Design and investigation of renewable natural gas and methane production systems

Abstract

This thesis presents the design and investigation of renewable natural gas and methane production systems. The thesis comprises a theoretical and an experimental portions. The experimental portion of the thesis includes the design, construction, and experimental testing of a new helical fixed-bed reactor, as well as a production system to support and monitor the reactor. Additionally, the experimental system integrates gas bending and the recycling of the coolant working fluid to pre-heat the reactant molecules prior to entering the reactor. The experimental tests include studying the effects of pressure variability at the inlet of the reactor, variations in the reactor starting temperature, and variations in the mole ratio between reactants. Most notably, the system is able to achieve a maximum CH4 production rate of 10.61 L/h. This equates to overall energy and exergy efficiencies of 13.36% and 12.46%, respectively. However, during the simulation aspect of the thesis, computational fluid dynamics (CFD) analyses are conducted. These analyses consider the design of four unique fixed-bed natural gas reactor concepts. Additionally, each of the reactor concepts is presented as having three unique configurations. The analyses show that Concept 4’s helical reactor design presents the greatest potential to mitigate elevations in the reactors’ temperature due to more of its surface area being exposed compared to the other reactor concepts. Additionally, Configuration 1 of Concept 4 is able to achieve a yield of 86.7%. The theoretical portion also investigates four novel multigeneration systems capable of synthesizing natural gas while simultaneously producing several useful outputs. System 1 considers a target location of Alberta, Canada, and uses biomass and solar energy as its source. The system achieves energy and exergy efficiencies of 61.0% and 28.6%, respectively, during heating mode. The other three multigeneration systems reduce CO2 emissions from industries that produce substantial amounts of greenhouse gas emissions (cement, steel, and glass industries), through the integration of chemical absorption techniques, the CO2 that is extracted can be used to synthesize CH4 renewably. These systems also harness solar, wind, hydro, and tidal as the energy sources.