Ammonia Cracking PSA Adsorbent Layering
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Solution Overview
Problem
Current processes for producing hydrogen from ammonia cracking are energy-intensive and have low hydrogen recovery rates, with residual ammonia posing a challenge in PSA systems due to strong adsorption by zeolitic materials, leading to ammonia breakthrough in the hydrogen product gas.
Innovation Solution
A method using a PSA system with two parallel units, each comprising an upstream layer of non-zeolitic adsorbent for ammonia removal and a downstream layer of zeolitic adsorbent for nitrogen removal, eliminating the need for energy-intensive washing and stripping steps and reducing ammonia 'creep' through the adsorbent bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If zeolitic adsorbent is used in PSA system to remove nitrogen, then nitrogen removal efficiency is improved, but ammonia breakthrough occurs due to strong adsorption of ammonia by zeolitic materials
Solution Approach 1:
The adsorbent bed is segmented into two distinct layers: an upstream non-zeolitic adsorbent layer for ammonia removal and a downstream zeolitic adsorbent layer for nitrogen removal. This segmentation allows each layer to perform its specific function optimally without interfering with the other, preventing ammonia breakthrough while maintaining nitrogen removal efficiency.
Solution Approach 2:
Different regions of the adsorbent bed are assigned different material properties suited to their specific functions. The upstream region uses non-zeolitic adsorbent with high ammonia affinity, while the downstream region uses zeolitic adsorbent with high nitrogen affinity. This local differentiation of material properties enables simultaneous optimization of both ammonia and nitrogen removal.
2Manufacturing precision
If traditional washing and stripping steps are used to remove residual ammonia, then ammonia removal is achieved, but energy consumption increases
Solution Approach 1:
The ammonia removal function is extracted from the energy-intensive washing and stripping process and integrated directly into the PSA adsorption cycle using a dedicated non-zeolitic adsorbent layer. This allows ammonia to be removed during the normal operation of the PSA system without requiring additional energy-consuming heating or washing steps.
Solution Approach 2:
The PSA system uses its own operational cycles (adsorption and desorption) to achieve ammonia removal through the non-zeolitic adsorbent layer, eliminating the need for external energy-intensive washing and stripping processes. The system serves its own purification needs using the inherent pressure and temperature changes during PSA operation.
3Productivity
If ammonia is compressed to high pressure for vehicle fueling, then hydrogen availability is improved, but storage volume and power requirements increase due to nitrogen dilution
Solution Approach 1:
The PSA system performs preliminary separation of ammonia from the cracked gas stream before the hydrogen is compressed for vehicle fueling. By removing ammonia in the upstream non-zeolitic adsorbent layer during the adsorption cycle, the hydrogen stream is pre-purified, reducing the burden on subsequent compression and storage systems.
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 hydrogen recovery, reduces energy consumption, and prevents ammonia breakthrough, producing a high-purity hydrogen stream with reduced nitrogen dilution, improving the efficiency of hydrogen production from ammonia cracking.
Implementation Method 1
an upstream layer of non-zeolitic adsorbent that is selectively adsorbent for at least ammonia
Implementation Method 2
a downstream layer of zeolitic adsorbent that is selectively adsorbent for nitrogen
Implementation Method 3
A method of separating hydrogen gas from an effluent gas of an ammonia cracking reactor operating at an elevated pressure, in a PSA system
Data Source
AI summary
Residual ammonia is removed effectively from ammonia cracked gas in a hydrogen PSA system using a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel.