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In comparison to borehole heat exchangers that rely on forced convection, super-long thermosyphons offer a more efficient approach to extracting shallow geothermal energy. This work conducted field tests on a super-long flexible thermosyphon (SFTS) to evaluate its heat transfer characteristics. The tests investigated the effects of cooling water temperature and the inclination angle of the condenser on the start-up characteristics and steady-state heat transfer performance. Based on the field test results, the study proposed a dynamic heat transfer modeling method for SFTSs using the equivalent thermal conductivity (ETC) model. Furthermore, a full-scale 3D CFD model for geothermal extraction via SFTS was developed, taking into account weather conditions and groundwater advection. The modeling validation showed that the simulation results aligned well with the temperature and heat transfer power variations observed in the field tests when the empirical coefficient in the ETC model was specified as 2. This work offers a semi-empirical dynamic heat transfer modeling method for geothermal thermosyphons, which can be readily incorporated into the overall simulation of a geothermal system that integrates thermosyphons. [ABSTRACT FROM AUTHOR]

A special biomass waste, Chinese herb residues (CHR) was considered to be disposed of by the (co-) pyrolysis and the steam gasification with anthracitic coal (AC) through TGA and horizontal tubular furnace reactor (HTFR) coupled with gas chromatography (GC). TGA results showed that the interaction effects between CHR and AC during co-pyrolysis were negligible at the low CHR blending ratio, but there existed an inhibiting effect at the high CHR blending ratio. Co-pyrolysis kinetics results showed that the activation energies rose with the reaction proceeding. The HTFR pyrolysis showed that, with the temperature growing, the contents of CO and H2 increased, but the content of CO2 and CH4 decreased. In the steam gasification tests, the main product in the syngas was H2, and the gasification performances were influenced by the temperature and steam flow rate. FTIR results showed that the absorption peaks of functional groups in the residues from the HTFR pyrolysis reduced with the temperature increasing. For the steam gasification of the 50CHR/50AC blend, the contents of CO and H2 increased obviously as compared to those from the gasification of CHR. The syngas yield of 50CHR/50AC increased with the gasification temperatures increasing, and the value was clearly higher than that from CHR. [ABSTRACT FROM AUTHOR]

Combustion characteristics and kinetics of camellia seed shell (CS) with additions of sludge ash (SA) and its active species of CaO, Fe2O3, and SiO2 were analyzed by thermogravimetry. The combustion paths of CS with the additives fell between "in situ combustion of carbon-containing components" and "complete volatiles release + char combustion." In the view of heat release, the additions of SA active species increased the combustion performance of CS. A higher heating rate greatly increased the combustion performance, but the addition of CaO decreased the combustion performance. The combustion kinetic parameters of CS with the 10% additions of SA, CaO, Fe2O3, and SiO2 were analyzed by combining Coats-Redfern and Malek methods. The distributions of the activation energies of the second combustion zone with certain additives were more centralized. It was found that the second combustion zones all followed f(x) = (1 − x)2 at varied heating rates, while those of the third zone were not identical, and those of the fourth zone of CS + 10%CaO followed f(x) = (1 − x)2/3. [ABSTRACT FROM AUTHOR]

Nanostructured Si exhibits superior photothermal performance and is a cost‐effective solar absorbing material for solar evaporation, photothermal catalysis, and solar power systems. Defects are effective nonradiative recombination centers and are suppressed in amorphous silicon (a‐Si) to benefit radiative recombination. In this research, a bottom‐up approach to optimize the disordered and defective structure of non‐hydrogenated a‐Si by magnetron sputtering for photothermal conversion is proposed. The 2D mesoporous structure is developed in a‐Si thin films under the growth scenario with reduced nucleation density. Local disorder and defects are analyzed based on the vibrational response of Si‐Si bonds. Accompanied by narrowed bandgap (Eg) of 1.06 eV (Eu) and elongated Urbach tail of 0.49 eV, prominent short‐range disorder and substantial amounts of dangling bonds contribute to enhanced solar absorption. Thereby, the full‐spectrum absorptance above 92% can be realized with antireflection coatings of SiO2/Si3N4. The electron–phonon behavior revealed by resonance Raman scattering provides a comparative study on phonon production. Stronger electron–phonon coupling originated from the defective structure can be achieved at larger Eu. Provided with narrowed Eg and elongated Eu, local disorder and coordinative defects benefit both broadband absorption and thermal production, which can be introduced with controlled nucleation density and arrival rates. [ABSTRACT FROM AUTHOR]

The multi-source hazardous waste co-disposal system, a recent innovation in the industry, offers an efficient approach for hazardous waste disposal. The incineration fly ash (HFA) produced by this system exhibits characteristics distinct from those of typical incineration fly ash, necessitating the use of adjusted disposal methods. This study examined the physicochemical properties, heavy metal content, heavy metal leaching concentration, and dioxin content of HFA generated by the new co-disposal system and compared them with those of conventional municipal waste incineration fly ash. This study investigated the solidification and stabilization of HFA disposal using the organic agent sodium diethyl dithiocarbamate combined with cement on a field scale. The findings revealed significant differences in the structure, composition, and dioxin content of HFA and FA; HFA contained substantially lower levels of dioxins than FA did. Concerning the heavy metal content and leaching; HFA exhibited an unusually high concentration of zinc, surpassing the permitted emission limits, making zinc content a critical consideration in HFA disposal. After stabilization and disposal, the heavy metal leaching and dioxin content of HFA can meet landfill disposal emission standards when a 1% concentration of 10% sodium diethyldithiocarbamate (DDTC) and 150% silicate cement were employed. These results offer valuable insights into the disposal of fly ash resulting from incineration of mixed hazardous waste. [ABSTRACT FROM AUTHOR]

Solar energy‐induced catalysis has been attracting intensive interests and its quantum efficiencies in plasmon‐mediated photothermal catalysis (P‐photothermal catalysis) and external heat‐coupled photocatalysis (E‐photothermal catalysis) are ultimately determined by the catalyst structure for photo‐induced energetic hot carriers. Herein, different catalysts of supported (TiO2‐P25 and Al2O3) platinum quantum dots are employed in photo, thermal, and photothermal catalytic dry reforming of methane. Integrated experimental and computational results unveil different active sites (hot zones) on the two catalysts for photo, thermal, and photothermal catalysis. The hot zones of P‐photothermal catalysis are identified to be the metal–support interface on Pt/P25 and the Pt surface on Pt/Al2O3, respectively. However, a change of the active site to the Pt surface on Pt/P25 is for the first time observed in E‐photothermal catalysis (external heating temperature of 700 °C). The hot zones contribute to the significant enhancements in photothermal catalytic reactivity against thermocatalysis. This study helps to understand the reaction mechanism of photothermal catalysis to exploit efficient catalysts for solar energy utilization and fossil fuels upgrading. [ABSTRACT FROM AUTHOR]

Van der Waals (VDW) heterojunctions in a 2D/2D contact provide the highest area for the separation and transfer of charge carriers. In this work, a top‐down strategy with a gas erosion process was employed to fabricate a 2D/2D carbon nitride VDW heterojunction in carbon nitride (g‐C3N4) with carbon‐rich carbon nitride. The created 2D semiconducting channel in the VDW structure exhibits enhanced electric field exposure and radiation absorption, which facilitates the separation of the charge carriers and their mobility. Consequently, compared with bulk g‐C3N4 and its nanosheets, the photocatalytic performance of the fabricated carbon nitride VDW heterojunction in the water splitting reaction to hydrogen is improved by 8.6 and 3.3 times, respectively, while maintaining satisfactory photo‐stability. Mechanistically, the finite element method (FEM) was employed to evaluate and clarify the contributions of the formation of VDW heterojunction to enhanced photocatalysis, in agreement quantitatively with experimental ones. This study provides a new and effective strategy for the modification and more insights to performance improvement on polymeric semiconductors in photocatalysis and energy conversion. [ABSTRACT FROM AUTHOR]

An external thermal high-temperature continuous feed moving bed tubular reactor was used for the gasification of high moisture content lignite (30.41 wt.%) under CO2 and an auto-generated steam atmosphere. The objectives of this study are to illustrate the synergistic gasification characteristics of high moisture content lignite and CO2 in the tubular reactor; CO2 and auto-generated steam (steam released from the lignite) were used as gasification agents for lignite gasification. The effects of temperature and CO2 flow rate were also investigated. Experimental results showed that when the gasification temperature increased from 800 °C to 1000 °C, the H2 yield also increased from 8.45 mol kg−1 to 17.86 mol kg−1. This may indicate that the H2O-CO2 gasification of semi-coke was enhanced with the rise in temperature. At 900 °C, the gas yield increased with the increase in CO2 flow rate, while the yield of char and liquid product showed an opposite trend. The lower heating value of the H2-rich syngas varied from 11.73 MJ m−3 to 12.77 MJ Nm−3. The experimental results proved that the high moisture content lignite in-situ CO2 gasification process is an effective methodology for the clean and efficient utilization of lignite. [ABSTRACT FROM AUTHOR]

A novel single-pass all-glass parabolic trough receiver (SPAG-PTR) that has a potential to improve the reliability of the parabolic trough collector was developed. Both heat losses with/without the ends insulation and thermal efficiency of the SPAG-PTR were numerically investigated and the bellows on the ends of the receiver were optimized. The results show that the three waves bellow SPAG-PTR with the ends insulation has a lower heat loss up to 10.5 W/m in the temperature of 540 K, which is about 15% less than the ends without insulation case. In addition, the results from the steady-state heat transfer model shows that the heat loss increases with the increase of vacuum pressure, wind velocity, and temperature. Thermal efficiency of this kind of SPAG-PTR is about 0.62 ~ 0.72 in the temperature range of 540 ~ 330 K. Furthermore, the thermal stress and heat loss of the receiver was simulated, the optimal structure with two waves of each bellow were obtained, which could decrease the heat loss about 2%~2.5% than the three waves-bellow type. All these results show that this optimized SPAG receiver is promising in the medium-low temperature solar thermal utilizations. [ABSTRACT FROM AUTHOR]

This paper concerned the thermal conversion characteristics, kinetics, thermodynamics, and incineration operation parameters and gas emissions of petrochemical wastewater (PW) and its sludge (PWS). The combustion properties of PWS were evaluated via thermogravimetric analysis, and the results showed that the combustion process of PWS had four stages, and the combustion pathway was typical "thermal degradation with char formation + char combustion". With heating rates increasing, thermal curves shifted toward lower temperatures, and the ignition, burnout, and comprehensive combustibility improved significantly. The kinetic parameters were determined by Coats–Redfern approach, and the results confirmed the existence of kinetic compensation effect. The thermodynamic parameters (ΔH, ΔG, ΔS) from PWS combustion at maximum degradation rate temperatures were estimated by the activated complex theory. To make the research practical, operation parameters and gas emissions from a petrochemical wastewater incinerator were tested. The results showed that, except HCl, and CO at 4.50 t h–1 PW injection, the gas pollutants in the flue gas after the PW incineration did not exceed the discharge limits in China. The parameters of combustion efficiency of the incineration plant at different PW injections were very high, and met the requirement in GB 18484-2001. [ABSTRACT FROM AUTHOR]

The effect of different reaction temperature, reaction pressure and the ratio of water to lignite on the H2 production by gasification of lignite in supercritical water was investigated by using lignite as raw material and intermittent high temperature and high pressure reactor. Then, the catalytic effect of Fe powder and Ni powder with different mass fractions on the production of H2 was studied separately. The experimental results showed that the increase of reaction temperature could greatly improve the yield of H2. The suitable reaction temperature was 405 °C. The effect of reaction pressure on H2 production was not obvious, but the higher reaction pressure would slightly increase the yield of CH4, the appropriate reaction pressure was chosen as 23 MPa; higher ratio of water to lignite was conducive to the production of H2, but the cost would also increase, the appropriate ratio of water to lignite was selected as 10 : 1; the addition of metal catalyst Fe powder and Ni powder could significantly improve the yield of H2. When the mass fraction was low, the catalytic effect of Ni powder was better than that of Fe powder. When the mass fraction was higher, the catalytic effect of Fe powder was better. [ABSTRACT FROM AUTHOR]

Solar energy can be transformed to storable chemical fuels through high temperature thermochemical processes driven by concentrated solar radiation. Solar thermochemical reactors (STRs) are the key equipment to these processes. An STR integrated with heat pipe technology is proposed. The core part of this reactor is a high temperature special shaped heat pipe (HTSSHP), which is composed of a flat disk-shape evaporator and multiple cylindrical condensers. A second generation HTSSHP with sodium as the working fluid was fabricated and tested in this work. The evaporating behaviors of sodium and isothermal characteristics were investigated at various operation conditions. A temperature pulsation phenomenon on heating surface was observed lasting for a short period during its startup when the heat flux beyond 47.2 kW/m2, implying the generation of film boiling. Further, the operation characteristic of HTSSHP was experimentally proven steady under various heat fluxes and inclination angles, and it showed a good ability to spread temperature at the cooling side where the thermochemical processes take place. This work will facilitate the preliminary understanding of the operation characteristics in HTSSHP. [ABSTRACT FROM AUTHOR]

In this paper, the co-pyrolysis characteristic of wet sewage sludge (60 mass%) with sawdust (40 mass%) at high temperature was investigated by Py-GC/MS and a bench-scale screw moving bed reactor. The Py-GC/MS analysis indicated that the main pyrolysis process has nearly accomplished below 700 °C, and the decomposition at high-temperature range of 800-1000 °C was the secondary cracking of macromolecule with the generation of non-condensable gas. According to the laboratory experimental results, it was found that the gas fraction increased with temperature increasing, especially H2 and CO, and the solid and liquid had an opposite tendency. Moreover, the moisture in raw material played an important role in the increase in gas fraction with temperature increasing. From the view of industrial application, a pilot-scale screw moving bed reactor with the handling capacity of 100 kg/h was designed and tested in a proper temperature range of 800-950 °C for syngas production. The exergy analysis of the pilot system was conducted, and the exergy values of gas took a large proportion in the output exergy and the exergy efficiency of gas increased from 50.58 to 57.38 mass%. The proposed intermediate pyrolysis of wet sewage sludge with additive, like sawdust, in screw moving bed reactor for syngas production would provide a promising method for wet sewage sludge treatment. [ABSTRACT FROM AUTHOR]

An in situ pyrolysis process of high moisture content lignite in an autogenerated steam agent was proposed. The aim is to utilize steam autogenerated from lignite moisture as a reactant to produce fuel gas and additional hydrogen. Thermogravimetric analysis revealed that mass loss and maximum mass loss rate increased with the rise of heating rates. The in situ pyrolysis process was performed in a screw kiln reactor to investigate the effects of moisture content and reactor temperature on product yields, gas compositions, and pyrolysis performance. The results demonstrated that inherent moisture in lignite had a significant influence on the product yield. The pyrolysis of L (raw lignite with a moisture content of 36.9 %, wet basis) at 900 °C exhibited higher dry yield of 33.67 mL g and H content of 50.3 vol% than those from the pyrolysis of the predried lignite. It was also shown that increasing reaction temperature led to a rising dry gas yield and H yield. The pyrolysis of L showed the maximum dry yield of 33.7 mL g and H content of 53.2 vol% at 1,000 °C. The LHV of fuel gas ranged from 18.45 to 14.38 MJ Nm when the reactor temperature increased from 600 to 1,000 °C. [ABSTRACT FROM AUTHOR]

For solar thermal systems, nanofluids have been proposed as working fluids due to their enhanced optical and thermal properties. However, nanoparticles may agglomerate over time, heating and thermal cycles. Even though pristine nanofluids have proven to enhance performance in low-temperature applications, it is still unclear if nanofluids can meet the reliability requirements of solar thermal applications. For this aim, the present study conducted experiments with several formulations of oil-based CuO nanofluids in terms of their maximum operational temperatures and their stabilities upon cyclic heating. In the samples tested, the maximum temperature ranged from 80 to 150 °C, and the number of heating cycles ranged from 5 to 45, with heating times between 5 to 60 min. The results showed that heating temperature, heating cycles, and heating time all exacerbated agglomeration of samples. Following these experiments, orthogonal experiments were designed to improve the preparation process and the resultant thermal-impulse stability. Thermal properties of these samples were characterized, and thermal performance in an "on-sun" linear Fresnel solar collector was measured. All tests revealed that thermal performance of a solar collecting system could be enhanced with nanofluids, but thermal stability still needs to be further improved for industrial applications. [ABSTRACT FROM AUTHOR]