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Simultaneous production of hydrogen as an energy carrier and chlorine as a valuable chemical from recycled hydrogen chloride was investigated employing a lab-scale membrane electrolysis setup. The effects of various process parameters including current density (1–4 kA m−2), cell temperature (45°–75°C), flow rate of hydrochloric acid feed (200–500 mL min−1), and concentration of acid (18–21 wt.%) on the cell voltage and chlorine current efficiency (ChCE) were studied. The Taguchi design of experiments (L16 array) was employed to design the minimum number of experiments necessary to fully study the process. A filter press type cell of 10 cm2 surface area comprising a DSA anode, an alloy of predominantly nickel cathode and Nafion 115 membrane, was used. It was observed that increasing anolyte flow rate, anolyte concentration, or cell temperature caused a decrease in cell voltage and an increase in ChCE, while increasing current density linearly increased cell voltage and decreased ChCE.

This study reports the effects of polar (acetone/methanol) and non-polar (chloroform/hexane) solvents on lipid yield, fatty acids methyl esters (FAMEs) composition, and biodiesel properties of microalgae. The lipids yield extracted by hexane and chloroform (100.01 and 94.33 mg/g) were higher than by methanol and acetone (40.12 and 86.91 mg/g). The polarity of solvents also affected FAMEs composition of microalgal lipids. Total saturated fatty acids and unsaturated fatty acids of extracted lipids were 61.53% and 38.47% by chloroform and 38.85% and 61.15% by methanol. Moreover, polar and non-polar solvents affected the biodiesel properties such as cetane number and oxidative stability. In addition, higher ratio of chloroform to methanol and higher temperature increased the lipid yield and saturation degree of lipids, through ultrasound-assisted lipid extraction method. Overall, the results revealed that the lipids yield, FAMEs composition, and biodiesel quality of microalgal biomass can be significantly affected by solvents polarity and extraction conditions.

Artificial intelligence (AI) plays a significant role in energy systems transformations in smart cities. Climate change and environmental sustainability imposed utilities to shift toward renewable energy resources and technologies applications in recent decades. Renewable energy technology deployment is associated with high initial investment and integration with the existing supply and demand systems. Operation stability has been challenging to integrate renewable energy with the customary old systems. On the other hand, renewable energy ensures sustainable energy and future development with minimum loss and greenhouse gas emissions. Therefore, AI is the primary mover of power systems modernization with high accuracy of management and control. This study tried to evaluate the efficiency and performance of AI in the renewable energy sector, focusing on the European Union as the case study. This study analyzes the first renewable energy processes in the chain and energy from gross to final consumption. Afterward economic consequences of renewable energy using natural resources (solar, wind, etc.) in smart cities are discussed. Finally, the efficiency of AI in renewable energy is examined, followed by future work.

Phenanthrene as the hazardous PAHs-component are extensively detected in industrial wastewater. However, the impacts of bioelectrostimulation process on Phenanthrene degradation in aerobic reactors remained unclear. Here, a novel bioelectrostimulation process equipped with carbon cloth as electrodes was developed to investigate the removal efficiency of Phenanthrene and ATPase enzyme activity in the synthetic wastewater. The results obtained from the present study indicated that a complete Phenanthrene degradation (100%) can be achieved using microbial electrostimulation systems steel mesh coated with carbon cloth (MES-CC) as anode under optimal operational conditions (electrical current: 4 mA, HA concentration: 15 mg L-1) within 18 h. The conductive carbon cloth provides a biofilm carrier to easily transfer the electrons between electrodes and microbial communities. In addition, the highest ATPase enzyme activity (5176 U) was observed when the aerobic MES-CC reactors were operated with electrical current 4 mA. Furthermore, the COD removal efficiency in MES-CC increased from 49% to 96% when the C: N ratio decreased from 20 to 5. The highest value of Vmax in MES-CC for suspended and attached growth were determined to be 2.87 and 0.54 g COD g-1 biomass. Overall, the results demonstrated that MES equipped with carbon cloth and continuous electrical current mode has good potential for efficient Phenanthrene wastewater treatment.

Abstract Large-scale hydrogen liquefaction (LHL) methods and different approaches of the configuration of hydrogen liquefaction cycles are chronicled. History landmarks of permanent gases liquefaction are quick reviewed and the basic hydrogen liquefaction cycles, the existing in-service LHL plants around the world, and LHL conceptual proposed plants, including the state of the art plants, are recorded and categorized based on the systems’ main parameters. In addition, a novel classification of hydrogen liquefaction systems in terms of heat exchange and expansion process method is introduced. As well as, the authors infer that renewable energy technologies section should be added to the old sectioning of the hydrogen liquefaction plants. In addition, hybrid conceptual hydrogen liquefaction plants, combining with renewable power cycles are reviewed and the increasing contribution of this new approach is demonstrated. Finally, the operational costs of the plants considering the systems’ efficiency are examined, and a trend in specific energy consumption (SEC) and exergy efficiency of hydrogen liquefiers is discussed. Accordingly, considering the existing technologies, SEC reduction of hydrogen liquefaction will not be abrupt in near future and it will remain within the range of 5–8 kWh / kg LH 2 . Moreover, exploiting of isentropic expansion processes instead of isenthalpic one, cascading of refrigerating cycles, using of new mixed refrigerants as working fluid of refrigeration cycles, and hybridization of renewable energy power cycles to refrigeration cycles are the main four growing approaches in the hydrogen liquefaction context.

Abstract Direct reduction of iron process in steel industry has special production conditions. Low quality cooling water, low cold and high hot cooling water temperature, space limitation for new equipment installation, high value-added of product and severe effect of cooling water temperature on production rate are of these conditions. Considering technical and economic constraints and limitations, this situation makes this process an attractive case study for converting the existing wet cooling tower to hybrid cooling system. In this paper, based on integration of process, dry and wet cooling system and ambient conditions profiles, a new method for designing hybrid cooling system has been proposed. The calculation program has been developed as a MATLAB code and resulted: 1) Calculation of annual water saving and energy consumption with reasonable accuracy, 2) Control system of dry and wet cooling blocks to maximize water saving under various ambient conditions, 3) Closed loop simulation of cooling system considering thermal feedback of process to cooling system and 4) Obtaining optimum values for 16 design parameters of dry block cooling (consisting air cooled heat exchanger and plate heat exchanger). The optimization has been done via genetic algorithm, considering annual response of each design under various ambient temperature and relative humidity. Considering design standards for new equipment and operational and technical constraints, made the optimization model reliable as well as checking the design parameters with process equipment constructors. In optimum point, converting existing wet cooling tower to hybrid cooling system in direct reduction of iron plant of Mobarakeh Steel Complex located in Isfahan province in Iran, will decrease the annual water consumption by 70.15% and production loss by 98% with payback period of 1 years and 10 months.

This review showcases a comprehensive analysis of studies that highlight the different conversion procedures attempted across the globe. The resources of biogas production along with treatment methods are presented. The effect of different governing parameters like feedstock types, pretreatment approaches, process development, and yield to enhance the biogas productivity is highlighted. Biogas applications, for example, in heating, electricity production, and transportation with their global share based on national and international statistics are emphasized. Reviewing the world research progress in the past 10 years shows an increase of ~ 90% in biogas industry (120 GW in 2019 compared to 65 GW in 2010). Europe (e.g., in 2017) contributed to over 70% of the world biogas generation representing 64 TWh. Finally, different regulations that manage the biogas market are presented. Management of biogas market includes the processes of exploration, production, treatment, and environmental impact assessment, till the marketing and safe disposal of wastes associated with biogas handling. A brief overview of some safety rules and proposed policy based on the world regulations is provided. The effect of these regulations and policies on marketing and promoting biogas is highlighted for different countries. The results from such studies show that Europe has the highest promotion rate, while nowadays in China and India the consumption rate is maximum as a result of applying up-to-date policies and procedures.

In this study, integration of RO desalination unit with power and water cogeneration plant located in Qeshm Island in Iran has been investigated. The desalination unit exists in this plant is MED-TVC type. In this regard, energy, exergy, exergoeconomic, and exergoenvironmental (4E) analyses have been performed by developing a computer code using Matlab. Validation of thermodynamic data has been performed through comparing the results of modeling by Matlab with the simulation done in Thermoflex software and the real data gathered from the Qeshm cogeneration plant. The results show the acceptable accuracy of thermodynamic modeling. The exergoenvironmental analysis has been conducted based on Life Cycle Assessment (LCA). In this regard, the weight function of TVC is proposed in this paper based on technical data in different nominal sizes in order to estimate the environmental impacts of this component. The cogeneration plant produces 25.7 MW power, consuming 6 kg/s steam can lead to production of 51.7 kg/s desalinated water. The gained output ratio (GOR) is about 8.7 for the MEDTVC unit. The performance ratio (PR) of RO desalination unit which is added to the downstream of MED-TVC has been calculated about 0.5. Integrating RO desalination unit with MED-TVC enhances the production of fresh water by 255.132 ton per hour.Exergetic efficiency, total cost rate of the system and total environmental impact rate of the system has been calculated 46.86 %, 64.01 $/min and 29.49 pts/min, respectively. Since the largest share of exergy destruction rate of the system belongs to the gas cycle and also Qeshm Island has a warm and muggy climate, adding a chiller type air cooling system to inlet of air compressor can decrease the power demand of air compressor and fuel consumption of combustion chamber which makes the system more efficient and reduce the cost and environmental impact rate of the system.