Hydrocracking Recycle Loop HPNA Removal
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Solution Overview
Problem
The accumulation of heavy polynuclear aromatics (HPNA) in two-stage hydrocrackers leads to equipment fouling and rapid catalyst deactivation, necessitating continuous bleeding of the recycle stream, resulting in significant material loss and operational challenges.
Innovation Solution
Incorporating a non-zeolite noble metal catalyst in the recycle loop of the hydrocracking process, operated at temperatures of 650° F. (343° C.) or less, to saturate and convert HPNA, thereby preventing their concentration and deposition, which enhances catalyst life and reduces the need for bleed streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-stage hydrocracking process is used to process heavy crudes and opportunity blends, then the refinery can handle heavier feedstocks and increase flexibility, but heavy polynuclear aromatics accumulate in the recycle loop causing equipment fouling and catalyst deactivation
Solution Approach 1:
The patent introduces an intermediary adsorbent material (such as activated carbon, silica gel, or alumina) in the form of a filter or adsorption bed within the recycle loop. This intermediary selectively adsorbs heavy polynuclear aromatics from the recycle stream, preventing their accumulation and subsequent deposition on catalyst surfaces and heat exchanger surfaces, thereby extending catalyst life and maintaining reliable operation
Solution Approach 2:
The patent implements a selective removal process where heavy polynuclear aromatics are discarded from the recycle loop through adsorption or extraction. The adsorbent material captures the harmful HPNA compounds, which are then separated and discarded, while the cleaned hydrocarbon stream is recycled back to the hydrocracker, maintaining process continuity and catalyst performance
2Reliability
If the recycle stream is continuously bled to prevent HPNA accumulation, then equipment fouling and catalyst deactivation are reduced, but significant material loss occurs
Solution Approach 1:
The patent extracts only the harmful heavy polynuclear aromatic components from the recycle stream using selective adsorption or extraction processes, while returning the bulk hydrocarbon material to the recycle loop. This selective extraction approach maintains catalyst protection without the need for continuous large-scale bleeding of the entire recycle stream, significantly reducing material loss
Solution Approach 2:
The patent applies local treatment to specific portions of the recycle stream that contain concentrated HPNA, such as the liquid recycle portion, rather than treating the entire recycle flow. This localized application of adsorbent materials or extraction processes targets HPNA removal precisely where needed, minimizing unnecessary material loss while maintaining catalyst protection
3Loss of substance
If HPNA are allowed to accumulate in the recycle loop, then material loss from bleeding is reduced, but equipment fouling and catalyst deactivation occur rapidly
Solution Approach 1:
The patent converts the harmful accumulation of HPNA into a beneficial selective adsorption process. The HPNA compounds, which would normally be harmful accumulators, become the target species for selective removal by adsorbent materials. By designing the system to specifically capture these harmful compounds, the process transforms the HPNA accumulation problem into an opportunity for selective purification, preventing fouling and deactivation while minimizing material loss
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 minimizes the bleed rate of the recycle stream, reduces material loss, and extends catalyst life by inhibiting HPNA accumulation, allowing for the processing of heavier feedstocks without the need for frequent bleeding.
Implementation Method 1
reacting a hydrocarbon stream in a reactor comprising a non-zeolite noble metal catalyst at a temperature of about 650° F. (343° C.) or less
Implementation Method 2
reacting a hydrocarbon stream in a reactor comprising a non-zeolite noble metal catalyst
Data Source
AI summary
Provided is a hydrocracking process with a recycle loop for converting a petroleum feed to lower boiling products, which process comprises reacting a stream over a non-zeolite noble metal catalyst at a temperature of about 650° F. (343° C.) or less in a reactor positioned in the recycle loop of the hydrocracking reactor.