Process for the separation and liquefaction of methane and carbon dioxide with pre-separation upstream of 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 require multiple operations, especially when recovering cold used in CO2 solidification is not possible.
Innovation Solution
A combined facility and process involving biogas mixing with a recycle gas, compression, cooling, separation, distillation, liquefaction, and thermal integration to recover cold, allowing for simultaneous separation and liquefaction of methane and carbon dioxide in a single operation while minimizing methane loss.
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 equipment is required and CO2 content remains too high for efficient liquefaction
Solution Approach 1:
The patent combines the purification function and liquefaction function into a single integrated cryogenic distillation system. The distillation column simultaneously achieves CO2 separation and methane liquefaction, eliminating the need for separate purification modules and subsequent liquefaction equipment.
Solution Approach 2:
The cryogenic distillation system performs multiple functions: it purifies biogas by removing CO2, separates methane from the mixture, and liquefies methane all in one process. This multi-functional approach replaces the need for separate purification and liquefaction systems.
2Productivity
If cryotrapping with multiple parallel exchangers is used for continuous biomethane production, then separation and liquefaction are achieved, but cold recovery is not possible and energy is wasted
Solution Approach 1:
The patent implements a feedback mechanism where the cold energy from the CO2-enriched liquid stream is recovered and fed back into the system through heat exchanger E01. This recovered cold is used to pre-cool the incoming biogas mixture, reducing the energy input required for liquefaction.
Solution Approach 2:
Instead of discarding the cold energy present in the CO2-enriched liquid stream after separation, the system recovers this cold energy through heat exchanger E01 and utilizes it for pre-cooling the feed mixture, thereby converting waste energy into a useful resource.
3Quantity of substance
If multiple separate operations are used for separation and liquefaction, then purification is achieved, but the process requires minimum number of operations is not met and complexity increases
Solution Approach 1:
The patent merges the separation operation and liquefaction operation into a single integrated cryogenic distillation process. The distillation column performs both CO2 separation and methane liquefaction simultaneously, reducing the total number of operational steps while maintaining high purification quality.
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 process achieves efficient separation and liquefaction of methane and carbon dioxide with reduced energy consumption and minimal methane loss, enabling cost-effective transportation of biomethane and recovering energy used in the liquefaction of CO2.
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
The thermal integration between the streams of the separation section and those of the refrigeration cycle enable the recovery of the cold used in the liquefaction of the CO2
Implementation Method 4
a separator vessel V05 for receiving the mixture from the exchanger E01 and for recovering an overhead vapour 2 and a CO2-enriched liquid 3
Implementation Method 5
a distillation column K01 supplied with the cooled overhead vapour 4 and making it possible to produce methane at the top of the column and a CO2-enriched liquid at the bottom of the column
Implementation Method 6
an exchanger E02 for liquefying the methane produced at the top of the column
Implementation Method 7
a means M3 for expanding and heating the CO2-enriched liquid recovered at the bottom of the column and for recovering the cold from the CO2-enriched liquid
Data Source
AI summary
A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.