Hydropyrolysis of a high-sulphur-high-calcite Italian Sulcis coal. 2. Importance of the mineral matter on the sulphur behaviour

The sulphur distribution among the char, oil and gas obtained after hydropyrolysis of a high-sulphur (4.3 wt%) and high-calcite (7.3 wt%) coal has been investigated. The chars were examined by scanning electron microscopy coupled with an energy dispersion analyser and by X-ray diffraction. The proportion of the combustible and non-combustible sulphur in the char has been determined. Hydrogen pressure promotes reaction with sulphur but the sulphur content of the chars increases from 3 to 4.5 wt% when the temperature is increased from 616 to 845 °C. This increase in sulphur is a consequence of the reaction between hydrogen sulphide, produced during hydropyrolysis of coal, with the alkaline-earth mineral matter to produce alkaline-earth sulphide. The SEM and X-ray diffraction images show that in the char formed at 780 °C the sulphur, calcium and magnesium are localized in the same compounds. This is not the case when hydropyrolysis is performed at lower temperature. Combustion of the chars produces only <0.6 S0₂ MJ^?1 compared to 2.2 g S0₂ MJ^?1 for untreated coal. X-ray diffraction has shown that the sulphur in the char is oxidized and fixed in the ashes mainly as CaS0₄ and also some as MgS0₄. Although sulphur remains partly in the chars after hydropyrolysis, 75% of it is non-combustible. The hydropyrolysis of a high-sulphur coal containing calcite, produces a char which may be used as a clean fuel.     

Hydropyrolysis of a high-sulphur,high-calcite Italian Sulcis coal: 3. Pyrite behaviour

The chars obtained from hydtopytolysis of Sulcis coal were examined by scanning electron microscopy coupled with an energy dispersion analyser. Under 3 MPa of He at 540 °C, pyrite is transformed into FeS_1.5. Under H₂ pressure, pyrite reduction depends on the temperature. At 780 °C, pyrite is completely reduced to iron. The complete reduction is made possible because the H₂S formed reacts with the caleite of this coal and thus does not limit the reducing reaction.     

提高煤加氢热解焦油产量的途径分析

结合煤加氢热解最新研究进展，从煤加氢热解焦油形成机理出发，综合论述了提高热解焦油产量的６条途径和方法。提出煤－焦炉气催化加氢热解的新构想，以期实现“煤→热解煤气内循环→焦油”新工艺。     

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。     

氢气预处理对煤加氢热解脱硫的影响

在固定床反应器中,研究了氢气预处理对兖州煤和大同煤加氢热解脱硫的影响.煤样首先在200～400 ℃,2 MPa,氢气体积流量1 L/min下预处理30 min,再在650℃,2MPa,氢气体积流量1 L/min下进行加氢热解20 min.研究结果表明:同直接加氢热解相比,氢气预处理会降低半焦和水的收率,同时会使焦油收率和脱硫率增加.在直接加氢热解中,大同煤和兖州煤半焦中硫的质量分数分别是2.07%和1.07%;而经适宜的氢气预处理后,其硫的质量分数分别降至1.93%和0.55%,对兖州煤和大同煤而言,其适宜的预处理温度分别为250℃和350℃.     

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.     

大同煤热解和加氢热解过程中产物生成规律的研究

在压力2MPa,温度350—650℃范围内,对比研究了大同煤分别在氮气和氢气气氛下热解过程中产物的分布和气体生成规律。研究表明,煤的热解和加氢热解转化率和水产率都随温度上升而增加;在热解条件下,焦油产率在500℃出现最大值。氢气对煤热解转化只有超过一定温度才具有促进作用,此时与热解相比具有较高的CO、CH4和C2^＋产率以及较低的CO2产率。     

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.     

Hydroliquefaction of Sulcis low-rank coal. 1. Conversion to low-sulphur fuel oil

A low-rank Italian coal was subjected to high-pressure and high-temperature hydroliquefaction with and without a hydrogenation catalyst. A low-sulphur oil was produced, showing properties similar to those of a standard fuel oil. The hydroliquefaction product may be used directly either as a fuel or as raw material for petrochemical processes. Sulcis coal displayed particular reactivity towards hydrogen, as shown also by comparison with a widely used North American coal.     

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.     

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.     

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.     

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.     

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.     

Statistical and mathematical analysis of the catalytic hydrogenating depolymerization of benzene-insoluble coal extract fraction

This Paper presents a statistical and mathematical analysis of hypotheses concerning the autoclave hydrogenating depolymerization of coal extract fractions insoluble in benzene. From comparison of theoretical and experimental data the most probable reaction mechanism was selected.     

Exxon catalytic coal gasification process: Fundamentals to flowsheets

This Paper reviews basic features of the reaction kinetics of potassium-catalysed coal gasification and describes how small-scale data were used for the conceptual design of large fluidized-bed gasifiers. It shows how potassium was chosen from among the alkali metals, the importance of the methanation reaction, and of steam conversion.     

Hydropyrolysis of kraft hardwood and softwood black liquor

The hydropyrolysis of hardwood and softwood derived black liquor was studied to develop material balance data and to investigate the potential yield of phenolic oils that might be obtained as chemical by-products of a kraft pulp mill. Hydropyrolysis reactions on softwood liquors were found to be more efficient in char formation than those on hardwood liquors. The yield of extractible phenolic oils was low, around 20–30 percent of black liquor organics, but the yields of simple phenols determined by gas chromatography were found to be even lower at 1–5 percent on black liquor organics.     

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.     

油酸包覆型Fe_2O_3对铁厂沟煤加氢热解特性的影响

采用固定床反应器考察了干混法添加油酸包覆型Fe2O3对煤加氢热解特性的影响,并与添加常规Fe2O3进行比较。对其催化作用下得到的半焦进行了TG、BET和XRD表征,焦油进行GC模拟蒸馏分析。结果表明:(1)采用常规Fe2O3考察铁的添加量时,在添加量为5%时焦油产率最高,由不加催化剂时的14.3%提高到16.3%。添加油酸包覆型Fe2O3时,煤的热解转化率更高,焦油产率由不加催化剂时的14.3%提高到18.0%。(2)添加油酸包覆型Fe2O3和常规Fe2O3得到的半焦反应性基本相同,半焦的孔结构则是添加油酸包覆型Fe2O3时最发达;添加油酸包覆型Fe2O3的半焦表面Fe晶粒的直径28 nm,小于添加常规Fe2O3的半焦表面Fe晶粒的直径39.5 nm。(3)加入常规Fe2O3和油酸包覆型Fe2O3都使得焦油品质得到提高,但两者相比,常规Fe2O3作用下得到的焦油品质更高。     

Low-temperature hydropyrolysis of coal under pressure of H2-CH4 mixtures

Hydropyrolysis of a Beringen bituminous coal (VM, 32.8wt%) has been studied in a fixed bed reactor with different gas flows of H₂-CH₄ and H₂-N₂ mixtures. At 580 °C, various hydrogen partial pressures between 0 and 1 MPa were used with a total pressure of 1 and 4 MPa. Oil yield increased significantly with increasing hydrogen partial pressure. However, if the difference between partial and total pressure is too large, the oil yield is affected more by the total than the hydrogen partial pressure. Similar effects are observed for the yields of BTX, PCX and naphthalenes except that for the latter the total pressure does not have a significant effect. In the conditions investigated the methane is chemically inert. Thus it is possible to recycle the gas during coal hydropyrolysis with only a slight decrease of the yields.