On-Stream Decoking in Pyrolysis Furnaces
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Solution Overview
Problem
Current on-stream decoking processes for pyrolysis furnaces face challenges such as the need for complete cessation of olefins production and reduced operator flexibility due to temperature control issues, especially when using steam alone, which can lead to excessive crossover temperatures and material capacity limitations.
Innovation Solution
Implementing a process that introduces steam at pressures of ≥690 kPag, particularly ≥930 kPag, into the pyrolysis furnace to remove coke deposits while maintaining hydrocarbon feed flow to other coils, allowing for simultaneous decoking and controlling crossover temperatures through automated firing rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam alone is used for decoking, then the decoking process can be performed, but the crossover temperature exceeds the capacity of commonly used materials
Solution Approach 1:
The patent changes the pressure parameter of the steam from low-pressure to high-pressure (≥690 kPag, particularly ≥930 kPag). This parameter change allows the steam to achieve effective decoking while maintaining crossover temperature within material capacity limits, resolving the contradiction between decoking effectiveness and temperature control
2Reliability
If steam-air-decoking is used to remove coke deposits, then coke removal is effective, but olefins production must be completely halted
Solution Approach 1:
The patent enables continuous decoking by introducing high-pressure steam into selected radiant coils while other coils continue to produce olefins. This maintains continuous useful action in both decoking and production processes simultaneously, eliminating the need to halt olefins production while ensuring effective coke removal
3Temperature
If water is added to steam or low-pressure steam is used to control crossover temperature, then temperature is controlled within material capacity, but operator flexibility is reduced
Solution Approach 1:
The patent changes the pressure parameter of the steam to high-pressure (≥690 kPag, particularly ≥930 kPag), which provides inherent temperature control capability without requiring water addition. This maintains operator flexibility while ensuring crossover temperature remains within material capacity limits
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 enables on-stream decoking without halting production, enhances operator flexibility, and maintains crossover temperature within safe limits, reducing light olefin production losses and extending radiant coil lifespan.
Implementation Method 1
Air is added to the steam passing through the furnace and the heated air/steam mixture removes the coke deposits by controlled combustion
Implementation Method 2
At least a portion of the hydrocarbon feed can be pyrolysed in the first radiant coil and the second radiant coil to produce a pyrolysis effluent and to deposit coke on an inner surface of each of the first radiant coil and the second radiant coil
Data Source
AI summary
In some examples, a flow of hydrocarbon feed can be introduced into a pyrolysis furnace that includes a first radiant coil and a second radiant coil. At least a portion of the hydrocarbon feed can be pyrolysed in the first radiant coil and the second radiant coil to produce a pyrolysis effluent and to deposit coke on an inner surface of each of the first radiant coil and the second radiant coil. The flow of the hydrocarbon feed can be decreased into the first radiant coil and the flow of the hydrocarbon feed into the second radiant coil can be maintained, wherein the flow of the hydrocarbon feed into the pyrolysis furnace can be decreased by about 10 vol. % to about 90 vol. %. A decoking feed including steam at a pressure of ≥690 kPag can be introduced into the first radiant coil of the pyrolysis furnace to remove at least a portion of the coke deposited on the inner surface of the first radiant coil.