Hydrotreating Hydrocracking Diesel Sulfur Removal
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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 diesel from mild hydrocracking reactors, which requires additional processing steps, increasing capital and operating costs.
Innovation Solution
Separating hydrotreating and hydrocracking reactors into distinct stages, with hydrotreating 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
1Ease of manufacture
If hydrotreating and hydrocracking are combined in a single reactor, then capital costs are reduced, but sulfur removal efficiency deteriorates and additional processing steps are required
Solution Approach 1:
The process separates hydrotreating and hydrocracking into distinct reactor stages. The first stage performs hydrotreating to remove sulfur and nitrogen, while the second stage performs hydrocracking to produce diesel. This segmentation allows each reactor to be optimized for its specific function, achieving both cost efficiency and high sulfur removal efficiency without requiring additional processing steps.
2Productivity
If mild hydrocracking is used to improve FCC feed quality, then gasoline yield is maintained, but sulfur content in diesel increases requiring additional processing
Solution Approach 1:
The process performs preliminary hydrotreating in the first reactor stage to remove sulfur and nitrogen from the feed before it enters the hydrocracking stage. This preliminary action ensures that when diesel is produced in the second stage, it already has low sulfur content, eliminating the need for additional sulfur removal processing while maintaining gasoline yield through mild hydrocracking.
3Productivity
If partial or full conversion hydrocracking is used to produce diesel, then diesel yield increases, but unconverted oil for downstream units decreases
Solution Approach 1:
The two-stage reactor system segments the conversion process to optimize both diesel production and unconverted oil yield. The first stage performs mild hydrotreating with minimal cracking, preserving most of the feed as unconverted oil for downstream FCC units. The second stage then performs controlled hydrocracking on this pre-treated feed to maximize diesel yield from the remaining material, achieving both objectives simultaneously.
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
Hydrocracking refers to a process in which hydrocarbons crack in the presence of hydrogen and catalyst to lower molecular weight hydrocarbons
Implementation Method 3
The liquid hydrotreating effluent stream is fractionated to provide a diesel stream
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. The second hydrocarbon stream may be a diesel stream from the hydrotreating unit. The diesel stream may be a diesel and heavier stream from a bottom of a hydrotreating fractionation column.