Rare earth elements in fly ashes created during the coal burning process in certain coal-fired power plants operating in Poland - Upper Silesian Industrial Region

The subject of the study covered volatile ashes created during hard coal burning process in ash furnaces, in power plants operating in the Upper Silesian Industrial Region, Southern Poland. Coal-fired power plants are furnished with dust extracting devices, electro precipitators, with 99-99.6% combustion gas extracting efficiency. Activity concentrations ofTh-232, Ra-226, K-40, Ac-228, U-235 and U-238 were measured with gamma-ray spectrometer. Concentrations of selected rare soil elements (La, Ce, Nd, Sm, Y, Gd, Th, U) were analysed by means of instrumental neutron activation analysis (INAA). Mineral phases of individual ash particles were identified with the use of scanning electron microscope equipped with EDS attachment. Laser granulometric analyses were executed with the use of Analyssette analyser. The activity of the investigated fly-ash samples is several times higher than that of the bituminous coal samples; in the coal, the activities are: 226Ra - 85.4 Bq kg⁻¹, 40 K-689 Bq kg⁻¹, 232Th - 100.8 Bq kg⁻¹, 235U-13.5 Bq kg⁻¹, 238U-50 Bq kg⁻¹ and 228Ac - 82.4 Bq kg⁻¹.     

Assessment of four turbulence models in simulation of large-scale pool fires in the presence of wind using computational fluid dynamics (CFD)

Pool fires are the most common of all process industry accidents. Pool fires often trigger explosions which may result in more fires, causing huge losses of life and property. Since both the risk and the frequency of occurrence of pool fires are high, it is necessary to model the risks associated with pool fires so as to correctly predict the behavior of such fires.Among the parameters which determine the overall structure of a pool fire, the most important is turbulence. It determines the extent of interaction of various parameters, including combustion, wind velocity, and entrainment of the ambient air. Of the various approaches capable of modeling the turbulence associated with pool fires, computational fluid dynamics (CFD) has emerged as the most preferred due to its ability to enable closer approximation of the underlying physical phenomena.A review of the state of the art reveals that although various turbulence models exist for the simulation of pool fire no single study has compared the performance of various turbulence models in modeling pool fires. To cover this knowledge-gap an attempt has been made to employ CFD in the assessment of pool fires and find the turbulence model which is able to simulate pool fires most faithfully. The performance of the standard k–? model, renormalization group (RNG) k–? model, realizable k–? model and standard k–ω model were studied for simulating the experiments conducted earlier by Chatris et al. (2001) and Casal (2013). The results reveal that the standard k–? model enabled the closest CFD simulation of the experimental results.     

总有机碳测定仪TOC-5000A与Aurora 1030W性能的比较

从仪器精密度、方法检出限、准确度、工作曲线线性范围等角度对总有机碳测定仪TOC-5000A(高温燃烧+非分散红外法)与Aurora 1030W(湿式氧化)的性能进行比较.研究结果显示,TOC-5000A方法检出限(0.535ppm)高于Aurora1030W(0.047ppm),且在较低有机碳浓度下(1ppm)精密度差于Aurora 1030W.但在较高有机碳浓度条件下(10ppm),TOC-5000A精密度优于Aurora 1030W.在不同水样中加入标准物质后计算方法回收率,两台仪器的测试结果均大于90%.在样品量较低的情况下,碳加入量与两台仪器响应值的线性关系均较差,响应因子随碳加入量的增加呈现显著降低的趋势,并分别在升至2μg(Aurora 1030W)与0.16μg(TOC-5000A)后达到稳定.     

煤矸石型煤着火燃尽性能的实验研究

研究开发适用于工业层燃炉和民用炉具的煤矸石型煤燃烧技术是解决煤矸石综合利用难题的一条新途径。通过对煤矸五型煤燃烧过程的实验研究,得出煤矸五型煤着火燃尽特性随温度和时间的变化规律及其关联式,并分析探讨了CR助燃剂的助燃效果和助燃机理,对完善煤矸石型煤的燃烧理论和工艺技术具有一定的参考价值。      

不同热辐射强度下秸秆燃烧特性实验研究

为了探讨秸秆在不同规模火灾中的燃烧特性,采用锥形量热仪测得秸秆点燃时间、热释放速率、一氧化碳产生率等参数进行模拟实验,结合热重分析法研究秸秆的热解过程。结果表明:随着辐射强度的升高,秸秆由阴燃向明火转化,热释放速率、烟释放速率随之加快,缩短了点燃时间并降低了CO等有毒气体排放速率。热重分析得到秸秆在各个温度段下的反应情况,解释了在不同辐射强度下秸秆点燃性能实验现象及其反应机理,为防止火灾事故发生提供了可靠的理论依据。     

大型气相化学动力学软件包CHEMKIN及其在燃烧中的应用

燃烧化学反应动力学是计算燃烧学中的重要内容之一。本文介绍了处理气相化学动力学的大型软件包ＣＨＥＭＫＩＮ的结构和不同版本的特点,并描述了它在燃烧问题中的应用。最后通过一个算例对Ｈ２／Ｏ２／Ｎ２均相绝热等压燃烧体系进行了处理和计算,以具体说明该软件包的应用效果。     

微重力波动与燃烧温度变化的研究

本文通过试验飞机抛物线飞行进行了微重力燃烧实验,采集得到微重力条件下一个采样点微重力波动和燃烧温度变化的数据,在此基础上将时间序列预测和神经网络相结合进行了微重力波动与燃烧温度变化的研究,揭示了试验飞机抛物线飞行中微策略波动和采样点燃烧温度变化的规律。     

新一代评估方法——锥形量热仪(CONE)法在材料阻燃研究中的应用

利用新一代评估方法———锥形量热仪法对材料阻燃机理、材料危险性等级划分、烟毒释放评价、材料燃烧性及阻燃性评价等方面的应用进行了分析讨论 ,结果表明锥形量热仪法对阻燃剂、阻燃制品的研究开发及阻燃剂在火灾中的行为研究具有重要意义。     

Response surface models for the formation of PCDD and PCDF in a pilot plant combustion of MSW

Experimental data on PCDD and PCDF emissions in raw gases from municipal solid waste combustion in a pilot plant were processed by Response Surface models to gain information on process parameter values which minimize both the total PCDD/PCDF concentrations and those of a selected congener group.     

Experimental study on the minimum explosion concentration of anthracite dust: The roles of O2 mole fraction,inert gas and CH4 addition

The explosion characteristics of anthracite coal dust with/without small amount of CH₄ (1.14 vol %) were investigated by using a 20 L spherical explosion apparatus with an emphasis on the roles of oxygen mole fraction and inert gas. Two methods based on overpressure and combustion duration time were used to determine the minimum explosion concentration (MEC) or the lower explosion limit (LEL) of the pure anthracite coal dust and the hybrid coal-methane mixtures, respectively. The experiment results showed that increasing oxygen mole fraction increases the explosion risk of coal dust: with increasing oxygen mole fraction, the explosion pressure (P_ex) and the rate of explosion pressure rise ((dp/dt)_ex)) increase, while MEC decreases. The explosion risk of anthracite dust was found to be lower after replacing N₂ with CO₂, suggesting that CO₂ has a better inhibition effect on explosion mainly due to its higher specific heat. However, the addition of 1.14% CH₄ moderates the inhibition effect of CO₂ and the promotion effect of O₂ on anthracite dust explosion for some extent, increasing explosion severity and reducing the MEC of anthracite dust. For hybrid anthracite/CH₄ mixture explosions, Barknecht's curve was found to be more accurate and conservative than Chatelier's line, but neither are sufficient from the safety considerations. The experimental results provide a certain help for the explosion prevention and suppression in carbonaceous dust industries.