Experiments on combustion of oil shale sludge and semicoke were conducted on TG-FTIR to investigate the mechanism of co-combustion involved. The synergy effect of sludge and semicoke was estimated by using the interaction coefficient and the relative error of mean square root. In addition, the activation energy was calculated by means of Coats− Redfern, DAEM, FWO, and Starink. The results show that the whole process contains three stages: light components combustion (130−350 °C), heavy components and volatiles co-combustion (350−650 °C), and fixed carbon combustion (650− 750 °C). During the combustion, synergy behaves differently with variation of mixing proportion in mixture and heating rates. DTG curves of mixtures can be decomposed into five Gaussian fitting peaks, respectively corresponding to five independent parallel reactions. From the results of Coats−Redfern, one can see that the kinetic triplets are related to mixture proportion, combustion stage, and heating rate. In addtion, the results of DAEM, FWO, and Starink indicate the three above are fit for calculating kinetic parameters of mixture and also suggest that combustion of mixture is a multiple reaction. It can be noted that there is a positive relationship between release rate of flue gas and proportion of sludge. Besides, the nonlinearity between A CO / A CO2 and the proportion of sludge indicates that an overlarge proportion of sludge is disadvantageous for sufficient burning. According to the combustion characteristics, the kinetic analysis, synergy, and FTIR analysis of flue gas, the optimal blending ratio is 20%/80% of sludge/semicoke.

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The study presented herein has been carried out in order to investigate the chloride diffusivity of recycled aggregate concrete (RAC). Meanwhile, the effect of the binder type, involving cement replacement materials such as, fly ash, slag and silica fume on the chloride diffusivity has also been investigated. For this purpose, RAC and concrete containing the different type of binders with w/b ratios of 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 were used. As a result, the chloride diffusion coefficient of RAC is higher than that of natural concrete and the partial replacement of cement with fly ash, slag and silica fume is effective in decrease in the chloride diffusion coefficient, measured by a rapid chloride conductivity test.

Utilization of the semi-coke collected from oil shale retorts is very important and advantageous. Due to the inflammable property, co-combustion of semicoke with other good quality solid fuels could be effectual. In this research, a kinetic study of the combustion of oil shale semi-coke (SC) mixed with bituminous coal (C) was carried out by thermogravimetric analysis at different heating rates. Popescu's method was applied to analyze the kinetic mechanisms of combustion of oil shale semi-coke, bituminous coal and their blends; Flynn-Wall-Ozawa method was employed to determine the activation energies of those combustion reactions. Based on the obtained results, it was concluded that three-dimensional diffusion model could be implemented either for the combustion process of oil shale semi-coke or for bituminous coal while for their blends the model of random nucleation and growth could be applied. The activation energies of oil shale semi-coke and the blends of semi-coke and bituminous coal decreased in the beginning, and then increased during the combustion process. Activation energies of the blends decreased with increasing amount of bituminous coal.

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