Removal of Resin from Mechanical Pulps by Selective Flotation: Mechanisms of Resin Flotation and Yield Loss of Fibers

Abstract

The amount of wood resin in mechanical pulp suspensions could be decreased using a selective flotation process. In selective flotation air‐bubbles are dispersed into low consistency pulp suspensions mechanically by an impeller or by injectors. Resin particles attach to the air‐bubbles and are lifted to the top of the pulp suspension from where they are removed, along with the flotation froth. The very small size of the resin particles (average diameter <1.0 micron) suggests that they are driven toward the air‐bubbles mainly by Brownian diffusion and that attachment of the resin particles to the air‐bubbles takes place through colloidal interactions. The resin flotation followed approximate first‐order kinetics. The mechanism of yield loss of fibers was entrainment, whereby they were hydraulically transported into the froth along with the water.     

Modeling and simulation of separation process in flotation system

In order to design a flotation circuit to remove ink and contaminants from slushed old corrugated container (OCC) pulp suspension, a model based on mass balance was developed. The model is a five fractional model, which handles mass flow rate of ink, fiber, fines, filler and dichloromethane (DCM) extractives. A detailed method of calculating the deinking selectivity of a material from experimental data, described in terms of reject ratio, is presented. Three flotation deinking systems were simulated. In a single stage flotation system, increasing the number of flotation cells improved cleanness of the accept pulp suspension while it decreased yield at the same time. Yield can be increased by adding a second stage and by introducing the accept flow of the second stage into the feed flow of the first stage. However, the cleanness of the accept pulp was deteriorated. It was shown that yield can be increased without compensating the cleanness of the accept pulp by utilizing the accept pulp from the second stage for another paper machine line instead of sending back to the feed flow of the first stage.     

Effects of residual concentration of collector CTAC on flotation behavior of illite

ABSTRACT

In present study, illite flotation behavior with Cetyl Trimethyl Ammonium Chloride (CTAC) as the collector has been studied to investigate the effects of its residual concentration on froth stability and flotation. Results showed that, with increasing conditioning time, the residual concentration (frother concentration) and froth height decreased simultaneously, while the adsorbed amount (particle hydrophobicity) increased. Increasing CTAC conditioning time decreased the residual concentration in solutions, resulting in poor froth stability and flotation recovery at high pH; the adsorption rate of CTAC on illite surface was relatively high at higher pH due to strong electrostatic mechanism, making CTAC residual concentration decrease.     

Distribution of clay minerals in the process streams produced by the extraction of bitumen from Athabasca oil sands

This study investigates the affinity of clay minerals in oil sands for the water‐continuous tailings and hydrocarbon‐continuous froth streams produced from the extraction of bitumen from oil sands. Clay minerals in oil sands processing impact bitumen flotation in separation vessels, emulsion formation during froth treatment, and fine tailings behaviour. X‐ray diffraction of oriented clay slides and random powder samples were used to quantify the clay minerals in the oil sands ore and process streams. Particle size distribution and clay activity balances were also conducted around the extraction process. The degree of partitioning during the conditioning and flotation stages in a batch extractor was determined by the surface properties of the clay minerals present. The water‐continuous tailings stream was further separated into fine and coarse tailings fractions through sedimentation. The bulk of the clay minerals reported to the fine tailings stream. Illite and mixed layered illite‐smectite partitioned less to the hydrocarbon‐continuous froth than kaolinite. Also, the illite‐smectite in the froth stream appeared to be different from the illite‐smectite in the water continuous streams.     

Improvement of the Flotation Selectivity in a Mechanical Flotation Cell by Ultrasound

In this study, the effect of ultrasound on froth and pulp phases has been investigated in the flotation of two different ore samples, namely barite and chalcopyrite. In order to determine the overall flotation rate constants at various froth depths, incremental recoveries obtained from the flotation tests with and without ultrasound were fitted to a first-order rate equation. Thus, the recoveries of froth and pulp phases were calculated.

The use of ultrasound speeded up the bubble coalescence and therefore reduced the froth phase recovery in the ultrasonic flotation of both barite and chalcopyrite. In addition, the results indicate that there is a considerable effect of ultrasound on the pulp phase recovery in the chalcopyrite flotation whereas no significant differences in the separation performance were obtained from the ultrasonic flotation of barite with and without ultrasound. The results also indicate that a pronounced selectivity effect was obtained from the ultrasonic flotation of both barite and chalcopyrite. The use of ultrasound in the froth remarkably improves the quality of the chalcopyrite concentrate, especially at the shallow froths. Therefore, either effective pulp volume can be increased without sacrificing the separation selectivity or the pulp density can be decreased to obtain better product quality at shallow froths in the ultrasonic flotation of chalcopyrite.     

Diesel Oil Removal by Froth Flotation Under Low Interfacial Tension Conditions II: Continuous Mode of Operation

Abstract

The objective of this study was to investigate the relationship between interfacial tension (IFT) and foam characteristics and the efficiency of diesel oil removal from water in a continuous froth flotation column. The effects of operational parameters, including surfactant concentration, salinity, oil-to-water ratio, foam height, air flow rate, and hydraulic retention time (HRT) on the oil removal were investigated in the continuous mode of a froth flotation operation and compared to batch operation results. Unlike the batch system, for the continuous system used in the present study, having only branched alcohol propoxylate sulfate sodium salt surfactant (C_14–15(PO)₅SO₄Na) and NaCl present in the solution yielded such poor foam characteristics that a stable froth which overflowed the flotation column could not be produced, so the addition of sodium dodecyl sulfate (SDS) as a froth promoter was used to improve the foam stability. Unlike the batch froth flotation system with only C_14–15(PO)₅SO₄Na, the continuous froth flotation with the mixture of C_14–15(PO)₅SO₄Na and SDS, it was not possible to find a SDS and a NaCl concentration at which both ultralow IFT and good foaming were both achieved. Foam formation, stability, and production rate were found to be crucial parameters to the froth flotation efficiency. The continuous froth flotation system offers a high diesel oil removal of 96% in the single stage unit. Demonstration of efficient operation in the continuous mode in this work is important to the practical application of froth flotation in large scale processing.     

The Influence of Reagent Dosage on the Floatability of Pyrite During Coal Flotation

Abstract

In general, as the quantity of frother and/or coal collector is increased, so too, does the flotation of the undesired pyrite. The problem is particularly serious with oily reagents. For some coals, however, a collector, such as fuel oil, is required to achieve a high coal recovery. This requires a compromise between the competing desires of a high coal recovery and a high pyrite rejection. This study gives the quantitative effect of reagent dosage on coal and pyrite floatability and details several means of minimizing pyrite floatability during coal flotation. The effect of fuel oil on coal flotation is especially interesting in that the flotation process changes from froth flotation to emulsion or agglomerative flotation as the amount of oil is increased. This phenomenon provides an additional method of rejecting pyritic sulfur.     

Effect of Temperature on the Stability of Froth Formed in the Recycle Process Water of Oil Sands Extraction

The formation of a stable froth on the top of separation vessels plays an important role in bitumen flotation during bitumen recovery from oil sands. The effect of temperature on the stability of froth using recycle process water employed in bitumen extraction was investigated using a water column. The froth became less stable with increasing solution temperature. Once the solution temperature increased above 50°C, irreversible precipitation of the surfactants present in the recycle process water was observed, resulting in a less stable froth.     

浮选起泡剂泡沫稳定性的评价方法研究

<正>在浮选起泡剂的研究中,充气法是进行起泡剂泡沫性能评价的常用方法之一,该方法是将气体以恒定速度注入溶液而测定泡沫高度（或泡沫体积）及泡沫持续时间。针对这一方法,为了得到最客观和具重现性的结果,在起泡剂泡沫稳定性的评价方面曾提出了各种各样的试验程序。一般为大家熟悉和接受的是Bikerman方法,他将起泡性能作为液体的物理性质,定义了一个所谓的“起泡性能单位”,即∑。Bikerman认为,在一定条件下,如果泡沫体相中气泡的聚并和液体的体积可以忽略,则∑就等于气泡寿命,但这里的假设通常是不实际的,尤其是在湿泡沫的情况。正如Malysa指出,对这样的体系,泡沫柱中液体的含量     

Effect of frothers on removal of unburned carbon from coal-fired power plant fly ash by froth flotation

The effect of single frothers and their blends on bubble size, froth stability, and unburned carbon (UC) flotation performance was studied. Methyl isobutyl carbinol that produces smaller bubbles is efficient in floating ultrafine particles and producing concentrate. DF-250 that gives higher froth stability is effective for recovering coarse particles and improving recovery. The presence of DF-250 in the blend increases bubble size and significantly enhances froth stability, and hence the optimal flotation performance is achieved with 75% DF-250. It indicates that the frother giving high froth stability is better in UC flotation due to the little effect of UC on froth stability.     

几种酶脱墨性能比较及机理探讨

对脂肪酶、木聚糖酶和纤维素酶进行脱墨性能的比较,结果表明,几种酶脱墨浆白度相近,但各有特点。脂肪酶脱墨得到的强度和得率最高;纤维素酶脱墨对滤水性的改善最佳,但对强度略有不利影响;木聚糖酶脱墨则有着适中的综合性能。通过尘埃度分析、还原糖测定和纤维形态观测等研究手段进行了脱墨机理的探讨,其结果较好地验证了上述结论。     

Optimization of some parameters in column flotation and a comparison of conventional cell and column cell in terms of flotation performance

In this study, a comparative evaluation was made between column and mechanical flotation cells for fine coal cleaning. In addition, the optimum values of operating parameters were examined, which are important to achieve a desired separation performance in column flotation, such as the frother concentration, the collector dosage, the froth thickness, the wash water rate, the air rate and the feeding rate. The coal sample was collected from a classifying cyclone overflow stream consisting of nominally −130 μm material. Ash, volatile mater, fixed carbon and total sulfur contents of the sample were found to be 47.50%, 20.80%, 31.70% and 0.75%, respectively. Comparison of the column and mechanical flotation results indicated that column flotation was considerably more efficient than mechanical flotation for fine coal cleaning. High froth thickness and wash water addition during column flotation made it possible to obtain cleaner coals. The column flotation produced a 15.60% product ash with a 50.92% clean coal yield and 81.85% combustible recovery.     

Performance of classic oils and lubricating oils in froth flotation of Ukraine coal

In this study, the appropriate collector and collector amount for Ukraine coal in froth flotation was determined. For this purpose, the performance of classic oils (kerosene, diesel-oil and fuel-oil) and lubricating oils (spindle oil, bright stock and heavy neutral) was evaluated by combustible recovery, ash rejection and efficiency index. It was found that the combustible recovery and ash rejection changed, depending on the type and concentration of oil. The maximum combustible recovery was obtained by using bright stock. It was determined that bright stock, fuel-oil and kerosene were suitable for the flotation of Ukraine coal. On considering the flotation efficiency index values, the best results were obtained with bright stock and diesel-oil. Consequently, it was shown that bright stock and spindle oil could be used as alternative oils instead of classic oils for cleaning of Ukraine coal by the froth flotation.     

Short-time tracer dispersion in a two-dimensional rising froth

Experimental results on the dispersion of a fluorescein tracer in a rising froth of water/glycerol mixture with SDS as the frother are described. These experiments illuminate the physical phenomena that are important to the application of washwater in flotation processes. Two-dimensional numerical solutions of foam drainage in rising systems are also presented at values of background liquid hold-up relevant to the flotation process. It is shown that, at short times, the dominant mechanism for tracer dispersion is due to liquid drainage in the froth rather than due to packed-bed type behaviour as liquid percolates through a network of Plateau borders in between the bubbles. Two foam drainage models, channel-dominated drainage and node-dominated drainage, have been previously described in the literature. It is shown that neither can adequately predict the phenomena of tracer dispersion in a rising froth. The reality appears to lie somewhere in between the two extremes. However, it has been observed that channel-dominated behaviour is approached as liquid disperses and local volumetric liquid hold-up decreases. Finally experimental results are presented for a tracer of very concentrated fluorescein solution that show dispersion behaviour quite unlike that described by the two established foam drainage models.     

Froth stability and entrainment evaluation of a novel frother for KCl/NaCl flotation

The rate of KCl recovery by froth flotation using low-grade carnallite is 70%–85%. Herein, a novel frother, dipropylene glycol butyl ether (DPNB), was prepared to increase the flotation efficiency of KCl recovery systems. DPNB could be applied at only half the dosage of the conventional frother methyl isobutyl carbinol (MIBC) and achieve a KCl recovery rate of 94.8%–98.6% with a high KCl grade (63.2%–66.5%). To date, these results are the best reported for pneumatic flotation. DPNB had a 10% higher maximum dynamic stability factor compared with MIBC; moreover, the apparent entrainment velocity of DPNB was half that of MIBC. The molecular structure of DPNB had hydroxyl and ether groups, which promoted interactions with water, thereby contributing to its excellent froth stability. DPNB is environment friendly owing to its low volatility and, thus, a promising frother for the green and highly efficient flotation of KCl/NaCl.     

Effect of fiber content and type,compatibilizer, and heating rate on thermogravimetric properties of natural fiber high density polyethylene composites

Natural fiber polyethylene composites containing kenaf fibers, wood flour, newsprint, and rice hulls at 25 and 50% (by weight) fiber content were sampled and studied using thermogravimetric analysis (TGA). The effects of fiber type and content, compatibilizer and heating rate on the thermal stability and degradation of the composites were evaluated. Among different natural fibers, kenef fibers were found to be the least thermally stable ones whereas newsprint fibers proved to be the most stable fibers in composite formulations. Composites containing higher amounts of natural fiber degraded at a higher rate and exhibited higher weight loss. The presence of the compatibilizer resulted in composites with slower thermal degradation. Heating rate increased both temperature and rate of main degradation peaks. FTIR and DSC results are also presented to discuss phenomena leading to thermal degradation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.     

Froth flotation as primary treatment of flowback water: Removal of total organic carbon and prediction of kinetics

Petroleum and exploration industries employ a hydrofracking process where a large volume of water (fracturing fluid) is injected and a fraction (known as flowback water) is returned to the surface. Froth flotation is a typical process employed for the primary treatment of water. In the present work, froth flotation has been used as a pretreatment method for real flowback water sourced from the petroleum and shale gas exploration industry. In the present work, a first-principle based convective mass transfer model has been developed to describe the froth flotation performance. The resultant equation was solved analytically and compared with the numerical solution, and a parametric sensitivity analysis of the process performance was also undertaken. In addition, a correlation to estimate the flotation rate constant was proposed, thereby circumventing the need to obtain a large number of cumbersome parameters experimentally. Overall, this study proposes froth flotation as an efficient primary treatment method towards the separation of dispersed oil droplets from the flowback water and the corresponding prediction of kinetics using a first-principle based transport model.     

Deinked and acetylated fiber of newspapers

Recently, the incorporation of lignocellulosic materials as reinforcing agents or as fillers in polymer composites has received an increased attention. Although natural fibers have a number of advantages over glass fibers, the strong polar character of their surface is a limiting factor, as compatibility with strongly apolar thermoplastic matrices is very low. Such problems of incompatibility may be overcome with fiber pretreatments, which can enhance compatibility, albeit having a negative impact on the economics. In this study, the newspaper is deinked and acetylated. The effect of esterification between the acetyl groups and the hydroxyl groups of the fiber was examined by Fourier transform infrared. X‐ray diffraction and scanning electron microscopy were used to characterize the crystallinity and the surface morphology of the untreated deinked and acetylated fibers (newspaper). The thermal stability of deinked and acetylated fibers was slightly decreased. It was also shown that the deinking increased the crystallinity of newspaper fibers while acetylating decreased this crystallinity. Cellulose acetate is one of the most important cellulose derivatives and its main applications are its use in composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

泡沫浮选耦合膜过滤回收有机废水中纳米TiO2光催化剂的工艺

本研究的目的是开发一种新型的泡沫浮选耦合超滤技术的方法,以实现从有机废液体系中经济、高效地回收纳米TiO₂光催化剂。首先,对超滤膜分离有机废液中纳米TiO₂光催化剂的使用效率,包括透过通量和截留率进行评价。随后,为了减少超滤操作进料液中纳米TiO₂光催化剂的浓度,在泡沫浮选阶段确定以阳离子表面活性剂——十六烷基三甲基溴化铵（CTAB）作为捕获剂,研究了CTAB浓度、气体体积流速、分布器孔径对泡沫浮选回收纳米TiO₂光催化剂富集效率的影响。最后,确定泡沫浮选耦合超滤耦合回收纳米TiO₂光催化剂的工艺条件。试验结果表明,采用耦合工艺,在pH 7.0、CTAB浓度0.20g/L、气体体积流速15mL/min以及分布器孔径180μm的条件下,纳米TiO₂光催化剂富集比和回收率分别为22.52和99%,同时膜的使用寿命较非耦合操作提高了133％。