Investigating azeotropic separation of hydrochloric acid for optimizing the copper-chlorine thermochemical cycle

In this paper, an atmospheric-pressure distillation system is designed and constructed for partial to separation of hydrochloric acid and water. The system concentrates HCl(aq) between the electrolyzer and hydrolysis processes of the Copper–Chlorine (Cu–Cl) cycle for hydrogen production. The motivation behind this study is to investigate azeotropic separation of HCl(aq), as needed for integration of unit operations in the Cu–Cl cycle. The separation is only partial, as the mixture is unable to cross the azeotrope with only a single pressure. The distillation system consists primarily of one packed distillation column, which employs heating tapes and thermocouples to achieve a desired axial temperature profile. The column can be operated in batch or continuous mode. The distillate is H 2O(l) and the bottoms is HCl(aq) near the azeotropic concentration; feed concentrations are less than azeotrope. Thus, the degree of separation is determined to be independent of the feed concentration. The bottoms concentration varies from experiment to experiment, but does so independently of feed concentration, likely the result of corrosion impurities affecting the calculation of its concentration. It is found that HCl(aq) can be concentrated up to approximately 0.1068 mol/mol from an initial concentration of 0.0191 mol/mol. A simulation of pressure-swing distillation (PSD) is also performed, but due to safety constraints (a column operating at 10 atm must be certified to CSA B51), a single-pressure (single-column) distillation is physically performed. A single-pressure column is beneficial to the Cu–Cl cycle because it partially recycles HCl, which reduces the cost of the cycle, and still provides valuable results for analysis. The maximum HCl concentration achieved experimentally is 0.1068 mol/mol and the maximum HCl concentration determined from simulation is 0.11 mol/mol (the azeotropic concentration). The novelty of this research is that the experimental column built to study HCl partial separation is designed to be simple yet safe to integrate within the Cu–Cl cycle for hydrogen production.     

Multi-objective optimization of an experimental integrated thermochemical cycle of hydrogen production with an artificial neural network

In this study, an experimental lab-scale copper-chlorine (Cu–Cl) cycle of hydrogen production is examined and optimized in terms of exergy efficiency and operational costs of produced hydrogen. The integrated process is modeled and simulated in Aspen Plus incorporating the reaction kinetic parameters with a sensitivity analysis of a range of operating conditions. An artificial neural network (ANN) method with machine learning is used to generate a mathematical function that is optimized based on a multi-objective genetic algorithm (MOGA) method. A sensitivity analysis of variations of each design parameter for both the objective functions and the effectiveness of exergy performance relative to operational costs of produced hydrogen is demonstrated. The sensitivity analysis and optimization results are presented and discussed.     

干湿循环对土体级配分形特性影响分析

为分析粗粒土受水体干湿循环作用时颗粒级配演化规律,采用颗粒筛分试验统计干湿循环作用后土体颗粒粒径分布,引入颗粒质量-粒径分形模型计算粒径分形曲线(GFC)及分形维数(D),揭示了D随围压及干湿循环次数变化的规律,量化了干湿循环作用对粗粒土D的影响,并建立了计算方程。结果表明,等效替代缩尺法对GFC及D影响较小;制样及筛分过程导致D增大0.63%,室内试验方法引起粗粒土颗粒破碎效应不可忽略。低围压条件下(围压小于0.60MPa),D随围压增大及干湿循环次数增多而增大,剪切作用及水体干湿循环作用加剧了粗粒土颗粒破碎效应。所建粗粒土D计算模型为评价干湿循环对涉水工程填筑土体级配劣化效应提供了依据。     

Integrating superstructure-based design of molecules,processes, and flowsheets

The key to many chemical and energy conversion processes is the choice of the right molecule, for example, used as working fluid. However, the choice of the molecule is inherently coupled to the choice of the right process flowsheet. In this work, we integrate superstructure-based flowsheet design into the design of processes and molecules. The thermodynamic properties of the molecule are modeled by the PC-SAFT equation of state. Computer-aided molecular design enables considering the molecular structure as degree of freedom in the process optimization. To consider the process flowsheet as additional degree of freedom, a superstructure of the process is used. The method results in the optimal molecule, process, and flowsheet. We demonstrate the method for the design of an organic Rankine cycle considering flowsheet options for regeneration, reheating, and turbine bleeding. The presented method provides a user-friendly tool to solve the integrated design problem of processes, molecules, and process flowsheets.     

Nitrogen-doped carbon stabilized LiFe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries

Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices. Herein, we report an interface engineered LiFe_0.5Mn_0.5PO₄/rGO@C cathode material by the synergistic effects of rGO and polydopamine-derivedN-doped carbon. The well-distributed LiFe_0.5Mn_0.5PO₄ nanoparticles are tightly anchored on rGO nanosheet benefited by the coating of N-doped carbon layer. The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li⁺ transfer path. Meantime, the high-speed conducting network has been constructed by rGO and N-doped carbon, which exhibits the face-to-face contact with LiFe_0.5Mn_0.5PO₄ nanoparticles, guaranteeing the rapid electron transfer. These profits endow the LiFe_0.5Mn_0.5PO₄/rGO@C hybrids with a fast charge-discharge ability, e.g. a high reversible capacity of 105 mAh·g^-1 at 10 C, much higher than that of the LiFe_0.5Mn_0.5PO₄@C nanoparticles (46 mA·h·g^-1). Furthermore, a 90.8% capacity retention can be obtained even after cycling 500 times at 2 C. This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-powerLi-ion batteries.     

Study on an original cobalt-chlorine thermochemical cycle for nuclear hydrogen production

In this paper, a theoretical and experimental study on a novel cobalt-chlorine thermochemical cycle for hydrogen production is presented. The cobalt-chlorine cycle comprises a closed loop of four thermochemical reactions occurring at 700 °C that is a reaction temperature compatible with the present generation of high-temperature gas-cooled reactors. Firstly, a thermodynamic analysis was done for determining whether this cycle is attractive for hydrogen production in terms of both energy and exergy efficiencies. Following, proof-of-principle experiments were carried out at laboratory scale in a batch reactor at temperatures in the range from 550 °C to 950 °C and holding times between 1 h and 72 h. Experimental results complemented by the characterization of condensed compounds deposited on the reactor walls allowed confirm the reaction pathway of thermochemical reactions originally proposed, define the slowest step of the global process, and explain the beneficial effect of increasing the system pressure on the hydrogen yield. Even both performance assessment and proof-of-principle experimental results look like promising more research will be required in the future to confirm these preliminary findings. Finally, a modified version of the cobalt-chlorine cycle is proposed for enhancing the global kinetics, based on the experimental evidence found in the proof-of-principle tests.     

生活垃圾焚烧炉渣水稳定性试验研究

以福州红庙岭生活垃圾焚烧炉渣为试验对象,测试不同吸水时间和干湿循环次数下炉渣试件无侧限抗压强度和CBR的变化规律,揭示炉渣填料在水作用下的强度变化特征。结果表明:炉渣试件无侧限抗压强度和CBR随吸水时间和干湿循环次数的增加而增大,具有良好的水稳定性。炉渣的强度主要依靠水泥熟料和活性物质化学反应产生水化产物形成的,这使得炉渣在潮湿路基的回填、管槽周边的回填具有显著优势。     

A specific exergy costing assessment of the integrated copper-chlorine cycle for hydrogen production

In this study the specific exergy costing (SPECO) approach is employed on a four-step integrated thermochemical copper-chlorine (Cu Cl) cycle for hydrogen production for a second-law based assessment purposes. The Cu–Cl cycle is considered as one of the most environmentally benign and sustainable options of producing hydrogen and is thus investigated in this study due to its potential of ensuring zero greenhouse gas (GHG) emissions. Several conceptual Cu–Cl cycles have been exergoeconomically examined previously, however this study aims at investigating the four-step integrated Cu–Cl cycle developed at the Clean Energy Research Laboratory (CERL) at the Ontario Tech University thereby contributing to the thermo/exergoeconomic assessments of the thermochemical hydrogen production. In this study, the cycle is first thermodynamically modeled and simulated in a process simulation software (Aspen Plus) through exergy and energy approaches. The basic principles of the SPECO methodology are applied to the system and exergetic cost balances are performed for each cycle component. The exergetic costing of each cycle stream is then performed based on the cost balance equations. The purchased equipment cost and the hourly levelized capital cost rates for each cycle component is also obtained. The exergoeconomic factor, relative cost difference and exergy destruction cost rate for various cycle components are also evaluated. Moreover, the effect of several parameters on the total and hourly levelized capital cost rates is analyzed by performing a comprehensive sensitivity analysis. Based on the analysis, the exergy cost, the unit or specific exergy cost, and the unit costs of hydrogen are evaluated to be 6407.55 $/h, 0.042 $/MJ, and 4.94 $/kg respectively.     

Performance assessment of steam Rankine cycle and sCO2 Brayton cycle for waste heat recovery in a cement plant: A comparative study for supercritical fluids

The main objective of this study is to investigate the feasibility of a waste heat recovery (WHR) closed Brayton cycle (BC) working with supercritical carbon dioxide (sCO₂). For this aim, an actual WHR steam Rankine cycle (RC) in a cement plant was evaluated thermodynamically. After, a sCO₂-BC was theoretically adapted to the actual WHR system for the performance assessment. Both systems were analyzed comparatively in terms of energy and exergy. According to the results, the sCO₂-BC showed higher performance than the actual steam RC with a net electricity generation of 9363 kW where it was calculated as 8275 kW for the actual cycle. In addition, the energy efficiencies were found to be 27.6% and 24.18% where the exergy efficiencies were calculated as 58.22% and 51.39% for sCO₂-BC and steam RC, respectively. In the following part of the study, the closed BC was examined for different supercritical working fluids, namely, CO₂, pentafluoroethane (R125), fluoromethane (R41), and sulfur hexafluoride (SF6). Parametrical analyses were conducted to determine the effects of the system parameters such as turbine inlet temperature, compressor inlet temperature, and pressure ratio on the cycle performance. The simulation results of the comparative study showed that, among the supercritical fluids, the CO₂ demonstrated a higher performance for the closed BC with an energy efficiency of 27.9% followed by R41, SF6, and R125. As a result, the utilization of sCO₂-BC for WHR can be sustainably adapted and extended for environmentally friendly energy generation.