tk_16_draft_assg2.docx

8/11/2019 TK_16_DRAFT_ASSG2.docx

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UNIVERSITY OF INDONESIA

PLANT DESIGN

PRELIMINARY DESIGN OF BIO LIQUIFIED PETROLEUM GAS

(LPG) FROM BIOMASS

ASSIGNMENT 2

GROUP 16

ALRISTO SANAL (1106070836)

ANANDA PUTRA SANGAJI (1106070703)

CAHYA TRI RAMA (1106070905)

GALIH MERY DAMAIATI (1206314610)

OLIVIA CESARAH TARIGAN (1106070754)


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FACULTY OF ENGINEERING

UNIVERSITY OF INDONESIA

DEPOK

2014


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CHAPTER IV

EQUIPMENT SIZING

4.1 Absorption Column

Equipment Specification

Name Absorption Column

Code V-101

Function To absorb CO2and H2S from

process gas

Material Carbon Steel

Operational Data

Temperature 30C

Pressure 10 bar

Mass flow in 0.7

Pressure Drop 30

Operational velocity 111.9

Dimensional Data

Type packed

Packing ring 1 in pall rings

Total height Carbon Steel

Diameter 1

Wall Thickness 939.8

Shell Thickness 2

Corossion Allowance Carbon Steel

Absorber has a function to absorbed the acid gas, especially H2S, that

contain in syngas gasification product before it enter to water gas shift reaction.

Solution used to absorbed acid gas is mixed amine (MEA and MDEA) with the

composition 0.35 MDEA, 0.06 MEA, and water. Steps to design absorber are:


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State operation condition

-

T = 45 C

- P = 1000 psia

-

Sour gas composition:

Composition Mole Fractions

Methane 0,0003

H2S 0,0288

CO 0,3248

Nitrogen 0,3994

CO2 0,0189

H2O 0,0009

Hydrogen 0,2269

- Feed sour gas = 2035 kgmole/h

- Mol fraction H2S in feed gas (yN+1) =0.0288

- Mol fraction H2S in top product (y1) = 0.01

Determine flow of amine solution that we need= 0.2988 = 0.1240 TOTAL molar flow is 601.35 kgmole/hr


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Determine Mass (Molar) Liquid to Gas Ratio Determine value of m

Determine Absorption Factor (A)

Determine Equilibrium Tray

Calculating Actual Tray

Calculating Height Absorber Column

For amine absorber, tray spacing that recommended is at least 2 ft or 61

cm (Campbell, 1992). Then, tray section will have a height: Calculating Diameter Absorber Column

Calculating Shell and Head Thickness


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4.2 Regeneration Column

Equipment Specification

Name Regeneration Column

Code V-102

Function To regenerate amine mixtures

from bottom outlet of

absorption column C

Material Carbon Steel

Operational Data

Temperature 70C

Pressure 5 bar

Mass flow in 0.7

Pressure Drop 30

Operational velocity 111.9

Dimensional Data

Type Flash Drum

Diameter 1

Total height Carbon Steel

Several step to design regeneration column is:

Determine Light Key and Heavy Key

Light Key is a componentthat almost coming out in the top of amine

stripper. Whereas, heavy key is a component that almost coming out in the bottom

of amine stripper. In this amine stripper, the light key (LK) is CO2and the heavy

key (HK) is H2O.


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Determine TdewandTbulb

To determine the dew and bubble temperatures, we need to know mole

fraction of each component first. The mole fraction of components is known by

the HYSYS Simulation. After we know the mole fraction, then we calculate the

vapor pressure of each component by the Antoine equation. After that, we

calculate the m by the equation of Psat/Ptotal and fraction mole of each

component in bottom. Known the Ptotal in the system is 610.5 kPa. Here are the

results attached in table below:

4.3 Compressor

An air compressor is a device that converts power (usually from an electric

motor, a diesel engine or a gasoline engine) into kinetic energy by compressing

and pressurizing air, which, on command, can be released in quick bursts. There

are numerous methods of air compression, divided into either positive-

displacement or negative-displacement types. Types of air compressor:

a) Reciprocating Air Compressors

Reciprocating air compressors are positive displacement machines,

meaning that they increase the pressure of the air by reducing its volume. This

means they are taking in successive volumes of air which is confined within a

closed space and elevating this air to a higher pressure. The reciprocating air

compressor accomplishes this by a piston within a cylinder as the compressing

and displacing element.

Single-stage and two-stage reciprocating compressors are commercially available.

Single-stage compressors are generally used for pressures in the range of

70 psig to 100 psig. Two-stage compressors are generally used for higher pressures in the

range of 100 psig to 250 psig.

1 HP ~ 4 CFM at 100 psi

and that 1 to 50 HPare typically for reciprocating units. Compressors 100 hpand

above are typically Rotary Screw or Centrifugal Compressors. The reciprocating

air compressor is single acting when the compressing is accomplished using only


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one side of the piston. A compressor using both sides of the piston is considered

double acting.

Load reduction is achieved by unloading individual cylinders. Typically

this is accomplished by throttling the suction pressure to the cylinder or bypassing

air either within or outside the compressor. Capacity control is achieved by

varying speed in engine-driven units through fuel flow control.

Reciprocating air compressors are available either as air-cooled or water-

cooled in lubricated and non-lubricated configurations and provide a wide range

of pressure and capacity selections.

b) Rotary Screw Compressors

Rotary air compressors are positive displacement compressors. The most

common rotary air compressor is the single stage helical or spiral lobe oil flooded

screw air compressor. These compressors consist of two rotors within a casing

where the rotors compress the air internally. There are no valves. These units are

basically oil cooled (with air cooled or water cooled oil coolers) where the oil

seals the internal clearances.

Since the cooling takes place right inside the compressor, the working

parts never experience extreme operating temperatures. The rotary compressor,

therefore, is a continuous duty, air cooled or water cooled compressor package.

Rotary screw air compressors are easy to maintain and operate. Capacity

control for these compressors is accomplished by variable speed and variable

compressor displacement. For the latter control technique, a slide valve is

positioned in the casing. As the compressor capacity is reduced, the slide valve

opens, bypassing a portion of the compressed air back to the suction. Advantages

of the rotary screw compressor include smooth, pulse-free air output in a compactsize with high output volume over a long life.

The oil free rotary screw air compressor utilizes specially designed air

ends to compress air without oil in the compression chamber yielding true oil free

air. Oil free rotary screw air compressors are available air cooled and water cooled

and provide the same flexibility as oil flooded rotaries when oil free air is

required.


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c) Rotary Screw Compressors

The centrifugal air compressor is a dynamic compressor which depends on

transfer of energy from a rotating impeller to the air.

Centrifugal compressors produce high-pressure discharge by converting

angular momentum imparted by the rotating impeller (dynamic displacement). In

order to do this efficiently, centrifugal compressors rotate at higher speeds than

the other types of compressors. These types of compressors are also designed for

higher capacity because flow through the compressor is continuous.

Adjusting the inlet guide vanes is the most common method to control

capacity of a centrifugal compressor. By closing the guide vanes, volumetric

flows and capacity are reduced. The centrifugal air compressor is an oil free

compressor by design. The oil lubricated running gear is separated from the air by

shaft seals and atmospheric vents.

Figure below is a general representation of the application range of most of

the compressor shown. Based on the inlet flow and discharge pressure of the

compressor, one is able to determine the compressor type.

Gambar 4.1General Range of Application of Compressor

In our plant, we use 4 air compressors, all of them are reciprocating

compressor, labelled as C-201 (air compressor) and C-202(air compressor).


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4.3.1 Operating Conditions Air Compressor C-201

Inlet : Air

Inlet Temperature 537 RInlet Pressure 0 psigOutlet Pressure 249,8 psigMolar Flow Rate 22,33 MMSCFD

Volumetric Flow Rate

0,365 ft /s

Specific Gravity 1 -Molecular Weight 28,92 lb/lbmoleCompressibility Factor 0,978 -Compressor Efficiency 0,76 -Stage number N 3 -

4.3.2 Operating Conditions Air Compressor C-202Inlet : CO2to Sequestering

Inlet Temperature 779,4 RInlet Pressure 50 psigOutlet Pressure 400 psigMolar Flow Rate 16,42 MMSCFD

Volumetric Flow Rate

0,365 ft /s

Specific Gravity 1 -Molecular Weight 28,92 lb/lbmoleCompressibility Factor 1,010 -Compressor Efficiency 0,79 -Stage Number N 2 -


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Reservoir CBM data:

Pressure: 400 psig with 500 meters depth.

4.3.3 Specification of Air Compressor

C-201

Operating conditions:

- Temperature at inlet () = 537 oR- Pressure at inlet () = 0 psig- Pressure at outlet () = 249,8 psig-

Molar flow rate = 22,33 MMSCFD

- Volume flow rate () = 0,365 ft3/s- Specific Gravity = 1- Molecular Weight = 28,92 lbf/lbmol

- Compressor efficiency () = 0,76Calculated using: T in Kelvin,

using pressure ratio:

-

Compressibility factor () = 0,9780Calculated conditions:

- Compressor type : Reciprocating

- Stage number : 3

- Compression ratio per stage :


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-

Compressor head :


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- Compressor power :

-

Discharge temperature :

[

]


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-

Impeller diameter :

-

Shaft speed :

4.4 Pump

Centrifugal pumps are a sub-class of dynamic axisymmetric work-

absorbing turbomachinery. Centrifugal pumps are used to transport fluids by the

conversion of rotational kinetic energy to the hydrodynamic energy of the fluid

flow. The rotational energy typically comes from an engine or electric motor. The

fluid enters the pump impeller along or near to the rotating axis and is accelerated

by the impeller, flowing radially outward into a diffuser or volute chamber

(casing), from where it exits.

Common uses include water, sewage, petroleum and petrochemical

pumping. The reverse function of the centrifugal pump is a water turbine

converting potential energy of water pressure into mechanical rotational energy.


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Centrifugal Pump

Like most pumps, a centrifugal pump converts mechanical energy from a

motor to energy of a moving fluid. A portion of the energy goes into kinetic

energy of the fluid motion, and some into potential energy, represented by fluid

pressure (Hydraulic head) or by lifting the fluid, against gravity, to a higher

altitude.

Advantages and Disadvantages of Centrifugal Pumps

Simpledesign

Compact

Lowcost

Wide rangeofcapacities

(22300m3/h)

Widerangeof liquids

(slurry, water,oil,

hazardous liquids,)

Smooth dischargeflow

Relatively quietoperation

Pumpwill not be damaged if

dischargelineis blocked.

Notsuitablefor viscousliquids

Theyarenotself-priming

Flowof liquid

bygravityisnotpreventedwhen

pump is stopped.

Poorly suitedtosmall capacities


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The transfer of energy from the mechanical rotation of the impeller to the

motion and pressure of the fluid is usually described in terms of centrifugal force,

especially in older sources written before the modern concept of centrifugal force

as a fictitious force in a rotating reference frame was well articulated. The concept

of centrifugal force is not actually required to describe the action of the centrifugal

pump.

The outlet pressure is a reflection of the pressure that applies the

centripetal force that curves the path of the water to move circularly inside the

pump. On the other hand, the statement that the "outward force generated within

the wheel is to be understood as being produced entirely by the medium of

centrifugal force" is best understood in terms of centrifugal force as a fictional

force in the frame of reference of the rotating impeller; the actual forces on the

water are inward, or centripetal, since that is the direction of force need to make

the water move in circles. This force is supplied by a pressure gradient that is set

up by the rotation, where the pressure at the outside, at the wall of the volute, can

be taken as a reactive centrifugal force. This was typical of nineteenth and early

twentieth century writings, mixing the concepts of centrifugal force in informal

descriptions of effects, such as those in the centrifugal pump.

4.4.1 Principle of Operation

The impeller of such a pump is magnetically coupled with the motor,

across a separation wall which is resistant to the fluid pumped. The motor drives a

rotor carrying one or several pairs of permanent magnets, and these drag around a

second pair(s) of permanent magnets attached to the pump impeller.

4.4.2 Principal Characteristics of Pump

The nomenclature define below is used by engineers to describe theoperating characteristics of a pump.

a. Flowrate

Flowrate(or capacity) refers to the volumeof liquid passing through the

pump per unit of time.

Normal flowrate is the volume of fluid actually delivered perunit of time at

the stated operating condition sindicated in the material balance established

for the nominal operating conditions.


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Design flowrate is equal to the normal capacity corresponding to the

nominal operating conditions increased by the overcapacity factor (or

pump design factor).

Overcapacity Factor Recomended for Pump

OvercapacityFactor

Recommended (%) Type of Pump

0 Loading pump(toatanker)

10 Utilitypumps andotherprocess pumps

15 Exportpump

20 Refluxpumpsand boiler feedwater pump

20 Boiler feedwater pumps

b. Head

The energy imparteed to a fluid by a pump consists of useful energy in the

form of pressure, velocity, or height above the datum point. The useful energy can

be expressed in terms of head in metres or feet.

Gambar 4.2Illustration of Pump Head

The term head is also used to express changes of energy. For example, the

static head refers to the difference between the suction and final discharge static

levels in an open system and the total differential head is the total discharge head

minus the total suction head

c.

Net Positive Suction Head (NPSH)

Two NPSH definitions areused in pumpingsystems:


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Net Positive Suction Head required (NPSHR) is the head required by the

pump in order to prevent the liquid stagnation pressure dropping below

the vapor pressure and resulting in liquidboiling. Liquid boiling can lead

to cavitation. The NPSHR is a characteristic of the pump it self and is

generally determined experimentally by the pump manufacturer.

Net Positive Suction Head available (NPSHA) is the excess pressure of

the liquid in height absolute over its vapor pressure as it arrives at the

pump suction. It is a characteristic of the system in which the

pumpoperates.

d. Power

Two power definitions are used in pumping systems:

Hydraulic Power is the amount of power imparted to the liquid as it passes

through the pump.

Brake Power (or shaft power) is the amount of power delivered to the

pump (asopposed to the power used by the motor). The brake power

required will depend on the pump efficiency.

e. Efficiency

Pump efficiency is equal to the ratio between the hydraulic power

required and the brake power. It refers to the mechanical efficiency of the pump

and does not take into account the motor efficiency.

In our plant, centrifugal pump is labelled as P-201, P-202, and P-301 in

our plant PFD and it is used to pump water from water pond to heat steam

recovery generation, utility system, and for the heat exchanger system. The

specifications of our centrifugal pumps P-201, P-202, andP-301 are explained as

follow:

For pump sizing, the reference is used to determine the type of the pump

used, calculate the pump pressure drop, NPSHA, shut-off pressure, minimum

suction pressure, maximum discharge pressure, brake power needed and the pump

head, all calculated manually using Microsoft Excel. The formulas used are as

follows:
http://en.wikipedia.org/wiki/Boilinghttp://en.wikipedia.org/wiki/Boiling


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To calculate pressure loss due to piping and component friction is

calculated with the following equation (Metric):

Where

To calculate pump head the following formula is used (Metric):

Where

To calculate pump differential pressure the following formula is used:

To calculate brake pumping power the following formula is used:


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The minimum suction pressure at rated capacity available at the centerline

of the pump suction flange is determined using the characteristics of thesuction section piping.

Where

The maximum discharge pressure at rated capacity available at the

centerline of the pump discharge flange is determined with the

characteristics of the discharge section piping.

Where

Net Positive Suction Head Available (NPSHA) is expressed by equation as

follows:

Where


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4.5 Conveyor

4.5.1 Bucket Conveyor

This operating unit serves to bring the EFB from storage to shredder that is

located higher, using baskets contained in a series of rotating belt.

a.

Type and Material of Bucket Elevator

- Type of elevator : supercapacity continous bucket

- Materials : melleable-iron (cheaper than steel bucket)

-

Operational condition : 28oC, 1 atm

b. Capacity and Distribution Rate

Distribution rate of raw materials is 4875 kg/hour, based on the literatureTabel 21.8 Perrys Chemical Engineering Handbook, than it must be provided

bucket spacing by 12%, so that the raw materials transported do not overload on

each bucket and fall. So that the space needed is:

Thus, the total rate of distributions obtained by:

c. Specification

For distribution rate of raw materials


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d. Power Requirement

Power required by bucket elevators to operate (refer to the literature, the

Plant Design and Economics for Chemical Engineers, Peters and Timmerhaus) is

described as follows:

with:

P = Power needed (kW/s)

m = Mass distribution rate(kg/s), is 5460 kg/hour or 1.52 kg/s

z = Height of the elevator (m), is 25 ft or 7,62 m

e. Amount of buckets on the elevator

The number of buckets on elevator depends on the dimensions of the raw

materials that will be distributed. The following are the dimensions of the EFB

- Length : 23 cm

- Width : 27 cm

-

Thickness : 2 cm

Thus, the estimated amount of EFB that can fit into each bucket on the

elevator, where the dimensions of the bucket is as precise as mentioned on the

specification. Thus, each bucket is only able to carry 1 piece EFB so that the

amount necessary to distribute the raw materials in accordance with the

distribution rate is as follows:

-

Height of the elevator: 25 ft = 7.62 m (based on specification)

- Approximate length of the belt : 7.62 m x 2 = 15.24 m 16 m

- Space between bucket : 18 in = 45.72 cm = 0.457 m (based on

specification)

- Velocity of the elevator : 1.32 m/s = 4752 m/hour

Then, within an hour, each bucket elevators will rotates as much:


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With a capacity of 5460 kg / hour and the average weight of EFB is 3,3 kg., then

the amount of EFB in each hour is:

4.5.2 Bucket ConveyorBelt conveyor is used to carry raw material from the shredder to size

pulverizer unit.

a. Operation Condition

- Temperature : 28oC

-

Pressure : 1 atm

b. Dimension and Type of Conveyor

- Belt type : horizontal wire mesh belt

-

Material : stainless steel and polymer belt

- Raw material capacity : 4445 kg/hour

Referring to the literature, it should provide space to avoid overloading

which can lead to the fall of the material by 20% of the volume of material to be

distributed, which is equal to:

Then total mass flow rate to be distributed by conveyor is:


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c. Belt Conveyor Specification

Based on Table 21.7 ofPerrys Chemical Engineering Handbook, forcapacity less than 32 ton/hour, the conveyor belt is used with the following

specifications:

- Widht of belt : 14 in = 35 cm

- Cross sectional area of load : 0.11 ft2= 0.010 m2

- Normal belt speed : 200 ft/min = 61 m/min

-

Maximum belt speed : 300 ft/min = 91 m/min

-

Belt rotational speed during operation adjusted wih bucket elevator rate,

which is 1.32 m/s.

-

Power: 0.44 hp = 0.33 kW

- Belt conveyor length estimation: 50 ft = 15.3 m

4.6 Fischer Tropsch Reactor

Equipment Spesification

Equipment name FT Reactor

Equipment code

Function to synthesis syngas into hydrocarbon

Catalyst Fe

Equipment type

Amount of equipment 1

Operation Data

Pressure (kPa)

Temperature (K)

Mass flow feed (kg/hr)

Superficial gas velocity (m/s)

Construction Data

Volume (m3)

Diamter (m)

Length (m)


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4.6.1 Mechanism Of Fischer Tropsch Reactor

In the Fischer-Tropsch process, the synthesis gas (H2 and CO) reacts in

presence of solid catalyst to produce a wide range hydrocarbon products, such as

olefins or paraffins. This selection of product will be based on operating condition

of the process. In this case, we want our product to be paraffins so use the

operating condition of LTFT (Low Temperature Fischer-Tropsch). The F-T

synthesis is a combination of oligomerization reaction which can be summarized

as follow: There is another reaction that is controlled by the type of catalyst used

may or may not be active to it such as: There are three possible reaction mechanisms which are carbide

mechanism, enol mechanism, and CO-insertion mechanism. We focus our

mechanism at carbide mechanism because it is still favourite mechanism among

the research communities. In this mechanism, both CO and H2 are dissociatively

adsorbed on the catalyst surface. The adsorbed C and O are then hydrogenated

into CH2 and H2O. the CH2 adsorbed can be further hydrogenated into CH3

and/or insert itself into carbon metal bond of an adsorbed CnHm species allowing

the chain to grow.

Figure X.X. Carbide Mechanism of Fischer Tropsch

(Source: van Dijk, H.A.J., The Fischer-Tropsch synthesis: A mechanistic study using transient

isotopic tracing. Ph.D. Dissertation)


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4.6.2 Operating Condition of Fischer Tropsch Reactor

In terms of operating condition, FTR can be divided into two types which

are LTFT (low temperature fischer tropsch) and HTFT (high temperature fischer

tropsch). The LTFT tends to make paraffins and HTFT tends to make olefins. In

this case, we use LTFT for our operating of condition:

T = 513 K

P = 2000 kPa

4.7 Hydrocraking Reactor


Equipment name HydrocrackerEquipment code

FunctionTo convert long chain HC into

short chain HC

Catalyst

Equipment type


Operation Data

Pressure (kPa)

Temperature (K)Mass flow feed (kg/hr)

Construction Data

Volume (m3)

Diamter (m)

Length (m)

4.8 Fractionator

Fractionation is aseparation process that is separating a certain quantity ofa mixture (gas, solid, liquid, suspension or isotope) which is divided during a

phase transition into a number of smaller quantities (fractions) in which the

composition varies according to a gradient. Fractions are collected based on

differences in a specific property of the individual components. A common trait in

fractionations is the need to find an optimum between the amount of fractions

collected and the desired purity in each fraction. Fractionation makes it possible to
http://en.wikipedia.org/wiki/Separation_processhttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/wiki/Isotopehttp://en.wikipedia.org/wiki/Phase_transitionhttp://en.wikipedia.org/wiki/Fraction_%28chemistry%29http://en.wikipedia.org/wiki/Fraction_%28chemistry%29http://en.wiktionary.org/wiki/compositionhttp://en.wikipedia.org/wiki/Gradienthttp://en.wikipedia.org/wiki/Gradienthttp://en.wiktionary.org/wiki/compositionhttp://en.wikipedia.org/wiki/Fraction_%28chemistry%29http://en.wikipedia.org/wiki/Phase_transitionhttp://en.wikipedia.org/wiki/Isotopehttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/wiki/Separation_process


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isolate more than two components in a mixture in a single run. This property sets

it apart from other separation techniques.

Fractionators 1


Equipment name Fractionators

Equipment code

Function to separate gas into product

Catalyst

Equipment type


Operation Data

Pressure (kPa)

Temperature (K)



Construction Data

Volume (m3)

Diamter (m)

Length (m)

Fractionation 1 is used to separate the desired product which are ethane

propane butane that contain in the stream. Distillation process is used to separate

several component from the stream. Several step to design distillation column is:

Minimum Number of Equilibrium Stages

*

+

()

Minimum Reflux Ratio


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Figure . Gilliland correlation for ordinary distillation

Fractionators 2


Equipment name Vertical Separator

Equipment code

Function to separate gas into product

Catalyst

Equipment type Fractionators


Operation Data

Pressure (kPa)

Temperature (K)




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Liquid Depth (hv)

Separator surface area Separator Height

Separator Thickness

Top Thickness

Separator Wight

Shell

Head and Bottom

tk_16_draft_assg2.docx

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