Energy Efficient Processes for the Production of Gaseous Biofuels - Reforming and Gas Upgrading

Replacing fossil fuels with biofuels is one way of reducing the emission of greenhouse gases into the atmosphere, thus decreasing our impact on the global climate. For this to be a viable option, several production routes are needed, as no single option can fully replace fossil fuels. One way of making biofuels more competitive with fossil fuels is by reducing the production cost. As most of the processes involved in biofuel production are very energy intensive, this can be achieved by employing more energy-efficient processes. The work presented in this thesis focuses on the development of energy-efficient processes in both biological and thermochemical production of gaseous fuels, such as biogas, synthetic natural gas and hydrogen. Two processes in the production chain have been studied, namely reforming and gas upgrading. Both existing and new technology have been investigated. The work performed on the reforming of a gasifier producer gas resulted in the modeling of a reverse-flow reformer using non-catalytic partial oxidation to produce synthetic natural gas, hydrogen or synthesis gas. The results of the modeling showed that the reverse flow reformer is more suited for the reforming of higher hydrocarbons and tars, than for reforming of methane, due to the increased soot formation at the high temperatures needed to reform methane. For the gas upgrading process, existing technology using piperazine-activated N-methyl diethanolamine was investigated in order to obtain more information on the heat of absorption of carbon dioxide in these solutions. The investigation showed that piperazine increased the heat of absorption of the solution significantly at low carbon dioxide loadings. New amine solutions for gas upgrading were also investigated, where a precipitate was formed during the absorption of carbon dioxide. These solutions allowed the regeneration of the amine using low-grade heat, which can greatly reduce the production cost of the biofuels