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
The process involves separating hydrotreating and hydrocracking reactors into distinct stages, removing hydrogen sulfide and ammonia from the diesel stream before hydrocracking, 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 production is improved, but sulfur content in the diesel increases
Solution Approach 1:
The process is divided into two distinct stages: a hydrotreating stage to remove sulfur and heteroatoms, followed by a hydrocracking stage to convert heavy hydrocarbons to diesel. This segmentation allows each stage to be optimized for its specific function, achieving both low sulfur content and high diesel production.
Solution Approach 2:
The hydrotreating stage is performed as a preliminary step before hydrocracking to remove sulfur and heteroatoms from the feedstock. This preliminary purification enables the subsequent hydrocracking process to operate more efficiently and produce higher quality diesel with lower sulfur content.
2Object-generated harmful factors
If additional processing steps are added to achieve ULSD, then sulfur removal is improved, but capital and operating costs increase
Solution Approach 1:
The hydrotreating and hydrocracking processes are merged into an integrated two-stage system where the hydrotreating unit removes sulfur and heteroatoms, and the hydrocracking unit converts heavy hydrocarbons to diesel. This merged approach achieves ULSD specifications while optimizing capital and operating costs through coordinated process design.
3Object-generated harmful factors
If hydrotreating and hydrocracking are performed in separate stages, then sulfur conversion is improved, but process complexity increases
Solution Approach 1:
The process is segmented into two functional units: a hydrotreating unit for sulfur and heteroatom removal, and a hydrocracking unit for hydrocarbon conversion. Each unit is designed with specific catalysts and operating conditions optimized for its function, achieving superior sulfur conversion while managing process complexity through modular design.
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 to below 10 wppm, meeting stringent ULSD requirements while minimizing additional processing costs and improving operational efficiency.
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 hydrotreating effluent stream is separated into a vaporous hydrotreating effluent stream comprising hydrogen and a liquid hydrotreating effluent stream
Implementation Method 4
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.