Hydrocarbon Separation Sequence Using C2/C4 Stage

Solution Overview

Problem

In hydrocarbon separation processes, especially in olefin plants, the existing methods require high energy expenditure and risk polymer formation due to high bottom temperatures during front end C3/C4 separation, making sharp separation into C3− and C4+ fractions difficult and costly.

Innovation Solution

Incorporating a C2/C4 separation stage between the C4 absorber and depropanizer in the separation sequence, allowing for a sharper separation by reducing refrigeration requirements and maintaining temperatures that prevent polymer formation, thereby minimizing energy expenditure and apparatus costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If front end C3/C4 separation is performed directly after compression, then separation into C3- and C4+ fractions is achieved, but high bottom temperatures cause polymer formation and increased energy expenditure

Engineering Contradiction:

Improveseparation sharpnessVSAvoidpolymer formation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The separation process is divided into multiple stages: a first separation stage (C4 absorber) that operates at lower temperatures to prevent polymerization, followed by a second separation stage (depropanizer) that handles the remaining separation. This segmentation allows each stage to operate under optimized temperature conditions, avoiding the harmful high temperatures that cause polymer formation while still achieving sharp separation overall.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If front end C3/C4 separation is performed directly after compression, then separation into C3- and C4+ fractions is achieved, but energy expenditure and apparatus costs increase

Engineering Contradiction:

Improveseparation sharpnessVSAvoidenergy expenditure

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The separation process is divided into multiple stages: a first separation stage (C4 absorber) that operates at lower temperatures to prevent polymerization, followed by a second separation stage (depropanizer) that handles the remaining separation. This segmentation allows each stage to operate under optimized temperature conditions, avoiding the harmful high temperatures that cause polymer formation while still achieving sharp separation overall.

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If high C4+ fractions are present in raw gas, then separation difficulty increases, but existing methods cannot handle high C4+ fractions efficiently

Engineering Contradiction:

ImproveC4+ fraction contentVSAvoidseparation efficiency

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The separation process is divided into multiple stages: a first separation stage (C4 absorber) that operates at lower temperatures to prevent polymerization, followed by a second separation stage (depropanizer) that handles the remaining separation. This segmentation allows each stage to operate under optimized temperature conditions, avoiding the harmful high temperatures that cause polymer formation while still achieving sharp separation overall.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the operating parameters of the separation stages, specifically controlling the temperature and pressure conditions in the C4 absorber and depropanizer. By operating the C4 absorber at lower temperatures and optimizing the pressure conditions, the process can efficiently handle high C4+ fractions without causing polymer formation or losing separation efficiency.

Inventive Principle:

Principle #35Parameter changes

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 configuration enables efficient separation of hydrocarbons into C3− and C4+ fractions without polymer or deposit formation, reducing energy consumption and maintaining process efficiency even with high C4+ fractions, particularly in raw gases with a propylene to ethylene ratio of 1.5 or less.

Implementation Method 1

a C4 absorber and a depropanizer, wherein a hydrocarbon fraction of hydrocarbons having a maximum of 3 carbon atoms is obtained as a gaseous overhead product of the C4 absorber

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

a C4 absorber and a depropanizer, wherein a liquid hydrocarbon fraction of hydrocarbons having at least 4 carbon atoms is obtained as a bottom product of the depropanizer

Methodology Applied

Scientific EffectDistillation: Distillation

Implementation Method 3

the raw gas is compressed and dried

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS9919989B2Separation sequence for hydrocarbons from a gentle thermal cleavage

Publication Date: 2018.03.20 LINDE AG

AI summary

The invention describes a method for separating hydrocarbons in an installation for generating hydrocarbons from a hydrocarbon-containing charge by cleavage. The product gas of the cleavage, which contains gaseous hydrocarbons, is compressed, dried, and supplied as charge material into a separation stage (a front end C3/C4 separation). The front end C3/C4 separation comprises a C4 absorber and a depropanizer. A hydrocarbon fraction consisting of hydrocarbons having a maximum of 3 carbon atoms is obtained as a gaseous overhead product of the C4 absorber. A liquid hydrocarbon fraction consisting of hydrocarbons having at least 4 carbon atoms is obtained as a bottom product of the depropanizer. The front end C3/C4 separation comprises an additional process technological C2/C4 separation stage is arranged between the C4 absorber and the depropanizer.