Resuspension of wall deposits in spray dryers

Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.     

Dynamic modeling of micro- and nano-sized particles impinging on the substrate during suspension plasma spraying

Suspension plasma spraying (SPS) can be utilized to manufacture finely structured coatings. In this process, liquid suspended with micro- or nano-sized solid particles is injected into a plasma jet. It involves droplet injection, solvent evaporation, and discharge, acceleration, heating, and melting of the solid particles. The high-speed and high-temperature particles finally impact on the substrate wall, to form a thin layer coating. In this study, a comprehensive numerical model was developed to simulate the dynamic behaviors of the suspension droplets and the solid particles, as well as the interactions between them and the plasma gas. The plasma gas was treated as compressible, multi-component, turbulent jet flow, using Navier-Stokes equations solved by the Eulerian method. The droplets and solid particles were treated as discrete Lagrangian entities, being tracked through the spray process. The drag force, Saffman lift force, and Brownian force were taken into account for the aerodynamic drag force, aerodynamic lift force, and random fluctuation force imposed on the particles. Spatial distributions of the micro- and nano-sized particles are given in this paper and their motion histories were observed. The key parameters of spray distribution, including particle size and axial spray distance, were also analyzed. The critical size of particle that follows well with the plasma jet was deduced for the specified operating conditions. Results show that in the downstream, the substrate influences the flow field structure and the particle characteristics. The appropriate spray distances were obtained for different micro- and nano-sized particles.     

Study on Predrying by Spin Flash Dryer for Granulation

Spin flash dryer has the advantages of both fluidized bed dryer and pneumatic dryer. It has predominance in dealing with thermal sensitive materials. In this paper, the distribution of the air velocity in the spin flash dryer is discussed,which indicates that the rotating air in the dryer chamber can be divided into two areas,potential flow area and plane swirl area. Experiments show that air tangent velocity effects the process of granulation most remarkably. The radial distribution and moisture content of the particles have their intrinsic rules along either the diameter or height of the drying chamber. Besides, the operating parameters of predrying on bleaching powder are optimized. To meet the strict standard of the wet-pressing granulator on the moisture content of the feeder,a narrow lap is made at proper height in the wall of the drying chamber,where a chute and a rotating valve are installed in order to predry the filter cake and remove a part of water. Then the material is fed into the wet-pressing granulator.     

Quasi 1D modeling of two-phase flow and deposit formation for urea-selective catalytic reduction systems

A quasi 1D model of two-phase flow for a urea-selective catalytic reduction (SCR) system is developed which can calculate not only the generation of reducing agent but also the formation of deposits in the exhaust pipe. The gas phase flow is solved through Euler method, variables are stored on staggered grids, and the semi-implicit method for pressure-linked equation (SIMPLE) algorithm is applied to decouple the pressure and velocity. The liquid phase is treated in a Lagrangian way, which solves the equations of droplet motion, evaporation, thermolysis, and spray wall interaction. A combination of a direct decomposition model and a kinetic model is implemented to describe the different decomposition behaviors of urea in the droplet phase and wall film, respectively. A new 1D wall film model is proposed, and the equations of wall film motion, evaporation, thermolysis, and species transport are solved. The position, weight, and components of deposits can be simulated following implementation of the semi-detailed kinetic model. The simulation results show that a decrease in the exhaust temperature will increase the wall film region and the weight of deposits. Deposit components are highly dependent on temperature. The urea-water-solution (UWS) injection rate can affect the total mass of wall film and expand the film region, but it has little influence on deposit components. An increase in exhaust mass flow can decrease the total weight of deposits on the pipe wall because of the promotion of the mass and heat transfer process both in the droplets and wall film.     

Prediction of wall deposition behaviour in a pilot-scale spray dryer using deposition correlations for pipe flows

INTRODUCTION Abbott (1990) reported that wall deposition inspray dryers may pose a potential fire risk and com-promise hygiene requirements, and reduce productquality and yield. Spray dryer hazards include igni-tion of explosible dust clouds, dust deposits, bulkpowder deposits and flammable vapour. Kieviet(1997) noted that wall deposition affected the resi-dence time distribution of particles, and particularlythat an important factor in determining residencetimes with high wall deposition…     

蒸压加气混凝土用抹面砂浆的研制及应用

采用干排粉煤灰、水泥、矿粉、干砂及复合外加剂，经配比、粉磨和搅拌混合等工艺，研制出蒸压粉煤灰加气砼(以下简称加气砼)专用抹面砂浆，其物理力学性能及施工性能满足加气砼墙体粉刷要求，并能实现干作业，综合效益与社会效益好，是解决目前加气砼墙体空鼓，开裂等质量通病的创新产品。     

循环式谷物烘干机的设计研究

本文论述了5HG-3型循环式谷物烘干机烘干工艺、工作原理及主要结构，分析计算了干燥仓内物料、热量和干燥介质消耗量的内在关系，试验研究了处理量、初始水份对烘后物料品质的影响。     

鄂西北地区疑似楚长城遗址考辩

楚长城是楚国兴建的大型军事防御工事。它以山、城、寨、堡、塞为墙,以长江、汉水为池,以河南省西部的鲁阳关为＂城轴＂,向东西两部展开,遍及河南、湖北、陕西、四川、重庆、安徽等6省10个县、市。鄂西北地区存在的近500处疑似楚长城遗址,到底是不是楚长城？从＂楚长城＂的发现及疑似楚长城遗址的争议、从鄂西北及相邻地区历史上发生的战事史实而论、方城方城山长城与楚长城之间的关联与区别、鄂西北地区疑似楚长城遗址不是楚长城的考古结论等四个方面,对鄂西北地区的长城文化资源进行考证,可以认为,鄂西北地区历史上可能出现过楚长城,但现在发现的疑似楚长城遗址是清代建造之防堵白莲教军的军事设施。     

基于EM78P419N单片机的消毒干手机的设计

为了改善传统烘干机烘手时间长、易交叉感染、可靠性低等问题,进行了消毒干手机的设计.该设计利用红外技术检测信号,将光信号转换成电信号送入EM78P419N单片机处理,相继启动消毒和烘干模块.整个过程完全自动控制,避免交叉感染,手伸即喷,手离即停.产品具有成本低、体积小、可靠性高、干手时间短等优点,在各类人员聚集或流动的场所具有推广价值.     

明长城的“师范”和“蓝本”——台州府城墙的特色与价值研究

台州府城墙兼具军事防御和防洪双重功能。早在宋仁宗庆历六年（1046）为增加牢固程度,将城墙两侧全面用砖石包砌。戚继光在台州抗倭时创建了空心敌台。担任蓟镇总兵时,以北调的戚家军为骨干,参考台州府城墙的形制和结构,大规模修建长城城墙敌台。因而台州府城墙被誉为明长城的“师范”和“蓝本”。     

体验旅游视阈下南京明外郭景观设计研究

以仙鹤门一麒麟门段为例,从体验旅游角度对南京明外郭的景观进行设计,提出应凸显明外郭本体,将南京明外郭优美的环境和丰富的历史文化知识作为重要体验元素,打造明文化体验主题,建设文化休闲廊道,使游客获得快乐和难忘的体验,从而提高旅游质量和明外郭的知名度、文化性与教育意义。     

柏林墙遗址

哨岗前是分隔东，西柏林的“柏林墙”遗址。柏林墙的正式名称为反法西斯防卫墙，全长超过155公里，高4米，其间设置瞭望塔，铁丝网，哨岗，武装警卫，车辆壕沟等警戒措施。该墙于1989年11月9日被拆毁，今天，在柏林仍保留着哨岗和一小段围墙遗址。作为纪念二战后冷战结束的历史见证。     

今西安城是“明城”还是“唐城”

今西安城是在唐皇城基础上筑建而成,但与唐皇城并不完全重合：西、南两个方向是利用原唐皇城城墙旧基,而东、北两个方向却分别向外拓展。其“拓城”工程实施于何时,说法不一。《明太祖实录》栽有明初耿炳文、濮英等“拓城”之事,现今多据此认为今城定型于明初,是为“明城”。而清嘉庆《成宁县志》据五代后周显德二年《永兴军牒》等文献记载,认为西安城自唐末天祜年间韩建筑“新城”时即“已越皇城而东,与今城无异”,即今城定型于唐末,是为“唐城”。本文对此两种说法及其依据作了较为深入的辨析。     

Experimental study on spray cooling performance of pressure atomizing nozzle

Aiming at the problem of air-cooled condenser output limit,a spray humidification system was presented to reduce the inlet air temperature.The pressure atomizing nozzle TF8 was chosen for inlet air spr...     

荷电水雾脱硫实验研究

提出塔内荷电水雾脱硫塔外固硫的新型湿法脱硫工艺,重点对荷电水雾的脱硫特性进行了研究,结果表明,增加荷电电压与液／气比均有利于增加脱硫效率,但仅采用水雾作为吸收剂,总的吸收效率相对较低;液／气比低时增加荷电电压对脱硫效率的影响并不明显,随着液／气比增加,荷电电压对脱硫效率的影响有所增强;水雾荷电后能够提高SO2溶解速率,提高SO2吸收率,有利于降低湿法脱硫初期投资及运行成本．     

地理区域视角下山西长城板块旅游产品的开发

从全国的长城分布来看,山西拥有从战国到明清各个历史时期的遗址,属于长城资源较多的省份之一,以山地、贫困地区为主要分布区。从山西境内长城分布的地理区域和旅游资源等因素入手,充分挖掘长城的边塞文化、军事遗存、农牧发展和贸易往来等历史元素,凝练爱国主义、民族融合主题,通过长城板块旅游产品体系的构建打造,推动长城沿线经济、社会、文化、生态全方位发展,力争使山西成为世界级文化遗产旅游地。     

“墙”文化之中西比较

“墙”作为一种文化象征蕴含着丰富的信息和深刻的传统文化思想。随着时代的发展,人们对跨文化交际的需求越来越迫切,而文化之墙阻碍了我国和世界的交流与合作。探讨“墙”在中西方传统文化中的角色以及“墙”语言折射出的中西文化和人们的思想特征,进而说明拆除文化之墙的必要性和重要性。     

氯化胆碱的微胶囊化

应用微胶囊技术进行了包埋氯化胆碱的研究。用多种水溶性物质做壁材 ,用喷雾干燥法进行包埋 ;通过测定包埋率 ,对壁材和芯材的配方数据进行筛选 ,得出了最佳壁材、芯材配方 ;同时 ,作了机理分析     

室温固相反应合成纳米材料碱式碳酸铝钠

用无水Na2CO3与加有表面活性剂的AlCl3.6H2O室温下进行固相反应,合成得到碱式碳酸铝钠纳米材料和可溶性无机盐,用水洗去可溶性盐,烘干,即得到碱式碳酸铝钠纳米晶体。用均匀试验设计方法安排试验方案,用多元逐步回归法建立数学模型,并用网格优化法确定了最佳的试验条件。产物最终经XRD表征,证实为纳米尺寸晶体。     

Multidimensional modeling of Dimethyl Ether （DME） spray combustion in DI diesel engine

INTRODUCTION The use of dimethyl ether (DME) as an alterna-tive fuel appears to be a promising approach for si-multaneously minimizing NOx and soot emissionfrom conventional diesel engines. The lowself-ignition temperature of 508 K and the high oxy-gen content of 34.8 percent (mass fraction) are twomajor factors characterizing low soot and unburnedtotal hydrocarbon (THC) emissions. Since the firstintroduction of the concept by Sorenson and Mik-kelsen (19…