Dual Riser FCC Unit for Oxygenate Conversion
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Solution Overview
Problem
Current methanol to olefins (MTO) conversion processes in fluid catalytic cracking (FCC) units are limited by reaction conditions, leading to suboptimal olefin production, especially when using a single riser, which restricts the economic feasibility of processing stranded natural gas reserves.
Innovation Solution
Implementing a dual riser configuration within the FCC unit, where a dedicated MTO riser operates under optimized conditions for catalyst activity, temperature, and weight hourly space velocity, allowing for separate processing of hydrocarbon and oxygenate feeds to enhance olefin production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single riser is used for both hydrocarbon and oxygenate cracking, then the device complexity is reduced, but the olefin production is limited by conventional FCC reaction conditions
Solution Approach 1:
The single riser is segmented into two separate risers: a first riser for hydrocarbon cracking and a second riser for oxygenate cracking. This segmentation allows each riser to operate under optimized conditions for its specific feed type, thereby maximizing olefin production from oxygenates without compromising hydrocarbon processing
Solution Approach 2:
Different catalysts are used in different risers to match specific reaction requirements. The first riser uses a catalyst optimized for hydrocarbon cracking, while the second riser uses a catalyst optimized for oxygenate conversion. This local quality differentiation enables each riser to achieve optimal performance for its designated function
2Productivity
If a dedicated MTO riser is added for oxygenate processing, then olefin production is maximized, but the device complexity increases
Solution Approach 1:
The FCC unit is designed with multi-functionality by incorporating both a first riser for hydrocarbon cracking and a second riser for oxygenate cracking within the same regenerative catalytic system. The shared regenerator and catalyst circulation system provide universal support for both functions, reducing the overall complexity increase despite the added dedicated MTO riser
3Reliability
If different catalysts are used in different risers, then reaction optimization is improved, but the catalyst management complexity increases
Solution Approach 1:
The catalyst circulation system is segmented into separate circulation paths for each riser. Spent catalyst from each riser is independently regenerated and returned to its respective riser, allowing different catalyst types to be managed separately. This segmentation simplifies catalyst management despite using different catalysts in different risers
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 configuration maximizes olefin production by tailoring the reaction conditions in the MTO riser, enabling higher yields and improving the economic viability of processing stranded natural gas reserves by utilizing existing refinery equipment.
Implementation Method 1
cracking a hydrocarbon feed in a first riser comprising a first catalyst under first riser conditions to form a first effluent enriched in olefins, light gasoil, gasoline
Implementation Method 2
cracking a hydrocarbon oxygenate feed in a second riser comprising a second catalyst under second riser conditions to form a second effluent enriched in olefins
Implementation Method 3
regenerating the recovered first and second catalyst in a regenerator using heat from the exothermic cracking of the hydrocarbon oxygenate feed
Data Source
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AI summary
Provided herein are dual riser fluid catalytic cracking processes for producing light olefins from an oxygenate feed, such as a methanol feed, in a conventional FCC unit. In certain aspects the processes comprise cracking a hydrocarbon feed in a first riser comprising a first catalyst under first riser conditions to form a first effluent enriched in olefins, light gasoil, gasoline, or a combination thereof; cracking a hydrocarbon oxygenate feed in a second riser comprising a second catalyst under second riser conditions to form a second effluent enriched in olefins; recovering the first and second catalyst from the first and second effluents in a common reactor; regenerating the recovered first and second catalyst in a regenerator using heat from the exothermic cracking of the hydrocarbon oxygenate feed; and recirculating the regenerated first and second catalyst to the first and second riser.