SOFC-SOEC Exhaust Recirculation for High-Purity CO2 Capture

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Solution Overview

Problem

Conventional solid oxide fuel cell (SOFC) systems face challenges in achieving high purity carbon dioxide (CO2) exhaust streams for efficient carbon capture without compromising system efficiency or incurring excessive operation costs, particularly due to the dilution effect of anode exhaust gases.

Innovation Solution

The integration of a solid oxide electrolysis stack (SOEC) module within the fuel cell system, which utilizes waste heat to perform co-electrolysis on unreacted fuel streams, producing a fuel-enriched stream that is recirculated, and using electrolysis-produced oxygen for thorough combustion, resulting in a nearly pure CO2 and H2O exhaust.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional SOFC systems directly export anode exhaust for carbon capture, then CO2 separation is achieved, but system efficiency decreases and operation costs increase due to the dilution effect of anode exhaust gases

Engineering Contradiction:

ImproveCO2 purityVSAvoidsystem efficiency

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent converts the harmful dilution effect of anode exhaust gases into a beneficial resource by recirculating the depleted fuel stream back to the fuel cell inlet. This allows the previously wasted CO2-rich exhaust to become a valuable input stream, improving overall system efficiency while maintaining high CO2 purity for capture applications.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Instead of discarding the anode exhaust stream directly, the system recovers useful components by separating CO2 for capture while recirculating the depleted fuel stream containing unreacted hydrocarbons and syngas back to the fuel cell, thereby recovering energy that would otherwise be lost.

Inventive Principle:

Principle #34Discarding and recovering

2Loss of energy

If anode exhaust is recirculated to improve system efficiency, then fuel utilization increases, but CO2 purity in the exhaust stream decreases

Engineering Contradiction:

Improvesystem efficiencyVSAvoidCO2 purity

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The patent segments the exhaust stream processing into two distinct pathways: one stream is recirculated back to the fuel cell inlet to improve efficiency, while another stream is directed to carbon capture to maintain high CO2 purity. This segmentation allows both objectives to be achieved simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the exhaust stream are treated differently based on their local composition and quality. The CO2-rich portion is directed to capture, while the fuel-containing portion is recirculated, optimizing both purity and efficiency in their respective destinations.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If CO2 separation processes are implemented to achieve high purity exhaust streams, then carbon capture capability improves, but device complexity increases

Engineering Contradiction:

ImproveCO2 purityVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses its own depleted fuel stream as the separation medium, eliminating the need for external separation agents or complex processing equipment. The depleted fuel stream naturally separates CO2 through its composition, providing a self-service separation mechanism that reduces device complexity.

Inventive Principle:

Principle #25Self-service

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 enhances system efficiency by reducing the net fuel supply requirement, stabilizes operation, and achieves a high-purity CO2 exhaust stream, improving overall efficiency and carbon capture capabilities.

Implementation Method 1

The exhaust processing module is configured to subject the first portion of the depleted fuel stream to co-electrolysis using the waste heat from the fuel cell module to produce a fuel-enriched stream

Methodology Applied

Scientific EffectCo-electrolysis: Electrolysis

Implementation Method 2

The exhaust processing module is disposed relative to the fuel cell module such that waste heat from the fuel cell module is usable by the exhaust processing module

Methodology Applied

Scientific EffectWaste heat transfer: Heat Exchanger

Implementation Method 3

using electrolysis-produced oxygen for thorough combustion, resulting in a nearly pure CO2 and H2O exhaust

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS20260074251A1Solid Oxide Fuel Cell System with Carbon Capture and Increased Efficiency

Publication Date: 2026.03.12 VERSA POWER SYST LTD

AI summary

A fuel cell system including a fuel cell module having an anode inlet configured to receive an anode inlet stream including fuel and an anode outlet configured to output an anode exhaust stream including carbon dioxide and steam, a solid oxide electrolysis cell module configured to receive waste heat and a first portion of the anode exhaust stream from the solid oxide fuel cell module and output an electrolysis output stream including hydrogen and carbon monoxide, wherein at least a portion of the electrolysis output stream is redirected to become a component of the anode inlet stream of the fuel cell module, and a controller configured to operate the solid oxide electrolysis cell module at an endothermic current density