Hydrocarbon Cracking Riser Spent Catalyst Temperature Control
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Solution Overview
Problem
Existing hydrocarbon cracking processes face issues with over-cracking and coking due to high temperatures at the base of the riser, which reduces product yield and increases mechanical corrosion from rapid gas expansion.
Innovation Solution
A process where at least 99% of the hydrocarbon feed is provided as a gas with an effective amount of C4-C6 olefins, using a mixture of catalysts with different pore sizes to prevent over-cracking and reduce coke formation, and positioning spent catalyst at the bottom of the riser to manage temperature and prevent mechanical corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regenerated catalyst is provided at the base of the riser, then catalyst activity is maintained, but temperature increases causing over-cracking and coking
Solution Approach 1:
The harmful hot regenerated catalyst is extracted from the base of the riser and replaced with cooler spent catalyst. This removes the temperature-raising element while maintaining catalyst circulation and activity through the spent catalyst's residual catalytic properties.
Solution Approach 2:
Spent catalyst acts as an intermediary substance that transfers the necessary catalytic function to the hydrocarbon feed without introducing the excessive heat that regenerated catalyst would bring. The spent catalyst mediates between the need for catalyst activity and the need to control temperature.
2Productivity
If high temperature is maintained in the riser, then cracking reaction rate increases, but over-cracking and coking increase reducing product yield
Solution Approach 1:
The temperature parameter in the riser is changed from high (regenerated catalyst condition) to lower (spent catalyst condition). This parameter change maintains sufficient cracking reaction rate while preventing over-cracking and coking, thereby improving product yield.
3Ease of manufacture
If hydrocarbon feed is provided as liquid, then feedstock handling is simplified, but heat requirements increase and mechanical corrosion occurs due to rapid gas expansion
Solution Approach 1:
The hydrocarbon feed is pre-heated and vaporized before entering the riser, transitioning from liquid to gas phase. This eliminates the need for additional heat input within the riser and prevents the rapid gas expansion that would cause mechanical corrosion, while still allowing simplified feedstock handling upstream.
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 over-cracking, minimizes coke formation, and increases production of light olefins like ethylene and propylene, while lowering heat requirements and mechanical corrosion in the riser.
Implementation Method 1
the presence of the spent catalyst at the bottom of the riser can prevent over-cracking of the hydrocarbon feed... due to the presence of the spent catalyst having a lower temperature
Implementation Method 2
Process for cracking a hydrocarbon feed... catalytically cracking a hydrocarbon feed
Data Source
AI summary
An embodiment can be a process for catalytically cracking a hydrocarbon feed. The process can include providing the hydrocarbon feed including an effective amount of one or more C4-C6 olefins for producing at least one light olefin to a riser. Typically, at least about 99%, by mole, of the hydrocarbon feed is a gas.