神府煤热解的结构变化及煤焦加氢反应性研究

将煤加氢过程分解为原煤热解和焦加氢两个过程,在固定床反应器内研究了煤热解和焦加氢反应。采用红外气体分析仪、拉曼光谱仪和X射线衍射仪,分析研究了煤热解过程中气体组分含量与煤焦微观结构变化的相互关系以及煤焦微观结构对其加氢反应特性的影响。结果表明,热解温度对煤焦的微观结构和加氢反应性有较大影响,400-800℃,随着温度升高,煤焦拉曼分峰面积比A_(D1)/A_G、A_(D2)/A_G、A_(D3)/A_G、A_(D4)/A_G均上升,A_G/A_(All)减小。800-900℃,A_G/A_(All)增大,无序碳的相对含量增加,石墨化进程明显。煤焦的XRD分析与拉曼光谱分析结果一致。400-800℃,随着温度升高,煤焦中碳结构晶面间距d_(002)先增加后减小,堆垛高度L_(002)增加,晶面间距与堆垛高度比d_(002)/L_(002)减小,煤焦中石墨碳结构的含量增加。800-900℃,d_(002)减小,L_(002)明显增大。采用拉曼分峰比(aA_(D1/G)+bA_(D2/G)+cA_(D3)/G+dA_(D4/G))与加氢反应性特征参数τ_(0.5)进行线性拟合,得到代表碳微晶结构加氢反应性的拟合因子,且拟合因子越大,相应碳微晶的加氢反应性越好。     

Investigation into the kinetics of pressurized steam gasification of chars with different coal ranks

The steam gasification of coal chars derived from three different ranks of typical Chinese coals was studied in a pressurized fixed-bed differential reactor at elevated pressure (up to 2.0 MPa). Three mathematical models [volumetric model (VM), grain model (GM), and random pore model (RPM)] for the gasification kinetics of different chars were validated, through which the kinetic parameters were obtained and discussed. The results show that the evolution trend of the coal char gasification rate with carbon conversion differs from coal ranks and has little change with pressure and temperature. The pressurized gasification process of the Shenmu sub-bituminous coal char (SM char) and the Jingcheng anthracite char (JC char) can be well-predicted by the RPM, while that of the Huolinhe lignite char can be better described by the VM. The pressure has little effect on the options of the reaction kinetic models for the three chars. The kinetic parameter E is almost a constant independent of pressure, while k ₀ changes with pressure, and it seems that k ₀ would be almost a constant over 1.0 MPa for SM and JC chars. The reaction order decreases with increasing the total system pressure and differs from different coal types.     

升温速率对神木煤热解半焦结构性能的影响

利用管式炉和微波材料工作站分别对神木煤煤样进行终温为750 ℃的慢速(3和5 ℃/min)、中速(10和15 ℃/min)及快速(50、100、225、350和750 ℃/min)热解,基于热解半焦X射线衍射谱图解析热解半焦的微晶结构参数,采用傅里叶变换红外光谱表征热解半焦的表面化学,并借助热重分析仪、选用气化活性参数R_T评价热解半焦的气化反应活性。结果表明,随着升温速率的增大,神木煤热解半焦总体上呈现的趋势是:表面含氧官能团含量降低,半焦的微晶层片尺寸L_a和石墨化度明显提高,层间距d₀₀₂和堆积高度L_c略微减小,说明神木煤半焦结构随升温速率的提高变得规整;随着升温速率的增大,半焦的气化活性R_T从0.178 2降低至0.103 6。热解终温为750 ℃的神木煤热解过程中,快速热解有利于获得易石墨化、表面非极性化、气化反应性低的产物。     

低温加压热解脱氧对胜利褐煤亲水性的影响

在固定床反应器中考察了低温（200~350 ℃）、加压（0.25~8.00 MPa）热解条件下胜利褐煤主要含氧官能团的变化规律,并进一步分析了褐煤中含氧官能团的脱除对其吸水能力的影响。结果表明,温度升高对胜利褐煤中羧基和酚羟基的脱除非常有效,压力变化对羧基脱除影响极小,而在3.00~4.00 MPa时对酚羟基脱除效果最佳;同时羧基对煤样的表面极性和亲水性具有决定性作用,当羧基含量不变时,固体比表面积对煤样的吸水性影响相对较明显。     

Physicochemical properties evolution of chars from palm kernel shell pyrolysis

To clarify the effect of the pyrolysis operating conditions of the biomass on the physicochemical properties of the char and its combustion reactivity, palm kernel shell was pyrolyzed at different temperatures (400–700 °C). Analyses such as proximate and ultimate analysis, XRD, FTIR, N₂ adsorption, and SEM were used to investigate the physicochemical properties of biochar samples. The results show that an increase in pyrolysis temperature led to a development of pore structure and specific surface area of the produced biochar, which was beneficial for improving the biochar combustion reactivity. Besides, with increase in pyrolysis temperature, the carbon content exhibits a raise trend, but the oxygen and hydrogen contents exhibit the opposite behavior, and the aromaticity and graphitization degree of biochar produced at high temperature also increase. The combustion reactivity of biochar was found to be highly dependent on the pyrolysis temperature, and the aromatic structure and graphitization degree have greater effects on biochar combustion reactivity than those of the specific surface area and pore structure.     

Structural and conductivity changes during the pyrolysis of polyaniline base

Polyaniline base has been exposed to various temperatures between 100 °C and 1000 °C for 2 h in air. The mass loss has increased with increasing temperature. FTIR and Raman spectroscopies show the gradual destruction of the PANI structure, the possible formation of intermediate oxime and nitrile groups, and the final conversion to graphitic material. The elemental analysis confirmed the dehydrogenation while the content of nitrogen was nearly constant even after treatment at 800 °C. The conductivity of PANI base, 10⁻⁸ S cm⁻¹, increased to ∼10⁻⁴ S cm⁻¹ after treatment at 1000 °C; most of the products, however, were non-conducting. Another series of experiments involved the polyaniline base heated at 500 °C for 1-8 h. The studies were performed in connection with the potential flame-retardant application of polyaniline.     

Insights on structural characteristic of Xilinguole lignite chars from low-temperature pyrolysis

The cleavage behavior of covalent bonds in Xilinguole (XLGL) lignite and changes in chemical structure of lignite and its chars during low-temperature pyrolysis were investigated by thermogravimetric (TG) analysis and Fourier-transform infrared (FTIR) spectroscopy. Based on the TG and differential thermogravimetric (DTG) analysis results, the cleavage of different types of chemical bonds in lignite occurred mainly at four certain temperatures, 170 °C, 376 °C, 432 °C, and 521 °C. The latter three were selected as the final pyrolysis temperatures of chars evaluated in this study. The FTIR analysis results indicate that thermal treatment increased the relative content of two and three adjacent H deformation structures but decreased that of four adjacent H deformation structure. This was caused by the cleavage of C_al–C_al and C_ar–C_al bonds. The oxygen-containing functional groups in lignite are dominated by C–O and C–OH groups with a lower chemical reactivity than C=O–C and conjugated C=O groups. Moreover, XLGL lignite has the highest ratio of CH₂/CH₃ which declines with increasing temperature, indicating the decrease in the length of aliphatic chains and increase in the degree of branching of aliphatic side chains. This change mainly resulted from the cleavage of C_al–O, C_al–C_al, and C_ar–C_al bonds. Furthermore, XLGL lignite and its chars contain five specific hydrogen bonds: OH–N, cyclic OH, OH–ether O, OH–OH, and OH–π hydrogen bonds. The relative content of OH–OH hydrogen bond was the highest, indicating that OH–OH hydrogen bond has the highest thermal stability.

     

The kinetics of CO2 gasification of coal chars

The gasification reactivities of three char samples derived from coals of varying ranks (“Turów” lignite, “Piast”, and “Wieczorek” sub-bituminous coals) toward CO₂ were investigated isothermally using thermogravimetric analysis. Kinetic behavior was studied at temperatures of 900, 950, and 1,000 °C under atmospheric pressure. Conditions for the chemical-controlled regime were established at these temperatures and pressure. In this paper, four kinetic models were applied to describe the varying conversion rate: volumetric model, grain model, modified volumetric model, and random pore model. From these models, only the random pore and the volumetric models positively corresponded to nearly the entire range of experimental results. Calculated values of activation energy for study samples were in the range of 180–250 kJ mol^?1, which is in accordance with other reported data. Moreover, the obtained results confirmed the significant impact of parent coal rank on its char reactivity, offering possibilities in the approximation of coal char kinetic behavior after further more detailed studies with a larger number of samples.     

神府烟煤水煤浆快速热解焦结构演化及其反应性的研究

利用高频热解装置对神府烟煤水煤浆及其原煤进行了600~1 200 ℃条件下的快速热解实验,考察了两者快速热解后的煤焦产率、焦-C产率随热解温度的变化规律.利用XRD、氮气气体吸附法、SEM等测试手段对比分析了水煤浆及煤粉热解后煤焦的微晶结构、孔隙特征及表观结构;在热重分析仪上进行CO₂气化反应活性的测定,对比了水煤浆和煤粉热解后煤焦的气化活性.实验表明,随着热解温度的升高,水煤浆和煤粉的热解焦产率、焦-C产率均逐渐降低,热解温度低于900 ℃时,两者热解焦产率、焦-C产率趋于一致,热解温度高于900 ℃时,水煤浆热解焦产率和焦-C产率明显低于煤粉热解焦;高温热解条件下,水煤浆热解焦的微晶有序化程度比煤粉热解焦略高,比表面积明显高于煤粉热解焦,水煤浆热解焦的气化活性优于煤粉热解焦.     

褐煤热解过程中半焦重整催化剂性质的变化

为降低焦油产率,提高褐煤气化效率,采用胜利褐煤热解所得的半焦作为催化剂,在二阶石英反应器中对煤热解的焦油进行原位催化重整,分析和讨论了反应前后半焦催化剂的性质变化。结果表明,反应后半焦质量较反应前普遍有所下降,半焦是一种消耗性催化剂;反应后半焦的比表面积由422 m~2/g降到231.8 m~2/g;Raman分析结果表明,反应后半焦含氧官能团、小环(3-5个缩合芳环)与大环(大于5个缩合芳环)体系之比均有所降低。在半焦-挥发分作用过程中,快速热解制得半焦主要将挥发分裂解为小分子气体,慢速热解制得的半焦则主要使挥发分缩聚结焦脱除。     

热态半焦和冷态半焦催化裂解煤焦油研究

对比研究了热态半焦(原位热解半焦)和冷态半焦(热解后温度降至常温的半焦)对煤焦油的催化裂解特性。结果表明,相同条件下,热态煤半焦比冷态煤半焦具有更高的催化裂解焦油能力。当裂解温度为1 100 ℃,热解气体在热态半焦层中的停留时间为1.2 s时,催化裂解后燃气中焦油含量可降至100 mg/m³。BET分析结果表明,热态半焦比冷态半焦具有更大的比表面积和更发达的微孔结构。同时,在不可避免经历相对明显的高温过程中,冷态半焦的碳微晶结构有序度增加,进而导致其活性有所降低。随着气体停留时间的延长或催化裂解温度的提高,燃气中焦油含量迅速降低,但热态半焦与冷态半焦催化裂解焦油的活性差异也变小。半焦催化裂解焦油后,活性明显降低,但使这种半焦与水蒸气发生部分气化反应后,其活性基本得到恢复。     

Reactivity and characterisation of various rank turkish bituminous coal chars

A set of seven bituminous coal chars has been characterised by IR spectroscopy (FTIR), thermogravimetry (TG) and elemental analysis. FTIR study provided suitable information to establish differences between coal samples according to their chemical compositions. The reactivity of these samples was also studied and correlated with the coal parameters of mean vitrinite reflectance, fuel ratio and H/C ratio. The data suggest that reactivity as determined can be correlated with the mean vitrinite reflectance, fuel ratio and H/C ratio (0.90). The order of reactivity of samples were; Amasra (S1) (R _m= 0.65)>Azdavay (S4) (R _m=0.99)»Armutcuk (S2) (R _m=0.81)»Acenta (S3) (R _m=0.92)>Ac2l2k (S6) (R _m=1.11) Cay (S5) (R _m=1.03)>Sogutozu (S7) (R _m=2.14).     

煤焦吸附和还原NO的动力学研究

利用固定床反应器研究了煤焦吸附和还原NO的动力学,分析了热解温度(500℃～900℃)和矿物质对煤焦脱除NO的影响。结果表明,在程序升温反应(TPR)和等温反应中,随着温度的升高(30℃～600℃),煤焦-NO经历了从化学吸附到还原反应的转变。低温时煤焦脱除NO的动力学符合Elovich方程,原煤焦的起始吸附速率随着温度的升高而增大,脱灰煤焦的起始吸附速率先增大后减小,等温吸附过程中煤焦的活化能随着吸附量的增大而增大。随着热解温度的升高,TPR中煤焦的NO转化率降低,等温还原反应的速率常数减小,高温热解导致煤焦脱除NO的活性降低。矿物质对煤焦-NO的吸附和还原反应存在催化作用。     

Cation exchange capability and reactivity of low-rank coal and chars

In this work the C.E.C. and its effect on the reactivity of low rank coal and chars were investigated. The C.E.C. was measured by potentiometric titration and was correlated with the solution pH, the carbonization extent and the oxygen content. Coal and chars presented permanent C.E.C. primarily derived from inorganic sites and was independent of solution pH, and variable C.E.C. derived from organic matter and was increased continuously, and reversibly, as the solution pH increased. The latter is due to the complete dissociation of the carboxylic groups of the organic matter of the coal and, thus, the C.E.C. is directly related with the oxygen content. The C.E.C. of chars decreased with the carbonization extents and its variation was described by a modified cumulative distribution function of the Weibull probability density function. A linear correlation was identified between the C.E.C. and the elemental oxygen conversion, justifying further the direct relation between the C.E.C. and the oxygen functional groups. Following the decrease of the C.E.C., the potassium chemisorption capacity of the chars also decreased. Chars of decreased C.E.C. were less reactive during CO₂ gasification and reduced maximum weight loss and CO formation rates were obtained, also shifted at higher temperatures.      

热解压力对生物质焦结构及气化反应性能的影响

利用加压固定床反应器、吸附仪、X射线衍射仪、元素分析仪、电感耦合等离子原子发射光谱仪等考察了热解压力对生物质半焦(以下简称半焦)产率、物化结构、元素组成的影响规律。同时,利用热天平对不同热解压力下所制半焦的气化行为进行了考察。结果表明,随热解压力升高,半焦产率增大,当压力升至1.0 MPa后,半焦产率基本不变;半焦中C元素含量随热解压力的升高而增加,而H元素含量和BET比表面积则减小;此外,随热解压力升高,玉米秸秆焦和锯末焦的石墨化程度增强,而稻壳焦的石墨化程度则基本不受热解压力影响。气化反应的研究表明,玉米秸秆焦及锯末焦的平均气化反应速率随热解压力的提高而减小,而稻壳焦的平均气化反应速率基本不受热解压力的影响。热解压力对半焦BET比表面积及碳微晶结构的影响规律与气化反应速率变化规律的对比研究表明,热解压力引起半焦微晶结构的变化是造成热解压力对半焦气化反应速率影响的主要原因。     

不同煤阶热解半焦的FT-Raman光谱研究

在热天平上采用慢速升温制备了褐煤、高挥发分烟煤和低挥发分烟煤的半焦。采用FT-Raman光谱对半焦进行了分析。半焦800cm^-1至1800cm^-1的Raman光谱可分解为10个谱带,以表征高度无序炭材料中的典型结构。光谱和谱带的强度比都可用来描述半焦的结构特征。在600℃低温热解时,三种煤半焦的结构差异明显。随热解温度升至800℃或900℃,这种差别消失。褐煤中可交换的钠离子影响热解过程中的成焦反应。     

煤焦表面官能团对甲烷裂解的影响

采用石英管固定床反应器,考察了1 123 K,CH_4/N_2=1∶4的状态下,煤焦表面官能团对甲烷裂解的影响。煤焦表面主要含有羟基、羰基和醚键等官能团,分别通过氢氧化钡、苯肼和碘化氢溶液对煤焦表面进行化学处理,除去煤焦表面相应的官能团,研究处理后煤焦的催化活性,得出煤焦中官能团对甲烷裂解的影响。氢氧化钡处理煤焦后,煤焦中部分羟基被氢氧化钡消耗,甲烷初始转化率和氢气初始收率分别为90.5%和65.2%,说明煤焦中的羟基不利于甲烷的裂解。通过苯肼处理煤焦中羰基并使之转化,甲烷初始转化率和氢气初始收率分别为55.4%和42.9%,说明煤焦中的羰基对甲烷裂解有利。碘化氢处理煤焦后,煤焦中的醚键转化成羟基,甲烷的转化率和氢气收率都明显下降,说明醚键的存在对甲烷裂解同样有利。随着反应时间的延长,甲烷的转化率和氢气的收率降低,催化剂逐渐失活。反应前后煤焦电镜扫描照片表明,甲烷裂解生成的积炭沉积在煤焦表面,堵塞煤焦的孔道,煤焦的比表面积减小,催化活性降低。     

A thermal analysis study of the oxidation of brown coal chars

The combustion of brown coal chars, obtained at different pyrolysis temperatures, have been investigated using TG, DTG and DTA thermal analysis methods. The burning profiles and the kinetic parameters derived from TG and DTA data show that all the chars are less reactive than the parent coal. The higher temperature chars have lower overall reactivity. From the corresponding infrared spectra, the chars obtained at 800 °C and 1000 °C appear to have graphitic structures.

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Zusammenfassung Mittels TG-, DTG- und DTA-Methoden wurde die Verbrennung von unter verschiedenen Pyrolysetemperaturen erhaltenen Braunkohlenschwelkoksen untersucht. Das Verbrennungsprofil und die kinetischen Parameter, erhalten aus TG und DTG, zeigen, daß die Schwelkokse eine geringere Aktivität haben, als die ursprüngliche Braunkohle. Die Schwelkokse höherer Temperatur besitzen eine niedrigere resultierende Aktivität. Aufgrund der entsprechenden IR-Spektren besitzen die bei 800 °C und 1000 °C erhaltenen Schwelkokse eine Graphitstruktur.

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神木煤流化床气化带出细粉的特性

采用灰熔点测定仪、扫描电镜-能谱分析仪和热重分析相结合,研究了神木煤流化床气化带出细粉的灰熔融特性、粒径分布和气化反应活性。结果表明,神木煤流化床气化带出细粉中酸性成分的减少和碱性成分铁、钙等的增加,使神木煤流化床气化带出细粉的灰熔点比原煤低。神木煤流化床气化带出细粉具有较宽的粒径组成,呈现出明显的多峰状分布,带出细粉表面的元素分布存在很大的差异。随着带出细粉粒径的减小,细粉中的水分逐渐减少,灰分含量逐渐增大。气化飞灰的孔隙结构比高温煤焦更发达,具有比较丰富的中孔和大孔,导致带出细粉的反应活性比神木煤焦高。