Slurry Oil Heating and Vacuum Separation for FCC Cycle Oil Recovery
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Solution Overview
Problem
The fluid catalytic cracking (FCC) process faces challenges in recovering and recycling lower-value slurry oil, which contains unconverted hydrocarbons and catalyst particles, due to operational constraints, leading to suboptimal diesel production and increased environmental contaminants like sulfur and nitrogen in petroleum products.
Innovation Solution
A process and apparatus that involves heating slurry oil under vacuum pressure to separate it into a cycle oil stream and a heavy stream, allowing for the recycling of the cycle oil back to the FCC unit, thereby enhancing the recovery of higher-value products and reducing contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If slurry oil is withdrawn from the bottom of the FCC main fractionation column as a final product, then the operational constraints of the fractionation column are satisfied, but valuable cycle oil material is lost and cannot be recycled to the FCC unit
Solution Approach 1:
The slurry oil processing system is segmented into multiple functional units: a vacuum separator for separating cycle oil from heavy slurry oil, and a heater for heating the slurry oil before separation. This segmentation allows the system to handle slurry oil recycling without complicating the main FCC fractionation column, thereby increasing productivity while managing device complexity.
Solution Approach 2:
A vacuum separator is introduced as an intermediary device between the FCC main fractionation column and the FCC reactor. This intermediary enables the separation and recycling of cycle oil from slurry oil without directly modifying the FCC fractionation column, thus improving productivity while maintaining operational simplicity.
2Quantity of substance
If more cycle oil is recovered from slurry oil for recycling, then diesel production and higher-value cracked products increase, but additional processing equipment and energy consumption are required
Solution Approach 1:
The slurry oil is heated before being fed to the vacuum separator to facilitate the separation of cycle oil. This preliminary heating action ensures that the subsequent separation process is more efficient, maximizing the amount of cycle oil recovered while using energy at the optimal point in the process sequence.
Solution Approach 2:
The vacuum separator operates under vacuum pressure conditions, changing the pressure parameter to enable separation at lower temperatures. This parameter change allows for efficient cycle oil recovery while reducing the overall energy consumption compared to atmospheric pressure separation.
3Manufacturing precision
If slurry oil is heated before vacuum separation, then cycle oil separation efficiency improves, but additional energy consumption occurs
Solution Approach 1:
The vacuum separator operates under reduced pressure conditions, which changes the boiling points and volatility characteristics of the hydrocarbon components. This parameter change enables more precise separation of cycle oil from heavy slurry oil at moderate temperatures, improving manufacturing precision while minimizing energy loss.
Solution Approach 2:
The heating system uses a heat exchanger that can be integrated with existing process streams, copying thermal energy from other parts of the FCC process to heat the slurry oil. This approach improves separation precision while reducing net energy loss by utilizing waste heat from the system.
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 the FCC unit to recycle more of the lower-value slurry oil, increasing the production of higher-value cracked products and improving diesel production while meeting stringent environmental regulations by reducing sulfur and nitrogen levels.
Implementation Method 1
A slurry heater is in downstream communication with a main outlet in a bottom of the main fractionation column for heating the slurry oil stream
Implementation Method 2
A vacuum separator is in downstream communication with the slurry heater for separating the heated slurry oil stream into a cycle oil stream and a heavy stream under vacuum pressure
Data Source
AI summary
A process and apparatus is for recycling LCO and/or HCO to an FCC unit to recover additional distillate. Spent catalyst recycle in the FCC unit may be used to improve distillate yield. A hydroprocessing zone may saturate cycle oil aromatics for cracking in an FCC unit. The recycle cracked stream may be recycled to a downstream hydroprocessing zone to avoid a first hydroprocessing zone for hydrotreating feed to the FCC unit. Additional recovery of cycle oil for recycle is obtained by heating slurry oil prior to vacuum separation.