EVALUATION OF NEW COAL SIZING TECHNOLOGIES TO IMPROVE PLANT PROFITABILITY
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Title
EVALUATION OF NEW COAL SIZING TECHNOLOGIES TO IMPROVE PLANT PROFITABILITY
ICCI Project ID
00-1/4.1A-1
Investigator
Mohanty
Institution
Southern Illinois University
ICCI Abstract
The performance from many Illinois coal preparation plant could be improved by enhancing the performance from the fine coal cleaning circuit. The integration of advanced technologies for achieving high efficient cleaning and dewatering performance in the coal cleaning plants may be a sure way of improving the fine coal circuit performance. However, by simply improving the size classification efficiency also a significant additional benefit can be realized from the existing cleaning technologies being used in the coal preparation plants.
Thus, the main objective of this study was to evaluate state of the art screening and classification technologies to improve fine coal sizing performance. The new technologies studied in this investigation include the Pansep screening technology, Krebs' new design gMax cyclone and the Cyclowash attachment with an industrial size cyclone. The Pansep screen's performance has been evaluated for 100 mesh particle size separation and compared with the performances of sieve bend and 15 inch cyclones operating in an Illinois coal preparation plant. The performances of 6-inch gMax cyclone with and without the Cyclowash attachment and the Pansep screen have been evaluated for 325 mesh size separation and compared with the 6-inch cyclone of conventional design operating in an Illinois coal preparation plant.
Statistically designed experimental programs were pursued for quick identification of the key operating parameters and the subsequent optimization of these operating parameters to achieve target classification performances. In addition, the statistical data analysis also intended to study the operating parameter effects on the various classification performance parameters. This experimental study was conducted at the Illinois Coal Development Park utilizing a Pansep screen having 0.5 m2 of screening surface area, 15 cm (6 inch) diameter g-Max classifying cyclone and a KH-3 Cyclowash. A 25-2 fractional factorial design and two 3-factor Box Behnken designs were conducted for optimizing the Pansep screen performance for 100 mesh and 325 mesh size separations. Similarly a 3-factor Box Behnken design was conducted to optimize the gMax cyclone performance, whereas 5-factor Plackett-Burman design and 4-factor Box Behnken design experimental programs were conducted for identifying and optimizing the key process parameters for the Cyclowash.
The optimized Pansep screen performance was found to be significantly better than the performance of 15-inch cyclone and sieve bend for classifying the minus 1 mm particle size slurry at 100 mesh. The undersize bypass was reduced from nearly 27% with 15-inch cyclone to nearly 2% with the Pansep screen. The corresponding improvement in the sharpness of size separation is indicated by an improvement in the corrected selectivity index and imperfection values from 0.51 and 0.33 to 0.23 and 0.64, respectively. An overall particle size separation efficiency of 57% obtained from the 15-inch Cyclone and 44% obtained from the VariSieve were improved to 98% by the Pansep screen. The improved size separation efficiency was achieved mainly due to the decreased undersize bypass to the overflow stream in comparison to the VariSieve, whereas both decreased undersize bypass and sharper separation caused the efficiency enhancement in comparison to the 15-inch cyclone.
The optimized new design gMax cyclone performance obtained for 325-mesh classification was significantly better than the conventional cyclone design used in the plants. The undersize and oversize bypass amounts were reduced from nearly 27% to 12% and 3% to nil respectively. Both undersize and oversize bypass were completely eliminated by the use of the Cyclowash, while improving the imperfection and selectivity index values from 0.34 and 0.56, respectively, to 0.22 and 0.64, respectively. However, the injection of high amount elutriation water to improve the Cyclowash performance also increased the separation size. The Pansep screen achieved excellent overall size separation efficiency of nearly 99% due to negligible amount of bypass materials and sharper separations.
An economic analysis was conducted to estimate the potential plant profitability achievable due to the integration of Pansep technology in place of 15 inch Cyclones to an Illinois coal preparation plant treating nearly 370 tph of coal in its fine circuit. Due to the inefficiency at the classifying Cyclone, an estimated 59 tph of minus 100 mesh size coal having an ash content of nearly 40% is directly lost to the plant thickener. This fine coal loss can be potentially reduced to 3 tph by using Pansep screens. The resulting increased coal recovery of 56 tph may generate additional annual revenue of $ 6.7 million dollars considering nearly 7000 working hours per year and a selling price of $1.05/mBtu. More than $ 6 million dollars of additional revenue will far offset the increased annual capital and operating cost of $136, 000 incurred due to the installation of Pansep screens in the plant in place of the existing 15-inch cyclones. By replacing the Sieve bends and VariSieves used for desliming the spiral product by the Pansep screens will potentially decrease the ash content of the screen overflow clean coal product. This will not only improve the overall quality of the clean coal from the fine coal circuit, but also aid the dewatering process due the reduced ultrafine ash material content of the dewatering feed slurry.
The 6-inch diameter Cyclone banks used to deslime the minus 100-mesh particle size fraction in the coal preparation plant produce very poor classification performance. Nearly 54% of the undersize materials present in the feed are misplaced to the Cyclone underflow and nearly 18% of the oversize material is lost to the overflow. The presence of extremely high amount of misplaced ultrafine materials having a very high ash content is highly detrimental to the conventional flotation process. In addition, the commercialization of the enhanced gravity separators to effectively clean the 28 x 325 mesh size fraction will warrant a significantly more efficient 325-mesh size classification. The Pansep screen providing nearly 99% overall size separation efficiency may prove to be the technology to solve the ultrafine classification problem. However, further investigation is recommended to improve the throughput capacity of the Pansep screen while maintaining high efficient size classification.
Thus, the main objective of this study was to evaluate state of the art screening and classification technologies to improve fine coal sizing performance. The new technologies studied in this investigation include the Pansep screening technology, Krebs' new design gMax cyclone and the Cyclowash attachment with an industrial size cyclone. The Pansep screen's performance has been evaluated for 100 mesh particle size separation and compared with the performances of sieve bend and 15 inch cyclones operating in an Illinois coal preparation plant. The performances of 6-inch gMax cyclone with and without the Cyclowash attachment and the Pansep screen have been evaluated for 325 mesh size separation and compared with the 6-inch cyclone of conventional design operating in an Illinois coal preparation plant.
Statistically designed experimental programs were pursued for quick identification of the key operating parameters and the subsequent optimization of these operating parameters to achieve target classification performances. In addition, the statistical data analysis also intended to study the operating parameter effects on the various classification performance parameters. This experimental study was conducted at the Illinois Coal Development Park utilizing a Pansep screen having 0.5 m2 of screening surface area, 15 cm (6 inch) diameter g-Max classifying cyclone and a KH-3 Cyclowash. A 25-2 fractional factorial design and two 3-factor Box Behnken designs were conducted for optimizing the Pansep screen performance for 100 mesh and 325 mesh size separations. Similarly a 3-factor Box Behnken design was conducted to optimize the gMax cyclone performance, whereas 5-factor Plackett-Burman design and 4-factor Box Behnken design experimental programs were conducted for identifying and optimizing the key process parameters for the Cyclowash.
The optimized Pansep screen performance was found to be significantly better than the performance of 15-inch cyclone and sieve bend for classifying the minus 1 mm particle size slurry at 100 mesh. The undersize bypass was reduced from nearly 27% with 15-inch cyclone to nearly 2% with the Pansep screen. The corresponding improvement in the sharpness of size separation is indicated by an improvement in the corrected selectivity index and imperfection values from 0.51 and 0.33 to 0.23 and 0.64, respectively. An overall particle size separation efficiency of 57% obtained from the 15-inch Cyclone and 44% obtained from the VariSieve were improved to 98% by the Pansep screen. The improved size separation efficiency was achieved mainly due to the decreased undersize bypass to the overflow stream in comparison to the VariSieve, whereas both decreased undersize bypass and sharper separation caused the efficiency enhancement in comparison to the 15-inch cyclone.
The optimized new design gMax cyclone performance obtained for 325-mesh classification was significantly better than the conventional cyclone design used in the plants. The undersize and oversize bypass amounts were reduced from nearly 27% to 12% and 3% to nil respectively. Both undersize and oversize bypass were completely eliminated by the use of the Cyclowash, while improving the imperfection and selectivity index values from 0.34 and 0.56, respectively, to 0.22 and 0.64, respectively. However, the injection of high amount elutriation water to improve the Cyclowash performance also increased the separation size. The Pansep screen achieved excellent overall size separation efficiency of nearly 99% due to negligible amount of bypass materials and sharper separations.
An economic analysis was conducted to estimate the potential plant profitability achievable due to the integration of Pansep technology in place of 15 inch Cyclones to an Illinois coal preparation plant treating nearly 370 tph of coal in its fine circuit. Due to the inefficiency at the classifying Cyclone, an estimated 59 tph of minus 100 mesh size coal having an ash content of nearly 40% is directly lost to the plant thickener. This fine coal loss can be potentially reduced to 3 tph by using Pansep screens. The resulting increased coal recovery of 56 tph may generate additional annual revenue of $ 6.7 million dollars considering nearly 7000 working hours per year and a selling price of $1.05/mBtu. More than $ 6 million dollars of additional revenue will far offset the increased annual capital and operating cost of $136, 000 incurred due to the installation of Pansep screens in the plant in place of the existing 15-inch cyclones. By replacing the Sieve bends and VariSieves used for desliming the spiral product by the Pansep screens will potentially decrease the ash content of the screen overflow clean coal product. This will not only improve the overall quality of the clean coal from the fine coal circuit, but also aid the dewatering process due the reduced ultrafine ash material content of the dewatering feed slurry.
The 6-inch diameter Cyclone banks used to deslime the minus 100-mesh particle size fraction in the coal preparation plant produce very poor classification performance. Nearly 54% of the undersize materials present in the feed are misplaced to the Cyclone underflow and nearly 18% of the oversize material is lost to the overflow. The presence of extremely high amount of misplaced ultrafine materials having a very high ash content is highly detrimental to the conventional flotation process. In addition, the commercialization of the enhanced gravity separators to effectively clean the 28 x 325 mesh size fraction will warrant a significantly more efficient 325-mesh size classification. The Pansep screen providing nearly 99% overall size separation efficiency may prove to be the technology to solve the ultrafine classification problem. However, further investigation is recommended to improve the throughput capacity of the Pansep screen while maintaining high efficient size classification.
Start Date
11/1/2000
End Date
12/31/2001
Year Funded
2000
Collection
Citation
“EVALUATION OF NEW COAL SIZING TECHNOLOGIES TO IMPROVE PLANT PROFITABILITY,” ICCI Reports, accessed May 20, 2024, https://isgswikis.web.illinois.edu/icci_reports/items/show/28.