低硫煤联产Q相水泥熟料的矿物生成反应热力学分析

以兖州低硫煤为试验煤种,在两段多相反应试验台上开展了联产Q相水泥熟料的试验,对联产熟料样品中的矿物组成进行了X射线衍射(XRD)分析,发现联产熟料矿物组成中的主要矿物种类为2CaO·SiO2和Q相.根据状态函数吉布斯自由焓,对兖州煤联产Q相水泥熟料中化学组成可能发生的矿物生成反应进行了热力学计算,并对熟料矿物生成反应的优先顺序进行比较.结果表明:根据熟料化学组成,优先发生的反应是2CaO·Al2O3·SiO2的直接合成反应,其次为2CaO·SiO2的直接合成反应,再次为Q相矿物的间接合成反应;联产熟料矿物组成最终应以2CaO·SiO2和Q相矿物为主体;对联产熟料矿物生成反应热力学分析的结论与兖州煤联产Q相水泥熟料试验的矿物组成结果基本一致.     

煤粉炉联产水泥熟料煤灰熔融特性的试验研究

选用高硫长广煤为试验煤种、分析纯 CaO 和 MgO 为添加剂,按照设定的配料方案配制为混合煤粉.依据 GB/T 219-1996煤灰熔融特性测试方法,使用 SE-AF 智能灰熔点测试仪对混合煤粉的灰熔点进行了测量.结果表明:随混合煤粉中 CaO 添加质量分数的逐渐增加,混合煤粉灰熔融特性温度呈现 V 型变化规律;按照联产 Q 相水泥熟料配料方案配制的混合煤粉煤灰的结渣趋势程度属于轻微,较长广煤的结渣趋势程度有所降低.对软化温度下混合煤粉煤灰的矿物组成进行了 XRD 分析,并利用 CaO-Al2O3一SiO2 三元系统相图,进一步分析了混合煤粉熔融特性温度变化机理.结果表明:随着混合煤粉中 CaO 添加质量分数的变化,煤灰矿物组成中不同程度地出现低温共融体是煤灰熔融特性温度变化的原因.     

循环流化床在水泥生产中的应用

一、前言水泥的生产由物料的烘干、预热、分解、熟料煅烧、冷却等几个部分组成。各水泥公司有各自不同的生产特点,大部分公司水泥生产过程是相似的,仅仅是分解炉型式不同而已。在水泥生产过程中,CaCO_3分解是水泥生产中一个很重要的环节,分解炉中煤粉燃烧放出的热量提供给了 CaCO_3 分解吸收热量。按照“未反应核”反应模型对颗粒进行近似计算,     

锡林浩特褐煤燃烧特性试验研究

在热天平上对通过程序升温静态燃烧系统的试验,根据锡林浩特褐煤在不同粒度、不同升温速度和不同反应气氛下的TG/DSC曲线,研究着火温度、燃尽温度等特征参数,并根据动力学反应方程确定试验煤种的表观反应动力参数;在一元煤粉气流燃烧模拟系统试验台上,研究直流燃烧情况下,氧浓度、煤粉浓度、煤粉细度、炉壁温度与褐煤燃烧特性、结渣特性及烟气污染物排放特性的关系;研究在分级燃烧条件下燃烧产物中有害成分的生成、燃尽度变化及结渣特性的关系;研究一次风速及煤粉浓度对试验煤种的着火特性、燃烧特性及有害物排放特性.     

超细煤粉燃烧氮氧化物释放特性的研究

通过试验和数值模拟，对超细煤粉在一维热态煤粉炉内燃烧时煤粉粒度、炉膛温度、过量空气系数、煤种等因素对NOx释放特性的影响规律进行了研究。研究结果表明：超细煤粉NOx的排放浓度低于常规粒度煤粉；NOx的排放浓度，随过量空气系数的增加而明显增加；煤种不同，NOx释放规律不同，煤粉超细化后，龙口褐煤的排放量明显减少，晋城无烟煤则变化不大；NOx的排放浓度随温度的升高而升高，但温度升高到一定值后，NOx的排放浓度却呈现下降趋势。以超细煤粉作为再燃燃料，NOx的还原率将比常规粒度煤粉再燃有所提高，褐煤作为再燃燃料时，效果更明显。模拟计算与试验结果较为吻合。图6表2参2     

燃煤飞灰中铁磁性物质及其形成机制

运用穆斯堡尔谱仪对徐州烟煤和内蒙褐煤煤粉在高温沉降炉中燃烧产生的燃煤飞灰中含铁物相及其相对含量进行定性和定量分析,探讨燃烧温度和燃烧气氛对含铁物相相对含量的影响规律.结果表明,煤种、温度和燃烧气氛对燃煤飞灰中含铁物相的种类没有影响,而对含铁物相中铁的相对含量有一定的影响,其中所含磁性铁相成分也有所不同.燃烧温度升高,灰中硅酸盐玻璃体中铁的相对含量有一定程度的减少,而铁氧化物中铁的相对含量相应增加,其中赤铁矿中铁的相对含量增大较为明显.相同燃烧温度不同燃烧气氛下,煤种对燃煤灰样中含铁物相成分的影响相对较小.     

石灰石炉内高温煅烧脱硫及产物活性的实验

以石灰石炉内喷入与烟气循环流化床的组合式燃煤锅炉烟气脱硫工艺方案为应用对象,选择辽宁地区富产的7种石灰石,在煤燃烧热态实验装置上,对其炉内煅烧高温脱硫效果及其影响因素进行了实验研究,并对煅烧产物的活性及其影响因素进行了实验研究。实验表明：煅烧温度、钙硫比、煅烧停留时间、石灰石粒度等因素对脱硫效果均有显著影响;煅烧温度、煅烧停留时间和石灰石粒度等因素对石灰石高温煅烧产物活性有显著影响;石灰石最佳煅烧温度区间为1000℃～1200℃,在此温度区间内,炉内脱硫效率最高,煅烧产物的活性最高。图7表2参2     

新型干煤粉气流床气化炉的气化特性研究

根据无焰氧化技术的思想提出了一种新型干煤粉气流床气化炉,运用试验和数值计算方法对高灰熔点煤粉在炉内气化反应过程进行了研究。试验和模拟结果证实了该炉型结构能够使炉内温度场均匀,炉内温度梯度显著降低,实现了无焰氧化技术的基本反应特征,使煤粉气化反应空间化;同时炉内平均温度水平上升,气化强度增强,排渣口处温度水平上升,满足了高灰熔点煤种的气化要求。     

低氧再燃条件下煤粉均相着火温度的测量

在一维炉试验台上研究了煤粉颗粒群在低氧浓度再燃条件下的均相着火规律.结果表明:在低氧浓度下(＜10% 体积分数),煤粉均相着火呈现出反应不剧烈、不连续的特点;氧浓度对于煤粉均相着火温度的影响近似成指数变化关系,即氧浓度越低,均相着火温度越高;在一定范围内,氧浓度越低,煤粉均相着火延迟时间越长;煤粉均相着火温度随粒径减小而提高,近似成线性关系;不同氧浓度前提下,粒径对着火温度的影响作用不同.     

不同煤种高温燃烧时NOx和SO2生成影响因素的实验

在一维沉降炉上进行了在煤粉高温燃烧时NOx和SO2生成影响因素的实验研究,系统考察了煤粉高温燃烧时NOx和SO2生成的影响因素.试验表明,SO2和NOx生成与炉内温度,煤粉细度,给粉量,煤种,二次风温,一、二次风比值及过量空气系数等有密切关系.通过SO2和NOx生成规律的研究,对煤粉炉的优化运行有一定的指导意义.     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.