Effect of Finely Ground Limestone and Dolomite on Compression Strength and Reduction Swelling of Vanadium-Titanium Pellets

Vanadium−titanium magnetite (VTM) is an important raw material for ironmaking under the situation of increasingly demanding scarce resources. To further improve the metallurgical properties of pellets, and to satisfy the requirements of blast furnace slag basicity, finely ground dolomite and limestone have been added to the pellet. In this study, the effect of finely ground dolomite and limestone on the metallurgical properties (green pellet drop strength, cold compression strength, reduction swelling index, and microscopic mineral structure) of VTM pellets were investigated. With the addition of finely ground dolomite and limestone, the drop strength of the green pellet was improved. The effect of adding finely ground limestone was greater than adding finely ground dolomite. Adding more finely ground dolomite and limestone compared to pellets without limestone and dolomite, the cold compression strength was decreased, which was attributed to the decomposition of limestone and dolomite during the induration of pellets. With the addition of dolomite, the reduction swelling index (RSI) increased firstly and then decreased. When the basicity of the pellet was 0.54 to 0.94, the slag phase with the lowest melting point was formed, corresponding to the maximum of the reduction swelling index. For the pellets with added limestone, the reduction swelling of the pellets deteriorated. The reduction index of the pellets increased and reached the maximum (26.6%) at a basicity of 1.54, which belongs to abnormal swelling.

Physical quality and digestibility in vitro determination of green pellet concentrate based on Indigofera zollingeriana

<p>This study aims to determine the physical quality and digestibility of green pellet concentrate based on <em>I.</em><em> zollingeriana</em>. The composition of green pellet concentrate feed contains <em>I. zollingeriana</em> and <em>C.</em><em> calothyrsus</em> in the following combinations: 1) <em>I.</em><em> zollingeriana</em> /<em>C.</em><em> calothyrsus</em> (90/0; R0), 2) <em>I.</em><em> zollingeriana</em>/<em>C. calothyrsus</em> (75/15; R1), 3) <em>I.</em><em> zollingeriana</em>/<em>C. calothyrsus</em> (60/30; R2) and 4<em>) I.</em><em> zollingeriana</em> / <em>C. calothyrsus</em> (45/45; R3). The physical quality study of green pellet concentrate was performed using a completely randomized design with four types of green concentrate as treatments of three replications. Green pellet concentrate studies conducted in vitro rumen fermentation were performed using in a randomized block design with four treatments and three sources of liquid rumen as a block. The results of the experiments conducted with pellet criteria containing <em>I.</em><em> zollingeriana/C. calothyrsus </em>composition (60/30; R2) have the best physical character (water activity = 0.58; particles size = 12.69 mm; degree value angles = 21.01^o; collision endurance = 99.78%; endurance friction = 90.42 %; bulk density = 590 kg/m3) compared to the other treatments. The quality of diet based on digestibility in vitro, dry matter and organic material having a pattern equal to R0 is higher (P&lt;0.05) compared with other treatments, while the rough digestibility of In Vitro protein is seen R0, R1, and R2 (P&gt;0.05), but (P&lt;0.05) was higher than the treatment of R3. There was no difference of pH and total bacteria on green pellet concentrate type. The treatment of R3 has the lowest NH3, VFA and total gas concentration (P&lt;0.5) compared with R2, R1 and R0. It was concluded that concentrate green pellet of <em>I.</em><em> zollingeriana</em> composition (60%) and <em>C.calothyrsus</em> (30%) had better physical and nutritional quality.</p>