加压喷动床中细颗粒喷动特性

在内径分别为 186mm和 80mm的加压喷动床中 ,以空气为喷动介质 ,在 10 1～ 70 0kPa的压力范围内考察了几种不同粒度的细颗粒在加压下的喷动特性 .研究结果表明在不同的Re_t 内压力对最小喷动速度的影响不同 .实验还发现 ,随着压力的升高 ,喷动区直径增大 ,稳定操作区域增大 ,加压可明显改善喷动床的操作稳定性     

喷动床研究与进展

叙述了近年来出现的几种改型喷动床，包括多喷头喷动床、喷动流化床、带导向管的喷动床、性粒子旋转射流式喷动床、射流喷动床的研究与进展。它们在传统柱锥形喷动床的基础上，通过增加喷口、导向管、流化气、惰性粒子或增加喷动气速等方法，来克服原有喷动床应用的局限性，拓展其应用领域。     

新颖环形喷动床颗粒喷动特性实验研究

一种新颖的环形喷动床由内外两个不同内径、同心的垂立圆筒组成,在环形空间底部设置多个喷口,在喷口两侧布置倾斜的导流板.研究颗粒在这种喷动床内的流动特性,探讨喷口结构、颗粒种类以及床内载料量对环形喷动床颗粒喷动特性的影响.实验结果表明:颗粒在环形喷动床内分为三个明显不同的区域,即颗粒填充移动区、密相喷动流化区以及稀相夹带区.当颗粒出现分区喷动后,随床内载料量的增多,填充移动区的高度维持不变,始终等于导流板的高度,而密相喷动区的高度不断增加.风量和颗粒种类对床层最大喷动量、密相喷动高度以及床层压力分布规律有着十分重要的影响.采用不同的喷口结构时,在相同的载料量下,直向喷口的密相喷动区高度更大,而且床内各测点的平均压力大于采用斜向喷口时的相应测点压力.     

大尺寸喷动床最低喷动速度的估算

最低喷动速度是喷动床设计的重要参数之一。过去人们习惯采用Mathur-Gisher公式来计算,但由于该公式是建立在小直径床层(D_c=0.076～0.3m)实验的基础上的,故在大直径床层上应用时,产生明显的偏差。本文通过实际数据分析,提出了大直径喷动床层最低喷动速度计算的经验公式。     

不同条件下水泥生料柱锥型喷动床压降的冷模试验

本文研究了密相条件下水泥生料柱锥型喷动床内的压降.探讨了不同喂料量、入口风速和锥体角度对喷动床压降的影响.结果表明,压降随喂料量的增加而增大;随风速的增加先增大后减小;锥体角度对压降变化有很大影响.     

应用生料催化剂技术煅烧水泥熟料

前言 应用高效复合生料催化剂技术，可提高水泥熟料强度、产量，降低烧成煤耗。为了改善生料易烧性，更快地完成水泥熟料矿物的形成过程，提高水泥熟料质量，降低熟料烧成热耗，借鉴其他水泥企业一些生产经验，结合我厂现有生产条件，在生料中掺加催化剂进行煅烧熟料。高效复合生料催化剂，     

喷动床干燥工艺综述

喷动床干燥是对传统流化床干燥的革新和改造 ,它不仅能顺利地干燥谷物等颗粒粗大的物料 ,而且适用于热敏性物料的干燥 ,同时还可以进行多项化工单元操作。与国外发展成熟的喷动床技术相比 ,国内这方面的进展则显得较为缓慢。因此 ,本文从喷动床的起步、特点、结构、流化形式及喷动机制等方面入手 ,对其进行了较为系统的介绍 ,并给出了部分参数的计算公式及热质传递方程。     

高铝水泥生料球失水试验与生产

０引言我厂高铝水泥１号窑原规格为Φ３．３m／２．５m×７８m,热端扩大,成球盘的湿料球直接入窑,预烧能力差。在２００１年５月份采用国外先进技术———微晶种预成球窑外加热技术进行了工艺改造,窑型改为Φ３．３m／２．５m／３．３m×５７m,窑尾增加固定床料球预热器,实施微晶种成球、失水烘干贮存、料球预热等一系列工艺措施,料球预热能力得到显著增加,熟料质量上了一个新台阶。在该生产线中设计的一条湿料球烘干系统,将成球盘新成的湿料球烘去表面水分,避免在以后的流程中发生堵料粘结,同时提高料球强度,使料球在输送和预…     

Study of Flow Characteristics of Ultrafine CaCO3 Powders in a Spouted Bed

The flow behavior of gas and ultrafine powder in a spouted bed was numerically investigated by using a two‐fluid model coupled with a population balance equation (PBE). The aggregation process is controlled by the PBE, which is solved by the direct quadrature method of moments. The agglomerate diameter is calculated according to the change in particle number. The solid pressure and viscosity were modified for agglomerates on the basis of the kinetic theory of granular flow. Distributions of diameter, solids volume fraction, and velocity are obtained by the new model. The influence of cohesive intensity and gas velocity on the diameter distribution were analyzed. The spout diameter, a vital parameter for the design of spouted beds, was calculated and a calculation formula is proposed.     

A Draft-Tube Conical Spouted Bed for Drying Fine Particles

A study has been conducted on the performance of a draft tube conical spouted bed for drying fine particles. Batch operation has been performed with nonporous, porous, and open-sided draft tubes in order to ascertain the optimum configuration of this internal device. The nonporous draft tube requires the lowest minimum spouting velocity. Nevertheless, the solid circulation rate and the drying efficiency of the open-sided draft tube are superior to any other spouted bed configuration. Moreover, it allows for reducing the height of the fountain and, consequently, the height of the drying equipment.     

A Draft-Tube Conical Spouted Bed for Drying Fine Particles

A study has been conducted on the performance of a draft tube conical spouted bed for drying fine particles. Batch operation has been performed with nonporous, porous, and open-sided draft tubes in order to ascertain the optimum configuration of this internal device. The nonporous draft tube requires the lowest minimum spouting velocity. Nevertheless, the solid circulation rate and the drying efficiency of the open-sided draft tube are superior to any other spouted bed configuration. Moreover, it allows for reducing the height of the fountain and, consequently, the height of the drying equipment.     

Drying Process on Inert Particles in Mechanically Spouted Bed Dryer

ABSTRACT

Suspensions, slurries and paste-like materials can be dried in the Mechanically Spouted Bed ( MSB) dryer with men packing. The circulation of the men particles characteristic of classical spouted beds is provided with a houseless conveyor screw mounted in the vertical axis of the bed. Radioactive isotopic tracer technique was used for measurement of the cycle time distribution ( CTD) of the spherical inert particles as a function of the operational parameters of drying. The variances ( σ²) of the CTDs and the particle velocity m the various zones of the MSB dryer were calculated. The circulation of the mert particles can be characterised by nearly plug flow. According to the physical model of drying on inert packing the heat and mass transfer coefficients were calculated. Que to the relativeiy uniform film-like, wet coating formed on the surface of the spheical inert particles, the drying process may be characterised with the constant rate of drying. A method has been elaborated for calculation of drying time, hereby the partial processes of drying on inert particles can be synchronised.     

Diffusion-Controlled Batch Drying of Particles in a Novel Rotating Jet Annular Spouted Bed

Results are presented for batch drying of rewetted wheat (used as model particles) in a newly developed annular spouted bed in which the drying air jet rotates slowly thus spouting bed intermittently. For particles drying in the falling rate period intermittent spouting is shown to result in significant energy savings with small increase in the drying time. A finite element simulation is employed to evaluate the effective moisture diffusivity of the test material which is nonspherical in geometry. Further, advantages of variable spouting and heating of the spouting air are demonstrated by a parametric study of the simulation model.