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Experimental investigation of constant and concentration-dependent diffusivity of a hydrocarbon solvents-heavy oil system: A comparative study

Nasirahmadi, E ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1080/15567030903581494
  3. Abstract:
  4. This work is concerned with the experimental investigation of mass transfer, which occurs during diffusion of hydrocarbon solvents in heavy oil based on constant and concentration-dependent diffusion coefficient. Here, a series of free fall diffusion experiments have been conducted in sealed test tubes at fixed temperatures. Pentane, hexane, and octane were used as solvents and were placed on heavy oil in tubes. The diffusivity of heavy oil into solvents was monitored by a digital camera. The image analysis technique was applied to extract concentration profiles in diffusion zones of solvents by means of calibration curves. Fick's second law was used to obtain both constant and concentration-dependent diffusion coefficient. The measured diffusion coefficients are in agreement with the data reported in the literature for different heavy oils. The results show that the diffusion coefficient experiences an increasing trend with oil concentration till it reaches its maximum and then tails off to a constant value. The observed maximum happens around 0.12 for pentane and around 0.05 for both hexane and octane. Moreover, all transient concentration profiles as a function of x/√t lie on a unique line. For all solvents, it has been found that the average values of measured concentration-dependent diffusion coefficients were smaller than that of constant diffusion coefficients. The results of this work illustrate that constant diffusion coefficient assumption overestimated the total mass transfer; therefore, it may lead to unrealistic predictions of solvent penetration in solvent-based enhanced oil recovery processes
  5. Keywords:
  6. Diffusion coefficient ; Fick's law ; Heavy oil ; Mass transfer ; Average values ; Calibration curves ; Comparative studies ; Concentration profiles ; Concentration-dependent ; Concentration-dependent diffusion ; Diffusion Coefficients ; Diffusion experiments ; Diffusion zones ; Enhanced oil recovery ; Experimental investigations ; Fick's Law ; Fick's second law ; Fixed temperature ; Free fall ; Heavy oil ; hydrocarbon solvent ; Hydrocarbon solvents ; Image analysis techniques ; Oil concentration ; Oil system ; Solvent based ; Test tube ; Transient concentration ; Concentration (process) ; Enhanced recovery ; Heavy oil production ; Hexane ; Mass transfer ; Organic compounds ; Paraffins ; Solvents ; Tubes (components) ; Diffusion
  7. Source: Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 34, Issue 3 , 2011 , Pages 235-245 ; 15567036 (ISSN)
  8. URL: http://www.tandfonline.com/doi/abs/10.1080/15567030903581494