酸洗脱灰对准东次烟煤结构和反应活性的影响

研究酸洗脱灰过程对煤的化学结构和反应活性的影响对煤的清洁高效利用十分重要。采用HCl-HF-HCl和HF-HNO₃-HCl两种方法对准东次烟煤进行处理,利用傅里叶红外光谱对原煤及其酸洗处理得到的脱灰煤进行结构表征,并用微型流化床多阶段气固反应分析仪对煤粉样品燃烧反应性进行分析。结果表明,酸洗处理可使煤中灰分含量降低到0.2%以下,脱灰煤中OH和COOH附近的吸收峰强度显著增强,脂肪侧链变短,芳香环上取代基减少。HF使得煤中硅铝类矿物质被大量脱除,HNO₃会与煤中有机物发生硝化反应,导致部分含氧官能团含量进一步增加。当温度在600和700℃时,脱灰煤燃烧反应性与原煤相比显著降低,但随着温度升高至800和900℃,脱灰煤与原煤的反应性差距变小。     

煤的结构对直接液化反应性影响的分析

系统地分析了煤的组成结构及液化前的预处理对直接液化反应性的影响，包括煤阶、岩相组成、各种矿物质及酸洗脱除、水分及烘干、孔隙性、物理结构及预溶胀、H／C比等，指出不同的工艺条件下它们对直接液化的影响是不同的。     

LaCoO3: Effect of synthesis conditions on properties and reactivity

Two nanostructured bulk LaCoO₃ powders were prepared by co-precipitation and with the citrate gel method and compared with the two nanocomposites obtained depositing, by wet impregnation, cobalt oxide on the La₂O₃ surface. All the prepared samples were characterized by means of X-ray photoelectron (XP) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic techniques, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis.

XRD results suggest that only the citrate gel method allows to obtain a single phase lanthanum cobaltite powder having a rhombohedral perovskite structure. Moreover, SEM images confirm the wide scale homogeneity. In contrast, a lanthanum hydroxide phase (hexagonal) is also evident in the sample obtained by co-precipitation method. In the nanocomposite richer in cobalt, besides the rhombohedral perovskite, the hexagonal lanthanum oxide and hydroxide phases are also detectable. Perovskite phase does not form when the amount of deposited cobalt oxide is too low. Both in the nanostructured sample prepared by citrate gel method and nanocomposite with [Co/La]_nominal = 1.0 XPS, DRIFT and TGA outcomes suggest a lower presence of hydroxyl groups and carbonates species.

The reactivity of the powders with respect to carbon monoxide was studied (at atmospheric pressure, between RT and 573 K) by means of the diffuse reflectance infrared Fourier transform spectroscopy. A significant signal around 2058 cm⁻¹ testifies about the interaction of CO with the Lewis acidic sites distributed on the surface of all the samples. The two nanostructured bulk LaCoO₃ show a high reactivity toward CO oxidation since 423 K. A similar oxidation capability is observed also for the nanocomposite richer in cobalt. In contrast, a rather low reactivity is displayed from the nanocomposite with lower Co/La nominal atomic ratio and La₂O₃.     

Coke reactivity: Effect of Fe2O3 and K2CO3 addition to the coal charge before carbonization

Six individual coals and one blended metallurgical coal were used in this investigation, and two additives, Fe₂O₃ (up to 1%) and K₂CO₃ (0.5%), were added to each coal before carbonization. Results showed that the additives strongly increase CRI (coke reactivity index) and decrease CSR (coke strength after reaction) of each coke, but there are no significant changes in coke microstructure.     

Fe2O3对高变质程度脱灰煤热解反应性与半焦结构的影响

利用热天平研究了共混合法负载Fe₂O₃高变质程度脱灰煤的热解反应性,结果表明煤粉负载Fe₂O₃后热解反应性高于无负载的热解反应性。负载Fe₂O₃煤样在程序升温加热的马弗炉中制备出半焦,利用FTIR、XRD和RAMAN 等分析了半焦结构。由TG和FTIR可知,负载Fe₂O₃煤样热解时,热解转化率增加,热解后自由基增加。由XRD可知,Fe₂O₃没有使得煤样半焦的002峰衍射角发生明显变化,但使L_a和L_c参数明显降低,说明半焦的微晶结构石墨化程度降低。另外,在XRD分析谱图中发现部分Fe₂O₃被还原成FeO。由RAMAN可知,Fe₂O₃使半焦的G峰峰面积降低,D峰峰面积增加,说明半焦的有机结构有序化程度降低。     

Mineral matter effects on the rapid pyrolysis and hydropyrolysis of a bituminous coal: 2. Effects of yields of C3-C8 hydrocarbons

Effects of minerals on yields of C₃-C₈ volatiles from rapid pyrolysis of a Pittsburgh Seam bituminous coal were investigated. Whole, demineralized, and mineral-treated samples of pulverized coal were heated in 101 kPa He or 6.99 MPaH₂ at 1000 K s⁻¹ to temperatures of up to 1300 K. Yields of C₃, C₄–C₆, and C₆–C₈ hydrocarbon gases were determined as a function of time-temperature history. Calcium minerals decrease yields of all three fractions in pyrolysis under He atmosphere but have little effect on hydropyrolysis. Kaolinite reduces yields in pyrolysis, but increases them in hydropyrolysis. Other minerals, notably FeSO₄, have varying effects on product yields depending on run conditions.     

羧酸钠对准东煤热解过程的影响

将酸洗后的准东煤（H-form coal）进行离子交换得到含羧酸钠的离子交换煤（Na-form coal）,再次酸洗脱钠得到的二次酸洗煤（H-form-1 coal）作为对照试样,在固定床反应器上进行热解。借助便携式气体分析仪、热重分析仪和红外光谱仪研究总挥发分和焦油产率、热解气体组分、焦炭反应活性以及焦炭官能团的变化。研究表明：温度高于600℃时,羧酸钠会减小挥发分产率,抑制CH₄、C₂H₄、C₂H₆气体的产生,高于800℃时促进了CO的生成;羧酸钠抑制了焦油的生成且在700℃时抑制作用最为明显;羧酸钠显著提高了焦炭的反应活性,700℃时效果更为明显。羧酸钠的存在对热解过程中煤焦官能团有显著影响。     

Modified carbonization of polyacrylonitrile by incorporation of FeCl2 and Fe(NO3)3—pore structure

The structure and texture of the pyrolysis product was modified by the incorporation of FeCl₂ or Fe(NO₃)₃ into polyacrylonitrile (PAN). The additives were added to a PAN solution in dimethylformamide. The incorporation of FeCl₂ and Fe(NO₃)₃ into PAN was found to result in carbons with a smaller interlayer spacing than the carbon derived from pure PAN, as well as a larger crystallite size and a larger volume of micropores with a radius of ca. 1.8 nm. FeCl₂ was more effective than Fe(NO₃)₃ in the modification of the carbonization behavior of PAN.     

离子液体预处理对桉木热解半焦结构和反应性的影响

生物质是可再生能源的理想原料,由于生物质有坚硬的木质素外壳保护而难以被有效利用。离子液体（IL）是一种绿色溶剂,可用于木质纤维素预处理从而提高其利用的效率。为了研究IL水溶液预处理对桉木热解产半焦的结构及其反应性的影响,将桉木粉经2%、4%和8%（质量）离子液体（[Bmim]Cl、[Bmim]OAc和[Bmim]H₂PO₄）水溶液在120℃下预处理2 h,然后将预处理后的桉木粉在650℃下热解。采用SEM、FTIR、XRD和Raman分析表征热解半焦的结构变化,利用热重分析仪（TGA）测定半焦与空气在450℃下的反应性。结果表明,随着预处理IL浓度的增加,半焦产率下降,半焦的晶化程度提高,在拉曼光谱中,I_D1/I_G变小,I_G/I_all变大,这表明IL预处理使半焦结构有序增大,并促进半焦中小芳香环向大芳香环聚并,因而降低了半焦的反应性。IL预处理可便捷调节热解半焦的反应性,为生物质的高值化利用提供有效的制备方法。     

Changes associated with natural in situ weathering of a coking coal from southeastern British Columbia

A suite of naturally oxidized coals from a single coal seam from southeastern British Columbia was examined by means of pyrolysis gas chromatography together with ultimate and petrographic analysis. With increasing degree of oxidation (FSI decreasing from 7.5 to 0) a consistent decrease in fixed carbon and hydrogen and an increase in oxygen and moisture were found. Comparing the mildly oxidized coal (FSI 7.5 to 3) with the unweathered coal, there is very little detectable change in pyrolysis gas composition or chemistry. At more advanced stages of oxidation (FSI 3 to 0) the pyrolysis gas is markedly depleted in CO, CH₄, C₂H₄ and C₂H₆ and correspondingly enriched in CO₂. The carbon and hydrogen contents decrease and the oxygen content increases significantly. In the mildly oxidized coal, oxidation rinds develop on vitrinite particles, whereas in the more oxidized coal, microfissures and a darkish cast are evident.     

Some physical properties of Canadian coals and their effects on coal reactivity

The pore volume, surface area and compressibility of eleven Canadian coals, varying in rank from lignite to semianthracite, have been determined by mercury porosimetry, gas adsorption method and relations derived from helium and mercury densities. The total pore volume was measured in the diameter range of 0.2 nm–2.98 μm, which was subdivided into two groups, namely the micropore region (< 0.0036 μm) and the combined meso- and macropore region (0.0036–2.98 μm). It has been determined that the porosity of the eleven coals studied varies from 2 to 39%. It has been found that the total pore volume, micropore volume, surface area and the apparent compressibility of these coals decrease with increase in the carbon content, or the rank of the coals. The effect of the total pore volume, micropore volume and surface area on chemical reactivity of the coal is discussed separately. A good correlation was obtained between the carbon content and helium density of the coal after correction is made for the mineral content.     

秸秆灰对煤焦气化反应性的影响

钾、钙对煤焦气化反应性具有重要影响,秸秆灰中含有丰富的钾、钙。以神木煤为制焦原料,通过STA409PC同步热分析仪研究了秸秆灰对煤焦气化反应性的影响,并通过测定煤焦的碘吸附值对其比表面积及孔隙结构进行了分析。结果表明：煤与玉米秸秆共焦化所得煤焦的气化反应性明显优于单独煤焦,且与玉米秸秆的添加比例有关;采用脱灰玉米秸秆与煤共焦化所得煤焦的气化反应性与单纯煤焦相近;将与玉米秸秆等效的秸秆灰添加到煤焦中,煤焦的气化效果明显优于等效玉米秸秆与煤共焦化所得煤焦。煤焦碘吸附值测定结果表明,脱灰秸秆与煤共焦化所得煤焦的碘吸附值最大,单纯煤焦的碘吸附值最小,说明玉米秸秆及秸秆灰对煤焦的比表面积及孔隙结构具有重要的影响,与煤焦的气化反应性评价结果基本一致。     

Changes in char reactivity and structure during the gasification of a Victorian brown coal: Comparison between gasification in O2 and CO2

Char reactivity is an important factor influencing the efficiency of a gasification process. As a low-rank fuel, Victorian brown coal with high gasification reactivity is especially suitable for use with gasification-based technologies. In this study, a Victorian brown coal was gasified at 800 °C in a fluidised-bed/fixed-bed reactor. Two different gasifying agents were used, which were 4000 ppm O₂ balanced with argon and pure CO₂. The chars produced at different gasification conversion levels were further analysed with a thermogravimetric analyser (TGA) at 400 °C in air for their reactivities. The structural features of these chars were also characterised with FT-Raman/IR spectroscopy. The contents of alkali and alkaline earth metallic species in these chars were quantified. The reactivities of the chars prepared from the gasification in pure CO₂ at 800 °C were of a much higher magnitude than those obtained for the chars prepared from the gasification in 4000 ppm O₂ also at 800 °C. Even though both atmospheres (i.e. 4000 ppm O₂ and pure CO₂) are oxidising conditions, the results indicate that the reaction mechanisms for the gasification of brown coal char at 800 °C in these two gasifying atmospheres are different. FT-Raman/IR results showed that the char structure has been changed drastically during the gasification process.     

Co-carbonization of coking coal with K2CO3: structure of the resulting chars

Oakdale coking coal was co-carbonized with up to 30 wt% of K₂CO₃ to 900 °C. The resulting chars were examined for optical texture and morphology by scanning electron microscopy. No changes in optical texture were observed with additions of < 1 wt% K₂CO₃. Increased additions created an isotropic, non-fusing layer of char around the particles and this prevented the formation of a coherent coke. The size of the remaining anisotropy was also reduced, some char fragments being composed of isotropic carbon. Severe fissuring occurred in the particles of char, causing fragmentation; this was presumably due to diffusion of potassium into the char structure. X-ray studies indicated increased peak half-widths of (002) diffractions for the isotropic carbon.     

载体孔结构对裂解汽油一段加氢Ni/Al2 O3催化剂性能的影响

氧化铝载体的孔结构对裂解汽油一段加氢催化剂性能的影响至关重要。通过优化原粉配比、载体焙烧温度和柠檬酸浓度优化载体孔结构,以获得较大比表面积、大孔容和大孔径的载体。与未优化载体相比,孔体积提高24%,孔径提高40%。在反应器入口温度50℃、反应压力2.6 MPa和体积空速3.0 h~(-1)条件下,使用优化载体制备的催化剂对裂解汽油进行加氢评价试验,结果表明,催化剂稳定性好于参比剂,双烯值稳定在1.5 gI_2·(100g油)~(-1)。     

Influence of pyrolysis conditions on the structure and gasification reactivity of biomass chars

The physical and chemical structure as well as gasification reactivities of chars generated from several biomass species (i.e. pinus radiata, eucalyptus maculata and sugar cane bagasse) were studied to gain insight into the role of heating rate and pressure on the gasification characteristics of biomass chars. Char samples were generated in a suite of reactors including a wire mesh reactor, a tubular reactor, and a drop tube furnace. Scanning electron microscopy analysis, X-ray diffractometry, digital cinematography and surface area analysis were employed to determine the impact of operating conditions on the char structure. The global gasification reactivities of char samples were also determined for a range of pressures between 1 and 20 bar using pressurised thermogravimetric analysis technique. Char reactivities were found to increase with increasing pyrolysis heating rates and decreasing pyrolysis pressure. It was found that under high heating rates the char particles underwent plastic deformation (i.e. melted) developing a structure different to that of the virgin biomass. Pressure was also found to influence the physical and chemical structures of char particles. The difference in the gasification reactivities of biomass chars at pressure was found to correlate well with the effect of pyrolysis pressure on the graphitisation process in the biomass char structure.     

Hydrogenation of Yūbari coal coated with ZnCl2-MCln (CuCl,CrCl3 and MoCl5) catalyst melts

Hydrogenation of Yūbari coal coated with 5 wt% of ZnCl₂-MCl_n (CuCl, CrCl₃ and MoCl₅) was carried out at 400 °C for 3 h with an initial hydrogen pressure of 9.8 MPa. The binary melt catalysts showed relatively higher activity in increasing the yield of hexane-solubles than did ZnCl₂ alone. The ZnCl₂-MoCl₅ catalyst melt was best in view of its highest conversion (90.9 wt%), the highest yield of hexane-soluble material (50.5 wt%) and the smallest hydrogen consumption. In terms of yield of monoaromatics of the hexane-soluble material relative to polar materials, ZnCl₂-CrCl₃ catalyst was superior to ZnCl₂-MoCl₅ although its hydrogen consumption was high. The roles of CuCl, CrCl₃ and MoCl₅ in association with ZnCl₂ in coal-hydrogenation are discussed.     

Differences in reactivity of pulverised coal in air (O2/N2) and oxy-fuel (O2/CO2) conditions

The reactivity of four pulverised Australian coals were measured under simulated air (O₂/N₂) and oxy-fuel (O₂/CO₂) environments using a drop tube furnace (DTF) maintained at 1673 K and a thermogravimetric analyser (TGA) run under non-isothermal (heating) conditions at temperatures up to 1473 K. The oxygen concentration, covering a wide and practical range, was varied in mixtures of O₂/N₂ and O₂/CO₂ in the range of 3 to 21 vol.% and 5 to 30 vol.%, respectively. The apparent volatile yield measured in CO₂ in the DTF was greater than in N₂ for all the coals studied. Pyrolysis experiments in the TGA also revealed an additional mass loss in a CO₂ atmosphere, not observed in a N₂ atmosphere, at relatively high temperatures. The coal burnout measured in the DTF at several O₂ concentrations revealed significantly higher burnouts for two coals and similar burnouts for the other two coals in oxy-fuel conditions. TGA experiments with char also revealed higher reactivity at high temperatures and low O₂ concentration. The results are consistent with a char–CO₂ reaction during the volatile yield experiments, but additional experiments are necessary to resolve the mechanisms determining the differences in coal burnout.     

Changes in pore structure of anthracite coal associated with CO2 sequestration process

Pore structure changing of coal during the CO₂ geo-sequestration is one of the key issues that affect the sequestration process significantly. To address this problem, the CO₂ sequestration process in an anthracite coal was replicated using a supercritical CO₂ (ScCO₂) reactor. Different coal grain sizes were exposed to ScCO₂ and water at around 40 °C and 9.8 MPa for 72 h. Helium pycnometer and mercury porosimetry provide the density, pore size distribution and porosity of the coal before and after the ScCO₂ treatment. The results show that after exposure to the ScCO₂-H₂O reaction, part of the carbonate minerals were dissolved and flushed away by water which made the true density increased as well as total pore volume and porosity most importantly in the micro-pore range. Hysteresis between mercury intrusion and extrusion was observed. Ink bottle shaped pores can be either damaged or created compared with the ScCO₂ treated coal samples. This suggests that the ScCO₂ treatment most likely increase the volumes of pores in anthracite coal, which also contributed to the increase in porosity of the treated samples. Therefore the CO₂ sequestration into coal appears to have the potential to increase significantly the anthracite microporosity which is very advantageous for CO₂ storage.