The investigation of grinding kinetics of Zonguldak-Catalagzi Power Plant solid fossil fuel

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In this study solid fossil fuel taken from Catalagzi Power Plant (CATES) and formed by blending of high-ash wastes of Kozlu, Uzulmez, Catalagzi washeries and private fields to meet desired ash and calorific value were used. The whole sample was crushed to 3350 µm below by a cone crusher. Washing tests were done to show heterogeneous structure. It was determined that the solid fossil fuel is composed of low-ash coal-rock mixture within high-ash shale. After proximate analysis it was determined that the sample has an ash of 47.58% (dry basis) and a maximum calorific value of 3825 Kcal/kg and also it was determined by a picnometer that the sample has a density of 1.8 g/cm3.

As a result of tests performed in Bond ball mill and Hardgrove device to determine the grindability characteristics of CATES sample it was found that Bond Work Index and Hardgrove index were 16.93 kWh/t and 77.45, respectively. CATES sample was dry screened and classified in narrow size groups of -3350+2360 µm, -2360+1700 µm, -1180+850 µm, -425+300 µm and -212+150 µm. The sample was exposed to grinding tests in a laboratory scale vertical pinned stirred mill and ball mill. After grinding tests in stirred mill 6 mm ball diameter and 360 rev/min stirring speed was found to be ideal in the determination of breakage behavior. In studies performed at ideal conditions first degree breakage behavior was obtained for 425+300 µm and -212+150 µm size groups and a nonlinear breakage behavior was obtained for the others. Specific rate of breakage was reached to the maximum in 425 µm particle size in the stirred mill and then it started to decrease. In ball mill first degree breakage behavior was realized in -1180+850 μm, -425+300 μm and -212+150 μm size groups. For other narrow size groups, however, as in ball mill, linear breakage behavior was totally diminished. Specific rate of breakage was reached to the maximum in 2360 µm particle size in ball mill and then it started to decrease. Breakage distribution parameters for both stirred and ball mill couldn’t be normalized and it was determined that these parameters depends on the initial size of material.

d80 values obtained by grinding of CATES sample all was -3350 µm (d80≈2100 µm) for 0.25, 0.50, 1 and 4 minutes were determined as 190 μm, 102 μm, 78 μm and 28 μm, respectively. Same sample was ground in ball mill for 1, 4, 8, 12 and 24 minutes. Obtained d80 values were 1802 μm, 1130 μm, 324 μm, 167 μm and 81 μm. d80≈78 µm was reached after by energy consumption of 10.53 kWh/t for 1 minute of grinding period for stirred mill, and d80≈81 µm was reached by energy consumption of 72.73 kWh/t for 24 minutes of grinding period for ball mill. These results showed that the stirred mill is superior to ball mill revealing shorter grinding period and lower energy consumption. In addition, grinding products were simulated by JKSimMet simulation software. A very good match was obtained between experimental and simulation results for ball mill products. Since the model used in simulation was developed for ball mills experimental results and simulation curves for the stirred mill didn’t reveal a nice fit. The results of the experimental work presented in this study displayed that the stirred mill is superior to other conventional mills in micronized grinding.

Selçuk Samanlı
Zonguldak-Çatalağzı Termik Santralı katı fosil yakıtı öğütme kinetiğinin araştırılması · 2008 · 202 sayfa.
Danışman: Yrd. Doç. Dr. Dilek Çuhadaroğlu ; Prof. Dr. Yaşar Uçbaş

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