Gas stream component removal system and method
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Solution Overview
Problem
Natural gas liquefaction processes are impaired by the freezing of heavy hydrocarbons and other components, which can damage heat exchangers, and there is a need to recover these components as products while producing a higher-purity liquefied natural gas that emits fewer greenhouse gases.
Innovation Solution
A system involving a heat exchanger, expander, separation device, and compressor to cool, expand, separate, and compress the gas stream, removing selected components and recovering them as liquids, while maintaining the vapor stream at a purified temperature to minimize heating and maximize efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If natural gas is cooled through indirect heat exchange by refrigeration cycles, then liquefaction is achieved, but heavy hydrocarbons freeze and impair heat exchanger operation
Solution Approach 1:
The patent extracts heavy hydrocarbon components from the natural gas stream before liquefaction by cooling a portion of the gas to a temperature range of -100°F to -150°F, where heavy hydrocarbons condense and can be separated. This prevents these components from freezing in the main heat exchanger during subsequent liquefaction operations.
Solution Approach 2:
The system performs preliminary cooling and separation of heavy components before the main liquefaction process. By pre-cooling a portion of the gas stream and removing condensed heavy hydrocarbons, the system prepares a cleaner feed stream for the main heat exchanger, preventing freezing issues during normal operation.
2Reliability
If heavy hydrocarbons are removed from the gas stream, then heat exchanger operation is maintained, but additional processing equipment and complexity are required
Solution Approach 1:
The patent makes the main heat exchanger serve multiple functions: it acts as both the primary cooling device for liquefaction and as a condenser for removing heavy hydrocarbon components. The refrigeration system also serves dual purposes by providing both the cooling needed for liquefaction and the additional cooling required to condense heavy hydrocarbons in the side stream.
Solution Approach 2:
The system merges the heavy hydrocarbon removal function with the existing liquefaction equipment. The heat exchanger and refrigeration system are configured to simultaneously perform both liquefaction cooling and heavy component condensation, eliminating the need for completely separate processing trains.
3Quantity of substance
If the gas stream is cooled to lower temperatures, then heavy hydrocarbons condense and can be removed, but refrigeration power requirements increase
Solution Approach 1:
The system changes the temperature parameter dynamically by cooling only a portion of the gas stream to the heavy hydrocarbon dew point range (-100°F to -150°F) rather than cooling the entire stream to liquefaction temperatures. This selective parameter change reduces the total refrigeration load while still achieving effective heavy component removal.
Solution Approach 2:
The patent applies partial cooling action by taking only a portion of the gas stream (e.g., 10-50%) and cooling it to the heavy hydrocarbon condensation temperature, rather than cooling the entire stream. This partial action is sufficient to remove the problematic components while minimizing the energy required for refrigeration.
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
The system effectively removes freezing components, reduces refrigeration power requirements, and enhances liquefaction efficiency, producing higher-purity liquefied natural gas with reduced greenhouse gas emissions.
Implementation Method 1
Liquefaction is typically accomplished by chilling the natural gas through indirect heat exchange by one or more refrigeration cycles in one or more heat exchangers
Implementation Method 2
An expander is configured to receive at least a portion of the cooled feed gas stream
Implementation Method 3
A separation device is configured to receive an expanded fluid stream from the expander and to separate the expanded fluid stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature
Implementation Method 4
A compressor is configured to receive the purified vapor stream at approximately the purified vapor temperature and to produce a compressed vapor stream that is returned to the heat exchanger
Implementation Method 5
Liquefaction is typically accomplished by chilling the natural gas through indirect heat exchange by one or more refrigeration cycles
Data Source
AI summary
A system for removing selected components from a gas stream has a heat exchanger including a first cooling passage configured to receive a feed gas stream and to provide a cooled feed gas stream. An expander receives at least a portion of the cooled feed gas stream. A separation device receives an expanded fluid stream from the expander and separates the expanded fluid stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature. A compressor receives the purified vapor stream at approximately the purified vapor temperature and produces a compressed vapor stream that is returned to the heat exchanger.