FCC Catalyst Recycling for Diesel Yield
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Solution Overview
Problem
The Fluid Catalytic Cracking (FCC) process faces challenges in producing diesel due to the degradation of diesel pool quality by Light Cycle Oil (LCO) and the inefficiency in recovering Heavy Cycle Oil (HCO), which are not fully utilized, leading to environmental concerns and operational constraints.
Innovation Solution
A process and apparatus that involves hydroprocessing the FCC feed stream with a higher proportion of spent catalyst to increase the selectivity of LCO, allowing for its conversion into diesel products, by recycling spent catalyst with a coke content of 0.7 to 1.1 wt% to enhance catalyst activity and product yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spent catalyst is recycled without regeneration, then LCO selectivity and diesel production are improved, but catalyst deactivation and process stability deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the coke content of recycled spent catalyst to fall within the specific range of 0.7 to 1.1 wt%. This parameter optimization allows the catalyst to maintain sufficient activity for LCO production while preventing excessive deactivation, thereby resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent implements feedback control by continuously monitoring and adjusting the coke content of recycled catalyst. The system feedbacks the coke content measurement to control the recycling process, ensuring that catalyst properties remain within the optimal range for both high LCO selectivity and sustained performance.
2Productivity
If HCO is not recovered from main fractionation column, then operational simplicity is maintained, but product value and diesel production are reduced
Solution Approach 1:
The patent merges the HCO recovery function with the existing main fractionation column by introducing a side draw outlet at an intermediate position. This integration allows HCO to be recovered without requiring a separate dedicated recovery system, thereby increasing diesel production while minimizing additional process complexity.
Solution Approach 2:
The patent segments the product stream from the main fractionation column by introducing a side draw outlet that selectively removes HCO at an intermediate position, separating it from both the overhead gasoline product and the bottom slurry oil. This segmentation enables targeted recovery of HCO without disrupting the main separation function.
3Productivity
If LCO is produced in FCC unit, then diesel pool can be augmented, but diesel pool quality degrades due to high aromaticity and low cetane value
Solution Approach 1:
The patent applies parameter changes by optimizing the coke content of recycled catalyst to the specific range of 0.7 to 1.1 wt%, which shifts the product distribution toward lower aromaticity and higher cetane value LCO, thereby improving diesel quality while maintaining production levels.
Solution Approach 2:
The patent applies local quality by selectively recovering LCO with specific quality characteristics (lower aromaticity, higher cetane value) through optimized catalyst recycling, rather than recovering all LCO uniformly. This allows the diesel pool to receive LCO with improved local quality properties.
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 increases the recovery of LCO, augmenting diesel production, and improves the quality of diesel products by optimizing catalyst activity and product distribution within the FCC unit.
Implementation Method 1
contacts a selected feedstock and hydrogen-containing gas with suitable catalyst(s) in a reaction vessel under conditions of elevated temperature and pressure
Implementation Method 2
Hydrotreating is a hydroprocessing process in which heteroatoms such as sulfur and nitrogen are removed from hydrocarbon streams to meet fuel specifications and to saturate olefinic and aromatic compounds
Implementation Method 3
Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products
Implementation Method 4
crack the hydrocarbons down to smaller molecular weight products
Implementation Method 5
coke tends to accumulate on the catalyst which is burned off in the regenerator
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.