Thermal Decomposition of Olive-Solid Waste by TGA: Characterization and Devolatilization Kinetics under Nitrogen and Oxygen Atmospheres

Despite the fact that a few countries in the Mediterranean and the Middle East have limited crude oil reserves, they have abundant biomass feedstocks. For instance, Jordan relies heavily on the importation of natural gas and crude oil for its energy needs;but, by applying thermochemical conversion techniques, leftover olive oil can be used to replace these energy sources. Understanding the chemical, physical, and thermal characteristics of raw materials is essential to obtaining the most out of these conversion processes. Thermogravimetric analysis was used in this study to examine the thermal behavior of olive-solid residue (kernel) at three different heating rates (5, 20 and 40 C/min) in nitrogen and oxygen atmospheres. The initial degradation temperature, the residual weight at 500 and 700˚C and the thermal degradation rate during the devolatilization stage (below 400˚C) were all determined. It was found that in N2 and O2 atmospheres, both the initial degradation temperature and the degradation rate increase with increasing heating rates. As heating rates increase in the N2 atmosphere, the residual weight at 500 or 700˚C decreases slightly, but at low heating rates compared to high heating rates in the O2 atmosphere, it decreases significantly. This suggests that a longer lignin oxidation process is better than a shorter one. Coats and Redfern approach was used to identify the mechanism and activation energy for the devolatilization stage of pyrolysis and oxidation reactions. The process mechanism analysis revealed that the model of first-order and second-order reactions may adequately describe the mechanism of heat degradation of the devolatilization step of olive-solid waste for pyrolysis and oxidation processes, respectively.

Effects of cooling rate on solidification behavior of dilute Al-Sc and Al-Sc-Zr solid solution

Six alloys with different compositions of Al 0.1%Sc, Al 0.3%Sc, Al 0.3%Zr, Al 0.1% Sc 0.1%Zr, Al 0.3%Sc 0.1%Zr and Al 0.3%Sc 0.3%Zr were prepared by casting in a wedge shaped copper mould. The hardness test, microstructure observation, and DSC thermal analysis were applied to fully investigate the solidification behavior of the wedge tip (whose cooling rate is 1 000 K/s) and the top surface (cooling rate 100 K/s) of each casting. The results show that the cast structures in the hypoeutectic region of Al Sc alloys are slightly affected by cooling rates during the solidification. In the case of hypereutectic alloy of Al 0.3%Sc 0.3%Zr , the cast grains were remarkably refined under the condition of a 100 K/s cooling rate, however, under a 1 000 K/s cooling rate condition, solute atoms contribute nothing to the grain refinement, due to the eutectic concentration becomes higher. The hardness can be improved to a greater degree by Sc single addition, compared to single Zr addition, but it can be improved even greater when Sc added together with Zr. It is sensitive to cooling rate, the higher the cooling rate, the greater the hardness. By combining the results of TEM examination and DSC analysis, it can be seen that a supersaturated Al solid solution forms during the solidification, and the solubility of Sc in Al solution can be improved by increasing the cooling rate.

Cu–Co–O nano-catalysts as a burn rate modifier for composite solid propellants

Nano-catalysts containing copper–cobalt oxides(Cu–Co–O) have been synthesized by the citric acid(CA) complexing method. Copper(II) nitrate and Cobalt(II) nitrate were employed in different molar ratios as the starting reactants to prepare three types of nano-catalysts. Well crystalline nano-catalysts were produced after a period of 3 hours by the calcination of CA–Cu–Co–O precursors at 550 °C. The phase morphologies and crystal composition of synthesized nano-catalysts were examined using Scanning Electron Microscope(SEM), Energy Dispersive Spectroscopy(EDS) and Fourier Transform Infrared Spectroscopy(FTIR) methods. The particle size of nano-catalysts was observed in the range of 90 nm–200 nm. The prepared nano-catalysts were used to formulate propellant samples of various compositions which showed high reactivity toward the combustion of HTPB/AP-based composite solid propellants. The catalytic effects on the decomposition of propellant samples were found to be significant at higher temperatures. The combustion characteristics of composite solid propellants were significantly improved by the incorporation of nano-catalysts. Out of the three catalysts studied in the present work, Cu Co-I was found to be the better catalyst in regard to thermal decomposition and burning nature of composite solid propellants. The improved performance of composite solid propellant can be attributed to the high crystallinity, low agglomeration and lowering the decomposition temperature of oxidizer by the addition of Cu Co-I nano-catalyst.

Effect of Sudden Increase of Solid Feed Rate on the Arching in Hoppers Connected to a Moving-Bed Standpipe with Interstitial Gas Flow

In this paper, a model is proposed for the prediction of the width of arching in hoppers resulted from sudden changes in solid feed rates. Such changes in solid feed rate usually come from the collision on the surface of the moving-bed in the standpipe. The model also takes into account the effect of the powder height in the standpipe of the hopper. The model proves to be adaptable for predicting operational conditions to avoid arching by keeping constant powder height in the main standpipe with interstitial gas flow.

Design of fan beam optical sensor and its application in mass flow rate measurement of pneumatically conveyed solids

The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source emits a 50° lamellar fan-beam through the gas-solid two phase flow, and the projection data resulting extinction effect of solid particles are detected at the same time. With the projection data, the flow rate mass can be calculated, and then the flow image can be reconstructed. In this paper, the design of the sensor including spatial arrangement of the structural parts, basic principle and measurement sensitivity distribution are introduced. The mathematical measurement model of solid mass flow rate is presented together with the testing results.

Determination and Evaluation of the Rate of Solid Wastes Generation in Health Care Centers in Montevideo, Uruguay

Decree 586/009 establishes the main guidelines related to the management of Health Care Wastes (RAS). For this reason, it is used as a reference in the definition of any methodological proposal that intends to address all the aspects related to Intra-institutional Management of Residues generated in Health Care Centers (CAS) in Uruguay. In the first instance, this paper presents an application case based on the experience of previous work in a CAS in Montevideo. Providing special importance to the Evaluation of rates of sanitary waste removal rates in the hospital centers, which were determined based on historical data for the period from 2008 to 2011, referring to rates of removal of contaminated, common and recyclable sanitary waste. Based on the analysis of these data, information on their behavior is obtained, such as: number of common waste removed per day in the period, evolution of the monthly average of the daily rate of removal of common waste, evolution of the average daily waste removal rate from month to month in the period, average daily waste removal rate for each month of the year in the period considered, average daily rate of common waste removal for each day of the week, evolution of the monthly average of the daily rate of removal of contaminated waste, evolution of the monthly average daily withdrawal rate of contaminated waste in the period and mean of the daily rate of removal of contaminated waste for each month of the year in the period considered. Finally, the conclusions of this article present the procedure to perform a weighing campaign, which should be carried out to determine the common and contaminated waste generation rates in each of the main services of the CAS.

Effects of Plasticizers,Antioxidants and Burning Rate Modifiers on Aging Performance of the HTPB/HMDI Composite Solid Propellant

The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.

Application of transient burning rate model of solid propellant in electrothermal-chemical launch simulation

A 30 mm electrothermal-chemical(ETC) gun experimental system is employed to research the burning rate characteristics of 4/7 high-nitrogen solid propellant. Enhanced gas generation rates(EGGR) of propellants during and after electrical discharges are verified in the experiments. A modified 0D internal ballistic model is established to simulate the ETC launch. According to the measured pressure and electrical parameters, a transient burning rate law including the influence of EGGR coefficient by electric power and pressure gradient(dp/dt) is added into the model. The EGGR coefficient of 4/7 high-nitrogen solid propellant is equal to 0.005 MW-1. Both simulated breech pressure and projectile muzzle velocity accord with the experimental results well. Compared with Woodley's modified burning rate law, the breech pressure curves acquired by the transient burning rate law are more consistent with test results. Based on the parameters calculated in the model, the relationship among propellant burning rate, pressure gradient(dp/dt) and electric power is analyzed. Depending on the transient burning rate law and experimental data, the burning of solid propellant under the condition of plasma is described more accurately.

脱萼剂对“浙梨6号”果实品质与着果率的影响

针对“浙梨6号”因部分萼片宿存或残存、果顶尖凸等而影响果实品相问题,选择PBO、氟硅唑、丙环唑3种脱萼剂,以清水为对照进行试验。结果表明:与对照相比,3种脱萼剂处理果实的脱萼率提高23.27~26.01百分点,果顶尖凸率降低24.55~26.44百分点,扁圆果占比、单果质量、可溶性固形物含量分别增加33.19~37.66百分点、37.9~57.1 g和0.68~0.94百分点,但果实偏斜度、全锈果率分别偏高0.54~0.74和18.36~19.23百分点,端正果率、着果率分别下降15.89~21.07和5.43~6.62百分点,差异达显著或极显著水平。上述3种脱萼剂分别选择4000、333.3、444.4 mg·L^(-1)和花序分离期进行喷施,在保证脱萼防凸效果的同时,可有效降低对着果率及果形端正度等的不利影响。

基于气-固两相流喷嘴实验的20G钢冲蚀机理研究

目的由天然气管道内壁减薄及穿孔导致的天然气泄漏事故频繁发生,输气管道面临着日益严重的冲蚀磨损问题。针对这一问题需要明确输气管道材料的冲蚀行为及机理,为抗冲蚀材料设计和延长管道使用寿命等工作的开展提供有效支撑。方法基于ASTM-G76测试标准,采取气-固喷嘴冲蚀试验研究方法,利用空气射流冲蚀实验机,开展不同冲击角度和冲击速度下天然气管道材料20G钢的气-固冲蚀实验;采用扫描电子显微镜、激光粒度分析仪等设备分析试样表面冲蚀形貌及特征;采用Ahlert冲蚀模型对实验数据进行拟合,建立20G钢的冲蚀率方程。结果当冲击速度(15~72 m/s)增大时,冲蚀率随之增大。当冲击角度(15°~90°)增加时,冲蚀率随之减小。冲蚀面积随着冲击角度的增加而减小。在低冲击角度下(15°、30°),固相颗粒的“犁削”为主要冲蚀及材料移除机制。在中等冲击角度下(45°、60°),冲蚀机制呈现混合形式,犁削、压实与开裂共同作用于材料表面。在高冲击角度下(75°、90°),以压实和开裂为主要冲蚀及材料移除机制。结论在气固两相流作用下,20G钢的冲蚀磨损过程符合典型的塑性材料冲蚀规律。颗粒冲击速度不会直接影响冲蚀机制,颗粒冲击能量的变化是影响冲蚀率的主要因素。建立了适用于天然气管道材料抗冲蚀性能对比和CFD冲蚀模型的冲蚀速率方程。

甲状腺良性结节单次微波消融治疗的短期疗效评价

目的评价甲状腺良性结节单次微波消融治疗的短期效果。方法选择2019年6月~2022年12月在西安交通大学第一附属医院耳鼻咽喉头颈外科诊治的甲状腺良性结节患者,采用微波消融治疗的连续病例,具有完善的随访数据者纳入分析。治疗后1个月复查甲状腺功能,治疗后3个月、6个月、1年复查超声和甲状腺功能,计算结节体积缩小率(volume reduction rate,VRR)。以1年内末次随访结果为结局变量,纳入性别、年龄、是否合并桥本甲状腺炎、结节纵径、结节实性体积等自变量,进行单因素和多因素分析。结果总计纳入151例患者,共计163个结节,围手术期并发症发生率为1.99%(3/151),治疗后6个月VRR为(79.58±17.70)%,6个月治疗成功率为93.43%(128/137),治疗后1年VRR为(81.24±24.29)%,1年治疗成功率为92.77%(77/83)。单因素及多因素分析显示,结节实性体积和年龄是影响消融后VRR的独立影响因素,年龄的回归系数为0.34,实性体积的回归系数为-0.47,P均<0.05,结节实性体积每增加1 cm3,1年内VRR(%)减少0.47。回归方程:1年内VRR=68.92+0.34×年龄-0.47×实性体积。消融治疗后6个月内血清FT4逐渐下降,促甲状腺激素(TSH)逐渐升高,差异有统计学意义(P<0.05),6个月后FT4逐渐恢复至正常水平,TSH亦逐渐恢复,但至治疗后1年时仍未达到术前水平;治疗后FT3逐渐减低,但各个时间点数值之间差异无统计学意义(P=0.40)。甲状腺结节消融治疗后,甲状腺功能指标平均值出现波动,但均在正常参考范围内。结论甲状腺良性结节微波消融治疗是一种安全有效的治疗方式,其总体治疗成功率可达90%以上。结节实性体积和年龄是影响甲状腺良性结节微波消融效果的独立影响因素。

新型MgH_(2)固态储氢装置放氢性能影响研究

为探究新型MgH_(2)固态储氢装置放氢性能的影响因素,设计构建了一种新型MgH_(2)固态储氢装置,数值研究了压力、换热流体入口温度、换热流体流速以及有无外环形换热流体层对放氢反应速率的影响。研究结果表明,当压力从0.4 MPa增加至0.6 MPa,放氢反应速率随之降低,但放氢反应完成时间几近一致;当换热流体入口温度从550 K提升至650 K,放氢反应速率迅速上升。与换热流体入口温度600 K相比,换热流体入口温度650 K下的放氢反应完成时间缩短50%;当换热流体流速从1 m/s增加至2 m/s时,放氢反应速率随之增大;增加外环形换热流体层可以大大缩短放氢反应所需时间。与未添加外环形流体层的换热装置的放氢反应时间相比,添加外环形流体层的装置的放氢反应时间可缩短31.25%。

冷却速率对Al-50%Si合金微观组织的影响

采用熔体水淬法(水冷法)、气雾化法和单辊熔融纺丝技术(甩带法)制备不同冷却速率的快速凝固过共晶Al-50%Si合金,并通过扫描电子显微镜(scanning electron microscope,SEM)和X射线衍射仪(X-ray diffractometer,XRD)分析了快速凝固与常规凝固的差异,以及快速凝固Al-50%Si合金微观组织的演变。结果表明:在水冷的Al-50%Si合金组织中观察到了树枝状的Al相,较大的过冷度导致这种亚共晶组织的形成,此组织属于非稳定状态,且共晶Si完全细化至纤维状;随着冷却速率的增加,在甩带试样中Al相的树枝状组织消失;通过甩带以及气雾化制备的Al-50%Si合金中,初晶Si颗粒被明显细化,由常规凝固的200μm细化至20μm左右,使Si在Al基体中的固溶度增大,造成Al基体晶格发生畸变。

降速剂及其作用位点对三组元推进剂燃烧性能的影响规律研究

针对两种典型季铵盐和金刚烷衍生物降速剂,研究了其作用位点对推进剂点火燃烧性能的影响。基于两种不同结构的Al@AP和AP@Al复合颗粒,将降速剂分布在不同作用位置:即AP颗粒内部和表面。利用扫描电子显微镜(SEM-EDS)和计算机断层扫描(CT)等技术对所制备复合颗粒微观形貌和结构进行表征,研究了降速剂对推进剂爆热、点火延迟和燃烧性能的影响。惰性降速剂的加入会使得推进剂爆热值降低,但Al@AP复合颗粒的高反应活性能部分抵消这一现象。与机械混合方式相比,当降速剂作用于AP表面时能明显延缓推进剂点火过程,其中金刚烷衍生物能使推进剂点火延迟时间增加至420 ms,比基础配方增加了192%。在基体中直接加入降速剂可以有效降低推进剂燃速,但其降压强指数效果有限。铝基复合颗粒和降速剂的共同作用能显著降低推进剂的高压燃速和压强指数:当作用位置在AP内时,两种降速剂使推进剂1~20 MPa内压强指数从基础配方的0.45分别降低至0.20和0.33,同时可使10~20 MPa压强指数分别减小了48%和49%。

气藏型低密度陶粒支撑剂的制备与性能研究

在开采煤层气、页岩气等气藏资源过程中,陶粒支撑剂的产品性能尤为关键,合成密度小、强度高的支撑剂是实现气藏高产率的重要指标。本文在传统矾土系陶粒支撑剂的基础上,添加煤矸石(RCG)、羧甲基纤维素钠(CMC)和白云石(DOL)进行固相烧结,借助以上造孔剂多温区的热解作用以及高温液相快速填充机制改善支撑剂的基体孔隙分布特征,降低支撑剂的结构密度并提升基体强度。当掺入质量分数为15%RCG+1%CMC+1%DOL添加剂时,支撑剂表现出最佳的综合性能并满足气藏资源开采的参数要求。

纳米气泡的特性及其在有机固体废物厌氧消化中的应用

基于国内外研究现状,分析了纳米气泡(NBs)的基本性质和产生方式,以及改善厌氧消化性能的作用机理,综述了NBs在有机固体废物厌氧消化中的研究进展,以及在增强厌氧消化稳定性、加快水解速率、提高甲烷产量等3个方面的应用,提出了加强不同气体NBs理化性质研究、开发多种气源、提升检测能力、降低能耗和成本等后续研究展望。

降速剂及其作用位点对丁羟四组元推进剂燃烧性能的影响规律

为研究降速剂对丁羟四组元推进剂燃烧性能的影响规律,将典型季铵盐和金刚烷衍生物两种高效降速剂引入核壳结构铝基复合颗粒Al@HMX和AP@Al,使其分别作用于HMX颗粒内部和AP颗粒表面,制备了4种含降速剂的铝基复合颗粒(Al/A@HMX,Al/B@HMX,AP@Al/A和AP@Al/B);采用扫描电子显微镜对样品形貌进行了表征;采用高速红外相机拍摄推进剂燃烧过程的火焰红外照片,并对推进剂的爆热、密度、点火延迟时间和燃速进行了测试。结果表明,加入惰性降速剂会导致推进剂爆热降低,而Al@HMX复合颗粒能部分抵消这一现象,使推进剂爆热值增加了338 J/g;降速剂能够抑制AP和HMX的热分解过程,使达到AlO辐射峰值前维持低强度的“平台段”;而引入Al@HMX后,推进剂的点火延迟时间比基础配方减小49.4%;在10~20 MPa范围内两种降速剂均能有效降低推进剂燃速,在此基础上采用Al@HMX可使含季铵盐丁羟四组元推进剂20 MPa下的燃速降低7.1 mm/s(38.4%),压强指数降至0.25;当降速剂作用于AP表面时,含质量分数1%季铵盐的推进剂在20 MPa下燃速可降低5.0 mm/s(27.3%)。

等温处理对Mg-7Zn-x La镁合金半固态组织的影响

采用等温热处理法制备Mg-7Zn-xLa(x=0,0.1,0.3,0.5,wt.%)合金的半固态坯料。探索La元素及其含量对Mg-7Zn-xLa合金半固态组织的影响,分析La元素对固相颗粒粗化常数值的影响。结果表明:在相同的等温热处理工艺下,随La元素含量的增加,固相颗粒的平均尺寸和形状因子先减小后增加。当合金中La元素含量为0.3 wt.%时,对半固态组织的优化效果最佳。同时,添加La元素可以有效降低固相颗粒的粗化常数值,抑制固相颗粒的粗化。此外,通过分析二次凝固组织发现:随初生固相颗粒的部分熔化,液相中的Mg含量增加,导致次生α_(2)-Mg的数量和晶粒尺寸均明显增加。

基于超声的标准发动机动态燃速测试技术

以标准发动机的动态燃速测试技术为研究对象,应用超声测厚原理获取固定声速点火条件下的发动机动态燃速、压强数据;分析提出一种基于特征点的动态燃烧信号辨识方法,获取发动机点火过程中推进剂退移厚度与时间变化数据;通过试验的方法建立常温状态不同压强下的声速校准模型,结合测试过程压强数据计算得到发动机点火过程中超声的实时声速,代入前期在固定声速条件下获取的推进剂退移厚度与时间数据中,通过求导获取点火过程中发动机的实时燃速。计算结果表明:基于超声的动态燃速测试方法能够实现整机的动态燃速测试,具有较高的时间分辨精度,其中基于超声的动态燃速测试燃烧时间与传统压强-时间曲线计算得到的燃烧时间误差为0.235%。此外,对比发动机点火后压强-时间与动态燃速-时间曲线发现,发动机建压完成后的动态燃速与压强曲线变化趋势呈一定相似性。

超级铝热剂在固体推进剂中的应用研究进展

超级铝热剂具有高放热和高活性的特点,其反应速率和能量释放效率均显著高于传统铝热剂,应用于固体推进剂有望改善释能速率、效率、感度等指标,已成为固体推进剂的发展方向。总结了超级铝热剂的制备工艺、特点及其工业化应用潜力;论述了超级铝热剂在固体推进剂中的适用性;综述了超级铝热剂的微结构(燃料/氧化剂界面控制、核壳结构、多层膜结构)和组分(金属氧化物、氟材料、碳纳米材料)对固体推进剂燃烧性能和能量释放的影响。超级铝热剂的添加显著提高了热反应活性和放热量,增强了推进剂的点火及燃烧性能,同时存在工业生产成本高、工艺控制要求复杂、燃烧过程精密控制难度大等问题,展望了未来超级铝热剂在固体推进剂中应用的研究重点和发展方向。