We made considerable progress towards completing the development of a thermogravimetric reactor with video microscopy imaging capabilities (TGA/VMI). The video micrOSCOPY components were designed, installed and are currently under testing. With the newly developed TGA/VNH apparatus we can directly observe macroscopic changes in the morphology of pyrolyzing particles and thermal ignitions of burning particles while simultaneously monitoring the weight of pyrolyzing or reacting samples. The systematic investigation on the effects of pyrolysis conditions and char macropore structure on char reactivity continued. Pyrolysis and gasification experiments were performed consecutively in our TGA reactor and the char reactivity patterns were measured for a wide range of temperatures (400--600[degrees]C). These conditions cover both the kinetic and the diffusion limited regimes. Our results show conclusively that chars produced at high pyrolysis heating rates (and, therefore, having a more open cellular macropore structure) are more reactive and ignite more easily than chars pyrolyzed at low heating rates. These results have been explained using theoretical models. We also investigated for the first time the effect of coal particle size and external mass transfer limitations on the reactivity patterns and ignition behavior of char particles combusted in air. Finally, we used our hot stage reactor to monitormore » the structural transformations occurring during pyrolysis via a video microscopy system. Pyrolysis experiments were videotaped and particle swelling and the particle ignitions were determined and analyzed using digitized images from these experiments.« less