Selective Diolefin Hydrogenation in Cracked Naphtha Streams
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Solution Overview
Problem
Diolefins in cracked naphtha and LPG streams from processes like FCC and delayed coking pose challenges due to fouling and catalyst poisoning, requiring an efficient method to remove these contaminants to prevent undesirable conditions in downstream petrochemical applications.
Innovation Solution
A process involving the selective hydrogenation of diolefins in cracked streams before debutanization, using a diolefin hydrogenation reactor in conjunction with fractionation and stripping columns, to produce diolefin-depleted streams that reduce fouling and catalyst poisoning, thereby improving the quality of naphtha and LPG for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diolefins are removed from cracked streams using conventional downstream treatment, then fouling and catalyst poisoning are prevented, but process complexity and operational steps increase
Solution Approach 1:
The patent applies preliminary action by performing diolefin hydrogenation upstream in the debutanizer overhead stream before the stream is separated into naphtha and LPG products. This prevents fouling and catalyst poisoning in downstream applications while avoiding the need for additional downstream treatment steps, thereby reducing overall process complexity
2Reliability
If diolefins are hydrogenated in the liquid cracked stream, then fouling is prevented, but additional hydrogen consumption and processing steps are required
Solution Approach 1:
The patent extracts the diolefin hydrogenation step from the conventional downstream treatment sequence and relocates it to the debutanizer overhead stream. By targeting specifically the diolefin-containing overhead fraction rather than treating the entire cracked stream, hydrogen consumption is reduced while still preventing fouling and catalyst poisoning in the final naphtha and LPG products
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 effectively eliminates the need for additional hydrotreatment, prevents polymerization fouling, and ensures the diolefin-depleted streams can be stored without gum formation, enhancing the stability and usability of cracked naphtha and LPG in downstream applications.
Implementation Method 1
selectively hydrogenating diolefins in the liquid, cracked stream to provide a diolefin depleted, liquid cracked stream
Implementation Method 2
The cracked stream is fractionated to provide a liquid, cracked stream
Implementation Method 3
The cracked stream is subsequently stripped to remove dry gas from the liquid, cracked stream
Implementation Method 4
The stripped, liquid cracked stream is debutanized to provide a naphtha stream and an LPG stream
Data Source
AI summary
The present invention discloses a process and apparatus for selectively hydrogenating diolefins in a cracked stream. The method combines a conversion unit and a recovery section. The recovery section includes the diolefin hydrogenation reactor that is used to selectively hydrogenate the diolefins in the cracked naphtha. The diolefin depleted naphtha may be debutanized to separate the stabilized naphtha and liquefied petroleum gas streams.