Multi-Adsorbent PSA for Hydrogen Purification From Cracked Ammonia
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Solution Overview
Problem
Existing methods for producing high purity hydrogen from decomposed ammonia gas are not yet commercialized, as they require adsorbents capable of both chemical and physical adsorption, and existing pressure swing adsorption processes are inefficient in removing moisture, ammonia, and nitrogen, leading to reduced adsorbent performance and increased costs.
Innovation Solution
A pressure swing adsorption apparatus with multiple adsorption towers, each packed with different adsorbents, including a pretreatment unit for moisture and ammonia removal and a hydrogen purification unit for nitrogen removal, using a multilayer structure of activated alumina, metal impregnated activated carbon, and zeolite LiX to achieve selective adsorption and maximize hydrogen recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single adsorption tower with unified adsorbent is used, then the device complexity is reduced, but the hydrogen purification efficiency and recovery rate deteriorate due to inability to selectively remove moisture, ammonia, and nitrogen
Solution Approach 1:
The adsorption system is divided into multiple adsorption towers (first adsorption tower with first adsorbent for moisture removal, second adsorption tower with second adsorbent for ammonia removal, third adsorption tower with third adsorbent for nitrogen removal) that can operate independently or in combination. This segmentation allows each tower to specialize in removing specific impurities, thereby improving overall purification efficiency while maintaining operational flexibility
Solution Approach 2:
The plurality of adsorption towers are designed to perform multiple functions: they can individually remove different impurities (moisture, ammonia, nitrogen), and can be operated in various configurations (single tower mode, parallel mode, or sequential mode) to adapt to different purification requirements and throughput demands, achieving multi-functionality
2Productivity
If temperature swing adsorption is used to remove ammonia, then ammonia removal efficiency is improved, but energy consumption increases due to heating requirements
Solution Approach 1:
The patent replaces the thermal field (heating) used in traditional temperature swing adsorption with a mechanical field (pressure variation). The second adsorption tower removes ammonia through pressure swing adsorption by utilizing the pressure difference between adsorption and desorption phases, eliminating the need for external heating sources and significantly reducing energy consumption while maintaining high ammonia removal efficiency
Solution Approach 2:
The patent changes the operating parameter from temperature (in TSA) to pressure (in PSA). By varying pressure levels between adsorption and desorption phases, the system achieves effective ammonia removal without thermal input. The third adsorption tower also uses pressure swing to remove nitrogen, further confirming this parameter change strategy
3Productivity
If existing pressure swing adsorption process is used, then device size is minimized, but selective adsorption of moisture, ammonia, and nitrogen is insufficient leading to reduced hydrogen recovery rate
Solution Approach 1:
Each adsorption tower is equipped with adsorbent specifically selected for its local function: the first adsorption tower uses adsorbent with high moisture selectivity, the second uses adsorbent optimized for ammonia removal, and the third uses adsorbent for nitrogen removal. This local quality differentiation ensures optimal performance for each impurity removal step, maximizing hydrogen recovery rate
Solution Approach 2:
The system employs different types of adsorbent materials in separate towers: activated alumina or silica gel for moisture, metal impregnated activated carbon for ammonia, and zeolite for nitrogen. This composite approach using multiple material types with complementary properties enhances overall purification effectiveness and hydrogen recovery
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
The apparatus achieves high purity hydrogen purification with improved selective adsorption of moisture, ammonia, and nitrogen, maximizing hydrogen recovery rate and reducing driving costs by eliminating the need for a heat source for regeneration.
Implementation Method 1
the adsorption towers of the pretreatment unit and the hydrogen purification unit are packed with different adsorbents... to selectively adsorb and remove moisture and ammonia
Implementation Method 2
The pressure swing adsorption purification method can be only used in physical adsorption by intermolecular forces such as van der Waals force between impurities and adsorbents
Implementation Method 3
the adsorption tower in the hydrogen purification unit is packed with a third adsorbent to purify hydrogen by selectively adsorbing nitrogen
Implementation Method 4
a vacuum pump connected to the adsorption towers to keep the adsorption towers in a vacuum state
Data Source
AI summary
The present disclosure relates to a pressure swing adsorption apparatus for hydrogen purification from decomposed ammonia gas and a hydrogen purification method using the same, and more particularly, the pressure swing adsorption apparatus of the present disclosure includes a plurality of adsorption towers including a pretreatment unit and a hydrogen purification unit wherein the adsorption towers of the pretreatment unit and the hydrogen purification unit are packed with different adsorbents, thereby achieving high purity hydrogen purification from mixed hydrogen gas produced after ammonia decomposition, making it easy to replace the adsorbent for ammonia removal, minimizing the likelihood that the lifetime of the adsorbent in the hydrogen purification unit is drastically reduced by a very small amount of ammonia, and actively responding to a large change in ammonia concentration in the raw material.Additionally, a hydrogen purification method using the pressure swing adsorption apparatus of the present disclosure physically adsorbs and removes impurities such as moisture (H2O), ammonia (NH3) and nitrogen (N2) included in mixed hydrogen gas produced after ammonia decomposition below extremely small amounts, thereby achieving high purity hydrogen purification with improved selective adsorption of moisture, ammonia and nitrogen and maximized hydrogen recovery rate and productivity. In addition, since the temperature swing adsorption process is not introduced, there is no need for a heat source for regeneration, thereby reducing the driving cost.