Mimicking the Crude Oil and Heavy Fuel Oil (HFO) Demulsification Process in Power Plants for Preparing a New Demulsifiers

Water–in–oil emulsions are a big challenge in the production and processing of crude oil due to its bad influence on the fundamental and practical aspects of industrial facilities. Researches for decades gave this phenomena a great deal in the planning to construct power plants, refineries, oil companies and other industrial facilities that uses crude oil as a raw material. In order to overcome the disadvantages and hazards of water– in–oil emulsions researchers used chemical, electrical, thermal and mechanical methods individually or in combination. The chemical method has gained the main interest due to its ease of use and economic feasibility. Demulsifiers have been used extensively to solve the problem of water in oil emulsions. The choice of using the right combination of chemicals had been reached after studying many factors such as cost and safety. This research addresses many fundamental and practical aspects regarding demulsifiers and oil demulsification aiming to find the best selection of chemicals that can be used to treat crude oil before using, refining or transporting it. The crude oil in this research had been demulsified and tested by the spectroil test method while the bottle test method had not been used to mimic the demulsification process used in power plant. The work was carried out using two types of oil, crude oil (containing 7 ppm Na and K salts concentration) and heavy fuel oil HFO (containing 12 ppm Na and K salts concentration). The crude oil No.29(12) 2020 Journal of Petroleum Research & Studies (JPRS) E166 samples were taken from Al – Hilla 2 power plant while the HFO samples were taken from South Baghdad 2 power plant. The results showed that the water miscible chemicals and chemicals with sufficient solubility that used as a demulsifiers like the acrylic derivatives gave the best demulsification when using more wash water percentage. While the combination of water miscible chemicals and chemicals with sufficient solubility and oil soluble chemicals gave the best results in treating heavy fuel oil while using less wash water percentage.


Introduction:
In order to eliminate the water in oil emulsions problem many methods have been used including electrical, chemical and thermal processes or a combination of them [14]. Thermal method involves the use of a specific temperature that is not high enough to cause a rise up in water solubility and sometimes the use of chemicals or electrostatic heat are commercially sufficient instead using a high temperatures [14]. Electrical method involves reorientation of the polar molecules and weakens the film around water droplets which lead to the disruption of surface tension of each droplet [14]. Sometimes this method applies alone in solving the emulsion problem and sometimes it requires the addition of heat or chemicals. The use of chemical methods is the most important method of treating the crude oil from emulsification problem. This method involves the breaking of the interfacial film around each droplet effectively by using a combination of chemicals and heat. The use of chemical demulsifiers was due to their high efficiency and economic success [33]. Crude oil is a complex mixture of thousands of components; these components differ in type and percentages due to age, depth and place of the oil field.
Crude oil consists mainly of carbon and hydrogen and small amounts of oxygen, nitrogen and sulfur with many metallic molecules like copper, vanadium, nickel and iron [31].
Crude oil main components are: 1-Asphaltenes: a brown to black amorphous powder which is the heaviest component in the crude oil [31]. The structure of asphaltenes is not well known yet but generally asphaltenes are non-volatile and polar fraction of crude oil, decomposes above 300 º C.
Asphaltenes are enhancing the formation and stabilization of water in oil emulsions [23].
Many studies on asphaltenes gave an average molecular weight for their molecules about 750 g/mole [15], while other studies gave a lower molecular weight value of about 400 g/mole [16]. Asphaltenes molecules are mainly aromatic base with cyclic and alkyl chains attached to it with the existence of other heteroatoms like nitrogen, oxygen and sulfur and sometimes a trace amounts of metals like nickel and vanadium [9].
2-Resins: the percentage of resins in crude oil is more than the percentage of asphaltenes but it increases with the increase of the percentage of asphaltenes and vice versa. Resins are brown to dark semi solids [13].Resins are polar and non-volatile consists mainly of carbon, nitrogen, oxygen, naphthenic acid and sulfur [32].
No.29-(12) 2020 Journal of Petroleum Research & Studies (JPRS) E168 3-Waxes: are a mixture of alkanes with a high molecular weight , alcohols with a long chain (more than C 16 ) and a long chain ester (more than C 16 ) [5]. The wax molecules can be attached with the carboxylic acids via their fatty tails and stabilize the mixture [26].
The reason for the stable combination of asphaltenes, resins, wax and solids is the crystal structure of wax.

4-Solids
: are very small particles materials consists mainly of wax crystals, clay particles and sand. These particles play a big role in stabilizing water in oil emulsions [17]. Solids 6-Oil field brine: the presence of inorganic salts like sodium chloride and calcium chloride in the crude oil has a big effect in the formation and stabilization of water in oil emulsions and size of water in oil droplets [8]. Many researchers have studied the effect of inorganic salts and pH values on the stability of water in oil emulsions and found that salt concentration has an adverse effect on water in oil emulsion stability and its effect decreased as pH increased [34] .The formation of emulsions happens if three main conditions exist: 1-Two immiscible liquids should mix with each other.

2-
The existence of a surface active material that works as the emulsifying agent.

3-Enough agitation or mixing should be present to result a dispersion of one liquid into
the other as droplets [28].
Researchers have come to a conclusion that the main reason for the stability of water in oil emulsions is the existence of a certain polar components like asphaltenes, waxes and resins which work as natural surface active agents [18]. And by studying the factors that lead to the stabilization of emulsions scientists succeeded in finding the ways to demulsify these emulsions [6].Chemical demulsification are the most important method for treating water in oil emulsions and the main types of demulsifiers according to their functional groups are polymers, polyhydric alcohols, amines and sulphonates [2]. A demulsifier should diminish the stabilization effect of the emulsifying agents exist in the water in oil emulsions [1]. Demulsifiers are surface-active components just like No.29-(12) 2020 Journal of Petroleum Research & Studies (JPRS) E169 emulsifiers and in order for the demulsifiers to work properly they should be chosen carefully through a wide range of surface-active chemicals. The good selection of the demulsifier components is vital for their efficiency, using the right quantity of the demulsifier, enough and accurate mixing, sufficient heat and sufficient retention time in separators are important factors for a good demulsification process [19].
According to [10] chemical demulsification process is the combination of three main effects: 1-The dispersion of the demulsifier into the water/oil interface and the displacement of the asphaltenic film [11,21].
2-Flocculation, which is the process of joining the small water droplets by the demulsifier and it involves the decrease in interfacial tension gradient and the thinning of the asphaltenic film around the water droplets [24].
3-Coalescence of the water droplets is happening by breaking the emulsifier film around the droplets and joining the droplets which became large enough to separate and settle out.

Aim of the Research:
Mimicking the crude oil demulsification process in power plants for preparing an efficient and economic water in oil demulsifier using a formula from a selection of chemicals and study the effect of the new formula on the Na and K salts concentration as a function of the demulsification process efficiency.

Materials and Equipments:
The chemicals used in this research are chosen according to their suitability, potency and economic feasibility and after reviewing many previous researches dealing with the water in oil demulsifiers. In this research we used the following chemicals:

E171
The main equipments used in this research was the Spectr Oil analyzer from Spectro Scientific company USA (Figure 1) beside other necessary lab equipments.

Experimental Methods:
This research was carried out using two types of oil, crude oil (containing 7 ppm of a total Na and K salts concentration ) and heavy fuel oil HFO (containing 12 ppm Na and K ( Figure 2) showed the salt concentration decreased after the treatment of crude oil (contains 7 ppm of Na and K salts) by selected demulsifiers as a function of the demulsification process that happened between water and oil using 30% wash water.
( Table 2) showed the components of demulsifier samples used in treating crude oil under test. The analysis data for the Na and K salts concentrations showed that the demulsifier combination of 20% acrylic acid, 20% di octyl amine, 20% methyl methacrylate, 20% trioctyl methyl ammonium chloride and 20% castor oil (Figure 2) gave the best result while the demulsifier combination of 40% acrylic acid, 40% butyl acrylate and 20% trioctyl methyl ammonium chloride gave the worst results ( Figure 2). Acrylic acid is miscible in water and that property helped in disperse the acid molecules in the water layer and that's why in the treatment process when using 30% wash water acrylic acid gave the best demulsification result. While adding the trioctyl methyl ammonium chloride to the

No.29-(12) 2020 Journal of Petroleum Research & Studies (JPRS)
E173 combination which is an oil soluble material somehow minimized the good results of acrylic acid and butyl acrylate alone. The combination of 40% methyl methacrylate, 40% di octyl amine and 20% castor oil also gave good results (Figure 2) mainly because the methyl methacrylate has sufficient water solubility (0.1 g / 100 mL) that led to a higher dispersion. The main components that gave the best results have either sufficient water solubility or miscibility so their active groups do not ionize to any great degree so these groups provides the hydrophilic groups that affects the demulsification process [27].
( Figure 3) showed the effect of the demulsifier concentration on the Na and K salts concentration (HFO containing 12 ppm of Na and K salts conc.) with using 30% wash water. Table ( (Table 4) using only 10% of wash water. Reducing the quantity of wash water has made a great negative influence on the separation of the water in oil emulsions.
The demulsifiers that gave good results when using 30% wash water in the demulsification process gave poor results in 10% wash water percentage and that might be because most of the used chemicals were either have a sufficient water solubility or miscibility so they gave good results when there was a big percentage of water [7].      should be made between the separated water from the bottle test method and the concentration of Na and K salts in the treated crude oil to understand exactly the relation between these two parameters.