Lowest Specific Energy Consumption Research Articles

BDD-persulfate-based anodic oxidation process for progestin degradation: Optimization of conditions, eco-compatibility tests, and cost evaluation

Considering the increasing presence of the hormones levonorgestrel (LNG) and gestodene (GES) in wastewater, the limited effectiveness of conventional treatment methods, and the demand for advanced complementary processes, our study aimed to optimize an anodic oxidation treatment with a focus on low specific energy consumption (SEC) and costs. An electrochemical system coupled to a boron-doped diamond anode (BDD) was continuously used to treat synthetic and real pharmaceutical wastewater from contraceptive production. The central design composite and response surface methodology were the tools employed for optimization. The lowest SEC was obtained as a response to the main process variables: current density, initial pH, and the concentration of the support electrolyte ([Na2S2O8]). The optimal condition ([Na2S2O8]0 = 0.07 mol L−1; [LNG]0,RPW = 1.02±0.05 mg L−1 and [GES]0,RPW = 1.05±0.05 mg L−1; j = 37.5 mA cm−2; pH = 6.75) was established considering an SEC ≤ 3.6 ± 0.8 kWh g−1 and progestins removal ≥70%, which was the experimental condition used to evaluate acute toxicity to Daphnia similis and the effect on estrogenic activity removal using the YES assay. Notably, our study evaluated, for the first time, a comparative investigation that highlights the substantial effect of support electrolytes over the eco-compatibility assessment of the anodic oxidation process investigated. The adaptability of the operation indicates the prospective suitability for the implementation of the process in wastewater treatment facilities in the pharmaceutical industry.

Navigating the balance between nanofiltration and oxidation to remove organic micropollutants from wastewater treatment plant effluent

The removal of organic micropollutants (OMPs) from wastewater treatment plant effluent is becoming more important due to the adverse effects of these compounds on the environment. To overcome the limitations of currently available technologies, this study proposes a combination of hollow fiber membrane filtration with advanced oxidation to remove OMPs. The possible synergy between these processes was investigated. The nanofiltration membrane ensures the removal of organic matter and thus an improvement of transmittance, after which oxidation with UV/H2O2 of the permeate can remove OMPs more effectively and at a significantly lower energy consumption than without a membrane. Six membranes were evaluated with a pure water permeability between 6.7 and 106 Lm−2 h−1 bar−1 and a MgSO4 retention ranging from 0.93 to 0. The molecular weight cut-off (MWCO) varied from 250 Da to more than 10 kDa. The measured MWCO can depend strongly on the applied flux. The UV-transmittance of NF permeate of treated wastewater was investigated experimentally to be between 97% and 50%. These values were used for an estimation of the specific energy consumption (SEC) for the membrane and the oxidation step, resulting in a combined SEC of 0.17–0.18 kWhm−3 for 70 or 80% removal of OMPs, respectively. Remarkably, this lowest SEC was not found for the combination with the most dense membrane, but for a slightly more open membrane. The reported SEC is comparable to the total energy consumption required for ozonation and adsorption, while producing clean water with a double barrier, high transmittance and 70–80% removal of OMPs.

Improving ammonia nitrogen removal and recovery by BMED stack optimization: The effect of ion exchange membrane thickness

Bipolar membrane electrodialysis (BMED) has emerged as an efficient and promising technology for the removal and recovery of ammonia nitrogen. Despite its potential, the optimization of BMED systems for enhanced performance and energy efficiency remains a critical challenge, particularly in the context of varying ion exchange membrane (IEM) thicknesses. Membranes with a thickness of < 80 µm have low resistance and are mainly used for processes requiring low energy consumption. Membranes with a thickness of 80–250 µm have moderate resistance and high ion selectivity and are widely used for electrodialysis applications. Membranes with a thickness of > 250 µm have higher ion selectivity than commercial membranes with a thickness of 80–250 µm and are suitable for processes that demand high purity. This study investigates the effect of IEM thickness ranging from 16–400 µm on BMED performance for ammonia nitrogen removal and recovery, and energy consumption. The BMED configuration comprising five cell triplets consisting of a cation exchange membrane, bipolar membrane, and anion exchange membrane was employed. The thickness of IEMs was divided into three categories: 16–17 µm (PCEM/ PAEM), 100–150 µm (CD100/AD100, InnoSep-C/InnoSep-A), and 380–400 µm (MC-3470/MA-3475). In membranes with a thickness of 100–150 µm, the ammonia nitrogen removal was exceptionally high at 99.2 %, with a recovery of 98.7 % (CD100/AD100: 100 µm) at a current density of 80 mA/cm2, and the system exhibited low specific energy consumption (SEC) of 8.87 kWh/kg-N (InnoSep-C/InnoSep-A: 150 µm) at a current density of 20 mA/cm2. However, when using the thinnest IEMs (PCEM: 16 µm, PAEM: 17 µm), an increase in total ammonia nitrogen loss (10.21–22.01 %) led to a reduction in ammonia nitrogen recovery. Conversely, when using the thickest IEMs (MC-3470: 380 µm, MA-3475: 400 µm), the SEC was extremely high (30.98–126.67 kWh/kg-N), making them unsuitable for the BMED process for ammonia nitrogen removal and recovery. Based on these experimental results, it is suggested to use an optimal thickness of IEM within the range of 80–250 µm in the BMED systems to achieve a balanced performance, maximizing ammonia nitrogen removal and recovery while minimizing the SEC. Consequently, the present study provides a comprehensive understanding of the effects of the IEM thicknesses on the BMED systems and could offer a practical perspective for optimizing the BMED stack with respect to improving the removal and recovery rate of ammonia nitrogen and reducing the energy consumption.

The effect of pretreatments on the drying of persimmon with infrared energy

AbstractThe effects of various pretreatments, including edible coatings, on drying kinetics and some physical quality parameters of persimmon varieties (Fuyu and Rojo Brillante) and differences between varieties were investigated. The experiments were conducted at an infrared radiation intensity of 1210 W m−2 and air velocity (v) of 1.5 m s−1. Drying time differed depending on pretreatments and varieties. Pretreatments generally shortened the Fuyu variety's drying time and increased the Rojo Brillante variety's drying time. Lower specific energy consumption and higher diffusion coefficient values were recorded for the Rojo Brillante variety compared to the Fuyu. In terms of quality parameters, the Fuyu variety generally obtained lower values for shrinkage. Rehydration rate was higher for the Rojo Brillante variety. Total color change was lower in the Rojo Brillante variety. Based on the pretreatments applied, xanthan gum gave better results in terms of operational parameters. In terms of quality parameters, ascorbic acid had better results for rehydration rate and shrinkage. For total color change, better results were obtained in arabic gum pretreatment. As a result, when an evaluation is made regarding variety differences and pretreatments applied, the Rojo Brillante variety can be recommended for drying.Practical applicationsPersimmon is a popular fruit in appearance, flavor, and rich nutritional content. The high moisture and sugar content in the fruit increases spoilage in a short time, making it difficult to consume in all seasons. For this reason, different preservation methods are being investigated to extend the shelf life. Sun drying and other drying methods developed as an alternative to these methods have many disadvantages. Different pretreatments prevent the negativities that occur in other drying methods. Especially, edible coatings can increase product quality by preserving color and appearance as well as controlling mass transfer, flavor, and aroma losses. This study investigated the effects of various pretreatments, including edible coatings, on drying kinetics and some physical quality parameters of persimmon varieties, as well the differences between varieties. Based on variety differences and pretreatments applied, the Rojo Brillante variety can be recommended for drying in terms of both processing and drying characteristics.

Study on a novel hydrogen liquification process applying mixed-refrigerant for pre-cooling and cryogenics

Reducing the energy consumption of hydrogen liquefaction process is an urgent issue to improve the economy of liquid hydrogen transportation. A novel large-scale hydrogen liquefaction system, with a capacity of 100 TPD, is proposed in this paper. The pre-cooling system is composed of a mixed-refrigerant (MR) refrigeration cycle and a CO2–NH3 cascade refrigeration cycle. Due to the auxiliary pre-cooling effect of the CO2–NH3 cascade cycle, temperature of the pre-cooled hydrogen can be as low as −200.9 °C. A modified MR Joule Brayton cycle with an additional compressor is used as the cryogenic system to cool the hydrogen from −200.9 °C to −252.2 °C. Besides, a four-stage ortho-to-para conversion (OPC) process is utilized. Performance of the novel system is investigated and optimized using the Aspen HYSYS software. According to the results, the lowest specific energy consumption (SEC) of the proposed process is 6.15 kWh/kgLH2 and the exergy efficiency is as high as 67.4%. Based on the energy analysis, the best system coefficient of performance is 0.1751 with a 96.3% of p-H2 in the liquid hydrogen. In addition, compared to the initial conceptual system, the proposed system exhibits significant performance enhancements, a 20% reduction in SEC and a 27.9% increase in exergy efficiency. A sensitivity analysis is conducted to assess the impact of refrigerant composition and hydrogen pressure on the system, resulting in the determination of the optimal proportions of refrigerant components and the optimal inlet pressure. Results of the study can provide theoretical reference for the further development of large-scale hydrogen liquefaction technology.

Energy and exergy analysis for fast drying of ribbed smoked sheets in a novel forced-convection rubber smoking room

Rubber sheet smoking rooms are widely used by small farmers in rubber growing regions: sheets of raw rubber latex are ‘smoked’ in them to remove moisture, preserve and prepare the rubber for transport. Energy and exergy for a novel forced-convection rubber sheet smoking room were analyzed. Inlet hot air velocity varied between 12 and 14 m/s and the fuel-wood moisture content was between 24–55 % dry basis. Thermal efficiency for drying ribbed smoked sheet (RSS) rubber was 13.4–16.7 %. The specific energy consumption (SEC) was between 13.5–16.9 MJ/kg of water evaporated. The highest thermal efficiency or lowest specific energy consumption was achieved when using the dry fuel-wood (inlet velocity 14 m/s, 53 % db fuel-wood), while the RSS quality was maximum (100 %). The overall second law (exergy) efficiency was from 2.2-5.8 %. The highest exergy efficiency was obtained for air at 12 m/s and 24 % db fuel-wood. However, in this condition, only 55 % of sheets showed good quality. The exergy efficiency for the most suitable condition (100 % high quality sheets) was 2.6 %. Compared to an earlier forced-convection smoking room, the new room reduced the drying time from 48 h to 36 h, while thermal efficiency increased from 14.3 % to 16.5 %. When compared to the original smoking room, 65 % fuel-wood and 50 % drying time were saved and the rubber sheet quality increased from ∼90 % to 100 %. Overall, our forced-convection room was more efficient, dried faster and produced better quality than all previous types.

Techno-exergy-economic assessment of humidification-dehumidification/reverse osmosis hybrid desalination system integrated with concentrated photovoltaic/thermal

Desalination is a process used to generate water for human consumption, irrigation, or industrial purposes. Assessment of desalination plants is crucial for freshwater productivity, energy consumption, exergy destruction, and economic feasibility calculations. Therefore, the study aims to conduct a technical, exergy, and economic analysis of a concentrated photovoltaic/thermal hybrid humidification-dehumidification reverse osmosis desalination system. The photovoltaic/thermal provides the electrical and thermal requirements for the hybrid desalination unit. Theoretical models for each unit are developed and integrated using the Engineering Equation Solver software. The sensitivity of system performance parameters was investigated under different climatic and operation factors. The analysis shows that the system produces 860 L per hour at the lowest specific energy consumption and water cost (3.3 kW-hours per cubic meter and 0.916 United States dollars per cubic meter), respectively, with a cost payback period of only 12 years compared to other green-powered desalination systems. The highest destruction portion of 84.6 % is at photovoltaic/thermal, while the largest cost portion of 68 % is at reverse osmosis. Productivity, energy consumption, and water cost are influenced by feed salinity, while destruction is most affected by solar irradiance. Ambient temperature, wind speed, and cooling fluid flow rate slightly affect the techno-exergy-economics of the system.

Efficiently removing dissolved organic pollutants in landfill leachate concentrate using dual-anode Fe2+/HClO system: The significance of insolubilization based on oxidative coupling of organics

The strategy to mineralize dissolved organics for the decontamination of landfill leachate concentrate (LLC) is expensive. Because mineralization requires high stoichiometric ratio of oxidants (e.g., •OH) or electron transfer (i.e., energy) to the pollutant molecules. Whereas, transferring the dissolved organic pollutants into separable insoluble matters is an energy-saving strategy. Herein, we developed a dual-anode Fe2+/HClO system for removing dissolved organic pollutants in LLC through insolubilization based on oxidative coupling. In this system, the majority of dissolved organic pollutants were transferred into insoluble substances, which could be removed easily. As a result, 89.8 % of the dissolved organic carbon (DOC) in LLC was fast removed in 3 h with a low specific energy consumption (SEC, 4.0 kWh kg−1 COD and 17.6 kWh kg−1 DOC), and the formation of toxic by-products can be well controlled to total organic chlorine (TOCl) < 0.1 mg/L. The formation of insoluble substances was attributed to the oxidative coupling of organic small molecules into the macromolecular ones. This was evidenced by the generation of insoluble compounds with the larger molecular mass, and the formation of coupling or polymerization products of the model pollutant (guaiacol). The predominant mechanism was proposed that Fe(IV) was generated in the dual-anode Fe2+/HClO system, and Fe(IV) oxidized pollutants to produce organic radicals, then the organic radicals coupled and polymerized to form larger molecules and insoluble compounds. This work offers a novel electrochemical method for efficient removal of organic pollutants in LLC with minimal toxic by-products generated, and revealed the significance of oxidative coupling process in the electrochemical Fe2+/HClO system.

Investigation on the operating capacity expansion through parallel schemes of reciprocating-switcher energy recovery device for desalination: Simulation, verification and parameterization

Parallel operation is a significant and feasible method to compensate the insufficient capacity of single reciprocating-switcher energy recovery device (RS-ERD) in membrane desalination system. To grasp the operating characteristics in capacity expansion, three parallel schemes of RS-ERD, single-operation scheme, two-parallel scheme and three-parallel scheme, are investigated through the numerical simulation, experimental verification and theoretical parameterization. Results indicate that, the two-parallel scheme and three-parallel scheme achieve the flowrate continuity of low-pressure seawater and the flowrate fluctuation amplitudes in parallel RS-ERDs decrease by 50 % and 83 % respectively when compared with single-operation scheme. Parallel operation schemes also broaden the flowrate range with high efficiency for RS-ERD. To ensure the 95 % energy recovery efficiency, two-parallel and three-parallel schemes expand the maximum flowrates to 140 m3/h and 210 m3/h in contrast with the 70 m3/h of single-operation scheme. In addition, the two-parallel and three-parallel schemes of RS-ERD realize the much lower specific energy consumption (SEC) of 2.11 kWh/m3 and 2.09 kWh/m3 than the 2.23 kWh/m3 in single-operation scheme which contributes to the operating costs savings about 63,830 CNY and 75,778 CNY in one year. This research provides a new perspective in capacity expansion through the parallel operation of energy recovery devices.

Novel Additives in Copper Electrorefining-Small Laboratory Scale.

This research aimed to evaluate the effectiveness of new organic substances, including a novel ionic liquid based on polyhexamethylenebiguanidine, polyhexamethyleneguanidine, and safranin in the copper electrorefining process. Experiments were conducted on a small laboratory scale using industrial copper anodes. Single doses of new additives did not improve process indicators (current efficiency, average cell voltage, specific energy consumption) or the quality of copper cathode deposits. However, a combination of a new ionic liquid based on polyhexamethylenebiguanidine and thiourea resulted in a satisfactory current efficiency of 97%, an average cell voltage of 0.110 V, a low specific energy consumption index of approximately 100 kWh/tCu, and smooth cathode surfaces. These results were superior to those obtained with industrial additives (bone glue and thiourea). The findings enhance our understanding of how these substances influence the electrorefining process and suggest the potential for more efficient and sustainable methods. Further research is recommended to validate these findings and explore their industrial applications.

Effects of operating parameters on the performance of an embedded two-piston compressor system for green hydrogen

The hydrogen compressor is a key component in the refuelling station. As one type of hydrogen compressor, the ionic compressor applied in the refuelling station is essentially a liquid piston compressor. The structure and operating condition would significantly influence the system efficiency of the liquid piston compressor. This paper investigated the impact of three key operating factors on the compressor performance of a novel embedded two-piston compressor, based on which the optimal operating values were identified by the Taguchi method when the hydrogen was compressed from 12 to 45 MPa. It was revealed that the movement time ratio of Piston A was the dominating factor for the power consumption and specific consumption while the upward time ratio of Piston B was the most influential parameter for the mass delivered. The optimal combination was 0.4 for the movement time ratio of Piston A, 0.45 for the upward time ratio of Piston A and 0.5 for the upward time ratio of Piston B. Under the predicted optimal operating conditions, the lowest specific energy consumption was obtained as 2733.75 kJ/kg.

Tuning Local Atomic Structures in MoS2 Based Catalysts for Electrochemical Nitrate Reduction.

In recent years, there has been a substantial surge in the investigation of transition-metal dichalcogenides such as MoS2 as a promising electrochemical catalyst. Inspired by denitrification enzymes such as nitrate reductase and nitrite reductase, the electrochemical nitrate reduction catalyzed by MoS2 with varying local atomic structures is reported. It is demonstrated that the hydrothermally synthesized MoS2 containing sulfur vacancies behaves as promising catalysts for electrochemical denitrification. With copper doping at less than 9% atomic ratio, the selectivity of denitrification to dinitrogen in the products can be effectively improved. X-ray absorption characterizations suggest that two sulfur vacancies are associated with one copper dopant in the MoS2 skeleton. DFT calculation confirms that copper dopants replace three adjacent Mo atoms to form a trigonal defect-enriched region, introducing an exposed Mo reaction center that coordinates with Cu atom to increase N2 selectivity. Apart from the higher activity and selectivity, the Cu-doped MoS2 also demonstrates remarkably improved tolerance toward oxygen poisoning at high oxygen concentration. Finally, Cu-doped MoS2 based catalysts exhibit very low specific energy consumption during the electrochemical denitrification process, paving the way for potential scale-up operations.

Energy, exergy and economic investigation of novel hybrid dryer, indirect solar dryer and traditional shade drying

By integrating a secondary energy source into solar dryers, more moisture can be removed from food products in the same time period. For this purpose, tomato slices of different thicknesses (7 mm, 15 mm and quarter size) were dried to see the drying, energy, exergy and economic performance of an innovative hybrid dryer consisting of an indirect solar dryer and geothermal heat exchanger unit. The hybrid dryer’s performance was compared simultaneously with indirect solar dryer and traditional shade drying. The analyzes were evaluated according to the feeding of drying air from the solar air collector and geothermal heat exchanger unit. Compared to the other two dryers, the hybrid dryer dried the 7 mm, 15 mm and quarter size samples in the earliest time, with an average of 1380, 2476.3 and 2397.3 min, respectively. The average highest specific moisture extraction rate (0.87 kg/kWh) and dryer efficiency (45.25 %) and the lowest specific energy consumption (4.75 kWh/kg) for hybrid dryer were obtained for the 15 mm. The highest exergy efficiency for the solar air collector and drying chamber of the hybrid dryer was determined at 7 mm with 3.08 % and 38.9 %, respectively. The lowest payback period for the hybrid dryer was found to be 0.37 years for 7 mm. The results showed that the hybrid dryer was superior to the other two dryers by drying continuously day and night. Hybrid dryer can create a successful commercial ecosystem as an important drying alternative for locations where geothermal energy is available.

Enhanced Quick-Cooking Red Beans: An Energy-Efficient Drying Method with Hot Air and Stepwise Microwave Techniques.

This research introduced an energy-efficient drying method combining hot-air drying with stepwise microwave heating for producing quick-cooking red beans. Crucial parameters such as the effective diffusivity coefficient (De), and specific energy consumption (SEC) were examined across varying conditions with the aim of optimizing the drying condition. The results showed that De and SEC varied in a range of 0.53 × 10-9-3.18 × 10-9 m2·s-1 and 16.58-68.06 MJ·(kg·h-1)-1, respectively. The findings from the response surface methodology indicated that optimal drying conditions for cooked red beans are achieved at a hot air temperature of 90 °C, a microwave power of 450 W (corresponding to an initial intensity of 2.25 W·g-1), and a rotational speed of 0.2 Hz. These conditions lead to the maximum effective diffusivity coefficient and the lowest specific energy consumption. Further investigations into step-up (150-300 W to 300-450 W) and step-down (300-450 W to 150-300 W) microwave heating modes were conducted to refine the drying process for enhanced energy efficiency. The synthetic evaluation index revealed that step-down microwave heating strategies of 450 W-to-150 W and 300 W-to-150 W, applied at a temperature of 90 °C and a rotational speed of 0.2 Hz, were notably effective. These methods successfully minimized energy use while preserving the quality attributes of the final product, which were comparable to those of traditionally cooked and freeze-dried red beans. The combined approach of hot-air drying with step-down microwave heating presents a promising, energy-saving technique for producing quick-cooking beans that retain their rehydration qualities and texture.

The impact of well spacing on three-dimensional in situ extraction of oil shale using high-temperature air injection

To explore the impact of well spacing on the in situ high-temperature air injection for three-dimensional shale oil recovery, this study constructed six different well-spacing physical models of shale oil for investigation. By comparing factors such as temperature distribution, cumulative oil production volume, heating rate factor, and specific energy consumption per unit volume of shale oil among the six different well-spacing models, the influence of well spacing on the in situ high-temperature air injection for three-dimensional shale oil recovery was analyzed. The results showed that all six shale oil models exhibited a ripple pattern, advancing along the fractured fissures from the heating well to the production well. Model I, Model II, Model III, Model IV, Model V, and Model VI completed the full decomposition of the shale region at 2610, 1530, 1800, 3510, 4050, and 6660 days, respectively. The heating rate factor reached its peak at 1800, 900, 1440, 2340, 3240, and 3960 days. Model III had the lowest specific energy consumption per unit volume of shale oil, which was 905.41 kW/m3. Using Model III for three-dimensional shale oil injection with high-temperature air in situ recovery will shorten the heating time and reduce heat loss.

Performance analysis of hydraulic excavators in complex excavation environments and different bucket trajectories

Simulations of excavation operations not only help understand how excavators perform in specific environments but also can be used to optimise operating parameters. In this work, we explore the performance of hydraulic excavators under conditions of cohesive and size-dispersed materials and different bucket trajectories. The results indicate that with the cohesion increasing, the spillage of particles from the bucket is reduced, but the hydraulic power fluctuates greatly due to the strong collision of particle aggregates on the bucket. As the particle size distribution turns wider, small particles exert an intensive interaction force on the bucket, and the stress distribution on the bucket becomes wider. Therefore, some suggestions are given for practical excavation operations in different stockpile scenarios. Additionally, the bucket can be initially placed close to the base of the stockpile to achieve low specific energy consumption and high productivity.

A High-Efficiency Radio-Frequency-Assisted Hot-Air Drying Method for the Production of Restructured Bitter Melon and Apple Chips.

Nowadays, consumers are increasingly demanding processed food products with high levels of beneficial components. Bitter melon and apple are both nutritious foods rich in bioactive compounds. In this study, restructured bitter melon and apple chips were processed using four drying techniques: hot-air drying with/without exhaust air recirculation (EAR), and radio-frequency-assisted hot-air drying (RFHAD) with/without EAR. The drying characteristics, effective moisture diffusivity (Deff), specific energy consumption (SEC), total energy consumption (TEC), and some selected quality characteristics of the dehydrated chips were evaluated. The experimental results show that the application of radio frequency (RF) energy significantly facilitates water evaporation in the drying material, resulting in a significant (p < 0.05) reduction of drying duration by 31~39% over the experimental test parameters. The higher Deff values obtained from RFHAD and RFHAD + EAR were 6.062 × 10-9 to 6.889 × 10-9 m2/s, while lower SEC values ranged from 301.57 to 328.79 kW·h/kg. Furthermore, the dried products possessed better or fairly good quality (such as a lower color difference of 5.41~6.52, a lower shrinkage ratio of 18.24~19.13%, better antioxidant capacity, higher chlorophyll, total flavonoid, and total phenolic content, a lower polyphenol oxidase activity of 49.82~52.04 U·min-1g-1, smaller diameter and thickness changes, and a lower hardness of 27.75~30.48 N) compared to those of hot-air-dried chips. The combination of RF-assisted air drying and partial recirculating of dryer exhaust air achieved the highest saving in TEC of about 12.4%, along with a lower moisture absorption capacity and no deterioration of product quality attributes. This drying concept is therefore recommended for the industrial drying of several food materials.

A novel hydrogen liquefaction process using dual mixed cryogenic refrigeration system: Energy, exergy, and economic analysis

In conventional hydrogen liquefaction plants, the liquefaction process consumes high portion of about 30 % of the liquid hydrogen (LH2) energy content. In addition, existing LH2 technology uses pure or single mixed refrigerants, which are susceptible to freezing problems. To address these challenges, this study introduces an innovative hydrogen liquefaction process utilizing dual mixed refrigeration (DMR) system. This process incorporates two interactive mixed refrigerants in two integrated refrigeration loops, offering flexible capability to handle large-scale capacities with minimal energy consumption and free of freezing problems. The proposed process achieved extremely low specific energy consumption (SEC) of 3.732 kWh/kgLH2, 48 % lower than the average SEC of the large-scale single mixed refrigerant (SMR) systems (7.128 kWh/kgLH2). Also, its exergy efficiency (59.65 %) is 33 % higher than the average exergy efficiency of the SMR-based systems (44.89 %). Furthermore, the proposed DMR-based process reduces the levelized cost of liquid hydrogen production to 1.89 $/kgLH2, which is 70 % lower than the small-scale processes and 21 % lower than the average cost of the large-scale SMR-based systems. This study of the dual mixed cryogenic refrigeration approach provides new methodology and guidelines for future research to significantly improve the technical and economic feasibility of LH2 production, making it competitive with other energy storage and transportation options.

Computer simulation of operation plant effective modes for water disinfection by electrical discharges in gas bubbles

Purpose. Determination by means of computer simulation of the most efficient modes of operation of the installation for water disinfection using discharges in gas bubbles, in which (modes) the amplitude of voltage pulses at the processing unit and on the layer of treated water is not less than the voltage amplitude immediately after the switching discharger. Methodology. To achieve this goal, we used computer simulation using Micro-Cap 10. We used two different electrical circuits that simulate the operation of the experimental setup in two different modes: in a mode with a restoring electrical strength of the discharge gap in the gas bubble between two adjacent voltage pulses on the discharge node and in the mode without restoring this dielectric strength. In computer simulation, we varied the following factors: the maximum simulation step, inductances, capacitances, active resistances, wave resistance of a long line, and the delay time for the operation of a spark gap simulating a discharge gap in a gas bubble. Results. Computer modeling has shown that in order to increase the voltage amplitude at the treatment unit and on the layer of treated water, it is necessary to reduce the load capacitance – the capacitance of the water layer in the treatment unit to 10 pF or less, to increase the active resistance of the water layer to 500 W or more. An important factor for increasing the voltage and electric field strength in the discharge unit and, consequently, for increasing the efficiency of treated water disinfection is the discharge delay time in gas bubbles. The most rational delay time for the operation of the arrester, which is the gap in the gas bubble inside the water, under the conditions considered by us is 4–5 ns. It is with this delay time that the amplitude of voltage pulses at the node of disinfecting water treatment and on the layer of treated water is maximum, all other things being equal. Furthermore, with such a delay time this amplitude of voltage pulses significantly exceeds the voltage amplitude directly after the main high-voltage discharger, switching energy from the high-voltage capacitive storage to the processing unit through a long line filled with water. Originality. Using computer simulation, we have shown the possibility of increasing the voltage at the discharge unit of the experimental setup by 35 % without increasing the voltage of the power source. This provides a higher efficiency of microbiological disinfection of water by nanosecond discharges in gas bubbles and lower specific energy consumption. Practical value. The obtained results of computer simulation confirm the prospect of industrial application of installations using nanosecond discharges for disinfection and purification of wastewater, swimming pools and post-treatment of tap water.

Assessment of the suitability of adsorption water treatment as a concentration process for resource recovery and wastewater treatment

Electroplating plants dispose of the diluted plating solution (DPS) as plating wastewater due to its reduced plating efficiency. Solid waste produced by various industries is discarded in landfills, leading to the generation of landfill leachate (LL). Employing suitable wastewater treatments is crucial for either recovering valuable resources from wastewater or ensuring that its discharge aligns with wastewater discharge standards. In this study, we examined the feasibility of an adsorption water treatment (AWT) process for recovering valuable resources from DPS and efficiently treating LL. The AWT process using DPS and LL demonstrated that the influence of feed quality (composition and concentration) on water treatment capacity was insignificant, with a water recovery of up to 50 %. In addition, the AWT process demonstrated its ability to efficiently concentrate DPS without the need for pre-treatment, resulting in a notable 12.1 % increase in the plating efficiency of the DPS. This made it reusable for electroplating, and it was realized with a low specific energy consumption (SEC) of 1.63 kWh/m3 by utilizing waste heat in electroplating plants. Furthermore, the freshwater produced by the AWT process, including simple pre- and post-treatments, met 26 water quality parameters of the landfill leachate discharge standard.