Ethylene-to-Propylene Catalytic Conversion in FCC Head Effluent
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Solution Overview
Problem
The catalytic cracking unit (FCC) produces ethylene in a gaseous form, highly diluted with nitrogen, carbon dioxide, hydrogen, methane, and other impurities, making it difficult to recover and typically sent to the refinery fuel gas, with existing methods for purification being expensive and inefficient.
Innovation Solution
A process that converts ethylene in the combustible gas into propylene and other recoverable products using a zeolite-based catalyst in a catalytic conversion unit integrated into the FCC head effluent fractionation scheme, with a two-reactor system for exothermic conversion and continuous operation, allowing for efficient recovery of propylene and other olefins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If ethylene is recovered from combustible gas using conventional methods, then ethylene can be separated, but the process becomes expensive and complex due to cryogenic fractionation requirements
Solution Approach 1:
The invention changes the approach from physical separation (cryogenic fractionation) to chemical transformation (catalytic conversion). By converting ethylene into higher-value products like propylene and aromatics through catalytic reactions, the process avoids the complexity of cryogenic equipment while effectively 'recovering' ethylene value in transformed form
Solution Approach 2:
Instead of treating diluted ethylene as a waste stream to be separated, the invention converts it into beneficial products (propylene, butenes, aromatics). The dilution problem is transformed into an advantage by using the combustible gas matrix as a carrier for catalytic conversion, turning a recovery challenge into a value-added opportunity
2Use of energy by moving object
If ethylene is burned with combustible gas, then energy is recovered, but valuable ethylene is lost and propylene production remains limited
Solution Approach 1:
The invention changes the fate of ethylene from combustion (energy release) to catalytic conversion (chemical transformation). By using zeolite catalysts at controlled temperatures, ethylene is converted into propylene and other valuable products, simultaneously increasing propylene yield while maintaining energy efficiency through the exothermic nature of the conversion reactions
Solution Approach 2:
The catalytic conversion unit serves multiple functions: it converts ethylene to propylene (increasing productivity), generates heat through exothermic reactions (energy recovery), and produces multiple valuable products (aromatics, butenes). This multi-functionality replaces the single-purpose combustion approach
3Productivity
If propylene yield is increased by changing charge type and operating conditions, then propylene production increases, but ethylene production also increases and becomes difficult to recover
Solution Approach 1:
The invention transforms the problem of excess ethylene production into a solution by converting it into additional propylene and other valuable products. The ethylene that would otherwise be a recovery challenge becomes a feedstock for further value addition, turning a loss into a benefit
Solution Approach 2:
The catalytic conversion unit is positioned to receive ethylene directly from the FCC unit overhead, performing the conversion action before the ethylene would need to be separated or disposed of. This preliminary conversion simplifies downstream processing and maximizes propylene yield
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
Increases propylene yield by approximately 10% and allows for the recovery of additional butenes and aromatics, with minimal modifications to existing FCC equipment, enhancing the efficiency and cost-effectiveness of the process.
Implementation Method 1
A process that converts ethylene in the combustible gas into propylene and other recoverable products using a zeolite-based catalyst in a catalytic conversion unit
Implementation Method 2
with a two-reactor system for exothermic conversion and continuous operation
Data Source
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AI summary
The present invention describes a process for fractionating the gaseous fraction exiting the top of the fractionation column of a catalytic cracking (FCC) unit using an ethylene-to-propylene conversion unit which allows the ethylene contained in the combustible gas to be recovered.