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Volume :23 Issue : 2 1996      Add To Cart                                                                    Download

A simple approach for the estimation of the mass transfer coefficients and diffusion coefficients of vanadium in Kuwait crude oils: an elution study

Auther : WALID S. BOUHAMRA, JOHNSON MATHEW1 AND FATMA H. JASSEM2

 

1Chemical Engineering Department, Kuwait University, P. O. Box 5969 13060 Safat, Kuwait, z Petroleum Technology 2Department, Kuwait Institute of Scientific Research, P. O. Box 24885, Safat 13109, Kuwait.

ABSTRACT

One of the major concerns following the Iraqi invasion is the possibility of ground water contamination due to massive oil spillage. Nickel and vanadium are the major metals which exist in trace amounts in crude oils. The leaching of vanadium was studied on a laboratory scale using four different crude oils. Kuwait export (KE), Burgan (B), Ratawi (R) and Weathered (W). Nitric, sulphuric and acetic acids (pH 4 and 6) were the leaching medium. The role of a polar medium like de-ionized water was also checked. In the case of an acid medium, the rate of leaching was found to be significantly dependent on the type of crude and the pH value of the leaching medium.

The values for the mass transfer coefficient of vanadium are in the range 0.04-6.4 × 10-3 cm3 min-1. The diffusion coefficient values for vanadium are in the range 0.06-45.4 × 10-7 cm2 day-1. An overall study of these values suggests that nitric acid is the most effective leachant for vanadium in the four crude oils. The values for the mass transfer coefficient and diffusion coefficient using de-ionized water as the eluent stresses the importance of hydrogen ion concentration in elution studies. Time for 10% leaching vanadium in the oils is estimated. A novel feature stemming from this study is the values for the rate for 10% leaching. The time required for the leaching of 10% of vanadium ranged between 4-54.6 × 10 years.

An analysis of variance (ANOVA) of different experimental parameters is presented. The confidence interval for the concentration of vanadium was estimated. Parameters such as the type of acid, pH value of the acid and the type of crude were considered. The ANOVA tests indicated that the leaching ability of the acids varied with the type of crude. The tests showed that there exists a relationship between the initial pH value of the acid and the metal concentra­tion. Better leaching results were obtained with acids having pH 4.


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