Staged Hydrotreating and Hydrocracking Process for Diesel Preservation
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Solution Overview
Problem
In hydrocracking processes, there is a need to preserve diesel production by preventing its conversion to naphtha, as hydrocarbon feed streams often contain significant diesel proportions that can be inadvertently cracked if not properly managed.
Innovation Solution
Separating diesel and lighter materials from the hydrotreated stream, allowing only the liquid hydrotreated material to be fed to the hydrocracking reactor, while routing a branch stream from the hydrogen processing stream around the hydrotreating reactor to supply hydrogen to the hydrocracking reactor, thus bypassing hydrogen sulfide and ammonia that could inhibit the hydrocracking catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrocarbon feed stream containing diesel is fed directly to hydrocracking reactor, then hydrocracking reaction proceeds, but diesel is cracked to naphtha which reduces diesel yield
Solution Approach 1:
The process separates the hydrocarbon feed stream into two distinct phases: a liquid phase containing diesel and heavier hydrocarbons that is fed to the hydrocracking reactor, and a gas phase containing lighter materials that is separated and removed. This segmentation prevents diesel from being cracked to naphtha while still allowing hydrocracking of desired heavier components.
Solution Approach 2:
The liquid hydrotreated stream is separated from the gas stream before entering the hydrocracking reactor. This preliminary separation action ensures that only the appropriate liquid phase components proceed to hydrocracking, preventing unwanted diesel cracking while maintaining reactor efficiency.
2Productivity
If hydrotreated stream is fed directly to hydrocracking reactor, then processing continues, but hydrogen sulfide and ammonia inhibit the hydrocracking catalyst
Solution Approach 1:
The process extracts and removes hydrogen sulfide and ammonia from the hydrotreated stream through phase separation. These harmful substances are concentrated in the gas phase which is separated before the liquid stream enters the hydrocracking reactor, thereby protecting the catalyst from inhibition while maintaining process throughput.
Solution Approach 2:
The phase separation unit acts as an intermediary between the hydrotreating reactor and the hydrocracking reactor. It mediates by removing harmful substances (hydrogen sulfide and ammonia) from the stream, allowing the liquid phase to proceed to hydrocracking without catalyst poisoning while the gas phase containing inhibitors is diverted.
3Productivity
If diesel and lighter materials are removed from hydrotreated gas stream, then diesel is preserved, but hydrogen is removed from the hydrocracking feed stream
Solution Approach 1:
The separated gas stream containing hydrogen, along with the hydrocracked stream, is fed to a fractionation column that simultaneously performs multiple functions: separating light gases from liquids, recovering hydrogen for recycle, and producing diesel and naphtha products. This multi-functionality addresses the hydrogen removal issue while preserving diesel.
Solution Approach 2:
The process discards the separated gas stream from the hydrocracking feed path but recovers the hydrogen contained within it by feeding it to the fractionation column. The hydrogen is then available for recycle to the hydrotreating and hydrocracking reactors, thereby preserving diesel yield while maintaining hydrogen availability for the hydrocracking reaction.
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 preserves diesel yield by preventing further cracking to naphtha, maintaining diesel boiling range products and reducing catalyst poisoning, thereby optimizing hydrocracking reactor capacity and efficiency.
Implementation Method 1
separating a hydrotreated stream from a hydrotreating reactor in a separator and sending only the liquid from the separator to a hydrocracking reactor
Data Source
AI summary
An apparatus and process is disclosed for hydrocracking a hydrocarbon feed stream following hydrotreating the feed stream. A separator removes diesel and lower boiling materials in a hydrotreated stream before a hydrocracking reactor, so only liquid materials heavier than diesel are hydrocracked in a hydrocracking reactor. A vapor hydrotreated stream and the hydrocracked stream are separated and fractionated together.