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Modeling and scaling processes to generate high-pressure hydrogen (H2) from ammonia

Problem statement

The increasing world energy demand accelerates the depletion of fossil fuels, which consequently boosts the research and development of alternative and viable energy sources. Ammonia (NH3) is a dense, carbon-free energy and hydrogen vector. It can provide on-site hydrogen via catalytic decomposition or cracking.

Our work covers the fundamentals of the microkinetics (using benchmark catalysts such as Ru-based and cheaper, novel alternatives such as Co-Ba-Ce-based) to the reactor modeling.

We use DFT-guided and microkinetic modeling to help understand the rates and catalyst performance. Whereas the reactor modeling from the laboratory scale to the industrial-scale mandates considering the heat-mass transfer effects for efficient implementation of the process.

Goals

  • Develop a microkinetic modeling framework to analyze the catalyst performance and the effect of the role of promoters
  • Dimensionless number analysis to transcend the scale of operation and scale up
  • Using reactive computational fluid dynamics and process modeling: model and simulate an ammonia cracker unit at different scales, including a repurposed steam reformer
  • Model and simulate different reactor configurations, such as packed bed reactors with and without membranes
AMD

Related People

Gontzal Lezcano

Related Publications

The technological prospects of repurposing methane steam reformers into ammonia crackers for decarbonized H2 production

by Realpe, Lezcano, Kulkarni, Sayas, Morlanes, Rakib, Aldilaijan, Solami, Gascon, Castaño
Appl. Energy Year: 2024 DOI: https://doi.org/10.1016/j.apenergy.2024.124244

Abstract

The decarbonization of hydrogen production can be accelerated by repurposing existing methane steam reformers into ammonia crackers. Through kinetic modeling, reactor optimization, and process integration, we demonstrated the viability of repurposing industrial reformers into NH3 crackers using a Co-Ba-Ce extrudate catalyst. First, we combined an improved kinetic rate expression, validated through experiments, with a high-fidelity 2-D model to optimize the operation of a multi-tubular reactor with a fixed capacity of 7000 Nm3 h−1. Subsequently, we used heat integration techniques to integrate the reactor with supplementary and separation units. We proved the process energy efficiency to be 65.7% before heat integration and 75.3% for the integrated plant. The integrated, optimized plant results demonstrated the necessity of implementing an adiabatic pre-cracker, an element typically omitted in catalytic NH3decomposition techno-economic models. Our findings underscore the importance of real-world constraints and operational aspects in designing and optimizing NH3 conversion processes.

Keywords

MKM AMD