Deashing Of Coal Research Articles

Separation performance of –0.5 mm fine coal in enhanced gravity field before and after desliming

ABSTRACT This study focused on the separation performance of a typical high-ash coal with high-mud content in the enhanced gravity field from the viewpoint of desliming. After necessity analysis of desliming, the EGS results of fine coal before and after desliming were examined. The EGS separation indicators and products were analyzed, and its separation characteristics were compared with FF and STS. The EGS results are unsatisfactory without desliming, and the sorting effect of −0.045 mm PS is inferior to other PSs. After desliming, the EGS performance of fine coal has been improved obviously. The optimal η a of 97.93%, η t of 85.99%, η c of 90.50%, and η d of 34.67% can be obtained through adjusting RF and RWP. In terms of deashing effect, FF > EGS > STS, but EGS can obtain the lowest clean coal ash of 3.02%, which reflects its advantages of preparing ultra-low ash coal. In terms of desulfurization effect, EGS > STS > FF. EGS is a clean and efficient method on fine coal deashing and desulfurization, and pre-desliming can significantly improve its separation performance. Pre-desliming EGS technology provides a new way for the sorting of fine coal with high-mud content.

A Study on Chemical Deashing of Coal from Bulupodo Area Sinjai Regency of South Sulawesi Province Using Hydrogen Peroxide

Bulupodo coal has a fairly high ash content and low total sulphur. The main objective of this research is to reduce the ash content in Bulupodo coal. The methods used was chemical washing of coal using hydrogen peroxide (H2O2) with washing variables such as time (30 minutes, 60 minutes, 120 minutes, and 180 minutes), H2O2 concentration (5%, 10%, 15%, and 20%), temperature (45°C, 60°C, and 80°C) and particle sizes (16 mesh, 40 mesh, and 70 mesh). The results of the quality analysis show that Bulupodo coal has a moisture of 6.37%; ash 53.3%; volatile matter 26.79%; fixed carbon 14.45%; and a total sulfur of 0.53%. Hence, mineral matter analysis using microscopic and XRD (X-Ray Diffraction) show that Bulupodo coal contains kaolinite, illite, quartz, and pyrite minerals. As a result washing with the highest reduction time variable of ash content at 180 minutes was 21.63%; the concentration variable of the highest ash content reduction solution was at a concentration of 20% of 14.78%; the temperature variable for the reduction of the highest ash content at 60°C was 13.45%; and the particle size variable for the reduction of the highest ash content was at a particle size of 40 mesh of 7.32%.

Study on deashing and desulphurization of coal with heavy medium in enhanced gravity field

ABSTRACT This study carried out component sulfur composition analysis, electron probe microscopic analysis, and particle size and density composition analysis of coal samples from a coal preparation plant in Liupanshui. The influence of various factors on the indexes of clean coal products under different separation medium conditions by enhanced gravity separation technology, including water medium (WM), magnet powder suspension (MPS), and zinc chloride solution (ZCS), is discussed. The results show that the addition of MPS or ZCS has an obvious improvement on coal deashing and desulfurization compared with the WM separation, especially the separation effect of ZCS, which is better than that of MPS because of better uniformity and stability of ZCS. The addition of MPS or ZCS can help the materials stratify strictly according to the density to enhance the sorting function. The clean coal ash and sulfur content are reduced to 13.24% and 2.51%, while the combustible recovery and desulfurization efficiency are up to 71.46% and 49.27%, respectively, under the optimal condition.

Performance optimization and parametric evaluation of coal deashing and desulfurization in a heavy-medium enhanced gravity field

ABSTRACT High-efficiency deashing and desulfurization of fine coal is an inevitable trend in the comprehensive utilization of coal resources. This work introducing heavy-medium into the enhanced gravity field to examine the effect of each parameter on the performance of fine coal separation. On this basis, the Response Surface Methodology (RSM) was conducted to study the influential significance of parameters, parametric interactions, and performance optimization of fine coal separation in the heavy-medium enhanced gravity field. The feed dosage and heavy-medium density influence the separation indexes obviously by changing the sorting environment, while the rotational frequency and recoil water pressure affect the separation effect apparently by adjusting the force on particles. The performance optimization results showed that the desired separation indexes – ηt of 81.11%, ηa of 80.00%, β of 44.93%, and λ of 44.76% can be obtained under the optimal combination of parameter levels – M of 27.23 g, ρ of 1.4 g/cm3, f of 30 Hz, and P of 0.03 Mpa. The verification experiments were carried out and the results were consistent with the results of performance optimization. The introduction of heavy-medium provides a new efficient way for the deashing and desulfurization of fine-grained high-sulfur coal in the enhanced gravity field.

Role of Magnesium Salts in Coal De-Ashing by Flotation

Abstract The most frequently investigated salts in coal flotation are chlorides. However, seawater contains additional salts such as sulfates. In coal flotation, magnesium chlorides showed the best results in terms of higher yield and lower ash content compared to the other magnesium salts studied. Therefore, two magnesium salts were tested in this investigation, namely magnesium chloride and magnesium sulfate. The effect of the magnesium salts as well as the optimization of coal flotation were investigated by statistical design of experiments in terms of pulp density, particle size, conditioning time and different dosages of MgCl2 and MgSO4. The flotation results obtained by statistical design show that the ash content was lowest at 8.2% when a mixture of 2 kg/t MgSO4 and 2 kg/t MgCl2 has been used, with pulp density 20%, particle size 400 lm and conditioning time 15 min. The particle size plays an important role in reducing the ash content when the conditioning time has been extended and pulp density has been reduced. The strong interaction between the salts hinders the reduction of the ash content to less than 8.2%.

Deashing and desulfurization of subbituminous coal from the East field (Bogovina Basin, Serbia) - insights from chemical leaching

The study is focused on the determination of the most effective chemical leaching process for the simultaneous demineralization/deashing and desulfurization of subbituminous coal from the Bogovina Basin. Coal was treated for 30 min, at different temperatures, using variable concentrations of hydrochloric, nitric, acetic and citric acids; hydrogen peroxide, mixture of hydrogen peroxide and nitric acid (pH 2), as well as by the stepwise leaching process (nitric acid + mixture of hydrogen peroxide and nitric acid, pH 2). The changes in mineral composition, caused by the chemical leaching, are followed using X-ray diffraction, whereas alterations of coal organic matter are tracked by Fourier-transform infrared spectroscopy and the content of fixed carbon. Inorganic acid leaching, regardless of the temperature and acid concentration, enabled the successful deashing of coal, whereas the percent of desulfurization was insufficient. The organic acid leaching was not satisfactory for both, deashing and desulfurization. Leaching by H2O2 and H2O2/HNO3 mixture (pH 2) resulted in moderate desulfurization, but the ash reduction was low. The most suitable method for the simultaneous effective ash (78 wt.%) and the sulfur (66 wt. %) removal from Bogovina coal is the two-step leaching, combining 10 vol. % HNO3 and mixture of 35 vol. % H2O2/10 vol. % HNO3 of pH 2 at 60?C.

The process optimization for separation performance and fluidization stability based on air dense-medium fluidized bed

Dry mineral separation methods are based on the pseudo-fluid properties of two-phase gas-solid fluidization during the air dense medium fluidized bed separation. In this paper, the air dense medium fluidized bed separation method was introduced for coal deashing. In order to better understand the impact of separation performance of air dense medium fluidized bed, the uniform stability of fluidized bed on separation performance the factors (fluidization number (N), height-to-diameter ratio (λ) and feeding volume fraction (γ)) were varied. The process optimization of these three factors was investigated. The results showed that the fluidization number was the main factor reflect on fluidized characteristics. The separation efficiency achieved the optimal value when the feeding volume fraction reached 13%. The segregation stabilized at 0.90–0.95, with the possible deviation ranged from 0.10 to 0.15. Further, the yield of cleaned coal is 78.5–80%, and ash content reduced by 75–78%. The dense medium fluidized bed can achieve efficient deashing of coal. Highlights Factors to influence the uniform stability of fluidization within ADMFB. The Process optimization for separation performance was conducted. Synthesizing the separation test results get formulas about feeding volume fraction y and feed rate q. The yield of the cleaned coal is around 80% while its ash decreased to 10%.

Effect of complexing agents on desulphurization and deashing of coal by H2O2/H2SO4 leaching

The present study was aimed at investigating the effect of the addition of complexing agents on the removal efficiency of sulphur and ash contents during chemical leaching by acidified hydrogen peroxide. Representative coal sample from Lakhra was subjected to chemical leaching under various conditions of the parameters including time (60 and 120 min), temperature (25 and 50°C), complexing agents (citric acid and phosphoric acid) and the concentration of complexing agents (100 and 1000 ppm). The addition of complexing agents, i.e. citric acid and phosphoric acid imparted significant effects on improving the removal efficiency of sulphur and ash contents. Under optimized conditions, it was found out that the addition of citric acid improved the removal efficiency for sulphur from 63.88 to 83.47% and from 33.12 to 66.25% for ash. In case of phosphoric acid, the removal in sulphur and ash contents was increased from 63.77 to 80.77% and from 33.12 to 59.18%, respectively. Apparently, citric acid happened to be the most effective complexing agent, as compared to phosphoric acid. These results warrant subsequent detailed studies for further optimization of the process, including the use of some other complexing agents, as well.

Low Rank Coal Pre-treatment to Increase Its Reactivity Towards Gasification with Biomass

Coal can be used to produce hydrogen through steam gasification process. Indonesia has abundant coal reserves and thus hydrogen production from coal is very attractive. However, steam gasification of coal usually requires high temperature due to its low volatile content. The use of catalyst, such as alkaline and alkaline earth metal (AAEM) may promote the hydrogen production. AAEM metal can be found in biomass and thus co-gasification of coal and biomass may become the attractive solution as the AAEM may volatilize during gasification and catalyze the coal when it attaches to the coal surface. However, the presence of silicate may decrease catalytic activity of the attached AAEM and thus it needs to be removed by deashing process. This research aims to determine the effect of the solution type, solution concentration, reaction temperature, and reaction time of coal deashing. The results showed that deashing process decreased the ash content of coal to some extent proved by the gravimetric analysis result. The decrease of ash content also affected to the surface morphology of the coal as some pores are formed and thus the surface area of coal increased slightly. The increase of surface area allows more AAEM to be attached to the coal surface so that the coal may become more reactive towards steam gasification.

Study of enhanced low-quality coal oxidative desulphurization and deashing by using HNO3 and microwave pretreatment

In this paper, the effect of urea-hydrogen peroxide (UHP) solution on desulphurization and demineralization of coal with high sulphur and high ash by using HNO3 and microwave pretreatment was investigated. The oxidation process is strongly dependent on irradiation power and time for microwave pretreatment, UHP concentration, leaching time and temperature of the UHP solution. X-ray diffraction and Fourier transform infrared technique have been performed for the raw and treated coals. Compared with the UHP alone, successive treatments with HNO3 and microwave pretreatment resulted in the significant removal of total sulphur and mineral matter from the coal. The proposed experimental method has the meaning of practical guide to the desulphurization and deashing of coal by microwave.

Feasibility of using ultrasound-assisted process for sulfur and ash removal from coal

The present work investigates utilization of ultrasound in reagent-based coal de-ashing and de-sulfurization. The coal under study was received from Girald mine, Rajasthan, India. Three different ultrasonic frequencies (25 kHz, Dual (58/192 kHz) and 430 kHz) and three reagents (HCl, HNO 3 and H 2O 2) were used. The study employed a Taguchi fractional-factorial L 27 DOE. Experimental data were used to derive an empirical model for the prediction of total sulfur removal. The model incorporates cavitational intensity, reagent concentration, sonication time, coal particle size and coal concentration as key parameters. Effects of above factors on reagent-based ultrasonic coal-desulfurization are presented here. An optimum set of process parameters are identified and validated. Larger-scale trial with high-ash and high-sulfur coals is strongly recommended.

Removal of Ash from Indian Assam Coking Coal Using Sodium Hydroxide and Acid Solutions

Mineral matter (ash) removal from Assam coking coal by leaching with different concentrations of sodium hydroxide and acid (HCl, H2SO4, HNO3, and HF) solutions has been investigated at a temperature of 75oC. The parameters tested were concentration of NaOH, type of acid, concentration of acids, and number of acid leaching steps. Total ash removed increased with increase of NaOH and acid concentrations up to the range studied. For the same experimental conditions, treatment of caustic leached coal in HCl acid resulted in better demineralization than in H2SO4 or HNO3 acid. In the NaOH-HNO3 leaching method, a higher concentration (> 20%) of HNO3 acid had an adverse effect on the de-ashing of coal. The NaOH-HF leaching process has been found to be the most effective method of coal de-ashing. The two acid treatment steps (HCl-H2SO4 / HCl-HNO3) after caustic leaching are the next most effective methods of coal de-ashing. The removal of mineral matter (including S) from coal is expected to decrease the graphite reactivity and thus the atmospheric pollution (due to the generation of smaller quantities of CO and SO2 gases).

Oil Agglomeration for Recovery of Coal Fines: Effect of Vegetable Oil and Bacterial Pretreatment

In the present study, the technique of oil agglomeration has been explored with the aim of employing the process for recovery of coal fines from washery/coal industry effluents as well as deashing of coal. Both edible and non-edible vegetable oils have been tested for agglomeration of five different types of Indian coals widely used in power and metallurgical sectors. The yield of agglomerates ranged from 40.0 to 87.5% and ash rejections from 13.5 to 62.0% using different coal-oil combinations. Bacterial pretreatment of coal with mixed culture prior to oil agglomeration improved the selectivity of vegetable oils resulting in higher ash rejections (59.0−76.0%). Also, pretreatment of high sulphur coal with Thiobacillus ferrooxidans culture resulted in significant enhancement in pyritic sulphur rejection from 69.0 to 98.5%. Various process parameters have been optimized for vegetable oil agglomeration. Higher rates of biodegradation observed with vegetable oils as compared to that with petroleum fractions further supported their use as environmentally safe agglomerants.

Charcoal deashing by an oil agglomeration process: effect of various operating parameters

This paper describes our attempt to transfer current knowledge on mineral coal deashing by selective oil agglomeration to charcoal. The effects of various operating variables, e.g. particle size, conditioning, oil dose, oil type, amount of volatile matter and time of agglomeration were studied. It was found that a ratio of 0.2% hydrochloric acid (32% concentrated) to charcoal and a 5 min conditioning time are ideal for deashing. Domestic fuel oil and crude palm oil were used as bridging liquids. The results show that by reducing the particle size (8 μm mean diameter), charcoal can be deashed to as low as 0.8% in weight, whilst recovery stay virtually at 100%. The use of charcoal with a high volatile matter content (more than 20%) allows easy deashing even with larger particle sizes (15 μm diameter).

オイルアグロメレーション法による石炭の脱灰の検討 脱灰率に及ぼす分散媒ｐＨの影響

The effect of the pH of the disperse medium on the deashing of coal was investigated in the oil agglomeration process. A coal-water slurry used in the experiment was prepared by suspending ground coal in water as the disperse medium the pH of which was adjusted to 2, 4, 7, 10 and 12. A-class heavy oil was used as the bridging liquid.The zeta potential ζ of the coal particle was negative at any pH condition of the disperse medium and |ζ| became the largest value at pH=12. The dispersion of coal particles in the slurry improved with increase in the value of |ζ|. The deashing efficiency of coal by oil agglomeration increased with the dispersibility of coal particles and attained the highest value at pH=12.

Coal deashing by alkali fusion

Deashing of Akabira coal was studied by NaOH or KOH fusion, followed by successive washing with water and hot water. Ash removal reached approximately 45% at 260 C and 80% at 380 C. Among major ash components, Fe[sub 2]O[sub 3] was least susceptible to removal, while SiO[sub 2] was removed by 55% even at 260 C. Pyridine extract yield reached maximum (56%) at 300 C and decreased at either higher or lower temperatures than 300 C.

Deashing of Coal by Selective Flocculation Using Polyelectrolyte.

疎水化度の異なるアニオン性ポリアクリルアミドを用い, 石炭の選択凝集法による脱灰特性について実験的に検討した.その結果, (1) フロック形成の点から最適な分離特性を得るための撹拌条件が明らかとなった. (2) 石炭と灰分粒子とを分散させるためには, スラリーのpH調整および分散剤添加が不可欠であった. (3) 高分子の疎水性が大きくなるほど炭質分回収率は増大するが, 脱灰率を最大とする最適高分子添加域は狭くなった. (4) 石炭化度の高い石炭ほど高分子の吸着量は多くなり, 回収率も増大した. (5) 脱灰率向上のためには, 炭質分に富む沈澱物中に混入した灰分粒子の洗い出しが有効であった.

炭酸ガス添加による石炭の粉砕・脱灰

炭酸ガス添加による石炭の粉砕・脱灰

アルカリ性水溶液による石炭の脱硫脱灰について （第２報）

アルカリ性水溶液による石炭の脱硫脱灰について （第２報）

オイルアグロメレーション法による石炭の脱灰の検討 脱灰率に及ぼす粉砕石炭粒度の影響

In the oil agglomeration process, the effect of ground coal partile size on the deashing of coal was experimentally investigated by adding various amounts of bridging liquid. Ash particle size was hardly affectedby the grinding of coal. The decreasing size of coal particles could promote the separation of combustibles and ash in coal, but the deashing efficiency is not always increased by oil agglomeration. The deashing efficiency for each coal species attained its highest value at a specific size of ground coal particles. It is considered that the low deashing efficiency of the slurry including fine coal particles was given by the deterioration of the selective agglomeration of combustibles. The deterioration was caused by the formation of coal particle aggregates in the slurry before the addition of the bridging liquid and by the incorporation of a number of high-ash particles into the agglomerates with water.