Hydrotreating Unit Integration for ULSD Diesel Production
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Solution Overview
Problem
Current hydrocracking processes produce diesel with high sulfur content, requiring additional hydrotreating steps to meet stringent ultra-low sulfur diesel (ULSD) standards, and there is a need for improved methods to bias diesel production over gasoline while ensuring environmental regulations are met.
Innovation Solution
A hydrotreating unit is integrated to treat hydrocracked vapors at the overhead of a hydrocracking separator, with a dedicated hydrotreating stripper producing ULSD without further fractionation, and the hydrocracked liquid is stripped and fractionated to produce a diesel stream that may be hydrotreated for ULSD compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mild hydrocracking is used to bias diesel production, then diesel yield is improved, but sulfur content in diesel increases making ULSD compliance difficult
Solution Approach 1:
The process segments the hydrocracking effluent into vapor and liquid phases, directing the vapor phase to a dedicated hydrotreating unit while the liquid phase undergoes conventional stripping and fractionation. This segmentation allows selective intensive hydrotreating of the vapor-derived diesel to achieve ULSD compliance while maintaining high diesel yield from mild hydrocracking operations.
Solution Approach 2:
A dedicated hydrotreating unit serves as an intermediary between the mild hydrocracking unit and the final product. This intermediary unit specifically treats the vapor phase effluent to remove sulfur and nitrogen contaminants, enabling the mild hydrocracking process to produce high diesel yield without compromising ULSD quality standards.
2Productivity
If conventional hydrocracking is used to produce diesel, then diesel production is achieved, but additional hydrotreating steps are required to meet ULSD standards
Solution Approach 1:
The process merges the hydrotreating function into the hydrocracking workflow by directing the vapor phase effluent through a dedicated hydrotreating unit. This integration allows simultaneous hydrocracking and hydrotreating operations to occur in a coordinated manner, reducing the need for separate sequential treatment steps and simplifying the overall process complexity while maintaining ULSD compliance.
Solution Approach 2:
Instead of applying uniform treatment to all effluent streams, the process applies local quality by directing only the vapor phase effluent through intensive hydrotreating while the liquid phase undergoes conventional processing. This localized approach optimizes sulfur removal where most needed while reducing overall process complexity and operational costs.
3Stability of the object's composition
If MHC reactor operates at low to moderate conversion, then diesel quality is maintained, but sulfur and nitrogen removal is insufficient for ULSD
Solution Approach 1:
The process performs preliminary hydrotreating action on the vapor phase effluent before final product formation. By applying intensive hydrotreating to the vapor-derived diesel stream in a dedicated unit, sulfur and nitrogen are removed in advance, ensuring ULSD compliance is achieved before the product enters storage or distribution, while the MHC reactor maintains optimal conversion conditions for diesel quality.
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 and nitrogen concentrations in diesel, enabling the production of ULSD directly from hydrocracked streams, enhancing diesel yield and meeting stringent environmental standards without the need for additional refining steps.
Implementation Method 1
hydrocracking a hydrocarbon feed stream over hydrocracking catalyst in the presence of hydrogen to provide a hydrocracked effluent stream
Implementation Method 2
hydrotreating the vaporous hydrocracked stream over hydrotreating catalyst in the presence of hydrogen to provide a hydrotreated effluent stream
Implementation Method 3
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 4
Hydroprocessed streams are typically stripped with an inert gas such as steam to remove volatile ammonia and hydrogen sulfide to reduce sulfur and nitrogen concentration in the product fuel stream
Data Source
AI summary
A process and apparatus are disclosed for hydrocracking a hydrocarbon feed in a hydrocracking unit and hydrotreating a vaporous hydrocracked stream. The hydrotreated effluent stream can be separated and stripped to produce a ULSD stream fit for storage without further processing. The hydrocracked liquid stream can be stripped and fractionated to produce a diesel stream that can be transported to the hydrotreating unit.