11. Calculation
11.1 Calculate the mass % of each distillate fraction and the residue to the 0.1 mass %, using Eq 1.
mass % = 100(m/M)
where:
m = mass of fraction or residue, g, and
M = mass of dry crude oil charged, g.
11.1.1 The first fraction is the gas fraction collected in the balloon. If this fraction is less than 0.1 mass %, it can be ignored.
11.1.2 The second fraction (or first, if no gas is collected) is the condensate in the dry ice trap. With density at 15°C calculated from the gas chromatographic data on a fixed gas free basis, its volume can be computed.
11.1.3 The holdup is treated either as a separate cut or added to the residue fraction, in accordance with agreement. The amount of holdup is determined by actual recovery by solvent washing, as directed in 10.5.8, or estimated from Fig. 4.
11.2 Calculate the percent loss to the nearest 0.1 mass %, using Eq 2.
The weight loss as calculated above must not be greater than 0.4 %, otherwise the distillation must be discarded. Losses less than this should be allocated two thirds to the trap cut and one third to the first naphtha cut. Where there is no trap cut, the acceptable losses are to be normalized among all cuts.
11.3 Calculate the volume of the sample of crude oil in millilitres at 15°C, using Eq 3.
V = (M/D)
where:
D = density of charge at 15°C, g/mL,
M = mass of dry charge, g, and
V = volume of charge, mL.
11.4 Calculate the volume of each fraction and of the residue in millilitres at 15°C, using Eq 4.
v = m/d
where:
d = density of the fraction or residue at 15°C, g/mL,
m = mass of fraction or residue corrected for loss, g, and
v = volume of fraction, mL.
11.5 Calculate the volume % of each distillate fraction to the nearest 0.1 volume %, using Eq 5.
vol % = 100(v/V)
11.6 Calculate the volume % gain or loss to the nearest 0.1 volume %, using Eq 6.
Usually, the above expression is negative due to volume expansion. Normalize any apparent expansion or contraction among fractions boiling below 150°C in proportion to their yields.
NOTE 6 - In view of the foregoing rules for establishing yields, the ratio of mass to volume is not precise enough to be used to calculate the density of any distillate fractions or residue.