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[en] Highlights: • A solid-particle receiver was firstly proposed for solar dish system. • For a single pass, the final particles temperature reached over 350 °C. • A Monte-Carlo ray-tracing method was coupled with a thermal conversion model. • The coupled model was used to forecast performances of solid-particle receiver. • The final temperature of particles would increase over 1100 °C on 150 kW/m2. - Abstract: A solid-particle solar receiver was proposed to convert concentrated solar beams into heat for high-temperature thermal storage in a two-stage dish system. Spherical Xe-arc lamps were used to simulate a solar light source. The performances of this receiver under a Xe-arc lamp array system were experimentally and numerically investigated. For a single pass, the temperature increase exceeded 350 °C, and the optical efficiency and thermal efficiency were ∼84% and 60%, respectively, when the average flux on the aperture was ∼19.3 kW/m2. A Monte-Carlo ray-tracing method was used to simulate concentrating beams, which was integrated with a thermal conversion model. The coupled model was validated under low radiation flux conditions and then used to predict the solid-particle receiver performance under high radiation flux conditions. The simulation results indicate that the final temperature of the single-pass particles would increase to over 1100 °C under an average flux of 150 kW/m2. In addition, the efficiency of the receiver could be enhanced by reducing the radiative emission
[en] A Lambertian CCD-camera method is convenient to measure concentrating radiation fluxes, where a crucial factor, a calibration factor, always varies with spectra and brings errors. In this paper, a new calibration method is proposed based on spectral normalization calculation and tries to reduce spectral errors in Lambertian CCD-camera measurement. The calibration factor for AM1.5 is standardized over a transmittance range by matching gray values of photos to readings of calorimeter. A spectrum is calculated by SMARTS (simple model of the atmospheric radiative transfer of sunshine) according to the local time, latitude and longitude. A calibration factor is adjusted by calculated spectral offsets accordingly. Therefore an absolute radiation flux distribution is obtained by a gray value captured by the CCD-camera without calorimeter. Calculated results indicate that spectral irradiance between 700 and 800 nm dominates gray values on the target for solar radiation flux measurement. The offsets are increasing continuously from AM1 to AM5, which are validated by experimental results. The difference between measured and calculated calibration factors is 11%, which fits to the results of error estimate. These indicate that the improved method was feasible and reliable to measure concentrating radiation fluxes easily. - Highlights: • An improved Lambertian CCD-camera radiation measurement method is proposed. • The spectral errors are reduced by the calculated offsets based on SMARTS (simple model of the atmospheric radiative transfer of sunshine). • The absolute radiation flux distributions can be obtained without calorimeter. • The total estimated error for the simulator is ±13.17%. • The results of validation experiment demonstrate an error of 11%
[en] Highlights: • A model that integrates life cycle energy, environment, and economy is developed. • The most important inconsistencies between LCC and LCA are unified. • The methodology improvement of MCDM is supplemented to be more logical. • A two-step sensitivity analysis is added to overcome subjectivity by decision makers. • MSW landfill and incineration are compared for model application. - Abstract: How to choose an energy-efficient, environmentally friendly and economically affordable municipal solid waste (MSW) management system has been a major challenge to be taken up by decision makers. Although life cycle assessment (LCA) has been widely used for the evaluation of energy consumption and environmental burden, the economic factor is not considered yet in LCA procedures. Thus, in the present study life cycle 2E (energy and environment) assessment is extended to a 3E (energy, environment, and economy) model. To evaluate economic performance, life cycle cost (LCC) is adjusted in accordance with LCA. Afterwards, multi-criteria decision making (MCDM) method is improved to integrate 3E factors. Besides, a two-step weight factor analysis is added, not only to test the robustness of the model, but also to adopt different preferences proposed by different stakeholder groups. This novel 3E model is then applied for the comparison of different MSW treatment technologies: (1) landfill; (2) landfill with biogas conversion to electricity; (3) incineration with energy recovery. Results show that incineration scores 0.944/1 and performs best among all scenarios; landfill with biogas to electricity, with final score 0.722/1, ranks second; and landfill without energy recovery (score: 0/1) is the worst choice. Furthermore, the weight factor analysis also shows a highly credibility of the results: when changing each factor’s weight from 0 to 1, less than 30% of the cases exhibit the variation in ranking order; almost no change in ranking order occurs when considering the different perspectives from government, enterprise and residents
[en] Graphical abstract: - Highlights: • Ordered mesoporous carbon (OMC) and Ce-OMC were used for NO adsorption. • The NO adsorption capacity of OMC was two times larger than that of activated carbon. • With the addition of cerium both adsorption capacity and adsorption rate increased. • The pseudo-second-order model was the most suitable model for NO adsorption on OMC. • Intraparticle diffusion was the rate controlling step for NO adsorption. - Abstract: Ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC) were prepared using evaporation-induced self-assembly (EISA) method and used to adsorb NO. N2 sorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm their structures. The results showed that the ordered and uniform structures were successfully synthesized and with the introduction of cerium pore properties were not significantly changed. The NO adsorption capacity of OMC was two times larger than that of activated carbon (AC). With the introduction of cerium both the adsorption capacity and the adsorption rate were improved. The effects of residence time and oxygen concentration on NO adsorption were also investigated. Oxygen played an important role in the NO adsorption (especially in the form of chemisorption) and residence time had small influence on the NO adsorption capacity. The NO adsorption kinetics was analyzed using pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion models. The results indicated that the NO adsorption process can be divided into rapid adsorption period, slow adsorption period, and equilibrium adsorption period. The pseudo-second-order model was the most suitable model for NO adsorption on OMC and Ce-OMC. The rate controlling step was the intraparticle diffusion together with the adsorption reaction
[en] Highlights: • A simulation model is proposed to couple optical and heat transfer processes. • The air outlet temperature is 662 °C at a flux of 120 kW/m"2 experimentally. • The temperature deviations are within 8% between simulation and experiment. • The model indicates the air outlet temperature can reach 800 °C at 300 kW/m"2. • The model provides detailed analysis and suggests ways to improve performances. - Abstract: High temperature air is a potential candidate as a heat transfer fluid to transport energy from concentrated solar power to gas turbines. A 15-turn helically coiled tube cavity receiver with an optical splitter at the bottom is designed and fabricated. Its performance is investigated with a five 7-kW Xe-arc lamps array system as heat source. Eight K-type thermocouples are placed from top to bottom with an equal interval. The outlet temperature experimentally ranges from 593 °C to 546 °C when the air flow rate increases from 1 m"3/h to 5 m"3/h for up-flows, while it ranges from 662 °C to 570 °C for down-flows, when the average flux on aperture is around 120 kW/m"2. The Monte-Carlo ray-tracing method and the Lambert testing method with a charge-coupled device (CCD) camera are used to simulate and evaluate the concentrating radiation energy distribution on the cavity’s internal walls, and then the actual flux distribution of each turn of the helically coiled tube is obtained. A comprehensive simulation model is proposed and validated by the experimental results, where the outlet temperature deviations are within 8.0% and 2.5% for down and up-flows, respectively. The model provides a detailed analysis of heat flows at different conditions, and indicates optimization ways to improve the efficiency and reduce heat losses. The simulation results show that the outlet temperature can increase up to around 800 °C at 5 m"3/h under an average flux of 300 kW/m"2, and the thermal efficiency can be improved from around 56% to around 64% by decreasing the inner radius from 6 mm to 4 mm at the expense of increasing pressure drop of around 56 kPa
[en] Highlights: • Multispectral flame images were used to reconstruct the soot temperature and volume fraction. • The proposed multi-wavelength method and the original two-color method were compared. • The effect of signal to noise ratio (SNR) was discussed. • The best number of selected wavelengths was determined to be 6–11. - Abstract: Charge-coupled device (CCD) cameras with liquid crystal tunable filters (LCTF) were introduced to capture the multispectral flame images for obtaining the line-of-sight radiation intensities. A least square QR decomposition method was applied to solve the reconstruction matrix equation and obtain the multi-wavelength local emission distributions from which temperature and volume fraction profiles can be retrieved. Compared with the original two-color method, the use of a wide range of spectral data was proved to be capable of reducing the reconstruction error. Reconstruction results of the two methods with different signal to noise ratio (SNR) were discussed. The effect of selected wavelength number is analyzed and the best number is determined to be in the range of 6–11. The proposed multispectral imaging system was verified to be feasible for the reconstruction of temperature and soot volume fraction distributions according to the experimental measurement results.
[en] Highlights: • An additional corona current induced by high temperature was proposed. • The reason for the additional corona current was investigated. • Electron current has the most important function at 873 and 973 K. • The additional corona current is smaller in gas with strong electronegativity. - Abstract: High-temperature ESPs are proposed to improve energy efficiency and avoid damage to downstream equipment in integrated gasification combined cycle and pressurized fluidized-bed combustion. In this study, the effects of temperature and pressure on negative corona discharge characteristics were compared. Gas temperature varied from 373 K to 1073 K, and pressure varied from 30 kPa to 100 kPa to achieve the same gas density. The additional corona current ΔI_t induced by high temperature was calculated, and the additional ion current ΔI_i and electron current ΔI_e were studied. A wire-type electrode, a spiral electrode, a ribbon electrode, and four gas compositions (N_2/CO_2/SO_2/air) were investigated in the plate-type discharge configuration. Results show that corona current increases more rapidly with increasing gas temperature than that with decreasing pressure at the same gas density. The current density is 0.87 mA/m at 973 K and atmosphere pressure, which is higher than 0.45 mA/m at 30.9 kPa and room temperature. An additional temperature effect on corona discharge is proposed apart from the decrease of gas density as temperature increases. ΔI_t increases with increasing temperature because of enhanced molecule kinetic energy and ionization rate. The electron-carried current is important at temperatures above 873 K. ΔI_e/ΔI_t increases from 0 to 0.941 when temperature increases from 773 K to 973 K. Compared with the ΔI_t of wire and spiral electrodes, the ΔI_t of ribbon electrode is significantly larger because of the enhanced electron avalanche and secondary electron emission. Negative corona discharge does not occur in N_2, and corona onset voltages are in the following sequence: CO_2 > SO_2 (6000 ppm) > air, which is determined by gas molecule ionization energy. ΔI_t/I_P is smaller in gas atmosphere with strong electronegativity.
[en] The reactive adsorption of NO2 over activated carbon (AC) was investigated at 50 C. Both the NO2 adsorption and its reduction to NO were observed during the exposure of AC to NO2. Temperature programmed desorption (TPD) was then performed to evaluate the nature and thermal stability of the adsorbed species. Adsorption and desorption processes have been proposed based on the nitrogen and oxygen balance data. The micropores in AC act as a nano-reactor for the formation of -C(ONO2) complexes, which is composed by NO2 adsorption on existing -C(O) complexes and the disproportionation of adsorbed NO2. The generated -C(ONO2) complexes are decomposed to NO and NO2 in the desorption step. The remaining oxygen complexes can be desorbed as CO and CO2 to recover the adsorptive and reductive capacity of AC. (author)
[en] The significance of research on PCBs (Waste Printed Circuit Boards) not only lies in avoiding negative impacts on peoples lives and local environment but also in recycling the resource and energy which means profound influence on sustainable development with positive ecology impacts and economic rewards. During high temperature combustion of scraped PCBs, the combustible fraction is burned out and the metals are mostly retained in the bottom of furnace containing molten slag and blister copper. By conventional treatment of blister copper, the copper and noble metals can be recovered effectively. High temperature combustion of scraped PCBs is the key process during this PCB recycling and very few published literature on this topic. In present study, experiments were carried on ia a lab-scale continue-feeding drop tube combustion system. Investigation included the interaction of combustion temperature, excess air factor and high temperature zone resident time. The CO, CO2, NOx, Br etc. emission were measured continuously. Ash deposits from different locations were collected and analyzed for their texture (SEM imaging), elemental (EDS) and mineralogical (XRD) characteristics. The results show that temperature has significance on the combustion performance, Br and metal transfer and transformation. The proposed process parameters are 1200 degree Celsius, excess air factor more than 1.3, high temperature zone residence more than >0.75 s, in which CO concentration in flue gas is less than 50 ppm, more than 93 % Br is transferred in the form of inorganic matter to flue gas while Br2/ HBr is more than 7. With temperature increased, heavy metals distribution in different kinds ash changed and its texture also changed. (author)
[en] In this work, a plasma-solution system was applied to the degradation of Acid Orange 7 (AO7). The effects of initial concentration and type of feed gases (air, oxygen, nitrogen or argon) were studied. As the initial concentration increased from 100 mg/L to 160 mg/L, the discolouration rate of AO7 decreased from 99.3% to 95.9%, whereas the COD removal rate decreased from 37.9% to 22.6%. Air provided the best discolouration and COD removal rates (99.3% and 37.9%, respectively). In the presence of a zero-valent iron (ZVI) catalyst, the AO7 COD removal rate increased to 76.4%. The degradation products were analysed by a GC-MS, revealing that the degradation of the dye molecule was initiated through the cleavage of the -N=N- bond before finally being converted to organic acids. (paper)