Is engineered wood China's way to carbon neutrality?

Dewatering of Juglans mandshurica Wood Using Supercritical Carbon Dioxide

Supercritical carbon dioxide (ScCO2), known for such features as good solubility and mass transfer properties, can be an efficient drying medium for various materials, such as wood, by filling the pore space and dissolving water in the cell cavity without altering the microstructure. In this study, two specimens of Juglans mandshurica wood with a length of 30 mm and 140 mm were subjected to ScCO2 dewatering under four different pressure and temperature conditions. The results showed that the drying rate is mainly influenced by pressure and temperature, with pressure having the more significant effect. Moreover, the efficiency of dewatering was not dependent on the sample length under the same conditions. The moisture content (MC) was the same along the longitudinal direction throughout both the surfaces and core of the wood. While there were no significant differences in dewatering rate between tangential and radial directions and lengths of samples, significant MC gradient differences were noted along wood in radial and tangential directions. During ScCO2 dewatering, the dominant water transfer occurred from the middle towards the end surfaces along the wood's longitudinal directions. Furthermore, ScCO2 dewatering did not result in any shrinkage or significant drying stress, but it did cause some swelling in Juglans mandshurica wood.

A comprehensive review of lignocellulosic biomass derived materials for water/oil separation

With rapid socioeconomic development, oil is widely used in all aspects of modern society. However, the extraction, transport, and processing of oil inevitably lead to the production of large quantities of oily wastewater. Traditional oil/water separation strategies are often inefficient, costly, and cumbersome to operate. Therefore, new green, low-cost, and high-efficiency materials must be developed for oil/water separation. As widely sourced and renewable natural biocomposites, wood-based materials have become a hot field recently. This review will focus on the application of several wood-based materials in oil/water separation. The state of research on wood sponges, cotton fibers, cellulose aerogels, cellulose membranes, and some other wood-based materials for oil/water separation over the last few years and provide an outlook on their future development are summarized and investigated. It is expected to provide some direction for future research on the use of wood-based materials in oil/water separation.

Transforming municipal cotton waste into a multilayer fibre biocomposite with high strength

We analyzed the problematic textile fiber waste as potential precursor material to produce multilayer cotton fiber biocomposite. The properties of the products were better than the current dry bearing type particleboards and ordinary dry medium-density fiberboard in terms of the static bending strength (67.86 MPa), internal bonding strength (1.52 MPa) and water expansion rate (9.57%). The three-layer, four-layer and five-layer waste cotton fiber composite (WCFC) were tried in the experiment, the mechanical properties of the three-layer WCFC are insufficient, the five-layer WCFC is too thick and the four-layer WCFC had the best comprehensive performance. The cross-section morphology of the four-layer WCFC shows a dense structure with a high number of adhesives attached to the fiber. The hardness and stiffness of the four-layer cotton fiber composite enhanced by the high crystallinity of cellulose content, and several chemical bondings were presence in the composites. Minimum mass loss (30%) and thermal weight loss rate (0.70%/°C) was found for the four-layer WCFC. Overall, our findings suggested that the use of waste cotton fiber (WCF) to prepare biocomposite with desirable physical and chemical properties is feasible, and which can potentially be used as building material, furniture and automotive applications.

Combustible wood dust explosions and impacts on environments and health - A review

Wood dust is the major wastes from timber and wood-based panel processing, including wood sawing, sanding, chipping, flaking, etc., which easily causes fire and explosions. The fine wood dust had risks of inhaling the dust air, causing problems to the respiratory system of workers, as well as the explosive risk of the wood dust-air mixture. Wood dust explosions occur worldwide, which have caused massive damages to equipment, buildings, and environments, killed people, and threatened human health. This study was aimed at exploring the causes, affecting factors, mechanisms, models of wood dust explosions, and their environmental/health impacts through reviewing and analyzing the collected data in order to minimize wood dust explosion risks by improving of safety procedures in the wood processing industry. To better understood and prevent wood dust explosion cases in the future, this review collected the explosion reports and analyzed the accident information through the following aspects: 1) Summarization of published review articles regarding wood dust explosions in Introduction, 2) Scrutinization of wood dust explosion cases and design of testing device, 3) Exploration of effects of wood dust properties and surrounding conditions on explosion and their mechanisms, 4) Investigation of methods for reducing wood dust explosion risks, 5) Modeling and simulation of wood dust explosions, 6) Examination of environmental and health impacts of wood dust explosions. Finally, the findings in this review were summarized in Conclusions. By collecting dust explosion reports, reviewing literature, and analyzing the collected data, wood dust explosions can be better understood. The results of this study can be useful for the design of equipment and dust absorption systems, as well as further suggestion of safety improvement procedures to minimize or eliminate risks of wood dust-related fire and explosion in the wood processing industry and mitigate its impacts on environments and health.

Thermodynamic Modeling and Exergy Analysis of A Combined High-Temperature Proton Exchange Membrane Fuel Cell and ORC System for Automotive Applications

A combined system consisting of a high-temperature proton exchange membrane fuel cell (HT-PEMFC) and an organic Rankine cycle (ORC) is provided for automotive applications in this paper. The combined system uses HT-PEMFC stack cathode exhaust gas to preheat the inlet gas and the ORC to recover the waste heat from the stack. The model of the combined system was developed and the feasibility of the model was verified. In addition, the evaluation index of the proposed system was derived through an energy and exergy analysis. The numerical simulation results show that the HT-PEMFC stack, cathode heat exchanger, and evaporator contributed the most to the total exergy loss of the system. These components should be optimized as a focus of future research to improve system performance. The lower current density increased the ecological function and the system efficiency, but reduced the system's net out-power. A higher inlet temperature and higher hydrogen pressures of the stack and the lower oxygen pressure helped improve the system performance. Compared to the HT-PEFC system without an ORC subsystem, the output power of the combined system was increased by 12.95%.

Performance Analysis Based on Sustainability Exergy Indicators of High-Temperature Proton Exchange Membrane Fuel Cell

Based on finite-time thermodynamics, an irreversible high-temperature proton exchange membrane fuel cell (HT-PEMFC) model is developed, and the mathematical expressions of exergy efficiency, exergy destruction index (EDI), and exergy sustainability indicators (ESI) of HT-PEMFC are derived. According to HT-PEMFC model, the influences of thermodynamic irreversibility on exergy sustainability of HT-PEMFC are researched under different operating parameters that include operating temperatures, inlet pressure, and current density. The results show that the higher operating temperature and inlet pressure of HT-PEMFCs is beneficial to performance improvement. In addition, the single cell performance gradually decreases with increasing current density due to the presence of the irreversibility of HT-PEMFC.

Performance Analysis of a HT-PEMFC System with 6FPBI Membranes Doped with Cross-Linkable Polymeric Ionic Liquid

In this paper, a high-temperature proton-exchange membrane fuel cell (HT-PEMFC) system using fluorine-containing polybenzimidazole (6FPBI) composite membranes doped with cross-linkable polymer ionic liquid (cPIL) is developed and studied. The reliability of the model is verified by a comparison with the experimental data. The performance of the HT-PEMFC system using 6FPBI membranes with different levels of cPIL is analyzed. The results show that when the HT-PEMFC uses 6FPBI membranes with a cPIL content of 20 wt % (6FPBI-cPIL 20 membranes), the single cell power density is 4952.3 W·m−2. The excessive cPIL content will lead to HT-PEMFC performance degradation. The HT-PEMFC system using the 6FPBI-cPIL 20 membranes shows a higher performance, even at higher temperatures and pressures, than the systems using 6FPBI membranes. In addition, the parametric study results suggest that the HT-PEMFC system should be operated at a higher inlet temperature and hydrogen pressure to increase system output power and efficiency. The oxygen inlet pressure should be reduced to decrease the power consumption of the ancillary equipment and improve system efficiency. The proposed model can provide a prediction for the performance of HT-PEMFC systems with the application of phosphoric-acid-doped polybenzimidazole (PA-PBI) membranes.

Finite Time Thermodynamic Modeling and Performance Analysis of High-Temperature Proton Exchange Membrane Fuel Cells

In order to improve the output performance of high-temperature proton exchange membrane fuel cells (HT-PEMFC), a finite time thermodynamic (FTT) model for HT-PEMFC was established. Several finite time thermodynamic indexes including power density, thermodynamic efficiency, exergy efficiency, exergetic performance efficient (EPC), entropy production rate and ecological coefficient of performance (ECOP) were derived. The energetic performance, exergetic performance and ecological performance of the HT-PEMFC were analyzed under different parameters. Results showed that operating temperature, doping level and thickness of membrane had a significant effect on the performance of HT-PEMFC and the power density increased by 58%, 31.1% and 44.9%, respectively. When the doping level reached 8, the output performance of HT-PEMFC wa optimal. The operating pressure and relative humidity had little influence on the HT-PEMFC and the power density increased by 8.7%% and 17.6%, respectively.