North China Municipal Engineering Design & Research Institute

In China, with the rapid development of renewable energy sources such as wind and solar power, green electricity-based hydrogen production technology has become a key solution to address the challenges of low efficiency and high volatility in renewable energy utilization. The alkaline liquid heat exchanger is a critical component of the thermal management system in alkaline water electrolysis. A well-designed heat exchanger not only enhances the efficiency of the hydrogen production system but also significantly reduces equipment and operating costs. Numerous factors influence the performance of heat exchangers. To optimize their design more effectively, this study focuses on four primary structural parameters: heat exchange tube configuration, tube spacing, tube layout, and baffle spacing. By investigating the structure of heat exchangers, this research aims to provide valuable guidance for their design in green electricity-based hydrogen production systems and to improve the efficiency of such systems effectively.

Sulfate-containing wastewater treatment is important for decreasing industrial pollution. This study investigated the operation of upflow anaerobic sludge blanket (UASB) in removing sulfate at high loading rates under light and dark environments, respectively. Then, sulfate reducing bacteria (SRB) and photosynthetic bacteria (PSB) were isolated from reactors and cultivated at different oxygen and illumination conditions to explore their sulfate removal performance. In UASB systems, photoreactors maintained approximately 60% sulfate removal at a COD concentration of 10,000 mg/L, whereas non-photoreactors exhibited a near-complete loss of sulfate removal under the same conditions due to sulfide toxicity. SRB survived in both aerobic and anaerobic environments; however, exposure to light slightly inhibited sulfate removal with a reduction of 7.72%. Besides, PSB exhibited 20% faster growth under anaerobic conditions. Natural light further enhanced sulfide removal efficiency, achieving 50% removal at 300 mg/L sulfide, compared to less than 40% under compact fluorescent light. Batch inoculation of domesticated SRB and PSB into photoreactors resulted in sulfate removal efficiencies of 85.14% and 91.10%, respectively, which is significantly higher than the corresponding 72.55% and 63.48% achieved in non-photoreactors. This study not only provided a clean pathway to sulfate removal but also helped fully understand the properties of sulfate removal via SRB and PSB, providing a precondition for their practical application.

Based on theoretical research on multifactor-based surrounding rock pressure calculation for tunnels, this paper considered more comprehensive and reasonable factors in the analysis of co-bearing mechanics, and the range of the resulting surrounding rock bearing results was more in line with observations made during engineering practice. The proposed multifactor surrounding rock pressure calculation theory was analyzed to analyze the bearing mechanism of three different convergent forms in the safe state under the joint bearing of the composite lining support and surrounding rock, and it was clarified that the joint bearing of the surrounding rock and support is the key factor to ensure construction safety. Only in the state of true convergence can the first lining and the second lining played an effective bearing role, which was the key factor to ensure the safety of the project. With data monitoring via a layout of representative pile position sensors of an experimental section in an engineering example, the displacement deformation and surrounding rock pressure of the tunnel section vault, arch waist, arch foot and other parts were measured, and the stability analysis and deformation analysis of the relevant results and temporal curves were carried out. It was concluded that the surrounding rock stress gradually stabilized during the monitoring period and that the settlement deformation of the surrounding rock was obvious and regular. Using numerical simulation, the pressure of the surrounding rock and the overall displacement of the tunnel under different working conditions of the tunnel excavation section were numerically simulated and analyzed, and it was concluded that the numerical simulation results were consistent with the measured values of the test section and that the deformation control, stability and safety of the supporting components on the surrounding rock were obvious.