Crude oil refining

Table of Contents

Introduction
Refining of Sunflower
Refining of soybean oil

Submitted by azaquar on Wed, 11/05/2011 - 15:12

Introduction

Refining is the set of operations used to transform crude oil into an edible product by removing impurities that make it unfit for consumption in the state.

In fact, the oils contain many compounds, some are very useful (vitamins, unsaponifiable, ...), others are harmful to their quality (erasers, free fatty acids, pigments, odor agents, ...).

The refinery is to eliminate the most of these compounds to obtain an oil chemical and organoleptic qualities satisfactory. It includes several operations:

Degumming (or degumming): it helps to rid the oil of gums after hydrolysis by an acid.
Neutralization: the free fatty acids are the most common impurities in oil refining. The neutralization step is to eliminate these compounds may accelerate the oxidation of oil. It is done by using caustic soda, followed by washing with water and drying.
Fading: it serves to eliminate the pigments in oil.
Filtration: this step allows to obtain a clear oil after removal of the bleaching earth.
Deodorization: This step helps to rid the oil of its odor by vacuum distillation at elevated temperature (180 ° C-200 ° C).

We will treat subsequently the refining of oil from two oil seeds whose oils are most used: sunflower oil and soybean oil.

Refining of Sunflower

Degumming and neutralization

Among the impurities of crude oils are mucilages, which substances are divided between water and oil. Chemically, mucilages are phospholipids, glycerides linked to phosphoric acid and a nitrogenous base.

These mucilages are flocculants by adding hot water acidulated with phosphoric acid. Just centrifuge to remove the products of hydration of phospholipids.

The neutralization is justified by the fact that organic acidity of the oil increases its instability. It is therefore necessary to neutralization by the hot aqueous soda, and soap is separated by centrifugation.

Finally, it washes the oil with water and dry on the vacuum and the outputs or pasta neutralization, soaps contain sodium and oil driven.

Conduct of the operation:

The diagram in Figure 6 represents an example of a process of neutralizing and degumming of sunflower oil. The main steps are described below:

Diagram degumming and neutralization of sunflower oil

Storage: crude oil is stored in storage tanks, oil is pumped at a rate usually between 8 and 10 tons per hour.

Heating: it takes place in a plate heat exchanger, by heating the crude oil by steam, oil, leaves the exchanger at a temperature greater than or equal to 85 ° C, while the steam loses its latent heat and part of its sensible heat before leaving the heat exchanger in the form of condensate at 80 ° c.

Acid injection: the phosphoric acid is added after dilution of the quantities estimated by the driver. The mixture is homogenized in a blender first before entering a tank first and then in a second tank. These so-called contact tanks are planned to increase the contact time and thereby the operation of degumming.

Sodium injection: the injection is done through a pump, the mixture of oil and soda are homogenized in the mixer.

Separation: The purpose of this step is to separate the pulp oil to give a neutral oil and free of mucilages know. The separation is achieved by centrifugation.

Cooling: it takes place in a plate heat exchanger exchanging against the current against the oil and oil against the incoming cold water in the tanks maturation through coils in the existing body of maturation and in which circulates the cold water. The role of these mature crystallized waxes to facilitate their separation in the centrifuge.

Winterisation: after being crystallized, waxes are separated by centrifugation, the goal is to improve the quality of the finished product that can be affected by the turbid appearance given the presence of waxes at room temperature.

Heating: It is on two stages, first in a heat exchanger by circulating oil against the relatively warm water, then in a steam heat exchanger. The oil leaves the second heat exchanger at a temperature of 70 ° C.

Washing: it takes place in a separator and is to eliminate alkaline substances such as soaps and welded over and the traces of phospholipids, metals and other impurities. Sunflower oil underwent a single wash, the same oil, once washed, is sent to the tank which will start fading.

b) Product Specifications:

The neutral oil should have the following characteristics, ie at the end of the neutralization process of neutral oil must verify the following conditions in terms of acidity and know:

Acidity (g/100g): 0.02 - 0.06
Soap (ppm): 800 - 1400

Discoloration

After the neutralization, the oil is still too dark to be marketed. Thus, the pigments responsible for color must be eliminated, for this oil is processed by a land turned to 90-100 ° C under agitation, this land will be removed by filtration.

a) Conduct of the operation of discoloration:

The diagram in Figure 7 represents an example of the fading process of sunflower oil.

Diagram fading sunflower oil

The main steps are described below:

Receipt of the degummed oil: The beginning of the bleaching takes place in a tray where the neutral oil falls to a temperature between 80 and 90 ° C. This oil will be pumped to the mixer.

Adding bleaching earth: The earth mixer / oil mix for role as oil with bleaching earth from the device. This one is where the tray bleaching earth is added to part of the neutral oil, it is equipped with a motor stirrer.

Bleaching: Upon exiting the mixer, the oil is sucked by a vacuum suction flow is controlled by a pneumatic valve located on the conduct between the mixer to fade, this one is equipped with a motor stirrer to homogenize the mixture.

Filtration: This operation aims to eliminate hunting and bleaching earth pigments and dyes, this process includes the following 7 phases:

Filling the tank filter: to start the pump just after opening the valves at inlet and return, filling usually lasts 4 minutes.
Recycling: it occurs when the valve reaches the overflow, the oil is returned to the tray with oil filter, the operation lasts 3 minutes.
Filtration: After a few minutes, open the valve allowing recovery of the filtered oil devoid of these pigments, the filtration cycle can last between 2 and 12 hours.
Drain the filter, just before stopping the filtration, we must reverse the valves on the oil filter to allow his return to the pan filter. It closes the valve at the pump and stop the latter.
Opens after the valve allowing the recycling of this volume tray to filter. The end of the filtration can be estimated using one of the following criteria:
The maximum allowable pressure in the tank filter has been reached.
Filtered flow is more suitable or very low.
Drying of the cake: to avoid the loss of oil on the one hand and allow for easy débatissage cakes. It closes the drain valve and sends live steam on the cake.
Débatissage of Niagara when the cake is dried, the overflow valve is open to break the pressure in the filter, then you open the door bottom and then makes the buzzer, after a few seconds the cake is completely eliminated. The débatissage lasts between 2 and 3 minutes.

At the exit of the filter (Figure 8), the oil goes to the tray milled, it is equipped with a viewfinder information about the flow of oil, its color and clarity. Then the oil goes to the polishing filters through a centrifugal pump.

Vertical oil filter land

b) specification of the oil bleached:

After fading, sunflower oil must have the following characteristics required by law and by clients:

Acidity (in%): 0.05 - 0.08
Soap (ppm): 0 - 15

Deodorization

Deodorization is the final phase of refining oil. Its purpose is to eliminate fatty acids and odoriferous substances (aldehydes and ketones), by steam and vacuum at elevated temperature.

Here the subsequent stages of the process of deodorization:

Preheating (deaeration and heating oil): The oil is heated in 3 stages:

In the heat exchanger by circulating oil deodorized at 140 ° C.
In the coils installed in the preheating tank.
In the heater through a coil of circulating mineral oil whose temperature is regulated by the thermostat of the boiler.

Deodorization of the oil: The deodorizer is cylindrical vertical. In this part of the process removes all the odoriferous compounds by the effect of a vacuum which is subject to all the plant deodorization. This operation is to inject dry steam into the oil under vacuum and maintained under a high temperature ranging between 220 and 260 ° C. The oil is maintained in the deodorizer in a state of agitation during a period of approximately 2 hours.

Cooling of the oil: The oil flows continuously deodorized last deodorizer compartment to the cooling tank. This reservoir is the same as the vacuum deodorizer and live steam is injected in order to eliminate the last traces of fatty acids and odoriferous substances. After cooling, the oil out at a temperature of 65 ° C and is directed to polishing filters.

Polishing oil: This step is essential to give an oil finished bright. This filtering helps to eliminate the last traces of bleaching earth, having escaped to filters Niagara. For this, filters are used presses consisting of stacked plates separated by cellulose paper, and pressed against each other (Figure 9).

oil filtration with a filter bag

Condensation of fatty acids: Vapors from deodorizer contain more water vapor, fatty acids, of odoriferous substances and unsaponifiable. These gases must be cooled in order to condense the fatty acids and thus, at the outlet of the barometric condenser, a water with a fat content considerably. The fatty acids are liquid collected at the bottom of the separator to be taken up by the pump and back.