Comparison study of thermochemical waste-heat recuperation by steam reforming of liquid biofuels

The concept of thermochemical exhaust heat recuperation by steam reforming of biofuels is considered. Thermochemical recuperation can be considered as an on-board hydrogen production technology. A schematic diagram of a fuel-consuming equipment with thermochemical heat recuperation is described. The thermodynamic analysis of the thermochemical recuperation systems was performed to determine the efficiency of using various fuels, in particular, methanol, ethanol, n-butanol, and glycerol. The thermodynamic analysis was performed by Gibbs free energy minimization method and implemented using the Aspen Hysys program. The thermodynamic analysis was performed for a wide temperature range from 400 to 900 K, for steam-to-fuel of 1, and pressures of 1 bar. The maximum fuel conversion reaches for the following temperatures: methanol - 600 K, ethanol - 730 K, n-butanol - 860 K, glycerol - 890 K. The dependence of the reforming enthalpy on temperature is determined. It was shown that the reaction enthalpy determines the heat transformation coefficient, which shows the ratio of the low heat value of synthetic fuel and the low heat value of the initial fuel. For all studied fuels, the maximum value of the transformation coefficient is observed for steam reforming of ethanol and the maximum heat transformation coefficient is 1.187. The temperature range is determined at which the maximum efficiency of the use of thermochemical recuperation occurs due to the reforming of biofuels. For methanol, the effective temperature is about 600 K, for ethanol is about 700 K, for n-butanol is 850 K, for glycerol is more than 900 K. The results obtained make it possible to efficiently select the type of fuel for thermochemical recuperation due to steam reforming.     

福建某低品位金矿新型浸金剂浸金试验

福建某斑岩型金矿品位低、规模大,金主要以自然金形式存在,可见金的粒度较粗,为高效利用该低品位金矿,开展新型浸金剂金蝉全泥浸出试验和柱浸试验,结果表明：全泥浸出在磨矿细度为-0.074 mm占80%、矿浆浓度25%、加石灰调pH 值11.0左右、初始金蝉浓度为500 mg/L和过程中控制金蝉浓度不小于300 mg/L条件下浸出20 h,金的浸出率为93.43%,金蝉耗量为1.02 kg/t；柱浸在矿石粒度为-30 mm条件下喷淋浸出23天,金累计浸出率和金蝉累计耗量分别为86.54%和1.22 kg/t。     

Predicting the damage development in epoxy resins using an anisotropic damage model

For fiber-reinforced plastics, the strain-rate dependent response is governed by the matrix behavior. In this work, the Goldberg model is considered for the epoxy matrix constitutive material model. Moreover, the strain-rate dependency is achieved by direct influence on the elastic modulus, the inelastic strain, and the material strain to failure. In addition, an anisotropic damage response is implemented and extended through a strain-rate dependent definition. Since the constitutive model relies on nonphysical parameters, a parameter study is further performed. Additional numerical investigations using a micro-mechanical model are performed. Tension and shear loading conditions are evaluated and the influence of different strain rates is explored. Furthermore, the implemented anisotropic damage model is compared and discussed against an isotropic damage model.     

地浸铀矿山浸出速度的影响因素

在地浸铀矿山生产过程中,铀的浸出速度是制约生产的重要参数,直接关系到矿山的服务年限。矿山生产采区往往存在严重的拖尾现象,为提高地浸铀矿山资源利用率,降低生产成本,研究了影响铀浸出速度的因素,提出了控制铀浸出速度的措施。     

55SiCr弹簧钢中的残留奥氏体与碳化物

通过扫描电镜(SEM)、电子背散射衍射(EBSD)、透射电镜(TEM)、X射线衍射仪(XRD)、热膨胀仪、洛氏硬度计等手段研究了弹簧钢55SiCr的组织和相变点以及残留奥氏体和碳化物在热处理过程中的组织演变。结果表明:55SiCr弹簧钢淬火后残留奥氏体以块状分布在基体上;随回火温度的升高,残留奥氏体减少并呈粒状和薄膜状分布;C在残留奥氏体中富集,使其稳定性增强;Si抑制了碳化物的析出,提高了残留奥氏体的稳定性。低温回火时,Si延缓了渗碳体析出;高温回火时,C原子扩散速率提高,促进渗碳体析出,引起体积的收缩。慢速加热回火时,C有足够的时间扩散,从而促进渗碳体的形成,使渗碳体的形成温度提前;快速加热回火时,C来不及扩散,抑制了渗碳体的析出。回火加热速率一样时,试验钢的硬度随回火温度的提高而下降。当回火温度为400 ℃时,硬度值最大为51 HRC;当回火温度为650 ℃时,硬度值最小为37 HRC。当加热速率为0.1 ℃/s时,硬度值最小为33 HRC;当加热速率为200 ℃/s时,硬度值最大为40 HRC。     

基于压力和流量守恒收敛准则的微织构端面机械密封数值计算

目前在研究微织构端面机械密封时,离散求解雷诺方程时采用的压力收敛准则,并不能完全保证得到准确的泄漏率。提出基于压力收敛和内外径流量守恒收敛双重收敛准则的微织构端面机械密封数值计算方法,针对圆柱形微孔端面机械密封,基于考虑JFO边界条件的二维雷诺方程,建立含一个计算域的数值计算模型,并采用不同的收敛准则对开启力和泄漏率进行数值计算。结果表明:仅使用压力收敛准则不能显式判断计算是否已经满足质量守恒,不能准确计算泄漏率;仅使用内外径流量守恒收敛准则可能出现迭代初始阶段就满足收敛条件,导致错误结果;使用压力收敛准则和内外径流量守恒收敛准则相结合的双重收敛准则,可保证泄漏率计算的正确性。     

采用绝热式自燃测试方法分析煤的自燃倾向

对煤的自燃倾向进行快速有效鉴别,有助于对煤的自燃倾向采取分级分类管理从而有效防治煤矿火灾,因而采用绝热式自燃测试方法对煤的自燃倾向进行准确分析很有必要。简要介绍绝热式自燃测试方法的测试原理及其仪器结构,模拟煤炭自燃的物理过程,通过采用包括反应器、气体预热铜管和跟踪温度控制方式等综合绝热措施以实现300 g煤样的自然发火实验,记录煤样从40℃上升到70℃的升温速率(或前30 h的升温速率),测试煤样的自燃特性曲线并分析曲线特征。即建立煤绝热氧化产热速率计算模型,结合实验数据计算所得的煤在绝热氧化条件下的升温速率和产热速率可鉴定煤自燃倾向性的强弱。采用绝热式自燃测试方法对不同煤的自燃倾向分析后表明,无烟煤和部分烟煤的自燃倾向较低,褐煤的自燃倾向较高,故而在煤矿开采时需特别注意褐煤的自燃倾向。     

镍钴电池Co-S负极材料的电化学特性研究

通过水热法制备Co-S材料,结合XRD分析其相结构,SEM和EDS分析其表面形貌及元素种类,采用充放电测试、循环伏安和交流阻抗法对其进行电化学特性研究。结果表明,该合金仅含有Co3S4、Co9S8和Co(OH)2, 结晶性良好,呈交叉生长的纳米薄片状,放电电流密度为150 mA/g时的最大放电容量为393.1mAh/g,50次循环后的容量保持率高达80.6%。当放电电流密度为1200 mA/g时,该电极的高倍率放电性能为79.3%。通过循环伏安和交流阻抗分析可知Co-S电极主要发生Co/Co(OH)2的法拉第反应,不可逆产物CoOOH的生成降低了活性物质的利用率,导致放电容量衰减。     

基于低影响开发理念的雨水控制设计计算

文中介绍了某电影文化综合体项目采用的集中雨水控制利用技术:透水性地面铺装、屋顶绿化、下凹式绿地、微生态雨水处理回用一体机。通过合理划分汇水面积,结合项目实际情况,计算给出了在限定年径流总量控制率的条件下,合理采用多种手段联合,使项目符合《绿色建筑评价标准》(GB/T 50378—2014)中的场地生态设计要求,实现了海绵城市的控制目标,也为类似工程提供了参考思路。     

Benchmark value determination of energy efficiency indexes for coal-fired power units based on data mining methods

The operational optimisation of coal-fired power units is important for saving energy and reducing losses in the electric power industry. One of the key issues is how to determine the benchmark values of the energy efficiency indexes of the units. Therefore, a new framework for determining these benchmark values is proposed, based on data mining methods. First, the energy efficiency key performance indicators (KPIs) associated with the net coal consumption rate (NCCR) were selected based on the domain knowledge. Second, the decision-making samples with minimal NCCR were acquired with the fuzzy C-means (FCM) clustering algorithm, and the corresponding clustering centres were employed as the benchmark values. Finally, based on the support vector regression (SVR) algorithm, the target values of the NCCR were obtained with the KPIs as input, and the energy saving potential was evaluated by comparing the target values with the historical values of the NCCR. An actual on-duty 1000 MW unit was taken as study unit, and the results show that the energy saving potential is remarkable when the operators adjust the KPIs based on the calculated benchmark values.