Coal Agglomeration Research Articles

Agglomeration of coal and polyethylene mixtures during fixed-bed co-gasification

The article presents the results of experimental studies on the gasification of mixtures of brown coal and polyethylene (up to 20 wt% fraction) in a laboratory reactor. The work aims to study the agglomeration process during the heating and oxidation of the mixtures. The measurement results (gas composition, pressure drop) provide indirect information on the dynamics of thermal decomposition and structural changes in the fuel bed. We have shown that the interaction between polyethylene and a coal surface leads to the formation of dense agglomerates, in which the molten polymer acts as a binder. Clinkers form as a result of interfacial interactions between components and filtration flow rearranging. The hydrogen/carbon ratio in the solid residue of coal-polyethylene co-gasification increases from 0.07–0.2 to 1.11, indicating the formation of stable hydrocarbon compounds on the carbon surface. The conducted research makes it possible to identify possible interactions between chemical reactions and transfer processes that lead to agglomeration in mixtures of coal with polyethylene.

The use of petroleum derivative mixtures as bridging liquid for oil agglomeration of lignite coal

ABSTRACT The aim of the present study was to investigate the use of mixtures of petroleum derivatives as bridging liquids for oil agglomeration of Sivas/Gemerek lignite coal. The study investigated the effect of various physical process parameters, such as type and dosage of bridging liquid, pulp pH, pulp density, agglomeration time, and coal particle size. Oil agglomeration experiments were evaluated along with yield, organic matter recovery and ash rejection values. The optimum conditions for agglomeration were found as follows: adding engine oil (0w-30) as a bridging liquid at a dosage of 30%, maintaining a pulp pH of 2, using a pulp density of 3.6% w/w, agglomerating for 25 minutes, and using coal particles with a size of −500 µm. Under these optimum oil agglomeration conditions, a yield of 85.4%, an organic matter recovery of 94.1% and an ash rejection of 51.6% were obtained. Under the optimum oil agglomeration conditions achieved, the ash content of the Sivas/Gemerek lignite coal was reduced from 19.1% to 15.5% level.

Flotation and oil agglomeration of high ash LVMC coal after deshaling by jigging: a comparative study using different collectors

ABSTRACT LVMC coal with an ash content of 38.70% was initially crushed to −4.0 to +0.50 mm and deshaled using a laboratory model Batac Jig. The resulting concentrate was further size reduced to −0.50 mm and combined with the original fines obtained during crushing. Froth flotation (of −0.50 mm size) and oil agglomeration (of −0.075 mm size) tests conducted using different collectors at varying dosages revealed that the combination of jigging and froth flotation processes can effectively reduce the ash content down to 26.29%. At this stated ash, an acceptable yield of 54.67% was obtained with the highest Separation Efficiency value of 18.20 when the Mahua oil collector was used. Kinetic studies of batch flotation indicated that both ash and non-ash components of the coal reported to concentrate at the same rates, demonstrated by the relative ratios of rate constants ( K N A K A ) , which was equal to 1.0404. It is concluded in the paper that the collector mahua oil outperformed in both the flotation and oil agglomeration processes. The uniqueness of the paper is the approach of beneficiating the newly graded high-high, high-NGM Indian coal using cost-effective bio-degradable oils after deshaling in a Jig. The characteristic size distribution curve plotted for the agglomerates is defined mathematically.

ENRICHMENT OF SİVAS/GEMEREK LIGNITE COAL BY OIL AGGLOMERATION USING DIFFERENT VEGETABLE OILS

The aim of this study was to investigate the use of various vegetable oils (almond oil, hazelnut oil, poppy oil, soybean (soya) oil, sunflower oil) for Sivas/Gemerek (in Turkey) lignite coal by oil agglomeration. The study examined the effect of bridging liquid type and dosage on oil agglomeration. Vegetable oil dosages of 2%, 5%, 10% and 20% were investigated in oil agglomeration experiments. The agglomeration of lignite coal with these bridging liquids was evaluated based on yield, combustible recovery and ash rejection. The agglomeration performances of these vegetable oils were compared. The highest ash rejection (70.30%) was observed by using soybean (soya) at 20% of the bridging liquid dosage. The yield and combustible recovery of lignite coal were achieved 36.46% yield and 38.05% combustible recovery in this soybean (soya) oil dosage, respectively. The lignite coal ash content was reduced from 19.08% to 15.54% under these optimum conditions.

Effect of pectin-modified dust suppressant with different methoxy levels on wetting and agglomeration of coal: Experimental and theoretical discussion

Low methoxy level pectin (LM-PC) and high methoxy level pectin (HM-PC) were utilized as materials to produce environmentally friendly dust suppressants, and the impact of pectin modification with different methoxy levels on wetting and agglomeration of coal was investigated. The results of contact angle and settling experiments reveal that the low methoxy level pectin-modified dust suppressant (LAT) can effectively wet coal, and the optimum modification conditions are determined. FTIR spectra of coal samples treated with LAT and high methoxy level pectin-modified dust suppressant (HAT) demonstrate that the absorption peak area ratios of hydrophilic functional groups increase by 4.00 % and 2.61 % compared to the original coal. XPS spectra indicate that the increases in carboxyl and hydroxyl functional groups are the reason for the improvement of wettability in bituminous coal. Compared to the coal samples treated with HAT, the increase of hydrophilic functional groups is higher in LAT treated coal samples. Through the dust suppression performance characterization experiments, it is concluded that LAT is more effective than HAT in reducing coal dust. The mechanism of dust suppressants on the wetting properties of coal was revealed at the molecular level. Experimental and mechanistic analyses show that LAT can effectively wet and agglomerate coal dust while remaining environmentally friendly and economical.

Improvement of lignite oil agglomeration by ultrasound process using waste engine oil

In the present study, it was aimed to clean fine coal with waste engine oil using the ultrasound process. The influence of ultrasound on the oil agglomeration of coal was determined using ultrasound at the pretreatment stage and at the agglomeration stage. In this context, the use of ultrasound at the pretreatment stage improved the oil agglomeration of coal, but the use of ultrasound at the agglomeration stage reduced the recovery of combustible matter. Also, the power of ultrasound and the time of treatment affected the success of agglomeration, and the optimal values were achieved at a power of 30 W of ultrasound and a treatment time of 3 min. In addition, the best ash content and combustible matter recovery values were obtained at the oil dosage value of 3 mL, but higher oil dosages adversely affected the success of agglomeration. Under optimal conditions, coal with an ash content of 15.02% was obtained with an efficiency of 61.29% in conventional experiments, while coal with an ash content of 9.65% with ultrasound pretreatment was obtained with an efficiency of 71.04%. These results show that ultrasound pretreatment is an effective method for the enrichment of fine particle coal.

Study of the Fluidized Separation Process of Irregular Coarse-Grained Pulverized Coal Agglomerates Based on Modified Computational Fluid Dynamics─Population Balance Method

In this work, the agglomeration, fragmentation, and separation process of coarse-grained pulverized coal agglomerates (CGPCA) obtained from a power plant were achieved using gas–solid fluidized bed sorting and analyzed through a combination of numerical simulations and actual experiments with CGPCA. To study the polydispersity and irregularity of CGPCA, the CGPCA surface fractal dimension was calculated using fractal dimension combined with scanning electron microscopy. The two-section fractal dimension of the particle size distribution was obtained by fitting the logarithmic particle size distribution of CGPCA. On the basis of the obtained data, the polydisperse particle drag force model, the agglomeration kernel function, and the breakage kernel function were modified. Thus, an irregular polydisperse gas–solid two-phase Eulerian–Eulerian model was constructed to simulate the sorting process of CGPCA in the fluidized bed. The results of the numerical simulation investigation were compared with the experimental results and showed that the simulation data, which considered the two section fractal dimension, was in better agreement with the experimental results. The cumulative logarithmic distribution of CGPCA’s size was segmented and fitted. The values of the two section fractals of the agglomerates were determined as D = 1.014 and D = 2.401, respectively. Analysis revealed that the optimal separation efficiency working condition in the simulation process, providing the highest separation efficiency of 54.7%, was generated at air velocity of 1.21 m/s.

Study on the Mechanism of Fiber Fracturing Fluid Controlling Pulverized Coal Transportation

In view of the problems associated with coal powder production in the development of Coalbed Methane (CBM), a fiber fracturing fluid technology is proposed to control pulverized coal production. Based on a force analysis of coal powder in the fracture and the microstructure of fiber-proppant, a critical intercepted particle size model of coal powder is established. This model is primarily related to fiber properties, proppant particle size and flow rate. To verify this, an FCES-100 device (Nantong Yichuang Experimental Instrument Co., Ltd., Nantong, China) was used to study the influence of fibers on the transportation of pulverized coal in the proppant pack. Five groups of comparative experiments were set up using no fiber, 0.25 g undegraded fiber, 0.25 g degradable fiber, 0.5 g undegraded fiber and 0.5 g degraded fiber, with the flow rate and closure pressures controlled, and, finally, particle size analysis of the discharged pulverized coal was performed using a laser particle size analyzer. The experimental results have shown that the space network structure formed by fiber-proppant can effectively intercept coal powder, reduce the coal powder migration and agglomeration, and eventually improve the fracture conductivity. The results further indicate that, with the increase of the flow rate, the coal particle size shows an increasing trend. The comparison between the particle size of the pulverized coal and the model calculation results demonstrate that the average error is 14.3% and the maximum error is 21.4%. Fiber fracturing fluid technology provides new directions for pulverized coal treatment.

Demineralization of high ash coal fines of Indian origin using Mahua oil

The cost of oil is perhaps the biggest prohibitive aspect of the oil agglomeration process. Furthermore, the high ash low grade coals of India are more difficult to demineralize owing to their unfavourable hydrophilic surface chemistry. The objective of our present study is to use an indigenous and underutilized oil derived from Mahua seeds as a potential bridging liquid for oil agglomeration of low grade coal from Kaniha (Odisha, India) with 35% ash. Based on experimental results, Mahua oil demonstrably proved efficient in demineralization by 45–50% at lower oil concentrations (10–15 wt%), devoid of surfactants. Wet grinding of the coal using a vibratory cup mill was an essential pre-treatment step. A detailed investigation of all the crucial process parameters was performed through variation of pH, oil dosages, solid to liquid ratio and agitation conditions. The results obtained were further validated by detailed characterization of both raw and clean coal using zeta potential, FTIR, SEM studies and petrography. FTIR and petrographic studies validated the inherent and surface hydrophilicity of Kaniha coal. Zeta potential studies clearly showed an increase in surface potential around neutral pΗ which was found to be optimum for oil agglomeration. SEM results conclusively supported the formation of porous large size agglomerates. To our knowledge, ours is the first thorough examination of agglomeration potential of Mahua oil, which is an industrially underutilized product, thus supporting the aim of waste utilization and cleaner fuel production. • Crude Mahua oil as bridging liquid for oil agglomeration of high ash low grade Indian coal (35% ash) has been investigated. • Lower dosage (15 wt%) of oil under neutral conditions gave satisfactory results. • Wet grinding in a vibratory cup mill has been implicated to be a crucial pre-treatment step. • Demineralization by 45–50% was observed. • No pre-conditioning step of surfactant was included.

Interactions between Kaolinite, Organic Matter, and Potassium Compounds at Elevated Temperatures during Pyrolysis of Caking Coal and Its Density-Separated Fractions

Large coal agglomerates (cakes), which form in slow heating fixed-bed commercial gasifiers, result in low carbon efficiency and carbon loss in the ash assemblage. In an earlier study, laboratory-sc...

Upgrading of qualitative characteristics of Yakutia brown coals

In Yakutia the fuel-and-energy balance involves low-grade brown coals originated from Kangalas, Kirov and Kempendyay deposits. The techniques to improve the efficiency of utilization and conservation of these coals involve classification of coals and burning of coarse-size products, enrichment, and briquetting of fine coal products. The last technique permits to upgrade the poor-grade coals of low demand and to produce the full-value fuel coal, convenient for transportation, long storage and effective combustion. The experimental results are given on the agglomeration of Kirov brown coal by briquetting with the introduction of polyethylene crumbs into the briquetting blend. This addition promotes 20 % increase in combustion heat as compared to this parameter for the original coal. The researchers propose the technological scheme for classification, preparation, follow-on briquetting of brown coals. The urgency of a local classification-and-briquetting plant is pointed out.

Efficient separation of fine coal assisted by surface nanobubbles

The separation performance of fine particles by flotation is significantly sensitive to particle size, which poses a limit to application of flotation in the separation of fine particles. In the present work an effective method that employs nanobubbles was investigated for the separation of fine coal. Nanobubbles were produced with the method of temperature change. Applying a series of techniques including atomic force microscopy (AFM), rheological measurement, the visualization of particle-bubble interaction and flotation test, it was found that surface nanobubbles are present on highly oriented pyrolytic graphite (HOPG) surface. Coal agglomeration occurred in the presence of nanobubbles, which was indicated by the shear thinning of coal slurry. Furthermore in an adhesion test, more coal particles attached to a bubble in the presence of nanobubbles, which suggested a positive effect of nanobubbles on the particle-bubble interaction. Thus, it could be concluded that, nanobubbles are responsible for the improved flotation performance of coal particles.

Insight into the effects of additive water on caking and coking behaviors of coal blends with low-rank coal

Additive water is usually needed to preserve 9–11% moisture content of blended coal in the stamp-charging coking process, which in fact is unfavorable for coking property. An insight into the improvement of coking property of coal blends with much low-rank coal (long flame coal SFC, lignite HLH) by regulating additive water was proposed in terms of its effects on the metaplast fluidity and the particle agglomeration behavior. The results indicate that the cohesiveness of gas coals (GC) can be properly enhanced by adding water. The restrictions on the condensation of aromatic structures and the break-up of –CH2– structure and the development of the polyhydroxy groups in aromatic structures are favorable to increase the fluidity of metaplast after adding water, as demonstrated by the optical texture and FTIR analysis of the semicoke (450 °C). The great difference in the hydrophilic properties for various rank coals leads to the particle agglomeration of gas coal and fat coal (GC and FC), which makes them difficult to mix uniformly with SFC after adding water, thus reduces the coking property. A reasonable approach of adding water suggests that H2O and SFC should be well mixed prior to blending with caking coals, which can lead to a uniform particle distribution and a better coking property. This approach promotes the direct and efficient utilization of low-rank coal (especially lignite) by the blending coking with no or less drying and dewatering processes.

Comprehensive coal quality index for evaluation of coal agglomeration characteristics

A comprehensive analysis of coal quality factors affecting coal agglomeration characteristics was carried out. The influence weight of seven main coal quality indices on agglomeration was calculated by the entropy method. Furthermore, a reliable and comprehensive coal quality index was obtained to evaluate the characteristics of coal agglomeration by the agglomeration experiment results. The proximate analysis, ultimate analysis, and petrographic analysis results were applied for the analysis of organic constituents. The XRF and ash fusion temperatures were applied for the analysis of inorganic constituents. Results show that there is an absolute positive correlation between the C/H, FC/V and the characteristics of coal agglomeration. Both of the vitrinite content and the average reflectivity of the vitrinite have a positive effect on the coking ability of coal. Alkali oxides not only have a low melting point but also can react with Si and Al to form low melting point eutectics. Both of these characteristics result in coal ash slagging. The entropy method was adopted to analyze the effect weight of C/H, FC/V, vitrinite content Vi, vitrinite average reflectivity Rave, ash deformation temperature (DT), Base/Acid ratio (B/A) and Silicon ratio (G) on the agglomeration characteristics of coal. The weights are 11%, 10%, 26%, 12%, 9%, 14% and 18%, respectively. Among them, vitrinite content had the largest effect, and DT had the least effect. In addition, an empirical index of coal agglomeration characteristics is proposed, and the discriminant limits are provided. The results are helpful to the evaluation of coal agglomeration, and useful to the safe and efficient operation of boilers.

Effect of stirring time on oil agglomeration of fine coal

Effect of stirring time on oil agglomeration of fine coal

The agglomeration of coal fines using wet microalgae biomass

South African coal generally contains a high percentage of non-carbon mineral matter, which necessitates processing to remove the bulk of the non-carbon material. Such processing results in the formation of some 60 million tons of discard coal and between four and eight million tons of very fine, unusable coal, called ultra-fines, each year. The objective of this study was to investigate factors that impact on the agglomeration of fine coal of <150 mm when using microalgae biomass as the sole binder. Mixtures of coal and wet microalgae biomass were prepared and pelletised. The proximate properties of the mixtures and coal were determined and the physical properties of the pellets measured, such as compression strength, water resistance and impact resistance. The results showed that pelletisation of Coalgae® is a promising technology for the recovery of coal fines. Moisture content, pressure and holding time influence the quality of the pellets. Compression resistance testing indicated that pellets made from the coal80%-algae20% (by weight) mixture were stronger than those made from the coal90%-algae10% (by weight) mixture. Pellets made from samples with ± 17% moisture content exhibited the strongest resistance, one of 1.8 kg/mm2 for the coal80%-algae20% mixture that was centrifuged after 24 hours. The water resistance index for all the pellets was lower than the recommended 95%, which was considered to put emphasis on handling, transportation and storage of the pellets.

Effect of a Dispersant Agent in Fine Coal Recovery from Washery Tailings by Oil Agglomeration (Preliminary Study)

Among the fine coal cleaning methods, the oil agglomeration process has important advantages such as high process recovery, more clean product, simple dewatering stage. Several coal agglomeration studies have been undertaken recently and effects of different variables on the process performance have been investigated. However, unlike flotation studies, most of the previous agglomeration studies have not used dispersing agents to minimize slime coating effects of clays. In this study, agglomeration process was applied for recovery of fine coals from coal washery tailings containing remarkable amount of fine coal. Negative effect of fine clays during recovery was tried to be eliminated by using dispersing agent instead of de-sliming. Although ash reductions over 90 % were achieved, performance remained below expectations in terms of combustible matter recovery. However, this study is a preliminary one. It is considered that more satisfied results will be obtained in the next studies by changing the variables such as solid ratio, oil dosage, dispersant type and dosage.

Influence of briquetting and coking parameters on the lump coke production using non-caking coals

In terms of transforming the energetic usage to the material usage of low-rank coals, the production of lump coke is a promising perspective. Therefore, two essential steps are necessary: Firstly, the processing and agglomeration of the non-caking coal is highly important, since they do not offer any baking capacity and thus the reachable quality of the coke is mainly set by the briquette quality. Secondly, to obtain high quality cokes the briquettes need to be coked using a well-adapted heating regime to ensure the gentle degassing of volatile matter with a minimum weakening of the briquette structure. The brown coal high temperature technology (BHT technology) developed in 1952 by Rammler and Bilkenroth was a milestone in coal conversion for brown coal but the coke strength was limited at that time. In current systematic studies, the lump coke quality of Lusatian brown coal and Indonesian brown coal was investigated varying the processing, briquetting and heating regime in laboratory scale. Those investigations should lead to a new processing and agglomeration technology to create lump coke from non-caking coals. The experiments varying the processing parameters of the coal showed that the briquetting of pre-granulated coal or pellets from a modified flat die press achieve the highest increase in briquette and coke quality. In the second step, the heating regime during pyrolysis was investigated. The results show, that the highest coke quality may be achieved using the Vollmaier regime. However, a single-stage heating regime with a heating rate of 2.85Kmin−1 shows promising results as well.

Properties of binderless coal slime briquette via hydrothermal hot pressing dewatering

ABSTRACTDewatering and binderless briquetting of Liulin coal slime by hydrothermal hot pressing (HHP) method were studied under a wide range of process conditions. Fourier transform infrared spectroscopy and XRD were used for characterization. Results indicated that the optimal conditions were a pressure at 4.2 Mpa, a temperature of 150℃, and additive NaOH at 3.0%. The increase of temperature caused the loss of absorbed water in clay minerals and also some organic species having functional groups, such as -CH3 and -CH2. The alkalinity caused the loss of oxygen functional groups and the formation of hydroxysodalite, which reduced the water storage capacity and promoted coal particles agglomeration.

Agglomeration of Makarwal coal using soybean oil as agglomerant

ABSTRACTThe study was carried out for beneficiation of Makarwal coal using soybean oil as agglomerant. The effect of six parameters – pH, mesh size of coal particles, slurry ratio, stirring speed, soybean oil concentration, and time of agglomeration – was investigated to reduce ash and sulfur from Makarwal coal and to enhance the gross calorific value. In the cleaned product obtained after the agglomeration process, the gross calorific value was increased from 4900 to 7115 Kcal/kg. The ash of agglomerates was reduced from 30% to 7.5% and sulfur was reduced from 5.4% to 2.0% The optimum operating conditions were concentration of soybean oil 10 mL, pH 9, stirring speed 2800 rpm, mesh size 200, coal to water ratio of 15:450 (W/V), and time of agglomeration 20 min. Significant reduction in ash and sulfur showed the effectiveness for agglomeration of Makarwal coal using soybean oil as the agglomerant. The final product thus obtained may be used efficiently in various energy recovery schemes.