Split Flow Hydrocracking for Heavy Feedstock Conversion
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Solution Overview
Problem
Refineries face challenges in processing heavy, high-sulfur, and high-nitrogen feedstocks to produce desirable distillate products due to increasing environmental regulations and declining market demands, leading to margin pressures and potential unit shutdowns, with existing hydrocracking processes struggling to efficiently convert these feeds into premium grade clean fuels.
Innovation Solution
A split flow hydrocracking process that divides a gas oil stream into portions, mixes them with hydrogen, and contacts them with multiple hydroconversion catalysts in separate reaction systems to achieve high conversion rates of hydrocarbons into distillate hydrocarbons, allowing for concurrent fractionation and recovery of various hydrocarbon fractions, including diesel and base oils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single hydrocracker unit processes heavy feedstocks, then conversion capacity is limited, but processing efficiency and product quality deteriorate due to excessive reaction severity requirements
Solution Approach 1:
The hydrocracking process is divided into multiple reaction systems (first, second, and third hydrocracker reaction systems) that process different portions of the gas oil stream separately. Each reactor operates at optimized reaction severity for its specific feed portion, avoiding the need to operate a single reactor at excessively severe conditions that would compromise product quality.
2Adaptability or versatility
If multiple separate hydrocracker units are built to process different feedstocks, then processing flexibility improves, but device complexity and investment cost increase
Solution Approach 1:
Multiple reaction systems are merged into a single integrated hydrocracking unit with common feed preparation and product separation systems. The first and third hydrocracker reaction systems process different portions of the gas oil stream in parallel, while sharing common hydrogen supply and effluent handling infrastructure, thereby achieving processing flexibility without requiring completely separate units.
Solution Approach 2:
The hydrocracking unit is designed to process multiple types of gas oil feedstocks (vacuum gas oil, coker gas oil, FCC gas oil) through the same integrated system by adjusting the split ratio and operating conditions of the parallel reaction systems, eliminating the need for dedicated units for each feedstock type.
3Productivity
If reaction severity is increased to improve conversion of heavy feedstocks, then productivity increases, but catalyst life and selectivity deteriorate
Solution Approach 1:
The gas oil stream is divided into portions that are processed in separate reaction systems with different reaction severity levels. The first hydrocracker reaction system operates at moderate severity to protect catalyst life, while the second system processes heavier portions at higher severity to achieve overall high conversion, thereby balancing productivity with catalyst durability.
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 process enhances the production of high-value distillate products, such as ultra-low sulfur diesel, while providing flexibility to adjust to seasonal demands and producing premium grade clean fuels, thereby improving refinery margins and reducing the need for separate hydrocracker units.
Implementation Method 1
contacting the mixed gas oil stream and hydrogen with a first hydroconversion catalyst in a first hydrocracker reaction system to convert at least a portion of the hydrocarbons in the mixed gas oil stream to distillate hydrocarbons
Implementation Method 2
contacting the mixed gas oil stream and hydrogen with a first hydroconversion catalyst
Implementation Method 3
fractionating the effluent from the first hydrocracker reaction system into one or more hydrocarbon fractions including a fraction comprising the unconverted hydrocarbons
Data Source
AI summary
Embodiments herein relate to a process flow scheme for the processing of gas oils and especially reactive gas oils produced by thermal cracking of residua using a split flow concept. The split flow concepts disclosed allow optimization of the hydrocracking reactor severities and thereby take advantage of the different reactivities of thermally cracked gas oils versus those of virgin gas oils. This results in a lower cost facility for producing base oils as well as diesel, kerosene and gasoline fuels while achieving high conversions and high catalyst lives.