Thermochemical Nitrogen Looping for Low-Pressure Ammonia Synthesis
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Solution Overview
Problem
Current ammonia synthesis processes, such as the Haber-Bosch process, require high pressures and temperatures, contribute to CO2 emissions, and rely on fossil fuels, while alternative methods face challenges like high temperatures, complex reactor designs, and expensive catalysts.
Innovation Solution
A two-stage thermochemical process using renewable thermal energy to produce nitrogen and ammonia, involving a reduction reactor and a nitridation reactor, utilizing metal oxides and nitrides to reduce environmental impact and operational pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Haber-Bosch process is used to produce ammonia, then ammonia synthesis is achieved, but high pressures and temperatures are required and CO2 emissions increase
Solution Approach 1:
The process is divided into two separate stages: (1) nitrogen production by oxidizing reduced metal oxide with air to remove oxygen, and (2) ammonia synthesis by reacting the produced nitrogen with hydrogen. This segmentation allows each stage to operate under optimized conditions, with the nitrogen production stage occurring at lower pressures and temperatures compared to conventional Haber-Bosch, thereby reducing CO2 emissions from fossil fuel combustion
Solution Approach 2:
Reduced metal oxide serves as an intermediary substance that facilitates oxygen removal from air to produce nitrogen. The metal oxide is reduced in a first step, then oxidized with air in a second step to produce nitrogen and regenerate the metal oxide. This intermediary approach enables nitrogen production without direct high-pressure combustion, reducing harmful emissions
2Productivity
If conventional ammonia synthesis is used, then ammonia is produced, but high pressures are required
Solution Approach 1:
By separating nitrogen production from ammonia synthesis into distinct stages, the process eliminates the need for high-pressure operations required in conventional one-step Haber-Bosch. The nitrogen production stage operates at lower pressures, and the subsequent ammonia synthesis can proceed under more favorable pressure conditions
Solution Approach 2:
The process changes the operational parameters by producing nitrogen at lower pressures through the metal oxide oxidation route, then introducing this nitrogen to the ammonia synthesis reactor. This parameter change from high-pressure direct synthesis to low-pressure nitrogen production followed by synthesis reduces the overall pressure requirements
3Object-affected harmful factors
If alternative ammonia production methods are used, then environmental impact is reduced, but high temperatures or complex reactor designs are required
Solution Approach 1:
The process uses two relatively simple reactor stages: a reduction reactor for metal oxide reduction and an oxidation reactor for nitrogen production. This segmentation into functional stages avoids the need for single complex high-temperature reactors while achieving lower environmental impact through reduced fossil fuel dependence
Solution Approach 2:
The use of reduced metal oxide as an intermediary enables oxygen removal at moderate temperatures without requiring the extreme temperatures of some alternative methods. The metal oxide acts as a reusable mediator that facilitates the reaction under milder conditions, reducing both environmental impact and device complexity
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
Reduces fossil energy consumption, decreases feedstock requirements, and minimizes greenhouse gas emissions by producing ammonia at lower pressures and temperatures, enabling efficient and sustainable nitrogen and ammonia production.
Implementation Method 1
The mass of metal oxide is heated by the heat source and reduced in the reduction reactor
Implementation Method 2
the mass of reduced metal oxide is oxidized in the nitrogen production reactor with air to produce an enriched nitrogen stream
Implementation Method 3
The mass of metal nitride is reacted with hydrogen in the ammonia production reactor to produce a mass of nitrogen-deficient metal nitride and ammonia
Data Source
AI summary
The present disclosure is directed to renewable pathways to nitrogen production and ammonia (NH3) synthesis that utilize renewable heat as process heat instead of fossil fuels and operates at low to medium pressures (from 0.2-3 MPa). The renewable pathways result in both a decrease or elimination of greenhouse gas emissions as well as avoid the cost, complexity and safety issues inherent in high-pressure processes. Renewable thermochemical looping technology is used that produces nitrogen from air for the subsequent production of ammonia via an advanced two-stage process.