Bangladesh University of Engineering & Technology

Course No: CHE 302
Course Name: Chemical Engineering Laboratory- II
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Experiment No: 01
Name of the Experiment: EXTRACTION OF OIL FROM OIL CAKE BY SOXHLET EXTRACTOR
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Date of Performance: 18/11/15
Date of Submission: 25/11/15
Partners’ Std. Id- 1202012 1202013 1202014 1202015 0902058
Submitted To- Md. Nazibul Islam Lecturer, Department of Chemical Engineering,
BUET

Partners’ Std. Id- 1202012 1202013 1202014 1202015 0902058
Submitted To- Md. Nazibul Islam Lecturer, Department of Chemical Engineering,
BUET

Submitted by,
Md. Touhidul Islam
Std. Id- 1202011
Level- 3, Term- 1
Dept. – Ch.E
Group- 03 (A1)

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1.0 SUMMARY
The objective of this experiment was to study Soxhlet Extractor and to determine the percent extraction of oil from oil cake and percent recovery of solvent used for extraction. In this experiment, a paper thimble was weighed and then measured amount of oil cake was taken in the thimble and placed in the Soxhlet holder. N-hexane, which was used as the solvent, was measured in a round bottom flask and then after setting up the apparatus, was heated by an electric heater up to its boiling point. The n-hexane vapor rose up to the condenser and absorbing heat from the cooling water it was condensed which fell in the thimble. Oil was extracted from the oil cake by n-hexane and after the level of the oil-hexane mixture rose to a certain level, it returned to the round bottom flask due to siphoning effect. This process was repeated several times until the hexane accumulating in the thimble became colorless which indicated that the extraction process was complete. Then, the apparatus was reassembled for recovery of the hexane. The n-hexane containing oil was distillated by successive vaporization and condensation of n-hexane which was collected in a conical flask. From the experimental result, it was found that, the percent extraction of oil from oil cake was 6.82 % and the percent recovery of n-hexane was 64.74 %.

2.0 INTRODUCTION

Separation technique is a regular or very usual phenomenon in every chemical process industry. This separation technique varies depending on the boiling point, solubility, volatility and last of all phase distinction. In solid liquid extraction, a liquid solvent is used to dissolve the soluble liquid from an insoluble solid. This process is also known industrially as leaching. In solvent extraction method, the dried, crushed and flaked raw material is brought into contact with a suitable solvent. This solvent dissolves the oil from the oilcake and then pure oil is obtained by evaporating the solvent.In this experiment, Soxhlet extractor was used to extract oil from the oilcakes. In this type of extractor, solvent falls by gravity on the top of the extractor, seeps through the cake and goes down below the false bottom. In the bottom, heating coils are provided to heat the solvent and the solvent vapor goes to the condensers placed at a height above the extractors. The condensed solvent again falls by gravity to the top of the extractor and the cycle is repeated until the oilcake is exhausted sufficiently. After the experiment was completed, the percentage of solvent recovery and percentage of extracted oil in oilcake were calculated.The oil extracted by solvent extraction method is usually not used for edible purposes as the presence of trace amount of solvent. Again the odor and flavor of oils are lost on solvent extraction process. So, solvent extracted oil is usually used in industrial purposes.

3.0 EXPERIMANTAL WORK

3.1 Apparatus * Electric heater * Round bottom flask * Soxhlet holder * Soxhlet thimble * Condenser * Conical flask * Thermometer etc.

Soxhlet extractor:

A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. However,a Soxhlet extractor is not limited to the extraction of lipids. Typically, a Soxhlet extraction is onlyrequired where the desired compound has a limited solubility in a solvent, and the impurity is insoluble in that solvent.Normally a solid material containing some of the desired compound is placed inside a thimblemade from thick filter paper, which is loaded into the main chamber of the Soxhlet extractor. The extraction solvent to be used is taken into a round bottom flask and the Soxhlet extractor is now placed onto this flask. The Soxhlet is then equipped with a condenser.The solvent is heated to reflux. The solvent vapor then travels up a distillation arm, and floods into the chamber housing the thimble of solid. The condenser ensures that any solvent vapor cools, and drips back down into the chamber housing the solid material.The chamber containing the solid material is slowly filled with warm solvent. Some of the desired compound will then dissolve in the warm solvent. When the Soxhlet chamber is almost full, the chamber is automatically emptied by a siphon side arm, with the solvent running back down to the flask. The thimble ensures that the rapid motion of the solvent does not transport any solid material to the still pot. This cycle may be allowed to repeat many times.During each cycle, a portion of the non-volatile compound dissolves in the solvent. After many cycles the desired compound is concentrated in the flask. The advantage of this system is that instead of many portions of warm solvent being passed through the sample, just one batch of solvent is recycled.

3.2 Experimental setup
Cooling water out
Cooling water out
Figure 01: Schematic diagram of Soxhlet Extractor for oil extraction
Figure 01: Schematic diagram of Soxhlet Extractor for oil extraction
Condenser

Solvent vapor
Paper thimble

Solvent vapor + oil

Round-bottom flask
Electric heater

Condenser

Solvent vapor
Paper thimble

Solvent vapor + oil

Round-bottom flask
Electric heater

Cooling water in
Cooling water in

Cooling water out
Cooling water out
Cooling water in
Cooling water in
Figure 02: Experimental setup for solvent recovery
Figure 02: Experimental setup for solvent recovery
Condenser
Thermometer

Round-bottom flask
Solvent (Hexane) + extracted oil
Electric heater
Liquid solvent (hexane)

Condenser
Thermometer

Round-bottom flask
Solvent (Hexane) + extracted oil
Electric heater
Liquid solvent (hexane)

3.3 Experimental procedure
1. A measured amount of n-hexane was put in the flask and a measured amount of oilcake in the Soxhlet thimble and then it was placed in the Soxhlet holder.
2. The flask was then put on the heater and the solvent was heated slowly. At that time condenser was put on the top of the Soxhlet holder and the cooling water was on.
3. After observing five complete siphons, the flask containing n-Hexane was weighed and then weight of extracted oil was calculated.
4. The apparatus was then reassembled incorporating the condenser for solvent recovery.Heating was continued until no more solvent was being recovered.
5. Finally recovered solvent was weighed and percent extraction of oil and percent recovery Of solvent were calculated

3.4 Safety precautions

Solvent extraction plants employ solvent like hexane for extraction of oil from oil-bearing materials. Hexane is inherently combustible material and the installation comes under the explosive’s directorate. It is therefore, necessary that one should observe good management practices in the operation of solvent extraction plants.

a) Protection against fire hazards
In some of the solvent extraction plants, especially of batch type, operating under pressure, special care should be taken to avoid fire hazards due to leakage of solvent. In some solvent extraction plants vacuum is created in their distillation units to avoid such mishaps.

b) Imperfect desolventisation
Care should be exercised that oil-bearing material which is being processed in the solvent extraction plant does not contain any trace of solvent after coming out from the extractors. If the material containing sizeable quantity of solvent is allowed to accumulate in open yard it can always cause a fire hazard besides heavy losses of solvent.

c) Purity of oil
Oil which comes out of the solvent extraction plants should not contain any trace of solvent since it will cause fire hazards besides losses in the solvent. The distillation units should be particularly efficient and the operator should carefully judge the number of times and the period for which the oil is allowed in the distillation unit.

d) Proper storage of solvent
It has already been said that hexane and other petroleum-based solvents are of inflammable nature and therefore, require proper storage facilities.

e) Electrical fittings
Proper installation of electrical fittings are necessary in the plant installation. It is more so in the case of solvent extraction plants where inflammable materials are involved. All the electrical fittings should be dust proof and properly guarded. The electrical installations must be done under the supervision of a qualified electrical engineer.

f) Proper separation of solvent from the mixture of matter
A mixture of water and solvent comes out form the water-cooled condensers. Generally, water solvent separators further separate the water and solvent. Due to inefficient design of the separator or inefficiency of the operator, the water coming out may contain a higher percentage of solvent.The draining of such a water-solvent mixture can again be a source of hazard. Sometimes a boiler is provided through which this water-solvent mixture is passed before a final discharge.

g) Instrumentation
For any process control instruments play a very important role. In the case of solvent extraction plants the temperature and the [pressures are very critical. Any malfunctioning of the control instruments can cause a serious damage.

4.0 OBSERVED DATA
Weight of empty thimble, X1 = 5.174 gm
Weight of (thimble + oil cake), X2 = 34.4 gm
Weight of empty round bottom flask, Y1 = 125.458 gm
Weight of (round bottom flask + n-Hexane), Y2 = 214.319 gm
Weight of conical flask, Z1 = 122.435 gm After distillation:
Weight of (conical flask + n-Hexane recovered), Z2 = 179.963 gm
Weight of (oil+ round bottom flask), Y3 = 127.451 gm
Table-1:Tabulated observed data Weight of empty thimble, X1 gm | Weight of (thimble + oil cake), X2 gm | Weight of empty round bottom flask,Y1 gm | Weight of (round bottom flask + n-Hexane), Y2 gm | Weight of (oil+ round bottom flask), Y3 gm | Weight of conical flask, Z1 gm | Weight of (conical flask + n-Hexane recovered), Z2 gm | 5.17 | 34.40 | 125.46 | 214.32 | 127.45 | 122.44 | 179.96 |

5.0 CALCULATED DATA
Weight of oil-cake = 29.226 gm
Weight of n-Hexane = 88.861 gm
Weight of oil extracted = 1.993 gm
Weight of n-hexane recovered = 57.528 gm
Percentage of extracted oil in oil cake = 6.82%
Percentage of n-hexane recovered = 68.84%
Table-2:Tabulated calculated data Weight of oil- cake gm | Weight of n-Hexane gm | Weight of oil extracted gm | Weight of n-hexane recovered gm | Percentage of extracted oil in oil cake | Percentage of n-hexane recovered | 29.23 | 88.86 | 1.99 | 57.53 | 6.82 % | 64.74% |

6.0 SAMPLE CALCULATION
Weight of oil cake = Weight of (thimble + oil cake) – weight of empty thimble = X2 –X1 = (34.4 – 5.174) gm = 29.226 gm

Weight of n-hexane = Weight of (round bottom flask + n-hexane) – weight of round bottom flask = Y2 – Y1 = (214.319 – 125.458) gm = 88.861 gm

Weight of oil extracted = Weight of (oil + round bottom flask) – weight of round bottom flask = Y3 – Y1 = (127.451 – 125.458) gm = 1.993 gm

Weight of n-hexane recovered = Weight of (conical flask + n-hexane recovered) – weight of conical flask = Z2 – Z1 = (179.963 – 122.435) gm = 57.528 gm

Percentage of extracted oil in oil cake =Weight of oil extracted Weight of oil cake×100% = Y3 - Y1X2- X1 × 100% = 1.993 gm29.226 × 100% = 6.82%

Percentage of n-hexane recovered =Weight of n-hexane recoveredWeight of n-hexane ×100% = Z2 - Z1Y2- Y1 × 100% = 57.528 gm88.861 × 100% = 64.74 %

7.0 RESULTS & DISCUSSIONS
The results obtained from this experiment are stated below – 1. The percentage of extracted oil from oil cake = 6.82% 2. The percentage of n-hexane recovery = 64.74 %
Table-3:Table for percent extraction of oil and percent recovery of n-hexane Percent extraction of oil | Percent recovery of n-hexane | 6.82% | 64.74 % |

From the results obtained from the experiment, it can be seen that both the value of percentage of oil extraction and percentage of n-hexane recovery were low. The reasons which might have contributed to the low recovery and extraction percentage are stated below –

* The oil cake used for extraction of oil was might have been collected from an oil factory, i.e., it might have been extracted once before. Consequently, the percentage of oil in the oil cake was very low. * In this experiment, extraction was executed in a single stage. Multistage extraction process might have yielded higher percentage of extracted oil. * Hexane was used as the solvent to extract oil from oil cake, which is a volatile substance. Although, cotton was used to prevent escape of hexane, during the experiment, a percentage of hexane might have been lost to the surroundings. * For recovering hexane, single stage condensation was used. Multistage condensation might have yielded better result. * Some of the hexane might have accumulated in the thimble or absorbed by the oil cake. * Carrying out the siphoning process a few more times might have led to better results.
There is a relation between percentage extractions of oil with time. It can be shown graphically:

Figure 3: typical % extraction vs. time curve

This graph shows that at 30 min, about 90 % of oil extracts from the oil cake. Above 30 min the recovery rate is very little. This experiment was performed at about 45 minutes and about eight cycles was fulfilled during this time. This time might be sufficient for extraction. Thus, for the above reasons the extraction was not good enough.

Precautions for using n-hexane as solvent
Hexane was used as the solvent in this experiment because of it has low boiling point, low sensible heat and it is easy to remove from other solids and liquids. * Hexane has one major weakness which is universally mentioned that is flammability. When hexane vapor is mixed with air in roughly a range from 1.2% - 7.7%, the mixture becomes flammable. * Hexane is costly and it is considered a pollutant if escapes from the process. Therefore, significant amounts of hexane escaping from the plant process in the process air, water, meal or oil, or simply in losses due to poor equipment maintenance, frequent shutdowns, or poor housekeeping.

Industrial application of solid-liquid extraction
Solid-liquid extraction process is used widely for industrial purpose. Some applications of solid-liquid extraction process for industrial purpose are given below: i. In metallurgical industry, this process is useful for separation of the minerals from their ores. ii. Solid-liquid extraction process is generally used in food industry to extract oil from the seeds containing oil such as groundnut; for vegetable oil production and for extraction of cod liver oil; good quality protein are also recovered from several seeds such as soybeans, cotton seeds etc. by direct extraction; iii. Solid-liquid extraction has a great application in the manufacture process of coffee. iv. It also maintains the property of de-oiled meal, which is rather increased due to less amount of residual oil content. Solvent extraction also permits maximum recovery of oil, leaving as little as a fraction of a percent in the meal.

Operating variables:
The rate of solid-liquid extraction process (i.e., Leaching) is influenced by different factors. The most important factors influencing the extraction process are as follows: 1. The particle size, 2. The solvent, 3. The temperature, and 4. The agitation of fluid.
Influences of the above operating variables are given below:

The particle size:
The particle size influences the extraction rate in a number of ways. The smaller the size, the greater is the interfacial area between the solid and liquid and therefore the higher is the rate of transfer of material. Further, the smaller is the distance the solute must diffuse within the sold as already indicated. On the other hand, the surface may not be so effectively used with a very fine material if circulation of the liquid is impeded, and separation of the particles from the liquid and drainage of the solid residue are made more difficult. It is generally desirable that the range of particle size should be small so that each particle requires approximately the same time for extraction. and, in particular, the production of a large amount of fine material should be avoided as it may wedge in the interstices of the larger particles and impede the flow of the solvent.

The solvent:
Nature of the solvent is an important factor for solid-liquid extraction process. . It is expected the higher solvent efficiency. The liquid chosen should be a good selective solvent and its viscosity should be sufficiently low for it to circulate freely. Generally a relatively pure solvent will be used initially, but as the extraction proceeds the concentration of solute will increase and the rate of extraction will progressively decrease, first because the concentration gradient will be reduced, and secondly because the solution will generally become more viscous.Again from Nernst’s distribution law it is seen that the more solvent is uses the more solute is extracted. To make the extraction efficient we should use large amount of solvent. But if we use large amount of solvent it will require more time and energy to separate the solute from the solvent.

The temperature:
In most cases, the solubility of the material which is being extracted will increase with temperature to give a higher rate of extraction will increase with temperature to give a higher rate of extraction. Further the diffusion coefficient will be expected to increase with rise in temperature and this will also improve the rate. In some cases, the upper limit of temperature is determined by secondary considerations, such as the necessity of preventing enzyme action during the extraction of a solute like sugar.

The agitation of the fluid:
Agitation of the solvent is important because it increases the eddy diffusion and therefore increases the transfer of material from the surface of the particles to the bulk of the solution as indicated in the following section. Further, agitation of suspensions of fine particles prevents sedimentation and more effective use is made of the interfacial surface.

Selection of solvent:
The selection of solvent for extraction process is very important for the efficient operation. The following criteria of the solvent must be considered while selecting solvent for an extraction process:

I. Separability Criteria II. Performance Criteria III. Acceptability Criteria

I. Separability Criteria
Solubility:
The solubility of the required substance will be very high in the solvent so that a less amount of solvent is required and the recovery rate of the desired product is high.

Viscosity:
High viscosity in either phase reduces mass transfer rates. In the non-dispersed phase, it slows the rate at which the dispersed drops rise or fall. High viscosity also makes pumping more difficult and slows heat transfer.

Density:
Small density difference can be augmented by centrifugal separators, but those cost more than gravity settlers.

II. Performance Criteria
Ability of the solvent to extract the solute from the seed attributes to performance. Here three properties must be considered: solubility, distribution co-efficient and selectivity.

Distribution coefficient:
The coefficient measures the tendency of the solute in the feed to concentrate in the solvent in presence of the feed. The higher the value of distribution coefficient is better.

Selectivity:
Selectivity measures the ability of the solvent to extract the solute in presence of the feed. For a solvent to be effective, its selectivity must be greater than one.

III. Acceptability Criteria
It is not enough for a solvent to have a higher selectivity than another; a number of additional factors enter into the choice, especially as they affect the cost of the entire operation.

Corrosiveness:
In selection of solvent, the corrosive solvent must be tried to avoid for the stability of the plant. If corrosive solvents are used, it will require special materials for construction of equipments. The extra cost of such construction must be weighed in the selection of solvent.

Flammability:
Low flammability is desirable due to ensure the safety. In this case, flash joint is used as the measure of the property. The flash point measures the temperature at which the solvent can be ignited. The solvent with high flammability will start to burn in air on its own with no spark of flame at the auto ignition temperature. For the perfect selection of solvent, the flammability should be low.

Toxicity:
Some solvents are responsible for environmental pollution although they are not hazardous to operations. Again, the solvent, which is used for the extraction of edible oil, must not be toxic as it is directly used by the consumers. Hence, the toxicity of the solvent affects the operation process, environment, and the consumers directly and indirectly. So, toxicity must be low for the selection of solvent. Volatilization:
Less volatile solvents are selected as because, solvent with high vapor pressure such as liquid ammonia or diethyl ether is difficult to keep as liquid. Here the loss of solvent to the surrounding will be costly and will complicate the operation.

Recoverability:
The choice of solvent, therefore, involves designing not only an extraction process but also a solvent separation system. A solvent of higher regenerability is chosen so that made up solvent feed requirement is low which leads to low operation cost.

Cost:
Cheaper solvents are selected for the minimization of operation cost and thus optimization is ensured.

Reasons for Selection of Hexane as Extractor:
Benzene, hexane, carbon disulfide and Trichloroethylene are used as the extractor for solid liquid extraction in general. In this experiment n-Hexane was used as the solvent rather than the Benzene, because the boiling temperature of Benzene (80.100C) is higher than that of n-Hexane (68.740C), though both have fewer boiling points than that of the oil. So it is easier to extract oil from oil cake using n-Hexane at a low temperature, and also the fuel cost is reduced. Again hexane is non-toxic but benzene is toxic and hexane is also cheaper than benzene. And thus the n-Hexane was preferred as solvent. Moreover n-Hexane is more soluble than the Benzene. So, hexane has the following properties:

* Hexane has a low latent heat of vaporization and it is much higher for carbon disulfide and trichloro ethylene. * Hexane does not react with any constituent of oil cake. * The recoverability is high for hexane. * Trichloro ethylene has a very high boiling point. Therefore, it is difficult to maintain it. * Solubility of oil in hexane is higher. * Again, Trichloro ethylene and carbon disulfide are more corrosive in nature than hexane and benzene. Carbon disulfide is very toxic and they also produce fume.

8.0 REFERENCES * Foust, A. S., Wenzel, L. A., Clump, C. W., Maus, L., Andersen, L. B., “Principles of Unit Operations”, 2nd edition, John Wiley and Sons, Singapore, P.15,60 (1980). * McCabe, W.L., Smith, J.C., Harriott, P., “Unit Operations of Chemical Engineering”, 5th edition, McGraw Hill, New York, P.614-616, (1993). * Bhatnagar, A.P., Singh, D., ”Edible Oil Technology”, International edition, Smale Publications,Delhi,p.19,46-48.(1975) * Mahatta, T.L., “Technology and Refining of Oils and fats”, International edition, Small Publications,Delhi,p-141-147.(1975)

Marking Scheme: Normal Report
Experiment name: Extraction of oil from oil cake by soxhlet extractor

Name: Md Touhidul Islam
Student ID: 1202011

Section and % mark allocated | Marks | Summary (1.0) | | Introduction (1.0) | | Experimental Work (1.0) | | Observed Data (1.0) | | Calculated Data (1.0) | | Sample Calculation (1.0) | | Graphs (1.0) | | Results and Discussions (1.5) | | References and Nomenclature (0.5) | | Writing Style (1.0) | | Total (10) | |