| dc.description.abstract | Ammonia is recognized as a promising marine fuel due to its potential to reduce emissions especially CO2, serving both as an energy carrier and a clean fuel. In 2018, the International Maritime Organization (IMO) set targets to reduce greenhouse gas emissions from international shipping by at least 50% by 2050, aiming for complete elimination by 2100.
This MSc thesis is a continuation of the work done in the MSc group project (at USN, autumn 2023). New contributions include addressing the weaknesses identified in that project by reducing some of the proposal simplifying assumptions.
In this study, a centralized ammonia cracking process is simulated using Aspen HYSYS V12 with available data from the literature. In the simulation phase, a base case was established, then four other cases were simulated to maximize energy recovery from the waste heat of the cracker product. The improvement evolved through different versions of the improved case, culminating in the final version. For the base case with no heat recovery, the produced H2/NH3 total feed on a kg/kg basis was evaluated as 0.1282 while for the final version of the improved case, it was calculated to be 0.1404.
To determine the most efficient case, the Levelized Cost of Hydrogen (LCOH) was evaluated and compared. The final version of the improved case, with the highest hydrogen production rate (585.8 kgmoles/h hydrogen from 500 kgmoles/h total ammonia feed) and the lowest LCOH (less than 6 USD/kg H2), was deemed the most efficient.
Recommendations for further work include tackling inherent uncertainties in the simulation like inclusion of catalyst data, defining furnace instead of Gibbs reactor, and using data from the adsorption module of Aspen to precisely model the adsorption phenomena and conducting uncertainty analysis on the LCOH evaluations to obtain more reliable techno-economic analysis. | |
