Inverted Riser Termination Device for Hydrocarbon Cracking

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Solution Overview

Problem

Existing gas-solid separation devices in hydrocarbon cracking units face challenges in achieving rapid and efficient separation of phases, leading to overcracking and the production of undesirable by-products, with limitations in scale-up potential and efficiency due to erosion issues and residual gas degradation.

Innovation Solution

A gas-solids separation device with a centrifugal turning portion, angular ledge for solid compaction, and a dipleg system that allows for efficient separation and pre-stripping, reducing vapor underflow and enabling operation in a sealed mode, utilizing a baffle and gap design to enhance separation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional cyclones or curvilinear conduit separators are used to separate gas from solids, then separation is achieved, but substantial quantities of gas flow past the withdrawal point to the solids outlet requiring additional conventional separators

Engineering Contradiction:

Improveseparation efficiencyVSAvoidnumber of separators required

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional separator design by having the gas outlet positioned at the bottom rather than the top, and by using a linear conduit with a sharp 90-degree turn instead of a curvilinear path. This inversion causes solids to be directed toward the outlet while gas is efficiently withdrawn, eliminating the need for additional separators.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The separator is divided into distinct functional zones: an inlet portion for receiving the mixed stream, a turning portion with a sharp 90-degree bend for directional change, a vertical portion for separation, and an outlet portion. This segmentation allows each zone to perform its specific function optimally, improving overall separation efficiency.

Inventive Principle:

Principle #1Segmentation

2Volume of moving object

If conduit diameter is increased for scale-up, then commercial size is achieved, but separator residence time increases approaching conventional cyclone times

Engineering Contradiction:

Improveconduit diameterVSAvoidseparator residence time

Core Design Contradiction:

Volume of moving objectVSLoss of time

Solution Approach 1:

By inverting the separator design with the gas outlet at the bottom and using a linear conduit with sharp turn, the patent achieves rapid separation even in large diameter conduits. The sharp 90-degree turn creates immediate directional separation that prevents prolonged residence time regardless of conduit size, enabling effective scale-up.

Inventive Principle:

Principle #13The other way round (Inversion)

3Speed

If velocity is increased to reduce residence time, then separation speed improves, but erosion by particles impinging on the conduit wall progressively worsens

Engineering Contradiction:

Improvegas-solids velocityVSAvoidconduit wall erosion

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The inverted design with sharp 90-degree turn and bottom gas outlet creates a flow pattern where solids are directed toward the outlet rather than impinging on conduit walls. This reduces erosion even at high velocities while maintaining rapid separation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The separation process is segmented into distinct zones with the turning portion handling directional change and the vertical portion handling separation. This segmentation allows high velocity flow to be contained in the turning portion where erosion is minimized by the sharp turn geometry, while the vertical portion operates at lower velocities.

Inventive Principle:

Principle #1Segmentation

4Loss of time

If curvilinear path radius is decreased to reduce path length, then residence time decreases, but angle of impact of solids against wall increases accelerating erosion

Engineering Contradiction:

Improveseparator residence timeVSAvoidsolids wall impact erosion

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the curvilinear path with a linear conduit featuring a sharp 90-degree turn. This inversion eliminates the progressive erosion problem of curvilinear paths by creating an immediate directional change that directs solids toward the outlet rather than along a long curved path where impact angles increase.

Inventive Principle:

Principle #13The other way round (Inversion)

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

The device achieves improved solid separation efficiency, reduces vapor underflow, and allows for pre-stripping, effectively preventing overcracking and enhancing the operational efficiency and scalability of gas-solid separation in catalytic and thermal cracking operations.

Implementation Method 1

a turning portion for imparting a centrifugal motion onto said spent solids and cracked product vapors

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS7429363B2Riser termination device

Publication Date: 2008.09.30 STONE & WEBSTER PROCESS TECHNOLOGY INC

AI summary

The present invention provides an improved separator for use in hydrocarbon cracking process.