assignment 3 of casein plant design2
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UNIVERSITAS INDONESIA
PRELIMINARY DESIGN OF CASEIN PLANT FROM SKIM MILK
PLANT DESIGN REPORT
ASSIGNMENT 3
GROUP 10
ADI KHAFIDH PERSADA 0906640702
FITRI ANISA 0906557871
LATIFANI AYU CHAERUNNISA 0906640822
MUHAMMAD IKHLAS 0906489896
PIJAR RELIGIA 0906557953
ENGINEERING FACULTY
BIOPROCESS ENGINEERING STUDY PROGRAM
DEPOK
SEPTEMBER 2012
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CHAPTER 5
HEAT EXCHANGER NETWORK AND UTILITY UNIT ANALYSIS
We need a heat to make a casein in a casein plant which the heat needs the big energy, so
we must make a plant to optimize the energy so that energy in our plant can be efficiently. To
save energy optimally, we can calculate Heat Exchanger Network (HEN). The purpose of
HEN calculating is to know the minimum of heat exchanger that is needed. The amount of
heat exchanger is affecting the minimum utility for temperature differences that is predicted.
Besides that, the calculating of HEN is also needed to know the cold utility is needed. To
calculate of Heat Exchanger Network (HEN), we must follow this procedure:
Determining the cold and hot stream Calculating the stream spesification and determining of Tmin Making of population streams Making of cascade diagram
To know about the calculating of HEN, we can calculate one by one of the procedure above:
1.1 Heat Exchanger Network
a. Determining The Cold and Hot streams
In the first step, we can determine the cold and hot stream from the super pro data.The cold and hot stream data from super pro data can be looked in table below:
Table 1.1. Hot Streams Data of Casein Plant
Number Stream Ts Tt Condition
1 R2 78 35 Hot
Table 1.2. Cold Streams Data of Casein Plant
Number Stream Ts Tt Condition
1 R1 25 40 Cold
2 R2 35 78 Cold
3 W1 25 65 Cold
4 W2 25 45 Cold
b. Calculating The Stream Spesification and Determining of Tmin
To calculate the stream spesification in our casein plant, we can use this formula below:
Assumption:Tmin : 10 C
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The Cp data is getting from process simulation in Hysys dan Super Pro software program.
To find the target and supply temperature for our heat utility in cold and hot streams can be
found with this formula:
For Hot Stream =
1
2 (3.1)
= 1
2 (3.2)
For Cold Stream = +
1
2 (3.3)
= +1
2 (3.4)
where Ts is supply temperature (C) and Tt is target temperature (C). For each hot and coldstream in our plant can be looked in the table below:
Table 1.3. Streams Spesification
Nama Condition kg/h Cp (KJ/kgC) Cp Q (kJ/h)
R1 cold 11200 4,2 47040,00 7,06E+05
R2 hot 12440 1,52 18908,80 8,13E+05
R2 Cold 12440 1,52 18908,80 8,13E+05
W1 cold 4309 4,2 18097,80 7,24E+05
W2 Cold 4088 4,2 17169,60 3,43E+05
Tabel 1.4. Supply and Target Temperature
Nama ConditionCp
(KJ/kgC)Ts(C) Tt(C) Ts* Tt* Tm (C)
R1 cold 4,2 25 40 30 45 10
R2 hot 1,52 78 35 73 30 10
R2 Cold 1,52 35 78 40 83 10
W1 cold 4,2 25 65 30 70 10
W2 Cold 4,2 25 45 30 50 10
After making the stream spesification, we can make a stream population to know thehot and cold stream distribution at the temperature something.
c. Making Of Stream Population
The temperature difference (H) is getting from this formula:
= (3.5)
From the formula above, if H interval has a positive value, it is called a deficit. But, if
H interval has a negative value, it is called a surplus.
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Figure 5.1. Stream Population Graphic
Stream population graphic is shown the hot and cold stream phenomenans in the
temperature range something. This graphic is using to calculate the value of Q (calor) which
is transmitted in the range of temperature where the value of Q will be used in cascade
diagram.
d. Making Of Cascade Diagram
Cascade diagram shows the clear energy in temperature interval. Cascade process can
be done during the energy can be transferred with the temperature gradient differences into
the temperature level below. From the cascade diagram, the needing of hot and cold utility
can be calculated based on energy distribution in each temperature interval. To know
furtherly about the cascade diagram in our casein plant, we can look in the figure below:
Interval Temp (C) T (C) CpC-CpH H interval (MW) Surplus/defisit
83
78 78 10 0,0 0 defisit
733 0,0 0 defisit
70
65 20 0,0 0 defisit
50
5 1,2 6 defisit
45
5 5,4 27 defisit
4035 35 10 12,6 126 defisit
30
25 25 25
Stream Population
cp4,2
cp1,52
cp1,52
cp4,2
cp4,2
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Figure 1.4. Cascade Diagram
From the cascade diagram above for heat exchanger network in our casein plant, we
conclude that we need a hot and cold utility. It can look from the hot utility line where the hot
utility in our plant is 126 MW atau sekitar 8,13 x 105 kJ/h. Besides that, the cold utility in our
plant is 33 MW atau sekitar 3,15 x 105 kJ/h. From the curve above, the pinch node in our
casein plant is 500C and 70
0C . So, our group decide the pinch node in our casein plant is
500C. After make the scheme, the grand composite curve can be made. This curve is to
determine utility type that will be used. The curve is:
Figure 1.5. Grand Composite Curve
From figure above it can be seen that hot utility is needed to increase temperature of
cold stream process. In this case, we need utility to fulfill the hot stream.
hot utility
83 0 MW
H = 0
73 0 MW
H = 0
70 0 MW
H = 0
50 0 MW
H = 6
45 -6 MW
H = 27
40 -27 MW
H = 126
30 -126 MW
cold utility
hot utility
83 126 MW
H = 0
73 126 MW
H = 0
70 126 MW
H = 0
50 126 MW
H = 6
45 120 MW
H = 27
40 93 MW
H = 126
30 -33 MW
cold utility
0
10
20
30
40
50
60
70
80
90
-50 0 50 100 150
Te
mperature(oC)
H (MW)
Grand Composite Curve
Grand
Composite
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1.2 Utility
1.2.1 Water Utility
Water supply system is needed to support the sustainability of the production plant.
Utility water is required as process water, cooling water in heat exchanger systems, boiler
feed water, equipment wash water and domestic water needs. The design of the water supply
system based on the ease of water collection, treatment system efficiency and economic
factors. In the casein plant used several types of water, namely, process water, cooling water,
boiler feed water, equipment wash water, domestic water and fire water. Can be explained as
follows:
1.2.1.1Water Utility Classification
a. Process Water
Most of the water used in the dissolution and dilution systems. In unit steam
explosion, water is required to dissolve sulfuric acid for coagulation process. Besides that,
process water is used in the last step of washing tank. Capacity of water needed in the process
in an casein plant is at 30255,22 kg/day.
b. Cooling Water
Cooling water system is used to maintain the temperature in the washing reactor. All
water used in the cooling system using water at ambient temperature is assumed to be 25oC.
Ice water is the most common form of cooling water used in dairies. Water is cooled in an ice
water tank where ice is formed on in chiller. The source of cooling water is come from the
PT. KIJA. The need for cooling water at the plant reached 156,97 kg/day. The cooling water
is needed in our plant can look in the table below:
Tabel 2.1.1.2. Cooling Water In Our Plant
Unit Cooling water needs (kg/h)
Acidification unit 117,28
Plate Heat Exchanger 39,69
Total 156,97
c. Domestic Water
This water is used to meet the water needs of the staff and factory workers. Domestic
water includes water MCK (bathing, washing, toilet), drinking water, water for watering
plants and other water needs. Assumed domestic needs for each person is 100 liters/day.
Thus, the total water needed for domestic water is 10,000 liters/day.
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d. Water Fire Extinguisher
Firefighting water used to extinguish the fire in case of fire. Water is one of the water
reserves that can be used at any time. Firefighting water used was water with the low specs,
but has undergone treatment first. The amount of water required for fire is assumed to 10,000
kg /day.
e. Water Resources
Water supply to the plant will be taken from Jababeka industrial area manager, PT.
KIJA. PT. KIJA independently manage all water providers to the needs of industries that
exist within the industry. Water supplied by PT. KIJA is considered clean enough and qualify
for use as water for industrial plants. So in the factory there is no clean water management
facilities further.
So, the total amount of water utility in our plant is 50412,196 kg/h or 50412,196
L/day.
1.2.2 Gas Utility
Gas Utility is need to make an air for spray drying. It comes from compressor. In
compresor, the refrigerant vapour is compressed to a high pressure in the compressor. This
increases the temperature of the vapour. The work carried out by the compressor is
transferred to the gas in the form of heat. This means that the gas leaving the Compressor
contains a greater quantity of heat than was absorbed in the evaporator. All this heat must
therefore be removed by cooling in the condenser. The most commonly used refrigerating
compressor is the piston compressor. The gas is drawn into cylinders and compressed by
pistons in the cylinders. The machines can be equipped with a varying number of cylinders.
They are available for refrigerating capacities between 0,1 and 400 kW. The screw
compressor (Figure 2.4), is also very common nowadays, especially for higher capacities.
The principal components are two helical rotors installed in a common housing. As the rotors
turn, gas is drawn into the gaps between the teeth and is trapped in the clearances. The
volume between the teeth is progressively reduced as the captive gas is conveyed along the
length of the rotors, so the gas is gradually compressed and the pressure increases. The
compressed vapour continues to the condenser. Oil is sprayed on the meshing faces in most
screw compressors in order to reduce leakage between the gaps in the rotors. In this way it is
possible to obtain high efficiency even at low speeds. The oil is removed from the vapour in
an oil trap before the condenser. Screw compressors are used in large installations. One of the
greatest advantages of the screw compressor is that the capacity can be varied down to 10 %
of full power without excessive electric power losses.
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Figure 2.4. Screw Conveyor
Source: Dairy Proceesing Handbook
Generally, diesel is used as fuel material in screw compressor. We can assumed that
efficient in screw conveyor as 40%. So, the fuel utility in the screw compressor is :
0,4 m = needing calor/heating value of fuel
0,4 m = 33875 J/0,00334 J/l
m = 25355538 ,92 l
1.2.3 Steam UtilityGeneration of the heating medium takes place in steam boilers which are sometimes
located in the heating plant. The boiler is usually fuelled with oil, coal or gas. Thermal energy
is released by the burning fuel and absorbed by the heating medium. The efficiency of the
boiler is in the range of 8092 %, and heat losses in the piping system often amount to about
15 %. Consequently, only between 65 and 77 % of the total thermal energy of the fuel can be
utilised in production. From the point of view of operating costs, it is most important that the
efficiency of the boiler does not drop below the minimum level, and for this reason, boiler
efficiency is very closely checked in the dairy. The steam temperature in the steam system
described below must be between 140 and 150 C. In the case of saturated steam, this is
equivalent to a gauge pressure of 270 385 kPa (2,7 3,8 bar). The boilers operate at a
considerably higher pressure, as a rule 900 1 100 kPa (9 11 bar), so that smaller piping
dimensions can be used to compensate for heat and pressure losses in the system.
Figure 2.1 is a simplified diagram of the steam system and the distribution network.
The water used for generation of steam is referred to as feed water. Makeup water often
contains calcium salts, which make the water hard. Treatment of feed water is often
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necessary, as it contains oxygen and carbon dioxide. If this is not done, the salts will be
deposited in the system and form scale in the boiler, resulting in drastically reduced
efficiency. Oxygen can cause severe corrosion in the water and steam parts. Water-softening
filters (10) are therefore included in the system. They remove the calcium and magnesium
salts, and a de-gassing apparatus (11) removes the gases in the feed water. Impurities in the
form of sludge are removed by blowing down the boiler. Chemical conditioning of boiler
water and treatment of boiler feed water are necessary to keep the steam system in good
operating condition.
Figure 2.1. Steam Production and Distribution Steam
Source: Dairy Processing Handbook
A feed water pump keeps the water in the boiler at a constant level. The water in the
boiler is heated by the burning fuel and converted to steam. It takes a great deal of heat, about
2 260 kJ (540 kcal) at atmospheric pressure, to convert one kilogram of water to steam. This
heat, which is referred to as vaporisation heat, will subsequently be released as the steam
Notes:
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condenses on the heat transfer surfaces at the points of consumption (5). The condensed
steam, condensate, is collected in steam traps (6) and a condensate tank (7) and pumped back
to the boiler by a condensate pump.
Two main types of boilers are used for the generation of steam: the fire tube boiler
(which is the most common type in dairies) and the water tube boiler. The choice is
influenced by the required steam pressure and steam power, i.e. the quantity of steam utilised
at a given time. Boilers for low pressures and small power outputs are often tubular boilers in
which the flue gases pass inside the tubes. Boilers for high pressures and large steam power
outputs are mostly water-tube boilers, in which the water is circulated inside the tubes.
Figure 2.2 shows the principle of the fire tube boiler. The hot flue gases are blown by a fan
through the tubes. Heat from the flue gases is conducted through the walls of the tubes to the
water surrounding the outside of the tubes. The water is heated to boiling point and the steam
is collected in the steam dome for distribution to the system.
Figure 2.2. Fire Tube Boiler
Source: Dairy Processing Handbook
When the pressure inside the steam dome reaches the required (pre-set) level, the
steam valve can be opened and the steam flows to the points of consumption. The burner is
started and stopped automatically, keeping the steam pressure at the required level. Feed
water is added so that the correct water level is maintained in the boiler. The safety valve
opens if the highest permitted pressure in the steam dome is exceeded.
Water-tube boilers (Figure 2.3) are available in a wide range of models. The principle
is that the feed water passes through tubes which are externally heated by the flue gases.
Steam generation takes place in the tubes, which are inclined so that the steam can rise to the
steam dome. The steam passes into the two upper domes via the superheater before being fed
into the distribution system. The steam is heated by the flue gases for a second time in the
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superheateri.e. the steam is superheated, and becomes dryer as a result. The lower dome also
collects sediment sludge, the impurities which were present in the feed water. The sludge is
removed from this dome by bottom-blowing the boiler. In other types of boilers, the sludge
collects in the bottom of the boiler.
Figure 2.3. Water-Tube Boiler
Source: Dairy Processing Handbook
The steam which passes through the piping system is cooled by the surrounding air
and consequently starts to condense. It is possible to reduce this condensation by insulating
the pipes, but condensation can never be completely avoided. The pipes must therefore be
installed with a slight slope towards the condensate collection points, which are located in
various parts of the piping system. Steam traps are installed at these points. They permit the
condensate to pass (and preferably also air), but not steam. The condensate is collected in the
same way at the various steam consumption points and is returned to a collecting tank in the
heating plant by condensate pumps and a piping system. Condensate can be returned to the
feed water tank by steam pressure without using a condensate tank or condensate pump. This
system is very often used.
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Figure 2.4. Stream Distribution
Source: Dairy Processing Handbook
Generally, the fuel which is used in boiler is diesel. It is assumed that the steam
required in the plant is entirely derived from fossil material. It is assumed that the boiler used
to use diesel as fuel. It is assumed that the efficiency of the boiler which is owned by the
boiler plant is 40%. Thus, the diesel fuel used to generate steam in the plant is equal to:
0,4 m = needing calor/heating value of fuel
0,4 m = 33875J/0,00334 J/l
m = 25355538 ,92 l
1.2.4 Electricity Utility
As the plant in general, to run the equipment contained in the bioethanol plant
required no small amount of energy. Equipment that requires a supply of energy, among
others:
Pump Plate Heat Exchanger Washing Tank Centrifugal Decanter Spray Drying Conveyor
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Electric needs at the casein plant can be seen in the following table:
Table 2.1. Needing Energy In Casein Plant
Demand Of Energy Hp kw kwh
Pump For Mixing Tank P-101 1 0,74 17,89
Pump For Dilution Of HCl P-102 0,5 0,37 8,94
Pump For Washing Tank P-103 0,5 0,37 8,94
Pump For Washing Tank P-104 0,5 0,37 8,94
Pump For Milk P-105 2 1,49 35,79
Pump For Curd Casein P-106 2 1,49 35,79
Plate Heat Exchanger 35444,11 26430,68 634336,32
Heat Exchanger 1 2,3 55,2
Heat Exchanger 2 2,3 55,2
Heat Exchanger 3 2,3 55,2
Washing Tank 1 0,01 0,01 0,24
Washing Tank 2 0,01 0,01 0,24
Mixing Tank 1,34 1 24
Decanter 1 170,89 127434 2986,42
Decanter 2 170,89 127,434 2986,42
Decanter 3 170,89 127,434 2986,42
Fan Spray Drying 4,80 3,58 143,2
Spray Drying 8,74 5 120
Pneumatic Conveyor 1 2,68 2 48
Pneumatic Conveyor 2 2,68 2 48
Pneumatic Conveyor 3 2,68 2 48
HCl Storage Tank 1,34 1 24
Water Storage Tank 1,34 1 24
Total kebutuhan listrik untuk proses 644057,15
Electricity is needed on the basis of casein plant from skim milk is a power type AC
(accuired current). The power requirement of the plant's total amounted to 644057,15 kWh /
day. While supporting the need for lighting and other assumed 5% of the total energy that is
32202,85 kwh / day. So the total electricity needs of the bioethanol plant 676260,01 kWh for
each day.
Electrical power is largely used for two main purposes. The first necessity that
requires electrical power is the need of the production process. The second purpose is to use
the power of production support facilities. Power to support facilities used for lighting andair-conditioning (AC) in the office, laboratory, workshop and control room, air supply (tap
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and clean), water supply (and the net), and the sewage treatment plant. Electricity in casein
plant is supplying from PT. Cikarang Listrisindo. To know about the all of utility in our plant
can be showed in table below:
Table 2.2. The Utility Of Casein Plant
Utility Source Demand per year
Water PT. KIJA 50412,196 kg/h
Electricity PT. Cikarang Listrisindo 676260,01 kWh
Diesel Pertamina 50711,07 Kl
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References:
Albert, Johan. 1991. Centrifugal Decanter Handbook. Newyork: McGraw Hill Book Co.
Paundhitro, Slamet. 2008. Spray Drying Handbook. Newyork: McGraw Hill Book Co.
Robert, Kevin. 2008. Unit Operation Of Chemical Engineering. Newyork: McGraw HillBook Co.
Smith, Julian 2008. Dairy Processing Handbook.. Newyork: McGraw Hill Book Co.