Thermal and chemical desulfurization of low sulfur coals

This paper describes desulfurization characteristics of low sulfur coals prior to combustion and optimum conditions of three different desulfurization processes. These processes include two thermal treatment processes (mild pyrolysis and air oxidation) and an H₂O₂ leaching process. Dual processes composed of thermal and leaching processes were also evaluated. Low sulfur coals employed were two imported bituminous coals and two domestic anthracite coals. The optimum reaction temperatures and times of the thermal processes were 500–550 °C and 15–20 minutes, respectively. The optimum condition for the leaching process was obtained when the experiment carried out for 60 min at 90 °C using 30% H₂O₂. The dual process showed the best sulfur removal efficiency as expected among the evaluated processes. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Ruthenium tetroxide catalysed oxidation of illinois no.6 coal and some representative hydrocarbons

The use of ruthenium tetroxide for the catalytic oxidation of coal molecules under mild conditions has been examined. The selectivity of the reagent for aromatic nuclei has been assessed by a study of the oxidation of selected benzene, naphthalene and phenanthrene derivatives. The catalysed oxidation of Illinois No.6 coal has been studied. The preliminary results described in this report suggest that this oxidant is effective for the selective oxidation of the aromatic structures in this coal.     

Supercritical gas extraction of Polish brown coals

Properties of nine selected samples of Polish brown coals from both strip mines and perspective deposits varying in lithotype have been determined. This involved technical analysis of the elementary, group and petrographie compositions. The coals were extracted with supercritical toluene at 410 °C and 13 M Pa. The humic acid content and humodetrinite content were found to be well correlated with the yield of coal extract. The optimal conditions of gas extraction for a selected coal sample were determined.     

Supercritical fluid extraction of two Indian coals

Results on the supercritical fluid extraction of two Indian coals (Ranigunj and Godavari Valley Coal fields) are reported using toluene as solvent. The effect of extraction time on supercritical toluene dissolution of these coals was studied in a tubular reactor, in a semi-continuous mode operating at constant operating conditions of 673 K and 9.8 MPa. Coal conversions in the range of 18–21% and the oil contents of the extracts varying from 40 to 75% were obtained.     

Gasification kinetics of coals and wood

The chemical reactivity and kinetics of nine Canadian coal samples ranking from lignite to semianthracite and one wood sample were examined in a fixed gasifier in the presence of air and steam at 950–1000°C. The reactivity of the coal and wood samples decrease with an increase in carbon content, but increase with increasing oxygen content of the parent coal. The reaction velocity decreases with an increase in carbon content of the coal. The reaction mechanism based on the shrinking core model for the present gasification has been found to be chemical reaction controlled for the coal-steam-air system and ash-layer diffusion controlled for the wood-steam-air system. The present reaction system favors the water gas shift reaction based on the chemical composition of the product gas from the gasification.     

Supercritical extraction and desulfurization of coal with alcohols

An investigation of extraction of coal with alcohols has been performed under a wide range of supercritical conditions. It was found that sulfur materials in coal were selectively removed from coal matrix. An empirical rate equation with first order kinetics can be used to fit the experimental data. The desulfurization selectivity ratio is between 2 and 4.4 for four coal samples studied. A pretreatment of coal with KOH solution demonstrated an enhancement of the desulfurization efficiency.     

Gasification of coals treated with non-aqueous solvents. 5. Properties of coals treated with liquid ammonia

Five coals of various ranks were treated with liquid ammonia at 373 K and 10 MPa, and some properties were examined. Although the equilibrium pore volume accessible to carbon dioxide was not affected, the rate of adsorption increased remarkably upon treatment. The pore volume determined by a larger molecule, say hexane, also increased greatly. When a nickel salt was impregnated among the coal surfaces, more satisfactory results were obtained on the treated coal. The treated coals were more easily comminuted than the parent coals. The relation between the change of these properties and the gasification reactivity is discussed.     

Carbonization of coals to produce anisotropic cokes: 5. Structural factors of coals influencing carbonization properties

The carbonization properties are studied of two particular coals (Zontag Vlei and Metla coals) which are markedly different despite their similar coalification rank, maceral composition, and oxygen and exinite contents. These coals possess different structural features which influence their carbonization. A demineralizing pretreatment improves the properties of Metla coal. However, this is still inferior to the Zontag Vlei coal. O-alkylation of the Metla coal improves fusibility in single carbonizations and susceptibilities, equalling those of the Zontag Vlei coal. Preheat-treatment differentiates between the coals: Metla coal loses its susceptibility at lower temperatures. The chemical analyses of oxygen functionalities of both the original and preheated coals show that their hydroxyl groups behave differently in carbonizations at lower temperatures, indicating that oxygen functionality may be another influential factor. Hydrogen shuttling within the coal may be a third factor as it may remove the oxygen functionality.     

In situ desulfurization during combustion of high-sulfur coals added with sulfur capture sorbents

Two Chinese coals, added with two types of sulfur capture sorbents, were combusted in a drop tube furnace to investigate effect of reaction temperature on sulfur removal during coal combustion. Limestone was used as sorbent and mixed with coal physically for sulfur removal. In addition, another sorbent, calcium acetate, synthesized from natural limestone, was also used for in situ removal of sulfur; it was impregnated into raw coals before combustion. The first series of experiments were carried out in the furnace having downside temperature of 1173 K (the upper side of furnace was at 1573 K). The results proved that calcium acetate captured more sulfur than limestone. In order to understand the effect of reaction temperature on in situ sulfur removal of sorbents, the second series of experiments were carried out at the uniform furnace temperature ranged from 1373 to 1673 K. Moreover, the sulfur removal capability of ashes, taken from combustion of coal with sorbents in drop tube furnace, was studied at 1173 K using thermogravity. The calcium distribution in ashes was analyzed using a novel calcium-based compounds CCSEM category. The results indicated that at certain temperature, higher sulfur removal efficiency was obtained for calcium acetate than that for natural limestone, which is mainly due to the fine dispersion of calcium in impregnated coal so that a good contact was obtained between calcium and sulfur-containing coal particles; increasing the temperature lowered the sulfur removal capabilities of sorbents since the sorbents were captured by inherent aluminosilicate; the sulfur content in raw coal affects the utilization of sorbents significantly in coal combustion. In addition, ashes, rich in calcium, can adsorb SO₂ at 1173 K; the sulfur removal efficiency of fly ash is at least the same as that of natural limestone.     

The kinetics of oxidation of humic coals in dimethyl sulfoxide

The alkali-catalyzed oxidation of humic coals of different metamorphic ranks with molecular oxygen at 75°C was studied. As a result of analysis of the rate curves, an equation was derived to describe the oxygen uptake as a function of time. It was found that the initial reaction rate depends on the class and grade of coal. It was shown that the amount of carboxyl groups in oxidized sample increased by a factor of 9. On the basis of the experimental data and the summarized results of investigation of organic substances of various structures in highly basic media, it was concluded that low-rank coals could be oxidized at quite a high rate due to the presence of highly acidic C-H groups in them, yielding humic acids as the main oxidation products.     

微生物烟气脱硫的生物膜系统动力学模型研究

为了研究生物滴滤塔净化废气中SO2的脱硫机制,文中应用Deep-Biofilm理论和微生物生长动力学方程Monod建立了生物膜脱硫系统的扩散-反应动力学模型,并结合平推流模型对整体塔器的脱硫过程进行了模拟。应用Matlab计算机编程语言对空塔停留时间、进口SO2质量浓度、填料比表面积、递增式进气和稳定式进气等因素对脱硫率的影响进行了数值模拟。与实验结果比较后发现模拟值和实验值吻合良好、日趋重合,证明了该模型的合理性,实现了微生物烟气脱硫技术实际脱除过程的模拟研究。     

Supercritical gas extraction of Victorian brown coals: The effect of coal properties

A selection of fifteen Victorian brown coals, which varied in lithotype but only slightly in rank, were subjected to supercritical gas extraction with toluene. Seven of these coals were also extracted with 5% tetralin/toluene under the same conditions of temperature and pressure (400 °C and 10 MPa). The overall conversion, the extract yield and the yield of toluene solubles (oil and asphaltene) were correlated with more easily obtained coal properties using simple linear regression analysis. Good correlations were obtained between the total conversions and the volatile matter content of the coals, and for the toluene extractions between both the extract yield and the yield of toluene solubles and the H/C atomic ratio. For the toluene solubles from the toluene extractions, the aromaticity decreased and the molecular weight increased as the H/C atomic ratio of the coal increased. Inorganic constituents of the coals did not appear to have a marked effect on total conversion and liquid yields. Removal of the cations from two coals increased conversion and liquid yields in one case and decreased these in the other, but in both instances the changes were not large.     

催化汽油氧气氧化脱硫的反应动力学

以氧气作为氧化剂,开展催化汽油氧化萃取脱硫实验及氧化动力学研究。实验结果表明,氧气氧化萃取脱硫对催化汽油具有较好的脱硫效果;随着相转移催化剂用量增加、温度提高、氧气分压增大、时间延长、水与汽油体积比增大,汽油脱硫率持续提高,而汽油收率呈现降低的变化趋势。根据反应动力学方程和萃取相平衡原理,确定了脱硫率和汽油收率模型,并开展模型参数估值、统计检验和预测分析。研究结果显示,所建模型具有较高的模拟精度,预测结果与脱硫实验结果的变化趋势相同。     

Pyrolysis—gas chromatography of Australian coals. 2. Bituminous coals

Pyrolysis—gas chromatography (Py—g.c.) was used to characterize quantitatively a series of high- to low-volatile bituminous Permian Australian coals. The levels of n-alkanes, n-alkenes and triterpenoids released by pyrolysis all decrease as a function of increasing rank and thus, the coal samples can be classified into three distinct groups. Carbon Preference Indices (CPI's) for alkanes and alkene/alkane ratios also decrease as a function of rank. The triterpenoids have exclusively the hopane skeleton. The hopane isomeric distributions exemplify the geological maturity of bituminous coals relative to brown coal (lignite). A significant correlation has been established between the level of n-alkanes and n-alkenes released under Py-g.c. conditions and the predicted oil yield by pyrolysis of these coals. Further development and application of the techniqueshould enable much to be learnt relating to the quality and yield of flash pyrolysis tars as well as the original coal macromolecular structure.     

Supercritical water gasification of glycerol: Intermediates and kinetics

In this paper, the liquid products from supercritical water gasification (SCWG) of glycerol were analyzed and some intermediates were identified. A simplified reaction pathway for gases production from SCWG of glycerol was proposed. The first quantitative kinetics model for describing the gaseous products (H₂, CO, CH₄ and CO₂) of SCWG of glycerol was developed. The model comprises seven reactions to describe the typical reactions in SCWG, and the reaction rate constant of each reaction was obtained by using the nonlinear least-square fitting method. The reaction rate analysis showed that the main sources of hydrogen yield were glycerol pyrolysis and steam reforming of intermediates, while the hydrogen yield from water–gas shift reaction (WGSR) was very small. The temperature estimated by the kinetics model for completely SCWG of glycerol solution was given. In addition, the sensitivity analysis of rate constant of WGSR was done based on the model.     

Determination of the kinetics of diffusion in coals by solvent swelling techniques

A simple technique has been developed for measuring the kinetics of solvent diffusion in coals at various temperatures. The technique is based on a well-known method for measuring the volumetric swelling of coals by solvents. Several coals have been examined in both pyridine and tetrahydrofuran, at temperatures between 298 and 332 K. The diffusion follows the well-established case II rate law at ambient temperatures, implying that the processes are controlled by relaxation in the coal network structure. As temperatures are increased, the process becomes more Fickian in nature. The activation energies for the diffusion-relaxation processes are in the range 31 to 82 kJ mol⁻¹.     

Microbial desulfurization of three different coals from Indonesia, China and Korea in varying growth medium

Shake flask studies on microbial desulfurization of three different coal samples (Indonesian lignite, Chinese lignite and Korean anthracite) were performed to optimize the best suitable growth medium. Among the three different growth mediums (basal salt medium, basal salt medium supplemented with 9 g/L Fe and basal salt medium supplemented with 2.5% S⁰) tested, the basal salt medium was found to be the best, considering process dynamics and economical factors. The extent of pyrite oxidation was highest with 95% in the experiments with Korean anthracite in basal salt medium supplemented with 9 g/L Fe, while the lowest pyrite oxidation of 70–71% was observed in the experiments with Indonesian and Chinese Lignite’s in only basal salt medium. The microbial sulfur removal in the experiments with basal salt medium supplemented with 9 g/L Fe for all the three coal samples was between 94–97%, while the experiments on basal salt medium supplemented with 2.5% S⁰ for all the coal samples were relatively much lower ranging between 27–48%. However, the overall study resulted with promising directions for further scaling up of microbial desulphurization in a best growth medium devoid of iron and sulfur supplement.     

Supercritical desulfurization of high rank coal with alcohol/water and alcohol/KOH

A high rank coal with total sulfur of 4.90% was extracted employing alcohol/KOH and alcohol/water under supercritical conditions both in a semi-continuous reactor and in a batch reactor. In the semi-continuous reactor it was found that supercritical desulphurization is mainly taking place within about one hour at 400°C. Pretreatment of coal with KOH up to 5% concentration was favourable for sulfur removal, but greater KOH concentration and longer soaking time brought about the opposite results. When the ethanol concentration was 95 vol % the organosulfur removal achieved the maximum. Ethanol/KOH solution as supercritical solvent enhanced the desulfurization process, in which the inorganic sulfur was removed preferentially. In the batch reactor it was found that there was reincorporation of both organic sulfur and inorganic sulfur. KOH addition can improve the sulphur removal greatly. When KOH/coal ratio was greater than 0.5, the tendency for sulfur removal was gradually slow.     

超临界水氧化丙烯氰废水的反应动力学理论研究

以丙烯氰为研究对象,探讨丙烯氰在超临界水氧化中的动力学研究。采用密度泛函理论研究氧负离子自由基与丙烯氰分子的反应。针对可能存在的抽氢反应、置换氢反应、生成水反应及羟基化反应通道,在B3LYP/6-311++G(2d,p)和HandHLY/6-311++G**的水平上得到反应物、产物、中间体复合物和过渡态的优化构型,并利用IRC计算证实反应通道。     

树脂催化重汽油烷基化硫转移的动力学研究

采用树脂催化剂,研究重汽油中噻吩类硫化物的烷基化硫转移性能,分析反应前后硫分布的变化,并对反应动力学进行研究。结果表明,在反应温度110℃和反应时间60 min条件下,烷基化硫转移率大于90%,其反应动力学为一级反应速率方程,反应活化能为20.32 kJ·mol~(-1),指前因子为1 364 h~(-1),噻吩类硫化物烷基化反应的动力学方程可表示为:r=1364exp(-2.445×10~3/T)c_T。