•Using biomass CO2-gasification to recover heat from granulated blast furnace slag was proposed.•The effects of heating rate and blast furnace slag on the biomass char CO2-gasification reaction were investigated.•The novel two-step method firstly used to obtain kinetic parameters.•The kinetic equations of biomass char CO2-gasification reaction within granulated BFS were established.The reactions of biomass char CO2-gasification within granulated blast furnace slag (BFS) were systematically conducted by the non-isothermal program using a thermogravimetric analyzer. At the same time during reaction proceeded, the conversion of biomass char CO2-gasification reaction increased with the increasing heating rate. However, at the same temperature during reaction proceeded, the conversion of biomass char CO2-gasification reaction decreased with the increasing heating rate. The granulated BFS could be used as a catalyst in the biomass char CO2-gasification reaction and its catalytic effect became more obvious with the increasing content of BFS in the mixture. The A4 model (nuclei production (m = 4) model) selected through the novel two-step method firstly proposed in the study was the best match with all the gasification reactions. The activation energy was from 52.75 kJ/mol to 64.42 kJ/mol and was lower with the increase of heating rate and the content of BFS in the mixture. The kinetic equations of biomass char CO2-gasification reaction within granulated BFS were developed through the selected model and calculated kinetic parameters.

Selective catalytic reduction of nitrogen oxides with carbonic oxide (CO-SCR) has been suggested as an attractive and promising method for removing NO and CO simultaneously from flue gas. Nevertheless, the presence of oxygen has an inhibitory effect on the catalytic reaction. Based on CO-SCR on a urea modified metal oxide catalyst, a novel method was proposed to achieve NO and CO removal under oxygen-rich conditions via heterogeneous catalysis (CO-SCR, CO oxidation and urea-SCR). The selection of suitable active metal elements for catalysts is the pivotal issue in present research. This paper shows a comprehensive thermodynamic study for screening active metals through studying the properties of 28 different metal oxide reduction reactions and 11 different oxidation reactions at different temperatures referring to 20 preselected elements. This research mainly includes thermodynamic equilibrium calculations at different oxygen concentrations, detailed analyses of the NO and CO removal mechanism and thermodynamic screening of active metal elements based on the Gibbs free energy change (ΔG) at different temperatures. On the basis of the systematic thermodynamic study, the metal elements Mn, Cu, Pb and V have been selected as suitable for removing NO and CO from flue gas at low temperatures (50–120 °C).

Thermo gravimetric analysis experiments were carried out on pyrolysis of three kinds of biomasses by temperature programming method. Employed by thermogravimetric analyzer, the effects of the type of biomass and the ratio of copper slag addition on pyrolysis were studied. Biomass pyrolysis process can be divided into four stages, dehydration, pre-pyrolysis, pyrolysis and carbonization. The experimental yields in this paper were modeled by CH4, C2H6, C3H8, C2H4 and C3H6, considering first-order primary reaction and reactions of alkanes and alkenes. Copper slag is beneficial for biomass pyrolysis. With Coats–Redfern method, nonlinear regression of biomass catalytic pyrolysis showed that reaction mechanism of pyrolysis process confirms well with shrinking core model (A3). The kinetic parameters and equations were also calculated. Copper slag promotes both the primary reactions of biomass pyrolysis and the Cracking reactions of alkanes and alkenes, but it cannot decrease the activation energy effectively.

•The CO2 desorption kinetics based on thermal analysis was investigated.•The CO2 desorption mechanism function is described by Avrami-Eroféev model.•The artificial isokinetic relationships for CO2 desorption process obtain by combination approach.The CO2 desorption kinetics of waste ion-exchange resin-based activated carbons was analyzed by model-fitting and model-free approaches using thermogravimetric analysis. A non-isothermal method was applied in the temperature range of 303–393 K with different heating rates. The experiments were performed under two different inlet CO2 concentrations. The experimental results showed that the extent of conversion of desorption is independent of inlet CO2 concentration during the adsorption process. At the range of 0.2 ≤ α ≤ 0.7, CO2 desorption on chemically activated carbon is complex, while physically activated carbon is simple. The kinetic models comply with Avrami-Eroféev models. The obtained artificial isokinetic temperatures lie in the region of the experimental temperatures, indicating that the reaction model for conversion 0.2 ≤ α ≤ 0.7 remains a proper choice. On the basis of the experimental results, the thermal analysis method can be used successfully in projecting CO2 desorption.Download high-res image (128KB)Download full-size image

•The kinetics of CO2 adsorption/desorption were studied by isothermal thermal analysis.•The adsorption and desorption kinetic models both follow Avrami-Eroféev model.•The activation energy of adsorption is negative, while desorption is positive.•Considering capacity and kinetics, CA is more suitable for CO2 adsorption than PA.This paper is first to investigate the kinetics of CO2 adsorption and desorption on waste ion-exchange resin-based activated carbons by the isothermal thermal analysis method. Not only the application of isothermal thermal analysis is expanded, but also a new method for study the kinetics of CO2 adsorption and desorption is provided in this paper. CO2 adsorption kinetics following Avrami-Eroféev model is A3/2 on chemically activated carbon (CA) and physically activated carbon (PA). The values of activation energy (E) of CA and PA are negative, and the absolute values of activation energy (E) reduce with the increase of CO2 concentration. Desorption kinetics also follow Avrami-Eroféev model, and CA is A3/2 while PA is A1. The values of activation energy are positive, which is opposite to adsorption. CO2 adsorption and desorption processes are similar to the nucleation and growth of the crystal, which starts from a point, then spreads to the surrounding.Download high-res image (266KB)Download full-size image

•SESR can obtain nearly 100%-purity H2 even if at low temperature and S/C ratio.•The parameters were optimized for less consumption of bio-oil and energy.•SESR has lower consumptions of bio-oil and energy than CSR.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 H2 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 H2, 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.Download high-res image (131KB)Download full-size image

•The equilibrium and kinetics of CO2 adsorption on WIRAC were investigated for the first time.•The Sips equation is the best model to describe the adsorption isotherms of CO2 and N2 in the chosen isotherm models.•The selectivity of CO2/N2 is calculated by the IAST-Sips model.•CO2 adsorption by WIRAC is one-dimensional growth of the nuclei with a decreasing rate of adsorption.•The activation energy of CO2 adsorption on WIRAC is negative.The equilibrium and kinetics of CO2 adsorption on waste ion-exchange resin-based activated carbon were investigated. Three adsorption isotherm models and four kinetic models were utilized to analyze the equilibrium and kinetic data. Sips model and Avrami model are the best ones to describe the equilibrium and kinetics, respectively. The isosteric heats of adsorption of CO2 and N2 were calculated according to the Sips model. The separation factor of CO2/N2, calculated by IAST-Sips model, decreases with the surface coverage increasing. The adsorption rate constant of Avrami model increases with the CO2 concentration increasing and reduces with the temperature increasing. The activation energies of CO2 adsorption are negative, due to the decrease of the reaction rate with the temperature increasing. And the activation energies of CO2 adsorption on CA are a bit smaller than that of PA, but the difference is not obvious.Download high-res image (139KB)Download full-size image

In this paper, a minimal skeletal mechanism involving 20 species and 56 reactions was generated for CH4/O2/CO2 mixtures from the GRI Mech 3.0 mechanism. The directed relation graph-aided sensitivity analysis (DRGASA) method was applied for mechanism reduction at the first step. Then, principle component analysis (PCA) was used for further reduction. The chemical reality of the generated skeletal mechanism was checked by the reaction pathways analysis of CH4/O2/CO2 mixtures in a constant-pressure ignition process. Finally, the generated skeletal mechanism was validated by the ignition delay times, laminar flame speeds, important species concentrations, and extinction turning points in the conditions of various pressures, temperatures, O2/CO2 ratios, and equivalence ratios. Results showed that the developed skeletal mechanism could reproduce the results from the detailed mechanism.

•Chemical effect of CO2 versus oxygen fractions and equivalence ratios was studied.•Changes of contribution of reactions were investigated by sensitivity analysis.•The effect of third body efficiency of CO2 on the laminar flame speed was studied.The chemical effect of CO2 on the laminar flame speeds of oxy-fuel mixtures was related to the oxygen concentrations and equivalence ratios. In order to study the chemical effect of CO2, we have adopted a premixed oxy-methane flame in the condition of various oxygen concentrations and equivalence ratios. Results show that the chemical effect was smaller than the thermal effect but much bigger than the radiative effect in the calculation domain. The chemical effect of CO2 changed a lot with the oxygen concentrations and equivalence ratios. The effect of third body efficiency of CO2 on the laminar flame speeds of oxy-methane mixtures was discussed. The reaction rate and sensitivity analysis were performed to identify the important reactions which have a third body efficiency of CO2. In addition, the contributions of the elemental reactions were studied with the sensitivity analysis.

Thermodynamic analysis and experiments of the steam reforming process of 1-methylnaphthalene as the tar model compound from coke oven gas (COG) were performed in this paper. In the thermodynamic analysis, as the temperature and steam/carbon (S/C) ratio rose, the hydrogen yield first increased and then flattened out yet with the compound completely converted and almost no coke deposition formed. In the experiments using a Ni/Mg catalyst with Ca12Al14O33 as a carrier, with the increases of the temperature and S/C ratio and the decrease of the methane-equivalent gas hourly space velocity (GC1HSV), the reforming result for hydrogen production became better gradually. After the temperature and S/C ratio increased to 800 °C and 12:1, respectively, and the GC1HSV decreased to 145 h–1, the hydrogen yield and carbon conversion could reach over 90% and 97%, respectively, even very close to the thermodynamic values. Additionally, the catalytic stability and resistance to coke formation of the used catalyst also improved in such conditions.

•Thermodynamic analysis of synergistic coal gasification was performed.•Gibbs free energy minimization for chemical equilibrium characterization was applied.•Synergistic effects of CO2 and H2O during gasification were investigated detailed.•Syngas applications were investigated by changing C/CO2/H2O in feed to modify H2/CO.In this paper, a thermodynamic analysis of the synergistic coal/CO2/H2O 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/CO2/H2O were investigated. Carbon, CO2 and H2O conversion, H2 and CO yield, and H2/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 H2O and CO2 could lead to the reduction of the carbon residue and increase of the production of H2 and CO, respectively. Meanwhile, it was beneficial to reduce the waste heat using to heating extra steam and enhance the coal/CO2 gasification reaction rate by controlling the addition of CO2 and H2O reasonably. Moreover, the production syngas application was also investigated by changing the relative CO2/C ratio and H2O/C ratio in the feed to modify the H2/CO ratio.

•Mn2O3 was used as oxygen carrier in CLG to produce syngas from biomass.•Mechanism of CLG of biomass using Mn2O3 was introduced.•Thermodynamic analysis of syngas generation from biomass was performed.•The optimal thermodynamic conditions were determined.•The feasibility of using steam to modify the H2/CO in the syngas was investigated.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 Mn2O3 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 Mn2O3/biomass, operation temperature, pressure, and steam/Mn2O3 on the gasification characteristics. The optimal thermodynamic conditions were determined to improve H2 and CO concentrations as high as possible. The optimal Mn2O3/corn cob is 0.18 to obtain the highest CO and H2 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 H2 is 98.8% in the syngas. Steam can be used in the CLG to modify the H2/CO in the syngas. The carbon conversion also increases under oxidizing atmosphere of steam.

•The kinetic of steam gasification with molten BFS as heat carrier was investigated.•The kinetic model (R2 model) of steam gasification with molten slag was established.•The global rate equation of gasification including kinetic parameters was developed.•BFS accelerated the gasification rate and acted as an active catalyst in gasification.In this study, we carried out a kinetic investigation to analyze the steam gasification of FS (Fu Shun) coal. The effect of reaction temperature (1573 K–1673 K) was studied, and the coal/slag ratios were in the range of 1:0–1:2. The reaction temperature and coal/slag ratio affected the carbon conversion and reactivity index of FS coal gasification. With reaction temperature increasing, the time for carbon conversion completing decreased. But the effect of temperature was non-significant, when it was above 1623 K. The reactivity index of coal at 1673 K was about 1.6 times faster than that at 1573 K, when the coal/slag ratio was 1:0. The BFS (blast furnace slag) acted as not only a heat carrier but also an effective catalyst in steam gasification. Compared with the steam gasification of “pure” FS coal, both carbon conversion and reactivity index of gasification were enhanced by BFS. Meanwhile, the Diffusion model (D1 model) and Shrinking core model (R2 model) were proved as the most appropriate model to describe the steam gasification without and with BFS as heat carrier, respectively. The kinetic parameters applicable to the established model with different coal/slag ratios were obtained. Under these conditions, the valid range of activation energy for gasification reaction was 20 kJ·mol−1–64 kJ·mol−1.

•CaO from calcium acetate showed the best CO2 adsorption efficiency.•Hydrogen purity was dramatically improved in the SR process with in situ CO2 capture.•The optimal temperature, CaO/C and S/C were obtained with continuous CO2 capture.Hydrogen production via steam reforming of the bio-oil from corn cob by fast pyrolysis with in situ CO2 sorption was investigated. The CaO obtained by calcining Ca(CH3COO)2·H2O showed the best CO2 adsorption efficiency among the three kinds of CaO from different precursors, and thus was selected as CO2 sorbent used in the sorption-enhanced steam reforming process. For the bio-oil steam reforming, when the liquid hourly space velocity was lower than 0.15 h−1, the yield and concentration of H2 tended to the maximum. With the comparison to the case without CO2 sorption, the yield and concentration of H2 with CO2 sorption were obviously improved with the carbon deposition effectively inhibited during the temperature range between 650 °C and 850 °C and the S/C range between 9 and 15. Through the sorption-enhanced steam reforming process, the highest hydrogen yield and concentration were obtained between 750 °C and 800 °C at S/C ratio of 12, and they were over 85% and 90%, respectively.

In this paper, the effects of high concentrations of CO2 on the lower flammability limits (LFL) of the CH4/O2/CO2 mixture were studied. For comparison, the LFL of the CH4/O2/N2 mixture were studied in the same way. First, the LFL of gas mixtures were measured using a cylindrical quartz glass tube in the condition of various oxygen concentrations. The experimental values of LFL of CH4/O2/CO2 decreased with the increase of oxygen concentrations, but the decreasing rate was small. Then, the chemical, thermal, and radiative effects of high concentrations of CO2 on the LFL were analyzed with the energy balance analysis. The thermal property of the gas mixture played the major role in the determination of the LFL. The radiative effect of CO2 on the LFL was much smaller than the thermal effect. The chemical effect of CO2 has little impact on the LFL of CH4/O2/CO2. Finally, the LFL of the CH4/O2/CO2 mixture were well-predicted using the calculated flame temperature method with a fixed critical temperature.

Waste ion-exchange resin was utilized as precursor to produce activated carbon by KOH chemical activation, on which the effects of different activation temperatures, activation times and impregnation ratios were studied in this paper. The CO2 adsorption of the produced activated carbon was tested by TGA at 30 °C and environment pressure. Furthermore, the effects of preparation parameters on CO2 adsorption were investigated. Experimental results show that the produced activated carbons are microporous carbons, which are suitable for CO2 adsorption. The CO2 adsorption capacity increases firstly and then decreases with the increase of activation temperature, activation time and impregnation rate. The maximum adsorption capacity is 81.24 mg/g under the condition of 30 °C and pure CO2. The results also suggest that waste ion-exchange resin-based activated carbons possess great potential as adsorbents for post-combustion CO2 capture.

The utilization of copper slag is an attractive option of iron resource. However, extra energy consumption is required and contributes to greenhouse gases. In this paper, biomass was introduced as a new kind of reductant for the reduction of copper slag to decrease the energy consumption. The reduction kinetics and reduction characteristics of three kinds of biomasses were studied by thermogravimetric analyzer (TG). The TG curves showed the reduction reaction of copper slag and biomass could be divided into three stages during heating process: drying and pyrolysis of biomass process (<959 K), pre-reduction process (959–1100 K) and reduction reaction process (>1100 K). Pine sawdust showed the best reducing property and the reduction ratios of pine sawdust, corncob and straw reached to 80.6, 76.1, and 60.0 %, respectively, when the mass ratio of biomass/slag was 2:1. As the additive, CaO had promotion effects on the reduction reaction. With the increase in CaO addition, the reduction ratio of copper slag increased firstly and reached a peak at CaO/slag was 0.3:1 and then it declined due to the changes of slag viscosity. By kinetics analysis, the reduction reaction confirmed well with shrinking core model (R1). The activation energy of reactions was affected by the addition of biomass and heating rate in experiments. With the increase in the addition of biomass, the activation energy of reduction reaction increased gradually; with the increase in heating rate, the activation energy of reduction reaction decreased.

•The process with continuous CO2 capture needs micro sorbent, large catalyst in size.•The large-size Ce–Ni/Co catalyst showed a good catalytic performance for SR.•Hydrogen purity was dramatically improved in the SR process with in situ CO2 capture.•The optimal CaO/C and S/C ratios were obtained with continuous CO2 capture.For microsized CaO calcinated from calcium acetate as CO2 sorbent, the CO2 adsorption efficiency increased with the increased of temperature, but decreased when the temperature was over 750 °C, due to the endothermic decomposition of CaCO3. The decreased CO2 partial pressure was unfavourable to CO2 adsorption. The steam reforming of the simulated bio-oil over the Ce–Ni/Co catalyst supported on Al2O3 balls was performed, and the optimal results for hydrogen production were obtained at 700 °C, the S/C ratio of 9 and the LsHSV of 0.23 h−1, with the actual hydrogen yield of 83.8% and the H2(+CO + CH4) yield of 94.1%. In the steam reforming experiment with in continuous situ CO2 capture, the feeding of CaO into the reforming reactor made the hydrogen concentration improved excellently upto 93.3%. However, the H2 yield decreased at higher CaO/C ratio, mainly because the excessive CaO restrained the contact between the reactants and the catalyst. Besides, the higher S/C ratio decreasing the CO2 partial pressure, was against the simultaneous CO2 adsorption, with the optimal S/C ratio of 9.

Chemical looping air separation used in the oxy-fuel combustion system resolves the oxygen source. Oxygen carrier releases oxygen in flue gas atmosphere and absorbs oxygen in air atmosphere. One of the most important properties is the sorption of the decomposed oxygen carrier. Aiming at investigating the sorption property in detailed, copper oxygen carrier with 40 mass% MgAl2O4 as inert binder was prepared. Thermodynamic calculations and the physical and chemical characterizations of the CuO–MgAl2O4 were carried out. The sorption property was investigated in the TG and fixed-bed reactor. The active phases of copper oxides do not react with MgAl2O4 during the preparation and reaction processes. The adding of MgAl2O4 hinders the grains growth of copper oxides. The decomposed oxygen carrier can react with oxygen when temperature is higher than 400 °C. The thermodynamic results indicate the highest sorption temperature should be lower than 1,027 °C in air atmosphere. Indeed, the sorption is not complete when temperature is 1,010 °C in TG experiment. Pressurized oxidation reactor is conducive to the oxidation of decomposed oxygen carrier at high temperature. The decomposed oxygen carrier has strong oxygen sorption capability. Low temperature is conducive to the sorption process. In all the gas flows and oxygen concentrations tested, the outlet oxygen concentrations all were kept in a low level. The effect of particle size on the sorption rate is little, and big particle size of oxygen carrier can be selected to reduce the pressure drop of the bed.

•A theory model for predicting the flammability limits of CH4/O2/CO2 is deduced.•Chemical effects of CO2 on the flammability limits were concerned in the model.•The flammability limits of CH4/O2/CO2 mixtures were measured.The flammability limits of CH4/CO2/O2 were studied using theory calculations and experimental investigation. A calculation model was re-deduced based on thermal theory. In this model, the chemical effects of CO2 on flammability limits are concerned. Results show that the chemical effects of CO2 decrease the upper flammability limits (UFL) of mixtures, while have little effect on the lower flammability limits (LFL). Experimental measurements were performed using a cylinder reactor. The measurements of the LFL of CH4/O2/CO2 increase from 5% to 8.25% with the increase of CO2 concentration, and the UFL of mixture CH4/O2/CO2 decrease from 61% to 8.25% accordingly. The model predicted the LFL very well, but the calculated values are an average 10.7% higher than the measurements at the UFL points. The differences between the predictions and measurements are mainly due to the two assumptions of this model.

•The blast furnace (BF) slag waste heat was converted and utilized.•BF slag acted as heat carrier for reaction and helped to produce hydrogen-rich gas.•The optimal operations were obtained by thermodynamic analysis.•Effect of BF slag and its basicity on gasification were investigated.Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for coal gasification with steam using blast furnace (BF) slag as heat carrier and recycling its waste heat to produce hydrogen-rich gas (HRG). Simulations were carried out to study the operation temperature, pressure, S/C and BF slag basicity based on chemical equilibrium calculations. The optimal thermodynamic conditions were determined to improve hydrogen concentration and total syngas production as high as possible. The results suggested that the preferential conditions for HRG from Datong coal were achieved at 775 °C, atmospheric pressure and S/C of 2.0–3.0. Under these conditions, hydrogen concentration reached to 62.36% and the total gas production was 2.45 mol per mole of carbon in the coal. What's more, not only was the quality of HRG improved significantly, but also the BF slag waste heat was recycled effectively when using BF slag as heat carrier. The effect of BF slag basicity upon the gasification characteristics was also investigated, and the production of hydrogen increased significantly when basicity was 1.3.

The kinetics of Datong coal gasification in solid BF (blast furnace) slag using carbon dioxide as gasifying agent was studied between 1223 and 1423 K. The relative mass change during the gasification reaction was continuously monitored using a high-resolution thermogravimetric system. The influence of reaction temperature and coal/slag mass ratio in the reaction rate was analyzed. The reaction rate has a strong dependence on reaction temperature and coal/slag ratio. With increasing reaction temperature, carbon conversion, the peak value of reaction rate, the intrinsic surface reaction rate, and the reactivity index increases, and the time for complete carbon conversion decreased. The activation energy decreases with an increasing coal/slag ratio. When the coal/slag ratio is 1:0, the intrinsic the activation energy is 112 kJ/mol; however, when the coal/slag is 1:3, it is 53 kJ/mol. This indicates that BF slag is an active catalyst for carbon gasification. Reaction model Am (volume reaction model as proposed by Avrami-Erofeev) has the best fit on coal gasification using BF slag as heat carrier. The kinetic parameters applicable to the Am model different coal/slag ratios were obtained. The global rate equation that includes these parameters was developed.

The knowledge of the kinetics of oxygen carriers is essential for the design of chemical looping air separation (CLAS) system. In this paper, the Cu-based oxygen carriers were prepared via a mechanical mixing method, and ZrO2, TiO2, and SiO2 were used as binder. The kinetics of the oxygen carriers in the process was determined using the distributed activation energy model via the thermogravimetry (TG) technique. TG experiments were performed in a thermal analyzer with heating rates of 5, 10, 15, and 20 °C/min. Preparation experiments were carried out first to obtain suitable sample masses and gas flow rates, to eliminate the effects of internal and external diffusion. The TG results show that the oxygen reduction and oxidation all have high reaction rates. The reaction rates of using different binders increase in the order of ZrO2 > TiO2 > SiO2, but the differences are minor. Besides the start and end points, the peaks of differential thermogravimetry (DTG) curves of oxygen-releasing regions all move forward to higher temperatures as the heating rate increases. Cyclic experiments show that the relativities of reduction and oxidation are stable during the cycles and the small dense grain of CuO has the tendency of growing bigger after 23 cycles, but the tendency is not apparent. The additions of binders can effectively inhibit the sintering and agglomeration of Cu-based oxygen carriers. The Starink approximation was used in the distributed activation energy model to calculate the distributed activation energies of the reduction reaction of oxygen carrier. The fitting lines of ln(β/Tk) and 1/T using the approximation have high linear correlations. The distributed activation energies of CuO/TiO2, CuO/ZrO2, and CuO/SiO2 obtained are 155.0 ± 2.2, 152.9 ± 6.9, and 144.9 ± 6.6 kJ/mol, respectively. The differences of distributed activation energies at different conversion ratios and among the three types of oxygen carriers are all very small. The reduction reaction of a Cu-based oxygen carrier is a one-step reaction, and the mechanism function of CuO reduction reaction was not affected by binders. The mechanism function is the nucleation and nuclei growth, and it is shown as f(α) = 3(1 – α)[−ln(1 – α)]2/3.

The coal/CO2 gasification reactions in molten BF (blast furnace) slag were studied kinetically by temperature-programmed thermogravimetry using a thermal analyzer. The effect of heating rates and molten BF slag on coal gasification were studied, and the activation energies, frequency factors, and most possibility mechanism functions were calculated. The results show that the order of reactivity sequence at these temperatures was DT (Datong) coal > FX (Fuxin) coal > coke. With the increase in heating rate, the carbon conversion, and the peak value of reaction rate increased at the same reaction time, the carbon conversion curve shifts to a higher temperature and the reaction rate curve shifts rightward systematically, both of the time required for the carbon conversion to reach nearly unity and the time necessary for reaction rate to reach its maximum decreased. The carbon conversion and reaction rates were sensitive to BF slag; at the same time, the carbon conversion and reaction rates of coal gasification with slag are higher than those without slag. The time required for the carbon conversion to reach nearly unity and the time required for the reaction rate to reach maximum with slag are both shorter than that without slag. In the presence of BF slag, the carbon conversion curve shifts to lower temperature, the peak value of reaction rate is higher than that without slag, and the reaction rate curve also shifts to lower temperature. The molten BF slag acts as a good catalyst to coal gasification. Without molten BF slag, the mechanism functions of coke and FX coal are a C1 model (phase boundary reaction (n = 2) model), while the mechanism function of DT coal is a C2 model (phase boundary reaction (n = 3/2) model). However, with molten BF slag, the mechanism function of coke is a D5 model (3-D diffusion (anti-Jander) model), the mechanism function of DT coal is a D4 model (3-D diffusion model), and the mechanism function of FX coal is a C2 model (phase boundary reaction (n = 3/2) model). The activation energies and frequency factors decrease as heating rates increase. The kinetic compensation effect of coal/CO2 gasification in molten BF slag exists.

In this work, coal gasification in molten blast furnace (BF) slag was performed at atmospheric pressure in a molten bath reactor in the temperature range from 1573 to 1773 K. The effects of coal samples and coal granularities on the gasification reaction rate, carbon conversion, and gas composition were studied, and the kinetic mechanism function was calculated. The results show that the method using coal gasification to recover sensible heat of molten BF slag is possible and effective. The coal gasification using molten BF slag as a carrier has wide adaptability on coal granularities and coal samples. It is effective to gasify lean coal. In this study, the gasification reaction rate of Shennan (SN) coal that represents lean coals is high and almost equal to that of Datong (DT) and Fuxin (FX) coals. The carbon conversion of all types of coal can become 0.99. Under the action of molten slag, the tar and hydrocarbon decompose fully; the content of other hydrocarbons in synthesis gas is almost zero. The reaction rates using different coal granularities increase in the order of 0.177 < 0.125 < 0.147 mm, but the difference is little. The calorific capacity of synthesis gas under different conditions is almost equal and can become 10 000 kJ/m3. The mechanism functions are different before and after the carbon conversion rate of 0.5. The mechanism function is shown as follows:

The steam reforming of four bio-oil model compounds (acetic acid, ethanol, acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg, Ce or Co in this paper. The activation process can improve the catalytic activity with the change of high-valence Ni (Ni2O3, NiO) to low-valence Ni (Ni, NiO). Among these catalysts after activation, the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds. After long-term experiment at 700 °C and the S/C ratio of 9, the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil (mixed by the four compounds with the equal masses). With CaO calcinated from calcium acetate as CO2 sorbent, the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed. With the comparison of the case without the adding of CO2 sorbent, the hydrogen concentration was dramatically improved from 74.8% to 92.3%, with the CO2 concentration obviously decreased from 19.90% to 1.88%.Large-scale catalysts is required in the novel process of bio-oil steam reforming with in situ CO2 capture for hydrogen production, and various catalysts were prepared and studied.Download full-size image

•A novel sorption-enhanced steam reforming process of raw COG was proposed.•The new SESR process has lower energy consumption and very small CO2 emissions.•As well as high-yield H2, high-purity CO2 is also obtained from the SESR process.A novel process for producing hydrogen from raw coke oven gas (RCOG), via CO2 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 CO2 emissions. The SESR process with CaO as CO2 sorbent, can obtain over 4.0-fold H2 amount amplification and over 95 vol% H2 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 CO2 gas as co-product, thus reducing CO2 emissions obviously, compared to the CSR process and the conventional cleaning processes (CCPs).