Process analysis of catalytic multi-stage hydropyrolysis of lignite

The process and the mechanism of multi-stage hydropyrolysis (MHyPy) of coal were investigated by analyzing the products of different MHyPy processes in detail. The results showed that the suitable holding temperature was near the peak temperature (350–500 °C) at which more free radicals were produced rapidly, thus more oil was formed and the hydrogen utilization efficiency was increased. The cleavage of organic functional groups in char from MHyPy was mostly affected by the pyrolysis temperature. The effect of retention was to change the product distribution through stabilization of the free radicals and hydrogenation of the heavier products. In the holding stage the specific surface area and average pore volume of the char were increased due to the escape of more hydrogenation products.     

Low-temperature catalytic conversion of lignite: 1. Steam gasification using potassium carbonate supported on perovskite oxide

The catalytic conversion of alkali metal carbonate (K₂CO₃) catalyst supported on perovskite oxide was carefully examined as an effective catalyst for low-temperature catalytic gasification of lignite. It showed much higher activity than K₂CO₃ alone as well as K₂CO₃ supported on γ-alumina under gasification conditions below 800 °C. Furthermore, catalyzed syngas had higher H₂ and lower CO₂ ratios than non-catalyzed syngas. Promisingly, there was also much less tar formation, less than 50 wt.% compared to non-catalyzed gasification. Also, less loss of K₂CO₃ and no coke formation on the catalyst surface were confirmed, comparing to the catalytic gasification with K₂CO₃ supported on γ-alumina.     

Thermogravimetric study of the devolatilization of hydropyrolysis chars

The devolatilization of hydropyrolysis (HyPy) chars formed at 485–850 °C under 3 MPa and chars formed at 580 °C under 0–5 MPa of H₂ and 3 MPa He is investigated in a thermobalance coupled to two gas chromatographs. The H₂, CH₄ and CO₂ released are analysed every 4 min and all are analysed at the end of the experiment. The amount of residual volatile matter in the chars decreases rectilinearly with the HyPy temperature, whereas their decrease is asymptotic with the HyPy pressure. The char formed under He contains 45% more residual volatile matter than that formed in the same conditions under H₂. The HyPy temperature must be limited if the char is to be burned in a boiler. The CH₄ formation is strongly dependant of the HyPy temperature.     

褐煤超临界醇解萃余物组成分析

通过工业分析、元素分析、灰成分分析和热值分析对褐煤超临界醇解萃余物进行了研究,结果表明,褐煤醇解萃余物水分含量为6.93％～11.35％,灰分含量高达22.10％～24.46％,挥发分为39.75％～45.53％,无黏结性和结焦性:褐煤醇解萃余物碳含量为66.74％～76.03％,氢含量为4.51％～5.06％,氮含量...     

多硫化铁纳米材料的制备及在煤催化加氢热解中的研究

以硫酸亚铁和硫化钠为起始原料,采用低温溶液蒸发法制备多硫化铁(NaFeS2)纳米材料,利用X-射线衍射仪和透射电子显微镜对NaFeS2纳米材料进行表征。研究了NaFeS2纳米材料在煤加氢热解中的催化性能。结果表明:在热解温度为500℃,NaFeS2用量为0.5%(w)时,在煤加氢热解过程中得到的液相产物和气相产物分别为31%,20%;与常规的硫铁矿催化剂相比,液相产物与气相产物分别提高了1.6倍,1倍。     

Effect of pressure on the hydropyrolysis of Manvers coal

Manvers weakly-coking coal was pyrolysed to 500 °C in a stirred autoclave under varying pressures of hydrogen and nitrogen. As expected the major changes produced by increase in nitrogen pressure were a decrease in tar yield accompanied by increases in gas and, to a smaller extent, in coke yields. Total pressures and hydrogen :coal ratios were altered to obtain maximum yields of tar, gases and liquor. All products were investigated. Tar fractions, separated into neutral, phenolic and basic components, were analysed by g.c.-m.s. Short-chain hydrocarbons were detected in the gas sample. Methanol densities and micropore surface areas the cokes were related to the conditions of pyrolysis. At the relatively low rates of heating employed, pressure had effects on tar composition similar to increasing the temperature of pyrolysis.     

煤多段加氢热解过程的研究(Ⅱ)焦油组成分析

采用色 -质联用技术分析了先锋褐煤多段加氢热解过程中所得焦油的主要组分及其相对含量 ,并与单段加氢热解过程的结果进行了比较 ,从中分析了焦油轻质化的机理 .结果表明 :煤的多段加氢热解过程所得油品与传统的单段加氢热解油品相比 ,含有更丰富的高经济价值组分 ,如苯、甲苯、二甲苯和酚、甲酚、二甲酚及萘 ,这主要是因为氢气在峰温处的停留促进了自由基的氢化饱和及抑制了其再聚合的反应 .通过调整反应条件 (如增加反应压力、增大氢气流量 )可使多段加氢热解过程中所得焦油进一步轻质化 .最后 ,还对合成气气氛下多段热解的油品进行了分析     

Relation of the chemical structure of coal to its hydropyrolysis

The hydropyrolysis of Illinois No. 6 coal has been studied in a batch reactor, in which the reactions were initiated by explosion of $\text{H}{}_2\text{O}{}_2$ mixtures. The ratio of H₂ to O₂ was kept at 8, while the total pressure of the gas mixture was changed to vary the reaction temperature. The heating rate was ≈ 50 000 °C s^?1, and the reaction time was < 50 ms. The conversion of the feed coal increased from 19% at 620 °C to 81%at ? 1500 °C. At conversions < 50%, the gaseous product consisted of mainly CH₄ and CO in almost equal proportions, and at conversions ? 60% the concentration of CO increased. Comparison with results from a large flow reactor revealed that comparable conversions were obtained in the present batch reactor, although product distributions were markedly different from each other. The dissimilar product distribution is attributed to different reacting media: preburning of H₂ and O₂ in the flow reactor versus in situ burning of the mixture in the batch reactor. The H/C ratios of solid residues after the hydropyrolysis decreased linearly as the conversion increased, revealing that the portions of coal having high H/C ratios were preferentially gasified. This observation was substantiated by a high H/C ratio, 1.74 of the first portion of coal gasified, and by a sharp decrease in H/C ratio in subsequent gasified portions. These data indicated that aliphatic side chains (or linkages) and single-ring aromatic clusters in the feed coal were gasified first, followed by larger aromatic clusters. Semi-quantitative determination of the distribution of different aromatic clusters showed good agreement with current structural information on coal. Thus, the effects of reaction variables were explained in terms of the structural features of coal, and the ratelimiting steps in the hydropyrolysis process were identified.     

Comparative reactivities of coal asphaltenes during hydropyrolysis

Comparisons have been drawn in the relative reactivities of three coal asphaltenes during hydropyrolysis. All were derived from hydrogen donor-solvent extracts of bituminous coal, but had different hydrotreatment histories and different carbon contents (87.1, 91.9 and 90.8 wt% for asphaltenes 1, 2 and 3, respectively). The hydropyrolyses were carried out in the presence of CoO–MoO₃ catalyst and gaseous hydrogen at 8.7 MPa. For two of the asphaltenes (1 and 2) systematic comparisons were made for different reaction times at 425°C; for all three asphaltenes comparisons were made for l h of hydropyrolysis at 425°C. The general pattern of asphaltenes conversion indicated that more pentane-soluble product was produced from asphaltene isolated from straight coal extract (asphaltene 1). For the asphaltenes isolated from hydrotreated extracts, the extent of conversion to liquids was limited when the carbon content was high (asphaltene 2) although the pattern of conversion was similar in the other hydrotreated asphaltene (asphaltene 3). The aliphatic content of the liquid products formed was low, and the distribution of hydrogenated species in the highly aromatic liquid products indicated that complete hydrogenation of the polyaromatics produced in pyrolysis is difficult. Altogether the aliphatics made up ≈ 10 wt% of the asphaltene 1 hydropyrolysate. Aromatic hydrocarbons made up 90% of the liquid product. Phenanthrene, pyrene and anthracene were prominent, and the largest component in the mixture was phenanthrene which, together with other polyaromatics such as fluoroanthene, dominated the liquid product.     

Pyrolysis and hydropyrolysis of Louisiana lignite

Pyrolysis and hydropyrolysis kinetics of five samples of Louisiana lignite have been studied in an atmospheric pressure TG system as a function of heating rate and atmosphere. Final pyrolysis temperature was always 800 °C. The total volatile yield (dry basis) was 33.5–43.8wt%. For all lignites the volatile yield in hydrogen was greater than that obtained in nitrogen at similar conditions. However, variation in heating rate produced an opposite result in the two atmospheres with volatile yield increasing with heating rate in nitrogen but decreasing in hydrogen. Results have been analysed using the distributed activation energy pyrolysis model and parameters compared to similar studies using North Dakota and Montana lignites.     

Zncl2 catalyzed flash hydropyrolysis of +525°C pitch from cold lake bitumen

Flash hydropyrolysis experiments have been performed on the vacuum bottoms fraction of Cold Lake bitumen, using zinc chloride as a catalyst. Milligram size samples of vacuum bottoms resid were heated rapidly (120–400°C/s) by passing a large electric current through the reactor tube. The variables studied included temperature, heating rate, catalyst/pitch ratio, vapour phase residence time and pressure. Temperature and catalyst/pitch ratio caused major changes in yields. In contrast pressure had little effect. It was found that high conversions could be obtained at hydrogen pressures which are much lower than those normally used in catalytically hydrocracking residual oils.     

Thermobalance hydropyrolysis of a bituminous coal sample and its macerals vitrinite and exinite: structural analysis of the relevant tars

Thermobalance hydropyrolysis experiments are carried out on a highly volatile coal sample and its main macerals, vitrinite and exinite. The results are discussed according to the characterization of the tars using ultrasound solvent extractions, extrography, liquid chromatography, capillary gas chromatography and mass spectrometry.     

工艺参数对高硫煤加氢热解脱硫率的影响

An orthogonal experiment design was adopted for studying the macroscopic reaction kinetics of sulfur removal of high sulphur coal hydropyrolysis. The experimental data of reaction desulfurization rate were analysed by margin and variance analyses. The optimal sulphur removal reaction conditions were recommended.     

Direct post-cracking of volatiles from coal hydropyrolysis: 1. Influence of post-cracking temperature

Direct post-cracking of volatiles from fixed-bed hydropyrolysis of bituminous coal at 580 °C and 1 MPa hydrogen pressure has been studied between 600 and 900 °C at residence times of 0.1 and 1 s. Results showed that post-cracking promotes the formation of gas, mainly methane, at the expense of oil yield. However, the oil composition was richer in benzene, toluene and xylenes (BTX fraction), in naphthalene and methylnaphthalenes, and poorer in phenol, cresols and xylenols (PCX) content. The optimum temperature for post-cracking under conditions investigated was ≈800 °C, but at this temperature the PCX yield was reduced by 40–60%. The PCX formation rate, from heavier phenols, was lower than the PCX dehydroxylation.     

Direct post-cracking of volatiles from coal hydropyrolysis: 2. Influence of pressure

Direct post-cracking of volatile material produced by hydropyrolysis of bituminous coal at 580 °C under hydrogen pressure 1–5 MPa has been investigated at 700 °C under constant hydrogen pressure with 0.1 and 1 s residence times. Results show that pressure promotes the formation of benzene, toluene and xylenes (BTX) and naphthalenes during post-cracking, while phenol, cresols and xylenols (PCX) are not affected. The transformation of heavy Ohenols into PCX is not influenced by the hydrogen pressure. During post-cracking the BTX yield can be more than doyble that reached in simple hydropyrolysis. Post-cracking applied to high oil yield hydropyrolysis processes will be a valuable BTX source.     

The effect of coal rank on flash hydropyrolysis of Chinese coal

Fourteen kinds of Chinese coal were flash hydropyrolysed in a small entrained reactor at 750°C and hydrogen atmosphere. The results indicated that carbon content and yields of liquid hydrocarbon, H/C and yields of gaseous hydrocarbon, oxygen content and yields of CO, CO₂ and H₂O show better corresponding relations. The correlations between yields of CH₄, C₂ and C₂H₆ and H/C can be expressed as Y_CH4=−42.2+100(H/C)(0.51<0.59), Y_CH4=15.8+1.67(H/C)(0.59<1.11), Y_C2=0.347+4.78(H/C), Y_C2H6=0.352+4.74(H/C); The correlations between yields of CO₂ and water and oxygen content can be expressed as: Y_CO2=−0.0437+0.0355(O); Y_H2O=0.726+0.467(O). The cutoff points of flash hydropyrolysis for coal are that H/C is 0.6 and carbon content is 85%. The coal which H/C is lower than 0.6 and carbon content is higher than 85% is usually not good for flash hydropyrolysis. It is found that influence of coal rank on yields of liquid, gas product and total yields of product in flash hydropyrolysis can be expressed as of H/C in coal.     

ATP技术用于褐煤热解提质的技术经济分析

介绍了ATP(A lberta-Taciuk Processor)技术的发展历程及应用领域,提出利用ATP技术加工处理内蒙古褐煤的设想,并进行了技术经济分析,得出利用ATP技术处理褐煤的可行性结论。     

煤炭快速加氢热解的研究现状及发展方向

介绍了各国煤快速加氢热解(FHP)的研究概况。讨论了温度、压力、加热速率等因素对FHP的影响。从长远看,将煤气化和FHP相结合,在原料煤产地建立大型加氢热解装置,是我国合理用煤的有效途径之一。     

Nitrogen evolution during rapid hydropyrolysis of coal

The behavior of nitrogen evolution during rapid hydropyrolysis of coal has been investigated at temperatures ranging from 923 to 1123 K and hydrogen pressure up to 5 MPa using a continuous free fall pyrolyzer. Three coals have been tested in this study. The dominant nitrogen gaseous species is ammonia, together with a little amount of HCN because most of HCN is converted to NH₃ through secondary reactions. The results show that the evolution of nitrogen in coal is caused mainly by devolatilization at temperatures below 973 K, while the evolution of volatile nitrogen in char is accelerated with increasing temperature and hydrogen pressure. The mineral matter in coal act as catalysts to promote the evolution of volatile nitrogen in char to N₂ apparently at high temperatures of 1123 K, as found during pyrolysis of coal by Ohtsuka et al. A pseudo-first-order kinetic model was applied to the evolution of nitrogen in coal during rapid hydropyrolysis. The model shows the activation energy for the nitrogen evolution from coal is 36.6–58.6 kJ/mol while the rate of the nitrogen evolution depends on hydrogen pressure in the order of 0.16–0.24.     

高硫煤加氢热解脱硫研究

在常压固定床上,温度450—750℃,氢气流速300—900 mL/m in和升温速度15℃/m in的实验条件下,对沟底高硫煤加氢热解脱硫的影响因素进行了研究。实验结果表明,适当增加氢气的流速,提高反应最终温度和延长停留时间,对高硫煤加氢热解脱硫效率的提高和降低残留物中的硫质量分数都是有利的;利用气相色谱研究了硫化氢气体的逸出规律,随着热解温度的提高,硫化氢气体逸出曲线表现为2个峰。研究认为,高温峰源于硫铁矿和噻吩类含硫化合物中硫的脱除,而低温峰源于脂肪族含硫化合物硫的脱除。煤脱硫反应的热力学也表明,随热解温度升高煤加氢热解脱硫分为2段。