Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.     

Chemical looping combustion of high-sulfur coal with NiFe2O4-combined oxygen carrier

Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its attractive advantage in the inherent separation of CO₂. In relative to the single metal oxide-based oxygen carrier (OC), combined OC owned superiority for CLC of coal. In this research, combined NiFe₂O₄ OC was synthesized using sol–gel combustion synthesis method, and its reaction with a typical Chinese high-sulfur coal as Liuzhi (LZ) coal was performed in a thermogravimetric analyzer (TG). And then, systematic investigation was carried out to explore the evolution of sulfur species and minerals involved in coal and their interaction with the reduced NiFe₂O₄ OC through different means, including fourier transform infrared (FTIR), field scanning electron microscopy/energy-dispersive X-ray spectrometry, X-ray diffraction, and thermodynamic simulation. TG–FTIR analysis of LZ reaction with NiFe₂O₄ indicated that two reaction stages were experienced at 350–550 and 800–900 °C, respectively, far different from LZ pyrolysis, and SO₂ occurred mainly related to oxidization of H₂S with NiFe₂O₄ over 550 °C. Meanwhile, lattice oxygen transfer rates of NiFe₂O₄ involved at the two reaction stages were higher than that of directly mixed NiO with Fe₂O₃ OC and thus more beneficial for LZ coal conversion. Both experimental means and thermodynamic simulation of the solid-reduced residues of NiFe₂O₄ with LZ coal indicated that the main-reduced counterparts of NiFe₂O₄ were Ni and Fe₃O₄. In addition, though good regeneration of the reduced NiFe₂O₄ was reached, the side products Ni₃S₂ and Ni₂SiO₄ should be noted as well for its detrimental effect on the reactivity of NiFe₂O₄ OC.     

Kinetics and mechanism of coal flotation

 The flotation kinetics of coarse coal particles was studied in a modified version of the Hallimond tube at 25 °C using nitrogen as the carrier gas, in the pH range 2–12. The kinetics was followed by measuring the volume of the particles accumulated in the collector tube as a function of time. At each pH, the rate constants were determined at several buffer concentrations and were extrapolated to zero buffer concentration. The observed first-order rate constant was represented as the product of separable constants and functions such as f _D, f _V and f _pH, which depend only on the particle size, gas flow and the pH of the dispersion, respectively. The diameter, D, of the particles was in the range 505–127 μm. The observed rate constant decreased linearly with the diameter of the particles at constant flow and it was calculated that f _D=exp(−1.56D). The dependence of f _V on the flow is a consequence of the fact that the flotation occurs when a single particle is captured by two bubbles. f _V was shown to be independent of the particle diameter. The effect of the pH on the rate of flotation was considered as resulting from the adsorption of protons (or hydroxide ions) by the particles and bubbles through multiple equilibria, assuming that there is no interaction between the binding sites. The pH–rate profile showed that there were two species responsible for the flotation: one stable at pH below 5 and the other at high pH. Comparison of f _V, f _D and f _pH for the flotation of coal and pyrite allowed the prediction of the optimum conditions for the separation of mixtures of these particles by flotation. Received: 6 August 2001  Accepted: 19 September 2001     

Kinetics of reduction of iron ore—coal pellets

Kinetic data on the reduction of iron ore-coal pellets are compared with similar data for lump ore. It is shown that, when ore and coal are mixed intimately, the reduction reactions are accelerated considerably. Ore-coal pellets offer some additional advantages, as discussed in the text.It is shown that the kinetics of ore-coal reduction can be studied by using a pseudo kinetic parameter,f (fraction of reaction), defined as the instantaneous weight loss divided by the maximum possible weight loss. Plots off versust have been analysed to establish the kinetic equations and evaluate the kinetic parameters.

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Zusammenfassung Die kinetischen Daten der Reduktion von Eisenerz-Kohle-Pellets wurde mit ähnlichen Daten von Stückerz verglichen. Es wurde gezeigt, daß die Reduktionsreaktionen im Falle einer intensiven Vermischung von Erz und Kohle erheblich beschleunigt werden. Erz-Kohle-Pellets besitzen einige zusätzliche Vorteile, auf die im Text näher eingegangen wird. Es wurde gezeigt, daß die Kinetik der Erz-Kohle-Reduktion mit Hilfe eines pseudokinetischen Parametersf (Reaktionsbruch) untersucht werden kann, der als Quotient aus aktuellem Gewichtsverlust und maximal möglichem Gewichtsverlust definiert wird. Zur Bestimmung der kinetischen Gleichungen und der Berechnung der kinetischen Parameter wurde einf–t Diagramm ausgewertet.

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- . , , . . , - , g ( ), . f t .

     

煤焦吸附和还原NO的动力学研究

利用固定床反应器研究了煤焦吸附和还原NO的动力学,分析了热解温度(500℃～900℃)和矿物质对煤焦脱除NO的影响。结果表明,在程序升温反应(TPR)和等温反应中,随着温度的升高(30℃～600℃),煤焦-NO经历了从化学吸附到还原反应的转变。低温时煤焦脱除NO的动力学符合Elovich方程,原煤焦的起始吸附速率随着温度的升高而增大,脱灰煤焦的起始吸附速率先增大后减小,等温吸附过程中煤焦的活化能随着吸附量的增大而增大。随着热解温度的升高,TPR中煤焦的NO转化率降低,等温还原反应的速率常数减小,高温热解导致煤焦脱除NO的活性降低。矿物质对煤焦-NO的吸附和还原反应存在催化作用。     

Kinetics of reactions of coal with polystyrene: TGA-DSC approach

Kinetics of thermal reactions of coal with polystyrene by TGA and DSC methods was studied. In the range of about 350-550°C a thermal degradation of coal proceeds, and gas, tar and coke are evolved. Simultaneously, decomposition of polystyrene occurs (360-470°C). Unsaturated products of polystyrene decomposition are hydrogenated by coal, because coal is a strong H-donor. Moreover, some aromatic products react with coal tar structures and new aromates are formed. The yield of tar from copyrolysis is then higher in comparison with pyrolysis of coal alone. Kinetic parameters of the process were evaluated and discussed.     

Kinetics and isotope effect of brown coal liquefaction in ethanol

Liquefaction kinetics are described by a first-order equation. Deuterium introduction into the -position of ethyl alcohol produces a considerable kinetic isotope effect. This effect is suggested to be due to the hydrogen donor capacity of the initial ethyl alcohol -CH₂-groups or of ethyl substituents inserted into the aromatic fragments of coal after alkylation.

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. -, , - -CH₂- , .

     

A study of biodegradation of polyethylene and biodesulfurization of rubber

Applied Biochemistry and Biotechnology - The present study provides preliminary data on the involvement of such microorganisms asAspergillus niger in the biodegradation of commercially available...     

随机孔模型应用于煤焦与CO2气化的动力学研究

考察970 ℃～1 165 ℃，北宿、神府、忻州、潞安煤焦与CO2在热天平中的气化反应，用恒温法进行热重分析，考察煤种、气化温度、灰分对煤焦气化的影响。用随机孔模型模拟北宿煤反应速率与碳转化率的关系曲线，与未反应芯缩核模型和混合模型模拟结果比较。在化学控制区内，实验数据用随机孔模型拟合最佳。1 066 ℃和1 165 ℃气化数据拟合的相关系数为0.99，970 ℃拟合效果较差。随机孔模型作为简单、精度高的模型可应用于煤炭气化反应中。应用此模型计算四种煤焦反应活化能、指前因子、孔结构参数、A0等动力学参数值。同一煤种气化反应温度越高初始反应速率越大，结构参数体现了孔结构变化对反应的影响，随着温度的升高值减小。     

Histochemical localization of high-sulfur keratins with silver nitrate

Colloid and Polymer Science - The treatment of merino wool with ammoniacal silver nitrate results in a selective staining of high-sulfur proteins. The method has been applied to unmodified and...     

Determination of PASHs by various analytical techniques based on gas chromatography-mass spectrometry: application to a biodesulfurization process

Polycyclic aromatic sulphur heterocyclic (PASH) compounds, such as dibenzothiophene (DBT) and alkylated derivatives are used as model compounds in biodesulfurization processes. The development of these processes is focused on the reduction of the concentration of sulphur in gasoline and gas–oil [D.J. Monticello, Curr. Opin. Biotechnol. 11 (2000) 540], in order to meet European Union and United States directives.

The evaluation of biodesulfurization processes requires the development of adequate analytical techniques, allowing the identification of any transformation products generated. The identification of intermediates and final products permits the evaluation of the degradation process.

In this work, seven sulfurated compounds and one non-sulfurated compound have been selected to develop an extraction method and to compare the sensitivity and identification capabilities of three different gas chromatography ionization modes. The selected compounds are: dibenzothiophene (DBT), 4-methyl-dibenzothiophene (4-m-DBT), 4,6-dimethyl-dibenzothiophene (4,6-dm-DBT) and 4,6 diethyl-dibenzothiophene (4,6 de-DBT), all of which can be used as model compounds in biodesulfurization processes; as well as dibenzothiophene sulfoxide (DBTO₂), dibenzothiophene sulfone (DBTO) and 2-(2-hydroxybiphenyl)-benzenesulfinate (HBPS), which are intermediate products in biodesulfurization processes of DBT [ A. Alcon, V.E. Santos, A.B. Martín, P. Yustos, F. García-Ochoa, Biochem. Eng. J. 26 (2005) 168]. Furthermore, a non-sulfurated compound, 2-hydroxybiphenyl (2-HBP), has also been selected as it is the final product in the biodesulfurization process of DBT [A. Alcon, V.E. Santos, A.B. Martín, P. Yustos, F. García-Ochoa. Biochem. Eng. J. 26 (2005) 168].

Since, typically, biodesulfurization reactions take place in a biphasic medium, two extraction methods have been developed: a liquid–liquid extraction method for the watery phase and a solid phase extraction method for the organic phase. Recoveries of the selected compound in both media were studied. They were in the range of 80–100% for the watery and in the range of 40–60% for the organic phase, respectively.

Gas chromatography coupled to mass spectrometry (GC–MS) has been employed for the identification of these selected compounds. Three different ionization modes were applied: conventional electron impact (EI); positive chemical ionization (PCI), using methane as the reagent gas; and a recently developed ionization mode known as hybrid chemical ionization (HCI), using perfluorotri-n-butylamine as the reagent gas. Limits of detection and identification capabilities have been compared between the three analytical techniques.

The sensitivity of the three analytical techniques was studied and LOD between 0.05 and 1, between 0.09 and 2 and between 0.001 and 0.043 were achieved for PCI, EI and HCI, respectively.

The developed method was applied in samples from a biodesulfurization process. The biodesulfurization reactions were conducted in resting cell operation mode, using Erlenmeyer flasks or an agitated tank bioreactor. The microorganism employed was Pseudomonas putida CECT 5279. The reaction was performed under controlled air flow, stirring and temperature conditions.     

Kinetics of a polysoap collapse

We study the dynamics of collapse of a polysoap by means of large-scale molecular dynamics simulation and scaling arguments. A polysoap consists of a hydrophilic backbone and hydrophobic side chains attached at regular intervals along the backbone. In selective solvent conditions, the hydrophobic components aggregate, forcing the hydrophilic backbone to form loops anchored at the surface of the core, ultimately forming a micelle. The kinetics of polysoap collapse includes two major mechanisms: (1) early aggregation of the hydrophobic side chains controlled by first-order kinetics whose rate constant is given by a contact probability and (2) coalescence into larger clusters which requires activation to overcome energy barriers due to excluded volume repulsions between intermediate micelle coronas. In the late stage, the energy barrier is increasing as p(3/2), with p the number of aggregated side chains in an intermediate micelle. The corresponding late-stage rate constant decays exponentially as approximately exp(-p(3/2)).     

Chromatographic methods applied in the monitoring of biodesulfurization processes - State of the art

Analytical methodologies employed in biodesulfurization processes have been reviewed; attention is primarily focused on the use of analytical techniques in the identification of degradation products and on the monitoring of degradation processes in which microbial sulphur-specific transformations take place. This is the first review of analytical techniques applied to biodesulfurization processes. Methodologies based on gas chromatography (GC) are the most frequently employed, in tandem with various detectors, mainly with the mass spectrometry (MS) detector, and the flame ionization detector (FID). High performance liquid chromatography (HPLC) coupled with ultra violet (UV) detection has also been widely employed. Different sulphurated compounds are used as model in biodesulphurization processes, naphtothiophene (NTH), benzothiophene (BTH), alkilated BTH, dibenzothiophene (DBT), alkilated DBT and their transformation products has been reviewed. DBT is the most frequently employed.     

高硫石油焦制备高储气性能天然气吸附剂

以高硫石油焦为原料,KOH为活化剂,十二烷基苯磺酸钠（SDBS）为表面活性剂制备天然气吸附剂,分析了高硫焦基吸附剂的孔结构和孔分布特征,讨论了高硫焦制备吸附剂的活化机理。结果表明,预活化中加入表面活性剂SDBS可提高KOH与原料的混合均匀度,对活化效果有利。最优活化条件下制备的吸附剂样品GSR3和GSR4的微孔容积分别达到1.0985cm3·g－1 和1.3193cm3·g－1,孔径分布集中在0.9nm~1.5nm;在25℃、充放气压力3.5MPa和0.1MPa下,GSR3、GSR4对甲烷的质量吸附量分别达到0.139和0.145,有效体积脱附量达到111和115。粉体高硫焦基吸附剂的性能非常接近于低硫焦基吸附剂。     

介绍一个变温动力学实验

本文介绍一个变温法研究酸催化蔗糖转化反应和乙酸乙酯水解反应速率的模型设计实验[1]。由lnc-t图求出近似活化能Ea和A。目前化学实验教材中变温动力学的内容很少[2],本文的实验设计内容可作为一个补充和参考。1数学模型近年来,由于计算机的普及和程序升温仪的改进,导致对程序升温研究药物稳定性方面的研究比较活跃,对计算模型的设计也有一些巧妙的构思[3,4]。但在化学实验教材中,变温动力学的内容却很少。在常温下,蔗糖转化反应和乙酸乙酯水解反应属于准一级反应,其速率方程为:-dc/dt=kc(1)将程序升温规律T=T(t)代入Arrhenius公式:(R=8.…     

高硫煤镜质组热解过程中结构变化及有机硫形态变迁规律研究

用手选富集与离心分离相结合的方法,从两种全硫含量相近的新西兰煤（NXL;S_t,ad=1.84%）和山西煤（SX;S_t,ad=1.80%）中分离出高纯度镜质组。在高纯Ar气氛下,分别制备了300、500、700和1 000 ℃下的镜质组焦。用FT-IR研究了两种镜质组中的脂肪氢、芳香氢随温度的变化,结果表明,SX镜质组中脂肪氢的相对含量较高,在热解过程中活性高于同温度下的NXL镜质组;两种镜质组中的脂肪氢相对含量都随温度升高而降低,温度高于500 ℃时,SX镜质组中脂肪氢相对含量基本不变,当温度高于700 ℃时,NXL镜质组中的脂肪氢相对含量基本保持不变;热解过程芳香氢都表现出先增大后减小的趋势。用XPS研究了镜质组中的有机硫含量及形态随温度的变化,结果表明,SX镜质组中易分解的有机硫化物较多,在300 ℃以下即可分解完全;NXL镜质组中的有机硫化物分解完全在700 ℃左右,两种镜质组中的噻吩类硫的含量都随热解温度的升高而增加,砜类硫的含量随热解温度的升高而降低。     

Kinetics of strain-induced crystallization of a trans-polypentenamer

The kinetics of the strain-induced crystallization of a crosslinked 89% trans-polypentenamer was studied as a function of temperature and strain by using a combined birefringence—stress relaxation technique. The crystallization rate was found to be extremely sensitive to both variables and was, within experimental error, a function of the degree of undercooling alone, the increase in crystallization rate with strain being a direct consequence of the melting point elevation. From the isothermal, isometric crystallization rates, the development of crystallinity in constant-rate-of-strain experiments was calculated and related to characteristics of the stress--strain curve and of the temperature-strain rate dependence of tensile strength. These calculations allow one to estimate under what conditions sufficient crystallinity may be expected for the attainment of high strength in absence of reinforcing fillers. Crystallinities measured in this work were of the order of 10% or less. A limited x-ray diffraction study confirmed the low order of crystallinity indicated by the stress-birefringence measurements. The relatively high precision of the latter makes this technique attractive for the estimation of small straininduced crystallinities in rubbers.     

Application of solid-phase extraction to the analysis of the isomers generated in biodesulfurization against methylated dibenzothiophenes

A solid-phase extraction (SPE) technique was applied to analyze and characterize the biodesulfurization reactions against asymmetrically methylated dibenzothiophenes (mDBTs) such as 1-, 2-, 3- and 4-methyldibenzothiophenes present in fossil fuels. Recently, we found that these mDBTs are efficiently degraded by the bacterial strain, Rhodococcus erythropolis KA2-5-1. Separation and concentration of the microbial desulfurization products from each of the mDBTs could be carried out with high efficiency and reproducibility by the SPE procedure. These desulfurization products were identified using the SPE technique combined with GC, GC-atomic emission detection, GC-MS and 1H nuclear magnetic resonance spectroscopy. The analytical data obtained suggested that the desulfurization reactions against mDBTs by this bacterial strain may occur through specific carbon-sulfur bond-targeted cleavages that can be affected by the positions of methyl groups.