30 mL maximum recovery of 78% was obtained but with further increase in the acid quantity the recovery started falling. Similar observation was made for 30% acid where 30 mL acid showed maximum recovery of 88% and with further increase in acid quantity recovery showed a declin- ing trend. However with 40% acid the maximum recovery was obtained at 40 mL of acid amount. The reason behind decrease in recovery with increase in acid is exactly not known. Though the decrease in recovery is not appreciable but it happened in all the cases. Generally in any dissolu- tion/leaching operation stoichiometric quantities of lea- chant does not show the optimum level of recovery. Invariably some more acid would be required to have the optimum value. In this case the role of acid quantity, quan- tity of water, salts like KCl and NaCl, formation of aluminium sulphate etc. will influence the leaching beha- viour. It has been mentioned that where washed dross is taken for dissolution studies, with stoichiometric quantity of acid, alumina recovery is higher.
It has been found, therefore that the optimum recovery of alumina for original dross is 88%, with 30 mL of 30% acid. But this 30 mL of acid is almost double the stoichiom- etric amount that is required for 100% solubilisation of available alumina.
Fig. 3 shows percentage of recovery of alumina plotted as a function of solids (dross) concentration at various acid quantities. It has been found that solid concentration of 10% showed maximum recovery. Similar results were also obtained with other percentages of acid considered in the present study. Therefore, pulp density of 10% may be taken as the optimum solid concentration to obtain maximum alumina recovery.
It has been observed from the above results that maxi- mum recovery of 88% can be achieved with 30 mL of
30 mL maximum recovery of 78% was obtained but with further increase in the acid quantity the recovery started falling. Similar observation was made for 30% acid where 30 mL acid showed maximum recovery of 88% and with further increase in acid quantity recovery showed a declin- ing trend. However with 40% acid the maximum recovery was obtained at 40 mL of acid amount. The reason behind decrease in recovery with increase in acid is exactly not known. Though the decrease in recovery is not appreciable but it happened in all the cases. Generally in any dissolu- tion/leaching operation stoichiometric quantities of lea- chant does not show the optimum level of recovery. Invariably some more acid would be required to have the optimum value. In this case the role of acid quantity, quan- tity of water, salts like KCl and NaCl, formation of aluminium sulphate etc. will influence the leaching beha- viour. It has been mentioned that where washed dross is taken for dissolution studies, with stoichiometric quantity of acid, alumina recovery is higher.It has been found, therefore that the optimum recovery of alumina for original dross is 88%, with 30 mL of 30% acid. But this 30 mL of acid is almost double the stoichiom- etric amount that is required for 100% solubilisation of available alumina.Fig. 3 แสดงเปอร์เซ็นต์ของการฟื้นตัวของอลูมินาลงจุดเป็นฟังก์ชันของความเข้มข้นของของแข็ง (dross) ที่ปริมาณกรดต่าง ๆ จะพบว่า แข็งเข้มข้น 10% แสดงให้เห็นว่ากู้คืนสูงสุด ผลคล้ายได้รับอื่น ๆ เปอร์เซ็นต์กรดที่พิจารณาในการศึกษาปัจจุบัน ดังนั้น อาจถือเป็นความเข้มข้นแข็งเหมาะสมเยื่อความหนาแน่น 10% รับกู้อลูมินาที่สูงสุดมันได้ถูกตรวจสอบจากผลข้างต้นว่า กู้คืนแม็กซี่มัม 88% สามารถทำได้ ด้วย 30 mL ของ
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