Aromatic Solvent Injection for HPNA Suppression in Hydrocracking

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Solution Overview

Problem

In hydrocracking processes, heavy polynuclear aromatic compounds (HPNA) precipitate and accumulate in refining equipment, leading to fouling and costly treatment processes, as well as downtime due to their limited solubility and tendency to form deposits when thermodynamic conditions change.

Innovation Solution

The introduction of an aromatic solvent, derived from aromatic bottoms, into the hydrocracking effluent to suppress the precipitation of HPNA compounds, utilizing solvents rich in heavy alkyl aromatic compounds and multi-ring aromatic compounds with a Hildebrand solubility parameter of at least 18 MPa1/2, which increases the solubility and prevents deposition in downstream processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If hydrocracking is performed at elevated temperature and pressure, then hydrocarbon feedstock is split into lighter compounds with higher economic value, but heavy polynuclear aromatic compounds form and precipitate downstream causing fouling

Engineering Contradiction:

Improveproduction of lighter hydrocarbon compoundsVSAvoidHPNA precipitation and deposition

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

An aromatic solvent stream is introduced as an intermediary substance between the hydrocracking reactor and downstream equipment. This solvent acts as a mediator that maintains HPNA solubility in the effluent stream, preventing precipitation and deposition on equipment surfaces while allowing the hydrocracking process to proceed at elevated temperatures and pressures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The chemical composition parameters of the effluent stream are modified by adding an aromatic solvent. This changes the solubility characteristics of HPNA compounds in the stream, allowing them to remain dissolved under downstream conditions where they would otherwise precipitate and cause fouling.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If HPNA compounds are removed through adsorption, hydrogenation, extraction, vacuum distillation, solvent-deasphalting, or purging, then HPNA build-up is reduced, but significant treatment costs are incurred

Engineering Contradiction:

Improvereduction of HPNA build-upVSAvoidtreatment costs

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The aromatic solvent system enables the process to handle HPNA compounds without requiring external treatment facilities. The solvent continuously suppresses HPNA precipitation throughout the process, allowing the system to manage its own byproducts without additional energy-intensive treatment steps.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Instead of treating HPNA compounds as harmful byproducts requiring expensive removal, the aromatic solvent converts the HPNA precipitation problem into a manageable solubility issue. The HPNA compounds remain in solution and can be handled more economically, transforming a harmful effect into a controllable process parameter.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Quantity of substance

If HPNA compounds precipitate downstream when thermodynamic conditions change, then they accumulate in the recycle system, but equipment fouling and cleaning interruptions occur

Engineering Contradiction:

ImproveHPNA accumulation in recycle systemVSAvoiddowntime for cleaning and process interruption

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The aromatic solvent is introduced before HPNA precipitation can occur downstream. This preliminary action of adding the solvent to the effluent stream prevents the precipitation process from starting, thereby avoiding subsequent accumulation, fouling, and the need for cleaning interruptions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The aromatic solvent provides a protective cushioning effect by maintaining HPNA solubility throughout the process. This preemptive measure cushions against the thermodynamic conditions that would otherwise cause precipitation, protecting downstream equipment from fouling and eliminating unplanned downtime.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 minimizes costly HPNA treatment processes, reduces downtime, and increases overall distillate yield by maintaining HPNA compounds in solution, thereby improving process efficiency and preventing equipment fouling.

Implementation Method 1

introducing an aromatic solvent that is derived from aromatic bottoms to the hydrocracked effluent to produce a HPNA-suppressed effluent

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentUS11066610B2Systems and processes for suppressing heavy polynuclear aromatic deposition in a hydrocracking process

Publication Date: 2021.07.20 SAUDI ARABIAN OIL CO

AI summary

The disclosure describes refinery processes and process units for suppressing the precipitation and deposition of heavy polynuclear aromatic (HPNA) compounds in a process unit of a refinery, by combining the effluent from a hydrocracking unit with an aromatic solvent stream. Certain costly HPNA treatment processes can be eliminated, downtime can be reduced, and overall distillate yield can be increased by suppressing HPNA precipitation. The aromatic bottoms—which are suitable solvents for this purpose—of an aromatic recovery complex can be used in certain embodiments to dissolve HPNAs and suppress HPNA precipitation.