Refinery of Palm OilJit Kang’s Homepage

Introduction to Palm Oil: From dust to dawn

The economical history of the oil palm (Elaeis guineensis) began in

the rain forests of western Africa in the late 19th century. Since its

introduction into Malaysia in the early 20th century until the early sixties its

impact on the economy was marginal. For many years the economy of

Malaysia had depended for its wealth and prosperity upon rubber. In 1961,

Malaysia embarked on an intensive agricultural diversification program, and

the crop that has achieved the most notable success since then is palm oil.

Within a relatively short period, Malaysia became the world's largest

commercial producer and exporter of palm oil in 1966. Diversification into

oil palm means that the country is now less dependent on the fortunes of

rubber as a plantation crop.

Palm Oil a Cost Effective Product

Palm oil is obtained from the flesh of the palm fruit. Each palm tree

produces approximately one fruit bunch, containing as many as 3000

fruitlets, per month. In addition, each palm tree continues producing fruit

economically for up to 25 years. This ensures a constant stable supply, as

compared with other annual crops.

Naturally, palm oil is characterized as stabilized oil due to its

chemical composition. As such, it can be used in most food applications

without hydrogenation, thus, reducing production cost by as much as 30%.

Palm oil also is priced competitively and can represent a saving of upto

several cents per pound, compared to other edible oils.

Palm oil is available in a variety of forms: crude palm oil, palm olein,

palm stearin, RBD palm oil, fractionated palm olein and pal mid-fraction.

While most of the oil Malaysia exports is RBD palm oil and RBD palm

olein, the range of products is available to suit a variety of manufacturing

needs and in forms that are ready-to-use and require no further processing.

Palm Oil Composition

Palm oil is extracted from the mesocarp of the fruit of the palm Elaeis

guineensis. There are a few varieties of this plant but Tenera, which is a

hybrid of the Dura and the Pisifera, present abundantly through out the

whole Peninsular.

The mesocarp comprises about 70 - 80% by weight of the fruit and

about 45 -50% of this mesocarp is oil. The rest of the fruit comprises the

shell, kernel, moisture and other non fatty fiber.The extracted oil is known as

crude palm oil (CPO) which until quite recently was known as the golden

commodity.

Palm oil like all natural fats and oils comprises mainly Triglyceries,

mono and diglycerides. Free fatty acids, moisture, dirt and minor

components of non oil fatty matter referred to collectively as unsaponifiable

matter.

1. Tryglyceride

It is a chemical compound of one molecule of glycerol bound to three

molecules of Fatty Acid.

CH2 – OH + R1-COOH CH2 – COOR1

CH – OH + R2-COOH CH – COOR2 + 3H2O

CH2 – OH + R3-COOH CH2 – COOR3

Glycerol Fatty Acid Triglyceride Water

The fatty acids could be of the same type or they could be different.

The property of a triglyceride will depend on the different fatty acids that

combine to form the triglyceride.

The fatty acids themselves are different depending on their chain

length and degree of saturation. The short chain fatty acids are of lower

melting point and are more soluble in water. Whereas, the longer chain fatty

acids have higher melting points. The melting point is also dependent on

degree of non-saturation. Unsaturated acids will have a lower melting point

compared to saturated fatty acids of similar chain length.

The 2 most predominant fatty acids in palm oil are C16:0(saturated)

palmitic acid and C18:1 (unsaturated) oleic acid. Typical fatty acid

composition of palm oil is given as:

C12:0 Lauric - 0.2%

C14:0 Myrstic - 1.1%

C16:0 Palmitic - 44.0%

C18:0 Stearic - 4.5%

C18:1 Oleic - 39.2%

C18:2 Linoleic - 10.1%

Others - 0.9%

2. Mono and di-glycerides and FFA

In the presence of heat and water the triglycerides break up by a

process known as hydrolysis to form free fatty acids thus yielding mono and

di-glycerides and FFA which is of crucial importance to the refiners.

Hydrolysis can be represented as below:

CH2 – COOR1 + CH2 – OH

CH – COOR2 + H2O CH – COOR2 + R1COOH

CH2 – COOR3 + CH2 – COOR3

Triglyceride Water Diglyceride FFA

Mono and diglycerides account for about 3 to 6% by weight of the

glycerides in the oil. Good oils having lower amount of mono and

diglycerides is said to be of great importance in the fractionation process

because they act as emulsifying agents inhibiting crystal formation and

making filtration difficult.

The amount of mono and diglycerides and FFA is reduced in the

process of refining as can be seen from their concentration in the

DFA(Distillate Fatty Acid).

3. Moisture and Dirt

This is a result of milling practice. Good milling will reduce moisture

and dirt in palm oil but normally it is in the range of 0.25%.

4. Minor Component

These are classified into one category because they are fatty in nature

but are not really oils. They are referred to as unsaponifiable matter and they

include the following:

a. Carotineoids

b. Tocopherols

c. Sterols

d. Polar Lipids

e. Impurities

As a conclusion, palm oil is one of the most widely consumed edible

oils in the world today. Beside, it contains more monounsaturated fatty acids

than many other vegetable oils. Recent scientific studies indicate that

consumption of monounsaturated has some beneficial effects in order to

maintain a healthy life style. In addition, compared with other vegetable oils,

palm oil is a rich source of the anti-oxidant vitamin E containing about 360 –

600 ppm in its refined form. There are certain reports show that:

Palm oil did not increase baseline serum cholesterol

Palm oil did not affect LDL/HDL ratio.

The vitamin E found in palm oil behaved as an anti-oxidant.

Physical Refinery: The first step toward edibility

Palm oils consist mainly of glycerides and, like other oils in their

crude form, small and variable portions of non-glyceride components as

well. In order to render the oils to an edible form, some of these non-

glycerides need to be either removed or reduced to acceptable levels.

In term of solubility study – glycerides are of two broad types: oil

insoluble and oil soluble. The insoluble impurities consisting of fruit fibres,

nut shells and free moisture mainly, are readily removed. The oil soluble

non-glycerides which include free fatty acids, phospholipids, trace metals,

carotenoids, tocopherols or tocotrienols, oxidation products and sterols are

more difficult to remove and thus, the oil needs to undergo various stages of

refining.

Not all of the above non-glyceride components are undesirable. The

tocopherols and tocotrienols not only help to protect the oil from oxidation,

which is detrimental to flavour and keep ability of the finished oil, but also

have nutritional attributes, a- and b-carotene, the major constituents of

carotenoids, are precursors of vitamin A. The other impurities generally are

detrimental to the oil’s flavour, odour, colour and keep ability and thus

influence the oil’s usefulness.

The aim of refining is therefore to convert the crude oil to quality

edible oil by removing objectionable impurities to the desired levels in the

most efficient manner. This also means that, where possible, losses in the

desirable component are kept minimal. The impurities which are contained

in the crude palm oil (CPO) is shown in table 1.0:

Substances ContentFree Fatty Acid (FFA) 3 - 5%Gums (phospholipids, phosphotides) 300 ppmDirt 0.01%Shell TraceMoisture and Impurities 0.15%Trace metal 0.50%Oxidation Products TraceTotal Carotenoids 500 - 1000 mg/ke

Table 1.0 Composition of CPO

General speaking, the refining routes of palm oil is quite identical.

There are two routes are taken to process crude oil into refined oil; which are

chemical (basic) refining and physical refining. The methods differ basically

in the way the fatty acids are removed from the oil. Physical refining, which

eliminates the need for an effluent plant for the soap stock, involves

subjecting the oil to steam distillation under higher temperature and vacuum

for removal of the free fatty acids. The physical refining is used to remove

the free fatty acids. The refining of physical plant is practiced to subject the

oil to steam distillation. The typical refining process is shown in Figure 1.0.

Physical Refinery Process Description

The raw material which is used by physical plant is crude palm oil

(CPO) from the CPO storage tank. CPO is feed at the flow rate about 35-60

tons/hour. The initial temperature of CPO is at 40 – 60°C. The feed is

pumped through the heat recovery system, that is plate heat exchanger to

increase the temperature around 60 – 90°C.

After that, there is about 20% of the CPO feed to into the slurry and

mix with the bleaching earth (6 – 12kg/ton CPO) to form slurry (CPO +

Bleaching earth). The agitator inside the slurry tank will mixed the CPO and

bleaching earth completely. Then, the slurry will go into the bleacher.

At the same time, another 80% of the CPO is pumped through another

plate heat exchanger (PHE) and steam heater to increase the CPO

temperature to 90 – 130°C (it is a desired temperature for the reaction

between CPO and phosphoric acid). Then, the CPO feed is pumped to static

mixers and the phosphoric acid is dosed at 0.35 – 0.45 kg/ton. Inside there,

the intensive mixing is carried out with the crude oil for precipitation up the

gums. The precipitation of gums will ease the later filtration process, avoid

the scale formation in deodorizer and heating surface. The degumming CPO

then will go into bleacher.

In the bleacher, there are 20% slurry and 80% degummed CPO will

mix together and the bleaching process occur. The practice of bleaching

involves the addition of bleaching earth to remove any undesirable

impurities (all pigments, trace metals, oxidation products) from CPO and

this improves the initial taste, final flavor and oxidative stability of product.

It also helps to overcome problems in subsequent processing by adsorption

of soap traces, pro-oxidant metal ions, decomposes peroxides, colour

reduction, and adsorbs other minor impurities. The temperature inside the

bleacher must be around 100°C – 130°C to get the optimum bleaching

process for 30 minutes of bleaching period. The low pressure steam is

purged into bleacher to agitate the concentrated slurry for a better bleaching

condition.

The slurry containing the oil and bleaching earth is then passed

through the Niagara filter to give a clean, free from bleaching earth particles

oil. The temperature must be maintain at around 80 – 120°C for good

filtration process. In the Niagara filter, the slurry passes through the filter

leaves and the bleaching earth is trapped on the filter leaves. Actually, the

bleaching earth must be clear from Niagara filter after45minutes in operation

to get a good filtration. Bleached palm oil (BPO) from Niagara filter is then

pumped into buffer tank as a temporary storage before further processing.

Usually, a second check filter, trap filter is used in series with the

Niagara filter to double ensure that no bleaching earth slips occur. The

presence of bleaching earth fouls deodorizer, reduces the oxidative stability

of the product oil and acts as a catalyst for dimerizaition and polymerization

activities. So, the “blue test” is carried out for each batch of filtration to

ensure the perfect filtration process. This test indicates whether any leaking

is occurring in Niagara filter or trap filter. Hence, any corrective actions can

be taken intermediately.

The BPO comes out from the filter and passes through another series

of heat recovery system, Schmidt plate heat exchanger and spiral (thermal

oil: 250 – 305°C) heat exchanger to heat up the BPO from 80 – 120°C until

210 – 250°C.

The hot BPO from spiral heat exchanger then proceeds to the next

stage where the free fatty acid content and the color are further reduced and

more important, it is deodorized to produce a product which is stable and

bland in flavor.

In the pre-stripping and deodorizing column, deacidification and

deodorization process happen concurently. Deodorization is a high

temperature, high vacuum and steam distillation process. A deodorizer

operates in the following manner: (1) dearates the oil, (2) heat up the oil, (3)

steam strips the oil and (4)cools the oil before it leaves the system. All

materials if contact are stainless steel.

In the column, the oil is generally heated to approximately 240 –

280°C under vacuum. A vacuum of less than 10 torr is usually maintained

by the use of ejectors and boosters. Heat bleaching of the oil occurs at this

temperature through the thermal destruction of the carotenoid pigments. The

use of direct steam ensures readily removal of residue free fatty acids,

aldehydes and ketones which are responsible for unacceptable odor and

flavors. The lower molecular weight of vaporized fatty acids rises up the

column and pulls out by the vacuum system. The fatty acid vapor leaving the

deodorizer are condensed and collected in the fatty acid condenser as fatty

acid. The fatty acids then is cooled in the fatty acid cooler and discharged to

the fatty acid storage tank with temperature around 60 – 80°C as palm fatty

acid distillate (PFAD), a by-product from refinery process.

The bottom product of the pre-stripper and deodorizer is Refined,

Bleached, Deodorized Palm Oil (RBDPO). The hot RBDPO (250 – 280°C)

is pumped through Schmidt PHE to transfer its heat to incoming BPO with

lower temperature. Then, it passes through another trap filters to have the

final oil polishing (120 – 140°C) to prevent the earth traces from reaching

the product tank. After that, the RBDPO will pass through the RBDPO

cooler and plate heat exchanger to transfer the heat to the CPO feed. The

RBDPO then is pumped to the storage with temperature 50 – 80°C.

Palm Fatty Acid Distillation Plant

The separation of liquid mixture into their several components is one

of the major process of the chemical industries, and distillation is the most

widely used method of achieving this end: it is the key operation of the oil

refinery. Though out the chemical industry the demand for pure products,

coupled with a relentless pursuit of greater efficiency, has necessitated

continued research into techniques of distillation. The distillation column is

used in this purpose.

The distillation column which have to be designed with a larger range

in capacity than any other types of chemical engineering equipment, with

single columns from 0.3 to 10m in diameter and from 3m to upwards of 75m

in height. The purpose of designing is to achieve the desired product quality

at minimum cost, but also to provide constant purity of product even though

there may be some variation in feed composition. The vertical cylindrical

column provides in a compact form, with the minimum of ground

utilization, a large number of separate stages of vaporization and

condensation.

In practice, distillation may be carried out by either of two principal

methods. The first method is based on the production of a vapor by boiling

the liquid mixture to be separated and condensing the vapors without

allowing any liquid to return to the still. There is then no reflux. The second

method is based on the return of part of condensate to the still under such

condition that this returning liquid is brought into intimate contact with the

vapor on their way to the condenser. Either of these methods may be

conducted as a continuous process or as a batch process.

PFAD Plant Description

a) Feed Raw Material - Palm Fatty Acid Distillate (PFAD)

b) i) Major Product Produced - Distillate Fatty Acids (DFA)

ii) By Product Produced - Precut-Lighter Fatty Acid Component

- Residue

PFAD Process Description

The feed Palm Fatty Acid Distillate (PFAD) from storage tank with

temperature around 50 – 100°C will first passes through a heat exchanger

network.

The temperature of PFAD will increase to approximately 200 –220°C. Then

the hot feed will enters to the Degasifier for separating some impurities and

light fatty acid presented in the feed under vacuum system.

After that, the heavy components of fatty acid (C10, C12, C14, C16 &

C18) come out from the bottom of Degasifier will go into column C for

more separation between light and heavy components of fatty acids. Before

that, there are three distillation column are used in distillation process. The

products of these 3 columns are as follow:

1. Column A: Precut

2. Column B: Distillate Fatty Acid (DFA)

3. Column C: Residue

In column C, the feed with temperature 220 – 255°C will further

heating by thermal oil boiler until temperature become 240 – 300°C under

vacuum system. The fatty acids will evaporate under the vacuum condition

and separation of light fatty acid and heavy fatty acid will occur. At the top

of column C, the light fatty acid (precut with lower carbon number <C16)

from the evaporation become vapor is continuously pulled out by the

vacuum system. The precut then passed through the heat exchangers and

cooled down by the soft water and PFAD feed before going to storage.

At the same time, the heavy fatty acid from the bottom of Column C

(C16 & C18) is pumped to Column B for further separation. There is high

temperature inside the column B which is supplied by thermal oil reboiler

(290 – 310°C) will contribute to the vaporization of fatty acids. Therefore

the temperature will increase (220 – 250°C) during the distillation process

because of the higher boiling point of the fatty acids feed. The light fatty

acid (DFA) from the vaporization of fatty acid is pulled out by the vacuum

system into a reflux holder. When the refluks is overflow, the excess DFA is

pumped to the heat exchangers and cooled down by the soft water and the

PFAD feed. The DFA then is further cooled down in spiral heat exchanger

(hot water/DFA) and plate heat exchanger (Cooling tower water/DFA)

before sending to storage at 60 – 90°C.

On the other hand, the bottom product of column B is residue, the

heavy fatty acids component is pumped to the heat exchanger

(Residue/PFAD feed and Residue/Hot Water) before going to storage tank.

The uncompleted distillate will recycles back to column B for further

separation.

Fractionation: Value added process?

The demand for liquid oils has increased in recent years, mainly for

salad and cooking uses and an important property for such oils is low cloud

point, which is the temperature at which turbidity appears when the oil is

cooled under standard conditions. Liquids oils with a low cloud point are

desirable because of the widespread use of household refrigeration.

In order to cater for a wide range of markets, the Malaysian refiners

start to offer product which are “harder”(Stearin) and “more liquid”(olein)

than palm oil. These are accomplished trough a simple process of

fractionation which is based on two fundamental operations:

1) Crystallization

2) Filtration

Fractionation of palm oil can be described as follow. The triglycerides found

in the oil have different melting points. At certain temperature, the lower

melting temperature triglycerides will crystallize into solid separating the

oils into both liquid (Olein) and solid (Stearin) fraction. The fraction can

then be separated by filtration.

It is worth mentioning that in palm oil fractionation, palm olein is the

premium product and the palm stearin is the discount product. In Malaysia,

fractionation of palm oil into palm olein and palm stearin is accomplished

using two types of processes which are “Viz Dry” and “Detergent

Fractionation”.

Fractionation Plant Description

a) Feed Raw Material - Refined Bleached deodorised Palm Oil (RBDPO)

b) i) Major Product Produced - Refined Bleached Deodorised Palm Olein (Olein)

ii) By Product Produced - Refined Bleached Deodorised Stearin (Stearin)

Fractionation Process Description

The dry fractionation is used to separate the palm olein and

palm stearin from the RBDPO produced by physical treatment. The RBDPO

is passed through the further fractionation process to get various grade of

palm olein and palm stearin. Usually, there are three types of olein are

produced: (1) normal grade olein, (2) super grade olein and (3) olein with

cloud point 7 – 8°C.

Crystallization Process

Firstly, the RBDPO feed must pass the quality specification,

colour<2.6R and FFA< 0.075 is fed into the heat exchanger. The RBDPO

feed is heated up by hot waters around 75°C. After that the oil is kept

homogenized at about 70°C in homogenizes before the start of

crystallization. The idea is to destroy any crystals present and to induce

crystallization in a controlled manner in the crystallizer.

After that, the oil is pumped to the crystallizer. The crystallization

system is a batch type and is equipped with special crystallizers operating

alternatively. These crystallizers are made up of vertical cylindrical vessel

full of thermo-regulated water which submerged barrels containing the oil to

be fractionated: each of these barrels is fitted with a mechanical agitator. An

automatic station controls the temerature in the various crystallizers.

The crystallization process is carried out to remove the higher melting

glycerides which cause liquid oils to become cloudy and more viscous at

low temperature. There are 3 factors (temperature, time and agitation), have

a fundamental importance on the formation and character of the crystal:

1. The lowering of temperature causes, because of supersaturating the

higher melting component to separate from a solution.

2. Agitation facilitates the formation of small crystals.

3. Time with a gradual decrease in temperature and stillness, promotes the

formation of longer crystals.

The solution is pumped batch-wise into the crystallizer according to a pre-

established programme. In the crystallizer, the crystal formation and growth

occurs as the oil is agitated and cooled sing chilled water and cool water

filled in the jackets or cooling coils of the crystallizer. Cooling can be

governed by controlling either the oil or water temperature.

Filtration Process

After the crystallization process, the slurry from buffer tank passses

through the filtration process for the physical separation between RBD palm

stearin and RBD palm olein. Presently, the membrane filter is used for this

filtration. Another alternative for this purpose is by employing drum filter

for separation.

The membrane filter is pressure filter where the filter pack comprising

alternatively plates and frames, or a series of chamber is compressed

between one fixed and one movable cover or bulk-head. The filter media are

located between each individual element. Cake will build up in the hollow

space between the elements and fall out of the press when the filter pack is

opened. Composition of the filter pack is by means of electrically driven

hydraulic system (75 bar), which controls the entire mechanical parts of

units, head plates, filter plates, plate shifting device with the built in panel

board.

Hydrogenation

Hydrogenation is the most widely used method of all the oil

modification processes, to reduce the degree of unsaturated in the fatty acid

groups of the glycerides. It is a catalytic process whereby the number of

double bonds are reduced and by the same time isomerization of the residual

fatty acids is promoted. Liquid oils with unsaturated triglycerides are thus

transformed into fats containing a higher % age of saturated triglycerides:

Hydrogenation is often called hardening of oils and soft fats.

Catalytic hydrogenation, which has been known in fat technology

since the beginning of this century, is used increasingly for the preparation

of ‘tailor-made’ fats. Depend on the condition of the reaction, the basic

reaction can be shown as follows:

H H

H H

R - C = C - R + H2 R- C – C – R

Hydrogenation

H H

The complex system consists of three phases: liquid oil, gaseous

hydrogen and solid catalyst. Hence there are many different internal surfaces

through which the hydrogen molecules have to pass until they reach the

double bonds of the unsaturated triglycerides adsorbed on the catalyst

surface. As soon as the unsaturated bonds are saturated, the triglyceride

moves off the catalyst surface, thus enabling the next unsaturated molecule

to be adsorbed and processed.

The overall hydrogenation rage depends on the quality of the reactant

involved, the degree of refining of the oil to be hydrogenated, the activity

and nature of the catalyst. In addition reaction parameters such as hydrogen

pressure, catalyst concentration, reaction temperature, stirring, etc have an

influence. In spite of these numerous reaction parameters that affecting the

quality of the desired product, fat-technologist have resolved the operating

conditions required for the preparation of tailor-made fats. This process is

established mainly to add value to by byproducts from the refinery. The raw

materials are from refinery: Palm Fatty Acid Distillate (PFAD) and Refined

Bleached Deodorized (RBD). Basically, stearin is the main raw material for

this plant.

Hydrogenation Process Description

There are various kind of oils used as the feed of this plant depends on

the market demands, there are DFA, PFAD, RBDSt, precut and split residue.

Firstly, the fatty acid feed from the storage tank (60 – 70°C) is pumped to

the feed preheater. In the feed preheater, the fatty acid feed is heated up by

the hot hydrogenated FA from plant until 140 – 170°C, before entering the

reactor for hydrogenation process.

Then, the hot feed is transferred to the reactor autoclave for reaction.

The reactor consisted of the nickel catalyst which play an important role in

the reaction as follow:

1. To avoid modifiers, such as sulphur, likely to give higher “trans” acid

contents.

2. Comparatively high temperature to accelerate reduction of poly-

unsaturated without formation of saturates.

3. Reduced the hydrogen gas pressure.

4. Lowering the iodine value to improve stability and good yield of liquid

oil when winterized.

5. To remove materials responsible for clouding and solidification at low

temperatures.