Fluidized Bed Dehydrogenation Process for Light Olefins
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Solution Overview
Problem
Existing catalytic dehydrogenation processes for producing propylene from propane face issues such as high catalyst inventory, operational and maintenance problems, use of expensive noble metals, chlorine-induced embrittlement, and loss of propylene yield due to undesired cracking in fuel-fired heaters.
Innovation Solution
A process utilizing a semi-continuously operated fixed fluidized bed reactor system with a common continuous regenerator, eliminating the need for intermittent heaters and large reactors, and maintaining isothermal conditions to enhance catalyst life and product yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed bed tubular reactors are used for catalytic dehydrogenation, then the dehydrogenation reaction can be carried out, but higher catalyst inventory is required resulting in large equipment size
Solution Approach 1:
The patent applies fluidization technology to the catalyst bed, transforming the fixed bed system into a fluidized bed system. Gas flow through the catalyst bed creates fluid-like behavior, improving heat and mass transfer efficiency. This allows the same production capacity to be achieved in a smaller reactor volume due to enhanced reaction efficiency and better utilization of catalyst inventory.
2Use of energy by moving object
If fuel fired charge heaters are used to provide additional heat to dehydrogenation reactors, then heat requirement is met, but loss of propylene yield occurs due to undesired cracking
Solution Approach 1:
The patent converts the harmful effect of high temperature (which causes undesired cracking) into a beneficial effect by using it selectively for catalyst regeneration. The regenerator burns coke on spent catalyst at high temperature to restore catalyst activity, while the fluidized bed system maintains appropriate temperature in the reactor to prevent cracking. This separates the heat generation function (in regenerator) from the reaction function (in reactor), eliminating propylene loss.
Solution Approach 2:
The patent segments the process into distinct functional units: the reactor for dehydrogenation and the regenerator for catalyst regeneration. This separation allows independent optimization of each unit - the reactor maintains temperatures suitable for propylene production while the regenerator uses high temperatures for coke combustion, preventing unwanted cracking reactions.
3Reliability
If fixed bed systems are operated with frequent cycling, then catalyst regeneration is achieved, but operational and maintenance problems occur
Solution Approach 1:
The patent implements continuous operation of the fluidized bed system where catalyst circulation between reactor and regenerator occurs without interruption. The fluidized bed allows continuous contact between catalyst and reactants, and continuous regeneration of spent catalyst, eliminating the need for frequent shutdowns and cycling. This maintains stable operational conditions and reduces maintenance requirements.
4Reliability
If chlorine is used to disperse active components of catalyst, then catalyst activity is maintained, but embrittlement of stainless steel reactors occurs
Solution Approach 1:
The patent employs a catalyst formulation that does not rely on chlorine for dispersion of active components, thereby avoiding the use of corrosive substances. By selecting alternative, non-corrosive catalyst supports and preparation methods, the system maintains catalyst performance without compromising reactor material integrity, eliminating the need for expensive chlorine-resistant materials.
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 reduces maintenance costs, increases propylene yield and selectivity, and extends catalyst life by maintaining consistent catalyst inventory and utilizing heat from coke combustion, while avoiding the need for inter-heaters and large reactors.
Implementation Method 1
semi-continuously operated fixed fluidized bed reactor system
Implementation Method 2
reactivating the spent catalyst in the regenerator by burning the coke deposited on spent catalyst using air or oxygen or oxygen containing gas
Implementation Method 3
catalytic dehydrogenation
Data Source
AI summary
The present invention discloses process and apparatus for the production of light olefins from their respective alkanes by catalytic dehydrogenation, where in the dehydrogenation reaction is carried out in multiple semi-continuously operated fluidized bed isothermal reactors, connected to a common regenerator and wherein the process is carried out in a sequence of steps in each cycle i.e., entry of hot regenerated catalyst, pre-treatment with reducing gas, dehydrogenation reaction, stripping, transfer of catalyst to regenerator and catalyst regeneration. Process cycle in each reactor starts at different times such that the catalyst inventory in the regenerator is invariable with time.