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We show that all of the Sch\"{u}tzenberger complexes of an Adian inverse semigroup are finite if the Sch\"{u}tzenberger complex of every positive word is finite. This enables us to solve the word problem for certain classes of Adian inverse semigroups (and hence for the corresponding Adian semigroups and Adian groups).
In recent years, cyclists seem to be taking over the streets of the capital. Does this increased visibility really reflect a return of cycling in Brussels? How can we obtain an accurate understanding of the evolution of cycling? In this fact sheet, the authors explore the different sources and approaches which make it possible to quantify cycling i...
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... The study was conducted with the aid of exergy analysis which allows analyzing thermodynamic systems from effective view point. Various evaluations are carried out using several analyzes and tools of thermodynamics and thermochemistry [20,21]. The three chemical reactions of the proposed system are newly introduced to a thermochemical cycle and validated with simulations and previous studies. ...
Most thermochemical cycles require complex thermal processes at very high temperatures, which restrict the production and the use of hydrogen on a large scale. Recently, thermochemical cycles producing hydrogen at relatively low temperatures have been developed in order to be competitive with other kinds of energies, especially those of fossil origin. The low temperatures required by those cycles allow them to work with heats recovered by thermal, nuclear and solar power plants. In this work, a new thermochemical cycle is proposed. This cycle uses the chemical elements Magnesium-Chlorine (Mg-Cl) to dissociate the water molecule. The configuration consists of three chemical reactions or three physical steps and uses mainly thermal energy to achieve its objectives. The highest temperature of the process is that of the production of hydrochloric acid, HCl, estimated between 350-450℃. A thermodynamic analysis was performed according to the first and second laws by using Engineering Equation Solver (EES) software and the efficiency of the proposed cycle was found to be 12.7%. In order to improve the efficiency of this cycle and make it more competitive, an electro-thermochemical version should be studied.
... Thermochemical dissociation of HCl is an energy-intensive process and the reaction happens at high temperatures. The electrochemical process is a low temperature operation compared to thermochemical dissociation [28]. Anhydrous HCl electrolysis is considered in the MgCl cycle, which can be achieved with a voltage of about 1.6 V at 8 kA/m 2 [28]. ...
... The electrochemical process is a low temperature operation compared to thermochemical dissociation [28]. Anhydrous HCl electrolysis is considered in the MgCl cycle, which can be achieved with a voltage of about 1.6 V at 8 kA/m 2 [28]. ...
... A new version of the magnesium-chlorine cycle was proposed by Ozcan [28] with a four-step and lower temperature requirement as shown in Fig. 29. This cycle is denoted as MgCl-MgO-MgOHCl and requires a maximum temperature of 723K. ...
In this chapter, an overview of solar energy systems utilized for thermochemical energy conversing processes are presented, covering the information from fundamentals to advanced cycles and from applications to case studies. In addition, numerous thermochemical cycles are included for discussion and evaluation, and among these cycles, sulfur iodine, copper chlorine, and magnesium chlorine thermochemical cycles are selected for further analyses and assessments. The discussion proceeds from single-step thermochemical water-splitting processes, to two-step and multistep processes, followed by introduction of hybrid cycles. Furthermore, multiple processes for solar-to-useful commodities conversion are defined, illustrated, and discussed in this chapter. Moreover, two case studies using solar thermochemical cycles are presented for multigeneration purposes.
... Partial derivatives of the variables are calculated from a correlated equation obtained from experimental results which is a function of all variables. A generic open source code for the uncertainty analysis can be found in Ref. [22]. ...
In this paper, an experimental study is undertaken to capture HCl in dry form in order to decrease the power consumption of the four-step Mg-Cl cycle using MgO as the capturing agent. A new experimental method is developed to capture HCl from its mixture with steam, and liberate HCl in a dry form. Several cases are studied to observe HCl capture performance, including testing of the resulting substances in detail using Thermogravi-metric Analysis (TGA), and X-ray diffraction (XRD) tests. The results of these experiments show 30.8% HCl capture by solid MgO particles in a semi-batch packed bed reactor design with an uncertainty value of ±1.17%. The XRD results indicate that an optimum reactor temperature of ~275 C is critical to prevent the process from side reactions and undesired products. The experimental results are adapted to the four-step Mg-Cl cycle to form a final design with HCl capture.
... Thermodynamic assessment of three configurations of the cycle has been conducted by Ref. [11], and it is concluded that a four-step cycle can be a more feasible option than the three-step configurations. An experimental study is undertaken to capture HCl in dry form which leads to a modified four-step cycle with lower electrical energy consumption using dry HCl gas for the electrolysis step of the cycle [12,13], resulting in~30% HCl capture in dry form. The modified four-step cycle shows a higher thermodynamic performance than all other configurations and is more competitive with other hybrid cycles and conventional water electrolysis. ...
... Produced Cl 2 from both electrolysis steps are used to chlorinate the MgO gas in the chlorination reactor. The HCl capturing agent is selected to be MgO in the HCl capturing process and detailed information on the thermochemistry of this process is discussed elsewehere [13]. ...
... The purchase equipment costs (PEC) of the components are calculated based on Eq (13). In this equation Z k is defined for the k th component of the cycle, and it is calculated with various correlations which are defined in terms of their key parameters. ...
In this study, an exergy based economic assessment of the four step MgCl cycle is performed and compared with other hybrid thermochemical cycles. The exergy values of streams are utilized to analyse the cost rate of all streams and component based cost rates of exergy destructions. A multi-objective optimization of the cycle is conducted to maximize the performance and hence minimize the cost of the cycle by using Genetic Algorithm (GA). The results of exergoeconomic analyses for the base design of the MgCl cycle give energy and exergy efficiency values of 44.3% and 53%, respectively, an annual plant cost of $458.5 million, and a hydrogen production cost rate of 3.67 $/kg for a 172.8 tons of daily H2 production. The multi-objective optimization results indicate an increase in exergy efficiency (56.3%), and decrease in total annual plant cost ($409.3 million). The results of both thermodynamic and thermoeconomic analyses indicate that the final design of the MgCl cycle shows lower hydrogen cost results than that of the Hybrid-sulfur Cycle (HyS) and shows a similar trend with the hybrid CopperChlorine (CuCl) cycle.
... Mg-Cl cycle was initially proposed as a three-step process where no consideration of higher steam requirement for hydrolysis reaction has been made, which leads to aqueous HCl electrolysis (1.8 V) at higher voltage requirements than dry HCl electrolysis (1.4 V). Various configurations of the Mg-Cl cycle are represented in Table 1 (Ozcan andDincer, 2014a,b, 2015a,b). A newly developed four-step Mg-Cl cycle is proposed to decrease electrical work requirement of the cycle and make it a more feasible one, and compete with the conventional water electrolysis (Ozcan and Dincer, 2015c). ...
... Here, the four-step cycle also carries the potential to decrease the electrical work consumption further by considering an HCl capture process after hydrolysis (Ozcan, 2015). This process is also included in the analysis by making a simple assumption of 30% HCl capture from the separation process. ...
... The reactions in Eqs. (5) and (6) have been studied in Refs. [17,20] where a very good conversion can be succeeded at elevated temperatures with better reaction kinetics. ...
... Flowsheet of the Four-Step MgeCl cycle[5,6]. ...
... Aspen Plus flowsheet of the modified Four-Step MgeCl cycle[5,6]. ...
In this study, a new four-step Mg–Cl cycle is introduced as an alternative to the conventional three-step cycle in order to capture the HCl from the hydrolysis reaction in dry form and enhance the cycle performance. Instead of direct hydrolysis of MgCl2, an intermediate step is considered to produce MgOHCl from the hydrolysis reaction where this product is then decomposed into fine MgO and dry HCl in a decomposition reactor. A separation process after the hydrolysis step is also introduced to capture HCl gas in dry form. The heat requirements of all individual cycle components are evaluated and compared with the conventional Mg–Cl cycle. Decreasing electrical work consumption enhances the exergy efficiency of the cycle and makes it a more feasible one compared to water electrolysis and the three-step Mg–Cl cycle configuration. A successful dry HCl capturing process makes this cycle 13% more efficient than water electrolysis, in terms of electricity consumption, and thermodynamically more efficient than the existing three-step configuration.
Hydrogen production and liquefaction using solar thermo-electrochemical water splitting systems can as an effective method for long-term renewable energy source storage are suggested. In this paper, a novel integrated configuration for the cogeneration of liquid hydrogen and oxygen by magnesium-chlorine thermo-electrochemical water splitting cycle, hydrogen liquefaction unit, and solar dish collectors is developed. The novel integrated structure produces 7116 kg/h liquid hydrogen and 57597 kg/h oxygen. Through the magnesium-chlorine cycle, pure hydrogen is produced and the required energy is supplied through solar renewable energy based on the climatic conditions of Isfahan city in Iran. Then the produced hydrogen enters the liquefaction process to generate liquid hydrogen. The heat and power consumption of the whole system for the cogeneration of liquid hydrogen and oxygen are 207.9 MW and 373.9 MW, respectively. The heat waste of the integrated structure is used to produce hot water as a by-product. The specific power consumption of the liquefaction cycle is 7.6 kWh/kg LH2 and also the total thermal efficiency of the whole integrated system is 71.4%. Through the pinch method, heat exchanger networks related to multi-stream heat exchangers of the present system are extracted. Sensitivity analysis is used to investigate the effects of changes in major parameters including operating conditions of the thermo-electrochemical cycle as well as changes in the solar dish collector main parameters and the results are reported.
In this study, a solar thermal based integrated system with a supercritical-CO2 (sCO2) gas turbine (GT) cycle, a four-step Mg–Cl cycle and a five-stage hydrogen compression plant is developed, proposed for applications and analyzed thermodynamically. The solar data for the considered solar plant are taken for Greater Toronto Area (GTA) by considering both daily and yearly data. A molten salt storage is considered for the system in order to work without interruption when the sun is out. The power and heat from the solar and sCO2-GT subsystems are introduced to the Mg–Cl cycle to produce hydrogen at four consecutive steps. After the internal heat recovery is accomplished, the heating process at required temperature level is supplied by the heat exchanger of the solar plant. The hydrogen produced from the Mg–Cl cycle is compressed up to 700 bar by using a five-stage compression with intercooling and required compression power is compensated by the sCO2-GT cycle. The total energy and exergy inputs to the integrated system are found to be 1535 MW and 1454 MW, respectively, for a 1 kmol/s hydrogen producing plant. Both energy and exergy efficiencies of the overall system are calculated as 16.31% and 17.6%, respectively. When the energy and exergy loads of the receiver are taken into account as the main inputs, energy and exergy efficiencies become 25.1%, and 39.8%, respectively. The total exergy destruction within the system is found to be 1265 MW where the solar field contains almost 64% of the total irreversibility with a value of ∼811 MW.
