Dynamic Determination of Asphaltene Aggregate Size Distribution in Shear Induced Organic Solvents

Abstract

A population balance model was developed to determine the evolution of crude oil asphaltene aggregate size distribution. The model predictions have good accuracy in comparison with experimental results that were obtained by the image processing method. The fractal nature of asphaltene aggregates was attended assuming fractal dimension equal 1.6. Effects of shear rate, solvent composition, and initial particle size were studied on the evolution of number average diameter. The average diameter of particles reaches a maximum value and then declines to a steady state size. Shear rate and initial average diameter affect the maximum diameter and its time, but initial size has no effect on the steady state size. The combination of the image processing method and fractal approach determines the asphaltene solid content of samples. Asphaltene was extracted from Iranian heavy crude petroleum using toluene and normal heptane.

Influence of Temperature on Aggregation and Stability of Asphaltenes. I. Perikinetic Aggregation

“…The collision efficiency is the number of successful collisions to the total number of collisions. The collision efficiency was set to a constant value of unity in the most previous studies on asphaltene aggregation. ,,,,, This assumption was based on this fact that the porous and irregular agglomerates collide each other more than nonporous and rigid particles. Besides this simplified approach, a few numbers of other researchers endeavored to improve the accuracy of their proposed models by applying the collision efficiency. ,, The collision frequency, β i , j , represents all collisions between two particles with sizes V i and V j and a number of presented expressions for it in the literature are shown in Table .…”

“…The main process of enlargement of asphaltene particles is aggregation in which the fine particles collide with each other and stick together and constitute larger particles. In the breakage process, the fragile particles are broken down into smaller parts due to shear stress which could be ignored in a motionless system. , Population balance modeling is a successful method which has been applied by many researchers during the last three decades to forestall the variation of particle size distribution over time in particulate suspensions. ,− …”

“…The evolution of asphaltene particles in a mixture of asphaltene, toluene, and heptane was investigated by Solaimany-Nazar and Rahimi using an image analyzing technique. They concluded that the maximum diameter is significantly affected by shear rate and initial average diameter of asphaltene aggregates whereas the initial particle size does not have any effect on the steady state size. ,, Additionally, the authors indicated that the fractal dimension of asphaltene particles is exponentially increased from 1.6 to 2.3 during the enlargement of particles . Khoshandam and Alamdari developed a population balance model considering the growth and aggregation mechanisms and using supersaturation as driving force.…”

Evolution of tar ball aggregates in Caspian Sea: Implications of connectionist tools linked with image analysis

“…This paper introduces a new insight into the size distribution of tar ball aggregates in the presence of a poloxamine copolymer in a solution containing organic solvent where a smart technique (e.g., ANN) is employed. Prior to this study, Solaymani‐Nazar and Rahimi used a population balance model to predict the asphaltene aggregate size distribution in a shear induced organic solvent . Rahmani et al .…”

“…As the aggregates grow, the possibility of the particles fragmentation will increase due to the interfacial/surface tension in a shear induced solution. Lastly, the size of the particles reaches a steady‐state extent and the fragmentation rate would be approximately equal to the aggregation rate or they might be comparable .…”