FCC Unit LCO Recovery via Spent Catalyst Coke Control
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Solution Overview
Problem
The Fluid Catalytic Cracking (FCC) process faces challenges in producing diesel fuel 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 involve hydroprocessing the FCC feed stream with a higher proportion of spent catalyst to increase the selectivity of LCO production, allowing for its conversion into diesel products, by recycling spent catalyst with a controlled coke content to the FCC reactor without regeneration, thereby enhancing diesel recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LCO is directed to the diesel pool, then diesel production is augmented, but the quality of diesel pool degrades due to high aromaticity and low cetane value
Solution Approach 1:
The patent extracts LCO from the main FCC product stream and directs it separately to the diesel pool, allowing selective recovery of diesel-range hydrocarbons while managing their quality impact through controlled blending ratios
Solution Approach 2:
The patent changes the operating parameters of the FCC unit, specifically adjusting the catalyst-to-oil ratio and using spent catalyst with controlled coke content (0.7-1.1 wt%), to optimize the production of LCO in the diesel boiling range while maintaining acceptable quality parameters
2Productivity
If spent catalyst is recycled without regeneration, then diesel recovery efficiency increases, but catalyst activity decreases due to coke accumulation
Solution Approach 1:
The patent applies partial regeneration by recycling spent catalyst with controlled coke content (0.7-1.1 wt%) rather than fully regenerating all catalyst, achieving optimal diesel production while maintaining sufficient catalyst activity through a blend of spent and regenerated catalyst
Solution Approach 2:
The patent optimizes the catalyst-to-oil ratio and controls the coke content on recycled catalyst to maximize diesel yield while preserving adequate catalyst activity for sustained operation
3Quantity of substance
If HCO is recovered from the main fractionation column, then additional diesel feedstock is obtained, but operational constraints prevent effective recovery
Solution Approach 1:
The patent makes the FCC unit multi-functional by simultaneously producing gasoline, augmenting diesel production through LCO, and recovering HCO as feedstock, thereby utilizing the same equipment for multiple product streams without adding complex separation infrastructure
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 yield of LCO, augmenting diesel production and improving the quality of diesel fuel by optimizing the catalyst-to-oil ratio and coke content, leading to higher selectivity and efficiency in diesel recovery within the FCC unit.
Implementation Method 1
contacting the FCC feed stream with a higher proportion of spent catalyst to obtain higher selectivity to LCO product
Implementation Method 2
Hydrotreating is a hydroprocessing process in which heteroatoms such as sulfur and nitrogen are removed from hydrocarbon streams
Implementation Method 3
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.