Method for preparing ethylene and apparatus for preparing ethylene
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Solution Overview
Problem
The pyrolysis method for producing ethylene faces challenges in managing changes in cracking yield due to variations in feedstock types, leading to increased methane content and overload issues in the purification process, especially when propane is used as a feedstock, which disrupts the process stability and efficiency.
Innovation Solution
The method involves using a series of heat exchangers and separators to manage the cracking yield by cooling and compressing the feed streams effectively, utilizing circulation flows and refrigerants to maintain process stability, and adjusting the process to handle changes in feedstock composition, particularly by using a second heat exchanger and third gas-liquid separator to control methane content and prevent ethylene loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an additional furnace using propane as feedstock is installed to increase ethylene production, then productivity is improved, but the content of methane in the product increases causing overload in purification process
Solution Approach 1:
The purification process is segmented into multiple stages with dedicated demethanizer columns. The first demethanizer handles methane removal from the main pyrolysis product stream, while a second demethanizer specifically processes the gas-phase pyrolysis product stream. This segmentation allows each column to be optimized for its specific feed composition and prevents methane overload in any single purification unit.
Solution Approach 2:
A methane removal system acts as an intermediary between the pyrolysis furnaces and the downstream purification process. The system includes compressors, heat exchangers, and demethanizer columns that specifically target and remove methane from the product stream before it enters the main purification train, preventing overload in subsequent processing units.
2Ease of manufacture
If the proportion of propane pyrolysis is increased to lower production cost, then ease of manufacture is improved, but process stability deteriorates due to large difference in cracking yield
Solution Approach 1:
The system incorporates dynamic control mechanisms including adjustable feed ratios between liquid-phase (naphtha) and gas-phase (propane/ethane) pyrolysis furnaces. The circulation system for C2-C4 hydrocarbons allows flexible adjustment of feed composition to maintain stable cracking yields. Process control systems monitor and adjust operating parameters in real-time to compensate for variations in feedstock composition and maintain process stability.
Solution Approach 2:
The patent employs parameter changes in the pyrolysis process including temperature control, residence time adjustment, and pressure regulation to optimize cracking yields for different feedstocks. The system can adjust pyrolysis conditions based on the specific feedstock being processed (propane vs. ethane vs. naphtha) to maintain consistent product distribution and process stability.
3Productivity
If additional processes for cooling, compressing, and purifying are added to increase ethylene yield, then productivity is improved, but device complexity increases due to space requirements
Solution Approach 1:
The patent merges multiple functions into integrated process units. The purification system combines cooling, compression, and separation functions in a coordinated sequence. The C2-C4 hydrocarbon circulation system integrates compression, heat exchange, and feed distribution functions. The demethanizer and deethanizer columns are designed to handle multiple separation tasks, reducing the total number of independent equipment units required.
Solution Approach 2:
Process equipment is designed with multi-functionality to reduce overall system complexity. The heat exchangers serve both cooling and heating functions at different stages of the process. Compressors handle multiple gas streams and can be adjusted for different operating conditions. The purification train is designed to accommodate variations in feed composition and production rates, providing universal handling capability across different operating scenarios.
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 allows for flexible operation of the ethylene production process, enabling the free installation and operation of additional gas furnaces and maintaining process stability even during interruptions in the liquid phase decomposition step, thereby minimizing ethylene loss and preventing overload in the purification process.
Implementation Method 1
passing a feed stream containing C1 and C2 hydrocarbon compounds through a first heat exchanger
Implementation Method 2
feeding the feed stream to a second gas-liquid separator
Implementation Method 3
feeding the overhead discharge stream of the second gas-liquid separator to a third gas-liquid separator
Data Source
AI summary
A method for preparing ethylene, including: passing a feed stream containing C1 and C2 hydrocarbon compounds through a first heat exchanger and feeding the feed stream passed through the first heat exchanger to a second gas-liquid separator; feeding a part of a bottom discharge stream of the second gas-liquid separator to a demethanizer, passing an overhead discharge stream of the second gas-liquid separator through a second heat exchanger, feeding the overhead discharge stream of the second gas-liquid separator passed through the second heat exchanger to a third gas-liquid separator; feeding a bottom discharge stream of the third gas-liquid separator to the demethanizer; feeding a bottom discharge stream of the demethanizer to a C2 separator; feeding an overhead discharge stream of the C2 separator to a second compressor; passing a part of a compressed discharge stream of the second compressor through the first heat exchanger and feeding the part of the compressed discharge stream of the second compressor passed through the first heat exchanger to the second compressor as a first circulation flow; passing a part of the compressed discharge stream of the second compressor through the second heat exchanger and feeding the part of the compressed discharge stream of the second compressor passed through the second heat exchanger to a first compressor as a second circulation flow; and feeding a compressed discharge stream of the first compressor to the second compressor, and an apparatus for preparing ethylene for implementing the same.