46 research outputs found
Economical e-Methanol Production: Dynamic Modelling and Optimal Scheduling of Power-to-Methanol Plant
No full textPower-to-methanol (PtMeOH) systems offer promising solutions for converting surplus renewable electricity into valuable energy carriers for hard-to-abate sectors. This work presents an integrated 50 MW PtMeOH production system with an annual demand of 25,000 tonnes of e-MeOH, addressing critical challenges such as high production costs and limited operational flexibility. Comprehensive steady-state and dynamic models were developed for all major components. A PEM electrolyser model was created in Simulink, capturing non-linear efficiency-load relationships varying from 76% at low loads to 67%. The methanol synthesis and distillation system was modelled using Aspen Tech, maintaining product specifications above 99.7% MeOH purity. System flexibility evaluation demonstrated that flexible operation (40--100% capacity) reduces e-MeOH production costs by 50 €/tonne compared to fixed-load operation. The system achieved 86% annual runtime with strategic partial load operation, minimising harmful start-stop cycles. Cost-effective optimisation determined optimal hourly schedules based on real electricity price data, achieving e-MeOH production cost of 1196.4 €/tonne. Economic analysis confirmed electrolyser costs dominate both CAPEX (90%) and OPEX (83%)
Design and Dynamic Modelling of a 40 kW Solid Oxide Electrolysis System
No full textHydrogen production using electrochemical processes has gained significant interest, as a cleaner alternative to fossil fuel-based methods. High temperature electrolysis has been growing due to its enhanced thermodynamics and kinetics at elevated temperatures in comparison to low temperature electrolysis. This thesis presents the design of a onedimensional dynamic model of a 40 kW Solid Oxide Electrolyser Cell (SOEC) stack. The model consisting of electrochemical kinetics,mass, and energy balances, is employed to study the dynamic behaviour of the SOEC stack under step load changes, with spatial discretization applied to resolve temperature and composition profiles along the cell length. Balance-of-plant components such as heat exchangers and electric heaters are also included. The results demonstrate that the system achieves over 80 % efficiency over the simulation period. Transient behaviour under step load changes was stable, with temperature gradients remaining below 10 K/cm. The stack produced approximately 7 kg of hydrogen over a 10 hour simulation with a specific energy consumption close to 34 kWh/kg. The model aims to demonstrate the SOEC’s suitability for dynamic hydrogen production scenarios, supporting its integration in renewable-based energy systems
Process Modelling and Optimization of Methanol-to-Jet for eSAF
No full textTo reach long-term greenhouse gas (GHG) neutrality in aviation, replacing fossil-based jet fuels with Sustainable Aviation Fuels (SAF) from renewable sources is crucial. This study investigates the process modeling and optimization of the Methanol-to- Jet (MtJ) pathway for e-SAF production using Aspen Plus V12.1, integrating methanol synthesis from CO2 and H2, methanol-to-olefins (MTO) conversion, oligomerization, and hydrogenation. A novel dynamic modeling approach was implemented for oligomerization, linking a custom MATLAB model to Aspen Plus via Excel to predict product distribution using the Anderson–Schulz– Flory (ASF) mechanism parameterized by reactor conditions. Process optimization through response surface methodology targeted maximization of kerosene yield and minimization of cost. The optimized process achieved a kerosene yield of 0.40 Cmole/Cmole, a sustainable aviation fuel production rate of 9395 tonnes/year, and a Levelized Cost of SAF (LCOSAF) of 6980 €/tonne. Overall, the results demonstrate the technical feasibility and optimization potential of the MtJ process, but further reductions in feedstock cost and improved heat integration are needed for economic viability at scale
Heat transfer characteristics of a two-phase, air-water direct contact evaporator
Full text linkThe purpose of the research was to carry out an experimental and theoretical investigation of the heat transfer on a direct contact column for desalination purposes. The effect of air and water mass flow rates and air inlet temperature on the temperature distribution and moisture content of the air outlet stream was measured. The experimental heat transfer coefficient was estimated and, in order to simulate the experimental results, a comparison with available correlations was performe
Thermodynamic analysis of steam reforming and oxidative steam reforming of propane and butane for hydrogen production
Full text linkThermodynamic analyses of cracking, partial oxidation (POX), steam reforming (SR) and oxidative steam reforming (OSR) of butane and propane (for comparison) were performed using the Gibbs free energy minimization method under the reaction conditions of T = 250–1000 °C, steam-to-carbon ratio (S/C) of 0.5–5 and O2/HC (hydrocarbon) ratio of 0–2.4. The simulations for the cracking and POX processes showed that olefins and acetylene can be easily generated through the cracking reactions and can be removed by adding an appropriate amount of oxygen. For SR and OSR of propane and butane, predicted carbon formation only occurred at low S/C ratios (<2) with the maximum level of carbon formation at 550–650 °C. For the thermal-neutral conditions, the TN temperatures decrease with the increase of the S/C ratio (except for O/C = 0.6) and the decrease of the O/C ratio. The simulated results for SR or OSR of propane and butane are very close under the investigated conditions
Thermodynamic Analyses of a Moderate-Temperature Process of Carbon Dioxide Hydrogenation to Methanol via Reverse Water–Gas Shift with In Situ Water Removal
No full textCO2 hydrogenation to methanol
via the reverse water–gas
shift (the CAMERE process) is an alternative method for methanol synthesis.
High operating temperatures (600–800 °C) are required
for the reverse water–gas shift (RWGS) process because of the
thermodynamic limit. In this study, moderate temperatures (200–300
°C) were used for the RWGS part of the CAMERE process by the
application of in situ water removal (ISWR). Thermodynamic analyses
were conducted on this process using the Gibbs-free-energy-minimization
method. The analyses show that by using ISWR with high water-removal
fractions (e.g., 0.80–0.99), the CO2 conversion
of the RWGS part can be significantly improved at moderate operating
temperatures. One-step CO2 hydrogenation to methanol (CTM)
with ISWR was also investigated, and it resulted in similar methanol
yields. Both processes showed high potential and the ability to promote
CO2 hydrogenation to methanol through the use of ISWR
Two-dimensional thermal analysis of radial heat transfer of monoliths in small-scale steam methane reforming
Full text linkMonolithic catalysts have received increasing attention for application in the small-scale steam methane reforming process. The radial heat transfer behaviors of monolith reformers were analyzed by two-dimensional computational fluid dynamic (CFD) modeling. A parameter study was conducted by a large number of simulations focusing on the thermal conductivity of the monolith substrate, washcoat layer, wall gap, radiation heat transfer and the geometric parameters (cell density, porosity and diameter of monolith). The effective radial thermal conductivity of the monolith structure, kr,eff, showed good agreement with predictions made by the pseudo-continuous symmetric model. This influence of the radiation heat transfer is low for highly conductive monoliths. A simplified model has been developed to evaluate the importance of radiation for monolithic reformers under different conditions. A wall gap as thin as 0.05 mm significantly decreased kr,eff, while the radiation heat transfer showed limited improvement. A pseudo-homogenous two-dimensional model combined with the symmetric model has been developed for a quick evaluation of geometric parameters for a monolith reformers. Monolithic reformers based on highly conductive substrates e.g., Ni and SiC showed great potential for small-scale hydrogen production
A comparative study on three reactor types for methanol synthesis from syngas and CO2
Full text linkIn this study, a comparative study was conducted on the three reactor types (the adiabatic, water-cooled and gas-cooled reactor) employed for the traditional syngas to methanol (STM) process to investigate their potential applications to the STM process with the CO 2-rich feed gas or the CO 2 hydrogenation to methanol (CTM) process. The temperature profiles in the axial and radial directions particularly the hot-spot temperatures, operating conditions and methanol yields for the reactors have been investigated using the thermodynamic analysis, the CFD method and the pseudo-homogeneous model. The capital costs for CTM process with the three reactor types have also been evaluated. Compared with the traditional STM process, the STM process with the CO 2-rich feed gas and CTM process exhibited reduced hot-spot temperatures. The simulation results showed that the single-bed adiabatic (without internal cooling) reactor and the gas-cooled reactor exhibited potentials for the CTM process, where the hot-spot temperatures the hot-spot temperatures in the reactors can be within the typical operating temperature range (e.g., 220–280 °C) for the catalyst. Regarding the comparison of the three reactor types for the CTM process, the water-cooled reactor showed advantages in terms of efficient heat removal, low hot-spot temperature and relatively wide range of inlet temperature for control. The adiabatic reactor and the gas-cooled reactor demonstrated a relatively low and medium performance, and also a relatively low and medium capital cost, respectively, which indicates the potentials of the two reactor types in a small-scale CTM process. </p
