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For achieving CO2 thermal reduction, a technology combining solid carbon activation and high-temperature CO2 reduction was proposed, named as activated-reduction technology. In this study, this technology is realized by using a circulating fluidized bed and downdraft reactor. Reduced agent parameters (O2/C and CO2 concentration) greatly affect the reduction effect of CO2. In addition, the effect of the activation process on different carbon-based materials can help to broaden the range of carbon-based materials used for CO2 reduction, which is also an important issue. The following three points have been studied through experiments: (1) the influence of the characteristics of the reduced agent (CO2 concentration and O2/C) on CO2 reduction; (2) the performance of different chars in CO2 reduction; and (3) the activation effect of solid carbon. The activation process can develop the pore structure of coal gasification char and transform it into activated char with higher reactivity. The CO concentration in the tail gas is a crucial factor limiting the effectiveness of CO2 reduction, with an experimentally determined upper limit of around 55% at 1200 °C. If CO concentration is far from the upper limit, temperature becomes the significant influencing factor. When the reduced agent O2/C is 0.18, the highest net CO2 reduction of 0.021 Nm3/kg is achieved at 60% CO2 concentration. When the reduced agent CO2 concentration is 50%, the highest net CO2 reduction of 0.065 Nm3/kg is achieved at 0.22 O2/C. Compared with CPGC, YHGC has higher reactivity and is more suitable for CO2 reduction. The activation process helps to reduce the differences between raw materials. [ABSTRACT FROM AUTHOR]

Instrumentation packages for eddy covariance (EC) measurements have been developed for unoccupied aerial vehicles (UAVs) to measure the turbulent fluxes of latent heat (LE), sensible heat (H), and CO2 (Fc) in the atmospheric boundary layer. This study aims to evaluate the performance of this UAV-based EC system. First, the measurement precision (1σ) of georeferenced wind was estimated to be 0.07 ms-1. Then, the effect of the calibration parameter and aerodynamic characteristics of the UAV on wind measurement was examined by conducting a set of calibration flights. The results showed that the calibration improved the quality of the measured wind field, and the influence of upwash and the leverage effect can be ignored in wind measurement by the UAV. Third, for the measurements of turbulent fluxes, the error caused by instrumental noise was estimated to be 0.03 µmolm-2s-1 for Fc , 0.02 Wm-2 for H , and 0.08 Wm-2 for LE. Fourth, data from the standard operational flights were used to assess the influence of resonance on the measurements and to test the sensitivity of the measurement under the variation (±30 %) in the calibration parameters around their optimum value. The results showed that the effect of resonance mainly affected the measurement of CO2 (∼5 %). The pitch offset angle (εθ) significantly affected the measurement of vertical wind (∼30 %) and turbulent fluxes (∼15 %). The heading offset angle (εψ) mainly affected the measurement of horizontal wind (∼15 %), and other calibration parameters had no significant effect on the measurements. The results lend confidence to the use of the UAV-based EC system and suggest future improvements for the optimization of the next-generation system. [ABSTRACT FROM AUTHOR]

The poor-reactivity anthracite urgently needs more ways for large-scale and high-quality utilization. Due to the advantage of good fuel adaptability, the circulating fluidized bed (CFB) gasification technology has the potential of high-quality utilization of anthracite. In this paper, one kind of anthracite from Shanxi province, China, was employed to be gasified in a pilot-scale CFB gasifier. It is found that at the operating temperature of 1049°C and oxygen concentration of 60.75%, the gas with a concentration of combustibles of 66% and a low heating value of 7.93 MJ/m3 (at about 25°C and 101.325 kPa) was produced in the CFB gasification process. However, the overall gasification efficiency was not desired because a large amount of gasification fly ash (GFA) escaped and its yield was up to 22%. In this case, the cold gas efficiency was below 48% and the carbon conversion ratio was only 62%. Further analysis reveals that the GFA was featured with a developed pore structure and the specific surface area (SBET) reached 277 m2/g. This indicates such GFA has a potential to use as activated carbon (AC) or AC precursor. Basis on this, steam activation experiments of the GFA produced were conducted to investigate the activation characteristics of GFA and thereby to determine its activation potential. Experimental results indicate that increasing temperature sharply accelerated the activation process, while did not impair the maximum activation effect. After activation, the SBET of GFA maximumly increased by 63%, reaching 452 m2/g. With the progress of activation, the pore structure of GFA presents a three-stage evolution process: development, dynamic balance, and collapse. Such a process can be divided and quantified according to the carbon loss. In order to achieve an optimal activation of GFA, the carbon loss shall be controlled at ~15%. This work provides a new scheme for high-quality utilization of anthracite. [ABSTRACT FROM AUTHOR]