Short contact time dissolution of Liddell coal

The thermal dissolution of Liddell coal in tetralin at 400 °C proceeds rapidly. The addition of hydrogen to coal under moderate, uncatalysed conditions is significant and initially proceeds without the elimination of nitrogen, oxygen or sulphur. At extended reaction times, however, oxygen is eliminated via hydrogenolysis reactions. The simulation of product distributions from the thermal dissolution of Liddell coal at 400 °C, and short contact times, has been undertaken using a system of second-order pseudo-kinetic equations. Excellent agreement between the experimental data and the calculated conversions has been obtained.     

Influence of mixing on short contact time coal liquefaction

The influence of mixing on the liquefaction behaviour of coal at short contact times (? 20 min) has been studied for bituminous coals from Powhatan (USA) and Liddell (Australia). Experiments were carried out in 1.0 and 0.3 dm³ reactors, respectively, both of which had facilities for varying stirrer speed and for rapid injection of coal and solvent. Results at 450 °C with the Powhatan coal revealed that at a low agitation rate (1500 rev min^?1) the yields of oil were negative. At a higher stirrer speed (2500 rev min^?1) the agitation was sufficient to eliminate this oil deficiency. In the Liddell experiments, the conversion rate at a stirrer speed of 865 rev min^?1 was significantly lower than at 1860 and 2380 rev min^?1. Rate coefficients calculated for stirrer speeds of 865 and 1860 rev min^?1 were found to differ by more than a factor of two. These data illustrate that the degree of agitation can have a significant bearing on the rate of total conversion of coal to soluble products and on the yield of oil, suggesting that mass transfer limitations can occur at the coal-solvent interface.     

Simulation of chemical rate processes in short contact time coal liquefaction

Conversions and product distributions from the thermal dissolution of Liddell coal in the presence of tetralin have been simulated by a system of second-order rate equations. Satisfactory correlation with experimental data is obtained over the range of temperatures studied, i.e. 380–420 °C.     

Short contact time liquefaction of coal using hydrogen donor solvent

Liquefaction of coals to form benzene-soluble materials was studied at 400 °C under autogenous pressure conditions using tetrahydroquinoline (THQ), tetrahydroisoquinoline (THIQ) and tetralin (TL) as the hydrogen donating solvents. THQ was the best solvent with a conversion rate of 90% within 15 min for low rank coals (< 80% C). In contrast, it took 50 min to achieve a conversion of 80% when TL was used as the solvent, although both solvents could achieve almost complete conversion of coals into quinoline-soluble material within 10 min. THQ also showed excellent activity with blended coals. Some binary solvents exhibited activities which varied with the THQ content. A 1:3 by weight mixture of THQ and petroleum pitch produced the highest conversion of 100%.     

Characterization of vitrinite concentrates: 3. Correlation of FT-i.r. measurements to thermoplastic and liquefaction behaviour

Measurements of aliphatic C–H content by FT-i.r. have been correlated to the plastic properties and liquefaction behaviour of a set of coals and vitrinite concentrates obtained from the Lower Kittaning seam. It has been found that for vitrinites a measure of total aliphatic C–H content correlates with Gieseler fluidity, displaying an abrupt change over a narrow range of aliphatic C–H content. Liquefaction conversion does not correlate with FT-i.r. measurements of total aliphatic C–H content but does correlate with the intensity of a band that is a measure of CH₂ content. These results confirm the general relationship between the mechanism of liquefaction conversion and plastic development, but also suggests there are some subtle differences.     

Direct liquefaction of vitrinite concentrates obtained by column flotation

In this paper, direct liquefaction of vitrinite maceral concentrates was studied. Coals from Cerrejon and Jagua collieries (Colombia, South America) were used. Vitrinite concentrates were obtained by column flotation at pH 7, air velocity of 1.4 cm/s and frother concentration of 4 ml of frother/kg of coal. Digestion runs were made at 380, 400 and 420 °C and ratios tetraline/coal (S/C) of 2/1, 2.5/1 and 3/1. Liquefaction time was 30 min. For all runs, tetraline was the hydrogen donor solvent. Feed and vitrinite concentrates were liquefied in order to compare their conversion, product distribution and oils selectivity. It was observed that, in general, conversion rates obtained from vitrinite concentrates were higher than those obtained from feed coal. The results showed that conversion tend to increase with temperature as well as the S/C ratio. Product distribution showed that both oils and gas fractions tend to increase with temperature and S/C ratio, whereas residues have a contrary behaviour.     

Aqueous sodium dichromate oxidation of Australian vitrinite concentrates

The aromatic structures present in vitrinite concentrates from Australian coals covering a range of rank have been investigated by aqueous sodium dichromate oxidation followed by analysis of the products by g.c.-m.s. Only 13 relatively simple aromatic carboxylic acids, principally the di- and triacids of benzene, combined in widely different proportions constituted the oxidation products. The largest compound found was a monoacid of naphthalene. There was no obvious pattern to be observed in the nature of the oxidation products that was consistent with the concept of coal maturation as a process of increasing aromatization. However, in agreement with earlier work, substantial yields of polynuclear aromatic compounds were obtained when two US coals and an Australian solvent-refined coal were similarly oxidized. It is suggested that this difference arises principally from the geological origins of the Australian samples.     

Initial solvation of coal with tetralin under liquefaction conditions

Secondary vitroplast, produced by treating a Liddell vitrinite concentrate with tetralin in a continuous flow, packed-bed microreactor under a nitrogen pressure of 13.8 MPa at 360, 410 and 460 °C, has been analysed by i.r. spectroscopy, gel permeation chromatography, solid state ¹³C n.m.r. and reflectance microscopy. Results showed that this intermediate in the liquefaction process had the same carbon aromaticity as the untreated vitrinite concentrate and that both its aromaticity and reflectance were independent of the temperature of formation. It was concluded that the initial solution of the vitrinite concentrate in tetralin involved no significant hydrogenation of the vitrinite.     

Effects of coal cleaning on the short contact time liquefaction of Illinois No. 6 coal

This study was carried out to determine the effect of coal cleaning by oil agglomeration and sink-float methods on yields from short contact time liquefaction of Illinois No. 6 coal. The runs were made in a continuous unit using SRC-II distillates as process solvent. Measured yields included hydrogen (consumption), hydrocarbon gas, distillate oil, SRC (the pyridine-soluble portion of the residue) and insoluble organic matter, the pyridine-insoluble organic residue. The solubility of product SRC in hexane, toluene and pyridine was also determined. The principal finding was that coal cleaning by density methods reduced the yield of IOM obtained in subsequent liquefaction and this is attributed to the removal of inert components from the feed coal. In addition, cleaning which significantly reduced pyrite content of the feed coal also reduced the yield of distillate oil and tended to give a less soluble SRC during liquefaction. Deep cleaning by gravity methods gave the lowest IOM, but reduced pyrite content to the point where distillate oil was consumed rather than produced. Oil agglomeration reduced total ash to 50% of that in the run-of-mine coal, but left the pyrite level in the coal high. The relevance of these results to two-stage liquefaction is discussed.     

宁夏庆华煤镜质组和惰质组显微组分的分子结构及对比分析

使用密度梯度离心法对宁夏庆华煤的显微组分进行分离,获得煤的镜质组和惰质组。通过元素分析、X射线光电子能谱（XPS）、固体¹³C核磁共振（¹³C NMR）技术、傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）技术等表征手段对不同显微组分进行物性表征。进一步基于统计平均的分子结构近似结合分子模拟计算,确定庆华煤镜质组和惰质组显微组分的分子结构可分别表示为C₂₆₉H₁₉₆N₄O₁₃S和C₂₅₅H₁₇₉N₃O₁₄S。通过FTIR光谱与¹³C NMR光谱验证,从而实现了不同显微组分的分子结构描述。对两种显微组分的分子模型和结构参数进行了系统对比分析,发现镜质组的芳碳百分数为51.95,惰质组的芳碳百分数为62.16。镜质组模型中芳碳结构数目较少,脂肪碳结构丰富,不饱和度较小,还原度最大。惰质组模型中芳碳结构数量最大,脂肪碳结构数目少,不饱和度最大,煤化程度高。镜质组在原煤中含量高,是原煤的主要组成。惰质组的含量少且大分子结构缩合度高,分布在镜质组构成的基体中。     

Deactivation of cracking catalyst in short contact time reactors: Alternative models

Several mathematical models have been used to describe the deactivation of cracking catalysts by coke. For the case of gas oil cracking under short contact times (less than 20 seconds) it was found, using data from two different experimental reactor units, that an exponential decay function or a power law function could equally represent the data. Both functions are forms of the general hyperbolic decay expression; however, the power law assumes the unrealistic limits of infinite catalyst activity at zero time-on-stream and requires two parameters to describe deactivation. This work shows that the simple first order decay function is an effective equation to be used in describing catalyst activity decay for short reaction times.     

Low temperature—long time,high temperature-short time liquefaction of coal: The Hokudai process

A Japanese cola was hydrogenated in wash oil with fine iron dust and sulphur as catalyst under a reaction pressure of 12–13 MPa at 420 °C for 2 h and then at 500 °C for 0–20 min. The liquid yield boiling up to 600 °C amounted to 55–66 wt%. Pyridine conversion was ≈ 100 wt%, benzene conversion 82–90 wt% and n-hexane conversion 53–70 wt%. Compared with direct hydrogenation at 500 °C for 10 min the low temperature-long time plus high temperature-short time liquefaction process (the Hokudai process) is a very effective method for obtaining high liquid yield under relatively low hydrogen pressure without coking, using disposable catalyst and non-donor solvent.     

Efficiency of hydrogen transferring liquefaction of a subbituminous coal using hydrogenated fluoranthene for short contact time at high temperature and low pressure

An Australian subbituminous coal (Wandoan) was effectively liquefied at 490 and 510 °C under nitrogen pressure of 2.5 MPa for 1.0–7.5 min using 1, 2, 3, 3a-tetrahydrofluoranthene (4HFL) as a hydrogen-donating solvent. The yields of oil and asphalthene could be as high as 58 and 24 wt%, respectively. The content of 4HFL was very influential on the oil yield although under appropriate liquefaction conditions, a considerable amount remained after reaction. The kinetics of the reaction and analytical study of the products and the solvent suggest consecutive as well as instantaneous depolymerization in the process. The coking or recondensation reaction was very rapid after 4HFL was consumed, confirming the efficacy of the short contact time liquefaction.     

Fluorometric analysis of inertinite

In coal petrology, fluorescence microscopy has mainly been used in the study of liptinite (exinite) macerals. Recently, its scope of application has been widened to investigate vitrinite. This paper describes the conditions under which inertinite can also be studied by fluorometry. The method makes use of relatively long-wave excitation. Although the strongest signals are received through a green exciter filter at 546 nm, blue light excitation (450–490 nm) is preferred because the fluorescence spectrum is broader, the microscopic image more polychromatic and maceral identification is easier compared with longer-wave excitation. Inertinite macerals are divided into fluorescent and non-fluorescent constituents on the basis of both visual distinction and relative intensity determinations at 650 nm measuring wavelength. It appears that fluorescent inertinite corresponds closely to reactive fractions determined by previous coking experiments.     

Investigation of the relationship between coal maturity and aromaticity: Characteristics of sodium dichromate oxidation products of Australian vitrinite concentrates

The nature of the sodium dichromate oxidation products of a suite of 15 Australian vitrinite concentrates has been considered in an investigation of the relationship between aromaticity and coal maturation. For this purpose, two numerical characteristics, Δ(H/C) and potential homocyclic aromatic condensation index (PHAC), were developed to describe the oxidation products, which enabled relationships with commonly used indicators of coal maturation to be discerned by using simple statistical techniques. Δ(H/C) is the difference between the H/C ratios of a sample and the unaltered structures in its oxidation product. The PHAC index is the proportion of molecules in an oxidation product with vicinal carboxylic acid groups, which could have been formed by the partial oxidation of some of the rings of polynuclear aromatic structures. The closest associations found were between Δ(H/C) and H/C and fixed carbon, with lower correlations between the PHAC index and the maturity indicators. These relationships support the hypothesis that virtually all polynuclear aromatic structures in Australian coals can be degraded by sodium dichromate and that those parts of coal molecules completely degraded by sodium dichromate have much in common, structurally, with those parts volatilized during pyrolysis.     

Short contact-time liquefaction of subbituminous coal: Directions for improving coal conversion

This study was undertaken to find ways to solubilize subbituminous coal in high yield at short contact times. Short contact-time hydroliquefaction runs were carried out in a continuous unit using Belle Ayr subbituminous coal with a solvent rich in hydrogen-donor molecules derived from the Lummus ITSL process, and also with solvents lower in donor concentration derived from the SRC processes. Catalysis by pyrite, molybdenum and supported cobalt-molybdenum was also studied. It was found that pyrite and other hydrogenation catalysts enhanced solubilization and also increased production of distillate oil. Solvent quality seemed to have no effect on the solubilization of Belle Ayr coal. The availability of H₂S also appeared to have no effect. Provided that pyrite was present, reaction could be carried out at severities high enough to give insoluble organic matter yields equivalent to those obtained with bituminous coals (5–10 wt% daf coal). At equivalent levels of solubilization, however, hydrocarbon gas and distillate yields were invariably higher for the subbituminous coal. Implications for two-stage processing of Belle Ayr coal are discussed.     

Coal dissolution in high boiling process solvents

The liquefaction of a bituminous coal has been studied using distillate and non-distillable, coal-derived solvents. Different classes of solvent components can interact non-additively during reaction with coal to either promote or retard the process of coal dissolution. Above certain concentrations, polyfunctional compounds in heavy coal-derived liquids effect a measurable reduction in coal conversion and product selectivity by accentuating the degree of condensation reactions. Substantial removal of these compounds can be achieved by precipitation in a paraffinic solvent. Retrogressive reactions are reduced and positive synergistic interactions can be realized by the blending of heavy solvents with selected components, such as polycondensed aromatics, and with lower boiling, hydrogen-donor species.     

一种新的煤直接液化方法

从煤直接液化反应机理入手,综述了在过去几十年采用“煤短时液化”的思想研究煤直接液化机理的成果,以及以该思想为基础开发的“煤的高温短时液化”工艺.在上述2种研究成果的基础上,提出了一种新的煤直接液化方法,即“煤的高温快速液化”,并列出了相关实验室实验成果,这些结果将对工业化装置的开发产生深远的影响.     

Lean catalytic combustion of alkanes at short contact times

The catalytic combustion of methane, ethane, propane, andn-butane in air over platinum coated ceramic foam monoliths at contact times ranging from 3 to 25 ms and catalyst temperatures between 800 and 1100°C has been examined for compositions leaner than the homogeneous flammability limits. The extinction limits for heterogeneous reaction for these fuels has been determined as a function of preheat temperature up to 700°C in order to simulate the performance of a catalytic combustor or incinerator with exhaust gas preheat. The effect of the superficial velocity on the extinction limits has also been examined. We observe that the extinction composition decreases with increasing preheat temperature and increases with increasing flow rate for all fuels, and the reactivity of the fuels increases with the length of the carbon chain. Methane can be made to react completely as lean as 2.3% in air, while ethane, propane, and butane can be made to react completely as lean as 0.6, 0.4 and 0.2% respectively. For butane we observe only a single steady state for preheat temperatures above 200°C and a bifurcation diagram showing the extinction behavior for this system was constructed.This research is partially supported by GRI under grant No. 5095-260-3404 and by NSF under grant No. CTS-9311295-02.     

Effect of contact time and temperature on adhesion between components of rubber-polyethylene thermoplastic composites

—The effect of contact time and temperature on the adhesion between rubber and polyethylene has been studied. The degree of adhesion between natural rubber (NR) and polyethylene (PE) was varied by using physical (EPDM) and chemical interaction promoters (ENR/PE_m). It was observed that the peel strength increases with an increase in time of contact at a particular temperature. The adhesion strength varies with the square root of the contact time for all the systems with the exception of NR/PE/DCP at 75 and 100°C, EPDM/PE at 100°C, and NR/ENR/PE_m/PE at 100°C. With an increase in temperature, however, only EPDM-containing systems show higher values of adhesion between components. EPDM enhances the strength of the interface of the NR/PE joint, especially at longer contact times and higher temperatures. However, the chemical modifier is active only when the joining temperature is 150°C. On mastication of NR up to 15 min, the adhesion between natural rubber and polyethylene increases. The tack strength of NR-PE composites is increased with the introduction of physical and chemical modifiers.