Alternate-Train Hydrotreating for Continuous FCC Feed
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Solution Overview
Problem
Hydrotreating of residue streams for catalytic cracking requires frequent shutdowns of hydrotreating units due to rapid catalyst deactivation, leading to incongruence in operational capacity between hydrotreating and fluid catalytic cracking units, resulting in suboptimal operational and economic performance.
Innovation Solution
Implementing an alternate-train hydrotreating process where one reactor train is smaller than the other, allowing the larger train to be taken off-stream for maintenance while the smaller train continues to operate, with a sulfide system preparing the catalyst for renewed processing, ensuring continuous feed to the FCC unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydrotreating reactor train is used, then the hydrotreating unit can be designed with a simple structure, but the unit requires frequent shutdowns for catalyst replacement, reducing productivity
Solution Approach 1:
The hydrotreating unit is divided into two separate reactor trains (first and second reactor trains), each capable of independently processing the hydrocarbon stream. This segmentation allows one train to be taken offline for catalyst replacement while the other continues operation, eliminating the frequent shutdowns that would occur with a single reactor train and thereby maintaining continuous productivity.
Solution Approach 2:
The invention changes the operational parameter of catalyst age by introducing a catalyst replacement cycle where catalysts in the two reactor trains are replaced alternately. This parameter change transforms the system from one requiring continuous operation with degrading catalyst to a system where catalyst replacement occurs during planned maintenance windows without interrupting overall process continuity.
2Reliability
If the hydrotreating unit is designed for high severity processing to handle metal-rich resid streams, then it can effectively demetallize and desulfurize the feed, but the catalyst deactivates rapidly requiring frequent shutdowns
Solution Approach 1:
By segmenting the catalyst system into two separate reactor trains with independently replaceable catalysts, the invention allows one catalyst bed to be replaced while the other continues to provide high-severity processing. This maintains reliable demetallization and desulfurization performance while extending the effective operational duration of the hydrotreating unit through alternating catalyst replacement cycles.
Solution Approach 2:
The dual reactor train configuration ensures continuous useful action by allowing one train to maintain high-severity hydrotreating processing while the other undergoes catalyst replacement. This eliminates idle time and ensures the hydrotreating function remains continuously effective, addressing both the need for high processing severity and extended operational duration.
3Manufacturing precision
If the hydrotreating unit is shut down for catalyst replacement, then the catalyst can be renewed to maintain processing efficiency, but the FCC unit cannot operate at full capacity
Solution Approach 1:
The segmentation of the hydrotreating system into two independent reactor trains enables catalyst replacement in one train without shutting down the other. This allows the FCC unit to receive continuous feed and operate at full capacity, while the hydrotreating train undergoing maintenance restores catalyst efficiency without disrupting overall production.
Solution Approach 2:
The invention implements preliminary action by planning and executing catalyst replacement in one reactor train while the other continues operation. This preliminary maintenance approach ensures that catalyst replacement is performed proactively during scheduled intervals without forcing unplanned shutdowns of the FCC unit, thereby maintaining both processing efficiency and full capacity utilization.
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 enables continuous hydrotreatment of hydrocarbon streams, reducing the need for frequent shutdowns and maintaining full operational capacity of the FCC unit, thereby enhancing operational and economic efficiency.
Implementation Method 1
hydrotreating catalysts which are primarily active for the removal of heteroatoms, such as sulfur, nitrogen and metals, such as iron, nickel, and vanadium and asphaltenes from the hydrocarbon feedstock
Implementation Method 2
Hydroprocessing includes processes which convert hydrocarbons in the presence of hydroprocessing catalyst and hydrogen to more valuable products
Implementation Method 3
A sulfide system also sulfides the catalyst volume in the reactor train that is off stream to prepare it for renewed hydroprocessing of feed when back on stream
Data Source
AI summary
A process and apparatus provides alternative hydrotreating reactor trains for hydrotreating a hydrocarbon stream. One hydrotreating reactor train is smaller than the other and the smaller train comes on stream to allow replacement or regeneration of catalyst in the larger train. A sulfide system also sulfides the catalyst volume in the reactor train that is off stream to prepare it for renewed hydroprocessing of feed when back on stream. The process and apparatus can be used to keep hydroprocessing reactors on stream to continuously provide feed to an FCC unit which has a longer period before shut down.