Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202507043
Municipal sludge with high moisture content and strong viscosity tends to form a dense crust during conventional rotary drum drying, reducing heat and mass transfer efficiency and prolonging drying time. This study proposes a thermal steel ball-enhanced rotary drum drying method that introduces high heat capacity, high thermal conductivity steel balls to achieve synergistic contact heat conduction and mechanical disturbance. An evaluation system incorporating dimensionless moisture ratio (MR), drying rate (DR), characteristic drying time (tdry), effective moisture diffusivity (Deff), and volumetric evaporation intensity (U) was established. Results show that compared with conventional drying, steel ball-enhanced drying increased maximum drying rate (DRmax) by 22.59%–41.19%, U by 38.06%–93.43%, and shortened tdry by 27.56%–48.30%, with more pronounced advantages under high load conditions. Deff was significantly higher throughout the process, with maximum increase up to 48.30%, indicating that ball rolling and collision effectively disrupt the crust and promote moisture migration. Mechanistic analysis reveals that the performance enhancement arises from the dual action of thermal-mechanical coupling and mechanical disturbance, which enhances local heat flux via contact conduction and dynamically renews the drying interface, shortening diffusion paths. This study elucidates the heat and mass transfer mechanisms of thermal steel ball-enhanced sludge drying, providing theoretical support and technical reference for efficient sludge volume reduction and dryer design optimization.
Journal of Environmental Engineering Technology•2026•DOI: 10.13205/j.hjgc.202607004
Pelletizing technology is widely applied in biomass and coal fuel processing, offering advantages in transport, storage, and energy density. Coal gasification fine slag (CGFS), a carbon-rich coal-based solid waste, holds potential as a fuel. This study prepared centimeter-scale composite pellets by blending CGFS with various biomass types under 6 MPa at room temperature for 2 minutes. Combustion and emission characteristics were investigated using a self-developed flat-flame macro-thermogravimetric reactor simulating high heating rate conditions. Results showed that biomass type significantly influenced combustion due to chemical composition differences. Introducing biomass altered fuel particle composition, enhancing combustion rates of single-component fuels by 3–5 times during volatile combustion. Co-combustion reduced NOx and CO emissions by over 50% compared to pure CGFS. Higher biomass ratios accelerated volatile release and shortened burnout time but increased NO emissions due to higher volatile nitrogen content. Conversely, CO emissions decreased due to improved char combustion conditions. These findings provide critical experimental support for optimizing clean and efficient solid fuel production from CGFS and biomass.
Journal of Environmental Engineering Technology•2026•DOI: 10.13205/j.hjgc.202608009
To investigate the flow and heat transfer characteristics of natural draft direct air-cooling towers (NDC) for large coal-fired power generating units, a three-dimensional CFD numerical model covering major plant buildings, air-cooled radiators, and ambient wind fields was established based on the NDC systems of a 2×660 MW unit of a power plant. The influences of meteorological factors, including ambient wind speed, ambient temperature, and ambient wind direction, as well as regulation measures such as rolling shutters, louvers, and bypass windows on the heat dissipation performance of NDC towers were systematically analyzed. The results demonstrate that ambient wind speed acts as the dominant factor governing the performance of the NDC system. As wind speed rose, the uneven distribution of air intake volume and heat dissipation among each cooling delta increased remarkably, which elevated the unit back pressure, and the upstream tower suffered more severe impacts than the downstream one. Ambient temperature exerted a slight effect on circumferential flow distribution, yet substantially changed the overall back pressure of the system. In terms of regulation strategies, closing rolling shutters in the windward zone and reducing the opening of partial louvers can improve air flow redistribution to a certain extent, but will reduce the total air flow rate and total heat dissipation of the entire tower. By contrast, bottom bypass windows can effectively optimize the air intake on the leeward side and boost heat dissipation under high-wind operating conditions, whereas top bypass windows deliver only limited improvement effects. This research can provide fundamental data and technical references for the optimal design, operational regulation, and energy-saving retrofitting of large NDC units.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4216-7
Flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells are promising for lightweight and mechanically pliable photovoltaics, yet their performance is limited by severe non-radiative recombination and residual stress. Here, we report a sealed constant temperature (SCT) annealing strategy that simultaneously optimizes the CZTSSe/CdS heterojunction and alleviates stress. Under uniform mild thermal conditions (85°C, 5 h), SCT annealing promotes gradient diffusion of Cd2+ into the absorber, partially substituting Zn2+, which optimizes band alignment, passivates interface defects, and suppresses near-interface CuZn defects. This reduces open-circuit voltage loss and improves fill factor. The flexible device achieves a power conversion efficiency of 13.07%, a significant improvement over the reference (12.1%). The SCT strategy also enhances mechanical flexibility by reducing residual stress. Our findings provide a controllable route to advance both efficiency and flexibility of flexible CZTSSe solar cells.