Run Of Mine Coal Research Articles

Application of the Response Surface Methodology to Optimise the Leaching Process and Recovery of Rare Earth Elements from Discard and Run of Mine Coal

The supply shortage of rare earth elements (REEs) for use in numerous high-tech applications has become an incentive for the prospecting of REEs from coal and coal discard. In this study, an optimised leaching process for the recovery of REEs from coal using the Design Expert (DOE) is reported. Response surface methodology (RSM) was used to investigate the effect and to determine the optimal leaching parameters for the two non-calcined coal samples. An optimised REE leaching recovery of 18.95% and 41.35% was obtained for the non-calcined Run-of-Mine (ROM) coal and discard coal, respectively. This optimised recovery was obtained as the HCl concentration increased from 0.5 M to 2 M, leaching temperature increased from 30 °C to 50 °C, whilst the solid:liquid ratio decreased from 40 g/L to 10 g/L. Statistical analysis indicated that the leaching parameters studied were important and controlled the REE leaching recovery model. Optimisation results also indicate that the calcined coals at 700 °C have the highest leaching recovery of 94.73% (ROM) and 98.17% (discard), respectively. Calcination also increased the concentration of REEs in the ROM sample from 225 ppm to 347 ppm and discarded the sample from 245 ppm to 363 ppm at 700 °C. Given the effect of the lixiviants investigated, the leaching efficiency of HClO4 for REE recovery was significantly lower than HCl and HNO3 under optimal leaching conditions. The discard coal used in this study had a significantly higher potential for REE recovery than ROM coal because it had a higher REE abundance and greater recovery.

The use of 1-methyl naphthalene as coal ash removal solvent

Solvent extraction method is one of the methods to reduce ash content in coal to improve the energy efficiency and reduce negative environmental impacts. The use of 1-methyl naphthalene (1-MN) as a solvent in the weight ratio of coal to solvent of 1: 3, 1: 6 and 1: 9 using three coal samples obtained from a coal washing plant, namely ROM (run of mine), DC (dirty coal) and RC (reject coal) was performed. Results show that the ash content of the extracted coals no or significantly low amount (<0.3%) ash contents. The highest extraction yield was obtained at 15.38 % (daf) at DC coal sample and coal to solvent ratio of 1:9, while the lowest at 3.09 % (daf) at ROM coal sample and coal to solvent ratio of 1:3. In addition, the extraction process with a solution of 1-MN also able to reduce moisture content of the coals, as a result the calorific value of the coals were significantly increased.

Evaluation of pneumatic inclined deck separator for high-ash Indian coals

Application of pneumatic separators in coal beneficiation is increasing rapidly over the last decade primarily due to their low capital and operating costs, and waste handling problems associated with traditional wet processing methods. Large amount of shale/rock that is extracted in coal production can be removed prior to transportation at the mine face by using this methodology. Due to the limited washing facilities in India, most of the thermal power plants burn raw coal from run-of-mine (ROM) to generate electricity. This practice causes poor utilization efficiency, high operating and maintenance costs, and high emission rates for the power plants. One potential method that can be utilized is the air-fluidized inclined vibrating deck technology. The technology was demonstrated on a pilot-scale at different coal washeries in India at a feed rate of 5-ton per hour. The pilot-scale evaluation showed that 20 %–25 % high-ash incombustible material can be eliminated from ROM feed with only minor losses in energy content (<10 %) from respective ROM coal. Furthermore, a feasibility analysis showed significant economic gains in terms of transportation cost, improving power-plant efficiency, and reducing emissions rates by using the technology.

Impact of HNO3 Solution Treatment of South Brazil Coal Matrices on Their Chemical Composition and Humic Acids Yield

In this study, changes on the chemical composition and on the humic acids yield of coal matrices promoted by 25% HNO3 treatment were investigated, by means of elemental, thermogravimetric analyses, and Fourier transform infrared spectroscopy (FTIR). The run of mine (ROM) matrix C-MTR (ROM coal) showed the highest C content (41%), highest C/N ratio (76) and lowest ash content (54%) of the studied samples. In contrast, coal tailings presented a higher degree of aromaticity. Treatment with HNO3 solution increased N content, but not that of C. Therefore, the C/N ratio of all samples decreased to values between 11 and 20. The insertion of N occurred in the aromatic structures, while the oxidation occurred in both the aromatic and aliphatic chains. HNO3 treatment increased the humic substances content and the largest increase being observed in the coal tailings (16 to 31% increment in comparison to the untreated sample). The generated humic acids showed in general a chemical composition similar to that of soil humic acids, but a greater aromaticity degree.

Effect of crushing on near-gravity material distribution in different size fractions of an Indian non-coking coal

remove physical impurities as effectively and economically as possible. The beneficiation process includes various operations on the asmined coal to make it more suitable for enduse application without destroying the physical identity of the coal. There are several coal beneficiation processes, but gravity-based separators remain the most efficient unit operation for removing the undesirable gangue material from run-of-mine coal. These separators exploit the difference in density between coal particles and gangue particles to effect a separation. The feed is introduced into an aqueous suspension of ultrafine magnetite with a particular density. The feed particles with a relative density less than that of the suspension (clean coal) float to the top surface of the suspension, whereas particles denser than the suspension density (gangue material) sink to the bottom. When the difference in density between the particle and the aqueous suspension is large, the separation is easy, but when this difference is less the separation becomes much more difficult since the settling velocity of the particles is very low. This lower settling velocity increases the probability that particles that should report to floats report to sinks, and vice versa, hence increasing the amount of misplaced material. Therefore, the degree of difficulty in beneficiating a typical coal at a particular specific gravity depends on the amount of material occurring within ±0.1 specific gravity range. This is known as ‘neargravity’ material, also termed ‘near-dense’ material, at that particular specific gravity of separation. As coal is heterogeneous in nature, the density of a daughter coal particle depends on the nature of the parent coal particle from which it has been produced and the fracture patterns involved during crushing, as shown in Figure 1. As the fracturing of particulate material is a random process and many factors contribute to the fracturing of any single particle, the result is never exactly predictable. Particles of the same material and similar in size and shape show a wide variation in individual fracture patterns. Therefore, when a bigger heterogeneous particle of particular density is subjected to crushing a broad spectrum of particles of various sizes and densities is produced. Similarly, when run-ofmine coal is crushed, a wide variety of smaller particles are generated, which alters the amount of near-gravity material present in a particular density class and accordingly changes the degree of difficulty in washing. Therefore, it is imperative that the change in mass of the near-gravity material at a particular specific gravity on crushing should be determined accurately. The difficulty in washing a particular coal can be interpreted from the steepness of the ‘characteristic curve’, which is derived from the sink-and-float data (Corriveau and Effect of crushing on near-gravity material distribution in different size fractions of an Indian non-coking coal

Washability Characteristics of Low Volatile Pakistani Coking Coal by Crushing

Through washability study, a couple of parameters were investigated for a low volatile Pakistani Coal (coking). The aim was to find out the effect of the action of reducing material release characteristics for low volatile Pakistani coal. The “Index of washability” (IW) and “Near gravity material Index” (NGMI) were used as parameters to express the ease of washability. Run of Mine coal is crushed to four different sizes as mentioned 80 mm, 30 mm, 18 mm and 11 mm in a pestle and mortar. Calculations of IW show that it is inversely proportional to top size of feed, indicating that washability increases with the decrease of size. From NGMI calculations it was concluded that gravity method is not recommended for separation at this specific gravity range. So study divulges that the critical specific gravity for crushing to 30 mm is 1.67 and for 11 mm is 1.56.

Pilot-Scale Baum Jig Washing for Beneficiation of a High-Ash Indian Noncoking Coal

Coal will continue to play an important role in overall energy scenario in India. Despite its high-ash content, the run-of-mine (ROM) Indian coals are used directly for thermal power generation. There is an urgent need to improve quality of coal by reducing ash so that a consistent supply of quality coal can be supplied to the power plants. Pilot-scale studies were conducted on beneficiation of High Ash Indian Non Coking Coal obtained from the Samleshwari mines using a 20-t/h Baum Jig Washer. The results of the pilot-scale studies revealed that the ROM coal, containing 50% ash content, could be cleaned with the Baum jig providing a clean coal containing 36% ash at a yield of 52%.

Production strategies for coal quality improvement at SLE, Turkey

The Seyitömer Lignite Enterprise of the Turkish National Coal Board (SLE) is one of the largest coal producers in Turkey and produces coal from an open cast mine close to the city of Kütahya. The most significant problem that the enterprise currently faces is the low quality run of mine coal which is mainly sold to the nearby power station. The excavation of the partings in the seam together with coal increases the ash content of the coal produced, which in turn decreases the efficiency of the coal burning process at the power station and results in high penalty costs for the mine.Since the main problems at SLE were caused by the current coal quality, not meeting the standards required by the power plant and the market, and the need for balanced pit development an attempt was made at quality planning to meet the various requirements. Factors related to quality improvement for current and proposed production strategies were determined, according to the customers' quality demands and the saleable coal quality reserves. Afterwards, the necessity and the degree of selectivity for each strategy and determining of an optimum excavation configuration was defined. The result was high selectivity mining at the B3 seam to increase the power plant coal quality up to 1761 kcal kg−1 using a production strategy based on maximum coal supply to the market.

Surface Properties of Coal Fines in Water. II. Isotherms, Electrokinetics and Chainlength Dependence for Cationic Surfactant Adsorption

The adsorption of the cationic surfactants, dodecylpyridinium chloride, tetradecyl-pyridinium bromide and hexadecylpyridinium bromide on run of mine coal at varying pH's has been studied. The effect of these surfactants on the zeta potential as a function of pH was determined. Surfactant adsorption increases in the order C16 > C14 > C12, and generally increases with increasing pH, especially for the longer chainlengths. Microelectrophoretic zeta potential measurements clearly show the effect of surfactant adsorption, and when pH > iep, i.e. when the coal is negatively charged, charge reversal of the coal surface occurs in all cases. It is concluded that adsorption of cationic surfactants involves both electrostatic (headgroup) and hydro-phobic (alkyl chain) interactions with the coal surface.

Heavy media separation of SRC-II feedstocks: 2. Effect on liquefaction yields

The objective of this investigation was to assess the potential effects of coal preparation on SRC-II liquefaction yields. Liquefaction yields were estimated from coal properties at standard SRC-II conditions using mathematical models. For Powhatan and Ireland Mine coals, the yields were most sensitive to changes in the total sulphur level and were not significantly affected by the small changes in total reactive macerals, H/C ratio or volatile matter. The fractions from both coals were ranked in order of decreasing liquid yields (or increasing organic vacuum bottoms yields) on a dry, ash-free basis as follows: middling > cleaned > ROM (run-of-mine) > deep cleaned. On a dry basis, all the washed fractions from each coal were superior to the ROM coal, giving higher liquid yields.

Kinetics of coal gasification

This work reports on a kinetic study on the gasification of Brazilian mineral coal with steam using a thermobalance. The coal is a high ash content (>50 wt %) subbituminous, run of mine coal (Charqueadas). Isothermal runs were made at temperatures between 800 and 1000/degree/C and at atmospheric pressure, using -14 +20 mesh Tyler size particles. The coal was devolatilized before the gasification. Initially, the influence of the particle size of coal and the flow of steam were studied in order to determine if diffusive effects are important. For certain conditions these effects are negligible and chemical reaction is the rate controlling step. The experimental results are well described by the unreacted core model above 850/degree/C and by the continuous model below this temperature. The gaseous products were determined at different times and temperatures and contained essentially H/sub 2/, CO, and CO/sub 2/. Comparison of the results with other data published shows that this coal is highly reactive. 15 refs.