Kinetic characteristics of in-situ char-steam gasification following pyrolysis of a demineralized coal

This study aims to examine the char-steam reactions in-situ, following the pyrolysis process of a demineralized coal in a micro fluidized bed reactor, with particular focuses on gas release and its kinetics characteristics. The main experimental variables were temperatures (925 °C?1075 °C) and steam concentrations (15%–35% H₂O), and the combination of pyrolysis and subsequent gasification in one experiment was achieved switching the atmosphere from pure argon to steam and argon mixture. The results indicate that when temperature was higher than 975 °C, the absolute carbon conversion rate during the char gasification could easily reach 100%. When temperature was 1025 °C and 1075 °C, the carbon conversion rate changed little with steam concentration increasing from 25% to 35%. The activation energy calculated from shrinking core model and random pore model was all between 186 and 194 kJ/mol, and the fitting accuracy of shrinking core model was higher than that of the random pore model in this study. The char reactivity from demineralized coal pyrolysis gradually worsened with decreasing temperature and steam partial pressure. The range of reaction order of steam gasification was 0.49–0.61. Compared to raw coal, the progress of water gas shift reaction (CO + H₂O ? CO₂ + H₂) was hindered during the steam gasification of char obtained from the demineralized coal pyrolysis. Meanwhile, the gas content from the char gasification after the demineralized coal pyrolysis showed a low sensitivity to the change in temperature.     

Hydrogen-rich gas from catalytic steam gasification of eucalyptus using nickel-loaded Thai brown coal char catalyst

Hydrogen gas production from eucalyptus by catalytic steam gasification was carried out in an atmospheric pressure of two-stage fixed bed. The gasifier was operated with the temperature range of 500–650 °C and steam partial pressure of 16, 30 and 45 kPa; nickel-loaded Thai brown coal char was used as a catalyst. The yields and compositions of the gasification products depend on the operating conditions, especially, the reaction temperature and the steam. The yield of H₂ increased at elevated temperatures, from 26.94 to 46.68%, while that of CO dramatically decreased, from 70.21 to 37.71 mol%. The highest H₂ yield, 46.68%, was obtained at the final gasifying temperature of 650 °C. Eucalyptus catalytic steam gasification indicated that the maximum H₂/CO ratio reached 1.24 at the gasification temperature of 650 °C and the steam partial pressure of 30 kPa. It can be concluded that eucalyptus is appropriate for synthesis gas production from eucalyptus volatiles by catalytic steam gasification while using nickel-loaded brown coal char as a catalyst.     

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11 MJ/N m³ for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16 g H₂/kg biomass. For biomass oxygen/steam gasification, the content of H₂ and CO reaches 63.27–72.56%, while the content of H₂ and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H₂/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.     

Distribution of Nitrogen Species During Vitrinite Pyrolysis and Gasification

The formation of HCN and NH₃ during pyrolysis in Ar and gasification in CO₂ and steam/Ar was investigated. Vitrinites were separated and purified from different rank coal from lignite to anthracite. Pyrolysis and gasification were carried out in the drop-tube/fixed-bed reactor at temperatures of 600–900°C. Results showed that with increase of reaction temperature the yield of HCN increased significantly during pyrolysis and gasification. Decrease of coal rank also increased the yield of HCN. Vitrinite from lower rank of coal with high volatile content released more HCN. The yield of NH₃ was the highest at 800°C during pyrolysis and gasification. And the yield of NH₃ from gasification in steam/Ar was far higher than that from gasification in CO₂, where the hydrogen radicals play a key role. Nitrogen retained in char was also investigated. The yield of char-N decreased with an increase of pyrolysis temperature. Vitrinite from lower rank coal had lower yield of char-N than that from the high rank coal.     

Inhibition of steam gasification of biomass char by hydrogen and tar

The influence of hydrogen and tar on the reaction rate of woody biomass char in steam gasification was investigated by varying the concentrations in a rapid-heating thermobalance reactor. It was observed that the steam gasification of biomass char can be separated into two periods. Compared with the first period, in the second period (in which the relative mass of remaining char is smaller than 0.4) the gasification rate is increased. These effects are probably due to inherent potassium catalyst. Higher hydrogen partial pressure greatly inhibits the gasification of biomass char in the first and second periods. By calculating the first-order rate constants of char gasification in the first and second periods, we found that the hydrogen inhibition on biomass char gasification is caused by the reverse oxygen exchange reaction in the first period. In the second period, dissociative hydrogen adsorption on the char is the major inhibition reaction. The influence of levoglucosan, a major tar component derived from cellulose, was also examined. We found that not only hydrogen but also vapor-phase levoglucosan and its pyrolysates inhibited the steam gasification of woody biomass char. By mixing levoglucosan with woody biomass sample, the pyrolysis of char proceeds slightly more rapidly than with woody biomass alone, and gas evolution rates of H₂ and CO₂ are larger in steam gasification.     

Performance of active nickel loaded lignite char catalyst on conversion of coffee residue into rich-synthesis gas by gasification

Performance of nickel-loaded lignite char catalyst on conversion of coffee residue into synthesis gas by catalytic steam gasification was carried out at low reaction temperatures ranging from 500 °C to 650 °C in the two-stage quartz fixed bed reactor. The effects of steam pressures (30, 36 and 50 kPa corresponding to S/B = 2.23, 2.92 5.16, respectively) and catalyst to biomass ratios (C/B ratio = 0, 1, 3) were considered. Nickel-loaded lignite char was prepared as a catalyst with a low nickel loading amount of 12.9 wt%. The gas yields in the catalytic steam gasification process strongly depended on the reaction temperature and C/B ratio. The total gas yields obtained in catalytic steam gasification was higher than that of catalytic pyrolysis, steam gasification and non-catalytic pyrolysis with steam absence by factors of 3.0, 3.8 and 7.7, respectively. To produce the high synthesis gas, it could be taken at 600 °C with total gas yields of 67.13 and 127.18 mmol/g biomass-d.a.f. for C/B ratios of 1.0 and 3.0, respectively. However, the maximum H₂/CO ratio was 3.57 at a reaction temperature of 600 °C, S/B of 2.23 and C/B of 1.0. Considering the conversion of coffee residue by catalytic steam gasification using the nickel-loaded lignite char catalyst, it is possible to covert the coffee residue volatiles into rich synthesis gas.     

Modelling and experimental investigations on gasification of coarse sized coal char particle with steam

The steam gasification characteristics of coal char produced two sub-bituminous coals of different origin have been investigated through modelling and experiments. The gasification experiments are carried out in an Isothermal mass loss apparatus over the temperature range of 800–900 °C using a gas mixture of 65% steam and 35% N₂. A fully transient single particle gasification model, based on the random pore model, is developed incorporating reaction kinetics, heat and mass transport inside the porous char particle and the gas film. Stefan-Maxwell equation and Knudson diffusion are incorporated in the multi-component diffusion of species and pore diffusion. The model is validated with the experimental data of the present authors as well as that reported in the literature. The particle centre temperature is found to increase, then decrease and increase again to reach the reactor temperature finally, and the trend is more prominent for the larger particles. The pore opening phenomenon is more evident in SBC2 char, leading to a final char porosity of 0.65 vis-à-vis 0.52 in SBC1 and making it more reactive. Temporal evolution of contours of carbon conversion and concentration of other gaseous species like steam, H₂O, H₂, CO and CO₂ in the particle are computed to investigate the gasification process. A higher temperature is found to favour both the rate peak and the total production of H₂ for both the chars. The total H₂ production from SBC2 char is found to be 0.0189 mol and 0.0236 mol at 800 and 850 °C, while the same for SBC1 char is0.0232 mol and 0.0290 mol respectively. The reaction follows the shrinking core model at the outset, shifting to the shrinking reactive core model subsequently.     

木屑水蒸气气化热重分析及合成气释放特性

试验研究了木屑在水蒸气气氛下的热失重行为及气化过程中合成气释放特性。首先采用TG-DTA对木屑样品进行了水蒸气气氛下的热重行为分析,结果表明,木屑气化过程可以分为挥发分释放和半焦气化两个阶段,分别可由二级反应动力学和三维扩散Ginstling-Broushtein方程描述,对应的表观活化能分别为87.014kJ/mol和103.35 kJ/mol。此外,在自制的固定床气化反应装置上,研究了生物质气化过程中挥发分释放和半焦气化阶段合成气释放特性。另外,半焦水蒸气气化阶段对气体中合成气含量和H2/CO起到决定性作用,通过合理调控半焦气化阶段反应条件,可以得到合适化学当量比的生物质合成气。     

Coal-gasification kinetics derived from pyrolysis in a fluidized-bed reactor

Coal pyrolysis and gasification reactions were carried out in a fluidized-bed reactor (0.1 m i.d. by 1.6 m height) over a temperature range from 1023 to 1173 K at atmospheric pressure. The overall gasification kinetics for the steam–char and oxygen–char reactions were determined in a thermobalance reactor. The compositions of the product gases from the coal-gasification reactions are 30–40% H₂, 23–28% CO, 27–35% CO₂ and 6–9% CH₄ with heating values of 2000–3750 kJ m⁻³. The heating value increases with increasing temperature and steam/coal ratio but decreases with increasing air/coal ratio. Our kinetic data derived from the two-phase theory on coal gasification in a thermobalance reactor and coal pyrolysis in a fluidized bed may be used to predict the product-gas compositions.     

Catalytic steam gasification of Mengdong coal in the presence of iron ore for hydrogen-rich gas production

Hydrogen-rich gas production from catalytic steam gasification of coal was investigated in the presence of iron ore in a vertical fixed bed reactor. The addition of iron ore significantly promoted the H₂ yields. The effects of operation parameters (upper zone temperature, lower zone temperature, steam concentration, and iron to coal ratio) on the yield of selected gaseous products (H₂ and CO) during catalytic steam gasification, were studied using Taguchi method. The results of signal-to-noise ratio indicated that steam concentration and iron to coal ratio were the most important parameters in determining the yield of H₂ and CO, respectively. Semi-quantification X-ray diffraction analysis of iron ores indicated that increase in steam concentration intensified the oxidization of low valence iron compounds to Fe₃O₄. In addition, formation of Fe₃O₄ was also favored with increasing reaction temperatures (600 °C–900 °C). However, the formation of Fe₃O₄ was inhibited at higher reaction temperature (1000 °C) due to the destruction of porous structures of the iron ore.     

Effect of CO2 and steam gasification reactions on the oxy-combustion of pulverized coal char

For oxy-combustion with flue gas recirculation, elevated levels of CO₂ and steam affect the heat capacity of the gas, radiant transport, and other gas transport properties. A topic of widespread speculation has concerned the effect of gasification reactions of coal char on the char burning rate. To asses the impact of these reactions on the oxy-fuel combustion of pulverized coal char, we computed the char consumption characteristics for a range of CO₂ and H₂O reaction rate coefficients for a 100 μm coal char particle reacting in environments of varying O₂, H₂O, and CO₂ concentrations using the kinetics code SKIPPY (Surface Kinetics in Porous Particles). Results indicate that gasification reactions reduce the char particle temperature significantly (because of the reaction endothermicity) and thereby reduce the rate of char oxidation and the radiant emission from burning char particles. However, the overall effect of the combined steam and CO₂ gasification reactions is to increase the carbon consumption rate by approximately 10% in typical oxy-fuel combustion environments. The gasification reactions have a greater influence on char combustion in oxygen-enriched environments, due to the higher char combustion temperature under these conditions. In addition, the gasification reactions have increasing influence as the gas temperature increases (for a given O₂ concentration) and as the particle size increases. Gasification reactions account for roughly 20% of the carbon consumption in low oxygen conditions, and for about 30% under oxygen-enriched conditions. An increase in the carbon consumption rate and a decrease in particle temperature are also evident under conventional air-blown combustion conditions when the gasification reactions are included in the model.     

Microwave pretreatment on microalgae: Evolution of gas and char in chemical looping gasification

Chemical looping gasification (CLG) of Chlorella vulgaris was investigated by TGA and FTIR technology. The release characteristic and evolution behavior of gaseous products and bio‐char in different conditions were analyzed to evaluate the effects of CLG and microwave pretreatment. The results indicated that the gas production of CLG was higher than that of SiO₂:Chlorella, and it would be higher after microwave pretreatment. CO, CO₂, and CH₄ were mainly produced in the pyrolysis and gasification stages. After adding Fe₂O₃, C―O, C═O, and C═C compounds decreased by 3.75%, 20.86%, and 24.72%, respectively. But more CO, CO₂, and CH₄ were produced. Microwave pretreatment was helpful for reducing the degrees of hydrogen‐rich, aliphatic structure, aromatization, and oxygen‐rich in char. Moreover, microwave pretreatment promoted the reduction of C―O, C═O, and C═C compounds. However, CO increased by 55.63%, and CO₂ decreased by 2.31% in this condition. Therefore, microwave pretreatment was beneficial to CLG reaction.     

Exergy analysis of biomass staged-gasification for hydrogen-rich syngas

Using Aspen Plus simulations, exergy analyses of hydrogen-rich syngas production via biomass staged-gasification are carried out for three configurations, namely, staged-gasification with pyrolysis gas combustion and char gasification (C-1), staged-gasification with pyrolysis gas reforming and char gasification (C-2), and staged-gasification with pyrolysis gas reforming and char combustion (C-3). The results show that, for the gasification and reforming processes, the exergy loss of pyrolysis gas with tar reforming is less than that of char gasification. As for the system, it is conducive to generating hydrogen by making full use of the hydrogen element (H) in biomass instead of the H in water. The benefits of C-1 are that it removes tar and produces higher yield and concentration of hydrogen. However, C-2 is capable of obtaining higher exergy efficiency and lower exergy loss per mole of H₂ production. C-3 theoretically has greater process performances, but it has disadvantages in tar conversion in practical applications. The appropriate gasification temperature (T_G) are in the range of 700–750 °C and the appropriate mass ratio of steam to biomass (S/B) are in the range of 0.6–0.8 for C-1 and C-3; the corresponding parameters for C-2 are in the ranges of 650–700 °C and 0.7–0.8, respectively.     

Novel hydrogen‐rich gas production by steam gasification of biomass in a research‐scale rotary tubular helical coil gasifier

The concept of biomass steam gasification offers platform for production (i) of hydrogen, (ii) hydrocarbons and (iii) value added chemicals. Majority of these developments are either in nascent or in pilot/demonstration stage. In this context, there exists potential for hydrogen production via biomass steam gasification. Gaseous products of biomass steam gasification consist of large percentage of CO, CH₄ and other hydrocarbons, which can be converted to hydrogen through water‐gas‐shift reaction, steam reforming and cracking respectively. Although there are many previous research works showing the potential of production of hydrogen from biomass in a two stage process, challenges remain in extended biomass and char gasification so as to reduce the amount of carbon in the residual char as well as improve conversion of heavy hydrocarbon condensates to hydrogen rich gas. In the current work, the characteristics of biomass steam gasification in an in‐house designed rotary tubular helical coil reactor at temperatures less than 850 °C, in the presence of superheated steam, were presented. The objectives were to obtain high carbon conversion in the primary biomass steam gasification step (upstream) and high product gas yield and hydrogen yield in the secondary fixed bed catalytic step (downstream). The influence of temperature, steam‐to‐biomass ratio and residence time on product gas yield in the rotary tubular helical coil gasifier was studied in detail using one of the abundantly available biomass sources in India‐rice husk. Further, enhancement of product gas yield and hydrogen yield in a fixed bed catalytic converter was studied and optimized. In the integrated pathway, a maximum gas yield of 1.92 Nm³/kg moisture‐free biomass was obtained at a carbon conversion efficiency of 92%. The maximum hydrogen purity achieved under steady state conditions was 53% by volume with a hydrogen yield of 91.5 g/kg of moisture‐free biomass. This study substantiates overall feasibility of production of high value hydrogen from locally available biomass by superheated steam gasification followed by catalytic conversion. Copyright © 2016 John Wiley & Sons, Ltd.     

Feed compositions and gasification potential of several biomasses including a microalgae: A thermodynamic modeling approach

This study presents the relation of the biomass properties with the gasification performance. The potential of microalgae (N. oculta) for gasification also has been investigated. Other biomasses such as palm frond, mangrove, and rice husk were considered as the benchmarks. The performance of a combined gasification process for different biomass was evaluated by developing a thermodynamic model using Aspen Plus. The performance of gasification process was evaluated based on the composition of the producer gas, the cold gas efficiency, and the gasification system efficiency. The effects of biomass composition on the gasification performance was studied by varying the gasification temperature, the oxygen equivalence ratio, and the steam to carbon ratio. It was found that the H/O ratio in the feed biomass has a considerable effect on the H₂/CO ratio of producer gas on the gasification without gasifying agent. The gasification of algae with oxygen exhibited the highest H₂/CO ratio. The highest cold gas efficiency was found during gasification of algae with oxygen, while the highest cold gas efficiency from gasification with steam was exhibited on gasification of palm frond. The highest gasification system efficiency was obtained for palm frond using the oxygen or steam as the gasifying agent.     

Steam gasification of Greek lignite and its chars by co-feeding CO2 toward syngas production with an adjustable H2/CO ratio

Low-rank lignite is among the most abundant and cheap fossil fuels, linked, however, to serious environmental implications when employed as feedstock in conventional thermoelectric power plants. Hence, toward a low-carbon energy transition, the role of coal in world's energy mix should be reconsidered. In this regard, coal gasification for synthesis gas generation and consequently through its upgrade to a variety of value-added chemicals and fuels constitutes a promising alternative. Herein, we thoroughly explored for a first time the steam gasification reactivity of Greek Lignite (LG) and its derived chars obtained by raw LG thermal treatment at 300, 500 and 800 °C. Moreover, the impact of CO₂ addition on H₂O gasifying agent mixtures was also investigated. Both the pristine and char samples were fully characterized by various physicochemical techniques to gain insight into possible structure-gasification relationships. The highest syngas yield was obtained for chars derived after LG thermal treatment at 800 °C, due mainly to their high content in fixed carbon, improved textural properties and high alkali index. Steam gasification of lignite and char samples led to H₂-rich syngas mixtures with a H₂/CO ratio of approximately 3.8. However, upon co-feeding CO₂ and H₂O, the H₂/CO ratio can be suitably adjusted for several potential downstream processes.     

Experimental simulate on hydrogen production of different coals in underground coal gasification

Research on hydrogen production from coal gasification is mainly focused on the formation of CO and H₂ from coal and water vapor in high-temperature environments. However, in the process of underground coal gasification, the water gas shift reaction of low-temperature steam will absorb a lot of heat, which makes it difficult to maintain the combustion of coal seams in the process of underground coal gasification. In order to obtain high-quality hydrogen, a pure oxygen-steam gasification process is used to improve the gasification efficiency. And as the gasification surface continues to recede, the drying, pyrolysis, gasification and combustion reactions of underground coal seams gradually occur. Direct coal gasification can't truly reflect the process of underground coal gasification. In order to simulate the hydrogen production laws of different coal types in the underground gasification process realistically, a two-step gasification process (pyrolysis of coal followed by gasification of the char) was proposed to process coal to produce hydrogen-rich gas. First, the effects of temperature and coal rank on product distribution were studied in the pyrolysis process. Then, the coal char at the final pyrolysis temperature of 900 °C was gasified with pure oxygen-steam. The results showed that, the hydrogen production of the three coal chars increased with the increase of temperature during the pyrolysis process, the hydrogen release from Inner Mongolia lignite and Xinjiang long flame coal have the same trend, and the bimodality is obvious. The hydrogen release in the first stage mainly comes from the dehydrogenation of the fat side chain, and the hydrogen release in the second stage mainly comes from the polycondensation reaction in the later stage of pyrolysis, and the pyrolysis process of coal contributes 15.81%–43.33% of hydrogen, as the coal rank increases, the hydrogen production rate gradually decreases. In the gasification process, the release of hydrogen mainly comes from the water gas shift reaction, the hydrogen output is mainly affected by the quality and carbon content of coal char. With the increase of coal rank, the hydrogen output gradually increases, mainly due to the increasing of coal coke yield and carbon content, The gasification process of coal char contributes 56.67–84.19% of hydrogen, in contrast, coal char gasification provides more hydrogen. The total effective gas output of the three coal chars is 0.53–0.81 m³/kg, the hydrogen output is 0.3–0.43 m³/kg, and the percentage of hydrogen is 53.08–56.60%. This study shows that two-step gasification under the condition of pure oxygen-steam gasification agent is an efficient energy process for hydrogen production from underground coal gasification.     

不同气化剂下海藻粉在气流床下气化特性试验研究

为考察O2/水蒸气和O2/CO2作为气化剂对海藻粉气化特性的影响,在自制的小型生物质气流床气化炉上开展海藻粉在气流床下气化特性试验研究。当氧气/生物质比（O/B）为0.3、气化温度为1200℃时,不同水蒸气/生物质比（S/B=0～1.2）对合成气组成有较大影响,其中H2产量的上升趋势最为明显,S/B=1.2时比单纯氧气气化提高了81.4%。而在O2/CO2气化条件下,由生物质产生的CO2随二氧化碳/生物质比（CO2/B）的增加而下降,当CO2/B=0.9时,H2、CO的产量分别比单纯氧气气化提高了33.9%和75.8%,热值由5521 kJ/m3上升至8576 kJ/m3。结果表明,如果以提高热值为制取合成气的目标时,添加CO2在一定范围内可以达到水蒸气的效果,同时降低了系统能耗及简化了气化设备。     

基于铁矿石载氧体的生物质化学链气化机理研究

在单批次进料小型流化床上,以稻壳为生物质燃料,研究了床料、气化温度、水蒸气体积分数以及载氧体载氧量与生物质含碳量的摩尔比(O/C)对生物质化学链气化反应特性的影响,并考察了铁矿石的长期交替氧化还原过程中的反应特性,分析了在小型流化床,水蒸气气氛气化条件下,铁矿石载氧体在反应过程中主要的反应以及反应后的铁矿石的床料变化。研究表明:在载氧体条件下,生物质的碳转化率显著增大,随着反应温度的升高,合成气中的H_2和CO的体积分数也相应升高。在温度不变情况下,随着水蒸气比例的升高,CO_2和H_2的体积分数显著上升。伴随着O/C摩尔比的升高,CO和H_2均显著下降。因此,在不同的反应条件下,铁矿石在生物质化学链气化过程中对反应速度、合成气比例等均有明显的作用,对研究生物质的综合利用具有一定的意义。     

Reactivity investigation on chemical looping gasification of biomass char using nickel ferrite oxygen carrier

Chemical looping gasification (CLG) involves the use of an oxygen carrier (OC) which transfers oxygen from air to solid fuel to convert the fuel into synthesis gas, and the traditional gasifying agents such as oxygen-enriched air or high temperature steam are avoided. In order to improve the reactivity of OC with biomass char, facilitating biomass high-efficiency conversion, a compound Fe/Ni bimetallic oxide (NiFe₂O₄) was used as an OC in the present work. Effect of OC content and oxygen sources on char gasification were firstly investigated through a TG reactor. When the OC content in mixture sample attains 65 wt.%, the sample shows the maximum weight loss rate at relatively low temperature, indicating that it is very favorable for the redox reactions between OC and biomass char. The NiFe₂O₄ OC exhibits a good performance for char gasification, which is obvious higher than that of individual Fe₂O₃ OC and mechanically mixed Fe₂O₃ + NiO OC due to the Fe/Ni synergistic effect in unique spinel structure. According to the TGA experimental results, effect of the steam content and cyclic numbers on char gasification were investigated in a fixed bed reactor. Either too low steam content or too high steam content doesn't facilitate the char gasification. And suitable steam content of 56.33% is determined with maximum carbon conversion of 88.12% and synthesis gas yield of 2.58 L/g char. The reactivity of NiFe₂O₄ OC particles shows a downtrend within 20 cycles (～64 h) due to the formation of Fe₂O₃ phase, which is derived from the iron element divorced from the Fe/Ni spinel structure. Secondly, the sintering of OC particles and ash deposit on the surface are also the reasons for the deactivation of NiFe₂O₄ OC. However, the carbon conversion and synthesis gas yield at the 20th cycle are still higher than those of the blank experiment. It indicates that the reactivity of NiFe₂O₄ OC can be maintained at a relatively long time and NiFe₂O₄ material can be used as a good OC candidate for char gasification in the long time running.