STEAM REFORMING OF BIOGAS FOR H2 PRODUCTION IN CATALYTIC PACKED BED AND MEMBRANE REACTORS: THERMODYNAMIC AND MODELING STUDIES

Abstract

In the last few decades, immense research efforts have been made in the search of new and alternate energy sources that are clean, renewable, affordable and sustainable due to ever increasing energy demands and environmental pollution and climate change issues, and depletion of currently used fossil fuel reserves. In this context, hydrogen is considered as one of the most promising energy carrier due to its various advantages. It is clean and environmentally innocuous fuel as its combustion does not add to GHG emissions and other pollutants. It also has highest calorific value (120.7 MJ/kg). Hydrogen is utilized as a primary feedstock for several chemical, fertilizer and petrochemical industries. It is widely used as a hydrogenating agent, a reducing agent in metallurgical industries, and an important commodity for petroleum refineries. Recently, hydrogen application as a fuel for combustion engines, gas turbines and fuel cells, has resulted in a huge increase in its demand. Further, syngas is considered as a chemical feedstock for the production of various types of higher hydrocarbons by different processes such as Fisher-Tropsh (F-T) process. Unfortunately, hydrogen production is presently being carried out by reforming of different hydrocarbons based on fossil fuels especially steam reforming of natural gas. Hydrogen production via steam reforming of natural gas stands at almost 50% of its total production. Hydrogen produced in such a way, is not truly carbon neutral as its production comes from fossil fuel which carries carbon footprints leading to numerous environmental issues. Therefore, hydrogen production should be based on the renewable and sustainable energy sources. Being carbon neutral, renewable and sustainable energy source, biogas is an attractive and potential alternative and / or support to the presently used natural gas for hydrogen and syngas production via its reforming. Biogas is typically obtained by anaerobic fermentation of a wide range of biodegradable organic fractions of agro-industrial waste, municipal solid waste, sewage sludge, animal farming and slaughter house wastes. The major components of biogas are methane and carbon dioxide; both are principal greenhouse gases (GHGs) which leads to global warming and climate change. It also contains trace amounts of H2S, H2O, N2, O2 and Siloxanes. Biogas composition depends on the feedstock used. It contains 45 – 80% CH4 and 55 – 20% CO2 depending on its source/feedstocks for biogas digester.