Bland-Ewing Thermochemical Hydrogen Compression With Heat Recovery
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Solution Overview
Problem
Existing methods for generating high-pressure hydrogen gas require physical compression processes, which are inefficient and energy-intensive, and do not fully utilize the thermal energy potential of thermochemical cycles.
Innovation Solution
The Bland/Ewing Thermochemical Cycle is utilized with a bi-pressure exothermic half-cycle that incorporates an Exothermic Reactor Exhaust Compressor (EREC) to efficiently pressurize hydrogen gas by leveraging thermal energy from a reversible chemical reaction between cyclohexane and benzene, using a synchronized thermal regenerator exchange pump (STREP) for heat exchange and a bi-pressure adiabatic expansion to generate additional work.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a physical compression process is used to generate high-pressure hydrogen gas, then the hydrogen gas can be pressurized to the required level, but the process becomes energy-intensive and inefficient
Solution Approach 1:
The patent replaces the traditional mechanical compression system with a thermochemical system. Hydrogen gas is generated through endothermic catalytic conversion of cyclohexane (C6H12) to benzene (C6H6) and hydrogen (H2), eliminating the need for mechanical compressors and significantly reducing energy consumption.
Solution Approach 2:
The patent changes the state parameters of the hydrogen carrier (cyclohexane) through temperature and pressure variations. By heating cyclohexane to high temperatures (around 500-700°C), the endothermic reaction produces high-pressure hydrogen gas directly, avoiding mechanical compression.
2Use of energy by moving object
If thermal energy from the thermochemical cycle is fully utilized, then the efficiency of hydrogen gas generation increases, but the system complexity increases
Solution Approach 1:
The patent employs periodic operation of the thermochemical reactor, alternating between endothermic hydrogen generation mode and exothermic benzene hydrogenation mode. This periodic action allows thermal energy to be recovered and reused, improving efficiency while managing system complexity through cyclic operation rather than continuous complex processing.
Solution Approach 2:
The patent recovers thermal energy from the exothermic reaction (when benzene and hydrogen convert back to cyclohexane) and uses it to preheat the endothermic reaction or generate power. This energy recovery reduces overall system complexity by eliminating the need for separate heating systems.
3Use of energy by moving object
If the endothermic reaction temperature is increased to achieve higher hydrogen pressure, then the thermal efficiency increases, but the equipment requirements and safety constraints increase
Solution Approach 1:
The patent utilizes phase transitions of the cyclohexane-benzene system to manage temperature and pressure. By controlling the liquid-vapor equilibrium and using the boiling point of cyclohexane (around 81°C at atmospheric pressure, higher under pressure), the system achieves high temperatures necessary for endothermic reaction while maintaining controlled conditions through pressure regulation.
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 thermal efficiency by utilizing thermal energy for compression, reducing the need for external work and achieving lower final temperatures, thereby increasing the overall efficiency of hydrogen gas pressurization.
Implementation Method 1
releasing H2 via an endothermic catalytic reaction which converts each mol of C6H12 into a mol of C6H6 and three moles of H2
Implementation Method 2
The conversion is reversible via an exothermic catalytic reaction that converts a mol of C6H6 and three moles of H2 back into C6H12
Implementation Method 3
the separated pressurized H2 may be adiabatically expanded to a lower pressure and thus lower than ambient temperature
Data Source
AI summary
The present application relates to systems and methods for utilizing the Bland/Ewing cycle as a thermochemical gas compressor. In some examples, it can be useful to view the Bland/Ewing Cycle as including two thermodynamic half cycles, which include an endothermic half cycle and an exothermic half cycle, as discussed herein.