Combustion of super fine particles is a new pulverized coal combustion technique. Compared with conventional combustion techniques, it has the advantages of good flame stability, high burnout, low NOx release, and low comprehensive cost. Using NETZSCH thermobalance, STA 409C, and maintaining the test conditions for all the samples at the heating rate of 20 °C/min, the paper investigated the combustion properties of Heshan (Hs) subbituminous coal and Jincheng (Jc) lean coal, each in four different average sizes. Significant improvement of combustion properties was observed when particle size was reduced down to 0-20µm.

In this paper, a model on attrition of quartzite particles as an inert bed material in fluidized beds has been established on the particle-particle collision. For the convenience of describing the attrition of quartzite particles in fluidized beds, we chose the attrition rate constant (kARC) as one main characteristic parameter to develop the model. In order to verify the validity of the developed model, an attrition experiment of quartzite articles has been carried out in a lab-scale circulating fluidized bed. The predicted results from the population model were close to the experimental data as far as the engineering use is concerned. Finally, a sensitivity analysis was performed by using the developed model to examine effects of initial particle diameter, attrition time, and fluidization number on kARC.

The comprehensive utilization of oil shale is a new promising technology achieving high utilization-factors for both oil shale’s chemical and energy potentials, and avoiding serious environmental impacts. For this technology, it is an urgent issue how to obtain shale oil with a high yield and as well as treat shale char efficiently and economically. In this present work, retorting experiments of three type I oil shales were performed using an aluminum retort, and the effect of retorting temperature, residence time, particle size and heating rate on the yield of shale oil was studied at low retorting temperatures ranging from 400℃to 520℃, respectively, at which shale char obtained has good combustion properties. The experimental data show that an increase in the retorting temperature, the residence time and the heating time has positive significant effect on improving the yield of shale oil, and a middle particle size is helpful for increasing the oil yield as well. The grey system method was applied to evaluate the effect of retorting factors on the yield of shale oil, showing that the retorting temperature is the most marked factor influencing the yield of shale oil.

Oil shale semicoke, formed in retort furnaces, is a source of severe environmental pollution and is classified as a dangerous solid waste. For the industrial application of oil shale semicoke in combustion, this present work focused on the thermal analysis of its combustion characteristics. The pyrolysis and combustion experiments of semicoke were conducted in a Pyris thermogravimetric analyzer. From the comparison of pyrolysis curves with combustion curves, the ignition mechanism of semicoke samples prepared at different carbonization temperatures was deduced, and was found to be homogeneous for semicoke samples obtained at lower carbonization temperature, shifting to heterogeneous with an increase in the carbonization temperature. The effect of carbonization temperatures and heating rates on the combustion process was studied as well. At last, combustion kinetic parameters of semicoke were calculated with the binary linear regression method, showing that activation energy will increase with increasing the heating rate.

Shale char, formed in retort furnaces of oil shale, is classified as a dangerous waste containing several toxic compounds. In order to retort oil shale to produce shale oil as well as treat shale char efficiently and in an environmentally friendly way, a novel kind of comprehensive utilization system was developed to use oil shale for shale oil production, electricity generation (shale char fired) and the extensive application of oil shale ash. For exploring the combustion properties of shale char further, in this paper organic matters within shale chars obtained under different retorting conditions were extracted and identified using a gas chromatography-mass spectrometry (GC-MS) method. Subsequently, the effects of retorting factors, including retorting temperature, residence time, particle size and heating rate, were analyzed in detail. As a result, a retorting condition with a retorting temperature of 460-490 ◦C, residence time of <40 min and a middle particle size was recommended for both keeping nitrogenous organic matters and aromatic hydrocarbons in shale char and improving the yield and quality of shale oil. In addition, shale char obtained under such retorting condition can also be treated efficiently using a circulating fluidized bed technology with fractional combustion.