Solid Liquid Extraction 694y2l

ABSTRACT The experiment Solid-liquid extraction was carried out in a way, where Peanut oil (PO) was extracted from crushed peanuts by using the continuous overflow extraction through a fixed solid bed method. N-hexane was used as the solvent to extract the oil. Calibration was done in order to determine the solute composition. Density and solute composition of affluent and reboiler were measured at different time intervals in order to study the effect of time on solute composition. In the end the total amount of solvent extracted was calculated and the effect of different components like temperature and solvent flow rate on the overall extraction were studied

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INTRODUCTION Separation processes by extraction are a fundamental part of almost every chemical process. Separations start with the extraction of raw materials and continue to the purification and isolation of the final product. Without an efficient separation technology, raw materials would be in short supply, more expensive and of a lower quality. Solid-liquid extraction allows soluble components to be removed from solids using a solvent. An everyday example is the preparation of coffee. Water (solvent) is used to remove the coffee flavours (transition component) from the coffee powder (extraction material, consisting of solid carrier phase and transition component). Ideally, this results in drinkable coffee (solvent with dissolved flavours), with the completely depleted coffee grounds (solid carrier phase) remaining in the coffee filter. To achieve the fastest and most complete solid extraction possible, the solvent must be provided with large exchange surfaces and short diffusion paths. This can be done by pulverising the solid to be extracted. The extraction material can also take the form of a fixed bed with the solvent flowing through it.

Figure 1: Schematic of solid-liquid extraction process The experiment conducted used the method of continuous overflow extraction through a fixed solid bed. Firstly the experiment consisted of the peanuts being crushed. The peanuts were then placed in the affluent cylinder of the operating machine. The solvent used was N2

hexane. N-hexane was used as it has low heat of vaporisation. The n-hexane is filled in the reboiler. The temperature of the reboiler is set and the rate of the feed flow rate is also set. As the solvent boils it goes up and es through the solid bed. After ing through the solid bed it is condensed again and ready for use for extraction of oil from the crushed peanuts in the affluent cylinder. After the solvent flows from the affluent cylinder, it has already extracted the peanut oil. After that the hexane is removed and the oil is collected. This method is therefore known as chemical solvent extraction and it is very profitable as the oil yield using this method is maximum. This method enables a high capacity, low power consumption, low maintenance and high extract efficiency.

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APPARATUS: The SOLTEQ® Solid-Liquid Extraction Unit (Model: BP 40) is designed to demonstrate the extraction process, where it operates as a fixed-bed extractor and components can be selectively extracted from solids with the use of a suitable solvent. The unit which can operate in batch mode or continues mode consists of a pre-heater, an extraction vessel, an evaporator, condenser, cooler, a packed column and a receiver vessel. Unit specifications: 1. Re-boiler (B1) 7.0L spherical evaporator vessel made of stainless steel Electrical safety heating mantle (W1), 2 kW with temperature and level switch. 2. Column (K1) DN50 x 1000 mm column made of borosilicate glass Packing: glass Raschig rings (8mm x 8mm) 3. Condenser (W2) Vertical coil heat exchanger DN50 made of stainless steel Heat transfer area: 0.3 m2 4. Product Cooler (W4) Vertical coil heat exchanger made of stainless steel Heat transfer area: 0.03 m2 5. Receiver Vessel (B3) 5-L spherical vessel made of stainless steel 6. Extraction Vessel (B2) Cylindrical vessel made of borosilicate glass with 4L solid sample container made of stainless steel with porous 7. Pre-Heater (W3) 150 W cartridge heater with temperature control 8. Instruments and Controls 3 temperature measurement points (TI-101, TI-102, TI-103) 2 temperature controller (TIC-101, TIC-103) 1 flow rate measuring point (FI-301) 1 pressure indicator (PI-201)

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1 level controller (LIC-101) 9. Framework Stainless steel tube with clamps 10. Operating Conditions Allowable pressure: -1 to 3 bar in tube -1 to 1 bar in shell Allowable temperature: 180°C in tube 150°C in shell 11. General Requirements Electrical: 230VAC / 1-phase / 50Hz / 10A Water supply: laboratory water Analytical instruments: density bottles Sample solids: e.g. crushed peanuts Solvent: e.g. n-hexane 12. Overall Dimensions Height: 1.730 m Width: 1.216 m Depth: 0.608 m

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Figure 2: Process flow diagram of SOLTEQ® Solid-Liquid Extraction Unit (Model: BP40)

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EXPERIMENT PROCEDURE: General Start-Up Procedures: The following was performed before starting the experiment: 1. All valves were initially closed. All vent valves V6, V7 and V9 were opened. 2. The re-boiler B1was charged with n-hexane solvent. 3. The cooling water was run through the product cooler W4 and condenser W2. 4. The heating system for the re-boiler was switched on as follows: a) Valve V12 was closed to allow for total reflux. b) The main power supply was switched on the control . c) The temperature controller TIC-101 set-point was adjusted to a few degrees above the boiling point of the solvent. In the case of n-hexane, it was adjusted to 70°C. d) The power for heater W1was switched on. e) The temperature rise in the re-boiler was observed. f) The system reached steady state at total reflux. Calibration of Solute Composition Chemicals needed: Peanut oil (solute) N-Hexane (solvent) 1. Mixtures of peanut oil and n-hexane were prepared in different compositions, from 0.0 to 1.0 g oil / g solvent. 2. The recommended calibration volumes in the sample table in Appendix D were used. With a basis of 100 g solvent. 3. For example (0.1 g oil / g solvent): a) 100 g of n-hexane solvent was weighed in a beaker. b) Then, 10 g of peanut oil (PO) was weighed in another beaker. c) The oil was added into the solvent to form a homogenous solution. 4. The density of the calibrated solution was measured. 5. A calibration curve of density vs. solute composition was plotted.

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EXTRACTION PROCEDURE: Continuous Downward Extraction of Peanut Oil (PO) From Peanuts Using n-Hexane

1. The general start-up procedures were performed. It was ensured that all valves were initially closed except the vent valves V6, V7 and V9. It was then ensured that the extraction vessel B2 is empty of solids. 2. Valves V2, V5 and V12 were opened. It was made sure that valve V12 was fully opened to obtain the maximum solvent flow rate. 3. The solvent was allowed to through the product cooler W4, flow indicator FI-301, pre-heater W3, extraction vessel B2 and back into the reboiler B1. 4. The solvent flow rate was monitored at the flow indicator FI-301. Once it was relatively constant, the value was recorded. 5. Valve V12 was closed to prevent any more solvent from entering the extraction vessel B2. Valves V2 and V5 were closed. 6. Fresh solid was charged in the extraction vessel. The solid’s weight was recorded. 7. The initial reboiler temperature was recorded. A sample was taken from the reboiler and its density was measured. 8. Valves V2 & V5 were first opened and valve V12 was then opened to start the extraction. The flow of solvent through the solids was observed in the extraction vessel B2. 9. Once the effluent started flowing into the reboiler B1 through valve V2, the timer was started and the first sample of the effluent at time t = 0 was collected. The density was determined. 10. The reboiler contents and effluent were continued to be sampled every 5 minutes. Each sample’s density was determined. Also the reboiler temperature at the specified time intervals were recorded. 11. The experiment was stopped when the effluent density was determined in step 11 and showed no significant solute composition (nearly pure solvent). 12. The heater W1 power was switched off and the reboiler was drained. The reboiler was refilled with fresh solvent.

Results:

4.1.1 Continuous downward extraction 8

Mass of solids: 1 kg. Solvent flow rate: 45 mL/min. Solvent feed temperature: 32C Total volume of Hexane: 50 mL Table1: The reboiler and effluent content at specific time Time (min) 0 5 10 15 20 25 30 35

Reboiler Contents Density Solute (g/mL) Composition 0.6926 0.4847 0.5900 0.4747 0.6296 0.4920 0.6130 0.4896 0.6090 0.5080 0.6212 0.5214 0.6214 0.5214 0.6138 0.5154

Effluent Density (g/mL) 0.6694 0.6532 0.6502 0.6390 0.5902 0.5722 0.5704 0.5770

Solute Composition 0.5153 0.5254 0.5080 0.5104 0.4920 0.4786 0.4786 0.4846

4.1.2 Calibration of solute composition Basis: 50g of n-Hexane

Table 2: Solute composition and density of hexane with different mass Mass of peanut oil added (g) 10 20 30 40 50

Solute composition (g oil/g solvent) 0.167 0.286 0.375 0.444 0.500

Density (g/mL) 0.632 0.729 0.733 0.750 0.770

4.2 Graph

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4.2.1 Graph of reboiler content composition versus time

Graph of reboiler content composition vs time

Reboiler content composition (g oil/ g solvent)

0.53 0.52 0.51 0.5 0.49 0.48 0.47 0.46 0.45

0

5

10 15 20 25 30 35 40

Time (min)

4.2.2 Graph of effluent composition versus time.

Graph of effluent composition vs time 0.53 0.52 0.51 0.5

Effluent composition (g oil/g solvent) 0.49 0.48 0.47 0.46 0.45

0

5 10 15 20 25 30 35 40

Time (min)

4.2.3 Graph of calibration of solute composition

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Graph of Density against Solute Composition 0.9 0.8 0.7 0.6 0.5 Density (g/mL) 0.4 0.3 0.2 0.1 0 0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

Solute composition (g oil/g solvent)

4.3 Sample of calculations 1) Reboiler content composition mass of hexane (reboiler) = mass of hexane (reboiler + effluent)

=

31.48 31.48+ 33.47 = 0.4847

2) Density mass of hexane (reboiler) = volume of hexane (reboiler)

31.48 g = 50 mL = 0.6296 g/mL

3) Total amount of extracted solute = Area under a graph (effluent composition vs time) x solvent flowrate = 17.46475x 45 mL/min = 785.914

DISCUSSION: 11

The method used was a continuous downward extraction. N-Hexane was used as the solvent to extract the solid. The Peanuts used in the experiment were crushed before being used for the extraction purpose as crushed peanuts have larger surface area and allow for more with hexane. The flowrate of the solvent was 45mL/min. The temperature recorded was 32 ċ of the solvent feed.

The graph of reboiler composition vs. time shows irregularities for a continuous process. The graph in theory should be linear or should show an increasing trend till a certain time limit as the solute is being extracted but there are irregularities at the 5 and 15 min mark. The highest solute composition is 0.5214 g oil/g solvent. The graph also shows that the reboiler content starts decreasing after the 30 min. The graph of affluent composition vs. time should complement the reboiler content vs. time and it does. The solute composition should decrease with time here and it does but there are irregularities as for a continuous process the graph should be in a continuous trend. The highest solute composition of the effluent is 0.5254 g oil/g. The graph for density vs. solute composition shoes that higher the density more the solute composition. From the graphs obtained, it generally shows that as the time increases mores oil is extracted. The initial high rate of extraction might be caused by the fast solubility of the oil that is present at the solid surface and higher driving force of the mass transfer by the low oil concentration in the fresh solvent. The irregularities were caused by the fault in the operating machine as there was leakage in the affluent container. This leaked solvent might have contained the extracted solute which in turn could prove why the readings did not follow the general trend. Moreover there was also leakage from the reboiler which in turn explains the irregularities from the reboiler composition vs. time graph.

These graph also show that time is a very important factor for this experiment as with more time, higher amount of peanut oil would have been extracted. The temperature used for this experiment was high in order to lower the solvent and extract viscosities and increasing the extract solubility in the solvent. Conclusion: 12

The basic aim of the experiment was achieved which was the extraction of solid by a liquid. Due to the faultiness of the operating machine, there were irregularities in the results which showed deviation from a continuous process. In order to improve the experiment, the equipment being used should be ensured to operate properly. The weight of n-hexane should be measured quickly as n-hexane is volatile and evaporates quickly.

REFERENCES

1. Joe Givens, Robert Jordheim and George Anderson, tests performed at a 750 ton per day soybean extraction plant in Dawson, Minnesota, March 10, 1977. 2. Engineers S.B.o.C. 1998. SBP Handbook of Oil Seeds, Oils, Fats and Derivatives. SBP Consultant & Engineers Pvt. Ltd., New Delhi. 3. Williams, M.A. Obtaining oils and fats from source materials. Bailey’s Industrial Oil and Fat Products, Fifth Edition, pp. 106-138 (John Wiley & Sons, New York) (1996).

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