Maximum Utilization Rate Research Articles

Improved adaptive genetic algorithm for dynamic multi-specification one-dimensional cutting problem

Rebar is an essential material in the construction of bridges and houses. Rebar cutting is an important link in rebar processing, but it is usually completed by manual experience, which is not only time-consuming, but also causes serious waste and reduces the economic benefits. As the country vigorously promotes the green construction method, the traditional rebar cutting method is difficult to meet the development requirements. So dynamic multi-specification one-dimensional cutting problem is studied in this paper. A mathematical model aiming at the maximum utilization rate of raw material is established, and an improved adaptive genetic algorithm is proposed. Large-scale, small-scale, single-specification masterbatch and multi-specification masterbatch are selected for simulation experiments, respectively. The results show that the proposed algorithm can deal with both large- and small-scale multi-specification or single-specification masterbatch cutting problems. Moreover, the algorithm has good performance in solving accuracy and convergence speed, which verifies its feasibility, effectiveness, and stability. Finally, aiming at the problem of dynamic insertion of orders, one-dimensional cutting software is developed, rapid and real-time cutting of rebars is realized, and the utilization rate of building rebars is improved, which plays a positive role in promoting the high-quality development of construction industries such as bridges.

Study on the Influence of Density and Water–Cement Ratio on the Cement Utilization, Fluidity, Mechanical Properties, and Water Absorption of Foam Concrete

In this paper, we study the influence of density and the water–cement (W/C) ratio on the slurry fluidity, compressive strength, and water absorption of foamed concrete (FC) and its mechanism of action, with the aim of proposing an optimal mix ratio for FC to reduce cement usage and carbon emissions in the construction industry and ensure the good overall performance of FC. In this experiment, two groups of experiments were designed using the control variable method. Fluidity and uniaxial compression tests showed that when the density was 600 kg/m3 and the W/C ratio was 0.6, the FC slurry had maximum fluidity, but its mechanical properties were poor and it collapsed easily. Conversely, by analyzing the uniaxial compressive strength/cement (UCS/C) ratio, it was observed that the mix ratio had a maximum cement utilization rate (W/C ratio) of 0.5 and a density of 1000 kg/m3. Nondestructive testing methods were used to measure the ultrasonic pulse velocity (UPV) and rebound value of the FC test block, and the strength and durability of FC were analyzed. The water absorption rate of the FC test block was tested, and the final analysis showed that the optimal mix ratio of FC in this test was W/C = 0.5, with a density of 1000 kg/m3.

Performance study of the bioreactor for the biodegradation of methyl orange dye by luffa immobilized Stenotrophomonas maltophilia and kinetic studies: A sustainable approach

The biodegradation of methyl orange dye was examined in a biofilm reactor with luffa immobilized Stenotrophomonas maltophilia ((HE963840.1), low-cost packing material. The bacteria were isolated from the sludge collected from a common effluent treatment plant at IOCL refinery Mathura, Uttar Pradesh. The bacteria were characterized using 16rRNA. The reactor performance was studied at 30 ± 5 oC temperatures over a period of thirty days. The reactor was operated with the flow rates of 60 mL/h, 90 mL/h, 240 mL/h, 360 mL/h and 432 mL/h. The pollutant load ranges from 151.6 mg/(L-day) to 1091 mg/(L-day) and the pH of the dye solution was maintained at 7.0 ± 0.4 during the study. The maximum removal efficiency (RE) and elimination capacity (EC) at steady state were determined as 90.2 % and 658.1 mg/(L-day) respectively. The rate of utilization of the methyl orange dye is described by modified stover-kincannon model with kinetic parameters- maximum utilization rate (Umax) and saturation constant (KB) to be 2.70 g/(L-day) and 2.34 g/(L-day) respectively. The toxicity studies confirm the non-toxic nature of the biodegraded products.

The Influence of Reduced Frequency on H-VAWT Aerodynamic Performance and Flow Field Near Blades

Studies demonstrate that the reduced frequency k is influenced by the incoming wind speed U0 and the rotor speed n. As a dimensionless parameter, k characterizes the stability of the flow field, which is a critical factor affecting the performance of vertical-axis wind turbines (VAWTs). This paper investigates the impact of k on the performance of straight-blade vertical-axis wind turbines (H-VAWT). The findings indicate that 0.05 is the critical value of k. The same k results in a similar flow field structure, yet the performance changes vary with different U0. A decrease in n or an increase in U0 leads to an increase in the average value and fluctuation of k, which subsequently reduces the rotor rotation torque Cm and decreases the maximum wind energy utilization rate Cpmax. This reduction in Cpmax weakens the stability of the flow field. Additionally, the high-speed area of the blade’s trailing edge velocity trajectory at θ=0°, θ=120°, and θ=240° expands with increasing range. Velocity dissipation in the high-speed area of the trailing edge affects the stability of the flow field within the rotor.

Methylosinus trichosporium OB3b drives composition-independent application of biogas in poly(3-hydroxybutyrate) synthesis

Biological conversion of biogas into poly(3-hydroxybutyrate) (PHB) via Type II methanotrophs holds great promise. However, a prerequisite for widespread biogas utilization is a comprehensive understanding of the effects of biogas composition on methanotrophic PHB synthesis. Herein, we explore the effects of biogas composition on the microbial growth and PHB accumulation of Methylosinus trichosporium OB3b under five different artificial biogas conditions with varying the ratio of methane (CH4) to carbon dioxide (CO2), the two main components of raw biogas. Stoichiometric and kinetic analyses revealed that increased CO2 concentrations correlated with higher maximum specific growth rates (0.021–0.029 h−1) and maximum CH4 utilization rates (0.029–0.042 mg CH4/mg TSS-h). Besides, no significant correlation was found between the CH4-to-CO2 ratio and other growth parameters. Consistent PHB contents (20.2–25.3 wt%) were achieved, irrespective of the CH4-to-CO2 ratio. Furthermore, the ability of M. trichosporium OB3b to grow and synthesize PHB (13.2 wt%) was confirmed using pilot-scale biogas. Our findings highlight the potential of biogas as a feedstock for producing valuable biodegradable polymers, thus contributing to waste-derived fuel (WDF) innovation and environmental sustainability.

Optimization of methanol yield and carbon dioxide utilization in methanol synthesis process

The method of CO2 hydrogenation to methanol can effectively reduce carbon emission and has wide application prospects in chemical industry and environment. Therefore, methanol synthesis is an important way to save energy, reduce emission and transform energy utilization. In this paper, the mathematical model of methanol synthesis reactor is established. Under the condition of controllable cooling temperature, the optimization is carried out with maximum methanol yield and CO2 utilization rate. The results show that the methanol yield can be increased by 6.57% and CO2 utilization rate can be increased to 39.1% by adjusting the cooling temperature control strategy. The comparative study found that the optimal cooling temperatures all show up and down variations, with local minima and maxima. In addition, an industrial application method of methanol yield maximization cooling strategy is proposed. When the stage cooling at different temperatures is adopted, the methanol yield could be increased by 5.38%.

In-situ grown ternary metal hydroxides@3D oriented crumpled V2C MXene sheets for improved electrocatalytic oxygen evolution reaction

High valence multi transition metal hydroxides are greatly enriched with OER redox active sites due to strong synergy of heteroatomic nuclei. The efficiency of these redox active sites could be efficiently improved by coupling with highly conductive substrate. The advanced three-dimensional (3D) architecture and hydrophilic terminal functionalities of MXene (MX) considerably enhance the maximum utilization rate of anchored redox active sites by triggering the direct growth of these at MX substrate. Here-in, the freeze-dried 3D network of crumpled Vanadium-Carbide (V2C) MX sheets regulates the crystallization of in-situ grown NiFeCr multi transition metal hydroxides on MX scaffold through co-precipitation process. The XPS results suggest a synergistic chemical interaction of 3D MX scaffold with NiFeCr that modifies the electronic structure of the composite ensuring reduced charge transfer resistance. Besides, as found in FESEM morphological investigation, the well-dispersed NiFeCr multi-transition metal hydroxides are immobilized on open pores like structure of V2C-MX facilitate thoroughly accessible active sites. As a result, the NiFeCr@3D V2C-MX composite has shown an excellent electrocatalytic activity with an overpotential of 410 mV at a current density of 200 mA cm−2, Tafel slope of 100 mV dec in 1M KOH. Besides, the significant interaction between metallic centers and MXene support prevent detachment or agglomeration of active centers providing maximum interaction with the electrolytic ions, quick ionic OH− transportation, speedy and stable electron transfer channels thus ensure the long-term stability of NV-5MX during 53 h continuous operation of OER. Furthermore, we have utilized a more accurate value of half-cell standard reduction potential of the Hg/HgO electrode in the Nernst equation to represent all test voltages and to determine the overpotential values. In essence, this study features a facile approach for the confined growth of multi transition metal hydroxides in the presence of morphologically unique 3D crumpled V2C MXene architectures. Consequently, the increased OER reaction kinetics and improved stability of the synthesized composites are potentially due to synergistic interplay between well dispersed active sites and the conductive substrate.

Optimization of merchandise delivery logistics: case studies at Bejaia port

The object of the study is the logistics of goods delivery by ports. This study presents a methodology designed to improve the efficiency of goods delivery logistics at the Bejaia port (Algeria). It prioritizes the optimization of empty container allocation to the ZEP zone, taking into account the geographical accessibility of the Tixter area, aiming to reduce the high costs linked with goods transportation. At the core of this strategy lies the use of simulation techniques to optimize truck fleets, ensuring maximum utilization rates and effective management of delivery operations by the Bejaia Mediterranean Terminal (BMT) for its clients. Addressing this challenge, the study offers an exhaustive analysis, integrating truck assignment models and accessibility assessments of logistic zones. The results highlight the paramount significance of optimal resource allocation and synchronized client coordination for achieving streamlined goods delivery. It becomes apparent that employing these methodologies can yield substantial productivity improvements, emphasizing their pivotal role in strengthening the port's logistical infrastructure. Via rigorous analysis and insights derived from data, this study elucidates avenues towards achieving operational excellence within the logistical infrastructure of the port. By harnessing innovative strategies to confront persistent challenges, such as optimizing truck fleets and strategically allocating resources, the research anticipates a profound transformation in the efficiency and cost-effectiveness of goods delivery operations. Ultimately, the integration of these methodologies holds the potential to propel the port of Bejaia towards enduring success and a competitive edge in the ever-evolving landscape of global trade. Through extensive efforts, this strategy can be extended to other national and international ports operating under similar conditions, as it provides valuable information and methodologies to optimize logistics and transportation operations.

Intelligent Education Managemnt System Design for Universities based on MTCNN Face Recognition Algorithm

Face recognition technique has made significant advancements in security and attendance, but its application in teaching management is minimal. To address the issues of insufficient teacher resources and declining educational quality, the paper designs an intelligent education management system for colleges and universities based on improved Multi-task Cascaded Convolutional Neural Networks (MTCNN) face recognition. The purpose is to achieve accurate recognition of faces through improved facial recognition technology, thereby analyzing the attendance status of students, and improving the efficiency and quality of educational resource utilization. Firstly, an improved MTCNN facial recognition technology is adopted to achieve realtime monitoring of student status and attendance in the classroom through a B/S network structure. Secondly, through cluster deployment and load balancing, system stability and response speed can be improved. The results indicated that the improved MTCNN had better facial recognition accuracy and GPU utilization than traditional systems under different occlusion conditions. When there was no occlusion, recognition accuracy was 99.4%. However, when occlusion was presented at 10%, 20%, and 30%, the accuracy dropped to 92.3%, 84.25%, and 73.4%, respectively. Additionally, when the number of concurrent users was 1000, the maximum GPU utilization rate was 75%, which was 11% lower than traditional MTCNN systems. The use of an improved MTCNN facial recognition-based intelligent education management system in universities can effectively enhance the quality of classroom teaching and monitor the status of students. Further optimization of algorithm performance is needed in subsequent research to support larger-scale concurrent user usage while reducing hardware resource consumption.

Semimetallic state transition in Two-Dimensional carbon nitride covalent networks and enhanced electrocatalytic activity for nitrate to ammonia conversion

Single-atom catalysts (SACs), due to their maximum atomic utilization rate, show tremendous potential for application in the electrocatalytic synthesis of ammonia from nitrate. Yet, the development of superior supports that preserve the high selectivity, activity, and stability of SACs remains an imperative challenge. In this work, based on first-principles calculations and tight-binding (TB) model analysis, a new two-dimensional (2D) carbon nitride monolayer, C7N6, is proposed. The C7N6 structure exhibits a strong covalent network, with dynamical, thermal, and mechanical stability. Surprisingly, the structural transition from C9N4 to C7N6 corresponds to a semimetallic state transition. Further symmetry analysis unveils that the Dirac states in C7N6 are protected by space–time inversion symmetry, and the physical origin of the Dirac cone was confirmed using the TB model. Additionally, a non-zero Z2 invariant and significant topological edge states demonstrate its topologically nontrivial nature. Considering the excellent structural and topological properties of C7N6, a three-step screening strategy is designed to identify eligible SACs for electrochemical nitrate reduction reaction (NO3RR), and Ti@C7N6 is identified as possessing the best activity, with the last proton-electron coupling step *NH2→*NH3 being the potential-determining step (PDS), for which the limiting potential is 0.48 V. Moreover, a free energy diagram shows that the *NOH reaction pathway is energetically preferred on Ti@C7N6, and ab initio molecular dynamics (AIMD) calculations at 500 K confirm its good thermal stability. Our study not only provides excellent CN-based support material but also offers theoretical guidance for constructing highly active and selective SACs for nitrate reduction.

Metagenomic insights into the improvement of CO2/H2 biomethanation or biogas upgrading using zirconium metal organic frameworks

The inefficient conversion of carbon dioxide (CO2) to methane often restricts the advancement of CO2 biomethanation technologies. This study explored the degrading performance, microbial community compositions, and functional gene abundance to examine the impact of zirconium metal-organic frameworks (Zr-MOFs) on the CO2 biomethanation process. The results showed that the maximum utilization rates of CO2 and H2 increased by 2.77 times and 2.36 times after the addition of Zr-MOFs, respectively, and the corresponding conversion rate of CO2 to methane also increased by 57.53%. Additionally, Zr-MOFs enhanced the COD removal efficiency and hydrolysis of tryptophan-like proteins and humic acid-like substances, resulting in more volatile organic compounds, such as tetradecane, 2-pentanone, and hexadecanoic acid. The analysis of microbial community structure revealed that the relative abundance of Methanothrix and Metanobacterium increased by 24.40% and 36.02% after the addition of Zr-MOFs, respectively. The methane metabolism revealed that Metanobacterium was a member of the same aceticlastic methanogenic pathway as Metanothrix, which encodes acetyl-CoA synthetase to catalyze the synthesis of acetyl-CoA from acetate, and Zr-MOFs also increased the relative abundance of genes that encode the enzyme responsible for converting intermediates to methane. Finally, Zr-MOFs improved the biogenesis and utilization of acetate and hydrogen (H2) by enhancing the activity of enzymes, thereby providing more nutrients for methanogenesis. This study provided thorough explanations for the application and improvement of Zr-MOFs in CO2 biomethanation technology.

Multi-objective optimization design of a grid-connected hybrid hydro-photovoltaic system considering power transmission capacity

The first step in creating a hybrid system that incorporates the adjustable hydropower station is selecting an appropriate scale of new energy. This study proposed a methodology for optimized design an on-grid hydro-photovoltaic (PV) system considering power transmission capacity. The concepts of short-term joint hydro-PV operation were first given. The on-grid hybrid hydro-PV system's two evaluation indicators were then proposed, integrating double carbon targets and new energy power curtailments. Then, an optimization design model was established with maximum carbon emission reductions and minimum PV power curtailments. Finally, the methodologies were applied to a case study in northwest China to test its rationality. Results manifested that (1) PV power curtailments increase with carbon emission reductions under the given PV size and runoffs, and the optimized PV size was 200 MW; (2) the utilization rate of the newly add transmission channel generally decreases gradually with an increase in power transmission capacity expansion, and the optimum power transmission capacity expansion was 10 MW with the maximum utilization rate of 12.36%; (3) the hydro-PV joint production was impacted by both the characteristics of PV output and runoff. Thus, this study helps to the joint development of flexible hydropower stations and volatile new energy sources.

Performance and optimization of a new spray cooling system with PV/T and heat recovery in sow houses: A case study in Nanchang, China

The uncertain cooling effect and additional huge primary energy consumption (EC) caused by humidity regulation are currently the main problems of traditional air-conditioning systems in sow houses. In this paper, a new spray cooling system (NSCS) is developed based on PV/T and heat recovery in sow houses. Compared with traditional spray cooling systems, the cooling efficiency of new system can be significantly improved due to solar dehumidification and its EC can be reduced due to PV/T and heat recovery. Meanwhile, the mathematical models are established for its key equipment and their reliability is verified according to literature data. The results show that the maximum error is less than 7.2 % for the models. Aiming at the maximum utilization rate of cooling and heating equipment, the annual operation modes are determined for NSCS based on the above models. The results show that cooling season is from May 21st to September 25th, heating season is from January 1st to March 16th and from November 1st to December 31st, and the transitional spring and autumn are from March 17th to May 20th and from September 26th to October 31st, respectively. Meanwhile, the optimal spray cooling power (SCP) and mass flow rate of circulating water (MFCW) are obtained by analyzing the operation characteristics of NSCS in cooling and heating seasons. The results show that in cooling and heating seasons, it is suggested to use the minimum ventilation required by sows (42763.5 kg/h) for the ventilation rate of NSCS. Meanwhile, the optimal SCP and MFCW are recommended as 40 kW and 12245 kg/h, respectively. Finally, the matching between exergy efficiency (EE) and EC is analyzed for NSCS in transition season through simulation. The operational control methods are further proposed for NSCS in transition season through optimization. The results show that in transition season, increasing mass flow rate of supply air (MFSA) and reducing equipment power are the operational control methods to obtain the optimal performance and minimum EC of NSCS. Specifically, in the transitional spring, the optimal MFSA, SCP and MFCW are recommended as 47812.0 kg/h, 30 kW and 10245 kg/h, respectively. In the transitional autumn, they are recommended as 55806.3 kg/h, 25 kW and 7245 kg/h, respectively. The above conclusions can provide new ideas for the development of new energy-saving air-conditioning systems in sow houses, and guide the operation control and performance optimization of NSCS.

DRL-Based Load-Balancing Routing Scheme for 6G Space–Air–Ground Integrated Networks

Due to the rapid development of the space–air–ground integrated network (SAGIN), a satellite communication system has the advantages of wide coverage and low requirements for a geographical environment and is gradually becoming the main competitive technology for 6G. The low-earth-orbit (LEO) satellite network has the characteristics of low transmission delay, small propagation loss, and global coverage, and its exploration has become the main research object of contemporary satellite communications. However, traditional routing algorithms cannot adapt to the characteristics of the high dynamics and load-balancing requirements of LEO satellite networks. In this paper, a load-balancing routing algorithm for LEO satellites based on Deep Q-Network (DQN-LLRA) is proposed by using deep reinforcement learning. Making use of the model obtained by the DQN training, satellite nodes can select the best routing results according to the delay, bandwidth, and queue utilization of the surrounding satellite nodes. The simulation and analysis show that the path load obtained by the proposed algorithm is low. Compared with the Q-learning-based algorithm, this algorithm reduces the maximum queue utilization rate of the routing path by 5%, reduces the average queue utilization rate of the routing path by 13%, and effectively balances the load in the network.

Organic mass and nitrogen removal kinetic modeling in sequencing batch reactor

In this paper, the novelty consists of determining kinetic parameters for sequencing batch reactor (SBR) operated for the experimental design Nº1 (ED-1) under single (oxic) and combined biological sequences in two phases (anaerobic-oxic) treating a Chemical Oxygen Demand (COD) influent around 5,466 mg/L. ED-2 comprised three phases (anoxic I-oxic-anoxic II) with the influent containing COD (1,119-1,598 mg L−1), NH4 +-N (63-94.5 mg L−1 and Total Kjeldahl Nitrogen (126 - 175 mg L−1). Kinetic parameters corresponded to the substrate maximum utilization rate r(m,S) and the half-saturation coefficient (K s) The r (m,COD) and K s was increased as the biological phases were increased from single oxic phase (−60 mg L−1 h−1; 2704 mg L−1), anaerobic-oxic phases (−100 mg L−1 h−1; 1,069.8 mg L−1) to the anoxic I –oxic-anoxic II phases (−250 mg L−1 h−1). The kinetic coefficients were significant in the first anoxic and the oxic phases of SBR, for conventional and simultaneous nitrification-denitrification.

Study of ultrasonic vibration-assisted particle atomic layer deposition process via the CFD-DDPM simulation

Atomic layer deposition (ALD) is a unique surface modification technology by providing conformal ultrathin films on particulate materials. Fluidized bed ALD (FB-ALD) shows excellent scale-up potential for the mass production of particle coating, where different external fields have been developed to enhance the fluidization quality of cohesive micro-nanoparticles. Ultrasonic vibration is a promising assisting method for it can promote effective agglomeration breakage as well as enhance the heat and mass transfer rates in the reactor. In this paper, a multiscale computational fluid dynamics (CFD) simulation based on the dense discrete phase method (DDPM) is developed to study the ultrasonic vibration-assisted FB-ALD process. Dynamic mesh method and discrete element method are adopted to introduce the ultrasonic field and compute the particle movement with an accurate description of particle-particle and particle-vibrating wall interactions. Results show that ultrasonic vibration effectively promotes the contact efficiency between uncoated particles and precursor molecules in the precursor pulsing process, leading to higher deposition rates and coating uniformity. During the purge process, ultrasonic vibration also increases the removal rate of ALD byproducts, thus shortening the purge time by 25%. Through the CFD-DDPM model, the maximum precursor utilization rate for uniform coating can be predicted quantitatively under a given precursor mass fraction and a ratio of the pulse time to the theoretical saturation time. The multiscale numerical model developed in this work can be adapted to optimize the process conditions for the scale-up of FB-ALD reactors.

ESTIMATION OF THE STOCK OF INDIAN SCAD FISH (Decapterus russeli) LANDED AT THE SIBOLGA ARCHIPELAGO FISHERY PORT, NORTH SUMATRA

Indian Scad Fish (Decapterus russeli) are the most dominant small pelagic fish resources landed in the Sibolga Archipelago Fisheries Port. The production of Indian Scad Fish catches that are landed in PPN Sibolga on average fluctuates every year. Therefore, it is necessary to analyze the catch of Indian Scad Fish to control the level of exploitation and create effective fishing operations so that the utilization of Indian scad fish resources can run optimally and sustainably. This study aims to determine the percentage level of utilization of Indian scad fish (Depterrus russeli) that landed at the Sibolga Nusantara Fisheries Port, North Sumatra. This research was conducted in March – April 2022. The method used in this research is the survey method. The type of data collected is secondary data. The data analysis used includes standardization of Indian scad fish fishing gear, sustainable potential and optimum effort, total allowable catch (TAC), utilization rate, and effort. From the research results, it was found that the highest production of Indian scad fish catches in 2019 was 6,392 tons. Based on the calculation of MSY and the optimum effort in 2017-2021 of 5,934.97 tons/year, meaning that the maximum catch of Indian scad fish that can be caught is 5,934.97 tons/year and the number of allowable catches is 4,747.98 tons/year or 80% of the maximum catch and utilization rate of Indian scad fish for 5 years is 81.41%.

Processing of automotive shredder residues: Economic evaluation of a process for energy and high-value metals recovery

Challenges in recycling heterogeneous waste remain untapped. Automotive shredder residue is one such heterogenous waste generated after processing End-of-Life Vehicles, making it difficult to process. There are two impediments to the recycling of ASR. One is the heterogeneity of the ASR (as received), and the other is not knowing what constituents to be extracted from the ASR. The ability of the thermochemical process to transform waste into beneficial products is well known. The objective of this work is based on a techno-economic evaluation of the recovery of energy and high-value metals from Automotive Shredder Residue. The equipment sizing and fabrication cost of each piece used in this process are calculated based on laboratory experiments. An integrated techno-economic study for processing heterogeneous waste ASR has not been studied in the literature previously. The economic evaluation was carried out assuming a plant life of 25 years. In addition, the plant's revenue was generated by the obtained products, and the payback period for energy and metal recovery was found to be 3 years respectively. The capital cost and operating cost for the ASR recycling plant with a combined approach of recovering energy and metals have been estimated from grass root stage. The outcome of this study confirms that ASR recycling has potential value for secondary resources and the process is economically viable. The resource recovery from ASR is an environmentally friendly technology where the maximum utilization rate is raised, along with energy saving and environmental protection by reduction of ASR waste in landfill.

Environmental and Economic Evaluation of Downflow Hanging Sponge Reactors for Treating High-Strength Organic Wastewater

This study evaluated the performance of a downflow hanging sponge (DHS) in reducing the concentrations of chemical oxygen demand (COD), ammonia (NH3), total suspended solids (TSS), and total dissolved solids (TDS) in high-strength organic wastewater (HSOW). The DHS unit was composed of three segments connected vertically and operated under different organic loading rates (OLRs) between 3.01 and 12.33 kg COD/m3sponge/d at a constant hydraulic retention time (HRT) of 3.6 h. The results demonstrated that the DHS system achieved COD, NH3, TSS, and TDS removal efficiencies of 88.34 ± 6.53%, 64.38 ± 4.37%, 88.13 ± 5.42%, and 20.83 ± 1.78% at an OLR of 3.01 kg COD/m3sponge/d, respectively. These removal efficiencies significantly (p < 0.05) dropped to 76.39 ± 6.58%, 36.59 ± 2.91%, 80.87 ± 5.71%, and 14.20 ± 1.07%, respectively, by increasing the OLR to 12.33 kg COD/m3sponge/d. The variation in COD experimental data was well described by the first-order (R2 = 0.927) and modified Stover–Kincannon models (R2 = 0.999), providing an organics removal constant (K1) = 27.39 1/d, a saturation value constant (KB) = 83.81 g/L/d, and a maximum utilization rate constant (Umax) = 76.92 g/L/d. Adding another DHS reactor in a secondary phase improved the final effluent quality, complying with most environmental regulation criteria except those related to TDS concentrations. Treating HSOW with two sequential DHS reactors was economically feasible, with total energy consumption of 0.14 kWh/m3 and an operating cost of about 7.07 USD/m3. Accordingly, using dual DHS/DHS units to remove organics and nitrogen pollutants from HSOW would be a promising and cost-efficient strategy. However, a tertiary treatment phase could be required to reduce the TDS concentrations.

Study on optimal operation conditions in the heating process of a crude oil single-disk floating roof tank: Insights from exergy transfer analysis method

Due to China’s high demand for foreign crude oil, reducing oil storage energy consumption has become the focus of national attention. In this paper, the mathematical model of the heating process of a single-disk floating roof tank is established. The variation law of the external exergy loss, internal exergy dissipation, exergy flow density and exergy transfer coefficient at different positions of the tank in the heating process are calculated and analysed. The obtained results show that the total exergy flow density is positively correlated with the coil temperature, the number of coil pipes and the diameter of the coil pipes. It is positively correlated with the tank level at the initial stage of heating. The exergy effective utilization rate is proposed to evaluate the energy consumption of the coil in the heating process of the storage tank. The obtained results show that the exergy effective utilization rate is negatively correlated with the liquid level and the temperature of the coil and positively correlated with the number and diameter of the coil, When the heating temperature is 100 °C, the maximum exergy effective utilization rate is 38.73 %.