Calculating boiling points in crude oil

Evaluation methods ① Determination of the general properties of crude oil: First, moisture and salt content are measured. If the moisture content is greater than 0.5%, dehydration is required. Then, properties such as density, viscosity, freezing point, wax content, residue, sulfur content, nitrogen content, gum content, and the levels of trace metals (iron, nickel, vanadium, copper) are determined. ②The content of light hydrocarbons from C1 to C8 was determined by gas chromatography using untreated crude oil. ③Actual boiling point distillation: A distillation unit with an actual boiling point rectifier (having 15 theoretical plates) is used to distill the narrow or wide fraction at temperatures up to 400–450°C, while another vacuum distillation unit is employed to separate the high-boiling-point fraction. ④The properties of narrow-range and heavy oils were determined, and actual boiling point curves as well as property curves were plotted (see figure). ⑤Straight-run products are prepared from wide-cut fractions, and the properties of gasoline, jet fuel, kerosene for lighting, diesel, and cracking feedstock oils are determined. ⑥The monomeric hydrocarbon composition or hydrocarbon group composition of the distillate oil is analyzed by gas chromatography or mass spectrometry, while the structural group composition (percentages of carbon atoms in alkanes, cycloalkanes, and aromatics, as well as the average number of rings in cycloalkanes and aromatics) is determined using methods based on refractive index, density, and molecular weight. ⑦The potential content (maximum content) and properties of lubricating oils are determined using solvent dewaxing and adsorption separation methods. ⑧Determine the contents of saturated hydrocarbons, aromatics, resins, and asphaltenes in heavy oil. Another literature source: [Title] Extension of the distillation curve for the true boiling point of crude oil [NO.] 942624 [Type] Journal [Classification number] TE622 [Journal name] Oil Refining Design [Volume and issue index] 1993, 23(3) [Page range] 50–51 [Author] He Liangzhi [Affiliation] Sinopec Beijing Design Institute [Publication year] 1993 [Reference figure] Fig. 4 [Keywords] Crude oil, boiling point, density, molecular weight, calculation methods [Free word] Residue [Abstract] It introduces the calculation methods for apparent boiling point and apparent density, which are parameters used to determine the physical properties of heavy oils and crude oil fractions. Based on the measured data of the residue molecular weight distribution, SARA content, and hydrogen content, the arbitrariness in extending the distillation curve of crude oil at its actual boiling point has been reduced. The sum of the estimated pseudo-densities of the narrow fractions, when compared with the measured average density of the residue, showed an error of less than 1.6% for the 5 crude oils. Using these pseudo-density and ebullioscopic temperature data as fundamental parameters, equilibrium flashing data calculated via the SRK equation and the virtual component method yielded good results.