Comparative study of the performance of conventional and column flotation when treating coking coal fines

Investigations were carried out on coking coal fines by conventional cell and column flotation techniques. The effects of different operating parameters were evaluated for both conventional and column flotation. The coal fines were collected from Bhojudih washery, India. These coal fines averaged 24.4% ash, 19.8% volatile matter and 53.8% fixed carbon on a dry basis. A commercial grade sodium silicate, light diesel oil and pine oil were used as depressant, collector and frother respectively. The flotation performance was compared with release analysis. The conventional flotation results indicated that a clean coal with 14.4% ash could be obtained at 78.0% yield with 88.4% combustible recovery. The ash of the clean coal could be further reduced to 10.1% at 72.0% yield with 85.6% combustible recovery by using column flotation. The column flotation results were close to those obtained by release analysis.     

充填浮选柱分选胶磷矿的工艺研究

充填浮选柱是一个复杂的气液固三相体系。本文考查了用充填浮选柱分选胶磷矿的主要操作参数的影响，讨论了Ｐ２Ｏ５的品位的沿柱高的分布，证实了充填浮选柱具有优良的分选性能，并为寻求缩短胶磷矿浮选工艺流程的途径提供了依据。     

Characterization and column flotation of bottom ashes from Tuncbilek power plant

Bottom ashes from the Tuncbilek power plant have been characterized by size fraction, X-ray diffraction and X-ray Fluorescence. These samples are potentially of class F type and have significant amounts of unburned coal. The unburned coal specimens studied using Fourier Transform Infrared Spectroscopy indicated a significant loss of the aliphatic hydrocarbon groups (C-H) and the carbon bond CC during their stay in the combustion environment. In contrast, they indicated insignificant levels of carbonyl group, CO, possibly due to the loss of CO₂ to air as well as carboxylic ions to disposal water. The effects of various operating variables on the combustible recovery and ash content determined using column flotation were limited due to severely oxidized state of unburned coal. Best set of results was obtained with the bottom ash sample from unit 3, which brought the ash content from 77.6% down to 42.6% at a combustible recovery of 53.8%, and the calorific value was increased from 1270 kcal/kg to 3840 kcal/kg.     

Gas holdup characteristics in a flotation column with different solids

This paper presents the effect of process variables on gas holdup. It was measured by volume expansion method in a continuously operating flotation column using coal and sphalerite. It was observed that addition of both solids reduced gas holdup. Increase in solid concentration and particle size reduced gas holdup. Also, increase in gas velocity and frother concentration increased the gas holdup as amount of gas increased and bubble surface property favored the formation of small bubbles. An empirical mathematical model was developed to predict gas holdup. The predicted results were in good agreement with the experimental and available published data.     

Performance,mixing and kinetics study in the flotation column reactor using coal

ABSTRACT

A flotation column has been designed and characterized with respect to gas velocity, slurry velocity, frother concentration, gas holdup, bubble surface area flux for the study of the mixing property, liquid phase residence time distribution, flotation recovery and rate constant. The study was performed using coal as solid. A strategy of integrating chemical kinetics into the flotation process to test the floatability behaviour of coal and to estimate floatability parameter of coal has been developed. The results indicate that the coal floatability parameter is 3.05 × 10^?4. A relationship between gas holdup and bubble surface area flux was developed.     

Optimization of design and operating parameters in a pilot scale Jameson cell for slime coal cleaning

The Jameson flotation cell has been commonly used to treat a variety of ores (lead, zinc, copper etc.), coal and industrial minerals at commercial scale since 1989. It is especially known to be highly efficient at fine and ultrafine coal recovery. However, although the Jameson cell has quite a simple structure, it may be largely inefficient if the design and operating parameters chosen are not appropriate. In this study, the design and operating parameters of a pilot scale Jameson cell were optimized to obtain a desired metallurgical performance in the slime coal flotation. The optimized design parameters are the nozzle type, the height of the nozzle above the pulp level, the downcomer diameter and the immersion depth of the downcomer. Among the operating parameters optimized are the collector dosage, the frother dosage, the percentage of solids and the froth height. In the optimum conditions, a clean coal with an ash content of 14.90% was obtained from the sample slime having 45.30% ash with a combustible recovery of 74.20%. In addition, a new type nozzle was developed for the Jameson cell, which led to an increase of about 9% in the combustible recovery value.     

胶磷矿浮选药剂添加点的优化改造

分析了安宁矿业分公司胶磷矿单反浮选的一次粗选中将浮选药剂加入二级搅拌槽存在的问题,经将加药点前移至一级搅拌槽后,浮选效果改善,精矿指标稳定,系统结垢周期延长,同时减少了浮选药剂的添加量。     

填料在充填浮选柱中的应用及研究

介绍了化工填料在浮选柱的应用及研究情况,探讨了填料在浮选柱中所起的作用,说明了今后的研究方法及方向。     

Optimization of some parameters on agglomeration performance of Zonguldak bituminous coal by oil agglomeration

In this study, the optimization of some parameters on agglomeration performance of Zonguldak bituminous coal by oil agglomeration was discussed. A three-level Box-Behnken design combining with a response surface methodology (RSM) and quadratic programming (QP) were employed for modeling and optimization some operations parameters on oil agglomeration performance. The relationship between the responses, i.e., grade and recovery, and four process parameters, i.e., amount of oil, agitation time, agitation rate and solid content were presented as empirical model equations for both grade and recovery on oil agglomeration. The model equations were then optimized individually using the quadratic programming method to maximize both for grade and recovery within the experimental range studied. The optimum conditions were found to be 14.61% for amount of oil, 8.94 min for agitation time, 1554 rpm for agitation rate and 5% for solid content to achieve the maximum grade. The maximum model prediction of 0.650 grade at these optimum conditions is higher than any value obtained in the initial tests conducted. Similarly, the conditions for maximum recovery were found to be 20.60% for amount of oil, 5 min for agitation time, 1800 rpm for agitation rate and 19.48% for solid content with a prediction of 96.90% recovery, which is also higher than any other recovery obtained in the initial tests conducted.     

Bubble size distribution in cyclonic zone of a novel flotation column

In order to investigate bubble size distribution (BSD) in the cyclonic flotation column, a series of tests were conducted to study flow velocity distribution (FVD) and BSD by using the method of particle image velocimetry (PIV). Foaming performance of the n-octyl alcohol is more applicable than both of n-butyl alcohol and terpenic oil. At different circulation volume conditions, BSD range lies in 0–800 μm, and a large number of tiny bubbles (<90 μm) are generated. Besides, the curve presents a normal distribution in 90–180 μm. With the increase in circulation volume, bubble size decreases. BSD determined by cyclonic flow effect plays a crucial role on bubble mineralization with fine particle in cyclonic zone of the flotation column.     

Effect of pulp fibres on gas holdup in a flotation column

Column flotation is an emerging technology in the deinking of recycled paper. Deinking efficiency depends primarily on the effect of four physical variables: gas and accepts flowrates, bubble size distribution, and pulp consistency. Experiments to establish operating ranges for these variables by determining their effect on gas holdup were conducted in a laboratory column installed at Bowater's Gatineau (Quebec) mill which processes a pulp (70% ONP/30% OMG) with about 1% consistency. The results showed the general trends expected from a review of previous studies: gas holdup increases with gas and accepts flowrates and with smaller bubble size, and decreases for higher pulp consistencies. However, the review also demonstrated that the published information is of limited application as the bubble size was much larger than that encountered in industrial flotation practice, primarily because of the use of pure water. Industrial pulps contain in most cases surface active agents which have a substantial effect on forming and preserving a small size bubble population.     

Effect of geometrical parameters of draft tubes and clear liquid height on gas holdup in a bubble column for gas dispersion into tubes

The effects of the geometrical parameters of draft tubes and the clear liquid height on the average gas holdup E_G in a 0.16 m I.D. bubble column for gas dispersion into the tubes were experimentally studied in an airtap water system. The gas holdup depended on the superficial gas velocity U(ING), the kinds of gas spargers, the diameter and length of the draft tubes, clearance C_b between the lower end of the draft tube and the bottom of the bubble column, and the clear liquid height H_L. E_G increased with decreasing hole diameter of the gas sparger at a small gas velocity U_G, but did not depend on the kinds of gas spargers at a large U_G. E_G decreased with increasing clear liquid height H_L. The effect of H_L on E_G was well expressed by the modified three-region model. The experimental data of E_G were correlated.     

The effect of different flotation operating parameters on the froth properties and their relation to clean coal ash content

Froth properties and their relation to the concentrate grade play an important role in monitoring flotation running conditions and predicting flotation concentrate quality. In this paper, the correlation between the froth properties and clean coal ash content was investigated under complicated conditions where the frother dosage, gas velocity, and froth height were changed together. For the froth properties under study, their degree of correlation with clean coal ash content decreased in the order of homogeneity, water recovery, gray value, and froth velocity. The coefficient of determination (R²) of the fitting relationship between homogeneity and clean coal ash content was as high as 0.9028, because homogeneity has a close correlation with the foam structure and foam destabilization behaviors.     

喷射式浮选机浸没式充气搅拌装置结构参数的试验

介绍了浸没式充气搅拌装置的结构,并与长喉管充气搅拌装置进行对比。通过浸没式充气搅拌装置结构参数的优化试验,确定了喉管内径、喉管长度及喉管出口至假底的距离3个参数。FJCA系列浮选机充气性能等指标达到了较高水平,具有使用寿命长、维护工作量小等特点,在多个选煤厂得到了推广应用。     

一种碳酸盐调整剂在海口中低品位磷矿正-反浮选中的应用

在海口中低品位磷矿正-反浮选工艺流程中添加一种碳酸盐调整剂(TZJ-L),使矿石在正浮选和反浮选作业中碳酸盐杂质都增加了排出率,降低了正浮精矿的产率和反浮选药剂消耗。不添加TZJ-L的反浮选磷精矿P_2O_5质量分数比添加TZJ-L的高0.82百分点,但精矿产率低3.44百分点。另外,加入碳酸盐调整剂TZJ-L改善了正浮选精矿泡沫的性质,大大提高了泡沫的流动性,有利于输送和降低消泡水量,提高浮选物料浓度。     

Quantitative comparison of dynamic controllability between a reactive distillation column and a conventional multi-unit process

A comparison of the steady-state economic optimum designs of two alternative chemical processes was presented in a previous paper [Kaymak, D. B., & Luyben, W. L. (2004). A quantitative comparison of reactive distillation with conventional multi-unit reactor/column/recycle systems for different chemical equilibrium constants. Industrial & Engineering Chemistry Research, 43, 2493–2507]. A generic exothermic reversible reaction A + B ↔ C + D occurs in both flowsheets, which consist of a conventional multi-unit reactor/separator/recycle structure and a reactive distillation column. Results showed that the reactive distillation process is significantly less expensive than the conventional process for a wide range of the chemical equilibrium constant when there is no mismatch between the temperature favorable for reaction and the temperature favorable for vapor–liquid separation.

A reactive distillation column has fewer control degrees of freedom than a conventional multi-unit system. Therefore a reactive distillation column may have worse dynamic response than a conventional process. The purpose of this paper is to compare the dynamic controllability of these two alternative processes.

Three different chemical equilibrium constants are considered. Several control structures are developed for each flowsheet, and their effectiveness is evaluated. Disturbances in production rate and fresh feed compositions are considered.

The conventional multi-unit process provides significantly better control. The operability region is much larger, there is less variability in product quality and the dynamic responses are faster than those of the reactive column. Thus, these results demonstrate that there is a significant trade-off in this system between optimum economic steady-state design and dynamic controllability.     

大处理量紧凑型气浮装置的数值模拟

目前鲜有关于大处理量气浮装置结构设计研究方面的报道,气浮装置国产化研究进程缓慢。为了解决这 一问题,本文以自主研发的处理量为120m³/h 紧凑型气浮装置为计算模型,采用Eulerian 模型和RNG k-ε 湍流模 型,运用Fluent 对其三维流场进行了数值模拟研究。分别研究了内筒高度、半径间隙及入口管径等结构参数和 含油量、处理量等操作参数的影响,以便考察和优化气浮装置的分离性能。结构参数影响的数值模拟结果表明: 随着半径间隙的减小,除油率先增大后减小;随着入口管径的减小,除油率先减小后增大;改变内筒高度对除 油率的影响较小。操作参数影响的数值模拟结果表明,装置的操作弹性相对较大,对水质水量一定程度的波动 具有良好的适应性。     

Simulation and analysis of extractive distillation process in a valve tray column using the rate based model

Valve trays are becoming popular in the chemical process industries owing to their flexibility to handle a wide range of vapor throughputs. Using the rigorous rate based model, the importance of the non-equilibrium approach is demonstrated for a typical extractive distillation process in a Glitsch V-1 valve tray column. Simulation results based on an in-house developed code indicated that the rate based model predictions for a valve tray column operation showed significant differences relative to the equilibrium model. Even small errors in product purities translated into nonoptimal feed stage locations and inaccurate number of stages required. The counter-intuitive effect of high reflux ratio on separation is explained.     

Effects of operational parameters on emission performance and combustion efficiency in small-scale CFBCs

A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emissions. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (two-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO_x and SO₂ emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure at the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO₂ and NO_x emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO_x emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal.     

小分子双水相浮选高效液相色谱法测定污水中痕量氯霉素

用乙醇/磷酸氢二钾双水相体系浮选污水中的氯霉素,通过对盐的质量分数、有机溶剂的体积、气体流速和浮选时间的选择和优化,在理想条件下,氯霉素的平均浮选效率可以达到94%。该方法用于河水和鱼塘水样品中氯霉素的检测,检出限为0.5 ng/mL,加标回收率为89.44%～100.16%,相对标准偏差RSD为1.1%～2.1%,适用于污水中痕量氯霉素的分离/富集及分析测定。