Counter-current fluidized bed reactor for olefin dehydrogenation
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Solution Overview
Problem
Current light olefin production methods, such as cracking heavier hydrocarbons, face inefficiencies in energy usage and product yield, with high temperatures leading to thermal cracking and undesirable side reactions, while the demand for ethylene and propylene exceeds supply.
Innovation Solution
A counter-current gas phase dehydrogenation process using a large reactor with downward flowing catalyst and upward flowing hydrocarbon process stream, maintaining a temperature gradient to minimize high-temperature contact times and optimize catalyst residence time, reducing thermal cracking and increasing yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam cracking or pyrolysis of hydrocarbons is used to produce ethylene and propylene, then light olefins can be produced, but energy consumption is high and equipment costs are very expensive
Solution Approach 1:
The patent changes the temperature parameter profile by using a temperature gradient in the reactor (600-900°C at top, decreasing to 400-600°C at bottom) and operates at lower overall temperatures compared to conventional steam cracking (800-900°C), reducing energy consumption while maintaining olefin production efficiency
Solution Approach 2:
The patent applies different temperature zones within the reactor - higher temperature at the top for catalyst regeneration and lower temperature at the bottom for dehydrogenation reaction, optimizing local conditions for each function and reducing overall energy requirements
2Productivity
If high temperature cracking is used to produce light olefins, then conversion rate increases, but thermal cracking and undesirable side reactions increase
Solution Approach 1:
The patent changes the temperature parameter to operate at lower temperatures (400-600°C at reactor bottom) compared to conventional cracking, and controls residence time by using a temperature gradient that increases toward the top of the reactor, minimizing thermal cracking and side reactions while maintaining conversion
Solution Approach 2:
The patent performs catalyst regeneration at higher temperatures in the upper region before the reactants reach that zone, so that when hydrocarbons pass through the upper regions, the catalyst is already regenerated and ready to promote selective dehydrogenation rather than thermal cracking
3Manufacturing precision
If conventional fractionation steps are used to separate ethylene and propylene, then purified products can be recovered, but the process becomes very complex
Solution Approach 1:
The patent extracts and eliminates the complex cryogenic fractionation section from the process by using selective catalytic dehydrogenation that directly produces purified olefin streams, simplifying the overall process while maintaining high product purity through catalyst selectivity
4Productivity
If dehydrogenation reaction is performed, then olefin yield increases, but the endothermic reaction requires continuous heat supply
Solution Approach 1:
The patent merges the dehydrogenation reaction and catalyst regeneration functions into a single continuous reactor system, where the exothermic regeneration of catalyst in the upper region provides heat that drives the endothermic dehydrogenation reaction in the lower region, eliminating external heat supply requirements
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 process enhances light olefin production efficiency by reducing thermal cracking, increasing yields, and maintaining a favorable reaction equilibrium, while minimizing equipment costs and energy consumption.
Implementation Method 1
The process stream picks up heat from the catalyst as it contacts the catalyst during the endothermic reaction of dehydrogenation. A temperature gradient is formed within the catalyst bed with the top of the catalyst bed at or near the highest temperature and the bottom of the catalyst bed at or near the lowest temperature.
Implementation Method 2
The process involves the counter-current flow of catalyst with respect to the process stream, and the process stream picks up heat from the catalyst as it contacts the catalyst during the endothermic reaction of dehydrogenation.
Implementation Method 3
the process stream picks up heat from the catalyst as it contacts the catalyst during the endothermic reaction of dehydrogenation
Data Source
AI summary
A process and apparatus for the dehydrogenation of paraffins is presented. The process utilizes a reactor that includes a slower flow of catalyst through the reactor, with a counter current flow of gas through the catalyst bed. The catalyst is regenerated and distributed over the top of the catalyst bed, and travels through the bed with the aid of reactor internals to limit backmixing of the catalyst.