Ammonia Decomposition Apparatus with Dual Catalyst Zones
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Solution Overview
Problem
Existing ammonia decomposition methods face challenges such as incomplete decomposition, high ammonia residue in the gas product, and low utilization efficiency, leading to inefficiencies in hydrogen production for fuel cells.
Innovation Solution
An ammonia decomposition apparatus with a casing featuring a heating zone and a heat exchange zone, utilizing nickel-based and ruthenium-based catalyst layers in successive reaction zones, along with a spirally wound heat exchange coil and a burner for efficient ammonia gas decomposition, coupled with a gas separation system for high-purity hydrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reaction zone with one type of catalyst is used, then the system structure is simple, but the ammonia decomposition is incomplete and ammonia residue in the gas product is high
Solution Approach 1:
The reaction system is divided into multiple reaction zones (first reaction zone with nickel-based catalyst, second reaction zone with ruthenium-based catalyst) arranged in series. Each zone performs partial decomposition, and the combined effect achieves complete ammonia decomposition with residue below 1000 ppm, resolving the contradiction between structural simplicity and decomposition completeness.
2Use of energy by moving object
If ammonia gas is directly introduced into the reaction zone without preheating, then the energy consumption is low, but the reaction efficiency is reduced and energy utilization is poor
Solution Approach 1:
Ammonia gas is preheated in a heat exchange coil before entering the reaction zones. The coil is positioned such that the preheated gas first contacts the nickel-based catalyst in the first reaction zone, then proceeds to the ruthenium-based catalyst in the second reaction zone. This preliminary heating action improves reaction efficiency without proportionally increasing energy consumption.
3Quantity of substance
If high pressure is applied to increase hydrogen volumetric energy density, then the energy density increases from 0.0108 MJ·L−1 to 3 MJ·L−1, but the investment cost increases and safety is reduced
Solution Approach 1:
The patent changes the physical state parameter of hydrogen from gaseous (low density) to liquid (high density) form. Liquid hydrogen achieves a volumetric energy density of 13 MJ·L−1 at only 2 MPa pressure, which is 3-4 times higher than compressed hydrogen at 35 MPa, while significantly reducing both investment cost and safety risks associated with high-pressure storage.
4Device complexity
If conventional ammonia decomposition methods are used, then the process is simple, but the catalyst utilization efficiency is low and energy is wasted
Solution Approach 1:
The patent combines two different catalyst systems (nickel-based and ruthenium-based) into a single integrated reaction system with series-connected reaction zones. This merging of catalyst functions improves overall catalyst utilization efficiency and energy utilization, achieving complete ammonia decomposition while maintaining a relatively simple process structure.
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 a high ammonia conversion rate of 99.9% with reduced ammonia residue, improved energy utilization, and efficient hydrogen production, providing a stable raw material for fuel cells.
Implementation Method 1
the first reaction zone is disposed in the heating zone and filled with a nickel-based catalyst to form a nickel-based catalyst layer, and the second reaction zone is disposed in the heat exchange zone and filled with a ruthenium-based catalyst to form a ruthenium-based catalyst layer
Implementation Method 2
a heat exchange coil, spirally wound on outer walls of the second reaction zone and the first reaction zone successively, provided with an ammonia gas inlet which is disposed near a hydrogen-nitrogen mixed gas outlet of the second reaction zone
Implementation Method 3
a burner, disposed in the heating zone and located between an inner wall of the casing and the first reaction zone, and used for maintaining a reaction temperature in the first reaction zone
Data Source
AI summary
An ammonia decomposition apparatus comprises a casing, a heating zone, a heat exchange zone, a reaction section and a heat exchange coil. The heat exchange coil is spirally wound on an outer wall of the reaction section to efficiently heat ammonia gas. The reaction section has a first reaction zone and a second reaction zone communicated successively, the ammonia gas decomposed into a nitrogen-hydrogen mixture after entering the first reaction zone, with the second reaction zone decomposing for the second time the residual ammonia gas in the nitrogen-hydrogen mixture produced in the first reaction zone, so that the ammonia gas is decomposed more thoroughly. The conversion rate of ammonia gas can reach 99.9% or more, and the residual amount of ammonia gas in the nitrogen-hydrogen mixture can be less than 1000 ppm.