高海拔对水泥生产过程影响的理论探讨(下)

(续上期) 9 气力提升机和气力输送 9.1 气力提升 新型干法生产普遍用立式气力提升泵向预热器或均化库供料,这种泵的结构和工作原理,是借助它底部喷嘴射出的高速气流,在与其上方一定距离的中心管口间造成一个负压区,把泵底的物料吹吸进中心管,达到向上输送的目的(图5);泵底的透气层由同一气源充入一定量空气,使物料流态化,加上泵体内料柱的重力作用,造成物料流源源不断进入输送区,实现连续送料.     

内旁通密相气力输送系统的技术特点

内旁通密相气力系统是20世纪80年代后期在国外发展起来的一种先进的气力输送技术。它从输送机理上有别于常规的正压气力输送系统,改悬浮输送为静压输送,从而改变了常规正压气力输送低密底、高气流、易磨损、易堵管的工况,是解决输送高磨损、大出力、密相输送磨损大的粉状物料的理想方案。该系统通过管道的自调节内旁通管实现稳态输送,并防止了堵管的发生。     

抛秧水稻田病虫草害的防治

水稻抛秧是近年来发展较快的稻作轻型栽培技术 ,多年实践充分显示了抛秧稻省工省力、高产高效的优势 ,故得已普遍推广。但抛秧稻田病虫草害发生复杂 ,较常规稻田更重 ,因此必须加强防治 ,并应以防为主。1　纹枯病水稻抛栽田间密度大 ,通气透光差 ,中下部湿度偏高 ,纹枯病发生偏重 ;进入分蘖盛期阶段 ,抛秧稻病情发展快 ,若遇连续阴雨 ,病势发展更快。据历年调查 ,所有水稻抛栽田均有不同程度的纹枯病发生 ,与相同品种对比 ,抛栽田纹枯病发病丛数比常规栽培田高 2 0 % ,发病株数多 5%以上。在分蘖末期病蔸率 1 0 %～ 1 5% ,即晒田前和复水后 …     

水稻田化学除草——移栽水稻杂草防治问题浅谈

正我国水稻从北自黑龙江省(北方为寒作水稻,一年一季,是我国主要高品质粳稻产区)南到海南省均有种植,栽培方式也多种多样,如人工插秧、机插秧、抛秧、水直播和旱直播等。东北的水稻多为机插秧和部分人工插秧,直播面积相对较小,在长江中下游或以南多为机插秧、抛秧、直播等方式为主,近年因直播水稻栽培便捷还有发展增多的趋势。水稻的品种也复杂,北方为粳稻区、     

立式管壳式换热器封头内部气相数值模拟研究

基于FLUENT软件,采用RNGk-ε湍流模型对立式管壳式换热器进气封头内部含二氧化碳浓度为42％的窑气流场进行数值模拟.结果表明:封头内部压力较大区域的平均值约为0.347MPa;压力较小区域的平均值约为0.31 MPa;分布于径向半径240 mm至400 mm的环形区域内的换热管入进气口下端形成了一定强度的涡流,且涡流的轴向范围在100 mm以内;气流轴向速度最大与最小的换热管分别位于径向半径为100 mm和300 mm左右的区域内,这两个区域的气流轴向速度差随着轴向距离的增大而增大.     

多孔陶瓷

一、绪言多孔陶瓷是具有气孔数目很多的陶瓷制品。一般陶瓷制品的气孔,有与外部完全不相连通的所谓封闭气孔,及与外部相连通的开口气孔。多孔陶瓷中的气孔,主要是开口气孔。当气流从这些气孔中通过时,在开口气孔的外表面或内部产生各种     

离心气力分级机的流场分析和性能研究

利用流体力学的能量方程,分析了分级机内的速度和压力分布.运用气流中颗粒分级原理.研制成功了一种干法气力分级机.并且通过实验,研究了不同操作参数对分级机分级性能的影响.     

复挡除沫器的流场测定——第一报

本文作者用五孔球头探针测定了圆形切向进口的复挡除沫器的气流流场,初步掌握了复挡除沫器内部的气流流动规律,并建立了该设备的分离效率计算式。这为进一步改进复挡除沫器的结构尺寸,提高其分离效率提供了理论依据。     

气流导向作用对中间相焦有序生长的影响研究

以催化裂化油浆为原料,采用带程序升温控制多管井式坩埚炉和单管井式坩埚炉,及带有气流导向结构的反应器制备了高度有序中间相焦.重点考察了两种反应器结构对中间相有序生长的影响,依此探索气流导向作用对中间相焦有序生长的影响和中间相有序结构在高温处理过程中的发展变化.结果表明,原料在带有气流导向装置反应器中进行热聚合反应的过程中,在上升气流的引导作用下中间相微球之间实现有序融并、逐步发展为区域结构,由此可制备得到有序性发展良好的中间相焦.合理的煅烧温度制度可以使中间相焦有序结构与性能进一步完善和提高.     

气力输送机在化盐工段的应用

氯碱厂化盐工序的上盐方法,各厂因地制宜采用型式各不相同。我厂过去采用人工铲,小车推的办法,用劳动力多,劳动强度大。自1974年5月改用气力输送机上盐(亦称为真空吸盐)后,四年来运转可靠,维修量很小,管理简单,操作方便,是可以在中小型氯碱厂推广应用的一种上盐方式。本文试就真空吸盐设计、安装等问题介绍如下。一、概述使粉粒状物料悬浮在气流中进行输送的装置,通常称为气力输送装置。而输料管道的压力低于大气压的又称为真空气力输送机。真空式系统的构成,一般由供料装置,输料管,分离器,抽气机四个部分,     

气流干燥过程的数学模拟

针对颗粒和空气在干燥管内的相互作用和传质传热机理,首先建立了直管式气流干燥数学模型,然后通过分析脉冲式气流干燥器的结构特点,求出了管径变化的微分方程,将其和直管式气流干燥的五个常微分方程耦合在一起,构成了脉冲式气流干燥的传质传热数学模型。根据模型方程的特点,运用四阶龙格-库塔法对其进行了数值求解。通过实验结果验证,该模型正确可靠。     

Influence des agrégats sur le rendement d'un réacteur à transport pneumatique

The evaluation of the performance of a pneumatic transport reactor operating at low gas velocity and high solid volumic concentration is presented. This reactor has a high length-diameter ratio and can be considered as a representative tube of a multitubular reactor with gas—solid suspension circulating inside the tubes. Two experimental techniques have been used: ozone adsorption or catalytic ozone decomposition on a porous solid. The agregation of the particles, which has an important effect on the hydrodynamics, does not contribute to the diffusional resistance. The design of an industrial reactor should be accordingly relatively simple.     

除草剂对不同栽培方式水稻药害的评价

选取酰胺类、磺酰脲类、硫代氨基甲酸酯类、杂环类、脲类、苯氧羧酸类等常用化学除草剂,以超常规剂量用移液和喷雾两种方式对抛栽和直播籼、粳稻进行药剂试验。研究结果明确了各种除草剂对水稻的药害症状;籼粳稻对各药剂的敏感差异;以及清水冲洗、搁田、施肥等措施对某些除草剂品种造成的水稻药害的缓解作用。     

Optimization of the Heat Transfer Rate and Pressure Drop of Inside Profiled Tubes – Part 1

Nine inside profiled tubes were developed and investigated for optimization of the heat transfer rate and pressure drop behavior. The results of this work are presented in two parts. This part describes the comparative investigation of five tubes with different inside profiles to simulate the heat transfer and friction loss of fired tubular heaters in petrochemical processes. In part 2, a further four tubes with different inside profiles will be compared. To test the efficiency of the new profiles a test rig was modified. Using the similarity laws by Reynolds, the Reynolds number calculated for the gas flow in the heater tubes was converted into the flow rate, as well as the pressure and temperature of a distilled water system. Axial and peripheral velocities were measured using a Laser‐Doppler‐Velocimeter (LDV). Friction pressure drop and heat transfer were measured to determine the efficiency of each tested tube under the constant conditions of the distilled water system. The results of the investigations on these five inside profiles showed that profiles with eight flat and symmetrically distributed straight fins (tube III) or with a twist angle of 30° to the tube axis (tube IV), produced heat transfer rates higher that that of the bare tube by 120 % and 156 %, respectively, with increases in pressure drop only 46 % and 76 %, respectively.     

高灰氧化煤的浮选试验研究

针对高灰氧化煤存在的细粒级含量大、灰分高、难浮选等问题,研究了浮选机、浮选柱对高灰氧化煤浮选效果的影响,考察了脂肪醇(乙醇和丁醇)对氧化煤的去氧化作用。浮选机试验表明:经促进剂处理后,煤样浮选效果明显改善,与空白试验相比,丁醇处理后煤样的可燃体回收率提高了12.99%,精煤灰分降低了16.63%;丁醇改善氧化煤浮选效果的能力要强于乙醇,可燃体回收率提高了1.30%～11.43%,精煤灰分降低了0.21%～1.46%。浮选柱试验表明:丁醇对高灰氧化煤的浮选柱分选效果较乙醇好,在循环泵压力为0.16 MPa时,煤泥浮选效果最好,可燃体回收率为38.55%,精煤灰分为19.49%,比相同药剂条件下浮选机试验的可燃体回收率提高了6.26%,精煤灰分降低了3.32%。因此,经脂肪醇预处理后,煤泥浮选效果明显提高,且浮选柱的分选效果要好于浮选机。     

SW4S－5S高速卷绕机油雾润滑气动控制系统分析

介绍了ＳＷ４Ｓ－５Ｓ高速卷绕机油雾润滑气动控制系统以及主要气动元件的工作原理。该系统通过两个程序控制器能自动、定时、定量地对高速卷绕机、辅助槽棍、摩擦辊等轴承进行油雾润滑。     

SW4S－5S高速卷绕机油雾润滑气动控制系统分析

介绍了ＳＷ４Ｓ－５Ｓ高速卷绕机油雾润滑气动控制系统以及主要气动元件的工作原理。该系统通过两个程序控制器能自动、定时、定量地对高速卷绕机、辅助槽棍、摩擦辊等轴承进行油雾润滑。     

Convective Drying Kinetics and Darkening of Okara

Okara pellets were dried in a pneumatic tube from 78% of moisture content (w.b.) to 64% and then in a rotational drum to 3%. Time, temperature, and drum rotation were correlated to the okara darkening. The temperatures used were 130, 150, and 170°C in the pneumatic tube and 50, 60, and 70°C in the rotational dryer. The rotations used for the drum were 27 and 47 rpm. When okara was dried only in the pneumatic tube it became dark; however, when dried in both the tube and the dryer the darkening level decreased significantly. The results showed that the first drying level temperature does not influence the drying time of the combined process.     

炭黑密相气力输送的节能试验

密相气力输送系统的输送效率是人们关注的焦点,从工程意义来讲,降低其输送能耗具有相当大的空间和重要的意义。以炭黑为输送物料进行了密相气力输送节能试验,对比了可控旁通管和双辅管输送系统的耗气量;验证了可调式LAVAL管的节能效果及其对降低粒子破碎率的作用。     

Experimental research of flow patterns and pressure signals in horizontal dense phase pneumatic conveying of pulverized coal

Understanding flow patterns and their variability is important for optimal design and trouble free dense phase pneumatic conveying of pulverized coal in a horizontal tube. Employing the electrical capacitance tomography (ECT), six flow patterns were identified and utilized for quantitative analysis based on the value and distribution of cross-sectional solid concentration. The dense-phase flow patterns in the horizontal tube of the pneumatic conveying system were somehow variable even when the operating conditions were unchanged. The probability calculation results suggest changing multiple flow patterns with one or two dominant flow for each of the seven sets of experimental conveying conditions and that a finite change in the dominant flow pattern would occur with an increasing superficial gas velocity. The power spectral density (PSD) function and the Hurst exponent of the pressure signals of the pulverized coal were well correlated with its flow patterns in a horizontal tube. The PSD functions and probability density functions (PDFs) of the void fraction signals from ECT are found to be related with flow patterns and can be used to quantitatively identify flow regimes. The ECT data may therefore be utilized for monitoring the flow patterns in a horizontal tube employed for pneumatic conveying of pulverized coal.