Removal Of Unburned Carbon Research Articles

Enhancing flotation removal of unburned carbon from fly ash by coal tar-based collector: Experiment and simulation

The unburned carbon (UC) in fly ash is a vital parameter that governs the further utilization of fly ash in mortar and concrete industry. Flotation is an effective methodology for removing the UC from fly ash. However, the specific physicochemical properties of the UC particle surface make them difficult to float. In this study, a coal tar-based (CTB) collector was used to remove the UC from fly ash through flotation process. The adsorption mechanism of the CTB collector and diesel on the UC particle surface was characterized by scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), molecular dynamics (MD) simulation, and induction time tests. The levels of oxygen-containing functional groups and aromatic ring compounds present in the CTB collector were considerably higher than those in diesel. The oxygen-containing functional group contents on the untreated UC surface, the diesel-treated UC surface, and the CTB collector-treated UC surface decreased in that order. The MD simulation results indicated that the aromatic compounds (dibenzofuran and naphthalene, etc.) in the CTB collector interacted strongly and adsorbed at deep locations with the UC surface compared to the alkanes (dodecane, diesel, etc.). The alkanes are indispensable as the collector in the fly ash flotation process and synergize with aromatic compounds to improve the mobility of water molecules on the UC surface. The CTB collector significantly enhanced the floatability of the UC particle and hence improved the flotation removal of UC from fly ash.

Adsorption mechanism of a new combined collector (PS-1) on unburned carbon in gasification slag

Coal gasification fine slag (CGFS) is a type of solid waste produced during coal gasification, in which unburned carbon (UC) severely restricts its resource utilization. The removal of UC from CGFS is considered an urgent problem. This study applies PS-1 (a mixture of kerosene and oleic acid at the ratio of 7:3) to improve the flotation separation effect of carbon from CGFS. The flotation adsorption mechanism of PS-1 on UC is revealed by experiment/molecular dynamics simulation and characterization analysis. Results show that long-chain hydrocarbons in PS-1 are adsorbed on the non-polar region of UC by Van der Waals force, while –COOH groups in PS-1 are adsorbed on the polar sites of –COOH and –OH of UC by hydrogen bonds. The synergistic effect of long-chain hydrocarbons and –COOH groups in PS-1 improves the hydrophobicity of the UC surface. Compared with traditional collector kerosene, the combustible recovery rate of foam products can be increased to 68.0%. Collector dosage can be reduced by approximately 50% using PS-1. This study can provide essential guidance for the design of CGS flotation collectors and help realize the comprehensive utilization of coal gasification solid waste.

Removal of unburned carbon from fly ash using enhanced gravity separation and the comparison with froth flotation

Fly ash is the by-products of electric power, which has potential application in construction industry after removing the unburned carbon. The density difference and favorable dispersion characteristics of fly ash provide the feasibility using gravity separation method. The present study had investigated the removal of unburned carbon from fly ash using enhanced gravity separation under different operation parameters such as rotational angular velocity and backwash water pressure, and the decarbonization performance was compared with the froth flotation. The results showed that both the rotational angular velocity and backwash water pressure had evident effect on the removal of unburned carbon from fly ash, and the rotational frequency adjusted more accurate relative to the coarse adjustment of backwash water pressure. The enhanced gravity separation could yield qualified Level II and Level III ash products with yield of 12%–23% and 23%–69%, while the froth flotation yield Level I, Level II and Level III ash products. The decarbonization results of enhanced gravity separation was slightly lower than froth flotation, while it provided the application value in industry without complex reagent system and high cost on the premise that met the requirements for Level II and Level III ash products.

The Process of the Intensification of Coal Fly Ash Flotation Using a Stirred Tank

Pulp preconditioning using a stirred tank as a pretreatment process is vital to the flotation system, which can be used to improve the flotation efficiency of mineral particles. The kinetic energy that is dissipated in the stirred tank could strengthen the interaction process between mineral particles and flotation reagents to improve the flotation efficiency in the presence of the preconditioning. In this paper, the effect of the conditioning speed on the coal fly ash flotation was investigated using numerical simulations and conditioning-flotation tests. The large eddy simulation coupled with the Smagorinsky-Lilly subgrid model was employed to simulate the turbulence flow field in the stirred tank, which was equipped with a six blade Rushton turbine. The impeller rotation was modelled using the sliding mesh. The simulation results showed that the large eddy simulation (LES) well matched the previous experimental data. The turbulence characteristics, such as the mean velocity, turbulent kinetic energy, power consumption and instantaneous structures of trailing vortices were analysed in detail. The turbulent length scale (η) decreased as the rotation speed increased, and the minimum value of η was almost unchanged when the rotation speed was more than 1200 rpm. The conditioning-flotation tests of coal fly ash were conducted using different conditioning speeds. The results showed that the removal of unburned carbon was greatly improved due to the strengthened turbulence in the stirred tank, and the optimal results were obtained with an LOI of 3.32%, a yield of 78.69% and an RUC of 80.89% when the conditioning speed was 1200 rpm.

Flotation kinetics of the removal of unburned carbon from coal fly ash

ABSTRACTUnburned carbon (UC) in coal fly ash indicates the waste of energy source and is an obstacle to the utilization of coal fly ash. The purpose of this study was to investigate the flotation kinetics of the removal of UC from coal fly ash. The collector and frother dosage are key factors for coal fly ash flotation. Six flotation kinetic models were applied to fit the flotation kinetic tests data. The fitted results showed that the classical first-order model had better consistency with the experimental data. The contact angle of flotation concentrates decreased as the flotation time was extended which revealed the decrease of flotation rate.

Effects of calcium chloride and sodium chloride on the flotation removal of unburned carbon from coal fly ash

ABSTRACTThe effects of calcium chloride and sodium chloride on the coal fly ash flotation were investigated by studying the surface properties of coal fly ash. X-ray photoelectron spectroscopy and scanning electron microscopy showed the presence of many lime particles in the coal fly ash, which, together with Ca(OH)2(s), could be adsorbed on the rough surface of unburned carbon particles. The flotation results indicated that calcium chloride reduced the performance of unburned carbon removal from the coal fly ash, whereas sodium chloride increased froth stability thereby improving the flotation performance.

아크방전을 이용한 플라이애시의 미연탄소 제거 및 표면개질 효과

플라이애시를 콘크리트의 혼화재료로서 사용하기 위해서는 알칼리 자극제의 첨가가 요구되며 미연탄소를 제거하는 과정이 필요하다. 현재까지는 플라이애시의 표면을 개질하기 위해 플라즈마를 이용하였으나, 플라즈마는 산소를 활성기체로 사용할 경우 오존이 생성되어 지구 환경 시스템을 파괴하는 문제점을 지니고 있으며, 오존은 주변 물질을 산화시킬 뿐만 아니라 플라즈마를 이용하고자 하는 사람의 폐 건강에 나쁜 영향을 미칠 수 있다. 따라서 본 연구에서는 기존 플라즈마의 문제점을 해결하고 경제적인 방법으로 플라이애시를 개질하고자 아크방전을 이용하는 방안에 대해 연구하였다. 이를 위하여 본 연구팀에서는 플라이애시 표면개질용 아크방전 기계를 자체적으로 제작하여 실험을 실시하였다. 실험 결과, 아크방전을 이용해 플라이애시의 표면개질 후 미연탄소가 제거되는 것을 확인하였으며, 강열감량 및 비중은 감소하였고 분말도가 증가하는 것을 확인하였다. 또한 아크방전을 이용해 표면개질 한 플라이애시를 사용했을 경우 압축강도가 증가하는 것으로 나타났다. 따라서 본 연구 범위 내에서는 아크방전을 이용하여 플라이애시의 미연탄소분을 제거하는 것이 가능하며, 플라이애시의 표면을 개질하는 것이 가능하다는 것을 알 수 있었다.

Removal of Unburned Carbon and Surface Treatment Effect of Fly Ash Using Arc Discharge

Removal of Unburned Carbon and Surface Treatment Effect of Fly Ash Using Arc Discharge

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

ABSTRACTThe 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.

1-21.フライアッシュ中未燃炭素の燃焼除去(Session(1)石炭利用)

1-21.フライアッシュ中未燃炭素の燃焼除去(Session(1)石炭利用)

The removal of unburned carbon from fly ash by kerosene extraction

The recycling process was developed to remove and recover unburned carbon from fly ash using kerosene extraction. The effects of experimental factors such as shaking time, initial unburned carbon content, and organic to suspension (O/S) ratio on the removal of unburned carbon were investigated to obtain the optimum conditions. The results indicate that the removal ratio of unburned carbon increased with increasing shaking times and decreasing the initial unburned carbon content, but the residual amount of unburned carbon was independent of O/S ratio. The content of unburned carbon decreased successfully to less than 3% under the following conditions; 15 min in shaking time, 10% in pulp density, 30 °C in temperature, 200 rpm in shaking speed, and 0.5 in O/S ratio.

A New Technique for Removing Unburned Carbon from Coal Fly Ash at an Industrial Scale

Removal of unburned carbon from the high-carbon fly ash (HCFA) is essential when it is used as an admixture in cement concrete. This article deals with processing of the HCFA from the Guangdong province of China. A cyclonic-static microbubble flotation column (FCSMC), a novel device with the characteristics of internal recycling process and multiple mineralization steps, was used to separate unburned carbon from ash materials. A commercial flotation plant with a handling capacity of 110 ton coal fly ash (dry basis) per hour was set up. Using the optimum operational parameters, a clean ash with loss on ignition (LOI) of 3.08% and a removal rate of unburned carbon (RUC) of 80.41% was obtained. The calorific value of the unburned carbon products reached 3534 cal/g. Industrial-scale flotation tests on the circulation pulp pressure demonstrated that the energy input mode and internal recycling process of FCSMC separator was effective in removing unburned carbon from HCFA.

Investigation of Removing Iron from Fly Ash

Fly ash, as an environmental pollutant, is generated in the process of coal combustion for energy conversion. It has been widely used in so many applications, such as, preparation of zeolite, extracting alumina, and so on. Iron composition has some side-effect on the purity and whiteness of the products prepared form fly ash. In this paper, removal of unburned carbon and iron composition was investigated. The results show that the carbon can be removed completely from fly ash after calcination under 800°C for 2h. Acid leaching was used to remove iron from the fly ash after decarburization. The optimum processing parameter is, hydrochloric acid concentration 5mol·L-1, reaction temperature 80°C and reaction time 2h.

Flotation process in coal bottom ash and their effect on the removal of unburned carbon

ABSTRACT In this study, the removal of unburned carbon (UC) from the coal bottom ash (CBA) by flotation was studied by explaining the relationship between adsorption characteristic with different solution pH and content of UC for increasing removal efficiency. Therefore some CBA samples were chosen for test and those samples contained 2.73%(sample A), 7.01%(sample B) and 10.49%(sample C) of UC respectively. The column flotation was carried out at the condition of 10 L/min flow rate with the reagents of 500g/ton kerosene and 80g/ton MIBC. The flotation method was employed using each samples ranged from 6.5 to 52g/L. From the adsorption kinetic curves, the rate of UC adsorption increased rapidly as the reaction approached to equilibrium. The isotherm characteristics on the UC adsorption of CBA were S-type, and these curves were fitted to the BET adsorption isotherm. Content of UC and pH influenced the adsorption; adsorption efficiency was high with increasing content of UC and decreased when pH sifted to acid or alkaline conditions.

04/02585 Removal of unburned carbon from municipal solid waste fly ash by column flotation: Huang, Y. et al. Waste Management, 2003, 23, (4), 307–313

04/02585 Removal of unburned carbon from municipal solid waste fly ash by column flotation: Huang, Y. et al. Waste Management, 2003, 23, (4), 307–313

Removal of unburned carbon from municipal solid waste fly ash by column flotation

Unburned carbon (UC) is the major source of organic contaminants in municipal solid waste (MSW) fly ash. So most organic contaminants can be removed by the removal of the UC from the MSW fly ash. In this paper, we first used a technique of column flotation to remove UC from MSW fly ash. The influences of column flotation parameters on the recovery efficiency of UC were systematically studied. It was found that the UC recovery efficiency was greatly influenced by the gas flow rate, pH value, collector kerosene's concentration and the types of fly ash. By optimizing the above parameters, we have successfully removed 61.2% of the UC from MSW fly ash having 5.24% UC content. The removal mechanism was well accounted for the kinetic theory of column flotation and surface-chemistry theory. The results indicate that the column flotation technique is effective in removing the UC from MSW fly ash, and show that there is a strong possibility for practical application of this technique in removing the organic contaminants from MSW fly ash.

The removal of unburned carbon from coal fly ash by flotation.

The purpose of this study is to determine the characteristics and to provide the technical data for the viable economic utilization of coal fly ash by using flotation tests. The main components of the sample are SiO2, Al2O3, and unburned carbon substance, which is enriched in coarse size fractions over 74 μm and under 37 μm is 7.13wt.%. Flotation tests were performed to determine the effects of various flotation parameters including reagents dosage, impeller speed, pulp pH, and grinding time of the test sample using aerofroth 73 (AF 73), pine oil, methyl isobutyl carbinol (MIBC) as frothers and kerosene as a collector. Unburned carbon recovery grew gradually according to the amount of reagents used, however, the flotation tests proved it necessary to improve the liberation of the ash from the unburned carbon fraction of the sample in order to increase the flotation efficiency prior to benecifiation. As the impeller speed increased from 1100 rpm to 1500 rpm, the unburned carbon recovery increased. According to the pH value variations, the unburned carbon recovery improved in the acidic pH range with an optimum at about 3.3. The relationship between the residual carbon content of the sink product and the grinding time indicated that the residual carbon contents tend to decrease as the grinding time increases and when the pH value was adjusted to 3.3, the residual carbon content of the sink product decreased to 0.75 wt.% at 1.6 kg/t of the AF 73 addition used and to 0.5 wt.% at 3.2 kg/t for 30 min of the ground sample.

回分式振動流動層による石炭灰中の未燃炭分の低減

This paper is concerned with the removal of unburned carbon from fly-ash with a continuous density distribution by means of a fluidized bed with tapping.It is indicated that tapping the fluidized bed is effective maintaining a good fluidization state of fly-ash and to promote the segregation of unburned carbon. The segregation takes place mainly place due to the apparent density difference between fly-ash with more unburned carbon content and other fly-ash. It is further shown that the segregation process is approximated by the first order rate equation under the condition of optimum fluidization velocity, which is in the range 1 to 4 times the minimum fluidization velocity.