Bubble size is a crucial parameter for predicting flotation performance and optimizing flotation equipment, attracting growing research interest. To predict bubble size in a turbulent vortex environment, high-speed dynamic camera experiments and Computational Fluid Dynamics (CFD) simulations were performed in both smooth tubes and 1-7 layers vortex generator (VG) tubes. The operating conditions included liquid flow rate of 0.21-0.56 m(3)/h (turbulent dissipation rate of 0.001-809.703 m(2)/s(3)), air flow rate of 0.5-1.5 L/min and sec-octanol concentration of 0-145 mg/L. Experimental characteristic parameters and Computational Fluid Dynamics (CFD) flow field parameters behind the VG layers were systematically investigated. The results indicate that increasing the number of VG layers, liquid flow rate, and sec-octanol concentration, while reducing the gas flow rate, effectively reduces bubble size. The cumulative turbulent dissipation rate epsilon(95) was utilized to characterize both the global weak turbulence and local strong turbulence induced by the VG layers. Finally, a prediction model of bubble Sauter diameter D-32 adopting cumulative turbulent dissipation rate epsilon(95) and dimensionless number including gas-water ratio A, liquid Reynolds number Re-L, surface tension ratio B, turbulent Weber number We(eta) was developed. The model's predicted values exhibited an average relative error of 12.06 % compared to experimental results. Furthermore, external validation was conducted using bubble size data from Venturi tube studies to extend the model's applicability. The validated application range of the model was 2400 < Re-L < 142102 and 0.0295

Liquid nitrogen assisted abrasive suspension jet (LN2-ASJ) is a combined machining method of cooling before cutting, which can greatly improve the efficiency of ASJ machining tungsten steel. The reduction in machining temperature changes the physical properties of the material, thereby affecting the fracture mode. This paper took YG8/YG20 tungsten steel as the research object, analyzed the failure process at low temperatures, established a mathematical model of the distribution of fracture modes. The research results showed that when cutting tungsten steel at different temperatures by LN2-ASJ, different proportions of ductile fracture area and brittle fracture area will form on the cutting section. Ductile fracture is dominated by yield failure, and brittle fracture is dominated by crack propagation caused by impact load. Ductile fracture area is always formed in the initial cutting stage, and brittle fracture area is easily formed when the kerf depth is large or the temperature is low. YG8 is more likely to be in the not completely cut through state and always occurring brittle fracture at a smaller kerf depth than YG20 under the same experimental conditions. At room temperature, the cutting section of YG20 may exhibit a pure ductile fracture state.

To further enhance the performance of power battery cooling systems, bionic wavy cooling plates were developed and investigated by numerical simulation via COMSOL Multiphysics. Effects of amplitude, angular frequency, and initial phase of wavy cooling plates on thermal-hydraulic performance were studied. Results showed that, compared to the traditional structure, the average temperature of the optimized wavy structure is decreased by 21.35 %. Moreover, Fe3O4-H2O nanofluids were used as the cooling medium, and a magnetic field was introduced. Two permanent magnets formed a magnetic field which can change its direction and intensity. Fe3O4-H2O nanofluids with a mass fraction of 0.3 % increase the comprehensive efficiency to a maximum, reaching 1.09. When the magnetic field is along the z-axis, the cooling effect is enhanced. When the direction is along the x-axis or y-axis, the cooling effect is weakened. Additionally, the magnitudes of the enhancement and reduction in the cooling effect are proportional to the intensity of magnetic field. Based on the results, the optimum magnetic field was determined, and its exergy efficiency was calculated. The data revealed that the exergy efficiency is improved. Temperature field, fluid flow, and magnetic field were constructed and simulated simultaneously, which has high reference values for engineering applications.

This study aims to investigate the evolution law of the material properties of rice husk (RH) hydrochar under quantitative process water recycling (QPWR) and to evaluate the changes in the adsorption performance of biomass hydrochar to malachite green (MG) with QPWR. In this study, 6 groups of RH samples were subjected to hydrothermal carbonization (HTC) experiments at 220°C, respectively. Except for the first HTC, which did not contain QPWR, the subsequent 5 HTC experiments all included the 100 mL process water from the previous HTC. The results demonstrated that after using QPWR, the mass yield (MY) of hydrochar increased from 68.51

Co-combustion of anthracite and hydrochar derived from hydrothermal carbonization with process water recirculation was proposed as an effective way to achieve a transition to low-carbon energy in industries that rely heavily on coal combustion. In this study, thermogravimetric analysis and model-free methods were employed to investigate the co-combustion characteristics and kinetics of anthracite and hydrochar. The results demonstrate that the carbon content of hydrochar is lower than that of anthracite, but the volatile content is higher than that of anthracite, indicating that hydrochar has better combustion performance. There is a synergistic effect in the co-combustion reaction of hydrochar and anthracite. With the increase of the hydrochar addition ratio, the ignition and burnout temperatures of anthracite decrease gradually. With the increase of temperature rise rate, the combustion reaction is enhanced and the combustion performance of anthracite is improved under the fixed mixing ratio. According to the calculation of combustion activation energy by Flynn-Wall-Ozawa and Kissenger-Akahira-Sunose methods, the apparent activation energy of the mixed samples gradually decreases with the increase of combustion conversion rate. When the addition of hydrochar is 60%, the average apparent activation energy of the mixed sample is the lowest, which is 66.51 kJ·mol-1 and 54.62 kJ·mol-1, respectively.

This work targets to study the influence of PW recirculation on hydrochars at 180, 220, and 260 degrees C. Rice husk was hydrothermal carbonized for 1 h and PW was cycled 5 times. The results showed that PW recirculation improved the mass yield and energy recovery efficiency (ERE) of hydrochars. With the increase of temperature, the mass yield of hydrochars decreased and ERE increased first and then decreased. PW recirculation promoted the increase of carbon content at 180 and 220 degrees C. When the temperature increased, the carbon content increased, while the hydrogen and oxygen content decreased. The high heating value (HHV) increased with the increase of PW recirculation and temperature. At 180 and 220 degrees C, the fixed carbon increased with the increase of PW recirculation and temperature. SEM analysis showed that PW recirculation promoted the formation of carbon microspheres. At 260 degrees C, carbon microsphere fusion occurred. After recirculation, the ignition temperature and burning temperature of hydrochars decreased. The aromatic vibration (C--C) intensified after the PW recircu-lation, indicating the occurrence of aromatization and polymerization. Overall, PW recirculation could improve the hydrothermal carbonization process to a certain extent.

To design a self-excited oscillation pulse jet (SOPJ) nozzle with excellent performance and improve the rock breaking efficiency of hard rock roadway, the nonlinear mathematical model of SOPJ is firstly established, and the relationship between jet pressure versus time and pressure gradient with different control parameters β of self-excited oscillation system is studied. In addition, the internal and external flow fields with different system pressure p , cavity length L c , cavity diameter D c and cone angle α c are studied by numerical simulation to obtain its influence on the oscillation effect of the SOPJ. The results show that the average velocity of SOPJ and continuous jet all shows a power function, but the velocity of SOPJ is lower than that of continuous jet due to the internal energy consumption. The average velocity and variance of the SOPJ are considered as the evaluation criteria for the oscillation effect, the pulse jet presents better oscillation effect with the cavity length, and the cavity diameter and the section cone angle are selected as 80 mm, 30 mm and 160°, respectively, which can provide the basis for the design of self-excited oscillation nozzle and application of pulse jet technology in hard rock roadway driving.

In the excavation of rock tunnels, conical picks face lots of problems, such as insufficient rock breaking capacity, low rock breaking efficiency and high wear rate. In order to solve these problems, a new rock breaking method is put forward to combine conical pick with abrasive water jet gridding kerfs (AWJGK). The effects of kerf depth cut by abrasive water jet (AWJ), grid geometry size and pick arrangement on rock breaking performance are studied by orthogonal experiment. Meanwhile, numerical simulations based on finite element method (FEM) model are carried out to study the performance of conical pick and obtain the optimum operating parameters The results show that the average rock breaking volume increases by 322.81

Abstract Carbon fiber reinforced plastics (CFRP) are widely used in many fields such as aerospace, nuclear reactors, automobiles, ships, and so on, due to their excellent mechanical and thermophysical properties. However, the cutting of CFRP with traditional cutting tools has many problems, such as tool wear, section delamination, large thermal stress zones, and poor surface roughness. As a precision cold cutting technology, abrasive suspension jet (ASJ) can effectively overcome these problems. In this paper, ASJ is used to cut various commonly-used CFRP, and the delamination, surface roughness, average inclination angle, and upper edge collapse of the cutting surfaces are analyzed by ultra-depth-of-field optical microscope. The effects of jet parameters upon the cutting quality of various CFRP are studied. The results demonstrated that an improved machining quality can be obtained for CFRP composites with a resin content of 33%, a carbon fiber content of 175 g/m2, and a ply direction of 0/45/90° or 0/90° by using ASJ with a standoff distance of 1 mm, a jet pressure of 20-30 MPa, and a feed speed of 30 mm/min.

Sewage sludge and red mud are industrial wastes that are potentially harmful to the environment. Their envi-ronmentally friendly treatment has been a global challenge due to their huge production and limited disposal capacity. Red mud, which contains Fe2O3 and Al2O3, can be used as an oxygen carrier. The organic matter contained in the sludge can be used as fuel. Based on the above characteristics, we propose a comprehensive waste reuse method: red mud was used as an oxygen carrier, sewage sludge was used as fuel and ultra-low concentration methane was used as an oxidizing gas. The method employs waste's heat and mass transfer properties to achieve comprehensive treatment and reuse of gas-solid phase waste. The factors influencing waste treatment efficiency as well as the mechanism of the reaction process have been thoroughly investigated. By adjusting the O/C ratio and water vapor percentage at 950celcius, the carbon conversion and CO2 selectivity could reach 94.34 %, 76.50 %, respectively. The methane conversion was close to 99.80 %, and the H2 and CO yields were up to 37.98 x 10-4 mol and 21.67 x 10-4 mol, respectively. The microscopic morphology and properties of used OC particles remained stable. The migration characteristics of heavy metal elements indicated that bed material composed of sludge and red mud has the potential to be used as a raw material for construction after sieving. This study proposes a new comprehensive method for reusing sewage sludge, red mud, and low -concentration methane that would be efficiently recycled in one process.

Abrasive suspension jet (ASJ), an accurate cold-cutting technology, can address traditional processing issues relating to carbon-fiber-reinforced plastics (CFRPs) like tool wear, interlayer delamination, large heat-affected zone, and low surface roughness. This study employed the use of an ASJ to cut CFRPs and an ultra-depth optical microscope to scan the cut surface to analyze interlayer delamination, surface roughness, kerf taper, and shoulder damage. Regression analysis was conducted to establish a prediction model for cutting quality based on surface roughness, kerf taper, and shoulder damage. Various types of CFRP cutting quality were analyzed using jet parameters. It was found that the use of ASJ to process CFRP results in the following defects: The range of surface roughness variation is from 0.112 μm to 0.144 μm. Surface roughness is most influenced by stand-off distance, followed by traverse speed and jet pressure. The range of kerf taper variation is from 4.737° to 10.1°. Kerf taper is most influenced by stand-off distance, followed by jet pressure and traverse speed. The range of shoulder damage variation is from 3.384 μm2 to 10 μm2. Shoulder damage is most influenced by jet pressure, followed by traverse speed and stand-off distance. A prediction model for cutting quality was developed based on surface roughness, kerf taper, and shoulder damage, providing data support for ASJ cutting of CFRPs. The optimal parameter combination is a stand-off distance of 1 mm, a jet pressure of 30 MPa, and a traverse speed of 30 mm/min.

3D printing technology is gradually considered to be a rapid development of a green revolution in the field of architecture. Recently, utilizing solid mine waste to replace natural sand not only greatly reduces the 3D printing costs, but also contributes to an environmental sustainability development. However, most solid waste inevitably has an impact on the inherent mechanical strength and printability of concrete materials. It is an urgent requirement to expand the alternative materials and improve the overall property of 3D concrete materials. This paper reported an innovative concrete material that replaced natural sand with fine limestone powders for 3D concrete printing applications. The experimental measurements were performed including microstructures characteristics, flowability, buildability, shrinkability, layer-interface properties, mechanical properties and interlayer bonding strength. Besides, an effective method was proposed to characterize the printable properties of concrete materials and then the reasonable limestone powder replacement ratio was determined. Based on the investigation results, appropriate substituting limestone powder (40%) can effectively improve the grading of the concrete, thus promoting its printability and buildability. Moreover, the microstructures of the 3D printing concrete materials after curing were denser and their mechanical property improved by approximately 45%. With the further increase of replacement ratio, the reduction in the flowability led to a decrease of the printability. A large number of fine particles increased the shrinkage of the curing process and some bubbles were stranded inside the materials due to its increase in the viscosity, thereby reducing the mechanical properties of the hardened material. The produced concrete for 3D printing can be treated as an eco-friendly building material that contributes to the rational development and resource utilization of solid water, thus promoting the sustainable development of construction field.

Fluidized beds are widely used in chemical reactors. Particles in fluidized bed usually circulate between reactors, and therefore, particle attrition cannot be avoided. Catalyst particle attrition in the fluidized bed significantly shortens their lifespan and raises operating costs. This study established an irregular polyhedron model of the particles to acquire their motion and force characteristics by the Euler-Lagrangian method and then employed the Ab-T10 breakage model to predict the particle's breakage process. The collision frequency and stress characteristics of the three-dimensional surface of a single particle were explored, as well as the time-dependent variations in the collision frequency and impact power between particles. The breakage and elutriation processes of a single particle were observed. The investigation found that the velocity differential between particles was the main factor that caused impact power. The particles were typically crushed one to six times before becoming completely fine powder, and their size evolution can be summarized in three stages. The complete process of particle breakage was revealed by tracing the size evolution of a single particle. This work would contribute to a deeper understanding of particle collision behavior and breakage mechanisms in fluidized beds.

Ultra-low concentration methane (UCM) from coal mines is difficult to be combusted or oxidized, and is usually emitted directly into the atmosphere, resulting in the waste of numerous clean energy and the deterioration of the greenhouse gas effect. In this study, a concept was presented as chemical looping catalytic oxidation (CLCO). The influencing factors on methane conversion and CO2 selectivity were explored on a laboratory-scale fluidized bed, and oxidation processes were investigated by theoretical calculations. The results suggest that Fe3O4 would not further reduce by CH4 in the presence of O-2 and CLCO is effective and feasible with around 95% methane conversion and near 99% CO2 selectivity of all experimental group above 850 degrees C. The oxidation of CLCO can be divided into two processes: (1) reduced oxygen carrier (OC) first adsorbs oxygen and be oxidized to achieve the transfer of lattice oxygen and (2) OC functions as a catalyst for the catalytic oxidation of methane after complete oxidation. Besides, exploratory experiments show that CLCO is also effective in treating VOCs with near 90% propene conversion rate.

Hydrothermal carbonization (HTC) is promising to convert moist lignocellulosic biomass into advanced fuels. However, it also generates a large amount of process wastewater (PW) which can't be discharged directly due to its protentional pollution to the environment. This study aims to investigate the effects of PW recycling on the hydrochar performance. Rice husk (RH) was hydrothermally carbonized under the temperature of 220 ? for 60 min and PW was recycled 5 times. In the first 3 times recycle, the yield and high heating value (HHV) of hydrochar was improved from 68.51% to 76.62%, 19.71 MJ/kg to 21.97MJ/kg, respectively, and the energetic recovery efficiency (ERE) was highly increased from 72.17% to 89.72%. Functional group analysis by titration shows that PW recycling promoted the formation of oxygen-containing functional groups. The decrease of H/C and O/C ratio shows that PW recirculation promoted dehydration and decarboxylation reactions, thus improving the thermal stability of generated hydrochars. The adsorption performance of hydrochar was evaluated by removal of malachite green (MG). The results imply that the PW recirculation could also improve adsorption capacity of hydrochar for MG. This study provides a new insight for the treatment of PW from HTC of ligno-cellulosic biomasses.

The Young’s modulus of abrasive and the material to be cut will have different influences on the cutting performance of the abrasive suspension jet (ASJ). It is found that the relative ratio of their Young’s modulus seems to show a better law on cutting performance of ASJ. In this paper, the concept of relative Young’s modulus was proposed, the influence of relative Young’s modulus on cutting performance of ASJ was explored, and the experiment of the influence of relative Young’s modulus on the kerf depth and surface roughness of ASJ was carried out. The results showed that the kerf depth increases with the increase of relative Young’s modulus. When the value is larger than 1, the density of the abrasive is the main factor affecting the kerf depth. When the value is smaller than 1, the Young’s modulus of the abrasive is the main factor affecting the kerf depth. The surface quality is divided into three degrees according to roughness. When the relative Young’s modulus is smaller than 1.5, it is a poor erosion degree. When the relative Young’s modulus is between 1.5 and 4, it is the best quality degree. When the relative Young’s modulus is larger than 4, it is an over erosion degree.

With high polymer added into suspension, the use of abrasive slurry jet (ASJ) has significant advantages in energy management. The quality and efficiency of ASJ are affected distinctly by its structure and the flow field feature, both of which depend on the rheological properties of the abrasive slurry. Therefore, this paper carries out a series of experiments to study the rheological properties of abrasive slurry with polyacrylamide (PAM) and carboxy methyl cellulose (CMC) commonly used in ASJ. The paper also explores the effect of temperature and abrasive on the apparent viscosity of the abrasive slurry. Experimental results show that PAM and CMC solutions behave as a pseudoplastic non-Newtonian fluid in the selected concentration range, whose apparent viscosity increases with the concentration. In addition, specific non-Newtonian fluid constitutive equations of the power-law model for PAM and CMC solution were obtained by nonlinear fitting calculation. The apparent viscosity decreases with the growth of temperature because it leads to the increase in spacing between molecules, making the attraction between molecules smaller and smaller. However, the abrasive has no influence on the apparent viscosity of abrasive slurry for these molecular bonds, and their mechanical entanglements are not destroyed by abrasive particles in the suspension.

Solar interfacial evaporation technology has been advanced rapidly in recent years due to its high efficiency and environment friendliness. However, the salt accumulation in the evaporation surface severely limits the stable evaporation performance of interfacial evaporator, especially for high-salinity brine. Here, we prepared a salt-rejecting solar evaporator with carbon blacks deposited on the super-hydrophilic polystyrene/lignocellulose (PS/LF) skeleton. By analyzing the factors that affect antifouling ability of evaporators, like the skeleton porosity and pore size, we obtained a continuous salt-rejecting porous structure with the porosity of about 70.4% and the pore size of 150-300 mu m. This evaporator with optimized porous structure could achieve continuous salt rejection in the high-salinity environment (15% NaCl), and exhibit a stable evaporation rate of 1.90 kg.m(-2).h(-1) and a high evaporation efficiency of 85.5% under a 1.5-sun irradiation. The good salt-rejecting property comes from the high porosity of evaporator which means numerous water channels to promote salt exchange, and large pores which means large hydraulic diameter and small tortuosity of pore channels to shorten the migration distance of salt ions back to bulk water. These two factors together promote the rapid reflux of salt ions, enabling the continuously self-cleaning of evaporator. Given the salt accumulation on the surface could contaminate the sunlight absorption, the high evaporation efficiency of the evaporator benefits from the salt rejecting. At the same time, the thermal insulation structure which was used to support the evaporator further ensures the high evaporation efficiency.

The motion of particle-laden bubbles is common in the gas-liquid-solid three-phase process like flotation. In this study, the motion of particle-laden bubbles in the stagnant deionized water was obtained by high-speed dynamic imaging. The experimental ranges of the mean bubble diameter and particle diameter were 2.76-3.95 mm and 58.2-196.35 mu m, respectively. Results show that the terminal rising velocity decreases with the increase in the diameter of covering particles and the decrease in bubble diameter. For the coverage below 50%, the terminal rising velocity decreases sharply as coverage increases; while for 50% to nearly 100%, decreases slowly. The sharp decrease is mainly because particles immobilize the bubble surface and increases the drag, which is similar to the effect of contaminants in liquid on bubble motion. When the coverage exceeding 50%, the interface mobility of particle-laden bubbles is completely retarded. The slow decrease is attributed to the decreasing net buoyancy caused by decreasing density difference between water and the particle-laden bubble. Based on the impact of particle coverage on bubble behavior, the measured data were compared with predictions by the available models of the terminal rising velocity and drag coefficient for the bare bubble in the contaminated liquid. Comparison results show that the terminal rising velocity model given by Zheng et al. (2020) and the drag coefficient model given by Wang et al. (2019) can be extended to particle-laden bubbles with a mean error of 4.8% and 0.6%, respectively. The aspect ratio of particle-laden bubbles is negatively correlated to the terminal rising velocity like that of bare bubbles. A new aspect ratio prediction model for particle-laden bubbles related to the ratio between coverage and the Eo number was introduced to facilitate direct prediction of the terminal rising velocity. The comprehensive prediction models of particle-laden bubbles behaviors given in this study are helpful for the design and optimization of equipment that contains bubble-particle aggregates.

As the only cold high-energy beam machining technology, abrasive water jet cutting has a lot of unique advantages to process a large variety of materials. The main factor restricting its development and application refers to its high processing cost. Abrasive consumption is considered as one of the main costs. Abrasive recycling is an effective way for reducing the cost. In addition, it is also beneficial to environmental protection. Abrasive suspension water jet (ASJ) is more suitable for abrasive recycling than traditional abrasive water jet (AWJ) because ASJ does not use dry abrasives. Based on the idea of strive for the recycling process simple and effective, the abrasive recycling of ASJ was studied in this work. It is found that the recycled abrasives with only big particle impurity being sieved out still have strong cutting ability. An simplified abrasive recovery scheme of ASJ cutting system has been proved to be feasible. With 30% of recharge in each cycle, the abrasive can be fully utilized and its cutting performance can remain basically the same in every reuse cycle of continuously recycling process. The abrasives between 90 and 180 μm are optimal abrasives for the cutting surface roughness, compared with the larger size abrasives; the smaller size abrasives have more negative influence on the surface roughness, which should be concerned in the recycling process.