Drag Reduction of AL-Ahdab Crude Oil Using Chemical Additives

The viscosity of crude oil has a crucial role in drag reduction during pipeline transportation; hence additives are required to enhancing the flow properties of AL-Ahdab crude oil. In this work, the potato starch biopolymer and CTAB surfactant are utilized to achieve the target. The drag reduction experiments were carried out at different crude oil flow rates (20-35-50 liters/min), pipe diameters (0.5-0.75 -1 inch), and different concentrations of potato starch (500-2000 ppm) and CTAB (100-500 ppm). The results showed that these additives had minimized flow resistance in various operating conditions, the drag reduction percent increased with increasing of additives concentration increase. The maximum drag reduction achieved using CTAB and potato starch is 41.6% and 36.3%, respectively, at 50 liters/min and 1-inch pipe diameter.


Introduction
AVariety of industries, including long distance liquid transport, district heating and cooling, fire-fighting activities, irrigation systems and the petroleum maintenance and transport This work is licensed under a Creative Commons Attribution 4.0 International License.

Feedstock and Chemicals
The crude oil feedstock was obtained from East Baghdad Field. The specifications of the Iraqi crude taking from the same refinery plant labortary shown in Table (

Chemical additives
Cetyl trimethyl ammonium bromide (CTAB): Cetyl ammonium ammonium bromide is a white powder surfactant detergent that is available from the Himedia business, containing molar mass (364.45)g per mole and 99% pure.
Potato starch: The starch (C6H10.3) n. (H2O) is a biopolymer supplied with a density of (0.81) g/m3, a molar mass of CDH-fine chemical company, soluble water (33.3) mg soluble in (1) mL and purity 99 percent. Any value of molar mass, density, solubility and purity for both potato starch or CTAB are taken from the cover of the tins.

Drag Reduction Experiments
Experiments on the reduction of crude oil drag in the drag reduction unit shown in Figure   (

Reservoir tank of crude oil
The reservoir tank was made from commercial steel plate. This tank is lifted about 30 cm from the ground by steel base and supported with two, exit pipes, connected to two centrifugal pumps. The volume of the tank is 60 L.

Pumps
A centrifugal pump of stork type with constant high speed (flowrate =45 m 3 /hr.; power =25 H.P.) provided with two flanges, was used to circulate the solution from the reservoir tank through pipes. This pump was provided with a bypass from tank at a point before the entrance of solution to the testing section, in order to control the flowrate.

Valves
In order to control the amount and direction of solution flowrate through the system, eight ball valves were used. Two valves (fifth and sixth) were opened that located in the bypass to control the flow rates of crude oil entering the first testing section (0.0127 m ) pipe.
While (first, second, third and fourth) valves were kept closed that located to ensure the crude oil pass through one of the three testing sections.
In the second step .two valves (third and fourth) were opened that located in the bypass to control the flow rate of crude oil entering the second testing section (0.0191 m) pipe .while (first ,second ,fifth and sixth) valves were kept closed that located to ensure the crude oil pass through only in the pipe we need to. And so on in the other testing pipes for all runs.

Pressure measuring devices
To measure the differences of the pressure drops between two points, nine calibrated pressure gauges were used. Three pressure gauges of one bar were located at the section pipe, discharge and pump. The three pressure gauges of one bar were manufactured by (Dura gauge, AISI 316 tube, steel socket, U.S.A).

Flow meter
The volumetric flowmeter of the solution passing through the testing section was measured by using calibrated flow meter of maximum flowrate (3.6 m 3 /hr.), which is located at the end of closed system pipe prevent any disturbance in the flow.

Pipes
Three sizes of pipes used in the drag reduction unit. The inner diameter of them was 1⁄2 inch   It is clear that the two additives have a strong effect on crude oil drag, but the influence of CTAB is significant. Higher additive rates have a micelle structure within the fluid flow which can minimize turbulent flux formation. Surfactants contribute to drag reduction in turbulent pipelines. Their drag reduction capacity is due to rod-like micellular forms at low concentrations. The micelles run in a system for suppressing friction and rising viscosity, which can be higher than in other polymers. The new characteristics of tensioners are due to the selfrepair capacity [8].
When we used the biggest diameter (0.0254 m or 1 inch) there were not drop pressure in the pipe at 20 L/min because the flow was not enough to cause pressure on the pipe so this value was zero.  (8944) and (22330). The results showed that, with increased crudity oil flow, the drag reductions were increased by 39% and 34% respectively, with CTAB and potato starch being decreased by a combined drag reduction of 50 liters per min. It should be pointed out that the increase in flow rate includes an increase in turbulence within the tube and provides the drag reducer with a more effective medium. The relationship between velocity and additive-managed turbulence that is agreed with the flow rate behavior can be clarified [9].
The drag-reduction behavior has demonstrated a major effect on the characteristics of the fluid flow in the turbulent area by the addition of a small amount of polymer (20 g) or surfactants (5g). This can be considered an effective drag reduction agent, especially at relatively high levels. The wider edges of a larger pipe using a lot of central flow power triggers an increase in drag reduction. In small pipes there is another activity that abundantly holds the number of small edges formed than large edges produced in the large pipes. Some small borders required excess energy to monitor and create a pattern from the main stream. In addition, the uneven energy absorbed by the small eddies that some did not succeed in overcoming viscous resistance and instead decreased the energy loss of the central flow [10]. Where DR% : drag reduction percentage.
µ: the viscosity of the crude oil While the maximum %Dr of 39%, 40.4% and 41.6% were obtained in the pipes but having different diameters using 500 ppm CTAB. This is because surfactants have the potential to restore themselves and return to the original form after they have passed through the high shear stress areas. The polymer degrades in many applications and can therefore maintain efficiency with a very high number of Reynolds without risk of shear degradation, when subject to high shear and cannot reform, therefore the polymer is not able to be successful in recirculating method.