Dual Fluid Catalytic Cracking Reactors for Olefin Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional systems for producing light olefins like ethylene and propylene face challenges in achieving high selectivity and yield, often resulting in the production of heavier hydrocarbons that reduce the efficiency of these valuable compounds.
Innovation Solution
A dual fluid catalytic cracking system is employed, where a hydrocarbon feed is processed in two fluid catalytic cracking systems arranged in series, with the first system operating at high-severity conditions to produce a naphtha effluent, which is then further processed with a cracking catalyst mixture including an additive in the second system at even higher severity conditions to enhance the yield of ethylene and propylene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fluid catalytic cracking systems operate under high-severity conditions to increase propylene yield, then propylene production increases up to four times greater than traditional systems, but substantial amounts of heavy olefins and larger hydrocarbons are also produced which reduce selectivity
Solution Approach 1:
The patent divides the single cracking process into two sequential cracking systems. The first system operates under high-severity conditions to maximize conversion and propylene yield, while the second system operates under severe conditions specifically to crack heavy olefins and larger hydrocarbons into lighter olefins, thereby resolving the selectivity issue without sacrificing productivity
Solution Approach 2:
The patent changes operating parameters between the two systems: the first system uses high-severity conditions (temperature ≥480°C, catalyst-to-oil ratio ≥1, residence time ≤30 seconds) while the second system uses even more severe conditions (temperature ≥580°C, catalyst-to-oil ratio ≥1, residence time ≤60 seconds). This parameter optimization allows each system to perform its specific function efficiently
2Productivity
If single fluid catalytic cracking system operates under severe conditions to maximize olefin production, then conversion levels increase, but the selectivity and yield of propylene and ethylene are reduced due to production of heavier hydrocarbons
Solution Approach 1:
The patent segments the cracking process into two distinct stages with different objectives: the first stage focuses on high conversion and propylene production, while the second stage specifically targets the cracking of heavy olefins into lighter olefins. This segmentation allows optimization of selectivity in the second stage without compromising overall productivity
Solution Approach 2:
The first cracked effluent acts as an intermediary between the two cracking systems. It contains the products from the first system including heavy olefins that need further processing. This intermediary stream allows the second system to specifically target and convert heavy olefins into lighter olefins, improving overall selectivity
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 significantly increases the selectivity and yield of ethylene and propylene, reducing the production of heavier hydrocarbons and improving the overall efficiency of the olefin production process.
Implementation Method 1
contacting the naphtha effluent with a cracking catalyst mixture comprising a second cracking catalyst and a cracking catalyst additive under high-severity conditions to produce a second cracked effluent
Implementation Method 2
operated under high-severity conditions... at a second cracking temperature greater than or equal to 580 degrees Celsius
Data Source
AI summary
A method for processing a hydrocarbon feed to produce olefins may comprise introducing the hydrocarbon feed to a first fluid catalytic cracking system, which may cause at least a portion of the hydrocarbon feed to undergo catalytic cracking and produce a spent first cracking catalyst and a first cracked effluent comprising one or more olefins. The method may further comprise passing the first cracked effluent to a separation system downstream of the first fluid catalytic cracking system, which may separate the first cracked effluent to produce at least a naphtha effluent comprising one or more olefins. Additionally, the method may comprise passing the naphtha effluent to a second fluid catalytic cracking system downstream of the separation system, which may cause at least a portion of the naphtha effluent to undergo catalytic cracking and produce a spent cracking catalyst mixture and a second cracked effluent comprising one or more olefins.