Absorber-Based C2+ Hydrocarbon Recovery Without Expansion Turbine
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Solution Overview
Problem
The existing methods for recovering C2+ hydrocarbons from residual refinery gases are complex and costly, requiring a dynamic expansion turbine and cold box, which increases initial investment, space requirements, and maintenance needs, limiting reliability and productivity.
Innovation Solution
A method involving the use of an absorber to separate cooled overhead flows by injecting a methane-rich stream, eliminating the need for dynamic expansion and simplifying the heat exchanger structure, allowing cooling without static or dynamic expansion, and utilizing a methane-rich stream to efficiently recover C2+ hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a dynamic expansion turbine and cold box are used to cool the overhead flow, then the temperature drop is sufficient to minimize losses of ethylene and ethane, but the device complexity and initial investment increase significantly
Solution Approach 1:
The invention extracts and eliminates the dynamic expansion turbine and cold box from the system. Instead of using these complex components, the patent uses a simpler cooling system where the overhead flow is cooled by heat exchange with the effluent stream, thereby achieving temperature reduction without the need for expansion turbines or complex cold boxes.
Solution Approach 2:
The overhead flow is cooled using the effluent stream as a heat sink, allowing the system to cool itself without external cooling equipment. The effluent stream, which is already cold from the distillation column, serves to cool the overhead flow through heat exchange, eliminating the need for separate cooling devices.
2Productivity
If a dynamic expansion turbine is installed to expand the effluent stream, then the recovery of C2+ hydrocarbons is improved, but the maintenance requirements and reliability issues increase
Solution Approach 1:
The invention removes the dynamic expansion turbine from the process. The effluent stream is not expanded through a turbine but is directly used to cool the overhead flow in a heat exchanger. This eliminates the reliability issues and maintenance requirements associated with expansion turbines while maintaining the productivity benefits through efficient heat exchange.
Solution Approach 2:
The mechanical expansion system (dynamic expansion turbine) is replaced with a thermal exchange system (heat exchanger). Instead of using mechanical expansion to cool the overhead flow, the patent uses thermal energy transfer between the effluent stream and the overhead flow, thereby eliminating moving parts and mechanical reliability concerns.
3Temperature
If a cold box of complex structure is used to circulate the gas leaving the dynamic expansion turbine, then the cooling function is achieved, but the space requirements and initial investment increase
Solution Approach 1:
The invention extracts and eliminates the cold box from the system. The cooling function previously performed by the complex cold box structure is achieved through a heat exchanger that uses the effluent stream to cool the overhead flow. This eliminates the need for large-scale cold box infrastructure and associated space requirements.
Solution Approach 2:
The cooling function is merged into the heat exchange process between the effluent stream and the overhead flow. Instead of having a separate cold box system for cooling, the patent combines the cooling function with the existing effluent stream, using it as a heat sink to achieve temperature reduction in a compact and integrated manner.
4Productivity
If successive cooling, condensation and separation steps are carried out in successive vessels, then the light hydrocarbon recovery is achieved, but the device complexity and operating costs increase
Solution Approach 1:
The invention merges multiple separation functions into a single distillation column. Instead of using successive vessels for cooling, condensation, and separation, the patent uses one distillation column that performs all these functions in an integrated manner. The overhead flow from the flash drum is cooled and fed into the distillation column, which simultaneously handles condensation and separation of C2+ hydrocarbons.
Solution Approach 2:
The distillation column is designed to perform multiple functions: it cools the overhead flow, condenses the hydrocarbons, and separates the C2+ components from lighter gases. This multi-functional approach eliminates the need for separate dedicated vessels for each function, thereby reducing device complexity and operating costs while maintaining light hydrocarbon recovery efficiency.
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 investment and operating costs, simplifies maintenance, and maintains reliable C2+ hydrocarbon recovery without the need for complex equipment, ensuring efficient operation during continuous and transitory shutdowns.
Implementation Method 1
cooling the overhead flow in a heat exchanger to form a cooled overhead flow
Implementation Method 2
separating the cooled overhead flow into a liquid lower stream feeding the distillation column and into a gaseous top stream
Implementation Method 3
feeding the bottom flow into a distillation column; recovering the stream of C2+ hydrocarbons at the bottom of the distillation column
Implementation Method 4
heating the or each effluent stream in the heat exchanger via heat exchange with the overhead flow
Data Source
AI summary
This method comprises passing a residual stream into a flash drum to form a gaseous overhead flow and liquid bottom flow, and feeding the bottom flow into a distillation column,It comprises cooling the overhead flow in a heat exchanger to form a cooled overhead flow.It comprises the extraction of a gaseous overhead stream at the head of the distillation column, and the formation of at least one effluent stream from the overhead stream and/or from the top stream.The separation of the cooled overhead flow comprises passing the cooled overhead flow into an absorber, and injecting a methane-rich stream into the absorber to place the cooled overhead flow in contact with the methane-rich stream.