Process for the separation and liquefaction of methane and carbon dioxide with solidification of carbon dioxide outside the distillation column
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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, and existing cryotrapping systems fail to recover the cold used in CO2 solidification.
Innovation Solution
A cryogenic separation unit with a distillation column and external containers for physically separating and regenerating CO2, allowing for the reuse of energy in the liquefaction process, and a combined plant for mixing biogas with a recycle gas, compressing, cooling, and distilling to produce methane and liquefied CO2 in a single operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cryotrapping based on reversible exchangers is used to separate and liquefy methane and CO2, then separation and liquefaction can be achieved in two separate steps, but the cold used in CO2 solidification cannot be recovered
Solution Approach 1:
The patent combines the CO2 solidification step and the methane liquefaction step into a single integrated distillation column operation. The cold generated by CO2 solidification in the cold section is directly used for methane liquefaction in the same column, eliminating the need for separate exchangers and enabling cold recovery within the unified system.
Solution Approach 2:
The patent recovers the cold energy that would otherwise be discarded in the CO2 solidification process. By positioning the CO2 solidification in the cold section and using the resulting cold for methane liquefaction in the same column, the system transforms waste cold into a useful resource, improving overall energy efficiency.
2Manufacturing precision
If purification processes based on absorption, permeation or adsorption techniques are used, then biogas can be purified, but a supplementary module is required to obtain biomethane in liquid form and CO2 content remains too high
Solution Approach 1:
The patent merges the purification function and the liquefaction function into a single distillation column. The column simultaneously achieves CO2 removal (purification) and methane liquefaction in one integrated operation, eliminating the need for separate purification modules and supplementary liquefaction equipment.
Solution Approach 2:
The distillation column is designed to perform multiple functions: it separates CO2 from methane, solidifies CO2, and liquefies methane all within the same device. This multi-functional approach reduces the number of required process steps and equipment components while maintaining high purification effectiveness.
3Manufacturing precision
If multiple operations are used for separation and liquefaction, then thorough separation can be achieved, but methane loss increases and energy efficiency decreases
Solution Approach 1:
The patent combines separation and liquefaction operations into a single integrated distillation column, allowing thorough CO2 removal and methane liquefaction to occur simultaneously. This integration minimizes methane loss by maintaining continuous operation and avoiding intermediate transfer steps between separate units.
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 solution enables efficient separation and liquefaction of methane and carbon dioxide in a single operation with minimal methane loss and energy recovery, optimizing the biogas processing by reintegrating the energy used in CO2 solidification into the cycle.
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
for trapping all the solid CO2
Implementation Method 3
a means for introducing this fluid into the external container(s) in regeneration so as to bring about the melting of the solid CO2
Implementation Method 4
for producing liquid methane and liquid carbon dioxide
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.