Reverse Flow Reactor Asymmetric Feed Purge
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Solution Overview
Problem
Current hydrocarbon pyrolysis processes face challenges in controlling the pyrolysis reaction, achieving low oxygen contamination, efficient reactant mixing, minimizing regeneration gas usage, and tailoring product slates for enhanced selectivity.
Innovation Solution
The use of an asymmetric feed flow profile and low maldistribution parameter in a reverse flow reactor (RFR) system, which includes a channeled thermal mass with a central vertical axis and void spaces, allows for optimized distribution of oxidant, fuel, and purge media during heating, pyrolysis, and purge modes, effectively purging residual oxygen and achieving uniform reaction zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional steam cracking furnace is used, then olefinic hydrocarbons can be produced, but energy efficiency is low and yield of light unsaturated hydrocarbon is limited
Solution Approach 1:
The patent employs periodic switching between heating mode and pyrolysis mode in a reverse flow reactor. During heating mode, fuel and oxidant are introduced to heat the thermal mass; during pyrolysis mode, hydrocarbon feed is introduced to undergo pyrolysis while heat is transferred from the thermal mass. This periodic action enables continuous operation with high energy efficiency and improved yield of light unsaturated hydrocarbons.
2Productivity
If a reverse flow reactor is used for pyrolysis, then energy efficiency and yield improve, but residual oxygen contamination in the reaction zone increases
Solution Approach 1:
The patent introduces a purge mode that operates between heating mode and pyrolysis mode. During this preliminary action, purge gas is introduced to remove residual oxygen from the reaction zone before pyrolysis begins. This preliminary purging action reduces oxygen contamination to acceptable levels while maintaining the high productivity benefits of reverse flow pyrolysis.
3Object-affected harmful factors
If purge gas is introduced to remove residual oxygen, then oxygen contamination decreases, but regeneration gas usage and cycle time increase
Solution Approach 1:
The patent employs asymmetric feed distribution where purge gas is introduced at specific locations and flows in specific directions to efficiently remove oxygen from critical reaction zones. The feed distribution is optimized to create favorable flow patterns that achieve thorough purging with minimal purge gas volumes and reduced cycle times, rather than uniform distribution throughout the reactor.
4Stability of the object's composition
If asymmetric feed flow profile is used, then reactant distribution and reaction homogeneity improve, but device complexity increases
Solution Approach 1:
The patent deliberately employs asymmetric feed distribution in the reverse flow reactor, where feeds are introduced at non-uniform locations and in non-uniform quantities to create optimal flow patterns. This asymmetric approach improves reaction homogeneity and product selectivity by ensuring proper mixing and contact between reactants and the thermal mass, while the complexity is managed through careful design of the feed introduction system.
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 enables efficient oxygen removal from the reaction zone, reducing residual oxygen levels to ≤20 ppm, improving reaction homogeneity, and enhancing the selectivity of pyrolysis products while minimizing regeneration gas usage and cycle time.
Implementation Method 1
Heat is transferred from the thermal mass to the hydrocarbon feed, which increases the hydrocarbon feed's temperature and results in conversion of at least a portion of the feed by pyrolysis
Implementation Method 2
a flow of the hydrocarbon-containing feed is established through the channel. Heat is transferred from the thermal mass to the hydrocarbon feed
Implementation Method 3
The thermal mass is preheated, and then a flow of the hydrocarbon-containing feed is established through the channel. Since the pyrolysis is endothermic, pyrolysis mode operation will eventually cool the thermal mass
Implementation Method 4
The heating can be carried out, e.g., by a transfer of heat to the reactor from combustion of fuel and oxidant
Implementation Method 5
conversion of at least a portion of the feed by pyrolysis. The pyrolysis produces a pyrolysis product comprising molecular hydrogen, methane, acetylene, ethylene, and C3+ hydrocarbon
Data Source
AI summary
Reverse flow reactor (RFR) apparatuses exhibiting asymmetric feed profiles and improved purge mode efficiency, and methods of using same to transform a hydrocarbon feed into a pyrolysed hydrocarbon product are disclosed. The RFR apparatus includes an RFR body with a reaction zone having at least one bed. The RFR body has a central vertical axis and flanked by first and second void spaces. The method utilizes at least two oxygen-containing feeds, a combustion fuel feed, a purge feed, and a hydrocarbon pyrolysis feed. The RFR apparatus can cycle between an exothermic heating mode (heated to ≥700° C. while maintaining a pressure drop across the reaction zone of ≤100 kPag), a purge mode (purging oxygen using <6 bed volumes of purge gas to achieve a residual oxygen level of ≤20 ppm while maintaining a pressure drop of ≤35 kPag), and an endothermic pyrolysis mode (feeding pyrolysis hydrocarbons through the reaction zone to form pyrolysis products, while maintaining a pressure drop across the reaction zone of ≤70 kPag).