Method for separation and liquefaction of methane and carbon dioxide with solidification of carbon dioxide outside the distillation column
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current biogas purification processes are inefficient in separating and liquefying methane and carbon dioxide with minimal methane loss and operational complexity, particularly due to high CO2 content and the need for additional modules for liquefaction.
Innovation Solution
A cryogenic separation unit with a distillation column and external containers for trapping and regenerating solid CO2, combined with a refrigeration circuit to recover and reintegrate energy, allowing for simultaneous separation and liquefaction of methane and carbon dioxide in a single operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If absorption, permeation, or adsorption techniques are used for biogas purification, then CO2 removal is achieved, but additional modules are required for liquefaction and operational complexity increases
Solution Approach 1:
The patent combines CO2 removal and methane liquefaction into a single integrated cryogenic distillation column. The column simultaneously performs separation of CO2 from biogas and liquefaction of methane, eliminating the need for separate purification modules and liquefaction equipment. This merging of functions directly reduces device complexity while maintaining CO2 removal efficiency.
2Productivity
If cryo-trapping system with multiple parallel exchangers is used for CO2 solidification, then continuous biomethane production is achieved, but cold recovery is not possible and energy loss occurs
Solution Approach 1:
The patent implements a feedback mechanism where cold energy recovered from the CO2-rich liquid stream is fed back to pre-cool the biogas feed entering the distillation column. The CO2-rich liquid from the column bottom is expanded through an expansion device, recovering cold energy that is then used in a heat exchanger to pre-cool the incoming biogas, thereby reducing the overall energy input required and preventing cold energy loss.
Solution Approach 2:
Instead of discarding the cold energy present in the CO2-rich liquid stream leaving the distillation column, the patent recovers this cold energy through an expansion device and utilizes it in a heat exchanger to pre-cool the feed gas. This recovery and reuse of cold energy eliminates waste while maintaining continuous production capability.
3Quantity of substance
If separation and liquefaction are performed in two separate stages, then CO2 solidification is achieved, but methane loss increases and operational complexity increases
Solution Approach 1:
The patent merges CO2 separation and methane liquefaction into a single cryogenic distillation column operating at optimized pressure and temperature conditions. The column is designed with specific theoretical plates and reflux ratios that enable simultaneous CO2 removal and methane liquefaction, preventing methane loss that would occur in two-stage processes where intermediate handling and transfer could lead to contamination or loss.
4Measurement precision
If biogas is compressed to distillation pressure and cooled, then separation efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary cooling to the biogas feed before it enters the distillation column. By pre-cooling the feed gas using recovered cold energy from the CO2-rich liquid stream, the system reduces the temperature difference that must be overcome during distillation, thereby improving separation efficiency while minimizing additional energy consumption during the main separation process.
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 enables efficient separation and liquefaction of biogas components with minimal energy loss and operational complexity, recovering energy used in the liquefaction process and maintaining control over mass and energy balance.
Implementation Method 1
A distillation column K01 comprising a cold section 2 at the top of the column and a hot section 3 at the bottom of the column
Implementation Method 2
at least two containers V04 A/B external to the distillation column for bringing the liquid of the cold section and the rising vapor from the hot section into contact and trapping all the solid CO2
Implementation Method 3
a means for introducing this fluid into the external container(s) being regenerated so as to cause the solid CO2 to melt
Data Source
Figure 1
Figure 2~3
AI summary
Cryogenic methane and carbon dioxide separation unit comprising: - A distillation column K01 comprising a cold section 2 at the top of the column and a hot section 3 at the bottom of the column, - A means 4 for physically separating the cold section and the hot section, - At least two external vessels V04 A/B outside the distillation column for bringing the liquid from the cold section into contact with the rising vapor from the hot section and for trapping all the solid CO2, and - A regeneration device for the external vessels comprising a means for extracting a fluid from the distillation column K01 suitable for liquefying the solid CO2, a means for introducing this fluid into the external vessel(s) being regenerated so as to cause the melting of the solid CO2 and a means for reintroducing the resulting liquid CO2 - vapor mixture into the distillation column K01.