Effect of Heating Rate on Latent Heat of Fusion of Waxy Crystals in Crude Oil

Crude-oil transportation requires a study of the latent heat of phase transitions and the melting parameters of solid paraffin in the oil. The latent heat of fusion and the effect of the heating rate on melting were measured for Daqing oilfield waxy oil using differential scanning calorimetry. The peak melting ranges of the waxes were determined. The results showed that the total latent heats at heating rate 5°C/min from —20°C to the end of melting were 3035 and 39.26 J/g for two crude-oil samples. The latent heat maximum temperatures were 24.5 and 25.5°C The maximum latent heat for both samples was attained at heating rate 1°C/min. The relative deviation for the other heating rates was less than 3%. It was shown that the heating rate affected the position of the latent heat peak. The peak temperature shifted from 24 to 28°C for one sample and from 25.5 to 28.0°C for the other as the heating rate increased from I to 15°C/min. The results of the present work could be useful for further research on the paraffin precipitation mechanism during transportation of crude oil.