Coal gasification for fuel synthesis: Multiphysics modeling and new concepts

<p>Fuel synthesis through gasification of carbonaceous materials (e.g. coal and biomass) has the potential to provide a solution to the increasing demand for energy and liquid transportation fuels. To theoretically understand the complex physical and chemical processes in a gasifier and to identify the most influential parameters for syngas production, we first developed a multi-physics and multi-scale model to simulate the gasification processes in a well-stirred reactor. This model is the first of its kind and considers detailed gas-phase chemistry, particle-phase reactions, moisture drying, devolatilization, porous structure evolution, convective and radiative heat transfer, as well as full coupling between the two phases at various scales for mass, species, and energy exchange. Numerical simulations were conducted to understand the gasification process and the effects of particle size, porous structure, radiative heat transfer, pressure, O₂ concentration, H₂ addition, moisture content, and devolatilization on gasification performance. The model was also used to study the effect of concentrated solar energy on the gasification process. The effects of concentrated solar energy flux on conversion time, syngas yield, solar-to-fuel conversion efficiency, and solar-to-chemical enthalpy conversion percentage were analyzed.^ Then, droplet breakup mechanism of carbon-in-water suspensions (CWS) under intense radiation were studied both experimentally and theoretically. CWS have unique optical properties and have received increasing interest recently for various applications. In the field of combustion science, CWS have been recommended as a substitute for the traditional fossil fuels. The idea is to suspend carbon (coal or coal) particles in water and then inject them as a spray into a gasifier or boiler. The potential benefits are lower emissions and higher combustion efficiency, in comparison to directly injecting coal particles into air or water steam. Nevertheless, few studies have examined CWS colloidal fuels. Especially, droplet breakup can occur when the droplets are exposed to radiation. The goal of this study was to understand droplet breakup mechanism of CWS under intense radiation. An experiment was developed to visualize the breakup process and to measure the threshold radiation intensity required for explosion at varying particle materials, particle sizes, particle concentrations, droplet sizes, base fluids as well as wavelengths of the radiation. The results showed that radiation absorption by the carbon particles play a critical role in the breakup behavior. A theoretical model was also developed to determine the effects of the particle material, the particle size, the particle concentration, the base fluid, and the wavelength of the radiation on the threshold radiation energy.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Aeronautics and Astronautics

Year

2014

Author dc:creator

• Xu, Jian

Contributors dc:contributor

• Li Qiao
• Haifeng Wang
• Stephen Heister
• Jay Gore

• Engineering
• Mechanical Engineering

Repository record dc:identifier

https://docs.lib.purdue.edu/open_access_dissertations/394

OAI identifier oai:identifier

oai:docs.lib.purdue.edu:open_access_dissertations-1583