Split Shell Stripper for Naphtha Desulfurization

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Solution Overview

Problem

Conventional fixed bed hydrotreating for naphtha desulfurization results in significant octane number loss due to reduction of olefin content, necessitating techniques that minimize sulfur levels while preserving olefin content and reducing operational costs.

Innovation Solution

A method involving fractionation and multiple stages of hydrotreating with a split shell stripper vessel, utilizing di-olefin hydroprocessing and subsequent hydrotreating reactors to convert sulfur to H2S while enriching olefin content, and using a single split shell stripper vessel for downstream H2S removal to minimize equipment and operational costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional fixed bed hydrotreating is used to desulfurize naphtha, then sulfur content is reduced to very low levels, but octane number is significantly lost due to extensive reduction of olefin content

Engineering Contradiction:

Improvesulfur contentVSAvoidolefin content

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The hydrotreating process is divided into two distinct stages: a first stage that selectively converts di-olefins to olefins, and a second stage that hydrodesulfurizes the olefin-enriched naphtha. This segmentation allows each stage to be optimized for its specific function, preventing excessive olefin reduction while achieving low sulfur content.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first hydrotreating stage performs preliminary conversion of di-olefins to olefins before the second stage processes the hydrodesulfurization. This preliminary action enriches the olefin content in the feed to the second stage, ensuring that the hydrodesulfurization occurs under conditions that preserve olefin integrity and maintain octane number.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If multiple separate equipment units are used for desulfurization and H2S removal, then processing effectiveness is improved, but device complexity and operational cost increase

Engineering Contradiction:

Improvesulfur and H2S removal effectivenessVSAvoidequipment quantity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The first and second vapor-liquid contacting chambers are combined into a single split shell stripper vessel with a dividing wall. This merging of equipment reduces the number of separate units while maintaining the functional separation of H2S removal stages, thereby reducing device complexity and operational cost while preserving processing effectiveness.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The split shell stripper vessel serves multiple functions: it acts as both a fractionation column for H2S removal and as a separation device for the two hydrodesulfurization stages. This multi-functionality eliminates the need for separate equipment units, reducing overall device complexity while maintaining processing effectiveness.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces sulfur levels in naphtha while preserving olefin content, maintaining octane number and minimizing additional equipment and operational costs, allowing for more robust processing conditions and improved product quality.

Implementation Method 1

contacting a naphtha feed stream that comprises sulfur, C6-C12 hydrocarbons, olefins, aromatics, and di-olefins with a di-olefin hydroprocessing catalyst in the presence of hydrogen at hydrogenation conditions effective to convert di-olefins to olefins

Methodology Applied

Scientific EffectHydrogenation: Hydrogenation

Implementation Method 2

contacting the olefin-enriched naphtha stream with a hydrotreating catalyst in the presence of hydrogen at hydroprocessing conditions effective to convert sulfur to H2S

Methodology Applied

Scientific EffectHydrodesulfurization: Hydrogenation

Implementation Method 3

The partially hydrodesulfurized, olefin-enriched naphtha stream is fractionated in a vapor-liquid contacting chamber to form a partially hydrodesulfurized, H2S-depleted, olefin-enriched naphtha stream

Methodology Applied

Scientific EffectFractionation: Fractionation

Data Source

PatentUS10144883B2Apparatuses and methods for desulfurization of naphtha

Publication Date: 2018.12.04 UOP LLC

AI summary

Embodiments of apparatuses and methods for desulfurization of naphtha are provided. In one example, a method comprises fractionating a partially hydrodesulfurized, olefin-enriched naphtha stream in a first vapor-liquid contacting chamber to form a partially hydrodesulfurized, H2S-depleted, olefin-enriched naphtha stream. The partially hydrodesulfurized, H2S-depleted, olefin-enriched naphtha stream is contacted with a hydrotreating catalyst to form an additionally hydrodesulfurized, olefin-enriched naphtha stream. The additionally hydrodesulfurized, olefin-enriched naphtha stream is fractionated in a second vapor-liquid contacting chamber to form a hydrodesulfurized, H2S-depleted, olefin-enriched naphtha product stream. The first and second vapor-liquid contacting chambers are enclosed in a split shell stripper vessel and separated by a dividing wall.