Activation Energy Of Gasification Research Articles

Gasification behavior and kinetics of chars derived from coal pyrolysis in a CO-containing atmosphere

Char gasification enables clean and efficient utilization of low-rank coal resources. The CO2 gasification behavior and kinetics of char samples produced via low-rank coal pyrolysis under the N2 and CO-containing atmospheres (char-N2 and char-CO) were investigated based on a series of thermogravimetric experiments, and the physicochemical structure of chars were characterized via Raman diffraction, X-ray diffraction, and CO2 adsorption methods, respectively. The apparent activation energies (Ea) of char-N2 and char-CO were obtained using the Flynn–Wall–Ozawa method and the reaction mechanism was determined via the Malek method. The results indicate that the graphitization and order degrees of the carbon chemical structure of char-CO are higher than those of char-N2 below gasification temperature (approximately 850 °C), whereas the specific surface area of char-CO is higher than that of char-N2 before gasification. Char-CO gasifies faster than char-N2 owing to its developed pore structure, and the gasification activation energy is lower than that of char-N2 (from 450 °C to 650 °C, the activation energy of char-N2 is 186.3 kJ mol−1, 192.4 kJ mol−1, and 203.6 kJ mol−1, and that of char-CO is 175.8 kJ mol−1, 187.5 kJ mol−1, and 199.1 kJ mol−1, respectively). The CO2 gasification reaction process of char-N2 and char-CO can be explained using a three-dimensional diffusion model. Moreover, the ash content in coal char affects the diffusion of reaction carrier gas and gas products during the gasification process, indicating that diffusion is the primary limiting factor in coal char CO2 gasification.

Effect of wet torrefaction on the physicochemical characteristics and gasification behavior of biochar

Wet torrefaction (WT) is an effective biomass upgrading technology that has recently received widespread attention. However, the effects of WT on the physicochemical properties and gasification behaviors of biochar remain unclear, which limits the practical application of WT biomass as a fuel for gasification. In this study, hydrochar was prepared from corn stalk (CS) and poplar sawdust (PS) by a batch reactor. Then, biochar was prepared by rapid pyrolysis of hydrochar in a fixed-bed reactor. The physicochemical structure and gasification characteristics of fuel were studied. It was found that the AAEMs content in WT biochar was significantly reduced. The contents of K and Mg in biochar were reduced by more than 90 % and the contents of Ca were reduced by more than 75 % compared with the raw biochar. Below 220 °C, the graphitization degree of biochar increased with WT temperature. The specific surface area of CS char increased after WT, while the PS char decreased. The gasification reactivity of biochar decreased dramatically with the increase of WT temperature, and the time required for complete gasification increased obviously. The random pore model (RPM) has a satisfactory fitting on biochar gasification behavior. Therefore, RPM can be used to predict the biochar gasification behavior for other gasification temperatures. Activation energy of WT biochar is increased and the gasification reactivity is decreased compared with the raw biochar. The gasification activation energy of WT biochar for CS and PS were 225.80–285.59 kJ/mol and 146.39–264.25 kJ/mol, respectively. The research on the gasification kinetics of WT biochar can provide very important information for the reasonable design and operation of the gasifier.

Evaluating performance of pyrolysis and gasification processes of agriculture residues-derived hydrochar: Effect of hydrothermal carbonization

In this study, corn straw and rice husk were hydrothermally carbonized at 180 °C and 240 °C. The effect of hydrothermal carbonization on the biomass/hydrochar characteristics, fate of heavy metals such as As, Cr, Pb, Ti, Cd, Zn, Fe, Cu, and Ni, global reactivity of the pyrolysis and gasification of biomass and hydrochar were investigated in a thermogravimetric analyzer, followed by kinetic modeling and reactivity prediction. Results showed that hydrothermal carbonization temperature 180 °C is more suitable for producing solid fuel in terms of low heavy metals content. Higher hydrothermal carbonization temperature (240 °C) decreased O/C content and improved various characteristics of the hydrochar such as coalification degree, carbon content, higher heating value and the specific surface area. While hydrothermal carbonization conducted at lower temperature of 180 °C, was advantageous for obtaining higher energy yield efficiency and hydrochar yield. The gasification reactivity of hydrochar was more sensitive to the heating rate than the pyrolysis process. The activation energy (Ea) of the pyrolysis process varied significantly with conversion, whereas the gasification activation energy changes were insignificant. Based on the reactivity prediction, the hydrothermal carbonization effect on corn straw and rice husk was almost similar. The hydrochar generated under severe hydrothermal carbonization temperature (240 °C) showed higher thermal stability during pyrolysis in comparison with gasification. Compared with the gasification of rice husk hydrochar, hydrochar gasification of corn straw had lower Ea, hence requires less energy to produce syngas. The results of this research imply that biomass hydrochar is a suitable alternative option to produce pulverized solid fuel.

Co-gasification characteristics of coke blended with hydro-char and pyro-char from bamboo

The renewable and carbon-neutral biomass is gaining a lot of interest in ironmaking as a substitute to metallurgical coke. The present study looked at partial replacement of coke with biochar obtained from hydrothermal carbonization (HTC) and pyrolysis of bamboo. Pyro-char has a higher carbon crystallinity, lower volatiles and better pore characteristics, while HTC is ideal for the removal of ash especially alkali metals. Devolatilization occurs at 500–900 °C for the hydro-char/coke mixture while the pyro-char/coke blend shows a continuous gasification reaction. The activation energy of gasification for the 50% pyro-char/50% coke is 200–320 kJ/mol, significantly lower than the competing mixture with hydro-char. Although the biochar obtained from pyrolysis of bamboo is more suitable for BF, the excellent ash removal and lower cost of hydrothermal treatment are offering benefits so that a combination of both may present an optimum blend for reducing the carbon footprint of ironmaking process.

Gasification characteristics and thermodynamic analysis of ultra-lean oxygen oxidized lignite residues

Recent developments in the in-situ transformation of coal resources have heightened the possibility of exploring the oxidized coal regasification in coalfield fires. For further understanding the regasification characteristics of oxidized lignite residues in coalfield fire, Shengli lignite was selected for conducting ultra-lean oxygen pre-oxidation under different isothermal temperatures and CO2 regasification experiments. Fourier transform infrared spectroscopy results indicate that higher temperature leads to the increase of aromatic hydrocarbon and reduction of aliphatic hydrocarbon side chains on the coal structure. It is found that the pre-oxidation of under 1% oxygen concentration and 300 °C will increase the specific surface area and pore volume, which would be beneficial for the following regasification. The analysis of gasification parameters suggests that the gasification quality and performance of lignite residues decline with the increasing oxygen concentration and rising isothermal temperatures in pre-oxidation. The kinetic analysis demonstrates that when the oxygen concentration ranges from 1% to 5%, the activation energy of gasification increases by 16.744 kJ/mol. The findings suggest that the lignite pre-oxidation under ultra-lean oxygen conditions will inevitably increase the activation energy of CO2 gasification, which causes the coal more difficult to be utilized effectively.

Investigation into the catalytic gasification of coal gasification fine slag residual carbon by the leachate of biomass waste: Gasification reactivity, structural evolution and kinetics analysis

In this study, the applicability of chicken manure leachate (CML) to catalytic gasification of coal gasification fine slag residue carbon (RC) was investigated in order to guide the large-scale application of RC as a potential gasification feedstock. Firstly, the effects of different CML loading amount and gasification temperature on RC reactivity were investigated. The structural evolution of RC loaded with CML in gasification was deeply analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and in-situ high temperature stage coupled with optical microscope system (HSOM). The results showed that CML is rich in water-soluble alkali and alkaline earth metallic species, especially potassium, which can significantly improve the gasification reactivity of RC. The gasification activity increased with the increase loading amount of CML, but higher gasification temperature will weaken the catalytic ability of CML. The model free method can well predict the kinetics of RC gasification reaction. The existence of CML reduced the activation energy of gasification obviously. The activation energy of RC20CML was 100.96 kJ/mol, which was 37.81 kJ/mol lower than that of RC. Furthermore, the surface complexes produced during RC gasification were determined by temperature programmed desorption (TPD) technique. The results showed that CML loaded RC released more CO during TPD process, which indicated that CML promoted the formation of more active sites on the RC surface, thus accelerating the gasification reaction. This work will contribute to the classification and resource utilization of coal gasification fine slag.

Hydrothermal carbonization of rape straw: Effect of reaction parameters on hydrochar and migration of AAEMs

Hydrothermal carbonization (HTC) can improve biomass quality in both physical and chemical aspects for energy application. This study aims to investigate the characteristics and reactivities of rape straw (RS) hydrochars. Hydrochars were prepared at 160–240 °C with residence time of 15–120 min. Mass yield, energy yield, microstructure, functional group and migration of alkali and alkaline earth metals (AAEMs) were studied to evaluate the influence of different conditions on properties of hydrochar. The results showed that O/C and H/C ratio decreased, while the higher heating value (HHV) increased with increasing temperature and residence time. The effect of increasing temperature on hydrochar properties was more significant than residence time. The structure was changed, and hydrochar possessed a more stable form after the aromatization reaction. For the gasification reactivity of hydrochar, decomposition rate curves showed that the peak of pyrolysis and gasification moved to a higher temperature region with the increasing of HTC temperature because of the developed aromatic structures in hydrochar. The pyrolysis activation energy decreased from raw RS 71.68 to 41.03 kJ/mol in 240 °C, while gasification activation energy increased from 80.42 to 251.30 kJ/mol. Moreover, it was found that HTC can reduce the content of AAEMs efficiently and the best removal condition is 200 °C. Ca content dropped to a minimum value at 200 °C and then increased at higher temperature which may be caused by well-developed pore structure in hydrochars. This study provides basic data for comprehensive utilization of rape straw and migration mechanism of AAEMs in HTC process.

Gasification of chars from tetralin liquefaction of < 1.5 g cm−3 carbon-rich residues derived from waste coal fines in South Africa

The float–sink density separation method was used to produce a < 1.5 g cm−3 coal density fraction. The sample was subjected to tetralin liquefaction experiments and pyrolysed to produce char samples. The < 1.5 g cm−3 coal density fraction and its liquefaction carbon-rich residue chars formed from the pyrolysis experiments were evaluated using the CO2 gasification tests. The chars were characterized using a thermogravimetric analyzer by heating the samples at isothermal temperatures between 880 and 940 °C under a CO2 atmosphere. The results obtained from the gasification experiments revealed that the gasification reactivity values (Ri, Rs, Rtf, Rt/0.5) of the liquefaction carbon-rich residue chars were higher than those of the < 1.5 g cm−3 coal density fraction chars. Some inherent mineral matter in the residues may play a catalytic role during gasification of South African lighter density waste coal density fractions and their liquefaction residue chars. The initial reactivity of the liquefaction residue chars was observed to be approximately double than those of the < 1.5 g cm−3 coal density fraction chars. Significant increases in a number of pores were associated with the liquefaction experiments of these carbon-rich particles, which aid in the acceleration of the gasification reactions. These increases in the number of pores assisted the reduction of the gasification activation energy values. The RPM was shown to fit the experimental data the best and used to determine kinetic parameters. The gasification activation energy of the < 1.5 g cm−3 coal density fraction chars was shown to be 190.5 kJ mol−1 and 236.7 kJ mol−1 for Highveld float (HF) and Waterberg float (WF) chars, respectively. The values of the apparent activation energy for the liquefaction carbon-rich residues from the same two < 1.5 g cm−3 coal density fraction residue samples were 145.3 kJ mol−1 for the Highveld coal sample and 196.0 kJ mol−1 for the Waterberg coal sample. The gasification results obtained in this study indicate that the possibility of utilizing the waste coal floats and their liquefaction carbon-rich residues in the thermochemical processes (pyrolysis and gasification) is high.

ВИЗНАЧЕННЯ КІНЕТИЧНИХ ХАРАКТЕРИСТИК ПРОЦЕСУ СПІЛЬНОЇ ГАЗИФІКАЦІЇ КАМ’ЯНОВУГІЛЬНИХ ФУСІВ З БУРИМ ВУГІЛЛЯМ ТА ШКАРАЛУПОЮ ВОЛОСЬКОГО ГОРІХА

Studied of co-gasification of heavy coal tars with lignite and walnut shell in the temperature ranged from 400 to 500 °С, the flow rate of oxidand (air) ranged from 0,0005 to 0,004 m3/min. It is established that the weigth loss of the sample mixtures in the gasification process has a S-shaped. Mathematical and graphical dependences of the influence of oxidant flow rate on the values of reaction rate constants and activation energy of gasification of experimental mixtures were developed.

Gasification Characteristics and Kinetics of Unburned Pulverized Coal in Blast Furnaces

Pulverized coal injected into a blast furnace (BF) burns incompletely in a very limited amount of time. A considerable amount of unburned pulverized coal (UPC) escapes from the raceway to the coke layer. The unburned pulverized coal reacts with CO2 in the coke layer, and this has a very significant impact on the operation of the BF. The gasification reaction characteristics of the UPC with CO2 were assessed by thermogravimetric analysis. The microstructure and specific surface area of the pulverized coal and UPC were characterized by scanning electron microscopy (SEM), and a specific surface area testing apparatus together with the Brunauer-Emmett-Teller (BET) method, respectively. The results showed that Qingding UPC requires a higher temperature to complete the gasification reaction. At the same heating rate, the Tm (maximum reaction rate temperature) of the Shenhua UPC is much lower and the reaction rate is larger than those of the Qingding UPC. An increased heating rate is beneficial for the gasification reaction of the two UPCs. The kinetics analysis results showed that the optimal mechanism function models for the Shenhua and Qingding UPCs are chemical reaction models. The apparent activation energies of gasification of the Shenhua UPC and Qingding UPC under different conditions were 269.89–223.41 KJ/mol and 266.70–251.54 KJ/mol, respectively.

Effect of atmosphere and temperature on syngas production during gasification of Zhundong lignite and water-washed Zhundong lignite in a fixed-bed reactor

The effect of temperature and atmosphere on the syngas yields of CO and H2 during gasification of Zhundong lignite (ZD) and water-washed Zhundong lignite (WWZD) in a fixed-bed reactor was investigated. The experiments were run over temperatures from 750 to 950 °C, atmospheres of pure steam or with CO2 addition ratios of 25–75%. The syngas yield rate, overall yield, carbon conversion rate and the activation energy for gasification of carbon in coal were obtained. Results showed that the yield rates of CO and H2 during pure steam gasification of ZD at 750 °C increased from 0 to a maximum of 5.4 and 19.4 ml/min and decreased afterwards, when H2 was found as the main syngas. Moreover, CO was not detected while H2 was identified at a later stage of gasification, indicating that the char-steam gasification and water–gas shift reaction were dominated at this stage. As the temperature increased to 950 °C, the maximum yield rates of CO and H2 increased, confirming that the increase in temperature promoted gasification. Likewise, the increase in CO2 ratio from 25 to 75% resulted in a maximum CO yield rate of 163.87 ml/min at 950 °C, promoting CO yield when CO2 was the gasifying agent. The maximum yield of H2 was, however, decreased while the Boudouard reaction was promoted. Water washing was found to significantly influence gasification. The maximum yield rates of CO and H2 were decreased and the gasification time was prolonged, indicating that the reactivity of char-steam gasification was decreased due to the removal of Na contents by water washing. In addition, the overall yield of CO was increased as temperature and the CO2 percentage increased, whereas that of H2 decreased. The activation energy for steam gasification of ZD as determined by the momogeneous model (HM), shrinking core model (SCM) and isoconversional method was in the range of 53.36–56.14 kJ/mol, all of which were applicable for determining the activation energy of ZD gasification under steam.

Kinetics of CO2 gasification of biomass char in granulated blast furnace slag

The CO2 gasification reactions of biomass char in granulated BFS (blast furnace slag) were isothermally investigated using a thermogravimetric analyzer with the temperature ranging from 1173 K to 1323 K. The effects of temperature, biomass type and granulated BFS on the kinetic characterizations of CO2 gasification of biomass char were illuminated. The kinetic mechanism models and parameters were obtained through a novel two-step calculation method. The results indicated that the CO2 gasification reactivity of biomass char as conversion and gasification index increased with the increase of temperature and it could be promoted through granulated BFS. The CO2 gasification reactivity of CS (cornstalk) char with lower alkali index was lower than that of PS (peanut shell) char. The A4 model (Avrami-Erofeev (m = 4) model) and A3 model (Avrami-Erofeev (m = 3) model) were demonstrated as the best appropriate models for CO2 gasification of CS char and PS char, respectively. The gasification activation energy of CS char ranging from 155.08 to 160.48 kJ/mol was higher than that of PS char whether with or without granulated BFS. Granulated BFS could decrease the activation energy of CO2 gasification of char at any biomass type.

Effect of mixing charge of highly reactive semicoke nut on the reaction of high Al2O3 ferrous burden in blast furnace

ABSTRACTIn order to improve the performance of blast furnace ironmaking when using the high Al2O3 iron ore, the technology of mixing charge of high reactive semicoke nut with ferrous burden was proposed and systematically investigated at laboratory scale in the present paper. The CO2 gasification activation energy of semicoke ranged from 136.5 to 150.3 kJ mol−1, which was lower than that of the traditional coke. At the temperature of 1200°C, the reduction degree of ferrous burden increased a little with the addition of semicoke nut and the consumption ratio of semicoke was 14.0 wt-% under the simulated blast furnace ironmaking condition. The mixing charge of semicoke could obviously reduce the softening beginning temperature, increase the melting temperature and improve the permeability compared with the standard and traditional coke mixing charge samples. During the total softening and melting process, about 90 wt-% of the semicoke nut and 45 wt-% of the traditional coke nut were consumed, respectively. The experiment results indicated that the mixing charge of high reactive semicoke nut could obviously improve the performance of blast furnace ironmaking when using high Al2O3 ferrous burden and the semicoke was more effective than traditional coke.

Influence of Wet Torrefaction Pretreatment on Gasification of Larch Wood and Corn Stalk

Biomass was wet-torrefied to improve its properties prior to gasification. Two kinds of biomass were employed as feedstock, including the larch wood and corn stalk. For both larch wood and corn stalk, the oxygen content of torrefied samples reduced greatly, while the carbon content increased. All of these features had a positive effect on the gasification process, which was discussed in the research. During steam gasification, all of the wet-torrified biomass samples yielded higher amounts of H2 and CO compared to the raw biomass samples, showing the superiority of the wet torrefaction (WT). During CO2 gasification, the CO production was also significantly improved by WT. The kinetic characteristic parameters for the gasification of raw and torrefied biomass samples were determined using the random pore model. It was found that the activation energy of gasification could be reduced by the WT process.

Non-isothermal study of gasification process of coal char and biomass char in CO2 condition

AbstractNon-isothermal method was used to study gasification characteristics of three coal chars and one biomass char. Four chars were made from anthracite coal (A), bituminous coal (B), lignite coal (L), and wood refuse (W), respectively. The gasification process was studied by random pore model (RPM), unreacted core model (URCM) and volumetric model (VM). With an increase in metamorphic grade, the gasification reactivity of coal char decreased, and the gasification reactivity of biomass char was close to that of low metamorphic coal char. With an increase in heating rate, the gasification of all samples moved towards high temperature zone, and the whole gasification time decreased. It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char, and the RPM fitted the best among the three models. In the RPM, the activation energies of gasification were 193. 9, 225. 3 and 202. 8 kJ/mol for anthracite coal char, bituminous coal char and lignite coal char, respectively. The gasification process of biomass char could be described by the URCM and VM, while the URCM performed better. The activation energy of gasification of wood refuse char calculated by the URCM was 282. 0 kJ/mol.

Analysis of energy consumption for lump coal degradation in melting gasifier

The volume hypothesis, a theory about the energy scale of comminution, was adopted to analyze the degradation behavior of lump coal under different heating time. The breakage energy of chars was determined by a compression test, and the results show that the ultimate strength of chars decreased at the early stage during the heating process, resulting in a decrease of the char breakage energy. At the late stage during the heating process, the char breakage energy increased with the increase of heating time. The power consumption coefficients CK of different chars were determined by a drum experiment, and then the char degradation behavior under different power consumptions was predicted. In addition, a gasification experiment was conducted to determine the gasification activation energy (with CO2) of lump coal heated for different time. The results show that the gasification activation energy increased greatly at the early stage during the heating process, which showed opposite change to the breakage energy of chars. Furthermore, the internal temperature and heat changes of the bonded coal briquette were calculated by using an unsteady heat conduction equation. The large difference between the surface and the center temperatures of coal and the large amount of heat absorption at the early stage during the heating process may have a negative effect on the breakage energy of chars.

Performance evaluation on co-gasification of bituminous coal and wheat straw in entrained flow gasification system

Co-gasification of coal and biomass can reduce the CO2 emission and the consumption of fossil fuel. Kinetic analysis and products distribution evaluation are essential to the gasifier design and operation optimization. In this paper, the thermal behavior on co-gasification of a kind of bituminous coal blended with wheat straw was investigated by the thermal gravimetric analyzer and distributed activation energy model. Gaseous products evolution during co-gasification was explored by entrained flow gasification system. The influence of gasification temperature (1100–1400 °C), biomass mixing ratio (0, 0.25, 0.5, 0.75, 1), and oxygen/carbon ratio (0.35–0.65) on H2 and other gaseous products was considered. The result indicated that the adding of wheat straw promoted the gasification performance. The value of Tgin (initial gasification temperature) and Gi (gasification reactivity index) increased as the increasing mass ratio of wheat straw. The distributed of gasification activation energy showed positive synergistic effect. The value of gasification activation energy gradually decreased from 193.58 to 100.62 kJ mol−1, 115.11 kJ mol−1, 129.57 kJ mol−1 as the mass ratio of wheat straw increased from 0.25 to 0.75. The content of H2 and CO increased with the rising of gasification temperature, and the content of CO2 and CH4 showed the opposite trend. At the same time, cold gas efficiency (CGE) increased with the raising of gasification temperature, indicating that the improvement of gasification temperature is beneficial to the improvement of co-gasification gas quality. The content of H2 and CO2 also increased the growth of wheat straw mass ratio. Synergistic effect of gaseous distribution was also observed, especially in 50% of biomass ratio. As the increasing of oxygen–fuel ratio, the content of H2 and CH4 decreases gradually. Synthesizes each kind of condition with the operation condition of gasification equipment and the quality of gaseous products, the gasification temperature of 1300 °C and the oxygen–fuel ratio of 0.45 were the optimum operating parameters for co-gasification of bituminous coal and straw. This research can provide basic information for process design and parameter selection of co-gasification.

Non-isothermal kinetics of metallurgical coke gasification by carbon dioxide

Under non-isothermal conditions, thermogravimetric analysis was applied to study carbon dioxide gasification of three metallurgical cokes. The cokes selected for the study were named Coke A, Coke B and Coke C. The experimental data are fitted using four common gas-solid kinetic models: the homogeneous model, the sharp interface model, the traditional model and the random pore model. It is found that the random pore model most closely reflects the kinetic behavior of coke gasification characteristics. Using the random pore model, the apparent activation energies for gasification of Coke A, Coke B, and Coke C were calculated to be 139.08, 127.78, and 116.32 kJ mol–1, respectively.

CO2 gasification characteristics of nascent pyrolyzed particles from coals and oil shale

Summary In this work, the co-pyrolysis characteristics of oil shale with two typical coals, bitumite and lignite, and the co-gasification characteristics of the mixture pyrolyzed fuels were studied via thermo-gravimetric analysis. The individual fuels and mixture fuels were first pyrolysis in N2 atmosphere to specified temperature (450, 550, and 620 °C) at the heating rate of 20, 30 and 40 °C/min, respectively, and then maintained at the given temperature for 20 min before converted to CO2 ambient to conduct the CO2 gasification tests. The kinetic behavior and effects of both fuel types and pyrolysis temperature were investigated. The shoulder peak at around 550 °C observed in the derivative of weight loss derivative thermogravimetry analysis (DTG) curve during the pyrolysis of oil shale has confirmed the existence of specific reactions of oil shale at around 550 °C that leads to a sharp trough in the differential curves of co-pyrolysis with coals and the unusual change in activation energies of gasification. In isothermal pyrolysis stage, oil shale lost its vast majority of organic matters at the temperature lower than 550 °C. The escape of pyrolysis gas and liquids in the coals is much harder than that in oil shale. The interaction between oil shale and bitumite was too weak to discriminate both in the pyrolysis and CO2 gasification process. The variation of the particle surface structure caused by the releasing of volatile gases is strongly affected by the reaction rate and temperature. Quick volatile decomposition and gas releasing lead to the increase of surface area, decrease of the average pore diameter as well as the uniformization of the pore structure, while the higher temperature results in the blockade and merging of fine pores. The two factors lead to the greatest mass loss rate in the pyrolyzed particles obtained at 550 °C in temperature programmed CO2 gasification stage. Two model-free methods, Friedman method and Flynn–Wall–Ozawa method, were used to extract kinetic parameters from the experimentally determined pyrolyzed fuel conversions. The volatile contend has a significant influence on the fixed carbon conversion during the partially pyrolyzed particles' CO2 gasification. In this study, significant interactions existed in co-thermal utilization, both pyrolysis and CO2 gasification, of oil shale and lignite. It is therefore surmised that co-gasification of pyrolyzed lignite and oil shale may represent a feasible, practical route to high-efficiency utilization of these fuels. Copyright © 2017 John Wiley & Sons, Ltd.

Gasification Reaction Characteristics between Biochar and CO2 as well as the Influence on Sintering Process

For achieving green production of iron ore sintering, it is significant to substitute biochar, which is a clean and renewable energy, for fossil fuels. In this paper, the gasification reaction between CO2 and biochar was investigated. The results showed the initial temperature and the final temperature of the gasification reaction between biochar and CO2 were lower, while the maximum weight loss rate and the biggest heat absorption value were much higher than those of coke breeze, which indicated gasification reaction between the biochar and CO2 occurred rapidly at lower temperature. The gasification activation energy of biochar was 131.10 kJ/mol, which was lower than that of the coke breeze by 56.26 kJ/mol. Therefore, biochar had a higher reactivity and easily reacted with CO2 to generate CO. As a result, when biochar replaced coke powder at equal heat condition in sintering process, the combustion efficiency of fuel decreased and was disadvantage to the mineralization of iron ores at high temperature. With the increase of substitute proportion, the sinter yield, tumble strength, and productivity were decreased. The proportion of biochar replacing coke breeze should not be higher than 40%. By reducing the heat replacement ratio of biochar, the yield and quality of sinter got improved.