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A new configuration of solar energy-driven integrated system for ammonia synthesis and power generation is proposed in this study. A detailed dynamic analysis is conducted on the designed system to investigate its performance under different radiation intensities. The solar heliostat field is integrated to generate steam that is provided to the steam Rankine cycle for power generation. The significant amount of power produced is fed to the PEM electrolyser for hydrogen production after covering the system requirements. A pressure swing adsorption system is integrated with the system that separates nitrogen from the air. The produced hydrogen and nitrogen are employed to the cascaded ammonia production system to establish increased fractional conversions. Numerous parametric studies are conducted to investigate the significant parameters namely; incoming beam irradiance, power production using steam Rankine cycle, hydrogen and ammonia production and power production using TEGs and ORC. The maximum hydrogen and ammonia production flowrates are revealed in June for 17th hour as 5.85 mol/s and 1.38 mol/s and the maximum energetic and exergetic efficiencies are depicted by the month of November as 25.4% and 28.6% respectively. Moreover, the key findings using the comprehensive dynamic analysis are presented and discussed. • A new solar energy driven integrated system for ammonia synthesis is proposed. • A detailed modelling is conducted on the solar-assisted cascaded ammonia synthesis. • The additional heat from ammonia synthesis is recovered using thermoelectric generators. • Maximum H 2 and NH 3 flowrates are found in 17th hour of June as 5.85 and 1.38 mol/s. • Maximum energetic and exergetic efficiencies are found in Nov as 25.4% and 28.6%. [ABSTRACT FROM AUTHOR]

Abstract This paper examines the performance and viability of a cement slag waste heat recovery system combined with a thermochemical copper-chlorine cycle for hydrogen production combined with hydrogen compression and a reheat Rankine cycle. The waste heat from the cement slag is recovered as a heat source for high-temperature reactions in the copper-chlorine cycle. The clean hydrogen production from waste heat recovery is examined with respect to both energy and exergy efficiencies. The integrated system is simulated and modeled in Aspen Plus. The multigeneration system utilizes the industrial waste heat and significantly reduces operating costs from the waste heat recovery. The overall energy efficiency of the integrated system is obtained as 32.5% while the corresponding exergy efficiency becomes 31.8%. Highlights • A new approach for clean hydrogen production via waste heat recovery. • Hydrogen and electricity are the two major outputs of the designed system. • The compressed H 2 production rate of the system is 19.6 mol/s. • The system overall energy and exergy efficiencies are 32.5% and 31.8%, respectively. [ABSTRACT FROM AUTHOR]

Abstract The thermochemical Cu Cl cycle has received greater attention by numerous researchers during the past decade as a promising hydrogen production method because of some operational advantages. The present paper analyzes three different configurations of the Cu Cl thermochemical cycle, namely three, four and five step ones thermodynamically. Some comparative parametric studies are conducted in order to investigate the overall energy and exergy efficiencies of the cycles considered. The Aspen plus is the software tool employed for the modeling and simulation of the cycles. The energy and exergy efficiencies of the five-step CuCl cycle are found to be 38.8% and 70.2% while the three-step CuCl cycle has an energy efficiency of 39.6% and an exergy efficiency of 68.1%, respectively. On the other hand, the four-step CuCl cycle provides the highest energy and exergy efficiencies of 41.9% and 75.7%. A parametric study is also conducted to investigate the effect of varying ambient temperature on the exergy efficiencies of all three cycles. The present study results further reveal that the cycle performance can be enhanced by improving the thermal management and reducing the exergy destructions. Highlights • Comparative assessment of the three different Cu Cl cycles for hydrogen production. • Numerous factors for heat and work requirements, operating conditions and exergy destructions are considered for analysis. • Aspen plus software tool is employed for the simulations of the cycles. • Four-step CuCl cycle offers the highest energy and exergy efficiencies. [ABSTRACT FROM AUTHOR]

A novel multi-generation integrated energy system is presented in this paper, consisting of a gas-steam combined cycle, four-step thermochemical copper-chlorine (Cu Cl) cycle, proton exchange membrane fuel cell (PEMFC) and a reverse osmosis (RO) desalination unit. Effective thermal management of waste heat is recognized as a key objective in the steel industry. Hydrogen, electricity, fresh water and heat are the useful outputs of the integrated system. The produced electricity supplies the electricity load required by the electrolyzer, compressor and pumps while the supplementary electricity is an additional system product. Aspen Plus and Engineering Equation Solver (EES) are used for modeling and simulation of the multi-generation system. The overall hydrogen production rate of the designed system is 51.8 kg/hr and the net power production is 1.7 MW. The overall energy efficiency of the multi-generation system is 63.3% and the exergy efficiency is 58.8%. Further sensitivity studies and outcomes are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

A novel integrated system for the production of hydrogen at a high pressure utilizing steel furnace waste heat is presented and analyzed in this paper. The system utilizes a hybrid thermochemical copper-chlorine (Cu-Cl) cycle. This study integrates the industrial waste heat source with the thermochemical Cu-Cl cycle combined with a hydrogen compression system. The electrical energy required by the system is provided by a supporting Rankine cycle. The hydrogen compression system compresses hydrogen to a pressure of 750 bars. The integrated system is simulated with Aspen Plus software. Energy and exergy analyses are performed for the integrated system. Results from the simulations are presented and discussed. The overall energy efficiency is 38.2% and overall exergy efficiency is found to be 39.8%. [ABSTRACT FROM AUTHOR]

Although there has been the commercially employed and widely used Haber-Bosch ammonia synthesis process which requires the high operating pressure and temperature in addition to the relatively low conversion rates, there is a need for a more compact and modular, but more efficient and effective approach. In conjunction with this, the present study develops, tests and investigates a cascaded ammonia synthesis system to explore the room for improvement in the ammonia conversion efficiencies. A lab-scale prototype is developed to investigate the effect of cascading two ammonia synthesis reactors in series employing pre-reduced KMR catalyst and the experimental investigations revealed the improved ammonia synthesis rates using cascaded configuration. The scanning electron microscopy (SEM) results of the KMR catalyst are also presented at different magnifications of 2.00 kx and 50.0 kx. The Aspen Plus simulation results of the cascaded ammonia synthesis system have also been validated using the experimental results and validation shows the percentage difference ranging from 1.62–6.61%. The experimentally developed cascaded ammonia synthesis system is investigated under different operating temperatures and pressures. The experimental results revealed that the ammonia conversion efficiencies that range from 4.58–7.88% using the single reactor with pressure rise from 6 to 12 bar at the temperature of 370 °C, increase to the conversion efficiencies of 5.42–9.16% by employing cascaded ammonia synthesis design. [Display omitted] • A new concept of cascaded ammonia synthesis is developed experimentally. • The experimental system performance is investigated with and without cascading. • The SEM results of KMR catalyst are presented at 2.00kx and 50.0kx magnifications. • Pressure rise from 6 to 12 bar increased NH3 conversion efficiencies from 5.42–9.16%. • The validation showed the percentage difference ranging from 1.62–6.61%. [ABSTRACT FROM AUTHOR]

• A new configuration of environmentally benign ammonia synthesis is proposed. • Three different natural gas reforming types are incorporated into designed system. • The system yields 10 mol/s of H 2 and 2.4 mol/s of NH 3. • The overall system energetic and exergetic efficiencies are found to be 66.83% and 68.55%. A new configuration to convert the traditional ammonia synthesis plants into an environmentally benign process is proposed in this study. The proposed design is implemented by integrating three different types of natural gas reforming for clean hydrogen, methanol and ammonia synthesis. The solar heat source provides the absorption cooling unit with heat and natural gas reformers with steam. The CO 2 emissions released by the natural gas reforming configuration reacts with hydrogen for methanol synthesis. A pressure swing adsorption unit separates oxygen for natural gas autothermal reforming and nitrogen for ammonia synthesis. A part of hydrogen produced by the natural gas reforming unit is designed to pass through a double-stage ammonia production reactor for ammonia synthesis. The proposed configuration yields 10 mol/s of H 2 and 2.4 mol/s of NH 3. The overall system energetic and exergetic efficiencies are found to be 66.83% and 68.55%. The present system yields 13.31 mol/s of CH 3 OH and 625.9 kW of cooling. Moreover, numerous sensitivity analyses are conducted on the proposed configuration and its performance assessment. [ABSTRACT FROM AUTHOR]

Hydrogen is acknowledged as a potential fuel as it can be used as an energy carrier, a storage medium, in fuel cells and as a fuel as well and offers carbon-free solutions. This paper investigates three renewable energy based configurations for hydrogen production. The renewable energy sources considered in this study are solar PV, geothermal power generation and biomass gasification. The proposed study also presents a novel configuration of biomass gasification for hydrogen production via multistage water gas shift reactors. The solar PV and geothermal energy based hydrogen production systems are analysed employing the EES software while the hydrogen production system employing biomass gasification is simulated employing Aspen Plus. All three designed configurations are proceeded through numerous parametric analyses to investigate the system behavior and effect on system efficiencies. The hydrogen production using biomass gasification technique provides with the energetic and exergetic efficiencies of 53.6% and 49.8% and the efficiencies for the geothermal power generation based hydrogen production system are found to be 10.4% and 10.2% respectively. The exergetic and energetic efficiencies of hydrogen production system employing solar PV system are found to be 17.45% and 16.95%, respectively and the system is designed to produce 1.13 mol/s of hydrogen. Furthermore, the results of the parametric studies and sensitivity analyses are presented and discussed. • This paper investigates three renewable energy techniques for hydrogen production. • The considered renewable energy sources are solar PV, geothermal and biomass. • Biomass gasification offers energy and exergy efficiencies of 53.6% and 49.8%. • The energy and exergy efficiencies of geothermal hydrogen are 10.4% and 10.2%. • The exergy and energy efficiencies of solar PV based H 2 are 16.95% and 17.45%. [ABSTRACT FROM AUTHOR]

• Improvement capability of ammonia fuel cells tested with hydrogen inclusion. • Thermodynamic energy and exergy analyses performed with different fuel blends. • Energy efficiency rises by 7.9% with 40% hydrogen addition. • Exergy efficiency rises by 7.6% with 40% inclusion as compared to pure ammonia. In this study, hydrogen is investigated as a source of performance improvement for alkaline electrolyte entailing direct ammonia fuel cells via dual fuel utilization. Membrane electrolytes are utilized with anion exchange characteristics and the fuel cell performance is investigated with pure ammonia, ammonia-hydrogen blends and pure hydrogen. The power density is observed to be 1990.8 mW/m2 for pure ammonia fuel at peak point. However, this is found to increase to 2853 mW/m2 and 4471 mW/m2 when fuel blends of 80%NH 3 -20%H 2 and 60%NH 3 -40%H 2 are utilized respectively. The exergy efficiency at the maximum point power density increases from 14.2% to 22.1% and the energy efficiency rises from 15.2% to 22.8% as the fuel input is changed from pure ammonia to 60%NH 3 -40%H 2 by mass. Also, the highest exergy efficiency of 29.1% and energy efficiency of 28.7% is obtained for the pure hydrogen fueled cell. In addition, the exergy destruction rate is determined to be 16.8 mW for the pure ammonia fuel cell at the maximum point power density, which decreases to 15.1 mW and 13.6 mW for 60%NH 3 -40%H 2 and 80%NH 3 -20%H 2 fuels respectively. [ABSTRACT FROM AUTHOR]