Hydrocracking Process HPNA Reduction via Upstream Stripper Column
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Solution Overview
Problem
Hydrocracking processes face challenges in reducing the concentration of heavy polycyclic aromatic compounds (HPNA) in recycle loops, leading to catalyst deactivation and operational issues, as existing methods either result in yield losses or high costs.
Innovation Solution
A process that uncouples the HPNA purge and unconverted product separation steps, using a separation column upstream of the fractionation section to treat the heavy effluent from the high pressure hot separator, allowing independent optimization of operating conditions for each step, thereby reducing HPNA accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If HPNA compounds are eliminated from the recycled fraction by means of an adsorbent or hydrogenation, then HPNA concentration is reduced, but device complexity and operating costs increase
Solution Approach 1:
The invention extracts HPNA compounds from the recycled fraction by separating the heavy effluent into a light fraction and a heavy fraction, where HPNAs concentrate in the heavy fraction. This heavy fraction is then purged from the system, effectively removing HPNAs without requiring complex adsorbent beds or hydrogenation units.
Solution Approach 2:
The fractionation column performs multiple functions: it separates unconverted products for recycling, removes HPNA compounds through purging, and produces a light fraction for further processing. This multi-functionality eliminates the need for separate dedicated HPNA removal units.
2Quantity of substance
If heavy fraction is withdrawn and recycled to reduce HPNA concentration, then HPNA accumulation is reduced, but yield losses and hydrogen costs increase
Solution Approach 1:
The heavy effluent is segmented into a light fraction and a heavy fraction based on boiling point ranges. The light fraction (boiling below 380°C) contains valuable unconverted products that are recycled, while the heavy fraction (boiling above 380°C) contains concentrated HPNAs that are purged. This segmentation maximizes yield while effectively removing HPNAs.
3Quantity of substance
If purge stream and recycle stream are separated into different streams, then HPNA removal efficiency is improved, but device complexity increases
Solution Approach 1:
The fractionation column serves as a multi-functional unit that simultaneously creates the purge stream (heavy fraction) and the recycle stream (light fraction) from the heavy effluent. This single column performs what would otherwise require multiple separate separation units, maintaining HPNA removal efficiency while minimizing added complexity.
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 significantly reduces HPNA concentration in the recycling loop, extending catalyst cycle time and service life while maintaining operational efficiency.
Implementation Method 1
a step d) for separation of at least one heavy effluent fraction 9a obtained from step b) or optionally from step b'), carried out in a separation column 20 selected from a stripper or a reboiler column
Implementation Method 2
a) a step a) for hydrocracking said feed 1, at a temperature of more than 200° C., a pressure of more than 1 MPa, a space velocity in the range 0.1 to 20 h−1
Implementation Method 3
b) a step b) for separating the effluent obtained from the hydrocracking step a) carried out in a hot separation zone comprising a high pressure hot separator
Data Source
AI summary
In the hydrocracking process in accordance with the invention, which comprises a hydrocracking section, a high pressure hot separator and a fractionation section, upstream of the fractionation section, a stripper or reboiler column type separation column is added which treats at least a portion of the heavy effluent obtained from the high pressure hot separator. All or a portion of the bottom fraction from said column, which is rich in polynuclear aromatic compounds, is purged. At least a portion of the bottom fraction obtained from the fractionation section, which is constituted by unconverted products, is recycled to the reaction section.