新型喷雾造粒喷嘴内闪蒸过程数值模拟

根据戊烷闪蒸相变中的传质传热规律,改进了戊烷闪蒸过程的经验模型,并将其植入到CFD软件Fluent中,较为准确地预测闪蒸雾化的非平衡热力学过程。对新型喷雾造粒喷嘴内气液戊烷和沥青的三相闪蒸流动过程进行了数值模拟,结果显示:介质在新型旋流喷嘴内呈现分层流动,能够控制戊烷闪蒸速率,可以制备质量较好的沥青颗粒。     

加入环戊烷对超临界溶剂脱沥青加工加拿大油砂沥青的影响

在超临界溶剂脱沥青耦合脱油沥青喷雾造粒装置上,将加拿大油砂沥青分离为脱沥青油及脱油沥青,通过对比在正戊烷中加入体积分数10%环戊烷前后得到的脱沥青油及脱油沥青性质变化来考察环戊烷对溶剂脱沥青的影响。结果表明,加入环戊烷可以提高脱沥青油质量收率1%～4%,当收率为67%～71%时,2种溶剂得到的脱沥青油性质接近,但是脱油沥青软化点比加入环戊烷之前却可以提高3～13℃,从而能够生产出优异的沥青粉。     

重油的燃烧(四)

四、重油喷嘴实现重油燃烧过程的装置就是重油喷嘴和燃烧室,其中重油喷嘴通常起主导作用,所以必须重点研究重油喷嘴。根据重油燃烧过程的特点,对重油喷嘴的基本要求是:一定的燃烧能力;在一定的调节范围内能保证雾化质量;能造成一定的空气与油雾混合的良好条件,调节倍数要满足生产中油量波动的要求;保证燃烧稳定,或根据生产要求允许调整火焰长度;喷嘴的     

重油燃烧器Y型喷嘴气液两相流动与雾化特性模拟

为改善重油雾化质量,针对沥青站重油燃烧器Y型喷嘴,运用CFD (Computational Fluid Dynamics)方法研究了喷嘴结构参数(混合室长度、入口直径比、入口夹角)与雾化参数(重油流量、空气入口压力、重油温度)对喷嘴气液两相流动与雾化特性的影响。结果表明,结构参数与雾化参数直接影响喷嘴内油膜厚度与气液两相速度差;不同参数下,喷嘴气耗率与液滴索泰尔平均直径的变化规律相反;综合考虑两个雾化性能指标,混合室的适宜长度为15~20 mm,入口夹角的合理范围为60°~75°,入口最佳直径比为1.0~1.1;为保证重油获得较好的雾化效果,空气入口压力应大于0.5 MPa,这为优化Y型雾化喷嘴的结构与运行参数提供了参考。     

脱油沥青喷雾造粒过程影响因素分析

利用重油梯级分离耦合萃余残渣喷雾造粒的方法将脱油沥青制成沥青粉,为脱油沥青提供了良好的应用前景.在连续溶剂脱沥青装置上考察了影响脱油沥青造粒的主要因素,原料为加拿大油砂沥青、委内瑞拉常压及减压渣油、中东减压渣油,溶剂为正丁烷、正戊烷、正己烷及其混合溶剂,萃取塔底温度分别为130、146、160℃,而副溶剂温度为130℃...     

多喷嘴水煤浆气化装置真空闪蒸系统改造总结

陕西未来能源化工有限公司煤制油分公司气化装置(六开两备)采用多喷嘴水煤浆加压气化工艺,单套气化装置设计投煤量2 000 t/d。运行过程中,气化装置真空闪蒸系统真空度低,导致黑水温度过高等,给后续系统带来了严重的影响。结合真空闪蒸系统的工艺流程及其运行状况,分析认为真空闪蒸分离罐可操作液位的高低决定了真空闪蒸系统真空度的大小,需对真空闪蒸分离罐进行改造。据现场实际情况,通过对真空闪蒸分离罐实施改造,实现了真空闪蒸分离罐液位可操作调节范围的拓宽,提高了真空闪蒸系统的真空度,降低了黑水温度,保证了系统的安全、稳定、长周期运行,带来了良好的经济效益和社会效益。     

跨临界CO2快速膨胀过程中非平衡冷凝和闪蒸机理的数值研究

跨临界CO₂在高速膨胀时,压力和温度剧烈下降,会发生非平衡相变。其中在天然气超声速分离设备和超临界CO₂离心压缩机中CO₂会发生非平衡冷凝相变;在引射膨胀制冷系统中,跨临界CO₂在引射器主动喷嘴中发生非平衡闪蒸相变。为解决跨临界CO₂在膨胀过程中物性变化剧烈,非平衡相变模拟困难的问题,构建了新型非平衡相变CFD模型,以研究跨临界CO₂在超声速缩放喷嘴中的非平衡冷凝和非平衡闪蒸的相变过程和膨胀机理,模型耦合了温度驱动的蒸发-冷凝相变机制和压力驱动的空化-冷凝相变机制,并用文献中的试验结果验证了模型的准确性。研究结果表明,在冷凝相变过程中,由压力驱动的冷凝传质具有主要影响,压力驱动的冷凝传质主要存在于喷嘴喉部与内流区域,温度驱动的冷凝传质主要存在于喷嘴渐扩段壁面。冷凝传质速率随着进口压力的增加和进口温度的降低而增加,从而使冷凝的非平衡程度和喷嘴内的干度降低,喷嘴渐扩段内达到声速的位置也相应延后。在闪蒸相变过程中,由温度驱动的蒸发传质占据主导,蒸发相变主要发生在喷嘴喉部附近,空化相变主要发生在喷嘴渐扩段,两相CO₂在喷嘴的渐扩段达到声速。随着喷嘴进口压力的增加和进口温度的降低,闪蒸的非平衡程度增加,使喷嘴内的干度减小。本研究有助于厘清跨临界CO₂快速膨胀中的非平衡闪蒸和冷凝相变机理,并为跨临界CO₂膨胀设备的分析和优化设计提供参考。     

跨临界CO2快速膨胀过程中非平衡冷凝和闪蒸机理的数值研究

跨临界CO₂在高速膨胀时,压力和温度剧烈下降,会发生非平衡相变。其中在天然气超声速分离设备和超临界CO₂离心压缩机中CO₂会发生非平衡冷凝相变;在引射膨胀制冷系统中,跨临界CO₂在引射器主动喷嘴中发生非平衡闪蒸相变。为解决跨临界CO₂在膨胀过程中物性变化剧烈,非平衡相变模拟困难的问题,构建了新型非平衡相变CFD模型,以研究跨临界CO₂在超声速缩放喷嘴中的非平衡冷凝和非平衡闪蒸的相变过程和膨胀机理,模型耦合了温度驱动的蒸发-冷凝相变机制和压力驱动的空化-冷凝相变机制,并用文献中的试验结果验证了模型的准确性。研究结果表明,在冷凝相变过程中,由压力驱动的冷凝传质具有主要影响,压力驱动的冷凝传质主要存在于喷嘴喉部与内流区域,温度驱动的冷凝传质主要存在于喷嘴渐扩段壁面。冷凝传质速率随着进口压力的增加和进口温度的降低而增加,从而使冷凝的非平衡程度和喷嘴内的干度降低,喷嘴渐扩段内达到声速的位置也相应延后。在闪蒸相变过程中,由温度驱动的蒸发传质占据主导,蒸发相变主要发生在喷嘴喉部附近,空化相变主要发生在喷嘴渐扩段,两相CO₂在喷嘴的渐扩段达到声速。随着喷嘴进口压力的增加和进口温度的降低,闪蒸的非平衡程度增加,使喷嘴内的干度减小。本研究有助于厘清跨临界CO₂快速膨胀中的非平衡闪蒸和冷凝相变机理,并为跨临界CO₂膨胀设备的分析和优化设计提供参考。     

PGSS法用于脱油沥青颗粒的制备

在超临界溶剂脱沥青装置上,以辽河稠油减渣为原料,得到脱沥青油的同时,用PGSS法直接对脱油沥青进行造粒实验。在压力为5.0～7.0MPa、温度为150～165℃的范围内考察了操作参数、喷嘴结构、脱油沥青性质对所得沥青颗粒分布的影响。压力增加、温度减小,50～100目沥青颗粒的质量分数增大,50目、40目、30目沥青颗粒质量分数减小,其中50～100目沥青颗粒的质量分数大于66%。喷嘴长度由13mm增加到40mm、内径由2.0mm减小到1.0mm,50～100目沥青颗粒的质量分数增大,50目、40目、30目沥青颗粒质量分数减小。压力增加、温度减小,脱油沥青的软化点增大。沥青性质的变化导致了沥青颗粒分布的变化。扫描电镜分析结果表明,所得沥青颗粒为不规则的多孔性物质,沥青颗粒的范围主要在50～100目。     

近年我国精细化工用干燥设备的进展

新型旋转闪蒸干燥几高效喷雾干燥造粒塔是目前国内新开发的快速和节能型干燥设备，特别适应于精细化工产品的干燥。本文介绍了该设备在化工应用中的工艺流程。技术性能指标和应有和效果明显。     

A Photographic Study of Flash-Boiling Atomization

To gain an insight into the mechanisms of flash-boiling atomization, heated water was injected from a single-hole orifice into heated air (steady injections, liquid pressure 697 kPa, air pressure ambient, test temperatures from 300 to 426 K, orifice diameter 0.34 mm, length 1.37 mm). The breakup regime of interest in the study was that where the spray divergence starts at the nozzle exit. Short-duration backlit photographs and laser diffraction dropsize measurements showed that these flashing jets comprise an inner intact core which is surrounded by the diverging fine spray. These details about the spray structure are not visible in conventional photographs of flashing sprays that use scattered light illumination. The present results cast doubt on a previously proposed theory of flash-boiling atomization that attributes the divergence of the spray cone to the expansion processes that occur in an underex-panded compressible flow, since that theory implies that the liquid is already atomized upon leaving the nozzle. Instead, the photographs show that drops are expelled from the unbroken liquid jet starting at the nozzle exit (presumably by rapid vapor bubble growth within the jet). The core region remains intact for some distance downstream of the nozzle exit, and its breakup eventually produces relatively large drops. As the liquid temperature approaches boiling, the intact length and the core drop size decrease. Thus operation close to boiling is desirable for effective atomization. However, the nozzle mass flow rate decreases and practical difficulties are found (owing to “vapor-lock”) as the liquid is heated near boiling.     

Production of granola breakfast cereal by fluidised bed granulation

In the fluidised bed granulation process the effect of nozzle air pressure and binder spray rate on key aggregate quality attributes were studied. The experimental results show that a decrease in nozzle air pressure leads to larger mean granule size. The combination of lowest nozzle air pressure and lowest binder spray rate results in granules with the highest levels of hardness and crispness. The combination of low nozzle air pressure and low binder spray rate results in the least distribution span. Granola hardness was affected by nozzle air pressure. Nozzle air pressure and binder spray rate did not have significant effect on crispness.     

An experimental and numerical study on sprays injected from two-hole nozzles for DISI engines

The objective of this study is to investigate the mixture formation process of sprays injected from two-hole nozzles for direct-injection spark-ignition (DISI) engines. Spray characteristics were examined for vapor and liquid mass distributions, spray tip penetration and spray angle using the laser absorption-scattering (LAS) technique and the computational fluid dynamics (CFD) simulation. Other characteristics including: the vapor phase concentration distribution, droplet spatial distribution and pressure distribution were acquired from the CFD simulation results. Comparison of measured and calculated results showed that as the hole-axis-angle (HAA) of the two-hole nozzle decreased, the droplet coalescence increased and vapor mass decreased. The spray with the HAA of 10° had the longest spray tip penetration and the spray with the HAA of 15° had the shortest one. The two jets of the two-hole nozzle spray had a tendency of offsetting to the central region of the spray. From 10 to 15 MPa, the increase in the injection pressure increased the vaporization rate and the spray tip penetration rate very much, but no such tendency was found when the injection pressure increased from 15 to 20 MPa.     

超临界抗溶剂制粒装置的现状及其展望

超临界抗溶剂法是一种新型超细微粒制备技术,现已在许多领域得到广泛应用。本文简要陈述了超临界抗溶剂技术的基本原理、装置组成和操作方式,详细阐述了超临界抗溶剂装置喷嘴部件的演进,从该角度介绍了GAS制粒装置、ASES制粒装置、SEDS制粒装置和SAA制粒装置的发展和优化历程,并对超临界抗溶剂制粒装置的多功能化、喷嘴的进一步优化、结晶釜的可视化等提出展望。     

Hot melt granulation of coarse pharmaceutical powders in a spouted bed

The hot melt granulation of a coarse pharmaceutical powder in a top spray spouted bed is described. The substrate was lactose-polyvinylpyrrolidone particles containing or not acetaminophen as a drug model. Polyethylene glycol (MW, 4000) used as binder was atomized onto the bed by a two-fluid spray nozzle. The granulation experiments followed a 2³ factorial design with triplicates at the center point and were carried out by varying the spray nozzle vertical position, the atomizing air flow rate and the binder feed rate. Granules were evaluated by their pharmacotechnical properties like size distribution, bulk and tapped densities, Carr index, Hausner ratio and tableting characteristics. Analysis of variance showed that granule sizes were affected by the PEG feed rate and atomizing air pressure at the significance levels of 1.0 and 5.0%, respectively, but spray nozzle distance to the substrate bed was not significant. The spray conditions also affected granule flow and consolidation properties, measured by the Carr index and Hausner ratio. Measured densities, Carr indexes and Hausner ratios proved that granules flowability and consolidation properties are adequate for pharmaceutical processing and tableting. Tablets prepared with acetaminophen-containing granules showed good properties and adequate release profiles in in vitro dissolution tests. The results indicate the suitability of spouted beds for the hot melt granulation of pharmaceutical coarse powders.     

流化床喷雾造粒技术进展

本文介绍了流化床喷雾造粒技术,包括造粒机理、操作方式、影响因素等。流化床喷雾造粒是将溶液、悬浮液或熔融液喷雾到已经干燥或不完全干燥颗粒的流化床床层内,在同一设备内一步完成蒸发、结晶、干燥或化学反应的造粒过程。流化床造粒操作对颗粒的尺寸、形状要求不高,所得到的产品无结块、具有良好的流动性能。与其他传统的造粒方法相比,流化床造粒具有工艺流程简单、设备装置紧凑、投资省、生产强度大等优点,越来越引起人们的关注。     

Fortschritte in der Zerstäubungstrocknungs-Technologie

Progress in the technology of spray drying . Stringent quality demands on spray-dried goods have led to increasing use of nozzle spray dryers. In contrast to disk spray dryers, nozzle dryers yield microgranules and low-dust products directly. Although the process of nozzle spray drying is over 50 years old, the volume of available calculation material necessary for general application is sparse and limited mainly to special products or problems. This article presents new advances in the technology of nozzle spray dryers. An analytical formulation of the drying of a drop within the first drying phase decisive for granulation constitutes the basis of the general applicability of the fresh insights gained.     

R134a闪蒸喷雾过程中喷管内流动形态对喷雾特性的影响

闪蒸喷雾过程中喷管内流动状态对喷雾形态及雾化效果具有重要的影响。为了观察喷管内流动状态及其对应的喷雾形态,使用高速相机对不同喷射压力条件下制冷剂R134a在石英玻璃直喷管中的流动状态及喷雾形态进行可视化研究,同时分析不同喷射压力条件下喷雾半径的动态变化情况。研究发现,喷管内的气化可以促进喷管出口处喷雾半径的迅速扩大,但同时限制了喷雾半径在喷雾过程中的进一步发展。喷管内流动状态在一定喷射压力下具有极强的不稳定性,在喷管内形成均匀的泡状流有利于形成均匀、稳定的喷雾形态。