Solid-oxide fuel cell system with bottoming cycle and reformer heating
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Solution Overview
Problem
Combined cycle fuel cell systems face efficiency limitations due to heat loss and partial fuel utilization, necessitating costly high-temperature blowers and heat exchangers for fuel and air recycling.
Innovation Solution
A solid-oxide fuel cell system that integrates a reforming process, water separator, and bottoming cycle, where the tail gas is diverted to drive the bottoming cycle and heat the reforming system, eliminating the need for fuel and air recycling by utilizing steam reforming without recirculation loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fuel and air recycling is implemented to improve fuel cell efficiency, then conversion efficiency increases, but device complexity and cost increase due to large reformers and high-temperature blowers
Solution Approach 1:
The patent extracts and eliminates the fuel recycling loop and high-temperature blower components from the system. By using a catalytic converter to treat anode exhaust directly and a bottoming cycle to recover energy from exhaust gases, the system achieves high conversion efficiency without the complex fuel and air recycling infrastructure.
Solution Approach 2:
The system uses its own anode exhaust gas, treated through a catalytic converter, to provide the oxygen needed for steam reforming of additional fuel. This self-service approach eliminates the need for external air recycling and high-temperature blowers, reducing device complexity while maintaining efficiency.
2Reliability
If high-temperature blowers are used for fuel and air recycling, then fuel cell performance improves, but cost and technical challenge increase
Solution Approach 1:
The patent replaces expensive, technically challenging high-temperature blowers with simpler, more cost-effective components including a catalytic converter and a bottoming cycle system. These alternatives achieve the necessary gas heating and circulation functions at lower cost and technical complexity.
Solution Approach 2:
The patent substitutes mechanical high-temperature blower systems with a combination of catalytic conversion and bottoming cycle energy recovery. The catalytic converter provides chemical energy conversion while the bottoming cycle recovers thermal energy, replacing the need for mechanical compression and heating systems.
3Productivity
If fuel utilization is increased to improve efficiency, then energy conversion improves, but heat loss increases limiting further efficiency gains
Solution Approach 1:
The patent converts the harmful waste heat from the fuel cell exhaust into useful energy through a bottoming cycle system. The exhaust gases drive a heat engine or turbine that generates additional electricity, transforming energy loss into energy production and enabling higher overall efficiency without the penalties of increased fuel utilization.
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 configuration enhances plant efficiency by up to 65% while minimizing temperature differences across the fuel cell, achieving high system efficiency at low fuel utilization rates without the need for costly recycling systems.
Implementation Method 1
The reforming system may be configured to receive and output at least a portion of the cathode exhaust stream and convert at least a portion of a mixture of input hydrocarbon fuel and input steam into a hydrogen-rich reformate
Implementation Method 2
The water separator may be configured to the receive the tail gas of the fuel cell and remove water from the tail gas to form residual tail gas
Implementation Method 3
The bottoming cycle may include a combustion engine. The residual tail gas pathway may be configured to divert a first portion of the residual tail gas to the bottom cycle to drive the bottom cycle
Implementation Method 4
A fuel cell produces electricity by electrochemically combining a fuel and an oxidant across an ionic conducting layer
Implementation Method 5
The reforming system may be heated to facilitate conversion of the input hydrocarbon fuel and the input steam into the hydrogen-rich reformate by directing through the reforming system at least a portion of heated cathode exhaust
Data Source
AI summary
The present application provides combined cycle fuel cell systems that include a fuel cell, such as a solid-oxide fuel cell (SOFC), comprising an anode that generates a tail gas and a cathode that generates cathode exhaust. The system or plant may include adding fuel, such as processed or refined tail gas, to the inlet air stream of a reformer to heat the reformer. The system or plant may include removing water from the tail gas and recycling the removed water into an inlet fuel stream. The inlet air stream may be the cathode exhaust stream of the fuel cell, and the inlet fuel stream may be input hydrocarbon fuel that is directed to the reformer to produce hydrogen-rich reformate. The system or plant may direct some of the processed or refined tail gas to a bottoming cycle.