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The demand for NH 3 as a new energy carrier will lead to a gradual increase in its production. The Haber-Bosch process, commonly used today, has high energy consumption, high operating pressure and high CO 2 emissions due to hydrogen extraction from fossil fuels. For efficient and environmentally friendly preparation of NH 3 , chemical looping ammonia generation (CLAG) of biomass and H 2 O is proposed. The selection of suitable nitrogen carriers is the key in CLAG. Since the variety of available substances is large, a systematic method is needed to perform screening efficiently. In this paper, 28 different oxide/nitride pairs were investigated. We mainly investigated the Gibbs free energy change and the equilibrium compositions in the N-absorption and N-desorption reactions. Suitable nitrogen carriers were selected by the minimum N-absorption temperature, nitrogen transport capacity, sintering resistance, price and by-product. When Al 2 O 3 /AlN was used as the nitrogen carrier, the minimum N-absorption temperature was 1371 °C, and the nitrogen transfer capacity was high. When TiO 2 /TiN was used as a nitrogen carrier, the minimum N-absorption temperature was 966 °C, the nitrogen transfer capacity was lower than Al 2 O 3 /AlN, and NH 3 and H 2 were generated simultaneously in the N-desorption step. Compared with SiO 2 /Si 3 N 4 , Cr 2 O 3 /Cr 2 N, Cr 2 O 3 /CrN, MnO/Mn 5 N 2 , Fe 2 O 3 /Fe 4 N, ZrO 2 /ZrN, and MoO 2 /Mo 2 N, Al 2 O 3 /AlN and TiO 2 /TiN produced less carbide in N-absorption step and had less mass decay in the cycle, making them more suitable as nitrogen carriers. Appropriately increasing the molar ratio of nitrogen carrier to carbon can improve feedstock utilization and the efficiency of CLAG. • Al 2 O 3 /AlN and TiO 2 /TiN were suitable nitrogen carriers for CLAG. • Increasing temperature and pressure can promote the N-absorption reaction. • Efficiency was improved as the molar ratio of nitrogen carrier to carbon increased appropriately. [ABSTRACT FROM AUTHOR]

In order to recover the waste heat of aluminum dross and carbon resource in carbon residue, the waste heat recovery process of aluminum dross by coupling of physical and chemical method was proposed. In this process, waste heat in the high-temperature range was recovered by carbon residue gasification reaction and waste heat in the low-temperature range was recovered by physical method (PM). Enthalpy and exergy analysis of PM and physical–chemical coupling method (PCCM) processing the aluminum dross was performed by thermodynamic compass method. Sensible heat of aluminum dross can be recovered by PM, but exergy efficiency is 20.4%. And the exergy loss (EXL) is 429 MJ. A lot of hot water is produced by this method, but the use of hot water is limited. The exergy efficiency for PCCM is 38.4% in System 2(a) and 51.2% in System 2(b), respectively. Compared with the PM, the EXL of PCCM is lower, and the exergy efficiency is higher. Each ton of aluminum dross can produce 47.11 m3 CO. in System 2(a) and Each ton of aluminum dross can produce 56.88 m3 CO and H2 in System 2(b). The carbon resources in carbon residue are effectively utilized. Comparing with the energy level of chemical reaction, the influence of specific temperature for exergy efficiency is more significant during the physical–chemical coupling of waste heat recovery process. [ABSTRACT FROM AUTHOR]

As a renewable resource of reducer, biochar prepared by pine sawdust is proposed for direct reduction of copper slag in this paper. Combined with thermodynamic analysis, effects of reduction time, temperature and CaO addition ratio on solid copper slag reduction characteristics are discussed. The oxides of iron in copper slag are Fe3O4 and 2FeO·SiO2. The reduction processes were carried out step by step for Fe3O4 and 2FeO·SiO2, respectively: Fe3O4 → FeO → Fe and 2FeO·SiO2 → Fe. The porous structure of biochar exhibits higher reduction reactivity and reaction rate than that of coal. CaO reduced the Gibbs free energy of reduction reactions and facilitated the reduction of 2FeO·SiO2 with C and CO. When CaO was added, separation reaction of FeO and SiO2 took place and α-SiO2 and β-SiO2 were produced. When the addition ratio of CaO is above 0.3, CaO·SiO2 and 2CaO·SiO2 are produced. The reduction process of copper slag was established as follows: (a) dehydration and fast pyrolysis; (b) reduction of iron oxides by C and CO; and (c) sweating metallic iron outflows from cracks in pellet. Besides, direct reduction reaction mechanism and transport process of Cu are established based on reduction experiments, XRD and SEM-EDS analysis. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of nitrogen oxides with loaded urea is a novel method for removing NO under excess oxygen and low temperature conditions. In present work, a comprehensive thermodynamic study for NO removal is executed based on the Gibbs free energy change. This research mainly includes the detailed analyses of NO removal mechanism, the feasibility analyses for manganese as the active element and the experimental study for synthesized manganese-based catalyst (preparation, characterization and performance test). The catalyst in present study can reach 82% NO conversion and near 98% N2 selectivity at 50 °C, which validates the correctness of the thermodynamic calculations. [ABSTRACT FROM AUTHOR]

The energy and exergy assessments of the dehydrogenation of propane for propene production process were performed. The results show that when the reaction temperature rises from 400°C to 1000°C, the range of inlet and outlet exergy is 2268∼2376 and 2265∼2341 kJ/mol C3H6, respectively, and the range of exergy destruction is 6.31∼33.24, 9.93∼35.15 and 3.59∼31.99 kJ/mol C3H6at 5, 25 and 45°C reference environment temperature, respectively. The range of exergy efficiency at discussed reference environment and reaction temperature is 98.52∼99.84%, and decreases with the increasing of reaction temperature and increases with the decreasing of reference environment. [ABSTRACT FROM PUBLISHER]

The CaO-based chemical looping gasification (CaO-based CLG) of biomass was considered as a potential technology to improve hydrogen-enriched syngas production and capture in situ CO2 effectively. Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for CaO-based CLG to produce hydrogen-enriched syngas. The analysis was conducted to investigate the effects of different operation parameters [including CaO/C ratio (0–3.0), pressure (0.1–5.0 MPa), gasification temperature (600–700 °C) and S/C ratio (0.5–3.0)] on hydrogen fraction, syngas yield, gas LHV and in situ CO2 capture efficiency. The results suggested that the preferential conditions for producing hydrogen-enriched syngas in CaO-based CLG were achieved at 600 °C, atmospheric pressure, S/C ratio of 2.0 and CaO/C ratio of 2.0. CaO-based could capture in situ CO2 effectively and the capture efficiency reached 92.6%. Under these optimal operation parameters, the hydrogen fraction, gas yield and gas LHV reached 98.5%, 1.87 mol molC−1 and 10.7 MJ Nm−3, respectively. Ultimately, the heat and mass balance of gasification was obtained at the optimal operation conditions, and gasifier did not need any external heating except from the heat carried by CaO. [ABSTRACT FROM AUTHOR]

Chemical looping gasification (CLG) is a novel technology to convert carbon-containing feedstock into syngas. In the technology, lattice oxygen of oxygen carrier is used as oxygen source for char gasification, and then the reduced oxygen carrier is regenerated in air atmosphere. In this paper, the mechanism of CLG of biomass using Mn 2 O 3 as oxygen carrier was discussed firstly and then thermodynamic analysis of syngas generation from biomass was performed by Gibbs free energy minimization method. Chemical equilibrium calculations were carried out to study the effects of Mn 2 O 3 /biomass, operation temperature, pressure, and steam/Mn 2 O 3 on the gasification characteristics. The optimal thermodynamic conditions were determined to improve H 2 and CO concentrations as high as possible. The optimal Mn 2 O 3 /corn cob is 0.18 to obtain the highest CO and H 2 yields. The results suggest that the preferential conditions are achieved at 1000 °C and atmospheric pressure, under these conditions, the total dry concentration of CO and H 2 is 98.8% in the syngas. Steam can be used in the CLG to modify the H 2 /CO in the syngas. The carbon conversion also increases under oxidizing atmosphere of steam. [ABSTRACT FROM AUTHOR]

In this paper, a thermodynamic analysis of the synergistic coal/CO 2 /H 2 O gasification process with BFS (blast furnace slag) as heat carrier was performed using the Gibbs free energy minimization approach through Lagrange multiplier method. The effect of temperature, pressure and C/CO 2 /H 2 O were investigated. Carbon, CO 2 and H 2 O conversion, H 2 and CO yield, and H 2 /CO ratio were used to characterize the synergistic gasification performance. The results showed that the atmospheric pressure was preferable for coal gasification and the increasing of temperature caused the increase in carbon conversion and syngas production. The optimal temperature of the synergistic gasification was 800–900 °C. Not only did it ensure the coal gasification reaction completely, but also it recovered the BFS waste heat effectively. The results clearly showed that the addition of H 2 O and CO 2 could lead to the reduction of the carbon residue and increase of the production of H 2 and CO, respectively. Meanwhile, it was beneficial to reduce the waste heat using to heating extra steam and enhance the coal/CO 2 gasification reaction rate by controlling the addition of CO 2 and H 2 O reasonably. Moreover, the production syngas application was also investigated by changing the relative CO 2 /C ratio and H 2 O/C ratio in the feed to modify the H 2 /CO ratio. [ABSTRACT FROM AUTHOR]

This article presented a model for the system of coal gasification with steam and blast furnace slag waste heat recovery by using the ASPEN Plus as the simulating and modeling tool. Constrained by mass and energy balance for the entire system, the model included the gasifier used to product syngas at the chemical equilibrium based on the Gibbs free energy minimization approach and the boiler used to recover the heat of the blast furnace slag (BF slag) and syngas. Two parameters of temperature and steam to coal ratio (S/C) were considered to account for their impacts on the Datong coal (DT coal) gasification process. The carbon gasification efficiency (CE), cold gasification efficiency (CGE), syngas product efficiency (PE) and the heating value of syngas produced by 1 kg pulverized coal (HV) were adopted as the indicators to examine the gasification performance. The optimal operating temperature and S/C were 800 °C and 1.5, respectively. At this condition, CE reached above 90% and the maximum values of the CGE, PE and HV were all obtained. Under the optimal operating conditions, 1000 kg/min BF slag, about 40.41 kg/min DT pulverized coal and 77.94 kg/min steam were fed into the gasifier and approximate 6.64 kmol/min syngas could be generated. Overall, the coal was converted to clean syngas by gasification reaction and the BF slag waste heat was also recovered effectively (reached up to 83.08%) in this system, achieving the objective of energy saving and emission reduction. [ABSTRACT FROM AUTHOR]

Through thermodynamic analysis, the CO2 sorbent(s) used in the steam reforming process of ethanol as the model compounds of bio-oil was selected from nine common metal oxides. Among them, calcium oxide shows the best CO2 adsorption capacity in the condition of the co-existence of CO2 and H2O in the temperature zone (600-1100 K) where ethanol steam reforming can obtain a higher hydrogen yield, and its carbonate (CaCO3) can easily decompose at slightly higher temperature. Compared to the ethanol steam reforming process with the addition of no any sorbent, the hydrogen yield and purity in the process with CaO as a sorbent were obviously improved, and the temperature range of more than 90% hydrogen yield is widened from 860-1010 K to 705-1085 K. Before the sorbent addition, the maximum hydrogen concentration appear at over 750 K, yet just around 74%, but the hydrogen concentration can overtake 90% in the range of 590-935 K after the addition of CaO. With thermogravimetric analysis, CaO from calcinated calcium acetate shows the highest CO2 adsorption capacity and the best cycle stability, as compared to the other two kinds of CaO, with analytical pure and from calcinated calcium hydroxide. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 1208-1214, 2015 [ABSTRACT FROM AUTHOR]

With the minimization of the Gibb's free energy, the thermodynamical analysis of the steam reforming processes for the four typical model compounds (ethanol, acetic acid, acetone, and phenol) of bio-oil was systematically performed. In the steam reforming process, the four model compounds can be completely converted. The higher hydrogen yields of the four compounds were obtained via steam reforming than via thermal decomposition. The hydrogen yields first increased and then remained constant and even decreased with temperature, monotonically decreased with the pressure increase, and obviously increased with the steam to carbon ratio. As the steam to carbon ratio rose, the temperatures of the maximum hydrogen yields move afterward to low temperature. When the S/C ratio was 6, the increase rate of hydrogen was decreased. In the co-existence of CaO/CO2/H2O, the reaction between CaO and CO2 was dominant to the reaction between CaO and H2O. By adding CaO, a CO2 sorbent in the steam reforming system, both the yields and the concentration of hydrogen were obviously more pronounced than the processes without CaO. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1008-1016, 2014 [ABSTRACT FROM AUTHOR]

• Diatomite is more suitable than SiC and zeolite molecular sieve as the carrier of Mn-based desulfurizer. • Mn4D6 sorbent has the highest sulfur capacity of 186 mg-SO 2 /g sorbent. • Valuable pure SO 2 and elemental sulfur are recycled in the regeneration process. • The mechanism of desulfurization-regeneration cycle for Mn4D6 is elaborated. An energy-saving isothermal chemical-looping system was proposed to remove SO 2 from flue gas choosing manganese oxide as the active component. To investigate the effect of pore structure on the desulfurization performance, desulfurizers were prepared via the sol-gel method with 60 wt% silicon carbide, diatomite and zeolite molecular sieves as the support material. Mn4Z6 had the largest specific surface area but lower desulfurization efficiency, resulting from the blocking and collapse of original channel in the desulfurization process. Mn4D6 exhibited the highest SO 2 removal efficiency, benefiting from the nanoscale oval crystalline phases, staggered micropores and stable frame structure. A better desulfurization performance with the sulfur capacity of 186 mg-SO 2 /g-sorbent was obtained by operating at 620 °C with the SO 2 concentration of 800 ppm and space velocity of 7500 h−1. After five desulfurization-regeneration cycles, 72% of the initial sulfur capacity was retained, revealing the high durability of Mn4D6. The hazardous flue gas was purified in the desulfurization process and valuable pure SO 2 and elemental sulfur could be recycled in the regeneration process. Furthermore, the mechanism of desulfurization-regeneration cycle was elaborated for the first time. Present investigation suggested that Mn4D6 operated at the isothermal chemical-looping system can be a potential candidate for flue gas desulfurization and recycling high value-added byproducts. [ABSTRACT FROM AUTHOR]

Blast furnace slag, a main by-product of ironmaking process, contained high-quality sensible heat, accounting for almost 30 % of total energy consumption in iron and steel industry. This paper proposed CO 2 coal gasification method aimed at recovering waste heat from blast furnace slag. Based on Gibbs free energy minimization, influence of temperature, CO 2 /C, pressure and steam were investigated. Under optimal operating conditions at 1023–1198 K, CO 2 /C of 1.5–2.0 and atmospheric pressure, total amount of syngas was 2.78 kmol, with 67.1 % CO and 8.79 % H 2. Addition of steam could adjust compositions of syngas. H 2 /CO of syngas reached 1.0, 1.5 and 2.0 when H 2 O(g)/CO 2 were 1.45/0.55, 1.73/0.27 and 1.95/0.05, which could be used as organic raw materials for chemical industry. Meanwhile, energy and exergy efficiencies of coal gasification were found to be 63.84 % and 62.58 %, respectively, under optimal operating conditions. For different syngas products, when H 2 O(g)/CO 2 was 1.95/0.05, exergy loss was the lowest, with internal and external exergy loss amounting to 31.80 % and 2.16 % respectively. These works provided theoretical guidance on use of the coal gasification reaction for recovering waste heat from blast furnace slag and contributed to the achievement of the strategic goal of CO 2 energy saving and emission reduction. [Display omitted] • A novel resource utilization method of the blast furnace slag was proposed. • The optimal operation conditions for gasification reactions were determined. • The energy and exergy destruction and distribution of the technology were analyzed. • The energy and exergy efficiencies were 63.84 % and 62.58 %, respectively. • By adjusting the addition of steam, different synthesis gas products could be obtained. [ABSTRACT FROM AUTHOR]

Combined steam/dry reforming of bio-oil with blast furnace slag as heat carrier for the syngas production with the H 2 /CO ratio of 3:1 for further methanation, was investigated. The increase of H 2 O addition can increase the total yield of H 2 and CO, but also increase the critical temperature at which 3:1-H 2 /CO syngas was obtained, while the increase of CO 2 addition can decrease the critical temperature, but the syngas yield was also decreased. When the steam/carbon (S/C) ratio was 3.0 and the CO 2 /carbon (CO 2 /C) ratio was 0.5, the critical temperature decreased to 804 °C, with the potential H 2 yield of over 90%. Although the addition of slag and how much slag to be added had almost no any thermodynamic effect on the combined reforming of bio-oil under the condition where higher potential H 2 yield can be obtained, the slag as heat carrier could supply all heat for the combined reforming process. When the added slag mass was 3.99 times bio-oil mass, the combined reforming at the S/C ratio of 3.0 and the CO 2 /C ratio of 0.5 can occur spontaneously for the production of 3:1-H 2 /CO syngas. The present study could offer important guidance toward utilization of this novel process for further methanation. • Combined steam/dry reforming for syngas production and further methanation. • BF slag as heat carrier supplies all the heat for the bio-oil reforming process. • Low consumptions of feedstock and energy were pursued. [ABSTRACT FROM AUTHOR]