Hydrocracker Recycle Stream Solvent Deasphalting for Polycyclic Aromatic Removal
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Solution Overview
Problem
The hydrocracking process faces issues with the buildup of polycyclic aromatic hydrocarbons in the heavy oil recycle stream, leading to catalyst deactivation, reduced conversion yields, and equipment fouling, particularly when processing heavy and aromatic feedstocks under high severity conditions.
Innovation Solution
Integrating a solvent deasphalting unit into the hydrocracking process to separate and remove heavy poly-aromatic hydrocarbons from the heavy oil recycle stream, with the deasphalted paraffinic oil being recycled back to the hydrocracker reactor, while controlling the weight ratio of the solvent deasphalting stream to the recycle stream to maintain optimal polycyclic aromatic concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high severity hydrocracker reactor conditions are used to achieve high conversion of heavy feedstock, then conversion yield is improved, but heavy polycyclic aromatic compounds accumulate in the heavy oil recycle stream causing catalyst deactivation and equipment fouling
Solution Approach 1:
The patent extracts and removes heavy polycyclic aromatic compounds from the heavy oil recycle stream using a solvent deasphalting unit. The solvent deasphalting unit selectively separates these harmful compounds from the recycle stream, preventing their accumulation and subsequent harmful effects on catalyst and equipment while maintaining high conversion yields.
Solution Approach 2:
The patent introduces a solvent deasphalting unit as an intermediary component between the hydrocracker reactor and the fractionator. This intermediary unit processes the heavy oil recycle stream to remove polycyclic aromatics before recycling, acting as a mediator that eliminates the harmful buildup problem without interfering with the main hydrocracking conversion process.
2Productivity
If heavy oil recycle rate is increased to achieve desired conversion of heavy feedstock, then conversion is improved, but the accumulation rate of heavy polycyclic aromatics in the recycle stream increases
Solution Approach 1:
The solvent deasphalting unit continuously extracts and removes heavy polycyclic aromatic compounds from the heavy oil recycle stream. This extraction process prevents the accumulation that would otherwise occur with high recycle rates, allowing the system to maintain high conversion while controlling polycyclic aromatic concentration through selective removal.
Solution Approach 2:
The patent changes the composition parameter of the heavy oil recycle stream by removing polycyclic aromatic compounds through solvent deasphalting. This parameter change (reducing PCA concentration) allows the system to operate at high recycle rates for improved conversion without suffering from the harmful effects of polycyclic aromatic buildup.
3Object-generated harmful factors
If solvent deasphalting is integrated to remove heavy polycyclic aromatics from the heavy oil recycle stream, then polycyclic aromatic buildup is reduced, but process complexity increases
Solution Approach 1:
The patent merges the solvent deasphalting function with the existing hydrocracking process by integrating the solvent deasphalting unit into the heavy oil recycle stream configuration. This integration combines multiple functions (hydrocracking, fractionation, and solvent deasphalting) into a unified process system, reducing overall complexity compared to separate standalone units.
Solution Approach 2:
The heavy oil recycle stream serves multiple functions: it provides unconverted feedstock back to the reactor for continued conversion and simultaneously serves as the feed stream for the solvent deasphalting unit. This multi-functionality reduces the need for additional separate processing lines and simplifies the overall process configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the concentration of polycyclic aromatics in the heavy oil recycle stream, preventing catalyst deactivation and fouling, while maintaining high conversion yields and process efficiency by recycling a deasphalted paraffinic oil that is depleted of heavy polycyclic aromatic compounds.
Implementation Method 1
a second portion of the heavy oil recycle stream is passed to a solvent deasphalting unit for separating the heavy poly-aromatic hydrocarbons from the second portion of the heavy oil recycle stream
Implementation Method 2
contacting in a hydrocracking reaction vessel or zone the heavy feedstock with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield the upgraded products
Data Source
Figure 1
AI summary
An integrated hydrocracking and solvent deasphalting process that provides for removal from the heavy oil recycle stream heavy polycyclic aromatic compounds formed in the hydrocracking step and recycling the resulting deasphalted paraffinic oil as a feed to the hydrocracker reactor of the process for further conversion.