Vacuum Flash Separation for Clarified Slurry Oil Recovery
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Solution Overview
Problem
The FCC process generates clarified slurry oil (CSO) that is less valuable due to its high aromaticity and low cetane value, which degrades diesel quality, and operational constraints limit the recovery of valuable hydrocarbons, leading to maintenance issues and loss of Light Cycle Oil (LCO).
Innovation Solution
Integrating an FCC unit with a hydrocracking unit to recover and upgrade CSO by separating cycle oil under vacuum pressure, allowing its use as additional feed for hydrocracking to produce higher-value diesel and petrochemical products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LCO flow rate is reduced and CSO flow rate is increased to lower main fractionation column temperature, then coking and maintenance issues are reduced, but valuable LCO is lost in the CSO stream
Solution Approach 1:
The CSO stream is separated into two distinct fractions: a light cycle oil fraction (boiling range similar to traditional LCO) and a heavy cycle oil fraction (higher boiling point). This segmentation allows the valuable LCO components to be recovered and returned to the main fractionation column, while the heavier fraction is routed to hydrocracking, thus preventing LCO loss while maintaining column reliability.
Solution Approach 2:
The light cycle oil fraction is extracted from the CSO stream through vacuum flash separation and returned to the main fractionation column. This extraction recovers the valuable LCO components that would otherwise be lost, while allowing the heavier fraction to be utilized in hydrocracking to produce additional diesel and gasoline.
2Ease of manufacture
If CSO is burned as fuel without recovery, then operational simplicity is maintained, but valuable hydrocarbons are wasted
Solution Approach 1:
The process utilizes vacuum flash separation to change the separation parameters, enabling the CSO stream to be divided into recoverable LCO fraction and hydrocracking feed fraction. This parameter change transforms the simple fuel burning process into a value-added recovery process while maintaining operational simplicity through integrated equipment design.
Solution Approach 2:
The vacuum flash drum serves multiple functions: it separates the CSO stream into LCO and HCO fractions, provides vacuum service for the main fractionation column, and prepares feedstock for hydrocracking. This multi-functionality maximizes hydrocarbon recovery while maintaining process efficiency.
3Reliability
If LCO is withdrawn to prevent coking, then main fractionation column maintenance needs are reduced, but the value of diesel pool quality is degraded by extra LCO in CSO
Solution Approach 1:
The CSO stream is segmented into LCO fraction and HCO fraction through vacuum flash separation. The LCO fraction is recovered and returned to the main fractionation column to prevent coking, while the HCO fraction is directed to hydrocracking. This segmentation eliminates the harmful effect of LCO contamination in the diesel pool while maintaining column reliability.
Solution Approach 2:
The LCO that would otherwise contaminate the diesel pool and reduce its value is converted into a beneficial stream by separating and returning it to the main fractionation column. This transforms a harmful contamination issue into a valuable feedstock recovery opportunity, simultaneously improving diesel quality and column reliability.
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 process enables the recovery and upgrading of LCO and Heavy Cycle Oil (HCO) from CSO, enhancing diesel quality and reducing maintenance needs by converting CSO into lighter products like gasoline, kerosene, and aromatics, thereby increasing the overall value of hydrocarbon yields.
Implementation Method 1
The slurry oil stream is separated into a cycle oil stream and a heavy stream under vacuum pressure
Implementation Method 2
Hydrocracking is a hydroprocessing process in which hydrocarbons crack at the carbon-carbon bonds in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons
Implementation Method 3
Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products
Data Source
AI summary
A process and apparatus for recovering cycle oil from FCC CSO is described. By feeding the additional cycle oil to a hydrocracking unit additional diesel, naphtha and petrochemical feedstock may be obtained. The additional cycle oil is obtained by vacuum separation of the CSO. The described process and apparatus can provide additional recovery for a refiner.