| Description |
The advancement of green coal conversion technologies is of great importance to global sustainable development. Two novel coal utilization methods are introduced in the current dissertation, underground coal thermal treatment (UCTT) and photoelectrochemical (PEC) coal gasification. UCTT is a proposed method for producing light hydrocarbon compounds from underground coal seams for a lower CO2 emission comparing with traditional coal use. By in-situ heating of coal in the absence of an oxidant, the coal would be thermally decomposed to a mixture of lighter (in terms of molecular weight) hydrocarbons and a solid product of char, the latter being left underground. In order to study coal pyrolysis behavior at UCTT conditions, a modified chemical percolation devolatilization (M-CPD) model was developed and evaluated using two scales of experiments, as well as two different coals, Utah Sufco and Illinois #6. Compared with the original CPD model, three major aspects were changed. The results predicted by the M-CPD model were compared with those from the CPD model and experiments, and reasons for observed differences between the two models and the experimental data are discussed. PEC coal gasification is a novel concept that converts coal to high concentrations of H2 and CO2 using solar energy. In this method, coal is oxidized and decomposed to CO2 in an acidic hydrothermal environment, with the aid of an iron-ion catalyst. Meanwhile, the depleted catalyst solution is regenerated using a PEC cell, which is iv equipped with a TiO2 nanotube array (TNA) based photoanode. The resulting electron potential energy is stored in the form of H2, achieved by the corresponding cathode. Many advantages are expected from this design compared with other relevant research. The current dissertation focuses on the validation of this concept and the optimization of the photoanode and reaction conditions. Two kinds of photoanodes, a black TiO2 nanotube array (BTNA) photoanode and a dye-sensitized TiO2 nanotube arrays (DSTNA) photoanode were designed and tested. The photocurrent and open-circuit voltage (Voc) obtained from both photoanodes were compared, and reasons for observed differences are discussed, indicating directions for future improvements. |
