Inlet Solution Research Articles

(Invited) Design of Hydrogel Material and 3D-Printed Molding for Imitating the Tactile Textured Properties of Moon Jellyfish

The current research on jellyfish robots designs a mechanical body that can assemble a waterproof and flexible drive system consisting of cables, motors and actuators to reproduce a swimming mechanism of jellyfish. On the other hand, research on jellyfish robots as visual art focuses on soft materials and demonstrates a technique to produce jellyfish swimming by the drag force received from the running water of the pump without using a special control mechanism. Most jellyfish robots that have been developed as toys imitate only their appearance, and they are being developed as commercial products with a low economic burden by using inexpensive materials such as vinyl and fishing line. The swimming of such jellyfish robots is far from the actual jellyfish. From this, it can be seen that the mechanism or material factor is largely due to the imitation of jellyfish. This study proposes a hydrogel jellyfish robot that approximates shape, water content, color and texture to a jellyfish. The body composition of moon jellyfish is gelatinous with a water content of 95% or more. The texture mimicry of jellyfish-inspired robots can be realized by using an equivalent hydrogel as a constituent material. Therefore, we develop a DMAAm gel that can artificially reproduce the tactile characteristics depending on the constituent materials. The chemical composition of the gel contains dimethylacrylamide (DMAAm) as the monomer, N, N'-Methylenebisacrylamide (MBAA) as the cross-linking agent, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) as the photopolymerization initiator, polyethylene glycol and water as the solvent. The gel of this formulation produces a white translucent color due to the solvent PEG and has a swelling ratio of about 2.5 times. Additionally, this study shows a three-dimensional modeling technology that molds this gel into the appearance of a jellyfish. Our hydrogel modeling adopts silicone resin using 3D printer. This mold consists of both an umbrella-shaped silicone and a silicone with the geometric pattern of a jellyfish stomach.The two molds are combined and the gel solution is poured from the solution inlet provided in the upper mold and cured by UV irradiation for molding. In addition, a gel film is created by sandwiching the pre-gel solution in a PET plate and UV curing. By irradiating the gel film and the gel jellyfish umbrella with UV again, we can develop a jellyfish robot with tentacles. Our jellyfish robot has a thickness accuracy on the order of a few millimeters and a hardness that can be crushed by its own weight outside water, and circulates in a liquid at a flow rate of about 40 L / min. Moreover, the tentacles have a thickness accuracy of the order of a few micrometers, and they are gel body structures with different thicknesses. We show that hydrogel jellyfish can imitate swimming by approximating the constituent material and shape to the actual moon jellyfish. Then, using our DMAAm gel and Wizard gel, we will compare and verify the visual effect caused by the difference in the texture of the blended gel from the time series change of the projected area by binary image processing. The results show that the wizard gel jellyfish does not deform under the conditions of circulating water flow in a water tank used for breeding commercial jellyfish, and it is difficult to exhibit jellyfish-like behavior. However, the millimeter-scale DMMAm gel reproduces the periodic contraction due to the elastic change, and the micrometer-order DMMAm gel has an aperiodic fluctuation behavior. Therefore, our gel jellyfish robot can simultaneously observe jellyfish contraction and tentacle fluctuation behavior. Finally, this study discusses a method for quantitatively evaluating from swimming by the gel jellyfish robot developed by soft body simulation based on Position Based Dynamics in virtual space. Figure 1

Numerical investigation of hydrodynamics and crystal growth in a forced circulation crystallizer

Industrial waste and brine discharge into nature, has had destructive effects on the environment; solution to which is using Zero Liquid Discharge (ZLD) waste water treatment. Crystallizer as a heart of Zero Liquid Discharge process undertakes creating and growing crystals from the inlet feed solution. Studying the hydrodynamics of the flow assisted by Computational Fluid Dynamics (CFD) is a powerful method of identifying microscopic phenomena in crystallizers. The present paper simulated a common industrial Forced Circulation (FC) crystallizer using the two phase Euler-Euler model, assisted by kinetic theory of granular flow. Turbulence is accounted for by Reynolds Stress Model (RSM), while inter-particle interactions are considered using the Population Balance Model (PBM). Results showed that approximately 65% of the increase in size of crystals happens in the boiling and mixing zone of the crystallizer. Applying the growth rate of 5e-9 [m/s], breakage and aggregation in the crystallizer dominates, contributing 84% of total size increase; while increasing the growth rate and reaching the value of 5e-7 [m/s] results in the growth mechanism surpassing the other mechanisms, contributing 55% of total size increase. Additionally, by 10% increase in particles concentration at the inlet, particles mean diameter at the outlet increases about 6.2%.

Conceptual design of a dynamic turbospacer for efficient low pressure membrane filtration

This study presented a conceptual design of a novel dynamic turbospacer to enhance the performance of a low pressure membrane filtration process. It consists of ladder type filaments and a series of microturbine networks within the filament cells. The rotation of the turbines leads to the formation of turbulence in the feed channel that prevents foulants accumulation. Direct numerical simulation (DNS) was conducted to characterize the fluid flow behaviors of the feed channel for the proposed turbospacer and compared with a standard symmetric non-woven feed spacer. Further, their performances were investigated for a low pressure ultrafiltration (UF) process in a lab-scale experimental setup using 2.8 mm thick 3D printed prototypes of the turbospacer and the standard spacer. Experiments for the proof of this concept were conducted at 173 mL/min and 250 mL/min feed solution inlet velocity when Reynolds number of the flow is 160 and 230 respectively. Substantial reductions in fouling effects using the turbospacer was confirmed by the in-situ Optical Coherence Tomography (OCT) scans of the fouling cake layer accumulated over the membrane during the filtration of seawater with high fouling potential. The proposed turbospacer also lowered the average pressure drop by 4 times and enhanced the specific permeate flux by more than 3 times at 173 mL/min inlet flowratre. At the same operating condition, the specific energy consumption for the turbospacer was found about 2.5 folds lower than the standard spacer.

Air-cooled absorbers for extreme-ambient absorption heat pumps

• Ammonia-water air-cooled absorber modeled and tested. • Single-pressure loop and air-handling unit used for experiments. • Baseline conditions with 51.7 °C ambient air. • Good agreement between experiments and models. An investigation of air-coupled absorbers for an ammonia-water absorption system operating in extreme ambient conditions was conducted. Heat and mass transfer modeling was used to predict the performance of round-tube corrugated-fin absorbers for a 2.64-kW absorption chiller operated at high ambient temperatures. A single-pressure ammonia-water test facility was used in conjunction with a temperature- and humidity-controlled air-handling unit to evaluate the absorbers at design and off-design conditions. Absorber performance was studied over a range of air temperatures and flow rates, inlet solution temperatures, and concentrated solution flow rates and concentrations. At design conditions, round-tube corrugated-fin absorbers of 394 and 551 fins per meter (FPM) demonstrated comparable performance, and measured heat transfer rates were predicted well. Results from this investigation can be used to guide the development of air-coupled heat and mass exchangers for compact absorption heat pumps.

Comparative Study of the Heat and Mass Transfer Characteristics between Counter-Flow and Cross-Flow Heat Source Towers

The heat source tower (HST), as a cleaner energy production, which can absorb the low-grade energy from ambient air to drive the heat pump unit without emissions has attracted more and more interest. In addition, HST has excellent economic applicability by using cooling tower equipment, which was idle in winter. However, there are few studies on comparative analysis of thermal behavior between counter-flow and cross-flow HST. A mathematical model suitable for both HST types was developed to identify the performance discrepancies between them. Then a parametric study was carried out in order to investigate the impact of solution and air as well as packing material properties on energy transfer of HSTs. Finally, the characteristics of solution dilution and dehumidification were investigated. As the inlet solution temperature increases, increases first, then decreases gradually, but a transition point occurs in the solution at −5 °C. Moreover, the transition section of moisture transfer direction for counter-flow HST was located in the 0.78 m and 0.26–1.56 m of packing material height, under the condition that the air relative humidity was 50%. In summary, this work intuitively indicates the thermal performance difference between counter-flow and cross-flow HST, also could assist the selection of proper operating conditions in HSTs.

The efficacy of sono-electro-Fenton process for removal of Cefixime antibiotic from aqueous solutions by response surface methodology (RSM) and evaluation of toxicity of effluent by microorganisms

The increasing use of antibiotics by humans and their persistence in the environment leads to the development of drug resistance, which is nowadays considered as an environmental problem. The aim of this study was to determine the efficacy of sono-electro-Fenton process for removal of Cefixime antibiotic from aqueous solutions by Response Surface Methodology (RSM) and to evaluate the toxicity of effluent by microorganisms. In the present study, the degradation of synthetic wastewater containing Cefixime was investigated in a reactor (with a useful volume of 1 L) located in the chamber of the ultrasonic device. The effects of pH, hydrogen peroxide concentration, voltage, initial antibiotic concentration, and electrolysis time were investigated using the Box-Behnken model, and the optimal conditions for elimination were obtained by analyzing the variance. The performance of the electro-Fenton and ultrasonic process was evaluated separately and in combination under optimal conditions. Toxicity of inlet and outlet was tested by Escherichia coli and Staphylococcus aureus, and growth inhibition percentage was calculated. The intermediates were determined by LC-MS with the lowest molecular mass. The results showed that the sono-electro-Fenton process under optimum conditions, including pH of 3.07, hydrogen peroxide concentration of 0.85 mL/L, voltage 15 V, initial antibiotic concentration 10.4 mg/L and electrolysis time of 81.5 min has a percentage of removal of 97.5%. Under optimum conditions, the percentage of removal by electro-Fenton and ultrasonic separately were 81.7% and 9%, respectively, and in the hybrid process of sono-electro-Fenton, the percentage of removal increased to 97.5%. The results also showed that the biological toxicity of the outlet effluent from the sono-electro-Fenton process, compared to the inlet solution, was significantly reduced. So, we conclude that the Sono-electro-Fenton process has a significant effect on the removal of Cefixime from aqueous solutions and can also significantly reduce the biological toxicity of the effluent.

Numerical study on the moisture transfer characteristics of membrane-based liquid desiccant dehumidifiers: Resistance distribution and concentration polarization

Membrane-based liquid desiccant dehumidifiers have received increasing attentions due to their main advantage of preventing liquid carryover in air handling process, but the low dehumidification efficiency limits their further applications. The underlying mechanism of their moisture transfer deterioration is not entirely clear yet, and further efforts are needed to effectively identify and reduce the mass transfer resistances in the dehumidification process. In this work, considering impressionable transmembrane permeation flux, the resistance distribution of moisture transfer in the quasi-counter flow flat-plate membrane-based liquid desiccant dehumidifier is studied by a three-dimensional conjugate heat and mass transfer model. The velocity, temperature and concentration fields in dehumidifying process are analyzed in baseline condition, especially on the membrane surfaces. Analogy to a thermal circuit, the normalized moisture transfer resistances through gaseous, solid and liquid phases are defined to describe their relative importance. Causes of these normalized resistances in variable conditions are analyzed in terms of concentration polarization and boundary layer theory. Furthermore, the resistance variation is compared with the latent effectiveness, to reveal their inherent relation. The results suggest that moisture transfer resistances are mostly originated from the membrane and air side, and thus dehumidifying enhancement is more likely to emerge from the air-side concentration polarization alleviation in synergy with the appropriate improvement of membrane porosity. Among all operating parameters, the air inlet temperature and solution flow rate have relatively limited effect on the total resistance, while increasing solution concentration, followed by decreasing solution temperature, can significantly reduce the moisture transfer resistances at a nondecreasing latent effectiveness. In addition, the latent effectiveness shows a similar variation tendency to that of the air-side moisture transfer resistance, but it cannot reflect the total resistance variation. These results can help researchers and designers make decisions on where and how to improve the performance of membrane-based liquid desiccant dehumidifiers.

Effectiveness of ozone pretreatment on bioconversion of oily bilge water into biopolymer

Oily bilge water (OBW) is complex wastewater generated from ship operation. In the present study, the application of ozonation pretreatment before the sequential batch reactor (SBR) for removing organics and polyhydroxyalkanoates (PHA) production from complex OBW were investigated. OBW was subjected to lab-scale ozone pretreatment under the various experimental conditions such as a specific reaction time (0 min–120 min), inlet ozone dose (0.5 g/L–2.5 g/L) and solution pH (4–8). Pretreatment of OBW by ozone improved biodegradability index (BDI) from 0.36 to 0.52. The GC–MS analysis revealed that the BDI enhancement was due to the formation of water-soluble carboxylic groups after 75 min of ozonation operated at solution pH 6 and 2 g/ L of O3 dose. The CODs removal efficiency was 68 % and 92 % for SBR and ozonized SBR respectively. Also, the biopolymer production rate was increased by 4.5 folds for ozonized SBR as the bioconversion of carboxylic compounds by using a mixed bacterial consortium (MBC) was stress-free. The functional groups and thermal property of the produced PHA were tested by various analytical techniques. These results confirmed that the bioconversion of ozonized OBW into valuable biological polyesters using MBC.

Metformin Removal from Water Using Fixed-bed Column of Silica-Alumina Composite

In the last decade, traces of pharmaceutical and personal care products (PPCPs) in the nano and microgram per litre range have been reported in the water cycle; this includes surface water, wastewater, groundwater, and to a lesser extent drinking-water. Their presence in water, even at low concentrations, has raised concerns among drinking-water regulators, governments and water suppliers, regarding the potential risks to human health from exposure to traces of pharmaceuticals via drinking-water. Metformin (MF) and its transformative product, guanyl-urea, are expected to be present in aquatic environments, due to their global consumption rate. Not surprisingly, guanylurea has also been detected in surface water, groundwater, and drinking water. The toxicological studies showed that availability of MF might cause ecotoxicological effects, which suggests that MF is a potential endocrine disruptor and thus further emphasising the threat this drug could pose to our environment. Thus, many treatment methods have been suggested by many investigators to reduce the high levels of MF. Adsorption with some novel materials, for instance, showed great potential in removing MF from water in the batch processes, while very limited investigation has been done in continuous mode. Therefore, an effective adsorption process should be well implemented with use of efficient adsorbent for MF removal from water. Herein, MF adsorptive removal from water by amorphous silica-alumina (SA) composite was carried out in a fixed-bed column under the influence of various dynamic conditions (i.e., inlet solution pH, initial concentration of MF, initial flow rate, and bed-height). Initially, batch adsorption experiments were conducted to determine the adsorption kinetic parameters. Then, the obtained kinetic parameters were used to investigate the continuous adsorption inside the fixed-bed column. In the column experiments, high adsorption of MF was obtained at low flow rate, high bed height, low influent concentration, and high pH. Breakthrough behavior under the influence of various dynamic parameters was also investigated using the advection-axial dispersion model, incorporating surface and intra-particle diffusion theory to identify the key process parameters controlling the rate of adsorption. Furthermore, the unused bed length (HUNU) approach was also employed to determine the best utilization conditions for the column by correlating the unused bed (inactive zone) fraction (FH) from the column with axial Peclet number (Pex).

Study on the heat and mass transfer characteristics of spray separation tower at low temperature and normal pressure

A one-dimensional mathematical model for the drying process of calcium chloride solution in a co-current spray separation tower based on the four-stage drying model of single droplet is proposed. A corresponding pilot system is set up and the reliability of the model is validated by a series of experiments. The maximum relative errors of the mathematical model are within 10% and 15% while the average relative errors are 4.0% and 7.0% when predicting the outlet air temperature and humidity, respectively. The effects of inlet parameters on the heat and mass transfer characteristics of the spray separation tower at low temperature and normal pressure are evaluated as well. Simulation results show that air mass flow rate, inlet solution concentration and solution mass flow rate have greater effect on the thermal efficiency than other inlet parameters while the inlet solution concentration plays a pivotal role on the drying strength. The most significant factor on the volumetric heat transfer coefficient is the inlet solution concentration. Besides, the back propagation (BP) neural network model of the spray separation tower is also established on the basis of experimental data, and the comparison between the one-dimensional mathematical model and the BP neural network model is conducted in detail.

Fast Fabrication of Localized Porous Alumina Patterns with 3D Printed Microdroplet Cell

A multicapillary 3D printed solution flow type microdroplet cell (Sf-MDC) is proposed for high-throughput local anodizing. The optimally designed 3D printed Sf-MDC offers low resin consumption, shorter fabrication time and increased throughput. The Sf-MDC consists of three solution inlets separately connected with inner capillaries, a common solution outlet for removing the excess solution from outer capillaries and a two-electrode system with a common Pt counter electrode. Three major acidic electrolytes, i.e. 0.3 M H2SO4, 0.22 M (COOH)2 and 0.1 M H3PO4 are used for simultaneous local anodizing. The simultaneously anodized lines exhibit uniform length, width and porous structure for each anodizing solution. Relationship between anodized line width, diameter of capillaries, inlet flow rate and vacuum pressure is studied. By varying the concentration of (COOH)2 electrolyte inside each inner capillary, three porous alumina membranes with different oxide thicknesses and pore diameters are simultaneously fabricated. The microcell showed good reproducibility and can be applied for fast fabrication of porous alumina filters and electronic components.

Efficiency comparison and performance analysis of internally-cooled liquid desiccant dehumidifiers using LiCl and CaCl2 aqueous solutions

Internally-cooled dehumidifiers are efficient liquid desiccant dehumidifiers, whose performance is mainly determined by the device structure and operating conditions. Based on energy and mass conservation in the air, solution, and cooling water in the device, mathematical models are built and their theoretical performance is simulated and analyzed in this paper. A novel measure of dehumidification efficiency is introduced to evaluate the performance of internally-cooled dehumidifiers, in which the equilibrium humidity ratio of the inlet solution is calculated according to the minimum temperature in the inlet solution and the cooling water. Numerical simulations show that a counter flow between air and solution is always the most efficient, followed by cross flow, and parallel flow is the least efficient. Cooling water with the same flow direction as the solution performs better than that with a counter flow, with approximately a 5% improvement in efficiency. Compared with CaCl2, the dehumidification efficiency of a LiCl solution is greater by 60%, while its exergy efficiency is less by 16%. Dehumidification efficiency can be improved with the number of air-solution heat transfer units (NTUa-s) increasing, and reduced with the air mass flow rate raised. With NTUa-s increasing, exergy efficiency can be improved, and an increase in mass flow rate of cooling water results in a decrease of efficiency. Higher solution concentration and lower inlet temperature of solution and air can achieve both higher dehumidification efficiency and exergy efficiency.

Experimental investigation on heat and mass transfer in a vertical glass bubble absorber with R124-NMP pair

Abstract An experimental study on heat and mass transfer characteristics of R124-NMP in a vertical glass bubble absorber has been conducted under operating conditions of air-cooled absorption system. The key operation parameters, solution volumetric flow rate, temperature and mass fraction at the absorption tube entrance, vapor volumetric flow rate, orifice diameter and absorption pressure, are converted into dimensionless numbers. A sensitive study of the key operation parameters on overall heat and mass transfer coefficients and two-phase mass transfer coefficient has been performed. The overall heat and mass transfer coefficients and two-phase mass transfer coefficient increase as Rev and absorption pressure increase and decrease as orifice diameter increases. The overall heat transfer coefficient increases as Res increases and decreases as solution temperature and mass fraction increase. This trend is reversed for overall mass transfer coefficient. The increase of solution inlet mass fraction can improve the two-phase mass transfer coefficient while the solution inlet temperature affects the two-phase mass transfer coefficient slightly. On the basis of the experimental data, dimensionless empirical correlations for overall and two-phase Sherwood numbers are proposed with error bands of ±10% to calculate the volumetric mass transfer coefficient for R124-NMP bubble absorption process in a vertical bubble absorber.

Performance optimization of the dehumidifier with parallel-plate membrane modules

A numerical model of a dehumidifier with parallel-plate membranes is established and validated, and the orthogonal optimization method is adopted to investigate the dehumidifier performance. The impact order of the main operating parameters, including dimensionless factors (mass flow rate ratio m∗ and number of heat transfer units NTU), air conditions (inlet air temperature and relative humidity) and solution conditions (inlet solution temperature and concentration), on the system effectiveness (i.e. sensible and latent effectiveness) is identified. The NTU is the most important parameter affecting the system effectiveness, followed by mass flow rate ratio m∗. Although the sensible and latent effectiveness increase with the NTU and m∗, no significant improvement can be achieved when their values are higher than 2 and 4 respectively. Increasing inlet solution concentration can enhance latent effectiveness without reducing sensible effectiveness. Inlet air temperature and relative humidity have weak influences on the system performance, but increasing the temperature difference between the inlet solution and air can make the outlet air achieve heat transfer balance within a shorter distance inside the dehumidifier.

Experimental investigation on flow patterns and absorption height in a vertical bubble absorber with R124-NMP pair and comparison for R124-DMAC pair

A visual experimental research was conducted to investigate the flow patterns and absorption height (AH) in a vertical bubble absorption tube employing R124-NMP as working fluid. The effects of various operation parameters, solution inlet mass concentration, temperature and volumetric flow rate, vapor volumetric flow rate, absorption pressure and orifice diameter, on the flow patterns and AH were examined. The key operation parameters were all converted into dimensionless numbers and the influences of dimensionless operation parameters on dimensionless absorption height (DAH) were studied. The results showed that the AH increases with increasing solution inlet mass concentration and temperature, vapor volumetric flow rate and orifice diameter and decreases with increasing solution volumetric flow rate and absorption pressure. DAH exhibits nearly linear change along with dimensionless operation parameters. Comparisons between the flow patterns and AH of R124-NMP and R124-DMAC were performed. The compared results illustrated that employing R124-NMP as working fluid can shrink the vertical bubble absorber size. Finally, the experimental correlations of AH and DAH were developed with ±20% and ±15% error bands, respectively. The correlation of DAH maybe used to predict absorption height in the design of bubble absorber employing refrigerant-organic absorbent as working fluid.

Experimental evaluation of a membrane-based microchannel desorber operating at low desorption temperatures

A membrane-based micro-desorber prototype fed by low temperature heat is experimentally evaluated. Working fluid is H2O–LiBr solution and it flows along 50 rectangular microchannels of 3 mm width, 0.15 mm height and 58 mm length, manufactured on a stainless steel plate. The effective volume of the micro-desorber is 104.6 cm3. Hot water flows countercurrently through identical channels manufactured on the opposite side of the plate. A microporous polytetraphluoroethylene (PTFE) membrane of pore diameter 0.45 µm is used to separate the solution from the vapour. Two operating parameters are modified, comprising the inlet solution mass flow rate, between 0.5 and 1.7 kg/h, and the hot water inlet temperature, using 62 and 66 °C. The solution is heated in the first part of the channels until desorption starts. The solution concentration and temperature measured at the inlet and outlet allowed the evaluation of the mass transfer performance of the micro-desorber. Results obtained for the desorption ratio, desorption rate, hot water and solution heat transfer coefficients and cooling power are provided.

Steady-state performance evaluation and energy assessment of a complete membrane-based liquid desiccant dehumidification system

A complete membrane-based liquid desiccant dehumidification system is investigated under the steady operating condition, which mainly consists of a dehumidifier, a regenerator, three heat exchangers, a cold and a hot water supply units. A finite difference mathematical model is developed for the complete system to investigate the system dehumidification performance and energy requirement, and validated by experimental data. The dehumidification performance is evaluated by the system sensible and latent effectiveness and moisture flux rate, while its energy performance is assessed by the total cooling capacity and coefficient of performance. It is found that the number of heat transfer units in the dehumidifier side and solution to air mass flow rate ratio have the most considerable impact on the system performance, while the number of heat transfer units in the regenerator side and solution inlet concentration in the dehumidifier have comparatively weak influences. The system sensible and latent effectiveness can be improved by increasing the dehumidifier side number of heat transfer units before reaching its critical value of 6. However, the amount of moisture being absorbed, total cooling capacity and coefficient of performance decrease with the dehumidifier side number of heat transfer units at the low air flow rate. The critical value of solution to air mass flow rate ratio varies with number of heat transfer units, and it is preferable to keep the flow rate ratio at or below its critical value as further increasing solution flow rate would reduce the system coefficient of performance.

Performance investigation on the liquid desiccant regeneration using rotating packed bed

The regenerator which is applied to recover the dilute solution plays a significant role in the liquid desiccant system. Rotating packed bed (RPB) has been demonstrated to heat and mass transfer process intensification, and successfully applied in the field of gas absorption. To validate the application of rotating packed bed in the regeneration of the dilute solution, a counter-flow RPB regenerator was studied in this work. Three groups of performance indices including moisture removal rate, heat and mass transfer coefficients, and regeneration effectiveness, were employed to evaluate the performance of the regenerator. The effects of the high gravity factor, air flux, solution flux, air inlet parameters, and solution inlet parameters on the performance indices were investigated and compared with the conventional regenerator. Correlations of heat and mass transfer coefficients were presented on the basis of the experimental data. The mass transfer coefficients of RPB regenerator locate within 12.5–35.6 kg m−3 s−1 which are higher than those in the conventional regenerators. According to the comparison, the RPB regenerator has superiority in the mass transfer performances.

A new thiosalt depuration bioprocess for water- recycling in metallic sulphide mineral processing

Economic and environmental imperatives force the metallic sulphide processing industry to re-use liquors that normally contain thiosalts; this processing entails difficulties in operation control and losses in metal-extraction performance. Bio-oxidation presents a promising option for thiosalt removal. Hitherto, this method has been tested to treat synthetic liquors containing only one thiosalt, either tetrathionate or thiosulphate, usually at low concentration (<1 g/L). In this article, bio-oxidation is studied of synthetic and real liquors containing mixtures of these thiosalts at concentrations close to 4.5 g/L. Coexistence of thiosulphate and tetrathionate in an acidic medium leads to strong and irreversible inhibition phenomena (performance losses close to 80%). In order to solve this problem, a previous treatment is proposed consisting of the 8-hour aeration of inlet solution after adding up to 20 mg/L and pH 1.5 of Cu2+ and sulphuric acid, respectively, resulting in the complete removal of thiosulphate and sulphite. Pre-treated real liquors were fed into a 1 L discontinuous stirred tank bioreactor and a 1 L continuous flooded packed-bed bioreactor, which were successfully started up and operated, thereby obtaining bio-oxidation rates close to the highest rates found in the literature with synthetic liquors.

Simulation and experimental studies on the liquid desiccant dehumidification of horizontal tubes having a staggered arrangement

Field synergy theory has been widely used in the field of single-phase heat transfer, which is of importance to heat transfer optimization. However, few scholars apply the field synergy theory to the field of mass transfer, especially to the field of liquid desiccant dehumidification. The innovation of this paper is the application of the technology of the falling-film evaporation of a horizontal tube and the theory of field synergy to liquid desiccant dehumidification. The objective of this paper is to study the falling film liquid dehumidifier and get the dehumidification performance and mass transfer synergy angle under the influence of multiple factors. The heat and mass transfer characteristics of the system are studied in simulation and experimentally. The mass transfer synergy angle comprising the velocity vector and concentration gradient vector is taken as a standard to measure the mass transfer synergy, while the moisture content of the outlet air is taken as a standard to measure the dehumidification performance of the system. Fluent simulation software is used to simulate the dehumidification process of the equipment with staggered horizontal pipes, establish physical and mathematical models and analyze the velocity field and moisture content field in the model. The moisture content of the outlet air and the distribution of the mass transfer angle are obtained. The mass transfer angle of the system is about 96°. The effects of various factors on the air moisture content at the outlet of the equipment are studied experimentally. Results show that the dehumidification amount decreases with an increase in air velocity. Increases in the solution concentration, air inlet moisture content and solution flow rate increase the amount of dehumidification, following the same trends as in simulation. A comparison of the simulation results with the experimental results shows the relative error is within 20%. This study shows that it is feasible to combine the field synergy theory with liquid desiccant dehumidification. On the basis of this study, researchers in related fields can further study the effect of mass transfer synergy angle on mass transfer synergy in liquid desiccant dehumidification system.