Hydrocracking Unconverted Oil Segmentation for HPNA Management
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Solution Overview
Problem
The integration of hydrocracking (HC) and solvent deasphalting (SDA) units in refineries faces challenges with the formation of heavy poly-nuclear aromatics (HPNAs), leading to reduced catalyst lifecycle and conversion efficiency, as HPNAs cause fouling and coking, necessitating effective management strategies.
Innovation Solution
Implementing a process that includes recycling unconverted oil streams through a carbon-bed adsorption technology and rerouting a portion of the unconverted oil purge as a feed component to the SDA zone, allowing for selective HPNA rejection and enhanced hydrocarbon fuel production, while separating UCO into light and heavy streams for targeted recycling and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If unconverted oil is recycled back to the hydrocracking unit, then conversion efficiency is improved, but HPNA accumulation causes catalyst coking and fouling
Solution Approach 1:
The patent segments the unconverted oil stream into two fractions: a light fraction (UCO) and a heavy fraction (HPNA-rich stream). This segmentation allows the light fraction to be recycled for maintaining conversion efficiency while the heavy fraction is directed to the SDA unit for HPNA removal, thus resolving the contradiction between productivity and harmful factor accumulation.
Solution Approach 2:
The patent extracts HPNAs from the unconverted oil stream using the SDA unit with a selective solvent system. This extraction removes the harmful HPNA component while preserving the valuable light UCO fraction for recycling, thereby maintaining conversion efficiency while eliminating the harmful accumulation effect.
2Object-generated harmful factors
If a steam stripper or wiped film evaporator is used for HPNA rejection, then HPNA removal is improved, but device complexity and operational challenges increase
Solution Approach 1:
The patent employs a solvent deasphalting unit that performs multiple functions: it removes HPNAs from the heavy fraction, separates the light UCO fraction for recycling, and provides a flexible operational platform that can adapt to different feed conditions. This multi-functionality reduces the need for separate dedicated HPNA removal equipment, thereby reducing device complexity while maintaining effective HPNA removal.
Solution Approach 2:
The patent utilizes parameter changes in the solvent system (temperature, pressure, solvent-to-feed ratio) to optimize HPNA removal efficiency. By adjusting these parameters, the SDA unit can effectively remove HPNAs without requiring complex additional equipment, thus resolving the contradiction between harmful factor removal and device complexity.
3Reliability
If catalyst cycle length is reduced to manage HPNAs, then catalyst performance is maintained, but productivity and conversion are lowered
Solution Approach 1:
The patent applies preliminary action by removing HPNAs from the unconverted oil stream before it is recycled back to the hydrocracking unit. This preliminary HPNA removal prevents catalyst coking and fouling from occurring in the first place, allowing the catalyst to maintain its performance over extended cycle lengths without sacrificing productivity or conversion efficiency.
Solution Approach 2:
The SDA unit acts as an intermediary between the hydrocracking unit and the recycled UCO stream. It mediates the conflict between catalyst performance and productivity by selectively removing HPNAs while preserving the light UCO fraction for recycling, thus enabling both extended catalyst cycle life and maintained conversion efficiency.
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 maximizes fuel production, lengthens catalyst cycle life, and increases conversion efficiency by effectively managing HPNAs, reducing off-plot UCO purge requirements, and enhancing extraction efficiency in the SDA zone.
Implementation Method 1
recycling at least a portion of an unconverted oil stream from the hydroprocessing fractionation zone, and sending one part of the at least a portion of the recycled unconverted oil stream to the unconverted oil fractionation zone
Implementation Method 2
the SDA unit extracts deasphalted oil (DAO) from the resid feed
Implementation Method 3
a hydrocracking (HC) unit integrated with a solvent deasphalting (SDA) unit has been considered as a viable and cost-effective option for resid upgrading
Implementation Method 4
providing a hydrocarbon feed to the hydrotreating zone, in turn providing an effluent to a hydrocracking zone
Data Source
AI summary
One exemplary embodiment can be a process for producing a diesel fuel. The process can include providing a hydrocarbon feed to a residue processing unit. Generally, the residue processing unit includes a solvent deasphalting zone, a hydroprocessing zone, and a hydroprocessing fractionation zone. The process can further include recycling at least a portion of an unconverted oil stream from the hydroprocessing fractionation zone, and sending one part of the at least a portion of the recycled unconverted oil stream to the unconverted oil fractionation zone providing a light unconverted oil stream downstream of the solvent deasphalting zone and a heavy unconverted oil stream to the solvent deasphalting zone.