Hydrotreating and Hydrocracking Integration for ULSD Production
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Solution Overview
Problem
Current diesel production methods face challenges in achieving ultra-low sulfur diesel (ULSD) due to high sulfur content in mild hydrocracking products and the need for additional processing steps, which increase capital and operating costs.
Innovation Solution
Separating hydrotreating and hydrocracking reactors into distinct stages, followed by fractionation to remove hydrogen sulfide and ammonia, allowing the hydrocracking reactor to operate in a cleaner environment for enhanced sulfur conversion and producing ULSD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mild hydrocracking is used to produce diesel, then diesel yield is improved, but sulfur content increases making ULSD production difficult
Solution Approach 1:
The patent divides the hydrocracking process into two distinct stages: a first hydrocracking stage that produces diesel and a second hydrocracking stage that treats the diesel stream. This segmentation allows the first stage to maximize diesel yield while the second stage specifically addresses sulfur removal, resolving the contradiction between high diesel yield and low sulfur content.
Solution Approach 2:
The first hydrocracking stage performs preliminary conversion of the hydrocarbon feed to diesel before the second stage. By pre-converting the feed in a controlled manner and then subjecting the diesel stream to additional hydrocracking with optimized conditions, the process achieves both high diesel yield and effective sulfur removal.
2Object-affected harmful factors
If additional processing steps are added to remove sulfur, then sulfur content is reduced, but capital and operating costs increase
Solution Approach 1:
The patent merges two hydrocracking functions into a single integrated process where diesel is produced and treated in sequence through two hydrocracking stages. This combines what would traditionally be separate processes (diesel production and sulfur removal) into one continuous flow, reducing the need for additional standalone processing units and associated infrastructure.
Solution Approach 2:
The second hydrocracking stage serves multiple functions: it further converts hydrocarbons to diesel and simultaneously removes sulfur from the diesel stream. This multi-functionality eliminates the need for separate dedicated sulfur removal units, reducing overall device complexity while achieving ULSD specifications.
3Device complexity
If hydrocracking operates in traditional configuration, then process simplicity is maintained, but sulfur conversion is insufficient for ULSD
Solution Approach 1:
The patent segments the hydrocracking process into two distinct stages with different optimization goals. The first stage focuses on diesel production while the second stage is optimized for sulfur removal. This segmentation allows each stage to operate under conditions best suited for its specific function, achieving ULSD levels without excessive complexity.
Solution Approach 2:
The patent applies different operating conditions and catalyst configurations to different stages of the process. The second hydrocracking stage uses conditions specifically tailored for sulfur conversion (such as higher hydrogen partial pressure and specific catalyst composition) while the first stage uses conditions optimized for diesel yield, creating local quality variations that maximize overall performance.
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 reduces sulfur levels in diesel, enabling the production of ULSD while minimizing additional processing requirements and associated costs.
Implementation Method 1
Hydrotreating refers to a process in which olefins and aromatics are saturated and heteroatoms, such as sulfur, nitrogen and metals are removed from the hydrocarbon feedstock over catalyst in the presence of hydrogen
Implementation Method 2
The hydrotreating effluent stream is separated into a vaporous hydrotreating effluent stream comprising hydrogen and a liquid hydrotreating effluent stream
Implementation Method 3
The liquid hydrotreating effluent stream is fractionated to provide a diesel stream
Implementation Method 4
Hydrocracking refers to a process in which hydrocarbons crack in the presence of hydrogen and catalyst to lower molecular weight hydrocarbons
Data Source
AI summary
A process and apparatus are disclosed for hydrotreating a hydrocarbon feed in a hydrotreating unit and hydrocracking a second hydrocarbon stream in a hydrocracking unit. The hydrocracking unit and the hydrotreating unit may share the same recycle gas compressor. A make-up hydrogen stream may also be compressed in the recycle gas compressor. A hydrocracking separator separates recycle gas and hydrocarbons from the hydrocracking unit to be processed with effluent from the hydrotreating unit.