Transcript
Page 1: Plant Design-Biscuit Manufacturing

DESIGN OF A PLANT TO PRODUCE ONE TONNE OF BISCUIT PER DAY

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EXECUTIVE SUMMARY

A process plant to produce one thousand kilograms or one tonne per day on a single

eight-hour shift basis has been carried out with much precision and consideration given to

the most optimum process route. An increase of 10% was given to the product so as to take

care of losses along the production line and also to the plant producing under capacity.

The materials needed for the production of the biscuit and their approximate

percentages are: Flour -- 50%, water--30%, sugar--2%, salt --2%, baking powder--2%,

additives --14%. The materials or equipment design are: one mixer, one extruder and

conveyor tunnel oven.Other equipments are sealing machines, water pump, filter, tables,

pre-printed nylon etc. 1492.96 kg of dough is mixed per day and 1000 kg of biscuit is the

target to be produced with a 10% increase to account for losses in the production line. The

heat generated over the whole production process is 650,358.92 kJ/hr. The profit at 75%

and 100% capacities are N12.678m and N 17.7135 m respectively. The recommended

sales price is estimated at N3.60.

The feasibility and technological requirement for the production of a biscuit plant

of total capacity of one tonne or 30,000 thousands packs per day running only one eight

hour shift. The approach used for the design of this process technology starts with the

selection of the process route that will give optimum yield and low cost. The route was

chosen after considering the existing routes industrially and modifying it to suite the

capacity of this plant.

The equipment for the plant were also chosen based on their ability to carry out the

expected functions of the plant, putting into consideration the working characteristics,

capacity and area. They are also chosen based on the characteristics of the materials. The

best were chosen and the process flow route with the equipment was determined.

The material and energy balance for the whole process units were done, to

determine the flow of material in and out of the system and to determine the heat generated

over the whole system. Each of the basic equipment like the oven, the extruder were

selected or modified using the material and energy balance, and some design parameters

from design books and companies.

Analysis of the cash flow for profitability of the plant was then looked into using

high expenditure ratio to low revenue rate of return. The analysis covers, the costing of

machinery and equipments, the working capital, factory and building cost, pre-operational

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expenses, contingency, cost of utilities and tax. The revenue generated at a selling rate of

3.60 per pack was determined. The depreciation of equipments (20 years), office building

and furniture (5 years each) and the trading profit was used to generate a good profit.

Site selection and plant location was also done, by looking into the market areas

available to the product, the nature of competition, rate of consumption of the product,

source of raw material, transportation of raw material and product, availability of both

skilled and unskilled labour, nature of utilities that will be needed for process and

recreation, environmental impact of process effluent (if any), climatic effect, topography,

and strategic economic consideration. Suggestion of the plant layout, safety of both

material/ product and man/machinery was also looked into, suggestion on waste

management and services was done.

After all the above consideration the results obtained during the study and design

show some very interesting results for any investor. The type of biscuit chosen for the

production plant is the southern type biscuit (trade name) with a simple recipe of flour,

sugar, salt, baking powder, additives and water with its own percentages by weigh. The

ingredients are readily available in the market locally or by importation. This type of

biscuit are already enjoying good acceptance in the market.

The process route selected is such that only one mixer is used and the paste or dough

is poured into an extruder below, from where the dough is extruded through a mould,

placed at the nozzles of the extruder which are then placed in trays for a two-in-one cutter

stamp to cut and stamp the company logo. A conveyor then conveys these trays through a

drying zone with three compartments for the final drying (baking) of the biscuit. Products

are then packed and sealed and cartooned for the market.

The equipments for the plant are mainly the mixer, extruder and the oven, the choice

of the mixer after careful consideration of material amount, characteristics and efficiency

expected is the sigma z-blade which belongs to the double arm kneading mixing equipment

group. It has good mixing action, readily discharges material, relatively easy to clean and

does not allow sticking of material. By the nature of extruders, a total design is needed

therefore, no choice was made, however the design follows the basic principle. The choice

of drying is the tunnel continuous dryer due to the amount of heat expected to be generated

and the nature of the product to be dried and also due to the nature of drying medium,

steam. It is very suitable for materials that form bed with open structure. High drying rate

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is achieved, with good quality of product, high thermal efficiency, usage of steam as

during medium as low as 1.5 kg/kg of water for evaporation, and good recycle of steam,

which gives cost effectiveness. The only disadvantage here is the cost for mechanical belt

maintenance for the conveyor. The source of heat is chosen to be steam, from plant boiler

and cooling water in the extruder nozzle as compared with electric heater which are

expensive, difficult to maintain and heating which is not uniform.

The capacity of the oven designed is 1m by 11.21m, the resident time in the

drying/cooking zone is 15 min, the amount of material per day is 1,306 kg/day, heat

generated as 99,990.82 kJ/hr and the process dynamic is subject to a pilot test.

The capacity for the extruder designed is 0.1103 m3, with the internal specification of

1m by 0.5 m long by 0.22 m high, resident time of 0.052 kg/s, the extrusion time is 0.141s,

the amount of material extruded per hour is 186.6 kg/hr, heat generated is 469,800 kJ/hr,

which is very high, about 70% of which is lost to the environment, thus adequate need for

cooling water at the nozzle. The mixer capacity is designed to handle 622 kg/hr over 20

min of mixing for homogeneity, tank diameter is 0.622 m, blade diameter is 0.25 m, the

blade tip velocity is 1.44 m/s, the power consumption per unit volume is 118.225 kN/m2s,

the design blade number is 2,700. The material in is also 186.6 kg/hr and the heat

generated is 80,568 kJ/hr, with a loss of 73, 641.28 kJ/hr. For every 1,492.8 kg of feed

material 1.1 tonne of product is produced which is estimated 10% above target to take care

of losses of materials that may occur along process line e.g. burnt products or loss during

mixing, extruding and cutting. The heat generated over the whole system is

650,358.82KJ/hr, most of which are lost, thus the mixer will be properly lagged and

extruder cooled. The cooling water from the extrusion unit is sent to the boiler to generate

treated water for oven i.e. conservation of energy.

The projected income and expenses evaluated is done with 75% capacity

production for the starting year, 2002 with 10% increase until the fourth year 2005. The

total product for the first year of production is 210 tonne of biscuit, with a market sales of

N 3.60 gives a revenue of N 22.50 million less than the yearly expenditure of N 9.022

million and loan on interest at 0.8% gives a yearly net profit of N 12.678 million, and this

increases as the plant grows to operate at full capacity.

Due to the market available for biscuit, the site of the plant should be close to the

market within a reasonable radius. The raw material, flour can be sourced locally from the

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northern part and transported. Transportation by road and rail are safe. Other additives are

more concentrated in the western part.

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C H A P T E R O N E

I N T R O D U C T I O N

1.1 GENERAL

Biscuit like bread is a bakery wheat or wheat composite product of valuable food

nutrition. Biscuit came to Nigeria through the colonialists but have become popular among

our people, especially children of school age. Its acceptance is based on the ready for

consumption nature of the product. It can also be eaten alone or with other foods like milk,

tea, butter, stew, pap (ogi) etc (Adeniyi, 1998; Onyia, 1997).

Biscuit is food and food is man's basic need. Being a food producer in a society

where food is not only very expensive but scarce, it certainly has a ready market for

investors. In the cities where there is little time for detailed cooking due to socio-economic

factors, ready-for-consumption foods like biscuits come to the rescue. This product is often

taken as breakfast, or taken to offices or schools for lunch by children and adult alike. The

use of biscuit for hospitality has become popular thereby creating huge demand for the

product. The unit packaging available make it affordable even by the poor.

With a good quality publicity as well as price, biscuit production can be a good

profit-earning business.

1.1.1 RAW MATERIALS

[1] FLOUR: This is the most important raw material, which can be made of whole

wheat or composite from maize, cassava, millet etc. It takes not less than 50% of all

ingredients required. A small packet of biscuit of 30 g contains at least 15 g of flour.

Wheat flour is produced locally (Ogunsola, 1999, Adeniyi, 1998).

[2] SUGAR: Sugar is essential for sweet taste which biscuit is known for. Sugar is

produced locally and allot is also imported to meet the huge national demand.

Nevertheless, there are other natural sweeteners like honey, sweet potato and some native

extracts that can be carefully incorporated as substitute or filler for sugar.

[3] ADDITIVES: These include flavouring, shortening, colourants and modifiers

like salt, eggs, milk, glucose, fat etc. They are added in very small quantities depending on

the type of biscuit needed.

[4] WATER: Water is essential for mixing the ingredients to a workable level.

Water takes up to 30% of the components. This however, must be hygienic and clean.

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[5] BAKING POWDER (AND/OR YEAST): Baking powder or yeast is

important, for biscuit making. Where fermentation is not done like in wafers, yeast is not

needed. The extent of swelling or rising of biscuits during production depends on the

baking powder or yeast as the case may be. All raw materials must of necessity be food

grade and hygienic (Ogunsola, 1999, Adeniyi, 1998).

1.1.2 EQUIPMENT/TOOLS FOR PRODUCTION

The following equipment/tools are necessary for commercial production of biscuits

(Crenan and Butter, 1990).

[1] OVEN (DRYER): This can fired by wood, electricity or gas depending on the

design.

[2] MIXER: This can be manually operated or motorized to make mixing efficient.

[3] MOULD/STAMP: The various designs that will appear on a biscuit depend on

the mould and stamp. There are manual and motorised types.

[4] CUTTER: The cutter cuts mixed and flattened biscuit parts into the desired

sizes. It can be manual or motorized too.

[5] Other tools such as wrapping and sealing machines, storage tanks, trolleys,

packing racks etc can be provided. These equipments and tools can be

fabricated locally to any desired standard.

1.2 DESIGN PROBLEM

The plant to be designed will have a capacity to produce one tonne (one thousand

kilograms) of biscuit per day. The manufacturing operation is to comprise of the following

units: mixing, extrusion, drying and packaging. The entire technological process is to be a

semi continuous operation where materials are only manually operated during transfer

from the horizontal drier to the packaging. Services available are normal services with

cooling water at a temperature of thirty degrees centigrade (30oC). A detailed chemical

engineering design is required with a flow diagram for the process accompanied with the

mass and energy balance for the equipments and units. At optimum operation the

technology is to produce a minimum of thirty thousand packs (30,000 packs or 1 tonne) of

biscuit per day or one for one eight our shift.

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C H A P T E R T W O

M A N U F A C T U R I N G O P E R A T I O N S

2.1 INTRODUCTION

The process of making biscuit comprises of various unit operations. Following the

formulation, the raw materials are carefully measured out and mixed in the dough mixer.

The dough when formed is passed through the moulds. This is then stamped either before

or after cutting depending on the design of the plant. The dough pieces are taken to the

oven where they are baked for at least 10-15 minutes at 200-250oC temperatures. This

however depends on the type and thickness of the biscuit to be produced. The baked

biscuits are removed and sorted out. They are then packed in polyethylene or waxed paper

previously printed and finally sealed on the sealing machine. The wrapped biscuits are in

turns packed in cartons and taken to the market.

2.2 SELECTION OF PROCESS ROUTE

Basically, the technology of biscuit production involves the thorough mixing of the

wheat four or other cereals (that can serve the same purpose) with other ingredients and

additives. After the mixing operation the dough is extruded and shaped to fancy, how be it

with some restriction in size and thickness. These shaped dough are then dried to reduce

the water content and invariably browning. The biscuits are then packaged as desired and

ready for market (Crenan and Butter, 1990).

This process demand the following unit operations and auxiliary services:

[1] Surface tanks [2] mixing equipment [3] extruder

[4] Cutting equipment [5] stamping equipment [6] drying oven

[7] Sealing machines [8] trays, rollers or conveyor

The flow of material through this equipment (units) is determined with the aim of

having optimum production cost and best quality of products. This influences the choice of

optimum process route (Fig. 2.1). This route is chosen after answering the following

questions:

[1] Is the flow diagram logical, are the units compatible?

[2] Is the technique feasible and logical?

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[3] What are the possible flows, can they be corrected and controlled?

[4] Which of the different kinds of the unit is the best considering cost, efficiency,

durability, capacity, energy consumption?

[5] Are the equipments readily available?

[6] How safe are the units to operate?

2.3 CHOICE OF PROCESS ROUTE

The choice of process route for the biscuit plant is basically dependent on the size

of the plant i.e. capacity. The basic process route (arrangement) of mixer, extruder, stamp,

drying and packaging is universally well known and documented.

However, depending on plant capacity, the type of unit used becomes important.

The use of other equipment such as pumps for supply of water to mixer, the need for

continuous flow of materials, recycling e.t.c. are factors to be considered. Therefore in the

design of the best process route, the route chosen should be seem to be at par with other

known good techniques used in the biscuit industries, it is safe from both operational,

human and environmental hazards, the technique is not technologically demanding. The

only improvement may be the use of sophisticated equipment, which is not wise

considering the economy of the proposed plant capacity.

Therefore the choice of the optimum route has been done based on breaking down

the technology in unit operations. The choice of the required equipment was done after

answering the questions stated above. Each unit is properly examined to choose the best

that will be compatible with others. This is to ensure the optimal operation of the

processing technique as shown on Fig 2.1 (Adeniyi, 1998).

Fig. 2.1: Block diagram of biscuit production

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Mixing Extruding Rolling Cutting Stamping

Packaging Cartooning Sealing Drying Trays

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2.4 PRODUCTION MACHINERY

A full list of the major production machinery needed for the production of one

tonne of biscuit per day is presented in Appendix A. The department will require a

minimum of one tonne of biscuit per day, per technological line. Water used for mixing

must pass through filters. The cooling system is necessary to avoid rapid evaporation of

water as well as the blockage of the nozzle of extruder.

The dryer stage comprises of:

1 horizontal oven with complete accessories.

Baking is a very important stage as it greatly determines the quality of the final products.

The packaging department consist of:

6 wooden silos

6 weighing machines

Nylon sealing machines

2.5 ANCILLARY OPERATIONS

In addition to the main production processes outlined above, several ancillary units

must be established for efficient operation of the factory. They include among others:

[1] QUALITY CONTROL UNIT:

A unit responsible for quality control at every stage of production will be set up

to ensures compliance with set National Standards for food and beverages by the National

Agency for Food, Drug Administration and Control (NAFDAC).

[2] MAINTENANCE UNIT:

A maintenance unit must be set up to ensure early fabrication of worn out parts It

should be equipped with the necessary workshop machines. The workers are under the

indirect production list, which is given in Appendix C.

2.6 FACTORY PERSONNEL

Manning levels have been estimated fairly generously in comparison with those,

which would be expected in a more developed industrial environment. The factory will

operate a single eight-hour shift system. The distribution of personnel along the

technological line is given in Appendix C under the direct production worker. It requires a

total of fifteen people. The indirect factory personnel are also given in Appendix C also

with a total of fifteen people.

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C H A P T E R T H R E E

M A S S A N D E N E R G Y B A L A N C E S

3.1 OVERALL BALANCE

The percentage compositions of the feed is known, what is not known is the masses

of the feed but the masses of the product is 1000 kg of biscuit.

A detailed calculation is in Appendix B and a computer program has been written

to solve the material and energy balances. The computer program is in Appendix D

(Adeniyi, 1998).

The percentage compositions of the feed materials are:

[1] Flour 50% [2] Sugar 2.0%

[3] Water 30% [4] Baking powder 2.0%

[5] Additives/modifiers 16%

Additives includes flavouring, shortening (about 14%), colourants and modifiers

includes salts (about 1.0%), eggs, milk, glucose and fat (They are added in very small

quantities depending on the types of biscuits)[Adeniyi, 1998, Ogunsola, 1999)]

3.1.1 MATERIAL BALANCE

From the material balance carried out it can be seen that to get a product of 1000 kg

(1 tonne) of biscuit, a feed mass of 1357.15 kg of the raw material is required. This will

require the following mass of feed:

[1] Flour 678.58 kg [2] Sugar 27.14 kg

[3] Water 407.15 kg [4] Baking powder 27.14 kg

[5] Addition/modifier 217.14 kg

3.1.2 HEAT BALANCE

At a moisture content of 30% the heat capacity of biscuit is estimated at 1.845

kJ/kgoC, the latent heat is 100.50 kJ/kgoC. The heat required to bake 1kg of biscuit in the

oven is 715.97 kJ (kW). The heat required to bake 1357.15 kg of biscuit in the oven is

1331960.46 kJ. The overall heat balance across the oven is calculated to be 1198766.35kJ,

this is different from the heat required to bake 1357.15 kg because some moisture will

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already be lost before the dough enters the oven. About 10% of moisture is expected to be

lost before the dough enters the oven and this amount to about 321.453 kg. Detailed

calculation of the heat balance is given in Appendix B. The results are summarised in

Tables 3.1-3.9.

Table 3.1: Overall material balance.

Mass In Amount

(kg)

Amount

(kg/hr)

Mass Out Amount

(kg)

Amount

(kg/hr)

Dry solid

Water

1045.12

447.84

130.64

55.98

Solid (dough)

Water

Losses

1045

55

392.96

130.63

6.87

49.12

Total 1492.96 186.62 Total 1492.96 186.62

Table 3.2: Unit material balance over the mixer.

Mass In Amount

(kg)

Amount

(kg/hr)

Mass Out Amount

(kg)

Amount

(kg/hr)

Dry solid

Water

1045.12

447.84

130.64

55.98

Solid (dough)

Water

1045.12

447.84

130.64

55.98

Total 1492.96 186.62 Total 1492.96 186.62

Table 3.3: Unit material balance over the extruder.

Mass In Amount

(kg)

Amount

(kg/hr)

Mass Out Amount

(kg)

Amount

(kg/hr)

Solid (dough)

Water

1045.12

447.84

130.64

55.98

Solid (dough)

Water

Losses

1045

261.25

186.71

130.63

32.66

23.34

Total 1492.96 186.62 Total 1492.96 186.66

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Table 3.4: Unit material balance over the dryer (oven).

Mass In Amount

(kg)

Amount

(kg/hr)

Mass Out Amount

(kg)

Amount

(kg/hr)

Dry solid

Water

1045

261.25

130.63

32.66

Solid (biscuit)

Water

Losses

1045

55

206.25

130.63

6.87

25.78

Total 1306.25 163.29 Total 1306.25 163.29

Table 3.5: Overall energy balance

Equipment Heat load (kJ/hr)

Mixer

Extruder

Dryer

80568

469800

99990.824

Total 650358.824

Table 3.6: Unit energy balance over the mixer

Heat generated Heat load (kJ/hr)

Heat load in dough

Heat loss in mixer

4226.72

76341.28

Total 80568

Table 3.7: Unit energy balance over the extruder

Heat generated Heat load (kJ/hr)

Heat load in dough

Heat loss in extruder

21283.2

448516.8

Total 469800

The unit energy balances across the dryer or oven is given in three zones namely: the

heating zone, the constant rate zone and the falling rate zone.

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Table 3.8: Unit energy balance over the dryer (oven)- Zone 1: Heating zone

Heat generated Heat load (kJ/hr)

Heat load for dough

Heat load for liquid

19725.13

13682.864

Total 33407.994

Zone 2 is the constant rate change zone and the heat in is equal to the heat out which is

estimated as 40953.265 kJ/hr using the computer program developed (Appendix D).

Table 3.9: Unit energy balance over the dryer (oven)- Zone 3: falling rate zone

Heat generated Heat load (kJ/hr)

Heat load in dough

Heat load in evaporated liquid

Heat loss in dryer

3944.12

21109.32

576.125

Total 25692.565

Table 3.10: Total Heat balance over the Dryer (Oven)

Heat generated Heat load (kJ/hr)

Zone 1: Heating

Zone 2: Constant rate change

Zone 3: Falling rate

33407.994

40953.265

25629.565

Total 99990.824

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C H A P T E R F O U R

E Q U I P M E N T D E S I G N

4.1 CHOICE OF EQUIPMENT

In any production process, the choice of the equipment from the different types is

very important, so as to meet the production capacity target, ensure good quality of

product, maximise cost, durability, safety to life and property and cost of production.

Equipment are built with different sizes and shapes, they are designed on different

working principle or operation, which are therefore characteristic of the use to which it will

be applied. It is therefore important to know the nature of the material in the process and

the equipment type that will serve ones purpose.

4.2 DOUGH AND PASTE

Dough and paste are mixed in machines, which have of necessity, to be heavy and

powerful. Because of the large power requirements, it is particularly desirable that the

motor posses reasonable efficiency; as the power dissipated in the form of heat may cause

substantial heating of the product. Such machines may require jacketing mixer to remove

as much heat as possible with cooling water (Richardson and Peacock, 1994).

The most commonly used mixers for these heavy material are the

(1) Z-blade mixers

(2) The pan mixers

(3) The Kneader, which employs two contra rotating arms of special shape, which fold and

shear the material across a cusp, or division, in the bottom

The blade of these mixers rotates at differential speeds, often in the ratio of 3:2.

Mixing action of the Z-blade mixers combines shearing and kneading which is brought

about by the specially shaped blades enabling it to mix, whip and knead materials ranging

from low viscosity paste to stiff dough.

Other types of machines employ very heavy contra-rotating paddles, whilst a

modern continuous mixers consist of an interrupted screw which oscillate with both rotary

and reciprocating motion between pegs in an enclosing cylinder. The important principle in

these machines is that the material has to be divided and folded and also displaced so that

fresh surfaces recombine as often as possible (Meyer, 1992; Perry and Green, 1997).

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4.2.4 DESIGN OF MIXER

SPECIFICATION

N= Rotational speed s-1

D=blade diameter m

T=Tank diameter m

P=Power Kgm2/s3

e=density Kg/m3

µ=viscosity Kg/ms

Ut=Tip velocity m/s

Np= Power number

V=volume m3

=mixing (blending) time s

Nb= Blend number

PHYSICAL DATA

Based on laboratory unit data and scale up exponent n see Appendix F

N=108 s-1

e=2200 kg/m3

µ=200 Ns/s2

P=22.38 kgm2/s3

v=0.1893 m3

L=laboratory unit data

DETERMINATION OF PARAMETERS

(1) SIZE OR CAPACITY

c=m/

where m= mass of dough

=blend time

c=622 kg/h

(2) BLADE DIAMETER

D=sqr(PPL.NL3.DL5/PL.µ.N3)5

D = 0.2549

(3) TANK DIAMETER

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T=sqr(TL3.V/VL)3

T=0.622 m

(4) TIP VELOCITY

Vt=ND=86.50 m/min

=1.44 m/s

(5) POWER PER UNIT VOLUME

P/V=118.23 kg/ms3

(6) POWER NUMBER

Np = P / eN3D5 = .1

(7) BLEND NUMBER

NB=N

=162000

4.3 EXTRUDER

Extrusion is an operation in which a mass of plastic or semi soft material inside a

heavy walled cylindrical container is forced to flow through an orifice (die or mould) at

one end of the container as a result of pressure applied to the material by a piston (ram)

acting at the other end of the container. The process is often successful on materials, which

are too brittle to work by other shaping methods such as rolling. The instruments for this

process are generally called extruders. They may come in many shapes and work with

different principles e.g. the extrusion mixer, presses the material via a kneader.

Extrusion is well suited to producing long bars of constant cross section. The shape

of the cross section, which is determined by the die opening, may be quite complex. The

force required for extrusion may be supplied by a hydraulic cylinder, which drives the ram.

The material to be extruded must have sufficient plasticity so that it begins to flow through

the die at a pressure less than the breaking point of the material. The ram pressure should

not be above 180,000lb/m2. The die is another limiting feature of the process since it may

lose its shape if pressure and temperature becomes excessive and abrasive wear may occur.

The pressure (force/area) required for extrusion is a function of the stiffness of the

material, surface friction and changes in cross sectional are from the billet to the rod or

shaped material (Perry and Green, 1997).

A useful expression is P = KlnR.

Where R = Ratio of the initial to final cross sectional area

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K = Constant which is a function of temperature

TABLE 4.1: EXTRUSION CONSTANT K OF SOME METALSMETAL TEMPERATURE K (lb/in2)

2S Aluminium 400

600

800

1,000

20,000

12,000

8,500

7,500

Iron 1,800 50,000

Powerful presses up to 15,000 tonnes capacity are used for extrusion, but the most

common size is about 2,500 tonnes. Suitable lubricants (ground nut oil) must be used to

reduce extrusion force, increase die life and give better surface on the extruded product. In

general the force required to overcome friction, even in well-lubricated operation is about

25% of total force (Richardson and Peacock, 1994).

Extruded product are usually or sometimes used as extruded, but it is more

common practice to employ a subsequent cold working operation, such as drawing to

improve the surface finish and to get greater dimensional accuracy or desired thickness.

4.3.1 DESIGN OF EXTRUDER

SPECIFICATION

e=Density of dough kg/m3

m=mass dough kg

Ut=Total volume of dough m3

T=extrusion time s

F=Force of extrusion N

A=Area of piston m2

P=Pressure N/m2

VE=Volume of dough extruded per sec m3

Ut=velocity of piston m/s

H=height of extruder chamber m

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L=length of extruder surface m

W=thickness of extruded surface m

DATA

e=2200 kg/m3

m=186.608 kg

L=0.97 m

W=0.40m

H=0.05m

4.4 OVEN (DRYER)

Drying (baking) is the removal of volatile substances (moisture) by heat from a

mixture that yields a solid product (biscuit). Dryers are classified by:

(1) HEATING METHOD: The manner whereby the moist material removes heat i.e. by

conduction heating from the sheets or very wet material. Convective heating is the most

common, where mild heating is necessary to avoid heavy degraded product, and radiation

drying is used in the microwave oven (Macrea and Robbinson, 1997).

(2) PROCESS CONDITION: The pressure and temperature of operation which are

constrained however by the nature of the materials to be dried. The thermal sensitivity of

the material fixes the maximum temperature to which the material may be heated. The

temperature rises with the time the material is held in the dryer.

(3) CONVEYING METHOD: The way the material is loaded or supported in the dryer.

The outward appearance of the dryer depends largely upon the way the drying material

moves through the equipment. Free flowing granules can be handled in many ways

(conveyor, rolling, trays etc), but more awkward materials often require special techniques.

Most modern dryers are operated continuously or semi-continuously over the working tray,

as a continuous dryer will require less labour, fuel and floor space than the batch dryers.

Certain factors are considered in the selection of dryer for particular purpose, they are:

(1) Feed Condition: is it solid, liquid, paste powder, crystals etc.

(2) Feed Concentration, the initial liquid content.

(3) Product Specification, dryers required, physical form.

(4) Throughput Required.

(5) Heat Sensitivity of The Product.

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(6) Nature of Vapour, toxicity and flow ability.

(7) Nature of the Solid: flammability (dust explosion hazard), toxicity.

4.4.1 CONVEYOR DRYERS(CONTINUOS CIRCULATION BAND DRYERS)

The conveyor dryer (oven) has been chosen for the production of one tonne of

biscuit per day, because of the complete accessories it has to offer.

In this type the solids are fed onto the endless, perforated conveyor belt, through

which hot air is forced. The belt is housed in a long rectangular cabinet, which is divided

into zones, so that the flow pattern and temperature of the drying air can be controlled. The

relative movement through the dryer of the solids and drying air can be parallel or more

usually counter-current (Marcel and Dekkar, 1987).

This type of dryer is clearly only suitable for materials that form a belt with an

open structure. High drying rate can be achieved with good product quality control.

Thermal efficiency are high and with steam heating, steam usage can be as low as 1.5 per

Kg of water evaporated.

4.4.2 DESIGN OF DRYERS (OVENS)

There may be more than one type of dryers suitable for a particular job, therefore

the choice based on optimal cost, fuel or power rating and space comes to mind during the

design for a process dryer. The design Engineer chooses for a given dryer conditions which

enable the specified properties of the product to be obtained. In this way performance

characteristics of alternative system can be expressed as a basis for the ultimate choice of

the specified plant (Ulrich, 1986). Almost always some small scale are needed to

determine the materials drying characteristics required to predict the way which the shift

will be in the commercial plant.

SPECIFICATION

A=Total surface area of dryer m2

AH=surface area of heating zone m2

AC=surface area of concentred drying zone

AF=surface area of falling rate zone m2

DTMF= log. mean temperature difference in the falling rate zone oC

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DTMH= log. mean temperature difference in the falling zone oC

Ti= zone heating medium (steam) inlet temperature

To=zone heating medium (steam) outlet temperature

ti=zone in process material, inlet temperature in a zone

to=zone in process material, outlet temperature in a zone

DATA

THi=270K (543oC)

THo=270K (543oC)

tHi=80K (353C)

tHo=180K (453oC)

QH=33407.994 kJ/h

QC=40953.265 kJ/h

QF=25629.565 kJ/h

UH = 142

UC = 227.13

UF = 852.2

LH = 1

LC = .8

LF = .6

Moisture drying ratios

25:40:15

5:8:3

142:227.2:85.2

DTMH = (543 - 453) - (543 - 353) / In((543 - 453) / (543 - 353))

=183.83 =133.83

DTMF = (543 - 513) - (543 - 453) / In((543 - 513) / (543 - 453))

=39.15 =54.61

AH=Q/UTL=33407.994/142x133.83x1=1.76m2

AF=Q/UDTL=25629.565/85.2x54.61x.6=9.18

AC=4953.265/227.13x(543-453)x0.8=0.267m2

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C H A P T E R F I V E

E C O N O M I C S U R V E Y

5.1 ECONOMIC ANALYSIS

5.1.1 ESTIMATED PROJECT COST

The following are the estimated costs of the project based on the prevailing

economy of the country.

TABLE 5.1: ESTIMATED PROJECT COST

DESCRIPTION COST (N m)

MACHINERY & EQUIPMENT 4.90

FACTORY & OFFICE BUILDING 2.00

WORKING CAPITAL 2.00

AUXILIARY ITEMS (UTILITIES) 0.80

PRE-OPERATIONAL EXPENSES 0.30

GROSS TOTAL

VALUE ADDED TAX (VAT, 5%)

NET TOTAL

10.00

0.50

10.50

The sales turnover is estimated at about thirty-million naira (N 30.0m) in the first

year of operation while a profit margin of four million-naira (N 4.0m) is obtainable from

the project.

The project can be financed through a mixture of equity contribution, term loan and

overdraft from commercial or merchant banks.

5.1.2 FIXED CAPITAL

Fixed capital refers to buildings, industrial plants, machinery and tools, motor

vehicles, office equipment (Max and Klaus, 1973). The cost of machinery and equipment

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is estimated at about five million naira (N 4.90 m) and that of factory space is estimated at

about two million (N 2.0m).

5.1.3 WORKING CAPITAL

Working capital is mostly referred to as circulating capital which are non-

renewable goods, such as raw materials, fuel and the funds required to pay wages and other

claims against the company ( Bauman, 1984; Ulrich, 1986). The estimated working capital

required for this project is two million naira (N 2.0m).

The raw materials are estimated for four months requirements including goods-in-

transit already paid for. The salary for the personnel should also be enough for three

months pay. Proper arrangement should also be made for contingencies.

TABLE 5.2: THE BREAKDOWN OF THE WORKING CAPITAL ITEM COST(N m)

4 MONTHS RAW MATERIALS

3 MONTHS SALARY

CONTINGENCIES

1.78

0.20

0.02

TOTAL 2.00

5.1.4 NET COST

The net cost of the biscuit production plant including provision for working capital

and the value added tax (VAT) at 5% is estimated at about ten million naira (N 10.5 m).

5.2 COST OF PRODUCTION

5.2.1 RAW MATERIALS

The main raw materials for the production of biscuit are flour, sugar, additives,

water, baking powder and yeast. Wheat flour and sugar are produced locally and this will

reduce the overall cost of production. Additives include; flavouring, shortening, colourants

and modifiers, which are also obtained locally while water, baking powder and yeast, are

readily available.

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Most of these materials are locally produced (although most of them are still

imported to meet the demand of the populace) and thus help reduce the overall cost of

production and consequently produce biscuit at a cheaper rate, but putting into

consideration that they must of necessity be good food grade and hygienic.

5.2.2 LABOUR COST

In estimating the labour requirement and cost for plant personnel, a one eight hour

shift was assumed for the direct production workers. The indirect production workers will

also operate a single shift for eight hours. The full labour requirement which are detailed in

Appendix C are summarised below:

TABLE 5.3: LABOUR COSTDESCRIPTION NO.OF PEOPLE COST (N m)

DIRECT PRODUCTION WORKERS

INDIRECT PRODUCTION WORKERS

15

15

840,000.00

1,548,000.00

TOTAL 30 2,388,000.00

5.2.3 OVERHEAD COST

The estimated overhead cost are enumerated in Appendix C. They are allocated

between production, administration and sales as follows:

TABLE 5.4: OVERHEAD COSTDESCRIPTION COST(N m)

PRODUCTION

ADMIN & SALES

1.012

0.280

TOTAL 1.292

5.3 DEPRECIATIONS

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In estimating the depreciation charges, the plant and building were written off over

a 20 years period, the equipment over 10 years, the office equipment and furniture over 5

years. The charges arrived at are as follows:

TABLE 5.5: DEPRECIATIONASSETS VALUE

(N m)DEPREC.RATE %

ANNUAL DEP.(N m)

OFFICE & FACTORY BUILDING

PLANT & EQUIPMENT

OFFICE FURNITURE & EQUIPMENT

2.00

4.90

0.20

5

5

10

0.100

0.245

0.020

TOTAL 0.365

5.4 PROJECTED INCOME AND EXPENSES STATEMENT (2002-2005)

Based on the production capacity of one tonne of biscuit per day, the total annual

output (allowing 30 days for planned maintenance work) is 280 tonnes.

The average output of 210 tonnes has been estimated for the plant first year of

operation (working at 75% capacity).

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TABLE 5.6: PROJECTED INCOME AND EXPENSES STATEMENTYEARS 2002 2003 2004 2005

TONNE

CAPACITY, %

REVENUE

NET SALES (N m)

EXPENDITURE

RAW MATERIAL (N m)

FACTORY LABOUR (N m)

DEPRECIATION (N m)

OVERHEAD (N m)

TOTAL (N m)

TRADING PROFIT

BEFORE INTEREST(N m)

LOAN INTEREST (N m)

210

75

22.50

5.34

2.39

0.3650

0.9270

9.0220

13.4780

0.8

238

85

25.50

6.24

2.42

0.3458

1.0506

10.056

15.4436

0.6

266

95

28.50

7.16

2.62

0.3277

1.1742

11.282

17.2181

0.4

280

100

30.00

7.72

2.82

0.3105

1.2360

12.087

17.9135

0.2

NET PROFIT (N m) 12.6780 14.8436 16.8181 17.7135

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C H A P T E R S I X

S A F E T Y , S I T E & C O N C L U S I O N

6.1 SAFETY

6.1.1 SANITATION

In the biscuit industries, sanitation is the planned control of the production

environment, equipment and personnel to prevent or minimize loss, product contamination

and condition offensive to the aesthetic senses of the discriminating consumer and to

provide clean, healthful and safe working conditions.

Some of the broad areas of sanitation concern are(Meyer, 1992):

[1] GOOD MANUFACTURING PRACTICES: This implies orderliness and

freedom from refuse in all areas.

[2] RODENT ELIMINATION: It involves knowledge of rodent habits,

recognition of problems and permanent control through structural changes, removal of

harbourages and food supplies, and supplementary poisoning and trapping.

[3] INSECT ELIMINATION: Insect elimination from finished products and

ingredients in the factory requires recognition of serious or incipient infestations,

identification and knowledge of habits and ecology. Control methods may involve changes

in structure, equipment or process and safe use of insecticide chemicals.

[4] MICRO-ORGANISMS: The type and significance of which vary with product

and type of operation, must often be controlled by process and equipment change, cleaning

and sanitising chemicals.

Construction and maintenance of buildings and equipment are of major importance

in sanitation. New units can be planned to simplify sanitation maintenance, reduce costs

and eliminate the hazards of contamination and spoilage.

Cleaning of plant and equipment involves careful organisation, training, work

scheduling and the use of the best available equipment, methods and materials. The trend is

to clean processing equipment in place, without dismantling. This is done by an automatic

system that circulates and sprays cleaning and sanitizing solutions inside equipment in time

sequence.

Employment facilities, such as rest room, locker rooms, drinking water, eating

facilities and working environment, must be well maintained for the comfort and safety of

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the workers if they are to remain happy and maintain production efficiency and product

quality.

Laboratory tests, of importance to the sanitation program in the biscuit plant, must

be understood to be utilized to the best advantages.

Water supply quality and plant distribution systems, as well as waste treatment and

disposal, lighting and ventilation are often a part of sanitation.

Inspection techniques tailored to the specific sanitation situation must be taught,

learned and applied for efficient functioning and adjustment of the sanitation program.

6.1.2 WASTE MANAGEMENT

This is a newer approach to cost-effective food-processing waste disposal. Through

waste management, modifications are applied to biscuit plant operation and manufacturing

processes. These modifications reduce the amount of solid and liquid wastes, recover more

product and by-products, often reduce energy consumption and exhibit other benefits. In

general, the principle is to convert waste liabilities into profitable assets.

One major objective of waste management is to eliminate or at least lessen the

dependence upon end-of-the-pipe sanitary engineering methods. This is achieved by

reducing both the amount of waste solids generated and the volume of the waste water

discharged (Adeniyi, 1998).

The following are examples of modifications, which can be made to biscuit plant

operations:

[1] Incorporating good manufacturing practices

[2] collecting culls and other solid wastes into containers rather than discharging to the

floor drain,

[3] recycling water

[4] reusing spent process water in another plant operation and

[5] using less or no water in plant operations that formerly used a fair to a large amount of

water.

Good manufacturing practices that reduce water usage and waste require good

personnel management and employee awareness of conservation practices. Such practices

as needless use of water or overloading of containers, thereby causing spillage, should be

discouraged.

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Recycling of water in the same plant operation can be achieved by treating spent

process water with activated charcoal or sand filter or by ion-exchange columns, chemical

treatment, pH adjustment, temperature adjustment, pasteurisation, or a combination of

these and other methods.

Counter currents water reuse systems can be established in many plant operations.

For example, spent wash water can be used again to initiate wash down of dirty floors or to

flume solid waste away from the process line.

6.1.3 HUMAN SAFETY

Any organisation has a legal and moral obligation to safeguard the health and

welfare of its employees and the general public safety is also good business; the good

management practices needed to ensure safe operation will also ensure efficient operation.

The term "loss prevention" is an insurance term, the loss being the financial loss

caused by an accident. This loss will not be the cost of replacing damaged plant and third

party claims but also the loss of earnings from lost production and lost sales opportunity.

Safety and loss prevention in biscuit industries can be considered under the

following broad headings;

1) Identification and assessment of hazards.

2) Control of the hazards.

3) Control of the process. Prevention of hazardous deviation in process variables

(pressure, temperature, flow), by provision of automatic control systems, interlocks,

alarms, trips together with good operating practices and management.

4) Limitation of loss. The damage and injury caused if an accident occurs; pressure relief,

plant layout, provision of fire fighting equipment.

6.1.4 THRESHOLD LIMIT VALUE

This is the most commonly used guide for controlling the long-term exposure of

workers to contaminated air. The threshold limit value is defined as the concentration to

which it is believed the average worker could be exposed to day to day, for eight hours a

day, five days a week, without suffering harm (Odigure, 1995).

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6.1.5 NOISE

Excessive noise is a hazard to health and safety. Long exposure to high noise level

can cause permanent damage to hearing. At lower levels, noise is a distraction and causes

fatigue. Excessive plant noise can lead to complains from neighbouring factories and local

residents. Due attention should be given to noise levels when specifying and when laying

out equipment that is likely to be excessively noisy and such as compressors, fans, barriers

and steam relief valves.

6.2 PLANT LOCATION AND SITE SELECTION

The location of the plant can have a crucial effect on the profitability of a project,

and the scope for future expansion. The principal factors are:

(1) Location with respect to the marketing area

(2) Raw material supply

(3) Transport facility

(4) Availability of labour

(5) Availability of utilities (water, fuel, power etc.)

(6) Availability of suitable land

(7) Environmental impact and effluent disposal

(8) Climate

(9) Political and strategic consideration

6.2.1 MARKETING AREA

For a product such as biscuit in which case the product per tonne is low the plant

should be located close to the primary market.

6.2.2 RAW MATERIALS

The availability of suitable raw materials will often determine the site location. A

plant that will produce biscuit should be sited close to where the major raw materials are

available.

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6.2.3 TRANSPORTATION

The transport of materials and products to and from the plant is an overriding

consideration in site location. The plant should be located close to at least two major forms

of transport: road, rail, waterway (canal and river) or airport. Choosing at least two will be

an added advantage for the two cannot be out of service at the same time.

6.2.4 AVAILABILITY OF LABOUR

Labour will be needed for construction of the plant and its operation. Skilled

workers will be brought in from outside the site area, but there should be an adequate pool

of unskilled labour locally and labour suitable for training, to operate the plant. Skilled

tradesmen will be needed for plant maintenance.

6.2.5 UTILITIES

A biscuit plant invariably requires large quantities of water for its operation

(process and general use). Hence the plant must be located near a source of water of

suitable quality. Process water may be drawn from borehole or purchased from local

authority. Electrical power will be needed for the plant production process (mixer, electric

pumping machine, oven heater etc.) and also for lightings.

6.2.6 ENVIRONMENTAL IMPACT

Full consideration must be given to the difficulties and cost of disposal of biscuit

plant's by-product.

6.3 LAND (SITE) CONSIDERATION

Sufficient suitable land must be available for the proposed plant and for future

expansion, the land should be ideally flat, well drained and have suitable load bearing

characteristics.

6.4 CLIMATE

Since weather in Nigeria is neither too hot nor too cold, the site consideration in

form of climate can be neglected since the raw materials will not degrade in quality over

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the little time for storage and production. Also the country is not situated within the

earthquake region of the world.

6.5 POLITICAL AND STRATEGIC CONSIDERATION

Capital grants and other inducement are often given by government to direct new

investment to preferred area or locations such as high unemployment prone zone. The

availability of such grants can be the overriding consideration in site selection.

6.6 SITE LAYOUT

The biscuit industry and ancillary building should be laid out to give the most

economical flow of material and personnel around the site. Consideration must also be

given to the future expansion of the biscuit factory. The ancillary buildings and services

required on a site in addition to the main processing units (buildings) will include:

(1) Storage for raw materials and products

(2) Maintenance workshop

(3) Stores for maintenance and operating supplies

(4) Laboratory for process control

(5) Fire station and other emergency services

(6) Utilities (storage tank, cooling water, steam)

(7) Effluent disposal plant

(8) Offices for general administration

(9) Canteens, car park, security post etc.

When roughing out the biscuit factory layout the process unit will normally be sited

first and arranged to give a smooth flow of material through the various processing steps,

from raw material to final step.

The location of principal ancillary buildings should then be decided. They should

be arranged so as to minimize the time spent by personnel in travelling between buildings.

The sitting of the main process route will determine the layout of the plant roads,

pipe alleys and drains. Access roads will be needed to each building for construction,

operation and maintenance. Utility buildings should be sited to give the most economical

runs of pipes to and from the process units. The main storage area should be placed

between the loading and unloading.

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R E F E R E N C E S

Adeniyi O.D. (1998) “ Design of a plant to produce one tonne of Biscuit per day” Plant

Design Thesis, Federal University of Technology, Minna, pp. 1-63

Bauman H.C. (1984) “Fundamental of cost engineering in the chemical industry” Reinhold

Publishing corporation, New York, pp. 16-67, 415-516

Crenan J.G. and Butter J.R. (1990) “ Food engineering operation,” George Godwin Inc.,

Vol. 3, London, pp. 571-603

Macrea J.A. and Robbinson D.K. (1987) “ Drying principles and practice,” Pergamon

Press, Oxford, pp. 14-21, 115, 231,412

Marcel and Dekkar (1987) “ Handbook of industrial drying” Munjar Inc., 4th edition, New

York, pp. 393-412

Max P. and Klaus D.T. (1973) “ Plant design and economics for chemical engineers”

McGraw Hill Book company, New York, 3rd edition, pp. 11-24

Meyers R.A. (1992) “Encyclopaedia of physical science and technology” vol. 15, 2nd

Edition, academic press Inc., London, pp, 519-520

Odigure J.O. (1995) “General chemical engineering technology” Jodigs and associate,

Minna, pp. 19-24, 129

Ogunsola V. (1999) “Food preparation recipes for Nigerians schools and homes” Update

Media ltd., Ilorin, pp. 116-128

Onyia C. (1997) “ Make your money producing biscuits” Success digest magazine, Lagos

Perry R.H. and Peacock D.G. (1994) “Coulson and Richardosn chemical engineering”

Vol. 3, 3rd edition, Pergamon Press, Great Britain, pp. 71-103

Ulrich G.D. (1986) “ A guide to chemical engineering process design and economics”

Wiley & sons company, New York, pp. 33,46,105

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A P P E N D I X A

LIST OF PRODUCTION PLANT MACHINERY

A list of the production machinery needed for the production of one tonne of

biscuit per day is (Adeniyi, 1998):

[A] THE MIXING UNIT

(a) 2 water tanks

(b) 1 mixer

(c) 1 weighing machine

(d) 1 measuring/regulating device for water

(e) 1 water pump

[B] THE EXTRUDER UNIT

(a) 1 extruder fitted with mould, cutting and stamping device

[C] THE DRYING UNIT

(a) 1 horizontal dryer with conveyor belt

(b) 1 collection table

(c) trays

[D] THE PACKAGING UNIT

(a) 6 wooden silos

(b) 6 tables

(c) 6 weighing machines

(d) Nylon sealing machines

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A P P E N D I X B

CALCULATION OF MASS & ENERGY BALANCE

B1.1 OVERALL BALANCE

The composition of the feed is as listed in chapter three. From the material balance

carried out it can be seen that to get a product of 1000 kg (1 tonne) of biscuit, a feed mass

of 1357.15 kg of the raw material is required. This will require the following mass of feed:

[1] Flour 678.58 kg [2] Sugar 27.14 kg

[3] Water 407.15 kg [4] Baking powder 27.14 kg

[5] Addition/modifier 217.14 kg

B1.1.1 MATERIAL BALANCE

Taking a basis of 1000 kg of feed; the masses of the feed based on the composition

is:

(a) Flour = 50%=500 kg

(b) Sugar = 2.0%=20 kg

(c) Water = 30%=300 kg

(d) Baking powder = 2.0%=20 kg

(e) Additives = 16%=160 kg

Initial moisture content = 30%=300 kg

Final moisture content = 5% = 50kg

300 kg of moisture is associated with 700 kg of dough

300 kg ---> 700 kg (i.e. 300 kg + 700 kg = 1000 kg)

50 kg ---> 950 kg of dry matter (i.e. 50 + 950 =1000 kg)

==> (50 x 700)/950 =36.84 kg moisture associated with 700 kg

1000kg of original matter must loss (300-36.84)=263.16 kg of moisture

==> weight of dried matter leaving the dryer

=1000-263.16 =736.84 kg

Working backward,

0.30T ---> 0.70T

0.05T ---> 0.95T

Y=(0.05T x 0.70T) / 0.95T =0.0368T

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x of the original matter must loss (407.15-49.998) = 357.15kg

0.3T - 0.0368T = 357.15 kg

T(0.3-0.0368) = 357.15 kg

T= 357.15/0.2632=1356.95 kg

The difference (1000-736.84) =263.16 kg of moisture lost

The difference (1356.95-357.15)= 999.8 kg of biscuit, this value is 0.2 short of the

expected 1000kg. This means that the original feed must be (1356.95 + 0.2)= 1357.15 kg.

B1.1.2 HEAT BALANCE

Heat capacity = ((4.19 P) +(0.84(100-P)))/100

where P= moisture content of biscuit dough =30%

Heat capacity=((4.19x30)+(0.84(100-30)))/100=1.845 kJ/kgoC

Latent heat = 335P/100= 335x30/100=100.50 kJ/kgoC

Heat required for 1kg original material:

= Heat energy to raise temp. to 100oC + Latent heat to vaporise water = m1Cp0 + m2L

=1 x 1.845(100-30) + (357.17 x 2257)/1357.15 = 715.97 kJ (kW/s)

The heat required in baking 1357.15kg

= 1357.15x1.845(240-30) + 357.17 x 2257

= 525827.77+806132.69 = 1331960.46 kJ

Since 10% of moisture is lost the overall heat balance over the oven is:

m1=(1357.15-(1357.15x10)/100 = 1221.44 kg

me=(357.17 - (357.17x10)/100 = 321.453 kg

Heat = 1221.44 x 1.845 (240-30)+ 321.453x2257 =1198766.35 kJ

From the material balance carried out, to get a product of 1000kg (1 tonne) of

biscuit we will need to feed a mass of about 1492.96 kg of the raw material. This will

require the following mass of feed:

[1] Flour 746.48 kg [2] Sugar 298.59 kg

[3] Water 447.84 kg [4] Baking powder 29.86 kg

[5] Addition/modifier 238.87 kg

The loss is estimated at 134.85 kg to make up to 1492.96 (1357.15 + 134.85)

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B1.1.3 OVERALL MATERIAL BALANCE

In a hourly basis:

Mass in

Total material in = (1492.96/8) =186.62 kg/hr

Total dry solid in = (1045.12/8) =130.64 kg/hr

Total water in = (447.84/8)= 55.98 kg/hr

Mass out

Total material out = (1100/8) = 137.5 kg/hr

Total dry solid out = (1045/8) = 130.63 kg/hr

Total water out = (55/8) = 6.875 kg/hr

Loss = 49.11 kg/hr

3.1.2 UNIT MATERIAL BALANCE

3.1.2.1 MIXER

Mass in

Total material in = 1492.96 kg

Water in = (30% of 1492.96) = 447.84 kg

Solid in = (70% of 1492.96) = 1045.12 kg

Since there is no loss in the mixer

Material in = material out

1492.96 kg = 1492.96 kg

On an hourly basis:

Total material in = Total material out

Water in = Water out = 55.98 kg/hr

Solid in = Solid out = 130.64 kg/hr

3.1.2.2 EXTRUDER

Mass in

Water in = 447.84 kg

Solid in = 1045.12 kg

Total material in = (447.84 + 1045.12)=1492.96 kg

Mass out

Water out = 261.25 kg

Solid out = 1045 kg

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Losses = 186.71 kg

Total material out =(1045 +261.25)= 1306.25 kg

On a hourly basis:

Water in = (447.84/8) = 55.98 kg/hr

Solid in = (1045.12/8) =130.64 kg/hr

Material in (total) =(55.98 + 130.64)= 186.62 kg/hr

Water out = (261.25/8)= 32.66 kg/hr

Solid out =(1045/8)= 130.63 kg/hr ; Losses = (186.71)/8=23.34 kg/hr

Total material out =32.66 + 130.63 = 163.29 kg/hr

3.1.2.3 DRYER

Basis: 1000kg/hr of product

Water in = 261.25 kg

Solid in = 1045.00 kg

Total material in = (261.25 + 1045)=1306.25 kg

Water out = 55 kg

Solid out = 1045 kg

Total material out =(55+1045) = 1100 kg

On a hourly basis:

Material in = 1306.25/8= 163.28 kg/hr

Material out =1100/8= 137.50 kg/hr

Dry solid in = 1045/8=130.63 kg/hr

Dry solid out =1045/8=130.63 kg/hr

Water in = 261.25/8= 32.656 kg/hr

Water out =55/8= 6.875 kg/hr

3.2 ENERGY BALANCE

3.2.1 OVERALL ENERGY BALANCE

HEAT GENERATED FOR THE MIXER + HEAT GENERATED FOR THE

EXTRUDER + HEAT GENERATED FOR THE DRYER = TOTAL HEAT LOAD

80568 + 469800 + 99990.824 = 650358.824 kJ/hr

3.2.2 UNIT ENERGY BALANCES

Most of the energy balances were done using the computer program developed (Appendix

D)

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3.2.2.1 MIXER

Heat in = 80568 kJ/hr

Heat load in dough = 4226.72 kJ/hr

Heat loss in mixer = 76341.28 kJ/hr

3.2.2.2 EXTRUDER

Heat in = Heat out

Heat generated in extruder = Heat load in dough + heat loss in extruder

Heat generated = 469800 kJ/hr

Heat loss in extruder = 448516.8 kJ/hr

Heat load in dough = 21283.2 kJ/hr

3.2.2.3 DRYER

The dryer zone has three zones:

Zone 1 (heating zone)

Heat generated for solid = 19725.13 kJ/hr

Heat generated for liquid = 13682.864 kJ/hr

Total heat load for zone 1

19725.13 + 13682.864 = 33407.994 kJ/hr

Zone 2 (constant rate change zone)

Heat in = Heat out

Heat generated = 40953.265 kJ/hr

ZONE 3 (falling rate zone)

Heat load for solid = 3944.12 kJ/hr

Heat load for evaporated water = 21109.32 kJ/hr

Total heat load in the filling rate zone

= Heat in solid + Heat in evaporated liquid

= 3944.12 + 21109.32 + 576.125

= 25629.565 kJ/hr

Total load for the dryer = 33407.994 + 40953.265 + 25629.565

= 99990. 824 kJ/hr

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A P P E N D I X C

F I N A N C I A L E V A L U A T I O N

C1.0 LABOUR REQUIREMENT AND COST

The total labour requirements were estimated on the basis that the direct production

workers will work one eight hour shift and the indirect production workers also a single

eight hours shift.

C1.1 DIRECT PRODUCTION WORKERSNUMBER UNIT COST

(N m)

TOTAL

COST(N m)

SUPERVISOR/ENGINEER

MIXING UNIT

EXTRUSION UNIT

DRYER UNIT

PACKAGING UNIT

1

2

2

4

6

40,000.00

16,000.00

16,000.00

20,000.00

16,000.00

40,000.00

32,000.00

32,000.00

80,000.00

96,000.00

TOTAL 15 280,000.00

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C1.2 INDIRECT PRODUCTION WORKERSNUMBER UNIT COST

(N m)

TOTAL

COST(N m)

MANAGING DIRECTOR

PRODUCTION MANAGER

ACCOUNTANT

ADM. MANAGER

SALES MANAGER

CASHIER

SECRETARY/TYPIST

SECURITY

QUALITY CONTROL

TECHNICIAN

TECHNOLOGIST

1

1

1

1

1

2

1

4

2

1

70,000.00

56,000.00

52,000.00

52,000.00

52,000.00

24,000.00

22,000.00

20,000.00

20,000.00

44,000.00

70,000.00

56,000.00

52,000.00

52,000.00

52,000.00

48,000.00

22,000.00

80,000.00

40,000.00

44,000.00

TOTAL 15 516,000.00

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Page 42: Plant Design-Biscuit Manufacturing

C1.3 OVERHEAD COSTPRODUCT-

ION(N m)

ADM. & SALES

(N m)

TOTAL

COST(N m)

FUEL,POWER & WATER

MAINTENANCE

CONSUMABLE MATERIAL

GROUND RATE & RENT

INSURANCE

VEHICLE RUNNING

TRAVELLING

POSTAGE & PHONE

ADVERTISEMENT

DEPRECIATION

140,000

240,000

120,000

-

60,000

40,000

12,000

-

-

400,000

60,000.00

-

-

60,000.00

-

20,000.00

40,000.00

40,000.00

60,000.00

-

200,000.00

240,000.00

120,000.00

60,000.00

60,000.00

60,000.00

52,000.00

40,000.00

60,000.00

400,000.00

TOTAL 1,012,000 280,000.00 1,292,000.00

C1.4 PROJECTED INCOME AND EXPENSES STATEMENT

1 Tonne of biscuit/day, in 1 year = 1x365 tonnes

Less 30 days of maintenance =365-30=326 tonnes

Less 48 days of non-working days in a year = 326-48= 278 280

Based on capacity the following tonnes are evaluated:

(a) 75%=0.75x280=210 (b)85%=0.85x280=238

(c) 95%=0.95x280=266 (d)100%=1.00x280=280

C1.4.1 REVENUE

Total sales revenue of N30m is expected on 100% capacity. So for other capacities:

(a) 75%=0.75x30= N 22.50m (b) 85%=0.85x30= N 25.50m

(c) 95%=0.95x30= N 28.50m (d) 100%=1.00x30= N 30.00m

C1.4.2 Depreciation

1st year (2002)=0.365

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2nd year (2003)

a. Factory= 0.1 – (5/100 x 0.1)=0.0950

b. Equipment= 0.245 – (5/100 x 0.245)=0.2328

c. Furniture = 0.02 – (10/100 x 0.02)=0.018

Depreciation = 0.0950 + 0.2328 + 0.018 = 0.3458

3rd Year (2004)

d. Factory= 0.0950 – (5/100 x 0.0950)=0.0903

e. Equipment= 0.2328 – (5/100 x 0.2328)=0.2212

f. Furniture = 0.018 – (10/100 x 0.018)=0.0162

Depreciation = 0.0903 + 0.2212 + 0.0162 = 0.3277

4th Year (2005)

g. Factory= 0.0903 – (5/100 x 0.0903)=0.08579

h. Equipment= 0.2212 – (5/100 x 0.2212)=0.2101

i. Furniture = 0.0162 – (10/100 x 0.0162)=0.01458

Depreciation = 0.08579 + 0.2101 + 0.01458 = 0.3105

C1.4.3 Overhead

Overhead = total – depreciation

1st year = 1.292 – 0.365= 0.927

2nd year = 0.927 x 85/75= 1.0506

3rd year = 0.927 x 95/75 =1.1742

4th year = 0.927 x 100/75 = 1.2360

C1.4.4 Trading profit

Trading profit before interest = revenue - expenditure

1st year = 22.50 – 9.022= 13.478

2nd year = 25.50 – 10.0564 =15.4436

3rd year = 28.50 – 11.2819 =17.2181

4th year = 30.00 – 12.0865 = 17.9135

C1.4.6 Net profit: net profit = trading profit – loan interest

1st year = 13.478 – 0.8 = 12.6780

2nd year = 15.4436 – 0.6 = 14.8436

3rd year = 17.2181 – 0.4 = 16.8181

4th year = 17.9135 – 0.2 = 17.7135

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Page 44: Plant Design-Biscuit Manufacturing

A P P E N D I X D

C O M P U T E R P R O G R A M

A computer program was written in basic to solve the material and energy balance,

the program is listed below (Adeniyi, 1998):

CLS

LOCATE 2, 20: PRINT "PLANT DESIGN PROJECT"

LOCATE 4, 2: PRINT "DESIGN OF A BISCUIT PLANT WITH 1 TONNE CAPACITY

PER DAY"

LOCATE 6, 20: PRINT "COMPILED BY GROUP TWO"

LOCATE 8, 20: PRINT "FEBRUARY 1998"

'A$ = INPUT$(1)

20 :

INPUT "Mass of feed (Kg)"; F

MA = .3 * F

MB = .7 * F

MC = .05 * F

MD = .95 * F

ML = (MC * MB) / MD

MM = MA - ML

WB = F - MM

HC = ((4.19 * 80) + (.84 * (100 - 80))) / 100

LH = (335 * 80) / 100

HR = ((100 - 80) * HC) + (.25 * 2257)

HR2 = HR / 3600

PRINT "OVERALL MATERIAL AND HEAT BALANCES"

PRINT "Weight of moisture lost by wet dough in dryer="; MM; "Kg"

PRINT "Weight of dried biscuit leaving the drier ="; WB; "Kg"

PRINT "Heat capacity of biscuit ="; HC

PRINT "Latent heat of biscuit="; LH; "KJ/KgC"

PRINT "Heat required to dry 1Kg of biscuit="; HR; "KJ"; "or"; HR2; "KW/h"

HH = ((240 - 80) * HC * F) + (MM * 2257)

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PRINT "Heat required to dry"; F; " Kg ="; HH; "KJ"

PRINT "IS THE MATERIAL BALANCE SATISFACTORY"

PRINT "THEN PRESS Y FOR YES AND N FOR NO"

30 :

A$ = INKEY$: IF A$ = "" THEN 30

IF A$ = "Y" THEN 50

IF A$ = "y" THEN 50

IF A$ = "N" THEN 20

IF A$ = "n" THEN 20

50 :

WIN = .3 * F

ASIN = .7 * F

TIN = WIN + AASIN

PRINT "MASS BALANCE OVER MIXER"

PRINT "Weight of water in is equal to weight of water out="; WIN; "Kg"

PRINT "Weight of solid in is equal to weight of dough out="; ASIN; "Kg"

A$ = INPUT$(1)

60 :

AD = (.95 * WB) / .8

WOUTD = .05 * WB

SOUTD = WB - AD

ASIND = .8 * AD

WIND = .2 * AD

PRINT "MASS BALANCE OVER DRYER"

PRINT "Weight of moisture entering dryer="; WIND; "Kg"

PRINT "Weight of moisture leaving dryer="; WOUTD; "Kg"

PRINT "Weight of dough entering dryer="; ASIND; "Kg"

PRINT "Weight of dough leaving dryer="; SOUTD; "Kg"

A$ = INPUT$(1)

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Page 46: Plant Design-Biscuit Manufacturing

70 :

WINE = .3 * F

WOUTE = WIND

WRE = WIN - WOUTE

ASINE = .7 * F

SOUTE = .2 * AD

PRINT "MASS BALANCE OVER THE EXTRUDER"

PRINT "Weight of moisture entering extruder="; WINE; "Kg"

PRINT "Weight of moisture leaving extruder="; WOUTE; "Kg"

PRINT "Weight of moisture removed from extruder="; WRE; "Kg"

PRINT "Weight of dough entering extruder="; ASINE; "Kg"

PRINT "Weight of dough leaving extruder="; SOUTE; "Kg"

A$ = INPUT$(1)

80 : HEE = 22.38 * 3600

HLD = WRE * 1.57 * 15

HLM = HLD - HEE

PRINT "HEAT BALANCE OVER THE DRYER"

PRINT "Heat load in dough="; HLD; "KJ/h"

PRINT "Heat loss in extruder"; HEE; "KJ/h"

90 :

PRINT "HEAT BALANCE OVER THE DRYER"

PRINT "Balance is estimated over 3 zones of the dryer"

PRINT "ZONE 1- HEATING ZONE"

PRINT "Inlet temperature =80C"

PRINT "Outlet temperature=180C"

QHL = (WIND * 4.19 * 100) / 8

QHS = (ASIND * 1.5 * 100) / 8

QH1 = QHL + QHS

PRINT "The heat load in liquid="; QHL; "KJ/h"

PRINT "The heat load on dough="; QHS; "KJ/h"

PRINT "The total heat load for zone 1="; QH1; "KJ/h"

A$ = INPUT$(1)

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Page 47: Plant Design-Biscuit Manufacturing

PRINT "ZONE 2- CONSTANT RATE ZONE"

PRINT "Inlet temperature =180C"

PRINT "Outlet temperature=220C"

QC = 2257 * 18.145

PRINT "The total heat load for zone 2="; QC; "KJ/h"

A$ = INPUT$(1)

PRINT "ZONE 3- FALLING RATE ZONE"

PRINT "Inlet temperature =220C"

PRINT "Outlet temperature=240C"

QFS = 130.6 * 1.51 * (240 - 220)

QFE = 7.635 * (2769 - 4.19)

QFV = 6.875 * 4.19 * (240 - 220)

Q3 = QFS + QFE + QFV

QT = Q1 + QC + Q3

QM = 469800

PRINT "The Heat load for the dough ="; QFS; "KJ/h"

PRINT "The heat load for the evaporated liquid="; QFE; "KJ/h"

PRINT "The heat load for the unevaporated liquid="; QFV; "KJ/h"

PRINT "The heat load for zone 3="; Q3; "KJ/h"

PRINT "The total heat load for the dryer= "; QT; "KJ/h"

PRINT "IS THE UNIT BALANCE SATISFACTORY"

PRINT "THEN PRESS Y FOR YES AND N FOR NO"

120 : A$ = INKEY$: IF A$ = "" THEN 120

IF A$ = "Y" THEN 200

IF A$ = "y" THEN 200

IF A$ = "N" THEN 20

IF A$ = "n" THEN 20

200 : QQT = QT + HEE + QM

PRINT "THE OVERALL HEAT GENERATED OVER THE WHOLE PROCESS=";

QQT; "KJ/h"

END

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Page 48: Plant Design-Biscuit Manufacturing

A P P E N D I X E

TYPICAL SUPPLIED HORSEPOWER FOR SIGMA BLADE

Table E1: Typical supplied horsepower (Hp) for sigma blade

Size number Capacity (Gallon) Horsepower

(Hp)

Floor space (ft2)

Working Maximum

4

6

8

11

12

14

15

16

17

18

20

21

22

23

0.7

2.3

4.5

10.0

20.0

50.0

100.0

150.0

200.0

300.0

500.0

600.0

750.0

1000.0

1.0

3.5

4.0

15.0

30.0

75.0

150.0

225.0

300.0

450.0

750.0

900.0

1125.0

1500.0

1.0

2.0

5.0

15.0

25.0

30.0

50.0

60.0

75.0

100.0

150.0

175.0

225.0

300.0

1 x 3

2 x 3

3 x 4

5 x 6

6 x 6

6 x 8

8 x 10

9 x 11

9 x 13

9 x 14

11 x 16

12 x 16

12 x 17

14 x 18

Conversion rating

1 Gallon = 0.003785 m2 = 3.785 litres

1 ft = 0.3048 m

1 Hp = 0.746 kW

48


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