硝基胍连续喷雾干燥数值模拟研究

在对喷雾干燥塔内流动特点认识的基础上,采用较为成熟的计算流体力学（CFD）模型及算法,建立适用于硝基胍物料喷雾干燥的应用模型。利用Gambit软件对几何模型进行网格划分,导入Fluent中进行数值计算,预测塔内流场分布情况、液滴含水率及颗粒平均粒径等。通过测试样机干燥产品的含水率、产品粒度分布及场内温度分布等发现,预测结果与实验结果大致吻合,说明模拟结果有一定的准确度和可靠性。     

黑索今粉料连续计量加料技术研究

黑索今（RDX）具有危险性大、流散性差的特性,因而在连续计量加料过程中会出现安全隐患以及计量不准确。为解决这些问题,设计了一种防静电电子皮带秤装置,并通过RDX粉体安息角测定,设计了合理的料仓。文章详细阐述了该装置的结构及工作原理,并对RDX粉料进行了多次计量试验。结果表明：该自动计量加料装置对RDX粉料的输送均匀稳定,料仓内不会出现”架桥断料”现象,安全性能好,且计量误差小于1．0％,能满足RDX粉料连续精确计量加料的需要。     

改性双基推进剂制备中硝化甘油的连续加料与计量技术

为了实现改性双基推进剂制备过程中硝化甘油的安全输送和精确计量,利用乳化喷射器、直管质量流量计及数据处理器(PLC)对硝化甘油(NG)与水的混合液进行了连续加料与计量试验研究。利用Fluent模拟软件对NG的乳化喷液过程进行模拟分析,得到最佳的乳化喷射器结构参数为:喉管直径14.33 mm,喉管长度60.03mm,喉嘴距12.00 mm;在此结构参数下进行模拟分析得到:乳化喷射器出口处NG最大体积分数小于30%,且所占节点比率小于0.05,说明NG与水混合均匀,确保了NG安全连续输送。研究了质量流量计在不同管道压力下对计量精度的影响,当管道压力为0.25~0.31 MPa时,能满足质量流量计的检测要求,计量误差≤1.0%,能满足改性双基推进剂连续制备的工艺要求。     

硝基胍发射药制备工艺过程中的流变本构方程研究

以硝基胍发射药实际生产加工过程中不同时段的药料为研究对象,采用自主研发的固体推进剂专业双料筒毛细管流变仪测试药料的流变特性,并对流变特性曲线进行拟合,获得硝基胍发射药的流变本构方程。结果表明：硝基胍发射药具有典型的假塑性流体特征;延长捏合时间有利于高分子链充分溶胀;剪切应力-剪切速率曲线采用自构函数y=Aln²x+Bln x+C时的拟合效果较好;剪切黏度-剪切速率曲线采用Williamson流变本构方程时的拟合效果好。     

硝基胍真空结晶工艺技术研究

针对军用棒状硝基胍现有喷雾结晶制造工艺存在的平均粒度粗、粒度分布较宽、晶型规整性不好的状况,以及针状晶型不适合在发射药中应用的技术问题,对硝基胍结晶特性、晶型转变原理、结晶工艺条件进行了分析研究,提出了采用真空结晶代替喷雾结晶制取粉状硝基胍的工艺技术途径。结果表明:采用合适的抑制剂聚乙烯醇、分散剂十二烷基苯磺酸钠,同时控制硝基胍溶液浓度,可以促进结晶向棒状形貌有效转化;采用抑制剂质量分数0.05%~0.08%、分散剂质量分数0.1%、结晶真空度0.096 MPa、结晶温度33℃、直喷闪蒸结晶法等工艺条件,可制备平均粒度3.3μm以下的棒状硝基胍晶体。     

改性硝基胍装药快烤响应特性研究

为了研究改性后的硝基胍装药在生产、储存、运输和使用过程中因意外爆燃而产生的响应特性,采用温度采集仪记录了火灾刺激条件下硝基胍的火球温度变化规律,通过压力测试系统测量了反应过程的冲击波压力,使用热辐射测试系统测量了爆炸火球的热通量,通过Baker公式计算了火球的理论热通量。结果表明:第1发快烤点火后108 s样品发生反应,最高温度为894.3 ℃;第2发快烤点火后142 s样品发生反应,最高温度为960.7 ℃;两发快烤反应持续时间均约为2 s,响应等级均为爆燃。分析快烤响应过程中的冲击波、破片、热辐射毁伤效应发现,热辐射是硝基胍遭受火灾刺激的主要毁伤形式。对比两发快烤及不同距离处的热通量发现,测量值与理论值的规律一致。     

硝基胍发射药管状尺寸对燃烧行为的影响

为了更为全面的了解单孔发射药的燃烧行为,应用硝基胍单孔发射药进行了中止燃烧实验(半密闭爆发器实验)和密闭爆发器实验,中止燃烧结果显示8 cm长的单孔药有明显侵蚀燃烧现象,密闭爆发器结果显示有侵蚀燃烧的药粒会在燃速系数u_1-Ψ曲线上对应出现一个侵蚀峰。实验结果的综合对比分析结论表明:药粒端面的占比对发射药的渐增性燃烧影响较大;分析密闭爆发器实验的u_1-Ψ曲线可以获知,当药粒达到8 cm长时侵蚀峰可达1个u_1单位的量。     

硝基胍发射药管状尺寸对燃烧行为的影响

为了更为全面的了解单孔发射药的燃烧行为,应用硝基胍单孔发射药进行了中止燃烧实验(半密闭爆发器实验)和密闭爆发器实验,中止燃烧结果显示8 cm长的单孔药有明显侵蚀燃烧现象,密闭爆发器结果显示有侵蚀燃烧的药粒会在燃速系数u_1-Ψ曲线上对应出现一个侵蚀峰。实验结果的综合对比分析结论表明:药粒端面的占比对发射药的渐增性燃烧影响较大;分析密闭爆发器实验的u_1-Ψ曲线可以获知,当药粒达到8 cm长时侵蚀峰可达1个u_1单位的量。     

硝化棉在线连续计量技术研究

根据硝化棉浆料特性,利用微波浓度仪和电磁流量计分别对输送过程的硝化棉(NC)浆料质量分数和流量进行测量。文中详细分析了微波浓度仪和电磁流量计工作原理。设计了硝化棉干量连续测量系统(PLC),PLC将来自微波浓度仪的质量分数信号和电磁流量计的流量信号进行处理,得到输送管道中NC浆料瞬时干量和一定时间内的累计干量。试验结果表明:硝化棉干量在线连续测量误差小于1.2%,能满足火药制造工艺连续化、自动化的需要。     

硝基胍纯度标准物质的定值和不确定度评定

采用杂质扣除法对硝基胍标准物质的纯度进行定值,并用化学分析法对定值结果进行验证.对定值过程中各杂质分量的A、B类不确定度进行了评定,计算了定值结果的合成不确定度和扩展不确定度.NQ标准物质的纯度值为99.51％,U=0.03％(k=2).     

Prediction of Powder Stickiness along Spray Drying Process in Relation to Agglomeration

The spray drying process consists of a fast convective drying of liquid droplets by hot air. Initially, the water activity (a_w) of a drop is close to 1. During drying, the drop surface a_w decreases while viscosity increases until reaching a sticky rubbery state before further drying. This can be observed for products such as carbohydrates, leading to particles sticking on walls (product losses) or to adhesion between particles leading to agglomeration. In this study, particle stickiness was investigated in a cocurrent pilot spray dryer by measuring drying air properties (temperature and relative humidity) at different positions. This allowed describing the evolution of temperature and mean water content of the drying drops. Two model products (maltodextrin DE12 and DE21) were spray dried varying process parameters liquid flow rate (1.8, 3.6, and 5.4 kg/h), air temperature (144°, 174°, and 200°C), airflow rate (80–110 kg/h), and rotary atomizer speed (22,500–30,000 rpm). The two products exhibit different drying behaviors in relation to their affinity towards water (sorption isotherms) and glass transition temperature evolution with a_w (stickiness). Depending on drying conditions and product, the drop stickiness was observed very rapidly, close to the atomizer, or later, along the chamber. This approach can be used to identify conditions and positions corresponding to sticky particles.     

喷雾干燥技术在制备超微及纳米粉体中的应用及展望

阐述了喷雾干燥技术的基本原理、工艺设备及特点,从理论上分析了影响喷雾干燥粉体粒度分布及形态的几个因素,探讨了该技术的应用现状,并展望了今后的研究工作.     

气流式喷雾干燥过程的计算流体力学模拟

基于计算流体力学技术和气-固两相流理论,对气流式喷雾干燥过程进行非稳态数值模拟,得到干燥塔内热空气的温度、速度场分布云图,以及颗粒的运动轨迹、停留时间和粒径分布。结果表明,改变热风温度、适当延长干燥时间都可使料液干燥完全,有助于提高粉体的干燥效率,改善产品质量。     

利用离心喷雾干燥制备球形粉体的工艺因素研究

研究了铝矾土料浆的离心喷雾造粒过程,考察了料浆固含量、粘度、喷雾头的旋转速度对粉体干燥的影响.从颗粒内部水分迁移的距离、空气进出口温度两方面,分析了蘑菇头颗粒、变形颗粒、球形颗粒和破裂颗粒等颗粒形貌的形成原因,并优化了一组工艺参数:喷雾头转速为12000r/min,料浆固含量为50%,热风入口温度为300℃,废气出口温度为115℃,塔内负压为-350Pa,料浆流速为4L/h,料浆的粘度为14s,在此条件下能制备出球形度高、颗粒粒径集中分布在55μm左右的粉体.     

Spray Drying of Aqueous Solutions of Inorganic and Organic Materials

Since the characteristics of the solution and the hot drying air have major influence on the physical, structural, and granulometric properties of the powders obtained by spray drying, it is very important to properly select the process conditions which will result with the formation of a powder of desired properties. For that reason, the influence of process conditions on the properties of the powders produced by spray drying has been investigated on a laboratory scale. The aqueous solutions of two organic (glycine and pentaerythritol) and three inorganic (sodium chloride, potassium chloride and potassium sulfate) materials have been chosen. During very fast spray drying it is impossible to distinguish individual steps of simultaneous processes (crystallization and drying). Knowledge of solubility data and crystallization kinetics of selected materials may help to explain what happens during spray drying.

The experiments have been performed at different drying air temperature, flow rate of the solution and of the spraying air. The obtained powders are mostly crystalline and agglomerated. Investigated process conditions influence the polymorphic composition of glycine obtained by spray drying. In order to have real information about the granulometric composition of powders it is necessary to perform microscopic analysis of the obtained crystals.     

喷雾干燥可控制备生物玻璃微球及其体外生物活性研究

CaO-SiO₂-P₂O₅体系生物玻璃(Bioglass,BG)微球具有良好的生物活性和骨传导性,在骨组织修复领域得到广泛研究与应用。传统熔融法制备BG粉体的能耗大、粉体形貌不可控、生物活性相对较低;溶胶–凝胶法制备BG粉体则需大量溶剂、制备周期长、不易量产。为快速、规模化制备形貌、粒径、化学组成可控的BG微球,本研究以水溶液为溶剂,以正硅酸四乙酯、磷酸三乙酯、四水硝酸钙为原料,采用喷雾干燥前驱体溶液方法制备BG微球,探讨喷雾干燥过程中进气风量、前驱体溶液浓度和进料速率等工艺参数对BG微球粒径的影响;前驱体溶液化学组成对BG微球的体外诱导磷灰石沉积能力的影响。结果表明,BG微球的粒径范围在40μm以下可控,且粒径随前驱体溶液浓度增大而增大,随进气风量增大而减小,进料速率则对微球粒径影响较小。不同化学组成的BG微球都具有良好的体外诱导磷灰石沉积能力,而且随CaO含量的增加而提高。     

Preparation and Optimization of Dry PLGA Nanoparticles by Spray Drying Technique

The aim of this article was to evaluate the potential of poly lactide-coglycolide (PLGA) nanoparticles (NPs) as carriers for controlling release of doxorubicin (DOX) via a spray drying technique. The challenge was to entrap a hydrophilic molecule into a lipophilic core molecule of PLGA. To achieve this objective, we modified conventional approach of drug loading to spray drying technique. The eight formulations of nanoparticles were prepared by modified double emulsion and solvent evaporation technique followed by spray drying using 2³ factorial designs. PLGA (A) and PVA (B) and stirring speed (C) were used as independent variables where particle size (Y₁), entrapment efficiency (Y₂) and percentage of drug release at the 32 hour (Y₃) were taken as dependant variables. The results showed that the method is easy and efficient for the entrapment of the drug as well as the formation of spherical nanoparticles. This modification improved DOX entrapment efficiency relative to controls real loadings up to 40%. The in vitro release studies indicated the DOX loaded PLGA nanoparticles provide controlled drug release over a period of 32 h. Hence, this investigation demonstrated the potential of the experimental design in understanding the effect of the formulation variables on the quality of DOX-PLGA nanoparticles.     

The Improvement of Ibuprofen Dissolution Rate Through Microparticles Spray Drying Processed in an Aqueous System

A study to enhance the dissolution rate of ibuprofen, a poorly water-soluble drug, was carried out through combining specific formulations and processes with the addition of a hydrophilic carrier for the preparation of microparticles. Microparticle production was performed by spray drying ibuprofen microsuspensions formulated in an aqueous system with the addition of ethanol containing Aerosil 200® and Tween 80®. We were able to consistently produce microparticles as much as 40% of the dry weight of the input microsuspension. Spray-dried microparticles were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, laser diffractometer mastersizer, and infrared spectroscopy. No modification to the crystalinity and chemical structure of ibuprofen was observed. Dissolution of ibuprofen microparticles reached 100% in 3 minutes compared with less than 10% for unmodified ibuprofen. We concluded that both by the modification of formulation and the spray drying process it is possible to increase the dissolution rate of the tested model drug.     

Properties of Nanostructured Hydroxyapatite Prepared by a Spray Drying Technique

In previous studies nano sized hydroxyapatite (HA) particles were prepared by solgel or precipitation methods, in which the products were washed by aqueous or non-aqueous liquids to remove impurities or undesired components. The washing is know to modify the surfaces of the cystalline particles. This study evaluated properties of nano HA materials prepared by a spray drying method in which the HA product was not exposed to any liquid after its formation. The spray drying apparatus consisted of a nozzle that sprayed an acidic calcium phosphate solution in the form of a fine mist into a stream of filtered air flowing through a heated glass column. The water and volatile acid were evaporated by the time the mist reached the end of the column, and the fine particles were collected by an electrostatic precipitator. Powder x ray diffraction patterns suggested the material was amorphous, exhibiting a single broad peak at 30.5° 2θ. However, high resolution transmission electron microscopic analysis showed that the particles, some of which were 5 nm in size, exhibited well ordered HA lattice fringes. Small area diffraction patterns were indicative of HA. Fourier transfer infrared spectroscopy showed patterns of typical of HA with small amounts of HPO₄²⁻. The thermodynamic solubility product of the nano HA was 3.3 × 10⁻⁹⁴ compared to 1 × 10⁻¹¹⁷ for macro scale crystalline HA. These results showed that a spray drying technique can be used to prepare nanometer sized crystalline HA that have significantly different physicochemical properties than those of its bulk-scale counterpart.