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Show ADV ANCED FROTH FLOTATION Column Performance Versus Flotation Conditions Sbakedown Tests. Shakedown testing was done initially to detennine general operating parameters. The following trends were observed during these tests: • Effect or Feed Rate - Increasing the feed rate from 150 - 200 to 350 - 400 pounds of dry coallhour decreased Btu recovery, while pyritic sulfur rejection increased. This is expected because at very high column feed rates the yield and Btu recovery are typically low. At the low yields, pyritic sulfur rejection tends to be high. At the high feed rate condition, the column was likely overloaded, and coal was lost with the tailings. The feed to the column should not exceed the capability of the column to remove all the froth product that is produced. This will be discussed in detail later. • Effect or Frotber Dosage - Bubble size is detennined by the sparger type and the frother dosage. A high frother dosage creates smaller bubbles which can be more selective in recovering coal particles. Based on the shakedown tests, the feed rate, frother dosage, and collector dosage were detennined for the perfonnance tests and are listed in Table 9. Perrormance Tests. Based on the ash contents of the clean coal and yields (calculated by ash balance) from the CAER column tests, six tests were selected for further evaluation. These results are shown in Table 9. All perfonnance tests resulted in high yield (93.81 % on average) and high Btu recovery (96.38% on average), with a low pyritic sulfur rejection (31.48% on average). The following trends were observed during operation: • Effect or Aeration Rate - At high aeration rates (greater than 3 cfm), the column perfonned very poorly. Due to the high volumes of air (with accompanying high turbulence), particle attachment becomes more difficult and separation efficiency decreases. Lower aeration rates (with low turbulence) are required for efficient coal particle attachment. • Effect or Wasb Water Rate - The wash water removes entrained ash material from the froth. Sufficient wash water must be used to spray the entire area of the froth bed or mineral matter is carried over in the froth. • Effect or Air Pressure - High air pressure has a similar effect as high aeration rate. Increasing turbulence makes it more difficult for the coal particles to attach to the bubbles; thus, lowering efficiency. The perfonnance testing was perfonned to verify - not optimize - the 12-inch diameter column perfonnance. A limited test matrix was run. Additional testing is necessary to optimize the perfonnance of the column cell. Column Performance Versus Wasbability Analysis A sample of the raw 325M Pittsburgh #8 coal was subjected to specific gravity washability analysis. A washability study of a coal is made by testing the coal sample at pre-selected, carefully controlled specific gravities. This is commonly tennedfloat-and-sink analysis and/or specific gravity fractionation. The specific gravity fractions are dried, weighed, and analysed, generally for ash, sulfur, and Btu. A table is then compiled showing the weight percent of each specific gravity fraction together with the analysis of each fraction. The data are mathematically combined on a weighted basis into cumulative float and cumulative sink, and are used to develop the washability curves that are characteristic for the coal(10). Table 9 12-1NCH DIAMETER ADVANCED FLOTA TION PERFORMANCE RESUL TS Feed Rate - 180 Ib of coal per hr; Collector - 2 Ib of kerosene I ton of coal; Frother - 1 Ib of MIBC I ton of coal Wash Pyritic Total Test Air Rate Water Rate Yield Sulfur Rejection Sulfur Rejection Btu Recovery Separation Efficiency 3 cfm, 30 psi 19pm 91.66% 36.37% 13.84% 94.96% 31.33 5 3 cfm, 30 psi 3gpm 93.89% 40.25% 12.28% 96.810/0 37.06 7 3 cfm, 60 psi 3gpm 94.31% 28.29% 7.04% 97.02% 25.31 8 5 cfm, 60 psi 3gpm 95.01% 25.41% 9.33% 97.44% 22.85 11 3 cfm, 30 psi 2gpm 94.83% 25.55% 10.05% 94.53% 20.08 12 2 cfm, 30 psi 1.8 gpm 93.15% 33.02% 13.24% 97.54% 30.56 Avg. --- , --- 93.81% 31.48% 96.38% 9 |