Extraction of a Pharmaceutical Jelly From Avocado
-
Upload
stephenbwogora -
Category
Documents
-
view
67 -
download
5
Transcript of Extraction of a Pharmaceutical Jelly From Avocado
-
MOI UNIVERSITY
EXTRACTION OF A PHARMACEUTICAL JELLY FROM
AVOCADO PULP
A Design Project Presented to the
DEPARTMENT OF CHEMICAL AND PROCESS ENGINEERING
SCHOOL OF ENGINEERING
In partial fulfillment of the requirements for the award of Bachelor of Engineering in
Chemical & Process Engineering
Moi University
DIAR ELIJAH GARANG CPE/1021/08
JOAKIM KISUA PIUS CPE/09/08
SUPERVISOR
Dr. Menzwa
-
i
DECLARATION
We declare that this project entitled Extraction of pharmaceutical jelly from avocado
pulp is the result of our own research except as cited in the references. The report has
not been accepted for any degree and is not concurrently submitted in candidature of
any other degree.
Signature: .
Name of candidate: DIAR ELIJAH GARANG (CPE/1021/08)
Signature: .
Name of Candidate: JOAKIM KISUA PIUS (CPE/09/08)
DATE: 21st May, 2013
-
ii
ACKNOWLEDGEMENT
We would like to thank the Almighty for the strength, inspiration and encouragement
given to us throughout the completion of this project without any obstacle. A lot of
experiences and knowledge has been gained along the way.
We wish to express our sincere appreciation to our supervisor, Dr. Menzwa, for his
critic, advice, motivation, friendship and input of ideas, relentless support, guidance and
endless encouragement throughout our entire project
We are also very thankful to our parents for their support and motivation. Without their
endless support and interest, this project would not have been same as presented here.
Unfortunately it is not possible for us to list all those involved in this limited space. We
are therefore grateful to everybody that was involved directly or indirectly in helping us
to complete this project.
-
iii
ABSTRACT
Avocado fruit is one valuable tropical produce which is highly utilized in Kenya and
even in most of African countries only on the nutritious aspect. This is due to the proven
presence high content of positive effects on lowering total blood cholesterol, controlling
weight and providing humans with essential nutrients and vitamins. Various studies
have also proven high content of tocopherols (vitamin E) and antioxidants in
unsaponifiable fraction in avocado oil which can help to hail skin ailments. Cosmetic
industries have taken up these studies positively and they have been producing
cosmetic products for years. However pharmaceutically, much attention has not been
paid to get high concentration of this unsaponifiable fraction so as it could be used to
treat skin ailments. However, this project will be targeting un-saponifiable fraction of
the oil obtained from molecular distillation which is in the light components of the
fractionated oil. During the molecular distillation, substantial amount of unsaponifiable
fraction is achieved in the light component. Process operating conditions (temperature
and pressure) are chosen so that much of this unsaponifiable fraction is obtained in the
light components without interfering with the desired pytochemicals.
-
iv
TABLE OF CONTENTS
DECLARATION --------------------------------------------------------------------------------------------- i
ACKNOWLEDGEMENT ---------------------------------------------------------------------------------- ii
ABSTRACT ------------------------------------------------------------------------------------------------ iii
LIST OF TABLES --------------------------------------------------------------------------------------- viii
LIST OF FIGURES -------------------------------------------------------------------------------------- viii
CHAPTER ONE -------------------------------------------------------------------------------------------- 1
1.0 Introduction -----------------------------------------------------------------------------------------------------------1
1.1Objectives of the Design project ----------------------------------------------------------------------------------2
CHAPTER TWO ------------------------------------------------------------------------------------------- 3
2.1: Literature review ----------------------------------------------------------------------------------------------------3
2.2: Historical Origin of the Plant--------------------------------------------------------------------------------------3
2.3: Agronomy -------------------------------------------------------------------------------------------------------------3
2.3.1: Growth Requirements ----------------------------------------------------------------------------------------3
2.3.2: Fertilization------------------------------------------------------------------------------------------------------4
2.3.3: Avocado Fruit & Human Health ----------------------------------------------------------------------------6
CHAPTER THREE --------------------------------------------------------------------------------------- 20
3.0: JUSTICATION -------------------------------------------------------------------------------------------------------- 20
CHAPTER FOUR ----------------------------------------------------------------------------------------- 21
4.0: PROCESS DESCRIPTION ------------------------------------------------------------------------------------------ 21
4.1 Pre-process treatment -------------------------------------------------------------------------------------------- 21
4.2 Extraction process-------------------------------------------------------------------------------------------------- 21
4.3 Preheating ----------------------------------------------------------------------------------------------------------- 21
BLOCK DIAGRAMS------------------------------------------------------------------------------------------------------- 28
CHAPTER FIVE ------------------------------------------------------------------------------------------ 31
5.0: MASS AND ENERGY BALANCES -------------------------------------------------------------------------------- 31
5.1.1: Mass balance ------------------------------------------------------------------------------------------------- 31
5.1.2: ENERGY BALANCE ----------------------------------------------------------------------------------------------- 37
CHAPTER SIX -------------------------------------------------------------------------------------------- 40
6.0 EQUIPMENT SELECTION, SIZING AND SPECIFICATION ---------------------------------- 40
6.1 CHOICE OF MATERIALS FOR EQUIPMENT FABRICATIONS ----------------------------- 40
CHAPTER 7 ---------------------------------------------------------------------------------------------- 44
7.0 Design of a centrifugal separator by DIAR ELIJAH GARANG CPE/1021/08 -------- 44
-
v
7.0.1 INTRODUCTION -------------------------------------------------------------------------------------------------- 44
7.0.2 SEDIMENTATION CENTRIFUGES ------------------------------------------------------------------------------ 44
7.0.3 CENTRIFUGE DESIGN THEORY -------------------------------------------------------------------------------- 47
7.0.4 CHEMICAL DESIGN ----------------------------------------------------------------------------------------------- 50
7.0.4.1 Bowl diameter ---------------------------------------------------------------------------------------------- 50
7.0.4.2 Disk diameter ----------------------------------------------------------------------------------------------- 50
7.0.4.3 Terminal velocity ------------------------------------------------------------------------------------------- 50
7.0.4.5 Sigma value -------------------------------------------------------------------------------------------------- 51
7.0.4.6 Number of discs -------------------------------------------------------------------------------------------- 51
7.0.4.7 Inner radius of the discs ---------------------------------------------------------------------------------- 51
7.0.4.8 Radius of the interphase --------------------------------------------------------------------------------- 51
7.4.0.9 Disc length --------------------------------------------------------------------------------------------------- 52
7.4.0.9 Bowl axial height ------------------------------------------------------------------------------------------- 52
7.4.0.10 Disc spacing ------------------------------------------------------------------------------------------------ 52
7.4.0.11Disc perforations ------------------------------------------------------------------------------------------ 53
7.4.0.12 Centrifugal force ------------------------------------------------------------------------------------------ 53
7.4.0.13 Centrifugal settling velocity ---------------------------------------------------------------------------- 53
7.4.0.14 Retention time -------------------------------------------------------------------------------------------- 53
7.4.0.15 The centrifugal pressure -------------------------------------------------------------------------------- 53
7.4.0.16 Power consumption ------------------------------------------------------------------------------------- 54
7.0.5 MECHANICAL DESIGN ------------------------------------------------------------------------------------------- 56
7.0.5.1 Stresses involved ------------------------------------------------------------------------------------------- 56
7.0.5.2 Material of construction --------------------------------------------------------------------------------- 57
7.0.5.3 Vibration problem ----------------------------------------------------------------------------------------- 57
7.0.5.4 Thickness of the centrifuge shell ----------------------------------------------------------------------- 58
7.0.6 SUMMARY OF CENTRIFUGAL --------------------------------------------------------------------------------- 58
7.1 Design of a wipe film evaporator by JOAKIM KISUA PIUS CPE/09/08 -------------- 60
7.1.1 Functions of an evaporator------------------------------------------------------------------------------------ 60
7.1.2 DESIGN METHODOLOGY OF WIPED FILM EVAPORATOR ---------------------------------------------- 61
7.1.3 Wiped Film Evaporator Principle ----------------------------------------------------------------------------- 62
7.1.4 Thermal Design Calculations ---------------------------------------------------------------------------------- 64
7.1.5 Calculations ------------------------------------------------------------------------------------------------------- 66
7.1.5.1 Log mean temperature difference (LMTD) method ----------------------------------------------- 67
7.1.6 MECHANICAL DESIGN ------------------------------------------------------------------------------------------- 69
-
vi
7.1.7 AGITATOR DESIGN ----------------------------------------------------------------------------------------------- 69
7.1.7.1 Number of blade calculations --------------------------------------------------------------------------- 69
7.1.7.2 ----------------------------------------------------------------- 70
7.1.7.3 ---------------------------------------------------------------------------------------- 70
7.1.7.4 ------------------------------------------------------------------------------------------ 70
7.1.7.5 Jacket thickness -------------------------------------------------------------------------------------------- 71
7.1.7.6 Feed nozzle -------------------------------------------------------------------------------------------------- 71
7.1.7.7 Design temperature --------------------------------------------------------------------------------------- 71
7.1.7.8 Design pressure -------------------------------------------------------------------------------------------- 72
7.1.8 Design summary ------------------------------------------------------------------------------------------------- 73
CHAPTER 8 ---------------------------------------------------------------------------------------------- 74
8.0 PROCESS CONTROL AND INSTRUMENTATION -------------------------------------------- 74
8.1 Introduction --------------------------------------------------------------------------------------------------------- 74
8.2 Objectives of process control and instrumentation ------------------------------------------------------- 75
8.3 Classification of process variables ------------------------------------------------------------------------------ 75
8.4 Control principles -------------------------------------------------------------------------------------------------- 75
CHAPTER NINE ----------------------------------------------------------------------------------------- 79
9.0 ECONOMIC AND PROFITABILITY ANALYSIS ------------------------------------------------ 79
9.1 INTRODUCTION ----------------------------------------------------------------------------------------------------- 79
9.2 Economic Evaluations --------------------------------------------------------------------------------------------- 79
9.2.1 Estimation of fixed capital investment ------------------------------------------------------------------ 83
9.2.2 Total capital investment estimates ---------------------------------------------------------------------- 84
9.2.3 Total product cost -------------------------------------------------------------------------------------------- 84
9.2.4 Raw materials cost estimates ----------------------------------------------------------------------------- 85
9.2.5 Annual utilities cost estimates ---------------------------------------------------------------------------- 85
9.2.6 Depreciation --------------------------------------------------------------------------------------------------- 85
9.2.7 Operating labor cost estimates --------------------------------------------------------------------------- 87
9.2.8 Annual Cash Flow Analysis --------------------------------------------------------------------------------- 89
9.2.9 Cumulative cash flow analysis ----------------------------------------------------------------------------- 91
9.2.10 Profitability Analysis---------------------------------------------------------------------------------------- 92
9.2.11 Break-Even Point (BEP) Analysis ------------------------------------------------------------------------ 95
CHAPTER 10 --------------------------------------------------------------------------------------------- 97
10.0 SAFETY AND ENVIRONMENT IMPACT ASSESSMENT ----------------------------------- 97
10.1 INTRODUCTION --------------------------------------------------------------------------------------------------- 97
-
vii
10.2 SAFETY --------------------------------------------------------------------------------------------------------------- 98
10.3 ADMINISTRATIVE CONTROLS ------------------------------------------------------------------------------- 99
10.4 ENGINEERING SAFETY CONTROL --------------------------------------------------------------------------- 100
10.5 DEVELOPMENT OF A SAFETY AND HEALTH PROGRAM ----------------------------------------------- 101
10.6 HAZARD COMMUNICATION --------------------------------------------------------------------------------- 101
10.7 ENVIRONMENTAL IMPACT ASSESSMENT (EIA) ---------------------------------------------------------- 102
10.8 ENVIRONMENTAL IMPACT AND MITIGATION MEASURES ------------------------------------------- 103
10.9 LEGISLATION ----------------------------------------------------------------------------------------------------- 105
10.10 HAZARD AND OPERABILITY ANALYSIS (HAZOP) ------------------------------------------------------- 107
CHAPTER 11 --------------------------------------------------------------------------------------------114
11.0 PLANT LOCATION AND LAYOUT ------------------------------------------------------------114
11.1 INTRODUCTION ------------------------------------------------------------------------------------------------- 114
11.2 SITE LAYOUT ----------------------------------------------------------------------------------------------------- 115
11.3 PLANT LAYOU ---------------------------------------------------------------------------------------------------- 117
CHAPTER 12 --------------------------------------------------------------------------------------------118
12.0 CONCLUSION AND RECOMMENDATIONS -------------------------------------------------118
APPENDICES --------------------------------------------------------------------------------------------120
Appendix A: Data --------------------------------------------------------------------------------------120
Table A-1: specific heat capacities of key components ------------------------------------------------------ 120
Appendix B: Detailed Sample Mass Balances --------------------------------------------------120
Table B-2: Summary of mass balance around peeler machine -------------------------------------------- 121
Appendix C: Sample energy balance calculation ---------------------------------------------121
Appendix D: Equipment Sizing Calculations ---------------------------------------------------123
-
viii
LIST OF TABLES
Table 1: Varieties of avocado --------------------------------------------------------------------------------------------4
Table 2: Typical analysis results of Avocado oil Composition -------------------------------------------------9
Table 3: Vitamin content of avocado oil (seasonal range) per 100g -------------------------------------- 10
Table 4: A Typical analysis of the Fatty Acid composition of Avocado Oil ------------------------------- 11
Table 6: Laboratory analysis equipment used for avocado oil compositional analysis ------------- 18
Table 7: mass balance around the stone remover -------------------------------------------------------------- 32
: mass balance around the stone remover -------------------------------------------------------------- 32
Table 11: mass balance around the tricanter --------------------------------------------------------------------- 34
Table 14: mass balance around the wiped film molecular evaporator ----------------------------------- 36
Table 15: energy balance around the wiped film evaporator ----------------------------------------------- 39
LIST OF FIGURES
Figure 1: Tocopherols structure -------------------------------------------------------------------------------------- 14
Figure 2: Key elements of a wiped film evaporator ------------------------------------------------------------ 23
Figure 3: L-type and P-type rotors ----------------------------------------------------------------------------------- 24
Figure 4: R-type rotor and the inside of a glass lined evaporator ------------------------------------------ 24
Figure 5: wiped film evaporator rotor blade operation ------------------------------------------------------- 25
Figure 6: Wiped film evaporator rotor onsite installation --------------------------------------------------- 26
Figure 7: Virgin avocado oil processing line ---------------------------------------------------------------------- 26
Figure 8: Simplified diagram showing installation of a wiped film evaporator ------------------------ 27
Figure 9: Disk bowl centrifuge ---------------------------------------------------------------------------------------- 46
-
1
CHAPTER ONE
1.0 Introduction
The avocado is a tropical tree which grows well and abundantly in Kenya. It is one of the
many agricultural produce which is highly utilized in the country only on the nutritious
purposes. Various industries for example Olivado limited company, are utilizing this
market niche to produce avocado oil. Besides being nutritious, avocado fruit is also rich
in vitamins e.g. A, B, C and antioxidants lutein and at the same time components which
lower cholesterol (all this vital components are present in unsaponifiable fraction of
avocado oil). Despite avocado being rich in pytochemicals, cosmetic and pharmaceutical
industries in the country have not been keen enough to venture in richness of this fruit
to produce their respective product leaving the monopoly to the nutritious ventures.
This has resulted in viewing avocado as being a nutritious plant only and the farmers
are therefore not motivated to plant avocado plants in large quantity since the market is
not wide enough to give them a reason of widening their produce.
It has been noted the richness of avocado in nutrients, high in proteins, antioxidants and
dietary fiber. He observed that this high content of avocado in high fat and calorie
content has led nutritionists and dieticians either to advise against it or to use it . Many
studies and research however have proven avocado to be highly advantageous for
human health due to its healthy fat composition. All this goodness of avocado is well
preserved in avocado oil and thus presents an excellent alternative for utilization of the
fruit.
However, avocado oil has been produced and used by South Americans for centuries but
only as a skin ointment. On the other hand these alternative cosmetic and
pharmaceutical aspects of avocado oil are being utilized in American and French
industries among others to produce pharmaceutical and cosmetic products.
-
2
1.1Objectives of the Design project
The objectives of the design project are listed below:
i. To provide an alternative method of producing pharmaceutical jelly from
avocado oil
ii. To design the selected process for the pharmaceutical avocado oil production
iii. To locate the best site for the plant
iv. To carry out an economic cost analysis of the design plant
v. To assess the impacts of the processes wastes to the environment
-
3
CHAPTER TWO
2.1: Literature review
2.2: Historical Origin of the Plant
The avocado (alligator pear or aguacate as commonly known) is scientifically known as
Persea americana of the family Lauraceae and is a native plant of Southern Mexico and
Central America . Historical records of the usage of the plant exist from 7000 B.C. of its
cultivation from 6000 B.C. and continuous use in all the well known archeological sites
of Mexico.
In Kenya, avocado (Persea americana) also called Mwembe mafuta in Kiswahili was
introduced by the Portuguese in the 16th and 18th centuries. By 1939, improved
cultivars such as Puebla, Nabal, Lyon, Lula, Linda and at least 2 strains of Fuerte - one
from California and one from South Africa - had been introduced .These varieties
especially Fuerte and Puebla were adapted to the highlands of Kenya. Statistics show
that during 1970 only 23 t of avocado were exported. In 1984, 1400 tonnes of avocado
were exported from Kenya. The cultivars introduction programme commenced in 1965
with a focus to evaluate cultivars suitable for highlands and also lower altitudes and/or
agro-ecological zones.
2.3: Agronomy
2.3.1: Growth Requirements
The avocado plant grows well in warm areas with tropical to subtropical climates. The
plant at various stages does not tolerate climate that is too cold, too wet, too hot or too
dry. Its flowers are very sensitive to very low temperatures and freezing temperatures
tend to kill the plants. Frost and very hot weather results in a substantial loss of fruits
and too much wind is also highly unfavorable. The plant is tolerant to a wide range of
soil types (acidic and alkaline) with the exception of saline conditions. It does require
well aerated soils and will not survive in areas with poor drainage due to excess water.
It tends to grow well on hillsides but should never be grown near stream beds. The use
of phosphorous (P) fertilizers after one year of growth for young plants and nitrogen
(N) and potassium (K) for the older trees is very favorable for growth and fruit yields.
The plant can be grown in the shade but is productive only in full sun. It has been
reported that fruits continuously exposed to the sun were more hardy and tolerant to
conditions like high and low temperatures, had a slower rate of ripening, and more
resistant to pathogen invasion than those growing in the shade. The sun exposed fruits
were also higher in oil, dry matter and minerals. This supports the importance of
sunlight and temperature on avocado fruit development and qualities.
-
4
2.3.2: Fertilization
The pollination of avocado with its flowers is a classic example of protogyny. This
means the females mature before the males, so the flower cannot self pollinate but
requires pollen from another flower or another plant and this type of pollination is
called cross pollination. Growing plants bearing the two different types of flowers
together will allow cross pollination to occur and increase the chances of production. A
typical tree produces around a million flowers a year but only produces a dozen to a few
hundreds of fruits
Varieties & Cultivars
There are three known varieties or horticultural races of avocado and these are the
Mexican, Guatemalan and the West Indian Types. The Mexican types thrive in
Mediterranean climate and are native to dry subtropical plateaus. The Guatemalan
types are native to cool, high altitude tropics while the West Indian variety thrive in
humid, tropical climates. There are now many hybrids resulting from cross-breeding of
these three varieties and also from the selection of certain favorable attributes. The
three varieties can be differentiated from each other using various attributes as
provided in Table 1.
Table 1: Varieties of avocado
PROPERTIES
Main Attribute Specific
Attribute
Mexican Guatemala Indian
Oil Scent Nice None None
Leaf Size Small Various Various
Size Thin Warty Leathery
Seed Skin Big Small Big
Cavity Loose Tight Loose
Tolerance Cold Yes No No
Salt No No No
Fruits Oil content High Medium Low
Maturity
(month)
6 9 6
-
5
Growers however tend to identify the fruits by cultivars rather than varieties. A list of
various existing cultivars is provided on and only a few of the most popular cultivars are
listed and noted below.
Haas Guatemalan race and regarded as the industry standard fruit. Tree and fruit are
medium sized, thick skin, roundish and purple at full maturity. Has a good shelf life,
wide consumer acceptance and oil content is around 19 30%. It produces from April
to
September and is the most popular cultivar used around the world. It bears well only in
alternate years and is an A cultivar.
Fuerte This tall tree is a hybrid and produces a shiny green, round pear shaped, large
to very large fruits. Oil content around 18-26%, good flesh but also tends to bear fruits
in alternate years. Season is December and is a B cultivar.
Gwen The most popular and productive dwarf tree. Fruits are small, elongated and
remain green when ripe. Season is February to October and is an A cultivar.
Pinkerton A dense productive tree and is an A cultivar. Fruits look like long pears
with pebbly green skin. The fruits darken when ripe, have small seeds and are in season
in November.
Reed Known as the summertime variety avocado. Is an A cultivar and produces a
large fruit with thick green skin which stays green when ripe. Its season is August and
its flesh becomes buttery yellow when ripe.
Zutano A hybrid and is a columnar tree bearing medium to large fruits. Fruit has a
shiny yellow skin and is pear shaped. It is similar to a Fuerte but is inferior and has
fibres. Is a B cultivar and its colour remains the same when ripe.
Propagation
Growing avocado directly from the seeds is not favorable because it bears fruits only
after 4-6 years of growth and it rarely resembles the parent cultivar. The avocado has
Hypo-geal germination meaning the shoot grows directly from the epicotyl in the soil.
Commercial orchards are thus usually propagated by either grafted trees or rootstocks.
Rootstocks are propagated by seeds (seedling rootstocks) and layering (clonal
rootstocks). One common method is the etiolation technique used for propagating the
desired clonal rootstocks specific for disease and soil conditions. Lateral and terminal
grafting is normally used and carried out for young plants after one year of growth in
greenhouses.
Pests & Diseases
-
6
A soil borne fungus known as Phytophthora cinnamomi is a very severe disease which
causes root rot of the trees. The disease is easily transported by equipment, tools and
shoes from infected soil and farmers are highly encouraged to use disease free and
certified plants or rootstocks. Once a tree is infected it is difficult to treat except to cut
back on water supply. Dothiorella (Botryosphaeria ribis) canker is another fungus which
infects the trunk and results in dead patches which spread to maturing fruits causing
rancid smelling, darkened spots on the flesh. This disease which starts upon harvest
cannot be detected on the outside and has no means of control. A viral disease known as
sun blotch causes crinkling of new leaves, yellowed streaking of young stems, cracking
of the trunk and occasional fruit deformation. It is spread by the use of contaminated
tools and scions and so using virus-free propagating wood is a must. Pests include rats,
leaf caterpillars, avocado brown mite, six spotted mite and also snails
Harvest and postharvest
Avocado fruits are strange in that they only start to ripen and turn soft when they are
picked. They remain hard and continue to grow when mature on the tree until they fall
off. The fruits can be left on the tree (4-6 months) after being fully developed and will
ripen very quickly once picked. The taste of the fruits at the time of harvest depends on
their oil content which in turn is dependant on their stage of maturity. Avocados can
ripen quickly when stored together with other fruits like bananas and apples due to the
production of ethylene gas. The fruits must be handled with care when harvested to
minimize physical damage and bruising which results in undesirable discoloration and
softening of the pulp. The fruit ripening process like many is slowed considerably by
low temperatures. Report show that it is high activities of wall hydrolytic enzymes
during ripening that result in ultrastructural changes in the cell walls of ripened
avocado fruits. Extended cold storage results in chilling injury, which is marked by
improper softening, off flavour development and discoloration of the mesocarp. The
major storage component of the avocado fruit is the oil contained in its mesocarp. It is
the breakdown of the structure of these specialized oil cells during prolonged cold
storage that results in chilling injury.
A study conducted and reported noted that differences in postharvest quality were
attributed to differences in cultivars, growing conditions, location and fruit maturity.
2.3.3: Avocado Fruit & Human Health
Avocado Benefits
Bergh described the avocado fruit to be nutrition-rich while others in the industry call it
a functional food due to its additional health benefits from certain phytochemicals. It
contains high amounts of vitamins A ,B, C, E, and other nutrients like folacin, niacin, iron
(Fe), magnesium (Mg),
-
7
folate, pantothenic acid and contains 60% more potassium than bananas.
Most of these nutrients are deficient in most typical diets and are all abundantly present
in avocado. In its unmodified natural state the avocado represents a more balanced and
wholesome diet than most food or even concentrated supplement pills. Vitamins E, C
and beta carotene (vitamin A precursor) are natural antioxidants which protect against
dangerous free radicals which are by-products of life processes due to oxygen . These
free radicals result in cataracts from eye tenses, cancer due to cell mutation, arthritis,
advanced aging process, and heart disease due to cholesterol buildup. These
antioxidants are specifically effective in reducing the oxidation of the low density
lipoprotein (LDL) which leads to plaque deposits in arteries. The role of Vitamin Es role
in slowing down the aging process makes avocado very important in the cosmetic
industry. Avocado protein has also been proven to contain all the essential amino acids
for human nutrition attributes not provided by any other plant source. Its fiber content
was also noted to be high in both the soluble and insoluble forms and this is considered
very advantageous due to fibers lowering effects on cardiovascular disease,
hypertension, diabetes, and obesity. Pectin in particular a water-soluble fiber is known
to be most effective in maintaining heart health.
The avocado fruit contains more calories per gram than most other foods and thus
people tend to avoid it because of the well known adverse effects of cholesterol on
humans. The fat content of avocado which is the cause for many misconceptions
however is another valuable aspect of the fruit. More than 70% of its fat is
monounsaturated fat with low levels of polyunsaturated and saturated fat with slight
variations according to cultivars and fruit maturity stage. Monounsaturated fat in
particular has been noted to be highly beneficial in that it not only lowers the level of
the harmful cholesterol (LDL) but also maintains the level of the beneficial high-density
lipoprotein (HDL) or good cholesterol which protects the heart. The desirable HDL is
lowered with diets low in fat, or high in complex carbohydrates which is usually used by
many people wanting to lose weight. A diet high in polyunsaturated fat on the other
hand not only reduces HDL but is highly prone to oxidation at the site of unsaturation in
its structure.
The use of avocado in human nutrition controlled experiments have either proven or
claimed the following findings:
Subjects on avocado enriched diets had a decrease in total cholesterol level
A reduction in body weights and;
A reduction in stroke incidences due to high potassium content.
Avocados are also highly recommended food for infants. The smooth, delicate flavor,
creamy consistency makes it an excellent food choice. More importantly it provides
them with essential nutrients and monounsaturated fat which is beneficial for babys
development. The more traditional uses of the fruit in particular for the South American
people is its use as a sexual stimulant.
Avocado Disadvantage
-
8
There is documented evidence that feeding any part of the avocado tree including its
fruit to any non-human animal is life threatening and lethal for some animals. Thus total
avoidance of any part of the tree is recommended by most animal organizations
Avocado Oil
Avocado oil is the major avocado product which utilizes this otherwise not very popular
fruit in Kenya. Only a few countries are actually involved in the production of oil namely
Mexico (34%), USA (8%), Israel (4%), South Africa (
-
9
Arpaia also noted differences in oil content for the same cultivar due to different
locations and growth conditions such as soil fertility. Sun exposed fruits were also found
to yield higher levels of oil than those fruits in the shade.
Biochemical Composition & Physiochemical Properties of Oil
Understanding the biochemical composition and physiochemical properties of the oil
help explain its functional properties and uses. Most of the beneficial attributes
associated with eating avocados are mostly preserved in the oil and for this reason is
very valuable.
The composition and in particular properties of the oil varies according to how it is
produced whether it be crude, virgin or refined according to the method and number of
successive operations involved in its production.
Various analyses have been done on the composition of avocado oil and Table 2 lists
typical results.
Table 2: Typical analysis results of Avocado oil Composition
Parameter Avocado Oil
Acidity Value (as oleic) (%) 2.0-0.8
Peroxide value (meq/kg fat) 3.3-0.1
Iodine value (from GLC) 87-75
Color (chlorophyll) (ppm) 40-70 virgin, 1-10 RBD
Specific Gravity (25o C) 0.912-0.916
Beta-sistosterol (%) 0.45-1.0
Total Vitamin E (mg/kg) 112-200
Alpha-tocopherol (mg/kg) 130
Beta/gamma-tocopherol
(mg/kg)
15
Delta-tocopherol (mg/kg) 5
Flash point 150-2550 C
Un-saponifiables 5.0-18%
Cholesterol 0
Sodium 0
Carbohydrate 0
-
10
The comparison of the compositional make up of avocado and olive oil shows very
similar results for most parameters. The Vitamin E, Beta-sistosterol and alpha
tocopherol levels however are much higher in avocado oil, the micronutrients with
significant proof of health benefits. The flash or smoke point of avocado oil is another
noticeable feature. This makes the oil highly applicable for high temperature cooking as
it will not burn until it reaches temperatures well above 1500C. The acidity value and
peroxide values indicate stability in terms of minimal hydrolysis and lipase activities.
The oil is also free of cholesterol and carbohydrate. Table 3 shows a Vitamin analysis of
avocado oil.
Table 3: Vitamin content of avocado oil (seasonal range) per 100g
Vitamins Result
Vitamin A (carotene) 370-870 IU
Vitamin B2 (Riboflavin) 0.08-0.16
Pyrodixine 0.19-0.26 mg
Pantothenic acid 0.78-1.2 mg
Folic acid 0.022-0.105 mg
Thiamine Hcl 0.08-0.125 mg
Ascorbic acid 4.0-13.0 mg
Niacin 1.05-2.42 mg
Choline 12.0-22.2 mg
Biotin 2.3-4.2 mg
Vitamin E 0.8-4.2 IU
As seen in the above table, the vitamin content of oil varies within a range for the
various parameters and the usual influential factors of cultivar, maturity and processing
method is likely to impact on these values. The list is extensive and most of the vitamins
is lacking in most diets. The presence of most of these vitamins in avocado oil gives it
the properties which makes the oil highly valuable in the cosmetic industry.
Fatty Acid Composition
As seen in Table 2 the iodine value is high indicating a high degree of unsaturation.
-
11
Typical avocado oil is comprised mostly of monounsaturated fatty acids (74%), 11%
polyunsaturated fatty acids and about 13% saturated. These percentages vary slightly
with cultivars and other influential factors but the oil is very similar to olive oil. It is this
high level of monounsaturated fat which gives the desirable effect of being
anticholesterol as it prevents the formation of clots the major cause of coronary heart
disease.
Table 4: A Typical analysis of the Fatty Acid composition of Avocado Oil
Fatty Acids Saturation Africa oil
analysis (%)
New Zealand oil Analysis
(%)
Palmetic Acid C16:1 11.85 12.5-14.0
Palmitoleic Acid C16:1 3.98 4.0-5.0
Stearic Acid C18:0 0.87 0.2-0.4
Oleic Acid C18:1 70.54 70-74
Linoleic Acid C18:2 9.45 9.0-10.0
Linolenic acid C18:3 0.87 0.3-0.6
Arachidic Acid C20:0 0.50 0.1
Gadoleic Acid C20:1 - 0.1
Eliosenoic Acid C20:1 0.39 -
Table 4 lists results from two different countries and their analysis of avocado oil
confirms the healthy composition of the oil in terms of fatty acid composition.
The analysis reported in Table 4 was done using the Fatty Acid Methyl Ester (FAME)
analysis on a Gas Chromatograph.
Phytochemicals
The naturally occurring phenolic compounds found in vegetables and fruits have been
proven to have equal or greater cholesterol lowering properties than unsaturated fatty
acids. Beta-sitosterol (a phytosterol) is one of the healthy plant compounds found to be
most abundant in avocado. It is widely proven to be responsible for the non-absorption
of the bad cholesterol (LDL) and maintaining the good HDL cholesterol in the intestine
which then lowers total plasma cholesterol. This compound was also reported by the
British Medical Journal the Lancet to be very effective in offering relief to men above 50
years who suffered from benign prostatic hyperplasia resulting in significant
improvements in urinary difficulties. The phytosterol content has the same skin
penetrating abilities of lanolin and for this reason avocado oil is highly valuable in the
cosmetic industry. Lutein or carotenoid is also highly abundant in avocado oil. This
-
12
phytochemical is effective in providing protection against prostate cancer, eye diseases
and mascular degeneration. Lozano noted that the unsaponifiable fraction from
immature fruits contained a much higher level for both total sterol (1.1 6.2%) and
tocopherol compared to matured fruits (sterol 0.8-2.0% & tocopherols 5.7-10.3 mg/100
g oil). This is very significant for the extraction of enriched amounts of these
Compounds as they are of high health significance.
Antioxidants
Phytochemicals in plants is reported to have greater antioxidant effects than minerals
and vitamins. Lutein for example is one very effective antioxidant. Vitamin E represents
a mixture of chemicals known as tocopherols and
tocotrienols and is another well known vitamin with antioxidant effects. tocopherol
is one powerful antioxidant which neutralizes the free radicals produced under the
normal metabolism of lipid compounds. As noted in table 2 this is also abundant in
avocado oil. All these antioxidants found in high levels in avocado oil neutralize the free
radicals which would otherwise result in the following:
eye deterioration;
inflammation of the joints;
damage to nerve cells in the brain;
accelerating the ageing process and;
Certain cancers.
Chlorophyll & Carotenoids
Crude and virgin oils have high chlorophyll and amounts of other soluble pigments
(carotenoids) which give it their distinctive brown green or emerald green colour. The
virgin oil with high chlorophyll content is highly desired by consumers due to the health
benefits associated with the presence of these micronutrients. The high chlorophyll
content makes the oil highly prone to oxidative effects upon exposure to light and for
this reason must be packed in dark bottles. Other carotenoids like lutein are also
present in high amounts while others like neoxanthin, violaxanthin, antheraxanthin are
present in very minute amounts. Further processing and refining removes the
chlorophyll and other pigments giving oil that is pale yellow in colour and also more
stable.
Unsaponifiable Fraction
The healthy plant micronutrients which have anti-oxidant, anti-inflammatory, and
cholesterol lowering properties are mostly contained in this portion of the oil. This part
of avocado oil is highly valued in the pharmaceutical and cosmetic industries for the
high skin penetration coefficient and the specific biological actions of its sterols.
-
13
Human journal also reported this fraction to contain an unknown factor known as the H
factor which has healing properties. Eyres reported that the healing properties may be
linked with lysyl oxidase which initiates cross linking in collagen and inhibits enzyme
activity. This would be very important for the treatment of wounds and burns.
The unsaponifiable fraction is also high in nutrients which are another reason why it is
highly sought after by the cosmetic industry. The French pharmaceutical industry filed
two separate patents No 17/245 and No 102888 for the extraction of this fraction
indicating its high value. Lozano reported that the unsaponifiable matter in oil from
immature fruits (15-40%) was always higher than the matured fruits (4-9%). This
fraction of the oil is where most of the healthy plant sterols are concentrated. This is
interesting as it presents another valuable option for farmers in using immature fruits
for extracting this highly valuable unsaponifiable matter from oil.
Oil Utilization
Cosmetic Industry
Avocado oil is well known for its anti-bacterial, anti-wrinkle and healing properties. The
multiple properties of avocado oil namely stability, emolliency, skin penetration,
softening and moisturizing results in its wide applicability for cosmetic products. The
high penetration ability of the oil in particular makes it very successful in its use as a
natural and effective beauty aid. It is used in a wide variety of creams and oils for skin
application as it acts as an effective carrier of other supplements incapable of
permeating the skin. The high content of lecithin and phytosterols facilitates its
spreadability. It is easy to emulsify as its low surface tension makes smoother creams
and soaps. Vitamin A helps prevent dry skin while Vitamins E and D are effective against
skin wrinkling and slow the process of ageing. A few New Zealand and US companies
now manufacture various skin care products using avocado oil, like body moisturizer,
replenishing facial crme, skin repair crme and natural oil for everyday use.
The oil is an ingredient for up-market skin care cosmetics, shampoos and baby
products.
The oil is highly priced to those with skin problems and is used as a base for ointments
used for treating dermatitis, acne, lacerations and other skin conditions. It is also used
as a post-operative dressing to prevent adhesions to wounds and skin burns while
accelerating the healing process. It also has strong UV absorption properties making it a
very good effective sunscreen.
Avocado oil for skin
As mentioned previously, avocado oil has been many a times as used on skin purposely
to provide protection of skin. The underlying reasons of its protective aspect are largely
due to the presence of antioxidant components (in Vitamin E) which are of course
tocopherols and tocotrienol. Tocopherols are best known and most widely used
antioxidants.
-
14
Figure 1: Tocopherols structure
Tocopherols function as antioxidants by donating the hydrogen of the hydroxyl group to
the lipids peroxyl radical. The hydrogen donating power of tocopherols is in fats and
oils is in the order >>. Tocopherol can also function as inhibitors of lipid
oxidation by scavenging singlet oxygen molecules and free radicals.
Food The oil is highly applicable for food preparation and because of its high quality
(Similar to olive oil) it provides another healthy alternative for consumers. It is
marketed as healthy oil due to its high content of monounsaturated fat, presence of
essential amino acids and high vitamin content. The high sterol content in particular
and its cholesterol lowering effect is what makes this oil a must for modern society. It
has a high smoke point making it suitable for high temperature cooking. It also has a
bland flavor which does not disguise the natural flavor of food. It is also used as a
dressing which does not disguise the natural flavour of food. It is also used as a dressing
for salads and vegetables and also as a dip for hot food like bread. There are naturally
infused oil available with different flavours like garlic, chilli, lemon and orange which
provide consumers more choices to choose from
Dietary supplement One of the most exciting products produced by New Zealand
based Olivado and Elysian Isle companies is the avocado oil capsule. It simply takes all
the beneficial attributes found in avocado oil and seal it in a health capsule which can be
taken daily. It contains all the healthy micronutrients and vitamins available in the oil
which can help fight bad cholesterol, inflammatory, osteoarthritis and prostate
problems.
Extraction of Avocado Oil
-
15
To produce a quality product requires high quality raw materials. For this reason it is
imperative that the fruits used are of high grade in particular must contain high
proportion of pulp, have high oil content, free of diseases and must not be physically
damaged as evident in pulp discoloration and/or off-flavors. The fruits have to be
carefully matured and ripened to allow for maximum oil development before they are
used. Various methods have been used in the extraction of oil from avocado fruits. The
methods vary in their degree of effectiveness for oil extraction and also subsequent
effect on the resultant oil quality. Heating and chemical extraction have been the
traditional methods used and now a new method has been developed in New Zealand
which allows oil to be expressed from the fruits with very minimal processing. Human
journal lists various methods used in the past for the extraction of avocado oil involving
steam pressure, hydraulic pressing, solvent extraction, centrifugation, freeze-drying,
rendering process and the use of a tube press plant. However the specific application of
the oil should determine the process and method chosen. Only the most practical and
suitable methods are discussed below.
Pre-Process Treatment
Avocado fruits destined for oil production must be firstly inspected for physical damage
and other abnormalities. They are then washed before being processed to remove the
skin and seed. The means used for washing, de-stoning and de-skinning of the fruits
vary but all processes involve this first critical step.
Rendering process
This method involves heating of the avocado pulp in avocado oil.
The moisture evaporates off leaving the oil and the dry matter behind. The oil can then
be decanted off while the remaining slurry is subjected to hydraulic pressure to press
out more or the remaining oil. It is reported that laboratory experiments resulted in
94% recovery of the oil using this method.
Tube Press Plant
This consists of either one or two tubes. The tubes are filled with avocado pulp and
then subjected to hydraulic pressure to press out the oil through perforations within the
inner tubes. This method was developed my Mess Alfa Laval and aims at extracting out
most of the oil with minimal damage to the oil quality.
Solvent Extraction
This is one of the traditional methods commonly used. Various solvents could be used
and organic solvents have mostly been utilized. Botha reported experimental solvent
extractions using hexane and a Soxhlet extractor on a 10g dried sample for 8 hours.
Subsequent removal of the solvent is followed by vacuum evaporation and drying until
constant mass. The resultant oil has a high chlorophyll content meaning the chlorophyll
is co-extracted along with the oil. Chlorophyll levels as high as 192.9 ppm was reported
by Werman & Neeman to have been extracted in the laboratory by ethanolic extraction.
-
16
Human journal reported this method to have the highest yield but industrial equipment
is very expensive to install plus the highly flammable solvents used are very dangerous.
The recovery and total removal of the solvent is also an issue which requires a highly
sophisticated plant. Thus because the raw material is an expensive fruit and the oil yield
is at maximum around 22% of the whole fruit it is not economical to extract avocado oil
in this way. Xiao reported the method does have other disadvantages like loss of volatile
compounds, long extraction times, toxic solvent residues and degradation of valuable oil
compounds.
Centrifugation
After the pre-processing treatment, the fruits are fed into a mill where it takes the form
of a guacamole. The malaxing (mixing) takes up to several hours until the release of the
fine emulsion of oil. The paste is then fed to a centrifugal decanter where the oil is
separated from the guacamole. Reported that extraction of oil was most efficient using
centrifugal force 12,300 kg, a 5:1 water to avocado ratio, temperature 75 OC, with a pH
5.5 and a 5% concentration of either NaCl, CaCO3 or CaSO4.
Cold Press
This relatively new method of extracting oil makes use of the modern Alfa
Laval centrifugal extraction method so is a variation of the above method. The fruit flesh
is firstly macerated by high speed grinders before the mixture is mixed in malaxers.
When this process is complete, a three phase decanter then separates the mixture into
oil, water and solids before polishing takes place with a multi-cone centrifuge. Extra
virgin oil is produced after the first press. The extraction efficiency is dependent on such
things like pH, centrifugation rate, salt, mixing temperature (
-
17
for baked goods. It can also be used as a simple drizzle on vegetables and
potatoes and also for shallow pan-frying of poultry and fish
The production of cold pressed oil requires little investment and the process
itself is simple. However the process has inefficiencies in that around 6-15% of
the oil remains in the pressed residue
Supercritical CO2
Botha reported extraction results for avocado oil extracted using supercritical carbon di
oxide under four different extraction conditions.
Spectroscopic quantification of the color of avocado oil extracted with
supercritical carbon dioxide at four different conditions:
Extraction Condition Absorption Value Visual Quantification
370C/350 atm 0.325 Straw-yellow
370C/532 atm 0.410 Straw-yellow greenish tint
810C/350 atm 0.526 Straw-yellow with strong
greenish tint
810C/532 atm 0.765 Green with yellow tint
The above Table 5 indicates that at higher temperatures and pressures, chlorophyll can
be co-extracted along with the oil. Xiao reported that the power of solubilization for
supercritical CO2 can be achieved with higher densities which are achieved at higher
pressures. This allows large amounts of organic compounds to be dissolved which can
later be separated from the fluid by means of reducing the temperatures or pressures.
Thus the extraction of the phytochemicals was only possible at higher pressures and
temperatures only due to the solubilisation of the organic compounds. Lower
temperatures and pressures will extract only the oil without chlorophyll. This method is
very important as it basically proves that more stable oil without chlorophyll can be
extracted this way which eliminates the need to refine the oil of its color pigments. The
oil however does not contain the healthy plant compounds which are highly attributed
for its health benefits.
Before analyzing the free fatty acid of the oil the CO2 must be totally removed as it
increases the acidity level. This can be done by subjecting the oil to vacuum evaporation.
The degree of oxidation of the oil in the dried material used for extraction is also
important as volatile acids are also co-extracted by this method. The free fatty acid
content however of the oil extracted by this method was not different to the FFA of the
oil extracted by hexane indicating no effect on pressure, temperature or supercritical
CO2 on the hydrolysis of the parent glycerides.
-
18
An important outcome of extracting with supercritical fluid as reported by Botha was
that the unsaponifiable fraction of the oil was found to be higher for the first fractional
extraction (20 minute intervals) and tend to decrease with subsequent extractions.
Thus the unsaponifiable fraction of the oil can be enriched by extracting at time
intervals.
The use of supercritical fluid is proven to be a cost-effective technique for laboratory
scale while large scale units still require experimentation for accurate economic
valuations. This method has advantages such as low operating temperatures, shorter
extraction periods, high selectivity in the extraction of compounds and no undesirable
solvent residue. It also uses a safe, readily available gas.
Effect of processing on the quality of the oil
The phenolic compounds which are well publicized for their health benefits are lost or
destroyed by most processing methods. Extra virgin oil loses its highly beneficial
micronutrients during the refining process and the cholesterol lowering and anti-
oxidant properties are significantly reduced as a result. The color or chlorophyll content
of the oil is noticeably lower than that of virgin oil due to the removal of these plant
compounds.
Xiao noted that the usual methods of hydrodistillation and organic solvent extractions
present problems like toxic solvent residues, degradation of the unsaturated
compounds and vitamins, and giving objectionable off-flavours due to heat. The change
from NaOH to Na2CO3 or NaHCO3 when refining is reported to achieve the same results
when refining with the extra benefit of retaining the phenolic compounds. Thus a more
stable and healthy oil can still be achieved after refining if Na2CO3 or NaHCO3 is used.
The cold pressing and supercritical fluid methods appear to be the most suitable and
beneficial methods to extract the avocado oil. Both utilise low temperatures which help
retain the healthful composition of the oil, involves minimal processing and requires
less capital investment.
Analysis Methods for Oil Components
The analysis of the various biochemical and physiochemical composition of the oil can
be analyzed using the following equipment given in Table 6.
Table 5: Laboratory analysis equipment used for avocado oil compositional
analysis
Equipment Components Extraction
Method
-
19
Gas Chromatography
FAME analysis
For fatty acid
composition
Cold press
centrifuge
Gas Chromatography
Mass Spectrometric
Major compounds Supercritical CO2
High Performance
Liquid
Chromatography
Triacylglycerols,
sitosterol &
tocopherol, lutein and
total chlorophyll
Other detailed analysis as given in tables 2 & 3 do not specify the methods of analysis
used. However the analysis equipment used for analysing other vegetable oils will
undoubtedly be suitable for the analysis of avocado oil.
-
20
CHAPTER THREE
3.0: JUSTICATION
The high content of pharmaceutical components like the unsaponifiables( which is rich
in tocopherols and lutein-are very effective in healing skin ailments and preventing skin
aging ) in avocado fruit and the abundance of the raw materials and specifically the
furte avocado variety in central and eastern provinces of Kenya presents a perfect
viability of the project since there will be continuous supply of the raw material.
Secondly, the extraction processes for both the virgin oil and the unsaponifiable fraction
of the avocado oil are comparatively cheap. Cold Press method of extraction of avocado
oil involves low temperature and minimal processing and as a result the oil retains all
its natural flavor, nutrients and healthy properties.
On the other hand, unsaponfiable fraction of avocado oil is extracted in a substantial
quantity without affecting the chemical properties of the fraction.
The oil which becomes the co-product is can be availed for further refining.
-
21
CHAPTER FOUR
4.0: PROCESS DESCRIPTION
4.1 Pre-process treatment
Do fruits destined for oil production must be firstly inspected for physical damage and
other abnormalities. They are then washed before being processed to remove the skin
and seed. The seed removal and skin removal are done by the de-stoning machine and
de-skinning machine respectively.
4.2 Extraction process
The fruit flesh is firstly macerated by high speed disintegrator before it is then is mixed
in mixer (malaxor). When this process is complete, the three phase decanter then
separates the mixture into oil, water and cake. Extract virgin oil is produced after the
first press. The process is carried out at normal temperature. At no time along the whole
process is the oil subjected to light or oxygen as this has a deteriorating effect on the
quality of the oil. The resultant oil is of high quality and is considered virgin oil because
of the minimal processes involved. The virgin oil is then pumped to a centrifuge for
polishing. Here the suspended solids and water traces are removed.
4.3 Preheating
The degassed oil is passed through heat exchangers for the purpose of temperature
elevation before the oil finally enters the wipe film molecular distiller where it
undergoes fractionation into a light phase that is rich in unsaponifiable fraction i.e.
sterol esters and a heavy phase that is rich in triglycerides and a small fraction of
esterified sterols that do not vaporize under the temperature conditions in the
evaporator.
Molecular evaporation
The wipe film molecular mollecular evaporator is widely applied in industry,in
which,the wiper renews the evaporating liquid film continously,and so the local
overheating of the materials is avoided and the internal mass and heat transfer
processes are enforced.this evaporater has the following advantages that make it
suitable for our process;
Low residence time
No liquid hold up
Very low pressure drop
Suitable for extremely heat sensitive products because of the short path
involved.
The traditional theory of molecular evaporation is based on mean free path theory of
gas molecule, and an equation given by Langmuir is as follows;
m=(k/2)(T/d2P)
this equation shows that mean free path m is related to temperature T(K),pressure
P(Pa) and size of the molecule d(m).k is the Boltzman constant 1.38010-23 J.K-1
-
22
How a molecular evaporator works
The process fluid enters the unit tangentially above the heated zone, and is distributed
evenly over the inner surface of the body wall by a distribution ring mounted on the
rotor. The rotor blades spread over the entire heated wall, and generate highly
turbulent flow conditions in the thin layer of liquid.
The product spirals down the wall, while the turbulent conditions developed by the
rotor blades generate optimal heat flux, rapidly evaporating volatile components. The
resulting vapors flow upwards through the unit into a centrifugal separator, which
returns entrained droplets or froth directly back to the heating zone. Clean vapors pass
through the vapor outlet ready for condensing or further processing. Meanwhile, the
concentrated liquid stream leaves the evaporator through its bottom conical outlet.
Continuous washing by the bow waves generated by the rotor minimizes surface fouling
of the thermal wall, where the concentrated liquid or residue is most prevalent.
-
23
Figure 2: Key elements of a wiped film evaporator
The wipe film evaporator is merely a single evaporation tube fitted with a mechanical
rotating device called a rotor. The distributer is welded to the rotor according to the
propriety design. This ensures that the liquid feed is evenly distributed on to the heated
surface of the evaporater.it then flows downwards in a spiral motion which is created
by the blades of the rotor. Turbulent eddies are formed at the rotor tips, which
continuously agitate and remix the liquid film. The resulting vapor normally rises
upwards, counter-currently to the liquid flow.it passes through a gas-liquid separator
mounted at the top of the evaporator and is then normally directed to the downstream
condenser the concentrate leaves the unit via the bottom of the evaporator.
The upper part of the rotor incorporates a liquid distributor and a centrifugal separator
to effectively dis-entrain liquid droplets from the vapor flows, rotating baffles mounted
-
24
on the rotor are complemented by static ones. The figures below show the different
rotor types used in this evaporator.
Figure 3: L-type and P-type rotors
Figure 4: R-type rotor and the inside of a glass lined evaporator
-
25
The figure below shows a cross-section of a wipe film evaporator showing the blade and
bow wave formed in front of it.
Figure 5: wiped film evaporator rotor blade operation
-
26
Figure 6: Wiped film evaporator rotor onsite installation
Figure 7: Virgin avocado oil processing line
-
27
Fig: Virgin avocado oil processing line.
Figure 8: Simplified diagram showing installation of a wiped film evaporator
Evaporation of virgin avocado oil is a fractionation step which at the end gives:
The distilled fraction that is rich in unsaponifiables generally representing 5% to
15% by weight of the starting virgin oil. This fraction is composed mainly of non-
esterified sterols.
The fraction that is rich in triglycerides representing 80% to 85% by weight of
the starting virgin oil. In this fraction there is a 0.5% to 1.5% unsaponifiables
(esterified sterols) in the form of fatty acid esters.
The high triglyceride content of virgin avocado oil and its low partial (mono and
di) glycerides content demonstrates that the oil is very pure and guarantees a
low degree of hydrolysis and good stability. This gives an assurance of no
chances of hydrolysis.
-
28
BLOCK DIAGRAMS
S5
MIXER (Malaxor)
Water (S4)
C3
(S3)
Skins
(S2)
DISINTEGRATOR
Pulp C2
(C2)
Seeds (S1)
Avocado fruits (C1)
SKIN REMOVER
STONE REMOVER
-
29
Oil (S11)
Cake S7
S5
STORAGE TANK 1
THREE PHASE
DECANTER
CENTRIFUGAL
SEDIMENTATION TANK
STORAGE TANK 2
S6
Virgin oil (S9)
Water (S8)
Water (S10)
Solids
(S12
)
-
30
S14
HEAT EXCHANGER
S12
S17
S15
WIPED FILM MOLECULAR
EVAPORATOR
S13
CONDENSER
STORAGE TANK 5
STORAGE TANK 4
S16
-
31
CHAPTER FIVE
5.0: MASS AND ENERGY BALANCES
5.1.1: Mass balance
Introduction
Material balances are the basis of process design. A material balance taken over the
complete process will determine the quantities of raw materials required and products
produced. Balances over individual process units set the process stream flows and
compositions.
Material balances are also useful tools for the study of plant operation and trouble
shooting. They can be used to check performance against design; to extend the often
limited data available from the plant instrumentation; to check instrument calibrations;
and to locate sources of material loss.
All mass/material balances are based on the principle of conservation of mass that is
mass can neither be created nor destroyed with an exception of nuclear processes
according to Einsteins equation; E=mc2.
The general conservation equation for any process system can be written as:
For a steady state process the accumulation term is zero and thus for a continuous
steady state process, the general balance equation for any substance involved in the
process can be written as:
In a case of a physical process as most of our operations are the general balance
equation reduces to:
Material In = Material Out
If no chemical reaction takes place, material balance is computed on the basis of
chemical compounds mass basis that are used whereas if a chemical reaction occurs
molar units are used.
Also it is worthwhile to note that when a reaction occurs an overall balance is not
appropriate but a reactant balance (a compound balance) is.
Choosing the basis
The correct choice of the basis for a calculation will often determine whether the
calculation proves to be simple or complex.
-
32
A time basis was chosen in which results will be presented.
Our basis of calculation shall be one hour and hence results will be presented in kg/hrs.
Basis
One hour
Avocado feed = 4999kg
STONE REMOVER
Table 6: mass balance around the stone remover
SKIN REMOVER
: Mass balance around the stone remover
INLET STREAMS OUTLET STREAM
Streams components Mass
(kgs)
streams components Mass (kgs)
C1 Pulps 4999 C2 Pulps 4999
Seeds 1365 Skins 580
Skins 580 S1 Seeds 1365
TOTAL 6944 TOTAL 6944
INLET STREAMS OUTLET STREAM
Streams Components Mass
(kgs)
Streams Components Mass (kgs)
C2 Pulps 4999 C3 Pulps 4999
Skins 580 S2 Skins 580
TOTAL 5579 TOTAL 5579
SKIN REMOVER
C2
C3 S2
C1
C2
DE-STONING
MACHINE
S1
-
33
THE MIXER (Malaxor)
INLET STREAMS OUTLET STREAM
Streams Components Mass
(Kgs)
Streams Components Mass (Kgs)
S3 Pulps 4999 S5 Slurry 7251
S4 Water 2252
TOTAL 7251 TOTAL 7251
MIXER
S3
a
S5
S4
-
34
THE THREE PHASE DECANTER
Table 8: mass balance around the tricanter
INLET STREAMS OUTLET STREAM
Streams components Mass
(kgs)
Streams Components Mass (kgs)
S6 Virgin oil 868 S7 Water 5031
Cake 1041 S8 Sludge 1437
Water 5342 S9 Virgin oil 783
TOTAL 7251 TOTAL 7251
S7
S9
S6
S8
THREE PHASE
DECANTER
-
35
CENTRIFUGE
N/B: mass of cake coming out from centrifuge (S 16) is assumed to be negligible.
INLET STREAMS OUTLET STREAM
Streams components Mass
(kgs)
Streams Components Mass (kgs)
S9 Virgin oil 781 S10 Water 2
Water 2 S11 Virgin oil 781
TOTAL 783 TOTAL 783
CENTRIFUGE
S10
S9
S11
-
36
WIPED FILM MOLECULAR EVAPORATOR
INLET STREAMS OUTLET STREAM
Streams Components Mass
(kgs)
streams components Mass (kgs)
S13 Preheated
oil
781 S14 Light phase 117.15
Steam S15 Heavy phase 663.85
Condensate
TOTAL 781 TOTAL 781
Table 9: mass balance around the wiped film molecular evaporator
S14 S15
S13
WIPE FILM MOLECULAR
EVAPORATOR
-
37
5.1.2: ENERGY BALANCE
The law of conservation of Enthalpy states that Enthalpy can neither be created nor
destroyed, but can only be transformed from one form to another. The general equation
of Enthalpy balance is given by;
For these calculations, Kinetic Enthalpy and Potential Enthalpy are assumed negligible.
In any unit operation that does not involve a chemical reaction, the Enthalpy balance
equation will take the form;
For these calculations, Kinetic Enthalpy and Potential Enthalpy are assumed negligible.
In any unit operation that does not involve a chemical reaction, the Enthalpy balance
equation will take the form;
Q = cpdt ; dt = T (change in temperature)
Cp (light phase) = 2.33 kj/kg O C
Cp (heavy phase) = 3.20 kJ/kg O C
CP (virgin oil) = 3.01 kJ/kg O C
Datum temperature = 25 O C
Assumptions
There are negligible energy losses in all the unit operations
Energy in Energy out + Energy generated + energy consumed Work done = Accumulation
Energy In Energy Out = Accumulation
Q = QFeed- QProduct
-
38
HEAT EXCHANGER
WIPE FILM MOLE CULAR EVAPORATOR
INLET STREAMS OUTLET STREAM
streams Component Mass
(kgs)
Enthalpy
(kJ/hr)
streams components Mass
(kgs)
Enthalpy
(kJ/hr)
S17 Virgin Oil 781 0 S18 Virgin Oil 781 293851.25
S20 Heavy
phase oil
663.85 362411.26 S21 Heavy
phase oil
663.85 68564.29
TOTAL 1484 362411.26 TOTAL 1484 362411.26
HEAT EXCHANGER
S17 S21
S18 S20
S20
S18
S19
WIPE FILM MOLECULAR
EVAPORATOR
-
39
INLET STREAMS OUTLET STREAM
streams Component Mass
(kgs)
Enthalpy
(kJ/hr)
streams components Mass
(kgs)
Enthalpy
(kJ/hr)
S13 Degassed
Oil
781 293851.25 S13 Light phase 117.15 35439.99
QGEN 104,000 S15 Heavy phase 663.85 362411.2
6
TOTAL 781 397851.25 TOTAL 781 397851.
25
Table 10: energy balance around the wiped film evaporator
-
40
CHAPTER SIX
6.0 EQUIPMENT SELECTION, SIZING AND SPECIFICATION
INTRODUCTION
The basis of material selection and specification is largely derived or brought about by
the specific operation of equipment. During the operation, the equipment are dutied to
withstand high pressures, high temperature conditions, equipment capacity among
other operating conditions which are likely to impact wears to the equipment. It is in
this light that the equipments materials are chosen so that they are not frequently
replaced. However, the cost of purchasing the equipment with these specifications is
high and therefore the factor of functionality is paramount when choosing the
equipment for various operations.
The equipment for extracting pharmaceutical avocado jelly from avocado pear fruit are
chosen in consistence with the type of operations they are expected to carry out.
6.1 CHOICE OF MATERIALS FOR EQUIPMENT FABRICATIONS
The main factors governing the choice of materials of construction for a specific
equipment unit include:
the corrosiveness of the content that it handles
the cost of material fabrication
the temperature of operation
the pressure of operation
the end use of the material
the ease of fabricating the equipment
-
41
The following are the equipment with their specifications used during the project
Units Specifications
De-stoning machine Code: DM
Service: removes avocado pear seeds
Type:
Material: stainless steel
Peeling machine: Code: PM
Service: removes avocado pear peels
Type: counter rotary drum
Material: 15 gauge stainless steel
Diameter: 0.41m
width: 0.10m
perforated drum: round holes diameter 0.64cm
Disintegrator: Code: SR
Service: reduces avocado pear pulps sizes
Type: high speed grinder
Material: stainless steel
Capacity: 5m3/hr
Mixer (malaxor): Code: MIX
Service: reduces avocado pear pulps into slurry
Type: flat topped
Material: stainless steel
Capacity: 1.578m
Diameter: 1.262m
Height: 2.524m
Surge tank 1 Code: ST 1
-
42
Service: temporal storage of water/avocado pulp mixture
Type: flat topped
Material: stainless steel
Capacity:1.6m3/hr
Three phase decanter: Code: DC 001
Service: separates oil, water and cake
Type: solid-liquid-liquid decanter
Material: stainless steel
Bowl:
Inner diameter: 500mm
L/D: 4.0
Speed maximum: 3450rpm
G force: 3333g
Centrifuge: Code: CF
Service: Separates solid particles from oil
Type: disc bowl
Material: Stainless steel
Capacity: 3.44m
Length: 2.59m
Height: 0.65m
Surge tank 2: Code: FT 001
Service: for temporal storage of crude oil
Type: dome topped
Material: stainless steel
Capacity: 3.44m
-
43
Length: 2.59m
Diameter: 0.65m
Heat exchanger Code: HE 001
Service: for preheating crude oil and cooling oil product
Type: shell and tube
Material: carbon steel
Length: 3m
Cross-sectional are: 0.2m2
Number of tube: 87
Length of tube: 2.8m
Area of a tube: 0.01m2
Wiped film molecular
distiller
Code: C 001
Service: separating unsaponifable fraction of oil from the
saponifiable fraction of avocado pear oil
Type: Vacuum column
Material: stainless steel
Condenser: Code: CD 001
Service: Cooling the light phase oil
Type: Water cooler
Material: Stainless steel
Capacity: 0.2 m3
-
44
CHAPTER 7
7.0 Design of a centrifugal separator by DIAR ELIJAH GARANG CPE/1021/08
7.0.1 INTRODUCTION
Centrifuges are extensively used for separating fine solids from suspension in a liquid.
They are classified according to the mechanism used for solids separation:
Sedimentation centrifuges: in which the separation is dependent on a difference
in density between the solid and liquid phases (solid heavier).
Filtration centrifuges: in which separation of the phases is by filtration. The walls
of the centrifuge basket are porous, and the liquid filters through the deposited
cake of solids and is removed.
The choice between a sedimentation or filtration centrifuge for a particular application
will depend on:
Nature of the feed
Product requirements.
A variety of centrifugal filter or sedimentation designs are classified according to:
Mode of operation - batch or continuous.
Orientation of the bowl/basket - horizontal or vertical.
Position of the suspension and drive - overhung or under-hung.
Type of bowl - solid, perforated basket, disc bowl.
Method of solids cake removal.
Method of liquid removal.
7.0.2 SEDIMENTATION CENTRIFUGES
In solid liquid separations, the weaker force of gravity can be replaced by more
powerful centrifugal force to ensure more rapid settling.
Mode of operation
If a solid suspension in a liquid is rapidly whirled in a cylindrical container about the
cylinders axis, the vessel imparts to the solid liquid system centripetal force acting in
the direction towards the center of rotation. The content in return, exerts an equal and
opposite force, called the centrifugal force, outward on the walls of the container. It is
the centrifugal force that brings about the sedimentation of heavy i.e. coarse solid
particles through a layer of liquid.
A sedimentation centrifuge consists of the following parts:
A bowl or rotor where the centrifugal is employed to effect phase separation
A drive shaft to transmit power from the prime mover to the rotor
-
45
Drive shaft bearings
A drive mechanism (usually an electric motor or turbine)
Seal system
A supporting framework
A casing to segregate the separated products
Types of sedimentation centrifuges
There are four main types of sedimentation centrifuges:
1. Tubular Bowl Centrifuge
It is a widely used machine. It comes in the popular ranges of 102-127 mm bowl
diameter and 760 mm length. The bowl is suspended from an upper bearing and drive
assembly is rotated at speed of about 15000 rpm. The feed suspension enters the bowl
under pressure through a statutory feed nozzle at the bottom of the bowl, gets
accelerated to rotor speed, moves upward and discharges out from the top.
Under the impressed centrifugal-force field both the solid particles and liquid receive
radial velocity. The particles whose trajectories intercept the wall deposited and the
rest escape with the effluent. Manual removal of the solids deposited against the bowl
wall is done when the mass of sediment solid is sufficient to degrade the quality. Solid
removal is facilitated by lining the bowl wall with parchment paper so that the
deposited solids can be taken out as a cylindrical package.
2. Multi-chamber Centrifuge.
This is a modified design of tubular-bowl centrifuge driven from below. It has a multi-
chamber bowl consisted of a series of tubular sections of increasing diameter arranged
to form a continuous tubular passage of stepwise increasing diameter.
The feed is charged to the smallest-diameter tube and as it passes through the
increasingly larger diameter tubes, it experiences increasingly higher magnitude of
centrifugal force. The heaviest particles settle in the smallest diameter tube while the
smaller and lighter particles migrate to the larger diameter zone where higher
centrifugal force comes into play. Such types of centrifuges may contain up to 6 annular
chambers in the bowl and the outer tubes may be spaced closer together to improve the
performance of the unit. Bowl holding capacity may range up to 75 liters of solids.
3. Disk Centrifuge
It consists of a stack of sheet metal disks 50-100 in number spaced at 0.4 to 3 mm and
set obliquely to form a half vertical angle of 35-50. These closely spaced disks are
actually cones of sheet metal set one above the other. Each disk is perforated (hole size
of 6mm to 12.75mm) and when the disks are assembled in the bowl, the perforations
give rise to several channels through which the liquid rises.
-
46
Feed is admitted to the center of the bowl and it rises through the stack of disks whose
primary objective is to reduce the sedimentation distance. Once a solid particle reaches
the underside of one of the disks, it is virtually removed from the liquid as its chances of
re-entrainment in the effluent are very little. However due to the centrifugal force, it
continues to move outward until it is deposited on the bowl wall.
In hermetic disk centrifuge, characterized by closed feed and discharge, the feed
suspension enters the bowl through a hollow spindle at the bottom. The deposited solid
is removed manually, for which the machine is periodically stopped, the bowl is
disassembled and the disk stack is removed. The clarified liquid leaves through the
central port at the top.
Disk centrifuges range in diameters from 100mm to 500mm and develop settling forces
as high as 4000 to 14000 times the force of gravity. They are nearly as effective as
tubular centrifuges.
Figure 9: Disk bowl centrifuge
4. Continuous Horizontal Helical-Conveyor Centrifuge
It consists of a solid-wall bowl with a horizontal axis of rotation. The bowl may be
conical or cylindrical or very often a cylindrical bowl with conical end section. Feed
suspension enters the centrifuge through a stationary axial pipe to an appropriate point
in the bowl and it is sprayed radially outward onto an annular layer of liquid inside the
bowl. The clarified liquid flows through the overflow ports at the larger radius and
discharge out continuously.
The heavy solid sediment through the liquid phase, and are deposited on the inner
surface of the bowl. A helical screw conveyor extending the full length of the bowl
continuously transports the deposited solid to the other end of the bowl. Wash liquid
may be sprayed on the sedimented mass during its transport to dissolve out soluble
impurities. However washing becomes fairly effective on solid particles no smaller than
-
47
80m.provided the deposited solid phase is reasonably porous. Drained sludge and
clarified liquor are drawn out through the different ports.
A differential speed is maintained between the bowl and the conveyor. The latter is
turned at a speed lower by 20 to 80 rpm than that of the bowl. Bowl diameter ranges
from 150mm to 1370mm; speed is 16 to 135 Hz (I