Low-grade waste heat recovery for wastewater treatment using clathrate hydrate based technology

Effectively recycling low-grade waste heat is crucial for advancing decarbonization and achieving net-zero emissions, yet current methodologies are limited by inefficiencies in extracting energy from sources with low exergy. This study introduces an innovative approach leveraging hydrate formation and dissociation to utilize low-grade waste heat in purifying wastewater. By directly heating (low-grade waste heat) liquid R134a, our method induces bubble formation, thereby enhancing hydrate nucleation and growth. Our system demonstrates exceptional energy efficiencies, reaching up to 23.5%, and exhibits a high removal efficiency for wastewater with high concentrations of organic and heavy metal contaminants, including methylene blue (86.4%), Cr3+ (98.0%), Ni2+ (98.3%), Zn2+ (98.0%), and Cu2+ (97.1%). This approach not only offers a sustainable pathway for waste heat utilization but also addresses critical challenges in wastewater treatment. This technology demonstrates substantial potential in both low-grade waste heat recovery and wastewater treatment

Formation, Exploration, and Development of Natural Gas Hydrates

Currently, natural gas hydrates (NGHs) have been proposed as promising and environmentally friendly carbon-based energy sources that are beneficial for mitigating the traditional energy crises [...

Multi-scale characterization of shell thickness and effective volume fraction during gas hydrates formation: A kinetic study

Gas hydrates have gained increasing attention in energy and environmental fields and have potential applications in gas storage and transport, carbon dioxide sequestration, and flow assurance. Nevertheless, the kinetics of hydrate formation are still not well understood. In situ high-resolution X-ray computed tomography measurements were performed to monitor xenon hydrate formation on water droplets and ice spheres. For the first time, three-dimensional thickness meshes were used to quantify and visualize the kinetics of hydrate formation. The evolution of the hydrate morphology was investigated, and the time-dependent kinetic parameters were obtained, including the hydrate shell thickness and inner and outer diameters and the effective volume fraction of hydrate particles. The results indicate that the formation of gas hydrates undergoes an initial reaction-controlled stage followed by a mass-transfer-limited growth stage. For hydrate formation from a water droplet with an initial diameter of 1.66 mm, the hydrate shell thickness was approximately 30 μm and the effective volume fraction of hydrate particles was approximately 11% at 12 h after hydrate formation began. The standard deviation of the shell thickness, which indicates the surface roughness of the hydrate shell, increased with time for hydrate formation from water droplets. The results presented in this study renew our knowledge on the kinetics of hydrate formation, which is essential for their use in flow assurance and other hydrate-related technologies

Principle and Feasibility Study of Proposed Hydrate-Based Cyclopentane Purification Technology

The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes due to the fact that components in the mixture will undergo gas–liquid phase transition at the same time. We proposed a method for separating azeotropes using hydrate formation as a solid–liquid phase transition. The feasibility of hydrate-based separation is determined by analyzing the crystal structure and chemical bonds of hydrate. Taking the azeotrope cyclopentane and neohexane in petroleum as an example, cyclopentane (95%) was purified to 98.56% yield using the proposed hydrate-based cyclopentane purification technology. However, this is difficult to achieve using conventional distillation methods. The proposed method is simple in operation and yields a good separation effect. This study provides a new method for separating cyclopentane and neohexane

Study on properties of SLM-NiTi shape memory alloy under the same energy density

In recent years, selective laser melting (SLM)-NiTi had developed rapidly due to the ability to achieve the complex shape and internal features, as well as high dimensional accuracy. The choice of parameters was particularly critical to the forming and performance of SLM-NiTi. In this work, we had designed and prepared five sets of SLM-NiTi shape memory alloys with the same energy density (range of 40–90 J/mm3). The microstructure, phase transition characteristic, mechanical properties and shape memory effect of SLM-NiTi shape memory alloys were investigated through various characterization methods of X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and stress-controlled cyclic tensile tests, etc. The results showed that the surface forming quality of SLM-NiTi was not only related to the energy density, but also related to the value of P/V, which higher than 0.3 or lower than 0.1 would lead to the formation of surface pores. Interestingly, the SLM-NiTi showed ultrahigh failure strength of 735 MPa and elongation of 10.88% under room temperature tensile conditions. In addition, stress-controlled cyclic tensile tests under 400 MPa indicated that the SLM-NiTi had excellent shape memory effect of 76.1% recovery ratio and 3.95% recoverable strain after ten times loading–unloading cycles. The design of multi-parameter variables can not only optimize the surface quality, but also provide a basis for the prediction of SLM-NiTi phase transition temperature

A study of the digestive enzyme activities in scaleless carp (Gymnocypris przewalskii) on the Qinghai-Tibetan Plateau

Two experiments were conducted to study the digestive enzyme activities in scaleless carp (Gymnocypris przewalskii) on the Qinghai-Tibetan Plateau. In experiment 1, the distribution of digestive enzymes in various digestive organs of G. przewalskii (body weight: 118.24 ± 9.48 g) was studied. Results showed that digestive enzyme specific activities in intestine were significantly higher than those in hepatopancreas (P <  0.05). In intestine, the highest levels of trypsin and chymotrypsin specific activities were found in foregut and hindgut, the highest levels of lipase and amylase specific activities were observed in foregut (P <  0.05). In experiment 2, temporal changes of the digestive enzyme specific activities after feeding were investigated in G. przewalskii (body weight: 305.32 ± 28.78 g). Results showed that lipase and amylase specific activities in foregut approached maximum levels at 2 h after feeding and then decreased to the basic level at 6 h after feeding. The trypsin specific activities in foregut and hindgut reached the maximum levels at 2 h after feeding and then to the basic level at 8 h after feeding. In conclusion, as stomach-less fish, foregut of G. przewalskii contributed more to the nutrients digestion. The fish could digest nutrients (protein, fat and carbohydrate) efficiently. Thus, increasing in the amount of G. przewalskii resources could be achieved by improving nutritional state in artificial culture systems. Keywords: Gymnocypris przewalskii, Digestive enzyme, Distribution, Temporal change

Heat Transport in Clathrate Hydrates Controlled by Guest Frequency and Host–Guest Interaction

The underlying mechanism of common limited lattice thermal conductivity (κ) in energy-related host–guest crystalline compounds has been an ongoing topic in recent decades. Here, the guest-triggered intrinsic ultralow κ of the representative xenon clathrate hydrate was investigated using the time domain thermoreflectance technique and theoretical calculations. The localized guest modes were observed to hybridize with acoustic branches and severely limit the acoustic κ contribution. Besides, the strong mode coupling enables the reshaping of the overall lattice dynamics, especially for optical branches. More importantly, we identified that guest fillers prompt great phonon scattering in wide frequencies, which originates from both the guest-frequency-controlled enhancement of phase space and the host–guest-interaction-governed lattice anharmonicity. The extremely low guest frequency and strong host–guest interaction and coupling were thereby underlined to play vital but distinct roles in κ minimization. Our results unveil the dominant factors of guest reduction effects and facilitate the design of efficient thermoelectric or other thermal-related materials