Cyclic Fixed-Bed Reactor for Light Olefins via Dry Gas Dilution
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Solution Overview
Problem
Catalytic cracking of paraffinic hydrocarbons to produce light olefins faces challenges such as high catalyst deactivation due to coke formation and structural damage at high temperatures, leading to low yields and frequent catalyst replacement in existing processes like Advanced Catalytic Olefins (ACO) technology.
Innovation Solution
A cyclic regenerative process using two trains of fixed bed reactors alternately operated to minimize coke formation and catalyst damage, where dry gas serves as a diluent to reduce coke deposition and extend catalyst life, allowing for continuous operation with minimal catalyst makeup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic cracking is carried out at high temperatures to convert paraffinic hydrocarbons to light olefins, then conversion efficiency is improved, but catalyst deactivation due to coke formation and structural damage increases
Solution Approach 1:
The process divides the catalytic cracking operation into two separate fixed-bed reactor trains that operate in alternating cycles. One train operates for cracking while the other undergoes regeneration, allowing continuous production while systematically managing catalyst deactivation through segmented operation rather than single-reactor continuous operation
Solution Approach 2:
The catalyst undergoes periodic regeneration cycles where it is switched from the reaction zone to the regeneration zone. This periodic action allows the catalyst to be restored by burning off coke deposits at controlled intervals, maintaining catalyst activity and stability over extended operation periods while continuing light olefin production
2Reliability
If catalyst is continuously regenerated by combusting coke, then catalyst activity is maintained, but energy balance becomes unstable when paraffinic feed is used due to insufficient coke formation
Solution Approach 1:
The process modifies operating parameters including temperature, pressure, and notably the catalyst-to-oil ratio to optimize both light olefin yield and coke formation. By controlling these parameters, sufficient coke is generated to maintain energy balance during regeneration while preserving catalyst activity and minimizing unwanted side reactions
3Productivity
If high catalyst-to-oil ratio is used to achieve acceptable yields, then light olefin production is improved, but catalyst cost increases due to rapid loss of catalyst activity
Solution Approach 1:
The catalyst is pre-regenerated and restored to full activity before being introduced to the reaction zone. This preliminary regeneration action ensures the catalyst enters the cracking reaction in optimal condition, maximizing its utilization efficiency and reducing the frequency of replacement, thereby lowering overall catalyst consumption despite high initial catalyst-to-oil ratios
Solution Approach 2:
Instead of discarding spent catalyst, the process recovers it by burning off coke deposits in the regeneration zone. This recovery action restores catalyst activity, allowing the same catalyst material to be reused multiple times, significantly reducing net catalyst loss and operational costs
4Productivity
If fixed bed reactor process is used to achieve higher yields per pass, then light olefin production is improved, but continuous operation becomes difficult due to catalyst deactivation
Solution Approach 1:
The continuous operation is achieved by segmenting the process into two alternating reactor trains. While one train operates for cracking with high yield per pass, the other undergoes regeneration. This segmentation allows the system to maintain continuous production capability without compromising the high yield advantage of fixed-bed operation
Solution Approach 2:
The dual-train configuration ensures continuity of useful action by alternating between the two reactors. When one reactor is in regeneration mode, the other maintains light olefin production, and vice versa. This continuous alternation eliminates downtime and maintains steady production output while managing catalyst deactivation
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 enhances catalyst stability and productivity by reducing coke formation, maintaining catalyst activity, and achieving higher yields of light olefins with reduced need for fresh catalyst, thereby improving the economic viability of light olefin production.
Implementation Method 1
catalytic cracking, where longer and heavier hydrocarbon molecules are contacted with a catalyst at high temperatures and pressures to break them into lighter and shorter hydrocarbon molecules
Implementation Method 2
As the cracking reaction occurs, coke, a carbonaceous material, is formed and deposits on the catalyst
Implementation Method 3
The spent catalyst is sent to a regenerator where the coke is removed from the catalyst by combusting the coke
Data Source
AI summary
A method of producing olefins by catalytic cracking of hydrocarbons is disclosed. The method may include catalytic cracking hydrocarbons in a feed stream that includes the hydrocarbons and the dry gas diluent. The catalytic cracking may be carried out in a process using a train of fixed bed reactors while one or more other trains of fixed bed reactors are being regenerated or are on standby after being regenerated. When the train of fixed bed reactors being used needs regenerating, it is taken out of service and the one or more other trains of fixed bed reactors put in service to carry out the catalytic cracking process. Dry gas instead of steam may be used to reduce the partial pressure of hydrocarbons.