5.major project

1

Chapter 1

INTRODUCTION

Vegetable oils has been used in areas involving chemical processing, and also for

direct consumption. With the rapid rise in conversion of non-vegetarian to

vegetarian process, an increase in usage of vegetable oil is seen. It also helps in

contributing to some extent to prevent environmental degradation. There are

various ways of extracting vegetable oils like by process of fluidization, solvent

extraction, mechanical expulsion etc. Here extraction is done by fluidization

process using a fluidized bed extractor.

FLUIDIZATION:

When a liquid or gas is passed at very low velocity up a bed of particles, the

particles do not move and this is the condition of fixed bed. If the velocity is

steadily increased, the pressure drop and drag eventually starts to increase on the

particles, as a result particles move away from each other some vibrate and move

in restricted regions now this is the condition of expanded bed. On further

increasing the velocity, the frictional force between the solid and fluid particles just

counter balances weight of the particles, and this condition is known as minimum

fluidization or incipient fluidization. This is noted that at condition of fluidization,

bed of suspended particles behave as either a fluid or gas.

TYPES OF FLUIDIZATION:

Fluidization is mainly of two types i.e. Particulate fluidization and aggregative

fluidization. Particulate fluidization occurs when the solid and fluid density

difference is not much and the solids are smaller in size. In this fluidization the

fluid velocity required to fluidize the bed is not much (example- liquid-solid

systems).

Aggregative fluidization occurs when the solid and fluid density difference is more

and solids are larger in size. In this fluidization the fluid velocity required to

fluidize the bed is quite high (example- gas-solid systems). In this case when

fluidization occurs then bubbles form in between the solids because of the large

particle size and high liquid velocity. These bubbles carry little or no solid particles

with them. When these bubbles rise from the bed then they eventually break at the

surface of bed. The superficial fluid velocity in which fluid bubbles form is called

the minimum bubbling velocity. Generally a bubbling fluidized bed is considered

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to be undesirable for industrial application. (Narayanan et.al, 2009)

THREE PHASE FLUIDIZED BED:

Simply it can be stated as a bed of particles suspended in a column, when gas or

liquid is inserted. Generally a three phase exists which is solid-liquid-gas under

three phase operations. It finds its immense use in wastewater treatment, certain

chemical and bio-chemical industries.

MODES OF OPERATION OF THREE PHASE:

There are several types of modes of operation which is due to difference in flow of

solid-liquid-gas in different directions, the velocity factor etc. Mainly these are

categorized into three main division:

1. Parallel mode of operation with liquid as the continuous phase.

2. Parallel mode of operation with gas as the continuous phase.

3. Inverse three phase fluidization.

ADVANTAGES OF THREE PHASE:

Three phase fluidization acts as reactors and it overcomes some of the problem that

may occur in conventional reactors. Some of them are pointed as:

1. Formation of local hotspots is prevented.

2. Smooth, localized flow with simple and automatically controlled operation.

3. Suitable for large scale operation.

4. High turbulence is achieved, better mixing facility, flexibility.

5. Heat recovery and temperature control.

6. It creates more gas-liquid interfacial area due to better gas phase

distribution.

DISADVANTAGES OF THREE PHASE:

1. As the solids are rapidly mixed in the bed, it leads to non-uniform residence

time of particles in reactor.

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2. Possibility of entrapment of solid particles in best becomes more because of

high turbulence and mixing, size of particles is reduced.

3. Inefficient contact system due to bubble formation in reactor.

USES IN VARIOUS FIELDS:

1. Hydrogenation of oil.

2. Hydro desulphurization of oil.

3. Coal liquefaction by H-coal process.

4. Fischer-tropsch process.

5. Non-catalytic coking of petroleum residues.

6. Catalytic oxidation of naphthalene to phthalic anhydride.

7. Contacting bed used for flue gas desulphurization process.

8. Treatment of waste water by bio-oxidation process.

9. Mass transfer operations.

10. Methanol processing bio-chemical industries.

11. Pharmaceutical industries.

FLUIDISED BED EXTRACTOR:

Fluidized-bed extractor has the ability to process large volumes of fluid. A

fluidized bed extractor is a type of extractor that can be used to carry out various

types of multiphase reactions.

A laboratory-scale fluidized bed extractor was designed and fabricated for the

purpose of the present study. The fluidized bed extractor is a thick boro-silicate

glass tube (SS compatible) of 100-mm inside diameter, 3-mm wall thickness, and

2000-mm length. The tube is fitted with a perforated stainless steel gas distributor.

The distributor has 2-3mm diameter holes on a triangular pitch which gives 13%

free area. A fine mesh of 0.1 mm is fixed over the distributor to arrest the flow of

fine particles through the perforations. The fluidized bed is heated by an electric

furnace, and the bed temperature is controlled by a computer based thermocouple

(MOC-Iron/Constantan).

The solid substrate in the extractor is typically supported by porous plate

known as a distributor. The fluid is then through the distributor up through the

solid material. At lower fluid velocities the solids remains in the place while the

fluids passes through the voids in the material.

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FLOW REGIME IN FLUIDISED BED EXTRACTOR:

With several operating variables in fluidized bed extractor, it is important to have

information about flow regimes in order to attain a stable operations separation

between flow regimes is yet not clear but still there are some patterns to be

differentiated and they are:

1. Dispersed bubble flow:

Low gas velocities.

High liquid velocities.

Small uniform size of bubbles occur.

2. Discrete bubble flow:

Low liquid and low gas velocities occur.

Bubble size is small.

3. Coalesced bubble flow:

Low liquid and intermediate gas velocity occur.

Bubble size is big.

4. Slug flow:

Bubbles in the shape of large bullets and diameter equal to that

of column diameter.

5. Churn flow:

Resembles the slug flow regime.

With an increase in gas flow, an increase in downward liquid

flow is observed.

6. Bridging flow:

Intermediate regime between annular and churn flow.

An interesting factor is solid and liquid forms “bridges” in

reactor that breaks and re-forms.

7. Annular flow:

At high gas velocity, a continuous gas phase develops in the

core of the column.

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VARIABLES AFFECTING THE PROCESS:

Certain variables affecting quality of fluidization. They are:

1. Fluid flow rate: Enough flow rate must be provided in order to keep

particles in suspension but it should be taken care to avoid bed from

channeling that generally occurs at very high fluid velocity.

2. Fluid inlet: Inlet should be designed in such a way that it provides uniform

distribution of fluid entering the bed.

3. Gas, liquid and solid densities: When the relative densities of gas, solid

and liquid are closer, then it is easiest to maintain smooth fluidization.

4. Particle size: Variation in particle size plays a key role in promoting an

efficient fluidization. Mainly it is recommended to have a wide range of

particle size rather than have uniform sizes for efficient mixing.

5. Bed height: As the bed height is increased, it is difficult to maintain smooth

and efficient fluidization.

6. Temperature: With an increase in temperature to a limited range, the

extraction efficiency also increases.

MINIMUM FLUIDIZING VELOCITY:

Fluidization will be considered to begin at the gas velocity at which the weight of

the solids gravitational force exerted on the particles equals the drag on the

particles from the rising gas. If the gas velocity is increased to a sufficiently high

value, however, the drag on an individual particle will surpass the gravitational

force on the particle, and the particle will be entrained in a gas and carried out of

the bed. The point at which the drag on an individual particle is about to exceed the

gravitational force exerted on it is called the maximum fluidization velocity.

Experimental data of minimum fluidization velocity in the cylindrical and conical

fluidized bed under both liquid-solid and gas-liquid-solid fluidized conditions were

obtained based on the pressure drop vs. the superficial velocity curve. For the

liquid-solid cylindrical bed, the experimental data were compared with the Ergun

equation.

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INTRODUCTION TO SOYABEAN:

Soyabean is one of the major food crops worldwide because of its favorable

agronomic characteristics, high quality edible oil products, high quality animal

feed meal, and it is available at reasonable prices. Figure 1.1 shows the production

of soyabeans in various countries. The use of soyabean and soyabean related

products started around about the 1920’s in the United States, with less around 50

million MT being produced in 2007. This has increased to about 80 million MT in

2011. Figure 1.1 gives a general idea of how the soyabean oil production has

grown in the past decade.

Figure 1.1 World Soyabean Production.

Soyabean Composition:

Commercial soyabeans consists of about 20 % oil, with the rest constituting of

proteins, carbohydrates, fatty acids, inorganics and minerals, amino acids,

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phospholipids, and sugar. The approximate composition of soyabeans is

summarized in Table 1.1.

Component Weight Percent

Moisture 11.0

Protein 37.9

Fat 17.8

Fiber 4.7

Ash 4.5

Table 1.1 Soyabean Composition.

Figure 1.2 Soyabean Seeds.

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Carbohydrates:

Whole soybeans consist of about 35% carbohydrates, of which about 20 % is

insoluble carbohydrate. Stachyose, raffinose, glucose and sucrose form the

majority of the carbohydrates found in soybeans. Sugar (sucrose and glucose) is a

major raw material used in the manufacture of ethanol. This high content of

carbohydrates can also be put to use, by either extracting the sugars for edible use

or for commercial chemical manufacture.

Fatty Acids:

Soybeans primarily consist of triglycerides and triglecerols, with linoleic, linolenic

and oleic acids forming the majority. Saturated fatty acids are the component that

contribute to bodily fats in humans and hence are considered to be anti-nutritional

when consumed. The low content of saturated fatty acids is what makes soybean

oil popular as an edible oil.

Minerals & Inorganics:

Minerals form a very important part of the human diet and a person requires a

minimum amount of minerals in his daily diet. Hence, the mineral content of

soybeans is very important. Soyabeans consist of about 2 % potassium, 0.5%

sodium, 0.3 ~ 0.7% phosphorous with trace quantities of magnesium, calcium and

iron.

Proteins:

Soyabean meal is a very popular animal feed because of its high protein content.

Proteins constitute about 40% of soyabeans. Soy proteins consist of amino acids in

varying compositions, trypsin inhibitors and haemagglutinins which are

nutritionally important. Soy proteins are generally heat inactivated, which is as a

major constraint when processing soy oil. Processing temperatures higher than

100oF generally tend to depreciate the quality of the soy oil produced.

Physical Properties of Soyabean:

The physical properties of soyabeans are a function of various parameters, which

include climatic conditions during growth, oil composition, temperature and

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pressure, molecular weight, fatty acid chain length, etc. The physical properties of

soybean are critical parameters which have to be considered when designing soy

processing equipment and processes such as extractor, dryer, etc. The physical

properties of soy oil are listed in Table 1.2.

Property Value

Specific Gravity at 25oC 0.9175

Refractive Index

1.4728

Viscosity at 25 oC (cP) 50.09

Solidification Point (oC) -10 ~ -16

Specific Heat at 19.7 oC (Cal/g) 0.458

Heat of combustion (Cal/g) 9478

Flash Point (oC) 328

Fire Point (oC) 363

Table 1.2 Physical Properties of Soyabean Oil

PROPERTIES OF SOLVENT:

A good extraction solvent should have a strong solubilizing capability for the

compound of interest, it should be immiscible or only weakly miscible with the

matrix solvent (the first solution or mixture containing the compound from its

natural source, e.g., water/ether. water/ chloroform, etc.). If possible the extraction

solvent should be non-flammable, non-toxic or of low toxicity, reasonably volatile,

and of low eco-impact. Inexpensive and available, of high purity, and shelf stable.

If one is determining the compound of interest by UV/Vis spectrophotometry or

fluorescence, the solvent should have extremely low absorbance or emission at the

wavelength of analysis.

Hexane is generally used as a solvent for extraction purpose due to its physical

and chemical properties. But, hexane is highly flammable and is also known to

10

cause nervous damage to people exposed to it in sufficient quantities. Using

hexane as solvent also results in a solvent loss of about 1 ~ 8 lit. / Metric ton of

seeds processed. All of these issues combined with the necessity of severe

extraction (temperature and pressure) conditions and environmental concerns have

resulted in renewed interests in using an alternative solvent for extraction. Typical

solvents of interest are alcohols and supercritical fluids such as carbon dioxide.

Alcohols require a high solvent to feed ratio, but solvent recovery becomes an

issue as alcohols usually tend to form an azeotrope when mixed with water.

Acetone is one of the chemicals, which satisfies most of the characteristics

required for a good solvent. The only disadvantage of using acetone in comparison

to hexane it requires a higher solvent to feed ratio. Table 1.3 compares the

properties of acetone and hexane and highlights important parameters such as the

flash point, the boiling point, toxicological data, and fluidic properties which

would suggest that acetone could be a good substitute.

Parameter

n-Hexane Acetone

Density of liquid @ 60 F

(lb / cu. ft.)

41.5 .791

Vapor Pressure @ 70 F

(Psia)

2.5 3.480

Boiling Point @ 1 atm (F) 156

133

Flash Point (F) -10

1.42

Oil Solubility Depends on

temperature

Depends on

temperature

Toxicological Limit(ppm) Inhalation: 12000

Inhalation: 5000

Inhalation (ppm/hr), Oral

(mg/kg)

Oral: 28700

Oral: 6500

Explosion Limit (%) 1.2 ~ 7.7 2.6 ~ 3

Table 1.3 Solvent Properties.

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As hexane have certain disadvantages such as highly flammable etc. it can be

blend with other solvent like acetone, propane and alcohols to give better

extraction efficiency. On blending with other solvents the properties of n-hexane

will be change to certain limit which is good for extraction purpose and recovery

percentage also increases.

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Chapter 2

LITERATURE REVIEW

The first fluidized bed was first found by Winkler in 1921 and industrial

fluidized bed was first used as large-scale in Winkler gasifier in 1926 (Kunii and

Levenspiel, 1991). Fluidized bed catalytic cracking of crude oil to gasoline (FCC)

was commercialized in 1942, and is still the major application of fine-powder

fluidization. Several catalytic applications such as acrylonitrile synthesis, phthalic

anhydride and Fischer-Tropsch synthesis of liquid fuels from coal-based gas

extended the range following the Fluidized bed catalytic cracking. Lurgi

commercialized the circulating fluidized bed (CFB) in the 1970’s, for coarse

powders, which would operate above the terminal velocity of all the bed particles.

Polyethylene was produced in a fluidized bed, and the technology is widely used in

industry.

Commercialization of circulating fluidized bed was done in 1980’s for the

combustion and production of polypropylene in fluidized beds. New areas of

application in fluidization were production of semiconductors and ceramic

materials by chemical vapour deposition and in biological applications the use of

liquid fluidized beds.

The successful design and working of a gas-liquid-solid fluidized bed system

depends on its ability to accurately predict the fundamental characteristics of the

system mainly the hydrodynamics, the mixing of individual phases, and the heat

and mass transfer characteristics. Three-phase fluidized beds are also often used in

physical operations. Here three phase fluidized bed extractor is used to extract soya

oil from soyabean seeds by using solvents like n-hexane and acetone for different

particle size, extraction time and temperature. Based on the different parameters,

the efficiency of extraction is determined.

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Chapter 3

EXPERIMENTAL SETUP

The fluidized bed assembly consists of three sections, viz., the test section, the

gas-liquid distributor section, and the gas-liquid disengagement section. Fig. 3.3

shows the schematic representation of the experimental setup used for extraction of

soya oil. Fig. 3.4 gives the photographic representation of the fluidized bed

extractor. The test section is the main component of the fluidized bed where

fluidization takes place. It is a vertical cylindrical Plexiglas column of 100 mm

internal diameter and 2000mm height. The gas-liquid distributor is located at the

bottom of the test section and is designed in such a manner that uniformly

distributed liquid and gas mixture enters the column. The setup consist of a

thermocouple made of iron-constantan which is connected to computer based

control system used to measure the temperature during the experiment. An electric

heater with temperature controller of 1/2 KW is wrapped around the column for

heating purpose. Other components with the specification and photographs are

mentioned below.

Main Column:

Height of column: 2000mm

Diameter of column: 100mm

MOC: Glass/ SS compatible with working condition

Distributor:

Diameter of hole: 2-3 triangular pitch as per design matching with expt.

Diameter of plate: Fit to column

Electric Heater:

(With Temperature controller)

Capacity: ½ KW

Type: Around the column

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Liquid Manometer:

Model: U Type

Type: Wall Mounted

Range: 500-0-500mmhg

Glass: Borosilicate Toughened

Thermocouple:

Type: “J”

MOC: Iron/Constantan

Condenser:

Type: Horizontal Shell and Tube Type

Size & Length: As required

MOC: SS-304

Insulation: 25mm thick glass wool insulation

Reservoir:

Capacity: 25Litre

MOC: SS-304

Accessories: Liquid level indicator, Drain valve

Compressor with pressure indicator:

Capacity: 0-5 kg/cm2

Motor: 1/3 HP

Dosing Pump:

Maximum head: 5meter

Flow rate: 800LPH

15

Rotameter:

Capacity: 0-3000LPH

Solvent: n-Hexane

Control Panel:

- Energy meters

- Necessary display meters for Instrumentation input and output indication

- ON/OFF switches and indicator lamps for all the electrical items etc.

Mimic Diagram of Experimental set-up:

It should be Suitable and Symmetrical

Specifications for Software:

- Equipment should be laboratory size and Computer liking arrangement is

to be provided and suitable PID SCADA software are to be provided.

- Software for experimentation, ID control, DATA logging, Trend Plot,

Offline analysis, Display and Printing etc.

- Software’s Instruction manual for Software Operations and

Experimentation etc.

Figure 3.1: Distributor plate Figure 3.2: Pump

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Figure 3.3: Schematic Representation of Experimental Setup.

17

Figure. 3.4: Photographic Representation of Fluidized Bed

Extractor.

18

Figure 3.5: Rotameter

Figure 3.6: Compressor

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Chapter 4

EXPERIMENTAL PROCEDURE

The experiment was carried out using crushed soya bean seeds as solid particle,

n-hexane and blend of n-hexane and acetone as liquid (solvent) and compressed air

as fluidizing medium. The soyabean seeds are crushed to particle size of 3 ~ 4 mm

using crushing equipment such as ball mill and then separated uniformly by using

mesh screen. The temperature is controlled by using computer based PID

controller which measure as well as helps in controlling the temperature during the

conduction of experiment.

At a time one parameter is varied and other parameters are fixed and efficiency

of extraction is determined. Efficiency of extraction is giving by:

Efficiency of Extraction (η)

= 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒆𝒆𝒅𝒔 𝒃𝒆𝒇𝒐𝒓𝒆 𝒆𝒙𝒕𝒓𝒂𝒄𝒕𝒊𝒐𝒏−𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒆𝒆𝒅𝒔 𝒂𝒇𝒕𝒆𝒓 𝒆𝒙𝒕𝒓𝒂𝒄𝒕𝒊𝒐𝒏

𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒆𝒆𝒅𝒔 𝒃𝒆𝒇𝒐𝒓𝒆 𝒆𝒙𝒕𝒓𝒂𝒄𝒕𝒊𝒐𝒏

= 𝑪𝒐 − 𝑪𝒕/𝑪𝒐

PROCEDURE:

Add crushed soyabean seeds into the column using funnel from the feed

point. Make sure that the crushed seeds size should not be less than the hole

diameter of distributer plate.

Fill the feed tank with solvent up to 60-70% of the capacity or as per as

requirement.

Keep the recirculation hand valve of a pump fully open.

Start the compressed air flow for fluidization and adjust the velocity

according to the requirement.

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Switch the pump for transfer of solvent to the column and recirculating to

tank with minimum flow rate. Adjust the flow rate using rotameter using

recirculation hand valve.

Switch on the electric heater around the column and start heating of fluid in

the column up to desired temperature (set point through computer controlled

HMI).

Adjust the inlet flow rate of the solvent to minimum fluidization velocity

through rotameter.

Run the software.

Set the controller in auto mode and set the solvent temperature to desired

value.

Run the system according to the desired experiment.

SHUT-DOWN PROCEDURE:

Switch off the Heating supply to heater around the column.

Switch off the feed Pump of solvent supply (P-1) and stop circulation by

hand valves.

Switch off the air supply to the compressor and make sure there is no back

flow to the compressor.

Close the water supply to condenser.

The column can also be drained with the help of the drain valve provided at

the bottom of the column.

Switch of the main supply of the panel.

The sample is collected from the sample point and it is simple distillated

at boiling point temperature of the solvent in order to remove the solvent

completely from the oil. The distillate oil is then examined in the UV

spectroscopy meter to find out the actual concentration of soya oil in the

product.

The spend seeds are collected and weight. The extraction efficiency can

be calculated by using the weight of processed seeds by using above

mentioned formula.

21

Figure 4.1 Temperature Controller Software.

22

Scope of Experiment:

S. No. Material Dp (mm) ρ ( kg/m3)

1. Soyabean seed 2-2.5 652

2. Soyabean seed 2-5 660

3. Soyabean Flakes 12-15

(thickness =

.35mm)

264

Table 4.1 Properties of Material, Soyabean

S. No. Fluidizing

medium

Viscosity (mPa.s) Density (g/mL)

1. n-Hexane 0.28 at 30oC 0.6548

2. n-Hexane 0.19 at 70oC 0.6548

3. Acetone 0.402 at 30oC 0.7910

4. Acetone 0.304 at 56oC

5. 50% n-Hexane

+ 50%Acetone

0.352 at 30oC 0.7229

Table 4.2 Properties of Fluidizing Medium

Superficial Gas Velocity 0-3 cm/s

Superficial Liquid Velocity 0-10 cm/s

Static Bed Heights 15.4 cm , 15.6 cm , 21.4 cm , 26.4 cm ,

31.4 cm

Temperature 28oC - 65oC

Table 4.3 Properties of Operating Conditions.

23

Chapter 5

RESULT AND CONCLUSION

The method of fluidized bed extractor is used to extract soya bean oil from soya

bean seeds by using n-hexane and blend of n-hexane and acetone and compressed

air as fluidizing medium. Effects of gas phase velocity, extraction time temperature

and fluidized solid types on the extraction efficiency in the extractor have been

studied by manipulating different parameters to find the optimum point between

efficiency and the time of extraction of soya bean oil. The result of the study are as

follows:

While studying the relation between the efficiency and the time of extraction

of oil when the gas velocity is kept constant at 3cm/sec, liquid velocity is

kept at 10 cm/sec, temperature at 50oC and varying the type of particle like

flake, cracker 1 and cracker 2 of sizes 12-18 mm, 2-5 mm, 2-2.5 mm in

diameter. It is found that with increasing the extraction time there extraction

efficiency increases.

When the gas velocity is kept constant at 3cm/sec, liquid velocity is kept at

10 cm/sec, particle size is kept constant at 12-18 mm in diameter and 0.35

mm in thickness and varying the temperature from 28oC to 65oC. It is found

that with increasing the extraction time, extraction efficiency is increased.

When the temperature is kept constant at 50oC, liquid velocity is kept at 10

cm/sec, particle size is kept constant at 12-18 mm in diameter and 0.5 mm in

thickness and varying the gas velocity from 0 to 5.0 cm/s. It is found that

with increasing the extraction time, extraction efficiency is increased.

When the gas velocity, liquid velocity, particle size, the temperature are

varied all together, it is found that maximum extraction is reached at certain

point called optimum point where there is maximum recovery of solvent.

Due to defects in the equipment the optimum point where efficiency is

maximum can’t be determined.

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With the use of blend of solvent (n-hexane and acetone) extraction

efficiency lies somewhat in the middle range but the recovery of solvent is

increased which in turn reduce the cost of extraction

CONCLUSION:

From the literature, it is revealed that fluidized beds are beneficial for efficacious

gas-liquid-solid contacting process and can be used for waste water treatment,

catalytic and non-catalytic reactors and in various chemical and bio-chemical

processes. In the recent years, novel applications of fluidized bed systems are

being discovered, which needs further understanding of the three phase fluidization

systems. Even though a large number of experiments have studied the various

hydrodynamic parameters of gas-liquid-solid fluidized beds, this complicated

phenomenon has not yet been fully understood. Here the extraction efficiency can be increased by:

Increasing extraction time or residence time.

Decreasing particle size.

Increasing operational temperature.

Increasing the gas phase velocity.

Increasing liquid phase velocity.

Decreasing the pressure drop.

Certain parameters on which the efficiency depend are just an assumption as the

original result couldn’t be obtained due to following reasons:

Climatic condition during operation.

Malfunctioning of temperature controller.

Leakage in the column due to which the volatile solvent gets

vaporized.

Defect in the manometer.

Pumping problems.

Defect in designing of equipment. Etc.

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