Hydrocracking FCC Cycle Oil to Boost Diesel Yield
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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 lead to losses of Light Cycle Oil (LCO), resulting in inefficiencies and maintenance issues in refineries.
Innovation Solution
Integrating an FCC unit with a hydrocracking unit to recover and upgrade CSO, where the CSO is separated into a cycle oil stream, which is then hydrocracked to produce lighter products such as gasoline, diesel, and petrochemicals, thereby enhancing the value of the final products and reducing operational challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LCO is withdrawn from the main fractionation column to prevent coking, then column temperature is reduced and maintenance is improved, but LCO is lost and refinery productivity decreases
Solution Approach 1:
The patent recovers LCO that would otherwise be discarded in the CSO stream. By implementing a side-draw LCO outlet and a fractionation column configured to separate LCO from CSO, the system recovers valuable LCO product while maintaining the ability to operate at lower temperatures to prevent coking. This resolves the contradiction by recovering the lost product rather than simply discarding it.
Solution Approach 2:
The patent segments the LCO/CSO separation process into distinct functional zones within the fractionation column. By creating a side-draw outlet specifically for LCO and maintaining different temperature zones (upper section for LCO condensation, lower section for CSO withdrawal), the system enables selective removal of LCO without compromising the main CSO product stream or the column's temperature control for coking prevention.
2Ease of operation
If CSO is used as fuel, then operational simplicity is maintained, but product value is reduced due to high aromaticity and low cetane value
Solution Approach 1:
The patent changes the chemical parameters of the CSO stream by selectively removing aromatic hydrocarbons through the LCO side-draw outlet. By controlling the temperature and pressure parameters in the fractionation column, the system separates and removes the high-aromaticity LCO fraction, thereby improving the cetane value and overall quality of the remaining CSO fuel product without complicating the operational process.
3Temperature
If HCO is pumped around to cool the main fractionation column, then column temperature control is achieved, but HCO is not recovered and product yield is reduced
Solution Approach 1:
The patent recovers HCO that would otherwise be discarded in the CSO stream. By implementing a fractionation column configured to separate HCO from CSO and providing a dedicated outlet for HCO recovery, the system recovers this valuable product while maintaining the ability to use HCO for temperature control purposes. This resolves the contradiction by recovering the lost product rather than simply discarding it.
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 integration allows for the recovery and upgrading of LCO and Heavy Cycle Oil (HCO) from CSO, improving diesel quality and reducing maintenance needs by converting CSO into more valuable products, thereby increasing refinery efficiency and product yield.
Implementation Method 1
The slurry oil stream is separated into a cycle oil stream and a heavy stream under vacuum pressure
Implementation Method 2
at least a portion of the cycle oil stream is hydrocracked over hydrocracking catalyst to provide an upgraded stream
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.