Method and unit for separating the light and heavy components of natural gas
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Solution Overview
Problem
Natural gas purification processes face challenges in efficiently separating carbon dioxide and paraffins due to high energy consumption and equipment freezing issues, particularly when dealing with high carbon dioxide contents and paraffins with high crystallization temperatures.
Innovation Solution
A process involving a deparaffinizing column followed by a distillation column, with thermal coupling heat exchanger for energy integration, to separate methane, carbon dioxide, and paraffins, reducing energy consumption and preventing equipment freezing by countercurrent reflux and staged expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If amine solution absorption is used to extract carbon dioxide from natural gas, then carbon dioxide removal is effective up to moderate contents (approximately 20 mol %), but power levels required to regenerate the amine solution become considerable and strain the economic balance when carbon dioxide content exceeds this threshold
Solution Approach 1:
The invention changes the fundamental separation mechanism from chemical absorption to physical cryogenic distillation, operating at temperatures below the critical point of the natural gas-carbon dioxide mixture. This parameter change allows effective separation of high carbon dioxide contents without the energy-intensive regeneration step required by amine solutions
Solution Approach 2:
The process exploits phase transitions by cooling the natural gas-carbon dioxide mixture below its critical point to induce condensation and enable distillation separation. The cryogenic temperatures cause the mixture to transition from supercritical to liquid phase, allowing gravitational and density-based separation followed by distillation
2Use of energy by moving object
If cryogenic distillation is used to separate carbon dioxide from natural gas, then energy consumption is reduced compared to amine absorption, but heavy constituents (paraffins) with high crystallization temperatures risk freezing and blocking the equipment
Solution Approach 1:
The invention applies preliminary action by removing heavy paraffinic constituents before the cryogenic distillation step. This preliminary removal prevents the paraffins from reaching the low temperatures where they would freeze and block equipment, ensuring reliable operation of the cryogenic separation unit
Solution Approach 2:
The separation process is segmented into distinct stages: first removing heavy paraffins through flash evaporation or distillation, then performing cryogenic distillation on the depleted gas. This segmentation allows each unit to operate within its optimal temperature range, preventing freezing issues in the cryogenic section
3Manufacturing precision
If multiple separating columns are used to remove both paraffins and carbon dioxide, then separation efficiency is improved, but device complexity and construction cost increase significantly
Solution Approach 1:
The invention merges the functions of paraffin removal and carbon dioxide separation into an integrated process where the first column's overhead product feeds directly into the second column. This combining reduces the number of independent units and simplifies the overall process configuration while maintaining high separation efficiency
Solution Approach 2:
The first separating column serves multiple functions: it removes heavy paraffins from the feed gas and also provides a depleted gas stream that is then processed in the second column for carbon dioxide removal. This multi-functionality reduces the total number of columns needed compared to completely separate processing trains
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 process effectively separates methane, carbon dioxide, and paraffins, reducing energy costs and operational complexity while preventing equipment freezing, achieving efficient separation and thermal integration.
Implementation Method 1
cooling of the top vapour stream in step c) and the reheating of the part of the liquid stream enriched with carbon dioxide D in step i) are carried out by passing said top vapour stream and said part of the liquid stream enriched with carbon dioxide D through a thermal coupling heat exchanger (4)
Implementation Method 2
extracting the paraffins from the natural gas G in the deparaffinizing column (3), and recovering a top vapour stream comprising carbon dioxide and methane, and, at the column bottom, said liquid stream enriched with paraffins P
Implementation Method 3
separating the constituents which are produced in the gas state without however being liquefied
Implementation Method 4
cooling the top vapour stream and then introducing into a separation unit (5), recovering a liquid stream and a vapour stream
Data Source
AI summary
The invention relates to a method for the treatment of natural gas containing carbon dioxide, methane and paraffins. The method comprising: a step of extracting the paraffins from the natural gas in a paraffin-removal column, and a step of separating the carbon dioxide and the methane in a distillation column. The operation of the two columns being provided by means of the thermal coupling of said two columns using a thermal coupling heat exchanger.