Pyrolysis Furnace Coil Switching for On-line Decoking
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Solution Overview
Problem
Current processes for producing olefins from hydrocarbon feedstocks, such as methane and natural gas, face challenges including coke formation in pyrolysis furnaces, which leads to frequent downtime for decoking and inefficiencies in converting lighter hydrocarbons due to high temperatures required.
Innovation Solution
A process utilizing a pyrolysis furnace with alternating coils carrying hydrocarbon feedstock and steam, where the coils are heated to specific temperatures and residence times for partial conversion, followed by an adiabatic reactor for further conversion, and on-line decoking is achieved by switching steam and hydrocarbon flows to reduce coke deposition, along with using ceramic insulation and high-temperature hydrogen combustion to convert methane to olefins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrocarbon feedstock is passed through pyrolysis furnace coils to convert to olefins, then olefin production is achieved, but coke forms on coil surfaces inhibiting heat transfer and requiring shutdown for decoking
Solution Approach 1:
The patent implements periodic switching between multiple coil sets, where coils are alternately used for hydrocarbon cracking and steam decoking. This periodic action allows the cracking process to continue while designated coils are cleaned, eliminating complete shutdowns and maintaining continuous olefin production.
Solution Approach 2:
By having multiple coil sets that can be switched between cracking and decoking modes, the patent ensures continuous olefin production. While some coils undergo decoking, others remain in service, maintaining uninterrupted useful action in the pyrolysis furnace.
2Productivity
If higher temperatures are used to convert methane to olefins, then conversion rate improves, but equipment damage and operational difficulty increase
Solution Approach 1:
The patent optimizes temperature parameters within a specific range (800-1100°C) for methane conversion, balancing conversion efficiency with equipment safety. By controlling residence time and temperature parameters, the process achieves high conversion rates while avoiding temperatures that would cause equipment damage or excessive operational difficulty.
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 extends run times between shut downs, improves olefin yields, and allows the use of less expensive methane or natural gas as feedstock, while minimizing coke formation and maintaining high conversion rates.
Implementation Method 1
the hydrocarbons are heated to a temperature sufficient to obtain partial conversion of the hydrocarbons to olefins
Implementation Method 2
the steam is superheated
Implementation Method 3
The energy required to convert the hydrocarbon feedstock to olefins in the adiabatic reactor is provided from the superheated steam
Implementation Method 4
high-temperature hydrogen combustion to convert methane to olefins
Data Source
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AI summary
Processes for production of olefins from hydrocarbon feedstocks are provided. In one aspect, the processes of the present invention utilize coils passing through a pyrolysis furnace to partially convert a hydrocarbon feedstock to olefins, followed by further conversion of the hydrocarbon feedstock in an adiabatic reactor. A portion of the coils in the pyrolysis furnace carry the hydrocarbon feedstock and the remainder carry steam only. After a selected period of time, the material flowing through the coils is switched. By flowing steam through the coils that had previously contained the hydrocarbon feedstock, on-line decoking can occur. In another aspect, a high temperature reactor is used to convert methane or natural gas to olefins.