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 oerflow extraction through a fixed solid bed method! method! "-hexane was used as the solent to extract the oil! #alibration #alibration was done in order to determine the solute composition! $ensity and solute composition of affluent and reboiler were measured at different time interals in order to study the effect of time on solute composition! %n the end the total amount of solent extracted was calculated and the effect of different components li&e temperature and solent flow rate on the oerall extraction were studied
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INTRODUCTION
Separation processes by extraction are a fundamental part of almost eery chemical process! Separations start with the extraction of raw materials and continue to the purification and isolation of the final product! 'ithout an efficient separation technology, raw materials would be in short supply, more expensie and of a lower quality! Solid-liquid extraction allows soluble components to be remoed from solids using a solent!
n eeryday example is the preparation of coffee! 'ater (solent) is used to remoe the coffee flaours (transition component) from the coffee powder (extraction material, consisting of solid carrier phase and transition component)! %deally, this results in drin&able coffee (solent with dissoled flaours), with the completely depleted coffee grounds (solid carrier phase) remaining in the coffee filter!
To achiee the fastest and most complete solid extraction possible, the solent must be proided with large exchange surfaces and short diffusion paths! This can be done by pulerising the solid to be extracted! The extraction material can also ta&e the form of a fixed bed with the solent flowing through it!
igure *+ Schematic of solid-liquid extraction process
The experiment conducted used the method of continuous oerflow extraction through a fixed solid bed! irstly the experiment consisted of the peanuts being crushed! The peanuts were then placed in the affluent cylinder of the operating machine! The solent used was "-
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hexane! "-hexane was used as it has low heat of aporisation! 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! s the solent boils it goes up and passes through the solid bed! fter passing through the solid bed it is condensed again and ready for use for extraction of oil from the crushed peanuts in the affluent cylinder! fter the solent flows from the affluent cylinder, it has already extracted the peanut oil! fter that the hexane is remoed and the oil is collected! This method is therefore &nown as chemical solent extraction and it is ery 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 SOT./ Solid-iquid xtraction 0nit (1odel+ 2P 34) is designed to demonstrate the extraction process, where it operates as a fixed-bed extractor and components can be selectiely extracted from solids with the use of a suitable solent! The unit which can operate in batch mode or continues mode consists of a pre-heater, an extraction essel, an eaporator, condenser, cooler, a pac&ed column and a receier essel!
Unit specifications:
*! 5e-boiler (2*) 6!4 spherical eaporator essel made of stainless steel lectrical safety heating mantle ('*), 7 &' with temperature and leel switch! 7! #olumn (8*) $"94 x *444 mm column made of borosilicate glass Pac&ing+ glass 5aschig rings (:mm x :mm) ;! #ondenser ('7)
! xtraction
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* leel controller (%#-*4*)
?! ramewor& Stainless steel tube with clamps *4! Operating #onditions llowable pressure+ -* to ; bar in tube -* to * bar in shell llowable temperature+ *:4@# in tube *94@# in shell **! Aeneral 5equirements lectrical+ 7;4<# B *-phase B 94=C B *4 'ater supply+ laboratory water nalytical instruments+ density bottles Sample solids+ e!g! crushed peanuts Solent+ e!g! n-hexane *7! Oerall $imensions =eight+ *!6;4 m 'idth+ *!7*> m $epth+ 4!>4: m
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igure 7+ Process flow diagram of SOT./ Solid-iquid xtraction 0nit (1odel+ 2P34)
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EXPERIMENT PROCEDURE:
General Start-Up Proce!res:
The following was performed before starting the experiment+
*! ll ales were initially closed! ll ent ales <>, <6 and
boiling point of the solent! %n the case of n-hexane, it was adDusted to 64@#! d) The power for heater '*was switched on! e) The temperature rise in the re-boiler was obsered! f) The system reached steady state at total reflux!
Cali"ration of Sol!te Co#position
#hemicals needed+ Peanut oil (solute) "-=exane (solent)
*! 1ixtures of peanut oil and n-hexane were prepared in different compositions, from 4!4 to *!4 g oil B g solent! 7! The recommended calibration olumes in the sample table in ppendix $ were used! 'ith a basis of *44 g solent! ;! or example (4!* g oil B g solent)+ a) *44 g of n-hexane solent was weighed in a bea&er! b) Then, *4 g of peanut oil (PO) was weighed in another bea&er! c) The oil was added into the solent to form a homogenous solution!
3! The density of the calibrated solution was measured! 9! calibration cure of density s! solute composition was plotted!
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EXTRACTION PROCEDURE:
Contin!o!s Do$n$ar E%traction of Pean!t Oil &PO' (ro# Pean!ts Usin) n-*e%ane
*! The general start-up procedures were performed! %t was ensured that all ales were initially closed except the ent ales <>, <6 and ! resh solid was charged in the extraction essel! The solidEs weight was recorded! 6! The initial reboiler temperature was recorded! sample was ta&en from the reboiler and its density was measured! :!
Res!lts:
+,, Contin!o!s o$n$ar e%traction 8
1ass of solids+ * &g! Solent flow rate+ 39 mBmin! Solent feed temperature+ ;7# Total olume of =exane+ 94 m
Table*+ The reboiler and effluent content at specific time Time (min) 4 9 *4 *9 74 79 ;4 ;9
5eboiler #ontents $ensity Solute (gBm) #omposition 4!>?7> 4!3:36 4!9?44 4!3636 4!>7?> 4!3?74 4!>*;4 4!3:?> 4!>4?4 4!94:4 4!>7*7 4!97*3 4!>7*3 4!97*3 4!>*;: 4!9*93
ffluent $ensity (gBm) 4!>>?3 4!>9;7 4!>947 4!>;?4 4!9?47 4!9677 4!9643 4!9664
Solute #omposition 4!9*9; 4!9793 4!94:4 4!9*43 4!3?74 4!36:> 4!36:> 4!3:3>
+,,. Cali"ration of sol!te co#position
2asis+ 94g of n-=exane
Table 7+ Solute composition and density of hexane with different mass 1ass of peanut oil added (g) *4 74 ;4 34 94
Solute composition (g oilBg solent) 4!*>6 4!7:> 4!;69 4!333 4!944
$ensity (gBm) 4!>;7 4!67? 4!6;; 4!694 4!664
+,. Grap/
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3!7!* Araph of reboiler content composition ersus time
Graph of reboiler content composition vs time
!eboiler content composition (" oil# " solvent
0.53 0.52 0.51 0.5 0.49 0.48 0.47 0.46 0.45
0
5
10 15 20 25 30 35 40
Time (min
3!7!7 Araph of effluent composition ersus time!
Graph of e$%ent composition vs time 0.53 0.52 0.51 0.5
&$%ent composition (" oil#" solvent 0.49 0.48 0.47 0.46 0.45
0
5 10 15 20 25 30 35 40
Time (min
3!7!; Araph of calibration of solute composition
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Araph of $ensity against Solute #omposition 0.9 0.8 0.7 0.6 0.5 $ensity (gBm) 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 co mpos ition (g o ilBg s olent)
3!; Sample of calculations *) 5eboiler content composition G
mass of hexane (reboiler) mass of hexane (reboiler + effluent)
31.48
G
31.48 + 33.47
G 4!3:36
7) $ensity
mass of hexane (reboiler) G volume of hexane (reboiler)
G
31.48 g 50 mL
G 4!>7?> gBm
;) Total amount of extracted solute G rea under a graph (effluent composition s time) x solent flowrate G *6!3>369x 39 mBmin G 6:9!?*3
DISCUSSION: 11
The method used was a continuous downward extraction! "-=exane was used as the solent to extract the solid! The Peanuts used in the experiment were crushed before being used for the extraction purpose as crushed peanuts hae larger surface area and allow for more contact with hexane! The flowrate of the solent was 39mBmin! The temperature recorded was ;7 H of the solent feed!
The graph of reboiler composition s! 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 9 and *9 min mar&! The highest solute composition is 4!97*3 g oilBg solent! The graph also shows that the reboiler content starts decreasing after the ;4 min! The graph of affluent composition s! time should complement the reboiler content s! 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 4!9793 g oilBg! The graph for density s! solute composition shoes that higher the density more the solute composition! rom 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 driing force of the mass transfer by the low oil concentration in the fresh solent! The irregularities were caused by the fault in the operating machine as there was lea&age in the affluent container! This lea&ed solent might hae contained the extracted solute which in turn could proe why the readings did not follow the general trend! 1oreoer there was also lea&age from the reboiler which in turn explains the irregularities from the reboiler composition s! time graph!
These graph also show that time is a ery important factor for this experiment as with more time, higher amount of peanut oil would hae been extracted! The temperature used for this experiment was high in order to lower the solent and extract iscosities and increasing the extract solubility in the solent! Concl!sion:
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The basic aim of the experiment was achieed which was the extraction of solid by a liquid! $ue to the faultiness of the operating machine, there were irregularities in the results which showed deiation from a continuous process! %n order to improe the experiment, the equipment being used should be ensured to operate properly! The weight of n-hexane should be measured quic&ly as n-hexane is olatile and eaporates quic&ly!
RE(ERENCES
*! Ioe Aiens, 5obert Iordheim and Aeorge nderson, tests performed at a 694 ton per day soybean extraction plant in $awson, 1innesota, 1arch *4, *?66! 7! ngineers S!2!o!#! *??:! S2P =andboo& of Oil Seeds, Oils, ats and $eriaties! S2P #onsultant F ngineers Pt! td!, "ew $elhi! ;! 'illiams, 1!! Obtaining oils and fats from source materials! Bailey’s Industrial Oil and Fat Products, Fifth Edition, pp! *4>-*;: (Iohn 'iley F Sons, "ew Jor&) (*??>)!
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