SIMULATION AND MODELLING OF HYDROGEN PRODUCTION FROM BIOGAS

Abstract

Hydrogen (H2) is the most abundant element in the universe. It can serve as a clean fuel when produced using environmentally friendly methods. Hydrogen production is a critical aspect of the global energy landscape, particularly in the context of transitioning to cleaner and sustainable energy sources. H2 fuel is adopted for the upcoming generation. Switching to H2 technology is caused of decrement in fossil fuel and changes in climate conditions. There are multiple methods for producing H2 from conventional and non-conventional resources. For sustainable decentralized power generation in remote and rural areas, development of large-scale H2 production technology is required. Biogas reforming is an auspicious process for the production of green hydrogen gas as well as for reducing overburden on natural gas and mitigation of greenhouse gas emissions. In recent times, there has been an amplified interest in exploring fresh applications of biogas, attributed to the rising concerns surrounding climate change and an enhanced emphasis on the utilization of renewable energy sources. The use of fossil fuels in energy systems has environmental consequences, which are driving investigations into H2 production. Steam-reforming of biogas is a beneficial procedure for producing eco-friendly hydrogen and minimizing the burden on fossil fuels. Steam methane reforming is the most well-known method for producing H2 using fossil fuels. In the present study, simulation and modeling of hydrogen production from biogas have been analyzed. This study introduces a zero-dimension (0-D) mathematical model to explore hydrogen production through steam reforming of methane and biogas with varying compositions. The model was simulated by using a batch reactor and incorporated both heat and mass transfer with the chemical reactions occurring in the reactor and calculated product distribution and temperature through the application of energy and mass balances. The model was also used to explain the reaction mechanism involved in the production of hydrogen, and the reaction performance was validated through a simulation analysis using the finite element analysis software (COMSOL Multiphysics 5.6). The presented reactor model closely predicts outcomes from both the 1-D and 2-D non-isothermal models of methane and v biogas steam reforming. Therefore, a zero-dimensional model is favored to simplify this study. The model reveals the hydrogen production reaction mechanism and validates its performance through simulation analysis using COMSOL Multiphysics 5.6 software (finite element analysis). The developed model has been validated by available previous experiments and simulation work for biogas reforming with various compositions as well as the methane reforming process. The core aim of this study is to estimate the yield of H2 for steam methane reforming, and H2 and CO for steam biogas reforming at steam carbon ratio (S/C) from 1-3 with various temperatures, and find the optimum temperature for the reforming process. The results of the present study show higher yields of hydrogen, achieving 6% and 8.2% respectively, compared to the previous simulation study at a steam-to-carbon (S/C) ratio of 2 and 3, and a temperature of 700°C through steam reforming method. The higher H2 yields are achieved as 5.33% at 800 oC, 3.87% at 1000 oC, and 2.9% at 1200 oC (average percentage of mol for steam carbon ratio from 1-3) and compared with previous simulation studies at the same operating temperatures through the steam biogas reforming method. It is observed and confirmed that the values obtained from the current simulation enhance the H2 production rate by almost 4% compared to the previous data. These findings indicate that the proposed work offers a viable method for utilizing renewable methane resources to fuel cells and generate local electricity. This study explored extensive literature on possibilities of biogas reforming techniques for hydrogen production as well as comprehensive assessment of recent advancements in the domains of dry, bi-, and tri-reforming. A comparative evaluation of various techniques and the exploration of recent catalysts employed in the reforming process and techno-economic biogas conversion applications are also explored in this analysis. Biogas conversion exhibits economic feasibility, typically with a payback period ranging from 4 to 8 years. Opting for a higher reaction temperature within the range of 830-900°C is typically favored as it results in increased CH4 and CO2 conversions within the bi-reforming of the biogas process. For Dry and Tri reforming, the temperature range is maintained between 750-850oC and 850-1000oC or above (depending on various factors). vi The study presented the thermodynamic analysis for hydrogen production through the steam reforming of biogas (with and without CO2), considering different CH4 and CO2 concentrations and the utilization of various steam-carbon ratios. The study has also discussed the detailed thermodynamic equilibrium study, the path of the reaction, and the kinetic model of these reforming processes. A technical analysis of the steam biogas reforming process and its related energy are also investigated. As the molar ratio of steam carbon (S/C) rises at a particular temperature, it has been noted that the conversion of CH4 to H2 results in an increase in the hydrogen output. If the ratio of steam carbon (S/C) is improved from 2:1 to 3:1, the water gas shift reaction occurs, which results in the highest hydrogen production yield (5-6%). The overall research work has undergone extensive analysis to produce reliable, system-effective results that are nourished by a detailed discussion of the results and conclusions, as well as recommendations for future research.