Hydrocracking HPNA Removal via Adsorbent Bed Segmentation
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Solution Overview
Problem
Heavy polynuclear aromatic (HPNA) compounds accumulate in hydrocracking units, leading to catalyst deactivation and handling challenges due to lack of suitable outlets and increased storage and transportation costs, as existing methods like bleeding unconverted oil or carbon bed absorption are economically and logistically undesirable.
Innovation Solution
A process and apparatus utilizing multiple adsorbent beds in series with adjustable space velocity, where the flow is directed through specific beds based on measured HPNA concentrations, allowing for controlled HPNA concentration adjustment in the unconverted oil stream, using control valves to manage the adsorption process and prevent catalyst deactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If unconverted oil is recycled to increase distillate yield, then productivity is improved, but HPNA compounds accumulate leading to catalyst deactivation
Solution Approach 1:
The patent extracts HPNA compounds from the recycled oil stream using an adsorption unit with multiple adsorbent beds. The adsorbent selectively removes HPNA compounds from the liquid recycle stream, preventing their accumulation and subsequent deposition on the catalyst, thereby maintaining catalyst performance while allowing continuous recycling of unconverted oil to maximize distillate yield.
2Object-affected harmful factors
If carbon bed absorption is used to remove HPNAs, then HPNA concentration is reduced, but disposal becomes problematic without fuel oil system or FCC unit
Solution Approach 1:
The patent controls the HPNA concentration in the recycled oil by adjusting operational parameters of the adsorption unit, specifically the space velocity and adsorbent bed configuration. By maintaining HPNA concentration below a threshold level (e.g., less than 100 ppm), the recycled oil can be directly reused without requiring external disposal facilities such as fuel oil systems or FCC units, thereby improving adaptability.
3Reliability
If multiple adsorbent beds are used to control HPNA concentration, then catalyst deactivation is reduced, but device complexity increases
Solution Approach 1:
The patent divides the adsorption system into multiple independent adsorbent beds arranged in series. Each bed contains adsorbent material and is equipped with control valves to regulate flow distribution. This segmentation allows the system to achieve superior HPNA removal performance and extended catalyst cycle length while maintaining operational simplicity through modular design and automated flow control.
4Object-affected harmful factors
If HPNA concentrated stream is produced, then HPNA removal efficiency is improved, but storage and transportation costs increase due to temperature control requirements
Solution Approach 1:
Instead of completely removing all HPNA compounds to produce a highly concentrated stream requiring expensive temperature-controlled storage and transportation, the patent applies partial action by removing HPNAs only to the extent necessary to prevent catalyst deactivation (maintaining concentration below a threshold). This approach achieves sufficient HPNA removal efficiency while avoiding the energy losses associated with handling highly concentrated HPNA streams.
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 maintains HPNA concentrations within a specified range, reducing catalyst deactivation and enabling safe handling and storage of the unconverted oil stream, thereby minimizing costs and environmental concerns.
Implementation Method 1
adsorbing HPNAs from the stripped stream to provide an adsorbed stream with an HPNA concentration
Data Source
AI summary
One exemplary embodiment can be a process for treating a hydrocracking fraction. The process can include obtaining a bottom stream from a fractionation column, stripping HPNAs from the bottoms stream and adsorbing HPNAs from the stripped stream to provide an adsorbed stream that can meet a desired HPNA concentration specification. The adsorption step can be adjusted to achieve an adjusted HPNA concentration.