Influence of oxidation regulation on flotation desulfurization of fine coking coal

To understand the distribution regularity of sulfur in coal formed during different geologic periods and their related controlling factors, we obtained statistics on the sulfur content in the coal samples from different regions of the Guangxi Province. Based on the results, we drew the following conclusions. First, the contents of the sulfur forms vary significantly in the coal samples. The sulfide and organic sulfur content account for a relatively high proportion of the total sulfur content while the sulfate sulfur content is relatively low (i.e., 1.29–15.72%, average = 4.83%). Between these factors, the sulfide sulfur content in early Carboniferous coal is slightly higher than the organic sulfur content, while the organic sulfur content in late Permian, Early Jurassic, and Tertiary coal is higher than the sulfide sulfur content, represented by Heshan coal. Second, coals formed in early Carboniferous, late Permian, and Early Jurassic mainly contain high-sulfur coals. In contrast, Neogene coals, with relatively poor sulfur content, are the major source of low-sulfur coals in the Guangxi Province. In this study, the sulfur content in coal formed in early Carboniferous and late Permian is ≥ 4%; thus, this coal belongs to the super-high organic sulfur (SHOS). Finally, we discuss the spatial distribution characteristics of the sulfur content in coals formed during various geologic periods and their controlling factors. The results indicate that the content and form depend on the paleogeographic conditions during the geologic period of formation.

Fine coal desulfurization and modeling based on high-gradient magnetic separation by microwave energy

The Mallawa Coal Formation in general, has a high sulfur content even though the calorific value is quite high. Deposition environment will affect the sulfur content in coal. This study aims to determine the relationship of sulfur content to the percentage of pyrite mineral content in coal by microscopy. The research method used is field data collection, each using the channel sampling method (ply by ply) in Pujananting Barru Regency and Massenrengpulu Bone regency. Then a proximate and petrographic analysis was carried out to obtain sulfur content, and the percentage of pyrite in coal. The analysis shows that coal in the Pujananting area shows no relationship correlation between total sulfur content in coal and the percentage of pyrite minerals, so it can be concluded that sulfur in Pujananting coal is organic sulfur, which is formed together with the formation of coal starting during the peat process. While Massenrengpulu coal shows a correlation and relationship between the increase in sulfur content and the increase in the percentage of pyrite minerals, it can be concluded that the sulfur content in Massenrengpulu coal is derived from pyritic sulfur, which is strongly influenced by the depositional environment where the coal is formed.

New flotation flowsheet for recovering combustible matter from fine waste coking coal

A novel high-sulfur fine coal clean desulfurization pretreatment：Microwave magnetic separation, high-gradient effect and magnetic strengthen

High-ash Indian coals are primarily used as thermal coal in power plants and industries. Due to the presence of sulfur in thermal coal, flue gas is a major environmental concern. Conventional methods (Ultimate Analysis of Coal) for sulfur content estimation are time-consuming, relatively costly, and destructive. In this study, Fourier-transform infrared (FTIR) spectroscopy has emerged as a promising alternative method for the rapid and nondestructive analysis of the sulfur content in coal. In the present study, the actual sulfur content in the coal samples was determined using Ultimate Analysis (CHNS analyzer). In contrast, mid-infrared FTIR spectroscopic data (4000–400 cm−1) were used to analyze the functional groups related to sulfur or its compounds in the coal samples to predict the sulfur content. A comparison of sulfur estimated using a CHNS analyzer and predicted using mid-infrared spectroscopy (FTIR) data shows that it can accurately predict sulfur content in high-ash Indian coals using the piecewise linear regression method (Quasi-Newton, QN). The proposed FTIR-based sulfur prediction model showed a coefficient of determination (R2) of up to 0.93, where the total no. of samples (Coal + KBr pellets, n) was 126 (using 17:1 split, K-fold cross validation). The root-mean-square error (RMSE, wt.%) is 0.0035, mean bias error (MBE, wt.%) is −0.0003, MBE (%) is 3.31% and mean absolute error (MAE, wt.%) is 0.0020. The two-tailed t-test and F-test for mean and variance indicated no significant difference between the pair of values of observed sulfur (SCHNS, wt.%) using CHNS data and the model predicted sulfur (SFTIR, wt.%) using FTIR data. The prediction model using mid-infrared FTIR spectroscopy data and the Quasi-Newton method with a breakpoint and loss function performs well for coal samples from the Johilla Coalfield, Umaria. Thus, it can be a valuable tool for analyzing sulfur in other ash-rich coals from various basins worldwide.

Multi-gravity separator (MGS) is a centrifugal gravity separator deployed for beneficiation of fine particles with relatively low concentration. It is for the first time that a statistical tool was engaged to evaluate effects of the most influencing process variables and their actual impact upon the performance of MGS with respect to its potential to clean the difficult-to-wash low volatile coking (LVC) coal fines. Characteristics of LVC coal sample were analyzed and discussed in terms of physical properties, petrographic composition, washability, XRD and SEM analysis. Three different feed sizes such as – 500 μm, – 250 μm and – 150 μm were used for assessing the separation mechanism and efficacy of MGS along with three different process variables such as drum speed, shaking amplitude and wash water rate to study and ascertain the most efficient experimental design for obtaining optimal result. Results revealed that drum speed and feed size turned out to be most significant parameters for reduction of ash concentration. In design of experiments, clean coal ash, combustible recovery and separation efficiency were considered as response functions. Material balance for MGS unraveled that about 74% clean coal produced with 10% ash reduction from the feed ash of 32.8% could be achieved in single stage, in optimized process conditions.

98/00052 Coal pond fines cleaning with classifying cyclones, spirals, and column flotation

Fine coal dry separation technology has been one of the international research hotspots in the field of coal preparation. This article proposes the shallow bed dense-phase gas–solid fluidized bed separation technology to remove gangue from the high ash fine coal. According to the criterion of center pressure drop, the CP value can be finally reduced by reducing the bed height, H, to decrease the bed pressure drop, ΔPB, under the condition of a fixed gas distributor pressure drop, ΔPD. A fluidized bed of uniform and stable density was formed. The medium of 33% fine particles showed a better performance in −6+3 mm, −3+2 mm, and −2+1 mm fine coal separation than the medium of different fine particles content by ash segregation. A 100 mm bed height with a medium of 33% fine particles was selected to separate −6+3 mm fine coal. The ash content of cleaned coal reached 9.66% under the optimized conditions, whereas the clean coal yield reached more than 77.75%. For −3+2 mm fine coal, the cleaned coal yield was 82.59%, the ash content of clean coal was 10.93%, and the deash rate could reach 51.96%. The shallow bed dense-phase gas–solid fluidized bed exhibited poor liquidity and high viscosity under conditions of low gas velocities. The shallow bed dense-phase gas–solid fluidized bed (100 mm bed height) with medium containing 33% fine particles can separate the −6+2 mm fine coal.

The paper deals with the problem of reliable definition of heating value, volatile yield and sulfur content in coal organic matter and develops the methods of calculation evaluation of these parameters for coals with real ash content. The amendments due to mineral matter thermal decomposition are accounted. 8 power coals of Donetsk and Lvov-Volyn basins are studied having volatile yield from1 to 40% in frameworks of ash content from 10 to 40%. Calculations based on parameters defined more precisely differ from laboratory results not more than allowed laboratory test error value

Effects of microwave/HAc–H2O2 desulfurization on properties of Gedui high-sulfur coal

Coking coal with generally 11% or lower ash content is termed as metallurgical coal and is used in the steel industry after the coking process. In Turkey, generally spirals and flotation machines are used for the production of metallurgical coal from high-ash fine coals. According to plant data, these devices are capable of producing clean coal with an ash content of 7%–15% from raw coal with 40%–60% ash content. This study aimed to produce metallurgical coal from high-ash coal using a modified water-only cyclone as this method is simple and easy to control. Firstly, the conventional water-only cyclone was modified, then some important operating parameters such as cyclone inclination, inlet pressure, and solids concentration were optimized. Following the optimization procedure, it was found that clean coal of metallurgical quality with 11% or lower ash content can be produced using a modified water-only cyclone.

Fine coal circuitry considerations in treatment of soft coal with difficult washabilities

Several tromising methods for the desulfurization and recovery of fine coal were subjected to further improvement and development. The methods include froth flotation, selective oil agglomeration, pelletization, and a chemical desulfurization process based on leaching coal with a hot, dilute solution of sodium carbonate containing dissolved oxygen under pressure (oxydesulfurization.) Numerous experiments with chemical leaching in an autoclave showed the effect of leaching time, oxygen partial pressure, temperature, and concentration of alkali on the reduction of sulfur in coal. Increased oxygen partial pressure and leaching time improved the removal of sulfur. An optimum temperature range was observed for maximum sulfur reduction. Coal-derived pyrite was leached in a tubular, flow-through reactor. The conversion of sulfur as a function of the length of the packed bed was studied. Chemical treatments of the surface of coal and pyrite were studied to effect a better separation by froth flotation and oil agglomeration.Treatment of acid-cleaned pyrite by an aerated alkaline solution decreased its floatability, whereas the floatability of coal was unaffected. Oil agglomeration was also effective in the reduction of sulfur content in coal when a mixture of No. 200 LLS and No. 6 fuel oils was used after a pretreatment with a hot, aeratedmore » solution of dilute sodium carbonate. The construction of a bench-scale flow system for demonstrating various methods of cleaning and recovering fine-size coal was continued and is nearing completion. The determination of sulfur in coal by the ASTM procedure was examined to assess the effect of the maceral type and coal rank on the dissolution of pyrite by nitric acid. The study was based on data obtained by scanning electron microscopy and energy-dispersive x-ray analysis.« less

India is having limited resources of coking coal, an essential input for production of iron and steel especially through blast furnace route. The coking coal sources are presently from the lower seams of Jharia coalfield, which are high in ash content and low in volatile matter and difficult to wash. This paper describes the washability characteristics of a typical coking coal from the Eastern and Western Jharia coalfields aiming at 18% ash level in the clean coal mainly to meet the specifications of coke making for blast furnace use. Conventional float-and-sink testing was used to determine the yield of clean coal for the coarser fraction, while the coal fines was subjected to flotation. The theoretical recovery of clean coal for the coal tested from Eastern and Western Jharia coalfields are 27% and 19.7% at the stipulated ash content. The coking propensities and the petrographic analysis of the clean coal strongly support its use for coke making either directly or as a blend with imported coal.