Contents
Neutralization/Bleaching Process: ................................................................................................................ 1
Soft Oil:...................................................................................................................................................... 1
Hard Oil: .................................................................................................................................................... 2
Neutralization/Bleaching Process:
The neutralization and bleaching process is carried out in the vessels known as
“Neutralization/Bleaching Vessels”. There are 6 vessels for this purpose namely NB1 to NB6. NB1 and
NB4 are used to for the production of Hard Oil, whereas NB2, NB3, NB5 and NB6 are used for the
production of soft oil. It is a batch-wise process where each batch produced has an amount of around 30
tons. The process involves the following steps:
Soft Oil:
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Amount of 30 tons of raw oil is charged to NB weighing scale, from where it is drawn to required
NB vessel by the use of a pump.
After charging the oil in the vessel, the oil is heated to a set point of around 92 °C. This heating is
done through coils installed in the vessels. The vessel also consists of an agitator, which shakes
the oil so that the heating is uniform.
When the temperature reaches to 60 °C, Phosphoric acid is charged into the vessel. This step is
known as “degumming”, where phosphoric acid converts the unhydratable phosphatide groups
into hydratable ones, so they can be easily washed away with the water. The oil is made thin
after this process due to removal of gums present in the oil.
When degumming is done, a water wash is given to the oil, where 5% warm water (around 9598 °C) is added to the oil. A settling time of around 30 min is given, to separate the oil from
water by difference of density. The water is then drained out, consisting of phosphatide groups
as well.
After draining the water, a caustic solution of 0.8 N is dozed into the oil to reduce the Free Fatty
Acid (FFA) content of oil. This step is known as “Neutralization”. The amount of caustic added
depends upon the original FFA content of the oil. FFA reacts with caustic and produces salt
(soap) and water.
After neutralization, again 10% warm water wash is given to the oil. The water along with soap,
allowed to settle down from where it is drained out. The neutralized oil remains in the vessel.
The oil is now dried under vacuum to remove the moisture content. The temperature in this
step reduces down to around 80 °C. Vacuum is created using Liquid Ring Pump.
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After removing the moisture, a sample is taken in which the FFA content of oil and Soap content
is checked. The standard to be followed is such that FFA should be less than 0.1%, and soap
content should be less than 500 ppm.
This oil is now heated to around 110 °C under vacuum (730 mm of Hg), after which activated
bleaching earth is added into the oil for bleaching purpose.
The color is observed between the spectrum of red and yellow. Bleaching earth absorbs the
colored pigments from the oil and makes the oil color more desirable.
After bleaching the oil is passed thorough AMA filters of 80 micron mesh size, which filters out
the earth and makes the oil clear to be sent into the storage tanks.
Hard Oil:
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The process of Neutralization and bleaching of hard oil is almost the same as with one additional
step.
Interesterification is done in case of hard oil, after neutralization and before bleaching, where
under high vacuum, a catalyst (sodium methylate) is added (around 20kg per batch) to the oil.
The agitator is set to maximum, and the temperature is maintained to around 110 °C. The
catalyst reduces the SMP of the oil and converts all the trans-bond present in the oil into cisbond which is good for health.
Vacuum is discarded and the oil is allowed to cool using cold water (90-92 °C).
A 10% warm water wash is given. Settling time is given, and the water is allowed to drain out
along with the catalyst.
Drying is done to remove the moisture, after which the bleaching is done.
Rest of the procedure is same as that of soft oil.
Deodorization Process:
Deodorization is a process in which the bad odor of the oil is removed by heating the oil at high
temperature. For this purpose, the refinery has 2 deodorizers, SCD (Semi-Continuous Deodorizer) and
DCD (Desmic Continuous Deodorizer). The neutralized and bleached oil is charged into these 2
deodorizers where the bad smell is removed. The production of SCD is about 300 tons per day. The steps
are given below:
SCD (Semi-Continuous Deodorizer):
This deodorizer consists of a 5 trays column separated by valves. The oil is charged batch-wise and then
allowed to pass through each tray with some retention time. The column of SCD is maintained under
high vacuum of 5 milli bar. The vacuum is created by using venturi vacuum system. The step by step
process is as follows:
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Using the pumps, oil is charged into the SCD weighing scale. A batch of 7.5 tons is taken, which is
sent to degasser for pre-heat treatment of oil. Degasser uses steam from the main boiler to heat
the oil to a temperature of about 120 °C.
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This pre heated oil is then allowed to travel to the 1st stage tray in the column of the SCD. Here,
the temperature of oil is further increased to about 160 °C. This heating is done through
thermo-syphon. The coils from 1st stage tray is connected with the 4th stage tray, inside the coils,
water is filled and sealed. Hot oil which travels down to 4th stage, transfers heat to the coils and
rises the temperature of the water present inside the coils. This vapor phase then travels to the
1st stage tray, where it transfers the heat to the oil, and condenses back to water which travels
down to the 4th stage. This cycle is repeated.
Oil from the 1st stage is allowed to fall down into the 2nd stage after a retention time of about
1400 sec. In the 2nd stage, the oil is heated again to around 240 °C using GEKA boiler. GEKA also
works under the principle of closed thermo-syphon cycle. The pressure of GEKA is maintained to
50 bar. When the temperature of 240 °C is achieved, the valves connecting the 2nd and 3rd stage
are open and the oil can fall to 3rd stage.
In the 3rd stage, the temperature is maintained to about 240 °C and low-pressure sparging steam
is used to shake the oil well to remove the volatile compounds present in oil. These volatile
gases and other fatty acid constituents get sucked through the high vacuum of the column from
where it is sent to a scrubber tank. It is used as a byproduct to produce soap.
After the retention time of about 1800 seconds, oil is passed into the 4th stage where it
exchanges its heat with the water present in sealed coils. The temperature reduces to around
180 °C.
This oil is then passed to the 5th stage where it exchanges its heat with the cold water. The
temperature in this stage reduces to around 110 °C. Citric acid of 0.01 % conc. Is added to this
oil as an antioxidant.
This deodorized oil is then sent to a buffer tank, where it is sampled and after checking the
sample, the oil is sent to Storage tanks.
DCD (Desmet Continuous Deodorizer):
This plant was set up to process Crude palm oil at first, but now it is also used to produce soft
deodorized oil. The process is same as that of SCD, except for the fact that this is a continuous process.
There are 6 trays in DCD and there are no valves present in between the trays. It also has a separate
section to bleach crude palm oil. The production of DCD is about 300 tons per day. The steps involved
are given below:
Bleaching of CPO:
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Crude palm oil contains greater amount of FFA but it can be separated by physical separation,
therefore there is no need to neutralize CPO using caustic.
The oil from the storage tank is charged into the tank from which it is sent to an exchanger
where it gains heat.
Oil at around 60 °C is sent to acid reactor where phosphoric acid is added for degumming
process.
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From there, the oil is charged to bleacher vessel. This vessel consists of 2 sections, one is coiled
(can heat) and the other one is uncoiled (cannot heat). Around 3% by weight of oil, earth is
dozed when the temperature of oil reaches to 110 °C.
After this the oil passes through AMA filter by means of pump. AMA filters out the spent earth
and the oil is then sent to a buffer tank from where it can be charged to DCD column.
Deodorization:
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Oil from the buffer tank/storage tank is charged to degasser by means of a pump. The Degasser
is installed inside the DCD column. The temperature is raised to about 50 °C.
After leaving the degasser, the oil travels to the 6th stage of the DCD column, from where it goes
up to the 5th stage. The purpose of this pathway is to utilize the heat of the already processed oil
falling to 5th and 6th stage of the DCD column and use it to heat the oil which is about to get
process. This oil from 5th stage after exchanging maximum heat travels to the top where the
temperature is further increased using a GEKA boiler. The temperature here reaches to around
240 °C.
The oil in the 1st stage then overflows to the 2nd stage, since it is a continuous process, no valves
are given. The trays are tilted and are built in such a fashion that oil takes all the retention time
it needs in a tray. The size of al the trays are different for the same purpose.
In the 2nd, 3rd, and 4th stage, sparging steam is used to shake the oil, deodorization occurs in
these three stages. The by product is collected in a scrubber tank by means of vacuum.
Oil in the 5th stage then exchanges its heat with the new oil coming from the bottom of the tank.
The temperature here reduces to around 155 °C.
The same happens in the 6th stage, oil exchanges its heat with the new oil and with the cold
water that is being flowing in the last stage.
The oil is then sent to a buffer tank, from where it travels to exchanger to lose its heat. It is then
passed to the GAF filters, from where it can be sent to the storage tanks.
Tundra:
Tundra is the newest refinery installed in 2018. It works on the principle of continuous process
and produces 600 tons per day. It has its own separate neutralization and bleaching sections, as well the
deodorizer section. Usually, soft oil is produced here. Raw crude oil can be charged into this refinery and
finished deodorized product can be obtained. The process involved are given below:
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Raw oil from storage tanks is charged into the tank 1100. From here using the pumps, the oil is
sent into the heat exchangers 1121A (oil to oil heat exchange) and 1121B (steam to oil heat
exchange), where the oil gains heat.
From here the heated oil (at about 80-90 °C), goes to the acid reactor tank 1104AC, passing
through a mixer shear pump, where phosphoric is added around 0.07% and mixed with the oil.
The oil and phosphoric gets in the acid reactor from the bottom and then can overflow from the
top so as to provide the retention time.
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After degumming, the oil is sent to caustic reactor 1103NA using another mixer shear pump
where caustic is added according to FFA content of oil (usually around 14%). Again, the oil and
caustic fills from the bottom and can overflow from the top, to provide the proper retention
time for better reaction.
After neutralization, the oil is sent to Centrifuge 1118NA where soap is removed. Water is then
added to this oil and it is sent to another centrifuge 1118W where water is separated out along
with the remaining soap content.
From centrifuge 1118W, oil is sent to the dryer where vacuum of 67 mb is applied. Moisture is
removed here. The same oil is then travels to heat exchanger 1121A to exchange its heat with
the new oil coming into the process. This cool oil can now be charged into PST tanks for storage,
or it can be sent into further processing as well.
If the oil is sent for further processing, then it enters the bleaching section at around 62 °C, from
where it passes through exchangers T521A (oil to oil heat transfer) and T521B (steam to oil heat
transfer) where it gains heat. It is then sent to bleaching.
The bleacher 635/622 consist of a vessel at the top of which, a hopper 609A is connected
through which bleaching earth is added into the vessel. The temperature of oil here is around
110 °C and pressure of the vessel is about 62 mb. This vessel is divided into three sections in
such a way that oil has maximum retention time, to ensure proper color removal.
The bleached oil is then sent to AMA filters (616A1/616A2) of 80-micron mesh size, which filters
the oil and separates out the sand. The oil is then passed to a buffer tank 682B.
From this buffer tank, oil is passed into the GAF filters, where the micron mesh size is less than
10. From these filters, only oil passes into the degasser 802, other impurities stay behind.
Oil is heated in the degasser to about 100 °C after which it is passed to the deodorization
column QE882. This column consists of 6 stages working of different temperatures. Before
charging the oil into column from the top, the oil is first sent to 5th stage of this column, where it
exchanges heat with the processed oil. The heated oil is then charged into the column from the
top, where it again gains heat from the GEKA working at 50 bars.
The charged oil in the column is at a temperature of 240 °C. it falls to the 1st stage. The vacuum
inside the column is around 2mb. The trays are designed in such a fashion that they are tilted
and maximum retention time of about 1800 secs in each tray is given. The temperature in the
first 4 stages remains almost the same. Low pressure purging steam is used to shake the oil as
well. The volatile gases and fatty acid compounds removed are collected in the scrubber at the
top of the column, from where they are sent to Fatty acid catcher tank 823LT.
After the 4th stage, deodorization is completed. In the 5th stage, the oil cools down by
exchanging its heats with the new oil coming into the column. The temperature reduces to
about 150 °C.
In the 6th stage, the oil is cooled by using cold water from the cooling towers. The temperature
reduces to about 110-120 °C. citric acid of 25% conc. is added in the amount on 0.01% of the
total weight of oil. It increases the shelf life and acts as an antioxidant.
The oil is drained out from the bottom of the tank from where it goes to the heat exchangers
821S (oil to Cool water heat transfer), where it loses its heat. After this, the oil is passed to
T521A where it loses more of its heat. Another exchanger T881B is used to cool this oil. Finally at
around 50 °C this oil is passed through GAF filters, from where it can be transferred to PST tanks.
Gas Cracking Plant (GCP):
Hydrogen is needed to convert the soft oil into hard oil. This hydrogen is produced within the DALDA
under GCP. Around 60m3 of hydrogen is produced every hour for the hydrogenation reactions. The
process involves the following steps:
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Natural Gas with inlet pressure of 0.5 bar and temperature of 30-35 °C is taken in and sent to
multistage compressor where the pressure is increased to about 16 bar and temperature
increases to about 90 °C.
This high pressurized gas is then sent to feed pre-heater E5 where it is heated to about 420 °C.
To remove Sulphur as it may poison catalyst in the further stages, the hot gas is sent to
desulphurizer, where catalyst cobalt and molybdenum along with zinc oxide is used to remove
Sulphur. As this is an endothermic reaction, some of the heat is lost.
The desulphurized gas is now sent to feed super heater E4, steam is added in this and the
temperature is raised to around 480 °C.
This mixture is sent to reformer where reforming reaction happens at around 724 °C.
The mixture of gases is then passed to process gas boiler E6 where it exchanges heat with water
and cools down to around 340 °C.
This process gas is then sent to high temperature shift converter where the carbon monoxide is
converted into carbon dioxide at around 450 °C.
This mixture of gases is then sent to boiler feed water heater where it exchanges heat with
water and cools down to about 200 °C.
Its temperature is further reduced by sending this mixture to process condenser E7,
temperature here falls to 90 °C. it is then sent to condenser separator.
From the condenser separator, the mixture is sent to pressure swing adsorber where zeolite
adsorbs the hydrogen, which is sent to hydrogen storage tanks. The rest of the mixture of gases
are passed to the reformer, where it serves as fuel to the burner.
Water Cycle:
The water cycle used in this process is given below:
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Demineralized water is sent to deaerator, where oxygen is removed from this water.
This deaerated water is then sent to steam drum.
From here, it is sent to the process gas boiler E6 where it gains heat from the process gas.
It is then sent to exchangers E 3A and E 3B (installed in convection box above the reformer)
where it further gains heat.
This steam is then sent back to steam drum, from where it is supplied to the feed super heater,
for the reforming reaction.