Mid-Column Reboiler Heat Integration in Alkylation

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Solution Overview

Problem

Existing solid bed alkylation processes for producing linear alkylbenzenes have high utility costs due to the large hot oil duty required by reboilers in separation processes.

Innovation Solution

Implementing a heat integration method using mid-column reboilers in benzene separation columns to reduce heat duty, where an n-paraffin rich stream is dehydrogenated to form a dehydrogenated stream, and heat is removed in mid-column reboilers to lower the temperature before aromatics removal, thereby minimizing hot oil duty on reboilers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If traditional reboilers are used in benzene separation columns, then separation function is maintained, but hot oil duty is excessively high

Engineering Contradiction:

Improvehot oil dutyVSAvoidseparation function

Core Design Contradiction:

Use of energy by stationary objectVSReliability

Solution Approach 1:

The patent changes the operational parameters of the reboiler by implementing mid-column steam injection, which modifies the heating mechanism from traditional external hot oil heating to internal steam heating. This parameter change reduces hot oil duty while maintaining the separation function through altered thermal distribution within the column.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces steam as an intermediary heating medium injected at the mid-column location. This steam acts as a mediator that transfers thermal energy directly to the vapor phase, reducing the reliance on hot oil and thereby reducing hot oil duty while maintaining effective separation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by stationary object

If mid-column reboilers with steam injection are implemented, then hot oil duty is reduced, but process complexity increases

Engineering Contradiction:

Improvehot oil dutyVSAvoidprocess complexity

Core Design Contradiction:

Use of energy by stationary objectVSDevice complexity

Solution Approach 1:

The mid-column steam injection system utilizes steam that is already generated within the distillation column from the boiling liquid. This self-service approach eliminates the need for separate external steam generation equipment, reducing process complexity while achieving reduced hot oil duty through internal heat recycling.

Inventive Principle:

Principle #25Self-service

3Use of energy by stationary object

If temperature is reduced in mid-column reboiler, then hot oil duty decreases, but separation efficiency may be compromised

Engineering Contradiction:

Improvehot oil dutyVSAvoidseparation efficiency

Core Design Contradiction:

Use of energy by stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by injecting steam at a specific mid-column location rather than uniform heating throughout. This localized heating approach reduces overall hot oil duty while maintaining separation efficiency by concentrating thermal energy where it is most effective for the specific separation requirements of that column section.

Inventive Principle:

Principle #3Local quality

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 the hot oil duty on reboilers by 15% in the alkylbenzene separation zone and 40% in the aromatics removal zone, while providing improved temperature control during start-up and shutdown.

Implementation Method 1

Heat is removed from at least a portion of the first dehydrogenated stream in a mid-column reboiler in a first benzene separation column to form a second dehydrogenated stream

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

dehydrogenating an n-paraffin rich stream in a dehydrogenation zone under dehydrogenation conditions to form a first dehydrogenated stream comprising n-paraffins, mono-olefins, di-olefins, and aromatics

Methodology Applied

Scientific EffectDehydrogenation: Chemical Transport Reactions

Implementation Method 3

Benzene is alkylated with the mono-olefin stream in an alkylation zone under alkylation conditions to provide an alkylation effluent stream comprising alkylbenzene, benzene, and n-paraffins

Methodology Applied

Scientific EffectAlkylation: Chemical Transport Reactions

Implementation Method 4

separating the alkylation effluent stream into an alkylbenzene stream and a second benzene stream in an alkylbenzene separation zone comprising the first benzene separation column

Methodology Applied

Scientific EffectDistillation: Distillation

Data Source

PatentUS10131591B2Heat reduction in alkylation process

Publication Date: 2018.11.20 CEPSA QUIMICA SA

AI summary

Processes using mid-column reboilers in at least one benzene separation columns to reduce the heat duty in alkylation processes are provided. The feed to the aromatics removal zone may exchange heat in a mid-column reboiler in the benzene separation column in the alkylbenzene separation zone followed by exchanging heat in a mid-column reboiler in the benzene separation column in the aromatics removal zone. This arrangement minimizes the hot oil duty on the reboilers in both benzene separation columns.