Pour Point blending

[bond0718]

I took a heavy end (FO grade) material with Pour Point (PP) of 30 Deg C and blended it with Light cycle oil (LCO) from FCCU having PP of 6 deg C. LCo was only 20% of the total blend.

The PP of the blend was lab tested and found to be only 6 deg C. theroetical blend cal results shows PP of 18 deg C.

I dont understand this phenomena of reduction in PP to such a huge extent.

Can anyone throw some light on this and can some body provide me with a better correlationn for PP blending

Thanks in advance

MOSCOS

 

[25362]

While the failure of heavy residual fuels to flow at the pour point (PP) is normally attributed to wax crystallization, it also can be due to effects of viscosity. Besides, PP may be influenced by the fuel's thermal history (e.g., broken wax structures).

LCOs are diluents, and as such they reduce the heavy fuel viscosity. LCOs produced in high severity modern FCC units are highly aromatic, containing two-ring naphthalene derivatives, reflected in their high density, typically between 0.94 to 0.98 g/cc @ 15^oC. I wonder whether these alkylated naphthalenes could also act as PP depressants.

BTW, it has been shown that a 1% addition of asphalt to a 50/50 blend of (hydrodesulfurized) VGO and DAO dropped the PP from +10^oC to -26^oC !

The existing procedures to predict PP are applicable to blends of distillates of the same crude, by the use of blending indices. (Refer to D.S.J.Jones: Elements of petroleum processing-Wiley).

My opinion: when residuals and/or cat-cracked products are blended, better carry out lab-bench checking to predict the final PP. To my knowledge, the degree of accuracy hasn't yet been established.

 

[Petro0707]

Are you sure about FO with 30 & LCO with 6 PP ? why am I asking this because usually, based on several experiments let us say 5 to 6 no. with diffrent blends ,specific mathematical correlation is developed & Generally speaking ,when I take FO with +12 C & LCO with -12 C ,blend PP comes around 9 C.Usually it varies on the qualities of LCO & FO.Pl. reconfirm your FO & LCO PP.

 

[25362]

Some issues to ponder:

[•] Alkylated naphthalenes are generally considered paraffin wax crystal modifiers.
[•] If I remember correctly, ASTM D 97/IP 15 includes a section on thermal effects on PP.
[•] I wonder whether thread481-154014 could be of some help.