煤液化铁基催化剂对煤焦气化特性影响和动力学研究

本研究以哈密原煤和脱矿煤为原料,研究煤液化铁基催化剂对煤焦结构和气化反应性的影响.利用扫描电镜能谱仪和物理吸附仪研究煤焦表面形貌、元素分布和介孔特性,利用热重分析仪研究煤焦气化特性,采用model-fitting和model-free方法研究反应动力学.结果表明,脱矿和负载催化剂对煤焦表面附着物的影响较主体基质明显.负...     

Study on the structure and reactivity of COREX coal

COREX is the primary process in the current smelting reduction method. The process has strict coal quality standards. Combustion processes of coal used in the COREX operating system were analyzed using a synchronous thermogravimetric analyzer combined with a mass spectrometer. The microcosmic structure and macerals were observed by an electronic scanning microscope. The qualitative and quantitative determinations of oxygen functional groups, such as phenolic hydroxyl, carboxyl, carbonyl, and methoxy groups were detected by the Fourier Transform Infrared spectrometer (FT-IR) and through chemical analysis methods. In addition, the evolution of the chemical structure and transformation mechanism of organic oxygen functional groups during COREX coal combustion have been thoroughly investigated. This study proposes a new coal-requirement index system and coal blending method, which will increase the expansion of coal selection and decrease the overall usage of coal during COREX.     

添加煤灰及混合氧化物对石油焦CO2高温气化反应的影响

以化学组成相近的燃烧煤灰、气化煤灰和混合氧化物为添加剂,分别通过干混法和湿混法加入石油焦中,并借助热重分析仪在1200-1400 ℃下进行CO₂气化实验,研究高温下煤灰掺混方式、含量及物相组成对石油焦CO₂气化的影响,并使用混合氧化物替代实际煤灰研究其对石油焦的高温气化催化作用。结果表明,石油焦气化反应速率随煤灰添加量的增加而提升;气化温度为1200、1300 ℃时,使用干混法和气化煤灰对石油焦的气化促进作用较弱;但气化温度为1400 ℃时,改变煤灰和石油焦的掺混方式及其中活性金属存在方式,对石油焦气化反应几乎没有影响。这是高温下煤灰熔融,导致液态熔体与石油焦表面接触良好、活性金属自由度高以及传质阻力增加共同作用的结果。此时混合氧化物的催化指数与混合物中铁钙含量具有线性关系,即添加高铁钙含量的煤灰可以促进石油焦CO₂气化反应。     

含氧/蒸汽气氛中煤高温分解产物分布及反应性

在流化床反应器中考察了含氧/水蒸气气氛中煤在850 ℃下的热解特性,包括产物分布特性及生成的半焦与焦油的反应性,研究了温度、过量空气比(Equivalence ratio: ER)和水蒸气/煤比(S/C, 质量比)的影响。结果表明,随热解温度、ER和S/C质量比的增加,气体产率增加,而半焦和焦油产率减少。O₂的加入使CO₂、CO含量明显增加,H₂含量降低。O₂和水蒸气的加入使半焦的比表面积显著增加,半焦气化活性增强,但半焦在900 ℃和 ER 为0.22的条件下出现轻微石墨化,降低了其气化活性。同时,反应气氛中含有O₂和水蒸气对焦油的性质有显著影响,与单纯的N₂气氛相比,O₂和水蒸气的存在使热解焦油中单环芳烃、酮类、酚类、脂肪烃都明显减少,这对于焦油的进一步裂解及重整更加有利。     

高压加热条件下油煤浆黏度测定的研究

高压、加热条件下油煤浆的黏度,对煤直接液化工艺中煤浆预热器和反应器的设计非常重要.……     

煤的缔合结构研究 Ⅰ 溶液缔合动力学

研究了煤可溶组分——吡啶不溶物（PI）在溶液中的缔合动力学，该PI系二硫化碳/N-甲基-2-吡咯烷酮（CS2/NMP）混合溶剂可溶组分。结果表明PI在NMP溶液中的缔合属于反应控制机理，并提出了二步动力学反应过程，即基本缔合单元的生成和缔合单元之间的缔合。通过实验获得了有关缔合的动力学参数，PI在NMP溶液中二步缔合的活化能分别为73.3 kJ/mol和21.6 kJ/mol。温度对缔合速率的影响显著，随着温度的升高，缔合速率增加。由于PI分子在CS2/NMP混合溶剂中相对NMP具有较高的扩散性，因而其在CS2/NMP混合溶剂中缔合速率较NMP快。此外，还讨论了PI在溶液中的缔合机理。     

Effects of minerals containing sodium,calcium, and iron on oxy-fuel combustion reactivity and kinetics of Zhundong coal via synthetic coal

Journal of Thermal Analysis and Calorimetry - The greatly high contents of alkali and alkali earth metals in Zhundong coal have a negative impact on the combustion and utilization of the coal,...     

石油焦高温气化反应性

常压，1 200 ℃～1 500 ℃，在自制管式反应器中，以二氧化碳为气化介质，研究了石油焦以及石油焦与后布连煤焦掺混后形成的混合焦的气化反应性，借助于XRD分析了高温处理后石油焦与煤焦在碳结构有序化方面的区别。研究结果表明，当碳转化率高于0.7，气化超过1 300 ℃，石油焦的反应速率出现急骤下降，气化温度越高，相应石油焦速率下降越快。混合焦气化反应性既不同于纯石油焦也不同于纯煤焦。随石油焦掺入比变化而改变的拐点主要源于石油焦与煤焦的反应性之间差异。较高转化率下出现的拐点，主要源于石油焦本身随气化温度提高导致气化速率下降。XRD测定显示，高温处理后石油焦中碳有序化程度要明显高于煤焦。高气化温度下石油焦碳结构发生明显有序化是导致其反应活性急剧下降的重要原因。     

煤高温快速热解规律研究

利用高温滴管炉在1000℃～1400℃考察了彬县烟煤在高温快速热解过程中失重的变化,同时比较了埃塞俄比亚褐煤和晋城无烟煤的热解规律。结果表明,热解失重率随温度的升高而增加,而且各种煤种的最大失重率在高温下大于工业分析的失重率。对于不同变质程度的煤种其热解特性也不相同,较低的热解温度对高阶煤的影响较小。彬县原煤经过热解后比表面积增加,且随着热解温度的提高而增大,当热解温度超过灰熔点时,总比表面积降低。通过数据回归,得到了三种煤的失重率和热解温度的关联式。     

水蒸气气氛煤中温催化气化动力学研究

以碳酸钾为催化剂,用热天平的等温热重法研究了四种不同变质程度煤焦常压下水蒸气催化气化反应动力学。在加和不加碳酸钾条件下,测定了温度为700~850℃煤焦的化学反应控制条件下的碳转化率与时间的关系。碳酸钾催化剂的加入对变质程度越高煤的气化催化作用越大。加碳酸钾的碳转化率与时间的关系用混合模型和修正随机孔模型可以良好的拟合关联,均相模型关联较差。利用修正随机孔模型拟合关联出了四种煤焦催化水蒸气气化反应的活化能和指前因子,活化能为90.317~167.861kJ/mol,指前因子和活化能之间具有补偿效应。     

煤高温快速液化影响因素的研究

用17mL微型盐浴共振搅拌反应釜研究了煤高温快速液化。结果表明,煤阶低且含矿物质少的烟煤液化性能较好;转化率主要受溶剂供氢性能的影响;氢气所做贡献很小,与氮气气氛下的转化率基本一样;催化剂作用不明显;煤的粒径对转化率影响不大,反应器振动影响较大。综合结论分析其机理为,在煤的一次热分解温度范围的高温段,一般在500℃附近,低变质程度烟煤结构中的桥键可充分断裂,形成大量自由基,用足量优秀供氢溶剂作氢源,可有效稳定自由基,形成液体产物,在几十秒钟到几分钟的时间内就达到很高的转化率。     

煤粉着火模式对再燃脱硝效率影响的实验研究

在一维携带流实验台上研究了烟煤煤粉着火模式,包括均相着火和非均相着火,对煤粉再燃还原NO的影响。实验结果表明,温度一定时,随着再燃区氧体积分数的增加,煤粉挥发分首先着火,脱硝效率明显下降;而非均相着火初期造成的颗粒高温有利于异相还原NO,脱硝效率得以回升;氧体积分数进一步提升,再燃区呈现富氧状态,脱硝效率再次下降。提高再燃区温度促进煤粉还原NO,脱硝效率更高,但是也促使挥发分在更低的氧体积分数下着火,着火后脱硝效率下降更多;粒径对煤粉着火以及还原NO的影响较为复杂,粒径在40μm以上,不同氧体积分数下脱硝效率基本上随粒径增大而下降。     

Study of poly(bisphenol A carbonate) relaxation kinetics at the glass transition temperature

In this work, the variations of the relaxation times are investigated above and below the glass transition temperature of a model amorphous polymer, the polycarbonate. Three different techniques (calorimetric, dielectric and thermostimulated currents) are used to achieve this goal. The relaxation time at the glass transition temperature was determined at the temperature dependence convergence of the relaxation times calculated with dynamic dielectric spectroscopy (DDS) for the liquid state and thermostimulated depolarisation currents (TSDC) for the vitreous state. We find a value of τ(T_g) = 110 s for PC samples. The knowledge of the temperature dependence, τ(T), and the value τ(T_g) enables to determine the glass-forming liquid fragility index, m. We find m = 178 ± 5.     

Exponential temperature change in thermal analysis at non-isothermal kinetics

The applying of exponential temperature programming: dT/dt=T orT=T ₀ e ^t in thermal analysis at non-isothermal kinetics is discussed. An approach for the integration of the temperature integral is presented.     

On the chemical kinetics of n-butanol: ignition and speciation studies

Direct measurements of intermediates of ignition are challenging experimental objectives, yet such measurements are critical for understanding fuel decomposition and oxidation pathways. This work presents experimental results, obtained using the University of Michigan Rapid Compression Facility, of ignition delay times and intermediates formed during the ignition of n-butanol. Ignition delay times for stoichiometric n-butanol/O(2) mixtures with an inert/O(2) ratio of 5.64 were measured over a temperature range of 920-1040 K and a pressure range of 2.86-3.35 atm and were compared to those predicted by the recent reaction mechanism developed by Black et al. (Combust. Flame 2010, 157, 363-373). There is excellent agreement between the experimental results and model predictions for ignition delay time, within 20% over the entire temperature range tested. Further, high-speed gas sampling and gas chromatography techniques were used to acquire and analyze gas samples of intermediate species during the ignition delay of stoichiometric n-butanol/O(2) (χ(n-but) = 0.025, χ(O(2)) = 0.147, χ(N(2)) = 0.541, χ(Ar) = 0.288) mixtures at P = 3.25 atm and T = 975 K. Quantitative measurements of mole fraction time histories of methane, carbon monoxide, ethene, propene, acetaldehyde, n-butyraldehyde, 1-butene and n-butanol were compared with model predictions using the Black et al. mechanism. In general, the predicted trends for species concentrations are consistent with measurements. Sensitivity analyses and rate of production analyses were used to identify reactions important for predicting ignition delay time and the intermediate species time histories. Modifications to the mechanism by Black et al. were explored based on recent contributions to the literature on the rate constant for the key reaction, n-butanol+OH. The results improve the model agreement with some species; however, the comparison also indicates some reaction pathways, particularly those important to ethene formation and removal, are not well captured.     

Dehydration kinetics of Portland cement paste at high temperature

Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also the increased pore pressure in the paste. In this article, the dehydration kinetic was characterized in term of the combination of kinetics of CSH and CH. The dehydration kinetics data of cement paste at different heating rates was collected by thermogravimetry. The influence of temperature on the reaction rate is analyzed by Arrhenius equation. The Arrhenius parameters of CSH and CH, activation energy, and pre-exponential factor are determined by isoconversional method. The calculated kinetics parameters were validated by further experimental data finally.     

热重法研究煤的燃烧反应及其动力学

我国是个多煤少油的国家,煤炭是我国的主要能源,在我国的一次能源中所占比列高达70%[1].煤炭被广泛用于人类生产与生活的各个方面,且它的利用主要是通过燃烧直接获得能量.然而由于先进技术的欠缺,我国在煤炭的利用中一直存在着燃烧效率不高和环境污染严重等缺点,这与现今能源短缺和环境保护日益受重视的现状不相适应.本文通过研究分析煤的燃烧反应及燃烧反应动力学,为煤炭在利用时燃烧的清洁化与高效化提供科学依据.     

高温弱还原气氛下煤中矿物质变化的研究

利用XRD、SEM-EDX 分析了神府煤中矿物质在高温下的变化,并针对不同停留时间对矿物质变化的影响作了考察。结果表明,高温下煤中矿物质在弱还原气氛中的变化基本与CaO-SiO2-Al2O3三元相图相符,矿物质的变化主要由钙质硅铝酸盐控制。 停留时间的变化主要影响玻璃体和晶体相对含量的变化和含铁矿物质的类型。非晶态物质的含量与共熔体生成有密切关系,与共熔体体系的稳定性有关。FeS-FeO体系的性质及变化对矿物质体系有重要的影响,利用SEM-EDX对FeS和FeO的分布和变化进行了考察。     

Effect of oxygen concentration and temperature on ignition time of polypropylene

The presented article deals with the assessment of combined impact of temperature and flow of oxidising atmosphere, its oxygen concentration and heat flux on the ignition time of isotactic polypropylene (PP). The ignition time was determined in a specially adapted hot air Setchkin furnace at temperatures (450 and 600?°C), density of heat flux (12.4 and?26.4?kW m^?2), flows of oxidation mixture (6 and 8?L?min^?1) and volume oxygen concentrations (3, 9, 15, 21, 27, 33, 39, 45 and 50?%). Obtained data allows us to assume that the temperature influence on PP induction period of ignition increases with decreasing flow rate of oxidising atmosphere. At the flow of oxidising mixture equal to 6?L?min^?1 and temperature of 600?°C, oxygen concentration had only a negligible impact on the the induction period of ignition in the analysed period. From the presented results, the induction period of ignition depends on the temperature and also on the flow rate of oxidising mixture and oxygen concentration in it. In addition, heat flux has a significant influence on the induction period. However, the quantification of the heat flux influence was not possible with the applied experimental device.     

A TG/DTA study on the effect of coal blending on ignition behaviour

Understanding the ignition behaviour of coal is of utmost importance for the design of boilers and control of the combustion process. In recent years there has been an increasing utilisation of coal blends for combustion, but information on the possible interactive effects during ignition of the individual components is scarce. In this work the ignition behaviour of a series of coal blends, made up from three coals of different rank, sub-bituminous, high volatile and low volatile bituminous, was studied. To this end a thermogravimetric analyser linked to a mass spectrometer for evolved gas analysis was used. Different ignition behaviour was observed for the coals studied; the sub-bituminous and low volatile bituminous coals ignited heterogeneously, while homogeneous ignition occurred for the high volatile bituminous coal. In the case of blends of the low and high volatile bituminous coals, different mechanisms of ignition were observed depending on the blends composition. This revised version was published online in July 2006 with corrections to the Cover Date.