Method for separation and liquefaction of methane and carbon dioxide with pre-separation upstream of the distillation column
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Solution Overview
Problem
Current biogas purification and liquefaction 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 multiple cryo-trapping systems that do not recover used cold effectively.
Innovation Solution
A combined installation and process for cryogenic separation and liquefaction of biogas components, involving biogas mixing with a recycle gas, compression, cooling, separation, distillation, and liquefaction, with thermal integration to recover cold and optimize energy use, allowing for simultaneous production of pure methane and liquefied CO2 with reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple cryo-trapping systems are used in parallel for continuous biomethane production, then continuous production is achieved, but the cold used in CO2 solidification cannot be recovered and device complexity increases
Solution Approach 1:
The patent combines the CO2 separation function and the refrigeration function into a single integrated distillation column system. The distillation column performs both CO2 removal from biogas and produces cold for refrigeration through its internal heat exchange mechanisms, eliminating the need for separate parallel cryo-trapping systems while achieving continuous biomethane production
2Quantity 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 CO2 content remains too high
Solution Approach 1:
The distillation column is designed to perform multiple functions simultaneously: it separates CO2 from biogas, liquefies the CO2-rich liquid phase, and produces refrigeration cold. This multi-functional approach eliminates the need for separate purification modules and directly produces biomethane ready for liquefaction with sufficiently low CO2 content
3Manufacturing precision
If biogas is compressed to distillation pressure and cooled, then separation efficiency improves, but energy consumption increases
Solution Approach 1:
The patent converts the energy consumed in compression and cooling into useful refrigeration cold through the distillation column's heat exchange mechanisms. The cold generated during the separation process is recovered and used for biomethane liquefaction, transforming the harmful energy loss into a beneficial resource that offsets the initial compression and cooling energy input
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 methane and CO2 in a single operation, minimizing methane loss and energy usage by recovering cold from the CO2 liquefaction process, thus enhancing the profitability of biogas utilization and compliance with environmental regulations.
Implementation Method 1
A compressor for compressing the mixture to the distillation pressure
Implementation Method 2
An exchanger E01 for cooling the compressed mixture
Implementation Method 3
A separator pot V05 for receiving the mixture from the exchanger E01 and recovering a top vapor 2 and a liquid 3 enriched in CO2
Implementation Method 4
A distillation column K01 fed by the cooled top vapor 4 and for producing methane at the top of the column and a liquid enriched in CO2 at the bottom of the column
Implementation Method 5
An exchanger E02 for liquefying the methane produced at the top of the column
Implementation Method 6
A means M3 for expanding and heating the liquid enriched in CO2 recovered at the bottom of the column and recovering the cold from the liquid enriched in CO2
Implementation Method 7
A separator pot V01 allowing to receive the CO2-enriched flow from the means M3 and to recover a head vapor and liquid CO2 7
Data Source
Figure 1
AI summary
Combined cryogenic separation and liquefaction installation for methane and carbon dioxide contained in a biogas stream, comprising: - A means M1 for mixing biogas 1 with a recycled gas R, - A compressor for compressing the mixture to distillation pressure, - A heat exchanger E01 for cooling the compressed mixture, - A separator pot V05 for receiving the mixture from heat exchanger E01 and recovering overhead vapor 2 and a CO2-enriched liquid 3, - A means M4 for cooling the overhead vapor, - A distillation column K01 fed by the cooled overhead vapor and producing methane at the top of the column and a CO2-enriched liquid at the bottom of the column, - A heat exchanger E02 for liquefying the methane produced at the top of the column, - A means M2 for separating the liquefied methane into two parts: a "reflux" part 6 and a "product" part 5.- A means M3 for expanding and heating the CO2-enriched liquid recovered from the bottom of the column and for recovering the cold from the CO2-enriched liquid, and - A separator pot V01 for receiving the CO2-enriched stream from means M3 and recovering overhead vapor and liquid CO2, with - means M1 such that the recycled gas R corresponds to the overhead vapor recovered at the outlet of separator pot V01, and - exchanger E01 and means M3 being considered as one.