Design and assessment of novel thermochemical plants for producing second and third generation biobutanol

Abstract

The use of biofuels as an alternative to gasoline in the transportation sector is seen by policy makers as an important strategy to reduce global greenhouse gas emissions. Biobutanol is one such biofuel that is gathering increasing attention in the biofuel community, because of its preferable fuel qualities over bioethanol. However, despite increasing research into biobutanol production, the thermochemical route for biobutanol production has not been adequately studied in the peer-reviewed literature. In light of this motivation, this thesis considers the design, and economic and environmental assessment of thermochemical plants for producing second and third generation biobutanol. In addition, the potential for using process intensification technology such as dividing wall columns (DWC) in place of conventional distillation columns is also investigated as a way to improve thermochemical biobutanol plants. As a first step, a novel thermochemical plant for producing second generation biobutanol is developed. Detailed economic analysis of this plant show that it is competitive with gasoline under certain process, and market conditions. The designed plant is then extended, with some modifications, to evaluate the economic and environmental potential of a thermochemical plant for producing third generation biobutanol from macroalgae. It was concluded from the results that the thermochemical route is preferable for producing second generation biobutanol over third generation biobutanol. The novel thermochemical plant design is then updated by using a kinetic model of a pilot-scale demonstrated catalyst to represent the critical mixed alcohol synthesis reaction step. This change allows optimal unreacted syngas recycle configurations for maximizing butanol yield to be established. Furthermore, integrating a DWC, designed using a methodology developed in the thesis, into the updated thermochemical plant leads to additional plant improvements. Overall, the work carried out in this thesis demonstrates that the thermochemical route is a viable option for producing second generation biobutanol.