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Thermal energy recovery of pyrometallurgy slags is a worldwide problem that is widely concerned for decades. As chemical recovery method, molten slag cascade recovery method (MS-WHCR) is proposed in this work. As typical endothermic chemical reactions, pyrolysis, gasification, calcination and reforming reactions are applied in this method. Gasification-pyrolysis system, calcination-pyrolysis system, enhanced pyrolysis system (R-SEP) and fixed carbon gasification and sorption-enhanced pyrolysis system (CG-SEP) systems of MS-WHCR method are designed. Based on the first law of thermodynamics and second law of thermodynamics, enthalpy-exergy compass analysis method is applied to analyze the exergy efficiency, consumption of reactants and products of designed MS-WHCR method, compared with traditional water quenched (WQ) method and gravity bed waste heat recovery (GWHR) method. As calculation example, 1000kg copper slag is used in this paper. The results showed that the exergy efficiency and exergy loss of WQ method are 20.7% and −947 MJ respectively. By WQ method, energy quality of molten copper slag is discounted. Copper slag particles should be fast cooled during granulation process. Thus, lots of air is blown in to make enough heat transfer with copper slag particles, which generate some exergy loss. And exergy efficiency of GWHR method is 76.9%. Using chemical endothermic reactions, MS-WHCR method improves the exergy efficiency of molten slag waste heat recovery. There is a slight fluctuation of exergy efficiency by MS-WHCR method for four kinds of systems from 66.6 to 70.1%. Fixed carbon and combustible syngas are acquired by MS-WHCR. And enhanced pyrolysis process in proposed R-SEP and CG-SEP systems improves hydrogen contents in syngas. [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]

Copper slag is a good valuable material resource with high iron content in the form of fayalite. Biomass as reduction reducer was proposed in this paper. For the basic research of the reduction in biomass, the biomass reducer was simplified as molding compound C, CO, H2 and CH4. The reactions of 2FeO·SiO2 with C, CO, H2 and CH4 could proceed spontaneously with the addition of CaO. The Gibbs free energy is decreased significantly by addition of CaO. The equilibrium compositions of products were calculated and analyzed combing with 19 basic reactions. Beginning temperature of C, CO, H2 and CH4 is 900, 623, 567 and 511 K, respectively The reduction degree of C, CH4, H2 and CO is 1, 0.851, 0.695 and 0.452, respectively, at 1773 K when the reducer addition ratio is 1.0 calculated by phase equilibrium calculating model. Direct reduction reaction of copper slag dominates at higher temperature, and temperature region of 700-1173 K is the transformational zone. Indirect reduction index curves are in the shape of reverse ‘S,’ and the higher temperature is in favor of indirect reduction in copper slag. There is a steady increase in reduction degree with the increase in reducer. Reduction reaction path of copper slag by C, CO, H2 and CH4 is established. [ABSTRACT FROM AUTHOR]

The combined CLG and CLHG is a novel technology for the co‐generation of syngas and H2‐riched gas. In CLG process, the reduction of oxygen carrier with biomass can produce syngas. In CLHG process, the oxidation of oxygen carrier with steam can produce H2‐riched gas. In this study, the Ce‐based oxygen carrier was selected as the candidate material based on the Gibbs free energy changes (ΔG) of the splitting water reactions. The redox mechanism of the Ce‐based oxygen carrier was discussed and thermodynamic analysis of syngas and hydrogen generation was performed by Gibbs free energy minimization method. The optimal O/C in the GR was determined as 0.6–0.8 and the total dry concentration of CO and H2 was higher than 95.0% under 850–1000°C. The optimal S/C in the SR was determined as 2–3 and the H2 fraction was higher than 70.0% under 850–1000°C. In the AR, all of the Ce oxides can be regenerated to CeO2 in the air flow of 0.5 kmol at 700°C. After one CLG–CLHG cycle, there was no carbon deposition on the surface of oxygen carrier. The redox mechanism of the Ce‐based oxygen carrier was defined as: CeO 2 ↔ CeO 1 . 83 ↔ CeO 1 . 72 ↔ Ce 2 O 3 . © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1132–1139, 2018 [ABSTRACT FROM AUTHOR]

Feasibility and energy analysis of chemical looping oxidative dehydrogenation of propane (CL-ODHP) process is performed by thermodynamic method. Results show that Mn2O3/MnO can be used for CL-ODHP, after one redox looping, about 100 kJ/mol energy can be generated. Energy analysis indicates that the process requires 8432.82 kJ/kgpropeneexternal fuel input at reaction temperatures with commercial propane conversion and propene selectivity. And process energy consumption decreases with decreasing of dehydrogenation and regeneration temperatures and increasing of propane conversion and propene selectivity. Recovering waste heat of hot streams from two reactors can cut by nearly 45% energy consumption of the process. [ABSTRACT FROM PUBLISHER]

At present, air cooling and water quenching are traditional treatment methods for molten copper slag. However, the waste heat and valuable metals cannot be recovered efficiently by these methods. Exergy efficiency (EE) of this method is only 21.0%. This paper describes a feasibility of waste heat recovery and direct reduction of copper slag. To investigate the feasibility of this new thermal energy recovery and direct reduction system (TER-DR), thermodynamic compass method was applied. Based on physical and chemical recovery methods, TER-DR1 and TER-DR2 systems are put forward. TER-DR1 system decreases the exergy loss (EXL) and improves the EE to 57.3%, and 0.489 t DRI is acquired for every ton of copper slag. Exergy of six kinds of typical endothermic chemical reactions was analyzed. The exergy of reforming reaction of CH4 by CO2 is the highest and suitable for TER-DR system. Combined with chemical method, TER-DR2 system decreases EXL further and improves the EE to 61.3%. Steam, synthesis gas and DRI are produced by this method. By TER-DR2, for every ton of copper slag, 0.489 t DRI, 67.3 m3 CO and 67.3 m3 H2 are acquired. [ABSTRACT FROM AUTHOR]

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]

The thermodynamic analysis of the sorption-enhanced steam reforming (SESR) process of bio-oil for hydrogen production was investigated in terms of equilibrium compositions, energy consumption, with the comparison with the conventional steam reforming (CSR) process. Compared to CSR process, the SESR process could obtain higher H 2 yield and concentration at lower temperature and S/C ratio, with both of the yield and concentration reaching over 90%. For decreasing the energy consumption, the sensible heat of the hot output streams from the two processes was recovered, with the recovered heat calculated by pinch analysis. To produce the same amount H 2 , the total energy demand of the SESR process was obviously lower the CSR process, especially under low temperature zone. Finally, the parameters of the two processes were optimized with a matrix analysis method. For SESR process, the optimal SR conditions were the temperature of 500 °C–600 °C, the S/C ratio of 3.0, under which the consumptions of bio-oil and energy were about 20% and about 30% lower than those under the optimal conditions of CSR process, respectively. [ABSTRACT FROM AUTHOR]

A novel process for producing hydrogen from raw coke oven gas (RCOG), via CO 2 sorption-enhanced steam reforming (SESR) was proposed in this paper, and was compared with a conventional steam reforming (CSR) process via thermodynamic analysis, in terms of equilibrium compositions, energy consumption and CO 2 emissions. The SESR process with CaO as CO 2 sorbent, can obtain over 4.0-fold H 2 amount amplification and over 95 vol% H 2 in the gaseous products after reforming, which were obviously higher than those in the CSR process, and meanwhile the corresponding optimal reforming temperature declined compared with that in CSR process. Although the SESR process has a unique desorbing reactor needing extra heat, its reforming reactor needs much less heat, resulting in the total demand energy was little different with and even lower than that of the CSR process. The SESR process also can convert the vast majority of carbon in RCOG into high-purity CO 2 gas as co-product, thus reducing CO 2 emissions obviously, compared to the CSR process and the conventional cleaning processes (CCPs). [ABSTRACT FROM AUTHOR]

The steam reforming processes of raw coke oven gas (RCOG) for hydrogen production without and with CO adsorption were studied via the thermodynamic analysis. Ordinary pressure (1 bar) was found as the best reaction pressure for RCOG steam reforming. The hydrogen yield increased with the increases in temperature and S/RCOG ratio and then flatted out around 160 mol per 100 mol RCOG at the temperature above 700 °C and S/RCOG ratio above 0.8, yet with hydrogen concentration of just about 70 %. After the addition of CaO as CO sorbent, the hydrogen yields increased on the whole as the CaO/C ratio and S/RCOG ratio rose, and the temperature range with the hydrogen yield around 160 mol and even higher was widened and moved to low temperature. The optimal conditions of sorption-enhanced RCOG steam reforming for hydrogen production were S/RCOG ratio above 0.8, CaO/C ratio above 2.0 and the temperature from 550 to 700 °C, with the hydrogen yield and concentration reaching around 160 mol and over 90 %, respectively. [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]

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]

Chemical looping air separation (CLAS) is based on the chemical looping principle: oxygen carriers release oxygen to carrier gas in a reduction reactor and absorb oxygen from air in an oxidation reactor. High oxygen transport capacity, high reactivity in reduction and oxidation reactions, and resistance to attrition and agglomeration are some of the criteria that feasible oxygen carrier materials should fulfill. Thermodynamic analysis was applied to prove the potential of Co3O4 as oxygen carrier. ZrO2 served as binder to improve the anti-sintering property and reactivity. Kinetic experiments were performed to determine the reaction rate and conversion of the oxygen carrier. Stability and durability of the oxygen carrier were characterized before and after cyclic experiments. The Co/Zr oxygen carrier proved to be a suitable candidate for the CLAS process. [ABSTRACT FROM AUTHOR]

Chemical looping air separation (CLAS), based on the chemical looping principle, is a novel and energy-efficient method to separate oxygen from air. The oxygen carriers used capture oxygen from air in an oxidation reactor and release oxygen in a reduction reactor. In this work, the adaptability of Cu/Zr oxygen carrier used for CLAS was investigated through thermodynamic analysis and experimental methods. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to measure the phases and surface morphology of oxygen carriers before and after experiments. The results show that CuO has the capability of releasing oxygen when the temperature is higher than 725 °C in the nitrogen atmosphere, and the minimum oxygen reduction temperatures increase with the increasing of oxygen concentrations. The Cu/Zr oxygen carrier has high oxygen reduction and oxidation rates when temperature is higher than a certain values. For reduction, the value is about 860 °C. For oxidation, the value is about 500 °C. The reactivity of oxygen carrier increases significantly with the temperature increasing. On overall, reactivity of oxygen carrier has little difference under different particle sizes. The oxygen carrier exhibits a stable oxygen reduction and oxidation behavior during reduction-oxidation cycles. XRD patterns show that the main phases in reduced samples are CuO and ZrO. The main phases in fresh and oxidized samples are CuO and ZrO. SEM images show that the fresh and reacted oxygen carriers are porous. The surface of reacted samples is smoother than fresh samples and no agglomeration has been found. [ABSTRACT FROM AUTHOR]

Chemical looping air separation (CLAS) has been suggested as a new and energy saving method for producing oxygen from air. The selection of suitable oxygen carriers is the key issue for CLAS system. This paper shows a comprehensive thermodynamic method for selecting oxygen carriers used for CLAS through studying the properties of 34 different oxygen releasing reactions referring to 18 elements at different temperatures. The research mainly includes analysis of oxygen releasing capacity by calculating the Gibbs free energy change (Δ G) and the equilibrium partial pressure of oxygen of the reduction or oxidation reaction at different temperatures. Oxygen content and transport capacity were calculated. The spontaneous reaction temperatures for oxygen releasing reactions were presented to determine the operating temperatures. Also, the minimum demand of the steam for the reduction reaction was discussed. On the basis of the comprehensive thermodynamic study, the oxide systems of CrO/CrO, PbO/PbO, PbO/PbO, PbO/PbO, MnO/MnO, and AgO/Ag have been found suitable for the CLAS process in low temperatures (500-800 K). The systems of PdO/PdO, PdO/Pd, PdO/Pd, MnO/MnO, and MnO/MnO were suitable for medium temperatures (800-1100 K) CLAS process. And CoO/CoO, CuO/CuO, MnO/MnO, and OsO/Os systems only worked successfully in high temperatures (1100-1400 K). In addition, the CaO/CaO system was not suitable for CLAS because of the reaction with steam. The various binders such as SiO, TiO, AlO, YO, ZrO, and YSZ which have been used for CLC could also be the supports for CLAS oxygen carriers. [ABSTRACT FROM AUTHOR]

• The Cu-Mn composite oxygen carrier with relatively low reaction temperature is constructed. • The reactivity and oxygen transport capacity of this oxygen carrier are determined. • The thermodynamic data including Δ G and K p of the redox reaction are obtained. • The redox kinetic models of the Cu-Mn composite oxygen carrier were established. The further development of the chemical-looping air separation (CLAS) technology is hindered by the required high redox temperature. Improving the thermodynamic properties of oxides by elemental composition is an effective way to decrease the reduction temperature of oxygen carrier. In this paper, a Cu-Mn composite oxygen carrier was prepared by the addition of Mn 2 O 3 to CuO, with Cu x Mn 3− x O 4 as the active phase, and the oxygen uncoupling properties of the Cu-Mn/Zr composite oxygen carrier were investigated, focusing on the redox reactivity under different oxygen concentrations of Cu x Mn 3− x O 4 ⇋ Cu x Mn 2− x + O 2 (g). The oxygen transport capacity of this type of oxygen carrier was determined as 0.0463 g O 2 /g oxygen carrier. With an increase in the oxygen concentration (0.001–50%) in the carrier gas, the required oxygen uncoupling temperature increases (625.5–921 °C). Based on relationship between initial reduction temperature and equilibrium oxygen concentration, the following thermodynamic characteristics of the redox reaction were obtained: ΔG = –0.119 T + 150.41 kJ/mol and K p = exp(14.31–18090.8/ T). Compared to a Cu-based oxygen carrier, the reduction temperature is significantly reduced and the equilibrium oxygen concentration at the same reaction temperature is greatly increased. The redox reactivity under different heating rates and reaction temperatures were also investigated, and the results show that both the reduction and oxidation reactions are temperature driven at the considered temperatures. The reduction and oxidation kinetic models were established by the iso -conversional method. When the relative conversion X < 0.5, the reduction of the Cu-Mn oxygen carrier follows a shrinking core model (n = 3), and the oxidation follows a shrinking core model (n = 2). When X ≥ 0.5, the reduction proceeds according to a one-dimensional diffusion model, whereas the oxidation follows a shrinking core model (n = 3). [ABSTRACT FROM AUTHOR]