我国高岭土精选新工艺述评

本文重点从下列几个方面介绍和分析了我国高岭土精选加工工艺的最新进展：（1）景德镇陶瓷原料──高岭土和瓷石──精选试验线（500t／a）工艺流程的研究；（2）福建龙岩某矿可生产多种不同档次高岭土产品的复合工艺流程；（3）高岭土干法加工过程中粉体密相脉冲输送的基本原理和基本流程；（4）由美国设计的湛江年产13万t高岭土项目精选工艺的基本特点和先进装备。     

Studies on gas–solid heat transfer during pneumatic conveying

Interactions between solids and gas during pneumatic conveying can be utilized for variety of applications including flash drying, solids preheating etc. Experiments on air–solid heat transfer were carried out in a vertical pneumatic conveying heat exchanger of 54 mm inside diameter, using gypsum as the solid material. The effect of solids feed rate (0.6–9.9 g/s), air velocity (4.21–6.47 m/s) and particle size (231–722.5 μm) on air–solid heat transfer rate, heat transfer area and air–solid heat transfer coefficient has been studied. Empirical correlations have been proposed for the prediction of Nusselt number based on the present experimental data. The proposed correlations predict Nusselt number within an error of ±15% for the present data.     

循环流化床煤燃烧/热解多联供工艺中循环灰的密相气力输送

为考察循环流化床煤燃烧/热解多联供工艺中循环热灰的密相输送特性,在实验室建立的密相气力输送装置上分别考察了发料罐内的压力、总松动气量以及特殊位置处的松动气量等对输送固气比的影响。结果表明,在发料罐内压力一定的情况下．固气比随着总松动气量的增加而增大；发料罐内压力的增加也有利于固气比的增大；在发料罐内的压力及总松动气量一定的情况下,随着特殊位置1处松动气量的增加,固气比也随之增大。该密相气力输送方式基本可以满足CFB煤燃烧/热解多联供工艺的要求。     

煤粉加压密相输送实验研究

该文建立了一个接收端压力为3MPa，输送压差可达1MPa的高压密相气力输送实验系统，在其上用氮气进行了干煤粉加压密相输送实验，研究了该系统作为干煤粉加压气化炉供煤装置的工作特性，包括输送稳定性、以及输送压差与煤粉输送速率和输送管中煤粉浓度的关系等。研究结果表明，该干煤粉加压密相输送系统工作稳定，实现了高浓度低速连续的密相输送。在3MPa下，输送煤粉的固气比达到586kg／m^3（气）、输送速率通量达到3775．6kg／（m^2．s），输送气体速率范围为4．2m／s-6．9m／s，达到了干煤粉加压气化炉的工艺要求。分析表明，在高压、高浓度密相输送情况下，输送管中的煤粉浓度是影响输送管道压降的主要因素。     

Analysis of Gas-Solids Feeding and Slug Formation in Low-Velocity Pneumatic Conveying

Gas and solids feeding is a key operation in pneumatic conveying of particulate materials. This article presents an analysis of the interfacing effects between a nozzle gas supplier, a rotary valve solids feeder with dropout box, and the pipeline of a pneumatic conveying test rig for low-velocity dense-phase flow. Experiments were carried out to examine the flow pattern of slugs in different combinations of gas flow conditions and solids loading ratios. The effect of gas and solids feeding on the formation of slugs is analyzed by using both experimental data and computer-modeled results. Solids accumulation and sliding motion at the bottom of the dropout box and near the entrance of the downstream pipe, which happen prior to the bulk motion in the form of a slug, are found important in determining the size of a slug. Gas retention and pressure buildup characteristics in the feed section are also found crucial in influencing the flow patterns of slugs.     

Pressure drop prediction for horizontal dense-phase pneumatic conveying of pulverized coal associated with feeding to gasifier

Based on extensive bench-scale data derived from the horizontal dense-phase pneumatic conveying of pulverized coal, a correlation of solids friction factor λ_z was proposed in an effort to establish a model to predict the pressure drop when coal fed to the gasifier. Further, it was also an attempt to modify some public models to verify their availabilities. Then, based on the data collected from an industrial-scale horizontal pipeline under the high pressure up to 2.0 MPa, the proposed model was found to be possibly among the best ones for predicting the pressure drops of the dense flow of pulverized coal. The modified Mallick and Wypych model can also provide satisfying predictions. The results suggest that the two models are both suitable for scale-up of dense-phase pneumatic conveying of pulverized coal at high pressures.     

小麦制粉行业脉冲气刀式气力输送系统的设备、工艺和调试

本文主要对脉冲气刀式气力输送系统的部件选用,工艺设计及安装调试的注意事项作简单介绍。     

FACTORAL DESIGN FOR COLUMN FLOTATION OF PHOSPHATE WASTES

ABSTRACT

The results of column flotation of fine particles of phosphate are presented in this paper. A factorial design was used to study effects and their interactions of the main parameters affecting column efficiency. Three-phase experiments were performed using a mixture of fatty acid and fuel oil as a collector for phosphate while pine oil was used as a frother, The results of 3-phase experiments were correlated to bubble diameter and air holdup. The results showed that factorial design of column flotation experiments and their analysis gave an insight on the effect of column parameters on grade and recovery of concentrates. From a feed sample containing about 7.8 % P₂O₅ (? 17.1% BPL) and 78.5 % silica, it is possible to obtain concentrates with different grade (23.4-29.0 % P₂O₅) and recovery (54.9-80.2%) depending on the operating conditions. Increasing frother concentration increased air holdup and in turn decreased bubble diameter. This caused a significant improvement for grade and recovery. Also, increasing superficial air velocity increased air holdup but the bubble size was increased with a resultant of improving the recovery at the expense of grade. The order of significant of the main effects of variables for grade was as follows: superficial wash water velocity (X₃) > frother concentration (X₂) > superficial air velocity (X₁), whereas the order of significance of the main effects of variables for recovery was as follows: superficial air velocity (X₁) > frother concentration (X₂) > superficial wash water velocity (X₃). The interaction between each two parameters is also determined.     

Modeling Dense-Phase Pneumatic Conveying of Powders Using Suspension Density

This article presents results of an investigation into the modeling of pressure drop in horizontal straight pipe section for fluidized dense-phase pneumatic conveying of powders. Suspension density and superficial air velocity have been used to model pressure drop for two-phase solids-gas flow. Two applicable models formats (developed by other researchers using two different definitions of suspension density) were used to represent the pressure drop due to solids-gas flow through straight pipe sections. Models were generated based on the test data of conveying power-station fly ash and electrostatic precipitator (ESP) dust (median particle diameter: 30 and 7 µm; particle density: 2300 and 3637 kg m^?3; loose-poured bulk density: 700 and 610 kg m^?3, respectively) through a relatively short length of a smaller diameter pipeline. The developed models were evaluated for their scale-up accuracy and stability by using them to predict the total pipeline pressure drop (with appropriate bend model) for 69 mm I.D. × 168 m; 105 mm I.D. × 168 m and 69 mm I.D. × 554 m pipes and comparing the predicted versus with experimental data. Results show that both the models with suspension density and air velocity generally provide relatively better prediction compared to the conventional use of solids loading ratio and Froude number. For fly ash, the two formats result in considerable different predictions, whereas they provide relatively similar results for ESP dust.     

高压煤粉密相气力输送垂直管阻力特性研究

该文通过试验和理论计算两种方法研究了高压下煤粉密相气力输送垂直管段的压力损失情况。理论计算是在Banh气力输送理论基础上，引用周建刚的垂直管附加压损系数的经验关系式进行计算的。经试验研究发现，尽管输送气体表观速度呈下降趋势，而垂直管段的单位压损随固气比增加而增大。引起垂直管段压损变化的主要因素是输送煤粉浓度。通过试验值与计算值之比较，发现理论计算值与试验值吻合得非常好，说明基于Barth附加压降法对高压煤粉密相气力输送垂直管阻力特性的计算具有较好的适应性。