Two-stage Flotation Process Research Articles

The Adjustment for Entrainment Behavior of Kaolinite in Coal Flotation

The entrainment of gangue particles always increases the ash content of coal flotation concentrate. In the present work, the adjustment for entrainment of kaolinite in coal flotation was studied focusing on the parameters including solid concentration and frother dosage. The results indicated that the ash contents of concentrates were always higher in the early or late stage (flotation time: 0–30 s or 120–180 s) than that in the middle stage (flotation time: 30–120 s). This is mainly because of the mechanical entrainment in the early stage and the entrainment caused by water transportation in the later stage. It has been confirmed that reducing the feed solid concentration and frother dosage effectively decrease mechanical entrainment in the early stage. Furthermore, better flotation results can be obtained under a high solid concentration and frother dosage in the late stage of the flotation process. Therefore, a novel two-stage flotation process was proposed for the coal flotation. A better flotation performance (combustible recovery: 91.28%; ash content: 4.09%) can be achieved by two-stage flotation, compared to the flotation results (combustible recovery: 93.12%; ash content: 5.16%) of the one-stage flotation process.

A flotation combined extraction process for improving the whiteness of phosphogypsum

Every year, the production of industrial phosphoric acid generates more than 100 Tg of phosphogypsum (PG), leading to significant environmental damage and the occupation of a vast amount of land space. The urgent need to explore applications for PG has become increasingly apparent. However, impurities such as organic substances, slime, phosphorite, and SiO2 reduce the whiteness of PG, making it difficult to utilize for high-value applications. To address this issue, this study employed a two-stage flotation process to remove the majority of impurities, including SiO2, organic substances, and fine slime adhered to the surface of PG particles. The raw PG sample was first sieved to remove some SiO2 particles. After flotation, sulfuric acid and tributyl phosphate were introduced to decompose the PG particles and remove the impurities wrapped inside. Following this flotation combined extraction process, the whiteness of the PG sample improved from 54.1% to 92.9%, meeting the requirements for building walls and filters.

Technological research on converting iron ore tailings into a marketable product

We present three technological scenarios for the recovery of valuable components from gangue, stored in the tailings dam at Kremikovtzi metallurgical plant in Bulgaria, into marketable iron-containing pellets. In the first approach the iron concentrate was recovered through a two-stage flotation process, desliming, and magnetic separation. In the second proposed process, the iron concentrate was subjected to four sequential stages of magnetic separation coupled with selective magnetic flocculation. The third route entails the not very common practice of magnetizing roasting, followed by selective magnetic flocculation, desliming, and magnetic separation. The iron concentrate was pelletized in a laboratory-scale pelletizer. Each technology has been assessed with regard to the mass yield of iron concentrate, the iron recovery. and the iron, lead, and zinc content in order to identify the most effective route.

South African Coal Tailings Bioflotation for Desulphurization Using <i>Mycobacterium phlei</i>

The large cost of the flotation reagents used in the first-of a two-stage desulphurization flotation process, developed for the treatment of South African waste coal ultrafine tailings, has motivated the investigation of Mycobacterium phlei as an alternative coal bioflotation reagent. Attachment experiments were used to confirm that the microbe attaches to South African coal selectively over pyrite or gangue material present in the coal. Subsequent small scale batch floats using M. phlei successfully showed that the bioflotation process can upgrade and desulphurize the coal tailings feed, and delivered approximately the same concentrate yields as the optimised chemical flotation conditions (37 – 39%). However, a projected financial feasibility analysis that assessed the incorporation of the M. phlei into the two-stage flotation process found that the bioflotation process was not profitable due to the very large flow rate of cells required (2×1016 cells/ton coal) and the associated additional equipment and growth media component costs.

A two-stage process for fine coal flotation intensification

Power input and flotation time are the two key factors influencing the efficiency of the fine coal flotation process. A new two-stage process is proposed in this investigation for intensifying fine coal flotation. The flotation process is divided into two parts: lowering energy input in the first stage and raising energy input in the second stage. Easily floated materials are recycled with low energy in the rapid floating section (first stage), and hard-to-float materials are compulsorily recycled using higher energy in the recycling section (second stage). A flotation energy consumption test system is established. Flotation tests were conducted in an XFD 0.75-L laboratory-scale flotation machine. The effects of energy input on the flotation rate constant in instantaneous flotation or flotation over a period of time were investigated. The results indicate that higher combustible matter recovery or lower concentrate ash content could be obtained using a two-stage process compared with a single-stage flotation process with the same energy consumption. Compared with energy input in the first stage of the flotation process, the energy added in the second stage of the flotation process would increase with flotation processing owing to the decreased rate of fine coal floatability in the first stage. The larger the floatability difference in the flotation process, the more energy must be used in the second stage of the flotation process. With the same energy input, the flotation tests indicate that lower ash content or higher combustible matter recovery could be obtained using the proposed two-stage flotation process.

Application of fine desulfurised coal tailings as neutralising barriers in the prevention of acid rock drainage

Sulfide-lean benign tailings obtained from a two-stage flotation process were used to reduce the permeability of acid-generating coal interburden or waste rock. These tailings present a means to conceal the exposed mineral surface from oxygen and water and more aggressive oxidants, including those generated by iron and sulfur oxidising microorganisms, preventing the generation of acid rock drainage (ARD). Packing configurations comprising either alternating layered covers or blends of co-disposed waste rock with benign tailings were investigated. Long-term results in the presence of irrigation of the rock bed indicated successful mitigation with either packing. Repeated exposure of the co-mingled minerals to extreme conditions showed promise where structural integrity of the ore bed and low permeability were maintained. Inhibition of oxidation reactions in acidic environments was postulated to be related to the restriction in flow of the leachate through the column and surface contact with the acid generating waste rock surface.

Two-stage coal flotation to remove pyritic sulfur, arsenic, selenium and mercury

This study focuses on partial leaching of coal pyrite with sodium sulfite in order to increase its degree of liberation from the coal matrix, which might help to increase the removal of coal pyrite, together with trace elements of arsenic (As), selenium (Se) and mercury (Hg) by froth flotation. The U.S. Bureau of Mines’ two-stage reverse flotation process was applied to further reject coal pyrite in the second stage, where pyrite was floated while coal was depressed. The residts show that the leached coal flotation with sodium sulfite produced lower pyritic sulfur content in the clean coal by approximately 25% compared to the flotation of unleached coal. The synergism mechanism between the leaching and the two-stage flotation is delineated. The rejection of trace elements (As, Hg and Se) after the two-stage flotation process with unleached coal followed approximately that of pyritic sidfur (64.6%). However, after the two-stage flotation with leached coal, the rejection ofSe was as high as that of pyritic sulfur (77.9%), while the rejections of As and Hg were 20% lower than that of pyritic sulfur, or followed approximately the same rejections obtained through the two-stage flotation with unleached coal.

Paper machine white water deaeration and two-stage flotation with channel flow

Detrimental substances that originate from deinked pulps and other raw materials tend to build up in paper machine circulation waters, hindering process efficiency and paper quality. The applicability of selective flotation to remove substances from circulation waters was investigated in a two-stage flotation process in which no chemical additives were used. The first stage of the process consisted of a flow channel for white water deaeration, including first-stage flotation. The overflow of the channel flow flotation was further treated in a separate second-stage flotation. The efficiency of the flow channel and a secondary flotation to remove bubbly gases, ink, stickies, and wood extractives were quantified in relation to the reject flow rates or solids yield. The total removal efficiency of a simulated two-stage flotation process was then analyzed for a specific case. The results showed that a considerable reduction of contaminant load can be obtained using a two-stage flotation process without affecting the deaerating function of the channel flow. Further optimization of the proposed internal white water purification scheme may provide substantial benefits to paper or board machine operations with reasonable solids recovery rate.

Mitigating acid rock drainage risks while recovering low-sulfur coal from ultrafine colliery wastes using froth flotation

Ultrafine coal wastes contain sulfide minerals, particularly pyrite, which oxidize and give rise to acid rock drainage (ARD) resulting in extensive and prolonged contamination of local ground and surface waters. Currently, mining operations emphasise an end-of-pipe approach to ARD management using costly chemical or biological treatment techniques, which do not address the long term problem of achieving sustainable closure solutions within the resource lifetime. Eliminating ARD potential before waste disposal would have a major beneficial impact on water quality and facilitate long term closure solutions. Recovering a saleable coal product would be an added economic incentive.This paper presents the results of an investigation to establish the feasibility of a two-stage flotation process to produce: (i) a low-volume sulfide-rich concentrate, (ii) a high-volume benign (low sulfur) tailings, and (iii) a coal concentrate. Laboratory-scale batch flotation experiments were carried out using an oily collector to float coal from samples of coal ultrafines and a xanthate collector to recover acid-generating sulfides. The results of acid generating potential tests (both static and biokinetic) indicate that a low-sulfur tailings with low ARD potential may be produced, together with a coal ultrafine concentrate stream with a low ash content.

Development of a method for separation of PVC and PET using flame treatment and flotation

Flame treatment can be used to modify the surface of plastics to allow water-based coatings to be attached. The effect of the treatment is to produce hydrophilic species on the surface of the plastic. The process is therefore potentially useful for the separation of plastics by froth flotation, provided that the production of the hydrophilic surface can be achieved selectively. Polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were selected for investigation as they are found as a co-mingled product from the recovery of beverage containers. In this paper we report on the development of a simple, but effective, flame treatment method for flaked plastics. The treatment involves the use of an acceleration chute that delivers the flakes through the flame of an angled burner. In experiments with virgin plastics the PVC was found to be less susceptible to surface modification than PET, as indicated by contact angle measurement. Separation of the treated virgin plastic by froth flotation was found to be possible, using careful control of frother addition. The technique was then considered for the treatment of post-consumer plastic bottles. It was demonstrated that flame treatment was effective in rendering the surface of both plastics hydrophilic, although the process alone was not sufficiently selective. Hydrophobic recovery of the PVC, but not the PET, was achieved by raising the temperature of the material to 140 °C for a period of 10 min. A two-stage flotation process was tested for the separation of the plastics. In the first stage the PET was floated away from the PVC utilising differences in particle thickness and surface contamination. The float product was then subjected to flame treatment and hydrophobic recovery prior to the second stage of flotation. In this stage the PVC reported to the float product leaving a PET-rich sinks fraction.

Pilot-plant evaluation of amine flotation of rougher phosphate concentrate in a column cell

In the Florida phosphate industry, a two-stage flotation process is employed for the recovery of phosphate mineral value. In both stages, conventional flotation cells are commonly used. In the present study, the authors evaluated the efficacy of using column flotation in the amine separation of silica from phosphate rougher concentrate. Pilot-plant studies carried out in a 0.45- by 1.2-m dual extraction flotation column (DEC) are presented and compared with plant performance employing conventional flotation cells on both fine and coarse amine feeds.

Removal of60Co and134Cs from radioactive process waste water by flotation

The removal of134Cs and60Co from radioactive process waste water using cetyl pyridinium chloride (CPC) as a collector and cobalt(II) hexacyanoferrate(II) as a precipitant for60Co and sorbent (ion exchanger) for134Cs was intensively investigated and the best removal conditions could be established. The results indicate that under the optimum conditions removals higher than 96% and 97% could be achieved for Co(II) and Cs(I), respectively. Cobalt(II) hexacyanoferrate(II) was found to have high affinity for cesium and can preferentially remove it in presence of relatively high amounts of other alkali or alkaline earth cations. A two-stage flotation process was successfully tested for the removal of both Cs(I) and Co(II) from waters containing both cations.