cooling to facilitate handling / filling.



The main parts of fluidized bed are:

The grid:

(Sieve, screen, perforated plate, conidur …) :

- Ensures a proper air distribution.

- Thus ΔP is a key parameter (typical value 5

mbar).

- Opening area approx. 2 - 8 %.- Conidur type is most typically used in food

industry.

The lower plenum:

- Distributes the air below the grid.

- Is often split in several sections in order to

control the temperature profile.

- Ducts supply air in each section with appropriate

quantity & temperature.

- Typical values are temperature: 100 °C,

superficial velocity: 0.2 - 0.3 m/sec.



Fluidized bed dryer



Project:Silo Losses

Objective

To know the root cause of variations in the loss on daily basis

To minimize the silo losses.



Problems at the STD

The sensor showing the volume of the milk in silo does not shows the

exact reading.

The flow meter installed by them can also not measure the exact

voume of milk.



The wrong reading on the sensor results in the less volume of milk

and thus the loss.

S.T.D. has maintained a set point of 11.08%, as 95% batch cards

show the same figure.

The test results always are different sometimes higher and

sometimes lower then 11.08%(resulting in silo loss).

Total solids could not be maintained at the required value,

fluctuations are always there.

The comparison of the LR test results of each silo taken by me on

daily basis are illustrared below.



Comparison of T.S. on the batch cards and the actual figure



Problems at NN

Fluidized bedThe Fluidized bed in not in proper balance due to which considerable

amount of powder while passing through after dryer and after cooler falls

down and goes to waste



The following pics illustrate the powder loss at fluidized bed dryer.

Powder on floor

Problem with the Gasket

After dryer



The poly bags are not properly placed under the points where powder falls

from the after dryer after cooler and other powder falling points during

operation and cleaning.



Financial loss

The price of base powder of L 1, L 2 and L 3 on average isabout 750 pkr. The cattle field produced in the month of july is approximatly

3249kg. This resulted in a loss of 2436750 pkr.



Cyclone Separators

The cyclone separator is a conical chamber in which air streamtogether with the powder is introduced tangentially.

The centripetal force push the powder particles on the wall of separator

allowing the separation and recovery of powder

Discharge of powder to the atmosphere should be minimized to minimizethe powder loss.

Cyclone separator has efficiency more then 90% for the particle size in the

range from 5-400 micron

Separation efficiency/powder loss depends on the following factors. Design of inlet and discharge section.

Speed of feed .

Size of particles.

Density of particles.

Humidity of air.

Differential pressure between inlet and outlet.



Cyclone separator.



How fines go to exhaust

Strong inward flow in the conical section brings fine particles toward theaxis of symmetry.

These fine particles reverse flow direction after passing their respective

equilibrium orbits, and move toward the vortex finder along with the

central upward flow.

As for the coarse particles, the large centrifugal force pushes them

toward the conical wall despite the strong inward flow. Then they join

the boundary-layer flow along the conical wall into the receiver.

Exhaust air volume

Separation efficiency of cyclone is a function of volume of exhaust air

Exhaust air volume is increased by increasing the speed of air in the

tower.

This reduces efficiency of cyclones and increases the losses.



Illustration of fines going to exhaust



Differential pressure leads

Differential pressure leads which lead to the gauges must be cleanedproperly. Otherwise there will remain some fluctuation in the tower suction

and will accordingly fluctuate the velocity, consequently will increase the

Stack losses.

Cyclones at egron



Fine separator:

Fine hoper blockage takes place because of extra suction via exhaust

fan. Heavy particles are also carried in hoper and not transferred in line. So

the Exhaust speed reduction is a good measure. Fine line blockage is

another shape it is related to line cleaning and line pneumatic air velocity.

High and low both velocities can create problem. So the velocity of air

should be optimised

Vortex find

The vortex finder should be fitted in its respective cyclone other it wil

not fit and will become the cause stack losses.



Separation should be 100% as the product is expansive

Any limitation in the efficiency can be improved by installing a

secondary separator such as

1. Wet Scrubbers.

2. Bag filters.

The Bag filter or wet scrubber must be CIP able.



Advantage:

All the fines discharged from the bag filter are returned to the process.This means that no powder is lost as waste, but sold as first-class

product.

Full utilization of energy is now possible if a heat recovery system is

installed after the bagfilter. As there are practically no powder particles

left in the exhaust air the heat recovery system can be designed so

that the air with the moisted - on vapor form - can be cooled to below

the condensation temperature and all the entrained energy can be

reserved and reutilized.

Losses counted as scrap factor:

Some milk goes to drain during the startup every time.This is because

when the silo starts there is water in the pipe and it is mixed with milk,

reduces its TS, also thermal conductivity sensors keeps the drain valve

open until the it crosses its set point value.

Some total solids are burned at the DSI station due to hightemperature.



Recommendations

Following are some recommendations which should be considered in order

to reduce the losses, increase the output and obtain financial benefit.

The design of cyclone seprators should be modified and made up to

date in order to maximixe their efficiency

If the cyclones could not be modified then secondary seprators such

as wet scrubbers or bag filters must be installed.

The secondary separators must be cip able in order to recover the

powder as first class base powder.

The fluidized bed after dryer and after cooler must be reparied in order

to reduce the powder loss which goes to waste as cattle field

Sensors at the egron which indicate the amount of milk in the silo

must be calliberated.



In order to have a proper check and balance on the SNF% we must

have our own equipments at egron to measure the LR of milk and

then calculate the actual quantity of total solids which we are receivingfrom STD.

The poly bags under ther fluidized bed must be placed properly so as

to reduce the formation of cattle field.

The vortex finders must be fitted in their respective cyclones in order

to avoid any fluctuation the process and to reduce the stack losses

The speed of air in the tower must be maintained at the defined rate in

accordance to the suction in the tower

The egron scale still shows a difference of 2.5 kg, this must also be

properly calliberated.

Internship Report by Ali

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Transcript of Internship Report by Ali