Tangential Wetting Fluid Injection for TLE Fouling Control
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Solution Overview
Problem
Current quenching processes in olefins plants face issues with fouling and heat loss, leading to short run times and reduced generation of superheated steam, particularly when handling heavy feeds or low hydrogen content feeds, which necessitate frequent decoking and inefficient heat recovery.
Innovation Solution
A process involving a minimal amount of wetting fluid injection into TLEs using a tangential nozzle, maintaining the tube wall wetted to prevent coking while allowing high-pressure steam generation, and extending the operational range to include secondary TLEs for heat recovery down to lower temperatures, using less viscous oils to control fouling and recover heat effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct quench is used to cool pyrolysis effluent, then quenching speed is improved, but coking on tube walls increases and steam generation decreases
Solution Approach 1:
The patent applies the wetted-wall principle where a thin film of wetting fluid continuously coats the inner surface of quench tubes. This flexible liquid film acts as a barrier between the hot pyrolysis effluent and the tube wall, preventing coking while allowing rapid heat transfer for efficient quenching and steam generation.
Solution Approach 2:
The wetting fluid serves as an intermediary substance between the pyrolysis effluent and the tube wall. It mediates the heat transfer process while preventing direct contact between the coking-prone effluent and the tube surface, thus eliminating coking without sacrificing quenching effectiveness.
2Quantity of substance
If TLE is used to cool pyrolysis products, then steam generation is improved, but fouling increases and run length decreases
Solution Approach 1:
The patent employs a continuous thin film of wetting fluid on the TLE tube walls to prevent tar and coke deposition. This maintains the heat transfer surface integrity over extended periods, allowing the TLE to generate steam efficiently while achieving much longer run lengths between decoking operations.
3Object-generated harmful factors
If quench oil is injected to wet tube walls, then coking is prevented, but heat recovery efficiency decreases
Solution Approach 1:
The patent uses a minimal amount of wetting fluid - just enough to form a thin protective film on the tube walls without substantially cooling the effluent. This partial action approach prevents coking while minimizing the energy consumed by the wetting fluid, thus maintaining high heat recovery efficiency.
Solution Approach 2:
The patent carefully controls the parameters of wetting fluid injection (flow rate, temperature, composition) to achieve the optimal balance between coking prevention and heat recovery. By adjusting these parameters, the system maintains effective tube wall wetting while minimizing the thermal energy consumed by the wetting process.
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 results in reduced fouling, longer TLE run-lengths, increased heat recovery as high-pressure steam, and the ability to process heavier feeds without frequent decoking, enhancing the overall efficiency and financial viability of olefins production.
Implementation Method 1
injecting a wetting fluid tangentially into said gaseous cracked effluent stream at said low-pressure zone at a momentum sufficient to cause said wetting fluid to flow circumferentially around the inside surface of said tube side
Implementation Method 2
cause said wetting fluid to flow circumferentially around the inside surface of said tube side; providing a sharp interface between said gaseous cracked effluent stream and said first wetting fluid
Implementation Method 3
a shell-and-tube heat exchanger where the hot gaseous cracked effluent stream is indirectly cooled on the tube side while generating high-pressure steam from boiler feed water on the shell side
Implementation Method 4
the hot gaseous cracked effluent stream is indirectly cooled on the tube side while generating high-pressure steam from boiler feed water on the shell side
Implementation Method 5
a flow obstruction means is positioned in said tube side of the second section to create a low-pressure zone in said gaseous cracked effluent stream immediately downstream of said flow obstruction means
Implementation Method 6
injecting a wetting fluid tangentially into said gaseous cracked effluent stream at said low-pressure zone at a momentum sufficient to cause said wetting fluid to flow circumferentially around the inside surface of said tube side
Data Source
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AI summary
The invention comprises a process for cracking liquid hydrocarbon feed to produce cracked gaseous hydrocarbons comprising feeding a liquid hydrocarbon feed stream to an olefins furnace; cracking the liquid hydrocarbon feed stream in the olefins furnace to produce a gaseous cracked effluent stream; feeding the cracked effluent from the olefins furnace to a primary transfer line heat exchanger (TLE) having two sections; injecting a first wetting fluid in a weight ratio of wetting fluid to hot gaseous effluent tangentially into the hot gaseous effluent stream at a particular location in the second section of the primary TLE; feeding the hot gaseous effluent stream exiting from the TLE to a separator; separating a separator bottoms stream comprising tar and heavier hydrocarbons and a separator product stream comprising an olefin product; and recovering an olefin product from the separator product stream.