HYDRAULIC TRANSPORT OF COAL IN PIPES WITH DRAG REDUCING ADDITIVES†

The aim of the investigations was to determine the drag reduction produced by polymer additives in the hydraulic transport of coal. As no systematic results were available in the literature, experiments were undertaken using a wide range of flow velocities and polymer concentrations (up to 440 ppm) to obtain a clear picture about the processes involved. Special attention was paid to the effects of polymer degradation. The experiments were carried out on two different facilities for hydraulic transport with pipe diameters of 40 and 250 mm

Two criteria were used for selecting the polymer with the most favourable properties. It was to produce the largest possible amount of drag reduction and have the greatest stability against degradation. Six different types of polymers were investigated. Experiments were undertaken to establish the dependence of drag reduction on the polymer concentration for the polymer showing the best results according to the above-mentioned criteria. It was found that the drag reduction on coal-watei mixtures containing polymer was less than in “pure” polymer solutions (not containing any solid particles). Furthermore, for both coal-water mixtures and “pure” polymer solutions there was always found to be a polymer concentration at which drag reduction reached a maximum and this concentration was higher for the coal-water mixtures. The value of drag reduction increased as the flow velocity was increased. In the polymer degradation experiments the decrease in drag reduction as a consequence of polymer degradation was stronger when the polymer concentration was lower for both the coal-water mixtures and the “pure” polymer solutions. Experiments of longer duration showed that even after several hours of transport in the facility, there was still considerable drag reduction. Finally, it was found that for coal-water mixtures polymer degradation was greater at higher flow velocities.     

流动单元分析法在低渗透油藏压裂中的应用

水力压裂是开发低渗透油藏的有效增产措施。桩74块低渗透，平面上相带和物性变化大，为了提高压裂效果和裂缝数值模拟的精确度，优选出合理的裂缝参数，压裂时需要充分考虑其非均质性。本文针对桩74块的特点，应用流动单元分析法，将储层分为四类流动单元，结合数值模拟方法，优选裂缝参数，现场取得了较好的开发效果，对于改善低渗透油田的开发效果，有着十分重要的意义。     

由中间相炭微球制备高密度各向同性炭

以中间相炭微球（ＭＣＭＢ）为原料,在常温下压制成型。所用ＭＣＭＢ由不同一次吡啶不溶物含量的煤焦油在不同条件下聚合反通过热过滤及吡啶抽提分离而得。考察了不同原料、成型压力、热处理温度及升温速率对炭制品的密度及收缩率的影响。１０００℃下炭化后炭制品的表观密度最高达１．７５ｇ／ｃｍ＾３。     

APPLICATION OF THE DISCRETE ELEMENT MODELLING IN AIR DRYING OF PARTICULATE SOLIDS

The Discrete Element Method (DEM) has been widely used as a mathematical tool for the study of flow characteristics involving particulate solids. One distinct advantage of this fast developing technique is the ability to compute trajectories of discrete particles. This provides the opportunity to evaluate the interactions between particle, fluid and boundary at the microscopic level using local gas parameters and properties, which is difficult to achieve using a continuum model. To date, most of these applications focus on the flow behaviour. This paper provides an overview of the application of DEM in gas-solids flow systems and discusses further development of this technique in the application of drying particulate solids. A number of sub-models, including momentum, energy and mass transfer, have been evaluated to describe the various transport phenomena. A numerical model has been developed to calculate the heat transfer in a gas-solids pneumatic transport line. This implementation has shown advantages of this method over conventional continuum approaches. Future application of this technique in drying technology is possible but experimental validation is crucial.     

浅谈全液压式注塑机液压系统功率损耗

液压传动具有结构紧凑、布局灵活、动作响应快、自润滑性好、易于实现过载保护等特点,因而在各类机器上得到广泛使用。全液压式注塑机采用液压传动来完成各种成型射出动作,实现注塑成型。本文简要探讨全液压式注塑机液压系统的功率损失及其相应的改善方法。     

水平气固两相高浓度输送流动机理

本文通过水平气固两相分层流动模型，分析了高浓度、高混合比、连续低速气力输送流动机理研究表明，稳定分层流动输送时，悬浮颗粒易集中于滑动床表面；层问颗粒剪切力是滑动床移动的上要驱动力；滑动床高度大于管道半径时将出现不稳定输送     

水力排烟机水轮叶片芯金属模的逆求工程设计

本文介绍了逆求工程技术在水力排烟水轮叶片芯金属模具设计中的具体应用，以及逆向工程的概念和集成系统组成。     

DRYING OF PARTICULATE SOLIDS: DETERMINATION OF THE CHARACTERISTIC CURVE OF BROWN COAL.

Variation on the rate of drying of brown coal powder as a function of environmental and intrinsic properties has been studied in a gravimetric laboratory-scale drier.

Raw data have been treated to correlate the constant rate of drying and the equilibrium moisture content as a function of flow rate and temperature of the gas phase, particle size and surface additives. The characteristic drying curve occurs when the reduced rate of drying is plotted as a function of a dimensionless moisture potetial.     

DRYING OF PARTICULATE SOLIDS: DETERMINATION OF THE CHARACTERISTIC CURVE OF BROWN COAL.

ABSTRACT

Variation on the rate of drying of brown coal powder as a function of environmental and intrinsic properties has been studied in a gravimetric laboratory-scale drier.

Raw data have been treated to correlate the constant rate of drying and the equilibrium moisture content as a function of flow rate and temperature of the gas phase, particle size and surface additives. The characteristic drying curve occurs when the reduced rate of drying is plotted as a function of a dimensionless moisture potetial.     

搅拌釜内液固悬浮体系的浓度分布

在120°锥底、内径为φ700mm、φ250mm 的有机玻璃釜中,采用直接取样称重法研究了液固系搅拌釜内桨的结构、桨的位置及转速、固含量、物系性质等因素对釜内固相浓度分布的影响,同时用两区沉降扩散模型对实验数据进行分析,得到了固相悬浮质量与操作条件的关系,并提出了均匀悬浮的判据,为放大设计搅拌反应器提供了可行的理论依据。     

散体颗粒架拱研究现状

把在立管中形成的拱分成气泡拱和颗粒拱两类，重点讨论了影响颗粒拱形成的因素，如散体的流动函数、气压及立管流动因子等，指出各种理论模型的优劣，对今后工作提出了建议．     

磷光颗粒示踪技术在循环流态化中的应用

<正> 1 引言 固体颗粒的停留时间分布(Residence Time Distribution简称RTD)在循环流态化研究中十分重要,它对于了解其两相流动特性、反应器的模拟计算和工程设计是必不可少的,对于流态化干燥过程及传热行为的研究也很重要。流化床中RTD的研究已有大量文献报道,发展了诸如染色颗粒、盐颗粒、磁性颗粒、放射性颗粒及热(冷)颗粒等众多的示踪方法,但是由于固体颗粒示踪本身存在着示踪剂的注入、在线检测、残留及示踪颗粒与床体物料一致性、示踪过程对床内流场的干扰等一系列技术上的困难,不但使实验操作繁琐,而且实验结果的可靠性、重复性均不理想,特别是在颗粒运动速度较快的循环流化床中,其颗粒示踪的难度更大。为了解决上述难题,本文参考了Jin Yong等和Yu Zhiqing及M.Kwauk在常规流化床中曾采用的磷光示踪方法,在循环流化床条件下进行了新的探索。     

单层砂滤料截污分布与反冲洗效果研究

原水浊度50～100度,采用单层石英砂滤料直接过滤,在过滤周期内测得表层200～250mm厚滤层中水头损失增大值占总增大值的92.5%,表明绝大部分悬浮颗粒均被截留在表层滤料中。最佳冲洗条件为:先用空气在12L/m·2s冲洗强度下对表层滤料搅拌擦洗15s,再用水在15L/m2·s的冲洗强度下冲洗2min,可以取得较好的冲洗效果。     

THE ROLE OF TEMPERATURE AND LENGTH SCALES ON THE SORPTION OF GASES IN MICROPOROUS SOLIDS

This paper presents an analysis of the effect of the temperature and length scales (size of microsphere and particle) on the controlling mechanism of adsorption uptake into a bimodal microporous sorbent. Their effect on the time scale of adsorption is also discussed in this paper. Systems of zeolite, activated carbon and molecular sieving carbon are analyzed to illustrate the applicability of the theory.     

HYBRID NEURAL APPROACHES FOR MODELLING DRYING PROCESSES FOR PARTICULATE SOLIDS

ABSTRACT

This work presents methods for synthesizing drying process models for particulate solids that combine prior knowledge with artificial neural networks. The inclusion of prior knowledge is investigated by developing two applications with the data from two indirect rotary steam dryers. The first application consisted in the modelling of the drying process of soya meal in a batch indirect rotary dryer, The external and internal mass transfer resistances were associated in the hidden layer of the network to linear and sigmoidal nodes, respectively. The second application consisted in the modelling of the drying process of soya meal in a continuos indirect rotary dryer. The model was constructed using the Semi-parametric Design Approach. The model predicts the evolution of solid moisture content and temperature as a function of the solid position in the dryer. The results show that the hybrid model performs better than the pure “ black box” neural network and default models. They also shows that prior knowledge enhances the extrapolation capabilities of a neural network model,     

CLOUD HEIGHT IN SOLIDS SUSPENSION AGITATION

The focus of this work is the experimental determination of cloud height (the height to which solids are suspendedrpar; in an agitated slurry as a function of the agitation intensity, solid physical properties, impeller type (pitched-blade or high efficiency), and system geometry. Cloud height is not strongly dependent on impeller type or solid physical properties, except for extremely rapidly-settling particles. However, it is dependent on the impeller diameter to tank diameter ratio (D/T), impeller off-botiom clearance to tank diameter ratio (C/T), and solids loading. The use of multiple impellers allows solids to be suspended to higher levels in tall batches. An intermediate impeller separation leads to optimal performance in terms of the power requirement to achieve a desired cloud height. Lower impeller separations do not yield significant performance improvements over a single impeller, while higher impeller separations lead to poor performance caused by “zoning” between the impellers.     

CHARACTERIZATION OF SELECTED SPECIATED ORGANIC COMPOUNDS ASSOCIATED WITH PARTICULATE MATTER IN AMBIENT AIR OF THE OUTSKIRTS OF ROME

The organic fraction of airborne particulate matter includes a wide variety of organic compounds, but the present research focus is on Polycyclic Aromatic Hydrocarbons (PAHs) and their nitrated derivatives (nitro-PAHs) because of the well-known health risk associated with these organics. In order to identify and assess the sources of hydrocarbon inputs into the environment n-alkanes content and the relative carbon preference index were utilized.

Special consideration was given to nitro-PAHs. The aim of this work was to demonstrate the presence in atmosphere of nitro-PAHs not usually studied, which may be responsible for part of the high direct-acting mutagenic activity of unknown origin observed for the airborne particulate material.

Of the 38 particulate-associated nitro-PAH compounds measured, 21 were described for the first time and 17 were detected in real samples, although those 21 nitro-PAHs were reported as positional isomers of corresponding PAHs, with the position of the NO₂ group not determined.     

上行气固两相流充分发展段的颗粒浓度

在Ф100mm× 16m循环床提升管实验装置上测试了134组操作条件下提升管 12个截面位置的平均颗粒浓度 ,其中 113组操作条件下提升管中的气固两相流展现出明确的充分发展段 .结果表明 ,充分发展段的颗粒浓度εs 随颗粒循环量G_s 的增加而增大且具有显著的线性关系 ,ε_s 随表观气速U_g 的增加以幂函数关系减小 .所提出的实验关联式不仅较好地拟合了本文所获得的充分发展段的平均颗粒浓度数据 ,而且诠释了以往有关提升管稀相段出口颗粒浓度预测结果之间的差异 ,更明确地反映了充分发展段颗粒浓度与操作参数之间的定量关系     

TRANSPORT OF PENETRANTS IN THE MACROMOLECULAR STRUCTURE OF COALS II. EFFECT OF POROUS STRUCTURE ON PYRIDINE TRANSPORT MECHANISMS

Pyridine transport in 600-850μm coal particles occurs by a non-Fickian mechanism which shows coupling of both diffusion and relaxation phenomena. In lignites (with carbon content less than 75%) the phenomenological pyridine transport mechanism is predominantly Fickian, whereas in bituminous coals (above 75% carbon) it approaches Case-II transport. However, when the porous structure of the coals is taken in consideration the true pyridine transport mechanism is Case-II transport.