Decoking Steam Cracking Furnace Quench Steam Injection
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Solution Overview
Problem
Conventional steam cracking processes face issues with rapid coking in radiant coils and quench connections, leading to frequent feed interruptions, thermal fatigue, and difficulty in controlling decoking effluent temperatures due to stratified flow caused by liquid water injection during the decoking process.
Innovation Solution
The use of steam instead of liquid water for cooling during the decoking process in steam cracking, which prevents stratified flow and allows for tighter temperature control, reducing mechanical fatigue and optimizing quench steam demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid water is injected into the quench fitting to cool the decoking effluent, then cooling is achieved, but stratified flow occurs causing thermal fatigue and difficult temperature control
Solution Approach 1:
The invention changes the physical state parameter of the quenching medium from liquid water to steam. This parameter change eliminates stratified flow because steam mixes uniformly with the hot effluent vapor, preventing the formation of separate liquid and vapor layers that cause thermal fatigue in liquid water injection systems.
Solution Approach 2:
The invention uses steam (a gas phase medium) instead of liquid water, allowing the quenching medium to mix and dissipate without creating persistent stratified flow patterns. The steam integrates into the vapor phase and disappears through condensation or exhaust, avoiding the reliability issues of liquid water accumulation and stratification.
2Temperature
If liquid water is used for quenching during decoking, then cooling is provided, but maldistribution and stratified flow result leading to uneven temperature gradients
Solution Approach 1:
The invention changes the quenching medium from liquid water to steam, altering its physical state parameter. Steam injection creates homogeneous mixing with the effluent vapor, eliminating stratified flow and ensuring uniform temperature distribution throughout the pipe cross-section, which greatly simplifies temperature control.
Solution Approach 2:
The invention achieves homogeneous mixing by using steam (gas phase) that naturally mixes with the hot effluent vapor. This creates a uniform temperature distribution throughout the flow, eliminating the stratified flow patterns and uneven temperature gradients that occur with liquid water injection.
3Quantity of substance
If quench oil flow rate is reduced below design rates during decoking, then water injection is required, but this causes stratified flow and thermal fatigue
Solution Approach 1:
The invention changes the quenching medium from liquid water to steam, allowing effective quenching at lower flow rates. Steam's high heat transfer coefficient and ability to mix uniformly with the effluent vapor provide efficient cooling without creating stratified flow, even when flow rates are below the original oil quench fitting design rates.
Solution Approach 2:
The invention uses steam as a disposable quenching medium that mixes and dissipates without creating persistent flow patterns. This allows effective quenching at reduced flow rates without the reliability problems associated with liquid water injection, as the steam integrates into the vapor phase and avoids stratification.
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 mechanical fatigue and improves temperature control by maintaining a non-stratified vapor phase flow, enabling the target effluent temperature to be set closer to the metallurgical limit, thus optimizing process efficiency and reducing costs.
Implementation Method 1
quench steam is supplied and injected into the decoking process effluent in an amount sufficient to cool the decoking process effluent below the metallurgical temperature limit
Implementation Method 2
quench steam is supplied and injected into the decoking process effluent
Implementation Method 3
a decoking feed comprising steam and air is supplied to the furnace under conditions sufficient to at least partially combust coke accumulated on the interior of the radiant coils
Implementation Method 4
combust coke accumulated on the interior of the radiant coils
Data Source
AI summary
A process for the decoking of a hydrocarbon steam cracking furnace having a firebox, radiant coils, a transfer line exchanger, and an oil quench connection wherein liquid quench oil is injected to directly cool the steam-cracked effluent. Decoking feed comprising steam and air is supplied to the furnace under conditions sufficient to at least partially combust coke accumulated on the interior of the radiant coils, the transfer line exchanger, and the quench connection. Quench steam is supplied and injected into the decoking process effluent in an amount sufficient to cool the decoking process effluent below the metallurgical temperature limit of downstream piping. Also, a pyrolysis furnace for the production of ethylene is also provided.