Biogas Upgrading Absorption Stages to Cut Methane Slip

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Solution Overview

Problem

Existing biogas upgrading processes face significant methane loss and high operational costs due to the high carbon dioxide content in biogas, which requires large volumes of absorbents and additional pressurization steps, leading to inefficient methane recovery and increased power consumption.

Innovation Solution

A biogas upgrading method involving a two-stage absorption process with a second absorber operating at a lower pressure, followed by depressurization and flashing, which recycles high-purity carbon dioxide gas to strip methane from the first absorber, reducing methane slip and optimizing gas stream recycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If physical absorption process is used to remove carbon dioxide from biogas, then carbon dioxide content is reduced, but methane is also transferred to the absorbing medium causing methane loss

Engineering Contradiction:

Improvecarbon dioxide removal efficiencyVSAvoidmethane loss

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

The absorption process is divided into multiple stages with different absorbing media. The first stage uses a physical absorbing medium to remove most carbon dioxide, while subsequent stages use other media to recover methane from the first absorbing medium, thereby segmenting the removal and recovery functions to minimize overall methane loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A first absorbing medium is used as an intermediary to temporarily hold both carbon dioxide and methane, then a second absorbing medium is introduced to selectively recover methane from the first medium. This intermediary approach allows indirect methane recovery without direct contact between the biogas and the final product stream.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If large volume of absorbent is used to remove high carbon dioxide content, then carbon dioxide removal is improved, but methane loss increases due to large absorbent volume

Engineering Contradiction:

Improvecarbon dioxide removal capacityVSAvoidmethane loss

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

Instead of discarding the loaded first absorbing medium after carbon dioxide removal, the system recovers methane from it using a second absorbing medium. This recovery step converts what would be waste (methane trapped in the absorbent) into a valuable product, thereby reducing overall methane loss while maintaining effective carbon dioxide removal capacity.

Inventive Principle:

Principle #34Discarding and recovering

3Manufacturing precision

If multiple pressurization and heating steps are used in the upgrade process, then biogas purification is improved, but utility and operational costs increase

Engineering Contradiction:

Improvebiogas purification qualityVSAvoidpower consumption

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The system combines carbon dioxide removal and methane recovery operations into an integrated process where the second absorbing medium serves dual purposes: removing carbon dioxide from the first absorbing medium and concentrating methane in a single operational framework, thereby reducing the number of separate pressurization and heating steps required.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The process utilizes changes in physical parameters such as pressure and temperature during the absorption and desorption cycles to achieve both carbon dioxide removal and methane recovery without requiring additional external energy inputs for each step, as the parameter changes drive the mass transfer processes naturally.

Inventive Principle:

Principle #35Parameter changes

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 method effectively reduces methane loss and power consumption by optimizing gas recycling, allowing for efficient biogas upgrading at lower pressures, thereby improving the commercial viability and environmental impact of biogas utilization.

Implementation Method 1

absorbing carbon dioxide and methane from the biogas stream into the first physical absorbing agent

Methodology Applied

Scientific EffectPhysical absorption: Absorption (physical)

Implementation Method 2

carbon dioxide released from the, optionally depressurized, first liquid effluent is subsequently absorbed into the second physical absorbing agent

Methodology Applied

Scientific EffectPhysical absorption: Absorption (physical)

Implementation Method 3

flashing the depressurized second liquid effluent thereby obtaining a flash gas effluent comprising methane

Methodology Applied

Scientific EffectFlashing: Flash Evaporation

Data Source

PatentUS12551841B2Method for reducing methane emissions from biogas upgrading

Publication Date: 2026.02.17 AIRCO PROCESS TECH AS

AI summary

The present invention relates to a method for upgrading biogas generated by a biological process wherein at least carbon dioxide is removed from the bio-gas. More specifically the present invention relates to method for upgrading a biogas comprising a first absorption step wherein the liquid effluent is subjected to a second absorption step and a flash step and the gas streams resulting therefrom are recycled. The present invention also relates a biogas upgrading plant.