0.8 Mt/a solvent de-asphalting unit
Location: Shandong Provice, China
Start-up time: August 2015
Subcritical extraction process and super critical stripping process were adopted in this unit where the solvent consisted of mixture of propane and butane. After heavy oil, such as offshore oil, was fed into atmospheric and vacuum distillation unit to get diesel and wax oil fraction, the rest of fraction, VR, was sent to solvent deasphalting unit. The characteristics of feed were unstable, high colloid-content and high viscosity, which led to adhension and block. After comparing with some vendors, client finally asked ZEHUA to design internals of this project.
Two design key points should be considered as following. The first one is that there should be supplied specified channels above feed inlet for coalescence of asphaltene and colloid from feed, then to make them settled into bottom of column. Secondly, prevent continuous phase backmixing in section of reverse flow of two phases.
Based on above two key points, the following proposal was supplied with ZEHUA’s know-how for extraction technology.
(1) SP-D series packing was adopted in order to supply channels for coalescence of asphatene and colloid above feed inlet.
(2) Redistributors were adopted and optimized in order to eliminate vertical backmixing, adhension and block.
(3) Inlet distributor was adopted to reduce disorderly flow and improve initial distribution of continuous phase and dispersion phase.
Products were able to meet requirements since unit ran in Aug. 2015. DOA and DAO were cut clearly. Carbon residue of DAO, was less than 3, could meet feed requirements of downstream unit, hydrocracking unit.
This solvent deasphalting unit was the first unit to get DAO product as a feed to hydrocracking by extracting VR from atmospheric and vacuum distillation unit of processing heavy oil, which unit also got gasoline, diesel and wax oil. It was a bond unit between atmospheric and vacuum distillation unit and hydrocracking unit. It was so meaningful that the unit successfully ran.