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(Gbg).
The products of the total final three cycles are combined to form the equilibrium rest product. Sieve analysis is carried out on the material and the results are plotted, to find the 80% passing size of the product (P80). The Bond work index values (Wi) are calculated from the Eq. (2) .
Fig. 1. Twin pendulum device.
V. Deniz / Advanced Powder Technology 22 (2011) 761–765 763
Fig. 2. Drop-weight test apparatus.
Table 1
Chemical composition of limestone samples using in experiments.
CaO 31.03 46.85 48.99
SiO2 0.05 8.45 10.60
Al2O3 0.90 1.02 1.07
Fe2O3 0.00 0.35 0.59
MgO 22.42 0.92 1.11
SO3 0.02 0.07 0.09
Na2O 0.07 0.02 0.04
44:5
Wi ¼ 1:1 P0i :23 G0bg:82 ½ð10=pffiffiffiffiffiffiffiP80Þ ð10=pffiffiffiffiffiffiffiF80Þ ð2Þ
3. Experiments
Firstly, standard Bond grindability tests were performed for three limestone samples. From the result of tests, Bond work index values were calculated 4.44, 10.10 and 13.53 kW h/t, respectively. Then, 1 kg sample of six mono-size fractions (6.7 + 4.75, 4.75 + 2.8, 2.8 + 1.7, 1.7 + 1.18, 1.18 + 0.600, 0.600 + 0.355 mm) were prepared by screens for determination of the t-family curves. The laboratory impact crusher (Fig. 4), used in the experiments,
Fig. 4. Impact crusher using in experiments.
Fig. 5. tn versus mean size fraction for limestone-I.
Fig. 6. tn versus mean size fraction for limestone-II.
works with driven by a 1.1 kW motor, rotating at 2840 rpm, carry three rows of hammers. Each sample was taken out of the laboratory impact crusher, and then samples were sieved for product size analysis.
Results of t-family curves versus mean particle size fraction for different limestones were shown in Figs. 5–7.
764 V. Deniz / Advanced Powder Technology 22 (2011) 761–765
Fig. 7. tn versus mean size fraction for limestone-III.
4. Proposed size distribution model equation
King [25] described a method of presenting the product size distributions obtained from drop weight tests. It is based on the observations made by Narayanan and Whiten [26], that the cumulative fraction of products passing 1/nth of the mean size was denoted by tn, is related to that passing one-tenth of the parent size denoted by t10. It was also reported that this relationship was applicable to different ore types tested under different impact loading conditions.
In this study, a different size distribution relationship has been exposed tn values for crushing products in the direct laboratory impact crusher. As a result of this study, the relationship between the cumulative percentage passing (tn) with Bond work index (Wi) and mean particle size (X) was empirically described by Eq. (3). tn ¼ 0406:921:351:1X0:108W0i :668n2:47Wi 1:184 ð3Þ
Wi n
The experimental values and the calculated results obtained by Eq. (3) were compared in Fig. 8.
Eq. (3) mostly satisfies the experimental values in a wide range of feed size, and Eq. (3) is useful especially when evaluating the particle size distribution in the actual operation by a high regression value (r2 = 0.88). Thus, the relationship between the cumulative
Fig. 8. Comparison of experimental and calculated tn value for limestone.
percentage passing (tn) with Bond work index (Wi) and mean particle size (X) was empirically described by Eq. (3).